JPH04303393A - Supply flow control device for working machine cylinder for forklift - Google Patents

Abstract

PURPOSE:To reduce engine noise and to enhance the working efficiency during elevation of a fork lift or the like. CONSTITUTION:Hydraulic pumps 22A, 22B are coupled tandem, and a solenoid valve 11A for a cylinder 1 is controlled in accordance with a manipulation machine lever 9a while a pump flow merging solenoid valve 11C is controlled in accordance with a load condition detected by a sensor 17, and an engine rotational speed detected by a sensor 25. Further, a throttle operating actuator 27 is controlled in accordance with a degree of manipulation of the lever 9a and a load condition.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to work machine cylinders such as forklift lift cylinders and tilt cylinders.
The present invention relates to a device that controls the 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. 14 and 15. 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 masts 2 as a guide as the piston rod 1a expands and contracts. It is supposed to be done. At this time,
The outer mast 2 is fixed to the vehicle body 7 at the front of the vehicle body 7. As a result, as the inner mast 3 moves up and down, an elevating section consisting of a bracket 5 suspended from a chain (not shown) and a fork 4 for directly loading cargo moves up and down. That is, the chain is suspended from a chain wheel (not shown) rotatably supported by the inner mast 3, and has one end attached to the bracket 5 and the other end attached to the outer mast 2.
are fixed respectively.

[0003] Thus, the fork 4 and the bracket 5, which are elevating parts, not only rise as the inner mast 3 rises, but also rise in relative position with respect to the inner mast 3 as the chain wheel rises with respect to the outer mast 2. do. That is, the amount of rise of the elevating section relative to the ground surface is the sum of the relative rise of the elevating section with respect to the inner mast 3 defined by the length of the chain to the amount of rise of the inner mast 3. Regarding the lowering of the elevating section, the same relationship as when ascending is established, only that the direction of movement is reversed.

Hydraulic cylinder 8 called tilt cylinder
is for tilting the elevating section together with the outer mast 2 and the inner mast 3 forward (towards the side opposite to the vehicle body 7) and backward (towards the vehicle body 7). That is, it tilts forward when unloading, and tilts backward when loading and transporting cargo, thereby maintaining good workability and ensuring safety.

The work equipment levers 9a and 9b are operated 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 are used to perform an emergency stop. It is housed in a joystick box 13 along with a safety switch 12 for use. Work machine levers 9c, 9d, 9
e is for the case where various attachments such as roll clamps, bail clamps, etc. are attached. The seat switch 14 is a switch that operates when an operator sits on the driver's seat 15, and its output signal is sent to the controller 10.

As shown in FIG. 15, the work machine lever 9a,
9b is formed by a potentiometer, and transmits a lever operation signal S1 whose voltage value is proportional to the amount of operation to the controller 1.
Send to 0. The controller 10 is mainly composed of a microprocessor (CPU), and receives a lever operation signal S.
Flow rate control signal (current signal) S2 that adjusts the opening degree of the spool of the electromagnetic proportional control valve 11 (spool control) based on 1
Send out. The electromagnetic proportional control valve 11 receives the flow rate control signal S2
By moving the spool in proportion to the current value, the flow rate of the pressure oil flowing through the hydraulic pipe 16 is controlled, and the operating speed of the lift cylinder 1 and tilt cylinder 8 is adjusted to the operation amount of the work equipment levers 9a and 9b. Control accordingly.

The hydraulic pressure sensor 17 is disposed in the hydraulic line 16 and sends out a hydraulic signal S3 representing the pressure of the pressure oil in the hydraulic line 16. Controller 10 receives oil pressure signal S3
is processed to calculate the load acting on the lift cylinder 1 or the tilt cylinder 8.

Furthermore, the controller 10 includes a warning light 18.
When the starter switch 20 housed in the console box 19 is turned on, power is supplied from the battery 21 to operate, and when the safety switch 12 is operated or the seat switch 14 is not operated, the current value of the flow rate control signal S2 is zero. As electromagnetic proportional control valve 11
The opening degree of the valve is controlled to be zero.

