JPH11106152A - Fluid pressure elevator - Google Patents

Abstract

(57) [Problem] To prevent negative pressure on the suction side of a fluid pressure pump during descent operation, thereby preventing equipment failure. SOLUTION: A cylinder pressure, a hydraulic pump pressure, or a fluid temperature is detected before a descent operation of a fluid pressure elevator, during acceleration during running, and when the detected value is lower than a predetermined value, a fluid is detected. The speed command value is output at a value lower than the rated speed so that the suction side of the pressure pump does not become a negative pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic elevator, and more particularly, to a motor and a hydraulic pump which are controlled at a variable speed by inverter control to supply a fluid to be discharged to a hydraulic cylinder, or to supply a fluid from a hydraulic cylinder. The present invention relates to a hydraulic elevator of a type that raises and lowers a car by controlling the speed of a hydraulic cylinder by discharging.

[0002]

2. Description of the Related Art In general, in a hydraulic elevator driven by inverter control, the speed of a car is controlled by controlling the flow rate of a hydraulic pump by controlling the rotation speed of a motor at a variable speed. The ascending operation of the car is performed so that the fluid is supplied from the hydraulic pump to the hydraulic cylinder according to the number of rotations of the motor according to the speed command, the hydraulic cylinder is pushed up, and the car travels in the ascending direction.
Further, the descending operation is performed by controlling the number of rotations of the motor according to the speed command and controlling the flow rate of the fluid from the fluid pressure pump.

[0003] In the above-described descending operation, if the weight of the car due to the car and the load is large, the pressure difference at the fluid pressure control valve becomes large, and the car speeds up beyond the speed command value. The vehicle is running in the descending direction while braking the motor. On the other hand, when the weight of the car due to the car and the load is small, the pressure difference at the fluid pressure control valve also becomes small, and the car travels at a speed equal to or less than the speed command value by the pressure difference alone. The motor is controlled so that the fluid pressure pump is rotated in the discharging direction, and the car is caused to travel at a rated speed in the descending direction.
However, at this time, if the pressure loss in the piping and the fluid pressure control valve further increases for some reason, the fluid flow rate on the suction side of the pump decreases, and the fluid pressure pump can discharge a fluid with a higher flow rate. Instead, a negative pressure may be generated on the suction side, resulting in equipment failure.

[0004] As a conventional technique for preventing the abnormal negative pressure of the fluid pressure pump that may be generated during the descending operation as described above, for example, a technique described in Japanese Patent Application Laid-Open No. 4-189273 is known. In this prior art, a limiter is provided for a torque that limits a torque command value for a motor that drives a pump when there is a possibility that an abnormal negative pressure is detected by detecting a pump pressure. However, this prior art describes a method of preventing a negative pressure by a limiter of a torque command value for a pump driving motor during traveling of a car. There is no mention of how to prevent negative pressure by changing the value.

As another conventional technique, for example, a technique described in Japanese Patent Application Laid-Open No. S61-136889 is known. This prior art relates to a hydraulic elevator of the type of reducing the motor capacity of the drive device by compensating the load of the car with the counterweight in order to reduce the size of the drive device, by installing a counterweight,
Since the pressure of the fluid pressure cylinder at the time of no load further decreases, a negative pressure is easily generated. However, even in this conventional technique, the negative pressure preventing method is not mentioned.

[0006]

The above-described hydraulic elevator driven by the inverter control according to the prior art described above detects a pump pressure abnormality during descending operation and applies a limiter to a torque command. There is a problem that it is not possible to detect an expected abnormal negative pressure on the suction side of the hydraulic pump and equipment such as a torque limiter is required.

It is an object of the present invention to provide a fluid pressure elevator controlled by an inverter which can prevent abnormal negative pressure by changing a speed command even when the car is stopped before running as well as during running.

[0008]

According to the present invention, the object of the present invention is to control the number of revolutions of a hydraulic pump by a control device so that a fluid passed from a fluid tank through a fluid pressure control valve can be fluidized by a hydraulic cylinder. In a hydraulic elevator that controls the speed of the hydraulic cylinder by controlling the speed of the hydraulic cylinder by supplying or discharging to the hydraulic cylinder, the hydraulic cylinder during operation of the car before driving in the descending direction or during driving in the descending direction, When the detected value of the fluid pressure pump or the fluid temperature is below the specified value, or when both the detected pressure value and the detected temperature value are below the specified value, the speed command value of the car speed should be lower than the rated speed. Achieved by limiting to a certain value.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a hydraulic elevator according to the present invention.

