JP5677866B2 - 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 vehicles used for industrial purposes.

  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 accumulate in the pressure accumulating section, and the hydraulic oil is used to brake as necessary. Control is taking place.

  In addition, there is an industrial vehicle that uses hydraulic oil for brake control as another driving oil by supplying the hydraulic oil to another cargo handling merging valve or a fan control valve when the hydraulic oil for brake control has been accumulated in the pressure accumulating section.

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

  Further, as another prior art, in a hydraulic circuit having a fixed displacement pump and a variable displacement pump driven by an engine, when the engine speed is small, the pump absorption torque or more suitable for a preset engine rotation torque curve is obtained. In some cases, the traveling motor can obtain a large torque by increasing the tilt angle of the variable displacement pump for traveling (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.

  Also, when the hydraulic oil for brake control is used as other driving oil, the hydraulic oil that is not used for other driving is returned to the tank without working, resulting in lost energy.

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. Patent Document 2 describes the tilt angle of the travel variable displacement pump when the engine speed is small. Since they are controlled, energy cannot be saved by controlling the hydraulic oil flow rate in the brake control circuit as in the present invention.

  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 for accumulating the hydraulic oil in the accumulator when the accumulator is below a predetermined pressure and supplying the hydraulic oil to another valve when the accumulator reaches a predetermined pressure. An unloader valve; a cargo handling merging valve that merges hydraulic oil from the unloader valve with cargo handling drive oil; and a fan control valve that supplies hydraulic oil from the unloader valve to a fan. The hydraulic pump includes the unloader valve The pressure control valve primary pressure, the cargo handling merge valve's cargo handling merge pressure, and the fan speed control pressure of the fan control valve are selected as high pressure. And characterized in that it is a variable displacement pump for controlling the tilt angle of the maximum pressure that the pressure selected as the load sensing pressure.

  As a result, 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 loss energy. Since it can be minimized, energy can be saved by controlling the discharge flow rate of the variable displacement pump to the required flow rate. That is, when accumulating hydraulic oil in the pressure accumulator for brake control, control is performed to increase the tilt angle of the variable displacement pump so that the required flow of hydraulic oil is discharged to the brake control circuit. When the set pressure is reached, the tilt angle is controlled so as to discharge the required flow rate of the valve with the highest pressure, thereby minimizing energy loss.

  In addition, the primary pressure of the pressure control valve of the unloader valve and the cargo handling merging pressure of the cargo handling merging valve are selected to be high, and the high pressure side pressure selected and the fan rotation speed control pressure of the fan control valve are selected to be high. The tilt angle of the variable displacement pump may be controlled using the selected pressure as a load sensing pressure.

  The order in which the pressure control valve primary pressure of the unloader valve, the cargo handling merging pressure of the cargo handling merging valve, and the fan speed control pressure of the fan control valve are selected is not limited to the above order, and may be changed as appropriate. Also good.

  Further, the hydraulic oil may be supplied from the unloader valve to the cargo handling merging valve, and the hydraulic oil may be supplied from the cargo handling merging valve to the fan control valve.

  In this way, hydraulic oil is supplied to the fan control valve from the cargo handling merging valve after hydraulic oil is supplied to the cargo handling merging valve that requires high-pressure hydraulic oil. Therefore, priority is given to the hydraulic oil for brake control. After the accumulation, the hydraulic oil is preferentially supplied for cargo handling, so that the hydraulic oil can be preferentially supplied from the configuration on the high pressure side.

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

  As a result, while having a brake priority circuit that preferentially accumulates hydraulic fluid for brake control over the pressure accumulator, it is possible to optimally control the flow rate discharged from the variable displacement pump to the required flow rate, thereby reducing energy loss. It becomes possible to configure an industrial vehicle capable of achieving energy.

  According to the present invention, it is possible to control the flow rate discharged from the variable displacement pump to the required flow rate according to the situation while giving priority to the accumulation of hydraulic fluid for brake control, thereby improving the efficiency of the hydraulic pump control system. Energy saving can be achieved.

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.

  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 accumulated in the front axle accumulator 33 and the rear axle accumulator 34 from the branch pipe 32 via the filter 31. 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 supplied from the accumulators 33 and 34 to the front axle (not shown) and the rear axle (not shown) by operating a brake valve (not shown).

  The variable displacement pump 5 is driven via a mission 6 driven by an engine. The variable capacity pump 5 includes a capacity adjustment mechanism 9 having a control valve 7 that is switched by a load sensing pressure (Pls), which will be described later, and a tilt angle adjustment unit 8 that is controlled by the control valve 7. 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 FIGS. 1 and 2, the unloader valve 10 preferentially starts from the first output port 13 when the original pressure to the brake control pressure (the circuit pressure on the accumulator 33 side) falls below the set pressure. 30 is a valve that controls to supply hydraulic oil to the second output port 14 when hydraulic oil is supplied to 30 and the brake control source pressure becomes equal to or higher than the set pressure. The unloader valve 10 is a known hydraulic valve unit, and a first valve 15 and a second valve that switch between accumulators 33 and 34 and accumulators 33 and 34 for switching between returning the operating oil to the tank 2 and supplying it to the secondary side. There are 16 two valves. 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. The accumulators 33 and 34 are accumulated 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 36.

  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. This state is a state in which 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 this specification and claims) The state in which hydraulic oil is not supplied from the unloader valve to the brake control circuit, and “cut-in” refers to the state in which hydraulic oil is supplied from the unloader valve to the brake control circuit). As shown in FIG. 1, the second output port 14 is connected to a cargo handling merging valve 50 via a pipe 22.

  On the other hand, when the accumulated pressure energy accumulated in the accumulator 33 is consumed by operating a brake valve (not shown), 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). Further, as will be described later, the discharge amount of the variable displacement pump 5 is increased and hydraulic oil is supplied to the brake control circuit 30 and is accumulated in the accumulators 33 and 34. As a result, the circuit pressure increases, and Pbreak is correspondingly increased. Rises.

  The cargo handling / merging valve 50 is provided with a switching valve 51. The switching valve 51 is switched by electrical control of an electromagnetic switching valve 56 provided on a branch pipe 55 branched from the secondary side of the variable throttle 52. The electromagnetic switching valve 56 is normally OFF, and hydraulic oil from the unloader valve 10 is supplied to the fan control valve 60. As shown in FIG. 1, when the switching valve 51 is switched, the cargo handling merging valve 50 sends hydraulic oil from the unloader valve 10 through a switching valve 51 with a built-in throttle, a variable throttle 52, and a check valve 53. The hydraulic fluid of the cargo handling confluence pressure is supplied from the cargo handling merging pipe 54 to the cargo handling (not shown).

  The fan control valve 60 is provided with an electromagnetic control valve 61, and the rotation direction of the fan 62 is controlled by switching control of the electromagnetic control valve 61. The fan control valve 60 is provided with an electromagnetic inverse proportional valve 64 that controls the rotational speed of the fan 62.

  In such a hydraulic circuit 1, the primary pressure of the first valve 15 (secondary circuit pressure (Pun) of the throttle 18 of the branch pipe 17) is guided to the high pressure selection valve 20 through the pilot pipe 21. At the same time, the cargo handling merging pressure (Pload) from the cargo handling merging valve 50 is guided to the high-pressure selection valve 20 via the pilot pipe 57, and the fan rotation speed control pressure (Pfan) of the fan control valve 60 passes through the pilot pipe 63. To the high-pressure selection valve 20.

  The respective pressures introduced to the high pressure selection valve 20 are first compared with the pressure (Pun) in the unloader valve 10 and the cargo handling merge pressure (Pload) of the cargo handling merge valve 50. Then, the high pressure side pressure of these pressures is compared with the fan rotational speed control pressure (Pfan). Thereby, the highest pressure (maximum pressure) is selected by the high pressure selection valve 20, and the pressure becomes the load sensing pressure (Pls). The load control pressure (Pls) selected by the high pressure selection valve 20 controls the control valve 7 of the capacity adjustment mechanism 9 via the pilot pipe 23. 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 oil having a flow rate corresponding to the highest pressure selected by the high pressure selection valve 20 is discharged.

  That is, the tilt angle control of the variable displacement pump 5 performs the primary side pressure (Pun; brake control circuit pressure) and the second output of the first valve 15 in the unloader valve 10 that accumulates the accumulated pressure energy of the brake control pressure with priority. The load handling merging pressure supplied from the port 14 to the cargo handling merging valve 50 and merging the cargo (Pload; changed according to the load of the cargo handling) is compared, and the fan speed control pressure (Pfan; fan speed) of the fan control valve 60 is compared. Change) and the pump tilt control is performed using the highest pressure as the load sensing pressure (Pls pressure).

  A specific example of pressure selection in the high-pressure selection valve 20 is as follows. First, when the first valve primary pressure (Pun) of the unloader valve 10 becomes the load sensing pressure, the cargo handling merging valve 50 is not operated (Pload = 0), and the unloader valve 10 is cut in, This is when the fan speed control pressure (Pfan) is lower than the cut-in pressure of the unloader valve 10. In this state, Pload (= 0 MPa) <Pfan <Pun. Further, when the fan rotation speed control pressure (Pfan) is higher than the cut-in pressure of the unloader valve 10 and lower than the cut-out pressure, the pressure of Pun becomes the load sensing pressure when Pun exceeds Pfan.

  On the other hand, when the fan rotation speed control pressure (Pfan) becomes the load sensing pressure, there is no operation of the cargo handling merge valve 50 (Pload = 0), and the fan rotation speed control pressure is higher than the cutout pressure (Pun) of the unloader valve 10. This is when (Pfan) is high. In this state, the relationship is Pload (= 0 MPa) <Pun <Pfan. Further, there is no operation of the cargo handling merge valve 50 (Pload = 0), and when the unloader valve 10 is cut out, the fan rotation speed control pressure (Pfan) becomes the load sensing pressure. Further, when the unloader valve 10 is cut in and the fan rotational speed control pressure (Pfan) is higher than the unloader valve 10 cut-in pressure (at high fan speed), the fan rotational speed control pressure (Pfan). Becomes the load sensing pressure.

  In addition, the load handling merge pressure (Pload) of the load handling merge valve 50 becomes the load sensing pressure when the unloader valve 10 is cut out (Pun) and the fan rotation speed control pressure (Pfan) is lower than the merge pressure. . In this state, the relationship is Pun <Pfan <Pload. Pfan is often high because Pload starts from a low pressure at the start of merging, but the maximum pressure is high because Pload is high, so eventually Pload becomes the load sensing pressure of the variable displacement pump 5 and the inclination of the variable displacement pump 5 Turn angle control is performed.

  As described above, when accumulating the accumulators 33 and 34, the pressure of the brake control circuit 30 decreases, the unloader valve 10 is cut in, the hydraulic oil is supplied to the brake control circuit 30, and the increased first valve 15 The discharge flow rate is increased by controlling so that the primary side pressure becomes the load sensing pressure and the tilt angle of the variable displacement pump 5 is increased. Then, until the brake control circuit 30 reaches the set pressure, the flow rate corresponding to the pressure is discharged from the variable displacement pump 5, and the required flow rate of hydraulic oil can be quickly accumulated in the accumulators 33 and 34.

  After that, when hydraulic oil having a set pressure is accumulated in the accumulators 33 and 34, as described above, the primary side and the secondary side of the first valve 15 of the unloader valve 10 are connected by the pressure of the brake control circuit 30, Hydraulic fluid is discharged from the second output port 14 through the second valve 16. The hydraulic oil discharged from the second output port 14 is supplied to the cargo handling merging valve 50 and the fan control valve 60. In the high pressure selection valve 20, the circuit pressure (Pun) of the unloader valve 10 and the cargo handling merging valve 50 are The highest pressure among the cargo handling combined pressure (Pload) and the fan rotation speed control pressure (Pfan) of the fan control valve 60 is selected as the load sensing pressure (Pls). Thereby, the tilt angle adjusting unit 8 of the capacity adjusting mechanism 9 is controlled by the highest load sensing pressure (Pls) required for the system, and the tilt angle of the variable capacity pump 5 is controlled. As described above, in a state where the hydraulic oil having a predetermined pressure is accumulated in the accumulators 33 and 34, the tilt angle of the variable displacement pump 5 is necessary in the other valves 50 and 60 to which the hydraulic oil is supplied from the unloader valve 10. Therefore, the flow rate discharged from the variable displacement pump 5 can be optimally adjusted to the required flow rate.

  As described above, according to the hydraulic circuit 1, when the accumulated pressure energy of the brake control pressure in the brake control circuit 30 is required, the discharge of the variable displacement pump 5 is performed using the circuit pressure of the unloader valve 10 as the load sensing pressure. In addition to having a function as a brake control priority circuit that gives priority to accumulators 33 and 34 for increasing the flow rate and accumulating pressure for brake control, if the brake control circuit 30 does not require hydraulic oil, the variable displacement pump 5 is the minimum required. Since the discharge flow rate is controlled, it is possible to configure a hydraulic pump control system capable of realizing energy saving by reducing the loss energy of the pump and improving efficiency.

  In addition, the high pressure selection valve 20 is configured to obtain the highest pressure from the pressure control valve primary pressure of the unloader valve, the cargo handling merge pressure of the cargo handling merge valve provided on the secondary side of the unloader valve, and the fan rotation speed control pressure of the fan control valve. Since a high pressure is selected and that pressure is used as the load sensing pressure of the variable displacement pump for pump tilt control, the discharge flow rate of the pump can always be optimally controlled and efficient variable displacement pump control Can do. In addition, the hydraulic oil pressure required at that time can be automatically determined, control using a controller or the like is unnecessary, and control can be simplified.

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

  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 (Pun)
22 Piping 23 Pilot piping (Pls)
30 Brake Control Circuit 33 Front Axle Accumulator 34 Rear Axle Accumulator 36 Pilot Piping (Pbreak)
50 Load Handling Merge Valve 54 Load Handling Merge Piping 57 Pilot Piping (Pload)
60 Fan control valve 62 Fan 63 Pilot piping (Pfan)

Claims (4)

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;
The pressure accumulating section first valve is in the case of less than the predetermined pressure for storing the hydraulic oil accumulating pressure section, and accumulating pressure portion second supplying hydraulic oil from the hydraulic pump reaches a predetermined pressure to other valves and the unloader valve having a valve,
A cargo handling merging valve that merges hydraulic oil from the unloader valve with cargo handling driving oil;
A fan control valve for supplying hydraulic oil from the unloader valve to the fan,
The hydraulic pump includes: a primary valve primary pressure of the unloader valve; a cargo handling merge pressure of hydraulic fluid supplied from the cargo handling merge valve to a cargo handling merge pipe; and a fan rotation of hydraulic oil supplied to the fan from the fan control valve. A hydraulic pump control system for an industrial vehicle, which is a variable displacement pump that selects a number control pressure as a high pressure, and controls a tilt angle using the selected high pressure as a load sensing pressure. Selecting the first valve primary pressure of the unloader valve and the cargo handling merge pressure of the cargo handling merging valve, selecting the high pressure side pressure selected as the high pressure and the fan speed control pressure of the fan control valve; 2. The hydraulic pump control system for an industrial vehicle according to claim 1, wherein a tilt angle of the variable displacement pump is controlled using a pressure selected as a high pressure as a load sensing pressure.   The hydraulic pump control system for an industrial vehicle according to claim 1 or 2, wherein hydraulic oil is supplied from the unloader valve to the cargo handling merge valve, and hydraulic oil is supplied from the cargo handling merge valve to the fan control valve. .   An industrial vehicle comprising the hydraulic pump control system according to any one of claims 1 to 3.

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