JP5380236B2 - Hydraulic drive unit for wheel type construction machine - Google Patents

Description

  The present invention relates to a hydraulic drive device for a wheel-type construction machine such as a wheel loader provided with a brake valve and an accumulator that stores pressure oil supplied to the brake valve.

  FIG. 5 is a hydraulic circuit diagram showing a hydraulic drive device of a conventional wheel type construction machine, and FIG. 6 is a diagram showing a pressure accumulation characteristic obtained when the engine is started in the hydraulic drive device of the conventional wheel type construction machine shown in FIG. The vertical axis in FIG. 6 indicates the pressure stored in the accumulator, and the horizontal axis indicates the time until the allowable maximum pressure, that is, the cutout pressure, is stored in the accumulator.

  The prior art shown in FIG. 5 is a hydraulic drive device provided in a wheel-type construction machine such as a wheel loader. The engine 10 is started by an engine starter (not shown), and a hydraulic pump driven by the engine 10 such as a pilot pump 11 is provided. It has. Although not shown, the engine 10 is also connected to a main pump having a large capacity for supplying pressure oil to various actuators related to work. The wheel loader also includes a hydraulic brake device on its front and rear wheels, and this brake device is operated by a brake valve, which will be described later, according to the amount of operation when a brake pedal provided in the cab is depressed. By generating The brake device is a traveling brake valve 12 that is operated by pressure oil discharged from the pilot pump 11, a brake pedal 13 that operates the brake valve 12, and pressure oil supply that connects the pilot pump 11 and the brake valve 12. A pipe line, that is, a pipe line 30, a pipe line 31 connected to the pipe line 30, and a pipe line 32 and a pipe line 33 connected to the pipe line 31 are provided.

  Further, a first accumulator 14 for front wheel brake that stores the pressure oil supplied to the pipe line 32 included in the pressure oil supply pipe line, and a second accumulator for rear wheel brake that stores the pressure oil supplied to the pipe line 33. 15, a first check valve 16 that holds the pressure of the first accumulator 14, and a second check valve 17 that holds the pressure of the second accumulator 15. In addition, a throttle 18 is provided in the pipe line 31 portion located upstream of the first check valve 16 and the second check valve 17, and the pipe line 31 is located in the pipe line 31 portion located upstream of the throttle 18. A check valve 19 for holding pressure is provided.

  Also, a branch pipe 34 branched from the pipe 30 included in the pressure oil supply pipe, and provided in the branch pipe 34, when the pressure in the accumulators 14 and 15 drops, the corresponding accumulators 14 and 15 are accumulated. And an accumulator control valve 21 for controlling as described above. The throttle 18 described above compensates for the inflow of pressure oil into the branch pipe 34.

  The pressure accumulation control valve 21 has a first switching position 21a that is a closed position and a second switching position 21b that is an open position. Further, a pressure reducing valve 20 that operates in accordance with the pressure drop of the accumulators 14 and 15 is provided, and the pressure accumulation control valve 21 is switched by the operation of the pressure reducing valve 20. That is, when the pressure of the accumulators 14 and 15 is low, the opening amount of the pressure reducing valve 20 is small, and the force applied to the spool so as to oppose the spring force of the pressure accumulation control valve 21 is weaker than the spring force. Tends to be switched to the first switching position 21a side, which is the closed position, and the pressure oil of the pilot pump 11 guided to the pipeline 30 is supplied to the accumulators 14 and 15 via the pipelines 31, 32, 33. Are accumulated in the accumulators 14 and 15. On the contrary, when the pressure of the accumulators 14 and 15 is high, the opening amount of the pressure reducing valve 20 is increased, and the force applied to the spool so as to oppose the spring force of the pressure accumulation control valve 21 is stronger than the spring force. As a result, the spool tends to be switched to the second switching position 21b side which is the open position, and the inflow of the pressure oil of the pilot pump 11 guided to the pipeline 30 to the branch pipeline 34 side is promoted.

  In addition, a dedicated conduit connected to the branch conduit 34, for example, a steering operation conduit 35 that guides pressure oil to the steering operation device 22 and a relief valve 23 that regulates the pressure of the steering operation conduit 35 are provided.

In the related art configured as described above, when an engine starter (not shown) is operated at the time of starting the engine 10 from a state where the pressure accumulated in the accumulators 14 and 15 is zero, the engine is associated with a load related to the engine starter. 10 is not started immediately, but the pilot pump 11 rotates via the engine crankshaft and the like, and the pressure oil discharged from the pilot pump 11 is supplied to the pipes 30 and 31, the check valve 19, the throttle 18, and the reverse. The accumulators 14 and 15 are supplied via the stop valves 16 and 17, and the accumulators 14 and 15 are accumulated. During this time, the pressure reducing valve 20 is controlled to close in accordance with the low pressure of the accumulators 14 and 15, and the pressure accumulation control valve 21 tends to be switched to the first switching position 21a which is the closed position by the force of the spring. When the pressure of the accumulators 14 and 15 becomes the above-described allowable maximum pressure, that is, the cut-out pressure, the pressure reducing valve 20 is opened, and the pressure accumulation control valve 21 is set to the second switching position 21b which is the open position, and the pilot pump 11 The pressure oil is guided to the steering conduit 35 via the branch conduit 34 and the pressure accumulation control valve 21 and is returned to the tank via the relief valve 23 when the steering operation is not performed. Therefore, the load on the pilot pump 11 is reduced, and the load on the engine starter is reduced accordingly, and the engine 10 is started.

  After the engine 10 is started, traveling is performed. When the brake pedal 13 is depressed during this traveling, the brake valve 12 is activated. At this time, the pressure of the accumulators 14 and 15 is supplied to the brake valve 12, and the front and rear wheels are braked. As described above, the pressure of the accumulators 14 and 15 is set in advance with the operation of the brake valve 12 or after the pressure accumulation from the cut-out pressure to the cut-out pressure of the accumulators 14 and 15 from the cut-out pressure. When the pressure decreases to the predetermined pressure that is the accumulated pressure starting pressure, that is, the cut-in pressure, the pressure accumulation control valve 21 is slightly switched in the direction of the first switching position 21a that is the closed position, and the pressure discharged from the pilot pump 11 A part of the oil is supplied to the accumulators 14 and 15 through the pipe line 31, the check valve 19, the throttle 18, the pipe lines 32 and 33, and the check valves 16 and 17, and pressure oil is supplied to these accumulators 14 and 15. Accumulated. The remainder of the pressure oil discharged from the pilot pump 11 is guided to the steering operation line 35 via the branch line 34 and the pressure accumulation control valve 21. Therefore, even when the pressure is accumulated from the cut-in pressure to the cut-out pressure of the above-described accumulators 14 and 15 during the operation, the flow of the pressure oil to the steering operation line 35 can be secured by the throttle 18. Stable operation of the steering operation device 22 becomes possible.

  Note that, as a hydraulic drive device that includes a brake valve and an accumulator that accumulates pressure oil supplied to the brake valve in a wheel-type construction machine, there is a conventional one disclosed in Patent Document 1.

JP 2002-89506 A

  In the prior art shown in FIG. 5 described above, in order to realize the operation of the steering operation device 22 by diverting the pressure oil discharged from the pilot pump 11 to the steering operation line 35 via the branch line 34. The diaphragm 31 is provided in the path 31. The opening amount of the diaphragm 18 is uniquely set to ensure stable operation of the steering operation device 22.

  By the way, when the engine 10 is started in a state where the pressures of the accumulators 14 and 15 are zero, the pilot pump 11 is rotated via the engine crankshaft or the like by operating the engine starter as described above, and the accumulator. 14 and 15 start accumulating, but when the viscous resistance of the hydraulic oil is high in a low temperature environment, the load of the pilot pump 11 is large, and this large load is applied to the engine starter. As shown, it takes time until the above-described cutout pressure is accumulated in the accumulators 14 and 15, and for this reason, the engine 11 may not be started easily. That is, in the low temperature environment, in the configuration of the prior art shown in FIG. 5, the engine 11 is started for a relatively long time from the state where the pressure of the accumulators 14 and 15 in FIG. 6 is zero to the cutout pressure. There is a problem that the startability of the engine 10 tends to deteriorate.

  In consideration of improving the startability of the engine 10 in a low temperature environment, the startability of the engine 10 is improved if the opening amount of the diaphragm 18 is set large. At the time of accumulating accompanying the pressure drop of the accumulators 14 and 15 during the subsequent normal operation, the pressure oil is smoothly supplied to the accumulators 14 and 15, but the pressure guided to the steering pipe 35 via the branch pipe 34. A situation where the oil is reduced occurs, and the steering operation becomes unstable. As described above, in the prior art shown in FIG. 5, the opening amount of the throttle 18 must be set in consideration of the stability of the steering operation when accumulators 14 and 15 are accumulating during work. As a result, there is a problem that it is difficult to ensure good startability of the engine 10.

The present invention has been made from the above-described prior art, and its purpose is to accumulator relatively quickly when starting an engine in a low-temperature environment where the pressure accumulated in the accumulator is zero. the it is possible for accumulating supplying pressurized oil, when the accumulator with the accumulator pressure drop after starting the engine, the required flow rate of the branch conduit a wheeled Ru can be diverted to a dedicated line through construction equipment It is in providing the hydraulic drive device.

In order to achieve this object, a hydraulic drive device for a wheel type construction machine according to the present invention is provided in the wheel type construction machine, and is discharged from the engine, a hydraulic pump driven by the engine, and the hydraulic pump. A brake valve that is operated by pressure oil, a pressure oil supply line that connects the hydraulic pump and the brake valve, an accumulator that stores pressure oil supplied to the pressure oil supply line, and a pressure of the accumulator A check valve, a branch line branched from the pressure oil supply line, a pressure accumulation control valve that is provided in the branch line, and that controls the accumulator to accumulate pressure when the accumulator drops in pressure, and In a hydraulic drive device for a wheel-type construction machine having a dedicated pipeline connected to the branch pipeline, below the branch point between the pressure oil supply pipeline and the branch pipeline The pressure oil supply line portion located at the pressure oil supply line portion located upstream of the check valve that holds the pressure of the accumulator is accumulated in the pressure after the start of the engine. When starting the engine in a state where the pressure does not reach the predetermined pressure corresponding to the start pressure, control is performed so as to increase the flow rate of the pressure oil flowing through the pressure oil supply pipe portion, and when the pressure of the accumulator is equal to or higher than the predetermined pressure, It is characterized by having a flow rate control valve for controlling the flow rate of the pressure oil flowing through the pressure oil supply pipe line portion to be reduced.

  In the present invention configured as described above, when the engine is started in a low-temperature environment and the pressure accumulated in the accumulator is zero, the engine is operated by applying a load along with the operation of the engine starter. Although not started, the hydraulic pump rotates and accumulates pressure in the accumulator. At this time, when the pressure of the accumulator is less than a predetermined pressure corresponding to the pressure for starting accumulation after the engine is started, the flow rate of the pressure oil flowing through the pressure oil supply pipe portion for supplying the pressure oil to the accumulator is controlled by the flow control valve. Controlled to increase. When the pressure of the accumulator becomes equal to or higher than a predetermined pressure, the flow rate control valve is controlled so that the flow rate of the pressure oil flowing through the pressure oil supply pipe portion for supplying the pressure oil to the accumulator becomes smaller than before. As a result, the time from when the pressure of the accumulator reaches a predetermined pressure until it reaches the maximum allowable pressure tends to take a little time. However, during the period from when the accumulator pressure reaches zero to the predetermined pressure, the flow rate of the pressure oil flowing through the pressure oil supply conduit is increased by the flow rate control valve as described above. Also, pressure oil can be quickly supplied to the accumulator to accumulate pressure. Accordingly, the load on the hydraulic pump can be reduced in a short time, thereby reducing the load on the engine starter and starting the engine in a relatively short time.

  In addition, during the work after the engine is started, when the pressure of the accumulator drops from the maximum allowable pressure to the accumulated pressure after starting the engine, that is, to a predetermined pressure, due to the operation of the brake valve by operating the brake pedal or over time, By controlling the flow rate control valve, a part of the hydraulic oil of the hydraulic pump is supplied to the accumulator with a relatively low flow rate and is accumulated in the accumulator. During this time, the remainder of the hydraulic oil of the hydraulic pump is supplied to the dedicated line via the branch line. That is, the required flow rate can be diverted to the dedicated pipeline via the branch pipeline.

  Further, the present invention is the above invention, wherein the flow rate control valve is controlled according to the pressure of the pressure oil supply line portion located between the check valve that holds the pressure of the accumulator and the flow rate control valve. It is characterized by being made up of.

  Further, the present invention is characterized in that, in the above invention, the flow control valve is controlled in accordance with an external pressure.

  Further, in the present invention according to the above invention, the wheel-type construction machine includes a wheel loader or a wheel-type hydraulic excavator, includes a brake pedal for operating the brake valve, the hydraulic pump includes a pilot pump, and the branch pipe. The dedicated pipe connected to the road is characterized by comprising a steering operation pipe for guiding pressure oil to the steering operation device.

The present invention relates to a pressure oil supply pipe portion that is located downstream of a branch point between a pressure oil supply pipe and a branch pipe that supplies the pressure of a hydraulic pump to a brake valve, and includes a check that maintains the pressure of an accumulator. When starting the engine in a state where the pressure of the accumulator does not reach a predetermined pressure corresponding to the pressure for starting accumulator after starting the engine , the pressure flowing through the pressure oil supply line portion located in the pressure oil supply line portion located upstream of the valve Since the flow rate of the oil is controlled so that the flow rate of the pressure oil flowing through the pressure oil supply line is reduced when the pressure of the accumulator is equal to or higher than the predetermined pressure, When starting an engine in an environment where the pressure accumulated in the accumulator is zero, pressure oil can be supplied to the accumulator relatively quickly. In this way, the engine startability can be improved compared to the conventional case, and the necessary flow rate is diverted to the dedicated line via the branch line when accumulator pressure drops after the engine starts. Thus, the operation with the pressure oil guided to the dedicated pipe line can be stably performed. That is, according to the present invention, it is possible to ensure both good engine startability and good operability by the pressure oil guided to the dedicated pipeline, and it is possible to realize a hydraulic drive device that is more reliable than before.

It is a side view showing a wheel loader mentioned as an example of a wheel type construction machine provided with one embodiment of a hydraulic drive concerning the present invention. It is a hydraulic circuit diagram which shows one Embodiment of the hydraulic drive device of this invention shown by the wheel loader shown in FIG. It is a figure which shows the pressure accumulation characteristic based on this embodiment obtained at the time of engine starting. It is a figure which shows the pressure accumulation characteristic which concerns on this embodiment obtained during the work after engine starting. It is a hydraulic circuit diagram which shows the hydraulic drive device of the conventional wheel type construction machine. It is a figure which shows the pressure accumulation characteristic acquired at the time of engine starting in the hydraulic drive device of the conventional wheel type construction machine shown in FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a hydraulic drive device for a wheel type construction machine according to the present invention will be described with reference to the drawings.

  FIG. 1 is a side view showing a wheel loader cited as an example of a wheel-type construction machine provided with an embodiment of a hydraulic drive device according to the present invention.

  The wheel type construction machine provided with the hydraulic drive device according to the present embodiment is, for example, the wheel loader shown in FIG. 1, and a main body 1 having front and rear tires 1 a and 1 a and a driver's cab 1 b, An arm 2 is attached to the main body 1 so as to be pivotable in the vertical direction, and a bucket 3 is attached to the tip of the arm 2 and can be pivoted in the vertical direction to be used for excavation work such as earth and sand.

  FIG. 2 is a hydraulic circuit diagram showing one embodiment of the hydraulic drive device of the present invention shown in the wheel loader shown in FIG. 1, and FIG. 3 is a diagram showing pressure accumulation characteristics according to this embodiment obtained when the engine is started. FIG. 4 is a diagram illustrating pressure accumulation characteristics according to the present embodiment obtained during work after engine startup. The vertical axis in FIG. 3 indicates the pressure stored in the accumulator, and the horizontal axis indicates the time until the predetermined pressure, that is, the cut-in pressure is stored in the accumulator, and the allowable maximum pressure, that is, the cut-out pressure, until the accumulator is stored. Shows time. The vertical axis in FIG. 4 indicates the pressure accumulated in the accumulator after the engine is started, that is, the pressure from the cut-in pressure to the cut-out pressure, and the horizontal axis indicates the cut when accumulating with the accumulator pressure drop. The time required from the in pressure to the cut out pressure is shown.

  The basic configuration of the hydraulic drive apparatus according to this embodiment provided in the wheel loader shown in FIG. 1 is the same as that shown in FIG. That is, although the description overlaps with that shown in FIG. 5, the hydraulic drive device according to the present embodiment also includes an engine 10 that is activated by an engine starter (not shown) and a hydraulic pump that is driven by the engine 10 as shown in FIG. 2. For example, a pilot pump 11 is provided. Although not shown, the engine 10 is also connected to a main pump having a large capacity for supplying pressure oil to various actuators related to work. Further, a traveling brake valve 12 that is operated by pressure oil discharged from the pilot pump 11, a brake pedal 13 that is disposed in the cab 1b shown in FIG. 1 and operates the brake valve 12, the pilot pump 11 and the brake A pressure oil supply line communicating with the valve 12, that is, a line 30, a line 31 connected to the line 30, and a line 32 and a line 33 connected to the line 31 are provided. ing.

  Further, the pressure oil supplied to the pipe line 32 included in the pressure oil supply pipe line is stored, and the first accumulator 14 provided in connection with the braking of the front tire 1a and the pressure oil supplied to the pipe line 33 are stored. A second accumulator 15 that is provided in association with the braking of the rear tire 1a, a first check valve 16 that holds the pressure of the first accumulator 14, and a second reverse that holds the pressure of the second accumulator 15. And a stop valve 17. Further, a check valve 19 for holding the pressure of the pipe line 31 is provided in the pipe line 31 portion.

  Also, a branch pipe 34 branched from the pipe 30 included in the pressure oil supply pipe, and provided in the branch pipe 34, when the pressure in the accumulators 14 and 15 drops, the corresponding accumulators 14 and 15 are accumulated. And an accumulator control valve 21 for controlling as described above.

  The pressure accumulation control valve 21 has a first switching position 21a that is a closed position and a second switching position 21b that is an open position. Further, a pressure reducing valve 20 that operates in accordance with the pressure drop of the accumulators 14 and 15 is provided, and the pressure accumulation control valve 21 is switched by the operation of the pressure reducing valve 20. That is, when the pressure of the accumulators 14 and 15 is low, the opening amount of the pressure reducing valve 20 is small, and the force applied to the spool so as to oppose the spring force of the pressure accumulation control valve 21 is weaker than the spring force. Tends to be switched to the first switching position 21a side, which is the closed position, and the pressure oil of the pilot pump 11 guided to the pipeline 30 is supplied to the accumulators 14 and 15 via the pipelines 31, 32, 33. Are accumulated in the accumulators 14 and 15. On the contrary, when the pressure of the accumulators 14 and 15 is high, the opening amount of the pressure reducing valve 20 is increased, and the force applied to the spool so as to oppose the spring force of the pressure accumulation control valve 21 is stronger than the spring force. As a result, the spool tends to be switched to the second switching position 21b side which is the open position, and the inflow of the pressure oil of the pilot pump 11 guided to the pipeline 30 to the branch pipeline 34 side is promoted.

  In addition, a dedicated conduit connected to the branch conduit 34, for example, a steering operation conduit 35 that guides pressure oil to the steering operation device 22 and a relief valve 23 that regulates the pressure of the steering operation conduit 35 are provided. About these structures, it is equivalent to what was shown in FIG. 5 mentioned above.

The present embodiment differs from that shown in FIG. 5 described above in that it is located downstream of the branch point between the pipeline 30 included in the pressure oil supply pipeline and the branch pipeline 34, that is, downstream of the check valve 19. The pressure of the accumulators 14 and 15 is included in the pipe line 31 portion included in the pressure oil supply pipe line that is located upstream of the check valves 16 and 17 that hold the pressure of the accumulators 14 and 15. When the engine 10 is started in a state that does not satisfy the predetermined pressure corresponding to the pressure for starting pressure accumulation after the engine 10 is started, that is, the cut-in pressure shown in FIG. 3, the flow rate of the pressure oil flowing through the pipeline 31 is increased. A flow rate control valve 40 is provided for controlling so that the flow rate of the pressure oil flowing through the pipe line 31 is reduced when the pressure of the accumulators 14 and 15 is not less than a predetermined pressure, that is, not less than the cut-in pressure. It is.

The flow rate control valve 40 includes, for example, a valve that is controlled in accordance with the pressure in the portion of the pipe line 31 positioned between the check valves 16 and 17 that hold the pressure of the accumulators 14 and 15 and the flow rate control valve 40. ing. In the flow control valve 40, when the pressure of the accumulators 14 and 15 is low, the force applied to the spool so as to oppose the spring force of the flow control valve 40 is weaker than the spring force. the first tends to be switched to the switching position 40 a side, the pressure oil conduit 31, 32 and 33 of the pilot pump 11 guided to the conduit 31, and an accumulator 14 via a check valve 16, 17 is, 15 and accumulated in these accumulators 14 and 15. On the contrary, when the pressure of the accumulators 14 and 15 is high, the force applied to the spool so as to oppose the spring force of the flow control valve 40 becomes stronger than the spring force, whereby the spool has the second throttle. tends to be switched to the switching position 40 b side, flows into the branch conduit 34 of the pressure oil of the pilot pump 11 is guided to the conduit 30 is promoted. The opening amount of the throttle provided at the second switching position 40b of the flow control valve 40 is set to a size equivalent to, for example, the opening amount of the throttle 18 shown in FIG.

  The hydraulic drive device according to the present embodiment configured as described above is a pressure accumulated in the accumulators 14 and 15 in a situation where, for example, the viscosity resistance of the hydraulic oil discharged from the pilot pump 11 is increased in a low temperature environment. When the engine 10 is started in a state where the engine is zero, the engine 10 is kept in a state in which it is not started due to a load in accordance with the operation of an engine starter (not shown). The pump 11 rotates and pressure is accumulated in the accumulator.

  At this time, when the pressure of the accumulators 14 and 15 is less than a predetermined pressure corresponding to the pressure for starting accumulation after the engine 10 is started, that is, the cut-in pressure shown in FIG. The force applied to the spool is weaker than the spring force, so that the spool is switched to the first switching position 40a, which is the open position, and the flow control valve 40 is used to supply pressure oil to the accumulators 14 and 15. Control is performed so that the flow rate of the pressure oil flowing through the supply pipeline portion, that is, the pipeline 31 portion is increased.

  When the accumulator pressure exceeds the predetermined pressure, that is, the cut-in pressure or higher, the force applied to the spool so as to oppose the spring force of the flow control valve 40 becomes stronger than the spring force. The flow control valve 40 controls the flow rate of the pressure oil flowing through the portion of the pipeline 31 that supplies the pressure oil to the accumulators 14 and 15 to be smaller than before. . As a result, as shown in FIG. 3, there is a tendency that it takes a little time from when the pressure of the accumulators 14 and 15 reaches the cut-in pressure until the maximum allowable pressure, that is, the cut-out pressure.

  However, since the flow rate of the pressure oil flowing through the pipe 31 is increased by the flow rate control valve 40 as described above until the pressure of the accumulators 14 and 15 reaches the cut-in pressure, the low temperature environment Even in such a case, pressure oil can be quickly supplied to the accumulators 14 and 15 to accumulate pressure. Accordingly, the load on the pilot pump 11 can be reduced in a short time, thereby reducing the load on the engine starter, and the engine 10 can be started in a relatively short time.

  Further, during the operation after the engine 10 is started, the pressure of the accumulators 14 and 15 is changed from the cutout pressure to the engine by the operation of the brake valve 12 by the depression operation of the brake pedal 13 or with time, as shown in FIG. When the pressure accumulation start pressure after the start-up, that is, the cut-in pressure is lowered, a part of the pressure oil of the pilot pump 11 is relatively controlled by the control of the flow rate control valve 40 held at the second switching position 40b having the throttle. The accumulators 14 and 15 are supplied to the accumulators 14 and 15 with a reduced flow rate, and are accumulated in the accumulators 14 and 15. During this time, the remainder of the pressure oil of the pilot pump 11 is supplied to the steering operation line 35 via the branch line 34. That is, the flow rate required for the operation of the steering operation device 22 can be stably diverted to the steering operation line 35 via the branch line 34.

  In a normal environment where the environmental temperature is relatively high, the viscous resistance of the hydraulic oil discharged from the pilot pump 11 is small, and the cutout pressure tends to be quickly stored in the accumulators 14 and 15. Therefore, the cut-out pressure is accumulated in the accumulators 14 and 15 after the engine starter (not shown) is operated, and the time until the load of the pilot pump 11 becomes light and the engine 10 starts is shorter than that in the low temperature environment. It takes time.

  According to the present embodiment configured as described above, since the flow control valve 40 is provided, as described above, in a low temperature environment, the pressure accumulated in the accumulators 14 and 15 is zero. When the engine 10 is started, pressure oil can be supplied and stored in the accumulators 14 and 15 relatively quickly, whereby the startability of the engine 10 can be improved, and the accumulator 14 after the engine 10 is started. , 15 during pressure accumulation, the required flow rate can be diverted to the steering operation line 35 via the branch line 34, whereby the steering operation device 22 can be operated stably. That is, the present embodiment can ensure both good startability of the engine 10 and good steering operability by the pressure oil guided to the steering operation conduit 35, and realize a highly reliable hydraulic drive device. it can.

  In the above embodiment, the flow control valve 40 is controlled in accordance with the pressure in the portion of the pipe line 31 positioned between the check valves 16 and 17 holding the pressure of the accumulators 14 and 15 and the flow control valve 40. However, the present invention is not limited to such a configuration, and the flow control valve 40 may be configured to be switched by an external pressure. For example, a detector that detects the cut-in pressure of the accumulators 14 and 15, and an external pressure supply means that can supply an external pressure for switching the flow control valve 40 to the second switching position 40 b to the control unit of the flow control valve 40. When the detector described above detects the cut-in pressure, the external pressure is supplied to the control unit of the flow control valve 40 by the external pressure supply means, and the flow control valve 40 is switched to the second switching position 40b. You may make it into a structure. What was comprised in this way can also obtain the effect similar to the said embodiment.

  Moreover, although the said embodiment is provided in a wheel loader, this invention is not restricted to providing in a wheel loader in this way, A wheel, a brake valve, this brake like a wheel type hydraulic excavator etc. The present invention is applicable to various wheel-type construction machines having an accumulator that supplies pressure oil to the valve.

1 Main Body 1a Tire 2 Arm 3 Bucket 10 Engine 11 Pilot Pump (Hydraulic Pump)
DESCRIPTION OF SYMBOLS 12 Brake valve 13 Brake pedal 14 1st accumulator 15 2nd accumulator 16 1st check valve 17 2nd check valve 19 Check valve 20 Pressure reducing valve 21 Accumulation control valve 21a 1st switching position 21b 2nd switching position 22 Steering operation Device 23 Relief valve 30 Pipe line (pressure oil supply line)
31 pipeline (pressure oil supply pipeline)
32 pipeline (pressure oil supply pipeline)
33 pipeline (pressure oil supply pipeline)
34 Branch pipeline 35 Steering operation pipeline (dedicated pipeline)
40 Flow control valve 40a First switching position 40b Second switching position

Claims (4)

An engine, a hydraulic pump driven by the engine, a brake valve operated by pressure oil discharged from the hydraulic pump, and a pressure oil communicating the hydraulic pump and the brake valve. A supply line, an accumulator for storing the pressure oil supplied to the pressure oil supply line, a check valve for holding the pressure of the accumulator, a branch line branched from the pressure oil supply line, A hydraulic drive device for a wheel-type construction machine, which is provided in a branch pipe and includes a pressure accumulation control valve that controls to accumulate pressure in the accumulator when a pressure drop of the accumulator, and a dedicated pipe connected to the branch pipe In
Pressure oil supply located upstream of the check valve that holds the pressure of the accumulator, the pressure oil supply pipe portion located downstream of the branch point between the pressure oil supply pipe and the branch pipe When starting the engine in a state where the pressure of the accumulator is less than a predetermined pressure corresponding to the pressure for starting pressure accumulation after starting the engine, the flow rate of the pressure oil flowing through the pressure oil supply conduit increases. A wheel-type construction characterized by comprising a flow rate control valve for controlling the flow rate of the pressure oil flowing through the pressure oil supply line portion when the pressure of the accumulator is equal to or higher than a predetermined pressure. Hydraulic drive device for the machine. In the hydraulic drive device of the wheel type construction machine according to claim 1,
The flow rate control valve is configured to be controlled in accordance with the pressure of the pressure oil supply pipe portion located between the check valve that holds the pressure of the accumulator and the flow rate control valve. Hydraulic drive unit for wheel type construction machinery. In the hydraulic drive device of the wheel type construction machine according to claim 1,
The hydraulic control apparatus for a wheel type construction machine, wherein the flow control valve is controlled according to an external pressure. In the hydraulic drive device of the wheel type construction machine according to any one of claims 1 to 3,
The wheel-type construction machine is composed of a wheel loader or a wheel-type hydraulic excavator,
A brake pedal for operating the brake valve;
The hydraulic pump consists of a pilot pump,
The hydraulic drive device for a wheel-type construction machine, wherein the dedicated conduit connected to the branch conduit comprises a steering operation conduit that guides pressure oil to the steering operation device.

Images