JPH0382675A - Operating oil flow control device for industrial vehicle - Google Patents

Abstract

PURPOSE:To reduce the excess operating oil flowing in a hydraulic circuit and reduce flow loss and pressure loss by detecting the action quantities of loading levers, and increasing the discharge flow of a hydraulic pump by the flow required for a loading operation. CONSTITUTION:The hydraulic circuit of a fork-lift has an oil tank 3, a hydraulic pump 20 driven by an engine 1, a lift cylinder 7 connected to a control valve 4, and a tilt cylinder 8. The hydraulic pump 20 is a variable-displacement type, and the discharge quantity is changed by a displacement changing mechanism 22. Loading levers 5 and 6 for lifting and tilting are connected to the control valve 4, and their action quantities can be detected by potentiometers 23 and 24. The displacement changing mechanism 22 is controlled by a controller 30 so that the discharge flow of the hydraulic pump 20 is increased by the quantity required for a loading operation in response to detected values of action quantities of levers.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a hydraulic circuit used in industrial vehicles such as forklifts and shovel loaders, and in particular to a device for controlling the flow rate of hydraulic fluid discharged from a hydraulic pump. It is related to.

[Prior Art] In a conventional general hydraulic circuit for a forklift, for example, as shown in FIG.
The hydraulic oil in the oil tank 3 is force-fed to the control valve 4, and the cargo handling lever 5 of the control valve 4 is driven.
．． By tilting the cylinder 6, a required amount of hydraulic oil is supplied to and discharged from the lift cylinder 7 or the tilt cylinder 8. In addition, a fixed-rate flow divider (not shown) is provided in the control valve 4, and the outflow [(one rule is that the brake booster 9, clutch booster 10, power steering gear box 11, etc.) is connected.

[Problems to be Solved by the Invention] Conventionally, since the hydraulic pump 2 is of a fixed capacity type, the discharge flow rate Q0 of the hydraulic pump 2 is always constant if the rotation speed of the engine 1 is constant. The flow rate Q supplied to the circuit 12 is also constant regardless of the presence or absence of a cargo handling operation, since the flow divider in the control valve 4 is of a fixed quantity type. Further, the discharge flow rate Q0 of the hydraulic pump 2 is the maximum value Q2+a of the flow rate Q1 to the travel control system circuit 12 and the flow rate Q2L%Q2T supplied to the lift cylinder 7 or tilt cylinder 8 when cargo handling operation is performed.
mx. Therefore, the 140th
As schematically shown in , the amount of movement of the cargo handling lever 5.6 is small, and the amount of hydraulic oil required for cargo handling operation Q2L, Q2?
If the amount of oil is low, the hydraulic oil that was not used for cargo handling operations is drained from the control valve 4 to the drain pipe 13 as a surplus.
It will be returned to the oil tank 3 via the. Particularly when no cargo handling operation is performed, all of the Q2mam is returned to the oil tank 3 as a surplus. Energy loss due to the flow of this excess hydraulic oil causes a rise in oil temperature, resulting in a problem of wasted fuel.

Therefore, a first object of the present invention is to provide a hydraulic oil flow rate control device that controls the flow rate of hydraulic oil discharged from a hydraulic pump as necessary, in order to solve the above technical problem.

Furthermore, when carrying out cargo handling operations with the vehicle stopped, conventionally it was necessary to press the accelerator pedal to increase the engine speed, which was troublesome.

Therefore, a second object of the present invention is to provide a hydraulic oil flow rate control device that allows cargo handling operations to be performed even when the accelerator pedal is not depressed.

Means for Solving the Problem] In order to achieve the first object, the hydraulic oil flow rate control device for an industrial vehicle according to the present invention includes a variable displacement hydraulic pump, in a cargo handling hydraulic circuit of an industrial vehicle, A lever movement amount detector detects the movement amount of a cargo handling lever, and a discharge flow rate of hydraulic oil from the hydraulic pump is increased by an amount necessary for cargo handling operation in response to a signal from the lever movement amount detector. It is characterized by comprising a controller that outputs a signal that changes the discharge amount per rotation of the hydraulic pump, and a discharge amount variable means that changes the discharge amount based on the signal from the controller.

