High lift work device

Abstract

To suppress shocks.SOLUTION: A high lift work device 1 comprises: a hydraulic cylinder 4 that lifts a work table 3; an electromagnetic proportional valve 201 that controls the flow rate of hydraulic oil discharged from the hydraulic cylinder 4 or hydraulic oil supplied to the hydraulic cylinder 4; and a controller 50A that controls an operation of the electromagnetic proportional valve 201. The controller 50A generates, when an on / off signal used for operating / stopping the work table 3 is switched between on and off, a current command signal which is a control command signal of the electromagnetic proportional valve 201 by attenuating the on / off signal with a time constant T, and the time constant T is set in accordance with a load applied on the hydraulic cylinder 4.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an aerial work device. [Background technology]

[0002] Patent Document 1 discloses a technique for reducing stopping shock by demagnetizing an electromagnetic pilot valve with a delay corresponding to the time constant of a capacitor and resistor connected in parallel to the electromagnetic pilot valve. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 05-132247 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above technique, the time constant is fixed, so the stopping position varies depending on the load, which causes stress during operation.

[0005] The present invention has been made in view of such problems, and has an object to reduce the work-related stress of workers. [Means for solving the problem]

[0006] The present invention is characterized in that it comprises a fluid pressure actuator that raises and lowers a work platform, an electromagnetic proportional valve that controls the flow rate of working fluid discharged from the fluid pressure actuator or the flow rate of working fluid supplied to the fluid pressure actuator, and a controller that controls the operation of the electromagnetic proportional valve, wherein when an on / off signal used to operate and stop the work platform is switched between on and off, the controller generates a control command signal for the electromagnetic proportional valve by slowing the on / off signal using a time constant, and the time constant is set according to the load acting on the fluid pressure actuator.

[0007] According to this invention, the control command signal for the electromagnetic proportional valve is generated by softening the on / off signal using a time constant set according to the load on the fluid pressure actuator, so the work platform can be operated and stopped gradually at an appropriate rate according to the load. This makes it easier for the operator to stop the work platform in a similar position regardless of the magnitude of the load while suppressing shock.

[0008] Furthermore, the present invention is characterized in that the controller sets the time constant T based on the equation T=T0(1 / √(√A / √A0)), where A is the load on the fluid pressure actuator during operation or the working fluid pressure corresponding to the load, A0 is the reference load on the fluid pressure actuator or the reference working fluid pressure, and T0 is the reference time constant corresponding to the reference load or the reference working fluid pressure.

[0009] According to this invention, by using the above-mentioned formula discovered by the inventors through trial and error, the time constant T can be set so that the amount of overrun when the descending work platform does not stop immediately in response to a stop command but slowly decelerates with a first-order delay remains constant regardless of the load on the fluid pressure actuator or the working fluid pressure A corresponding to the load. Therefore, while suppressing shock, the operator can easily stop the work platform at a constant position regardless of the magnitude of the load.

[0010] The present invention is also characterized in that the work table has a plurality of stop positions, and the controller generates a stop command signal for the electromagnetic proportional valve according to a time constant based on a signal from an indicator capable of indicating the plurality of stop positions and a signal from a sensor capable of detecting the position of the work table before each of the plurality of stop positions, and controls the operation of the electromagnetic proportional valve based on the generated stop command signal at the same timing.

[0011] According to this invention, signals can be output at the same timing regardless of the load, and the workbench can be stopped at the same position. In other words, the same control (program) can be used, with only the time constant used being different depending on the load. [Effects of the Invention]

[0012] These inventions can reduce the work-related stress of workers. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic configuration diagram of a high-altitude work device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing a fluid pressure circuit of the fluid pressure control device. [Figure 3] FIG. 2 is a block diagram showing the main parts of a controller. [Figure 4] FIG. 10 is a diagram showing the change in height of the work platform when the lowering stops with a time constant according to the applied load. [Figure 5] FIG. 10 is a diagram showing a comparative example in which the time constant is constant regardless of the load. [Figure 6] FIG. 10 is a diagram illustrating a first application example of a controller according to a first modified example. [Figure 7] FIG. 10 is a diagram illustrating a second application example of the controller according to the first modified example. [Figure 8] FIG. 10 is a block diagram showing a main part of a controller according to a second modified example. [Figure 9] FIG. 10 is a diagram showing a work site of a high altitude work apparatus according to a third modified example. [Figure 10] FIG. 10 is a diagram showing a fluid pressure circuit of a fluid pressure control device according to a third modified example. [Figure 11] FIG. 11 is a block diagram showing a main part of a controller according to a third modified example. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0015] Fig. 1 is a schematic diagram of a high-altitude work apparatus 1. The high-altitude work apparatus 1 includes a base 2, a work platform 3 mounted on the base 2 so as to be able to rise and fall, a hydraulic cylinder 4 as a fluid pressure actuator for raising and lowering the work platform 3, a support member 5 mounted on the tip of a piston rod 4b of the hydraulic cylinder 4, a sheave 6 rotatably supported on the support member 5, a wire 7 whose both ends are fixed to the base 2 and the work platform 3 via the sheave 6, and a guide 8 that guides the work platform 3 in the up and down direction. Note that one end of the wire 7 fixed to the base 2 is hidden behind the hydraulic cylinder 4 in Fig. 1.

[0016] The base 2 is a cart that makes the aerial work equipment 1 portable. When viewed from the side, the base 2 is U-shaped with the front and rear portions extending upward, and the floor 3a of the work platform 3 is located in the center of the base 2. The rear portion of the base 2 is shaped like a housing and houses the fluid pressure control device 10.

[0017] The workbench 3 has front and rear walls 3b, 3c that extend upward from the floor 3a. A platform 3d extending forward is provided on top of the front wall 3b. The rear wall 3c extends higher than the front wall 3b and then rearward. The portion extending rearward forms a guide section 3e that is guided by a guide 8. An openable safety bar 3f is provided on the rear wall 3c to protect a user standing on the workbench 3.

[0018] The hydraulic cylinder 4 is provided on the base 2 and stands on the upper rear surface of the base 2. The hydraulic cylinder 4 has a cylinder tube 4a, a piston rod 4b inserted into the cylinder tube 4a with one end (upper side in Figure 1) extending outside the cylinder tube 4a, and a piston 4c provided at the end (lower end in Figure 1) of the piston rod 4b and sliding along the inner circumferential surface of the cylinder tube 4a.

[0019] When the hydraulic cylinder 4 extends, the sheave 6 rises, the length of the wire 7 between the sheave 6 and the base 2 increases, and the length of the wire 7 between the sheave 6 and the work table 3 decreases, causing the work table 3 to rise. When the hydraulic cylinder 4 contracts, the length of the wire 7 between the sheave 6 and the base 2 decreases, and the length of the wire 7 between the sheave 6 and the work table 3 increases, causing the work table 3 to descend. The work table 3 is guided in the vertical direction by a guide 8, and the supply and discharge of hydraulic oil (working fluid) to the hydraulic cylinder 4 is controlled by a fluid pressure control device 10.

