FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
& The Patent Rules, 2003
COMPLETE SPECIFICATION
1. TITLE OF THE INVENTION:
PRESSURE CONTROL VALVE
2. APPLICANT:
Name: NABTESCO CORPORATION
Nationality: Japan
Address: 7-9, Hirakawa-cho 2-chome, Chiyoda-ku, Tokyo 102-0093, Japan.
3. PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the invention and the manner in
which it is to be performed:

BACKGROUND
[0001] 1. Field
[0002] The present invention relates to a pressure control valve that controls pressure of a
brake pipe.
[0003] 2. Description of Related Art
[0004] Japanese Unexamined Utility Model Publication No. 64-30769 discloses a pressure
control valve that controls pressure of a brake pipe. The pressure control valve disclosed in
Japanese Unexamined Utility Model Publication No. 64-30769 includes an air chamber for
boosting pressure ("second pilot chamber" in this publication).
[0005] When releasing the brake of a vehicle during operation of the vehicle, the pressure
control valve sets pressure of a brake pipe to be greater than a predetermined pressure so that
the control valve is actuated to exhaust a brake cylinder, thereby releasing the brake.
[0006] For example, when switching a locomotive, the pressure of a brake pipe may be
readjusted. In this case, air is supplied to the pressure boosting air chamber to make the
pressure of the brake pipe greater than a predetermined pressure. Thereafter, the air is
gradually discharged from the pressure boosting air chamber to gradually decrease the
pressure of the brake pipe. As a result, each constant pressure air reservoir of a control
valve obtains an appropriate pressure. This limits occurrences of non-releasing of the brake.
[0007] When readjusting pressure of a brake pipe, the pressure of the brake pipe needs to
be gradually decreased. Thus, in Japanese Unexamined Utility Model Publication No. 64-
30769, an exhaust throttle device is provided in an exhaust system of the pressure boosting
air chamber. The exhaust throttle device discharges air through a valve and a throttle.
Such discharging obtains a linear reduction in the pressure of the brake pipe.

[0008] However, according to Japanese Unexamined Utility Model Publication No. 64-
30769, when the pressure of the pressure boosting device through the exhaust throttle device
cannot resist an urging force of a pressure regulation spring of the exhaust throttle device,
the adjustment valve is constantly open. This reduces the exhaust amount and limits a
decrease in the pressure for pressure boosting. Thus, an amount of time taken to discharge
the air (also referred to as pressure boosting state cancellation time) is extended. The
extension of the pressure boosting state cancellation time limits shortening of the time to
switch a locomotive.
SUMMARY
[0009] Therefore, the following description provides a pressure control valve that shortens
the pressure boosting state cancellation time.
[0010] This Summary is provided to introduce a selection of concepts in a simplified form
that are further described below in the Detailed Description. This Summary is not intended
to identify key features or essential features of the claimed subject matter, nor is it intended
to be used as an aid in determining the scope of the claimed subject matter.
[0011] (1) To solve the above problem, a pressure control valve includes an input chamber
to which a target pressure is input, an output chamber having an output pressure controlled to
be balanced with pressure of the input chamber by switching between pressure application to
the output chamber and pressure release from the output chamber, and a pressure boosting
chamber that boosts the output pressure when a pressure boost command pressure is applied
to the pressure boosting chamber. The pressure control valve further comprises a damping
speed decrease limiter configured to limit a decrease in a damping speed of the pressure
boost command pressure when the application of the pressure boost command pressure is
stopped.
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[0012] According to this configuration, the damping speed decrease limiter limits decreases
in the damping speed of the pressure boost command pressure when the application of the
pressure boost command pressure is stopped. Thus, the pressure boost command pressure
is reduced without delay. This shortens the pressure boosting state cancellation time.
[0013] (2) In the above pressure control valve, the pressure boosting chamber includes a
pressure boosting diaphragm, and the damping speed decrease limiter applies a force to the
pressure boosting diaphragm in a direction opposite to a direction in which the output
pressure boosts.
[0014] According to this configuration, the exhausting of the pressure boosting chamber is
accelerated. This limits decreases in the exhaust speed or the exhaust amount.
[0015] (3) In the above pressure control valve, damping speed decrease limiter includes a
spring that generates the force.
[0016] According to this configuration, the damping speed decrease limiter is simply
configured.
[0017] (4) In the above pressure control valve, the damping speed decrease limiter
generates the force from air pressure.
[0018] According to this configuration, the air pressure for actuating the pressure control
valve is used to generate the force of the damping speed decrease limiter. This eliminates
the need for a power source that actuates the damping speed decrease limiter.
[0019] (5) In the above pressure control valve, the damping speed decrease limiter
generates the force from the pressure of the input chamber.
[0020] According to this configuration, the pressure of the input chamber is used. Thus,
the damping speed decrease limiter is simplified.
[0021] (6) In the above pressure control valve, the damping speed decrease limiter includes
a diaphragm connected to the pressure boosting diaphragm of the pressure boosting chamber,
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and the diaphragm receives the pressure from the input chamber as the force.
[0022] According to this configuration, there is no need to provide additional space for the
damping speed decrease limiter. Thus, miniaturization is achieved.
[0023] (7) In the above pressure control valve, the damping speed decrease limiter includes
a magnet that generates the force.
[0024] Magnetic force affects a smaller range than air pressure and spring force. The
range affected by magnetic force is limited to a section immediately before the discharging
of air completes. Thus, the configuration described above reduces interference with the
force acting in a direction that accelerates the pressure application to the output chamber
based on the pressure boost command pressure.
[0025] (8) To solve the above problem, a pressure control valve includes an input chamber
to which a target pressure is input, an output chamber having an output pressure controlled to
be balanced with pressure of the input chamber by switching between pressure application to
the output chamber and pressure release from the output chamber, a pressure boosting
chamber that boosts the output pressure when a pressure boost command pressure is applied
to the pressure boosting chamber, a pressure boosting diaphragm that applies force
corresponding to a pressure boost in the pressure boosting chamber to a balance diaphragm
that separates the input chamber from the output chamber, and a spring that applies force to
the pressure boosting diaphragm in a direction opposite to a pressure boosting direction of
the pressure boosting diaphragm when boosting the output pressure.
[0026] According to this configuration, the force of the spring acting in the direction
opposite to the pressure boosting direction is applied to the pressure boosting diaphragm to
limit decreases in the damping speed of the pressure boost command pressure when the
application of the pressure boost command pressure is stopped. Thus, the pressure boost
command pressure is reduced without delay. This shortens the pressure boosting state
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cancellation time.
[0027] (9) To solve the above problem, a pressure control valve includes an input chamber
to which a target pressure is input, an output chamber having an output pressure controlled to
be balanced with pressure of the input chamber by switching between pressure application to
the output chamber and pressure release from the output chamber, a pressure boosting
chamber that boosts the output pressure when a pressure boost command pressure is applied
to the pressure boosting chamber, a pressure boosting diaphragm that applies force
corresponding to a pressure boost in the pressure boosting chamber to a balance diaphragm
that separates the input chamber from the output chamber, and a pressure reducing
diaphragm that applies force to the pressure boosting diaphragm in a direction opposite to a
pressure boosting direction of the pressure boosting diaphragm when the pressure reducing
diaphragm receives the pressure of the input chamber and boosts the output pressure.
