0001] The present disclosure relates generally to the technical field of internal
combustion (IC) engines. In particular, the present disclosure pertains to an improved
variable valve lift system for the IC engines to improve engines efficiency during varying
load conditions.
BACKGROUND
[0002] As is well known in the art, an IC engine is provided with intake valves and
exhaust valves in a cylinder head of the engine, and a cam shaft which is rotated in
conjunction with a crank shaft and integrally has a plurality of cams that function to open and
shut the intake and exhaust valves. Engine generates power by burning air-fuel mixture in a
combustion chamber. The intake valves are operated by the camshaft for intake of air or airfuel mixture, and the air or air-fuel mixture is drawn into the combustion chamber while the
intake valves are open. In addition, exhaust valves are operated by the camshaft, and a
combustion gas is exhausted from the combustion chamber while the exhaust valves are
open. In the conventional engine, the valve lift and opening time duration are fixed as
specific values, and the fixed timing can facilitates best engine efficiency only for specific
engine speed and load. As the engine load and speed varies continuously in real situation, it
requires continuously variable valve timing and lifts to achieve optimum efficiency of the
whole system including a fuel consumption ratio, power output of and controlled emission of
the engine.
[0003] Effort have been made in past to overcome above sated problems experienced
with the conventional arts. Most of exiting arrangements and techniques which are able to
variably adjust valve lift of the intake and exhaust valves are based a cam shaft which moves
axially along length of the cam shaft and a plurality of cams having cam lobes with different
height are mounted on the cam shaft to operate the intake and exhaust valves. Generally, for
each valve two cams are used including a small cam with a small cam lobe to actuate the
valve when the engine speed is low, and a large cam with a large cam lobe to actuate the
valve when the engine speed is high. An actuating mechanism is used to axially move the
cam shaft to allow access of the various cams with different height of the cam lobes to
facilitate variation of valve lifts, opening and shutting times and periods of the intake and
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exhaust valves in order to increase fuel efficiency and power output of the engines. However,
the conventional arrangement has limitation of slow response time and cannot meet the
requirement of swift change in valve lift with change in engine speed due to time lag due to
cam shaft movement time.
[0004] Patent document DE112004001450 discloses a valve lift mechanism for an
internal combustion engine, having a main rocker arm and a secondary rocker arm that
engage with a cam of a rotatable cam shaft to transmit the movement of the cam to an
inlet/outlet valve. The secondary rocker arm is coupled with a hydraulic piston of a hydraulic
cylinder that enables switching of the secondary rocker arm between at least two different
working positions. The cam is arranged to act on both rocker arms during each revolution of
the camshaft. The opening of the intake valve is controlled by the main rocker arm and the
closing of the intake valve is controlled either by the main rocker arm alone or by the main
rocker arm and the secondary rocker arm. The cited reference provides a valve lift
mechanism that varies the duration of valve opening, but fails to provide any solution to the
problem of slow response time when change in valve opening time and/or closing time is
required.
[0005] There is, therefore, a need to provide an efficient and cost-effective solution
which can obviate foregoing limitations in the art.
OBJECTS OF THE INVENTION
[0006] A general object of the present disclosure is to provide a simple and cost effective
solution which can overcome the aforementioned limitation in the art.
[0007] An object of the present disclosure is to provide an improved valve lift
arrangement for the IC engines that improves fuel efficiency during varying engine speed and
load conditions.
[0008] Another object of the present disclosure is to provide a simple and efficient
variable valve lift arrangement for an IC engine which is able to variably adjust valve lift and
opening duration of intake and exhaust valves to improve engine efficiency and reduce
overall engine emission.
[0009] Yet another object of the present disclosure is to provide a valve lift system for IC
engines which reduces response time for change in valve lift and opening duration of intake
and exhaust valves.
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SUMMARY
[0010] Aspects of the present disclosure relate to IC engines. In particular, the present
disclosure pertains to an improved variable valve lift system for the internal combustion
engines to vary lift amount/timings of engine valves, such as intake valves and exhaust
valves, in accordance with engine operating conditions to improve the engine efficiency. In
particular, the disclosed variable valve lift system reduces response time for change in valve
lift amount/timing of the corresponding valves, thereby enabling the engine to run under
optimum conditions for a relatively higher duration improving the fuel efficiency and
emission control.
[0011] In an aspect, the present disclosure provides a variable valve lift system for an IC
engine having at least one cam coupled to a cam shaft provided in a cylinder head of the IC
engine. The at least one cam includes a varying height cam lobe profile. The cam shaft is
configured to move axially along a length of the cam shaft. The variable valve lift system
further includes at least one valve; at least one tappet coupled to the valve through a stem of
the valve; and at least one lever slidably configured between the cam and the tappet, wherein
the lever is configured to work as a follower of the cam. The lever is configured to move
axially in a direction opposite to a direction of movement of the cam shaft between a first
position and a second position.
[0012] In an aspect, a height of the cam lobe profile varies axially so that movement of
the lever and the cam shaft in opposite directions provides variable lift to the valve. The lever
and the cam shaft are configured to simultaneously move in opposite directions to reduce
response time for change in the lift of the at least one valve.
[0013] The cam shaft is configured to move for a distance equal to a half of a width of
the cam lobe profile, and the lever is configured to move in the opposite direction for a
distance equal to the remaining half of the width of the cam lobe profile so that simultaneous
movement of the lever and the cam shaft in opposite directions covers the width of the cam
lobe profile, thereby response time for variable valve lift (VVL) or variable valve timing
(VVT)is reduced to half compared to the known arrangements in the art.
[0014] In an embodiment, the first position of the lever corresponds to a position in
which the lever engages with a portion of the cam having maximum height and the second
position of the lever corresponds to a position in which the lever engages with another
portion of the cam having minimum height.
[0015] The lever can be in a sliding engagement with the tappet through a groove on an
upper surface of the tappet. The groove can be oriented in the direction of length of the cam
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shaft to enable lever to move axially in the direction opposite to the direction of movement of
the cam shaft.
[0016] In an embodiment, the variable valve lift system includes at least one hydraulic
actuator coupled to the lever to facilitate the movement of the lever between the first position
and the second position. The hydraulic actuator can include a cylinder, a lever moving shaft
slidably configured with the cylinder at one end of the lever moving shaft, and configured
with the lever at other end of the lever moving shaft through a slot of the lever. The hydraulic
actuator further includes a spring configured between a base wall of the cylinder and the lever
moving shaft. The slot of the leaver is configured to allow lowering and lifting of the lever
with respect to engagement of the lever with the cam lobe profile.
[0017] In an embodiment, a high pressure oil can be supplied to the cylinder to move the
lever moving shaft towards the base wall of the cylinder to move the lever to the first position
resulting in compression of the spring. The compressed spring pushes the lever moving shaft
away from the base wall of the cylinder in absence of the high pressure oil to move the lever
to the second position.
[0018] The lever moving shaft can include at least two flanges that engage with sides of
the lever to enable transfer of movement of the lever moving shaft to the lever even as the
lever is free to move up and down relative to the lever moving shaft through the slot of the
lever.
[0019] In another aspect, the present disclosure provides an IC engine comprising a
cylinder head and a variable valve lift system as disclosed above to provide variable lift to at
least one valve of the engine IC engine. The variable valve lift system is adapted to reduce
response time for change in the lift of the at least one valve.
[0020] Various objects, features, aspects and advantages of the inventive subject matter
will become more apparent from the following detailed description of preferred
embodiments, along with the accompanying drawing figures in which like numerals represent
like components.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The accompanying drawings are included to provide a further understanding of
the present disclosure, and are incorporated in and constitute a part of this specification. The
drawings illustrate exemplary embodiments of the present disclosure and, together with the
description, serve to explain the principles of the present disclosure.
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[0022] FIG. 1 illustrates the proposed variable valve lift system for an IC engine, in
accordance with embodiments of the present disclosure.
[0023] FIGs. 2A and 2B illustrate working of the proposed variable valve lift system, in
accordance with embodiments of the present disclosure.
[0024] FIGs. 3A and 3C illustrate an isometric view and a top view of a cylindrical tappet
with a valve of the proposed variable valve lift system, in accordance with embodiments of
the present disclosure.
[0025] FIGs. 3B and 3D illustrate an isometric view and a top view of a rectangular
tappet with a valve of the proposed variable valve lift system, in accordance with
embodiments of the present disclosure.
[0026] FIGs. 4A and 4B illustrate sectional views of a lever of the proposed variable
valve lift system, in accordance with embodiments of the present disclosure.
DETAILED DESCRIPTION
[0027] The following is a detailed description of embodiments of the disclosure depicted
in the accompanying drawings. The embodiments are in such details as to clearly
communicate the disclosure. However, the amount of detail offered is not intended to limit
the anticipated variations of embodiments; on the contrary, the intention is to cover all
modifications, equivalents, and alternatives falling within the spirit and scope of the present
disclosure as defined by the appended claims.
[0028] Embodiments explained herein relate to an improved variable valve lift system
for internal combustion engine which can vary lift amount/timing of engine intake valves and
exhaust valves in accordance with engine operating conditions to improve the engine
efficiency. The variable valve lift system can reduce response time for variable valve lift
(VVL) to half compared to the known variable valve lift system.
[0029] In an aspect, the disclosed variable valve lift system is compact and includes less
number of components which reduces complexity so that it requires less space for
implementation in the IC engine to adjust the intake and exhaust valves opening and closing
timings and valves lift based on the engine’s load conditions to improve the engine fuel
consumption as well as to reduce carbon dioxide emission. The disclosed variable valve lift
system also helps in Noise, vibration, and Harshness (NVH) reduction of the engines.
[0030] In conventional arrangement and techniques, a cam shaft moves axially to
provide access to cam lobes having different heights for different valve lift/opening-closing
timings. In the proposed system, a half of the required movement to access a desired cam
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lobe profile can be taken care by a lever mounted on top of a valve tappet and a remaining
half can be travelled by the cam shaft itself. Thus, the amount of cam shaft movement gets
reduced to half as compared to existing arrangement. The lever, which works as the follower,
slides over an top surface of the tappet, where it is engaged through a groove for sliding
movement. Instead of two separate cam lobes with high and low lift for each valve in the
conventional arrangements, the cam shaft of the proposed system is provided a single three
dimensional cam lobe profile with varying height in the direction of the length of the cam
shaft to provide multiple valve-lift and valve timings. The cam lobe profile width may be
designed almost double of a convention cam lobe width. The variable valve lift system
efficiently provides variable valve lift (VVL) and variable valve timing (VVT) together with
short actuation time.
[0031] With the proposed system faster and more flexible responses is observed from the
cam shaft. Two tappets of intake side or two tappets of exhaust side of one cylinder can be
combined so that one cam lobe profile can operate two valves together. Thus overall space
and mass can be optimized, and better engine efficiency can be achieved which helps in
reducing overall engine CO2 emission.
[0032] Referring to FIG. 1, where the proposed variable valve lift system for an IC
engine is shown, the proposed variable valve lift system 100 can be easily implemented in a
cylinder head of the IC engine to generate multiple CAM-lifts and CAM-timings. The
proposed variable valve lift system 100 can include a cam shaft 102 provided in the cylinder
head of the IC engine (hereinafter, also referred to as engine) and rotates in conjunction with
a crank shaft of the engine. The cam shaft 102 can be configured to move axially along a
length of the cam shaft 102.The proposed variable valve lift system (hereinafter, also referred
to as system) 100 can have at least one cam, such as a cam104,coupled to the cam shaft 102
to rotate with the cam shaft in conjunction with the crank shaft. The cam 104 includes a
varying height there dimensional (3D) cam lobe profile 106, where a height of the cam lobe
profile 106 varies axially along length of the cam shaft 102.
[0033] In an embodiment, any suitable arrangement known in the art can be used to
move the cam shaft 102 axially.
[0034] The disclosed system 100 further includes at least one valve, such as a valve 108
(shown in FIGs. 3A and 3B); at least one tappet 110 coupled to the valves 108 through stems,
such as stems 112-2 and 112-2 (collectively referred to as stems 112) of the valves 108; and
at least one lever 114 slidably configured between the cam 104 and the tappet110.The lever
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114 is configured to work as a follower of the cam 104. The lever 114 is configured to move
axially in a direction opposite to a direction of movement of the cam shaft 102.
[0035] In an embodiment, coupling of the two valves 108 with one tappet 110 facilitates
actuation of the two valves 108 using a single cam so that the space required for the system
100 is reduced as compared to the conventional systems, which use separate cam lobes for
each valve in the engine.
[0036] In an embodiment, the valves 108 can be any of intake valves and exhaust valves
of the engine. In another embodiment, to avoid valve stem buckling, two tappets of intake
side or two tappets of exhaust side of one cylinder can be combined. Thus overall space and
mass can be optimized. This way one cam lobe can be sufficient to operate two valves
together.
[0037] In an embedment, the height of the cam lobe profile 106 varies axially so that
movement of the lever 114 and the cam shaft 102in opposite directions variably adjusts valve
lift and opening duration of the valves 108. The lever 114 and the cam shaft 102 can be
configured to move simultaneously in opposite directions, which reduces response time for
change in the lift of the valves108.
[0038] In an embodiment, the disclosed system 100 can include at least one hydraulic
actuator, such as a hydraulic actuator 116, coupled to the lever 114 to facilitate the axial
movement of the lever114 in the direction of length of the cam shaft 102. The hydraulic
actuator116 can include a cylinder 118, a lever moving shaft 120 slidably configured with the
cylinder 118 at one end of the lever moving shaft 120, and configured with the lever 114 at
other end of the lever moving shaft 120. The hydraulic actuator 116 further includes a spring
122 configured between a base wall 128 of the cylinder 118 and the lever moving shaft 120.
[0039] In an embodiment, the lever 114 includes a slot 124 extended along length of the
lever to enable mounting of the lever moving shaft 120 with the lever 114. The slot 124 is
adapted to allow lowering and lifting of the lever 114 with respect to engagement of the lever
114 with the cam lobe profile 106.The lever 114 can include a roller 130 pivotally coupled to
an upper portion of the lever 114. The roller 130engages with the cam lobe profile 106, and
helps in reduction in friction between the cam lobe profile and the roller surfaces.
[0040] In an embodiment, two flanges, such as flanges 126-1, and 126-2 (collectively
referred to as flanges 126), are provided on the lever moving shaft 120. The flanges 126
engage with sides of the lever 114 to enable transfer of movement of the lever moving shaft
120 to the lever 114.
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[0041] In an embodiment, the tappet 110 can include a groove 132 on a top surface of
the tappet 110. The groove 132 is configured to guide movement of the lever 114 along the
direction of the cam shaft length.
[0042] Referring to Figs. 2A and 2B, where working of the proposed variable valve lift
system is shown, the cam shaft 102 is configured to move for a distance equal to a half of a
width (W) of the cam lobe profile 106, and the lever 114 is configured to move in the
opposite direction for a distance equal to the remaining half of the width (W) of the cam lobe
profile 106,so that simultaneous movement of the lever 114 and the cam shaft 102 in opposite
directions covers the width (W) of the cam lobe profile 106. Thus, the cam shaft movement
amplitude can be reduced to halfso that response time for variable valve lift (VVL) or
variable valve timing (VVT) can also be reduced to half compared to the existing techniques
in the art.
[0043] In an embodiment, the lever 114 is configured to move between a first position
(shown in FIG. 2A) and a second position (shown in FIG. 2B) with respect to the cam shaft
102. The first position of the lever 114 corresponds to a position in which the lever 114
engages with a portion of the cam lobe profile 106having maximum height and accordingly,
provides the valves 108 a maximum lift. A second position of the lever 114 corresponds to a
position in which the lever 114 engages with another portion of the cam lobe profile 106 that
provides a minimum lift to the valves 108.
[0044] The hydraulic actuator116 is configured to move of the lever 114 between the
first position and the second position. The lever moving shaft 120 can be slidably configured
with the cylinder 118 though a disk 202 coupled at one end of the lever moving shaft 120,
and engaged with the slot 124 of the lever 114 through the flanges 126,at other end of the
lever moving shaft 120.The slot 124 of the lever 114 is configured to allow lowering and
lifting of the lever 114 on account of engagement of the roller 130 with the cam lobe profile
106, while remaining engaged with the lever moving shaft 120 through the flanges 126.
[0045] In an embodiment, when a high pressure oil 134 is supplied to the cylinder 118
the lever moving shaft 120 moves towards the base wall 128 of the cylinder 118 to move the
lever 114 to the first position resulting in compression of the spring 122 (shown in FIG.
2A).The compressed spring pushes the lever moving shaft 120 away from the base wall 128
of the cylinder 118 in absence of the high pressure oil 134 to move the lever 114 to the
second position (shown in FIG. 2B).
[0046] The two flanges 126 of the lever moving shaft 120 engages with sides of the lever
114 to enable transfer of movement of the lever moving shaft 120 to the lever 114 even as the
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lever 114 is free to move up and down relative to the lever moving shaft 120 through the slot
124.
[0047] The lever 114 is in a sliding engagement with the tappet 110 through the groove
132 provided on the upper surface of the tappet 110. The groove 132 is oriented in the
direction of length of the cam shaft 102 to enable lever 114 to move axially in the direction
opposite to the direction of movement of the cam shaft 102.
[0048] In an embodiment, the tappet 110 can be of a cylindrical shaped as shown in FIGs.
3A and 3C.
[0049] In an embodiment, the tappet 110 can be of a rectangular shaped as shown in
FIGs. 3B and 3D.
[0050] Thus, the present disclosure provides a simple and efficient continuously variable
valve lift system for an engine which is able to variably adjust valve lift and opening duration
of valves, such as intake and exhaust valves with minimized response time. The valves are
operated by rotation of a varying height cam lobe profile coupled to a cam shaft which is
configured to move simultaneously in a direction opposite to a direction of a movable lever
that is slidably engaged between the cam lobe profile and a tappet coupled to the valves. The
disclosed system is compact hence require less space a cylinder head of the engine.
[0051] While the foregoing describes various embodiments of the invention, other and
further embodiments of the invention may be devised without departing from the basic scope
thereof. The scope of the invention is determined by the claims that follow. The invention is
not limited to the described embodiments, versions or examples, which are included to enable
a person having ordinary skill in the art to make and use the invention when combined with
information and knowledge available to the person having ordinary skill in the art.
ADVANTAGES OF THE INVENTION
[0052] The present disclosure provides a simple and cost effective solution which can
overcome the limitation of the conventional arrangements for varying valve lift/ timings.
[0053] The present disclosure providesan improved valve lift system for the IC engines
to improve engines fuel efficiency during varying engine load conditions.
[0054] The present disclosure provides a simple and efficient variable valve lift
arrangement for an IC engine which is able to variably adjust valve lift and opening duration
of intake and exhaust valves to improve engine efficiency and reduce overall engine
emission.
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[0055] The present disclosure provides a valve lift system for IC engines which reduces
response time for change in valve lift and opening duration of intake and exhaust valves.

We Claim:

1. A variable valve lift system (100) for an internal combustion (IC) engine, the system
(100) comprising:
at least one cam (104) coupled to a cam shaft (102) provided in a cylinder head
of the IC engine, the at least one cam (104) having a varying height cam lobe profile
(106); wherein the cam shaft (102) is configured to move axially along a length of the
cam shaft (102);
at least one valve (108);
at least one tappet (110) coupled to the at least one valve (108) through a stem
(112) of the at least one valve (108); and
at least one lever (114)slidably configured between the at least one cam and the
at least one tappet (110), the at least one lever (114) working as a follower of the at least
one cam (104), wherein the at least one lever (114) is configured to move axially in a
direction opposite to a direction of movement of the cam shaft (102) between a first
position and a second position;
wherein a height of the cam lobe profile (106) varies axially so that movement of the at
least one lever (114) and the cam shaft (102) in opposite directions provides variable lift
to the at least one valve (108).
2. The system (100) as claimed in claim 1, wherein the at least one lever (114) and the cam
shaft (102) are configured to simultaneously move in opposite directions to reduce
response time for change in the lift of the at least one valve (108).
3. The system (100) as claimed in claim 2, wherein the cam shaft (102) is configured to
move for a distance equal to a half of a width (W) of the cam lobe profile (106), and the
at least one lever (114) is configured to move in the opposite direction for a distance
equal to the remaining half of the width (W) of the cam lobe profile (106) so that
simultaneous movement of the at least one lever (114) and the cam shaft (102) in opposite
directions covers the complete width (W) of the cam lobe profile (106).
4. The system (100) as claimed in claim 1, wherein the first position of the at least one lever
(114) corresponds to a position in which the at least one lever (114) engages with a
portion of the cam lobe profile (106) having maximum height, and the second position of
the at least one lever (114) corresponds to a position in which the at least one lever (114)
engages with another portion of the cam lobe profile (106) having minimum height.
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5. The system (100) as claimed in claim 1, wherein the at least one lever (114) is in a sliding
engagement with the at least one tappet (110) through a groove (132) on an upper surface
of the at least one tappet (110), the groove (132) being oriented in the direction of length
of the cam shaft (102) to enable at least one lever (114) to move axially in the direction
opposite to the direction of movement of the cam shaft (102).
6. The system (100) as claimed in claim 1, wherein the system (100) comprises at least one
hydraulic actuator (116) coupled to the at least one lever (114) to facilitate the movement
of the at least one lever (114) between the first position and the second position.
7. The system (100) as claimed in claim 6, wherein the at least one hydraulic actuator (116)
comprises a cylinder (118), a lever moving shaft (120) slidably configured with the
cylinder (118) at one end of the lever moving shaft (120), and configured with the at least
one lever (114) at other end of the lever moving shaft (120) through a slot (124) of the at
least one lever (114), and a spring (122) configured between abase wall (128) of the
cylinder (118) and the lever moving shaft (120), wherein the slot (124) being configured
to allow lowering and lifting of the at least one lever (114) with respect to engagement of
the at least one lever (114) with the cam lobe profile (106)
8. The system (100) as claimed in claim 7, wherein a high pressure oil (134) is supplied to
the cylinder (118) to move the lever moving shaft (120) towards the base wall (128)of the
cylinder (118) to move the at least one lever (114) to the first position resulting in
compression of the spring (122), and wherein the compressed spring pushes the lever
moving shaft (120) away from the base wall (128)of the cylinder (118) in absence of the
high pressure oil (134) to move the at least one lever (114) to the second position.
9. The system (100) as claimed in claim 7, wherein the lever moving shaft (120) comprises
at least two flanges (126) that engage with sides of the at least one lever (114) to enable
transfer of movement of the lever moving shaft (120) to the at least one lever (114) even
as the at least one lever (114) is free to move up and down relative to the lever moving
shaft (120) through the slot (124).
10. An IC engine comprising:
a cylinder head;
a variable valve lift system (100) configured in the cylinder head, the variable
valve lift system (100) comprising:
at least one cam coupled to a cam shaft (102), the at least one cam having a
varying height cam lobe profile (106); wherein the cam shaft (102) is configured to
move axially along a length of the cam shaft (102);
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at least one valve (108);
at least one tappet (110) coupled to the at least one valve (108) through a
stem of the at least one valve (108); and
at least one lever (114) slidably configured between the at least one cam and
the at least one tappet (110), the at least one lever (114) working as a follower of
the at least one cam, wherein the at least one lever (114) is configured to move
axially in a direction opposite to a direction of movement of the cam shaft (102)
between a first position and a second position;
wherein a height of the cam lobe profile (106) varies axially so that movement of
the at least one lever (114) and the cam shaft (102) in opposite directions provides
variable lift to the at least one valve (108); and
wherein the at least one lever (114) and the cam shaft (102) are configured to
simultaneously move in opposite directions to reduce response time for change in
the lift of the at least one valve (108).