JP3347496B2 - Hydraulic cylinder control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic cylinder control device, and more particularly to a hydraulic cylinder control device suitable for controlling a tilt cylinder of a battery-powered forklift.

[0002]

2. Description of the Related Art In a forklift, a mast provided at a front portion of a vehicle is expanded and contracted by the operation of a lift cylinder, and the fork is raised and lowered. By the operation of a tilt cylinder, the mast is tilted to tilt the fork. In a battery-powered forklift, a hydraulic pump of a hydraulic device for cargo handling including each of the cylinders is driven by a motor driven by a battery. Then, the fork is raised and lowered based on the operation of the lift lever, and the fork is tilted based on the operation of the tilt lever.

As shown in FIG. 5, a tilt control valve 63 is provided between a tilt cylinder 61 of a forklift and a hydraulic pump 62. Tilt control valve 63
Is connected to the tilt lever 64, and the tilt lever 64
And a spool that moves in accordance with the forward, neutral and rearward tilting operation positions. The tilt control valve 63 is connected to a line 65a.
Is connected to a rod chamber 61a of the tilt cylinder 61 via a pipe 65b, and is connected to a bottom chamber 61b of the tilt cylinder 61 via a conduit 65b. The tilt control valve 63 is connected to the hydraulic pump 62 through a line 66a.
6b, it is connected to the tank 67. Then, when the tilt lever 64 is operated to the forward tilt position, the tilt control valve 63 connects the pipe 66a to the pipe 65b and also connects the pipe 66b to the pipe 65a. When the tilt lever 64 is operated to the rearwardly inclined position, the tilt control valve 63 allows the pipe 66a to communicate with the pipe 65a and also allows the pipe 66b to communicate with the pipe 65b.
Also, when operated to the neutral position, the tilt control valve 63 shuts off the pipes 65a and 65b from the pipes 66a and 66b,
Fluctuations in the flow rate of hydraulic oil in the tilt cylinder 61 are prevented, and the piston rod 61c is held at a predetermined position.

In general, the load is larger during the lift operation than during the tilt operation. Therefore, when the hydraulic pump is driven at the same discharge rate as during the lift operation during only the tilt operation, noise increases and energy is increased. Is wasted. Therefore, during the tilt operation, the number of revolutions of the hydraulic pump is reduced to reduce the discharge amount.

The tilting speed of the fork is controlled by the tilt cylinder 6
The flow rate is determined by the supply flow rate and discharge flow rate of the hydraulic oil supplied to the unit 1. In general, the fork tilts at a constant speed both forward and backward. However, there is also disclosed a configuration in which an operation amount detection sensor for detecting the operation amount of the tilt lever is provided, and the electric motor is driven at a rotation speed corresponding to the operation amount of the tilt lever (for example, Japanese Patent Application Laid-Open No. 2-193899).

[0006]

When the fork is tilted forward, the weight of the fork and mast acts in a direction in which the piston rod 61c of the tilt cylinder 61 projects, so that the pressure in the rod chamber 61a of the tilt cylinder 61 increases. However, in the conventional apparatus, the hydraulic oil in the rod chamber 61a is returned to the tank 67, and the hydraulic pump 6 is supplied to the bottom chamber 61b.
Only the hydraulic oil discharged from the nozzle 2 was supplied. That is, in the conventional apparatus, in both cases of the forward tilting operation and the backward tilting operation of the fork, the pipeline communicating with the chamber on the side opposite to the chamber on which the hydraulic oil is supplied is held in communication with the tank. You. Then, the hydraulic oil in the chamber is discharged to the tank as the piston moves, and the hydraulic oil on the side of the rod chamber 61a in the pressurized state has not been effectively used. As a result, when power is wasted and a battery is used as a power source, there is a problem that the charging cycle is shortened.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a hydraulic cylinder capable of reducing the load on a drive source for driving a hydraulic pump and reducing power consumption. It is to provide a control device.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, the piston rod is used in a state in which the pressure in the cylinder chamber on the piston rod side is increased when the piston rod is stopped in a protruding state. In a hydraulic device provided with a cylinder, a second pipeline communicating a supply pipeline of hydraulic oil with a first pipeline communicating with a rod chamber of the cylinder and a return pipeline to a tank with a bottom chamber. And a second state in which communication between the supply line and the return line of the hydraulic oil and the first and second lines is interrupted.
A hydraulic circuit for connecting a hydraulic oil supply pipe to the second pipe and switching the first pipe to a third state for communication with the second pipe is provided between the cylinder and the hydraulic pump. Detecting means for detecting which of the first to third states the hydraulic circuit is in, and an operation supplied from the rod chamber when the hydraulic circuit is in the third state
Control means for reducing the discharge amount of the hydraulic pump by an amount corresponding to the amount of oil, as compared with when in the first state.