[0028] According to this configuration, the force of the pressure reducing diaphragm acting
in the direction opposite to the pressure boosting direction is applied to the pressure boosting
diaphragm to limit decreases in the damping speed of the pressure boost command pressure
when the application of the pressure boost command pressure is stopped. Thus, the
pressure boost command pressure is reduced without delay. This shortens the pressure
boosting state cancellation time.
[0029] The pressure control valve according to the present disclosure shortens the pressure
boosting state cancellation time.
[0030] Other features and aspects will be apparent from the following detailed description,
the drawings, and the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Fig. 1 is a schematic diagram of railway vehicles.
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[0032] Fig. 2 is a schematic diagram of a brake valve device according to a first
embodiment.
[0033] Fig. 3 is a schematic diagram of a pressure control valve in a balanced state.
[0034] Fig. 4 is a schematic diagram of the pressure control valve when air is discharged
from the input chamber.
[0035] Fig. 5 is a schematic diagram of the pressure control valve when air is supplied to
the input chamber.
[0036] Fig. 6 is a schematic diagram of the pressure control valve when boosting pressure.
[0037] Fig. 7 is a chart showing pressure of a brake pipe in a typical pressure control valve.
[0038] Fig. 8 is a chart showing pressure of the brake pipe in the pressure control valve
according to the first embodiment.
[0039] Fig. 9 is a schematic diagram of a brake valve device according to a second
embodiment.
[0040] Throughout the drawings and the detailed description, the same reference numerals
refer to the same elements. The drawings may not be to scale, and the relative size,
proportions, and depiction of elements in the drawings may be exaggerated for clarity,
illustration, and convenience.
DETAILED DESCRIPTION
[0041] This description provides a comprehensive understanding of the methods,
apparatuses, and/or systems described. Modifications and equivalents of the methods,
apparatuses, and/or systems described are apparent to one of ordinary skill in the art.
Sequences of operations are exemplary, and may be changed as apparent to one of ordinary
skill in the art, with the exception of operations necessarily occurring in a certain order.
Descriptions of functions and constructions that are well known to one of ordinary skill in
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the art may be omitted.
[0042] Exemplary embodiments may have different forms, and are not limited to the
examples described. However, the examples described are thorough and complete, and
convey the full scope of the disclosure to one of ordinary skill in the art.
[0043] First embodiment
[0044] A pressure control valve 50 will now be described with reference to Figs. 1 to 8.
In Figs. 2 to 6, "Ex" indicates an exhaust port.
[0045] A train including a locomotive 1 will now be described with reference to Fig. 1.
The locomotive 1 includes a brake pipe 10, a brake cylinder 11, a control valve 20, a brake
valve device 40, and a main reservoir pipe 12. The brake valve device 40 includes a
pressure control valve 50 (refer to Fig. 2). The brake valve device 40 controls the pressure
(hereinafter, referred to as brake pipe pressure BP) of the brake pipe 10 through the pressure
control valve 50. The brake valve device 40 controls the brake pipe pressure BP to actuate
the control valve 20 of each of the vehicles in the train. The actuation of the control valves
20 controls the brakes on wheels of the locomotive 1.
[0046] In the train shown in Fig. 1, the locomotive 1 is disposed at the head. Connected
vehicles 2 are connected to the locomotive 1. Hereinafter, when the locomotive 1 and the
connected vehicles 2 are collectively referred to, the term "vehicles" will be used.
[0047] The main reservoir pipe 12 stores air that is supplied to the brake pipe 10. The air
is supplied from the main reservoir pipe 12 to the brake pipe 10 through the pressure control
valve 50. The main reservoir pipe 12 is supplied with air from an air compressor (not
shown) at a predetermined pressure.
[0048] The brake pipe 10 is filled with air for controlling the control valve 20. The brake
pipe pressure BP may have, for example, the following values. The brake pipe pressure BP
may be set to a braking pressure BP1 (e.g., 40 to 360 kPa) when applying the brake, a
9
releasing pressure BP2 (e.g., 500 kPa) when releasing the brake, and a readjustment pressure
BP3 (e.g., 550 kPa) when the brake pipe pressure BP is readjusted without causing nonreleasing
of the automatic air brake. The readjustment pressure BP3 is greater than the
releasing pressure BP2. The braking pressure BP1 is less than the releasing pressure BP2.
[0049] The control valve 20 controls the pressure of the brake cylinder 11 based on the
brake pipe pressure BP.
[0050] The brake cylinder 11 is controlled based on the actuation of the control valve 20.
When air is supplied based on the actuation of the control valve 20, the brake cylinder 11
applies the brake to the wheels. When the air is discharged based on the actuation of the
control valve 20, the brake cylinder 11 releases the brake from the wheels.
[0051] Each connected vehicle 2 includes a brake pipe 10, a control valve 20, and a brake
cylinder 11.
[0052] The brake pipe 10 of the locomotive 1 and the brake pipe 10 of each connected
vehicle 2 are connected to define a common pressure chamber. The connected brake pipes
10 are supplied with air from the main reservoir pipe 12 of the locomotive 1. Since air
slightly leaks from connected portions between the brake pipes 10 of the vehicles, the
pressure of the brake pipes 10 decreases from the head to the tail of the train.
[0053] The control valve 20 will now be described with reference to Fig. 1. The control
valve 20 supplies air to the brake cylinder 11 and discharges air from the brake cylinder 11
based on the brake pipe pressure BP. For example, when the pressure of the brake pipe 10
is the braking pressure BP1, the control valve 20 supplies air to the air chamber in the brake
cylinder 11 to apply the brake to the wheels. When the pressure of the brake pipe 10 is a
predetermined pressure that is higher than the braking pressure BP1, the control valve 20
discharges air from the air chamber of the brake cylinder 11 to release the brake from the
wheels.
10
[0054] The control valve 20 is configured by, for example, a three-pressure type control
valve. More specifically, the control valve 20 is configured as follows. The control valve
20 includes an air supply-exhaust valve 35. The air supply-exhaust valve 35 moves based
on the brake pipe pressure BP so that the air supply-exhaust valve 35 is switched between
supply of air to the brake cylinder 11 and discharge of air from the brake cylinder 11. The
movement of the air supply-exhaust valve 35 is controlled based on a difference in pressure
between the brake pipe pressure BP and the pressure CR of the constant pressure air
reservoir 36. More specifically, the control valve 20 includes a first pressure chamber 31 to
which the brake pipe pressure BP is applied, a second pressure chamber 32 to which the
pressure CR of the constant pressure air reservoir 36 is applied, and a control diaphragm 33
that separates the first pressure chamber 31 from the second pressure chamber 32. The
control diaphragm 33 moves in accordance with changes in the pressure difference between
the brake pipe pressure BP and the pressure CR of the constant pressure air reservoir 36.
Since the control diaphragm 33 is connected to the air supply-exhaust valve 35, the air
supply-exhaust valve 35 moves together with the control diaphragm 33 in accordance with
changes in the pressure difference between the brake pipe pressure BP and the pressure CR
of the constant pressure air reservoir 36. In the present embodiment, the pressure CR of the
constant pressure air reservoir 36 connected to the second pressure chamber 32 is set to a
predetermined pressure. The movement of the air supply-exhaust valve 35 is controlled by
boosting and decreasing the brake pipe pressure BP applied to the first pressure chamber 31
in relation to the pressure of the second pressure chamber 32.
