JP2000095493A - Bucket leveler shock reducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bucket leveler shock reducing device capable of reducing the shock caused when a bucket stops during the operation of a bucket leveler without decreasing work efficiency in an industrial or construction vehicle with a bucket. SOLUTION: This bucket leveler shock reducing device is provided with a switch valve having a throttle valve position G between a tilt pilot pressure operating valve 51a, which outputs pilot pressure to the tilt pilot operating section 33b of a bucket control valve 33, and the tilt pilot operating section 33b of the bucket control valve 33. When boom operating lever 71 is set to the 'Lowering' of 'Floating' position, the switch valve is switched to the throttle valve position G.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bucket leveler for automatically controlling a bucket such as a loader to a predetermined posture position, and more particularly to a shock reduction device for a bucket leveler capable of reducing a shock when the bucket is stopped.

[0002]

2. Description of the Related Art Conventionally, in an industrial vehicle or a construction vehicle having a bucket, such as a loader, the posture of the bucket after discharging (dumping) the soil and the like is improved in order to improve workability in loading operation by the bucket. A bucket leveler that automatically controls a position where it is easy to scoop is used. After unloading to the dump truck bed, move the vehicle backward slightly to avoid interference with the dump truck, lower the boom by operating the boom operation lever to the `` lower '' or `` floating '' position, and lower the bucket operation lever to `` Raise the bucket by operating to the "tilt" position. The "tilt" position is held by the detent solenoid. At this time, the hydraulic circuit for driving the bucket and the boom generally includes a series circuit in which a bucket control valve for controlling the bucket cylinder and a boom control valve for controlling the boom cylinder are connected in series, and Driving is prioritized.

[0003] Therefore, by the above operation, first, the bucket cylinder is extended, the bucket is driven in the tilt direction, and then, when the bucket is in a predetermined posture (that is, when the bottom surface of the bucket is in contact with the ground, the bucket is easily scooped). (A substantially horizontal attitude), the position detection sensor provided near the bucket cylinder operates, and based on this detection signal, the detent solenoid of the bucket operation lever operates and the bucket operation lever suddenly moves. Return to the "neutral" position (the means for detecting the position and operating the detent solenoid is called a bucket leveler). Thereby, the tilting of the bucket is completed, and the driving of the boom cylinder in the lowering direction is immediately performed.

[0004]

However, when the bucket is brought into a predetermined position and the bucket leveler is operated, the bucket operating lever suddenly returns to the "neutral" position. Further, the boom cylinder suddenly starts driving. At this time, a large shock occurs and the bucket and the boom shake. In particular, in a large model, since the flow rate to the cylinder is large, the shock at this time and the accompanying shaking are large. As a result, there arises a problem that the ride comfort, operability and work machine operability of the operator are not good.

To alleviate this shock, it is conceivable to perform an operation such as releasing the accelerator pedal of the engine when the bucket comes close to the bucket leveler operating position. During the simultaneous operation of “floating”, bucket “tilt”, and running of the vehicle, it is very troublesome for the operator to perform such an operation. In such a case, there is a problem that the working efficiency is significantly reduced.

In order to reduce the shock, a slow return valve is interposed in the tilt pilot pressure circuit of the bucket control valve for controlling the pressure oil supplied to the bucket cylinder, and the bucket operation lever returns to the neutral position suddenly. However, it is conceivable that the speed of returning the bucket control valve to the neutral position is slowed down and the stoppage of the bucket cylinder is moderated.
However, in this case, since the stop of the tilt of the bucket is always gradual, the bucket swing cannot be performed by itself, and the mud is always stuck in the bucket, and the work efficiency is significantly reduced. is there.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a shock reducing device for a bucket leveler capable of reducing a shock at the time of stopping the bucket during the operation of the bucket leveler without lowering work efficiency. With the goal.

