JP4585607B2 - Work vehicle direction switching valve - Google Patents

Description

  The present invention makes it possible to increase the hydraulic pressure on the cylinder port side and to generate the cylinder force at the full stroke position where the direction switching valve of the work vehicle is in the lowered position.

  Conventionally, an operation lever has been provided in a driver's seat to rotate a boom, an arm, a bucket, and the like, which are working machines of an excavating and turning work vehicle, and the operation lever is directly connected to a switching valve spool or via a pilot valve. The switching valve is switched by being connected and sliding the spool. As shown in FIG. 14, the switching valve in the boom cylinder 23 is composed of a 6-port / three-position switching pilot-type switching valve. When the control lever is rotated from neutral to down, the spool of this switching valve gradually changes the area of the three oil passages in the process from neutral to full stroke, thereby performing speed control. .

  This area is as shown in FIG. 12, and in the neutral position, the third oil passage 43 connecting the first pump port P1 and the tank port T1 is in communication with the bottom cylinder port CB of the boom cylinder and the rod side. The cylinder port CR, the second pump port P2, and the second tank port T2 are blocked so that hydraulic fluid does not flow. Then, when the spool is slid from the neutral side to the lower side, the area (c) of the third oil passage 43 is abruptly reduced at the initial stage of rotation, and then gradually reduced, at the lowered full stroke position. Closed. The area (a) of the first oil passage 41 connecting the bottom side cylinder port CB and the second tank port T2 is gradually opened, and a full stroke is achieved with a certain degree of restriction. The area (b) of the second oil passage 42 connecting the second pump port P2 and the rod side cylinder port CR is gradually opened and opened abruptly before the full stroke, and the opening area is larger than that of the first oil passage 41. It is also bigger.

  However, as shown in FIG. 13, when the lowering operation is performed, t1 to t2 start to descend due to their own weight while accelerating. However, if the amount of oil fed from the second oil passage increases, There was a problem that the rise caught up, and from the time of catching up (t3), the speed was suddenly accelerated and a shock occurred. Therefore, in order to mitigate sudden acceleration, the first oil passage is narrower than the second oil passage. However, as a result, the cylinder bottom pressure increased, and accordingly, the cylinder rod pressure and the pump pressure increased, resulting in a large power loss. Further, as a technique for reducing power loss, there is a technique disclosed in Japanese Patent Laid-Open No. 10-89317. This technique is designed to reduce the pump discharge amount when the boom is lowered, and detects the pressure of the oil passage that drains to the tank side. Thus, the discharge amount of the variable hydraulic pump was changed. However, the circuit becomes complicated and it is necessary to use an expensive variable hydraulic pump.

JP-A-10-89317

  As shown in FIG. 6, the present invention is such that when the crawler type traveling device 1 is inspected, maintained, etc., the upper revolving body is set so that the boom 6 is in a lateral position with respect to the traveling direction of the crawler type traveling device 1. In the state of turning, the boom 6 is lowered to lift one of the crawlers. This is called jack-up. In this case, if the bleed at the full stroke position is too large, the rod side pressure does not increase, and operations such as jack-up cannot be performed. On the other hand, the larger the bleed of the third oil passage 43, the lower the pump pressure (c1) and the higher the energy saving effect, but in order to be able to jack up, it is necessary to limit the bleed to some extent. . In the present invention, a bleed amount switching valve (34) is provided in addition to the direction switching valve of the work vehicle to enable operations such as jacking up.

  The present invention employs the following means in order to solve the above-described problems.