[0055] The constant pressure air reservoir 36 is connected to the brake pipe 10 through a
pilot check valve 37. When the brake pipe pressure BP is the braking pressure BP1, the
pilot check valve 37 prohibits the flow of air from the constant pressure air reservoir 36 to
the brake pipe 10. Thus, the pressure CR of the constant pressure air reservoir 36 is
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maintained at a predetermined value. When the brake pipe pressure BP is the releasing
pressure BP2, the pilot check valve 37 permits the flow of air so that the brake pipe pressure
BP and the pressure CR of the constant pressure air reservoir 36 have a predetermined
pressure relationship (relationship in which pressure ratio is within predetermined range).
The pilot check valve 37 allows the constant pressure air reservoir 36 to maintain a constant
pressure.
[0056] However, the predetermined pressure relationship between the brake pipe pressure
BP and the pressure CR of the constant pressure air reservoir 36 may collapse. For
example, when the locomotive 1 is switched, the upstream side and downstream side of the
brake pipe pressure BP are reversed. Hence, after the switching of the locomotive 1, the
brake pipe pressure BP of each control valve 20 differs from that before the switching of the
locomotive 1. This collapses the predetermined pressure relationship between the brake
pipe pressure BP and the pressure CR of the constant pressure air reservoir 36 when the
brake pipe pressure BP is the releasing pressure BP2. In particular, after the switching of
the locomotive 1, in the control valve 20 located at the downstream side, even when a brake
releasing operation increases the brake pipe pressure BP to the releasing pressure BP2, the
pressure of the first pressure chamber 31 connected to the brake pipe 10 will not be
sufficiently increased in relation to the pressure CR of the constant pressure air reservoir 36,
and the air supply-exhaust valve 35 may not sufficiently move toward the exhaust side.
This generates a non-releasing state of the brake (state in which brake is not released).
"Non-releasing" does not occur in a railway vehicle of AAR (Association of American
Railroads) standard but may occur, for example, in a railway vehicle of UIC (Union
Internationale des Chemins de fer) standard. Thus, in a vehicle that uses an automatic air
brake complying with the UIC standard, the brake pipe pressure BP is readjusted when nonreleasing
may occur (e.g., when the locomotive 1 is switched). More specifically, after the
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switching of the locomotive 1, the brake pipe pressure BP is increased to a pressure
(readjustment pressure BP3) that is greater than the releasing pressure BP2, and thereafter,
the pressure of the brake pipe pressure BP is gradually reduced to the releasing pressure BP2.
In the process of gradually reducing the pressure of the brake pipe pressure BP to the
releasing pressure BP2, the pressure CR of the constant pressure air reservoir 36 and the
brake pipe pressure BP reach the predetermined pressure relationship in each control valve
20. The time taken to reduce the brake pipe pressure BP from the readjustment pressure
BP3 to the releasing pressure BP2 is, for example, several hundred seconds (e.g., 300
seconds).
[0057] The brake valve device 40 will now be described with reference to Fig. 2. As
described above, the brake valve device 40 controls the brake pipe pressure BP.
[0058] The brake valve device 40 includes a pressure control valve 50 and a switching
valve 55 that actuates the pressure control valve 50 by operation. The pressure control
valve 50 includes a pressure forming unit 51 and a pressure boosting device 80. The
pressure control valve 50 further includes a damping speed decrease limiter 84.
[0059] The pressure forming unit 51 supplies air to the brake pipe 10 (the brake pipe
pressure BP) and discharges air from the brake pipe 10 (the brake pipe pressure BP).
[0060] The pressure boosting device 80 boosts the output pressure (see description below)
of the pressure forming unit 51 using a pressure boost command pressure based on a
predetermined operation.
[0061] The pressure forming unit 51 includes an input chamber 73 (see description below)
connected to an input pipe 56. When a handle 54 is operated, the switching valve 55
connects the input pipe 56 to one of the main reservoir pipe 12 and the exhaust pipe 13.
The main reservoir pipe 12 includes a pressure adjustment valve 19.
[0062] In the brake valve device 40, an operation for applying the brake to the wheels is
13
referred to as a "braking operation." An operation of releasing the brake from the wheels is
referred to as "releasing operation." In the braking operation, the input pipe 56 is
connected to the exhaust pipe 13. In the releasing operation, the input pipe 56 is connected
to the main reservoir pipe 12.
[0063] The pressure forming unit 51 will now be described.
[0064] The pressure forming unit 51 includes an air supply chamber 61, an exhaust
chamber 62, an output chamber 63, a balance chamber 70, and an air supply-exhaust valve
75.
[0065] The air supply chamber 61 is connected to the main reservoir pipe 12. Thus, the
pressure of the air supply chamber 61 is equal to the pressure of the main reservoir pipe 12.
[0066] The exhaust chamber 62 includes an exhaust port 62a. The exhaust chamber 62 is
generally equal to atmospheric pressure.
[0067] The output chamber 63 is connected to the brake pipe 10. The pressure of the
output chamber 63 (hereinafter, referred to as an "output pressure") determines the brake
pipe pressure BP. The output pressure of the output chamber 63 is controlled to be
balanced with the pressure of the input chamber 73 by switching between pressure
application (see description below) and pressure release (see description below).
[0068] The output chamber 63 is connected to one of the air supply chamber 61 and the
exhaust chamber 62 by actuation of the air supply-exhaust valve 75. When the output
chamber 63 is connected to the exhaust chamber 62, the pressure of the output chamber 63
decreases. When the output chamber 63 is connected to the air supply chamber 61, the
output pressure of the output chamber 63 increases.
[0069] The output chamber 63 and the air supply chamber 61 are connected through an
opening 63a which is opened and closed by a lid 64. The lid 64 is urged by a spring 65 to
seal the opening 63a. When the lid 64 is pushed by the air supply-exhaust valve 75 and the
14
opening 63a is open, the output chamber 63 is connected to the air supply chamber 61. The
"pressure application" refers to the supply of air from the air supply chamber 61 when the
output chamber 63 is connected to the air supply chamber 61.
[0070] When the opening 63a is sealed by the lid 64 and the air supply-exhaust valve 75 is
separated from the lid 64, the output chamber 63 and the exhaust chamber 62 are connected
through a communication hole 76 of the air supply-exhaust valve 75. The "pressure
release" refers to a decrease in the pressure of the output chamber 63 when the output
chamber 63 is connected to the exhaust chamber 62 and air is discharged from the output
chamber 63.
[0071] The air supply-exhaust valve 75 is connected to a balance diaphragm 71 via a
connecting portion 77 and moves integrally with the balance diaphragm 71.
[0072] The air supply-exhaust valve 75 includes the communication hole 76. The air
supply-exhaust valve 75 includes an output open end 75a, which is one end of the
communication hole 76 disposed at the side of the output chamber 63, and an exhaust open
end 75b, which is the other end of the communication hole 76 and is disposed at the side of
the exhaust chamber 62.
[0073] The air supply-exhaust valve 75 is movable from an exhaust position to an air
supply position through a balance position.
[0074] The exhaust position indicates a position where the output open end 75a of the air
supply-exhaust valve 75 is separated from the lid 64 and disposed in the exhaust chamber 62.
When the air supply-exhaust valve 75 is disposed at the exhaust position, the pressure of the
output chamber 63 decreases because the exhaust chamber 62 is connected to the output
chamber 63.