In FIG. 15, 22 is a gear pump, and 23 is a hydraulic oil tank. Further, hydraulic components such as the electromagnetic proportional control valve 11, the hydraulic conduit 16, and the hydraulic pressure sensor 17 are provided in a number corresponding to the number of work machine levers 9a to 9e. This embodiment has two working machine levers 9a and 9b for lifting and tilting to perform lift and tilting operations, so two hydraulic systems are provided.

0010

SUMMARY OF THE INVENTION As mentioned above, in forklift trucks, gear pumps are used as working machine pumps for supplying pressure oil. This is extremely inexpensive compared to variable flow pumps.

[0011] However, the capacity of the gear pump is fixed at 90 to 95% of the idle output horsepower of the forklift engine, and when the engine speed increases, the horsepower absorbed is only 60 to 70% of the engine output, and the rest is wasted. This becomes the output.

Therefore, if the load on the lift cylinder or tilt cylinder is low, for example, if the flow rate is increased in an attempt to obtain the maximum lift rising speed, the engine speed will increase, noise will increase, and the output will be wasted. This results in poor fuel efficiency.

An object of the present invention is to provide a forklift working machine cylinder supply flow rate control device that solves the problems of the prior art described above.

[0014]

[Means for Solving the Problems] The structure of the forklift work machine cylinder supply flow rate control device according to the present invention includes two hydraulic pumps connected to the engine of the forklift, and a connection to the discharge side of these two hydraulic pumps. A merging solenoid valve that merges the output of one hydraulic pump with the other hydraulic pump, a cylinder solenoid valve connected between the merging solenoid valve and the work equipment cylinder, and an actuator that operates the engine throttle lever. , a sensor that detects the engine rotation speed, a sensor that detects the load on the work equipment cylinder, and a sensor that fully opens the solenoid valve for the cylinder when the work equipment lever opening is more than a predetermined intermediate opening. The spool control unit maintains a constant opening of the cylinder, and changes the opening of the cylinder solenoid valve from fully closed to a constant opening according to the opening of the work equipment lever when the opening is below the intermediate opening. When the opening is below the intermediate opening, the actuator is kept at a constant position equivalent to idle rotation, and when the opening is above the intermediate opening, the engine rotation speed is used to operate the actuator according to the opening of the work equipment lever and the load on the work equipment cylinder. If the load on the control unit and work equipment cylinder is less than a predetermined small value, the merging solenoid valve is kept at a certain large opening such as fully open, and if it is greater than a predetermined large value, the merging solenoid valve is fully closed. a merging pump control unit that maintains the merging solenoid valve at a constant small opening degree and changes the merging solenoid valve between the constant large opening degree and the constant small opening degree depending on the engine rotation speed when the opening degree is between the small value and the large value; It is characterized by comprising a controller consisting of:

[0015]

[Operation] When the work equipment lever is below a certain intermediate opening, the engine remains almost idling, and the opening of the cylinder solenoid valve increases in accordance with the increase in the lever opening, reducing the supply to the work equipment cylinder. Flow rate increases. Therefore, the noise is low.
It also has good fuel efficiency. However, if the load on the work equipment cylinder is large, the output from one hydraulic pump should be released instead of merging to prevent the engine from stalling. Furthermore, when the work equipment lever is at a certain intermediate opening or higher, the cylinder solenoid valve is fully open, but as the lever opening increases, the engine speed increases and the flow rate supplied to the work equipment cylinder increases. . In this case, the engine speed is changed according to the size of the load to ensure the necessary flow rate, and the degree of merging of the outputs of one hydraulic pump is changed depending on the engine speed and the size of the load. Therefore, noise is low, fuel efficiency is good, and engine stall does not occur.

Furthermore, the supply flow rate can be easily adjusted simply by operating the working machine lever, improving work efficiency.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 13.

FIG. 1 shows a hydraulic circuit, and FIG. 2 shows an electric control system thereof. In Figure 1, two gear pumps 2
Forklift engine 2 with 2A and 22B in tandem
It is connected to 4. For convenience, one gear pump 22A is used as the main pump, and No. Also referred to as 1 pump. In addition, the other gear pump 22B is used as a sub-pump, and No.
Also referred to as 2 pumps.

