JP2010261196A - Hydraulic drive unit of construction machinery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic drive unit of construction machinery, which can restrain a speed-up effect from being deteriorated by a fluctuation in load pressure of a hydraulic actuator. <P>SOLUTION: This hydraulic drive unit of the construction machinery includes: a direction switching valve group 32 which is supplied with pressure oil from a variable-displacement hydraulic pump 29; a direction switching valve group 33 which is supplied with pressure oil from a fixed-capacity hydraulic pump 30; and a center bypass line which is connected so that the lowermost downstream side of the center bypass of the direction switching valve group 33 can merge into the upstream side of the center bypass of a direction switching valve 35 for an arm of the direction switching valve group 32. The hydraulic drive unit also comprises a return channel 44 which is connected in such a manner as to branch off the lowermost downstream side of the center bypass of the direction switching valve group 33 and which makes the pressure oil from the hydraulic pump 30 flow out into a tank, and a flow control valve 45 with a pressure compensation function, which is provided in the return channel 44. The flow control valve 45 leads a preset flow of flows, which are discharged from the hydraulic pump 30, to the tank, without reference to differential pressure between inlet-side pressure and outlet-side pressure. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hydraulic drive device for a construction machine provided with a plurality of center bypass type directional switching valve groups, and in particular, a construction machine that supplies a specific directional switching valve with a combination of pressure oil from a plurality of hydraulic pumps. The present invention relates to a hydraulic drive device.

  Conventionally, for example, a hydraulic drive device mounted on a hydraulic excavator that is one of construction machines has been disclosed (for example, see Patent Document 1). The hydraulic drive device includes a first hydraulic pump, a second hydraulic pump, and a third hydraulic pump that are driven by an engine, and a plurality of hydraulic actuators (more specifically, a left hydraulic pump supplied with pressure oil from the first hydraulic pump). Center bypass type (open center type) directional control valve (specifically, left directional control valve for left travel) that respectively controls the flow of pressure oil to the traveling hydraulic motor, boom cylinder, bucket hydraulic cylinder) , A directional switching valve for a boom, and a directional switching valve for a bucket) and a plurality of hydraulic actuators (specifically, for right travel) supplied with pressure oil mainly from a second hydraulic pump Multiple center bypass type directional control valves that control the flow of pressure oil to the hydraulic motor, swing hydraulic cylinder, and arm hydraulic cylinder (specifically, right-hand drive direction) A plurality of hydraulic actuators (more specifically, a hydraulic cylinder for blades and a hydraulic cylinder for blades) supplied with pressure oil from a third hydraulic pump and a second direction switching valve group consisting of a change valve, a swing direction switching valve, and an arm direction switching valve A third directional control valve group comprising a plurality of center bypass type directional control valves (specifically, a directional control valve for blades and a directional control valve for rotation) each controlling the flow of pressure oil to the hydraulic motor for rotation) And.

  Further, in the hydraulic drive device described in Patent Document 1, the most downstream side of the center bypass of the third direction switching valve group (in other words, the downstream side of the center bypass of the turning direction switching valve on the most downstream side) Via the center bypass upstream of the arm direction switching valve in the second direction switching valve group. For example, when the arm is operated alone (in other words, the blade direction switching valve and the turning direction switching valve in the third direction switching valve group, and the right traveling direction switching valve and the swing direction switching in the second direction switching valve group). When the valve is in the neutral position), the pressure oil from the third hydraulic pump merges with the pressure oil from the second hydraulic pump, is supplied to the arm direction switching valve, and is supplied to the arm hydraulic cylinder. As a result, the effect of increasing the speed of the arm can be obtained by effectively using the pressure oil discharged from the third hydraulic pump.