[0075] The balance position indicates a position where the output open end 75a of the air
supply-exhaust valve 75 is in contact with the lid 64 in a state sealing the opening 63a of the
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output chamber 63. At this time, the output open end 75a is sealed by the lid 64, and the
opening 63a of the output chamber 63 is sealed by the lid 64. Thus, the air flow between
the output chamber 63 and the exhaust chamber 62 and the air flow between the output
chamber 63 and the air supply chamber 61 are both interrupted. This obtains a neutral state
and maintains the output chamber 63 at a constant output pressure.
[0076] The air supply position indicates a position where the output open end 75a of the air
supply-exhaust valve 75 is sealed by the lid 64 and disposed in the air supply chamber 61.
When the air supply-exhaust valve 75 is disposed at the air supply position, the opening 63a
opens and connects the air supply chamber 61 and the output chamber 63. This increases
the output pressure of the output chamber 63.
[0077] The balance chamber 70 is partitioned by a balance diaphragm 71 into a sub-output
chamber 72 (see description below) and the input chamber 73.
[0078] The balance diaphragm 71 receives the pressure from the sub-output chamber 72
(this pressure is equal to the output pressure of the output chamber 63) and the pressure from
the input chamber 73. As described above, the balance diaphragm 71 is connected to the
air supply-exhaust valve 75 through the connecting portion 77. The balance diaphragm 71
and the air supply-exhaust valve 75 move integrally in the same direction.
[0079] The sub-output chamber 72 configures a portion of the output chamber 63. That is,
the output chamber 63 includes a main output chamber 63A, the sub-output chamber 72, and
a passage 74 that connects the main output chamber 63A and the sub-output chamber 72.
The sub-output chamber 72 accommodates a spring 72a that pushes the balance diaphragm
71 toward the input chamber 73.
[0080] The input chamber 73 is controlled to obtain a target pressure. More specifically,
the target pressure is input to the input chamber 73. For example, the input chamber 73 is
connected to the input pipe 56. The input chamber 73 is connected to one of the main
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reservoir pipe 12 and the exhaust pipe 13 through the switching valve 55. When the input
chamber 73 is connected to the main reservoir pipe 12, air is supplied to the input chamber
73. When the input chamber 73 is connected to the exhaust pipe 13, air is discharged from
the input chamber 73. The input pipe 56 has a path that extends from the input chamber 73
to the switching valve 55 and includes a balance air reservoir 91. The balance air reservoir
91 limits variations in the pressure of the input chamber 73.
[0081] The balance diaphragm 71 and the air supply-exhaust valve 75 are arranged to
satisfy the following relationship. The direction in which the balance diaphragm 71 moves
when the pressure of the input chamber 73 rises is referred to as "first direction D1." The
direction opposite to the first direction D1 is referred to as "second direction D2."
[0082] The position of the balance diaphragm 71 when air is supplied to the input chamber
73 is defined as a "high pressure position" of the balance diaphragm 71. When the balance
diaphragm 71 is disposed at the high pressure position, the air supply-exhaust valve 75 is
disposed at the air supply position (see description above).
[0083] The position of the balance diaphragm 71 when air is discharged from the input
chamber 73 is defined as a "low pressure position" of the balance diaphragm 71. When the
balance diaphragm 71 is disposed at the low pressure position, the air supply-exhaust valve
75 is disposed at the exhaust position (see description above).
[0084] When the balance diaphragm 71 moves from the low pressure position toward the
high pressure position, the air supply-exhaust valve 75 moves from the exhaust position to
the air supply position through the balance position. When the balance diaphragm 71
moves from the high pressure position toward the low pressure position, the air supplyexhaust
valve 75 moves from the air supply position to the exhaust position through the
balance position.
[0085] The pressure boosting device 80 will now be described.
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[0086] The pressure boosting device 80 does not actuate when a normal braking operation
is performed. The pressure boosting device 80 is used, for example, when switching the
locomotive 1. More specifically, the pressure boosting device 80 is used when the brake
pipe pressure BP is temporarily set to the readjustment pressure BP3 (e.g., 550 kPa).
[0087] The pressure boosting device 80 generates a pressure boost command pressure for
boosting the output pressure. For example, when setting the brake pipe pressure BP to the
readjustment pressure BP3, the pressure boosting device 80 is actuated. The pressure boost
command pressure generated by the pressure boosting device 80 boosts the output pressure
as will be described later. The pressure boost command pressure increases the brake pipe
pressure BP to the readjustment pressure BP3. When a predetermined operation (referred
to as "release of pressure boost command pressure") is performed on the pressure boosting
device 80, the boosted amount of the output pressure gradually decreases. The pressure
boosting device 80 includes the damping speed decrease limiter 84. The damping speed
decrease limiter 84 limits decreases in the damping speed of the pressure boost command
pressure when the application of the pressure boost command pressure is stopped.
[0088] An example of the pressure boosting device 80 will be described below.
[0089] The pressure boosting device 80 includes a pressure boosting chamber 81 and a
pressure boosting diaphragm 82. When the pressure boost command pressure is applied,
the pressure boosting chamber 81 boosts the output pressure. The pressure boosting
chamber 81 is connected to the input pipe 56 through a bypass pipe 86. The bypass pipe 86
includes a push button valve 90 which allows and prohibits the flow of air in the bypass pipe
86. When the push button valve 90 is pushed, air is allowed to flow in the bypass pipe 86
and is supplied from the input pipe 56 to the pressure boosting chamber 81. The pressure
boosting chamber 81 is connected to an exhaust passage 85 through an air reservoir 92.
[0090] In the exhaust passage 85, an exhaust throttle device 95 and a throttle 96 are
18
arranged in series. The exhaust throttle device 95 sets the exhaust flow rate to a constant
rate (discharge amount per unit time is constant).
[0091] The exhaust throttle device 95 and the throttle 96 adjust the exhaust amount so that
the pressure reduction speed of the brake pipe pressure BP is less than a reference speed.
The exhaust throttle device 95 discharges air so that the pressure of the input chamber 95a
connected to the exhaust passage 85 decreases at a predetermined pressure reduction speed.
More specifically, the exhaust throttle device 95 includes an input chamber 95a, an output
chamber 95b, and an adjustment valve 95c for adjusting the opening degree of an opening in
the wall between the input chamber 95a and the output chamber 95b. The adjustment valve
95c is configured to receive the pressure of the input chamber 95a, the pressure of the output
chamber 95b, and the atmospheric pressure, and adjusts the opening degree. With this
configuration, the pressure of the input chamber 95a is decreased at the predetermined
pressure reduction speed. However, when the differential pressure between the
atmospheric pressure and the pressure of the input chamber 95a decreases, the pressure
reduction at the predetermined pressure reduction speed becomes less effective and the
exhaust amount decreases.
[0092] The pressure boosting diaphragm 82 of the pressure boosting device 80 contacts the
balance diaphragm 71 of the pressure forming unit 51 through a contact portion 83. When
the pressure boosting diaphragm 82 moves from the initial position (see description below)
in the pressure boosting direction D3 (see description below), the contact portion 83 comes
into contact with the balance diaphragm 71 and transmits force of the pressure boosting
diaphragm 82 to the balance diaphragm 71. When the pressure boosting diaphragm 82 is
located at the initial position, the contact portion 83 is out of contact with the balance
diaphragm 71 and does not transmit the force of the pressure boosting diaphragm 82 to the
balance diaphragm 71.