Hereinafter, this invention will be referred to as the first invention.

Further, in order to achieve the second object, a second invention provides a hydraulic oil flow rate control device according to the first invention, comprising:
an engine that drives a hydraulic pump, a transmission that converts the output of the engine into driving power for the vehicle, and a throttle actuator that adjusts the amount of fuel supplied to the engine;
an engine rotational speed detector that detects the rotational speed of the engine; a clutch disengagement detector that detects clutch disengagement; or a neutral detector that detects that the transmission is in neutral; and the clutch disengagement detector or the neutral. When it is determined that the clutch is disengaged or the transmission is in neutral and the cargo handling lever is tilted based on the output signal from the detector and the output signal from the lever operation amount detector, and a controller that outputs a signal of the operation amount of the throttle actuator so as to increase the rotation speed of the engine to a predetermined value in response to signals from the engine rotation speed detector and the lever operation amount detector. There is.

According to the first invention, the flow rate required for the hydraulic circuit can be determined from the operation amount of the cargo handling lever, and the variable displacement hydraulic pump can be controlled to achieve the determined flow rate. Therefore, unnecessary hydraulic fluid flowing through the hydraulic circuit is reduced.

Further, according to the second invention, when performing a cargo handling operation when the vehicle is stopped, the vehicle stop state is determined by detecting that the clutch is engaged or the transmission is in neutral, and the engine rotation speed is automatically adjusted. , making it unnecessary to press the accelerator pedal.

[Embodiments] Preferred embodiments according to the first and second inventions will be described in detail below with reference to the drawings, in which the same reference numerals are used for the same or corresponding parts.

FIG. 1 shows a hydraulic circuit of a forklift to which a first embodiment of the first invention is applied, and is connected to an oil tank 3, a hydraulic pump 20 driven by an engine 1, and a discharge port of the hydraulic pump 2. The control valve 4 includes a control valve 4, and a lift cylinder 7 and a tilt cylinder 8 connected to the control valve 4. Further, a travel control system circuit 12 consisting of a brake booster 9, a clutch booster 10, and a power steering gear box 11 is connected to an outlet of a quantitative flow divider (not shown) in the control valve 4.

The above configuration is almost the same as the conventional configuration described earlier, but
In the present invention, the hydraulic pump 20 is of a variable displacement type.

- In this embodiment, a swash plate type radial piston pump is used as the variable displacement hydraulic pump 20, and the swash plate 2
By adjusting the angle of 1 with the variable capacity machine l'122, the discharge amount per rotation can be changed.

Lift and tilt cargo handling levers 5.6 are connected to the control valve 4, and by tilting these levers, the required amount of hydraulic oil can be supplied and discharged to and from the lift cylinder 7 and tilt cylinder 8. It has become.

Each cargo handling lever 5.6 is provided with a potentiometer 23.24 as a lever movement amount detector for detecting its movement amount. These potentiometers 23.24
For example, as shown in FIG. 2, the potentiometer 2 is attached to the frame 25 near the control valve 4.
3 is fixed, and the lever 28 is welded to the rod 27 between the cargo handling lever 5 and the spool 26 of the control valve 4.
It is conceivable to connect this lever 28 and the movable shaft 29 of the potentiometer 23. In this case, when the cargo handling lever 5 is tilted, the movement is caused by the movement of the rod 27 and the lever 28.
The signal is transmitted to the movable shaft 29 via the potentiometer 23, and a signal corresponding to the amount of movement is emitted from the potentiometer 23.

Each potentiometer 23 , 24 is connected to an input of a controller (eg microcomputer) 30 . Further, the output part of the controller 30 is connected to the variable capacity mechanism '1lI22 of the hydraulic pump 20, and the variable capacity mechanism 22 is connected to the variable capacity mechanism '11I22 of the hydraulic pump 20.
The angle of the swash plate 21 is adjusted by outputting a control signal to the swash plate 21.