  In Claim 1, it is a direction switching valve (51) of the hydraulic cylinder (23) descend | falling with dead weight of a working machine (2), Comprising: The 1st oil path (Cylinder port (CB) and tank port (T2) which connects) 41), a second oil passage (42) connecting the pump port (P2) and the cylinder port (CR), and a third oil passage (43) connecting the pump port (P1) and the tank port (T1), respectively. (61) · Second throttle (62) · Third throttle (63) are provided, and the cylinder port (CR) side hydraulic pressure is increased at the full stroke position with the direction switching valve (51) in the lowered position. In the configuration enabling the cylinder force to be output, a bleed amount switching valve (34) is interposed in the tank oil passage connected to the third oil passage (43), and the bleed amount switching valve (34) has two ports. Consists of a two-position switching valve, The spool operation portion of the cylinder amount switching valve (34) is connected to the secondary oil passage connected to the cylinder port (CR) via the pilot oil passage (44), and the bleed amount switching valve (34) When the cylinder port (CR) side hydraulic pressure is increased, the spool of the bleed amount switching valve (34) is slid through the pilot oil passage (44) and the bleed amount switching valve ( 34), the bleed amount is limited by the throttle (64), the hydraulic pressure on the cylinder port (CR) side is increased, and the cylinder force can be generated.

  According to a second aspect of the present invention, in the directional control valve for the work vehicle according to the first aspect, the bleed amount switching valve (34) is provided in a spool (70) of the directional switching valve (51). 51) A valve hole (70a) is formed at the axial center position of the spool (70), and the valve element (71) of the bleed amount switching valve (34) and the valve element (70a) are formed in the valve hole (70a). 71) is inserted with a spring (72) for biasing.

In the present invention, since the hydraulic circuit of the excavation turning work vehicle is configured as described above, the following effects can be obtained.
The first oil for connecting the cylinder port (CB) and the tank port (T2) as the direction switching valve (51) of the hydraulic cylinder (23) that descends due to the weight of the work machine (2). The first oil passage (41), the second oil passage (42) connecting the pump port (P2) and the cylinder port (CR), and the third oil passage (43) connecting the pump port (P1) and the tank port (T1), respectively. One throttle (61), second throttle (62), and third throttle (63) are provided, and the hydraulic pressure on the cylinder port (CR) side is adjusted at the full stroke position with the direction switching valve (51) in the lowered position. In the configuration that enables the cylinder force to be increased, a bleed amount switching valve (34) is interposed in the tank oil passage connected to the third oil passage (43), and the bleed amount switching valve (34) Consists of a 2-port 2-position switching valve, The spool operation portion of the valve amount switching valve (34) is connected to the secondary oil passage connected to the cylinder port (CR) via the pilot oil passage (44), and the bleed amount switching valve (34). Is in the communication state at the normal position, and when the hydraulic pressure on the cylinder port (CR) side becomes high, the spool of the bleed amount switching valve (34) is slid through the pilot oil passage (44), and the bleed amount switching valve (34) is switched, the bleed amount is limited by the throttle (64), the hydraulic pressure on the cylinder port (CR) side is increased, and the cylinder force can be output, so the tank connected to the third oil passage By providing a bleed amount switching valve in the oil passage, the bleed amount can be automatically changed without the operator's operation according to the work when the boom is operated, and jack-up operation is possible To, also, it is possible to realize energy saving.

  According to a second aspect of the present invention, in the direction switching valve for the work vehicle according to the first aspect, the bleed amount switching valve (34) is provided in a spool (70) of the direction switching valve (51), and the direction switching valve is provided. A valve hole (70a) is formed at the axial center position of the spool (70) of the valve (51), and the valve element (71) of the bleed amount switching valve (34) is formed in the valve hole (70a). The spring (72) that urges the body (71) is inserted, so the bleed amount can be automatically changed without the operator's operation according to the work when the boom is operated, and jacking up is easy. It is possible to save energy, and the specifications can be easily changed by simply changing the spool.