According to the second aspect of the present invention, the hydraulic circuit is integrally formed as a direct-acting three-position switching spool valve. According to the third aspect of the present invention, the spool valve has a detecting means for detecting a position of the spool.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the cylinder is a tilt cylinder for tilting a fork of a forklift.

[0011]

According to the first aspect of the present invention, the cylinder is used in a state in which the pressure in the cylinder chamber on the piston rod side becomes high when the cylinder is stopped in the projecting state of the piston rod. When the hydraulic circuit provided between the cylinder and the hydraulic pump is switched to the first state, the supply line of the hydraulic oil is communicated with the first line communicating with the rod chamber of the cylinder, A return line to the tank communicates with a second line communicating with the bottom chamber. Then, the piston rod is moved to the immersion side. When the hydraulic circuit is switched to the third state, the state is detected by the detection means, and the discharge amount of the hydraulic pump is supplied from the rod chamber by the control means.
In the first state. In addition, the supply line for the hydraulic oil is connected to the second line, and the first line is connected to the second line. Then, the piston rod is moved to the protruding side. At this time, the pressurized hydraulic oil in the rod chamber is supplied to the bottom chamber, and the amount of hydraulic oil to be supplied from the pump to the bottom chamber decreases. Therefore, there is no problem even if the discharge amount of the hydraulic pump is reduced. When the hydraulic circuit is switched to the second state,
The supply line and the return line of the hydraulic oil are disconnected from the first and second lines, and the piston rod stops.

According to the second aspect of the present invention, the hydraulic circuit is switched by the linear movement of the spool. Other functions are the same as those of the first aspect. According to the third aspect of the present invention, the detection means provided in the spool valve detects the position of the spool to detect which of the first to third states is in. Other functions are the same as those of the second aspect.

In the invention described in claim 4, the cylinder is a tilt cylinder for tilting a fork of a forklift, wherein the first state is at the time of the backward operation, the second state is at the time of the neutral operation, and the third state is at the time of the neutral operation. The state corresponds to each of the forward leaning operations. That is, at the time of the forward leaning operation, the hydraulic oil in the rod chamber in the pressurized state is supplied to the bottom chamber, and a shortage is supplied from the hydraulic pump.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a battery type forklift will be described below with reference to FIGS.

As shown in FIG. 1, a fork (not shown)
Is connected to a lift control valve 3 via a pipe 2, and a tilt cylinder 4 for tilting the fork is connected to a tilt control valve via a first pipe 5 a and a second pipe 5 b. 6 is connected. Both control valves 3,
6, a direct-acting spool valve is used. A 7-port, 3-position switching valve is used for the lift control valve 3, and the lift control valve 3 is set in three states a, b, and c corresponding to the ascending, neutral, and descending operation positions of the lift lever 7 for instructing the ascent and descent of the fork. It can be switched. A 7-port, 3-position switching valve is also used for the tilt control valve 6, and three, a, b, and c, corresponding to the forward tilt, neutral, and rear tilt operating positions of the tilt lever 8 for instructing the tilt and stop of the fork, respectively. The state can be switched.

