JPH10265193A - Tilt cylinder controller of industrial vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent cargo from shitting and the rear wheels of a forklift from floating even in the event of erroneous operation by enabling even an unskilled operator to easily perform forward tilting action at a great lift height. SOLUTION: A tilt cylinder 9 is controlled via a manually operated tilt control valve and a control valve whose pilot pressure is controlled by a proportional solenoid valve 43. An outer mast 3a is provided with a lift height sensor 14. The tilt angle of the mast 3 from its vertical position is detected by a potentiometer 15. The live load of a fork 6 is detected by a pressure sensor 17. A CPU 53 computes the maximum allowable forward tilt angle of the mast 3 on the basis of the lift height and the live load. During the forward tilting action of the mast 3, once the mast angle detected by the potentiometer 15 has reached the maximum allowable forward tilt angle, the CPU 53 outputs a signal whereby the opening of the proportional solenoid valve 43 is set to zero irrespective of the operated position of the manually operated tilt control valve.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tilt cylinder control device for an industrial vehicle in which a mast for raising and lowering a cargo handling attachment is tiltably mounted and the mast is tilted by the operation of a tilt cylinder. This relates to tilt angle control.

[0002]

2. Description of the Related Art In a forklift, which is an industrial vehicle of this kind, a fork is raised 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. .

[0003] In a forklift, when a load is loaded on a fork, the center of gravity moves forward, and when the forklift height is increased, the moment acting on the mast increases. When the mast is tilted forward with a load being loaded, the center of gravity moves forward, and the stability of the forklift in the front-rear direction deteriorates. In addition, if the rearward inclination angle is too large in a state where the load is large, the center of gravity may be too close to the rear side, and the front wheels may be slightly lifted and slippage may occur. Therefore, conventionally, the forward tilt angle and the backward tilt angle of the mast have been set to predetermined values. Generally, the forward tilt angle is set to 6 degrees and the rear tilt angle is set to 12 degrees. However, in a special forklift having a high mast, the front tilt angle is set to 3 degrees and the rear tilt angle is set to 6 degrees. There is also.

[0004]

When a load is placed at a high place in a cargo handling operation, it is necessary to tilt the mast forward by setting the fork to a high elevation. At this time, if the mast leans forward at a high forward leaning speed due to erroneous operation or the like, load collapse or lifting of the rear wheel of the forklift (that is, unstable state in the longitudinal direction of the vehicle) occurs. Therefore, it is necessary for the worker to perform the forward leaning operation carefully and at a low speed by the inching operation so that the mast does not lean forward too much, which is a great mental burden. In addition, in the conventional apparatus, the operation of tilting the mast by setting the fork to a high elevation required skill.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object thereof is to enable a non-skilled worker to easily perform a tilting operation with a high elevation and a forward tilt. Another object of the present invention is to provide a tilt cylinder control device for an industrial vehicle that does not cause collapse of a load or lifting of a rear wheel of a forklift (that is, an unstable state in the longitudinal direction of the vehicle) even if an erroneous operation is performed.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, a mast for raising and lowering the cargo handling attachment is tiltably provided, and the mast is tilted by the operation of the tilt cylinder. The industrial vehicle further includes control means for controlling the supply of hydraulic oil to the tilt cylinder in order to regulate the forward inclination angle of the mast so as to secure a stable state in the longitudinal direction of the cargo or the vehicle during the cargo handling operation.

According to the second aspect of the present invention, in an industrial vehicle in which a mast for raising and lowering the loading / unloading attachment is tiltably provided and the mast is tilted by the operation of a tilt cylinder, the lifting and loading of the loading / unloading attachment is performed. Control means is provided for controlling the supply of hydraulic oil to the tilt cylinder so as to regulate the forward inclination angle of the mast in accordance with the load.

According to the third aspect of the present invention, in an industrial vehicle in which a mast for raising and lowering the loading / unloading attachment is tiltably provided and the mast is tilted by the operation of the tilt cylinder, the lift of the loading / unloading attachment is detected. Height detecting means, a mast angle detecting means for detecting a tilt angle of the mast from a reference position, a loading load detecting means for detecting a loading load of the cargo handling attachment, a height and a loading load and a maximum allowable load. A storage unit that stores a map or a relational expression representing a relationship with the inclination angle, and a maximum allowable forward inclination of the mast based on the lift detected by the lift detection unit and the load detected by the load detection unit. Calculating means for calculating an angle, and detecting the mast angle when the tilt cylinder is operated when rotating the mast toward the front side. Is detected mast angle and a control means for controlling the supply of hydraulic oil to the tilt cylinder to stop the pre-tilting operation of the tilt cylinder reaches the maximum allowed forward tilt angle by means.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the height detecting means is a sensor capable of continuously detecting the height. In the invention according to claim 5,
In the invention according to claim 3, the height detecting means is a sensor capable of detecting whether or not the height is equal to or higher than a predetermined height.

According to the invention described in claim 6, in the invention described in any one of claims 1 to 5, the control means for controlling the supply of hydraulic oil to the tilt cylinder includes:
A manually operated directional control valve for switching and controlling the supply and discharge of hydraulic oil to and from the tilt cylinder, an electromagnetic valve provided in the middle of a pipe connecting the manual operated directional control valve and the tilt cylinder, And a control device for controlling the solenoid valve to be in a state in which the mast angle becomes a predetermined angle when the tilt cylinder is actuated when the tilt cylinder is rotated toward the closed state.

According to a seventh aspect of the present invention, in the sixth aspect of the invention, the solenoid valve is switched by a pilot pressure, and the pilot pressure is controlled by a proportional solenoid valve.

According to the invention described in claim 8, in the invention described in any one of claims 1 to 5, the control means for controlling supply of hydraulic oil to the tilt cylinder includes:
An electromagnetic proportional control valve for switching between supply of hydraulic oil from the hydraulic oil source to the tilt cylinder and discharge of hydraulic oil from the tilt cylinder, and operation of the tilt cylinder when the mast is rotated toward the front side A control device for controlling the electromagnetic proportional control valve to be in a cutoff state of a pipe connecting the hydraulic oil source and the tilt cylinder when the mast angle reaches a predetermined angle.