[0020] Fig. 2 is a diagram showing a fluid pressure circuit of the fluid pressure control device 10. Note that Fig. 2 shows the workbench 3 and the hydraulic cylinder 4 in a simplified form.

[0021] The fluid pressure control device 10 includes a tank 11, a pump 12 that sucks hydraulic oil from the tank 11, a motor 13 that drives the pump 12, a first flow path 14 that connects the tank 11 to an inlet 12a of the pump 12, a second flow path 15 that connects a discharge port 12b of the pump 12 to a bottom-side chamber 4d of the hydraulic cylinder 4, a check valve 16 that is provided in the second flow path 15 and allows hydraulic oil to flow from the pump 12 toward the bottom-side chamber 4d and blocks hydraulic oil from flowing in the opposite direction, an electromagnetic switching valve 17 that is provided in the second flow path 15 downstream of the check valve 16 and connects and blocks the second flow path 15, and a valve 18 that is provided in the second flow path 15 downstream of the check valve 16 and controls the operation of the second flow path 15. The hydraulic system includes a variable throttle 18 that throttles the flow rate of the hydraulic oil, a third flow path 19 that branches off from the second flow path 15 downstream of the variable throttle 18 and communicates with the tank 11, a pressure compensating electromagnetic proportional flow control valve 20 that is provided in the third flow path 19 and controls the flow rate of the hydraulic oil discharged from the hydraulic cylinder 4 while performing pressure compensation, a fourth flow path 21 that communicates with the second flow path 15 upstream of the check valve 16 and communicates with the third flow path 19 downstream of the pressure compensating electromagnetic proportional flow control valve 20, a relief valve 22 that is provided in the fourth flow path 21 and returns the hydraulic oil from the second flow path 15 through the fourth flow path 21 to the tank 11, and filters 23 that are provided in the first flow path 14 and the second flow path 15 and filter the hydraulic oil.

[0022] The solenoid directional control valve 17 has a first position (the state shown in FIG. 2) in which the second flow path 15 is blocked (one-way blocked), and a second position in which the second flow path 15 is open. In the first position, the solenoid directional control valve 17 functions as a check valve that blocks the flow of hydraulic oil from the pump 12 toward the bottom-side chamber 4d of the hydraulic cylinder 4, while allowing the flow of hydraulic oil from the bottom-side chamber 4d toward the pump 12.

[0023] The pressure compensated electromagnetic proportional flow control valve 20 has an electromagnetic proportional valve 201 that controls the flow rate of hydraulic oil discharged from the hydraulic cylinder 4, and a pressure compensating valve 202 that is provided upstream of the electromagnetic proportional valve 201 and suppresses changes in the flow rate of hydraulic oil due to the pressure difference between before and after the electromagnetic proportional valve 201.

[0024] The solenoid proportional valve 201 has a first position (the state shown in FIG. 2) in which the third flow path 19 is blocked (one-way blocked), and a second position in which the third flow path 19 is open. In the first position, the solenoid proportional valve 201 functions as a check valve that blocks the flow of hydraulic oil from the bottom-side chamber 4d of the hydraulic cylinder 4 toward the tank 11, while allowing the flow of hydraulic oil from the tank 11 toward the bottom-side chamber 4d. In the second position, the solenoid proportional valve 201 functions as a throttle.

[0025] The pressure compensating valve 202 has a first position (the state shown in FIG. 2) in which the third flow path 19 is in a communicating state, and a second position in which the third flow path 19 is in a blocked state. The pressure compensating valve 202 has ports 202a and 202b that introduce pressure acting on both ends of the spool, and the pressure before and after the electromagnetic proportional valve 201 is introduced to the ports 202a and 202b. In the pressure compensating valve 202, the position is switched by the movement of the spool in accordance with the pressure difference before and after the electromagnetic proportional valve 201, thereby adjusting the flow rate of the hydraulic oil to be approximately constant.

[0026] In the pressure compensated electromagnetic proportional flow control valve 20, the electromagnetic proportional valve 201 is configured as an electromagnetic proportional flow control valve that functions as a throttle in the second position. For this reason, the pressure compensating valve 202 is provided as a pressure compensating valve common to the throttle and the electromagnetic proportional flow control valve, so there is no need to provide separate pressure compensating valves for the throttle and the electromagnetic proportional flow control valve. Furthermore, because the electromagnetic proportional valve 201 functions as a check valve in the first position, it has a higher ability to block hydraulic oil than a spool valve, and there is no need to provide a separate poppet-type valve such as the solenoid directional control valve 17 that switches between communication and cut-off before the electromagnetic proportional valve 201.

[0027] The solenoid directional control valve 17 and the pressure compensated solenoid proportional flow control valve 20 are electrically connected to a controller 50A, and their operation is controlled by the controller 50A. The solenoid proportional valve 201 of the pressure compensated solenoid proportional flow control valve 20 is electrically connected to the controller 50A, and the operation of the pressure compensated solenoid proportional flow control valve 20 is controlled by controlling the operation of the solenoid proportional valve 201 with the controller 50A.

[0028] The controller 50A is a control device for the fluid pressure control device 10, and is composed of a microcomputer equipped with a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and I / O interface (Input / Output Interface). The RAM stores data for CPU processing, the ROM stores the CPU's control program and other programs in advance, and the I / O interface is used for inputting and outputting information to and from connected devices. The operation of the solenoid directional control valve 17 and the pressure compensated solenoid proportional flow control valve 20 is controlled by operating the CPU, RAM, and other programs in accordance with the programs stored in the ROM.

[0029] The controller 50A is programmed to be able to execute at least the processes necessary to execute the control according to this embodiment. The controller 50A may be composed of multiple microcomputers. The controller 50A may be configured as a single device, or may be divided into multiple devices and configured to perform distributed processing of the control according to this embodiment among the multiple devices.

[0030] A signal is input to the controller 50A from the lift switch 30A, which is an indicator. The lift switch 30A is an operation switch for raising and lowering the workbench 3, and is provided on the workbench 3. The controller 50A can also be provided on the workbench 3.

[0031] The lift switch 30A has an up push button switch 30a as an up instruction section and a down push button switch 30b as a down instruction section, and the lift switch 30A inputs to the controller 50A an up side on / off signal that is turned on when the up push button switch 30a is pressed and turned off when the up push button switch 30a is not pressed, and a down side on / off signal that is turned on when the down push button switch 30b is pressed and turned off when the down push button switch 30b is not pressed.

[0032] The controller 50A controls the operation of the solenoid directional control valve 17 based on the on / off signal for the lifting side. When the on / off signal for the lifting side is on, the controller 50A excites the solenoid directional control valve 17 to bring it into communication (second position). This allows hydraulic oil to be supplied from the pump 12 to the bottom-side chamber 4d of the hydraulic cylinder 4 through the solenoid directional control valve 17, so that the hydraulic cylinder 4 can be extended to lift the work platform 3. In addition, because the hydraulic oil is supplied to the bottom-side chamber 4d through the variable orifice 18, the work platform 3 can be lifted at an appropriate speed according to the degree of restriction of the variable orifice 18.

