JP2716875B2 - Forklift working machine cylinder supply flow control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a working machine cylinder such as a lift cylinder or a tilt cylinder of a forklift,
The present invention relates to an apparatus for controlling a flow rate when pressure oil is supplied from a gear pump.

[0002]

2. Description of the Related Art First, an example of a forklift will be described with reference to FIGS. FIG. 14 is a perspective view showing an example of a forklift. As shown in the figure, a hydraulic cylinder 1 called a lift cylinder is fixed to a pair of left and right outer masts 2, and moves up and down a pair of left and right inner masts 3 using the outer mast 2 as a guide as the piston rod 1 a expands and contracts. It is supposed to. At this time,
The outer mast 2 is fixed to the vehicle body 7 in front of the vehicle body 7. As a result, as the inner mast 3 is moved up and down, the elevating unit composed of the bracket 5 suspended on the chain (not shown) and the fork 4 for directly loading the cargo is moved up and down. That is, the chain is suspended on a chain wheel (not shown) rotatably supported on the inner mast 3, and has one end fixed to the bracket 5 and the other end fixed to the outer mast 2.

Thus, the fork 4 and the bracket 5, which are the elevating portions, not only rise with the rise of the inner mast 3, but also the relative position with respect to the inner mast 3 rises due to the rise of the chain wheel with respect to the outer mast 2. I do. In other words, the amount of rise of the elevating unit with respect to the ground surface is a value obtained by adding the amount of rise of the inner mast 3 to the amount of relative rise with respect to the inner mast 3 defined by the length of the chain. With respect to the descent of the elevating unit, the same relationship as that at the time of ascent is established, except that the moving direction is reversed.

A hydraulic cylinder 8 called a tilt cylinder
Is for tilting the elevating portion forward (toward the vehicle body 7 side) and rearward (to the vehicle body 7 side) together with the outer mast 2 and the inner mast 3. That is, in the case of unloading, it tilts forward, and in the case of unloading and transporting luggage, it tilts rearward, so that the respective workability is maintained well and safety is ensured.

The work machine levers 9a and 9b are used by an operator to control the operation of the lift cylinder 1 and the tilt cylinder 8 via the controller 10 and the electromagnetic proportional control valve 11, and perform an emergency stop. Is stored in the joystick box 13 together with the safety switch 12. Work implement levers 9c, 9d, 9
"e" is for dealing with a case where various attachments such as a roll clamp and a bale clamp are attached. The seat switch 14 is a switch that operates when the operator sits on the driver's seat 15, and outputs an output signal to the controller 10.

As shown in FIG. 15, the working machine levers 9a,
Reference numeral 9b denotes a potentiometer, which outputs a lever operation signal S ₁ whose voltage value is proportional to the operation amount to the controller 10.
To send to. The controller 10 is mainly composed of a microprocessor (CPU) and has a lever operation signal S
Adjusting the opening of the spool of the electromagnetic proportional control valve 11 based on ₁ sends a (spool control) flow control signal (current signal) S _2. The electromagnetic proportional control valve 11 controls the flow rate of the pressure oil flowing through the hydraulic line 16 by moving the spool in proportion to the current value of the flow rate control signal S ₂ , thereby controlling the operating speed of the lift cylinder 1 and the tilt cylinder 8. The working machine lever 9
Control is performed so as to correspond to the operation amounts of a and 9b.

A hydraulic pressure sensor 17 is provided in the hydraulic line 16 and sends out a hydraulic signal S ₃ indicating the pressure of the hydraulic oil in the hydraulic line 16. The controller 10 processes the hydraulic signal S ₃ to calculate the load acting on the lift cylinder 1 or the tilt cylinder 8.

Further, the controller 10 includes a warning light 18
Together with supplied power from battery 21 to operate by introduction of a starter switch 20 are housed in the console box 19, when he operates the safety switch 12 and the current value of the flow rate control signal S ₂ when the seat switch 14 is not operated Control is performed such that the opening of the electromagnetic proportional control valve 11 becomes zero as zero.