According to the ninth aspect of the present invention, the sixth to eighth aspects are provided.
In the invention according to any one of the above, the solenoid valve or the electromagnetic proportional control valve, of the oil chamber of the tilt cylinder of the oil chamber of the side to which a large pressure is applied at the time of forward tilt of the mast of the mast, A pilot-operated check valve that regulates the flow of hydraulic oil from the oil chamber to the electromagnetic valve or the electromagnetic proportional control valve is provided on the way.

Therefore, according to the first aspect of the present invention, the supply of the hydraulic oil to the tilt cylinder is controlled by the control means. When the mast is tilted forward, the forward tilt angle of the mast is regulated so as to secure a stable state in the longitudinal direction of the load or the vehicle, and the tilt cylinder is operated. Therefore, unlike the conventional device, the unstable state of the vehicle, in which the load collapses and the rear wheels are lifted, is avoided.

According to the second aspect of the present invention, the supply of the hydraulic oil to the tilt cylinder is controlled by the control means. Then, the tilt cylinder is operated such that the mast has a proper forward inclination angle in accordance with the lifting height and the load of the cargo attachment during the forward leaning operation of the mast. Therefore, there is no possibility that the collapse of the load or the lifting of the rear wheel occurs unlike the conventional device.

According to the third aspect of the present invention, the lift of the cargo handling attachment is detected by the lift detecting means. The tilt angle of the mast from the reference position is detected by the mast angle detecting means. The load of the cargo attachment is detected by the load detector. The maximum allowable forward inclination angle of the mast is calculated by the calculating means based on the lift detected by the lifting height detecting means and the loading load detected by the loading load detecting means. When the mast angle detected by the mast angle detection means reaches the maximum allowable forward inclination angle during the operation of the tilt cylinder when rotating the mast toward the front side, the supply of hydraulic oil to the tilt cylinder is controlled by the control means. , And the forward tilting operation of the tilt cylinder is stopped. That is, when the mast leans forward,
It is reliably prevented that the mast leans forward until it becomes larger than an appropriate angle corresponding to the load and the lift.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the lift of the cargo handling attachment is continuously detected by the lift detecting means. Therefore, the forward tilt angle of the mast is regulated to a more appropriate value.

According to a fifth aspect of the present invention, in the third aspect of the invention, the height detecting means detects whether the height is equal to or higher than a predetermined height. That is, the lift is 2
Since the determination criteria are provided at each stage, the control for the determination is simplified.

According to a sixth aspect of the present invention, in the invention according to any one of the first to fifth aspects, the supply and discharge of the hydraulic oil to and from the tilt cylinder are performed by a manual operation direction switching valve and an electromagnetic switch. Controlled by a valve. The solenoid valve controls the flow of hydraulic oil in a pipe connecting the manually operated directional control valve and the tilt cylinder. When the mast angle reaches a predetermined angle in a state where the manual operation direction switching valve is switched to the forward tilt operation position and the tilt cylinder is operated to rotate the mast toward the front side, the solenoid valve is controlled by the control means. Is controlled to be in a line cutoff state. Therefore, even if the manual operation direction switching valve is held at the forward tilt operation position, the operation of the tilt cylinder is stopped, and the mast is held at the predetermined forward tilt angle.

According to a seventh aspect of the present invention, in the sixth aspect, the solenoid valve is switched by a pilot pressure, and the pilot pressure is controlled by a proportional solenoid valve. Accordingly, the operation speed of the tilt cylinder can be easily controlled during the operation.

According to an eighth aspect of the present invention, in the first aspect of the present invention, supply of hydraulic oil from a hydraulic oil source to the tilt cylinder and operation of the tilt cylinder from the tilt cylinder Switching to oil discharge is performed by an electromagnetic proportional control valve. When the mast angle reaches a predetermined angle during the operation of the tilt cylinder when rotating the mast toward the front side, the electromagnetic proportional control valve is actuated by a command from a control device to supply a hydraulic oil source and the tilt cylinder. Is controlled to be in a state in which the pipeline connecting to is maintained in the cutoff state.

According to the ninth aspect of the present invention, the sixth to eighth aspects are provided.
In the invention according to any one of the above, in the middle of a pipeline connecting the electromagnetic valve or the electromagnetic proportional control valve and the oil chamber of the tilt cylinder to which a large pressure is applied when the mast is tilted forward in the oil chamber. The hydraulic oil in the oil chamber is returned to the tank via a pilot-operated check valve provided in the tank. When the pilot pressure is not supplied to the pilot operation check valve, the flow of hydraulic oil from the oil chamber to the electromagnetic valve or the electromagnetic proportional control valve is blocked. Therefore, when the mast is in the state in which the forward tilt angle is restricted, the hydraulic oil does not easily leak from the oil chamber of the tilt cylinder, and the mast is held at a predetermined angle.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIGS. 1 to 5 show a first 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.
It will be described according to.

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 is attached to the lift bracket 5. Innamasto 3
A chain wheel 7 having a first end connected to the lift cylinder 4 or the outer mast 3a and a second end connected to the lift bracket 5 is mounted on the chain wheel 7 at an upper portion of the chain wheel 7. Have been.
The fork 6 is moved up and down together with the lift bracket 5 via the chain 8 by the expansion and contraction of the lift cylinder 4.

A base end of a tilt cylinder 9 is rotatably supported on both left and right sides of a front portion of the body frame 2, and a distal end of a piston rod 9a is rotatably connected to 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.

In the front of the cab 10, a steering wheel 11,
A lift lever 12 as a lift operation means and a tilt lever 13 as a tilt operation means are provided, respectively. FIG. 3 shows both levers 12 and 13 in an overlapping state. The operation of the lift lever 12 causes the lift cylinder 4 to expand and contract, and the tilt lever 13
The tilt cylinder 9 is expanded and contracted by the operation described above.

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. 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 mast angle detecting means. 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 rotation piece 15a rotates together with the tilt cylinder 9 in accordance with the expansion and contraction of the piston rod 9a, and a detection signal corresponding to a tilt angle (tilt angle) from a reference position at which the mast 3 is vertical is transmitted to the potentiometer 15.
Is output.

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 detecting switch 18 and a rear tilt detecting switch 19 as tilt operation detecting means are provided. Both detection switches 18 and 19 are composed of micro switches,
The forward tilt detection switch 18 is turned on when the tilt lever 13 is at the forward tilt position, and is turned off when the tilt lever 13 is at any other position. The backward tilt detection switch 19 is turned on when the tilt lever 13 is in the backward tilt position, and is turned off when the tilt lever 13 is in any other position.

