JP3147033B2 - Fault diagnosis device for industrial vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manually operated directional control valve for controlling the supply of hydraulic oil to a cylinder for actuating a cargo handling attachment, and controlling the supply and discharge of hydraulic oil to and from the cylinder, and a solenoid valve. Diagnosis device for industrial vehicles performed jointly by

[0002]

2. Description of the Related Art In a forklift which is an industrial vehicle provided with a cargo handling attachment, a fork is lifted and lowered together with a lift bracket by a mast provided with an outer mast and an inner mast provided at a front portion of the vehicle. The mast is expanded and contracted by the operation of the lift cylinder based on the operation of the lift lever, and the fork is raised and lowered accordingly. Further, in order to facilitate the cargo handling operation and to improve the stability during traveling of the forklift, the mast is tilted forward or backward with respect to the vertical reference position by operating the tilt cylinder based on the operation of the tilt lever. .

Conventionally, when the mast is tilted forward, the tilting speed becomes slower than during the backward tilting operation in order to prevent the collapse of the load and the lifting of the rear wheels of the forklift (that is, the unstable state in the longitudinal direction of the vehicle). As described above, the flow path is provided with a restriction to restrict the flow rate of the hydraulic oil. In addition, the worker also carefully leans forward at a low speed by performing inching operation so that the mast does not lean forward too much when the load is placed at a high place in the cargo handling operation. However, during backward tilting operation, stability is relatively good even when the load is large and the lift is high,
No throttle was provided in the flow path.

[0004] Generally, at the time of loading or unloading work, it is necessary that the fork is in a state parallel to the pallet on which the load is loaded, that is, the fork is horizontal. However, it requires skill to accurately level the fork by manual operation. In addition, it is necessary to perform the tilt operation and the traveling and lift operations during the actual cargo handling work, which increases the burden on the operator.

[0005] In addition, in the case of a high elevation with a load being loaded, the operator adjusts the operation amount of the tilt lever and the engine speed during the backward tilting operation to perform the backward tilting operation at a relatively slow speed. Was. However, when the mast is stopped at the last inclined position at a high speed due to an erroneous operation or the like while the load is being loaded, the shock is large, and the durability is reduced. Further, even when no load is loaded, if the rearward tilting operation is performed at a high elevation and at a high speed, the shock when the mast stops at the last tilted position is large, which causes a decrease in durability.

[0006]

In order to solve the above problem, it is conceivable that the supply of hydraulic oil to the cylinder is controlled by a solenoid valve instead of a manually operated valve, and a forklift which performs automatic level control is also known. ing. However, when the switching of the flow path of the hydraulic oil and the switching of the flow rate for the tilting, neutral, and backward tilting operations of the tilt cylinder are all performed by the solenoid valve, the solenoid valve becomes large and complicated. The hydraulic oil leaks from the sliding surface when a large pressure is applied to the spool valve.However, in the case of a solenoid valve, the spool and its sliding surface are compared with a manual valve to improve the operability of the spool. There is a problem that the clearance is large and the amount of leakage increases accordingly.

In order to solve this problem, the applicant of the present invention controlled the supply of hydraulic oil to the tilt cylinder by switching between the supply and discharge directions of hydraulic oil to and from the tilt cylinder, and a solenoid operated valve. Invented a hydraulic device that works jointly. In this configuration, when the detection signal (ON signal) indicating that the tilt lever 13 has been operated to a position other than the neutral position is output from the detection means for detecting the operation position of the tilt lever, the electromagnetic valve is connected to the electromagnetic valve. An operation command is output.

In this configuration, even if the detection means (detection switch) is fixed in a state of outputting an ON signal, the solenoid valve is kept open, so that the solenoid valve operates in response to the operation of the tilt lever by the operator. The switching between the oil supply and discharge directions is performed smoothly. Therefore, even if the detection means is fixed in the ON state, the operator does not notice it. Also, the control means for performing the demagnetization control of the solenoid valve cannot grasp the state,
As a result, even when the tilt lever has returned to the neutral position, it is expected that the exciting current will continue to flow through the solenoid valve and the hydraulic oil and the controller will overheat.

As a countermeasure for solving this inconvenience, it is conceivable to forcibly terminate the tilt operation when the ON signal is continuously output from the detection means for a predetermined time (for example, one minute). However, even in such a state, since the operator may actually continuously operate the tilt lever to the forward or backward tilt position,
There is a problem in forcibly terminating the tilt operation only by time.

Further, not only in the tilt cylinder but also in the lift cylinder, the supply control of the hydraulic oil to the cylinder is controlled by
A similar problem arises when a configuration in which a manually operated direction switching valve that switches and controls the supply and discharge directions of hydraulic oil to and from a cylinder and a solenoid valve are used in combination is adopted.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to control the supply of hydraulic oil to a cylinder for operating a cargo handling attachment, and to supply and discharge hydraulic oil to and from the cylinder. In the industrial vehicle that is jointly operated with a manually operated directional switching valve for switching and controlling the solenoid valve and a solenoid valve,
An object of the present invention is to provide a failure diagnosis device for an industrial vehicle, which is capable of detecting a failure in which the cargo handling operation detection means is fixed in an ON state.

[0012]

In order to achieve the above object, according to the first aspect of the present invention, the supply of hydraulic oil to a cylinder for operating a cargo handling attachment is controlled by the supply of hydraulic oil to the cylinder. In an industrial vehicle operated in cooperation with a manually operated direction switching valve for switching and controlling the discharge direction and an electromagnetic valve, the cargo handling operation means for operating the manual operation direction switching valve, and the cargo handling operation means are operated to the cargo handling operation position. Loading / unloading operation detection means for detecting whether or not the operation of the cylinder, an operation amount detection means for detecting an operation amount of an object to be operated by the cylinder, a current detection means for detecting a current flowing through the solenoid valve, and the current detection While the appropriate output signal is being output from the means, a change in the output signal of the operation amount detection means while the cargo handling operation means is being operated to the cargo handling operation position is observed, and the amount of change is observed. For less than a predetermined value and a determination means for the loading operation detection means determines a failure.

