JPH0513819Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a vibration suppression device for suppressing vibrations during running in a wheel-type working machine such as a wheel loader.

(Prior art) A wheel-type working machine consists of a traveling body equipped with wheels, a working device attached to the front part of the traveling body so that it can be raised and lowered (moved up and down), and a hydraulic cylinder that raises and lowers this working device. It is well equipped.

This wheel-type working machine does not have a running shock absorber, so when running,
Vibration is likely to occur due to uneven road surfaces, sudden acceleration, deceleration, etc.

Conventionally, as a means to suppress this vibration during driving,
BACKGROUND ART Machines are known in which vibration energy acting on a working device is absorbed by a supporting portion of the working device, thereby suppressing vibrations of the entire machine. Specifically, as shown in Japanese Patent Application Laid-Open No. 59-182195, a spring and a dump mechanism are provided inside the piston rod of a hydraulic cylinder in a working device, or as shown in Japanese Patent Application Laid-Open No. 60-119830. As shown in Fig. 1, a shock absorbing cylinder provided separately from a hydraulic cylinder is known, but it has drawbacks such as a complicated structure, high manufacturing cost, and low vibration suppression effect. It was hardly suitable for practical use.

(Purpose of the invention) Therefore, the present invention provides a vibration suppressing device for a wheel-type working machine that has a simple configuration and can obtain a high vibration suppressing effect.

(Structure of the invention) The present invention provides a wheel-type working machine that includes a traveling body, a working device attached to the traveling body so as to be able to be raised and lowered, and a hydraulic cylinder that raises and lowers the working device. A vibration suppression circuit including an accumulator and a switching valve that is switched on and off based on an electric signal is connected to the oil chamber on the side where pressure is generated due to the load in the direction of lowering the working equipment, and the above-mentioned A control circuit for controlling the switching valve on and off is provided with a switch means for detecting the height of the working device above the ground and outputting an off signal to the switching valve when the detected value is less than a set value.

With this configuration, the vibration energy acting on the work equipment can be effectively absorbed by the spring action of the accumulator, even though the configuration is as simple as connecting a vibration suppression circuit equipped with an accumulator and a switching valve to a hydraulic cylinder. , thereby achieving a vibration damping effect for the entire machine.

In addition, by switching the switching valve, it is possible to switch between a travel mode in which the accumulator works effectively and a work mode in which the accumulator is disabled. Contact with the road surface can be prevented.

(Example) An embodiment of the present invention will be described with reference to the drawings.

In this embodiment, a wheel loader is taken as an example of a wheel-type working machine to which the present invention is applied.

The overall configuration of this wheel loader is shown in FIG. In the figure, reference numeral 1 denotes a loader main body as a traveling body equipped with wheels 2, and this loader main body 1
A working device 4 is attached to the front frame 3 of the machine so as to be able to move up and down (move up and down).

This working device 4 includes a boom 5 attached to a front frame 3 so as to be rotatable up and down, and a bucket 6 attached to the tip of the boom 5 so as to be movable up and down.
and a bendable link member 7 provided between the middle part of the boom and the upper surface of the bucket. It is adapted to be supported and driven. The configuration of the hydraulic circuit that controls both cylinders 8 and 9 is shown in FIG.

In FIG. 1, 10 is a tank, 11 is a hydraulic pump, 12 is a first directional control valve for the dump cylinder 9, 13 is a second directional control valve for the boom lift cylinder 8; , both the head side and rod side oil chambers 9a, 9b of the dump cylinder 9 are connected via the pressure oil supply and discharge pipes 14, 15 to the second oil chamber 9a, 9b.
The head side and rod side oil chambers 8a, 8b of the boom lift cylinder 8 are connected to the directional control valve 13 via pressure oil supply/drain lines 16, 17, respectively.

Further, in the boom lift cylinder 8,
A branch pipe 18 is connected in the middle of a pressure oil supply/drain pipe 16 connected to the head side oil chamber 8a where pressure is generated by the load of the working device 4, and an electromagnetic switching valve 19 and An accumulator 21 is connected via the diaphragm 20 to form a vibration suppression circuit 22. In addition, the accumulator 21 includes:
Usually, a bladder type accumulator is used.

23 is a main relief valve, 24, 25, 26 are overload relief valves, and 27 is a cavitation prevention check valve.

In the configuration up to this point, when performing excavation work, the solenoid switching valve 19 is turned off (blocked) as shown.
position. In this state, by switching the second directional control valve 13, pressure oil from the pump 11 is supplied to the head side oil chamber 8a or rod side oil chamber 8b of the boom lift cylinder 8, and the cylinder 8 is extended or contracted. Then, the boom 5 operates to raise and lower. In addition, by switching the first directional control valve 12, pressure oil from the pump 11 is supplied to the head side oil chamber 9a or rod side oil chamber 9b of the dump cylinder 9, and the cylinder 9 is expanded or contracted, and the bucket is opened. 6 performs scooping or dumping operation. During this work, since the pipe line 16 and the accumulator 21 are cut off, the working device 4
is maintained in its original supported state in which it is integrated with the loader main body 1. Furthermore, even if the load pressure applied to the oil chamber 8a of the boom lift cylinder 8 becomes high during this work, this high-pressure oil will not flow into the accumulator 21, and damage to the accumulator 21 will be prevented. At times, the electromagnetic switching valve 19 is switched to the on position on the right side of the figure while the first and second bidirectional control valves 12 and 13 are set at the neutral position shown. Further, during this running, the bucket 6 is set at a predetermined height above the ground in the maximum upward position shown in the figure, as a normal so-called running position.

While driving in this state, vibrations occur in the loader body 1 due to uneven road surfaces, sudden acceleration or deceleration, etc.
The vibration energy that acts on the working device 4 is applied to the boom lift cylinder 8 that supports the working device 4, thereby causing the head side oil chamber 8a of the cylinder 8 and the pressure oil supply connected to the same oil chamber 8a to Pressure fluctuations occur in the exhaust line 16.

In this case, since the conduit 16 communicates with the accumulator 21 via the electromagnetic switching valve 19 and the throttle 20, the oil in the oil chamber 8a flows through the conduit 16, the branch conduit 18, the electromagnetic switching valve 19, It flows into and out of the accumulator 21 through the throttle 20, and at this time, the so-called spring action of the accumulator 21 and the throttle 20
The vibration energy is absorbed by the damping effect due to the pressure loss at.

That is, according to the wheel loader having the above configuration, it can be considered as a dynamic vibration damper in which the loader main body 1 is the main vibration system and the working device 4 side, which has a smaller weight (mass) than the loader main body 1, is the sub vibration system. By selecting the capacity of the accumulator 21 and the pressure of the filled gas so that the natural frequency of the auxiliary vibration system on the working device 4 side is approximately equal to the natural frequency of the main vibration system on the loader main body 1 side, This provides an effective vibration damping effect and suppresses the vibration of the entire machine.

By the way, the normal running posture is Bucket 6.
is set as low as possible (normally, the height H above the ground is about 10 cm) so as not to make contact with the road surface and not obstruct driving visibility. In this state,
By switching the electromagnetic switching valve 19 from the OFF position to the ON position, the working device support state is switched from the working mode to the travel mode. However, when this mode is switched, oil in the head side oil chamber 8a of the boom lift cylinder 8 is absorbed into the accumulator 21, causing a phenomenon in which the bucket suddenly descends. The lowering amount of the bucket 6 increases as the bucket weight increases, and if the bucket height H from the ground is not sufficient, the bucket 6 may come into contact with the road surface. Moreover, such a situation also occurs due to severe vibrations during driving, and becomes a major hindrance to driving.

Therefore, in this device, the following measures are taken as a countermeasure for this point.

As shown in Figures 1 and 3, a normally closed limit switch 28 is provided on the front frame 3 of the wheel loader 1, and a cam 29 is provided at the base end of the boom 5 for contacting the limit switch 28 to turn it off when the boom angle falls below the set value θ, that is, when the bucket height H above the ground falls within the dangerous height range where the bucket 6 may come into contact with the road surface due to the bucket descent at the time of mode switching and vibration during traveling. The limit switch 28 is connected in series with a mode switching switch 30 operated by the operator in a control circuit which sends an ON/OFF signal to the solenoid operating unit 19a of the solenoid switching valve 19, as shown in Figure 1, and is configured so that an ON signal, i.e., a switching signal to the traveling mode, is output to the solenoid operating unit 19a of the solenoid switching valve 19 only when both of these switches 28, 30 are in the ON state.

Therefore, when the bucket height H is within the dangerous height range at the time of mode switching, the limit switch 28 is turned off and the electromagnetic switching valve 19 is held in the off position, so that the mode switching switch 30 is turned on. However, mode switching is not performed. Furthermore, even if the bucket 6 falls to a dangerous height due to vibration while traveling in the travel mode, the limit switch 28 is turned off and the electromagnetic switching valve 19 is switched to the OFF position, so that the supporting state of the working device 4 is changed. The travel mode is switched to the work mode, and the vibration damping action by the vibration suppression circuit 22 is stopped. This prevents the bucket 6 from coming into contact with the road surface due to lowering of the bucket at the time of mode switching or vibration during driving, thereby ensuring running safety.

Note that the dangerous height of the boom 5 changes depending on road conditions, cargo load, etc., so the limit switch 2 is set so that the set boom angle θ can be adjusted as appropriate.
8 or cam 29 is preferably mounted in a variable position.

Other Embodiments (a) In the vibration suppression circuit 22, the so-called slow return valve consisting of a throttle and a check valve may be used in place of the throttle 20. Alternatively, instead of providing such a constriction section, the constriction effect due to the pressure loss of the conduit may be utilized.

(b) In addition to the limit switch 28 of the above embodiment, a magnetic sensor, optical sensor, etc. may be used as the switch means for detecting the height of the bucket (working device) above the ground and outputting an on/off signal to the electromagnetic switching valve 19. You can.

(c) In the above embodiment, the vibration suppression circuit 22 is branch-connected in the middle of the pressure oil supply and discharge pipe 16 to the hydraulic cylinder 8.
It may be directly connected to the oil chamber 8a.

Further, although the present invention is particularly suitable for the above-mentioned wheel loader, it is also applicable to other wheel-type working machines that have the same circumstances as wheel loaders.

(Effects of the invention) As described above, the present invention has a simple configuration in which a vibration suppression circuit equipped with an accumulator is connected to a hydraulic cylinder that supports a working device.
Easy to manufacture and integrate into existing machines,
Moreover, a high vibration suppression effect can be obtained due to the spring action of the accumulator.

In addition, the vibration suppression circuit is provided with a switching valve that connects and disconnects the accumulator and the above-mentioned pipe line, and this switching valve allows the vibration suppression circuit to be set in a running mode in which it is enabled and a work mode in which the circuit is disabled. Since the working device is configured to be able to be switched to, during work, it is possible to maintain the working device in its original supported state in which it is integrated with the traveling body, and it is also possible to prevent high pressure oil from flowing into the accumulator.

In addition, according to the present invention, when the height of the work equipment above the ground is below the set value, the switching valve is turned off and the vibration suppression circuit is disabled. This can prevent contact with the road surface and ensure driving safety.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic and electrical circuit configuration diagram of a vibration suppressing device according to an embodiment of the present invention, FIG. 2 is a side view of a wheel loader incorporating the same device, and FIG. 3 is an enlarged view of a portion of the same. 1...Wheel loader main body, 4...Working device,
5...Boom of working equipment, 6...Bucket, 8
...Boom lift cylinder that raises and lowers the working equipment, 8a...Oil chamber in which pressure is generated by the load in the cylinder, 16...Pressure oil supply and drainage pipe connected to the oil chamber, 18...Branch pipe 22... Vibration suppression circuit, 19... Solenoid switching valve of the same circuit, 21...
...The same accumulator.

Claims (1)

[Scope of utility model registration request] In a wheel-type working machine comprising a traveling body, a working device attached to the traveling body so that it can be raised and lowered, and a hydraulic cylinder that raises and lowers the working device, a load on the hydraulic cylinder in the direction of lowering the working device is applied. Therefore, a vibration suppression circuit including an accumulator and a switching valve that is switched on and off based on an electric signal is connected to the oil chamber on the side where pressure is generated, and a control circuit that controls the switching valve on and off is connected to the oil chamber on the side where pressure is generated. A vibration suppressing device for a wheel-type working machine, comprising a switch means for detecting the height of the working device from the ground and outputting an off signal to the switching valve when the detected value is less than a set value.