[0008]

In order to achieve the above object, the invention according to the first aspect is directed to a bucket 14 of an industrial vehicle or a construction vehicle, a bucket cylinder 21 for driving the bucket 14, a bucket Operation lever 6
1, a bucket control valve 33 for controlling the bucket cylinder 21 based on the operation amount, a boom cylinder 17 for driving the boom 11, a boom control valve 41 for controlling the boom cylinder 17 based on the operation amount of the boom operation lever 71, And has a hydraulic circuit in which the bucket control valve 33 and the boom control valve 41 are connected in a series circuit, and when the bucket 14 is in a predetermined posture position during the tilt drive of the bucket 14, the bucket operation lever 61 is operated. In the bucket leveler returning to the "neutral" position, the bucket pilot valve 51a for tilting, which outputs a pilot pressure to the pilot pilot operation unit 33b of the bucket control valve 33 based on the tilt operation amount of the bucket operation lever 61, and the bucket A direct flow path interposed between the control valve 33 and the tilt pilot operation unit 33b. A switching valve 53 having a position F and a throttle valve position G, and control means for switching the switching valve 53 to the throttle valve position G when the boom operation lever 71 is operated to a “down” or “floating” position. I have.

According to the first aspect of the present invention, when the boom operation lever is operated to the "lower" or "floating" position, an interposition is provided between the tilt pilot pressure operation valve and the tilt operation section of the bucket control valve. Since the mounted switching valve switches to the throttle position, even if the bucket leveler is operated and the bucket operating lever is suddenly returned to the "neutral" position, the tilt pilot pressure gradually decreases without suddenly decreasing. . Therefore, the bucket control valve returns to the neutral position at a low speed, so that the bucket cylinder is gently stopped, and the shock during the operation of the bucket leveler is eliminated. When operating only the bucket alone, the bucket control valve operates at a normal speed because the switching valve is in the direct communication position, and the movement of the bucket is not slowed down. Therefore, since the "bucket swing" operation can be performed, the sediment accumulated in the bucket can be removed at any time, and the workability does not decrease.

According to a second aspect of the present invention, in the bucket leveler shock reducing device according to the first aspect, the control means lowers the boom operation lever 71 based on an operation amount in a "lower" or "lift" direction. The pilot pressure output from the pilot pressure operating valve 52b to the lowering pilot operating portion 41c of the boom control valve 41 is changed to the switching valve 53.
The switching valve 53 is switched to the throttle valve position G when the boom operation lever 71 is operated to "lower" or "float". According to the invention described in claim 2, when the boom operation lever is operated to the “down” or “floating” position, the position between the tilt pilot pressure operation valve of the bucket operation lever and the tilt operation portion of the bucket control valve is changed. The interposed switching valve switches to the throttle position by the pilot pressure output from the lowering pilot pressure operation valve. Therefore, even if the bucket leveler is actuated and the bucket operation lever is suddenly returned to the "neutral" position, the pilot pressure for tilting gradually decreases without suddenly decreasing due to the throttle position of the switching valve. The valve returns to the neutral position at a slow speed. As a result, the bucket cylinder stops gently, and there is no shock when the bucket leveler operates.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a bucket leveler shock reduction device according to the present invention will be described below in detail with reference to the drawings. First, a first embodiment will be described with reference to FIGS. FIG. 1 shows a scooping posture of a bucket on the ground, and a working machine will be described with reference to FIG. A boom 11 is provided at the front end of the vehicle body 1 of the vehicle.
The base end of the boom 11 is rotatably attached to the front end of the boom 11 by a pin 12, and the bracket 14 a of a bucket 14 is rotatably attached to the front end of the boom 11 by a pin 13. The bottom of the boom cylinder 17
The end of the piston rod is rotatably attached to a lower portion of the base end side of the boom 11 by a pin 19. Due to the expansion and contraction of the boom cylinder 17, the boom 11 rotates up and down around the pin 12, and moves up and down. A substantially central portion of a tilt lever 16 is rotatably attached to a substantially central portion of the boom 11 via a pin 15. The bottom portion of the bucket cylinder 21 is rotatably attached to the vehicle body 1 by a pin 22.
The piston rod end 21 a at the rod tip is rotatably attached to the upper end of the tilt lever 16 by a pin 23. Further, the lower end of the tilt lever 16 and the bucket 14
Between the bracket 14b and the vicinity of the upper end thereof.
5 is rotatably attached by pins 24 and 26, respectively. The bucket 14 rotates up and down around the pin 13 via the tilt lever 16 and the rod 25 by expansion and contraction of the bucket cylinder 21 to perform tilting and dumping.