According to a second aspect of the present invention, in the first aspect of the present invention, when the determining means determines that a failure has occurred, a signal for operating the solenoid valve is output from the cargo handling operation detecting means. Also, a control means for stopping an operation command to the solenoid valve is provided.

According to a third aspect of the present invention, in the first or second aspect of the invention, the industrial vehicle is a forklift, the cylinder is a tilt cylinder, and the cargo handling operation means is an operation of the tilt cylinder. It is a tilt operation means for issuing a command, and the operation amount detection means is a tilt angle detection means for detecting a tilt angle of the mast.

According to a fourth aspect of the present invention, in the third aspect of the invention, the tilt angle detecting means outputs a voltage corresponding to a tilt amount of the mast from a reference position. Therefore, according to the first aspect of the present invention, the supply control of the hydraulic oil to the cylinder that operates the cargo handling attachment is performed by a manual operation direction switching valve that controls the supply and discharge directions of the hydraulic oil to the cylinder, It is done in collaboration with the valve. The manual operation direction switching valve is operated by the cargo handling operation means. Whether or not the cargo handling operation means has been operated to the cargo handling operation position is detected by the cargo handling operation detection means. An operation amount of the operated body operated by the cylinder is detected by an operation amount detection unit. A current flowing through the solenoid valve is detected by current detection means. While the appropriate output signal is being output from the current detection means, a change in the output signal of the operation amount detection means while the cargo handling operation means is being operated to the cargo handling operation position is observed by the determination means. And
When the change amount is equal to or less than a predetermined value, the judging means judges that the cargo handling operation detecting means is out of order.

According to a second aspect of the present invention, in the first aspect of the present invention, when the cargo handling operation detecting means determines that the failure has occurred by the determining means, the control means for controlling the electromagnetic valve includes the following: The operation command to the solenoid valve is stopped even if a signal to operate the solenoid valve is output from the cargo handling operation detection means. Therefore, overheating of the hydraulic oil, the solenoid valve and the control means is prevented.

According to a third aspect of the present invention, in the first or second aspect, the industrial vehicle is a forklift, and the cylinder is a tilt cylinder. Then, when the forklift is tilted, the judging means observes the change amount based on the output of the tilt angle detecting means while the tilt operating means is operated to the forward tilt or the backward tilt position. If the amount of change is equal to or less than the predetermined value, the cargo handling operation detecting means determines that the failure has occurred.

According to a fourth aspect of the present invention, in the third aspect of the invention, a voltage corresponding to a tilt amount of the mast from a reference position is output from the tilt angle detecting means.
The determining means determines whether a failure of the cargo handling operation detecting means has occurred based on whether or not the amount of change in the output voltage during a predetermined time during which the tilt operating means has been operated to the forward or backward tilt position from the cargo handling detecting means. Make a decision.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a forklift as an industrial vehicle to which a fork is attached as a cargo handling attachment will be described with reference to FIGS.

As shown in FIG. 3, a mast 3 is provided at the front of the body frame 2 of the forklift 1. The mast 3 includes a pair of left and right outer masts 3a that are supported to be tiltable with respect to the body frame 2, and inner masts 3b that are provided inside the masts 3 so as to be able to move up and down. A lift cylinder 4 is fixed to the rear side of both outer masts 3a in parallel with the outer mast 3a, and the tip of a piston rod 4a is connected to the upper part of the inner mast 3b. A lift bracket 5 is provided inside the inner mast 3b so as to be able to move up and down along the inner mast 3b, and a fork 6 as a cargo handling attachment is attached to the lift bracket 5. A chain wheel 7 is supported on an upper portion of the inner mast 3b, and a chain 8 having a first end connected to an upper portion of the lift cylinder 4 and a second end connected to the lift bracket 5 is mounted on the chain wheel 7. I have. Then, the chain 8 is extended and retracted by the lift cylinder 4.
The fork 6 is moved up and down together with the lift bracket 5 via.

A base end of a tilt cylinder 9 is rotatably supported on both left and right sides of the body frame 2, and a distal end of a piston rod 9a is rotatably connected to an outer surface of the outer mast 3a. Then, the mast 3 is tilted by the expansion and contraction of the piston rod 9a of the tilt cylinder 9.

A steering 11 is provided at the front of the cab 10.
And a lift lever 12 as a lifting operation means, and a tilt lever 13 as a cargo handling operation means and a tilt operation means. FIG. 3 shows both levers 12 and 13 in an overlapping state. The lift cylinder 4 is operated (expanded or contracted) by operating the lift lever 12, and the tilt cylinder 9 is operated (expanded or contracted) by operating the tilt lever 13.

As shown in FIG. 2, the outer mast 3a is provided with a lift sensor 14 as a lift detecting means at a predetermined height position. The lift sensor 14 is composed of a proximity switch, and when a detected portion (not shown) fixed to the inner mast 3b is detected, the lift of the fork 6 is turned on when the lift is equal to or higher than the set value H0. It is turned off. The elevation sensor 14 outputs a predetermined voltage of a high level (H) in an on state, and outputs a predetermined voltage of a low level (L) in an off state. In this embodiment, the set value H0 is set to approximately half the maximum lift Hmax.

The body frame 2 is provided with a rotary potentiometer 15 as tilt angle detecting means for detecting the tilt angle of the mast. The potentiometer 15 is provided on a support portion rotatably supporting the base end of the tilt cylinder 9, and includes a rotary piece 15 a for holding a pin 16 protruding from the tilt cylinder 9. The turning piece 15a turns together with the tilt cylinder 9 in accordance with the expansion and contraction of the piston rod 9a, and the potentiometer 15 outputs a detection signal corresponding to the turning amount of the turning piece 15a. In this embodiment, the mast 3 functions as an actuated body actuated by a cylinder, and the potentiometer 15 functions as an actuation amount detecting means for detecting the actuation amount.

