JPH10316387A - Mast backward tilting speed controlling device for industrial vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mast backward tilting speed controlling device for an industrial vehicle, which controls a mast to optimal backward tilting speed considering its load and lift height. SOLUTION: A mast 3 is inclined longitudinally relative to a body frame by a tilt cylinder 9. When a tilt lever is operated to tilt the mast backward and a backward tilt detecting switch 15 is turned on, a controller 53 selects optimal solenoid current value Is of solenoid current values Is corresponding to preset 6 stages of backward tilting speed, on the basis of value detected by a lift height sensor 17 which determines whether a lift height is more than a predetermined lift height H1 and load (w) which is detected by a pressure sensor 19. The controller 53 controls an electromagnetic valve using the derived solenoid current value Is and controls aperture of a control valve. Based on the aperture of the control valve, flow of hydraulic fluid which flows on an oil path of the tilt cylinder 9 changes and backward tilting speed of the mast 3 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an industrial vehicle in which a mast for lifting and lowering cargo handling equipment such as a fork is tiltably provided, and a flow rate of hydraulic oil supplied to a tilt cylinder for tilting the mast is controlled by a solenoid valve. The present invention relates to a mast rearward tilt speed control device.

[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. .

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 throttle so that the flow rate of the hydraulic oil is reduced. 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. On the other hand, when the mast is tilted backward, in order to improve the working capacity at low lift or low load, and because the stability is relatively good even when the load is large and the lift is high, the throttle is restricted in the flow path. Was not provided. Then, when the load is high and the load is high, the worker adjusts the operation amount of the tilt lever and the engine speed during the backward tilting operation and performs the backward tilting operation at a relatively slow speed.

In the apparatus disclosed in Japanese Patent Application Laid-Open No. 7-61792, the opening degree of an electromagnetic control valve for tilting a mast provided on an oil passage of a tilt cylinder is determined by an operator operating a tilt lever. Independently, the controller controls the mast tilting speed. In this device, only when the load of the load exceeds the predetermined value and the lifting height of the cargo handling equipment exceeds the predetermined value, the opening degree of the control valve is controlled to the predetermined value, and the tilting speed of the mast is reduced. I have. Also,
This device is designed to prevent the mast from leaning forward due to the forward leaning speed of the mast, and does not consider the problem of backward leaning.

[0005]

However, when the tilt lever is operated at a relatively low speed by adjusting the operation amount of the tilt lever and the engine speed at the time of a high load and a high lift, an erroneous operation or the like causes a backward tilt at a high speed. When the operation is performed, the shock when the mast stops at the rearmost tilt position is large, which causes a decrease in durability. Also, depending on the vehicle, for example, even when no load is loaded, when performing a high-speed backward tilt operation at the highest lift, or at a low lift, performing a high-speed backward tilt operation with the heaviest load. However, the shock when the mast stops at the last inclined position is large, which causes a decrease in durability and a collapse of the load.

In the apparatus disclosed in Japanese Patent Application Laid-Open No. 7-61792, the mast tilting speed is reduced to 1 only when the load exceeds a predetermined value and the lifting height of the cargo handling equipment exceeds a predetermined value. Slow down in stages. However, the magnitude of the shock when the mast stops at the last inclined position changes three-dimensionally due to the relationship between the load and the lift. Therefore, when the predetermined values of the load and the lift are set, if the two predetermined values are set small so that the shock when the mast stops at the rearmost tilt position is not always large, even if the shock does not increase, In some cases, the backward inclination speed may be reduced. In this case, there is a problem that the working capacity of the mast is unnecessarily reduced. Conversely, if the two predetermined values are set large with priority given to the work capability of the mast, the rearward tilting speed of the mast may not be reduced even in the range where the shock increases. In this case, there is a problem that the durability is reduced or the load collapses due to a large shock.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an industrial vehicle for controlling a mast to an optimum backward tilting speed in consideration of a load and a height of a lift. It is an object of the present invention to provide a rearward tilting speed control device for a mast.

