JP3333334B2 - Work vehicle suspension - Google Patents

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 working vehicle such as a wheel type hydraulic excavator or a truck crane.

[0002]

2. Description of the Related Art A suspension system for a work vehicle of this type is disclosed, for example, in Japanese Utility Model Laid-Open Publication No. 63-12417. The suspension device suspends an axle constituting a lower traveling body on a chassis frame by a hydraulic cylinder, and communicates a cylinder chamber of the hydraulic cylinder with an accumulator to absorb an impact from a road surface with gas pressure sealed in the accumulator. In addition, the posture of the chassis frame is held horizontally based on the amount of expansion and contraction of the hydraulic cylinder detected by the stroke sensor. The reason why the attitude control is performed by the suspension device using the hydraulic cylinder is to satisfy both requirements of ride comfort and vehicle stability during traveling.

[0003]

However, for a vehicle such as a hydraulic excavator that requires work in a poor environment such as muddy ground, it is difficult to use a precision sensor such as a stroke sensor. This leads to a decrease in reliability. Also, since the attitude control of a hydraulic excavator does not require as high accuracy as the attitude control of a truck crane, it is necessary to accurately measure the amount of expansion and contraction of the hydraulic cylinder with a stroke sensor and control the hydraulic cylinder for attitude control according to the measurement result. Is low.

[0004] It is an object of the present invention to provide a suspension system for a work vehicle that can achieve both ride comfort and vehicle stability without increasing the cost and with improved reliability.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 to 5 showing one embodiment, the present invention relates to a hydraulic cylinder 11 for suspending an axle 8 on a chassis frame 1, and a cylinder of the hydraulic cylinder 11. An accumulator 23 connected to the chamber 11c, a suspension operation setting valve 22 for communicating the cylinder chamber 11c with the accumulator 23 to set a suspension operation state, and blocking the cylinder chamber 11 and the accumulator 23 to set a suspension lock state; , Suspension state setting valve 22 and accumulator
High-pressure oil or low-pressure oil is selected for the line 51 connecting the
The attitude control valve 24, which is selectively supplied, and the chassis frame 1
Of relative displacement between the axle 8 and the attitude control valve 24
When the relative displacement increases, low hydraulic pressure is supplied to the pipeline 51.
To supply high oil pressure to the pipeline 51 when it becomes smaller.
An interlocking mechanism 27 for switching the attitude control valve 24;
Operating the suspension state setting valve 22 to operate the suspension
Or means 2 for selecting a suspension lock state
8 is applied to a suspension device for a work vehicle including: Soshi
The opening and closing valve 31 for shutting off the communication between the conduit 51 and the attitude control valve 24 and the opening and closing valve 31 when the selector 28 is operated to switch from the suspension locked state to the suspension operating state. The above object is achieved by providing a valve control means 32 that opens the valve for a predetermined time and closes the on-off valve 31 after a predetermined time has elapsed . Claim 2
According to the invention, when the selection means 28 is operated to switch from the suspension lock state to the suspension operation state,
The valve switching operation by the interlocking mechanism 27 allows a predetermined time, comprising an interlocking mechanism control means 41 and 42 to disable the valve switching operation by the interlocking mechanism 27 after a predetermined time has elapsed that
Thereby, the above object is achieved.

[0006]

The relative displacement between the chassis frame 1 and the axle 8 is mechanically directly transmitted to the attitude control valve 24 by the interlocking mechanism 27. When the relative displacement increases, that is, when the chassis frame 1 is displaced away from the axle 8, a low oil pressure is supplied to the pipeline 51, the gas pressure of the accumulator 23 is reduced, and the spring constant of the suspension decreases. The chassis frame 1 sinks. When the relative displacement becomes small, that is, when the chassis frame 1 is displaced so as to approach the axle 8,
A high oil pressure is supplied to the pipeline 51, the gas pressure of the accumulator 23 increases, the spring constant of the suspension increases, and the chassis frame 1 is displaced away from the axle 8. Thus, the attitude of the chassis frame 1 is controlled. Suspension from suspension lock state
When setting to the operation state, the invention according to claim 1
The valve closing valve 31 is opened for a predetermined time.
The valve switching operation by the driving mechanism 27 is enabled for a predetermined time.
You. As a result, posture control is performed for a predetermined time, and
After a lapse of time, posture control is prohibited and normal suspension
Run only by operation.

In the means and means for solving the above problems which explain the constitution of the present invention, the drawings of the embodiments are used to make the present invention easy to understand. However, the present invention is not limited to this.

[0008]

1 to 3 show an example of a suspension device of a wheel type hydraulic shovel to which the present invention is applied. FIG. 2 is a side view of the wheel hydraulic excavator, and a suspension device 10 for suspending an axle (not shown) is installed on the chassis frame 1. The chassis frame 1 is also provided with a swivel frame 2 which can be swiveled.
And a work attachment 7 including a boom 4, an arm 5, a bucket 6, and the like.

FIG. 3 is a front view of the lower traveling body of the wheel hydraulic excavator as viewed from the direction of III-III in FIG. 2, and 8 is an axle on the front wheel side. A drive shaft is inserted into a hollow portion of the axle 8, and tires 9 are provided on left and right sides of the drive shaft, respectively. To the drive shaft, traveling drive force is transmitted from a transmission (not shown) via a shaft, and the tire 9
Is rotated.

A suspension device 10 for suspending the axle 8 with respect to the chassis frame 1 has a pair of return cylinders 11L and R provided at a predetermined distance in the vehicle left-right direction. Pins 12a and 12a are attached to chassis frame 1 and axle 8, respectively.
b. The suspension device 10 also has a link 13 that restricts horizontal displacement in the vehicle front-rear and left-right directions between the chassis frame 1 and the axle 8, and allows vertical displacement, and one end of the link 13 is connected to the chassis frame by a pin 14a. 1, the other end is connected to the vehicle center of the axle 8 by a pin 14b.

FIG. 1 is a hydraulic circuit diagram of the suspension system 10 shown in FIGS. 2 and 3, and the same parts as those in FIGS. As described above, the left and right hydraulic cylinders 11L, R (hereinafter, the symbols L and R are omitted).
The tip of the piston rod 11b is pin-connected to the axle 8, and the cylinder tube 11a is pin-connected to the chassis frame 1. That is, the axle 8 and the chassis frame 1 are connected via the hydraulic cylinder 11. The rod chamber 11d of the hydraulic cylinder 11 is connected to a tank 21, and the bottom chamber 11c is connected to an accumulator 23 via a suspension state setting valve 22, which is an electromagnetic on-off valve. Suspension state setting valve 2
The pipeline 51 between the valve 2 and the accumulator 23 can be connected to the hydraulic pressure source 25 or the tank 26 via the attitude control valve 24 which is a three-position switching valve.

An operation lever 24a for operating the spool of the attitude control valve 24 is connected to a spring receiver 8a installed on the axle 8 via a spring 27, and the valve block of the attitude control valve 24 is fixed to the chassis frame 1. Is established. Therefore, the operation lever 24a is operated by the relative displacement between the chassis frame 1 and the axle 8, and the attitude control valve 24 is switched. The solenoid 22S of each suspension state setting valve 22 is connected to the battery 2 via a selection switch 28.
When the selection switch 28 is closed, power is supplied to the suspension state setting valve 22 to switch to the open position, and when the selection switch 28 is opened, the suspension state setting valve 22 is switched to the closed position by the return spring 22a. When the suspension state setting valve 22 is in the open position, the bottom chamber 11c of the hydraulic cylinder 11 is communicated with the accumulator 23 and enters the suspension operation state.
Such a suspension circuit includes an accumulator 23
The shock from the road surface is absorbed by the spring constant determined by the gas pressure of the vehicle. When the suspension state setting valve 22 is closed, the bottom chamber 11c is shut off from the accumulator 23 and enters a suspension locked state.

[0013] The operation of the suspension device configured as described above will be described. When the selection switch 28 is open as shown in FIG. 1, the suspension state setting valve 22
The bottom chamber 11c and the accumulator 23 are shut off, and the suspension is locked. Therefore, even when the chassis frame 1 is heavy, such as during excavation work, the chassis frame 1 does not sink, and work such as excavation can be performed while holding the chassis frame stably.

On the other hand, when the selection switch 28 is closed, the suspension state setting valve 22 is switched to the open position, the bottom chamber 11c of the hydraulic cylinder 11 and the accumulator 23 are communicated, and the suspension is in the operating state. Therefore,
For example, when the tire rides on unevenness of the road surface, the hydraulic cylinder 11 contracts and the pressure oil discharged from the bottom chamber 11c flows into the accumulator 23 to absorb the impact.

In a work vehicle equipped with such a suspension device, various work may be performed by changing various front attachments. The attachment replacement operation is performed in a suspension locked state with the selection switch 28 opened. After the replacement operation, when the selection switch 28 is closed and the suspension is activated to run, if the weight acting on the chassis frame 1 is greater than a predetermined value, the hydraulic cylinder 11 contracts and the front of the chassis frame 1 The shaft side sinks, and the chassis frame leans forward. Therefore, the vehicle cannot travel as it is.

However, at this time, the distance between the chassis frame 1 and the axle 8 becomes shorter, the spring 27 contracts, and the attitude control valve 24 is switched to the position a by the spring force. At the position a of the attitude control valve 24, the pressure oil of the hydraulic source 25 is supplied to the accumulator 23 and the bottom chamber 11 of the hydraulic cylinder 11.
c, the gas pressure of the accumulator 23 increases, and the spring constant of the suspension increases. As a result, the hydraulic cylinder 11 extends and the chassis frame 1 rises. When the chassis frame 1 rises, the distance between the axle 8 and the chassis frame 1 increases, and the posture control valve 2
4 switches toward the position b, and when the distance reaches a predetermined length, the attitude control valve 24 switches to the position b, and the bottom chamber 11c of the hydraulic cylinder 11 and the accumulator 23 are disconnected from the hydraulic source 25. Is done. As a result, the chassis frame 1 changes from the forward tilted state to the horizontal state. After the chassis frame 1 is in the horizontal state in this way, the work vehicle is caused to travel.

Next, the selection switch 28 is opened to set the suspension state setting valve 22 to the closed position to lock the suspension. After replacing the heavy front attachment with a light attachment, the selection switch 28 is closed to return to the suspension operating state. Then, since the front axle weight is reduced and the gas pressure of the accumulator 23 is increased, the chassis frame 1 is raised and the posture control valve 24 is moved.
Switches toward the c position. Therefore, the accumulator 23 and the bottom chamber 11c of the hydraulic cylinder 11
And the pressure oil flows into the tank 26, and the gas pressure in the accumulator 23 decreases. Accordingly, the spring constant of the suspension is reduced, the hydraulic cylinder 11 contracts, and the chassis frame 1 is in a horizontal state.

FIG. 4 is a hydraulic circuit diagram showing a second embodiment. The same parts as those in FIG. 1 are denoted by the same reference numerals and differences will be described. An electromagnetic on-off valve 31 is arranged between the attitude control valve 24 and the conduit 51, and the opening and closing operation of the electromagnetic on-off valve 31 is controlled by a controller 32. The open / close state of the selection switch 28 is input to the controller 32. When the selection switch 28 is turned on from off, the solenoid 31S of the electromagnetic on / off valve 31 is energized for a predetermined time to switch the on / off valve 31 to the open position. After a lapse of a predetermined time, the energization is stopped and the on-off valve 31 is switched to the closed position.

According to this embodiment, the selection switch 28 is opened, the suspension state setting valve 22 is closed, the front attachment is replaced in the suspension locked state, and then the selection switch 28 is closed and the suspension operation state is changed. The following operational effects can be obtained when the vehicle starts traveling. For example, when the attachment is replaced with a heavy attachment and the selection switch 28 is closed to bring the suspension into an operating state, the electromagnetic on-off valve 31 is switched to the open position for a predetermined time. Since the front axle weight increases due to the replacement of the front attachment, the chassis frame 1 sinks and the attitude control valve 24 switches to the position a. Therefore, the accumulator 23 and the bottom chamber 11c of the hydraulic cylinder 11 communicate with the hydraulic source 25, and the pressure oil flows into the accumulator 23 and the bottom chamber 11c of the hydraulic cylinder 11, and the gas pressure in the accumulator 23 increases. Accordingly, the spring constant of the suspension is increased, the hydraulic cylinder 11 is extended, and the chassis frame 1 is in a horizontal state.

When a predetermined time has elapsed, the controller 32
Switches the on-off valve 31 to the closed position. As a result, the accumulator 23 and the bottom chamber 11c of the hydraulic cylinder 11 are cut off from the hydraulic source 25 and the tank 26. Therefore, during traveling, the distance between the chassis frame 1 and the axle 8 fluctuates due to unevenness of the road surface, and the posture control valve 24
Is switched, the spring constant of the suspension does not change, and the chassis frame 1 runs in the suspension operating state while maintaining the horizontal state. As a result, the spring 27
The degree of freedom in setting the spring force is increased, and the design becomes easier.

FIG. 5 is a hydraulic circuit diagram showing still another embodiment. The same parts as those in FIG. 1 are denoted by the same reference numerals and differences will be described. The axle 8 and the operation lever 24a of the attitude control valve 24 are not directly connected by the spring 27 but are connected via a ram cylinder 41, and the ram cylinder chamber 41a of the ram cylinder 41 is connected to the tank 26 via an electromagnetic opening / closing valve 42. Connecting. The solenoid on-off valve 42 is opened and closed by a controller 43,
The controller 43 switches the on-off valve 42 to the closed position for a predetermined time when the selection switch 28 is turned on from off,
After a lapse of a predetermined time, the position is switched to the open position. When the on-off valve 42 is in the closed position, the ram cylinder 41 transmits the displacement of the axle 8 to the operation lever 24a of the attitude control valve 24, and the on-off valve 42
Is in the open position, the ram cylinder 43 moves the axle 8 even if the axle 8 is displaced.
Do not communicate to

Therefore, in such an embodiment,
Similarly to the second embodiment, when the selection switch 28 is closed to start traveling, the attitude control for the weight change of the front attachment is performed for a predetermined time to set the chassis frame 1 to the horizontal state. After a lapse of a predetermined time, the ram chamber 41 a of the ram cylinder 41 is communicated with the tank 26. When the distance between the chassis frame 1 and the axle 8 becomes shorter, oil is discharged from the ram chamber 41a to the tank 26, the ram 41b does not rise, and therefore the spring 27 is not contracted, and the switching of the attitude control valve 24 is performed. It is forbidden. As a result, even if the distance between the chassis frame 1 and the axle 8 changes due to unevenness of the road surface during running, the spring constant of the suspension does not change, and the chassis frame 1 can run while maintaining a horizontal state.

The mechanism itself of the suspension of the present invention is shown in FIG.
However, the present invention is not limited to the embodiments shown in FIGS. The interlocking mechanism for switching the attitude control valve 24 in conjunction with the relative displacement between the chassis frame 1 and the axle 8 is not limited to the spring 27, but the scope of the present invention is limited to mechanical means for applying the displacement to the attitude control valve 24. The point is that they are linked. Further, the hydraulic circuit is not limited to the one shown in FIG. 1, the hydraulic suspension is composed of a hydraulic cylinder and an accumulator, and the spring constant of the suspension can be changed by the gas pressure of the accumulator. Any circuit configuration can be adopted as long as the suspension can be selected between the operating state and the locked state by cutting off the communication.

[0024]

As described above in detail, according to the present invention, the relative displacement between the chassis frame and the axle is directly transmitted to the attitude control valve such as the switching valve by the interlocking mechanism, and the relative displacement is transmitted. As the displacement increases, the gas pressure of the accumulator is reduced, and as the relative displacement decreases, the gas pressure is increased.As in the past, the amount of expansion and contraction of the hydraulic cylinder is measured with a stroke sensor, etc. As compared with the case where the attitude of the chassis frame is controlled, it is possible to provide an inexpensive attitude controllable suspension device, and to improve reliability in a severe work site because a precise sensor is not used. In addition, set to the suspension operation state
At this time, the posture control is performed for a predetermined time, and after the predetermined time elapses,
Posture control is prohibited, so normal driving
The chassis frame is leveled by the spence operation.
Can travel.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of a suspension device according to the present invention.

FIG. 2 is a side view of one embodiment of a wheel type hydraulic excavator to which the present invention is applied.

FIG. 3 is a front view of the suspension device as viewed from the line III-III in FIG. 2;

FIG. 4 is a hydraulic circuit diagram showing another embodiment of the suspension device according to the present invention.

FIG. 5 is a hydraulic circuit diagram showing still another embodiment of the suspension device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Chassis frame 8 Axle 10 Suspension device 11L, 11R Hydraulic cylinder 22 Electromagnetic suspension state setting valve 23 Accumulator 24 3 Position and attitude control valve 25 Hydraulic power source 27 Spring 28 Switch 31 Electromagnetic open / close valve 32 Controller 41 Ram cylinder 42 Electromagnetic open / close valve 43 Controller

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60G 17/005 B60G 17/056

Claims (2)

(57) [Claims] A hydraulic cylinder for suspending an axle on a chassis frame; an accumulator connected to a cylinder chamber of the hydraulic cylinder; a cylinder chamber and the accumulator communicating with each other to set a suspension operation state; and the suspension state setting valve to set the suspension locked state by disconnecting the said accumulator, a front Symbol high pressure oil or low pressure oil selectively supplying attitude control valve to the conduit which connects the suspension state setting valve and the accumulator Transmitting the relative displacement between the chassis frame and the axle to the attitude control valve, supplying a low hydraulic pressure to the pipeline when the relative displacement increases, and supplying a high hydraulic pressure to the pipeline when the relative displacement decreases. an interlocking mechanism for switching the position control valve, service by manipulating the suspension status setting valve Pensho
Select the operating state or suspension lock state
Selecting means, an opening / closing valve for shutting off communication between the conduit and the attitude control valve, and determining whether the selecting means is operated and the suspension is locked.
When the suspension is switched to the suspension operation state, the on-off valve
Is opened for a predetermined time, and the on-off valve is closed after a predetermined time has elapsed.
A work vehicle, comprising:
Suspension system. 2. An oil for suspending an axle on a chassis frame.
Pressure cylinder and an accumulator connected to the cylinder chamber of this hydraulic cylinder.
And the cylinder chamber communicates with the accumulator.
Set the pension operation state, and set the cylinder chamber and the
Shut off the accumulator to lock the suspension
The suspension state setting valve to be set, and the suspension state setting valve and the accumulator are connected.
Selective supply of high-pressure oil or low-pressure oil to a continuous pipeline
Force control valve and the relative displacement between the chassis frame and the axle.
To the attitude control valve, and when the relative displacement increases,
Supply low oil pressure to the pipeline, and when it gets smaller, high oil
Interlocking mechanism for switching the attitude control valve to supply pressure
If, Suspension by operating the suspension status setting valve
Select the operating state or suspension lock state
Selection means, and whether the selection means is operated and the suspension is locked.
When the suspension is switched to the suspension
The valve switching operation by the system is enabled for a predetermined time, and
After the lapse of time, the link that disables the valve switching operation by the interlocking mechanism
Work vehicle, comprising a dynamic mechanism control means.
Suspension system.