In this embodiment, the potentiometer 15
Is such that the output voltage is the smallest when the mast 3 is arranged at the most inclined position, becomes the largest when the mast 3 is arranged at the most inclined position, and changes in proportion to the rotation amount during that time. It has become. Therefore, as shown in FIG. 6, the relationship between the tilt angle θ and the output voltage V of the potentiometer 15 decreases from the output value at the reference position when the mast 3 is tilted forward from the reference position where the mast 3 is vertical, and tilts backward. Then, the output value at the reference position is increased. That is,
The potentiometer 15 outputs a voltage corresponding to the amount of tilt of the mast 3 from the reference position.

The lift cylinder 4 has a pressure sensor 17 as a load detecting means for detecting the load of the fork 6.
Is provided. The pressure sensor 17 is a lift cylinder 4
And outputs a detection signal corresponding to the load of the fork 6.

As shown in FIG. 4, near the tilt lever 13, a forward tilt detection switch 1 as forward tilt operation detecting means is provided.
8 and a rearward tilt detection switch 19 as a rearward tilt operation detecting means
Are provided. Both detection switches 18 and 19 are micro switches, and the forward tilt detection switch 18 is turned on when the tilt lever 13 is in the forward tilt position, and is turned off when the tilt lever 13 is in any other position. Back tilt detection switch 19
Turns on when the tilt lever 13 is in the backward tilt position,
It is off when it is in any other position. A cargo handling operation detecting means is constituted by the two detection switches 18 and 19, and the cargo handling operation detecting means outputs an ON signal when the tilt lever 13 is operated to the cargo handling operation position.

An operation switch 13a is provided above the tilt lever 13. Operation switch 13a
Is used to perform an automatic horizontal operation. The operation switch 13a outputs an ON signal when the pressing operation (pressing) is performed, and outputs an OFF signal when the pressing operation is released. Has become.

Next, a hydraulic circuit for driving the lift cylinder 4 and the tilt cylinder 9 will be described with reference to FIG. As shown in FIG. 5, the bottom chamber 4 of the lift cylinder 4
b is connected to a lift control valve 21 via a pipe 20. A manually operated 7-port, 3-position switching valve is used as the lift control valve 21. The lift control valve 21 is a, b, c corresponding to the lift, neutral and lowering operation positions of the lift lever 12 for instructing the fork 6 to move up and down. It is possible to switch between the three states. Tilt control valve 2 as manually operated direction switching valve
The 2 uses a 6 port 3 position switching valve, and corresponds to three states of c, b and a corresponding to the forward tilt, neutral and rear tilt operation positions of the tilt lever 13 for instructing the fork 6 to tilt and stop. It can be switched.

A hydraulic pump 24 for supplying hydraulic fluid in an oil tank 23 to each of the cylinders 4 and 9 is driven by an engine E (shown in FIG. 3). The hydraulic pump 24 is connected to a port P1 of the lift control valve 21 via a hydraulic oil supply line 25. The hydraulic oil supply pipe 25 is provided with a flow divider 27 that divides the hydraulic oil supplied from the hydraulic pump 24 to the cargo handling device side (the lift cylinder 4 and the tilt cylinder 9) and the power steering valve 26 side. I have. The hydraulic oil supply line 25 is a flow divider 2
7, branch pipelines 25a and 25 branched on the downstream side
b are connected to ports P2 and P3, respectively. The hydraulic oil supply line 25 is connected to a return line 30 via a line 29 a provided with a relief valve 28. The lift control valve 21 is connected to the return line 30 at the port T1, to the line 20 at the port A1, to the line 29b at the port A2, and to the line 31 at the port A3. The pipe 29b is connected to the return pipe 30, and a relief valve 32 is provided on the way. The set pressure of the relief valve 32 is set to a value smaller than the set pressure of the relief valve 28.

When the lift lever 12 is at the neutral position, the lift control valve 21 is disposed at the position b. At the position b, the communication between the line 20 and the branch line 25a and the return line 30 is cut off. 4 is kept in a state in which the movement of the hydraulic oil is prevented. Lift control valve 2
Reference numeral 1 denotes a position which is arranged at the position a based on the lifting operation of the lift lever 12, and connects the branch line 25a and the line 20 at the position a to extend the lift cylinder 4. Further, the lift control valve 21 is disposed at the position c based on the descending operation of the lift lever 12, and connects the pipeline 20 and the return pipeline 30 to the hydraulic oil supply pipeline 25 and the pipeline 31 at the c position. The lift cylinder 4 is contracted by connecting the branch pipe 25b and the pipe 29b.

The hydraulic pump 24 is connected to the port P11 of the tilt control valve 22 via a hydraulic oil supply pipe 33 branched from the hydraulic oil supply pipe 25. A line 31 is connected to a port P12 of the tilt control valve 22.
The tilt control valve 22 is connected to the return line 3 at the port T11.
0a and the return line 30b at port T12. The tilt control valve 22 is connected to the pipe 34a at the port A11 and to the pipe 34b at the port A12. The pipe 34a is connected to the rod chamber 9b of the tilt cylinder 9, and the pipe 34b is connected to the bottom chamber 9c.

The tilt control valve 22 is a tilt lever 1
When the valve 3 is in the neutral position, it is arranged at the position b in FIG. 5 and shuts off the communication between the two pipes 34a, 34b, the pipe 33 for supplying the hydraulic oil and the return pipe 30a. It is kept in a state that prevents the movement of oil. The tilt control valve 22 is disposed at the position a based on the backward tilting operation of the tilt lever 13, and connects the hydraulic oil supply line 33 and the line 34 a with the return line 30 a and the line 34 b at the position a. The tilt cylinders 9 are arranged so as to be communicated with each other so that the tilt cylinder 9 can be contracted. The tilt control valve 22 is arranged at the position c based on the forward tilt operation of the tilt lever 13. In the position c, the hydraulic oil supply line 33 and the line 3
4b, and the pipeline 34a is returned to the pipeline 3
0a and the tilt cylinder 9
Can be extended.