[0008]

According to the first aspect of the present invention, a mast supported so as to be capable of tilting with respect to a vehicle body frame is provided between the vehicle body frame and the mast, and the mast is tilted forward and backward. In an industrial vehicle provided with a hydraulic cylinder to be lifted, and a loading / unloading device supported on the mast so as to be able to move up and down, the hydraulic cylinder is driven to tilt the mast backward, and the leaning operation is performed. Backward tilt operation detecting means for detecting that the means has been operated; lifting height detecting means for detecting the lift of the cargo handling equipment; load detecting means for detecting the load of the cargo handling equipment; When a detection signal indicating that the rearward tilt operating means has been operated is input from among the rearward tilting speeds set in two or more stages in advance, based on a continuous value of at least one of the detected lift and load, Decide 傾速 degree after corresponding, and the gist that a control means for indirectly controlling the flow rate of the oil flowing through the oil path of the hydraulic cylinder in two or more stages depending on the speed.

In the invention according to a second aspect, the gist is that the control means determines the backward inclination speed based on the stepwise value of the lift and the continuous value of the load. In the invention according to claim 3, the control means determines the rearward inclination speed based on the continuous values of the detected lift and load from the continuously set rearward inclination speed. I have.

According to a fourth aspect of the present invention, in the rearward speed control device for a mast of an industrial vehicle according to any one of the first to third aspects, the rearward tilt operating means is operated on the oil passage. Accordingly, a gist of the present invention is that a manual switching valve which is switched and driven by the above operation and a solenoid valve which is controlled by the control means and controls the flow rate of oil flowing on the oil passage are provided in series.

(Operation) According to the first aspect of the present invention,
The mast is tilted forward and backward with respect to the body frame by a hydraulic cylinder. When the rearward tilt operation detecting means detects that the rearward tilting operation means has been operated, the control means selects at least one of the detected lift and the load from the backward tilting speeds set in two or more stages in advance. The backward tilt speed is determined based on the continuous value, and the flow rate of the oil flowing on the oil passage of the hydraulic cylinder is indirectly controlled in two or more stages according to the speed. Therefore, the backward tilting speed of the mast is controlled based on a continuous value of at least one of the lift and the load. as a result,
The mast can be tilted rearward at an optimum rearward speed based on load and lift.

According to the second aspect of the present invention, since the control means controls based on the stepwise value of the height and the continuous value of the load, the height detecting means is, for example, a general-purpose proximity type. The load detecting means may be a general-purpose type, for example, a pressure sensor for detecting the hydraulic pressure in a hydraulic cylinder. Therefore, it is not necessary to provide a new sensor or the like in order to control the backward tilting speed of the mast.

According to the third aspect of the present invention, the backward tilting speed of the mast can be made to coincide with the ideal backward tilting speed that changes three-dimensionally according to the values of the lift and the load. According to the fourth aspect of the present invention, since the manual switching valve and the solenoid valve are provided in series on the oil passage of the hydraulic cylinder, the solenoid valve is provided on the oil passage of the conventional manual switching valve. It is possible to control the flow rate of the oil flowing on the oil passage simply by adding the oil.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a rearward tilting speed control device of a mast in a forklift will be described below with reference to FIGS.

As shown in FIG. 4, a body frame 2 of a forklift 1 as an industrial vehicle has a mast 3 at a front portion thereof.
Is erected. The mast 3 includes a pair of left and right outer masts 3a supported so as to be tiltable back and forth with respect to the vehicle body frame 2, and inner masts 3b sliding up and down.
Consists of A lift cylinder 4 as a second hydraulic cylinder is disposed at the rear of each outer mast 3a. The tip of the piston rod 4a of the lift cylinder 4 is connected to the upper part of the inner mast 3b. A chain 7 having one end fixed to the body of the lift cylinder 4 and the other end connected to a lift bracket 6 is mounted on the chain wheel 5 supported on the upper portion of the inner mast 3b. The fork 8 as a cargo handling device is lifted and lowered by the expansion and contraction of the lift cylinder 4 together with the lift bracket 6 suspended from the chain 7.

The mast 3 is connected to and supported by the body frame 2 via a pair of left and right tilt cylinders 9 as hydraulic cylinders. Tilt cylinder 9
Has a base end rotatably connected to the vehicle body frame 2 and is rotatably connected to the outer mast 3a at a distal end of the piston rod 9a. The mast 3 tilts back and forth as the tilt cylinder 9 is driven to expand and contract.

The driver's cab 10 has a steering wheel 11 in front of it.
Lift lever 12 and tilt lever 1 as operation unit
3 (however, in FIG. 4, both levers 12, 1 are provided).
3 are shown superimposed). Lift lever 12
Is operated when raising and lowering the fork 8, and the tilt lever 13 is operated when tilting the mast 3.