The discharge sides of the main pump 22A and the sub-pump 22B are connected to a two-position electromagnetic proportional control valve 11C, and the controller 10 determines whether or not the outputs of both pumps are to be combined, and if they are to be combined, the combined flow rate of the sub-pump outputs. The flow rate control signal S2C is used to control the flow rate. Pressure oil is supplied from this electromagnetic proportional control valve 11C to the lift cylinder 1 via the 3-position electromagnetic proportional control valve 11A, and pressure oil is supplied to the tilt cylinder 8 via the 3-position electromagnetic proportional control valve 11B. The controller 10 is arranged so as to supply
The supply flow rate is controlled by the flow rate control signals S2A and S2B from the above.

In the state shown in FIG. 1, each flow rate control signal S
The current values of 2 A, S2 B, and S2 C are zero, and the merging electromagnetic proportional control valve 11C does not combine the outputs of both pumps, and only the output of the main pump 22A is connected to the two cylinder electromagnetic proportional control valves 11A, 11B. Sub pump 22B
The output is returned to the tank 23. In addition, the two cylinder electromagnetic proportional control valves 11A and 11B close the hydraulic circuits of the corresponding cylinders 1 and 8, and the merging electromagnetic proportional control valve 11C
Pressure oil from the tank is returned to the tank 23.

The controller 10 includes work machine levers 9a, 9b for lift and tilt, a hydraulic sensor 17, and
Engine rotation sensor 2 that detects the rotation speed of the engine 24
5 are connected, and from these the lever operation signal S1 A
, S1 B, oil pressure signal S3, engine speed signal S4
Enter. The controller 10 also includes the three
In addition to connecting the three electromagnetic proportional control valves 11A, 11B, and 11C and outputting flow control signals S2 A, S2 B, and S2 C to these, an electromagnetic proportional solenoid 27 is connected to the throttle lever 26 of the engine 24 to operate it. is connected, and a throttle opening control signal (current signal) S5 is output to this solenoid.

As shown in FIG. 2, the controller 10 is mainly composed of a central processing unit (CPU) 28, and mainly stores software in a ROM 29 and a RAM 30.
Store data in . Since the work equipment levers 9a and 9b are potentiometers, the A/D converter 31 converts each potentiometer voltage, which is the lever operation signal S1A, S1B, into a digital signal and sends it to the controller CPU2.
Give to 8. Further, the input interface 32 receives the oil pressure signal S3 from the oil pressure sensor 17 and the engine rotation sensor 25.
The engine rotational speed signal S4 is converted for use by the CPU and is provided to the CPU 28. The solenoid valve drive circuit 33 is the CPU 28
A current corresponding to the calculation result of is applied to each electromagnetic proportional control valve 11A.
, 11B, 11C have flow rate control signals S2 A, S2 B
, S2C, and is applied to the electromagnetic proportional solenoid 27 as a slot opening degree control signal S5. 34 is CPU28
The clock circuit 35 is an internal power supply circuit that stabilizes the voltage of the battery 21 by lowering it to a predetermined value.

Next, details of the controller 10 will be explained with reference to FIGS. 3 to 13. The controller 10 uses software to perform spool control for adjusting the spool openings of the electromagnetic proportional control valves 11A and 11B, engine rotation speed control for adjusting the rotation speed of the engine 24, and merging of the sub-pump 22B by the electromagnetic proportional control valve 11C. Each functional unit is configured to control the merging pump. These control functions include the amount of operation of the work equipment levers 9a and 9b, that is, the opening degree, the load applied to the lift cylinder 1 obtained from the oil pressure sensor 17, that is, the magnitude of the load, and the engine speed obtained from the engine rotation sensor 25. It operates depending on the rotation speed.

In this embodiment, as shown in FIGS. 3 and 4,
Spool control is performed when the lever opening degree of the lift work equipment lever 9a is from the neutral position to the intermediate opening degree on the lift upward side, and when the lever opening degree is from this intermediate opening degree to the maximum opening degree on the lift upward side, the engine rotation speed is It is assumed that control will be carried out. However, when the lever opening is on the lift lowering side, the explanation will be made assuming that spool control is performed in all cases, as can be seen from FIG. Further, regarding the lever opening degree of the tilting working machine lever 9b, the description will be made assuming that spool control is performed in both the forward tilting side and the backward tilting side.