A control valve 35 and a pilot operated check valve 36 are provided in the middle of the pipe 34a. The pilot operation check valve 36 is provided between the control valve 35 and the rod chamber 9b so as to regulate the flow of hydraulic oil from the rod chamber 9b side to the control valve 35 side. The control valve 35 is a one-way valve, and has a direct-acting spool that opens and closes the pipeline 34a. The control valve 35 is a normally-closed type (normally closed type) control valve. A 2-port 2-position valve operated by pilot oil pressure is used. , Can be switched between two positions, a position b communicating with the pipe line 34a. When the spool is disposed at the position b, a passage 38 is formed to communicate with the conduit 34a, and the passage 38 has an orifice. Pilot pressure to the control valve 35 and the pilot operated check valve 36 is supplied by a proportional solenoid valve 39. The control valve 35 and the proportional solenoid valve 39 constitute an electromagnetic valve that opens and closes a pipe 34a that connects the tilt cylinder 9 and the tilt control valve 22.

The pilot pressure supply means for supplying pilot pressure to the pilot operation check valve 36 and the proportional solenoid valve 39 is provided by the flow divider 2 of the hydraulic oil supply line 25.
On the upstream side from 7, a pipeline 40 branched from the hydraulic oil supply pipeline 25 is provided. A pressure reducing valve 41 and a filter 42 are provided in the middle of the pipe 40.

The proportional solenoid valve 39 has a tank port T2 connected to the return line 30a, and an A port connected to the line 4
Connected to 0. In addition, B of the proportional solenoid valve 39
The port is connected to a pressure chamber (not shown) provided at one end of a spool of the control valve 35. In the control valve 35, a pressure chamber (not shown) at the other end of the spool is connected to a return line 30.

The proportional solenoid valve 39 is a normally closed type (normally closed type) solenoid valve. When the solenoid is demagnetized, the spring 43
The port and the tank port T2 communicate with each other. Also,
The proportional solenoid valve 39 is configured such that the operation amount of the spool is proportional to the current supplied for excitation,
When the solenoid is excited, the spool operates to connect the A port and the B port, and the pilot pressure set at the operating position of the spool is supplied to the spool of the control valve 35. By this pilot pressure, the spool of the control valve 35 is moved against the spring force of the spring 37.

The lift control valve 21, the tilt control valve 22, the pilot operated check valve 36, the relief valve 2
8, 32, the control valve 35, the proportional solenoid valve 39, and the pressure reducing valve 41 are formed in one housing, and constitute one control valve 44 as a whole.

Next, an electrical configuration for controlling the hydraulic circuit will be described. As shown in FIG. 2, the control device 45 for controlling the opening of the control valve 35, that is, the output pilot pressure of the proportional solenoid valve 39 includes a microcomputer 46, input / output interfaces 55 and 56, EEPROM 51b, a solenoid drive circuit 48, A current detection circuit 49 is provided. The microcomputer 46 includes a central processing unit (hereinafter, referred to as a CPU) 50 as an arithmetic unit, a judgment unit, and a control unit, a read-only memory (ROM) 51a, a readable and rewritable memory (RAM) 52, and a counter 53. , A clock circuit 54, and an analog / digital conversion circuit (A / D conversion circuit) 47.

The ROM 51a stores various control programs and data necessary for executing the control programs. The control programs include, for example, a backward tilt speed limit control program, a horizontal control program, and a failure diagnosis program. The EEPROM 51b stores, among the data necessary to execute the control program, data that is likely to be changed and corrected, for example, a current value for limiting the backward tilt speed.

The CPU 50 is connected to the potentiometer 15 and the pressure sensor 17 via the input interface 55 and the A / D conversion circuit 47, respectively. CPU 50
Is the operation switch 13 via the input interface 55
a, the elevation sensor 14, the forward tilt detection switch 18, and the rear tilt detection switch 19, respectively. CPU 50
Is connected to the solenoid drive circuit 48 via the output interface 56.

The current detection circuit 49 includes a proportional solenoid valve 39
And the input interface 5
5 and the CPU 50 via the A / D conversion circuit 47. The current detection circuit 49 detects a current flowing through the solenoid of the proportional solenoid valve 39, and outputs a voltage signal corresponding to the current amount to the input interface 55. That is, the current detection circuit 49 functions as current detection means for detecting the amount of current flowing through the solenoid valve.

The CPU 50 controls each of the sensors 14, 15, 1
7, operation switch 13a and both detection switches 18, 19
And operates according to various control programs stored in the ROM 51a to output a control command signal to the proportional solenoid valve 39 via the solenoid drive circuit 48 when the tilt cylinder 9 is operated.

The CPU 50 determines whether an appropriate current corresponding to the command current value is actually flowing through the solenoid of the proportional solenoid valve 39 based on the output signal of the current detection circuit 49. Then, the CPU 50 controls the proportional solenoid valve 39.
In the state where the amount of current flowing through the clock circuit is an appropriate value, the failure diagnosis program is executed at a predetermined cycle based on the clock signal of the clock circuit 54. CPU 50 is tilt lever 13
A change in the output voltage of the potentiometer 15 is observed while the switch is operated at the cargo handling operation position. If the change is equal to or less than a predetermined value, the detection switches 18 and 19 are determined to have failed.
When the CPU 50 determines that the detection switches 18 and 19 are out of order, the CPU 50 stops the operation command to the proportional solenoid valve 39 even if an ON signal is output from the detection switches 18 and 19.

Next, the operation of the above-configured apparatus will be described. When the engine E is operated and the hydraulic pump 24 is driven, the hydraulic oil in the oil tank 23 is discharged to the hydraulic oil supply pipe 25. Therefore, the pipeline 40 for supplying the pilot pressure is ready to supply the pilot pressure as soon as the hydraulic pump 24 is driven.