FIG. 3 shows the control logic of the controller 30. As shown in 54, in the controller 30,
A zero-order system receives a signal corresponding to the amount of movement of the cargo handling lever 5.6 from each potentiometer 23.24, and calculates the discharge amount q2L and Qzt per rotation required for the lift cylinder 7 and tilt cylinder 8 from the signal, respectively. , these discharge amounts Q2L, Q2? The larger one is selected as the true discharge amount q2 required for cargo handling work. Furthermore, add the discharge amount q per revolution corresponding to the required flow tQ to the travel control system circuit 12 to this discharge fir, q 2,
The discharge amount q per revolution required for the entire hydraulic circuit is determined, and the corresponding control signal V is sent to the variable capacity mechanism 2.
Output to 2. As a result, the inclination angle of the swash plate 21 of the hydraulic pump 20 is adjusted, and the rotation speed of the engine 1 is adjusted to the reference rotation speed n.
6, the discharge flow rate Q0 from the hydraulic pump 20 becomes the flow rate Q required for cargo handling. In addition, in this example,
It is assumed that the engine 1 is operated at a reference rotation speed n0.

When cargo handling operation is not performed, the cargo handling flow rate Q is zero, so the flow rate Q required for the hydraulic circuit is the traveling control system circuit 12.
There is only a flow rate Q1 to. Therefore, under the control of the controller 30, the pump discharge flow Jl:Q is set to Ql.

When the hydraulic pump 20 is controlled in this manner, as schematically shown in FIG.
Since Q increases, almost no surplus hydraulic oil is generated in the hydraulic circuit, and the amount of hydraulic oil returned from the control valve 4 through the drain pipe 13 becomes minute.

Note that the volume of the hydraulic oil changes depending on the oil temperature and pressure, so for example, an oil temperature gauge 31 is placed in the oil tank 3, and a pressure gauge 32 is provided in the pipe line 14 on the discharge side of the hydraulic pump 2. Input the detected value of - to the controller 30, and -
In measuring the discharge amount q per rotation, a more accurate flow rate can be supplied by, for example, making a correction as shown in the following equation.

q=q/(α×β) v = func(q') In the formula, q: Required discharge amount q': Required discharge amount after correction α: Temperature correction coefficient β: Pressure correction coefficient fine (q'): Control signal Conversion calculation to V In the above embodiment, the rotation speed of the engine 1 is determined in advance, and the discharge amount q per rotation is calculated based on that value. However, if the rotation speed of the engine 1 is the reference rotation speed n0
If this is not set, excess or deficiency will occur in the pump discharge amount.Therefore, in the second embodiment belonging to the first aspect of the present invention, as shown in FIG. Attach the controller 42 to the engine l, and connect the controller 30
In this case, the discharge 1q per rotation of the hydraulic pump may be determined from the engine rotation speed and lever operation amount during cargo handling operation.The bottom of the tank shown in FIG. Since the configuration is the same as that of the first embodiment, only the control logic of the controller 30 and its operation will be explained.

FIG. 6 shows the control logic of the controller 30. As shown in FIG.
A signal corresponding to the amount of movement of the load handling lever 5.6 is received from each potentiometer 23.24, and based on the signal, the flow rate Q, L, . . . required for the lift cylinder 7 and tilt cylinder 8 is
0th order to calculate Qo respectively, these flow rates Q2L,
Compare the size of Qt・ and select the larger one to determine the true flow rate Q required for cargo handling work.

shall be. Furthermore, the required flow rate Q+ for the traveling control system circuit 12 is added to this flow rate Q2 to determine the flow rate Q required for the entire hydraulic circuit. On the other hand, the controller 30 receives a signal from a rotation speed detector 42 that detects the rotation speed of the engine 1, and divides the flow rate Q by the rotation speed n of the engine 1, thereby increasing the discharge per rotation of the hydraulic pump 2o. The discharge amount q is determined, and the control signal V corresponding to the discharge amount q is sent to the variable capacity mechanism 2.
Output to 2.