A hydraulic pump 10 for supplying hydraulic oil in an oil tank 9 to each of the cylinders 1 and 4 is driven by an electric motor 11 powered by a battery E. The hydraulic pump 10 is connected to a port P of the lift control valve 3 through a hydraulic oil supply line 12.
_1, the port P ₂ through the branch conduit 12a, are connected to the port P ₃ through the branch conduit 12b.
The branch pipe 12a is provided with a check valve 13. or,
The hydraulic oil supply pipe 12 is connected to a return pipe 16 via a pipe 15 a provided with a relief valve 14. A return line 16 in the lift control valve 3 port T _1, the conduit 2 at the port A _1, conduit at the port A ₂ 1
To 5b, it is connected to the conduit 17 at port A _3. The pipe 15b is connected to the return pipe 16, and a relief valve 18 is provided on the way. Pipe line 2
Is connected to the bottom chamber 1b of the lift cylinder 1.

The lift control valve 3 is arranged at the position a based on the lifting operation of the lift lever 7, and connects the pipe 12a and the pipe 2 at the a position to extend the lift cylinder 1. The lift control valve 3 is disposed at the position c based on the lowering operation of the lift lever 7, and connects the pipe 2 and the return pipe 16, the hydraulic oil supply pipe 12 and the pipe 17 at the c position. The lift cylinder 1 is contracted by making the path 12b communicate with the pipe 15b. The lift control valve 3 is disposed at the position b based on the neutral operation of the lift lever 7, and connects the hydraulic oil supply pipe 12 and the pipe 17 with the pipe 12b and the pipe 15b at the b position. Communicate.
Then, the communication between the pipe 2 and the pipes 12a and 16 is cut off to prevent movement of the hydraulic oil in the lift cylinder 1, and
This is held without expanding and contracting.

The hydraulic pump 10 is connected to the port P ₁₁ of the tilt control valve 6 through a hydraulic fluid supply pipe 19 branched from the hydraulic fluid supply pipe 12. A check valve 20 is provided in the hydraulic oil supply pipe 19. Branch conduit 17a to the port P ₁₂ of the tilt control valve 6, the port P ₁₃
Are connected to pipes 17, respectively. Tilt control valve 6 in the port T ₁₁ in the return line 16a, are connected to the return line 16b in port T _12. In tilt control valve 6 port A ₁₁ to the first conduit 5a, are connected to the second conduit 5b at port A _12. Restriction (orifice) in conduit 16b
21 are provided. Pipe 5a is tilt cylinder 4
The pipe line 5b is connected to the bottom chamber 4b.

As shown in FIG. 2, in this embodiment, the lift control valve 3 and the tilt control valve 6 are integrally formed as one control valve 22, and the lift spool 3a and the tilt spool 6a are parallel to each other. Is provided so as to be capable of linear movement. Therefore, in the control valve 22 of FIG. 2, each pipe in FIG. 1 corresponds to a passage formed in the valve housing 23. The passages having the same role as the respective conduits in FIG. 1 are denoted by the same reference numerals as the conduits. Both spools 3a and 6a are provided slidably with both ends protruding from the valve housing 23. Flat connecting portions 3b, 6b are integrally formed at the first ends of the spools 3a, 6a, respectively. The spools 3a, 6a are connected to the lift lever 7 or the tilt lever 8 at the connecting portions 3b, 6b by link members (see FIG. (Not shown).

As shown in FIG. 2, the valve housing 23
Bulges 24 on the second end sides of both spools 3a, 6a.
A second end 25 of each of the spools 3a, 6a protrudes into the bulging portions 24, 25.
A pair of spring seats 26 is provided at the second end of each spool 3a, 6a.
Are loosely fitted in a state where they are opposed to each other and at a distance slightly larger than the amount of movement of each of the spools 3a and 6a from the neutral position, and a coil spring 27 is interposed between the two spring seats 26. The spools 3a and 6a are biased toward the neutral position by the spring force of the coil spring 27.
Each of the bulging portions 24 and 25 has a stroke sensor 2 as detecting means for detecting the position (state) of the spools 3 a and 6.
8, 29 are attached.