When the lift lever 12 is moved upward from the neutral position, the spool of the lift control valve 21 is disposed at the position a, and the hydraulic oil discharged from the hydraulic pump 24 is supplied to the bottom chamber 4b of the lift cylinder 4 and lifted. Cylinder 4
Extend and the fork 6 rises. When the lift lever 12 is lowered, the spool of the lift control valve 21 is disposed at the position c, and the hydraulic oil in the bottom chamber 4b is discharged from the oil tank 2
3, the lift cylinder 4 contracts, and the fork 6 descends. The lift spool is arranged at the position b based on the neutral operation of the lift lever 12, the movement of the hydraulic oil in the lift cylinder 4 is prevented, and the fork 6 is held at the desired lift position.

When the tilt lever 13 is in the neutral position, the spool is held at the position b in FIG. 5, and the two pipelines 34a and 34b are connected to either the hydraulic oil supply pipeline 33 or the return pipeline 30a. However, the communication is maintained in a disconnected state. Then, movement of the hydraulic oil of the tilt cylinder 9 is prevented, and the mast 3 is maintained at a desired tilt angle.

When the spool is positioned at the position c by the tilting operation of the tilt lever 13, the hydraulic oil supply pipe 33 and the pipe 34b are connected, and the pipe 34a and the return pipe 30a are connected.
Is in a state of being communicated with. Also, the tilt lever 13
Is operated to tilt forward, the CPU 50 causes the forward tilt detection switch 1
8 is input. Then, an excitation command signal is output from the CPU 50 to the proportional solenoid valve 39 via the solenoid drive circuit 48, and pilot pressure is supplied to the control valve 35 and the pilot operation check valve 36 in the pipe 34a, so that hydraulic oil is supplied to the pipe 34a. Can be flowed.
As a result, the hydraulic oil is supplied to the bottom chamber 9c via the hydraulic oil supply pipe 33 and the pipe 34b, and the hydraulic oil in the rod chamber 9b is supplied to the oil tank 23 via the pipe 34a and the return pipe 30a. Because of the discharge, the tilt cylinder 9 is extended, and the mast 3 is rotated toward the front side. If the mast 3 is rotated (tilted) forward from the vertical state, the mast 3
That is, the fork 6 is tilted forward.

When the spool is disposed at the position "a" by the tilting operation of the tilt lever 13, the hydraulic oil supply pipe 33 and the pipe 34a communicate with each other, and the pipe 34b and the return pipe 30a.
Is in a state of being communicated with. Also, the tilt lever 13
Is operated, the CPU 50 causes the CPU 50 to detect the backward tilt switch 1.
9 are input. Then, an excitation command current is output from the CPU 50 to the proportional solenoid valve 39 via the solenoid drive circuit 48, and a pilot pressure is supplied to the control valve 35 and the pilot operation check valve 36, so that hydraulic oil flows through the pipeline 34a. It is possible. As a result, the hydraulic oil is supplied to the rod chamber 9b through the hydraulic oil supply pipe 33 and the pipe 34a, and the hydraulic oil in the bottom chamber 9c is supplied to the oil tank 23 through the pipe 34b and the return pipe 30a. Because of the discharge, the tilt cylinder 9 is contracted, and the mast 3 is rotated rearward. When the mast 3 is rotated (tilted) rearward from the vertical state, the mast 3, that is, the fork 6 is tilted rearward.

When the CPU 50 receives an ON signal from the rearward tilt detection switch 19, the CPU 50 determines whether the output signal of the elevation sensor 14 is high (H) or low (L). If the signal is low, the backward tilting speed is not limited, and a command signal for supplying a command current value for fully opening the proportional solenoid valve 39 is output to the solenoid drive circuit 48. As a result, the proportional solenoid valve 39 is fully opened, the control valve 35 is moved to the fully open position and is held in that state, and the operating oil is supplied to the rod chamber 9b at a flow rate corresponding to the operation amount of the tilt lever 13 by the operator. The mast 3 is pivoted rearward (backward tilt). Therefore, when the amount of tilting operation of the tilt lever 13 is maximized when the engine is fully opened, the mast 3 is tilted backward at the maximum speed.

On the other hand, if the output signal of the elevation sensor 14 is high, the CPU 50 executes the backward inclination speed limitation. That is,
The CPU 50 stores the EEPROM 51 in the proportional solenoid valve 39.
A command signal for supplying the command current value for limiting the backward tilt speed stored in b is output to the solenoid drive circuit 48. As a result, the proportional solenoid valve 39 is maintained at a predetermined opening, and the control valve 35 is also maintained at a predetermined opening. Therefore, even if the operator maximizes the amount of tilting operation of the tilt lever 13 when the engine is fully opened, the mast 3 is operated to tilt backward at a predetermined limited speed.

While the operation switch 13a is depressed while the fork 6 is tilted forward, the tilt lever 13
When the backward tilt operation is performed, the operation switch 13
a and ON signals from the rearward tilt detection switch 19 are input. At this time, the CPU 50 performs automatic horizontal control. CPU
50 is based on the ON signal of the rearward tilt detection switch 19,
A valve opening command signal is output to the solenoid drive circuit 48. The CPU 50 inputs the output signal of the potentiometer 15 while the ON signal is input from the operation switch 13a, and the tilt angle of the mast is 0 degree, that is, a value corresponding to the voltage indicating the horizontal state of the fork 6. Compare with
The value based on the output voltage of the potentiometer 15 is a value representing the horizontal state of the fork 6 (tilt angle 0).
CPU 50 outputs a valve closing command signal to the solenoid drive circuit 48 when a predetermined difference is obtained. At this time, C
The PU 50 outputs a valve closing command signal such that the command current value gradually decreases to a command current value at which the control valve 35 is slightly opened. As a result, the opening of the proportional solenoid valve 39 gradually decreases from the start of the horizontal control, and is maintained at the opening at which the control valve 35 is slightly opened. When the tilt angle becomes 0 degree in this state, a command to reduce the exciting current to the proportional solenoid valve 39 is output from the CPU 50, the pilot pressure becomes 0, the control valve 35 is completely closed, and the fork 6 is leveled. Held in state.

Therefore, even though the tilt lever 13 is located at the backward tilting operation position, the communication of the pipe line 34a is blocked, and the movement of the hydraulic oil into the rod chamber 9b of the tilt cylinder 9 is blocked. The tilt cylinder 9 is held without contracting. That is, the fork 6 is held in a horizontal state.