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. 1, the lift cylinder 4 is connected to a lift control valve 22 via a pipe 20. Pipe line 20
The pilot operated check valve 21 for restricting the flow of hydraulic oil from the bottom chamber 4b side to the lift control valve 22
Is provided. As the lift control valve 22, a direct-acting spool valve is used. The lift control valve 22 is a manually operated 7 port 3 position switching valve.
Can be switched to three states a, b, and c in accordance with the lift, neutral, and lower operation positions of the lift lever 12 for instructing the lifting, lowering, and stopping of the operation. A 6-port, 3-position switching valve is used as the tilt control valve 23 as a manually operated direction switching valve, and corresponds to the forward tilt, neutral, and rear tilt operation positions of the tilt lever 13 for instructing the fork 6 to tilt and stop. ,
The state can be switched to three states of c, b, and a.

A hydraulic pump 25 for supplying hydraulic oil in an oil tank 24 to each of the cylinders 4 and 9 is driven by an engine E (shown in FIG. 3). The hydraulic pump 25 is connected to a port P1 of the lift control valve 22 via a hydraulic oil supply line 26 as a main line. Hydraulic oil supplied from the hydraulic pump 25 is supplied to the hydraulic oil supply line 26 with the cargo handling device side (lift cylinder 4 and tilt cylinder 9).
A flow divider 28 is provided for diverting to the power steering valve 27 side. Hydraulic oil supply line 26
Are ports P2 and P3 via branch pipes 26a and 26b branched downstream of the flow divider 28.
Connected to each other. A check valve 29 is provided in the branch conduit 26a. The hydraulic oil supply line 26 is connected to a return line 32 via a line 31 a provided with a relief valve 30. Lift control valve 22 is connected to return line 32 at port T1, to line 20 at port A1, to line 31b at port A2, and to port A3.
Are connected to the pipeline 34 respectively. Conduit 31
b is connected to the return line 32, and a relief valve 33 is provided on the way. The set pressure of the relief valve 33 is set to a value smaller than the set pressure of the relief valve 30. The conduit 20 is connected to a bottom chamber 4b as an oil chamber on the bottom side of the lift cylinder 4.

The lift control valve 22 is disposed at the position a based on the lifting operation of the lift lever 12, and connects the branch line 26a to the line 20 at the position a to extend the lift cylinder 4. The lift control valve 22 is disposed at the position c based on the lowering operation of the lift lever 12, and branches the line 20 and the return line 32, the hydraulic oil supply line 26 and the line 34 at the position c. The pipe 26b and the pipe 31b are communicated with each other to contract the lift cylinder 4.

The lift control valve 22 is disposed at a position b based on the neutral operation of the lift lever 12, and connects the hydraulic oil supply line 26 and the line 34 with the branch line 26b at the position b. 31b. And
The communication between the pipe 20 and the branch pipe 26a and the return pipe 32 is interrupted, and the state in which the movement of the hydraulic oil in the lift cylinder 4 is prevented is maintained.

The hydraulic pump 25 is connected to a port P11 of the tilt control valve 23 via a hydraulic oil supply pipe 35 branched from the hydraulic oil supply pipe 26. A check valve 36 is provided in the hydraulic oil supply pipe 35. A pipe 34 is connected to a port P12 of the tilt control valve 23. The tilt control valve 23 is connected to the return line 32a at the port T11 and to the return line 32b at the port T12. Port A for tilt control valve 23
11 at line 37a and port A12 at line 37.
b. The pipe 37a is in the rod chamber 9b of the tilt cylinder 9, and the pipe 37b is in the bottom chamber 9c.
Connected to each other.

The tilt control valve 23 is arranged at the position a based on the backward tilting operation of the tilt lever 13, and connects the hydraulic oil supply pipe 35 and the pipe 37a at the a position and the return pipe 32a and the pipe 37b, and the tilt cylinder 4 can be contracted. The tilt control valve 23 is arranged at the position c based on the forward tilt operation of the tilt lever 13. At the position c, the hydraulic oil supply pipe 35 and the pipe 37b are communicated with each other, and the pipe 37a is placed in communication with the return pipe 32a so that the tilt cylinder 9 can be extended. The tilt control valve 23 is disposed at the position b in FIG. 1 based on the neutral operation of the tilt lever 13, and cuts off the communication between the two pipes 37a, 37b, the hydraulic oil supply pipe 35, and the return pipe 32a. As a result, the state in which the movement of the hydraulic oil in the tilt cylinder 9 is prevented is maintained.

A control valve 38 and a pilot operation check valve 39 are provided in the middle of the conduit 37a. The pilot operation check valve 39 is provided between the control valve 38 and the rod chamber 9b so as to regulate the flow of hydraulic oil from the rod chamber 9b to the control valve 38. The control valve 38 is a one-way valve, and includes a direct-acting spool that opens and closes the conduit 37a. The control valve 38 is a normally-closed control valve, and a 2-port 2-position valve operated by pilot hydraulic pressure is used. The control valve 38 closes the conduit 37 a by the spring force of the spring 40 and the conduit 37 a. It is possible to switch between two positions, that is, the communicating position b. A passage 41 is formed in the spool so as to communicate with the conduit 37a when the spool is located at the position b. The passage 41 has an orifice. Pilot pressure to control valve 38 and pilot operated check valve 39 is supplied by proportional solenoid valve 43. Control valve 38
And the tilt cylinder 9 by the proportional solenoid valve 43.
An electromagnetic valve that opens and closes a conduit 37a that connects the control valve 23 with the tilt control valve 23 is configured.

The pilot pressure supply means for supplying the pilot pressure to the pilot operation check valves 21 and 39 and the proportional solenoid valve 43 is provided at the upstream side of the flow divider 28 of the hydraulic oil supply line 26 with the hydraulic oil supply line. It is constituted by a pipeline 44 branched from 26. A pressure reducing valve 45 and a filter 46 are provided in the middle of the pipe 44.

The proportional solenoid valve 43 has a tank port T2 connected to the return line 32a, and an A port connected to the line 4
4 is connected. In addition, B of the proportional solenoid valve 43
The port communicates with a pressure chamber (not shown) provided at one end of the spool of the control valve 38. In the control valve 38, a pressure chamber (not shown) at the other end of the spool is connected to the return line 32.