19
[0093] The pressure boosting diaphragm 82 moves in the same direction as the first
direction D1 of the balance diaphragm 71 (hereinafter referred to as "pressure boosting
direction D3") based on a boost in the pressure of the pressure boosting chamber 81, and
moves in the direction opposite to the pressure boosting direction D3 (hereinafter referred to
as "anti-pressure boosting direction") based on a reduction in the pressure of the pressure
boosting chamber 81. When there is no boost in the pressure of the pressure boosting
chamber 81, the pressure boosting diaphragm 82 is disposed at the initial position in the
pressure boosting chamber 81.
[0094] The pressure boosting diaphragm 82 applies the pressure boost command pressure
(see description below) to the balance diaphragm 71 based on a boost in the pressure of the
pressure boosting chamber 81. The application of the pressure boost command pressure to
the pressure boosting diaphragm 82 boosts the output pressure. A decrease in the pressure
boost command pressure applied to the pressure boosting diaphragm 82 decreases the boost
of the output pressure.
[0095] The damping speed decrease limiter 84 applies force to the pressure boosting
diaphragm 82 in a direction (anti-pressure boosting direction) opposite to the direction
(pressure boosting direction D3) of boosting the output pressure. The direction of boosting
the output pressure conforms to the direction of the force applied to the pressure boosting
diaphragm 82 when air is supplied to the pressure boosting chamber 81. In the present
embodiment, the damping speed decrease limiter 84 is configured to be an urging spring 84A
(spring) that applies force to the pressure boosting diaphragm 82 in the anti-pressure
boosting direction.
[0096] The pressure boost command pressure generated by the pressure boosting device 80
is a difference between the pressure obtained based on the air in the pressure boosting
chamber 81 applied to one surface of the pressure boosting diaphragm 82 and the pressure
20
applied to the other surface of the pressure boosting diaphragm 82 by the damping speed
decrease limiter 84.
[0097] When the push button valve 90 is pushed so that air is supplied to the pressure
boosting chamber 81, the pressure boost command pressure is generated. When the
pressure of the pressure boosting chamber 81 is greater than the pressure obtained based on
the damping speed decrease limiter 84, the pressure boost command pressure is generated.
Since the pressure boost command pressure pushes the pressure boosting diaphragm 82 in
the pressure boosting direction D3, the output pressure is boosted. When the push button
valve 90 is released from the pushing operation ("release of pressure boost command
pressure"), the air is discharged from the pressure boosting chamber 81 through the exhaust
throttle device 95 so that the pressure of the pressure boosting chamber 81 gradually
decreases. When the pressure of the pressure boosting chamber 81 approaches the
atmospheric pressure, the pressure obtained based on the damping speed decrease limiter 84
becomes greater than the pressure obtained based on the pressure boosting chamber 81 in the
pressure boosting direction D3. Thus, air is discharged based on the pressure obtained
based on the damping speed decrease limiter 84. As described above, if the damping speed
decrease limiter 84 is not provided, when the pressure boosting chamber 81 approaches the
atmospheric pressure in the process of discharging air from the pressure boosting chamber
81, the damping speed will significantly decrease. However, according to the present
embodiment, the operation of the damping speed decrease limiter 84 limits decreases in the
damping speed.
[0098] The pressure boosting diaphragm 82 operates as follows.
[0099] When air is supplied to the pressure boosting chamber 81 and the pressure of the
pressure boosting chamber 81 increases to a pressure that is greater than the pressure
obtained based on the force of the urging spring 84A, the pressure boosting diaphragm 82
21
pushes the balance diaphragm 71 in the first direction D1. As a result, the movement
amount of the balance diaphragm 71 in the first direction D1 increases, and the opening
degree of the opening 63a increases. This increases the output pressure of the output
chamber 63.
[0100] When air is discharged from the pressure boosting chamber 81 and the pressure of
the pressure boosting chamber 81 decreases, the force of the pressure boosting diaphragm 82
pushing the balance diaphragm 71 in the first direction D1 decreases. As described above,
since the exhaust passage 85 includes the exhaust throttle device 95 and the throttle 96, the
pressure reduction speed of the brake pipe pressure BP does not exceed the reference speed,
and the pressure of the pressure boosting chamber 81 gradually decreases. As the pressure
of the pressure boosting chamber 81 decreases, the pressure reduction speed is reduced.
When the pressure of the pressure boosting chamber 81 approaches the atmospheric pressure,
the pressure obtained based on the pressing force of the urging spring 84A becomes greater
than the pressure of the pressure boosting chamber 81. Consequently, the force of the
urging spring 84A forcibly discharges air from the pressure boosting chamber 81. Thus, the
pressure reduction speed is maintained at a predetermined value or greater until the pressure
boosting chamber 81 reaches the atmospheric pressure.
[0101] The actuation of the pressure control valve 50 will be described with reference to
Figs. 3 to 8.
[0102] The pressure control valve 50 shown in Fig. 3 is in a "balanced state" in which the
output pressure of the output chamber 63 is balanced with the pressure of the input chamber
73. In the balanced state, the balance diaphragm 71 is located at the same position when
the input chamber 73 is at high pressure (pressure obtained based on the pressure of main
reservoir pipe 12) and at low pressure. Hereinafter, in the pressure control valve 50, a
balanced state in which the balance pressure is high is referred to as "high pressure balanced
22
state," and a balanced state in which the balance pressure is low is referred to as "low
pressure balanced state." In the "high pressure balanced state," the brake pipe pressure BP
is the releasing pressure BP2. In the "low pressure balanced state," the brake pipe pressure
BP is the braking pressure BP1. Fig. 3 shows the pressure control valve 50 in the "high
pressure balanced state."
[0103] When the pressure control valve 50 is in the high pressure balanced state and the
braking operation is performed to discharge air to the input chamber 73 of the balance
chamber 70, the pressure of the input chamber 73 decreases and moves the balance
diaphragm 71 in the second direction D2 from the balance position. Accordingly, the air
supply-exhaust valve 75 moves in the second direction D2.
[0104] As shown in Fig. 4, when the output open end 75a of the air supply-exhaust valve
75 is separated from the lid 64, the output chamber 63 is connected to the exhaust chamber
62, and air is discharged from the output chamber 63. As a result, the output pressure of
the output chamber 63 gradually decreases. When the output pressure of the output
chamber 63 decreases, the force acting on the balance diaphragm 71 in the second direction
D2 decreases based on the output pressure of the output chamber 63. This switches the
moving direction of the balance diaphragm 71 from the second direction D2 to the first
direction D1. When the air supply-exhaust valve 75 again contacts the lid 64, the output
open end 75a of the air supply-exhaust valve 75 is sealed by the lid 64, the airflow is stopped
between the output chamber 63 and the exhaust chamber 62, and the air supply-exhaust
valve 75 is stopped at the balance position. At this time, the output chamber 63 is
connected to neither the air supply chamber 61 nor the exhaust chamber 62. Thus, the
brake pipe pressure BP is maintained at the predetermined pressure (braking pressure BP1).
[0105] As described above, when the brake pipe pressure BP is set to the predetermined
pressure (braking pressure BP1), the control valve 20 supplies air to the brake cylinder 11.
23
The brake cylinder 11 actuates and applies the brakes to the wheels.
