JP2017136887A - Work machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a work machine capable of serviceably using discharge oil from a hydraulic pump.SOLUTION: A work machine comprises a hydraulic control device having a variable capacity type hydraulic pump 2 having a regulator 11 for adjusting the discharge volume, a hydraulic motor 5 for rotatingly driving a cooling fan 4, a fan circuit 6 for controlling rotation of the hydraulic motor 5, a steering circuit 3 for controlling expansion operation of a steering cylinder 105 and a priority valve 8 for supplying surplus oil being a difference between a hydraulic fluid from the hydraulic pump 2 and a hydraulic fluid sent out to the steering circuit 3 to the fan circuit 6 by preferentially supplying the hydraulic fluid from the hydraulic pump 2 to the steering circuit 3, and also comprises a variable orifice 10 provided in an oil passage of connecting the priority valve 8 and the fan circuit 6 and capable of varying an orifice quantity in response to a target flow rate of the hydraulic motor 5, and the regulator 11 adjusts the discharge volume of the hydraulic pump 2 so that differential pressure between inflow side pressure and discharge side pressure of the variable orifice 10 becomes predetermined pressure.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a work machine.

  Patent Document 1 discloses a hydraulic system in which a steering circuit and a work machine are driven by a single pump so that pressure oil is preferentially supplied to the steering circuit and the pump discharge amount is controlled.

  In the technique described in Patent Document 1, a priority valve is provided downstream of the pump so that pressure oil is preferentially supplied to the steering circuit, and then a fixed throttle is provided in the return oil line of the working machine hydraulic circuit. Yes. Then, the tilt of the pump is controlled so that the differential pressure across the fixed throttle is constant, and when controlling the work machine, the bypass means provided in parallel with the fixed throttle is opened to open the front and rear of the fixed throttle. By reducing the differential pressure and setting the pump to the maximum discharge amount, a pump discharge amount sufficient to simultaneously drive and control the steering circuit and the work machine is ensured.

JP 2008-162410 A

  However, since the pump discharge amount is maximized when the work implement is operated, the pump discharges the maximum flow rate regardless of the required flow rate of the work implement. Therefore, if the required flow rate of the work implement is small, a part of the surplus oil from the priority valve is discharged to the tank without being used by the work implement, and energy is wasted.

  A work machine according to the present invention includes a variable displacement hydraulic pump including a regulator that adjusts a discharge volume, a hydraulic motor that rotationally drives a cooling fan, a fan circuit that controls rotation of the hydraulic motor, and a steering cylinder. A surplus that is a difference between the hydraulic fluid from the hydraulic pump and the hydraulic fluid that is supplied to the steering circuit preferentially by supplying the hydraulic fluid from the hydraulic pump to the steering circuit and controlling the telescopic operation A working machine having a hydraulic control having a priority valve for supplying oil to the fan circuit, wherein the working machine is provided in an oil passage between the priority valve and the fan circuit, and a throttle amount according to a target flow rate of the hydraulic motor Is provided with a variable throttle, and the regulator is configured to maintain a constant differential pressure between the inlet side pressure and the outlet side pressure of the variable throttle. And controlling the discharge capacity of the serial hydraulic pump.

  According to the present invention, in a work machine that is configured to supply pressure oil from a common hydraulic pump to a steering circuit and a fan circuit, and that includes a hydraulic control device that supplies pressure oil preferentially to the steering circuit, The oil amount of the pressure oil discharged from the pump can be controlled to the oil amount necessary for the steering circuit and the fan circuit, and energy waste can be prevented.

FIG. 1 is a view showing a wheel loader which is an embodiment of a work machine according to the present invention. FIG. 2 is a schematic diagram showing a hydraulic circuit of the hydraulic control device. FIG. 3 is a diagram illustrating an example of a steering circuit. FIG. 4 is a diagram illustrating an example of a fan circuit. FIG. 5 is a functional block diagram showing processing contents in the calculation unit. FIG. 6 is a diagram illustrating a modification of the hydraulic control device.

  Hereinafter, a working machine according to an embodiment of the present invention will be described in detail with reference to the drawings. Hereinafter, a wheel loader will be described as an example of a work machine on which the hydraulic control device is mounted. However, the present invention is not limited to the wheel loader and can be applied to various work machines.

-First embodiment-
FIG. 1 is a diagram showing a wheel loader 200 which is an embodiment of a work machine according to the present invention. The wheel loader 200 includes a front vehicle body 203 having an arm 201, a bucket 202, front wheels 101a and 101b, and a rear vehicle body 204 having a cockpit 102, an engine (not shown), rear wheels 101c and 101d, and the like. The arm 201 is pivoted up and down (up and down) by driving the arm cylinder 103. The bucket 202 is rotated (dumped or clouded) in the vertical direction by driving the bucket cylinder 104. Hereinafter, the front wheels 101a and 101b and the rear wheels 101c and 101d are collectively referred to as wheels 101.

  The front vehicle body 203 and the rear vehicle body 204 are rotatably connected to each other by a connecting shaft 205. The wheel loader 200 is an articulated work vehicle in which a front vehicle body 203 and a rear vehicle body 204 are bent by a connecting shaft 205. One end and the other end of a pair of steering cylinders 105a and 105b around the connecting shaft 205 are rotatably engaged with the front vehicle body 203 and the rear vehicle body 204, respectively. One of the pair of steering cylinders 105a and 105b is extended and the other is retracted by a hydraulic device to be described later, thereby rotating the front vehicle body 203 and the rear vehicle body 204 about the connecting shaft 205, respectively. As a result, the relative angle between the front vehicle body 203 and the rear vehicle body 204 changes. That is, the vehicle is steered by operating the steering wheel.

  The rear vehicle body 204 is provided with a cooling fan 4 and a hydraulic motor 5 for rotationally driving the cooling fan 4. By rotating the cooling fan 4, cooling air is blown to the radiator 106 that cools the coolant of the engine 1 and the oil cooler 107 that cools the hydraulic oil.

  FIG. 2 is a diagram showing an outline of a hydraulic circuit of the hydraulic control device. The wheel loader 200 includes an engine 1, a variable displacement hydraulic pump 2 driven by the engine 1, a steering circuit 3 for controlling expansion and contraction of the pair of steering cylinders 105 a and 105 b, and pressure oil supplied to the hydraulic motor 5. A fan circuit 6 for adjusting the direction and flow rate, a priority valve 8, a variable throttle 10, a regulator 11 for adjusting the tilt (discharge volume) of the hydraulic pump 2, and a controller 12 are provided.

  When pressure oil is discharged from the hydraulic pump 2, the discharged oil from the hydraulic pump 2 passes through the priority valve 8 and is supplied to the steering circuit 3. As will be described later, the steering circuit 3 includes a steering valve 31 that supplies pressure oil to the pair of steering cylinders 105a and 105b in accordance with the operation of the steering wheel. The steering valve 31 shuts off the supplied pressure oil when the steering wheel is not operated. Therefore, when the steering wheel is not operated, the priority valve 8 is switched to the R position, and the entire amount of oil discharged from the hydraulic pump 2 is supplied to the fan circuit 6 through the variable throttle 10. As will be described later, the variable aperture 10 is driven based on an output signal from the controller 12, and the aperture amount is variable. The differential pressure across the variable throttle 10 acts as a driving pressure for the regulator 11, and the greater the differential pressure, the smaller the tilt amount (discharge volume) of the hydraulic pump 2, and the less oil is discharged from the hydraulic pump 2. .

  FIG. 3 is a diagram illustrating an example of the steering circuit 3. The steering circuit 3 includes a steering valve 31, relief valves 32a and 32b, and check valves 33a and 33b. The steering valve 31 is operated according to the operation of the steering wheel, and adjusts the flow of pressure oil so as to control the driving direction and speed of the pair of steering cylinders 105a and 105b. The relief valves 32a and 32b define the maximum driving pressure of the steering cylinders 105a and 105b. The check valves 33a and 33b are make-up check valves for preventing the steering cylinders 105a and 105b from becoming negative pressure.

  When a pilot pressure corresponding to an operation amount of a steering wheel (not shown) is applied to the pilot port a of the steering valve 31, the steering valve 31 is switched from the neutral position C to the A position direction. The pressure oil supplied to the steering valve 31 through the priority valve 8 is adjusted in flow rate by the steering valve 31 and sent to the steering cylinders 105a and 105b. When the operation of the steering wheel is stopped at a predetermined steering angle, the steering valve 31 returns to the neutral position C. As a result, the expansion / contraction operation of the steering cylinders 105a and 105b ends, and the extended position corresponding to the steering angle of the steering wheel, that is, the steering angle is maintained.

  The priority valve 8 operates so as to make the circuit differential pressure of the steering circuit 3 constant. When the steering valve 31 is operated by operating the steering wheel and the steering cylinders 105a and 105b are extended / retracted, the priority valve 8 is switched to the R position side, and the hydraulic oil discharged from the hydraulic pump 2 is supplied to the steering circuit 3 To be preferentially supplied. Then, excess oil, which is the difference between the flow rate of pressure oil supplied from the hydraulic pump 2 and the flow rate of pressure oil flowing from the steering circuit 3 to the steering cylinders 105a and 105b, passes to the fan circuit 6 via the variable throttle 10 and the oil passage 9. Supplied.

  FIG. 4 is a diagram illustrating an example of the fan circuit 6. The fan circuit 6 includes a direction control valve 21, a relief valve 22, check valves 23 a and 23 b, an electromagnetic proportional pressure reducing valve 24, an electromagnetic proportional relief valve 25, and a fixed throttle 26. The direction control valve 21 controls the direction of pressure oil supplied to the hydraulic motor 5. The relief valve 22 defines the maximum pressure of the pressure oil sent to the direction control valve 21 via the oil passage 9. The check valves 23a and 23b are provided to prevent the occurrence of cavitation by introducing pressure oil from the tank T into the port when the pressure at the ports 51 and 52 of the hydraulic motor 5 falls below the tank pressure.

  The electromagnetic proportional pressure reducing valve 24 receives an electrical command from the controller 12 and provides a switching control pressure to the direction control valve 21. In response to the electrical command from the controller 12, the electromagnetic proportional relief valve 25 changes the command pressure port of the relief valve 22, that is, the pressure of the pilot port, and changes the set pressure of the relief valve 22. The fixed throttle 26 is provided on the oil passage connecting the oil passage 9 and the electromagnetic proportional relief valve 25 so that the set pressure of the relief valve 22 can be controlled by the electromagnetic proportional relief valve 25.

  In order to reverse the cooling fan 4, a pressure reduction command is input from the controller 12 to the electromagnetic proportional relief valve 25. The electromagnetic proportional relief valve 25 operates so as to reduce its primary pressure, and the pipe line from the downstream of the fixed throttle 26 to the pilot port of the relief valve 22 is reduced. When the pilot port pressure of the relief valve 22 is reduced, the set pressure of the relief valve 22 is lowered, and the primary pressure of the relief valve 22, that is, the maximum pressure of the oil passage 9 is kept low. As a result, part of the pressure oil in the oil passage 9 escapes from the relief valve 22 to the tank, and the rotational speed of the hydraulic motor 5 decreases. The controller 12 sends a pressure increase command to the electromagnetic proportional pressure reducing valve 24 after waiting for a time sufficient for the rotational speed of the hydraulic motor 5 to sufficiently decrease. When receiving a pressure increase command from the controller 12, the electromagnetic proportional pressure reducing valve 24 increases the secondary pressure. As a result, the direction control valve 21 is switched from the forward rotation position to the reverse rotation position.

  Next, when a pressure increase command is sent from the controller 12 to the electromagnetic proportional relief valve 25, the primary pressure of the electromagnetic proportional relief valve 25 is increased. Thereby, since the set pressure of the relief valve 22 is set high, the pressure of the oil passage 9 increases and the hydraulic motor 5 is driven in reverse.

  On the other hand, when the cooling fan 4 is returned from the reverse rotation state to the normal rotation state, the set pressure of the relief valve 22 is reduced via the electromagnetic proportional relief valve 25. After waiting for the time to decrease to the required number of revolutions, the direction control valve 21 is switched from the reverse rotation position to the normal rotation position via the electromagnetic proportional pressure reducing valve 24, and the relief valve 22 is switched via the electromagnetic proportional relief valve 25. Increase the set pressure. Through such a process, the hydraulic motor 5 is switched from the reverse rotation state to the normal rotation state.

  Next, operations of the variable aperture 10 and the regulator 11 will be described. The regulator 11 is a hydraulically controlled regulator that uses the differential pressure across the variable throttle 10 as a drive pressure. The upstream pressure Pu of the variable throttle 10 is guided through the oil passage 13 and the variable throttle 10 through the oil passage 14. The downstream pressure Pd is introduced. The regulator 11 adjusts the tilt of the hydraulic pump 2 so that the differential pressure ΔP = Pu−Pd between the upstream pressure Pu and the downstream pressure Pd becomes the set pressure Ps.

Thus, since the tilt of the hydraulic pump 2 is controlled so that the differential pressure ΔP = Ps, the differential pressure of the variable throttle 10 is constant without being affected by the operation of the steering cylinders 105a and 105b. The passage flow rate Q of the variable throttle 10 is expressed by the following formula (1) using the orifice formula, where S is the opening area of the variable throttle 10 and ΔP is the differential pressure.
Q∝S√ (ΔP) (1)

  As described above, since the regulator 11 adjusts the tilt of the hydraulic pump 2 so that ΔP = Ps, the passing flow rate Q is equal to the opening area S of the variable throttle 10 regardless of the operation of the steering cylinders 105a and 105b. Determined by the value of. For example, when the steering cylinders 105a and 105b are expanded and contracted to reduce the flow rate of excess oil to the variable throttle 10, the differential pressure ΔP of the variable throttle 10 decreases. Therefore, the regulator 11 increases the discharge flow rate of the hydraulic pump 2 by adjusting the tilt of the hydraulic pump 2 so that the differential pressure ΔP increases. On the contrary, when the expansion / contraction operation of the steering cylinders 105a and 105b is stopped and the flow rate of the surplus oil is increased, the differential pressure ΔP is increased. Therefore, the regulator 11 is configured so that the discharge flow rate of the hydraulic pump 2 is decreased. Adjust the tilt (discharge volume).

  The controller 12 controls the rotation speed of the hydraulic motor 5 based on the temperature detected by the temperature sensor 15. In general, a plurality of temperature sensors used for controlling the rotational speed of the hydraulic motor 5 are provided. For example, a temperature sensor that detects the temperature of hydraulic oil, a temperature sensor that detects the temperature of engine coolant, and a temperature in the cockpit There are a temperature sensor for detecting, a temperature sensor for detecting the outside air temperature, and the like. In FIG. 2, these temperature sensors are represented by a temperature sensor 15. The controller 12 is detected by at least one of a temperature sensor that detects the temperature of the hydraulic oil, a temperature sensor that detects the temperature of the engine coolant, a temperature sensor that detects the temperature in the cockpit, and a temperature sensor that detects the outside air temperature. The opening degree of the variable throttle 10 is controlled based on the temperature to control the rotational speed of the hydraulic motor 5.

  For example, when the coolant temperature of the engine 1 becomes higher than the set value by the temperature sensor 15, the controller 12 increases the number of rotations of the hydraulic motor 5 to improve the cooling performance of the radiator 106. Specifically, the controller 12 increases the passage flow rate Q by increasing the opening area S of the variable throttle 10 and increases the rotation speed of the hydraulic motor 5.

  FIG. 5 is a functional block diagram illustrating processing contents in the calculation unit 121 of the controller 12. The calculation unit 121 includes a target rotation number calculation unit 121a, an opening area calculation unit 121b, and a control signal calculation unit 121c. In the target rotational speed calculation unit 121a, the target rotational speed of the cooling fan 4, that is, the target rotational speed of the hydraulic motor 5, based on the measured temperature Ts input from the temperature sensor 15, is a correlation map between the target rotational speed and the measured temperature Ts. Ask for. In the opening area calculation unit 121b, the opening area S of the variable diaphragm 10 is calculated based on the correlation map between the opening area S of the variable diaphragm 10 and the target rotation number and the target rotation number calculated by the target rotation number calculation unit 121a. Ask. The control signal calculation unit 121c calculates the drive current i based on the correlation map between the drive current (control signal) i of the solenoid of the variable diaphragm 10 and the opening area S and the opening area S calculated by the opening area calculation unit 121b. Calculate. Note that, in the target rotation speed calculation unit 121a, the opening area calculation unit 121b, and the control signal calculation unit 121c, a calculation formula may be used instead of the correlation map.

  The controller 12 outputs a drive current (control signal) i to the variable diaphragm 10 to change the opening area S of the variable diaphragm 10. When the opening area S of the variable throttle 10 is changed, the differential pressure ΔP of the variable throttle 10 changes from the set pressure Ps. Therefore, the regulator 11 changes the tilt of the hydraulic pump 2 according to the change of the differential pressure ΔP. When the tilt of the hydraulic pump 2 is changed and the discharge flow rate changes, the flow rate of excess oil flowing from the priority valve 8 into the variable throttle 10 changes, and the differential pressure ΔP is returned to the set pressure Ps.

  As described above, in the present embodiment, hydraulic oil from the hydraulic pump 2 is preferentially supplied to the steering circuit 3 by the priority valve 8, and surplus oil controls the rotation of the hydraulic motor 5. To be supplied.

  A variable throttle 10 having a variable throttle amount according to the target flow rate of the hydraulic motor 5 is provided in the oil passage between the priority valve 8 and the fan circuit 6, and the upstream pressure Pu, which is the inflow side pressure of the variable throttle 10, and the discharge. The discharge volume of the hydraulic pump 2 is adjusted by the regulator 11 so that the differential pressure ΔP = Pu−Pd with respect to the downstream pressure Pd, which is the side pressure, becomes a predetermined pressure.

  For this reason, when the flow rate of the hydraulic oil sent to the steering circuit 3 changes with the operation of the steering cylinders 105a and 105b, the regulator 11 increases the discharge volume of the hydraulic pump 2 so that the differential pressure ΔP of the variable throttle 10 becomes constant. adjust. As a result, the flow rate of the hydraulic oil passing through the variable throttle 10 becomes a flow rate corresponding to the throttle amount, and the excess oil flow rate from the priority valve 8 is not excessive or insufficient with respect to the target flow rate necessary for driving the hydraulic motor 5. Flow rate. That is, the hydraulic pump 2 can always output the sum of the flow rate required by the steering circuit 3 and the required flow rate of the fan circuit 6 given by the opening area S of the variable throttle 10. Therefore, conventionally, a part of the surplus oil is not used and energy is wasted, but in this embodiment, such wasted energy can be prevented.

  Since the required flow rate of the fan circuit 6 is proportional to the target rotational speed of the cooling fan 4 (that is, the hydraulic motor 5), the cooling fan 4 is supplied according to the target rotational speed while supplying the flow rate required by the steering circuit 3. Can be driven.

  Further, based on at least one of the temperature detected by the temperature sensor 15, that is, the outside air temperature, the cockpit temperature, the hydraulic oil temperature, and the coolant temperature, the target flow rate is calculated in the calculation unit 121, and the controller 12 The throttle amount of the variable throttle 10 is controlled based on the target flow rate. As a result, the cooling fan 4 is rotationally driven at an optimum rotational speed corresponding to the temperature detected by the temperature sensor 15, and even at that time, excess oil from the priority valve 8 is only necessary for the fan circuit 6. The amount of oil is adjusted by the regulator 11.

  FIG. 6 is a diagram showing a modification of the hydraulic control device shown in FIG. In the configuration shown in FIG. 2, the upstream pressure Pu and the downstream pressure Pd of the variable throttle 10 are input to the hydraulic control regulator 11 so that the regulator 11 is controlled by the hydraulic pressure.

  On the other hand, in the modification shown in FIG. 6, a pressure sensor 17 for detecting the upstream pressure Pu and a pressure sensor 18 for detecting the downstream pressure Pd are provided, and detection signals from the pressure sensors 17 and 18 are input to the controller 12. I made it. The controller 12 calculates the difference ΔP = Pu−Pd between the detected upstream pressure Pu and downstream pressure Pd by the calculation unit 121 and inputs a control signal based on the calculation result to the regulator 11. The regulator 11 in the modified example is an electronically controlled regulator, and adjusts the discharge volume of the hydraulic pump 2 based on the input control signal. The control of the hydraulic pump 2 based on the differential pressure ΔP is the same as the control described in FIG. 2, and the discharge volume is adjusted so that the differential pressure across the variable throttle 10 (difference ΔP) becomes a predetermined pressure.

  The present invention can also be applied to a work machine such as a wheeled hydraulic excavator having a steering circuit, a priority valve, and a fan circuit.

  In addition, the above description is an example to the last, and this invention is not limited to the said embodiment at all unless the characteristic of this invention is impaired. Moreover, you may use embodiment mentioned above and each modification individually or in combination.

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Hydraulic pump, 3 ... Steering circuit, 4 ... Cooling fan, 5 ... Hydraulic motor, 6 ... Fan circuit, 8 ... Priority valve, 10 ... Variable throttle, 11 ... Regulator, 12 ... Controller, 15 ... Temperature Sensors 17, 18 ... Pressure sensor, 31 ... Steering valve, 105a, 105b ... Steering cylinder, 121 ... Calculation unit, 121a ... Target rotational speed calculation unit, 121b ... Opening area calculation unit, 121c ... Control signal calculation unit, 200 ... Wheel loader (work machine), Pd ... downstream pressure, Ps ... set pressure, Pu ... upstream pressure

Claims (4)

A variable displacement hydraulic pump with a regulator to adjust the discharge volume;
A hydraulic motor that rotationally drives the cooling fan;
A fan circuit for controlling rotation of the hydraulic motor;
A steering circuit that controls the expansion and contraction of the steering cylinder;
Priority to supply hydraulic oil from the hydraulic pump to the steering circuit preferentially, and to supply excess oil to the fan circuit that is the difference between the hydraulic oil from the hydraulic pump and the hydraulic oil sent to the steering circuit A working machine with hydraulic control having a valve,
Provided in an oil passage connecting the priority valve and the fan circuit, comprising a variable throttle whose throttle amount is variable according to the target flow rate of the hydraulic motor,
The work machine is characterized in that the regulator adjusts the discharge volume of the hydraulic pump so that a differential pressure between an inflow side pressure and an exhaust side pressure of the variable throttle becomes a predetermined pressure. The work machine according to claim 1,
An engine for driving the hydraulic motor;
A calculation unit for calculating the target flow rate based on at least one of an outside air temperature, a temperature of hydraulic oil, a temperature of a coolant of the engine, and a temperature in a cockpit;
A work machine comprising: a controller that controls a throttle amount of the variable throttle based on a target flow rate calculated by the calculation unit. The work machine according to claim 1,
The regulator is a hydraulic device that adjusts the discharge volume with a differential pressure across the variable throttle, and adjusts the discharge volume so that the differential pressure across the front becomes a predetermined pressure. . The work machine according to claim 1,
A first pressure sensor for detecting an inflow side pressure of the variable throttle;
A second pressure sensor for detecting a discharge side pressure of the variable throttle;
A work machine comprising: a controller that causes the regulator to adjust the discharge volume based on pressure detected by the first and second pressure sensors.

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