FIGS. 1 and 2 are block diagrams showing an overall configuration example of a hydraulic elevator according to an embodiment of the present invention by inverter control to which the present invention is applied. 1 and 2
, 1 is a car, 2 is a hydraulic cylinder, 3 is a hydraulic pump, 4 is a motor, 5 and 17 are pulleys, 6, 18
Is a rope, 7 is a fluid pressure control valve, 8 is a fluid tank, 9, 1
0 and 15 are springs, 11 is a temperature detector, 16 is a counterweight, 19 is a control device, 20 and 21 are pressure detectors, 12 to
14 is a pipe.

The hydraulic elevator shown in FIG. 1 comprises a car 1, a hydraulic cylinder 2 for pushing up the car 1 through a pulley 5, a rope 6, and springs 9 and 10 installed at both ends of the rope 6. A fluid pressure pump 3 for supplying fluid to the fluid pressure cylinder 2, a control device 19 for giving a rotation speed command to the motor 4 and a drive command to the fluid pressure control valve 7, a fluid pressure cylinder 2, the fluid pressure control valve 7, Piping 12, 13, 14 connecting the fluid pressure pump 3 and the fluid tank 8, respectively; a pressure detector 20 for detecting the pressure of the fluid pressure pump 3; a pressure detector 21 for detecting the pressure of the fluid pressure cylinder 2; The temperature sensor 11 detects the temperature of the fluid in the fluid tank 8.

The hydraulic elevator shown in FIG.
The structure is the same as that shown in a except that a balance weight 16 is provided via a rope 18, a pulley 17, and a spring 15 in order to compensate for the weight of the car 1, and the others are the same. .

In the hydraulic elevator constructed as described above, oil is usually used as the fluid. In addition, the control device 19 supplies the motor 4 that drives the hydraulic pump 3 with a variable voltage and a variable frequency AC power by inverter control to the motor 4 based on a control command such as a speed command for the car 1 to control the motor 4. Control.

The control device 19 drives the motor 4 in accordance with the speed command when the car 1 is to be raised,
By driving the fluid pressure pump 3 to supply the fluid to the fluid pressure cylinder 2, the car 1 is operated in the upward direction.

When the car 1 is driven to descend from the stopped state, the control device 19 drives the motor 4 and once stops.
Control is performed so that the pressure of the hydraulic pump 3 becomes substantially equal to the pressure of the hydraulic cylinder 2. At the same time, the control device 1
9 provides a drive signal for opening the fluid pressure control valve 7 and
Is rotated in the reverse direction to control the fluid pump 3 to discharge the fluid, and the fluid is discharged from the hydraulic cylinder 2 to the hydraulic tank 8. Thereby, the car 1 can be driven in the descending direction.

At the time of the above-described descent operation, the fluid pressure control valve 7 and the pipes 12, 13, and 14 generate a pressure loss according to the flow rate of the fluid, but there is a limit value in the pressure loss for flowing the required flow rate. In some cases, the amount of fluid that can be removed from the fluid control valve 7 in the pump direction may not be the required flow rate. Therefore, when exceeding the limit value, the fluid pressure pump 3 keeps rotating in accordance with the speed command so as to discharge a constant flow rate of fluid, so that the pressure inside the fluid pressure control valve 7 and the pipes 12, 13, 14 becomes negative pressure. In such a case, air bubbles may be mixed in or cavitation may occur, resulting in equipment failure. Therefore, it is important to control the hydraulic elevator as shown in FIGS. 1 and 2 so as not to generate the negative pressure as described above. In particular, FIG.
In the hydraulic elevator shown in (1), since the weight of the car is equivalently reduced, the hydraulic cylinder pressure at the time of no load is further reduced, so that the negative pressure is lower than in the case of FIG. It is more likely to occur and it is more important to prevent negative pressure.