FIG. 2 shows an example of a hydraulic circuit for driving the boom and the bucket. The hydraulic circuit will be described with reference to FIG. The oil discharged from the main hydraulic pump 31 is supplied to the pipeline 3
2 and flows into the bucket control valve 33. Bucket control valve 33 is normally operated by springs 33a, 33a.
The position is switched to the position A or the position B when the pilot pressure is applied to each of the pilot operation sections 33b and 33c. The bucket control valve 33 is connected to the pump port a
1, a2, bypass port a3, cylinder port a4,
a5 and a tank port a6. The pump ports a1 and a2 are connected to the main hydraulic pump 31 via a pipe 32, and the bypass port a3 is connected to a boom control valve 41 via a pipe. The cylinder ports a4 and a5 are connected to the bottom port 21b and the head port 21c of the bucket cylinder 21 via pipes 35 and 36, respectively. Tank port a6 is connected to line 37
And to a tank 39 via a conduit 38.

A proximity switch 27 is provided near the bucket cylinder 21. This proximity switch 27
Has one end attached to the piston rod end 21a,
The other end of the bucket leveler bar 28 arranged in parallel with the bucket cylinder 21 is installed so as to be activated when it comes to a predetermined position as the bucket cylinder 21 expands and contracts. 29.

The boom control valve 41 is usually provided with a spring 4
When the pilot pressure is applied to each of the pilot operation portions 41b and 41c, the position is switched to the C position or the D position, respectively. Boom control valve 41
Has pump ports b1, b2, a bypass port b3, cylinder ports b4, b5, and a tank port b6. The pump ports b1, b2 are connected to a pipe 34, and the bypass port b3 is connected to a pipe 42, and further connected to a tank 39 via a pipe 38. Cylinder ports b4 and b5 are connected to pipe 4 respectively.
3 and 44, and connected to the bottom port 17b and the head port 17c of the boom cylinder 17. The tank port b6 is connected to the pipe 45 and to the tank 39 via the pipe 38.

The discharge oil of the pilot hydraulic pump 46 is maintained in a pressurized state at a predetermined pressure or higher by a relief valve 47, and the pump port of a pilot pressure operating valve 51 for a bucket and a pilot pressure operating valve 52 for a boom are connected via a pipe 48. c1,
flows into d1. The bucket pilot pressure control valve 51 has a tilt pilot pressure control valve 51a and a dump pilot pressure control valve 51b. When the lever 51c is operated in the tilt direction, the pilot pressure corresponding to the operation amount is changed to the tilt pilot pressure control valve. The output from the output port c3 of the valve 51a is input to the pilot control section 33b of the bucket control valve 33 through the pipe 52, the switching valve 53, and the pipe 54. Similarly, when the lever 51c is operated in the dump direction,
The pilot pressure corresponding to the manipulated variable is output from the output port c4 of the dumping pilot pressure control valve 51b,
5 is input to the pilot operation section 33c of the bucket control valve 33. Boom pilot pressure control valve 52
Has a raising pilot pressure operating valve 52a and a lowering pilot pressure operating valve 52b. When the lever 52c is operated in the raising direction, a pilot pressure corresponding to the operation amount is output from the output port d3 of the raising pilot pressure operating valve 52a. Output
The signal is input to the pilot operating section 41b of the boom control valve 41 via the conduit 56. Similarly, when the lever 52c is operated in the lowering direction or the floating direction, a pilot pressure corresponding to the operation amount is output from the output port d4 of the lowering pilot pressure operating valve 52b, and the bucket control valve 41 is connected via the pipe 57. Is input to the pilot operation unit 41c.

When the lever 52c is operated in the floating direction, the boom control valve 41 remains in the D position, and a switching valve (not shown) attached to the boom control valve 41 (called a float selector valve) and an unload valve By the operation of
The oil discharged from the main hydraulic pump 31 and the oil on the bottom side and the head side of the boom cylinder 17 all return to the tank 39 via the conduit 38, and the boom cylinder 17 (that is,
The boom 11) is in a floating state (free state).

When the levers 51c and 52c are at the "neutral" position, the output ports c3 and c4 and the output ports d3 and d4 of the pilot pressure control valve 51 for the bucket and the pilot pressure control valve 52 for the boom are respectively connected to the drain port c2 and the drain port c2.
d2 and to the tank 39 via a pipe 49.

The bucket operating lever 61 is linked to the lever 5 of the bucket pilot pressure operating valve 51 by a link 62.
1c, the movement of the bucket operation lever 61 is transmitted to the lever 51c. Bucket operating lever 61
A rotatable cam 63 is provided. A roller 64a provided at the tip of the drive shaft of a detent solenoid 64 for assisting holding at the "tilt" position of the bucket operating lever 61 is fitted into the cam 63. A groove 63a is formed. The controller 29 is connected to the operation solenoid of the detent solenoid 64, and when the proximity switch 27 provided on the bucket cylinder 21 is operated, the roller 6 is actuated by the operation command from the controller 29.
4a comes off the groove 63a of the cam 63, and returns the bucket operation lever 61 to the "neutral" position.

The boom operation lever 71 is connected to a lever 52 of the boom pilot pressure operation valve 52 by a link 72.
The movement of the boom operation lever 71 is transmitted to the lever 52c. The boom operation lever 71 is provided with a cam 73 rotatably. The cam 73 is provided at a tip end of a shaft of a detent mechanism 74 for assisting holding the boom operation lever 71 at an “up” position and a “floating” position. Grooves 73a into which the provided rollers 74a are fitted,
73b are formed. The roller 74 is urged toward the cam 73 by a spring (not shown) built in the detent mechanism 74.

The switching valve 53 is normally held at a position F having a direct flow path by a spring 53a. However, when the boom operation lever 71 is at a "lower" or "floating" position, the pilot of the boom control valve 41 is controlled. The pilot pressure acts on the operation portion 41c, and the pilot pressure acts on the pilot operation portion 53b of the switching valve 53, thereby switching to the G position having the throttle passage.

The controller 29 is composed of, for example, a microcomputer, an electronic circuit or a relay circuit. When a detection signal of the proximity switch 27 is input, the controller 29 performs a predetermined judgment process and outputs an operation command to the detent solenoid 64. It has become.

Next, the operation will be described with reference to FIGS. After dumping the bucket 14 at the raised position of the boom 11 (FIG. 3 shows the dumping posture of the bucket at the boom raised position), the boom operating lever 71 is operated to the “lower” or “floating” position to lower the boom 11. Along with
The bucket 14 is raised by operating the bucket operation lever 61 to the “tilt” position. At this time, the bucket operating lever 61 is held at the “tilt” position by the detent solenoid 64. Thereafter, when the bucket 14 reaches the predetermined posture position, the bucket leveler operates, the bucket operation lever 61 returns to the “neutral” position, and the process until the bucket 14 stops will be described below. When the boom operation lever 71 is operated to the “down” or “floating” position,
The roller 74a of the detent mechanism enters the groove 73a or 73b of the cam 73 of the boom operation lever 71, and the boom operation lever 71 is fixed at this position. As a result, the lever 52c of the boom pilot pressure control valve 52 is fixed at the “lower” or “floating” position, and the lower pilot pressure control valve 5
The pilot pressure is output from 2b and input to the pilot operating section 41c of the boom control valve 41 via the pipe line 57, and the boom control valve 41 switches to the D position. at the same time,
This pilot pressure is supplied to the switching valve 53 via lines 57 and 58.
The switching valve 53 is switched to the G position.