Since the lever opening degree and the potentiometer voltage of the work equipment lever are in a proportional relationship as shown in FIG. 4, as shown in FIG. voltage V corresponding to
m or more, lift electromagnetic proportional control valve 11A
The current value of the flow rate control signal S2 A is fixed at the maximum value Imax required to fully open the valve, and only when the value is less than Vm, the current value of the flow rate control signal S2 A is changed between zero and Imax in proportion to the potentiometer voltage. to perform spool control. However, since the potentiometer voltage near zero is near the neutral position of the work equipment lever, it is considered a dead zone for safety reasons, and the current value is set to zero.

In the above-mentioned spool control in which the work equipment lever 9a is at an intermediate opening on the lift upward side from the neutral position,
If the load detected by the oil pressure sensor 17 is larger than a predetermined small value WL, the merging electromagnetic proportional control valve 11C
The current value of the flow rate control signal S2C is set to zero, and the output oil of the sub pump 22B is returned to the tank 23, so that it does not merge. If the load is smaller than WL, the current value of the flow rate control signal S2C is set to the value required to fully open the electromagnetic proportional control valve 11C, and all of the output oil of the sub pump 22B is merged with the output oil of the main pump 22A. As a result of this merging pump control, the relationship between the lever opening degree in spool control and the lift upward supply flow rate to the lift cylinder 1 is shown in FIG.
The characteristics shown in (a) are obtained.

On the other hand, as shown in FIG. 6, when the potentiometer voltage of the lift working machine lever 9a is lower than the voltage Vm corresponding to the intermediate opening at the lift increase value, the throttle opening signal S5 to the electromagnetic proportional solenoid 27 is The current value is fixed at the value I0 corresponding to idling, and Vm
Only in cases above, potentiometer voltage (lever opening)
Accordingly, the current value is increased from I0 to increase the engine speed. However, the relationship between the potentiometer voltage and the current value varies depending on the load, and if the load is larger than a predetermined large value WH, the current value will be changed with a steep characteristic that follows paths a and b in Fig. 6. Increase or decrease between I0 and the maximum value Imax. In addition, if the load is smaller than the above-mentioned small value WL, route c in FIG.
, d, the current value is increased or decreased with a slow characteristic. In the case of a medium load between WL and WH, Figure 6
The current value is increased or decreased according to the characteristics of following paths a, e, and d. That is, when the potentiometer voltage is close to Vm, path a with a large load is followed, when it is close to the maximum value Vmax, a path d with a small load is followed, and in the middle, a path e is taken that transitions between both a and d. .

[0028] In the above-mentioned engine speed control in which the work equipment lever 9a is at an intermediate opening degree or more on the lift rising side,
The confluence pump control is performed as follows.

First, if the load is larger than the aforementioned large value WH, the current value of the flow rate control signal S2C to the merging electromagnetic proportional control valve 11C is set to zero, and the output oil of the sub pump 22B is transferred to the tank 23. Return it and do not let it merge. When the load is smaller than the above-mentioned small value, the current value of the flow rate control signal S2C is set to the value required for full opening, and all of the output oil of the sub pump 22B is merged with the output oil of the main pump 22A. In addition, in the case of a medium load between WL and WH, if the engine speed is lower than a certain value S that is higher than the idle speed, the current value of the flow rate control signal S2C is set to zero as in the case of a large load. If the current value is higher than a certain value M, which is larger than S, the current value is set to the value required for full opening and all are merged, and if it is between S and M, the current value is changed from zero to the value required for full opening according to the engine speed. Adjust the degree of confluence by increasing or decreasing between

By controlling the merging pump according to the engine speed and the load, the relationship between the engine speed and the lift supply flow rate to the lift cylinder 1 has the characteristics shown in FIG. That is, in the case of a large load, the lift rising supply flow rate increases or decreases according to the engine speed with a slow characteristic that follows paths a and b in FIG. 7, and in the case of a small load, it follows paths c and d in FIG. 7.
The lift supply flow rate increases or decreases depending on the engine speed due to the steep characteristic that follows this. In addition, in the case of medium load, if the rotation speed is less than or equal to S, the route a with a large load is followed, and if it is more than M, a route d with a small load is followed, and in the middle of S and M, both routes a. The lift upward supply flow rate increases or decreases following the path e that transitions between d and d.

As a result, by engine speed control and merging pump control, the relationship between the opening degree of the lifting work implement lever 9a above the intermediate opening degree and the lift supply flow rate to the lift cylinder 1 is as shown in FIG. The characteristics shown in b) are obtained. That is, in the case of a large load, the lift rising supply flow rate increases or decreases according to the lever opening with a slow characteristic that follows paths a and b in Fig. 8(b), and in the case of a small load, the flow rate increases or decreases as shown in Fig. 8(b). With the steep characteristics that follow the middle paths c and d, the lift upward supply flow rate increases or decreases depending on the lever opening degree. In addition, in the case of medium load, if the lever opening is close to the intermediate opening, follow path a at high load, and if it is close to the maximum opening, follow path d at small load, Then, the lift upward supply flow rate increases or decreases following the path e that transitions between both a and d. In addition, at the intermediate opening degree, Fig. 8 (
The lift upward supply flow rate by the spool control and the merging pump control in a) is set to match the lift upward supply flow rate by the engine rotation speed control and the merging pump control in FIG. 8(b).

Next, the software operations of the CPU 28 of the controller 10 will be collectively explained based on the flowcharts for controlling the merging pump shown in FIGS. 9 to 12 and the flowchart for controlling the lever output and engine speed shown in FIG.

First, the merging pump control will be explained with reference to FIGS. 9 to 12. As shown in FIG. 9, the controller 10
From the initialized state, first, press the work equipment lever 9a.
Based on the potentiometer voltage, it is determined whether the lift is to be increased (step A1). For example, if the potentiometer voltage is negative, it is determined that the lever 9a is operated on the lift lowering side, and in step A2, based on the lever opening degree as in the past, if it is outside the dead zone, the lift electromagnetic proportional control valve 1
Flow rate control signal S2 A required for 1A lift lowering side control
Also, the current value Imax of the merging electromagnetic proportional control valve 11C is determined and output so that the sub pump 22B is merging regardless of the load or the lever opening degree, for example, and this is output (step A3). Note that the current of the electromagnetic proportional solenoid 27 for throttle operation may be set to I0, and the engine may be left idling.

If the potentiometer voltage is positive, it is determined that the lever 9a is operated to the lift upward side, and in the next step A4, it is determined whether the lever opening exceeds the dead zone. If it is a dead zone, in step A5, the flow rate supplied to the lift cylinder 1 is cut off, and in order to keep it stationary, the current value flowing through the electromagnetic proportional control valve 11A is set to zero, for example.
Further, in order to cut off the merging of the sub pump 22B, the current value flowing through the electromagnetic proportional control valve 11C is set to zero, for example, and each is outputted (step A3). Further, in step A5, the load on the lift cylinder 1 is calculated based on the oil pressure signal S3 from the oil pressure sensor 17, and this value is stored.

If the lever opening exceeds the dead zone on the lift rising side, first, in step A6, the set value W where the load is large is set.
It is determined whether or not it exceeds WH, and if it is less than WH, the current value is set to a value that cuts off the merging, for example, zero (step A7).
, and outputs this to the merging proportional control valve 11C.

If the load is larger than WH, the process moves to step A8 shown in FIG. 10, and a small set value WL (WL <
WH). If it is smaller than WL, a current value for merging all the sub pumps 22B is determined in step A9, and this is output to the electromagnetic proportional control valve 11C (step A3) to fully open it.

If the load is a medium load between WH and WL, it is determined in step A10 whether the engine speed exceeds a large set value M, and if it exceeds M, the engine speed is determined in step A11. The engine flag is set, and the current value is set to the value that causes all the sub pumps 22B to merge in step A9.

If the engine speed is less than or equal to M, it is determined in step A12 whether the engine flag has already been set. If it is not set, it is determined whether the engine speed is lower than a small set value S (idle speed < S < M), and if it is lower than S, there is no need to control the degree of merging, so in step A14. The current value is set to a value that cuts off the merging, for example zero, and is applied to the electromagnetic proportional control valve 11C (step A3), thereby bypassing all of the output of the sub pump 22B to the tank 23.

If it is determined in step A12 that the engine flag is set, it means that the engine speed has been decreasing from M, so step A1 in FIG.
5 to A21, the degree of confluence is decreased. First step A
In step A15, it is determined whether a decrease holding flag, which will be described later, is set, and if it is not set, in step A16, the current value is calculated by subtracting a certain 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 that cuts off the merging, for example zero, and if it is greater than or equal to the value that cuts off the merging, a current of that value is caused to flow through the electromagnetic proportional control valve 11C (step A
3).

If in step A17 the current calculated value is less than the current value for cutting off the merging, then in step A18 a value for cutting off the merging, for example zero, is set as the current current value and this is output. Furthermore, since the degree of confluence has reached its limit, a decrease holding flag is set to indicate this.

If it is determined in step A15 that the reduction hold flag is set, it is determined in step A19 whether the engine speed is smaller than a small set value S, and if it is above S, the merging is cut off. The value is output as a current value (step A20). If it is less than S, step A1
The engine flag set in step A1 is cleared, and the reduction hold flag set in step A18 is also cleared.

If it is determined in step A13 of FIG. 10 that the engine speed is equal to or higher than the small value S, since the engine speed has tended to increase from S, the degree of merging is determined in steps A22 to A26 of FIG. increase. First, in step A22, it is determined whether an increase holding flag, which will be described later, is set. If not, in step A23, a constant value is added to the previous current value in order to increase the degree of merging from the previous time. Calculate the current current value. Then, in step A24, it is determined whether the current calculated value is larger than the value Imax for fully opening the merging, and if it is less than that, the calculated current value is output to the electromagnetic proportional control valve 11C (step A3). .

[0043] If the calculated value exceeds the value required for full opening,
In step A25, the current value required for full opening is output. Furthermore, since the increase in the degree of merging has reached its limit, an increase retention flag indicating this fact is set. Step A2
If it is determined in step A26 that the increase hold flag has already been set, the current value required for full opening is outputted, and the electromagnetic proportional control valve 11C is fully opened. Note that the increase retention flag may be cleared, for example, when the engine speed becomes less than S.

Next, lever output calculation, ie, spool control and engine speed control will be explained with reference to FIG. Figure 1
3, from the initialized state, the controller 10 first determines whether or not the lift is to be 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 operated on the lift lowering side, and step B2
As in the conventional case, the current value of the flow rate control signal S2A required for the lift lowering side control of the lift electromagnetic proportional control valve 11A is calculated if it is outside the dead zone based on the lever opening degree, and,
For example, regardless of the load or lever opening, the current of the electromagnetic proportional solenoid 27 for throttle lever operation is set to a value I0 corresponding to idling, and this is output (step B3).
.

If the potentiometer voltage is positive, it is determined that the lever 9a is being operated to the lift upward direction, and in the next step B4 it is determined whether the lever opening exceeds the dead zone. If it is a dead zone, in step B5, the flow rate supplied to the lift cylinder 1 is cut off, and in order to keep it stationary, the current value flowing through the electromagnetic proportional control valve 11A is set to zero, for example.
Further, in order to keep the engine 24 idling, the current value to be passed through the electromagnetic proportional solenoid 27 is determined as I0, and each value is outputted (step B3).

If the lever opening exceeds the dead zone on the lift rising side, it is determined in the next step B6 whether or not it exceeds the intermediate opening, and if it is below the intermediate opening, step B7
The current value to be passed through the electromagnetic proportional control valve 11A is calculated based on the relationship shown in FIG. 5, and this is applied to the electromagnetic proportional control valve 11A as an output corresponding to the work implement lever 9a. In this case, the current value of the electromagnetic proportional solenoid 27 for throttle operation is set to a value I0 corresponding to idling, and the solenoid 2
7 (step B3).

If the lever opening is equal to or greater than the intermediate opening, it is first determined in step B8 whether the load is greater than a small set value WL, and if it is less than WL, the path is changed to the route shown in FIG. 6 in step B9. The current value to be passed through the electromagnetic proportional solenoid 27 is calculated in accordance with the lever opening degree based on the relationship between c and d, and in order to use this calculated value as the engine output (Step B10), the calculated current value is passed through the solenoid 27 (Step B10). B3)
.

