JPH0930229A - Work vehicle suspension system - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a suspension device for a work vehicle capable of suppressing the vibration and impact of the vehicle body caused by the action of a large load and the ground cutting. [Composition] Proportional solenoid valve 2 for no load or light load
The opening degree of 3 is in the fully open state shown in the figure, and the vibration of the vehicle body 2 is absorbed and damped by the inflow and outflow of oil between the hydraulic cylinder 6 and the pressure accumulator 11, and the throttle 12. When the load increases, the stroke of the hydraulic cylinder 6 contracts, the control unit 24 throttles the proportional solenoid valve based on the detection value of the stroke sensor 22, and when the stroke becomes less than a predetermined value s ₁ , the proportional solenoid valve 23 is shut off and the hydraulic cylinder is closed. Lock 6 This allows
You can perform work with a large load without hindrance,
In addition, before the hydraulic cylinder 6 is locked, the proportional solenoid valve 23
Is reduced and its speed is reduced, so shock and vibration are suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension system for a work vehicle used in a work vehicle that moves by wheels with tires.

[0002]

2. Description of the Related Art In a work vehicle that moves by wheels with tires, for example, a wheel shovel or a wheel loader, an axle for driving the wheels and a vehicle body are directly fixed to each other or are connected by a pin joint. However, in recent years, work vehicles are often moved and moved on general roads, which hinders the travel of other vehicles at low speeds, causing road congestion. For this reason, a means for making the work vehicle have high-speed traveling performance and traveling at high speed on an ordinary road has been used.However, when a work vehicle in which the axle and the vehicle body are fixed or pin-jointed is driven at high speed, the road surface becomes uneven. The vertical movement of the wheels is directly transmitted to the vehicle body, the ride comfort of the operator is extremely deteriorated, and further, due to the elasticity of the tires, the resonance vibration of the vehicle body is generated and the entire vehicle body bounces and the ground contact with the road surface is deteriorated. Therefore, there is a problem that the stability of the operation of the work vehicle is adversely affected.

In order to solve this problem, a hydraulic cylinder is mounted between the axle and the vehicle body, and even if the hydraulic cylinder is mounted in this way, there will be no hindrance to work under a large load. For example, Japanese Patent Application No. 7-71746 proposes a work vehicle in which a stopper is provided in parallel with a hydraulic cylinder. An example of such a work vehicle will be described with reference to the drawings.

FIG. 4 is a side view of the work vehicle, and FIG. 5 is a front view of the work vehicle shown in FIG. In each figure, 1 is a work vehicle, 2
Is a vehicle body, 3 is an axle attached to the vehicle body 2, and 4 is left and right wheels driven by the axle 3. The front or rear axle 3 (rearward in FIG. 4) is directly coupled to the vehicle body 2 to increase the rigidity of the vehicle body against rolling. 6
Is a hydraulic cylinder mounted between the vehicle body 2 and substantially the center of the axle 3 on one axle 3 of the work vehicle 1, and is pin-connected to the vehicle body 2 and the axle 3 by pins 8 and 9. . Reference numeral 7 denotes a link mounted between the axle 3 and the vehicle body 2, and the axle 3 has a hydraulic cylinder 6
And a pin 8 common to the vehicle body 2 and a pin 10 to the vehicle body 2. The hydraulic cylinder 6, the link 7, and the vehicle body structure between the pin 9 and the pin 10 constitute a triangular link mechanism. Reference numeral 11 denotes a pressure accumulator connected to the hydraulic cylinder by piping, and 12 denotes a throttle provided between the pressure accumulator 11 and the hydraulic cylinder 6.

Numeral 15 is a stopper mounted in parallel with the hydraulic cylinder 6, and comprises a stopper element 15a made of a highly rigid member fixed to the vehicle body 2 side and a highly rigid member fixed to the axle 3 side. Stop element 15b
It is composed of A gap g exists between the stopper elements 15a and 15b, and when the hydraulic cylinder 6 contracts due to a large load acting between the vehicle body 2 and the axle 3, this gap g has a stroke end on the contraction side. Before reaching 0
(Stopper element 15a and stopper element 15b collide).

Reference numeral 17 is an upper revolving structure, and 17a is an upper revolving structure 1.
7 is a driver's cab, 18 is a boom rotatably attached to the upper swing body 17, 19 is an arm rotatably attached to the boom 18, and 20 is rotatably attached to the arm 19. It is a bucket. Boom 18 and arm 19
The bucket 20 constitutes a front mechanism 21. Note that, in FIG. 5, the upper swing body 17 and the front mechanism 21 are not shown.

Next, the operation of the work vehicle 1 will be described.
Since the hydraulic cylinder 6 and the pressure accumulator 11 are in communication with each other when the vehicle body 2 is stationary, their pressures are the same. Next, when the work vehicle 1 travels, the wheels 4 move up and down due to the unevenness of the road surface, and accordingly, the piston of the hydraulic cylinder 6 expands and contracts through the axle 3 while deforming the triangular link mechanism, The pressure of the hydraulic cylinder 6 decreases when the pressure increases, and the pressure of the hydraulic cylinder 6 increases when the pressure decreases.

When the pressure of the hydraulic cylinder 6 decreases, pressure oil is supplied from the pressure accumulator 11 to the hydraulic cylinder 6, and when the pressure of the hydraulic cylinder 6 increases, the pressure oil from the hydraulic cylinder 6 is accumulated in the pressure accumulator 11. When the hydraulic cylinder 6 receives an external force due to the unevenness of the road surface due to the supply and accumulation of the pressure oil between the hydraulic cylinder 6 and the pressure accumulator 11, the piston strokes to absorb the external force and the vehicle body 2 Absorbs the transmission of vibrations to. The relationship between the change in the pressure of the hydraulic cylinder 6 and the stroke of the piston is determined by the compression elasticity of the gas accumulated in the pressure accumulator 11, and the compression elasticity of this gas absorbs the vibration and acts as a spring function.

Further, when the stroke of the piston of the hydraulic cylinder 6 changes rapidly (oscillation cycle is short), the movement of the pressure oil between the hydraulic cylinder 6 and the pressure accumulator 11 is restricted by the throttle 12 interposed in the pipe. As a result, short cycle vibrations are damped.

Further, since the axle 3 is rotatable around the pin 8, the ground pressure of each wheel 4 can be kept equal even if the road surface has irregularities, and the grounding property of the work vehicle can be improved. The adverse effect on performance can be eliminated.

With the work vehicle 1 stationary, the boom 1
8. When excavation work is performed by the arm 8, the arm 19, and the bucket 20, the hydraulic cylinder 6 contracts due to the excavation reaction force, but the stopper element 15 is contracted before the contraction reaches the stroke end.
The a and the stopper element 15b collide with each other, and thereafter, the excavation reaction force is received by the stopper 15. That is, during excavation, the excavation reaction force is applied to the bucket 20, the arm 19, the boom 18, and the upper swing body 1.
7, the hydraulic cylinder 6 is transmitted through the route of the vehicle body 2, the stopper 15, and the axle 3, and is removed from the route for transmitting the excavation reaction force, so that high rigidity required for excavation can be maintained.
If the bucket 20 moves away from the ground during excavation, the excavation reaction force disappears, and the reaction causes the hydraulic cylinder 6 to extend.
With the hydraulic cylinder 6 interposed, the hydraulic cylinder 6 and the accumulator 1
The suspension consisting of 1 and the diaphragm 12 works, and the body 2
Absorbs and damps the vibration of.

[0012]

The work vehicle described above can absorb and damp vibrations during traveling to improve traveling performance, and can also prevent the large excavation reaction force from being generated by the stopper 15.
Can fully withstand. However, stopper 1
When 5 is in a non-contact state, when a large force (excavation reaction force) acts on the vehicle body 2 via the front mechanism 21 and the stopper 15 comes into contact with the vehicle body 5, the force is directly transmitted to the tire 4 to deform the tire 4, Then, the tire 4 rebounds, and the operation of returning to the original shape again occurs. This operation is particularly promoted when the entire front mechanism 21 is in an extended state, and the vehicle body 2 vibrates and cannot follow the operation of the tire 4,
By repeating the operation several times, the stopper 15 is impacted with the vibration of the vehicle body 2 each time.
Such a situation also occurs when digging. These vibrations and shocks are transmitted to the operator in the cab 17a, hindering the operation of the operator and increasing fatigue.

An object of the present invention is to solve the above-mentioned problems in the prior art and to provide a suspension system for a work vehicle capable of suppressing the vibration and impact of the vehicle body caused by the action of a large load and ground cutting.

[0014]

In order to achieve the above object, the present invention provides a vehicle body equipped with a working mechanism, an axle mounted on the front and rear of the vehicle body, and a tire mounted and driven by each of the axles. Left and right wheels, a hydraulic cylinder pin-connected between at least one of the axles and the vehicle body, a pressure accumulator connected to the hydraulic cylinder by a pipe, and a throttle interposed in the pipe. In a work vehicle having, a sensor for detecting the magnitude of the load acting on the hydraulic cylinder, a solenoid valve interposed in the pipe and controllable to full open, shutoff, and an intermediate opening degree therebetween, and the sensor A control unit for controlling the opening of the solenoid valve according to the detected value is provided.

[0015]

When the load acting on the vehicle body changes, the stroke or pressure of the hydraulic cylinder changes accordingly. The sensor detects the stroke or pressure and outputs it to the controller. The control unit controls the opening degree of the solenoid valve according to the input stroke or pressure. When the load becomes large and the stroke contracts below a predetermined value or the pressure becomes larger than a predetermined value, the control unit sets the opening of the control valve to 0 (control valve is closed), thereby locking the hydraulic cylinder. . This state corresponds to the state in which the stopper is in contact with the conventional device, and no impact is generated and no vibration is generated. Further, when the load is small, the control unit fully opens the opening of the solenoid valve, and at this time, the same running performance as the conventional device can be secured.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. FIG. 1 is a diagram showing a suspension system for a work vehicle according to an embodiment of the present invention. In this figure, the same or equivalent parts as those shown in FIGS. 4 and 5 are designated by the same reference numerals and the description thereof will be omitted. A stroke sensor 22 detects the stroke of the hydraulic cylinder 6, and is composed of, for example, a potentiometer. The stroke of the hydraulic cylinder 6 contracts when the load acting on the vehicle body 2 is large and expands when the load is small. Further, the bottom side and the rod side of the hydraulic cylinder 6 are connected by a pipe line as shown in the figure. Reference numeral 23 is a proportional solenoid valve interposed in a pipe between the hydraulic cylinder 6 and the pressure accumulator 11, and its opening changes from a fully open state to a shutoff state according to a signal given to the solenoid 23S.

Reference numeral 24 denotes a control unit, which is the stroke sensor 2
A signal for controlling the opening of the proportional solenoid valve 23 is calculated according to the detected value of 2. This calculation is shown in the illustrated block showing the controller 24. That is, the command signal given to the proportional solenoid valve 23 is large in the range a (where the load is large) where the stroke is less than the predetermined value s ₁ , and is proportional in the range c (when the load is small) where the stroke exceeds the predetermined value s _2. The command signal given to 23 is small, and the command signal given to the proportional solenoid valve 23 changes in proportion to the stroke in the range b between the predetermined value s ₁ and the predetermined value s ₂ .

Next, the operation of this embodiment will be described with reference to the timing chart shown in FIG. 2A shows a change in stroke with respect to time, FIG. 2B shows a change in speed of the hydraulic cylinder with respect to time, and FIG. 2C shows change in acceleration of the hydraulic cylinder with respect to time. A solid line shows a change in the apparatus of this embodiment. , Dashed lines show changes in conventional devices. When the load acting on the vehicle body 2 is no load or light load and the stroke exceeds the value s ₂ (in the case of range c), no command signal is output from the control unit 24 and the opening degree of the proportional solenoid valve 23 is As shown in FIG. 1, it is in a fully opened state. The operation in this case is the same as that of the conventional device. In this range c, the vehicle body 2
When the load acting on is increasing at an almost constant rate,
Although the stroke of the hydraulic cylinder 6 is reduced as shown in (a) of FIG. 2, its speed does not change as shown in (b) of FIG.

The stroke of the hydraulic cylinder 6 is a predetermined value s.
_{When the} value further decreases from ₂ and reaches a predetermined value s ₁ , during this period (between range b), a command signal that increases from the control unit 24 according to the stroke is sent to the solenoid 23 of the proportional solenoid valve 23.
Then, the proportional solenoid valve 23 decreases its opening. As the opening of the proportional solenoid valve 23 decreases, the speed of the hydraulic cylinder 6 decreases as shown in (b) of FIG.
As a result, the change in stroke also becomes gentle as shown in FIG. However, in the conventional device, the speed of the hydraulic cylinder continues to be constant from the range c, and the stroke reduction rate is also constant, as indicated by the broken lines in FIGS. 2 (a) and 2 (b).

When the load acting on the vehicle body 2 is further increased and the stroke of the hydraulic cylinder 6 becomes less than the predetermined value s ₁ (range a), the command signal of the control unit 24 becomes the maximum value and the proportional solenoid valve 23 is in the shut-off state. (The opening becomes 0, and the illustrated check valve is interposed between the hydraulic cylinder 6 and the pressure accumulator 11). At this time, the stroke of the hydraulic cylinder 6 has reached near the stroke end as shown in FIG. 2A, and the proportional solenoid valve 23 is in the closed state, so the speed of the hydraulic cylinder 6 is shown in FIG. ), The hydraulic cylinder 6 is locked. In this state, the state becomes equal to the state in which the vehicle body 2 and the axle 3 are directly connected (the state in which the stopper in the conventional device is in contact),
The load acting on the vehicle body 2 does not expand and contract the hydraulic cylinder 6,
As it is transmitted to the axle 3 and the tire 4, the work can be performed without any trouble.

Here, considering the state when the stroke becomes less than the predetermined value s ₁ , in the conventional device, the speed of the hydraulic cylinder 6 is constant until the stroke reaches the predetermined value s ₁ .
When the stroke becomes less than the predetermined value s ₁ , the stopper comes into contact and the hydraulic cylinder stops rapidly, so that the hydraulic cylinder 6 is suddenly and greatly accelerated as shown by the broken line in FIG. Causes a large impact.
On the other hand, in this embodiment, the proportional solenoid valve 23 is operated in the range b.
Is gradually throttled, and the speed of the hydraulic cylinder 6 is also reduced as shown in FIG.
As shown by the solid line in FIG.
As shown by the solid line in (c), although a small acceleration occurs in the range b, the acceleration does not change even when the stroke is less than the predetermined value s ₁ , and a large impact is not generated as in the conventional device. Absent.

With the hydraulic cylinder 6 locked as described above, when the load acting on the vehicle body 2 decreases,
The internal pressure of the hydraulic cylinder 6 decreases. Therefore, the pressure accumulator 1
The pressure of 1 becomes higher than the internal pressure of the hydraulic cylinder 6, the oil of the pressure accumulator 11 flows to the hydraulic cylinder 6 via the check valve of the proportional solenoid valve 23, and the locked state is released.

As described above, in this embodiment, the proportional solenoid valve 23 is controlled according to the stroke of the hydraulic cylinder 6 without using the stopper, and the oil flows between the hydraulic cylinder 6 and the pressure accumulator 11 to flow in and out. Therefore, when a large load is applied to the vehicle body 2, it is possible to suppress vibration and impact without hindering work.

FIG. 3 is a front view of a suspension system for a work vehicle according to another embodiment of the present invention. In this figure, the same or equivalent parts as those shown in FIG. In the previous embodiment, one hydraulic cylinder and a link were used as the suspension device, while in this embodiment, the vehicle body 2
And hydraulic cylinders are used at both ends of the axle 3, respectively. Each of these hydraulic cylinders has a reference numeral 6A, 6
B is attached. For the hydraulic cylinder 6A, the stroke sensor 22A, the proportional solenoid valve 23A, and the control unit 2
4A is provided, and for the hydraulic cylinder 6B, the stroke sensor 22B, the proportional solenoid valve 23B, and the control unit 2 are provided.
4B is provided. The functions of the stroke sensor 22A, the proportional solenoid valve 23A, and the control unit 24A for the hydraulic cylinder 6A, and the functions of the stroke sensor 22B, the proportional solenoid valve 23B, and the control unit 24B for the hydraulic cylinder 6B are the same as those in the previous embodiment. The operation and effect are also the same as those in the previous embodiment.

In the description of each of the above embodiments, the example using the stroke sensor has been described. However, the pressure sensor detects the pressure of the hydraulic cylinder, and the control unit uses the detected value to calculate the command signal. You may do it.

[0026]

As described above, according to the present invention, the stopper is not used, the solenoid valve is controlled according to the stroke of the hydraulic cylinder, and the oil leaks between the hydraulic cylinder and the pressure accumulator.
Since the inflow is controlled, when a large load is applied to the vehicle body, it is possible to suppress vibration and impact without hindering work.

[Brief description of drawings]

FIG. 1 is a front view of a suspension device for a work vehicle according to an embodiment of the present invention.

FIG. 2 is a time chart showing the operation of the device shown in FIG.

FIG. 3 is a front view of the suspension device for the work vehicle according to the embodiment of the present invention.

FIG. 4 is a side view of a conventional suspension device for a work vehicle.

5 is a front view of the suspension system for the work vehicle shown in FIG. 4. FIG.

[Explanation of symbols]

 2 vehicle body 3 axle 4 wheel 6 hydraulic cylinder 7 link 11 accumulator 12 throttle 22 stroke sensor 23 proportional solenoid valve 24 control unit

Claims (6)

[Claims] 1. A vehicle body having a working mechanism, axles attached to the front and rear of the vehicle body, left and right wheels to which tires are attached and driven by each of the axles, and at least one of the axles. In a work vehicle having a hydraulic cylinder pin-connected to the vehicle body, a pressure accumulator connected to the hydraulic cylinder by a pipe, and a throttle interposed in the pipe, a magnitude of a load acting on the hydraulic cylinder And a solenoid valve that is interposed in the pipe and that can be controlled to fully open, shut off, and an opening degree between them, and a control unit that controls the opening degree of the solenoid valve according to the detection value of the sensor. A suspension system for a work vehicle, characterized by being provided with. 2. The suspension system for a work vehicle according to claim 1, wherein the hydraulic cylinder is one hydraulic cylinder pin-connected to substantially the center of the one axle, and
A suspension system for a work vehicle, comprising a link which shares pin connection on the axle side of the hydraulic cylinder between the one axle and the vehicle body and which is pin-connected to the vehicle body. 3. The suspension system for a work vehicle according to claim 1, wherein the hydraulic cylinders are mounted between both end portions of the one axle and the vehicle body. 4. The control unit according to any one of claims 1 to 3, wherein the solenoid valve is in a shut-off state when the load has a large value, in a fully open state when the load has a small value, and A suspension system for a work vehicle, characterized in that when a load has an intermediate value, control is performed so as to change the opening degree according to the load. 5. The suspension system for a work vehicle according to claim 1, wherein the sensor is a stroke sensor that detects a stroke of the hydraulic cylinder. 6. The suspension system for a work vehicle according to claim 1, wherein the sensor is a pressure sensor that detects the pressure of the hydraulic cylinder.