When outputting a command signal to the solenoid drive circuit 48, the CPU 50 does not immediately output a command signal corresponding to a predetermined command current value, but takes a predetermined time to output a predetermined command current as shown in FIG. Outputs a command signal to reach the value. Therefore, as indicated by the dashed line, the shock at the start of the backward tilting operation is smaller than when the command signal corresponding to the predetermined command current value is immediately output. Also, when stopping at the horizontal position, the shock is reduced,
It can be reliably stopped at the horizontal position.

Further, while the fork 6 is tilted backward, the operation switch 13a is depressed and the tilt lever 13 is pressed.
The CPU 50 also performs substantially the same horizontal control as described above when the forward leaning operation is performed. That is, while the ON signal is being input from the operation switch 13a, the CPU 50 inputs the output signal of the potentiometer 15 and
The CPU 50 outputs a valve closing command signal to the solenoid drive circuit 48 when the output signal of the fork 6 has a predetermined difference (horizontal control start value) from the value indicating the horizontal state of the fork 6.

The CPU 50 is connected to both detection switches 18,
When no ON signal is output from any of the control signals 19, no operation command is issued to the proportional solenoid valve 39. Therefore,
Since the pilot pressure is not supplied to the control valve 35 and the pilot operation check valve 36, the flow of the hydraulic oil from the rod chamber 9b side to the tilt control valve 22 side is maintained in a blocked state.

Next, a description will be given of a failure diagnosis method for determining whether or not the cargo handling operation detecting means, that is, both the detection switches 18 and 19 are in the ON state and the failure state is fixed. The CPU 50 executes the failure diagnosis program at a predetermined cycle based on the clock signal of the clock circuit 54 when the amount of current flowing through the proportional solenoid valve 39 has an appropriate value. The CPU 50 controls the proportional solenoid valve 3 based on the output signal of the current detection circuit 49.
It is determined whether an appropriate current corresponding to the command current value is actually flowing through the solenoid 9. Then, the failure diagnosis process shown in the flowchart of FIG. 1 is performed in a state where it is confirmed that an appropriate current is flowing.

In step S1, the CPU 50 determines whether one of the forward tilt detection switch 18 and the rear tilt detection switch 19 is on, that is, whether the cargo handling operation detecting means is on.
If the ON signals are not output from both the detection switches 18 and 19, the process proceeds to step S2, and the counter 53 is cleared (reset). Then, the process proceeds to a step S3, wherein an operation stop command to the proportional solenoid valve 39, that is, a solenoid off command is output to the solenoid drive circuit 48.

If one of the detection switches 18 and 19 is turned on in step S1, the CPU 50 proceeds to step S4, and determines whether the count value of the counter 53 is 0 or not. If the count value is 0, the process proceeds to step S5, where the output voltage V of the potentiometer 15 is read, and the voltage value V1 is stored in the RAM 52. Thereafter, the process proceeds to step S6, where 1 is added to the counter 53 (increment). If the count value is not 0 in step S4, the process directly proceeds to step S6, and 1 is added to the counter 53. Next, in step S7, the CPU 50 determines whether or not the count value of the counter 53 is less than a predetermined count value Cα corresponding to a predetermined time (10 seconds in this embodiment). If the count value is less than the predetermined count value Cα, the CPU 50 proceeds to step S8 and outputs an operation command to the proportional solenoid valve 39, that is, a solenoid ON command, to the solenoid drive circuit 48.

If the count value is equal to or larger than the predetermined count value Cα in step S7, the CPU 50 proceeds to step S9, and in step S9, the output voltage V of the potentiometer 15 is determined.
And the difference ΔV between the voltage value V2 and the previously read voltage value V1 is calculated. Next, in step S10, the CPU 50 determines whether or not the difference ΔV is larger than a predetermined value β.
Proceed to 11. Then, in step S11, the counter 53 is cleared, and the voltage values V1 and V2 stored in the RAM 52 are deleted. Then, the process proceeds to step S8. The predetermined value β is a value corresponding to the amount of swing of the potentiometer 15 due to the vibration of the forklift 1, and is set to the same size as that in which the operation of the tilt cylinder 9 is substantially stopped.

If the difference ΔV is equal to or smaller than the predetermined value β in step S10, it means that the mast 3 is substantially stopped even though the tilt lever 13 is held at the tilt operation position for a predetermined time or more. Therefore, the CPU 50 proceeds to step S12, determines that the cargo handling operation detecting means is fixed, and stores the data in the RAM 52. At this time, the CPU 50 stores the data of the failure (short) of the front tilt detection switch 18 when the ON signal is output from the front tilt detection switch 18 and stores the data of the failure (short) when the ON signal is output from the rear tilt detection switch 19. 19 stores failure (short) data. Next, the process proceeds to step S3, where an operation stop command to the proportional solenoid valve 39, that is, a solenoid off command is output to the solenoid drive circuit 48. Therefore, the excitation of the proportional solenoid valve 39 is released even if either the forward tilt detection switch 18 or the rear tilt detection switch 19 outputs an ON signal.

This embodiment has the following effects. (A) Supply control of hydraulic oil to a cylinder for operating a cargo handling attachment, a manual operation direction switching valve (control valve 22 for tilt) for switching between supply and discharge directions of hydraulic oil to the cylinder, and a solenoid valve In an industrial vehicle operated in cooperation with the (control valve 35 + proportional solenoid valve 39), it is possible to detect a failure in which the cargo handling operation detecting means (the front tilt detection switch 18 and the rear tilt detection switch 19) is stuck in the ON state. Therefore, a failure can be dealt with early.

(B) When the cargo handling operation detecting means detects a failure which is fixed in the ON state, even if a signal for operating the solenoid valve is output from the cargo handling detecting means, the actuation to the solenoid valve is performed. Stop the command. Therefore, it is possible to prevent overheating of the hydraulic oil due to an increase in the load on the hydraulic pump 24 due to supply of unnecessary hydraulic oil, and overheating of the electromagnetic valve and its control means due to continuous useless current flowing through the electromagnetic valve.

(C) When the forklift 1 is tilted, the front tilt detection switch 18 or the rear tilt detection switch 1
9 is turned on, the energization of the proportional solenoid valve 39 is stopped.
In addition, overheating of the control device 45 can be prevented.

(D) Since a voltage corresponding to the amount of tilt of the mast 3 from the reference position is output from the tilt angle detecting means (potentiometer 15), a change in the tilt angle can be easily detected based on the amount of change in the output voltage. .

(E) When the current value for limiting the backward inclination speed is EEPR
The control valve 44 is stored in the OM 51b.
When the current value for restricting the backward tilting speed is newly set for the exchange of the data, it is easy to rewrite the current value. (F) Since the opening of the control valve 35 can be controlled by the pilot pressure supplied via the proportional solenoid valve 39, it is easy to control the opening of the control valve 35 to gradually change.

(G) A pilot pressure supply means for supplying pilot pressure to the pilot operation check valve 36 and the proportional solenoid valve 39 is constituted by a line 40 branched from the hydraulic oil supply line 25 to the lift cylinder 4. This simplifies the configuration of the pilot pressure supply means.

(H) The control of the supply of hydraulic oil to the tilt cylinder 9 is controlled by a tilt control valve 22 (manual operation direction switching valve) for switching between supply and discharge of hydraulic oil to the tilt cylinder 9, and a tilt. The control is performed by a control valve 35 provided in the middle of a pipeline 34a connecting the control valve 22 for use with the tilt cylinder 9. Therefore, the operator can perform the tilting operation by substantially the same operation as the conventional manually operated valve, and can perform the automatic horizontal control and the backward tilting speed control by controlling the solenoid valve as needed. The burden on the worker during the work is reduced.

(I) Since the directional switching valve having a large moving amount of the spool is a manually operated valve and an electromagnetic valve is used for adjusting the flow rate with a small moving amount of the spool, the structure of the electromagnetic valve can be simplified and reduced in size. At the same time, the clearance between the spool and the sliding surface can be reduced, and the amount of hydraulic oil leaked decreases.

(G) The hydraulic oil leaks from the sliding surface when a large pressure is applied to the spool valve, but is provided in the pipe line 34a connecting the tilt control valve 22 and the rod chamber 9b when the spool valve is not tilted forward. The pilot operated check valve 36 is closed, so that the tilt control valve 22 and the control valve 35 are closed.
Large pressure does not act on Accordingly, when the mast 3 is held at the predetermined forward tilt position for a long time, leakage of hydraulic oil from the tilt control valve 22 or the control valve 35 is prevented, and the tilt is reliably maintained at the predetermined forward tilt angle.

The embodiment is not limited to the above, and may be embodied as follows, for example. The mast angle detecting means is only required to be able to detect the tilt angle of the mast 3 from the reference position, and the rotary potentiometer 1 for detecting the rotation angle of the tilt cylinder 9
For example, a linear potentiometer that detects the amount of expansion and contraction of the tilt cylinder 9, that is, the amount of protrusion of the piston rod 9a may be used. Further, the rotation angle of the shaft that rotates together with the mast 3 may be detected by a potentiometer or a rotary encoder.

The forward tilt detecting switch 18 and the backward tilt detecting switch 19 may be any switches that can detect that the tilt lever 13 has been moved to the operation position, and are not limited to micro switches, but may be formed by using a proximity switch or an optical switch. Is also good.

A notification means is provided on the forklift 1,
When the CPU 50 determines that the forward tilt detection sensor 18 or the rearward tilt detection sensor 19 has failed, the CPU 50 outputs an operation stop command to the proportional solenoid valve 39, that is, a demagnetization command, and outputs an operation command signal to the notification means. I do. The notification means includes a buzzer, a warning light, a display (display device), and the like. In this case, the operator can confirm the operation of the notification means and take an action such as repairing a failed part at an early stage.

When the CPU 50 determines that the forward tilt detecting sensor 18 or the backward tilt detecting sensor 19 has failed, instead of outputting an operation stop command to the proportional solenoid valve 39,
It is configured to output an operation command signal to the notification means as described above. In this case, the supply of unnecessary pilot pressure to the solenoid valve is not automatically stopped when a failure is detected. However, when the worker confirms the operation of the notification means, it is possible to take measures such as stopping the cargo handling work.

The solenoid operated valve may be replaced with a solenoid operated valve instead of the pilot operated proportional valve. The present invention is not limited to the tilt cylinder 9, but may be applied to a case where the control of the lift cylinder 4 is performed by a combination of a manual lift control valve 21 and an electromagnetic valve.

The elevation sensor 14 may be any sensor that can detect whether or not there is a portion to be detected, and a limit switch or an optical switch may be used instead of the proximity switch. A plurality of height sensors 14 are provided instead of two stages of whether the height is high or not, so that the height can be detected in three or four or more stages. When the load is loaded, the backward tilt speed is limited in three or more stages in combination with the load. In this case, the rearward tilting speed can be set to a more appropriate value as compared with a case where the rearward tilting speed is limited at two levels of lift regardless of the presence or absence of the load.

In this case, a sensor capable of continuously detecting the height may be used as the height detection means. For example, a conventionally used reel-type lift sensor is used as a sensor capable of continuously detecting the lift. Further, a sensor other than a reel-type lift sensor may be used as a sensor for continuously detecting the lift.

Instead of configuring the pilot pressure supply means with a pipe 40 branched from the hydraulic oil supply pipe 25,
A hydraulic pump having a small capacity driven by the engine E may be provided separately, and hydraulic oil for pilot pressure may be supplied to the pipeline 40 from the hydraulic pump. In this case, the pressure reducing valve 42 may not be provided.

The pilot operation check valve 36 may be omitted. If the pilot operation check valve 36 is not provided, the control valve 35 may be provided in the conduit 34b connecting the bottom chamber 9c and the tilt control valve 22. Pilot operated check valve 3
When there is no 6, since leakage of hydraulic oil from the control valve 35 and the tilt control valve 22 in the forward tilt state is not prevented,
The same effect can be obtained by providing the control valve 35 on either side of the two pipelines 34a and 34b.

The lift control valve 21, the tilt control valve 22, the control valve 35, the proportional solenoid valve 39 and the like are integrated into one control valve 44, but the control valves 21, 22, 35 are separately provided. May be formed.

Attachment other than the fork 6 as an attachment for cargo handling, for example, a roll clamp used for transporting roll paper, a block clamp used for transporting blocks or stacking work, or a coiled wire or cable such as a coil. Alternatively, the present invention may be applied to a forklift equipped with a ram or the like used for transporting a cylindrical load, or a shovel loader, a backhoe, an aerial work vehicle, etc. other than the forklift.

The present invention is not limited to an industrial vehicle using an engine as a driving source, but may be applied to an industrial vehicle using a battery as a driving source. In this specification, "to operate the cargo handling attachment" means not only the case where the attachment is directly operated but also the case where a member supporting the attachment, for example, a mast of a forklift is operated. Further, "industrial vehicle" refers to a vehicle having a hydraulic cylinder and a work body reciprocated by the hydraulic cylinder, and includes not only forklifts but also aerial work vehicles, shovel loaders, backhoe vehicles, and the like. .

The technical ideas (inventions) other than those described in the claims which can be understood from the above embodiments will be described below together with their effects. (1) In the invention according to any one of claims 1 to 4, the solenoid valve is operated by a pilot pressure, and the pilot pressure is controlled by a proportional solenoid valve. In this case, it becomes easy to control the operation speed of the cylinder when it operates.

(2) In the invention according to any one of claims 1 to 4 and (1), the solenoid valve is of a normally closed type. In this case, it is possible to prevent the cylinder from operating even if the cargo handling operation means is operated while the industrial vehicle is stopped.

(3) In the invention according to any one of claims 1 to 4, when the cargo handling operation detecting means determines that a failure has occurred, an operation command signal to a notifying means (buzzer, warning light, etc.) is output. It is configured to include a control unit. in this case,
An operator can confirm the operation of the notification means and take an early action such as repairing a failed part.

[0086]

As described in detail above, claims 1 to 4 are provided.
According to the invention described in (1), it is possible to detect a failure in which the cargo handling operation detection means is fixed in the ON state, and thus to deal with the failure early.

According to the second aspect of the present invention, even if a failure occurs in which the cargo handling operation detecting means is fixed when the cargo handling operation detecting means is on, unless the cargo handling operating means is operated at the cargo handling operation position, the operation of the electromagnetic valve is not performed. The command is stopped. Therefore, it is possible to prevent overheating of the hydraulic oil due to an increase in the load on the hydraulic pump due to supply of unnecessary hydraulic oil, and overheating of the solenoid valve and its control means due to continuous useless current flowing through the solenoid valve.

According to the third aspect of the invention, the effects of the first and second aspects of the invention are exerted in the tilt control of the tilt cylinder of the forklift. According to the fourth aspect of the present invention, a change in the tilt angle can be easily detected based on the amount of change in the output voltage.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating a failure diagnosis procedure according to an embodiment.

FIG. 2 is a block diagram showing an electrical configuration of the control device.

FIG. 3 is a side view of the forklift.

FIG. 4 is a side view of a tilt operation lever.

FIG. 5 is a hydraulic circuit diagram for operating a tilt cylinder and a lift cylinder.

FIG. 6 is a diagram showing a relationship between a tilt angle and an output voltage of a potentiometer.

FIG. 7 is a diagram showing a relationship between a command current value and a tilt angle during a backward tilt operation.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Forklift as an industrial vehicle, 3 ... Mast as an actuated body, 6 ... Fork as a cargo handling attachment, 9 ... Tilt cylinder, 13 ... Tilt lever as cargo handling operation means, 15 ... Potentiometer as actuation amount detection means , 18: forward tilt detection switch as cargo handling operation detecting means, 19: similarly rearward tilt detection switch, 22 ...
Tilt control valve as manual operation direction switching valve, 35 ...
A control valve constituting an electromagnetic valve; 39, a proportional solenoid valve; 45, a control device; 49, a current detection circuit as current detection means; 50, a CP as control means and determination means;
U.

Claims (4)

(57) [Claims] The control of supply of hydraulic oil to a cylinder for operating a cargo handling attachment is performed jointly with a manually operated directional switching valve for controlling the supply and discharge directions of hydraulic oil to the cylinder and an electromagnetic valve. In an industrial vehicle, cargo handling operation means for operating the manual operation direction switching valve; cargo handling operation detection means for detecting whether the cargo handling operation means is operated to a cargo handling operation position; and an actuated body operated by the cylinder. An operation amount detecting means for detecting an operation amount of the current detecting means, a current detecting means for detecting a current flowing through the solenoid valve, and a state in which a proper output signal is outputted from the current detecting means, the cargo handling operation means performs a cargo handling operation. A change means for observing a change in an output signal of the operation amount detection means during operation to a position, and when the change amount is equal to or less than a predetermined value, a determination means for determining that the cargo handling operation detection means is out of order. Trouble diagnosis device for industrial vehicle equipped with. 2. When the determining means determines that a failure has occurred,
The failure diagnosis device for an industrial vehicle according to claim 1, further comprising a control unit that stops an operation command to the solenoid valve even when a signal to operate the solenoid valve is output from the cargo handling operation detection unit. 3. The industrial vehicle is a forklift,
The cylinder is a tilt cylinder, the cargo handling operation means is a tilt operation means for issuing a tilt cylinder operation command, and the operation amount detection means is a tilt angle detection means for detecting a tilt angle of a mast. The fault diagnosis device for an industrial vehicle according to claim 2. 4. The fault diagnosis device for an industrial vehicle according to claim 4, wherein said tilt angle detecting means outputs a voltage corresponding to a tilt amount of the mast from a reference position.