1 is an overall side view of an excavation turning work vehicle equipped with a switching valve according to the present invention. It is a hydraulic circuit diagram of the hydraulic drive device of the present invention. It is an expansion hydraulic circuit diagram of the direction switching valve for booms. It is a figure which shows the relationship between the downward stroke and the oil path area between ports. It is a figure showing the relation between lowering operation time and oil pressure. It is a figure which shows the state of jackup. It is a hydraulic circuit diagram of the Example which provided the bleed amount switching valve in the tank oil path. It is a hydraulic circuit diagram which provided the bleed amount switching valve in the spool of the direction switching valve for booms. It is sectional drawing which provided the bleed amount switching valve in the spool of the direction switching valve for booms. It is sectional drawing which similarly shows the state in the middle of lowering. It is sectional drawing at the time of a downward full stroke similarly. It is a figure which shows the relationship between the conventional downward stroke and the oil path area between ports. It is a figure which shows the relationship between the conventional lowering operation time and oil_pressure | hydraulic. It is a hydraulic circuit diagram of the conventional boom direction switching valve.

  Next, embodiments of the present invention will be described with reference to the accompanying drawings.

  1 is an overall side view of an excavating and turning work vehicle equipped with a switching valve according to the present invention, FIG. 2 is a hydraulic circuit diagram of a hydraulic drive device of the present invention, and FIG. 3 is an enlarged hydraulic circuit diagram of a directional switching valve for a boom. 4 is a diagram showing the relationship between the lowering stroke and the oil passage area between the ports, FIG. 5 is a diagram showing the relationship between the lowering operation time and the hydraulic pressure, FIG. 6 is a diagram showing the jack-up state, and FIG. 7 is the bleed amount switching valve. 8 is a hydraulic circuit diagram of an embodiment provided in a tank oil passage, FIG. 8 is a hydraulic circuit diagram in which a bleed amount switching valve is provided in a spool of a boom direction switching valve, and FIG. 9 is a spool of a boom direction switching valve. FIG. 10 is a cross-sectional view showing a state in the middle of lowering, and FIG. 11 is a cross-sectional view at the time of a full stroke.

  First, a schematic configuration of the excavation turning work vehicle according to the present invention will be described. As shown in FIG. 1, the turning work vehicle supports a turning frame 8 so as to be turnable through a turntable bearing 7 having an axis in the vertical direction at the upper center of the crawler type traveling device 1. A blade 10 is disposed at one end of the front and rear of the apparatus 1 so as to be rotatable up and down. A bonnet 9 that covers an engine or the like is disposed on the rear portion of the revolving frame 8, and a cabin 22 that houses an operation unit is disposed in the front portion of the bonnet 9.

  The work machine 2 is attached to the front end of the revolving frame 8, and the work machine 2 has a boom bracket 12 attached to the front end of the revolving frame 8 so as to be rotatable left and right. The lower end portion is supported so as to be freely pivotable back and forth. The boom 6 is bent forward in the middle, and is formed in a substantially “<” shape in a side view. An arm 5 is rotatably supported at the other end of the boom 6, and a bucket 4 as a work attachment is rotatably supported at the tip of the arm 5.

  Further, a boom cylinder 23 is interposed between the boom bracket 12 and a boom cylinder bracket 25 provided in the middle of the boom 6, and an arm cylinder bottom bracket 26 and an arm 5 base end provided on the rear of the middle of the boom 6. An arm cylinder 29 is interposed between the bucket cylinder bracket 27 provided in the section, and a bucket cylinder 24 is interposed between the bucket cylinder bracket 27 and the stay 11 connected to the bucket 4.

  Thus, the boom 6 is rotated by the boom cylinder 23, the arm 5 is rotated by the arm cylinder 29, and the bucket 4 is rotated by the bucket cylinder 24. The boom cylinder 23, the arm cylinder 29, and the bucket cylinder 24 are constituted by hydraulic cylinders, and each cylinder 23, 29, and 24 is operated by operating an operation lever disposed in the cabin 22 to switch a switching valve disposed below the cylinder. It is expanded and contracted by supplying pressure oil from a hydraulic pump.

