JP2005096704A - Hydraulic drive device for traveling construction machine - Google Patents

Abstract

An object of the present invention is to drive a left and right traveling motor by independently supplying pressure oil from two hydraulic pumps, and to reliably perform straight traveling correction of traveling meanders without replacing large equipment such as a hydraulic pump and a traveling motor. To be able to do.
A meandering correction circuit comprising a valve device and a travel detection pilot circuit is provided in pressure oil supply pipelines. When the pilot control pressure is introduced to the pressure receiving portion 23b, the valve device 23 is switched from the shut-off position to the throttle communication position. The travel detection pilot circuit 25 has on / off valves 35 and 36 for controlling the shutoff and communication of the first pilot pipe 34. When the direction switching valves 6 and 7 are switched from the neutral position to the operating position, the on / off valves 35 and 36 are opened. The pilot control pressure generated on the upstream side of the open / close valves 35 and 36 is guided to the pressure receiving portion 23b of the valve device 23 through the second pilot pipe line 37, and the valve device 23 is set to the throttle communication position. Switch.
[Selection] Figure 1

Description

  The present invention relates to a hydraulic drive device for a traveling construction machine such as a hydraulic excavator, and more particularly to a hydraulic drive device for a traveling construction machine that supplies pressure oil to left and right traveling motors independently from two hydraulic pumps.

  In a traveling construction machine such as a hydraulic excavator, usually, left and right traveling motors are provided, and pressure oil is supplied to the left and right traveling motors independently from two hydraulic pumps, and is also supplied to the two traveling motors. The flow of pressure oil is controlled by two directional control valves. The two directional control valves are of an open center type and constitute an open circuit. This type of hydraulic drive is described in, for example, Japanese Patent Application Laid-Open No. 8-291539.

JP-A-8-291539

  However, the above prior art has the following problems.

  In the hydraulic drive device of a traveling construction machine, the rated traveling speed is determined by the discharge flow rate of the hydraulic pump and the capacity of the traveling motor. In the design specification, the specifications of the two hydraulic pumps and the left and right traveling motors are set to the same specification. In this case, the actual speed difference (rotational speed difference) between the left and right traveling motors is affected by the performance of the hydraulic pump and the efficiency of the traveling motor. In actual products, there are variations such as machining errors, and there are variations in the yielding performance of the hydraulic pump, the efficiency of the travel motor, and the like, and a speed difference occurs between the left and right travel motors during straight travel operation. When a speed difference occurs between the left and right travel motors, the vehicle body meanders and cannot perform the intended straight travel.

  In response to such problems, current countermeasures depend on replacement of a hydraulic pump or replacement of a traveling motor. However, hydraulic pumps and traveling motors are large devices, and replacement of these requires excessive costs and work. Also, the certainty was low.

  An object of the present invention is to supply the right and left traveling motors with pressure oil independently from the two hydraulic pumps to perform traveling, so that the traveling meander can be surely performed without exchanging large equipment such as the hydraulic pump and traveling motor. It is an object of the present invention to provide a hydraulic drive device for a traveling construction machine that can perform straight-ahead correction.

  (1) In order to achieve the above object, the present invention provides a flow of pressure oil supplied to the left and right traveling motors from the first and second hydraulic pumps, the left and right traveling motors, and the first and second hydraulic pumps. In a hydraulic drive system for a traveling construction machine, comprising first and second directional switching valves for controlling the pressure, first pressure oil is supplied from the first and second hydraulic pumps to the first and second directional switching valves. In addition, a meandering correction circuit for communicating the first and second pipes via a throttle portion is provided in the middle of the second pipe.

  By providing a meandering correction circuit that communicates the first and second pipes via the throttle portion in this way, there are variations in the performance of the first and second hydraulic pumps and the efficiency of the left and right traveling motors. Even if there is a side (high pressure side) and a driven side (low pressure side), pressure oil on the high pressure side flows into the low pressure side, so that a speed difference (rotational speed difference) between the left and right travel motors is prevented, and travel meandering Can be corrected straight ahead.

  (2) In the above (1), preferably, the meandering correction circuit cuts off the communication between the first and second pipes and the throttle communication position where the first and second pipes communicate with each other through the throttle part. And a switching operation means for switching the valve device from the blocking position to the throttle communicating position in conjunction with the operation of the first and second directional control valves.

  Accordingly, when the first and second directional control valves are operated with the intention of traveling straight, the valve device is switched from the shut-off position to the throttle communication position, so the first and second pipe lines communicate with each other via the throttle portion, It is possible to correct straight travel of the running meander.

  In addition, when the first and second directional control valves are operated with the intention of steering (curvature) during travel, the intentional difference in the flow rate supplied to the left and right travel motors is invalid due to the setting of the opening area of the throttle part Therefore, steering can be performed reliably.

  Further, since the first and second pipe lines communicate with each other through the throttle portion, when the crawler of the traveling device is made of rubber rubber, it is possible to reduce vehicle body vibration that occurs in the operation of changing the direction of the vehicle body.

  (3) In the above (1), preferably, the meandering correction circuit has an adjusting means for adjusting an opening area of the aperture portion.

  By making the aperture area of the throttle portion adjustable in this way, the meandering correction flow rate can be adjusted. Further, since the adjustment of the meandering correction flow rate is performed by the adjusting means, even when the setting of the opening area of the throttle portion is inappropriate, it is not necessary to replace the throttle element. Further, the meandering correction circuit can be easily calibrated at the time of product shipment.

  (4) Further, in the above (1), preferably, the opening area of the throttle portion is such that the throttle portion passes the flow rate of the pressure oil supplied from the first and second hydraulic pumps to the left and right traveling motors. The flow rate ratio is set to be 2 to 3%.

  As a result, it is possible to secure the passage flow rate of the throttle part necessary for straight-line correction with respect to the load pressure difference between the left and right traveling motors during straight-ahead correction, and the steering part flow rate with respect to the maximum load pressure difference assumed during steering invalidates the steering. Therefore, the necessary steering can be performed appropriately.

  According to the present invention, in a hydraulic drive device that travels by independently supplying pressure oil to the left and right traveling motors from two hydraulic pumps, traveling reliably without replacement of a large device such as a hydraulic pump or a traveling motor. The meandering correction of meandering can be performed.

  Further, according to the present invention, when the crawler of the traveling device is made of rubber rubber, it is possible to reduce vehicle body vibration that occurs in an operation of changing the direction of the vehicle body.

  Furthermore, according to the present invention, it becomes possible to adjust the meandering correction flow rate, and the adjustment of the meandering correction flow rate is performed by the adjusting means. However, it is not necessary to replace the aperture element. Further, the meandering correction circuit can be easily calibrated at the time of product shipment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In these embodiments, the present invention is applied to a hydraulic excavator as a construction machine.

  FIG. 1 is a diagram showing a hydraulic drive apparatus according to the first embodiment of the present invention. In FIG. 1, the hydraulic drive apparatus according to the present embodiment includes a pump apparatus 3 having two hydraulic pumps 1 and 2, left and right traveling motors 4 and 5, and two hydraulic pumps 1 and 2. Two directional control valves 6 and 7 for controlling the flow of pressure oil supplied to the traveling motors 4 and 5 are provided. When the direction switching valves 6 and 7 are switched, the pressure oil discharged from the discharge ports of the two hydraulic pumps 1 and 2 is the meter-in flow path (inflow side flow path) 6a1 or 6a2 of the direction switching valves 6 and 7; The return oil from the traveling motors 4 and 5 is guided to the respective traveling motors 4 and 5 via 7a1 or 7a2, and the meter-out flow paths (outflow-side flow paths) 6b1, 6b2 or 7b1, It is returned to the tank via 7b2.

  The hydraulic pumps 1 and 2 are of a variable displacement type, and by controlling the tilt position, the displacement (displacement volume) can be changed and the discharge flow rate can be increased or decreased. A horsepower control actuator (not shown) is provided as a control means for the hydraulic pumps 1 and 2, and the tilt position is controlled so as to reduce the flow rate accordingly when the discharge pressure of the hydraulic pumps 1 and 2 rises.

  The direction switching valves 6 and 7 are of an open center type (center bypass type) and have center bypass passages 6c and 7c located in the center bypass lines 8 and 9, respectively. When the directional control valves 6 and 7 are in the neutral position (non-operating position), the center bypass flow paths 6c and 7c are fully opened, the meter-in flow paths 6a1 and 6a2; 7a1 and 7a2 are fully closed, and the hydraulic pumps 1 and 2 Is discharged to the tank via pressure oil supply pipes 11 and 12 connected to the discharge ports of the hydraulic pumps 1 and 2, center bypass lines 8 and 9, center bypass flow paths 6 c and 7 c, and tank lines 13 and 14. Returned. When the direction switching valves 6 and 7 are switched from the neutral position to the operating position, the center bypass flow paths 6c and 7c reduce the opening area according to the amount of operation, and the maximum switching position of the direction switching valves 6 and 7 (full Fully closed immediately before the stroke position. On the other hand, the meter-in flow paths 6a1 or 6a2; 7a1 or 7a2 of the direction switching valves 6 and 7 increase the opening area according to the operation amount of the direction switching valves 6 and 7, and the maximum switching position (full stroke) of the direction switching valves 6 and 7 is reached. Fully open immediately before (position). As a result, a flow rate corresponding to the operation amount of the direction switching valves 6 and 7 is supplied to the traveling motors 4 and 5, and the rotational speed of the traveling motors 4 and 5 is controlled. The pressure oil supply pipes 11 and 12 are provided with main relief valves 15 and 16 as safety means for regulating the maximum discharge pressure of the hydraulic pumps 1 and 2.

  A meandering correction circuit 20 is provided in the pressure oil supply pipes 11 and 12. This meandering correction circuit 20 detects the operation of the valve device 23 installed in the pipelines 21 and 22 connecting the pressure oil supply pipelines 11 and 12 and the direction switching valves 6 and 7 and switches the valve device 23. A travel detection pilot circuit 25 is provided.

  The valve device 23 is a two-position switching valve having a shut-off position and a throttle communication position. The valve device 23 shuts off the communication between the pipelines 11 and 12 at the shut-off position, and communicates the pipelines 11 and 12 via the throttle portion 23a at the throttle communication position. Let Further, the valve device 23 is a hydraulic switching valve, and when the pilot control pressure is not guided to the pressure receiving portion 23b, the valve device 23 is held at the illustrated cut-off position by the spring 23c, and the travel detection pilot circuit 25 applies the pilot control pressure to the pressure receiving portion 23b. Is led to switch from the shut-off position to the aperture communication position.

  The travel detection pilot circuit 25 includes a pilot pump 31, a pilot relief valve 32 and a fixed throttle 33 that keep the discharge pressure of the pilot pump 31 constant, and a first pilot pipe line 34 that connects the downstream side of the fixed throttle 33 to the tank. The on / off valves 35 and 36 for controlling the shutoff / communication of the first pilot pipe 34 and the portion 34a between the fixed throttle 33 and the on / off valve 35 of the first pilot pipe 34 are connected to the pressure receiving portion 23b of the valve device 23. And a second pilot pipeline 37. The on-off valves 35 and 36 can be switched in conjunction with the operation of the direction switching valves 6 and 7, and when the direction switching valves 6 and 7 are in the neutral position, the on-off valves 35 and 36 are in the open position, and the direction switching valve 6 , 7 are switched from the neutral position to the operating position, the on-off valves 35, 36 are switched from the open position to the closed position. When the on-off valves 35 and 36 are in the open position, the downstream side of the fixed throttle 33 communicates with the tank, so that no pilot control pressure is generated in the pipe portion 34a on the upstream side of the on-off valves 35 and 36, and the valve device 23 At the blocking position, the communication between the pressure oil supply pipes 11 and 12 is blocked. On the other hand, when the on-off valves 35 and 36 are switched from the open position to the closed position, a pilot control pressure is generated in the pipe portion 34 a upstream of the on-off valves 35 and 36, and this pilot control pressure is generated by the second pilot pipe line 37. Therefore, the valve device 23 is switched to the throttle communication position, and the pressure oil supply pipes 11 and 12 communicate with each other via the throttle portion 23a of the valve device 23.

  FIG. 2 shows the external appearance of the hydraulic excavator. The hydraulic excavator includes a lower traveling body 100, an upper swing body 101, and a front work machine 102. The lower traveling body 100 includes right and left crawlers 100a and 100b. The front work machine 102 includes a boom 103, an arm 104, and a bucket 105. It has. A blade 106 is attached to the front portion of the lower traveling body 100, and the upper swing body 101 includes a cab 107.

  The right and left crawlers 100a and 100b of the lower traveling body 100 are provided with the traveling motors 4 and 5, and the traveling motors 4 and 5 are driven to rotate to travel. The front work machine 102 includes a boom cylinder 113, an arm cylinder 114, and a bucket cylinder 115, and the boom 103, the arm 104, and the bucket 105 rotate in the vertical direction by extending and contracting them.

  In FIG. 1, only the direction switching valves 6 and 7 for traveling are shown for the sake of simplification. However, in the actual circuit configuration, the center bypass lines 8 and 9 include other than the direction switching valves 6 and 7 for traveling. In addition, direction switching valves for boom, arm, bucket, and swing are also installed, and pressure oil is supplied from the hydraulic pump 1 or the hydraulic pump 2 to the boom cylinder 113, arm cylinder 114, bucket cylinder 115, and a swing motor (not shown). The boom 103, the arm 104, the bucket 105, and the upper swing body 101 can be driven.

  Next, the operation of the present embodiment configured as described above will be described.

  When the directional control valves 6 and 7 are in the neutral position, the on-off valves 35 and 26 are in the open position, so that no pilot control pressure is generated downstream of the fixed throttle 33 and the valve device 23 is kept in the shut-off position. The communication between the pipes 11 and 12 is blocked. As a result, the circuit on the hydraulic pump 1 side and the circuit on the hydraulic pump 2 side are completely independent from each other. When a direction switching valve (not shown) provided on each side circuit is operated, the hydraulic oil is appropriately applied to the related actuator. Can be operated without any trouble.

  When the directional control valves 6 and 7 are operated in full stroke with the intention of traveling straight, the open / close valves 35 and 36 are switched from the open position to the closed position, and a pilot control pressure is applied to the pipeline portion 34a upstream of the open / close valve 35. Therefore, the valve device 23 is switched to the throttle communication position, and the pipe line 11 and the pipe line 12 communicate with each other via the throttle part 23 a of the valve device 23. As a result, even if there are variations in the propulsion performance of the hydraulic pumps 1 and 2 and the efficiency of the traveling motors 4 and 5 and the driving side (high pressure side) and the driven side (low pressure side) occur, the pressure oil on the high pressure side is low pressure side Therefore, it is possible to prevent a speed difference (rotational speed difference) from occurring in the traveling motors 4 and 5, and to correct the straight traveling of the traveling meander.

  When the direction switching valves 6 and 7 are operated with different stroke amounts for the purpose of steering (curvature) during traveling, or when only one of the direction switching valves 6 and 7 is operated by one side operation of the traveling lever, or traveling When the direction switching valves 6 and 7 are operated in the reverse direction by the reverse operation of the lever, the valve device 23 is switched to the throttle communication position, and the conduits 11 and 12 are the valves as in the case of the operation intended for straight traveling. The devices 23 communicate with each other via a throttle 23a. However, in this case, by setting the opening area of the throttle portion 23a appropriately, the load pressure of the travel motor on the side with the larger operation amount of the direction switching valves 6 and 7 is made higher than the load pressure of the travel motor on the other side. It is possible to perform a turning operation.

  The operation principle of the present invention will be described with reference to FIGS.

  In FIG. 3, the left side of the figure is an explanation of the operation of the conventional example, and the right side of the figure is an explanation of the operation of the present invention. In the conventional example, when there is a difference in the rotation speed of the left and right traveling motors when the straight running operation is performed, the faster rotation speed of the traveling motor is the driving side, and the motor load pressure on the driving side is higher than the motor load pressure on the driven side. Become. This is because the crawlers 100a and 100b (see FIG. 2) have a straight traveling property, and a drive side (high pressure side) and a slave side (low pressure side) are generated. In this state, if the load pressure difference between the driving side and the driven side becomes a magnitude that cannot be compensated by the straightness of the crawlers 100a and 100b, meandering occurs.

  In the configuration of the present invention, the pressure oil supply pipes 11 and 12 of the left and right traveling motors 4 and 5 are communicated by the valve device 23, so that the difference between the left and right load pressures generated due to the rotational speed difference is utilized. A correction flow rate is generated on the low pressure side. By generating the corrected flow rate (communication of the valve device 23), it becomes possible to compensate for the straightness of the crawlers 100a and 100b.

  Further, in the present invention, the throttle portion 23a is provided at the communication position of the valve device 23, and the throttle element is set. By setting the aperture element, the meandering correction circuit 20 can be made to function so as not to cancel the intentional difference between the supply flow rates to the left and right traveling motors intended for steering during traveling.

  FIG. 4 is a diagram illustrating the function of the aperture element that enables the intended steering. In FIG. 4, the horizontal axis represents the load pressure difference ΔP of the left and right traveling motors, and the vertical axis represents the passage flow rate Q of the valve device 23. QL is a flow rate that invalidates steering.

  As shown in FIG. 4, by setting the opening area A0 of the throttle portion 23a to be small, the flow rate characteristic of the throttle portion 23a becomes as shown in the figure FC, and the load pressure difference between the left and right traveling motors 4 and 5 at the time of straight travel correction is shown. On the other hand, the flow rate QA required for straight-ahead correction can be secured, and the flow rate QB for the maximum load pressure difference assumed during steering can be made smaller than the flow rate QL that invalidates steering. As a result, it is possible to set so that only the correction flow rate necessary for the meandering correction during straight traveling flows.

  As a result of the analysis, the passage flow rate of the valve device 23 with respect to the flow rate (traveling flow rate) of the pressure oil supplied from the hydraulic pump 1 or 2 to the traveling motor 4 or 5 is 2-3%, that is, the opening area of the throttle portion 23a. It has been found that it is preferable to set A0 so as to obtain such a passing flow rate ratio (the passing flow rate of the valve device 23 with respect to the traveling flow rate is 2 to 3%). When the passage flow rate of the valve device 23 exceeds 3%, it is difficult to perform gentle steering (curvature), and when it is less than 2%, the meandering correction effect cannot be obtained.

  Further, in the present embodiment, even when an operation intended for steering (curving) is performed by one-side operation of the traveling lever (when only one of the direction switching valves 6 and 7 is switched from the neutral position), the valve device 23 Is switched to the throttle communication position, and the pipe line 11 and the pipe line 12 communicate with each other. As a result, the following effects can be obtained.

  In small hydraulic excavators, crawlers 100a and 100b made of rubber rubber are often used. When the vehicle body actually changes direction with such a hydraulic excavator, the crawler is deformed by friction between the ground contact surface and the rubber rubber crawler. This deformation generates a repulsive force on the rubber rubber crawler. In this case, since the crawler repulsive force becomes a resistance force for traveling, the driving pressure of the traveling motors 4 and 5 increases. The traveling motors 4 and 5 rotate when the driving pressure overcomes the resistance force, but the vehicle body vibrates due to the reaction.

  On the other hand, in the present invention, a part of the pressure oil in the drive-side (high-pressure side) pressure oil supply oil passage 11 or 12 is removed from the non-drive-side pressure oil supply line via the throttle portion 23a of the valve device 23. It returns to the tank via the bypass flow path 7c or 6c of the direction switching valve 7 or 6. With this function, it is possible to suppress a sudden increase in pressure on the driving side, and to reduce the crawler repulsive force that causes the vibration of the vehicle body. As a result, it is possible to reduce vehicle body vibration that occurs in an operation of changing the direction of the vehicle body by the operation of one of the crawlers.

  The same effect can be obtained also when steering is performed when the direction switching valves 6 and 7 are operated with different stroke amounts, or when the direction switching valves 6 and 7 are operated in the reverse direction by the reverse operation of the travel lever. In these cases, a part of the pressure oil in the pressure oil supply passage 11 or 12 on the driving side (high pressure side) flows into the driven side (low pressure side) via the throttle portion 23a of the valve device 23. It is supplied to the traveling motor 5 or 4 via 7 or 6.

  A second embodiment of the present invention will be described with reference to FIGS. In FIG. 5, the same components as those shown in FIG.

  In FIG. 5, the pressure oil supply pipes 11 and 12 are provided with a meandering correction circuit 20A having a valve device 23A. As with the valve device 23 in the first embodiment, the valve device 23A is installed in the pipelines 21 and 22 connecting the pressure oil supply pipelines 11 and 12, and is a two-position switch having a blocking position and a throttle communication position. It is a valve. Further, the valve device 23A has a variable spring 23Ac as means for holding the valve device 23A in the cutoff position when the pilot control pressure is not guided to the pressure receiving portion 23b, and the setting of the variable spring 23Ac can be adjusted by the adjusting tool 24. It is. The restricting portion 23Aa of the valve device 23A is configured as a variable restrictor. The adjusting tool 24 is, for example, a screw member that can be manually operated by an operator and can be locked at a desired rotational position.

  FIG. 6 shows a change in the relationship between the pilot control pressure and the spool stroke of the valve device 23A by adjusting the setting of the variable spring 23Ac, and FIG. 7 shows the opening area of the variable throttle 23Aa of the valve device 23A due to the change in the spool stroke. Showing change. When the setting of the variable spring 23Ac is increased, the relationship between the pilot control pressure and the spool stroke changes from SS1 to SS2, and the spool stroke decreases from L1 to L2 even with the same pilot control pressure, and the opening of the variable restrictor 23Aa The area decreases from A1 to A2. Conversely, when the setting of the variable spring 23Ac is weakened, the relationship between the pilot control pressure and the spool stroke changes from SS1 to SS3, and even with the same pilot control pressure, the spool stroke increases from L1 to L3, and the variable restrictor 23Aa The opening area increases from A1 to A3.

  FIG. 8 is a diagram showing a change in flow rate characteristic when the opening area of the variable throttle 23Aa is changed from A1 to A2 or from A1 to A3. By changing the opening area of the variable restrictor 23Aa from A1 to A2 or A1 to A3, the flow characteristic of the variable restrictor 23Aa changes from FC1 to FC2 or FC1 to FC3. It changes from QA1 to QA3. Further, the flow rate with respect to the maximum load pressure difference assumed at the time of steering also changes from QB1 to QB2 or from QB1 to QB3. This function makes it possible to adjust the meandering correction flow rate.

  As described above, according to the present embodiment, the meandering correction flow rate can be adjusted by adjusting the setting of the variable spring 23Ac and adjusting the opening area of the variable restrictor 23Aa.

  In the case where the spring cannot be set and adjusted, if the intended flow rate characteristic (corrected flow rate) cannot be obtained due to product variations, it is necessary to replace the throttle element of the valve device. In the present embodiment, the adjustment of the meandering correction flow rate is an operation of operating the adjusting tool 24 to adjust the setting of the variable spring 23Ac, and it becomes unnecessary to replace the throttle element. Further, the meandering correction circuit 20A can be easily calibrated at the time of product shipment.

  A third embodiment of the present invention will be described with reference to FIG. In the figure, the same components as those shown in FIG.

  In FIG. 9, 51 and 52 are left and right operation lever devices. The operation lever devices 51 and 52 include a pair of pilot valves (reducing valves) 51 a and 51 b; 52 a and 52 b, respectively. Operation levers 51c and 52c for operation are provided. When the operation lever 51 is operated in the right direction in the figure, the pilot valve 51a is operated, and the pilot operation pressure corresponding to the operation amount of the operation lever 51 is obtained using the discharge pressure of the pilot pump 31 kept constant by the pilot relief valve 32 as a source pressure. Occur. This pilot operation pressure is sent to the pressure receiving part 6a of the direction switching valve 6 via the pilot pipe line 54, and the direction switching valve 6 is switched from the neutral position. When the operation lever 51 is operated in the left direction in the figure, the pilot valve 51b is activated, and the pilot operation corresponding to the operation amount of the operation lever 51 is performed using the discharge pressure of the pilot pump 31 kept constant by the pilot relief valve 32 as a source pressure. Generate pressure. This pilot operating pressure is sent to the pressure receiving portion 6b of the direction switching valve 6 via the pilot line 55, and switches the direction switching valve 6 in the opposite direction. The same applies to the operation lever device 52, and the pilot operation pressure is sent to the pressure receiving portion 7a or 7b of the direction switching valve 7 via the pilot line 56 or 57 according to the operation amount and operation direction of the operation lever 52c. The switching valve 7 is switched from the neutral position.

  Reference numeral 20B denotes a meandering correction circuit according to the present embodiment. The meandering correction circuit 20B detects the operation of the valve device 23 installed in the pressure oil supply pipes 11 and 12 and the direction switching valves 6 and 7, and detects the valve device 23. A travel detection pilot circuit 25B for switching is provided. The configuration of the valve device 23 is the same as that of the first embodiment.

  The travel detection pilot circuit 25B includes a shuttle valve 57 that detects pilot operation pressures of the pilot valves 51a and 51b, a shuttle valve 58 that detects pilot operation pressures of the pilot valves 52a and 52b, and a pilot operation detected by the shuttle valve 57. And a shuttle valve 59 for detecting the pilot operation pressure detected by the shuttle valve 58. The pilot operation pressure detected from the shuttle valve 59 is received by the valve device 23 via the pilot line 61 as a pilot control pressure. Guided to part 23b.

  In the present embodiment configured as described above, when the operation levers 51c and 52c of the operation lever devices 51 and 52 are operated to switch the direction switching valves 6 and 7 with the intention of traveling straight, the pilot valves 51a and 51b; The highest pressure among the pilot operating pressures generated at 52a and 52b is selected by the shuttle valves 57, 58 and 59, and is guided to the pressure receiving portion 23b of the valve device 23 as the pilot control pressure, so that the valve device 23 is brought into the throttle communication position. Switch. When the direction switching valves 6 and 7 are operated with different stroke amounts for the purpose of steering (curvature) during traveling, or when only one of the direction switching valves 6 and 7 is operated by one side operation of the traveling lever, or traveling The same applies when the direction switching valves 6 and 7 are operated in the reverse direction by the reverse operation of the lever. As a result, in an operation intended for straight traveling, straight traveling correction of the traveling meander can be performed as described above. In addition, an operation intended to be steered can appropriately perform a turning operation, and can reduce vehicle body vibration generated in an operation of changing the direction of the vehicle body.

  As described above, this embodiment can provide the same effects as those of the first embodiment.

  In the above embodiment, the valve devices 23 and 23A of the meandering correction circuit are two-position switching valves that can be switched between the shut-off position and the throttle communication position. However, the passing flow rate at the throttle communication position is 2 to 2 of the traveling flow rate. Since the amount is as small as 3%, a fixed throttle (or variable throttle) that always functions may be provided instead of the two-position switching valve.

It is a figure which shows the system outline | summary of the hydraulic drive device of the traveling construction machine concerning the 1st Embodiment of this invention. It is a figure which shows the external appearance of the hydraulic excavator by which the hydraulic drive device of this invention is mounted. It is a figure explaining the principle of meandering correction of the present invention. It is a figure explaining the function of the aperture element which enables the intended steering in the meandering correction circuit of this invention. It is a figure which shows the system outline | summary of the hydraulic drive unit of the traveling construction machine concerning the 2nd Embodiment of this invention. It is a figure which shows the change of the relationship between the pilot control pressure by the setting adjustment of a variable spring, and the spool stroke of a valve apparatus. It is a figure which shows the change of the opening area of the variable aperture part of the valve apparatus by the change of a spool stroke. It is a figure explaining the principle of meandering correction by setting adjustment of a variable spring. It is a figure which shows the system outline | summary of the hydraulic drive unit of the traveling construction machine concerning the 3rd Embodiment of this invention.

Explanation of symbols

1, 2 Hydraulic pump 3 Pump device 4, 5 Left and right traveling motor 6, 7 Direction switching valve 6 a, 6 b; 7 a, 7 b Pressure receiving portion 8, 9 Center bypass line 11, 12 Pressure oil supply pipeline 20, 20 A, 20 B Serpentine correction Circuits 21, 22 Pipes 23, 23A Valve device 23a Throttle part 23Aa Variable throttle part 23b Pressure receiving part 23c Spring 23Ac Variable spring 24 Adjuster 25, 25B Travel detection pilot circuit 31 Pilot pump 32 Pilot relief valve 33 Fixed throttle 34 units 1 pilot Pipe lines 35, 36 Open / close valves 51, 52 Operation lever devices 51a, 51b for left and right traveling; 52a, 52b Pilot valves 51c, 52c Operation levers 57, 58, 59 Shuttle valve 61 Pilot conduit 100 Lower traveling body 100a, 100b Crawler 101 Upper swing body 102 Front work machine

Claims (4)

Traveling comprising first and second hydraulic pumps, left and right traveling motors, and first and second directional control valves that control the flow of pressure oil supplied from the first and second hydraulic pumps to the left and right traveling motors. In the hydraulic drive device of the construction machine,
The first and second pipes communicate with each other through a throttle portion in the middle of the first and second pipes that supply pressure oil from the first and second hydraulic pumps to the first and second directional control valves. A hydraulic drive device for a traveling construction machine, characterized in that a meandering correction circuit is provided. The hydraulic drive device for a traveling construction machine according to claim 1,
The meandering correction circuit includes a valve device that is switchable between a throttle communication position that allows the first and second pipe lines to communicate with each other via a throttle section and a blocking position that blocks the communication between the first and second pipe lines. And a switching operation means for switching the valve device from the shut-off position to the throttle communication position in conjunction with the operation of the first and second directional switching valves. The hydraulic drive device for a traveling construction machine according to claim 1,
The meandering correction circuit has an adjustment means for adjusting an opening area of the throttle portion, and is a hydraulic drive device for a traveling construction machine. The hydraulic drive device for a traveling construction machine according to claim 1,
The opening area of the throttle unit is set so that the ratio of the flow rate of the throttle unit to the flow rate of the pressure oil supplied from the first and second hydraulic pumps to the left and right traveling motors is 2 to 3%. A hydraulic drive device for a traveling construction machine.

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