  By the way, the third hydraulic pump is a fixed displacement pump, and has a discharge capacity set corresponding to the blade hydraulic cylinder and the turning hydraulic motor. Therefore, especially in a small hydraulic excavator or the like, if all of the pressure oil from the third hydraulic pump is combined with the pressure oil from the second hydraulic pump and supplied to the arm hydraulic cylinder, the combined flow rate is too large, The arm speed may become too fast. Therefore, in the hydraulic drive device described in Patent Document 1, a return flow path is provided so as to branch off from the center bypass most downstream side of the third direction switching valve group, and a fixed throttle (throttle valve) is provided in the return flow path. ing. As a result, part of the pressure oil from the third hydraulic pump flows out to the tank via the return flow path, and the remaining pressure oil merges with the pressure oil from the second hydraulic pump via the merge flow path. To the directional control valve. Therefore, the combined flow rate to the arm direction switching valve is suppressed, so that the operating speed of the arm does not become too fast.

Japanese Patent Laid-Open No. 10-88627 (see FIG. 10 etc.)

  However, there are the following problems in the above-described prior art. That is, in the above prior art, in order to suppress the combined flow rate to the directional switching valve for the arm, a return flow path is provided so as to be branched and connected from the most downstream side of the center bypass of the third directional switching valve group, and fixed to this return flow path An aperture is provided. However, for example, when the load pressure of the arm hydraulic cylinder rises, the pressure on the most downstream side of the center bypass of the third direction switching valve group rises via the merging passage, and accordingly, the flow rate of the return passage increases. As a result, the flow rate of the merging channel decreases, and the speed-up effect of the arm is reduced.

  The present invention has been made in view of the above, and is to provide a hydraulic drive device for a construction machine that can suppress a decrease in the speed-up effect associated with a change in load pressure of a hydraulic actuator.

  (1) In order to achieve the above object, the present invention provides a variable displacement type first hydraulic pump and a fixed displacement type second hydraulic pump driven by an engine, and pressure oil mainly from the first hydraulic pump. A first directional control valve group comprising a plurality of center bypass type directional control valves that respectively control the flow of pressure oil to the plurality of hydraulic actuators, and a plurality of pressure oils supplied from the second hydraulic pump A second directional control valve group comprising a plurality of center bypass type directional control valves for controlling the flow of pressure oil to the hydraulic actuator, and the center bypass most downstream side of the second directional control valve group in the first direction A center bypass line connected so as to merge upstream of the center bypass of a specific direction switching valve in the switching valve group, and a pressure from the first hydraulic pump is supplied to the specific direction switching valve. And a hydraulic drive unit for a construction machine that supplies the pressure oil from the second hydraulic pump in a combined manner, and is connected so as to branch from the most downstream side of the center bypass of the second directional switching valve group. And a flow rate control valve with a pressure compensation function provided in the return channel, wherein the flow rate control valve has an inlet side pressure and an outlet side of the flow rate control valve. Regardless of the pressure difference from the pressure, a preset set flow rate of the flow rate discharged from the second hydraulic pump is guided to the tank.

  (2) In the above (1), preferably, the flow control valve is configured to introduce a variable throttle and an inlet side pressure of the flow control valve so as to reduce the opening area of the variable throttle. A second pressure receiving portion that introduces pressure on the outlet side of the flow control valve to act in a direction to increase the opening area of the variable throttle, and a spring that acts in a direction to increase the opening area of the variable throttle. And the set flow rate can be changed by adjusting the biasing force of the spring.

  ADVANTAGE OF THE INVENTION According to this invention, the fall of the acceleration effect accompanying the fluctuation | variation of the load pressure of a hydraulic actuator can be suppressed.

It is a side view showing the structure of a small hydraulic excavator to which the present invention is applied. 1 is a hydraulic circuit diagram showing a configuration of a hydraulic drive device of a hydraulic excavator in one embodiment of the present invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a side view showing the structure of a small hydraulic excavator to which the present invention is applied. In the following, the driver's front side (left side in FIG. 1), rear side (right side in FIG. 1), left side (paper surface in FIG. 1) when the driver is seated in the driver's seat in the state shown in FIG. The front side) and the right side (back side toward the paper surface in FIG. 1) are simply referred to as front side, rear side, left side, and right side.

  In FIG. 1, a hydraulic excavator includes a lower traveling body 2 having left and right crawler belts 1, an upper revolving body 3 that is turnably mounted on the upper portion of the lower traveling body 2, and the upper revolving body 3. A swing frame 4 that forms the lower part of the foundation, a swing post 5 that is mounted on the front portion of the swing frame 4 so as to be pivotable in the horizontal direction, and can be pivoted up and down (to be able to be lifted and lowered). ) The multi-joint type front work machine 6 attached, the canopy type cab 7 provided on the left side of the swivel frame 4, and a plurality of covers 8 covering most of the swivel frame 4 other than the cab 7 And. Equipment such as an engine is mounted in the cover 8 of the upper swing body 3.

  The lower traveling body 2 drives a substantially H-shaped track frame 9, left and right drive wheels 10 rotatably supported in the vicinity of the left and right rear ends of the track frame 9, and the left and right drive wheels 10, respectively. Left and right traveling hydraulic motors 11, left and right driven wheels (idlers) 12 that are rotatably supported in the vicinity of the left and right front ends of the track frame 9, and are respectively rotated by the driving force of the driving wheels 10 via the crawler belt 1. It has.

  A soil removal blade 13 is provided on the front side of the track frame 9 so as to move up and down. The blade 13 is moved up and down by a blade hydraulic cylinder 14. Further, a turning wheel (not shown) is provided between the center portion of the track frame 9 and the turning frame 4, and the turning frame 4 is disposed with respect to the track frame 9 on the radially inner side of the turning wheel. A turning hydraulic motor 15 for turning is provided.

  The swing post 5 is rotatable in the horizontal direction with respect to the swing frame 4 via a vertical pin (not shown). Then, the swing post 5 is rotated in the horizontal direction by the swing hydraulic cylinder 16, whereby the front work machine 6 swings left and right.

  The front work machine 6 includes a boom 17 that is pivotally connected to the swing post 5, an arm 18 that is pivotally coupled to the tip of the boom 17, and a pivot that can be pivoted to the tip of the arm 18. And a combined bucket 19. The boom 17, the arm 18, and the bucket 19 are operated by a boom hydraulic cylinder 20, an arm hydraulic cylinder 21, and a bucket hydraulic cylinder 22. The bucket 19 can be replaced with an optional attachment (for example, a crusher).

  The driver's cab 7 is provided with a driver's seat (seat) 23 on which the driver is seated. In front of the driver's seat 23, left and right traveling operation levers 24 that can be operated by both hands and feet for driving the left and right traveling hydraulic motors 11 are provided. An optional hydraulic actuator 25 (for example, a hydraulic cylinder incorporated in a crusher attached in place of the bucket 19; see FIG. 2 described later) is driven at the left foot portion of the left travel operation lever 24. An optional operation pedal (not shown) is provided, and a swing operation pedal (not shown) for driving the swing hydraulic cylinder 16 is provided at the right foot portion of the right travel operation lever 24. Is provided.

  On the left side of the driver's seat 23 is a cross-operating turning / arm operating lever 26 that drives the turning hydraulic motor 15 by operating in the left-right direction and drives the hydraulic cylinder 21 for arm by operating in the front-rear direction. And a gate lock lever 27 for preventing erroneous operation that can shut off the original pressure from a pilot pump (not shown). On the right side of the driver's seat 23, a cross-operated bucket / boom operation lever (operating in the left-right direction and driving the hydraulic cylinder 20 for the boom by operating in the front-rear direction is used. (Not shown) and a blade operation lever (not shown) for driving the blade hydraulic cylinder 14 are provided.

  For example, when the left and right travel operation levers 24, the option operation pedal, the swing operation pedal, the turning / arm operation lever 26, the bucket / boom operation lever, or the blade operation lever are operated, the operation direction and operation Depending on the amount, a corresponding pressure reducing valve (not shown) reduces the original pressure from the pilot pump to generate an operating pilot pressure, and the generated operating pilot pressure is output to a corresponding direction switching valve (details will be described later). It is supposed to be.

  FIG. 2 is a hydraulic circuit diagram showing the configuration of the hydraulic drive device of the hydraulic excavator in one embodiment of the present invention.

  In FIG. 2, the hydraulic drive device includes variable displacement hydraulic pumps 28 and 29 (only the hydraulic pump 29 is shown) driven by an engine (not shown), a fixed displacement hydraulic pump 30, and the hydraulic pump 28. A center bypass type (open center type) direction switching valve group 31 (not shown) to which pressure oil is supplied from, and a center bypass type direction switching valve group 32 to which pressure oil from mainly the hydraulic pump 29 is supplied. And a center bypass type directional switching valve group 33 to which pressure oil from the hydraulic pump 30 is supplied.

  The hydraulic pumps 28 and 29 are provided with horsepower control actuators (not shown). The horsepower control actuators adjust the discharge pressures of the hydraulic pumps 28 and 29 so that the horsepower of the hydraulic pumps 28 and 29 is constant. Accordingly, the tilt (capacity) of the hydraulic pumps 28 and 29 is variably controlled.

  Although not shown in detail, the direction switching valve group 31 includes a center bypass type left direction switching valve, a boom direction switching valve, and a bucket direction switching valve. The center bypass section, the center bypass section of the boom direction switching valve, and the center bypass section of the bucket direction switching valve are connected in series via a center bypass flow path.

  The left travel direction switching valve is switched when a pilot operation pressure corresponding to the operation of the left travel operation lever 24 is input to control the flow of pressure oil from the hydraulic pump 28 to the left travel hydraulic motor 11. . The boom direction switching valve is switched by receiving a pilot operation pressure corresponding to the operation of the bucket / boom operation lever in the front-rear direction, and controls the flow of pressure oil from the hydraulic pump 28 to the boom hydraulic cylinder 20. The bucket direction switching valve is switched by receiving a pilot operation pressure corresponding to the operation of the bucket / boom operation lever in the left-right direction, and controls the flow of pressure oil from the hydraulic pump 28 to the bucket hydraulic cylinder 22. It has become.

  The direction switching valve group 32 includes a center bypass type right direction switching valve 34, an arm direction switching valve 35, and an option direction switching valve 36, and the center bypass portion of the right direction switching valve 34. The center bypass portion of the arm direction switching valve 35 and the center bypass portion of the option direction switching valve 36 are connected in series via the center bypass passage 37 in that order. The meter-in portion of the right travel direction switching valve 34 is connected on the upstream side of the center bypass passage 37 so as to have priority over the meter-in portion of the arm direction switching valve 35 and the meter-in portion of the option direction switching valve 36. Yes. The meter-in part of the arm direction switching valve 35 and the meter-in part of the option direction switching valve 36 are connected in parallel to each other on the downstream side of the right traveling direction switching valve 34 in the center bypass flow path 37.

  The direction switching valve group 33 is composed of a center bypass type blade direction switching valve 38, a turning direction switching valve 39, and a swing direction switching valve 40. The center bypass portion of the direction switching valve 39 and the center bypass portion of the swing direction switching valve 40 are connected in series via the center bypass passage 41 in that order. The meter-in part of the blade direction switching valve 38, the meter-in part of the turning direction switching valve 39, and the meter-in part of the swing direction switching valve 40 are connected in parallel to each other on the upstream side of the center bypass passage 41.

  The downstream side of the swing direction switching valve 40 in the center bypass channel 41 is connected so as to join the upstream side of the arm direction switching valve 35 in the center bypass channel 37 via the junction channel 42. A check valve 43 is provided in the flow path 42. Thereby, for example, the blade direction switching valve 38, the turning direction switching valve 39, the swing direction switching valve 40 in the direction switching valve group 33, and the right traveling direction switching valve 34 in the direction switching valve group 32 are in the neutral position. In some cases, the pressure oil from the hydraulic pump 30 merges with the pressure oil from the hydraulic pump 29 and is supplied to the arm direction switching valve 35 and the option direction switching valve 36. Thereby, the pressure oil discharged from the hydraulic pump 30 can be effectively used to obtain the speed increasing effect of the arm 18 and the like.

  The right travel direction switching valve 34 is switched by receiving a pilot operation pressure corresponding to the operation of the right travel operation lever 24 and controls the flow of pressure oil from the hydraulic pump 29 to the right travel hydraulic motor 11. To do. The arm direction switching valve 35 is switched by receiving a pilot operation pressure corresponding to the operation of the turning / arm operation lever 26 in the front-rear direction, and is switched from the hydraulic pump 29 (and the hydraulic pump 30) to the arm hydraulic cylinder 21. Control the flow of pressure oil. The option directional control valve 36 is switched by receiving a pilot operation pressure corresponding to the operation of the option operation pedal, and controls the flow of pressure oil from the hydraulic pump 29 (and the hydraulic pump 30) to the option hydraulic actuator 25. It is supposed to be.

  The blade direction switching valve 38 is switched by receiving a pilot operation pressure corresponding to the operation of the blade operation lever, and controls the flow of pressure oil from the hydraulic pump 30 to the blade hydraulic cylinder 14. The turning direction switching valve 39 is switched by receiving a pilot operation pressure corresponding to the left / right operation of the turning / arm operation lever 26 to control the flow of pressure oil from the hydraulic pump 30 to the turning hydraulic motor 15. To do. The swing direction switching valve 40 is switched by receiving a pilot operation pressure corresponding to the operation of the swing operation pedal, and controls the flow of pressure oil from the hydraulic pump 30 to the swing hydraulic cylinder 16. .

  Here, as a major feature of this embodiment, a return flow path 44 is branched and connected to the downstream side of the swing direction switching valve 40 in the center bypass flow path 41, and this return flow path 44 is connected to the hydraulic pump 30. Pressure oil flows out into the tank. The return flow path 44 is provided with a flow rate control valve 45 with a pressure compensation function. The flow rate control valve 45 is hydraulic regardless of the differential pressure between the inlet side pressure and the outlet side pressure of the flow rate control valve 45. Of the flow rate discharged from the pump 30, a preset flow rate set in advance is guided to the tank.

  The flow rate control valve 45 introduces a variable throttle 45a, a pressure receiving part 45b that acts in a direction to reduce the opening area of the variable throttle 45a by introducing the inlet side pressure, and an opening area of the variable throttle 45a by introducing the outlet side pressure. It has a pressure receiving portion 45c that acts in the direction of increasing, and a spring 45d that acts in the direction of increasing the opening area of the variable throttle 45a. For example, even if the inlet pressure of the flow control valve 45 increases, the flow rate is kept constant by reducing the opening area of the variable throttle 45a. In order to change the set flow rate of the flow control valve 45, the urging force of the spring 45d can be adjusted by hand tightening or the like.

  The effect of this embodiment comprised as mentioned above is demonstrated. For example, when the arm is operated alone (in other words, when the blade direction switching valve 38, the turning direction switching valve 39, the swing direction switching valve 40, and the right traveling direction switching valve 34 are in the neutral position), the hydraulic pump 30 is operated. A part of the pressure oil from the oil flows out to the tank via the return flow path 44, and the remaining pressure oil merges with the pressure oil from the hydraulic pump 29 via the merge flow path 42 to the arm direction switching valve 35. Supplied. As a result, the pressure oil discharged from the hydraulic pump 30 can be effectively used to obtain the speed increasing effect of the arm 18. Further, the flow rate to the arm direction switching valve 35 can be suppressed so that the operating speed of the arm 18 does not become too fast. Even when the load pressure of the arm hydraulic cylinder 21 rises and the pressure on the downstream side of the center bypass of the swing direction switching valve 40 rises via the merging passage 42, the return passage 44 has a pressure compensation function. Since the flow rate control valve 45 is provided, the flow rate of the return flow channel 44 does not vary, and the flow rate of the merge flow channel 42 can be stabilized. Therefore, it is possible to suppress a decrease in the speed-up effect of the arm 18 due to a change in the load pressure of the arm hydraulic cylinder 21.

  In the above embodiment, the flow control valve 45 has been described by taking as an example a mechanical configuration in which the urging force of the spring can be adjusted by hand tightening or the like so that the set flow rate can be changed. Not limited. That is, for example, an operation unit that can be operated by an operator, a signal generation unit that generates an electric signal in accordance with the operation of the operation unit, and a variable diaphragm in proportion to the magnitude of the electric signal from the signal generation unit. It is good also as an electrical structure which has a solenoid part which produces | generates the force made to act in the direction which makes an opening area small or enlarge. In this case, the same effect as described above can be obtained.

29 Hydraulic pump (first hydraulic pump)
30 Hydraulic pump (second hydraulic pump)
32 direction switching valve group (first direction switching valve group)
33 direction switching valve group (second direction switching valve group)
34 Direction switching valve for right travel 35 Direction switching valve for arm 36 Direction switching valve for option 37 Center bypass flow path 38 Direction switching valve for blade 39 Direction switching valve for turning 40 Direction switching valve for swing 41 Center bypass flow path 42 Confluence Channel 44 Return channel 45 Flow control valve with pressure compensation function 45a Variable throttle 45b Pressure receiving part (first pressure receiving part)
45c pressure receiving part (second pressure receiving part)
45d spring

Claims (2)

The variable displacement type first hydraulic pump and the fixed displacement type second hydraulic pump driven by the engine, and the pressure oil from the first hydraulic pump are mainly supplied to flow the pressure oil to the plurality of hydraulic actuators, respectively. A first directional control valve group consisting of a plurality of center bypass type directional control valves to be controlled, and a plurality of pressure oils supplied to the second hydraulic pump to control the flow of pressure oil to the plurality of hydraulic actuators, respectively. A second directional switching valve group including a directional switching valve of a center bypass type, and a center bypass upstream of a specific directional switching valve of the first directional switching valve group on a most downstream side of the center bypass of the second directional switching valve group. And a center bypass line connected so as to join to the side, and the pressure oil from the first hydraulic pump and the pressure oil from the second hydraulic pump are joined to the specific direction switching valve. In the hydraulic drive device for supplying a construction machine,
A return flow path that is connected to branch from the most downstream side of the center bypass of the second direction switching valve group, and that discharges the pressure oil from the second hydraulic pump to the tank;
A flow control valve with a pressure compensation function provided in the return flow path,
The flow rate control valve guides a preset set flow rate out of the flow rate discharged from the second hydraulic pump to the tank regardless of the differential pressure between the inlet side pressure and the outlet side pressure of the flow rate control valve. A hydraulic drive device for construction machinery.   2. The hydraulic drive device for a construction machine according to claim 1, wherein the flow control valve is configured to introduce a variable throttle and an inlet side pressure of the flow control valve so as to reduce an opening area of the variable throttle. A pressure receiving portion; a second pressure receiving portion that introduces an outlet side pressure of the flow control valve to act in a direction to increase the opening area of the variable throttle; and a spring that acts in a direction to increase the opening area of the variable throttle. A hydraulic drive device for a construction machine, characterized in that the set flow rate can be changed by adjusting the biasing force of the spring.

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