[0106] When the pressure control valve 50 is in the low pressure balanced state and the
releasing operation is performed to supply air to the input chamber 73 of the balance
chamber 70, the pressure of the input chamber 73 increases and moves the balance
diaphragm 71 in the first direction D1 from the balance position (see Fig. 5). Accordingly,
the air supply-exhaust valve 75 moves in the first direction D1.
[0107] Consequently, as shown in Fig. 5, the lid 64 is lifted from the opening 63a and
connects the output chamber 63 to the air supply chamber 61, and air is supplied to the
output chamber 63. As a result, the output pressure of the output chamber 63 gradually
increases. When the output pressure of the output chamber 63 increases, the force acting
on the balance diaphragm 71 in the second direction D2 increases based on the pressure of
the output chamber 63. This switches the moving direction of the balance diaphragm 71
from the first direction D1 to the second direction D2. When the lid 64 again seals the
opening 63a of the output chamber 63, the airflow is stopped between the output chamber 63
and the air supply chamber 61, and the air supply-exhaust valve 75 is stopped at the balance
position. At this time, the output chamber 63 is connected to neither the air supply
chamber 61 nor the exhaust chamber 62. Thus, the brake pipe pressure BP is maintained at
the releasing pressure BP2.
[0108] As described above, when the brake pipe pressure BP is set to the releasing pressure
BP2, the control valve 20 discharges air from the brake cylinder 11. The brake cylinder 11
actuates and releases the brake.
[0109] The actuation of the pressure control valve 50 when the pressure boosting device 80
is actuated and the releasing operation is executed will now be described with reference to
Fig. 6. As described above, when switching the locomotive 1, the actuation of the pressure
boosting device 80 based on the operation of the push button valve 90 and the releasing
24
operation are simultaneously performed.
[0110] When the pressure control valve 50 is in the low pressure balanced state (state in
which brake is applied) and the releasing operation is performed to supply air to the input
chamber 73 of the balance chamber 70, the pressure of the input chamber 73 increases and
moves the balance diaphragm 71 in the first direction D1 from the balance position.
Accordingly, the air supply-exhaust valve 75 moves in the first direction D1. Additionally,
since the pressure boosting device 80 is actuated by the operation of the push button valve
90, the balance diaphragm 71 receives force from the pressure boosting diaphragm 82 of the
pressure boosting device 80 in the first direction D1 based on the pressure boost command
pressure. Thus, the movement amount of the balance diaphragm 71 in the first direction D1
increases as compared to the case in which the pressure boosting device 80 is not actuated.
Therefore, the lid 64 is lifted from the opening 63a to a higher position (height from a
reference plane that is the position of the opening 63a) than when the pressure boosting
device 80 is not actuated. The amount of air supplied to the output chamber 63 also
increases. Thus, the output pressure of the output chamber 63 is higher than when the
pressure boosting device 80 does not actuate. When the output pressure of the output
chamber 63 increases, the force acting on the balance diaphragm 71 in the second direction
D2 increases based on the output pressure of the output chamber 63. This switches the
moving direction of the balance diaphragm 71 from the first direction D1 to the second
direction D2. When the lid 64 again seals the opening 63a of the output chamber 63, the
airflow is stopped between the output chamber 63 and the air supply chamber 61, and the air
supply-exhaust valve 75 is stopped at the balance position. At this time, the output
chamber 63 is connected to neither the air supply chamber 61 nor the exhaust chamber 62.
The brake pipe pressure BP is maintained at the readjustment pressure BP3, which is higher
than the releasing pressure BP2.
25
[0111] Cancellation of the pressure boosting state of the pressure boosting device 80 will
be described.
[0112] Since the pressure boosting chamber 81 of the pressure boosting device 80 is
connected to the exhaust passage 85, air gradually leaks from the pressure boosting chamber
81. When the operation of the push button valve 90 is stopped and the supply of air to the
pressure boosting device 80 is stopped, the amount of air in the pressure boosting chamber
81 is gradually reduced. When the air is discharged from the pressure boosting chamber 81
through the exhaust throttle device 95 and the throttle 96, the discharge amount is limited.
Thus, the reduction in pressure boost based on the pressure boosting device 80 decreases
linearly. At this time, the pressure reduction speed of the brake pipe pressure BP is less
than the reference speed, which is not affected by the control valve 20.
[0113] As the pressure of the pressure boosting chamber 81 decreases, the pressure
obtained based on the pressing force of the urging spring 84A exceeds the pressure of the
pressure boosting chamber 81. Consequently, the pressure boosting diaphragm 82 is
separated from the balance diaphragm 71, and the balance diaphragm 71 receives only the
pressure of the input pipe 56, so that the brake pipe pressure BP is set to the releasing
pressure BP2 (e.g., 500 kPa). Even after that, the pressure of the pressure boosting
chamber 81 continues to decrease, but the pressure boosting chamber 81 is completely
exhausted without affecting the brake pipe pressure BP.
[0114] The operation of the pressure boosting device 80 will be described with reference to
Figs. 7 and 8.
[0115] Fig. 7 is a graph showing reduction in the brake pipe pressure BP of a typical
pressure control valve. As shown in Fig. 7, the brake pipe pressure BP decreases linearly
toward the point of a predetermined reference time (e.g., about 250 seconds). However,
when the brake pipe pressure BP is close to the releasing pressure BP2 (e.g., 500 kPa), which
26
is the target pressure of the brake pipe pressure BP, the brake pipe pressure BP is less than a
pressure reduction setting value of the exhaust throttle device 95. As a result, the
adjustment valve 95c is constantly open, and the pressure reduction of the pressure boosting
chamber 81 becomes extremely slow. Thus, it takes a long time (e.g., 300 seconds or
longer) to reach the releasing pressure BP2, which is the target pressure of the brake pipe
pressure BP.
[0116] Fig. 8 is a graph showing reduction in the brake pipe pressure BP of the pressure
control valve 50 according to the present embodiment. As shown in Fig. 8, in the range of
about 250 seconds from when the brake pipe pressure BP starts to decrease, the brake pipe
pressure BP is reduced at a constant speed (see solid line) while generally maintaining the
initial reduction speed until the brake pipe pressure BP reaches the target releasing pressure
BP2. The broken line in Fig. 8 is extension of the solid line indicating reduction of the
brake pipe pressure BP and has the reduction speed (slope of solid line) of the brake pipe
pressure BP at 250 seconds. Thus, it takes the brake pipe pressure BP about 250 seconds to
reach the target releasing pressure BP2.
[0117] As described above, the pressure boosting device 80 pushes the balance diaphragm
71 based on force of the difference between force (force based on pressure boosting chamber
81) of pushing the balance diaphragm 71 in the first direction D1 and force (force of urging
spring 84A) countering the force (force based on pressure boosting chamber 81). When the
pressure boost is cancelled, the force pushing the balance diaphragm 71 in the first direction
D1 gradually weakens. When the force pushing the balance diaphragm 71 in the first
direction D1 approaches "0," the countering force (force of urging spring 84A) exceeds the
force pushing the balance diaphragm 71 in the first direction D1. This limits decreases in
pressure reduction.
[0118] In the typical structure, there is no active force against the force pushing the balance
27
diaphragm 71 in the first direction D1. Thus, when there is little difference between the
pressure of the pressure boosting chamber 81 and the atmospheric pressure, the pressure
reduction speed significantly decreases. On the other hand, according to the pressure
boosting device 80 having the structure described above, the force (force based on pressure
in pressure boosting chamber 81) acting in the first direction D1 and its countering force
(force based on damping speed decrease limiter 84) act on the balance diaphragm 71 so that
the balance diaphragm 71 moves in the second direction D2 without delay. This shortens
the time taken to cancel the pressure boosting (hereinafter referred to as "pressure boosting
state cancellation time").