In FIG. 15, reference numeral 22 denotes a gear pump, and reference numeral 23 denotes a hydraulic oil tank. Also, hydraulic system components such as the electromagnetic proportional control valve 11, the hydraulic pipeline 16, and the hydraulic sensor 17 are provided in a number corresponding to the number of the working machine levers 9a to 9e. In this embodiment, since two working machine levers 9a and 9b for lift and tilt are provided to perform lift and tilt operations, two hydraulic systems are provided.

[0010]

As described above, in a forklift, a gear pump is used as a working machine pump for supplying pressurized oil. This is extremely inexpensive compared to a variable flow pump.

However, the capacity of the gear pump is determined by 90 to 95% of the idle output horsepower of the forklift engine, and when the engine speed is increased, only 60 to 70% of the engine output is absorbed horsepower. Output.

Therefore, when the load on the lift cylinder or the tilt cylinder is low, for example, if the flow rate is increased in order to obtain the maximum lift ascending speed, the engine speed increases, the noise increases, and the wasteful output increases. As a result, fuel efficiency will deteriorate.

It is an object of the present invention to provide a work machine cylinder supply flow control device for a forklift which solves the above-mentioned problems of the prior art.

[0014]

According to the present invention, a work machine cylinder supply flow control device for a forklift according to the present invention comprises two hydraulic pumps connected to an engine of a forklift and connected to the discharge sides of the two hydraulic pumps. A solenoid valve for joining the output of one hydraulic pump to the other hydraulic pump, a solenoid valve for a cylinder connected between the solenoid valve for joining and the cylinder of the working machine, and an actuator for operating a throttle lever of the engine. A sensor that detects the engine speed, a sensor that detects the load on the working machine cylinder, and a full opening of the cylinder solenoid valve if the working machine lever opening is more than a predetermined intermediate opening. The spur that changes the opening of the solenoid valve for the cylinder from fully closed to a certain opening in accordance with the opening of the work equipment lever when the opening is below the intermediate opening. When the opening of the control unit and the work implement lever is less than the intermediate opening, the actuator is kept at a fixed position equivalent to idle rotation, and when the opening is more than the intermediate opening, the actuator is set according to the work implement lever opening and the load of the work implement cylinder. When the load on the engine speed control unit and the working machine cylinder that operates the actuator is less than a predetermined small value, the merging solenoid valve is kept at a certain large opening such as full open, and when it is more than a predetermined large value, it merges. The solenoid valve for use is kept at a fixed small opening such as fully closed, and when between the small value and the large value, the joining solenoid valve is moved between the fixed large opening and the fixed small opening according to the engine speed. And a controller comprising a merging pump control unit for changing the pressure.

[0015]

When the working machine lever is below a certain intermediate opening, the opening of the cylinder solenoid valve increases in accordance with the increase of the lever opening while the engine is almost in an idling state, and the supply to the working machine cylinder is performed. The flow rate increases. Therefore, the noise is low,
Good fuel economy. However, when the load on the working machine cylinder is large, the output of one hydraulic pump is released without merging so as not to stall the engine. When the work implement lever is at or above a certain intermediate opening, the solenoid valve for the cylinder is fully open, but the engine speed increases with an increase in the lever open degree, and the supply flow rate to the work implement cylinder increases. . In this case, the engine speed is changed according to the magnitude of the load to secure a required flow rate, and the degree of merging of the output of one hydraulic pump is changed according to the engine speed and the magnitude of the load.
Therefore, noise is low, fuel consumption is good, and engine stall does not occur.

Further, the supply flow rate can be easily adjusted only by operating the working machine lever, and the working efficiency is improved.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a hydraulic circuit, and FIG. 2 shows an electric control system thereof. In FIG. 1, two gear pumps 2
2A, 22B tandem forklift engine 2
4 is connected. For convenience, one gear pump 22A is referred to as a main pump, and is also referred to as a No. 1 pump. Also,
The other gear pump 22B is a sub-pump and is also referred to as a No. 2 pump.

The discharge sides of the main pump 22A and the sub-pump 22B are connected to a two-position electromagnetic proportional control valve 11C to determine whether or not the two pump outputs are to be merged. Is controlled by the flow control signal S ₂ C. Then, from the electromagnetic proportional control valve 11C, the electromagnetic proportional control valve 1
1A to supply pressurized oil to the lift cylinder 1;
The pressure oil is supplied to the tilt cylinder 8 via the three-position electromagnetic proportional control valve 11B, and the supply flow rate is controlled by flow rate control signals S ₂ A and S ₂ B from the controller 10, respectively. .