According to the present invention, the generation of a negative pressure is prevented by changing the speed command from the control device 19 to the motor 4 before the above-mentioned state is attained. I do.

FIG. 3 is a view for explaining the descending operation of the hydraulic elevator according to the embodiment of the present invention. The example shown in FIG. 3 is an example for preventing abnormal negative pressure during traveling. Less than,
With reference to FIG. 3, a description will be given of an example of a low-load, low-temperature case in which the hydraulic pump pressure during the descending operation traveling becomes the lowest. FIG. 3 shows the normal and abnormal car speed commands V1,
V2, pump pressure Pp1, Pp2, and cylinder pressure P
j1 and Pj2.

First, normal operation will be described. At the start of the descent operation, the pump pressure Pp1 is once increased by the start command so as to be substantially equal to the pressure Pj1 of the fluid pressure cylinder, the fluid pressure control valve 7 is opened, and at the same time, the car speed command from the control device 19 is transmitted. Start outputting (time t
1). After the end of acceleration (time t2), the car is caused to run at full speed at a constant speed of V1, and when the car reaches a predetermined position (time t3), deceleration is started and the car is stopped (time t6). . Thereafter, with the pump pressure Pp1 substantially equal to the fluid pressure cylinder pressure Pj1, the fluid pressure control valve 7 is closed to reduce the fluid pressure.

Next, an abnormal operation will be described. At the time of abnormality, it is conceivable that the cylinder pressure is low before the car travels or that the pump and cylinder pressures become too low during the travel. In the example shown in FIG. 3, in both cases, control is performed as follows.

At the start of the descending operation according to the start command, the pump pressure Pp2 is changed by the start command to the pressure P of the hydraulic cylinder.
The pressure is once increased so as to be substantially equal to j2, the fluid pressure control valve 7 is opened, and at the same time, the control device 19 starts outputting a car speed command (time t1). After that, the car starts accelerating, but for some reason, the pump pressure Pp
2. The pressure Pj2 of the fluid pressure cylinder may drop abnormally. In order to prevent such an abnormal decrease in pressure, in the illustrated example, the detected pressure of the pressure detector 20 that detects the pump pressure is equal to the set value P1 of the pressure for preventing negative pressure.
Is detected, or that the pressure detected by the pressure detector 21 that detects the cylinder pressure becomes equal to or less than a set value P2 of the pressure for preventing negative pressure (time t2). To change the speed command. That is, when the above-mentioned pressure drop is detected by the pressure detectors 20 and 21, the speed command value for the car is changed to V2 having a maximum speed smaller than V1 and the motor is controlled so as to reduce the pump flow rate. Perform speed control. As a result, the fluid pump pressure becomes equal to or higher than P1, and the cylinder pressure becomes P1.
The pressure can be raised so as to be 2 or more, and a negative pressure can be prevented. The car, the maximum speed of which has been changed to V2 by the change of the speed command, completes the full-speed running at the speed V2 (time t5), starts deceleration, and is stopped (time t7). Thereafter, the fluid pressure control valve 7 is closed with the pump pressure Pp2 substantially equal to the fluid pressure cylinder pressure Pj2, and the fluid pressure pump pressure is also reduced.

In the above description, if the value of the pump pressure value P1 set for preventing the negative pressure is at least substantially equal to or higher than the atmospheric pressure (0 line in the drawing), even if the negative pressure may be momentarily applied, the negative pressure is immediately obtained. There is no problem because it is within the range of positive pressure
The value is set to a value slightly higher than the atmospheric pressure, for example, about 2 atm when the atmospheric pressure is 1 atm. Further, the value of the fluid pressure cylinder pressure P2 is determined by the piping,
The value may be set to be substantially equal to the sum of the pressure loss and the friction loss of the control valve, the fluid pressure cylinder, the car, and the like. The above-mentioned set values P1 and P2 of the pressure are not limited to the above-mentioned values, but may be set to any values.

In the case of the control example shown in FIG. 3, since the speed command is reduced, the time required for stopping the car is longer than when the car is driven at the rated speed.