[0033] When the on / off signal on the ascending side is off, the controller 50A de-energizes the solenoid directional control valve 17 to function as a check valve (first position). This prevents hydraulic oil from being supplied from the pump 12 to the bottom-side chamber 4d of the hydraulic cylinder 4 through the solenoid directional control valve 17, allowing the work platform 3 to stop.

[0034] The controller 50A controls the operation of the solenoid proportional valve 201 based on the descending-side on / off signal. The descending-side on / off signal is time-constant controlled by the controller 50A as described below, and when switched between on and off, the signal changes transiently due to the time constant control, and then becomes steadily on (steady on) or steadily off (steady off).

[0035] When the lowering-side on / off signal is steadily on, the controller 50A excites the electromagnetic proportional valve 201 to function as a throttle (second position). This allows hydraulic oil to be discharged from the bottom-side chamber 4d of the hydraulic cylinder 4 to the tank 11 through the electromagnetic proportional valve 201, thereby contracting the hydraulic cylinder 4 and lowering the work platform 3. In addition, because the hydraulic oil is discharged to the tank 11 through the electromagnetic proportional valve 201, which functions as a throttle, the work platform 3 can be lowered at an appropriate speed according to the degree of throttling of the electromagnetic proportional valve 201, which functions as a throttle.

[0036] When the downward-side on / off signal is steadily off, the controller 50A de-energizes the electromagnetic proportional valve 201 to function as a check valve (first position). This prevents hydraulic oil from being discharged from the bottom-side chamber 4d of the hydraulic cylinder 4 to the tank 11 through the electromagnetic proportional valve 201, allowing the work platform 3 to stop.

[0037] When the falling-side on / off signal is switched between on and off, it is time-constant controlled by the controller 50A as will be described next.

[0038] FIG. 3 is a block diagram showing the main components of the controller 50A. The controller 50A includes an on / off signal acquisition unit 50a that acquires an on / off signal from the lift switch 30A, a current command signal generation unit 50b that generates a current command signal as a control command signal for the solenoid proportional valve 201 by smoothing the on / off signal acquired by the on / off signal acquisition unit 50a based on a time constant T, and a current driver 50c that generates a solenoid current for controlling the solenoid proportional valve 201 based on the current command signal generated by the current command signal generation unit 50b and a fed-back solenoid current. Note that the on / off signal acquisition unit 50a and other components of the controller 50A shown in FIG. 3 are virtual units representing the functions of the controller 50A and do not represent physical entities. Furthermore, the above functions are only a part of the control executed by the controller 50A, and the controller 50A also executes control related to other functions as needed.

[0039] The on / off signal acquiring unit 50a acquires a descending on / off signal, and the acquired descending on / off signal is input to the current command signal generating unit 50b. The time constant T is also input to the current command signal generating unit 50b from the time constant setting switch 51, and the current command signal generating unit 50b generates a current command signal by dulling the input on / off signal using the input time constant T. Dulling means delaying the peak by gradually changing a rectangular signal that changes stepwise (step input, impulse input), and the on / off signal dulled by the time constant T has a first-order lag response.

[0040] The time constant setting switch 51 is a dial switch and is provided on the workbench 3. By setting the time constant T using the time constant setting switch 51, the user can set the gradualness of the movement of the workbench 3 when it starts to descend (operate) and when it stops (when it starts to stop).

[0041] For example, when a user descends the work platform 3 carrying a heavy load, setting the time constant T to a larger value than when there is no load can reduce the acceleration shock caused by the work platform 3 starting to descend suddenly and the deceleration shock caused by the work platform 3 suddenly stopping. Therefore, by setting the time constant T using the time constant setting switch 51, the time constant T (time constant T1) can be set according to the load acting on the hydraulic cylinder 4. For example, the time constant setting switch 51 can be provided with a scale that indicates, at multiple positions, the load on the hydraulic cylinder 4 corresponding to the time constant T that should be set from the perspective of suppressing shock. The scale can display, for example, multiple numerical values ​​in kilograms. Depending on the mode of use of the aerial work apparatus 1, the scale may display, for example, the number of occupants or the weight of the load, or, if the weight of the load is known, the number of pieces of load.

[0042] When the input on-off signal is switched from off to on, the current command signal generating unit 50b dulls the on-off signal on the decreasing side based on the input time constant T1. As a result, the current command signal does not increase in a stepwise manner, but gradually increases with a first-order lag. Also, when the input on-off signal is switched from on to off, the current command signal generating unit 50b dulls the on-off signal on the decreasing side based on the input time constant T1. As a result, the current command signal does not decrease in a stepwise manner, but gradually decreases with a first-order lag. The dulled on-off signal can be generated as a current command signal by conversion. The current command signal generated by the current command signal generating unit 50b is input to the current driver 50c.

[0043] The current driver 50c generates a solenoid current (control value) so that the solenoid current (actual value) of the solenoid proportional valve 201 becomes a target value of current given by a command through PWM (Pulse Width Modulation) control. The current driver 50c generates a solenoid current (control value) based on the deviation between the input current command signal (target value) and the fed-back solenoid current (actual value) so that the solenoid current (actual value) follows the current command signal (target value). The generated solenoid current is input to the solenoid proportional valve 201.

[0044] As a result, the flow rate of hydraulic oil discharged from the hydraulic cylinder 4 is controlled in accordance with the time constant T1. Therefore, the movement of the work platform 3 when it starts to descend and when it stops can be made gentler to an appropriate degree according to the load acting on the hydraulic cylinder 4, thereby suppressing shock. In addition, by appropriately setting the time constant T1 according to the load on the hydraulic cylinder 4 using the time constant setting switch 51, the amount of overrun OR (see FIG. 10) can be made approximately the same, as will be described later. This makes it easier for the worker to stop the work platform 3 in a similar position regardless of the magnitude of the load, reducing work-related stress.

[0045] Note that instead of the solenoid directional control valve 17 and the variable throttle 18 (see FIG. 2), a valve similar to the pressure compensating solenoid proportional flow control valve 20 may be provided to provide a solenoid proportional valve (similar to the solenoid proportional valve 201) that controls the flow rate of hydraulic oil supplied to the hydraulic cylinder 4, and the on / off signal on the lifting side may be rounded by the time constant T1 to generate a current command signal for controlling the solenoid proportional valve. This prevents sudden operation and sudden stopping of the work platform 3 when it starts to lift and when it stops, thereby reducing shock. Furthermore, it becomes easier for the worker to stop the work platform 3 in a similar position regardless of the magnitude of the load, reducing stress during work.

[0046] (First Modification) In the above embodiment, the time constant T is set using the time constant setting switch 51. In this first modified example, the method for setting the time constant T differs from that in the above embodiment.