  Further, a swing cylinder 17 is disposed on the side of the swing frame 8, a base portion thereof is pivotally supported by the swing frame 8, and a tip of a cylinder rod of the swing cylinder 17 is connected to the boom bracket 12, With the swing cylinder 17, the boom bracket 12 can be turned left and right with respect to the turning frame 8, and the work implement 2 can be turned left and right.

  Further, the swing frame 8 can be rotated 360 degrees left and right by the operation of a hydraulic motor 13 (FIG. 2) provided on the upper part of the swivel bearing 7. The blade cylinder 14 interposed between the frame 3 and the frame 3 can be moved up and down. Furthermore, traveling hydraulic motors 15R and 15L are disposed inside the drive sprocket disposed on the front and rear sides of the track frame 3 so that the crawler traveling device 1 can be driven to travel.

  A hydraulic circuit in the excavation turning work vehicle in which the hydraulic cylinder and the hydraulic motor as the hydraulic actuator are arranged in this manner will be described with reference to FIG. First, the first hydraulic pump 91, the second hydraulic pump 92, and the third hydraulic port P3 are linked and driven in parallel to the output shaft of the engine housed in the bonnet 9. A switching valve 20 is provided in the output oil passages of the first hydraulic pump 91 and the second hydraulic pump 92 so as to be opened by driving of the hydraulic pump, and the first center oil passage 31 on the output side of the first hydraulic pump 91 is provided. A relief valve 35 for setting the output hydraulic pressure is connected in parallel, and a traveling motor direction switching valve 50R for switching the oil feeding to the traveling hydraulic motor 15R on the left and right side (right side in this embodiment) and the feeding to the boom cylinder 23. A boom direction switching valve 51 that switches oil and a bucket direction switching valve 52 that switches oil feeding to the bucket cylinder 24 are connected in tandem.

  Further, the second center oil passage 32 is connected to the output oil passage of the second hydraulic pump 92, and the relief valve 36 for setting the output oil pressure is connected in parallel to the second center oil passage 32, so In the example, the traveling motor direction switching valve 50L for switching the oil supply to the traveling hydraulic motor 15L (left side in the example), the swing direction switching valve 58, the arm direction switching valve 55, and the PTO direction switching valve 56 are connected in tandem. . Further, the turning direction switching valve 54 and the blade direction switching valve 53 are tandemly connected to the output oil passage of the third hydraulic pump 93. 37 is a relief valve for setting the output hydraulic pressure.

  Next, the configuration of the boom direction switching valve 51 that controls expansion and contraction of the boom cylinder 23, which is the main part of the present invention, will be described. As shown in FIG. 3, when the boom direction switching valve 51 is in the neutral position, the oil path between the first pump port P1 and the first tank port T1 is communicated, and the bottom side cylinder port CB and the rod side cylinder port CR. The second pump port P2 and the second tank port T2 are blocked so that hydraulic fluid does not flow.

  In the lower-side switching valve 51, a first throttle 61 is provided in the first oil passage 41 connecting the bottom cylinder port CB and the second tank port T2, and the second pump port P2 and the rod cylinder port CR are connected to each other. A second throttle 62 is provided in the second oil passage 42 that connects, and a third throttle 63 is provided in the third oil passage 43 that connects the first pump port P1 and the first tank port T1.

  The opening areas of the throttles provided in the respective oil passages 41, 42, 43 in the lowering process from the neutral direction to the full lowering position of the boom direction switching valve 51 are set as follows. That is, as shown in FIG. 4, first, as shown in (a2), the area change of the throttle 61 of the first oil passage 41 is gradually opened and the speed when falling due to the weight of the work machine 2 is appropriate. Is set to be In the present invention, the opening area is set larger than the conventional area in order to set the area so as not to be pushed by hydraulic pressure. For example, when comparing the opening area at the full stroke position, if the conventional opening area is S1 (FIG. 12) and the opening area of this embodiment is S2, S1 <S2.

  Next, the throttle 62 provided in the second oil passage 42 is configured to prevent the rod side pressure from increasing during the boom lowering operation as shown in the alternate long and short dash line (b1) shown in FIG. Set as follows. The opening area gradually opens and is smaller than the opening area of the first oil passage 41 (b2 in FIG. 4). Conventionally, the hydraulic pressure a1> b1 (shown in FIG. 5) is used in this embodiment, whereas the hydraulic pressure b0> a0 (shown in FIG. 13). The third oil passage 43 has an opening area set to S3 so that the area from the k1 position to the k2 position in the initial stroke is reduced so that it does not drop suddenly, and the pump outlet pressure does not rise excessively at the full stroke position. is doing.

  Further, the bleed pressure at the full stroke position is set so that it can be jacked up. That is, as shown in FIG. 6, when the crawler traveling device 1 is inspected or maintained, the upper swinging body is swung so that the boom 6 is positioned laterally with respect to the traveling direction of the crawler traveling device 1. In this state, the boom 6 is lowered to lift one of the crawlers. This is called jack-up. In this case, if the bleed at the full stroke position is too large, the rod side pressure will not increase and jacking up will not be possible. On the other hand, the larger the bleed of the third oil passage 43, the lower the pump pressure (c1) and the higher the energy saving effect. However, in order to be able to jack up, it is necessary to limit the bleed to some extent. . Therefore, in the present invention, the bleed amount at the full stroke position is set to a limit amount that can be jacked up while the engine is at low idle.

  By configuring in this way and setting the opening area, the pump outlet pressure (FIG. 5) can be lowered as compared with the conventional outlet pressure c0 (FIG. 13) as shown by c1, and the power loss can be reduced. It is. In addition, even during boom lowering acceleration, there is no sudden acceleration shock, and operability can be improved. And jack-up is also possible.

  Further, as shown in FIG. 7, a bleed amount switching valve 34 may be provided in the tank oil passage 46 connected to the second throttle 63 on the secondary side of the first tank port P1 to reduce the power loss. That is, the bleed amount switching valve 34 is constituted by a 2-port 2-position switching valve, and the spool operating portion of the bleed amount switching valve 34 is connected to the secondary oil passage connected to the rod side cylinder port CR via the pilot oil passage 44. It is connected. When the bleed amount switching valve 34 is in the communication state at the normal position, the bleed amount is reduced by the throttle 64 when the rod side pressure is increased and the bleed amount switching valve 34 is switched, so that the pump pressure can be increased and jacked up. Yes. As shown by a two-dot chain line (c2 ') in FIG. 4, the opening area of the throttle 63 is made larger than when the bleed amount switching valve 34 is not provided.

  Thus, since the amount of bleed increases, the pump pressure can be lowered and the power loss can be greatly reduced as shown by c3 in FIG. When jacking up, the rod side hydraulic pressure becomes high, so the spool of the bleed amount switching valve 34 is slid through the pilot oil passage 44 so that the bleed amount is limited to allow jackup. is there.

  The bleed amount switching valve 34 may be built in the boom direction switching valve 51. That is, as shown in FIGS. 8 and 9, a valve hole 70a is formed at the axial center position of the spool 70 of the boom direction switching valve 51, and the valve element 71 of the bleed amount switching valve 34 is formed in the valve hole 70a. A spring 72 for urging the valve body 71 is inserted, and a fixing bolt 73 is screwed to close the valve hole 70a. Oil passage holes 74, 75, and 76 that penetrate from the side surface of the spool 70 to the valve hole 70a are provided.

  In such a configuration, when the boom direction switching valve 51 is neutral, the state is as shown in FIG. 9, the pressure oil is flowing from the pump port P to the tank port T, and the valve body 71 is biased by the spring 72. The oil passage 74 and the oil passage 75 are closed.

  When the boom direction switching valve 51 is switched to the lowering direction, as shown in FIG. 10, the spool 70 is slid leftward on the paper surface and flows from the first pump port P1 to the first tank port T1 via the oil path 63. At the same time, the pump pressure rises and the valve body 71 slides to the right against the urging force of the spring 72 by the pressure oil from the oil passage hole 75. When the area is increased by this sliding, the same effect is obtained, which is substantially the same as the two-dot chain line (c2 ') in FIG. 4, and the bleed amount increases.

  When jack-up is performed, when the fall of the work machine 2 due to its own weight stops and the pump pressure c1 and the rod pressure b1 become substantially the same pressure, the valve element 71 is closed in the closing direction by the urging force of the spring 72 as shown in FIG. Thus, the flow of oil from the oil passage hole 75 is stopped, the amount of bleed is limited, and the boom 6 is lowered by the rod pressure so that jack-up can be performed.

  First, in the boom lowering position of the boom direction switching valve for the excavating and turning work vehicle, the first oil passage connecting the bottom side cylinder port and the tank port, the second oil passage connecting the pump port and the rod side cylinder port, the pump port and the tank In the third oil passage connecting the ports, a first throttle, a second throttle, and a third throttle are provided, respectively.The first throttle is a throttle that allows the work implement to descend by its own weight, and the second throttle is more pressurized than the bottom side. Since the throttle is set so as not to increase, when lowering the boom, in addition to lowering due to the weight of the work equipment, the lowering hydraulic pressure is not applied, and there is no shock when lowering, improving operability. At the same time, power loss can be reduced. Further, this power loss can be reduced with a configuration that only changes the setting of the throttle area of the direction switching valve for the boom, and can be realized at low cost.

  Since the throttle amount at the full stroke position of the third throttle provided in the third oil passage is set to a throttle amount that can be jacked up by idle rotation of the engine, the power loss can be reduced and the jack can be saved with energy saving. Can be improved and maintainability is not deteriorated.

P1 Pump port P2 Pump port T1 Tank port T2 Tank port CB Bottom side cylinder port CR Rod side cylinder port 1 Crawler type traveling device 6 Boom 34 Bleed amount switching valve 41 First oil passage 41
42 Second oil passage 43 Third oil passage 51 Boom direction switching valve 61 First throttle 62 Second throttle 63 Third throttle 70 Spool

Claims (2)

  A direction switching valve (51) of a hydraulic cylinder (23) that is lowered by its own weight of the work machine (2), and includes a first oil passage (41) connecting a cylinder port (CB) and a tank port (T2), a pump port ( P2) and the second oil passage (42) connecting the cylinder port (CR), and the third oil passage (43) connecting the pump port (P1) and the tank port (T1), respectively, the first throttle (61) and second In the full stroke position where the throttle (62) and third throttle (63) are provided and the directional control valve (51) is in the lowered position, the hydraulic pressure on the cylinder port (CR) side is increased to produce the cylinder force. The bleed amount switching valve (34) is interposed in the tank oil passage connected to the third oil passage (43), and the bleed amount switching valve (34) is a two-port two-position switching valve. The bleed amount switching valve (34) The spool operating portion is connected to a secondary oil passage connected to the cylinder port (CR) via a pilot oil passage (44), and the bleed amount switching valve (34) is in a communication state at a normal position. When the hydraulic pressure on the cylinder port (CR) side becomes high, the spool of the bleed amount switching valve (34) is slid through the pilot oil passage (44), the bleed amount switching valve (34) is switched, and the throttle (64 ) Restricts the amount of bleed, further increases the hydraulic pressure on the cylinder port (CR) side, and makes it possible to output the cylinder force.   The direction switching valve for a work vehicle according to claim 1, wherein the bleed amount switching valve (34) is provided in a spool (70) of the direction switching valve (51), and the spool (70) of the direction switching valve (51). The valve hole (70a) is drilled at the axial center position of the), and the valve body (71) of the bleed amount switching valve (34) and the valve body (71) are urged into the valve hole (70a). A directional control valve for a work vehicle, wherein a spring (72) is inserted.

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