When the bucket operating lever 61 is operated to the "tilt" position, the roller 64a of the detent solenoid 64 enters the groove 63a of the cam 63 of the bucket operating lever 61,
At this position, the bucket operation lever 61 is fixed. Thereby, the lever 5 of the bucket pilot pressure control valve 51 is
1c is fixed at the “tilt” position, the pilot pressure is output from the tilt pilot pressure control valve 51a, and the pipeline 5
2. It is input to the pilot operation unit 33b of the bucket control valve 33 via the throttle passage of the switching valve 53 and the pipeline 54. Then, the bucket control valve 33 is switched to the position A, and the discharge oil of the main hydraulic pump 31 is supplied to the pipeline 32, the pump port a.
2. The oil flows into the bottom port 21b of the bucket cylinder 21 through the cylinder port a4 and the pipe 35, and the oil from the head port 21c flows through the pipe 36, the cylinder port a5, the tank port a6, the pipe 37 and the pipe 38. Then, it returns to the tank 39. Thereby, the bucket cylinder 21
Extend, and the bucket 14 tilts.

When the bucket 14 is tilted to a predetermined attitude position (an attitude in which the bottom surface of the bucket is substantially horizontal on the ground), the piston rod end 21 of the bucket cylinder 21 is rotated.
The bucket leveler bar 28 fixed to the bucket a moves to a predetermined position, the proximity switch 27 provided on the bucket cylinder 21 is deactivated, and a signal is sent to the controller 29.
Output to The output signal is an ON signal (NC)
Alternatively, an off signal (NO) may be used. Upon receiving this signal, the controller 29 outputs an operation command to the detent solenoid 64. As a result, the detent solenoid 6
4, the roller 64a is disengaged from the groove 63a of the cam 63, and the bucket operating lever 61 is returned to the "neutral" position. The lever 51c of the bucket pilot pressure control valve 51 is also returned to the "neutral" position, and the output port c3 of the tilt pilot pressure control valve 51a is connected to the drain port c2.

At this time, as described above, the boom operation lever 7
1 is fixed in the "down" or "floating" position,
A predetermined pilot pressure acts on the pilot operating portion 41c of the boom control valve 41, and the switching valve 53 is switched to the G position where the throttle flow path is located. Therefore, the bucket control valve 3
The pilot pressure oil that has acted on the third pilot operating portion 33b gradually flows through the throttle passage of the switching valve 53 to the drain port c2 of the tilt pilot pressure operating valve 51a, and the pilot pressure gradually decreases, thereby controlling the bucket pressure. The valve 33 is gradually switched from the position A to the position N. Thereafter, the discharge oil from the main hydraulic pump 31 is input to the boom control valve 41 via the bucket control valve 33, and the boom control valve 41
Since the position has been switched to the position, the boom 11 starts to descend and eventually assumes the posture shown in FIG. The operation of the boom control valve 41 will not be described here.

According to the first embodiment, even if the bucket leveler operates and the bucket operating lever 61 suddenly returns to the "neutral" position, the bucket control valve 33 gradually moves from the position A to the position N. The switching is performed, and the bucket 14 is gradually stopped. Therefore, no shock occurs when the bucket 14 is suddenly stopped. When the bucket 14 is operated independently, the switching valve 53 is at the F position where the direct flow path is present, and the bucket control valve 33 operates at a normal speed, so that the movement of the bucket 14 does not become slow. Therefore, since the "bucket swing" operation can be performed, the earth and sand stuck in the bucket can be removed at any time, and the workability does not decrease.

Next, a second embodiment will be described with reference to FIG. This embodiment is different from the first embodiment in that the switching valve 53 is replaced by an electric switching valve 53A.
The switching operation of A is performed by an operation signal of the bucket leveler. FIG. 4 is an example of a hydraulic circuit diagram, and components denoted by the same reference numerals as those in the first embodiment are the same components, and description thereof is omitted. The controller 29 responds to a signal from an unillustrated operating lever position detector to operate the bucket operating lever 6.
1 and the operation position of the boom operation lever 71 are determined. The switching valve 53A is normally held at a position F having a direct passage by a spring 53c. When the bucket operating lever 61 is at the tilt position and the boom operating lever 71 is at the lowered position or the floating position,
When a bucket leveler operation position detection signal of the proximity switch 27 provided near the bucket cylinder 21 is input, the controller 29 outputs an operation command to the solenoid operating portion 53d of the switching valve 53A to move to the G position having the throttle passage. Switch. The operation after the switching is the same as in the first embodiment, and a description thereof will be omitted.