The proportional solenoid valve 43 is a normally closed type solenoid valve. When the solenoid is demagnetized, the B port and the tank port T
2 is communicated. The proportional solenoid valve 43 is configured so that the amount of operation of the spool is proportional to the current supplied for excitation. When the solenoid is excited, the spool operates and the A port and the B port are connected. In communication, the pilot pressure set at the operating position of the spool is supplied to the spool of the control valve 38. By this pilot pressure, the spool of the control valve 38 is moved against the spring force of the spring 40.

The lift control valve 22, the tilt control valve 23, the pilot operated check valves 21, 39, the check valve 2
9, 36, the relief valves 30, 33, the control valve 38, the proportional solenoid valve 43, and the pressure reducing valve 45 are formed in one housing, and one control valve 48 as a whole.
Is composed.

Next, an electrical configuration for controlling the hydraulic circuit will be described. As shown in FIG. 2, a control device 49 for controlling the opening of the control valve 38, that is, the output pilot pressure of the proportional solenoid valve 43, includes a microcomputer 50, an analog / digital conversion circuit (A / D conversion circuit) 51, and a solenoid drive. A circuit 52 is provided. Microcomputer 5
0 is a central processing unit (hereinafter, referred to as a CPU) 53 as arithmetic means, a read-only memory (ROM) 54a,
EEPROM (Electrical Erasabl) as storage means
e Programmable ROM) 54b, readable and rewritable memory (RAM) 55, and input interface 5
6 and an output interface 57. In this embodiment, control means for controlling the supply of hydraulic oil to the tilt cylinder 9 is constituted by the tilt control valve 23, the control valve 38, the proportional solenoid valve 43, and the control device 49.

The ROM 54a stores (stores) various control programs and data necessary for executing the programs.
Have been. The control program includes, for example, a forward leaning angle restriction control program. The EEPROM 54b stores a map representing the relationship between the lift and the load and the maximum allowable forward tilt angle as data necessary to execute the forward tilt angle restriction control program. For example, as shown in FIG. 5, there are two types of maps: a case of a high lift (solid line) and a case of a low lift (dashed line). Is the maximum allowable forward tilt angle θmax (for example, 6 °). On the other hand, when there is a load, the maximum allowable forward inclination angle is different between the high lift and the low lift. In the case of a high lift, the maximum allowable forward tilt angle decreases with an increase in the load, and in the case of a low lift, the maximum allowable forward tilt angle reaches the maximum allowable forward tilt angle θmax up to a certain load. The maximum allowable lean angle decreases with increasing load. However, the maximum allowable forward tilt angle is a larger value than in the case of high elevation. The minimum value of the maximum allowable forward tilt angle at the time of low lift and high lift varies depending on the mounting position of the lift sensor 14, that is, the criterion value for determining whether the lift is high or low. The minimum value θmin of the maximum allowable forward tilt angle at the time of high is set to about 2 °.

The CPU 53 is connected to the potentiometer 15 and the pressure sensor 17 via the A / D conversion circuit 51 and the input interface 56, respectively. CPU53
Are connected to the elevation sensor 14, the forward tilt detection switch 18 and the rear tilt detection switch 19 via the input interface 56, respectively. CPU 53 is an output interface 5
7, and is connected to a solenoid drive circuit 52.
The CPU 53 inputs the output signals of the sensors 14, 15, 17 and both switches 18, 19, and
It operates according to various control programs stored in 54a, and outputs a control command signal to the proportional solenoid valve 43 via the solenoid drive circuit 52 when the tilt cylinder 9 operates.

Next, the operation of the above-configured apparatus will be described. When the engine E is operated and the hydraulic pump 25 is driven, the operating oil in the oil tank 24 is discharged to the operating oil supply pipe 26. Therefore, the pipeline 44 for supplying the pilot pressure is in a state where the pilot pressure can be supplied as soon as the hydraulic pump 25 is driven, and the pilot operation check valve 21 provided on the pipeline 20 is moved from the bottom chamber 4b side. The state where the flow of the hydraulic oil to the lift control valve 22 side is also allowed is maintained.

When the lift lever 12 is raised from the neutral position, the spool of the lift control valve 22 is disposed at the position a, the hydraulic oil supply line 26 is in communication with the line 20, and the hydraulic pump 25 Hydraulic oil discharged from the hydraulic oil supply line 26, the lift control valve 22, and the line 20
Is supplied to the bottom chamber 4b of the lift cylinder 4 via
The lift cylinder 4 extends and the fork 6 rises.

When the lift lever 12 is lowered, the spool of the lift control valve 22 is located at the position c, and the line 2
0 is communicated with the return pipe 32, and the hydraulic oil in the bottom chamber 4b is returned to the oil tank 24. Then, the lift cylinder 4 contracts and the fork 6 descends. Lift lever 1
Based on the second neutral operation, the lift spool is arranged at the position “b”, and the communication of the pipeline 20 to both the hydraulic oil supply pipeline 26 and the return pipeline 32 is cut off. as a result,
The movement of the hydraulic oil in the lift cylinder 4 is prevented, and the fork 6 is held at a desired position.

When the engine E is stopped and the hydraulic pump 25 ceases to discharge the hydraulic oil, the pilot pressure is no longer supplied to the pipeline 44, and the pilot operation check valve 21 is moved from the lift control valve 22 to the bottom of the lift cylinder 4. This is a state where only the movement of the hydraulic oil toward the chamber 4b is permitted. Therefore, when the operation of the forklift 1 is stopped in a state where the fork 6 is arranged at the ascending position, a third party operates the lift lever 12 to move the forklift 1 to the descending position.
Even if the pipe 20 is in communication with the return pipe 32, the hydraulic oil in the bottom chamber 4 b cannot flow through the pipe 20,
The fork 6 is reliably prevented from lowering.