As shown in FIG. 3, near the operation force transmitting mechanism 13a of the tilt lever 13, a tilt lever 13 is provided.
A tilt detection switch 14 for detecting that the tilt lever 13 has been tilted forward, and a rear tilt detection switch 15 as a tilt detection operation detecting means for detecting that the tilt lever 13 has been tilted backward. ing. Both switches 14 and 15 are, for example, micro switches. Forward tilt detection switch 1
4 turns on when the tilt lever 13 is tilted forward,
The rearward tilt detection switch 15 is turned on when the tilt lever 13 is tilted rearward. When the tilt lever 13 is at the neutral position, both switches 14 and 15 are turned off.

As shown in FIG. 2, a lift sensor 17 is provided above the outer mast 3a. The lift sensor 17 is, for example, a proximity sensor. The lift sensor 17 is turned on when the fork 8 is at a high lift higher than the predetermined height H1.
It is turned off when the height is lower than the low. Further, a pressure sensor 19 is provided below the lift cylinder 4 as load detecting means for detecting the oil pressure of the bottom chamber 4b. The pressure sensor 19 outputs a detection signal corresponding to the load of the fork 8.

FIG. 1 shows a hydraulic circuit of a cargo handling system provided in the forklift 1. As shown in the figure, a hydraulic pump 21 for pumping and discharging hydraulic oil from an oil tank 20 to each of the cylinders 4 and 9 is driven by an engine E (shown in FIG. 4). The hydraulic oil from the hydraulic pump 21 is discharged to the flow divider 22 through the pipe 23. The flow divider 22 is for increasing the operating oil from the hydraulic pump 21 to a predetermined pressure or more and then diverting the hydraulic oil to a hydraulic circuit for the cargo handling system and a hydraulic circuit for the steering system. The pressure oil diverted from the flow divider 22 to the steering system is returned to the oil tank 20 via a pipe 25 passing through a steering valve 24.

A hydraulic oil supply line 26 through which the pressure oil diverted from the flow divider 22 to the cargo handling system passes is connected to a return line 27 returning to the oil tank 20, and is used for a lift as a second manual switching valve. The control valve 28 and the tilt control valve 29 as a manual switching valve are connected to the hydraulic oil supply line 26.
It is arranged in series above.

The lift control valve 28 is a 7 port 3 position switching valve, and its spool is mechanically connected to the lift lever 12. Lift the lift lever 12
By performing the lowering operation, the lift control valve 28 is set to the a position,
The state can be manually switched between three positions, b and c.

The lift control valve 28 includes a branch pipe 26a branched from the hydraulic oil supply pipe 26 and the return pipe 2
7 is connected to a conduit 30 connected to the bottom chamber 4b of the lift cylinder 4. When the lift control valve 28 is switched to the position a (up position), the branch pipe 26a and the pipe 30 communicate with each other to supply hydraulic oil to the bottom chamber 4b, and the lift cylinder 4 is extended. In addition, lift control valve 2
When the position 8 is switched to the position c (down position), the line 30 communicates with the return line 27, and the hydraulic oil in the bottom chamber 4b is discharged to the oil tank 20 through the lines 30, 27, and the lift cylinder 4 shrinks. Further, when the lift control valve 28 is at the position b (neutral position), the pipe 30 is disconnected from the pipes 26a and 27, and the piston rod 4a of the lift cylinder 4 is held at a predetermined amount. At the position c, the hydraulic oil in the bottom chamber 4b is discharged by the load pressure acting on the piston rod 4a.

The pressure transmission line 32 for transmitting the discharge pressure of the hydraulic pump 21 for use in pilot control is connected to the line 23.
It is connected to the. The pressure reducing valve 33 provided on the pressure transmission line 32 is for adjusting the discharge pressure of the hydraulic pump 21 to a predetermined pilot pressure (set pressure). The pilot check valve 34 provided on the line 30 is connected to the pressure transmission line 3.
The valve is operated by the second oil pressure, and when the oil pressure becomes equal to or higher than a predetermined pressure after the engine is started (for example, after 1-2 seconds), the valve is held open. That is, the pilot check valve 34 is kept closed when the key is turned off (engine is stopped), opens only when the key is turned on (engine is started), and has a function of stopping the flow of hydraulic oil from the bottom chamber 4b in the key-off state.