FIG. 4 is a view for explaining another example of the descending operation of the hydraulic elevator according to the embodiment of the present invention.
The example shown in FIG. 4 predicts an abnormal negative pressure before traveling,
It is an example of preventing abnormal negative pressure during traveling. Hereinafter, with reference to FIG. 4, as in the case of FIG. 3, a description will be given of an example of the case of no load and low temperature at which the hydraulic pump pressure during the descending operation traveling becomes the lowest. FIG. 4 shows normal and abnormal car speed commands V1, V2, pump pressures Pp3, Pp4, and cylinder pressures Pj3, Pj4.

The normal descent operation in this example is as follows.
Since the operation is performed in the same manner as shown in FIG. 3, the description here will be made only for the case where an abnormal negative pressure is predicted.

There are three control methods for controlling negative pressure when abnormal negative pressure is expected to occur.
These will be described sequentially.

(1) In the case where the fluid pressure cylinder pressure is detected in a state where the motor is not started (time t0), the control is performed by controlling the temperature of the fluid immediately before the descent operation (time t0).
If the pressure of the fluid pressure cylinder is detected and the value is equal to or less than a predetermined limit set value P4, the speed command pattern is changed from the command pattern having the rated speed V1 from the beginning to the rated speed V1.
The control is performed by changing to a speed command pattern having a speed V2 of a smaller value.

That is, when the fluid pressure cylinder pressure immediately before the descent operation (time t0) is equal to or higher than the limit set value P4 as indicated by Pj3, the control device determines that normal running is possible, and the command pattern having the rated speed V1 is obtained. Is output to control the traveling of the car. When the fluid pressure cylinder pressure immediately before the descent operation (time t0) is equal to or less than the limit set value P4 as indicated by Pj4, the control device outputs a command pattern having the rated speed V1 and performs normal running. It is determined that a negative pressure may be generated, and a speed command pattern having a speed V2 smaller than the rated speed V1 is output to control the traveling of the car.

By performing the above-described control, the fluid pressure cylinder pressure Pj4 does not fall below the lower limit pressure P2 described with reference to FIG. 3, and the pump pressure Pp4 falls below the lower limit pressure P1 described with reference to FIG. The traveling of the car can be controlled without the pressure, that is, without reducing the pressure on the suction side of the pump to a negative pressure.

(2) When detecting the hydraulic pump pressure in the car stopped state (time t1) after starting the motor In the case of the above (1), the hydraulic pump pressure immediately before the start is almost atmospheric pressure. In this case, the control by detecting the pressure of the hydraulic pump is performed by first increasing the pressure of the hydraulic pump, detecting the pressure when the pressure almost reaches the hydraulic cylinder pressure, and confirming the state to control. Is what you do. That is, this control is performed at the start of the descent operation according to the start command, and at the time when the pump pressure is once increased so as to become substantially equal to the pressure of the hydraulic cylinder by the start command (time t1), the limit pressure of the hydraulic pump pressure is set. Let the value be P3,
The control device controls the traveling of the car by detecting the pressure of the hydraulic pump at time t1.

When the pump pressure at time t1 is equal to or higher than the limit set value P3 as indicated by Pp3, the control device determines that normal traveling is possible, outputs a command pattern having the rated speed V1, and outputs a command pattern having the rated speed V1. Control running. Further, the control device determines that the pump pressure at time t1 is Pp4
When the speed is equal to or less than the limit set value P3, it is determined that an abnormal negative pressure may be generated if a command pattern having the rated speed V1 is output and normal running is performed. The traveling of the car is controlled by outputting a speed command pattern having the speed V2.

Even when such control is performed, the traveling of the car can be controlled without reducing the hydraulic cylinder pressure and the pump pressure to a negative pressure, as in the case of the above-described example.

(3) In the case of detecting the temperature of the fluid This control is applied simultaneously with the above-mentioned methods (1) and (2), thereby making it possible to more reliably prevent negative pressure. It is.

That is, in this control, the temperature of the fluid is detected before the traveling in the descending operation, and if the detected value is higher than the preset limit temperature, it is considered that normal traveling is possible, and the speed command is changed to the rated speed command. When the detected value of the fluid temperature is lower than the limit set temperature, the speed command value is output lower than the rated speed, and the lowering operation of the car is controlled.

As described above, by detecting the fluid pressure cylinder pressure, the pump pressure, and the temperature when the car is stopped, it is possible to reliably prevent the negative pressure during the descending operation of the car.

FIG. 5, FIG. 6, and FIG. 7 are diagrams for explaining an operating region in which a negative pressure can be prevented during the descending operation based on the detected values of the fluid pressure cylinder pressure and the fluid temperature.
Hereinafter, this will be described, and an area usable in the control according to the present invention will be described.

Generally, the operable range of the hydraulic elevator is determined with respect to the fluid temperature and the hydraulic cylinder pressure when the car is stopped. That is, the fluid temperature is determined because it is necessary to maintain the performance of the equipment even if the viscosity of the fluid changes, and the pressure is determined by the performance of the fluid pressure control valve, the pressure resistance of the equipment, and the pressure of the fluid pressure control valve and piping. The limit value is determined in consideration of the safety factor from the loss, the capacity of the motor, and the like.
For example, as shown in FIG. 5, if the lower limit of the temperature range of the operating range of a certain fluid pressure elevator is TL, the upper limit is TH, the lower limit of the pressure range is PL, and the upper limit is PH, the area surrounded by the solid line in the drawing is This is the area where normal operation is possible.

Generally, the hydraulic elevator is provided with an electric countermeasure against the overload when the hydraulic cylinder pressure exceeds the upper limit PH of the above-mentioned pressure range.
It is legally required to provide a safety valve mechanically as a safety measure against equipment pressure.However, no special legal obligation is imposed on abnormally low pressure during descent operation. The operating range is set with a certain margin so that a negative pressure does not occur even if the pump pressure drops abnormally in case of emergency. For this reason, for example, as shown in FIG. 5, conventionally, a region in which the cylinder pressure detected before traveling in the descending operation is lower than the limit value PN for preventing the negative pressure is not used, and A0-B1-C1-D0 is used. Used only in enclosed areas.

The above-described elevator according to the embodiment of the present invention can be used when the hydraulic cylinder pressure before traveling is low.
By outputting the speed command of the car at a speed lower than the rated speed, it is possible to use a region indicated by R1 which is likely to become a negative pressure when the speed command is output at the rated speed. That is, conventionally, A0-B1-C1-D0
A hydraulic elevator that could only be used in the area enclosed by
It becomes possible to use the area surrounded by 0-C0-D0.

For this reason, the embodiment of the present invention is designed to minimize the pressure margin as much as possible in order to reduce the size of equipment and to use the motor capacity to the limit as compared with the conventional fluid pressure elevator. Even when the present invention is applied to a fluid pressure elevator having a weight, traveling control with a margin can be performed. The operation of the hydraulic elevator at this time is almost the same as that described with reference to FIG.

In the description of FIG. 5, the operation region conventionally used is the region surrounded by A0-B1-C1-D0. There is a case where a limit value TN for preventing a negative pressure is set for the temperature of, and an area below the limit value TN is not used. In this case, the unused operation area corresponds to the area R in FIG.
2 and the usable operation range is shown in FIG.
A1-B2-C1-D0.

The elevator according to the embodiment of the present invention described above outputs the speed command of the car lower than the rated speed and outputs the speed command when the fluid pressure cylinder pressure and the fluid temperature before traveling are low. Can be used in a region indicated by R2, which has a high possibility of becoming a negative pressure when is output at the rated speed. That is, conventionally, A1-B2-
Embodiments of the present invention allow a hydraulic elevator that could only be used in the area enclosed by C1-D0 to be used up to the area enclosed by A0-B0-C0-D0.

Therefore, similarly to the case described with reference to FIG. 5, the embodiment of the present invention can perform traveling control with an allowance even when applied to a hydraulic elevator having a counterweight. The operation of the hydraulic elevator at this time is almost the same as that described with reference to FIG.

In the description of FIG. 6, the operation region conventionally used is the region surrounded by A1-B2-C1-D0. However, in the example described with reference to FIG. 6, the operation region becomes narrow. The pressure before operation of the hydraulic elevator, and
When both the temperatures are detected, and when the detected values are both low, that is, both the limit values PN and TN for preventing the negative pressure, the region is not used. In this case, the unused operation region is a region shown as a region R3 in FIG. 7, and the usable region is A0-B1-B2-B3-C0-D in FIG.
The area is surrounded by 0.

The elevator according to the embodiment of the present invention described above outputs the speed command of the car lower than the rated speed and outputs the speed command when the fluid pressure cylinder pressure and the fluid temperature before traveling are low. Can be used in a region indicated by R3, which is likely to be a negative pressure when is output at the rated speed. That is, conventionally, A0-B1-
According to an embodiment of the present invention, a hydraulic elevator that could only be used in an area surrounded by B2-B3-C0-D0 can be used up to an area surrounded by A0-B0-C0-D0. Become.

Therefore, similarly to the case described with reference to FIG. 5, the embodiment of the present invention can perform traveling control with a margin even when applied to a hydraulic elevator having a counterweight. The operation of the hydraulic elevator at this time is almost the same as that described with reference to FIG.

FIG. 8 is a flowchart for explaining a control operation in the case where control is performed by detecting only the pressure in the elevator according to the embodiment of the present invention. This will be described below.

First, the hydraulic cylinder pressure or the hydraulic pump pressure is detected, and this pressure value is compared with a preset limit pressure value (step 30). If the detected pressure value is higher than the limit pressure value, If the detected pressure value is lower than the limit pressure value, the speed command is lowered below the rated speed (step 31), and the car is controlled to run.

By this control, generation of an abnormal negative pressure on the suction side of the fluid pressure pump can be prevented. In addition, this control can be applied to both control in which the pressure detection is performed before and during traveling of the car.

FIG. 9 is a flowchart for explaining a control operation in a case where both the pressure and the temperature are detected and controlled in the elevator according to the embodiment of the present invention. This will be described below.

First, the pressure of the fluid pressure cylinder or the pressure of the fluid pressure pump is detected, and this pressure value is compared with a preset limit pressure value (step 40). If the detected pressure value is higher than the limit pressure value, The vehicle is caused to travel at a normal speed command (step 42). If the detected pressure value is lower than the limit pressure value, the detected value of the fluid temperature is compared with a preset limit temperature (step 41), and if the detected temperature value is higher than the preset limit temperature value, a normal The vehicle travels according to the speed command (step 42). If the detected temperature value is lower than the limit temperature value, the speed command is lowered from the rated speed (step 4).
3) The traveling control of the car is performed.

By this control, it is possible to prevent an abnormal negative pressure from being generated on the suction side of the fluid pressure pump. In addition, this control can be applied to both control in which the pressure detection is performed before and during traveling of the car.

The hydraulic elevator according to the above-described embodiment of the present invention has been described on the assumption that the rope is wound around the pulley provided on the upper part of the cylinder and the car is hung. The present invention can also be applied to a fluid pressure elevator having a structure in which a.

[0054]

As described above, according to the present invention, in a hydraulic elevator controlled by an inverter and a hydraulic elevator controlled by an inverter having a balance weight, the detected value of the pressure or the temperature is regulated during the descent operation. If there is a danger that a negative pressure may occur on the suction side of the fluid pressure pump below this value, the pump flow rate can be reduced by changing the speed command value to a speed lower than the rated speed. And a highly reliable hydraulic elevator capable of preventing failure of the hydraulic pressure elevator.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration example of a hydraulic elevator according to an embodiment of the present invention under inverter control.

FIG. 2 is a block diagram showing an example of the overall configuration of a hydraulic elevator according to an embodiment of the present invention under inverter control.

FIG. 3 is a diagram illustrating a descending operation of the hydraulic elevator according to the embodiment of the present invention.

FIG. 4 is a view for explaining another example of the descending operation of the hydraulic elevator according to the embodiment of the present invention.

FIG. 5 is a diagram for explaining an operation region in which a negative pressure during a descending operation traveling can be prevented by a detected value of a fluid pressure cylinder pressure and a fluid temperature.

FIG. 6 is a diagram for explaining another example of an operation region in which a negative pressure during traveling in a descending operation can be prevented based on detected values of a fluid pressure cylinder pressure and a fluid temperature.

FIG. 7 is a diagram for explaining still another example of an operation region in which a negative pressure during the descending operation traveling can be prevented based on the detected values of the fluid pressure cylinder pressure and the fluid temperature.