When the tilt lever 13 is in the neutral position, the spool is held at the position b in FIG. 1, and the two pipes 37a and 37b are connected to either the hydraulic oil supply pipe 35 or the return pipe 32a. 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 disposed at the position c by the tilting operation of the tilt lever 13, the hydraulic oil supply pipe 35 and the pipe 37b are connected, and the pipe 37a and the return pipe 32a.
Is in a state of being communicated with. On the other hand, the tilt lever 13
Is operated forward, the CPU 53 causes the forward lean detection switch 1
8 is input. Then, an excitation command signal is output from the CPU 53 to the proportional solenoid valve 43 via the solenoid drive circuit 52, and a pilot pressure is supplied to the control valve 38 and the pilot operation check valve 39 of the pipe 37a, and the operating oil is supplied to the pipe 37a. Can be flowed.
As a result, the hydraulic oil is supplied to the bottom chamber 9c via the hydraulic oil supply pipe 35 and the pipe 37b, and the hydraulic oil in the rod chamber 9b is supplied to the oil tank 24 via the pipe 37a and the return pipe 32a. 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 an ON signal of the forward tilt detection switch 18 is input to the CPU 53, the CPU 53 executes a forward tilt angle restriction control program. In this control program, the CPU
53 is a fork 6 based on the output signal of the pressure sensor 17
Is calculated. Also, it is determined from the output signal of the lift sensor 14 whether or not the lift is high, and the maximum allowable forward tilt angle corresponding to the lift and the load is calculated from the map. Then, the CPU 53 sequentially calculates the tilt angle of the mast 3 based on the output signal of the potentiometer 15 and compares the calculation result with the maximum allowable forward tilt angle. When the difference becomes 0, the forward tilt detection switch 1
The excitation command to the proportional solenoid valve 43 is stopped even when the ON signal is output from the controller 8. As a result, the supply of the pilot pressure to the control valve 38 and the pilot operation check valve 39 is stopped, and the flow of the hydraulic oil from the rod chamber 9b to the tilt control valve 23 is stopped. That is, even if the operator does not stop the tilting operation of the tilt lever 13 when the forward tilt angle of the mast 3 reaches the maximum allowable forward tilt angle corresponding to the load, the maximum allowable tilt angle corresponding to the load is ensured. It is held at the forward tilt angle.

If the tilt lever 13 is operated to the neutral position before the mast 3 reaches the maximum allowable forward tilt angle, the CPU
53 terminates the execution of the forward lean angle restriction control program.
Therefore, at this time, the mast 3 stops at a desired position of the operator at a forward inclination angle smaller than the maximum allowable forward inclination angle.

When the spool is disposed at the position a by the backward tilting operation of the tilt lever 13, the hydraulic oil supply pipe 35 and the pipe 37a are connected, and the pipe 37b and the return pipe 32a are connected. It will be in the state to be done. On the other hand, when the tilt lever 13 is tilted backward, an ON signal of the rearward tilt detection switch 19 is input to the CPU 53. And the CPU 53
An excitation command signal is output to the proportional solenoid valve 43 via the solenoid drive circuit 52 from the control valve 3 of the pipe 37a.
The pilot pressure is supplied to the pilot valve 8 and the pilot operation check valve 39, so that the operating oil can flow through the pipeline 37a. As a result, the hydraulic oil supply pipe 35 and the pipe 37a
The hydraulic oil is supplied to the rod chamber 9b through the bottom chamber 9b.
Since the hydraulic oil in c is discharged to the oil tank 24 via the pipe 37b and the return pipe 32a, 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 53 receives an ON signal from the forward tilt detecting switch 18 or the backward tilt detecting switch 19, the CPU 53 calculates an appropriate tilting speed corresponding to the loaded load and the lift, and sets the pilot pressure corresponding to the speed to the pilot pressure. Is output to the solenoid drive circuit 52 to output the excitation current supplied to the control valve 38 to the proportional solenoid valve 43. Therefore, the mast 3 is rotated forward or rearward at an appropriate tilting speed corresponding to the load and the lift.

The CPU 53 has two detection switches 18,
If no ON signal is output from any of the control signals 19, the excitation command to the proportional solenoid valve 43 is not issued. Therefore,
Since the pilot pressure is not supplied to the control valve 38 and the pilot operation check valve 39, the flow of the hydraulic oil from the rod chamber 9b side to the tilt control valve 23 side is kept in a blocked state.

This embodiment has the following effects. (A) Since the control means for controlling the supply of the hydraulic oil to the tilt cylinder 9 is provided so as to regulate the forward inclination angle of the mast 3 in accordance with the lifting height and the load of the fork 6 (loading attachment), The mast 3 is prevented from leaning forward beyond an appropriate forward tilt angle. Therefore, the mental load on the operator is reduced during the forward leaning operation at a high elevation in the loaded state of the load, and the operation can be easily performed even by a non-expert. In addition, even if the tilt lever 13 is operated to the forward most inclined position due to an erroneous operation, the mast 3 is restricted to the forward inclination at an appropriate forward inclination angle, and the collapse of the load or the lifting of the rear wheel of the forklift (that is, the improper longitudinal movement of the vehicle). Stable state) does not occur.

(B) The control means for controlling the supply of the hydraulic oil to the tilt cylinder 9 comprises a tilt control valve 2 for switching between supplying and discharging the hydraulic oil to and from the tilt cylinder 9.
3 (manual operation direction switching valve), and a control valve 38 controlled by a command signal from a control device 49 provided in the middle of a pipe 37a connecting the tilt control valve 23 and the tilt cylinder 9. I have. Accordingly, the operator can perform the tilting operation by the same operation as the conventional manual operation valve, and when the mast angle reaches the maximum allowable forward inclination angle during the forward tilting operation of the mast 3, the control valve is instructed by the control device 49. 38 is controlled to the blocked state of the conduit 37a, and the forward inclination of the mast 3 is regulated.

(C) Since the lift is determined in two stages as to whether the lift is high or not, and the maximum allowable forward tilt angle is set, the calculation by the CPU 53 becomes easy. (D) Since the opening of the control valve 38 can be controlled by the pilot pressure supplied via the proportional solenoid valve 43, the control of the forward tilt speed and the backward tilt speed during the tilt operation is facilitated. Further, during the forward leaning operation, the forward leaning speed is increased (the opening degree of the control valve 38 is increased) until the forward leaning angle of the mast 3 approaches the maximum allowable forward leaning angle, and at the time when the forward leaning angle approaches the maximum allowable forward leaning angle. Deceleration (decreasing the opening of the control valve 38) is also facilitated, and the shock at the time of stoppage can be reduced.

(E) Since a map representing the relationship between the lift and the load and the maximum allowable forward tilt angle is stored in the EEPROM 54b, even when a different map is required depending on the model, a part of the stored contents of the EEPROM 54b is stored. Modifications or additions can be easily accommodated with the same control unit.

(F) 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 37a connecting the tilt control valve 23 and the rod chamber 9b when the spool valve is not tilted forward. Since the pilot operated check valve 39 is closed, no large pressure acts on the tilt control valve 23. Therefore, 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 23 or the control valve 38 is prevented, and the tilt angle is reliably maintained at the predetermined forward tilt angle.

(G) The lift cylinder 4 is manually operated.
An operation from the bottom chamber 4b side to the lift control valve 22 in the middle of the pipe line 20 connecting the lift control valve 22 for switching the supply and discharge of the hydraulic oil to the bottom chamber 4b of the lift cylinder 4. A pilot operation check valve 21 for regulating the oil flow is provided, and a pilot pressure for opening the check valve 21 can be supplied to the pilot operation check valve 21 when the hydraulic pump 25 is driven. Therefore, even if a third party operates the lift lever 12 or the operator mistakenly moves the lift lever 12 to the lowered position in a state where the fork 6 is arranged at the raised position and the operation of the forklift 1 is stopped, The fork 6 is prevented from lowering. (H) A pilot pressure supply means for supplying pilot pressure to the pilot operation check valves 21 and 39 and the proportional solenoid valve 43 is provided by a hydraulic oil supply line 26 to the lift cylinder 4.
, The configuration of the pilot pressure supply means is simplified.

(1) Each valve such as the lift control valve 22, the tilt control valve 23, the pilot operated check valves 21 and 39, the control valve 38, and the proportional solenoid valve 43, which constitute the hydraulic circuit, is provided in one housing. To form one control valve 48 as a whole, the device becomes compact. Also, the number of steps for assembling the forklift 1 is reduced.

(Second Embodiment) Next, a second embodiment will be described with reference to FIGS. This embodiment differs greatly from the previous embodiment in that an electromagnetic proportional control valve is used for controlling the lift cylinder 4 and the tilt cylinder 9. The same parts as those in the above-described embodiment are denoted by the same reference numerals, and detailed description is omitted.

As shown in FIG. 6, a lift electromagnetic proportional control valve 58 replaces the manually operated lift control valve 22, and a tilt electromagnetic proportional control valve 59 replaces the manually operated tilt control valve 23. Is provided.

As shown in FIG. 7, the control device 49 includes a lift lever operation amount sensor 60 as a lift lever operation amount detecting means for detecting an operation amount from the neutral position of the lift lever, and a neutral position of the tilt lever. And a tilt lever operation amount sensor 61 as a tilt lever operation amount detecting means for detecting an operation amount from the camera. Each of the sensors 60 and 61 is configured to output a detection signal corresponding to the amount of change from the neutral position of each of the levers 12 and 13. In this embodiment, for example, a potentiometer is used.

The CPU 53 has a lift lever operation amount sensor 6
Based on the output signal of 0, the opening of the electromagnetic proportional control valve for lift 58 corresponding to the output signal is calculated. Then, a control signal is output to the lift electromagnetic proportional control valve 58 via the electromagnetic valve drive circuit 62 so that the opening degree is obtained. As a result, the lift electromagnetic proportional control valve 58 is controlled to the opening corresponding to the operation amount of the lift lever 12.

Based on the output signal of the tilt lever operation amount sensor 61, the CPU 53 calculates the opening of the tilt electromagnetic proportional control valve 59 corresponding to the output signal. Then, a control signal is output to the tilt electromagnetic proportional control valve 59 via the electromagnetic valve drive circuit 62 so as to achieve the opening. As a result, the tilt electromagnetic proportional control valve 59 is controlled to the opening corresponding to the operation amount of the tilt lever 13, and the mast 3 is tilted at a speed corresponding to the opening. When the tilt lever 13 is tilted forward, the CPU 53 executes a forward tilt angle restriction control program as in the first embodiment. That is, the tilt angle of the mast 3 is sequentially calculated based on the output signal of the potentiometer 15, and the calculation result is compared with the maximum allowable forward tilt angle. When the difference becomes 0, a command signal for setting the opening of the electromagnetic proportional control valve 59 for tilt to 0 is output from the CPU 53 even in a state where the forward tilt signal is output from the tilt lever operation amount sensor 61. You. As a result, the mast 3 stops at the position of the maximum allowable forward tilt angle.

This embodiment has the same effects as (a) to (f), (h) and (li) of the first embodiment. In addition, since the supply and discharge of the hydraulic oil to and from the lift cylinder 4 are controlled by the electromagnetic proportional control valve for lift 58, that is, the electromagnetic valve, even when the lift lever 12 is operated from the neutral position when the operation of the vehicle is stopped, the lift electromagnetic valve is operated. The proportional control valve 58 does not operate. Therefore, even if the pilot operation check valve 21 is omitted, the fork disposed at the raised position is prevented from lowering.

The embodiments are not limited to the above embodiments, but may be embodied as follows, for example. The height sensor 14 may be any sensor that can detect whether or not there is a detected portion, and a limit switch or an optical switch may be used instead of the proximity switch.

In both of the above embodiments, the forward leaning angle may be limited in accordance with the load only in the case of a high lift without restricting the forward leaning angle in the case of a low lift. At this time, the reference position for determining whether or not the vehicle is at a high elevation is set to a height at which the vehicle is maintained in a stable state even when the vehicle is inclined forward to the maximum forward inclination angle θmax with the maximum load being loaded. In this case, the forward leaning angle regulation is performed only when the height is high, so that the control is simplified.

A sensor that can continuously detect 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. The reel-type lift sensor includes a wire having one end connected to the fork 6 or the lift bracket 5, a reel around which the wire is wound,
A rotation detector (potentiometer) for detecting the rotation amount of the reel. As the map, a map showing the loading load and the maximum allowable forward tilt angle as shown in FIG. 5 for each lift is stored in the storage means (for example, the EEPROM 54b), or the map of the lift, the load and the maximum allowable forward tilt angle is stored. A three-dimensional map indicating the relationship is stored in the EEPROM 54b. In this case, since the lift can be continuously detected, the maximum allowable forward tilt angle can be set finely in accordance with the load and the lift, and the workability during the tilt operation is improved. Further, a sensor other than a reel-type lift sensor may be used as a sensor for continuously detecting the lift.

Even if the height is not detected continuously,
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. Then, the number of maps indicating the relationship between the load and the maximum allowable forward tilt angle is increased accordingly. For example, when detecting in three stages, three types of maps are provided, one for low elevation, one for medium elevation, and one for high elevation. Two types of maps are provided to control the forward inclination angle at the medium lift and the high lift.
In this case, the maximum allowable forward tilt angle can be set to a more appropriate value as compared with the case where the maximum allowable forward tilt angle is set in two stages.

The maximum allowable forward tilt angle is not necessarily set to change linearly and continuously with the load, but may be set to change continuously in a curve or may change stepwise. Good.

In the configuration of the first embodiment, the control valve 3 whose opening can be adjusted by the pilot pressure is provided in the pipe 37a.
In place of 8, a solenoid valve (on / off solenoid valve) that does not adjust the flow rate and only opens and closes the conduit 37a is provided. That is, as shown in FIG. 8, the control valve 38, the pilot operation check valve 39, and the proportional solenoid valve 43 are omitted, and the solenoid valve 63 is provided in the conduit 37a. And
When the operation of the tilt cylinder 9 is required, the solenoid valve 63 is kept open, and when the operation of the tilt cylinder 9 is unnecessary, the solenoid valve 63 is kept closed. That is,
When the tilt angle of the mast 3 reaches the maximum allowable forward tilt angle during the tilting operation of the tilt cylinder 9, the solenoid valve is switched from the open state to the closed state by a command from the control device 49. In this configuration, instead of the control valve 38 and the proportional solenoid valve 43 operated by the pilot pressure, the forward tilt angle can be regulated by a simple on / off solenoid valve.

As shown in FIG. 9, only the pilot operation check valve 39 is provided in the pipeline 37a, and the supply of the pilot pressure to the pilot operation check valve 39 is controlled by a solenoid valve (on / off solenoid valve) 64. Configuration. And
The solenoid valve 64 is kept open when the operation of the tilt cylinder 9 is required, and is kept closed when the operation of the tilt cylinder 9 is unnecessary. In this case, although the number of components is larger than that of the configuration in which the solenoid valve 63 is provided in the pipe line 37a, leakage of hydraulic oil from the tilt control valve 23 can be prevented during stoppage in the forwardly inclined state.

The mast angle detecting means may be any as long as it can detect the tilt angle of the mast 3 from the reference position, and is not limited to the rotary potentiometer 15 for detecting the rotation angle of the tilt cylinder 9; A linear potentiometer that detects the amount of expansion and contraction of the 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.

In the second embodiment, the lift control valve 22 of the same manual operation as in the first embodiment is used in place of the lift proportional control valve 58 in the second embodiment. That is, the electromagnetic proportional control valve is used only for controlling the tilt cylinder 9. In this case, the manufacturing cost is lower than in the second embodiment.

Instead of configuring the pilot pressure supply means with a pipe 44 branched from the hydraulic oil supply pipe 26,
A configuration is also possible in which a small-capacity hydraulic pump driven by the engine E is separately provided, and hydraulic oil for pilot pressure is supplied to the pipeline 44 from the hydraulic pump. In this case, the pressure reducing valve 45 may not be provided.

The pilot operated check valves 21 and 39 may be omitted. If the pilot operated check valve 39 is not provided, the control valve 38 is connected to the bottom chamber 9c and the tilt control valve 23.
May be provided in the conduit 37b for connecting. If the pilot operation check valve 39 is not provided, the leakage of the hydraulic oil from the control valve 38 and the tilt control valve 23 in the forward tilted state is not prevented, so that the control valve 38 is connected to either side of the two pipe lines 37a and 37b. The same effect can be obtained by providing the same.

Instead of a map representing the relationship between the high elevation and the loading load and the maximum allowable forward inclination as the data required to execute the forward inclination angle restriction control program, the high elevation and the loading load and the maximum allowable An equation expressing the relationship with the forward tilt angle is E
The information may be stored in the EPROM 54b.

A map or a relational expression representing the relationship between the lifting height and the load and the maximum allowable forward leaning angle as data necessary for executing the forward leaning angle restriction control program is stored in the ROM.
54a, and the EEPROM 54b may be omitted. Further, a map or a relational expression representing the relationship between the lift and the load and the maximum allowable forward tilt angle may be stored in a RAM provided with a backup power supply. In this case, it is easy to correct the map or the relational expression.

The determination as to whether or not the forward leaning angle is to be restricted may be made as long as a stable state of the load or the vehicle in the longitudinal direction can be ensured when performing the forward tilting operation. There is no need to make a judgment based on this. For example, the forward inclination angle may be restricted only by the height. When restricting the forward tilt angle only by the height of the lift,
The maximum allowable forward tilt angle is set based on the state of the maximum load. Therefore, unnecessary forward tilt angle regulation is performed when there is no load. However, there is no problem if a sensor for detecting the presence or absence of a load is provided, and if there is no load, the forward tilt angle restriction is released. Further, the forward inclination angle may be restricted only by the magnitude of the load. When the forward leaning angle is restricted only by the magnitude of the load, the maximum allowable forward leaning angle is set based on the state of high elevation.

Although the lift control valve 22, the tilt control valve 23, the control valve 38, the proportional solenoid valve 43 and the like are formed integrally, the control valves 22, 23 and 38 may be formed separately.

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

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 special forklifts with a high mast, the rearward tilt angle is made smaller than usual in consideration of stability at high lifts. However, when the load is transported at a low lift, the stability increases when the load is tilted to the backward tilt angle similar to that of a normal forklift. Therefore, in such a case, a rearward tilting angle restriction function may be provided to restrict the rearward tilting angle at a high elevation, so that the rearward tilting angle at a low elevation can be increased.

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 claim 1, the control means sets the maximum allowable forward tilt angle based on the lift, and controls the supply of the hydraulic oil to the tilt cylinder so as not to exceed the maximum allowable forward tilt angle. I do. In this case, since the maximum allowable forward tilt angle is set only by the magnitude of the lift, control becomes easy.

(2) In the first aspect of the present invention,
The control means sets a maximum allowable forward tilt angle based on the loaded load, and controls the supply of hydraulic oil to the tilt cylinder so as not to exceed the maximum allowable forward tilt angle. In this case, since the maximum allowable forward tilt angle is set only by the magnitude of the load,
Control becomes easy.

[0088]

As described in detail above, claims 1 to 9 are provided.
According to the invention described in (1), when performing a tilting operation with a high elevation and a forward tilt, the work can be easily performed even by a non-expert. In addition, even if there is an erroneous operation, it is possible to prevent the collapse of the load and the lifting of the rear wheel of the forklift (that is, the unstable state in the longitudinal direction of the vehicle).

According to the second and third aspects of the present invention, the forward leaning angle regulation is required based on both the lifting height and the load, so the forward leaning angle regulation is performed based on only one of them. , It is possible to perform more appropriate forward lean angle regulation.

According to the fourth aspect of the present invention, the maximum allowable forward tilt angle can be finely set in accordance with the load and the lifting height, so that the maximum allowable forward tilt angle of the mast can be increased, and the operator can be free. The workability during tilt work is improved.

According to the fifth aspect of the present invention, since the criteria for determining the lift are provided in two stages, the control for the determination is simplified. According to the sixth and seventh aspects of the present invention, the operator can perform the tilting operation by the same operation as the conventional manually operated valve.

According to the seventh aspect of the present invention, the operation speed of the tilt cylinder can be easily controlled when the tilt cylinder is operated.
According to the eighth aspect of the invention, the switching between the supply and the discharge of the hydraulic oil to the tilt cylinder is performed by the electromagnetic proportional control valve, so that the burden on the operator is reduced.

According to the ninth aspect of the present invention, when the mast is in a state where the forward inclination angle is restricted, the working oil is less likely to leak from the oil chamber of the tilt cylinder, and the mast is held at a predetermined angle.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of a first 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 diagram showing a map for forward lean angle restriction control.

FIG. 6 is a main part hydraulic circuit diagram of the second embodiment.

FIG. 7 is a block diagram showing an electrical configuration of the control device.

FIG. 8 is a main part hydraulic circuit diagram of another embodiment.

FIG. 9 is a main part hydraulic circuit diagram of another embodiment.

[Explanation of symbols]

1: Forklift as an industrial vehicle, 3: Mast, 6
... Fork as an attachment for cargo handling, 9... Tilt cylinder, 9b... Rod chamber as an oil chamber to which a large pressure is applied when the mast is tilted forward, 14... Lift sensor as a lift detecting means, 15. A potentiometer as a means, 17 a pressure sensor as a load detection means, 23 a tilt control valve as a manually operated direction switching valve constituting a control means, 25 a hydraulic pump as a hydraulic oil source, 37a a pipeline, 38: a control valve constituting a control means and an electromagnetic valve; 43: a proportional solenoid valve;
... Control device constituting control means, 59 ... Electromagnetic proportional control valve constituting control means.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeto Nakajima 1671 Asano, Toyono-cho, Kamiminochi-gun, Nagano Pref. (72) Inventor Makio Tsukada 1671 Asano, Toyono-cho, Kamiminochi-gun, Nagano Pref.

Claims (9)

[Claims] An industrial vehicle in which a mast for lifting and lowering an attachment for loading and unloading is tiltably provided, and the mast is tilted by the operation of a tilt cylinder, so that a load or a stable state in the front-rear direction of the vehicle is ensured during a loading operation. A tilt cylinder control device for an industrial vehicle, further comprising control means for controlling supply of hydraulic oil to the tilt cylinder so as to regulate a forward inclination angle of the mast. 2. An industrial vehicle in which a mast for lifting and lowering a cargo handling attachment is tiltably provided, and the mast is tilted by the operation of a tilt cylinder. A tilt cylinder control device for an industrial vehicle, comprising: control means for controlling supply of hydraulic oil to the tilt cylinder so as to regulate a forward inclination angle of the tilt cylinder. 3. An industrial vehicle in which a mast for lifting and lowering a cargo handling attachment is tiltably provided, and the mast is tilted by the operation of a tilt cylinder. A mast angle detecting means for detecting a tilt angle of the mast from a reference position; a loading load detecting means for detecting a loading load of the cargo attachment; A storage unit that stores a map or a relational expression; and a calculation unit that calculates a maximum allowable forward tilt angle of the mast based on the lift detected by the lift detection unit and the load detected by the load detection unit. When the tilt cylinder is actuated when rotating the mast forward, the mast angle is detected by the mast angle detecting means. A tilt cylinder control device for an industrial vehicle, comprising: control means for controlling supply of hydraulic oil to the tilt cylinder so as to stop the forward tilt operation of the tilt cylinder when the mast angle reaches the maximum allowable forward tilt angle. 4. The tilt cylinder control device for an industrial vehicle according to claim 3, wherein said height detecting means is a sensor capable of continuously detecting the height. 5. The tilt cylinder control device for an industrial vehicle according to claim 3, wherein said height detecting means is a sensor capable of detecting whether or not the height is equal to or higher than a predetermined height. 6. A control means for controlling the supply of hydraulic oil to the tilt cylinder includes a manually operated directional control valve for controlling the supply and discharge of hydraulic oil to and from the tilt cylinder; An electromagnetic valve provided in the middle of a pipe connecting a cylinder and the tilt cylinder when the mast is rotated toward the front side when the mast angle reaches a predetermined angle. 2. A control device for controlling a pipe line to be cut off.
The tilt cylinder control device for an industrial vehicle according to any one of claims 1 to 5. 7. The tilt cylinder control device for an industrial vehicle according to claim 6, wherein the solenoid valve is switched by a pilot pressure, and the pilot pressure is controlled by a proportional solenoid valve. 8. A control device for controlling supply of hydraulic oil to the tilt cylinder, comprising: an electromagnetic proportional switch for switching between supply of hydraulic oil from a hydraulic oil source to the tilt cylinder and discharge of hydraulic oil from the tilt cylinder. A control valve connects the electromagnetic proportional control valve to the hydraulic oil source and the tilt cylinder when the mast angle reaches a predetermined angle during operation of the tilt cylinder when rotating the mast toward the front side. The tilt cylinder control device for an industrial vehicle according to any one of claims 1 to 5, further comprising: a control device configured to control a pipe line to be cut off. 9. The electromagnetic valve or the electromagnetic proportional control valve,
The flow of hydraulic oil flowing from the oil chamber to the solenoid valve or the electromagnetic proportional control valve in the middle of a pipeline connecting the oil chamber on the side to which a large pressure is applied when the mast of the tilt cylinder is tilted forward. The tilt cylinder control device for an industrial vehicle according to any one of claims 6 to 8, further comprising a pilot operation check valve that regulates the pressure.