The tilt control valve 29 is a 6 port 3 position switching valve, and its spool is mechanically connected to the tilt lever 13. Tilt lever 13 backward
By performing the neutral / forward tilt operation, the tilt control valve 29 can be manually switched to three states of a position, b position, and c position. The tilt control valve 29 includes a branch pipe 26 b branched from the hydraulic oil supply pipe 26 and a return pipe 2.
7, a pipe 36a connected to the rod chamber 9c of the tilt cylinder 9, and a pipe 36b connected to the bottom chamber 9b.

A control valve 37 for opening and closing an oil passage of hydraulic oil flowing through the pipe 36b and a proportional solenoid valve 38 for controlling a pilot pressure for operating the control valve 37 are provided on the pipe 36a. Is provided. The solenoid valve 39 is provided on a tilt-type oil passage in order to perform the later-described tilting speed control of the mast 3 that is performed independently of the operation of the tilt lever 13. The opening of the control valve 37 is controlled by the current value (solenoid current value) flowing through the proportional solenoid valve 38.

The control valve 37 is a two-port, two-position one-way normally closed valve, and is closed by the urging force of the spring 40 when the pilot pressure is less than a predetermined value. Proportional solenoid valve 3
Reference numeral 8 denotes a normal close valve, which closes by the urging force of the spring 41 when the solenoid current value is less than a predetermined value. The proportional solenoid valve 38 is connected to the pressure transmission line 32, and applies a pilot pressure to the control valve 37 according to the opening determined by the solenoid current value.

In the state where the control valve 37 is opened, when the tilt control valve 29 is switched to the position a (backward tilt position), the pipelines 26b and 36a communicate with each other, and the operating oil is supplied to the rod chamber 9.
c, the hydraulic fluid in the bottom chamber 9b is discharged to the oil tank 20 through the pipelines 36b, 35, and 27, and the tilt cylinder 9 contracts. When the tilt control valve 29 is switched to the position c (forward tilt position) in a state where the control valve 37 is opened, the pipes 26b and 36b communicate with each other, and the hydraulic oil is supplied to the bottom chamber 9.
b, the pipes 36a, 35 communicate with each other, the hydraulic oil in the rod chamber 9c is discharged to the oil tank 20 through the pipes 36a, 35, 27, and the tilt cylinder 9 is extended. . The tilt control valve 29
Is in the position b (neutral position), each of the conduits 36a,
36b is cut off from the conduits 26b and 35, so that the piston rod 9a of the tilt cylinder 9 is maintained at a predetermined protrusion amount. At the position c (the forward tilt position) of the tilt control valve 29, since the flow path is restricted by the orifice 42, the opening of the control valve 37 is narrowed, and the flow rate is limited by the opening of the control valve 37. Unless it comes to
The forward leaning speed of the mast 3 is set to be relatively lower than the backward leaning speed.

A pilot check valve 43 is provided on the conduit 36a between the control valve 37 and the tilt cylinder 9 in such a direction as to be able to prevent the hydraulic oil from flowing out of the rod chamber 9c in a closed state. The pilot check valve 43 operates at the same pilot pressure that operates the control valve 37, and is set to open at a pilot pressure lower than the control valve 37 starts to open.

A relief valve 44 is provided on a pipe 45 connecting the hydraulic oil supply pipe 26 and the return pipe 27, and a relief valve 46 connects the tilt control valve 28 and the return pipe 27. It is provided on a pipeline 47. Pipe 47
When the lift control valve 28 is in the position b (neutral position) or the position c (down position) where the hydraulic oil supply pipe 26 is not shut off, the lift control valve 28 communicates with the pipe 48 branched from the pipe 45. Has become.

When the lift control valve 28 is switched to the position a (up position) in which the lift control valve 28 shuts off the hydraulic oil supply line 26, the pressure oil flowing through the lift system oil passage is set to the lift set pressure. This is for allowing the hydraulic oil to escape so that When the tilt control valve 29 is switched to either the a position (backward tilt position) or the c position (forward tilt position) in which the tilt control valve 29 shuts off the hydraulic oil supply line 26, the tilt valve of the tilt system is used. This is for releasing the hydraulic oil so that the pressure oil flowing through the oil passage becomes the tilt set pressure. The check valves 49, 50, and 51 are for preventing backflow of hydraulic oil. The filter 52 is provided for removing dust in oil because the proportional solenoid valve 38 is precise. The pipes 26b, 36a,
36 b and 35 constitute an oil passage of the hydraulic cylinder 9.

Next, the electrical configuration of the backward tilt speed control device will be described. As shown in FIG. 2, the controller 53 as a control means for controlling the opening degree of the control valve 37, that is, the output pilot pressure of the proportional solenoid valve 38, includes a microcomputer 54, an analog / digital conversion circuit (A / D conversion circuit) 55 And a solenoid drive circuit 56. The microcomputer 54 includes a central processing unit (hereinafter referred to as a CPU) 57 and a read-only memory (ROM).
58a and an EEPROM (Electrical Erasable P
a read / write memory (RAM) 59, an input interface 60 and an output interface 61.

The ROM 58a stores program data and various program data for the backward tilt speed control process shown in the flowchart of FIG. Here, the backward leaning speed control processing is performed in consideration of the load w applied to the fork 8 and the lift H of the fork 8 in order to optimize the backward leaning speed of the mast. And outputs a command value corresponding to the solenoid current value Is to the solenoid drive circuit 56. The solenoid current value Is is a current value for controlling the proportional solenoid valve 38, and the control valve 3 is set so as to be substantially proportional to this current value.
7 is controlled.

The EEPROM 58b stores data necessary for executing the program of the backward tilt speed control process as shown in FIG.
A map representing the relationship between the load w and the current value Iw with respect to the load w is stored, and a map representing the relationship between the lift H and the current value Ih with respect to the lift H shown in FIG. 7 is stored. This current value Iw decreases as the load w increases, and I
The values of max, I1, I2, I4, and I5 are set.
Also, the current value Ih decreases as the height H increases, and I
The values of max and I3 are set. In the present embodiment, the solenoid current value Is is set to Imax, I1 to Imax shown in the maps of FIGS.
One of I5. That is, the solenoid current value Is
Are set in six types, and the backward tilting speed of the mast 3 is the load w
And six stages in accordance with the lift H. The data in the EEPROM 58b can be individually set for each machine by operating a setting operation unit (not shown) in consideration of the type of the vehicle, the type of the vehicle, the variation of the device accuracy, and the like. I have.

The pressure sensor 19 is connected to the CPU 57 via the A / D converter 55 and the input interface 60. In addition, the elevation sensor (proximity sensor) 17, the forward tilt detection switch 14, and the rear tilt detection switch 15 are connected to the CPU 57 via the input interface 60. The pressure sensor 19 continuously detects the load w of the fork 8 and outputs the detected value to the CPU 57. The lift sensor 17 outputs the lift H as an ON signal when the lift H is equal to or higher than the predetermined height H1, and outputs an OFF signal when the lift H is lower than the predetermined height H1.

The solenoid drive circuit 56 is connected to a CPU 57 via an output interface 61. CP
U57 outputs a command value for commanding a solenoid current value for controlling the current value of the proportional solenoid valve 38 to the solenoid drive circuit 56 via the output interface 61. Then, the solenoid drive circuit 56 controls the current flowing through the proportional solenoid valve 38 based on the command value.

Next, the operation of the rearward tilt speed control device configured as described above will be described. When the tilt lever 13 is operated, the tilt control valve 29 is switched to the a position or the c position. At this time, when the forward tilt detection switch 14 is turned on, the CPU 57 outputs a command value corresponding to the current value Imax for fully opening the control valve 37 to the solenoid drive circuit 56. When the rearward tilt detection switch 15 is turned on, the CPU 57 executes a rearward tilt speed control process described later. In the backward tilt speed control processing, a command value corresponding to the obtained solenoid current value Is is output to the solenoid drive circuit 56.

From the solenoid drive circuit 56, a solenoid current corresponding to the command value is output to the proportional solenoid valve 38, and the proportional solenoid valve 38 opens to an opening corresponding to the current value. The pilot pressure corresponding to the opening of the proportional solenoid valve 38 is applied to the control valve 37 and the pilot check valve 43.
And both valves 37 and 43 are opened at a pilot pressure equal to or higher than a predetermined pressure. The control valve 37 is opened and closed by the CPU 5
7 is indirectly controlled by controlling the current value of the proportional solenoid valve 38.

When the tilt lever 13 is tilted forward, the control valve 37 is fully opened and the tilt control valve 29 is switched to the position c. When the tilt lever 13 is tilted backward, the control valve 37 will be described later. As described above, the opening degree is switched in six stages to the opening degree corresponding to the load w and the lift H at that time, and the tilt control valve 29 is switched to the position a.

When the tilt control valve 29 is switched to the position c, the operating oil in the operating oil supply line 26 is supplied from the branch line 26b to the bottom chamber 9b through the line 36b and the rod chamber. 9c of hydraulic oil is supplied to the conduits 36a, 3
The oil is discharged to the oil tank 20 through 5, 27. As a result, the tilt cylinder 9 is driven to extend, and the mast 3 tilts forward. When the tilt control valve 29 is switched to the position a, the operating oil in the operating oil supply pipe 26 is supplied from the branch pipe 26b to the rod chamber 9c through the pipe 36a, and the bottom chamber 9b Hydraulic oil is in line 36b, 3
The oil is discharged to the oil tank 20 through 5, 27. As a result, the tilt cylinder 9 is driven to contract, and the mast 3 is tilted backward. At this time, the backward tilting speed of the mast 3 is controlled in six steps by the opening degree of the control valve 37.

Next, the backward tilt speed control process will be described with reference to the flowchart shown in FIG. First, in step 1, the CPU 57 reads the detected values of the load w and the lift H, and proceeds to step 2. In this embodiment, the lift H is data indicating whether it is less than the predetermined value H1 or not less than the predetermined value H1. In step 2, the current value Iw is calculated from the load w using the map shown in FIG. 6 stored in the EEPROM 58b.
Ask for. The current value Iw is Imax when the load w is less than w1, I1 when the load w is w1 or more and less than w2, I2 when the load w is w2 or more and less than w3, and I4 when the load w is w3 or more and less than w4. , When the load w is more than w4, I5
Becomes

Next, in step 3, the EEPROM 58
The current value Ih is obtained from the lift H using the map shown in FIG. The current value Ih is Imax when the height H is less than H1, and I3 when the height H is more than H1. still,
The relation between the six types of current values is Imax>I1>I2> I
3>I4> I5.

Next, in step 4, steps 2 and 3
The current value Iw and the current value Ih obtained by the above are compared. If the current value Iw and the current value Ih are the same value, the value is compared. If the current value Iw and the current value Ih are different values, the smaller value is used. A command value corresponding to the current value Is is output to the solenoid drive circuit 56.

Here, in the backward tilt speed control apparatus of the present embodiment, one of five current levels Iw based on the detected value of the load w and two levels of the current value Iw based on the detected value of the lift H are provided. By obtaining one current value Ih and switching the solenoid current value Is flowing to the proportional solenoid valve 38 in six steps based on the two current values Iw and Ih, the opening of the control valve 37 is indirectly switched, and the tilt is backward. The speed is controlled in six steps. Even when the load w is 0 and the lift H is higher than H1, the backward tilting speed of the mast 3 is set to a low speed, and when the lift is 0 and the load w is more than w1, the load w
Becomes larger, the backward tilting speed of the mast 3 is made lower in four stages. As a result, when the load w is less than w1 and the lift H is less than H1, the mast 3 tilts backward at a normal speed, and the workability is not impaired. When the load w is equal to or greater than w1 or the lift H is equal to or greater than H1, the mast 3 tilts backward at a low speed, and the shock when stopping at the last tilt position does not increase.

According to the first embodiment described in detail above, the following effects can be obtained. (1) In the above embodiment, the load w is continuously changed to the lift H
Are detected in two stages, current values Iw and Ih are determined for each value so that the shock at the time of stopping at the last tilt position is not increased, and the solenoid current flowing to the proportional solenoid valve 38 based on both current values Iw and Ih is determined. The value Is is switched in six steps. Therefore, the mast 3 has a load w
And the lifting height H, the vehicle leans backward at six stages of backward leaning speed. As a result, the vehicle can be tilted backward at an optimum backward tilt speed based on the load w and the lift H, and the shock when stopping at the last tilt position does not increase.

(2) In the above embodiment, the vehicle leans backward at the optimum backward tilt speed among the six backward lean speeds based on the load w and the lift H. Therefore, in order not to increase the shock at the time of stopping at the last tilt position, even if the shock does not increase, it is possible to keep the rearward tilting speed of the mast from being low. As a result, even if the control is performed so as not to increase the shock, it is possible to prevent the working ability from being reduced.

(3) In the above embodiment, since the load w is detected continuously and the height H is detected and controlled in two stages, the height sensor 17 such as a general-purpose proximity sensor and the bottom chamber are controlled. The pressure can be detected and controlled using the pressure sensor 19 that detects the oil pressure of 4b. Therefore, mast 3
It is not necessary to provide a new sensor or the like in order to perform the backward tilt speed control. As a result, the backward tilting speed control of the mast 3 can be performed with less change in mechanical design.

(4) In the above embodiment, the tilt control valve 29 and the solenoid valve 39 are provided in series on the oil passage of the tilt cylinder 9 in order to control the backward tilting speed of the mast 3. Since the tilt control valve 29 is the same manual switching valve as that used in the general-purpose type mechanical control system, an electromagnetic valve 39 is provided in series with the tilt control valve 29 on the oil passage of the tilt cylinder 9. It only needs to be added.
Therefore, there is little design change. Also, due to the thermal expansion of the spool and the body due to the temperature rise of the hydraulic oil, and foreign matter in the oil entering the gap between the spool and the body,
Even if the tilt control valve 29 sticks (sticks), switching can be performed by operating the tilt lever 13 with some force. Therefore, compared to the electric control system in which the controller controls the opening of the electromagnetic control valve and the tilting operation of the mast independently of the operation of the tilt lever described in the related art, the sticking of the valve is caused even if the tilt lever is operated. This makes it difficult for the mast to tilt.

In the above-described embodiment, the lift H is determined to be equal to or higher than H 1 or H
Although it was seen only in two stages of less than 1, the lift H was continuously detected, and the backward tilt speed of the mast 3 was changed to the load w and the lift H.
May be continuously changed in accordance with the continuous change of. For example, as shown in FIG. 8, a lift sensor 92 that detects the rotation of the reel 91 is used. The reel 91 is urged in a direction in which the wire connected to the fork 8 and the inner mast 3b can be wound. I do. For example, a three-dimensional map as shown in FIG.
It is stored in the PROM 58b or the like. In this map,
The solenoid current value Is is set to be directly obtained three-dimensionally with respect to a continuous change in the load w and the lift H.

In this manner, the solenoid current value Is is continuously obtained directly from the continuous load w and the lift H in the backward inclination speed control process. Therefore, in response to the magnitude of the shock at the time of stopping at the rearwardly inclined position that changes three-dimensionally, the rearward tilting speed of the mast is multi-step or continuous so that the shock when stopping at the lastly inclined position does not increase. Control. That is, the rearward tilting speed of the mast 3 can be made to coincide with the ideal rearward tilting speed that changes three-dimensionally according to the values of the load w and the lift H. As a result, even if the control is performed so as not to increase the shock, the working ability can be prevented from being reduced. In this case, the ROM 58
The load w and the lift H are read from the program data of the rearward inclination speed control process stored in a, the solenoid current value Is is obtained from the values w and H using a map, and a command corresponding to the current value Is is obtained. It needs to be changed to output the value. The lift H may be continuously detected in two stages of the load w, and the backward tilting speed of the mast 3 may be controlled in multiple stages or continuously.

In the above-described embodiment, a map in which the current value Iw in five steps is obtained from the load w is used, and a map in which the current value Ih in two steps is obtained from the lift H is used. Although the six-step solenoid current value Is is obtained from Ih, each step may be changed to any number of steps as needed, or may be obtained continuously.

In the above embodiment, the manual switching valve 29 and the solenoid valve 39 are provided in series, and the tilt lever 1
3 controls the manual switching valve 29 to control the tilting operation of the mast, and the controller 53 controls the solenoid valve 39 to control the backward tilting speed. An electromagnetic control valve that controls the tilting operation and controls the backward tilting speed may be changed so that the controller controls the tilt lever independently of the tilt lever operation.
Even in this case, the effects (1) to (3) of the above embodiment can be obtained.

The position of the solenoid valve 39 provided in series with the manual switching valve 29 on the oil passage is not limited to the above embodiment. As long as it is on a tilt-type oil path, it may be on the pipe 36b, or may be provided on the pipe 26b or the pipe 35. In other words, when the manual switching valve is switched to the valve opening position, the position at which the flow rate of the hydraulic oil flowing through the oil passage of the hydraulic cylinder (however, the portion that does not also serve as the oil passage of another cylinder) can be adjusted (including shut-off). If so, it can be changed as appropriate.

In the above-described embodiment, the industrial vehicle is embodied as a forklift. However, the present invention can be applied to other industrial vehicles having cargo handling equipment and a tiltable mast. For example, the present invention may be applied to a construction machine such as a power shovel or an aerial work vehicle.

In this specification, the term "backward tilting speed" means not only the speed at which the mast moves backward than the vertical state (reference position), but also the movement of the mast from the forward tilting state toward the reference position. It also means the speed when you do.

In the present specification, the "backward tilting operation" means not only the operation when the mast is tilted backward than the vertical state (reference position), but also the movement of the mast from the forward tilted state toward the reference position. The operation at the time of doing also means.

A technical idea (invention) other than the claimed invention, which has been grasped from the embodiment, will be described below together with its effects. ○ The industrial vehicle is a forklift.
A rearward tilting speed control device for a mast in an industrial vehicle according to any one of claims 1 to 3.

[0058]

As described in detail above, according to the first aspect of the present invention, the mast can be tilted rearward at an optimum rearward tilting speed based on the load and the lift.

According to the second aspect of the present invention, it is not necessary to provide a new sensor or the like, and the number of changed portions can be reduced to obtain the effect of the first aspect of the present invention. According to the third aspect of the present invention, it is possible to match the mast rearward tilting speed with the ideal rearward tilting speed that changes three-dimensionally according to the values of the lift and the load.

According to the fourth aspect of the present invention, the flow rate of oil flowing through the oil passage can be controlled only by adding an electromagnetic valve to the oil passage of a conventionally used manual switching valve.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of a forklift according to an embodiment.

FIG. 2 is an electric circuit block diagram of the forklift according to the embodiment.

FIG. 3 is a side view of a tilt lever according to the embodiment.

FIG. 4 is a side view of the forklift according to the embodiment.

FIG. 5 is a flowchart of a backward tilt speed control process according to the embodiment.

FIG. 6 is a map diagram for a backward tilt speed control process in the embodiment.

FIG. 7 is a map diagram for a backward tilt speed control process in the embodiment.

FIG. 8 is a partial side view of a forklift including a lift sensor according to another example.

FIG. 9 is a map diagram for a backward tilt speed control process in another example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Forklift as an industrial vehicle, 2 ... Body frame, 3 ... Mast, 8 ... Fork as cargo handling equipment, 9 ...
A tilt cylinder as a hydraulic cylinder, 13 a tilt lever as a backward tilt operating means, 15 a backward tilt detection switch as a backward tilt detecting means, 17, 92 a lift sensor as a lift detecting means, 26b, 35, 36a, 36b
... Pipe line as oil passage, 29... Tilt control valve as manual switching valve, 53. Controller as control means.

Claims (4)

[Claims] 1. A mast supported to be tiltable with respect to a vehicle body frame, a hydraulic cylinder provided between the vehicle body frame and the mast, and configured to tilt the mast back and forth, and supported by the mast so as to be able to move up and down. In an industrial vehicle including a cargo handling device for loading a load, a rearward tilting operation unit that drives the hydraulic cylinder to tilt the mast rearwardly, and detects a rearward tilting operation that detects that the rearward tilting operation unit has been operated. Means, a lift detecting means for detecting a lift of the cargo handling equipment, a load detecting means for detecting a load of the cargo handling equipment, and a detection signal for operating the rearward tilt operating means from the rearward tilting operation detecting means. Then, based on at least one continuous value of the detected lift and the load, from among the backward tilt speeds set in advance in two or more stages, a backward tilt speed according to the time is determined, and the backward tilt speed is determined according to the speed.傾速 degree control device after the mast in the industrial vehicle and a control means for indirectly controlling the flow rate of the oil flowing through the oil path of the hydraulic cylinder in two or more stages. 2. The control device according to claim 1, wherein the control means determines the rearward tilting speed based on a stepwise value of the lift and a continuous value of the load. 3. The industrial vehicle according to claim 1, wherein the control means determines the backward leaning speed based on the detected continuous values of the lift and the load from the continuously set backward leaning speed. Back mast speed control device in the mast. 4. The backward tilting speed control device for a mast in an industrial vehicle according to any one of claims 1 to 3, wherein a switching drive is performed on the oil passage by operating the backward tilting operating means. A rearward tilting speed control device for a mast in an industrial vehicle, wherein a manual switching valve and an electromagnetic valve controlled by the control means and controlling the flow rate of oil flowing on the oil passage are provided in series.