Each stroke sensor 28, 29 is connected to the second end of each spool 3a, 6a. Each of the stroke sensors 28 and 29 is electrically connected to a controller C for controlling the electric motor 11. The controller C includes a hydraulic pump 1 corresponding to the positions of the spools 3a and 6a.
A memory is provided which stores data relating to an appropriate discharge amount of 0, that is, an appropriate rotation speed of the electric motor 11. Controller C
Calculates the positions of the two spools 3a, 6a based on the detection signals of the stroke sensors 28, 29, and calculates the rotational speed command value of the electric motor 11 corresponding to the state. The controller C controls the power supplied from the battery E to the motor 11 based on the calculated rotation speed command value, and drives the motor 11 at a rotation speed according to the rotation speed command value to discharge the hydraulic pump 10. Adjust the volume.
That is, the lift speed of the fork and the tilt speed of the mast are controlled in accordance with the operation amount of the lift lever 7 in the ascending direction and the operation amount of the tilt lever 8.

A tilt lock mechanism is built in the tilt spool 6a. That is, the tilt spool 6
A plunger 30 is slidably disposed inside the second end portion a. Plunger 30 is an action for opening and closing a passage 31 for communicating the port P ₁₁ and the port A _11. That is, when the hydraulic oil pressure state in the passage 32 which communicates with the port P ₁₂ is supplied, the throttle passage 33 the plunger 30 against the urging force of the coil spring 30a is passage 31
It is arranged in an open position that communicates with the user. When the pressure of the hydraulic oil supplied to the passage 32 decreases, the plunger 3
0 is the throttle passage 3 due to the urging force of the coil spring 30a.
3 is disposed at a closed position where communication between the passage 3 and the passage 31 is interrupted. An orifice 34 is provided in the passage 32.

When the tilt spool 6a is located at the position c in FIG. 1, that is, at the position shifted rightward from the neutral position in FIG.
Passage 36 communicating 1 the passage 35 for communicating the P ₁₁ and the port A ₁₂ is formed. Further, when placed in the position b in the tilt spool 6a, passage 37 for communicating the port P ₁₃ and port T ₁₂ is formed, the passage 37 is c
Port T through the orifice 38 when positioned.
Communicates with ₁₂ . The tilt spool 6a, a position tilt spool 6a is shown in FIG. 1, i.e., when placed in a position moved leftward from the neutral position shown in FIG. 2, passage connecting the port P ₁₁ and the port A ₁₁ 39 and port A
A passage 40 which communicates is formed between ₁₂ and port T _11.

The tilt control valve 6 is arranged at the position a based on the tilting operation of the tilt lever 8 at the position a. At the position a, the hydraulic oil supply line 19 and the first line 5a are connected to the return line 16a. The tilt cylinder 4 is contracted by being arranged in the first state in which the second cylinder 5b communicates with the second pipe 5b. The tilt lift control valve 6 is arranged at the position c in FIG. 1 based on the forward tilt operation of the tilt lever 8. At the position "c", the hydraulic oil supply pipe 19 and the second pipe 5b communicate with each other, and the first pipe 5a communicates with the second pipe 5b via the passages 31, 36 and 35. And the tilt cylinder 4 is extended. The tilt control valve 6 is arranged at a position b in FIG. 1 based on a neutral operation of the tilt lever 8. In the position b, the pipes 17 and 16b
And cut off the communication between the first pipe line 5a and the second pipe line 5b and the hydraulic oil supply pipe 19 and the return pipe line 16a to prevent the movement of the hydraulic oil in the tilt cylinder 4. Then, it is held without shrinking.

Next, the operation of the control device for a hydraulic cylinder configured as described above will be described. When the lift lever 7 is raised, the lift spool 3a is disposed at the position a,
The hydraulic pump 10 is driven by the electric motor 11 rotated at a rotation speed command value according to the operation amount of the lift lever 7. The hydraulic oil discharged from the hydraulic pump 10 is supplied to the bottom chamber 1b of the lift cylinder 1 through the hydraulic oil supply pipe 12, the pipe 12a, the lift control valve 3, and the pipe 2, and the lift cylinder 1 Extend and the fork rises.

When the lift lever 7 is lowered, the lift spool 3a is disposed at the position c, the pipe 2 is connected to the return pipe 16, and the hydraulic oil in the bottom chamber 1b is returned to the oil tank 9. Then, the lift cylinder 1 contracts and the fork descends. The lift spool 3a is disposed at the position b based on the neutral operation of the lift lever 7, and
Is disconnected from both the pipeline 12a and the pipeline 16. As a result, movement of the hydraulic oil in the lift cylinder 1 is prevented, and the fork is held at a desired position.

[0027] In a state where the tilt spool 6a is positioned at the neutral position shown in FIG. 2, the port P ₁₃ and port T
₁₂ is in communication with the end face of the plunger 30 from the port P ₁₂ via the orifice 34 through the passage 37. The pressure of the hydraulic oil in the passage 32 that communicates with the end face of the plunger 30 With less than the spring force, the passage 31 is kept closed.

When the tilt lever 8 is tilted forward, the tilt spool 6a is moved rightward in FIGS. 1 and 2, the cross-sectional area of the passage 37 is reduced, and the tilt spool 6a operates through the check valve 20. The operating oil flowing through the oil supply pipe 19 is port P
_11, passage 35, is supplied to the bottom chamber 4b of the tilt cylinder 4 through the port A ₁₂ and the second conduit 5b. Moreover, the working oil from the port P ₁₂ to the orifice 34 is supplied, the plunger 30 is moved to the right in FIGS. 1 and 2, passageways 31
Communicates with the throttle passage 33, and the passage 31 and the passage 36
Is communicated. Therefore, the hydraulic oil first conduit 5a port A _11, passage 31, a state in communication with the passage 35 through the throttle passage 33 and the passage 36, the hydraulic oil from the rod chamber 4a is supplied via line 19 And is supplied to the bottom chamber 4b.

When the tilt spool 6a is located at the forwardly inclined position, the stroke is detected by the stroke sensor 29, and the controller C controls the rotation speed of the electric motor 11 to be a predetermined value smaller than the rotation speed at the time of backward inclination. The drive of the electric motor 11 is controlled. When the fork is tilted forward, the weight of the fork and mast acts in a direction in which the piston rod 4c of the tilt cylinder 4 protrudes, so that the pressure of the hydraulic oil in the rod chamber 4a increases. Accordingly, the high-pressure hydraulic oil is combined with the hydraulic oil discharged from the hydraulic pump 10 and the amount of hydraulic oil discharged from the hydraulic pump 10 is reduced by an amount corresponding to the amount of hydraulic oil supplied from the rod chamber 4a. There is no problem even if it is reduced.

[0030] tilt lever 8 is tilted backward operation, tilt spool 6a is moved to the left in FIGS. 1 and 2, together with the passage 37 is cut off, the port A port P ₁₁ via the passage 39 _The hydraulic oil flowing through the hydraulic oil supply line 19 through the check valve 20 through the check valve 20 communicates with the port P ₁₁ ,
Passage 39, is supplied to the rod chamber 4a of the tilt cylinder 4 through the port A ₁₁ and the first conduit 5a. Moreover, the port A ₁₂ is communicated with port T ₁₁ via a passage 40, the hydraulic oil return line 16a of the bottom chamber 4b of the tilt cylinder 4
And returned to the oil tank 9.

When the tilt lever 8 is at the neutral position, the tilt spool 6a is located at the neutral position, and the first conduit 5a and the second conduit 5b are connected to the return conduit 16a and the hydraulic oil supply conduit. Communication is interrupted for any of the nineteen. As a result, movement of the hydraulic oil in the tilt cylinder 4 is prevented, and the fork is held in a state where the tilting is prevented.

The plunger 30 is moved to the open side, that is, the right side in FIG. 2 only when the pressurized hydraulic oil is supplied from the orifice 34. Therefore, when the operation key of the forklift is not operating and the hydraulic pump 10 is stopped, the plunger 30 is always kept in the closed position, and even if the tilt lever 8 is operated, the supply of the hydraulic oil to the tilt cylinder 4 is not performed. The fork is kept in its initial state. Therefore, even if the tilt lever 8 is accidentally touched while the operation of the forklift is stopped, the fork does not move.

As described above, in the forklift hydraulic control apparatus, pressurized hydraulic oil discharged from the rod chamber 4a of the tilt cylinder 4 when the fork is tilted forward is supplied to the bottom chamber 4b. As a result, the amount of hydraulic oil to be supplied to the bottom chamber 4b is reduced by the action of the hydraulic pump 10, and the electric motor 11 that drives the hydraulic pump 10
Can be reduced, the load on the electric motor 11 is reduced, and the power consumption is also reduced.

In this embodiment, the third state is established in which the first pipe 5a and the second pipe 5b communicate with each other in order to supply the hydraulic oil in the rod chamber 4a of the tilt cylinder 4 to the bottom chamber 4b. Since the switching hydraulic circuit is integrally formed as a direct-acting three-position switching spool valve, the device is compact. In addition, since the stroke sensor 29 for detecting the position of the spool 6a is provided on the spool valve, it is not necessary to attach the detecting means to another position.

The present invention is not limited to the above embodiment, but may be embodied as follows, for example. (1) Although the lift control valve 3 and the tilt control valve 6 are formed integrally, the control valves 3 and 6 may be formed separately. In addition, the tilt lock mechanism is connected to the tilt spool 6a.
However, a tilt lock mechanism may be separately provided.
In this case, as shown in FIG.
The outer periphery of when the tilt spool 6a is moved to the forward tilting position from the neutral position, may be formed port P ₁₁ and the port A ₁₁ and capable of communicating annular groove 41 a. In this case, when the tilt spool 6a moves to the right side in the figure from the neutral position shown in FIG.
1 also moves to the right, and the port P ₁₁ and the port A ₁₁ are communicated via the annular groove 41. When the tilt lock mechanism is not built in, the structure is simplified.

(2) Instead of integrally forming a hydraulic circuit for switching to the third state for communicating the first pipe line 5a and the second pipe line 5b as a direct-acting three-position switching spool valve, a separate hydraulic circuit is provided. May be provided. For example, as shown in FIG. 4, a normal three-position switching valve is used as the tilt control valve 6, the first conduit 5a is divided into conduits 5aA and 5aB, and an electromagnetic three-port two-position valve is interposed therebetween. A switching valve 42 is provided. A branch line 5bA is provided in the line 5b, and the branch line 5bA is provided.
bA is connected to the switching valve 42. When the tilt lever 8 is located at the forward tilt position, the switching valve 42 is connected to the controller C.
Is held in a state where the position a, that is, the line 5aA and the branch line 5bA are communicated with each other, and in other cases, the position b is held in a state where the line 5aA and the line 5aB are connected. This configuration can be easily implemented by adding an electromagnetic switching valve 42 to the conventional device.

(3) A rotation sensor may be provided as a detecting means instead of the stroke sensor. In this case, for example, a rotation sensor is provided on the side of the end of the spool, and a linear motion of the spool is converted into a rotary motion by a lever connected to the rotation shaft. Further, the detection valve may not be provided on the control valve, and may be provided at a position where the movement of the rod connecting the tilt spool 6a and the tilt lever 8 is detected or a position where the movement of the tilt lever 8 is detected.

(4) Instead of adjusting the rotation amount of the electric motor 11 in accordance with the movement amount of the tilt spool 6a at the time of tilt operation, the motor is not limited to the position of the tilt spool 6 at the time of the backward tilt operation, but at a predetermined rotation speed. Alternatively, the motor 11 may be rotated at a constant rotation speed that is smaller by a predetermined ratio during the forward tilting operation than during the backward tilting operation. Also in this case, the load on the electric motor 11 is reduced at the time of the forward leaning operation, and the power consumption is reduced. Therefore, wasteful consumption of electric power is reduced and the life of the battery E is extended as compared with the conventional device. In this case, the detecting means need only be able to detect that the tilt spool 6a has been moved from the neutral position to the forward inclined position or the backward inclined position without continuously detecting the movement amount of the tilt spool 6a. Therefore, a limit switch or a proximity switch may be used as the detecting means.

(5) The present invention is not limited to a tilt cylinder control device of a forklift, and is applicable to a hydraulic device having a cylinder used in a state where the pressure in a cylinder chamber on the piston rod side becomes high when the piston rod is stopped in a protruding state. May be.

The inventions other than those described in the claims which can be grasped from the embodiment and the modified examples will be described below together with their effects. (1) In the invention described in claim 2 or 3, the cylinder is a tilt cylinder for tilting a fork of a forklift, and a tilt lock mechanism is built in the spool valve. In this case, the tilt lock mechanism becomes compact.

[0041]

As described in detail above, claims 1 to 4 are provided.
According to the invention described in (1), the load on the drive source for driving the hydraulic pump can be reduced, and power consumption can be reduced. According to the second aspect of the present invention, the device becomes compact. Further, according to the third aspect of the invention, there is no need to attach the detecting means to another position. Claim 4
According to the invention described in (1), the life of the battery of the battery type forklift is prolonged, and the charging cycle can be prolonged.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of an embodiment.

FIG. 2 is a sectional view of a control valve.

FIG. 3 is a partial cross-sectional view of a control valve according to a modified example.

FIG. 4 is a hydraulic circuit diagram showing a main part of a modified example.

FIG. 5 is a hydraulic circuit diagram of a conventional device.

[Explanation of symbols]

4 ... Tilt cylinder, 4a ... Rod chamber, 4b ... Bottom chamber, 5a ... First pipeline, 5b ... Second pipeline, 6 ... Tilt control valve as 3 position switching spool valve, 6a ... Tilt spool Reference numerals: 10: hydraulic pump, 12, 19: hydraulic oil supply line, 16, 16a: return line, 22: control valve, 28, 29: stroke sensor as detection means, 41: annular groove, 42: switching valve , 5bA: branch line, C: controller.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yukio Makino 3-22-41 Yoshida, Nagano City, Nagano Prefecture Nishina Kogyo Co., Ltd. (72) Inventor Makio Tsukada 3-22-41 Yoshida, Nagano City, Nagano Prefecture Nishina Industry (56) References JP-A-2-28499 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B66F 9/22

Claims (4)

(57) [Claims] 1. A hydraulic device comprising a cylinder used in a state where the pressure in a cylinder chamber on the piston rod side is increased when the piston rod is stopped in a protruding state, wherein a supply line of hydraulic oil is connected to a rod chamber of the cylinder. And a first state in which a return line to the tank communicates with a second line in communication with the bottom chamber, and a supply line and return line for hydraulic oil. A second state in which communication with the first and second pipes is cut off, and a supply pipe for hydraulic oil in communication with the second pipe;
A hydraulic circuit that switches between the cylinder and the hydraulic pump is provided between the cylinder and the hydraulic pump, and the hydraulic circuit is in any one of the first to third states. Detecting means for detecting whether the hydraulic circuit is in the third state, and the amount of hydraulic oil supplied from the rod chamber when the hydraulic circuit is in the third state.
Control means for reducing the discharge amount of the hydraulic pump by a corresponding amount from that in the first state. 2. The hydraulic cylinder control device according to claim 1, wherein the hydraulic circuit is integrally formed as a direct-acting three-position switching spool valve. 3. The control device for a hydraulic cylinder according to claim 2, wherein the spool valve includes a detection unit that detects a position of the spool. 4. The tilt cylinder for tilting a fork of a forklift, wherein the cylinder is a tilt cylinder.
The hydraulic cylinder control device according to any one of claims 1 to 3.