In this way, when the hydraulic pump 20 is rismed,
Even when the engine rotational speed n is not the reference rotational speed n0, the flow rate corresponding to the operation amount of the cargo handling lever 5.6 is supplied in just the right amount, which is effective by reducing excess hydraulic oil.
Even when the engine speed n is less than the reference speed n0,
The required flow rate Q is supplied, allowing for faster cargo handling operations. Furthermore, when cargo handling is not carried out, the pump discharge flow rate Q
is only the required flow rate Q to the travel control system circuit 12, but since the flow rate Q1 is always controlled to a predetermined level using the rotational speed signal, the surplus flow rate due to an increase in the engine rotational speed is reduced. This is effective in reducing surplus hydraulic fluid, which is the objective of the present invention.

In the second embodiment, the hydraulic oil flow rate Q2 was set in accordance with the operating amount of the cargo handling lever, and the hydraulic pump discharge flow rate Q was adjusted by adding the required flow rate Q of the travel control system circuit 12. However, a combination with the first embodiment is also easily conceivable. That is, the flow rate Q1 required for the travel control system circuit 12
is controlled to a predetermined value using an engine rotational speed signal, and the flow rate required for cargo handling exceeding Ql is determined by the discharge amount q2 per bomb revolution corresponding to the operating amount of the cargo handling lever. The control signal V to the variable capacity mechanism 22 is the discharge amount q per bomb rotation, which is Q divided by the engine rotation speed n,
A value corresponding to q, which is the sum of , q corresponding to the amount of operation of the cargo handling lever, and q is used. By controlling the hydraulic pump 20 in this way, the travel control system circuit 1 when cargo handling is not performed
The flow rate in step 2 is set to a predetermined value regardless of the engine speed, and is effective in reducing surplus flow. During cargo handling, the operator can adjust the discharge amount per revolution of the pump corresponding to the amount of operation of the cargo handling lever, In other words, it is possible to control both the swash plate inclination angle and the engine speed, which is set by depressing the accelerator, and allows for freedom in cargo handling operations such as control of minute flow rates, i.e. gradual cargo handling operations, continuous cargo handling operations, etc. This increases the flow rate, reduces surplus flow rate, and improves work efficiency.

In the embodiment E, the potentiometer 23.6 is used as means for detecting the amount of movement of the cargo handling lever 5.6.
24, but other means are also possible. For example, a limit switch may be used instead of the potentiometer. In this case, the load handling lever 5 is
．． 6 is moved by a predetermined amount, the limit switch is turned on, and in response to this signal, the controller 30 issues a control signal to the variable capacity mechanism 22 so that the discharge amount q per revolution of the hydraulic pump 2 is maximized. During non-cargo handling operations, the limit switch remains off and the controller 30 controls the hydraulic pump 20 to minimize the discharge amount q, so no wasteful reflux occurs except during cargo handling operations. As shown in the figure.

However, if only one limit switch is provided for each cargo handling lever 5.6, the discharge capacity Q0 can only be adjusted in two stages, large and small, as understood from the seventh leap, which is necessary for cargo handling work. When the flow IQ is low, excess hydraulic fluid is generated. Therefore, those skilled in the art will easily understand that it will be more effective if a plurality of limit switches are provided to switch the pump discharge flow rate Q0 in multiple stages.

FIG. 8 shows a third embodiment of the present invention in which the first invention is applied to a hydraulic circuit using a tandem type hydraulic pump.

The tandem hydraulic pump is composed of two large and small hydraulic pumps 40 and 41 driven by the same engine 1, and the large capacity hydraulic pump 40 is connected to the control valve 4. Further, the travel control system circuit 12 is connected to a small-capacity hydraulic pump 41. Both of these hydraulic pumps 40 and 41 are of variable displacement type. The engine 1 is provided with an engine rotation speed detector 42 for detecting its rotation speed.