[0119] The effects of the pressure control valve 50 will now be described.
[0120] (1-1) The pressure control valve 50 includes the damping speed decrease limiter 84
that limits decreases in the damping speed of the pressure boost command pressure when the
application of the pressure boost command pressure is stopped.
[0121] When the application of the pressure boost command pressure is stopped, the
damping speed decrease limiter 84 limits decreases in the damping speed of the pressure
boost command pressure so that the pressure boost command pressure is reduced without
delay. This shortens the pressure boosting state cancellation time.
[0122] (1-2) The damping speed decrease limiter 84 applies force to the pressure boosting
diaphragm 82 of the pressure boosting chamber 81 in the direction (anti-pressure boosting
direction) opposite to the direction (pressure boosting direction) of boosting the output
pressure. According to this configuration, the exhaust of the pressure boosting chamber 81
is accelerated, and decreases in the exhaust are limited.
[0123] (1-3) The damping speed decrease limiter 84 includes a spring (urging spring 84A)
that generates a force acting in the direction (anti-pressure boosting direction) opposite to the
direction (pressure boosting direction) of boosting the output pressure. According to this
28
configuration, the damping speed decrease limiter 84 is simply configured.
[0124] (1-4) The pressure control valve 50 includes the input chamber 73, the output
chamber 63, the pressure boosting chamber 81, the pressure boosting diaphragm 82, and a
spring (urging spring 84A) that applies a force to the pressure boosting diaphragm 82 in the
direction opposite to the pressure boosting direction of the pressure boosting diaphragm 82
when boosting the output pressure. The pressure boosting diaphragm 82 applies force
corresponding to the pressure boost of the pressure boosting chamber 81 to the balance
diaphragm 71 separating the input chamber 73 from the output chamber 63. According to
this configuration, the force of the spring acting in the direction opposite to the pressure
boosting direction is applied to the pressure boosting diaphragm 82 so that when the
application of the pressure boost command pressure is stopped, decreases in the damping
speed of the pressure boost command pressure are limited. Thus, the pressure boost
command pressure is reduced without delay. The pressure boosting state cancellation time
thus can be shortened.
[0125] Second embodiment
[0126] A second embodiment of a pressure boosting device 180 will now be described with
reference to Fig. 9. In Fig. 9, "Ex" indicates an exhaust port.
[0127] The pressure boosting device 180 and the pressure boosting device 80 of the above
embodiment are the same in the following points. More specifically, the pressure boosting
device 180 includes the pressure boosting chamber 81 and the pressure boosting diaphragm
82. The pressure boosting device 180 generates a pressure boost command pressure for
boosting the output pressure of the output chamber 63. The pressure boosting diaphragm
82 applies the pressure boost command pressure to the balance diaphragm 71. The pressure
boost command pressure is the difference between pressure that is obtained based on the air
in the pressure boosting chamber 81 and applied to one surface of the pressure boosting
29
diaphragm 82 and the pressure applied to the other surface of the pressure boosting
diaphragm 82 by a damping speed decrease limiter 184.
[0128] In the pressure boosting device 180, the configuration of the damping speed
decrease limiter 184 differs from that of the damping speed decrease limiter 84 of the first
embodiment.
[0129] The difference will be specifically described below.
[0130] The pressure boosting diaphragm 82 has one surface that receives the pressure of
the pressure boosting chamber 81. This point is the same as that of the above-described
embodiment.
[0131] The other surface of the pressure boosting diaphragm 82 receives force obtained
based on the damping speed decrease limiter 184.
[0132] A stopper restricts movement of the pressure boosting diaphragm 82 beyond a
predetermined position in the anti-pressure boosting direction (direction opposite to the
pressure boosting direction D3).
[0133] The damping speed decrease limiter 184 is configured to be a pressure reducing
diaphragm 185 that receives pressure in a direction opposite to the pressure boosting
direction D3. The pressure reducing diaphragm 185 receives the pressure of the input
chamber 73. The pressure reducing diaphragm 185 is disposed between the balance
diaphragm 71 and the pressure boosting diaphragm 82 so as to face the balance diaphragm
71 in the input chamber 73. The pressure reducing diaphragm 185 moves independently
from the balance diaphragm 71. The pressure reducing diaphragm 185 is coupled to the
pressure boosting diaphragm 82. Thus, the pressure reducing diaphragm 185 moves
integrally with the pressure boosting diaphragm 82.
[0134] The coupled body of the pressure boosting diaphragm 82 and the pressure reducing
diaphragm 185 contacts the balance diaphragm 71 of the pressure forming unit 51 via the
30
contact portion 83. When the pressure boosting diaphragm 82 moves from the initial
position (see description below) in the pressure boosting direction D3, the contact portion 83
comes into contact with the balance diaphragm 71 and transmits the force of the pressure
boosting diaphragm 82 to the balance diaphragm 71. When the pressure boosting
diaphragm 82 is located at the initial position, the contact portion 83 is out of contact with
the balance diaphragm 71 and does not transmit the force of the pressure boosting diaphragm
82 to the balance diaphragm 71.
[0135] When there is no boost in the pressure boosting chamber 81, that is, when the
pressure boosting diaphragm 82 is disposed at the initial position and movement in the antipressure
boosting direction is restricted, the volume of the input chamber 73 remains the
same. Thus, the supply of air to the input chamber 73 increases the pressure of the input
chamber 73.
[0136] The pressure boosting diaphragm 82 actuates as follows.
[0137] When air is supplied to the pressure boosting chamber 81 and the pressure of the
pressure boosting chamber 81 increases and exceeds the pressure of the input chamber 73,
the pressure boosting diaphragm 82 pushes the balance diaphragm 71 in the first direction
D1. As a result, the amount of movement of the balance diaphragm 71 in the first direction
D1 increases, and the opening degree of the opening 63a increases. This increases the
output pressure of the output chamber 63.
[0138] When air is discharged from the pressure boosting chamber 81 and the pressure of
the pressure boosting chamber 81 decreases, the force of the pressure boosting diaphragm 82
pushing the balance diaphragm 71 in the first direction D1 decreases. As described above,
the exhaust passage 85 includes the exhaust throttle device 95 and the throttle 96. Thus, the
pressure reduction speed of the brake pipe pressure BP does not exceed the reference speed,
and the pressure of the pressure boosting chamber 81 decreases linearly. When the pressure
31
of the input chamber 73 exceeds the pressure of the pressure boosting chamber 81, the
pressure reducing diaphragm 185 separates from the balance diaphragm 71. The balance
diaphragm 71 receives only the pressure of the input pipe 56, and the brake pipe pressure BP
is set to the releasing pressure BP2 (e.g., 500 kPa). Even after that, the pressure of the
pressure boosting chamber 81 continues to be reduced, but the pressure boosting chamber 81
is completely exhausted without affecting the brake pipe pressure BP.
[0139] The operation of the pressure boosting device 180 will now be described.
[0140] The pressure boosting device 180 pushes the balance diaphragm 71 based on force
of the difference between the force (force based on pressure boosting chamber 81) pushing
the balance diaphragm 71 in the first direction D1 and force (force based on pressure of input
chamber 73) countering the force (force based on pressure boosting chamber 81).
[0141] When weakening the force pushing the balance diaphragm 71, the force pushing the
balance diaphragm 71 in the first direction D1 is gradually weakened. When the force
pushing the balance diaphragm 71 in the first direction D1 approaches "0," force opposite to
the force pushing the balance diaphragm 71 in the first direction D1 acts.
[0142] In a typical structure, there is no active force against the force pushing the balance
diaphragm 71 in the first direction D1. Thus, if there is little difference between the
pressure of the pressure boosting chamber 81 and the atmospheric pressure, the pressure
reduction speed significantly decreases. On the other hand, according to the pressure
boosting device 180 having the structure described above, the force (force based on pressure
in pressure boosting chamber 81) acting in the first direction D1 and its countering force
(force based on damping speed decrease limiter 184) act on the balance diaphragm 71 so that
the balance diaphragm 71 moves in the second direction D2 without delay. This shortens
the pressure boosting state cancellation time, which is the time taken to complete the
movement of the balance diaphragm 71.
32
[0143] The effects of the pressure control valve 50 will now be described.
[0144] (2-1) The damping speed decrease limiter 184 generates force from air pressure
acting in the direction (anti-pressure boosting direction) opposite to the direction (pressure
boosting direction) of boosting the output pressure. According to this configuration, the air
pressure for actuating the pressure control valve 50 is used to generate the force of the
damping speed decrease limiter 184. This eliminates the need for a power source that
actuates the damping speed decrease limiter 184.
[0145] (2-2) The damping speed decrease limiter 184 generates force from the pressure of
the input chamber 73 acting in the direction opposite to the direction of boosting the output
pressure. According to this configuration, the use of the pressure of the input chamber
simplifies the damping speed decrease limiter 184.
[0146] (2-3) The damping speed decrease limiter 184 includes the pressure reducing
diaphragm 185 (diaphragm), which is a diaphragm connected to the pressure boosting
diaphragm 82 of the pressure boosting chamber 81 and receives the pressure of the input
chamber 73 as force. According to this configuration, there is no need to provide additional
space for the damping speed decrease limiter 184. Thus, miniaturization is achieved.
[0147] (2-4) The pressure control valve 50 includes the input chamber 73, the output
chamber 63, the pressure boosting chamber 81, the pressure boosting diaphragm 82, and the
pressure reducing diaphragm 185. The pressure boosting diaphragm 82 applies force
corresponding to the pressure boost of the pressure boosting chamber 81 to the balance
diaphragm 71 that separates the input chamber 73 from the output chamber 63. The
pressure reducing diaphragm 185 applies pressure to the pressure boosting diaphragm 82 in a
direction opposite to the direction in which pressure of the pressure boosting diaphragm 82
is increased by receiving the pressure of the input chamber 73 when boosting the output
pressure.
33
[0148] This configuration limits decreases in the damping speed of the pressure boost
command pressure when the force of the pressure reducing diaphragm 185 acting in the
direction opposite to the pressure boosting direction is applied to the pressure boosting
diaphragm 82 and the application of the pressure boost command pressure is stopped. Thus,
the pressure boost command pressure is reduced without delay. This shortens the pressure
boosting state cancellation time.
[0149] Modified Examples
[0150] The pressure control valve 50 is not limited to the examples shown in the above
embodiments. For example, the pressure control valve 50 can be modified as follows.
[0151] In the first embodiment, the damping speed decrease limiter 84 is configured to be
the urging spring 84A. However, a magnet may be used in place of the urging spring 84A.
Magnetic force affects a smaller range than air pressure and spring force. The range
affected by magnetic force is limited to a section immediately before the discharging of air is
completed. This reduces interference with force applied in a direction that accelerates the
pressure application to the output chamber 63 based on the pressure boost command pressure.
[0152] Various changes in form and details may be made to the examples above without
departing from the spirit and scope of the claims and their equivalents. The examples are
for the sake of description only, and not for purposes of limitation. Descriptions of features
in each example are to be considered as being applicable to similar features or aspects in
other examples. Suitable results may be achieved if sequences are performed in a different
order, and/or if components in a described system, architecture, device, or circuit are
combined differently, and/or replaced or supplemented by other components or their
equivalents. The scope of the disclosure is not defined by the detailed description, but by
the claims and their equivalents. All variations within the scope of the claims and their
equivalents are included in the disclosure.
34
WE CLAIM:
1. A pressure control valve including:
an input chamber to which a target pressure is input;
an output chamber having an output pressure controlled to be balanced with
pressure of the input chamber by switching between pressure application to the output
chamber and pressure release from the output chamber; and
a pressure boosting chamber that boosts the output pressure when a pressure boost
command pressure is applied to the pressure boosting chamber,
the pressure control valve being characterized in that the pressure control valve
further comprises a damping speed decrease limiter configured to limit a decrease in a
damping speed of the pressure boost command pressure when the application of the pressure
boost command pressure is stopped.
2. The pressure control valve according to claim 1, wherein
the pressure boosting chamber includes a pressure boosting diaphragm, and
the damping speed decrease limiter applies a force to the pressure boosting
diaphragm in a direction opposite to a direction in which the output pressure boosts.
3. The pressure control valve according to claim 2, wherein damping speed
decrease limiter includes a spring that generates the force.
4. The pressure control valve according to claim 2, wherein the damping
speed decrease limiter generates the force from air pressure.
35
5. The pressure control valve according to claim 4, wherein the damping
speed decrease limiter generates the force from the pressure of the input chamber.
6. The pressure control valve according to claim 5, wherein
the damping speed decrease limiter includes a diaphragm connected to the pressure
boosting diaphragm of the pressure boosting chamber, and
the diaphragm receives the pressure from the input chamber as the force.
7. The pressure control valve according to claim 2, wherein the damping
speed decrease limiter includes a magnet that generates the force.
8. A pressure control valve including:
an input chamber to which a target pressure is input;
an output chamber having an output pressure controlled to be balanced with
pressure of the input chamber by switching between pressure application to the output
chamber and pressure release from the output chamber; and
a pressure boosting chamber that boosts the output pressure when a pressure boost
command pressure is applied to the pressure boosting chamber;
the pressure control valve being characterized by:
a pressure boosting diaphragm that applies force corresponding to a pressure boost
in the pressure boosting chamber to a balance diaphragm that separates the input chamber
from the output chamber; and
a spring that applies force to the pressure boosting diaphragm in a direction opposite
to a pressure boosting direction of the pressure boosting diaphragm when boosting the output
pressure.
36
9. A pressure control valve including:
an input chamber to which a target pressure is input;
an output chamber having an output pressure controlled to be balanced with
pressure of the input chamber by switching between pressure application to the output
chamber and pressure release from the output chamber; and
a pressure boosting chamber that boosts the output pressure when a pressure boost
command pressure is applied to the pressure boosting chamber;
the pressure control valve being characterized by:
a pressure boosting diaphragm that applies force corresponding to a pressure boost
in the pressure boosting chamber to a balance diaphragm that separates the input chamber
from the output chamber; and
a pressure reducing diaphragm that applies force to the pressure boosting diaphragm
in a direction opposite to a pressure boosting direction of the pressure boosting diaphragm
when the pressure reducing diaphragm receives the pressure of the input chamber and boosts
the output pressure.