If the load is greater than WL, it is further determined in step B11 whether the load is greater than a large set value WH, and if it is less than WH, the relationship between routes a and b shown in FIG. 6 is determined in step B12. The current value to be passed through the electromagnetic proportional solenoid 27 is calculated in accordance with the lever opening degree, and in order to use this calculated value as the engine output (step B10), the calculated current value is caused to flow through the solenoid 27 (step B3).

If the load is a medium load between WL and WH, in step B13, the current value to be applied to the electromagnetic proportional solenoid 27 in accordance with the lever opening degree is determined according to the relationship between paths a, e, and d shown in FIG. is calculated, and in order to use this calculated value as the engine output (step B10), the calculated current value is caused to flow through the solenoid 27 (step B3).

In the embodiment described above, gear pumps 22A and 22B are used as hydraulic pumps, but other types of pumps may be used. Furthermore, although two hydraulic pumps are connected in tandem, even if three or more hydraulic pumps are connected, the same control can be performed by simply extending the embodiment. Furthermore, the supply flow rate can be controlled not only on the lift ascending side of the lift cylinder 1, but also on the lift descending side.
The supply flow rate control can also be performed in the same way.

[0051]

According to the present invention, hydraulic pumps are provided in tandem, and a load detection sensor, an engine rotation speed detection sensor, a merging solenoid valve, and a throttle operation actuator are used to control the opening of the work equipment lever. Since hydraulic pump merging control and engine speed control are performed based on the load condition and engine speed at that time, it is possible to achieve low engine noise and fuel efficiency, and furthermore, the operator's operations can be controlled by the work equipment. It is extremely easy to use with just a lever, and work efficiency is greatly improved.

[Brief explanation of drawings]

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

FIG. 2 is a diagram showing the electrical control system of FIG. 1.

FIG. 3 is a diagram showing the correspondence between the opening degree of the work equipment lever and control.

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

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

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

FIG. 7 is a diagram showing the relationship between engine rotational speed and lift rising supply flow rate.

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

FIG. 9 is a diagram showing the flow of control of the combined pump.

FIG. 10 is a diagram showing the flow of control of the confluence pump.

FIG. 11 is a diagram showing the flow of control of the confluence pump.

FIG. 12 is a diagram showing the flow of control of the confluence pump.

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

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

FIG. 15 is a diagram showing the entire conventional control device.

[Explanation of symbols]

1 Lift cylinder 8 Tilt cylinder 9a Lift work machine lever 9b Tilt work equipment lever 10 Controller 11A Solenoid proportional control valve for lift 11B Solenoid proportional control valve for tilt 11C Solenoid proportional control valve for merging 17 Oil pressure sensor 22A, 22B gear pump 23 Tank 24 Engine 25 Engine rotation sensor 26 Throttle lever

Claims (1)

[Claims] Claim 1: Two hydraulic pumps connected to the engine of a forklift, and a solenoid valve for merging that is connected to the discharge sides of these two hydraulic pumps and that merges the output of one hydraulic pump with the other hydraulic pump. , a cylinder solenoid valve connected between this merging solenoid valve and the work equipment cylinder, an actuator that operates the engine throttle lever, a sensor that detects the engine rotation speed, and a sensor that detects the load on the work equipment cylinder. When the opening of the sensor and the work equipment lever is above a predetermined intermediate opening, the cylinder solenoid valve is kept at a constant opening such as fully open, and when it is below the intermediate opening, the opening of the work equipment lever is maintained. The spool control unit changes the opening of the cylinder solenoid valve from fully closed to a constant opening according to the operating conditions, and when the work equipment lever opening is below the intermediate opening, the actuator is kept at a constant position equivalent to idle rotation. , when the opening is above the intermediate opening, the engine rotation speed control section operates the actuator according to the opening of the work equipment lever and the load on the work equipment cylinder, and when the load on the work equipment cylinder is less than a predetermined small value, it is used for merging. Keep the solenoid valve at a certain large opening such as fully open,
If it is above a predetermined large value, the merging solenoid valve is kept at a certain small opening such as fully closed, and if it is between the small value and the large value, the merging solenoid valve is kept at a certain opening according to the engine speed. A forklift work machine cylinder supply flow rate control device comprising: a controller consisting of a merging pump control unit that changes between a constant large opening degree and a constant small opening degree.