In such a configuration, the controller 30 reads the rotational speed of the engine 1 and the amount of operation of the cargo handling lever 5.6 from the engine rotational speed detector 42 and the potentiometer 23.24, respectively, and adjusts the discharge of each hydraulic pump 40.41. The capacitances Q', ,Q', are controlled. That is, since the large-capacity hydraulic pump 40 is used exclusively for cargo handling, the discharge flow rate Q' of the hydraulic pump 40 when cargo handling is not performed. is limited to zero or a minimum, and during a cargo handling operation, the variable capacity mechanism 43 is controlled according to the operation amount of the cargo handling lever 5.6 and the engine rotational speed as described above, and the discharge flow rate Q'. is increased.

Furthermore, since the small-capacity hydraulic pump 41 is dedicated to the travel control system circuit 12, when the engine 1 reaches a set rotation speed, for example, the idle rotation speed, its discharge flow rate Q'1 is kept constant at a predetermined value. Thus, the variable capacity mechanism 44 of the hydraulic pump 41 is controlled according to the engine speed. 9th
The figure shows the lever operation amount and pump discharge flow rate Q' for a large-capacity hydraulic pump 40. FIG. 10 shows the relationship between the engine rotation speed and the pump discharge flow rate Q' for the small-capacity hydraulic pump 41. This refining method can eliminate the flow divider, which has the advantage of reducing pressure loss and further improving the efficiency of the hydraulic system.

Next, the second invention will be explained. FIG. 11 shows a hydraulic circuit of a forklift to which the second invention is applied, and is almost the same as the hydraulic circuit shown in FIG.
1 in that it includes a throttle actuator 50 attached to the engine, a clutch disengagement detector 52 that detects engagement and disengagement of the clutch 51, a neutral detector 53 of a transmission (not shown), and an engine rotation speed detector 42. It is different from that of. The clutch disengagement detector 52, the neutral detector 53, and the engine speed detector 42 are connected to the input section of the controller 30, and the throttle actuator 50 is connected to the output section of the controller 30.

In the controller 30, as shown in FIG.
The flow rate Q2 required for cargo handling is determined by receiving signals corresponding to the amount of lever operation from the potentiometers 23 and 24, and the actual rotation speed n from the engine rotation speed detector 42 is also included. Calculate the discharge amount q per rotation. Also, based on signals from the clutch disengagement detector 52 and the neutral detector 53, it is recognized whether the clutch 51 is engaged or not and whether the transmission position is neutral. When the clutch 51 is engaged and the transmission position is not neutral, the controller 30 sends a control signal corresponding to the previously calculated discharge amount q to the variable capacity of the hydraulic pump 20, as in the embodiment shown in FIG. On the other hand, when the clutch 51 is disengaged or the transmission is in neutral and the cargo handling lever 5.6 is tilted, The controller 30 is the throttle actuator 5
0, an engine rotation speed increase command is output to increase the rotation speed of the engine 1, and when the detected value from the engine rotation speed detector 42 reaches a predetermined value, the engine 1 is maintained at that rotation speed.

This rotational speed is preferably set to a reference rotational speed n0 necessary for cargo handling operations. Furthermore, at the same time as issuing an engine speed increase command to the throttle actuator 50, the controller 30 issues a control signal according to the lever operation amount to the variable displacement mechanism 22 to increase the discharge flow rate Q0 of the hydraulic pump 20. In this way, when carrying out cargo handling work while the vehicle is stopped, the rotational speed of the engine 1 is automatically increased by simply tilting the cargo handling lever 5.6 without pressing the accelerator pedal. Able to carry out necessary cargo handling operations.

Effects of Invention E] As described in E, according to the first invention, when a cargo handling operation is performed, the discharge flow rate of the hydraulic pump increases by the flow rate required for the cargo handling operation, so that the flow rate in the hydraulic circuit is increased. The excess amount of hydraulic oil flowing is reduced. Therefore, flow loss and pressure loss are significantly reduced, increasing the efficiency of the hydraulic system and improving fuel efficiency.