FIG. 8 is a flowchart illustrating a control operation in a case where control is performed by detecting only pressure in the elevator according to the embodiment of the present invention.

FIG. 9 is a flowchart illustrating a control operation in a case where control is performed by detecting both pressure and temperature in the elevator according to the embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 car 2 fluid cylinder 3 fluid pump 4 motor 5, 17 pulley 6, 18 rope 7 fluid pressure control valve 8 fluid tank 9, 10, 15 spring 11 temperature detector 16 counterweight 19 controller 20, 21 pressure detection Container 12-14 piping

Continued on the front page (72) Inventor Shigeto Kojima 2477 Takaba, Hitachinaka City, Ibaraki Prefecture Within Hitachi Car Engineering Co., Ltd.

Claims (7)

[Claims] A control device controls the number of revolutions of a hydraulic pump, thereby supplying or discharging a fluid passed through a hydraulic pressure control valve from a fluid tank to a hydraulic cylinder to reduce the speed of the hydraulic cylinder. In a hydraulic elevator that controls the traveling of a car by controlling, the detected value of the fluid pressure cylinder, fluid pressure pump, or fluid temperature before or during operation of the car in the descending direction is less than a specified value. A fluid pressure elevator characterized by limiting a speed command value of a car speed to a certain value smaller than a rated speed when the following condition is satisfied. 2. The speed of the hydraulic cylinder is controlled by controlling the number of revolutions of the hydraulic pump by a control device to supply or discharge the fluid passed through the hydraulic pressure control valve from the fluid tank to the hydraulic cylinder. In a hydraulic elevator that controls the traveling of the car by controlling, the detected value of the hydraulic cylinder pressure during operation of the car in the descending direction is running at the rated pressure and the hydraulic cylinder pressure at the time of stopping the car. A fluid pressure elevator characterized in that, when the pressure loss is equal to or less than the pressure loss of piping or the like, the speed command of the car is limited to a value lower than the rated speed. 3. The speed of the hydraulic cylinder is controlled by controlling the number of revolutions of the hydraulic pump by a controller to supply or discharge the fluid passed through the hydraulic pressure control valve from the fluid tank to the hydraulic cylinder. In the hydraulic elevator that controls the traveling of the car by controlling, the detected value of the pressure of the hydraulic pump during the driving operation of the car in the descending direction becomes equal to or less than a preset value slightly higher than the atmospheric pressure. A fluid pressure elevator wherein the speed command of the car is limited to a speed lower than a rated speed. 4. The speed of the hydraulic cylinder is controlled by controlling the number of revolutions of the hydraulic pump by a control device to supply or discharge the fluid passed through the hydraulic pressure control valve from the fluid tank to the hydraulic cylinder. In a hydraulic elevator that controls the traveling of the car by controlling, the detected value of the hydraulic cylinder pressure before the operation traveling of the car in the descending direction of the car is running at the hydraulic cylinder pressure at the time of stopping the car and the rated speed A fluid pressure elevator characterized by limiting the speed command of the car to a value lower than the rated speed when the difference between the pressure loss and the pressure loss of the piping or the like is equal to or less than the rated speed. 5. The speed of the hydraulic cylinder is controlled by controlling the number of revolutions of the hydraulic pump by a controller to supply or discharge the fluid passed through the hydraulic pressure control valve from the fluid tank to the hydraulic cylinder. In a hydraulic elevator that controls the traveling of the car by controlling, when the detected value of the hydraulic pump pressure before the driving traveling in the descending direction of the car becomes equal to or less than a preset value slightly higher than the atmospheric pressure, A fluid pressure elevator characterized by limiting a speed command of a car to a value lower than a rated speed. 6. A fluid temperature is detected, and when the detected temperature value is equal to or less than a preset value, the speed command of the car is limited to a value lower than the rated speed regardless of the magnitude of the detected pressure value. The hydraulic elevator according to any one of claims 2 to 5, wherein: 7. A fluid temperature is detected, and when the detected temperature value is equal to or less than a preset value and the detected pressure value is equal to or less than the set value, the speed command of the car is limited to a value lower than the rated speed. The hydraulic elevator according to any one of claims 2 to 5, wherein