[0047] If the on / off signal is softened by the time constant T, even if a stop command is issued by turning off the down push button switch 30b at the desired position to stop the work platform 3, the work platform 3 will not stop immediately but will overrun. On the other hand, the amount of overrun OR (see FIG. 10), which is the distance from when a stop command is issued until the work platform 3 stops, can be adjusted by the time constant T, but the greater the load on the hydraulic cylinder 4, the greater the amount of overrun OR of the descending work platform 3. For this reason, if the amount of overrun OR can be kept constant regardless of the load, the work platform 3 can be stopped at approximately the same position with the same operation timing regardless of the magnitude of the load while suppressing shock within an allowable range, improving workability.

[0048] Based on this knowledge, the inventors have found, through trial and error, the following equation for determining the time constant T that keeps the amount of overrun OR constant regardless of the magnitude of the load on the hydraulic cylinder 4. [Number 1] T=T0(1 / √(√A / √A0)) A is the load W of the hydraulic cylinder 4 during work as a load element or the operating oil pressure P corresponding to the load, A0 is the reference load W0 or reference operating oil pressure P0 of the hydraulic cylinder 4 as a reference load element, and T0 is the reference time constant corresponding to the reference load load W0 or reference operating oil pressure P0 (the time constant T when the load load W is the reference load load W0 or when the operating oil pressure P is the reference operating oil pressure P0). The load load W or operating oil pressure P during work is the load load or operating oil pressure when a user is on the work platform 3 with luggage.

[0049] The reference load W0 is set in advance together with the reference time constant T0. For example, the reference load W0 is set to the mass of an empty work platform 3 with no person on board: 500 kg, and the reference time constant T0, which is determined to be an appropriate amount of overshoot corresponding to the reference load W0, is set to 0.5, thereby setting these in advance. The reference working oil pressure P0 is a reference load element that can be used in place of the reference load W0, and is expressed by the following equation 2, where D is the bore diameter of the hydraulic cylinder 4. A similar relationship also holds between the working oil pressure P during work and the applied load W, as shown in the following equation 3. Therefore, the following equation 4 can be obtained from equations 2 and 3. [Number 2] P0 = W0 × 9.80665(D 2 ×π / 4) W0 is, for example, the mass of an empty workbench 3 on which no one is standing. [Number 3] P=W×9.80665(D 2 ×π / 4) It should be noted that W is, for example, the mass of the workbench 3 when a person is sitting on it. [Number 4] P / P0=W / W0

[0050] According to equation 4, it can be seen that in equation 1, the time constant T can be calculated by a load-based calculation using the applied load W as the load element A, or by a pressure-based calculation using the hydraulic oil pressure P as the load element A.

[0051] In the first variant, the controller 50B (see Figures 6 and 7) sets the time constant T (time constant T2) (see Figures 6 and 7) when lowering the workbench 3 based on the equation T = T0 (1 / √(√A / √A0)) in equation 1.

[0052] By setting the time constant T2 in this manner, the overrun amount OR of the work platform 3, which does not immediately stop in response to a stop command but gradually decelerates with a first-order delay, becomes approximately the same regardless of the load on the hydraulic cylinder 4. For example, according to Equation 1, when the reference load W0 is 500 kg and the reference time constant T0 is 0.5, if the load W is 700 kg, the time constant T2 is set to 0.4597, and if the load W is 1500 kg, the time constant T is set to 0.3799. This makes the overrun amount OR approximately the same when the load W is 700 kg and 1500 kg. Note that Equation 1 may also be used for the time constant T when raising the work platform 3. In this case, as described above, a valve similar to the pressure-compensated electromagnetic proportional flow control valve 20 can be provided in place of the solenoid-operated directional control valve 17 and the variable orifice 18 (see FIG. 2).

[0053] Figure 4 shows the change in height (stroke position of hydraulic cylinder 4) of the work platform 3 when the descent stops depending on the load W, and Figure 5 shows a comparative example in which the time constant T is kept constant (0.5) regardless of the load W.

[0054] 4 and 5, the solid lines show the case where the load W is 500 kg and the time constant T is zero. In this case, when the on / off signal for the lowering side of the work platform 3 turns off at time t1, the work platform 3 immediately stops and the height becomes constant, causing a deceleration shock. Note that even when the time constant T is zero, there is a delay in the hydraulic response, etc., so a slight overrun occurs after time t1 as shown in the figure.

[0055] As shown in FIG. 5, in the comparative example where the time constant T is set to 0.5 regardless of the load weight W, as the load weight W increases from 500 kg to 700 kg to 1500 kg, the height at which the work platform 3 stops decreases, resulting in variations in the stopping position of the work platform 3. As a result, the operator riding on the work platform 3 has to adjust the work platform 3 to the desired stopping position or overcome steps, causing stress during work. In contrast, as shown in FIG. 4, by changing the time constant T2 to time constants T21, T22, and T23 according to the load weight W, the stopping position of the work platform 3 becomes approximately the same regardless of the load weight W, and the amount of overrun OR becomes similar. This allows the work platform 3 to be stopped at a similar position while suppressing shock. As a result, the operator riding on the work platform 3 can easily stop the work platform 3 at the desired stopping position without feeling any shock, reducing stress during work and improving workability.

[0056] Next, an application example of the controller 50B according to the first modification will be described.

[0057] (First application example) 6 is a diagram showing a controller 50BA that is a first application example of the controller 50B according to the first modified example. The controller 50BA (controller 50B) according to the first application example further includes a calculation unit 50d that calculates a time constant T2 based on the formula 1, and differs from the controller 50A (see FIG. 3) in that it dulls the descending on / off signal based on the time constant T2.

[0058] Load parameters are input to the calculation unit 50d from a communication terminal 60 communicatively connected to the calculation unit 50d, and the communication terminal 60 is configured to be able to set and input the load parameters. The load parameters include load elements of the hydraulic cylinder 4, such as the mass of the work platform 3, the weight of the occupant, and the mass of luggage, as well as the cylinder bore diameter of the hydraulic cylinder 4. The load when a user is on the work platform 3 without luggage (the sum of the mass of the work platform 3 and the weight of the occupant) is set as the reference load load W0. When the calculation unit 50d performs a pressure-based calculation using Equation 1, the cylinder bore diameter can be used to calculate the reference operating oil pressure P0 from the reference load load W0 based on Equation 2. Hereinafter, the case when a user is on the work platform 3 without luggage will also be simply referred to as an empty case.

[0059] The calculation unit 50d further receives a reference time constant T0 from a reference time constant setting switch 52. The reference time constant setting switch 52 is a switch for setting the reference time constant T0 according to the reference load weight W0, and is configured as a dial switch similar to the time constant setting switch 51 described above. The reference time constant setting switch 52 is provided on the workbench 3 together with a reference characteristic setting switch 53 for reading the reference time constant T0 and the reference load weight W0 into the calculation unit 50d.

[0060] The user sets the reference time constant T0 according to the reference load weight W0 using the reference time constant setting switch 52. Specifically, the user can determine and set the reference time constant T0 by dialing in the reference time constant T0 temporarily and then checking whether the overrun amount OR is within the allowable range and whether the shock is at an allowable level when the lowering of the work platform 3 is stopped in an unloaded state (i.e., a loaded state with the reference load weight W0).

[0061] When the reference characteristic setting switch 53 for reading, which is configured as a push button switch, is turned on, the reference time constant T0 and the reference load weight W0 are read into the calculation unit 50d from the reference time constant setting switch 52 and the communication terminal 60. The calculation unit 50d can be configured in advance to perform load-based calculations or pressure-based calculations using Equation 1, and when the calculation unit 50d performs load-based calculations, the reference load weight W0 is read from the communication terminal 60. When the calculation unit 50d performs pressure-based calculations, the reference working oil pressure P0 can be calculated by additionally reading the cylinder bore diameter from the communication terminal 60. The reference working oil pressure P0 may be calculated by the communication terminal 60, or when the calculation unit 50d performs pressure-based calculations, the reference working oil pressure P0 may be read in instead of the reference load weight W0.

[0062] The calculation unit 50d also reads the luggage mass from the communication terminal 60. The luggage mass is known in advance, and the sum of the mass of the work platform 3, the occupant's weight, and the luggage mass constitutes the load weight W. When pressure-based calculations are performed by the calculation unit 50d, the operating oil pressure P can be determined using the cylinder bore diameter. Therefore, when the reference characteristic setting switch 53 for reading is turned on, the calculation unit 50d obtains the reference time constant T0, the reference load weight W0, and the load weight W (or the reference time constant T0, the reference operating oil pressure P0, and the operating oil pressure P), and can calculate the time constant T2 based on equation 1.

[0063] The time constant T2 calculated by the calculation unit 50d is input to the current command signal generation unit 50b, which generates a current command signal by rounding the on / off signal on the descending side based on the time constant T2, thereby making it possible to keep the overrun amount OR at the same level regardless of the load.

[0064] In the first application example, the mass of the cargo is known in advance as described above, and therefore the first application example is suitable for unloading a plurality of identical cargoes, for example, as described below.

[0065] In this case, the user first sets the reference time constant T0 using the reference time constant setting switch 52, inputs the reference load W0 and the previously determined luggage mass into the communication terminal 60, and turns on the reference characteristic setting switch 53. This sets the time constant T2 according to the load on the hydraulic cylinder 4 during work, i.e., the time constant T2 reflecting the luggage mass.

[0066] Next, the user gets on the work platform 3 and turns on the lift push button switch 30a, raising the work platform 3 while it is empty. The user also turns off the lift push button switch 30a at the height at which the user wants to pick up the luggage, stopping the work platform 3, and then picks up the luggage.

[0067] When the work platform 3 is raised, the load of the hydraulic cylinder 4 acts in the direction opposite to the direction in which the work platform 3 is raised, and therefore the behavior of the work platform 3 when it starts and stops operating differs from when it is lowered. For this reason, when the work platform 3 is raised, for example, in a configuration in which a valve similar to the pressure compensated electromagnetic proportional flow control valve 20 is used instead of the solenoid directional control valve 17, shock can be suppressed by applying the control of the controller 50A (see FIG. 3) to a solenoid proportional valve similar to the solenoid proportional valve 201 and dulling the on / off signal on the rise side based on the time constant T1.

[0068] Next, while the user is standing on the work platform 3 with the baggage he or she has picked up, he or she turns on the descent push button switch 30b to lower the work platform 3. When the work platform 3 starts to lower, the on / off signal on the descent side when switching from steady-off to steady-on is softened by the time constant T2. This prevents the work platform 3 from suddenly lowering at the start of descent, causing an acceleration shock.

[0069] Next, the user turns off the down push button switch 30b according to the height at which the load is to be lowered, stopping the work platform 3. When the work platform 3 is stopped, the on / off signal for the down side, which switches from steady-on to steady-off, is softened by the time constant T2. This prevents the work platform 3 from stopping suddenly and causing deceleration shock when it is stopped. In addition, because the load mass is reflected in the time constant T2, the overrun amount OR is approximately the same as when the load is empty, and the work platform 3 can be stopped at approximately the same position. After the user has lowered the load from the work platform 3, they can unload multiple identical loads by repeating the same operation.

[0070] Thus, according to the first application example, it is possible to suppress acceleration shocks and deceleration shocks when the workbench 3 is lowered, and it is also possible to easily stop the workbench 3 at a desired position, thereby reducing stress during work.

[0071] (Second application example) 7 is a diagram showing a controller 50BB that is a second application example of the controller 50B according to the first modified example. The controller 50BB according to the second application example differs from the controller 50BA according to the first application example (see FIG. 6) in that it further includes a detection unit 50e that detects the reference working oil pressure P0 and the working oil pressure P based on signals from the pressure sensor 41, and a calculation unit 50d that calculates a time constant T2 based on the reference working oil pressure P0 and the working oil pressure P detected by the detection unit 50e.

[0072] The pressure sensor 41 detects the hydraulic oil pressure in the bottom-side chamber 4d of the hydraulic cylinder 4, and the detected hydraulic oil pressure is input to the detection unit 50e. A signal from a reference characteristic setting switch 53 for reading is also input to the detection unit 50e. When the user turns on the reference characteristic setting switch 53 in an unloaded state, the detection unit 50e detects the hydraulic oil pressure input from the pressure sensor 41 at that time as the reference hydraulic oil pressure P0 and inputs it to the calculation unit 50d.

[0073] After detecting the reference hydraulic pressure P0, the detection unit 50d inputs the hydraulic pressure from the pressure sensor 41 directly to the calculation unit 50d, and the hydraulic pressure detected by the pressure sensor 41 is input to the calculation unit 50d in real time as the hydraulic pressure P. In this case, the hydraulic pressure P includes the hydraulic pressure when the vehicle is unladen (i.e., the reference hydraulic pressure P0). However, according to Equation 1, the reference time constant T0 is simply set as the time constant T2, so there is no need to distinguish between cases with and without luggage. Alternatively, the detection unit 50d may process the hydraulic pressure input from the pressure sensor 41 as appropriate and input the processed hydraulic pressure to the calculation unit 50d as the hydraulic pressure P. The calculation unit 50d calculates the time constant T2 based on the hydraulic pressure P input from the detection unit 50e through a pressure-based calculation using Equation 1.

[0074] In this way, the controller 50BB according to the second application example can set the time constant T2 based on the signal from the pressure sensor 41, so similar to the first application example, acceleration shocks and deceleration shocks when the work platform 3 is lowered can be suppressed, and the work platform 3 can be easily stopped at the desired position. Furthermore, in the second application example, the hydraulic pressure P can be detected in real time, so even when multiple loads of different weights are being unloaded, the time constant T2 can be appropriately set according to the weight of each load. Therefore, even if the weights of the loads differ, the work platform 3 can be stopped at the desired position by keeping the overrun amount OR at approximately the same, thereby reducing stress during work.

[0075] The controller 50BB may be configured to include a load cell capable of detecting the applied load acting on the hydraulic cylinder 4, and to calculate the time constant T2 based on the signal from the load cell instead of the signal from the pressure sensor 41. This allows the applied load W to be detected in real time and the time constant T2 to be set, even when performing load-based calculations.

[0076] (Second Modification) Fig. 8 is a block diagram showing the main components of a controller 50C according to the second modified example. The controller 50C according to the second modified example differs from the controller 50B according to the first modified example in that it is configured to perform shockless landing, as described below. Note that Fig. 8 shows the second modified example using the controller 50BA according to the first application example (see Fig. 6) as an example, but similar modifications can also be applied to the controller 50BB according to the second application example (see Fig. 7).

[0077] In the second modified example, a position sensor 42 capable of detecting the position of the piston 4c of the hydraulic cylinder 4 is installed in the cylinder tube 4a of the hydraulic cylinder 4. The position sensor 42 is a magnetic proximity sensor that is turned on when it detects a magnet M installed on the piston 4c. By detecting the position of the piston 4c, the position sensor 42 detects the position of the workbench 3 connected to the piston 4c, and a signal from the position sensor 42 is input to the controller 50C.

[0078] The controller 50C has an AND gate 50f that outputs an on signal as a trigger signal when an on signal from the on / off signal acquisition unit 50a and an on signal from the position sensor 42 are input, a shockless grounding signal output unit 50g that outputs a current command signal (shockless grounding signal) that gradually decreases from a current command signal for a steady on state to a current command signal for a steady off state when an on signal from the AND gate 50f is input, and a switching unit 50h that switches the current command signal to be input to the current driver 50c from the current command signal generated by the current command signal generation unit 50b to the shockless grounding signal output by the shockless grounding signal output unit 50g when an on signal from the AND gate 50f is input.

[0079] Shockless touchdown means that the work platform 3 is stopped just before the base 2 (see FIG. 1), which serves as a lower limit mechanical stopper for the work platform 3, to avoid shock due to collision with the base 2, and the profile (profile of the amount of current flow) of the shockless touchdown signal output by the shockless touchdown signal output unit 50g is set in advance. The position sensor 42 is provided so as to detect the piston 4c at a position higher than the position of the piston 4c when the work platform 3 is in contact with the base 2. The position sensor 42 is provided at a height that allows a sufficient margin so that the work platform 3, which is stopped based on the shockless touchdown signal, will not come into contact with the base 2, regardless of the load on the hydraulic cylinder 4.

[0080] When attempting to lower the workbench 3 to just before the base 2, if the timing for turning off the descent push button switch 30b is delayed, the workbench 3 may collide with the base 2, causing a shock. In the second modified example, even if the descent push button switch 30b remains on, when the position sensor 42 detects the piston 4c and turns on, an on signal from the AND gate 50f is input to the shockless ground signal output unit 50g and the switching unit 50h, and the shockless ground signal is input to the current driver 50c.

[0081] As a result, even if the down push button switch 30b remains on, the work platform 3 can be stopped in front of the base 2 by shockless landing, and shock due to collision with the base 2 can be avoided.

[0082] (Third Modification) Fig. 9 is a diagram showing a work site of the aerial work apparatus 1 according to the third modified example. Fig. 10 is a diagram showing a fluid pressure circuit of the fluid pressure control device 10 according to the third modified example. Fig. 11 is a block diagram showing the main parts of a controller 50D according to the third modified example.

[0083] As shown in Fig. 9, in the third modified example, the aerial work device 1 is used to unload goods from a multi-story (multiple-tiered) store shelf 100 on the first to fifth floors (first to fifth tiers). A plurality of items are stored on the store shelf 100 on the first to fifth floors. The multiple items may be the same or different.

[0084] From the first floor, it is possible to pick up luggage without using the aerial work device 1. On the second to fifth floors, the work platform 3 is stopped so that users can pick up luggage. The work platform 3 also stops near the base 2 (ground stopping position) so that users can get on and off and unload luggage. For this reason, the work platform 3 has predetermined ground stopping positions where it will stop, and multiple stopping positions S (see Figure 10) corresponding to the second to fifth floors.

[0085] When the work platform 3 has multiple stop positions S, if the work platform 3 is raised or lowered by operating the above-mentioned lift switch 30A (see FIG. 2), the work platform 3 stops when the lift switch 30A is turned off, so the work platform 3 must be stopped at the same height multiple times, and if the stop position shifts, adjustment is required, which results in poor work efficiency. In the example shown in FIG. 9, the work platform 3 has multiple stop positions S2 to S5 in addition to stop position S1, so the work platform 3 must be stopped at the same height multiple times more frequently each time work is performed, which increases stress. For this reason, in the third modified example, the aerial work equipment 1 is configured as described below.

[0086] 10, a plurality of ascent position sensors 431 to 434 are provided on the cylinder tube 4a of the hydraulic cylinder 4 for stop positions S2 to S5, and a plurality of descent position sensors 441 to 444 are provided for stop positions S1 to S4. Each of the plurality of ascent position sensors 431 to 434 and the plurality of descent position sensors 441 to 444 is configured as a magnetic proximity sensor, similar to the above-mentioned position sensor 42 (see FIG. 8), and detects the position of the piston 4c, thereby detecting the position of the workbench 3.

[0087] The multiple ascent position sensors 431 to 434 are capable of detecting the position of the work platform 3 in front of each of the multiple stop positions S in the direction in which the work platform 3 is ascending. The multiple descent position sensors 441 to 444 are capable of detecting the position of the work platform 3 in front of each of the multiple stop positions S in the direction in which the work platform 3 is descending. For example, in the case of the ascent position sensor 431, the position slightly lower than stop position S2 is the nearer position, and in the case of the descent position sensor 441, the position slightly higher than stop position S1 is the nearer position.

[0088] The front position of each of the multiple lowering position sensors 441 to 444 is set based on the overrun amount OR of the work platform 3. The overrun amount OR is made to be approximately the same regardless of the load on the hydraulic cylinder 4 by the time constant T2, so it is possible to set such a front position for each sensor. The front position of each of the multiple lowering position sensors 441 to 444 is set to, for example, a position equal to or greater than the overrun amount OR, which is made to be approximately the same regardless of the load on the hydraulic cylinder 4 by the time constant T2. Note that instead of the multiple raising position sensors 431 to 434 and the multiple lowering position sensors 441 to 444, stroke sensors, for example, may be used.

[0089] When the work platform 3 is raised, in a configuration in which a valve similar to the pressure compensated electromagnetic proportional flow control valve 20 is used instead of the solenoid directional control valve 17, the on / off signal on the lifting side can be softened based on the time constant T1 by applying the control of the controller 50A (see FIG. 3) to a solenoid proportional valve similar to the solenoid proportional valve 201. To prevent overrun of the work platform 3 caused by softening the on / off signal on the lifting side, for example, by setting the front position of each of the multiple lift position sensors 431 to 434 according to the state in which a user is on the work platform 3 with the heaviest load known in advance (that is, the state in which overrun is least likely to occur), the position of the work platform 3 can be detected by each sensor.

[0090] In the third modified example, instead of the lift switch 30A (see FIG. 2), a lift switch 30B is used, which has a selection switch 30c as an up / down instruction unit and 1st floor push button switches 30d to 5th floor push button switches 30h as stop position instruction units. Note that the 1st floor (1st floor of the 1st floor push button switch 30d) for the work platform 3 means the stop position S1 as a ground stop position.

[0091] The selection switch 30c is composed of a change-over switch that can selectively instruct the work platform 3 to rise, fall, or stop. The first floor push button switch 30d to the fifth floor push button switch 30h are push button switches that can indicate multiple stop positions S, and are configured to maintain the on state once turned on. The first floor push button switch 30d to the fifth floor push button switch 30h can indicate any one of the multiple stop positions S even when none of the multiple stop positions S is indicated. The lift switch 30B, which has the first floor push button switch 30d to the fifth floor push button switch 30h, constitutes an indicator that can indicate multiple stop positions S.

[0092] The lift switch 30B is operated as follows. For example, if it is desired to raise the work platform 3 from the first floor to the fifth floor, the fifth floor push button switch 30h is turned on and then the selection switch 30c is switched to the up position. This causes the work platform 3 to rise, with stop position S5 as stop position S. On the other hand, if it is desired to lower the work platform 3 from the fifth floor to the first floor, the first floor push button switch 30d is turned on and then the selection switch 30c is switched to the down position. This causes the work platform 3 to descend, with stop position S1 as stop position S.

[0093] In the third modified example in which the workbench 3 is raised and lowered in this manner, as will be described below, the controller 50D generates a current stop command signal as a stop command signal for the electromagnetic proportional valve 201 according to the time constant T2 based on a signal from the lift switch 30B and signals from the multiple lowering position sensors 441 to 444, and controls the operation of the electromagnetic proportional valve 201 based on the generated current stop command signal at a timing according to the signal input from the multiple lowering position sensors 441 to 444.

[0094] As shown in FIG. 11, the controller 50D according to the third modification includes an instruction confirmation unit 50i that outputs an ON signal indicating that the stop position S is instructed when a target floor signal (ON signal) indicating the instructed stop position S is input from the lift switch 30B, an AND gate 50j that outputs an ON signal indicating that the control state is in a control state (lowering stop position stop mode) in which the lowering work platform 3 is stopped at the instructed stop position S when an ON signal from the ON / OFF signal acquisition unit 50a and an ON signal from the instruction confirmation unit 50i are input, and an AND gate 50j that outputs an ON signal indicating that the control state is in a control state in which the lowering work platform 3 is stopped at the instructed stop position S when a target floor signal (ON signal) is input from the lift switch 30B and a position signal (ON signal) corresponding to the target floor signal is input from any of the lowering position sensors 441 to 444. The controller 50BA differs from the controller 50BA according to the first application example of the first modified example (see FIG. 6) in that it further includes an AND gate 50k that outputs an ON signal as a trigger signal, a current stop command signal generator 50m that generates a current command signal (current stop command signal) that gradually decreases from a current command signal for a steady ON state to a current command signal for a steady OFF state according to time constant T2 when an ON signal is input from the AND gate 50k while an ON signal is input from the AND gate 50j, and a switching unit 50n that switches the current command signal to be input to the current driver 50c from the current command signal generated by the current command signal generator 50b to the current stop command signal generated by the current stop command signal generator 50m when the ON signal from the AND gate 50k is input. Note that similar changes can also be applied to a controller 50BB according to the second application example of the first modified example (see FIG. 7).

[0095] The target floor signal is a signal that is turned on or off by the first floor push button switch 30d through the fifth floor push button switch 30h, and can be input to the instruction confirmation unit 50i and the multiple AND gates 50k for each of the first floor push button switch 30d through the fifth floor push button switch 30h via multiple wiring. The position signal is a signal that is turned on or off by the descent position sensors 441 through 444, and can be input to the multiple AND gates 50k for each of the descent position sensors 441 through 444 via multiple wiring. Note that in FIG. 11, the target floor signal, position signal, and multiple AND gates 50k for each of the multiple wirings are simplified to avoid cluttering the diagram.

[0096] The instruction confirmation unit 50i receives a target floor signal from any one of the first-floor pushbutton switches 30d to 5th-floor pushbutton switches 30h, thereby confirming that the stop position S has been specified, and an ON signal is input from the instruction confirmation unit 50i to the AND gate 50j. The AND gate 50j receives an ON signal from the ON / OFF signal acquisition unit 50a, thereby confirming that a descent instruction has been issued. The AND gate 50j further confirms that the descent stop position stop mode is in effect when the ON signal from the ON / OFF signal acquisition unit 50a and the ON signal from the instruction confirmation unit 50i are input, and an ON signal is input from the AND gate 50j to the current stop command signal generation unit 50m.

[0097] As described above, the AND gate 50k can be configured with a plurality of AND gates, each of which corresponds to a respective one of the descent position sensors 441 to 444, and for example, the target floor signal from the first floor push button switch 30d and the position signal from the descent position sensor 441 corresponding to the first floor push button switch 30d are input to the same AND gate. In the AND gate 50k, for example, when the first floor push button switch 30d is on, and the work platform 3 descends toward the first floor and the descent position sensor 441 turns on, the AND gate corresponding to the first floor push button switch 30d and the descent position sensor 441 confirms that the work platform 3 has arrived just before the instructed stop position S, and an on signal serving as a trigger signal is input to the current stop command signal generating unit 50m and the switching unit 50n.

[0098] When the current stop command signal generating unit 50m receives an ON signal from the AND gate 50k while receiving an ON signal from the AND gate 50j, the current stop command signal generating unit 50m generates a current command signal that switches from a steady-state ON magnitude (amount of current flowing) to a steady-state OFF magnitude (amount of current flowing) and then smooths the signal based on the time constant T2, thereby generating a current stop command signal. The magnitudes of the current flowing in the steady-state ON and steady-state OFF states are determined in advance, and the time constant T2 is input from the calculation unit 50d. Therefore, the current stop command signal generating unit 50m generates a pseudo-current command signal that switches as described above and then smooths the signal based on the time constant T2, thereby generating a current stop command signal. Note that, when the control of the controller 50A (see FIG. 3) is applied as described above, the time constant T1 can be input to the current stop command signal generating unit 50m instead of the time constant T2. The generated current stop command signal is input to the switching unit 50n.

[0099] In the switching unit 50n, for example, when the first floor push button switch 30d is on and the downward position sensor 441 is turned on, an on signal from the AND gate 50k is input as a trigger signal, and the input to the current driver 50c is switched to the current stop command signal from the current stop command signal generating unit 50m.

[0100] As a result, the current driver 50c generates a solenoid current based on the current stop command signal, and the generated solenoid current is input to the solenoid proportional valve 201, thereby controlling the operation of the solenoid proportional valve 201 at a timing according to the signal input from the lowering position sensor 441, thereby controlling the operation of the solenoid proportional valve 201 at the same timing. The solenoid proportional valve 201 is controlled by the solenoid current input from the current driver 50c to gently lower the work platform 3 and stop it near the stop position S1.

[0101] The first floor push button switch 30d that has been turned on can be turned off when the work platform 3 stops near the stop position S1 (for example, when the current stop command signal is steadily turned off or when a predetermined time has passed since the lowering position sensor 441 was turned on). The same applies to the second floor push button switch 30e to the fifth floor push button switch 30h. The controller 50D can be used for unloading between any two floors.

[0102] In the third modified example configured as described above, each of the lowering position sensors 441 to 444 detects the position of the work platform 3 in the direction of descent, before the corresponding stop position S among the multiple stop positions S. Therefore, even if the work platform 3 does not immediately stop at the stop position S in response to detection and overruns, the work platform 3 can be stopped near the instructed stop position S. By outputting a signal at the same timing regardless of the load, the work platform 3 can be stopped at the same position. In other words, the same control (program) can be used, although only the time constant T used varies depending on the load. Furthermore, when there are multiple desired stop positions S, the work platform 3 is stopped at the timing according to the signal input from the multiple lowering position sensors 441 to 444. This suppresses shock, and the worker can easily stop the work platform 3 at approximately the same position regardless of the magnitude of the load, thereby reducing stress during work. Furthermore, when there are multiple desired stopping positions S, it is only necessary to specify the desired stopping position S, which makes it easy to stop the workbench 3 at the same stopping position S multiple times while suppressing shock, thereby improving workability.

[0103] The configuration, operation, and effects of the embodiment of the present invention will be described below.

[0104] The high-altitude work device 1 includes a hydraulic cylinder 4 that raises and lowers the work platform 3, an electromagnetic proportional valve 201 that controls the flow rate of hydraulic oil discharged from the hydraulic cylinder 4, and controllers 50A, 50B, 50C, and 50D that control the operation of the electromagnetic proportional valve 201. When a lowering on / off signal used to operate and stop the work platform 3 is switched between on and off, the controllers 50A, 50B, 50C, and 50D soften the on / off signal using a time constant T to generate a current command signal that is a control command signal for the electromagnetic proportional valve 201, and the time constant T is set according to the load acting on the hydraulic cylinder 4.

[0105] According to this configuration, the current command signal for the electromagnetic proportional valve 201 is generated by blunting the on / off signal using the time constant T set in accordance with the load on the hydraulic cylinder 4, so the work platform 3 can be operated and stopped gradually at an appropriate level depending on the load. This makes it easier for the operator to stop the work platform 3 at a consistent position regardless of the magnitude of the load while suppressing shock. As mentioned above, an electromagnetic proportional valve that controls the flow rate of hydraulic oil supplied to the hydraulic cylinder 4 may be provided, and the on / off signal on the lifting side may be blunted using the time constant T1 to generate a current command signal for controlling the electromagnetic proportional valve. This makes it possible to suppress sudden operation and stopping of the work platform 3 and suppress shock even when the work platform 3 is raised.

[0106] The controllers 50B, 50C, and 50D set a time constant T2 based on the equation T=T0(1 / √(√A / √A0)), where A is the load W of the hydraulic cylinder 4 during operation or the operating oil pressure P corresponding to the load, A0 is the reference load W0 or the reference operating oil pressure P0 of the fluid pressure actuator, and T0 is the reference time constant corresponding to the reference load W0 or the reference operating oil pressure P0.

[0107] According to this configuration, by using the above-mentioned formula found by the inventors through trial and error, the time constant T can be set so that the amount of overrun OR when the descending work platform 3 does not stop immediately in response to a stop command but slowly decelerates with a first-order delay remains roughly the same regardless of the load on the hydraulic cylinder 4 or the working fluid pressure A corresponding to the load. Therefore, while suppressing shock, the operator can easily stop the work platform 3 at roughly the same position regardless of the magnitude of the load.

[0108] The workbench 3 has a plurality of stop positions S from stop positions S1 to S5. The controller 50D generates a current stop command signal for the electromagnetic proportional valve 201 according to the time constant T based on a signal from the lift switch 30B that can indicate the plurality of stop positions S and signals from lowering position sensors 441 to 444 that can detect the position of the workbench 3 before each of the plurality of stop positions S, and controls the operation of the electromagnetic proportional valve 201 based on the generated current stop command signal at the same timing.

[0109] According to this configuration, a signal can be output at the same timing regardless of the load, and the workbench 3 can be stopped at the same position. In other words, the same control (program) can be used, although the time constant T used differs depending on the load.

[0110] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments. [Explanation of symbols]

[0111] 1···Aerial work device, 3···Work platform, 4···Hydraulic cylinder (fluid pressure actuator), 30B···Lift switch (indicator), 50A, 50B, 50C, 50D···Controller, 50a···ON / OFF signal acquisition unit, 50b···Current command signal generation unit, 50d···Calculation unit, 50m···Current stop command signal generation unit, 201···Solenoid proportional valve, 441, 442, 443, 444···Descent position sensor (sensor), S, S1, S2, S3, S4···Stop position, T, T1, T2···Time constant

Claims

1. a fluid pressure actuator for raising and lowering the work table; an electromagnetic proportional valve for controlling the flow rate of the working fluid discharged from the fluid pressure actuator or the working fluid supplied to the fluid pressure actuator; a controller for controlling the operation of the electromagnetic proportional valve; the controller, when an on / off signal used to operate and stop the work platform is switched between on and off, dulls the on / off signal by a time constant to generate a control command signal for the electromagnetic proportional valve; the time constant is set in accordance with a load acting on the fluid pressure actuator. A high-altitude work device characterized by:

2. The high altitude work apparatus according to claim 1, The controller sets the load of the fluid pressure actuator during operation or the working fluid pressure according to the load to A, and sets the reference load of the fluid pressure actuator or the reference working fluid pressure to A ０ , the reference time constant corresponding to the reference load or the reference working fluid pressure is T ０ Then, T = T ０ (1 / √(√A / √A ０ )) The time constant T is set based on the equation A high-altitude work device characterized by:

3. The high-altitude work apparatus according to claim 1 or 2, the work platform has a plurality of stop positions; The controller generates a stop command signal for the electromagnetic proportional valve according to the time constant based on a signal from an indicator capable of indicating the plurality of stop positions and a signal from a sensor capable of detecting the position of the work table before each of the plurality of stop positions, and controls the operation of the electromagnetic proportional valve based on the generated stop command signal at the same timing. A high-altitude work device characterized by:

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