Further, since the rise in the temperature of the hydraulic oil is also suppressed, various troubles caused by the rise in the oil temperature, such as deterioration of gaskets and seals, wear of the pump, and deterioration of the hydraulic oil, can be prevented. These lead to longer lifespans of hydraulic components and improved reliability of the entire vehicle.

Furthermore, according to the second invention, in addition to achieving the above-mentioned effects, when carrying out cargo handling work when the vehicle is stopped, the engine rotational speed necessary for cargo handling operation is automatically obtained without operating the accelerator pedal. Cargo handling work becomes easier.

Further, according to the first and second inventions of the present invention, even if the cargo handling lever is replaced with a variable attachment operating lever for other special operations, or even if these are configured in parallel, the same effect as described above can be achieved. Effects can be obtained.

4. Explanation of the four aspects No. 1 I54 is a circuit diagram of a hydraulic circuit of a forklift to which the first embodiment of the first invention is applied, and FIG. 2 is a schematic explanation showing how to install a potentiometer that is a lever operation amount detector. 3 is a diagram schematically showing the control logic in the controller of FIG. 1, FIG. 4 is a graph showing the relationship between lever operation amount and pump discharge flow rate according to the first invention, and FIG.
The figure is a circuit diagram of a hydraulic circuit of a forklift to which the second embodiment of the first invention is applied, FIG. 6 schematically shows the control logic in the controller of FIG. 5, and FIG. 7 is a lever operation amount detection A graph showing the relationship between lever operation amount and pump discharge flow rate when a limit switch is used as a limit switch, and FIG. 8 shows a third embodiment in which the first invention is applied to a hydraulic circuit using a tandem hydraulic pump. Circuit diagram, No. 9
The figure is a graph showing the relationship between lever operation amount and pump discharge flow rate for the large capacity hydraulic pump in Figure 8, and Figure 10 is a graph showing the relationship between engine speed and pump discharge flow rate for the small capacity hydraulic pump in Figure 8. 1215N1 is a diagram schematically showing the control logic in the controller of FIG. 11, and FIG. 13 is a diagram of a conventional hydraulic circuit. The circuit diagram and FIG. 14 are graphs showing the relationship between the amount of lever operation and the pump discharge flow rate in the prior art. In the diagram, 1...Engine 4...Control valve 5.6...Cargo handling lever 12...Travel control system circuit 2
0.40.41...Variable displacement type pressure pump 22, 4
3.44... Capacity variable mechanism 23.24... Potentiometer 30... Controller 42... Engine speed detector 50... Throttle actuator 51... Clutch 52... Clutch disconnection detector 53 ...neutral detector

Claims (1)

[Claims] 1. In a hydraulic circuit for cargo handling of an industrial vehicle, a variable displacement hydraulic pump, a lever movement amount detector for detecting the movement amount of a cargo handling lever, and a signal from the lever movement amount detector are provided. a controller that outputs a signal to change the discharge amount per revolution of the hydraulic pump so that the discharge flow rate of hydraulic oil from the hydraulic pump is increased by an amount necessary for cargo handling operations; and a signal from the controller. A hydraulic oil flow rate control device for an industrial vehicle, comprising a discharge amount variable means that changes the discharge amount based on. 2. The hydraulic oil flow rate control device for an industrial vehicle according to claim 1, comprising: an engine that drives the hydraulic pump; a transmission that converts the output of the engine into driving power of the vehicle; and a transmission that controls the amount of fuel supplied to the engine. a throttle actuator to be adjusted, an engine rotation speed detector to detect the rotation speed of the engine, a clutch disengagement detector to detect engagement and disengagement of the clutch, or a neutral detector to detect that the transmission is neutral, and the clutch The clutch is disengaged or the transmission is in neutral and the cargo handling lever is tilted based on the output signal from the intermittent detector or the neutral detector and the output signal from the lever operation amount detector. and a controller that outputs a signal of the operation amount of the throttle actuator to increase the rotation speed of the engine to a predetermined value in accordance with the signals from the engine rotation speed detector and the lever operation amount detector. A hydraulic fluid flow control device for an industrial vehicle, characterized by: