JP5758137B2 - Industrial vehicle hydraulic pump control system and industrial vehicle - Google Patents

Description

  The present invention relates to a control system for a hydraulic pump used in an industrial vehicle such as a construction machine or an industrial vehicle, and an industrial vehicle including the control system.

  Conventionally, industrial vehicles such as wheel loaders (“industrial vehicles” in this specification and claims are construction machines such as “wheel loaders” and “tire rollers”, and “forklifts”, “ A system that performs hydraulic brake control is used for industrial vehicles such as “aerial work vehicles” and all other industrial vehicles.

  As such a brake control system, for example, generally, a fixed capacity pump is used to discharge hydraulic oil at a flow rate corresponding to the engine speed, and the brake control is performed with the hydraulic oil as necessary. .

  As a prior art of this type, in a hydraulic circuit having a fixed displacement pump and a variable displacement pump driven by an engine such as a hydraulic excavator, the variable displacement pump is controlled according to a change in the discharge flow rate of the fixed displacement pump driven by the engine. Some have been made (see, for example, Patent Document 1).

  As another prior art, similarly to Patent Document 1, in a hydraulic circuit including a fixed displacement pump and a variable displacement pump driven by an engine, when the engine speed is small, a preset engine rotation torque In some cases, the traveling motor can obtain a large torque by increasing the tilt angle of the variable displacement pump for traveling so that a torque greater than the pump absorption torque corresponding to the curve can be obtained (see, for example, Patent Document 2). ).

JP 2001-271758 A Japanese Patent Laid-Open No. 2002-213609

  However, as described above, when a fixed capacity pump discharges hydraulic oil at a flow rate corresponding to the engine speed, a large flow rate corresponding to the engine speed is discharged even during work that does not require brake control. Since the discharge amount exceeding the required flow rate at that time is returned to the tank without working, there is a lot of energy loss.

On the other hand, in recent years, in order to prevent global warming, reduce CO ₂ , etc., efforts have been made to reduce the size of engines, regulate exhaust gases, increase the efficiency of each device, and the like. Therefore, even in the brake control circuit as described above, there is a need to save energy by reducing the flow rate of hydraulic oil that is discharged from the hydraulic pump and does not work as much as possible.

  Patent Document 1 controls the tilt angle of the variable displacement pump by changing the discharge flow rate of the fixed displacement pump, and Patent Document 2 controls the tilt angle of the travel variable displacement pump when the engine speed is small. However, none of them can save energy by controlling the hydraulic oil flow rate in the brake control circuit.

  Therefore, an object of the present invention is to provide a hydraulic pump control system for an industrial vehicle that can save energy by controlling a flow rate discharged from a hydraulic pump to a brake control circuit to a necessary flow rate.

  In order to achieve the above object, a hydraulic pump control system of the present invention is a hydraulic pump control system for an industrial vehicle that performs brake control with hydraulic oil discharged from the hydraulic pump, and accumulates the hydraulic oil for brake control. And a pressure control valve that stores the hydraulic oil in the pressure accumulator when the pressure accumulator is below a predetermined pressure, and switches the hydraulic oil back to the tank when the pressure accumulator reaches a predetermined pressure. The hydraulic pump is a variable displacement pump that controls a tilt angle using a primary pressure of the pressure control valve in a switching state of the control valve as a load sensing pressure.

  As a result, the hydraulic oil for brake control is accumulated prior to the accumulator, and when the accumulator reaches a predetermined pressure, the control valve is switched to return the hydraulic oil to the tank, and the pressure control with the control valve switched By using the valve primary side pressure as the load sensing pressure of the variable displacement pump, the tilt angle of the variable displacement pump can be reduced. As described above, the hydraulic oil discharged from the variable displacement pump is preferentially accumulated for brake control, and when the hydraulic fluid for brake control is unnecessary, the tilt angle of the variable displacement pump is reduced to reduce the energy loss. Therefore, energy saving can be achieved by controlling the discharge flow rate of the variable displacement pump to the required flow rate.

  The control valve is switched when the pressure accumulating unit reaches a predetermined pressure, and returns a part of the hydraulic oil by returning the hydraulic oil from the first valve to the tank. The unloader valve provided with the 2nd valve | bulb supplied to another apparatus may be sufficient.

  In this way, the primary pressure of the valve for switching the unloader valve used for controlling the flow rate and pressure supplied to the pressure accumulator for brake control is used as the load sensing pressure of the variable displacement pump, and the variable displacement pump Can be easily controlled according to the required flow rate.

  Further, the primary side pressure of the first valve and the secondary side pressure of the second valve are selected to be high pressure, and the tilt angle of the variable displacement pump is controlled by the high pressure side pressure selected. May be.

  In this way, when hydraulic oil is accumulated in the pressure accumulator for brake control, the tilt angle of the variable displacement pump is controlled to be large so that the required flow of hydraulic oil is discharged to the brake control circuit. When the brake control circuit reaches the set pressure and hydraulic fluid is not supplied, the tilt angle of the variable displacement pump can be controlled so that the hydraulic fluid at a flow rate required for other devices is discharged from the unloader valve.

  On the other hand, an industrial vehicle according to the present invention includes any one of the hydraulic pump control systems described above.

  This makes it possible to save energy by controlling the loss energy by optimally controlling the flow rate discharged from the variable displacement pump, while providing a brake priority circuit that preferentially accumulates hydraulic fluid for brake control over the pressure accumulator. It is possible to configure an industrial vehicle capable of

  The present invention can provide a hydraulic pump control system for an industrial vehicle that can save energy by controlling the flow rate discharged from the hydraulic pump to the brake control circuit to the required flow rate.

1 is a hydraulic circuit diagram showing an embodiment according to a hydraulic pump control system of the present invention. It is an enlarged view of the unloader valve shown in FIG. It is drawing which shows the unload state of the unloader valve | bulb shown in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, a hydraulic circuit of a wheel loader will be described as an example. An unloader valve will be described as an example of the control valve.

  As shown in FIG. 1, the hydraulic circuit 1 is provided with a variable displacement pump 5 that supplies hydraulic oil from a tank 2 via a pipe 3. The hydraulic oil supplied from the variable displacement pump 5 is supplied to the input port 11 of the unloader valve 10 via the pipe 4. The hydraulic oil supplied to the input port 11 is supplied to the first output port 13 through the throttle 12, and is supplied from the first output port 13 to the brake control circuit 30. The hydraulic oil supplied to the brake control circuit 30 is supplied to the branch pipe 32 via the filter 31 and is accumulated from the branch pipe 32 to the front axle accumulator 33 and the rear axle accumulator 34. The branch pipe 32 is provided with a check valve 35 to prevent the backflow of hydraulic oil stored in both accumulators 33 and 34. The pressure accumulation energy of the hydraulic oil stored in these accumulators 33 and 34 becomes the original pressure of the brake control pressure.

  The hydraulic oil stored in the accumulators 33 and 34 is connected to a brake valve 37 via a pipe 36. By operating the brake valve 37, the hydraulic oil from the accumulators 33 and 34 is used as a brake operating pressure for the front axle 38 and the rear axle 39. When the operation of the brake valve 37 is completed, the hydraulic oil supplied to both axles 38 and 39 is returned to the tank 2 via the pipe 40.

  The variable displacement pump 5 is driven via a mission 6 driven by an engine. As will be described later, the variable displacement pump 5 has a control valve 7 that is switched by the load sensing pressure (Pls) from the unloader valve 10 and a tilt angle adjusting unit 8 that is controlled by the control valve 7. An adjustment mechanism 9 is provided. The displacement adjusting mechanism 9 controls the tilt angle of the variable displacement pump 5. The tilt angle control by the capacity adjusting mechanism 9 will be described later.

  As shown in FIG. 2, the unloader valve 10 is preferentially operated from the first output port 13 to the brake control circuit 30 when the original pressure of the brake control pressure (circuit pressure on the accumulator 33 side) falls below the set pressure. It is a valve that controls to supply hydraulic oil to the second output port 14 when oil is supplied and the brake control source pressure becomes equal to or higher than the set value. The unloader valve 10 is a known hydraulic valve unit, and includes two valves, a first valve 15 and a second valve 16, that switch between accumulator 33 and 34 accumulating hydraulic oil or returning hydraulic oil to the tank 2. ing. The unloader valve 10 has a switching pressure set by the set pressure of the first valve 15 and the second valve 16.

  As a function of such an unloader valve 10, when the circuit pressure on the accumulator 33 side is equal to or lower than the set pressure, the hydraulic oil supplied to the input port 11 passes through the throttle 12 and is supplied to the first output port 13. And accumulated in the accumulators 33 and 34 via the check valve 35. The circuit pressure (Pbreak) on the accumulator 33 side is guided to the first valve 15 via the pilot pipe 41.

  When the hydraulic oil is accumulated in the accumulator 33 and the circuit pressure reaches the set pressure, the circuit on the primary side and the secondary side of the first valve 15 are connected by the circuit pressure (Pbreak) to communicate with the pipe 19. The primary pressure of the first valve 15 is reduced to the tank pressure.

  Thereby, as shown in FIG. 3, the primary and secondary circuits of the second valve 16 are connected, and the hydraulic oil supplied to the input port 11 passes through the second valve 16 to the second output port 14. Supplied to. Further, in this state, the hydraulic oil is not supplied to the brake control circuit 30, and the hydraulic oil is cut out by the second valve 16 ("Cutout" in the document of this specification and claims). Is a state in which hydraulic oil is not supplied from the unloader valve to the brake control circuit, and “cut-in” is a state in which hydraulic oil is supplied from the unloader valve to the brake control circuit). The second output port 14 is connected to an actuator control pilot port of another device 50 through a pipe 22 as shown in FIG.

  On the other hand, when the hydraulic energy accumulated in the accumulator 33 is consumed by operating the brake valve 37, the Pbreak of the brake control circuit 30 is lower than the set pressure of the unloader valve 10. When this Pbreak falls below the set pressure, the passage of the first valve 15 of the unloader valve 10 is closed.

  As a result, the primary pressure of the first valve 15 increases, and the primary and secondary circuits of the second valve 16 are disconnected (this pressure is referred to as cut-in pressure). When the passage of the second valve 16 is closed, the hydraulic oil discharged from the variable displacement pump 5 flows preferentially to the brake control circuit 30 side (brake circuit priority). When hydraulic oil is supplied to the brake control circuit 30, the circuit pressure increases due to accumulation in the accumulators 33 and 34, and Pbreak increases accordingly.

  In such a hydraulic circuit 1, the primary pressure of the first valve 15 (the pressure of the branch pipe 17) is guided to the high pressure selection valve 20 through the pilot pipe 21 and from the second output port 14. The discharged hydraulic oil is led to the high pressure selection valve 20 via the pipe 22, and the high pressure side pressure is selected by the high pressure selection valve 20. The high pressure selection valve 20 selects the high pressure side pressure of the discharge pressure of the second output port 14 and the primary side pressure of the first valve 15, and the pressure of the capacity adjusting mechanism 9 via the pilot pipe 23 is selected by the pressure. The control valve 7 is controlled. As a result, the tilt angle of the variable displacement pump 5 is controlled by the tilt angle adjusting unit 8 so that the hydraulic fluid having a flow rate corresponding to the high pressure side pressure selected by the high pressure selection valve 20 is discharged.

  That is, the higher one of the primary side pressure (pressure of the branch pipe 17) of the first valve 15 of the unloader valve 10 and the pressure of the second output port 14, which gives priority to accumulation of brake control pressure, is the load sensing pressure (Pls). Is used for tilt control of the variable displacement pump 5.

  As a result, when the flow rate is required for the brake control circuit, the primary pressure of the first valve 15 becomes the load sensing pressure (Pls), and the variable displacement pump 5 is controlled at the flow rate required for the brake control circuit, and cut out. Thereafter, the pressure of the second output port 14 becomes Pls, and the flow rate required on the secondary side of the second output port can be controlled.

  Therefore, according to the hydraulic circuit 1, the hydraulic pump can control the variable displacement pump 5 so as to discharge the required amount of hydraulic fluid to the brake control circuit 30, thereby reducing the energy loss of the pump and realizing energy saving. A control system can be configured.

  In the above embodiment, the wheel loader including the front axle 38 and the rear axle 39 has been described as an example. However, the present invention can be similarly applied to other industrial vehicles and is limited to the above embodiment. It is not a thing.

  Moreover, although the structure of the variable displacement pump 5 also shows a general structure, other structures may be used as long as the tilt angle can be controlled, and the structure is not limited to the structure of the above embodiment. .

  Furthermore, the above-described embodiment shows an example, and various modifications can be made without departing from the gist of the present invention, and the present invention is not limited to the above-described embodiment.

  The hydraulic pump control system according to the present invention can be used for construction machines such as wheel loaders, industrial vehicles such as aerial work vehicles, and other industrial vehicles.

1 Hydraulic circuit
5 Variable displacement pump
7 Control valve
8 Tilt angle adjuster
9 Capacity adjustment mechanism 10 Unloader valve (control valve)
11 Input Port 12 Restriction 13 First Output Port 14 Second Output Port 15 First Valve (Pressure Control Valve)
16 Second valve (pressure control valve)
17 Branch pipe 18 Restriction 19 Piping 20 High pressure selection valve 21 Pilot piping 22 Piping 23 Pilot piping (Pls)
24 Relief Valve 30 Brake Control Circuit 33 Front Axle Accumulator 34 Rear Axle Accumulator 41 Pilot Piping (Pbreak)
50 Other equipment

Claims (3)

An industrial vehicle hydraulic pump control system that performs brake control with hydraulic oil discharged from a hydraulic pump,
A pressure accumulator for accumulating the hydraulic oil for brake control;
An unloader valve having a pressure control valve that switches the hydraulic oil to accumulate in the pressure accumulator when the pressure accumulator is below a predetermined pressure and switches the hydraulic oil back to the tank when the accumulator reaches a predetermined pressure; Prepared,
The hydraulic pump is a variable displacement pump that controls a tilt angle using a primary pressure of the pressure control valve in a switching state of the unloader valve as a load sensing pressure,
The unloader valve is switched when the pressure accumulating unit reaches a predetermined pressure, and returns a part of the hydraulic oil to the tank by returning the hydraulic oil from the first valve to the tank. A hydraulic pump control system for an industrial vehicle , comprising: a second valve that supplies the device. The primary pressure of the first valve and the secondary pressure of the second valve are selected to be high pressure, and the tilt angle of the variable displacement pump is controlled by the high pressure side pressure selected. The hydraulic pump control system for industrial vehicles as described in 1 . Industrial vehicles, characterized in that it includes a hydraulic pump control system according to claim 1 or 2.

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