In the state shown in FIG. 1, each flow control signal S
The current values of ₂ A, S ₂ B, and S ₂ C are zero, and the electromagnetic proportional control valve 11C for merging does not merge the outputs of the two pumps, but only the output of the main pump 22A. , 11B and the output of the sub-pump 22B is returned to the tank 23. In addition, the two cylinder electromagnetic proportional control valves 11A and 11B
Is closed, and the pressure oil from the merged electromagnetic proportional control valve 11C is returned to the tank 23.

The controller 10 includes, in addition to the lift and tilt working machine levers 9a and 9b and the hydraulic pressure sensor 17,
Engine rotation sensor 2 for detecting the number of rotations of engine 24
5 are connected, and the lever operation signals S ₁ A,
S ₁ B, a hydraulic pressure signal S ₃ , and an engine speed signal S ₄ are input. The controller 10 is connected to the three electromagnetic proportional control valves 11A, 11B, and 11C described above, and outputs flow rate control signals S ₂ A, S ₂ B, and S ₂ C thereto. so that by connecting connects the electromagnetic proportional solenoid 27 for operating this, and outputs a throttle opening control signal (current signal) S ₅ to the solenoid.

As shown in FIG. 2, the controller 10 mainly comprises a central processing unit (CPU) 28, which mainly stores software in a ROM 29 and a RAM 3
Data is stored in 0. Since the working machine levers 9a and 9b are potentiometers, the A / D converter 31
Each potentiometer voltage, which is a lever operation signal S ₁ A, S ₁ B, is converted into a digital signal, and the controller CPU 2
Give 8 The input interface 32 converts the oil pressure signal S ₃ from the oil pressure sensor 17 and the engine speed signal S ₄ from the engine speed sensor 25 for the CPU, and
Give to U28. The solenoid valve drive circuit 33 supplies a current corresponding to the calculation result of the CPU 28 to each of the electromagnetic proportional control valves 11A, 1A.
1B and 11C have flow control signals S ₂ A, S ₂ B and S ₂ C
As, in the electromagnetic proportional solenoid 27 provided as the throttle opening control signal S _5. Reference numeral 34 denotes a clock circuit for the CPU 28, and reference numeral 35 denotes an internal power supply circuit for lowering the voltage of the battery 21 to a predetermined value and stabilizing the same.

Next, the details of the controller 10 will be described with reference to FIGS. The controller 10 uses software to control spool control for adjusting the spool opening of the electromagnetic proportional control valves 11A and 11B, engine speed control for adjusting the number of revolutions of the engine 24, and merging of the sub pump 22B by the electromagnetic proportional control valve 11C. Each function unit called a merging pump control to be adjusted is configured. These control functions include the amount of operation of the working machine levers 9a and 9b, that is, the degree of opening, the load applied to the lift cylinder 1 obtained from the hydraulic sensor 17, that is, the magnitude of the load, and the engine obtained from the engine rotation sensor 25. It operates according to the rotation speed.

In this embodiment, as shown in FIGS. 3 and 4,
Spool control is performed when the lever opening of the lift working machine lever 9a is between the neutral position and the intermediate opening on the lift ascending side, and when the lever opening is between this intermediate opening and the maximum opening on the lift ascending side, the engine speed is controlled. Control is to be performed.
However, in the case where the lever opening is on the lift lowering side, as will be understood from FIG. In addition, the description will be made on the assumption that the spool control is performed for all the lever opening degrees of the tilting working machine lever 9b on both the forwardly inclined side and the backwardly inclined side.

Since the lever opening and the potentiometer voltage of the working machine lever are in a proportional relationship as shown in FIG. 4, as shown in FIG. Voltage V corresponding to
For more values _m, and fixed to the maximum value I _max requiring current value of the flow rate control signal S ₂ A for lifting solenoid proportional control valve 11A to the valve fully opened, the flow control signal only if the following values V _m S the current value of ₂ a is changed in proportion to the potentiometer voltage between zero and I _max performs spool control.
However, since the potentiometer voltage is near zero near the neutral position of the work implement lever, the dead zone is set for safety and the current value is zero.

Then, the working machine lever 9a is moved from the neutral position.
In the aforementioned spool control at the lift-up side intermediate opening,
The load detected by the hydraulic pressure sensor 17 is a predetermined small value.
Value W _LIf larger, the electromagnetic proportional control valve for merging 11C
Flow control signal S_TwoSet the current value of C to zero and
Return the output oil of the pump 22B to the tank 23 and do not join it.
No. When the load is W_LLess than the flow control signal
S_TwoThe current value of C is required for fully opening the electromagnetic proportional control valve 11C.
And output oil of the sub pump 22B to the main pump
Combine with 22A output oil. This combination pump control
As a result, lever opening and lift cylinder in spool control
FIG. 8 (a) shows a relationship between the lift-up supply flow rate and the lift-up flow rate of the fuel cell 1.
The characteristics shown in FIG.

On the other hand, as shown in FIG.
Potentiometer voltage of lever 9a is medium at lift rise value
Voltage V corresponding to the opening_mIn the following cases,
Throttle opening signal S for the solenoid 27_FiveThe current value of
Value I corresponding to idling ₀Fixed to V_mMore places
Only when the potentiometer voltage (lever opening)
The current value is I₀To increase the engine speed.
Let However, the relationship between potentiometer voltage and current value is
The load varies depending on the load, and the load is a predetermined large value W_H
In the case of a larger load, the routes a and b in FIG.
Current value with sharp characteristics₀From the maximum value I_maxIncrease between
Reduce. In addition, when the load is the aforementioned small value W_LSmaller
In the case of a small load, the slow characteristic following the paths c and d in FIG.
Increase or decrease the current value depending on the nature. And the load is W_LAnd W_HBetween
In the case of a medium load, the routes a, e, and d in FIG.
Increase or decrease the current value according to the characteristics. That is, potentiometer
Voltage is V_mIf it is nearby, follow the path a with a large load,
Maximum value V_maxIf nearby, follow the path d with a small load,
On the way, a path e transitioning between the two a and d is followed.

In the aforementioned engine speed control in which the working machine lever 9a is at or above the intermediate opening on the lift ascending side,
The joint pump control is performed as follows.

First, when the load is a large load larger than the above-mentioned large value W _H , the current value of the flow control signal S ₂ C to the merged electromagnetic proportional control valve 11C is set to zero, and the output oil of the sub pump 22B is stored in the tank. Return to 23 and do not merge.
When the load is a small load smaller than the aforementioned small value, the output oil of the sub-pump 22B is all joined to the output oil of the main pump 22A with the current value of the flow control signal S ₂ C as a value required for full opening. Further, if the load in the load is between the W _L and W _H is large load as well as the flow control signal S if the engine speed is lower than a certain value S above idle speed
₂ The current value of C is not set to zero and merged. If the current value is higher than a certain value M larger than S, the current value is set to a value required for full opening and all merged. If it is between S and M, it depends on the engine speed. The degree of merging is adjusted by increasing or decreasing the current value from zero to the value required for full opening.

By the control of the merging pump according to the engine speed and the load, the relationship between the engine speed and the lift increasing supply flow rate to the lift cylinder 1 has the characteristic shown in FIG. That is, in the case of a large load, the lift increasing supply flow rate increases or decreases according to the engine speed with a slow characteristic following the paths a and b in FIG. 7, and in the case of a small load, the paths c and d in FIG.
With the steep characteristic of following, the lift ascending supply flow rate increases and decreases according to the engine speed. In the case of a medium load, the path a with a large load is followed when the rotational speed is equal to or less than S, and the path d with a small load is followed when the number of rotations is M or more. Following the path e transitioning between d, the lift ascending supply flow rate increases or decreases.

As a result, the relationship between the opening degree of the lift working machine lever 9a at an intermediate opening degree or more and the lift increasing supply flow rate to the lift cylinder 1 by the engine speed control and the merge pump control is shown in FIG. The characteristics shown in b) are obtained. That is, in the case of a large load, the lift ascending supply flow rate increases and decreases according to the lever opening degree with a slow characteristic following the paths a and b in FIG. 8B, and in the case of a small load, FIG. With the steep characteristic of following the middle paths c and d, the lift ascending supply flow rate increases and decreases according to the lever opening. In the case of a medium load, if the lever opening is close to the intermediate opening, the path a with a large load is followed, and if the lever opening is close to the maximum opening, a path d with a small load is followed. In this case, the lift ascending supply flow rate increases and decreases following the path e transitioning between the two a and d. In the case of the intermediate opening, FIG.
The lift-up supply flow rate by the spool control and the merge pump control in FIG. 8A is set to be equal to the lift-up supply flow rate by the engine speed control and the merge pump control in FIG. 8B.

Next, the software operation of the CPU 28 of the controller 10 will be described collectively based on the flow chart of the merge pump control shown in FIGS. 9 to 12 and the flow chart of the lever output and engine speed control shown in FIG.

First, the control of the merging pump will be described with reference to FIGS. As shown in FIG.
From the initialized state, first, the work implement lever 9a
Is determined based on the potentiometer voltage (step A1). For example, if the potentiometer voltage is negative, it is determined that the lever 9a is being operated on the lowering side of the lift.
The current value of the flow control signal S ₂ A required for the lift lowering side control of 1A is calculated, and the current value I of the merged electromagnetic proportional control valve 11C is adjusted so that the sub-pump 22B is merged irrespective of the load or lever opening. _max is determined and output (step A3). The current of the throttle proportional electromagnetic solenoid 27 may be set to I ₀ and the engine may be kept idling.

If the potentiometer voltage is positive, it is determined that the lever 9a is being operated on the lift ascending side, and in the next step A4, it is determined whether or not the lever opening exceeds the dead zone. If it is a dead zone, in step A5, the value of the current flowing through the electromagnetic proportional control valve 11A is determined to be, for example, zero in order to cut off the supply flow rate to the lift cylinder 1 and keep it stationary.
Further, a current value flowing through the electromagnetic proportional control valve 11C is set to, for example, zero in order to cut off the merging of the sub-pump 22B, and each is output (step A3). The step A5, the oil pressure signal S ₃ from the oil pressure sensor 17, calculates a load of the lift cylinder 1, and stores this value.

If the lever opening exceeds the dead zone on the lift ascending side, first, at step A6, the load W
Determines whether exceeds the _H, W if _H below the value zero, for example sever merging the current value (step A7), and outputs it to the confluence proportional control valve 11C.

If the load is larger than W _H , the process proceeds to step A8 shown in FIG. 10 and a small set value W _L (W _L <W _H ).
It is determined whether it is smaller than. Smaller than W _L, set the current value for combining all sub-pump 22B in step A9, and outputs it to the electromagnetic proportional control valve 11C (step A3), it is fully open.

If the load is a medium load between W _H and W _L ,
In step A10, it is determined whether or not the engine speed has exceeded a large set value M. If it has exceeded M, an engine flag is set in step A11 and step A9
The value at which all the sub-pumps 22B are joined is referred to as a current value.

If the engine speed is equal to or lower than M, it is determined in step A12 whether or not the engine flag has already been set. If it is not set, it is determined whether or not the engine speed is lower than a small set value S (idle speed <S <M). If it is lower than S, it is not necessary to control the degree of confluence, so in step A14 The current value is set to a value at which the merging is stopped, for example, zero, and is supplied to the electromagnetic proportional control valve 11C (step A3), so that all the output of the sub pump 22B is bypassed to the tank 23.

If it is determined in step A12 that the engine flag is set, the engine speed tends to decrease from M.
The degree of merging is reduced at 5-A21. Step A
At 15, it is determined whether or not a decrease holding flag, which will be described later, is set. If not, at step A16, the current value is calculated by subtracting a constant value from the previous current value in order to reduce the degree of merging from the previous time. . Then, in step A17, it is determined whether or not the current calculated value is smaller than a value at which the merging is interrupted, for example, zero.
3).

If the current calculation value is less than the current value at which the merge is stopped at step A17, a value at which the merge is interrupted, for example, zero is set as the current value at step A18 and is output.
In addition, since the decrease of the merge degree has reached the limit, a decrease hold flag indicating this is set.

If it is determined in step A15 that the decrease holding flag is set, it is determined in step A19 whether or not the engine speed is smaller than a small set value S. The value is output as a current value (step A20). If less than S, step A1
The engine flag set in step 1 is cleared, and the decrease holding flag set in step A18 is also cleared.

If it is determined in step A13 in FIG. 10 that the engine speed is equal to or larger than the small value S, the engine speed tends to increase from S. Therefore, in steps A22 to A26 in FIG. Increase. First, in step A22, it is determined whether or not an increase holding flag, which will be described later, is set. If not, a constant value is added to the previous current value in step A23 to increase the degree of confluence from the previous time. Calculate the current value this time. Then, in step A24, it is determined whether the value I _max is greater than or not to fully open the current operation value is merged, and outputs a current value calculated if less electromagnetic proportional control valve 11C (Step A3 ).

If the calculated value exceeds the value required for full opening,
In step A25, a current value required for full opening is output. Further, since the increase of the merging degree has reached the limit, an increase holding flag indicating this is set. Step A2
If it is determined in step 2 that the increase holding flag has already been set, in step A26, the current value required for full opening is output, and the electromagnetic proportional control valve 11C is fully opened. The increase holding flag may be cleared when, for example, the engine speed becomes lower than S.

Next, calculation of lever output, that is, spool control and engine speed control will be described with reference to FIG. FIG.
As shown in FIG. 3, from the initialized state, the controller 10 first determines whether or not the lift is raised based on the potentiometer voltage of the work implement lever 9a (step B).
1). If the potentiometer voltage is negative, it is determined that the lever 9a is being operated on the lift lower side, and step B2 is performed.
In the same manner as in the prior art, the current value of the flow control signal S ₂ A required for the lift lowering-side control of the lift electromagnetic proportional control valve 11A is calculated based on the lever opening degree except for the dead zone based on the lever opening degree. regardless time, determines the current of the throttle lever operation electromagnetic proportional solenoid 27 to the idling equivalent value I _0, and outputs it (step B3).

If the potentiometer voltage is positive, it is determined that the lever 9a is being operated on the lift ascending side, and in the next step B4, it is determined whether or not the lever opening exceeds the dead zone. If it is a dead zone, in step B5, the current value flowing through the electromagnetic proportional control valve 11A is set to, for example, zero in order to cut off the supply flow rate to the lift cylinder 1 and keep the flow rate stationary.
Further, the current value flowing through the electromagnetic proportional solenoid 27 to keep the engine 24 idling is determined as I _0, and each is output (step B3).

If the lever opening exceeds the dead zone on the lift ascending side, it is determined in step B6 whether or not the lever opening exceeds the intermediate opening.
Calculates the value of the current flowing through the electromagnetic proportional control valve 11A according to the relationship shown in FIG. 5 and gives the calculated value to the electromagnetic proportional control valve 11A as an output corresponding to the work implement lever 9a. Further, in this case, the current value of the electromagnetic proportional solenoid 27 for throttle operation is set to a value I ₀ corresponding to idling, and the solenoid 27
(Step B3).

[0047] If the lever turning degree is more than half open, it is determined first whether the load in step B8 is larger than the small set value W _L, equal to or less than W _L, FIG step B9 6
In step B10, the value of the current flowing through the solenoid 27 is calculated in accordance with the degree of opening of the lever, and the calculated value is used as the engine output (step B10). (Step B3).

[0048] If the load is greater than W _L, further load is determined whether or not the higher value W or _H is greater than in step B11, if less W _H, the path a shown in step B12 in FIG. 6, A current value flowing through the electromagnetic proportional solenoid 27 is calculated corresponding to the lever opening degree in relation to b, and the calculated current value is passed through the solenoid 27 (step B3) in order to use the calculated value as an engine output (step B10). .

[0049] If the load in between the load is W _L and W _H,
In step B13, the value of the current flowing through the electromagnetic proportional solenoid 27 is calculated in accordance with the lever opening in relation to the paths a, e, and d shown in FIG. 6, and the calculated value is used as the engine output (step B10). Then, the calculated current value is supplied to the solenoid 27 (step B3).

Although the gear pumps 22A and 22B are used as hydraulic pumps in the embodiment described above, other types of pumps may be used. Although two hydraulic pumps are connected in tandem, the same control can be performed by simply expanding the embodiment even if three or more hydraulic pumps are connected. Further, not only the supply flow rate control on the lift rising side of the lift cylinder 1 but also the same control can be performed on the lift lowering side.
Can be similarly controlled.

[0051]

According to the present invention, the hydraulic pump is provided in tandem, the load detection sensor, the engine speed detection sensor, the merge solenoid valve, and the throttle operation actuator are used to open the working machine lever. Control of the hydraulic pump and engine speed control based on the load state and engine speed at that time, so that noise reduction and fuel economy of the engine can be achieved, and operator It is extremely easy with only the lever and the work efficiency is greatly improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a hydraulic circuit according to one embodiment of the present invention.

FIG. 2 is a diagram showing an electric control system of FIG. 1;

FIG. 3 is a diagram illustrating a correspondence relationship between an opening degree of a working machine lever and control.

FIG. 4 is a diagram showing a relationship between a lever opening and a potentiometer voltage.

FIG. 5 is a diagram showing a relationship between a potentiometer voltage and a current of an electromagnetic proportional control valve for lift.

FIG. 6 is a diagram showing a relationship between a potentiometer voltage and an electromagnetic proportional solenoid for throttle operation.

FIG. 7 is a diagram showing a relationship between an engine speed and a lift increasing supply flow rate.

FIG. 8 is a diagram showing a relationship between a lever opening and a lift ascending supply flow rate.

FIG. 9 is a diagram showing a flow of a merge pump control.

FIG. 10 is a diagram showing a flow of a merge pump control.

FIG. 11 is a diagram showing a flow of a merge pump control.

FIG. 12 is a diagram showing a flow of a merge pump control.

FIG. 13 is a diagram showing a flow of lever output and engine speed control.

FIG. 14 is a perspective view showing a forklift to which the embodiment of the present invention is applied.

FIG. 15 is a diagram showing the whole of a conventional control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lift cylinder 8 Tilt cylinder 9a Lifting work implement lever 9b Tilt work implement lever 10 Controller 11A Lifting electromagnetic proportional control valve 11B Tilting electromagnetic proportional control valve 11C Merging electromagnetic proportional control valve 17 Oil pressure sensor 22A, 22B Gear pump 23 Tank 24 engine 25 engine rotation sensor 26 throttle lever 27 electromagnetic proportional solenoid for throttle operation

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Toshiyuki Midorikawa 3000 Tana, Sagamihara-shi, Kanagawa M.H.I.Sagami High-Tech Co., Ltd. (56) References JP-A-56-113700 (JP, A) Hei 2-221643 (JP, A) Full-scale sho 61-44497 (JP, U)

Claims (1)

(57) [Claims] 1. Two hydraulic pumps connected to an engine of a forklift, and a merge solenoid valve connected to the discharge side of the two hydraulic pumps to merge the output of one hydraulic pump with the other hydraulic pump. A cylinder solenoid valve connected between the merge solenoid valve and the working machine cylinder, an actuator for operating an engine throttle lever,
A sensor that detects the number of revolutions of the engine, a sensor that detects the load on the working machine cylinder, and a fixed opening such as a fully opened cylinder solenoid valve when the opening of the working machine lever is greater than or equal to a predetermined intermediate opening. A spool control unit that changes the opening of the solenoid valve for the cylinder from fully closed to a fixed opening in accordance with the opening of the work equipment lever when the opening is maintained at an opening below the intermediate opening, and the opening of the work equipment lever Is smaller than the middle opening, keeps the actuator at a fixed position equivalent to idle rotation.If it is larger than the middle opening, the engine speed control unit operates the actuator according to the opening of the work implement lever and the load on the work implement cylinder. If the load on the working machine cylinder is less than a predetermined small value, the merging solenoid valve is kept at a certain large opening such as full open, and if it is more than a predetermined large value, the merging solenoid valve is fully closed and so on. Small opening In the case where the value is between the small value and the large value, there is provided a controller including a joining pump control unit that changes the joining solenoid valve between the fixed large opening and the fixed small opening according to the engine speed. Work machine cylinder supply flow control device for forklift