According to the second embodiment, the following effect is added to the effect of the first embodiment. In other words, the pilot pressure oil output from the tilt pilot pressure control valve 51a is maintained until the bucket leveler operates.
Since the bucket passes through the direct passage (F position) of the switching valve 53A, the bucket can be started quickly.

In the second embodiment, the switching valve 53A and the detent solenoid 64 are electrically operated. However, the switching valve 53A and the detent solenoid 64 may be operated mechanically or hydraulically using a kickout mechanism. It is.

[Brief description of the drawings]

FIG. 1 shows a bucket scooping posture on the ground of a loader to which a bucket leveler shock reduction device according to the present invention is applied.

FIG. 2 shows an example of a hydraulic circuit for driving a boom and a bucket in the first embodiment of the bucket leveler shock reduction device according to the present invention.

FIG. 3 shows a dump posture of a bucket at a boom raising position according to the first embodiment.

FIG. 4 shows an example of a hydraulic circuit for driving a boom and a bucket according to a second embodiment.

[Explanation of symbols]

1 ... front, 11 ... boom, 14 ... bucket, 16 ...
Tilt lever, 17: boom cylinder, 21: bucket cylinder, 25: rod, 27: proximity switch, 28:
Bucket leveler bar, 29 ... Controller, 31, 4
6 ... hydraulic pump, 33 ... bucket control valve, 33b, 33
c ... operation part, 41 ... boom control valve, 41b, 41c ... operation part, 51 ... bucket pilot pressure operation valve, 51a ...
Tilt pilot pressure control valve 51c: lever, 52: boom pilot pressure control valve, 52b: lowering pilot pressure control valve, 52c: lever, 53, 53A: switching valve, 5
3b, 53d: operation unit, 61: bucket operation lever, 6
3 ... Cam, 64 ... Detent solenoid, 64a ... Roller, 71 ... Boom operating lever, 73 ... Cam, 74 ... Detent mechanism, 74a ... Roller.

Claims (2)

[Claims] A bucket (1) for an industrial vehicle or a construction vehicle.
4) and a bucket cylinder (21) for driving the bucket (14)
A bucket control valve (33) for controlling a bucket cylinder (21) based on an operation amount of a bucket operation lever (61), a boom cylinder (17) for driving a boom (11), and a boom operation lever (71) A boom control valve (41) for controlling the boom cylinder (17) based on the operation amount of the
(33) and a boom control valve (41) have a hydraulic circuit connected in series with the bucket (14) during tilt drive of the bucket (14).
The bucket operating lever (61) is
The bucket control valve (33) based on the amount of tilt operation of the bucket operating lever (61).
3b) a direct flow path position interposed between the tilt pilot pressure control valve (51a) for outputting the pilot pressure and the tilt pilot control section (33b) of the bucket control valve (33).
(F) and a switching valve (53) having a throttle valve position (G), and when the boom operating lever (71) is operated to the `` down '' or `` floating '' position, the switching valve (53) is moved to the throttle valve position ( G), and a control means for switching to (G). The control means includes a boom operation lever (71).
The pilot pressure output from the lowering pilot pressure operating valve (52b) to the lowering pilot operating portion (41c) of the boom control valve (41) is switched based on the amount of operation in the "lower" or "floating" direction. Acts on the pilot operation part (53b) of the valve (53), and switches the switching valve (53) to the throttle valve position (G) when the boom operation lever (71) is operated to `` lower '' or `` float ''. The apparatus for reducing a shock of a bucket leveler according to claim 1, wherein: