TITLE OF THE INVENTION SPACE-SAVING ELEVATOR
FIELD OF THE INVENTION

[0001]

The present invention relates to an elevator that detects the speed of an elevator car; particularly the present invention is suitable for a space-saving elevator in which an emergency stop unit and a governor are electronized to obtain advanced functions.
BACKGROUND OF THE INVENTION

[0002]

Conventionally, an elevator safety unit is known, in which, to stop an elevator car when it reaches an abnormal speed, a governor rotated by a governor rope in conjunction with the up and down movements of the elevator car detects the speed of the elevator car.
[0003]

To safely measure the car speed of an elevator with a small top clearance or another type of elevator, it is also known that a roller attached to the car is pressed against guide rails and the running speed of the car is detected from a pulse that is proportional to the travel speed of the elevator car, which is
obtained from the rotation of the roller. This

technology is described in, for example, Patent

Document 1.

[0004]

Furthermore, to reduce an installation space, it is described in, for example, Patent Document 2 that an encoder is attached to a bottom diverting pulley for a rope that suspends an elevator car to detect the car speed.
[0005]

Furthermore, to shorten a braking distance to a point at which a car stops, it is described in Patent Document 3 that a car speed sensor and a rope sensor that detects rope breakage are entered into a monitoring unit (safety controller) and that, when an abnormal speed of the car or rope breakage is detected, an emergency stop unit (electronic emergency stop unit) operated by an electromagnetic actuator will be operated.
[0006]

Furthermore, to improve safety by preventing accidents due to slippage between a rope and a main sheave, it is described in Patent Document 4 that a frictional wheel is brought into contact with a rope on the main sheave to detect the rotation of the
frictional wheel that rotates in conjunction with the
rope.

PRIOR ART DOCUMENTS

Patent Documents

[0007]

Patent Document 1: Japanese Patent Laid-open No. Sho 61 (1986)-277573 Patent Document 2: Japanese Patent Laid-open No. Hei 4 (1992)-41377 Patent Document 3: International Patent Application WO 2005/115904 brochure Patent Document 4: Japanese Patent Laid-open No. Sho 59 (1984)-177285
SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

[0008]

With the technology in Patent Document 1 in the above prior art, the roller is attached to the moving car, so self-check is difficult. The position of the roller, which functions as a car speed sensor, is distant from a take-up machine, depending on the position of the car. Accordingly, the signal cable has to be prolonged for comparison with the rotational
speed of the take-up machine, so the waveform of the

pulse signal may become obtuse and external noise may be included. This may prevent the car speed from being
detected with high precision.

[0009]

With the technology in Patent Document 2, since the bottom diverting pulley is disposed on an elevator shaft side, self-check is easier than in Patent Document 1. However, the bottom diverting pulley is a requisite. Nevertheless, the pulley becomes useless depending on the roping method, and becomes an obstacle to space saving. Furthermore, the position of the encoder cannot always be brought close to the take-up machine.
[0010]

Furthermore, with the technology in Patent Document 3, the safety controller is just used to operate the electric emergency stop machine. The locations of the car speed sensor, take-up machine, and safety controller are not considered, so the technology is not suitable for the high precision of the car speed sensor and self-check. More safety improvements are desired.
[0011]

Furthermore, with the technology in Patent Document 4, to bring the frictional wheel into contact with the
rope on the main sheave, the frictional wheel has to be placed on the outer circumference of the main sheave. From the viewpoint of space saving, it is hard to say that this arrangement is suitable. A side of the frictional wheel has to be brought into point-contact with a bent rope to prevent the frictional wheel from coming in contact with the main sheave, making it difficult to detect speed with high precision.
[0012] Accordingly, a space-saving electronic safe elevator is required to periodically perform self-check to reduce the failure ratio, and is preferably suitable for self-check. To stop the elevator car in an emergency manner, the brake of the take-up machine is operated at a speed 1.3 times faster than the rated speed and the emergency stop unit is operated at a speed 1.4 times faster. For elevators with a low speed rating, therefore, a difference between these operation speeds is small and thereby a car speed sensor with higher precision is necessary. [0013] The present invention addresses the problems in the prior art described above, with the object of detecting a car speed with higher precision and improving the safety of a space-saving electronic safe elevator.
Another object is to have an elevator suitable as a

space-saving elevator even when it is made highly-

precise from the viewpoint of safety and has advanced

functions.

Means for Solving the Problems

[0014]

To achieve the above objects, in a space-saving elevator that has an elevator car that moves up and down in an elevator shaft, a take-up machine provided between the elevator shaft and the elevator car, and a sheave on which a rope is wound, the rope being driven by the take-up machine and tensioned to support the elevator car, and the elevator detecting the speed of the elevator car, the present invention has a diverting pulley disposed opposing to the sheave and a roller disposed so as to be pressed against the rope, which is tensioned between the sheave and the diverting pulley, and detects the speed of the elevator car from the rotation of the roller.
Advantages of the Invention

[0015]

According to the invention, since the speed of an elevator car is detected from the rotation of a roller disposed so as to be pressed against a rope tensioned between a sheave and a diverting pulley, a speed sensor
by means of the roller is disposed in a dead space on the perpendicular projection plane of the sheave, and thereby a need to reserve an additional space for the speed sensor is eliminated, resulting in space saving and enabling the car speed to be detected with higher precision. As a result, more improved safety is assured for a space-saving electronic safety elevator.
BRIEF DESCRIPTION OF THE DRAWINGS

[0016]

FIG. 1 is a perspective view showing the main parts in a first embodiment of the present invention.
FIG. 2 is a cross sectional view of the main parts (in FIG. 1) in the first embodiment of the present invention.
FIG. 3 is a side view showing a car speed sensor section in FIG. 1 in detail. FIG. 4 is a plan view showing the car speed sensor section in FIG. 1 in detail. FIG. 5 is a plan view showing a state in which the car speed sensor in the first embodiment is inspected.
FIG. 6 is a side view illustrating a relationship between the concaves and convexes of a rope and a roller in the first embodiment.
FIG. 7 is a side view illustrating a relationship

between a step of the rope and the roller in the first embodiment. FIG. 8 is a side view illustrating details of a car speed sensor that differs from the first embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017]

The entire structure of a space-saving electronic safety elevator will be described with reference to the drawings.
[0018]

An elevator car 1 is guided along guide rails 3 (3a, 3b) disposed in the height direction of an elevator shaft 2. Guide units (not shown) are attached to the tops and bottoms of the side surfaces on the right and left of the elevator car 1. The guide units are brought into contact with the guide rails 3 and guided.
[0019]

Two lower car pulleys 4 are attached to the bottom of the elevator car 1. A rope 5 is tensioned to support the elevator car 1 in such a way that the rope 5 encloses the elevator car 1 from below the lower car pulleys 4. One end of the rope 5 is fixed to a vertex 6a of the elevator shaft 2. The other end is wound on a diverting pulley 7a opposing to a sheave, proceeds downward, is wound on the sheave 9 of a take-up machine
8 disposed in a space next to the guide rail 3b, proceeds upward, passes through a diverting pulley 7b at the back and through a pulley 11 for a balance weight 10, and is fixed to a vertex 6b of the elevator shaft 2. The balance weight 10 moves up and down along guide rails 47 for the balance weight 10 disposed in a space next to the guide rail 3b. The method of tensioning the rope 5 as described above is referred to as the underslung method, in which the speed of the elevator car 1 is half the speed of the rope 5. This is advantageous for gearless motors, so low-speed elevators are desirable.
[0020]

A car speed sensor 13 is disposed above the sheave 9 and on the perpendicular projection plane of the sheave 9. A roller 14 is disposed so that the rotational axis 31 of the roller 14 is substantially parallel to the rotational axis of the sheave 9. A spring 15 presses the roller 14 against the rope 5. An encoder 16 is attached to the rotational axis 31 of the roller 14 and generates a pulse signal proportional to the rotational speed thereof. It is desirable to attach two encoders 16 because even if one encoder 16 fails, the operation can be continued.
[0021]

An electric emergency stop unit is attached on the right and left of the elevator car 1, and includes an actuator that holds the guide rail 3a and applies a brake to the elevator car 1. When power to the actuator is turned off, the elevator car 1 is braked by friction with the guide rail 3a.
[0022]

A main controller 12 is disposed at the lower part of the elevator shaft 2, in which the take-up machine 8 is mounted, and moves the elevator car 1 up and down by driving the take-up machine 8. A take-up machine encoder 43, indicated by the dotted line, is attached in the take-up machine 8. The main controller 12 controls the rotational speed of the take-up machine 8 by using information from the take-up machine encoder
43. A safety controller 20, which is a microcomputer or the like, performs calculation in response to an input signal, and is disposed at the lower part of the elevator shaft 2, in which the take-up machine 8 and car speed sensor 13 are disposed. The emergency stop unit, which electrically operates, functions as a safety unit, together with a brake by the take-up machine 8.
[0023]
The pulse from the encoder 16 of the car speed

sensor 13 is transferred to the safety controller 20 through a signal cable 21. A pulse signal from the take-up machine encoder 43 in the take-up machine 8 is transferred to both the main controller 12 and the safety controller 20 through a cable 44. The safety controller 20 calculates the speed of the elevator car 1 and the rotational speed of the take-up machine 8 by counting the number of pulse signals from the encoder 16 and take-up machine encoder 43 in a predetermined time.
[0024]

The safety controller 20 calculates the speed of the elevator car 1 (the travel speed of the rope 5) and the peripheral speed of the sheave 9 from pulse signals from the encoder 16 of the car speed sensor 13 (which detects the rotational speed of the roller 14) and the take-up machine encoder 43 in the take-up machine 8, and compares these speeds (or directly compares the rotational speeds of the roller 14 and take-up machine 8). If the comparison result indicates that the difference between the speeds (or the rotational speeds) exceeds an allowable range, a fault is determined and the brake of the take-up machine 8 is operated to stop the operation of the elevator. When self-check by the safety controller 20 is carried out
at a high frequency, an advanced function is obtained

in that a failure to detect an excess speed caused by a

fault of the car speed sensor 13 is prevented.

[0025]

When two encoders 16 of the car speed sensor 13 are attached, it can be determined which encoder 16 has failed by comparing the two encoders 16 with the take-up machine encoder 43 in the take-up machine 8, so the operation can be continued while the speed of the elevator car 1 is correctly detected. Accordingly, reliability for safety is improved in that frequent stops of the elevator operation due to faults are prevented while achieving enhanced functionality.
[0026]

Since the take-up machine 8, main controller 12, car speed sensor 13 (roller 14), and safety controller 20 are all disposed at the lower part of the elevator shaft 2, there is no need to connect these units with long cables and thereby the system can be made compact. When the take-up machine 8 is disposed at an upper part of the elevator shaft 2, it is desirable to dispose the main controller 12, car speed sensor 13, and safety controller 20 together at the upper part of the elevator shaft 2.
[0027]

The car speed sensor 13 uses the roller 14 pressed against the rope 5, which suspends the elevator car, and the encoder 16 attached to the rotational axis of the roller 14. The encoder 16 generates pulse signals with a frequency proportional to the rotational speed of the roller 14. The safety controller 20 calculates the travel speed of the rope 5 by counting the number of pulses from the encoder 16 per unit time, and reduces the calculated speed by a factor of 1/2 to detect the speed of the elevator car 1.
[0028]

The roller 14 is disposed on the rope 5 tensioned by the sheave 9 and the diverting pulley 7a opposing to the sheave 9 in such a way that the roller 14 is vertically stacked above the sheave 9. The axis of the roller 14 is supported by an arm 32. The roller 14 is pressed against the rope 5 by pressing the arm 32 with the spring 15. Since the car speed sensor 13 is accommodated in a dead space above the sheave 9 and take-up machine 8, there is no need to reserve an additional installation space and the conventional space for the governor and governor rope becomes unnecessary, resulting in space-saving.
[0029]

To correctly detect the speed of the elevator car 1

by using the car speed sensor 13, the contact state between the roller 14 and the rope 5 must be stable. If the rope 5 swings due to an earthquake, a strong wind, or the like, a midpoint between the sheave 9 and the diverting pulley 7a opposing to the sheave 9 becomes an anti-node of string vibration on a waveform with the maximum wavelength, which is reference vibration, at which the swing of the rope 5 is maximized. Therefore, the roller 14 is preferably disposed between the sheave
9 and the midpoint between the sheave 9 and the diverting pulley 7a, rather than the midpoint at which a large swing is caused, so that the contact state between the roller 14 and the rope 5 is stabilized.
[0030]

To precisely self-check the car speed sensor 13 by using the take-up machine encoder 43 in the take-up machine 8, it is necessary to prevent the rope 5 from causing a difference between the speed at the position of the sheave 9 and the speed at the position of the roller 14 due to expansion and contraction of the rope 5 between the sheave 9 and the roller 14. When the roller 14 is disposed at a position nearer the sheave 9 than the midpoint between the sheave 9 and the diverting pulley 7a opposing to the sheave 9, the effect of the contraction and expansion of the rope 5
can be reduced.
[0031]

Therefore, even if the rope 5 swings or expands and contracts by being affected by an earthquake or movement of passengers, the speed detection results of the take-up machine encoder 43 in the take-up machine 8 and of the car speed sensor 13 well match, enabling self-check to be accurately carried out. Thus, although it is desirable to stop the elevator car 1 when a detection failure of the car speed sensor 13 itself occurs, that is, self-check error occurs, it is possible to prevent the elevator car 1 from being stopped based on the self-check error at that time.
[0032]

FIG. 2 is the horizontal cross section of the elevator shaft 2 at the midpoint, when viewed from above; the elevator car 1 is placed at the center of the elevator shaft 2, and the balance weight 10 is disposed between the elevator car 1 and a wall 28 of the elevator shaft 2. Since the elevator car 1 and balance weight 10 move up and down, other units cannot be placed on the perpendicular projection plane thereof. The guide rails 3 and rope 5 are disposed over the entire area of the elevator shaft 2. A space for a door 29 and a sill 30 for supporting the door 29, which is
opened and closed, must also be reserved in the elevator shaft 2. [0033]
The guide rails 3 and rope 5 are also disposed over the entire area of the elevator shaft 2. A space for the door 29 and the sill 30 for supporting the door 29, which is opened and closed, must also be reserved in the elevator shaft 2. To reduce the cross sectional area of the elevator shaft 2, that is, an area occupied by the elevator in the building, a thin take-up machine 8 is used and disposed in a space between planes that cover the movable range of the elevator car 1 and the walls 28 of the elevator shaft 2. The thin take-up machine 8 is shaped so that it has a small dimension in the axial direction and a large diameter. To minimize the cross sectional area of the elevator shaft 2, the space in which units can be installed is limited as shown in the drawing. Furthermore, the depth of the elevator shaft 2 is reduced for space-saving.
[0034]

The roller 14 of the car speed sensor 13 causes variations in the rotational speed because the roller 14 is affected by concaves and convexes, which are formed on the surface of the rope 5 by its stranded wires. To be highly precise when detecting the speed,
the radius of the roller 14 is preferably 3 to 6 times larger than an interval among the concaves and convexes on the surface of the rope 5. That is, the diameter of the roller 14 cannot be reduced from the viewpoint of required precision, so it is important to reserve a space for the roller 14. Therefore, the roller 14 is vertically stacked above the sheave 9, that is, the roller 14 is disposed on the perpendicular projection plane of the sheave 9 so that the depth of the elevator
shaft 2 can be reduced more.

[0035]

A space for the spring 15 that presses the roller 14 against the rope 5 is a requisite. If the car speed sensor 13 is disposed in the space between the sheave 9 and the sill 30 or the space between the sheave 9 and the guide rail 3b, the area of the elevator shaft 2 becomes large. Therefore, the radius of the roller 14 is made smaller than the radius of the sheave 9 and the spring 15 and arm 32 are vertically stacked above the sheave 9 and take-up machine 8 to reserve, in the elevator shaft 2, a space for the spring 15 and arm 32.
[0036]

The rope 5 is wound on the lower half of the sheave

9. If the roller 14 is pressed against this portion, the elevator shaft 2 needs to be prolonged downward by
a space for the roller 14 and encoder 16 to prevent the encoder 16 from interfering with the take-up machine 8. As higher precision is pursued by enlarging the diameter of the roller 14, space-saving is lessened.
[0037]

In FIG. 2, the car speed sensor 13 is vertically stacked above the sheave 9, and the roller 14 is pressed against a surface of the rope 5 on which the rope 5 is brought into contact with the sheave 9. This eliminates the need for reserving an additional space for the car speed sensor 13. This is also true when the take-up machine 8 is disposed by being shifted upward; the car speed sensor 13 may be disposed in a space reserved above the sheave 9.
[0038] FIG. 3 is a detailed side view of the car speed sensor 13, take-up machine 8, and sheave 9. [0039]
Since the diameter of the take-up machine 8 is larger than the diameter of the sheave 9, the car speed sensor 13 is spaced away from the sheave 9 to a position where the car speed sensor 13 does not interfere with the take-up machine 8. A bracket 34 is fixed to a beam 45 extending from the elevator shaft 2, and the car speed sensor 13 is attached thereto. A
shaft 5b for the spring 15 passes below the encoder 16. [0040] A bracket 38 is disposed to the left of the roller
14. A dent is formed in the bracket 38 so that a speed meter is fixed when the car speed sensor 13 is checked. [0041]
A protective plate 35 is shaped so as to have, above the roller 14, a perpendicular plane along the rope 5, and is fixed to the beam 45. The width of the protective plate 35 is wider than the width of the roller 14. The perpendicular plane is further separated from the rope 5 than the rope contact surface of the roller 14 and is brought closer to the rope 5 than the rotational axis of the roller 14. The protective plate 35 is shaped so that its upper end is bent to cover a portion above the roller 14. A clearance between the lower end of the protective plate 35 and the roller 14 is smaller than the diameter of the rope 5. Accordingly, if the rope 5 is cut, the rope 5 always drops in a direction in which it moves apart from the roller 14 and thereby the car speed sensor 13 is protected.
[0042]

If the rope 5 is cut for some reason, the speed of the rope 5 and the speed of the elevator car 1 do not match and the speed of the elevator car 1 cannot be
detected by the car speed sensor 13. However, the

elevator car 1 is stopped by the brake of the take-up

machine 8 when one or more ropes 5 are cut and by the

emergency stop unit when all ropes 5 are cut.

[0043]

FIG. 4 shows a state of the take-up machine 8 and sheave 9 when the car speed sensor 13 is viewed from above. For the roller 14, its cross section is shown so that the inside is seen.
[0044]

The roller 14 has a bowl-like shape in which the same side as the take-up machine 8 is open. The outer peripheral width on a side on which the roller 14 comes in contact with the rope 5 is preferably large enough to allow the roller 14 to touch at least one rope 5. In the drawing, the rotational axis 31 of the roller 14 is placed so as to be substantially parallel to the rotational axis of the sheave 9, and comes in contact with the nearest rope 5a. The rotational axis 31 of the roller 14 is attached to the bottom of the bowl-like part, supported by a bearing provided at an end of the arm 32 included inside the roller 14, and fixed to the beam 45 extending from the elevator shaft 2 above the take-up machine 8 through the bracket 34. The arm 32 is axially supported by an axis 33 on the bracket 34. The
arm 32 is swung by the rotational axis 33 orthogonal to the axis 31. [0045]
A coupling 50 is attached to the rotational axis 31, linking an extension axis 51. The extension axis 51 is fixed to hollow axes of the two encoders 16a and 16b. An end of the extension axis 55 is included in the encoder 16b. The casings of the encoders 16a and 16b are fixed to the arm 32 through a flexible bracket 52.
[0046]

The rotational axis 31 is disposed at an end of the sheave 9 so that the bowl-like hollow interior of the roller 14 is enlarged, wherein a space for the encoder 16 is reserved in the hollow interior. Accordingly, even when two encoders 16 are attached, the car speed sensor 13 fits within the width dimension of the sheave 9 and take-up machine 8, so there is no need to reserve an additional space for the car speed sensor 13.
[0047]

A retaining plate 53 for retaining the spring 15 is attached at the bottom of the arm 32. The spring 15 is pressed against the retaining plate 53 to press the arm 32 toward the rope and to press the roller 14 against the rope 5.
[0048]

A bracket 54 is attached to the beam 45 on a side opposite to the spring 15 of the arm 32 to fix the basal portion of the shaft 55. The shaft 55 passes below the encoder 16 attached to the arm 32, and extends to the opposite side of the arm 32. The end of the shaft 55 passes through a hole 57 formed in the retaining plate 53 and passes through the center of the spring 15. A spring retainer 56 is attached to a point at which the end of the shaft 55 exits from the spring 15 to press and urge the end of the spring 15.
[0049]

As described above, the roller 14 can always come in contact with one rope 5a. That is, even if the rope 5a swings and its position changes, the angle of the arm 32 changes accordingly and the roller 14 is always in contact with the one rope 5a. In addition, when the rope 5 is passed below the encoder, the distance from the basal portion of the shaft 55 to the retaining plate 53 can be prolonged. Therefore, even if the arm 32 follows the swing of the rope 5 and the angle of the arm 32 changes accordingly, the change in the angle of the shaft 55 is small, preventing interference with the rope 5 and elevator car 1, which would otherwise be caused by a swing of the spring 15 and the end of the shaft 55.
[0050]
The safety controller 20 calculates the speed of

the elevator car 1 (the travel speed of the rope 5) and

the peripheral speed of the sheave 9 from pulse signals

from the encoder 16 of the car speed sensor 13 and from

the take-up machine encoder 43 in the take-up machine 8,

and compares these speeds. That is, the safety-

controller 20 self-checks the car speed sensor 13. If a

difference between these speeds exceeds an allowable

range, a fault is determined and the brake of the take-

up machine 9 is operated to stop the operation of the

elevator. If a mismatch occurs between the speed by the

encoder of the car speed sensor 13 and the speed by the

encoder of the take-up machine 8, the safety controller

20 operates the brake of the take-up machine 8 to stop

the elevator car 1. Accordingly, even if the encoder 16

fails or the rope 5 is cut and comes off the roller 14,

a mismatch occurs between the speed calculated from the

encoder 16 of the car speed sensor 13 and the speed

calculated from the take-up machine encoder 43 in the

take-up machine 8 and the brake of the take-up machine

8 operates. A mismatch in speed also occurs even in a

case in which the roller 14 is pushed away from the rope 5 and does not come in contact with the rope 5, in
which case the brake of the take-up machine 8 also

operates.
[0051]

The safety controller 20 can prevent a failure to detect an excess speed caused by a fault of the car speed sensor 13 by carrying out self-check out at a high frequency during operation of the elevator.
[0052]

In the drawing, two encoders 16 of the car speed sensor 13 are attached, so each encoder is compared with the take-up machine encoder 43 in the take-up machine 8. For example, if a mismatch in speed is caused by the two encoders 16a and 16b of the car speed sensor 13, the safety controller 20 selects either speed that matches the speed by the take-up machine encoder 43 in the take-up machine 8. That is, even if one encoder 16 of the car speed sensor 13 fails, it can be decided which encoder 16 has failed, so the operation can be continued while the speed of the elevator car 1 is correctly detected. This prevents the operation of the elevator from being frequently stopped due to faults of the encoder 16 of the car speed sensor
13. If neither of the speeds by the two encoders 16a and 16b of the car speed sensor 13 matches the speed by the take-up machine encoder 43 in the take-up machine 8, however, the safety controller 20 operates the brake of
the take-up machine 8 due to a mismatch in speed. [0053] FIG. 5 shows a state of the car speed sensor 13,
when viewed from above, illustrating a procedure for inspecting the car speed sensor 13. [0054] The edge of the roller 14 is wide because a speed meter 40 is abutted to the roller 14.
(1) The roller 14 is pushed to the right against the force of the spring 15 so that the roller 14 is separated from the rope 5a. A roller 58 of the speed meter 40 is abutted to the roller 14.
(2) The speed meter 40 is fixed to the bracket 38 with a band 42 or the like.
(3) The roller 14 is rotated at high speed by, for example, abutting a rotation roller of a drill (not shown) to the roller 14. A speed by the speed meter 40 and a speed by the car speed sensor 13 are compared for inspection.

[0055]

The roller 14 of the car speed sensor 13 may be affected by concaves and convexes, which are formed on the surface of the rope 5 by its stranded wires, causing variations in the rotational speed. FIG. 6(1) shows a state in which the roller 14 rides on a convex
on a stranded wire. The rope 5 can be regarded as a column as indicated by the dotted lines. Then, the roller 14 with a radius of r can be regarded as being in contact with the column. If the travel speed of the rope 5 is v, then the rotational speed co of the roller
14 is v/r, which is inversely proportional to the

radius r of the roller 14.

[0056]

In a state in which the roller 14 completely sinks in a concave on a stranded wire as shown in FIG. 6(2), the roller 14 comes in contact with the rope 5 at two points. Therefore, the substantial radius of the roller 14 is reduced. Due to these states, concaves and convexes on the rope 5 cause variations in the rotational speed of the roller 14.
[0057]

The apparent radius r' of the roller when the roller 14 sinks in a concave on a stranded wire is obtained in a simplified manner from an isosceles triangle formed by the center 0 of the roller and two contact points A and B at which the roller 14 comes in contact with the rope 5. The radius r of the roller 14 was obtained so that a varying speed width indicated by
(r - r')/r x 100 (%) is 1% or less.

[0058]

The stranded wire pitch Pr of the rope 5 is preferably about 10 mm, and the radius of the roller 14 is preferably 36 mm or more. That is, the roller 14 becomes suitable for high precision if its radius is 3 to 6 times (preferably, 4 to 5 times) larger than the stranded wire pitch Pr on the surface of the rope 5. Furthermore, since the diameter of the roller 14 cannot be reduced from the viewpoint of required precision, it is important to reserve a space for the roller 14.
[0059]

Error is generated in speed detection due to an effect by a step formed by dust adhering to the rope 5. FIG. 7 shows an angle 9 by which the roller 14 rotates before and after a step 8, a traveled distance 1 calculated from the angle 0, and a distance x actually traveled by the rope 5.
[0060] The roller 14 comes in contact with the rope at the two points A and B before the step 8. The angle 9 formed by line segments OA and OB drawn from the center O of the roller 14 is equivalent to the rotational angle of the roller 14 when the roller 14 passes through the step 8 and proceeds to a position indicated by the dotted line. As the radius r of the roller 14 becomes larger, a difference between the actually
traveled distance x and the distance 1 calculated from the rotational angle 0 of the roller 14 becomes smaller, enabling the speed to be detected with high precision. To reduce the speed detection error to 1% or less of the rated speed, the radius of the roller 14, which allows a step 8 of up to 1.5 mm, is 50 mm or more. As for an upper limit of the radius of the roller 14, since the roller 14 is vertically stacked above the sheave 9, the radius of the roller 14 is preferably-smaller than the radius of the sheave 9. Specifically, when the radius of the sheave 9 is 200 mm, the radius of the roller 14 is preferably smaller than 200 mm.
[0061]

As described above, the radius of the roller 14 is preferably 36 mm or more (desirably, 50 mm or more) and 200 mm or less.
[0062]

Unlike the example described above, FIG. 8 shows an example in which the axis 33 at the basal portion of the arm 32 is disposed parallel to the rotational axis 31 of the roller 14. The reason why the axis 33 at the basal portion of the arm 32 is the rotational axis 31 of the roller 14 is described below.
[0063]
In the case shown in FIG. 8, when the arm 32

rotates due to a step formed by dust adhering to the
rope 5 or a swing of the rope 5, the encoder 16 fixed
on the arm 32 rotates by A0 together with the arm 32.
In this case, even if the roller 14 has rotated by an
angle of θ at a speed that matches the travel speed of
the rope 5, the encoder 16 detects a relative
rotational angle θ' between the arm 32 and the roller

14. That is, the relative rotational angle θ' between
the arm 32 and the roller 14 is A0 smaller than the
angle θ by which the roller 14 has rotated. When a
speed is detected with high precision, the effect of
the error due to the rotation of the arm 32 cannot be
ignored. Accordingly, the axis 33 at the basal portion
of the arm 32 is preferably orthogonal to the
rotational axis 31 of the roller 14 to prevent the axis
of the encoder 16 from rotating even when the arm 32
follows the rope 5 and rotates together.

Legend
[0064]
1 Elevator car
2

Elevator shaft
3

Guide rail
4

Lower car pulley
5

Rope
6

Elevator shaft vertex

7a, 7b Diverting pulley 8 Take-up machine 9 Sheave 10 Balance weight 11 Pulley 12 Main controller 13 Car speed sensor 14 Roller 15 Spring 16, 16a, 16b Encoder 20 Safety controller 21 Signal cable 32 Arm 34 Bracket 35 Protective plate 38 Bracket 40 Speed meter 43 Take-up machine encoder 45 Beam

WHAT IS CLAIMED IS:

1. A space-saving elevator that has an elevator car that moves up and down in an elevator shaft, a take-up machine provided between the elevator shaft and the elevator car, and a sheave on which a rope is wound, the rope being driven by the take-up machine and tensioned to support the elevator car, the elevator detecting speed of the elevator car, and the elevator comprising:
a diverting pulley disposed opposing to the sheave;
and

a roller disposed so as to be pressed against the rope, which is tensioned between the sheave and the diverting pulley;
wherein speed of the elevator car is detected from the rotation of the roller.
1 The space-saving elevator according to claim 1, wherein the roller is disposed between the sheave and a midpoint between the sheave and the diverting pulley.
2 The space-saving elevator according to claim 1, wherein the take-up machine is shaped so that the take-up machine has a small dimension in an axial direction thereof and a large diameter and disposed in a space between planes that cover a movable range of the elevator car and walls of the elevator shaft, and

wherein the roller is vertically stacked above the
sheave.

1 The space-saving elevator according to claim 1, wherein a rotational axis of the roller is disposed so as to be parallel to a rotational axis of the sheave and is axially supported by an arm, and wherein the arm is swingable around an axis orthogonal to the rotational axis of the roller.
2 The space-saving elevator according to claim 1, wherein a protective plate is disposed above the roller, the protective plate being shaped so as to have a plane along the rope and an upper end that is bent to cover a portion above the roller.
3 The space-saving elevator according to claim 1, wherein a plurality of encoders is attached to a rotational axis of the roller, each encoder generating a pulse signal proportional to a rotational speed.
4 The space-saving elevator according to claim 1, wherein the roller has a bowl-like shape in which the same side as the take-up machine is open; an encoder that generates a pulse signal proportional to a rotational speed of the roller is disposed in a hollow interior of the roller.
5 The space-saving elevator according to claim 1, wherein a safety controller for comparing a rotational

speed of the roller and a rotational speed of the take-

up machine is provided; if a difference between the

rotational speeds exceeds an allowable range, the

safety controller determines that there is a fault.

9. The space-saving elevator according to claim 1, wherein a safety controller for comparing a rotational speed of the roller and a rotational speed of the take-up machine is provided; the take-up machine, the roller, and the safety controller are disposed at a lower part of the elevator shaft.