JP2009046013A - Hydraulic circuit used in independent suspension mechanism for work vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic circuit that is used in an independent suspension mechanism for a work vehicle composed of a simple hydraulic circuit and enabling lowering of a vehicle height at fixed speed. <P>SOLUTION: The hydraulic circuit used in an independent suspension mechanism for a work vehicle is provided with a first oil path 50, which connects between suspension cylinders 27, 27, respectively provided in right-and-left independent suspensions 23, 23, so as to make them communicate with each other, and a second oil path 51 composed of an oil path that connects between the first oil path 50 and a transmission case 12 so as to make them communicate with each other. The halfway part of the second oil path 51 is provided with a rasing solenoid valve 54, which allows hydraulic oil to circulate from the transmission case 12 toward the first oil path 50, and a lowering solenoid valve 55 arranged between the rasing solenoid valve 54 and the first oil path 50 so as to allow the hydraulic oil to circulate from the first oil path 50 toward the transmission case 12. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a suspension mechanism for a work vehicle used for farm work, construction, transport work, and the like. More specifically, the present invention relates to a configuration of a hydraulic circuit related to the suspension mechanism.

Conventionally, a technique related to the configuration of a hydraulic circuit of an independent suspension mechanism for a work vehicle has been publicly known. For example, it is like the technique described in Patent Document 1. The technique described in Patent Document 1 relates to a double wishbone suspension.
European Patent Application No. 807543

In the configuration disclosed in Patent Document 1 described above, the hydraulic oil can be supplied to the actuator constituting the suspension mechanism by operating one electromagnetic valve, and the vehicle height of the work vehicle can be raised. Further, by operating another electromagnetic valve, the hydraulic oil in the actuator can be discharged, and the vehicle height of the work vehicle can be lowered.
However, since the solenoid valve for raising the vehicle height and the solenoid valve for lowering the vehicle height are provided in different oil passages, it is disadvantageous in that the hydraulic circuit becomes complicated. Further, when the vehicle height is lowered, the hydraulic oil discharge flow rate is not constant, which is disadvantageous in that the vehicle height lowering speed is not stable.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a hydraulic circuit for an independent suspension mechanism for a work vehicle that includes a simple hydraulic circuit. It is another object of the present invention to provide a hydraulic circuit for an independent suspension mechanism for a work vehicle that can be lowered at a constant speed when the vehicle height is lowered.

  The problems to be solved by the present invention are as described above. Next, means for solving the problems will be described.

  That is, according to the first aspect of the present invention, there is provided a first oil passage that connects the hydraulic cylinders provided in the left and right independent suspensions, and a single oil passage that connects the first oil passage and the oil tank. And a hydraulic oil distribution direction switching means for switching a hydraulic oil distribution direction in the middle of the second oil path.

  In claim 2, the inflow permission means for allowing the working oil flow direction switching means to flow the working oil from the oil tank toward the first oil path, the inflow permission means, and the first oil path, And an outflow permitting means that allows the working oil to flow from the first oil passage toward the oil tank.

  According to a third aspect of the present invention, there is provided an outflow flow rate control unit that is disposed between the inflow permission unit and the outflow permission unit and that maintains a constant flow rate of the hydraulic oil flowing out from the first oil passage to the oil tank. Is.

  As effects of the present invention, the following effects can be obtained.

  By configuring as in claim 1 or claim 2, the hydraulic oil can be flowed into and out of the first oil passage with a single hydraulic circuit, and the hydraulic circuit of the independent suspension for the work vehicle is simply configured. Thus, the space of the hydraulic circuit can be saved. In addition, the production cost can be reduced by reducing the number of parts.

  By configuring as in claim 3, the vehicle height of the work vehicle can be stably lowered at a constant speed.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

First, the whole structure of the tractor which is one Embodiment of the working vehicle which concerns on this invention is demonstrated using FIG.
The work vehicle according to the present invention is not limited to a tractor that is an agricultural vehicle described in the present embodiment, but can be used for a work vehicle such as a construction machine such as a loader or a backhoe.
In the following description, the direction of arrow A in the figure is described as the front of the tractor 1.

As shown in FIG. 1, the tractor 1 includes front wheels 3 and 3 and rear wheels 4 and 4 at front and rear portions of a body frame 2, respectively, and an engine 6 as a prime mover is installed in a hood 5 at the front portion of the tractor 1. 2 is fixed. A cabin 7 is provided behind the bonnet 5. A steering handle 8 is disposed at the front of the cabin 7, and a driver seat 9 is disposed behind the steering handle 8. Fenders 10 and 10 are fixed to the left and right sides of the cabin 7 so as to cover the rear wheels 4 and 4.
A clutch 11 is disposed at the rear portion of the engine 6, and the power of the engine 6 is transmitted via the clutch 11 to a transmission (not shown) in a transmission case 12 fixed to the rear portion of the body frame 2.
Rear wheels 4 and 4 are attached from the left and right side surfaces of the mission case 12 via rear axles 13 and 13 that are projected in both the left and right directions. Power from the engine 6 is shifted by the transmission and distributed in the longitudinal direction of the machine body. The power distributed to the rear of the fuselage is transmitted to the rear wheels 4 and 4 via the rear axles 13 and 13.
A suspension mechanism 20 is provided at the front of the body frame 2. The left and right front wheels 3 are supported by the suspension mechanism 20. The power of the engine 6 distributed to the front of the aircraft by the transmission is transmitted to a differential device 22 provided in a center case 21 constituting the suspension mechanism 20 (see FIG. 2). By the differential device 22, the power of the engine 6 is distributed in the left-right direction of the fuselage and transmitted to the front wheels 3.

Next, the configuration of the suspension mechanism 20 of the tractor in the present embodiment will be described in detail with reference to the drawings.
As shown in FIG. 2, the suspension mechanism 20 in this embodiment is a double wishbone suspension, but the present invention is not limited to this, and may be an independent suspension such as a McPherson strut type. .

As shown in FIG. 2, the suspension mechanism 20 includes a center case 21, suspensions 23 and 23, and the like.
The center case 21 is fixed to the front lower part of the body frame 2.
The suspensions 23 and 23 are provided on the left and right sides of the body frame 2 and the center case 21, respectively.

The suspension 23 includes an upper arm 24, a lower arm 25, a joint 26, and a suspension cylinder 27.
Since the left and right suspensions 23 and 23 have the same configuration, only the configuration of the right suspension 23 will be described below.

The upper arm 24 is a substantially A-shaped member in plan view. One end of the upper arm 24 is rotatably attached to the right side surface of the body frame 2 via an upper arm bracket 28. The other end of the upper arm 24 is rotatably attached to the upper portion of the joint 26.
The lower arm 25 is a substantially A-shaped member in plan view. One end of the lower arm 25 is rotatably attached to a perforation provided in the lower right portion of the center case 21 in the longitudinal direction of the fuselage. The other end of the lower arm 25 is rotatably attached to the lower part of the joint 26.

  The suspension cylinder 27 is a hydraulic cylinder that operates by hydraulic pressure. The tube-side end of the suspension cylinder 27 is rotatably attached to the right side surface of the body frame 2 via a cylinder bracket 29. The rod side end of the suspension cylinder 27 is rotatably attached to the middle part of the lower arm 25.

A differential device 22 is provided inside the center case 21. The power of the engine 6 is transmitted to the differential device 22 via a transmission or the like. The power of the engine 6 is distributed to the left and right sides of the body by the differential device 22.
The power distributed to the left and right of the machine body is transmitted to the final reduction gear 32 via the front wheel drive shaft 30 and the universal joint 31. The final reduction gear 32 is rotatably provided on the right side surface of the joint 26. The front wheel 3 is fixed to the final reduction gear 32, and the front wheel 3 is driven by the power decelerated by the final reduction gear 32.

  Next, a hydraulic circuit of the independent suspension for a tractor which is an embodiment according to the present invention will be described.

  As shown in FIG. 3, the hydraulic circuit in this embodiment mainly includes a first oil passage 50, a second oil passage 51, a transmission case (oil tank) 12, a suspension cylinder 27, a hydraulic oil flow direction switching means 52, a pressure. Compensation type flow control valve 53 etc. are comprised.

  The first oil passage 50 is an oil passage that communicates and connects suspension cylinders 27 and 27 respectively provided to the left and right independent suspensions 23 and 23.

  The second oil passage 51 is a single oil passage that connects the first oil passage 50 and the transmission case 12 that is an oil tank in communication.

In the middle of the second oil passage 51, hydraulic oil distribution direction switching means 52 that switches the distribution direction of the hydraulic oil is provided. The hydraulic oil flow direction switching means 52 includes an ascending electromagnetic valve 54 that is an inflow permission means and a descending electromagnetic valve 55 that is an outflow permission means.
The ascending electromagnetic valve 54 is an electromagnetic valve that allows hydraulic oil to flow from the mission case 12 toward the first oil passage 50.
The descending electromagnetic valve 55 is an electromagnetic valve that is disposed between the ascending solenoid valve 54 and the first oil passage 50 and allows hydraulic oil to flow from the first oil passage 50 toward the transmission case 12.
In this embodiment, the solenoid valve operated by electromagnetic force is used as the inflow permission means and the outflow permission means. However, the present invention is not limited to this, for example, a mechanically operated one or a manually operated one. It may be operated.

  The pressure-compensated flow control valve 53 is an outflow flow rate control means that keeps the flow rate of hydraulic oil flowing out from the first oil passage 50 to the transmission case 12 constant. The pressure compensation flow control valve 53 is disposed between the ascending solenoid valve 54 and the descending solenoid valve 55.

  A hydraulic pump 60 is disposed in the second oil passage 51. The hydraulic pump 60 is driven by the power of the engine 6 and sucks up the hydraulic oil in the mission case 12. The working oil sucked up by the hydraulic pump 60 is removed of foreign matters and the like mixed in the working oil by the suction filter 61 provided at the end of the second oil passage 51 on the mission case side. The hydraulic oil that has passed through the suction filter 61 is pumped to the hydraulic oil flow direction switching means 52.

The unloading electromagnetic valve 62 is provided between the hydraulic pump 60 and the rising electromagnetic valve 54 in order to suppress energy loss when the second oil passage 51 is blocked by the hydraulic oil flow direction switching means 52. An unloading oil passage 63 branched from the passage 51 is provided.
In the state shown in FIG. 3, the second oil passage 51 is blocked by the rising electromagnetic valve 54. In this case, the hydraulic oil pumped by the hydraulic pump 60 is returned to the mission case 12 via the unloading electromagnetic valve 62.
When the ascending solenoid valve 54 is switched and hydraulic oil can be pumped to the first oil path 50 via the second oil path 51, the unloading solenoid valve 62 is also switched at the same time, and the unloading oil path 63 is switched. Shut off.

  A relief valve 65 is provided in the relief oil passage 64 branched from the second oil passage 51 between the hydraulic pump 60 and the ascending electromagnetic valve 54. By providing the relief valve 65, the pressure in the pipe is set, and damage to the circuit when an abnormal pressure occurs in the circuit is prevented.

The pressure compensation type flow control valve 53 includes a throttle 66, a check valve 67, a spool and the like.
When the ascending solenoid valve 54 is switched and hydraulic fluid is pumped from the mission case 12 to the first oil passage 50, the hydraulic fluid passes through the check valve 67 and the descending solenoid valve 55 of the pressure compensation flow control valve 53, and It flows into one oil passage 50.
When the ascending solenoid valve 54 is switched to the normal position and the descending solenoid valve 55 is switched, and the hydraulic fluid returns from the first oil passage 50 to the transmission case 12 via the pressure compensation flow control valve 53, the pressure difference before and after the throttle 66 As a result, the spool moves and the oil passage area in the pressure compensation flow control valve 53 changes. That is, when the pressure difference is large, the oil passage area decreases, and when the pressure difference is small, the oil passage area increases. The operation of the pressure compensation type flow control valve 53 makes it possible to keep the flow rate of the hydraulic oil constant even if the pressure difference before and after the throttle 66 fluctuates.

The accumulators 68 and 68 are connected to the first oil passage 50 through an accumulator oil passage 69 branched from a middle portion of the first oil passage 50.
The impact received from the road surface while the front wheels 3, 3 of the tractor 1 are traveling is transmitted to the suspension cylinder 27 via the suspensions 23, 23. This impact can be transmitted to the accumulators 68 and 68 through the first oil passage 50 and the accumulator oil passage 69 and absorbed.
A suspension lock switching electromagnetic valve 70 is disposed in the middle of the accumulator oil passage 69. By switching the suspension lock switching electromagnetic valve 70, the accumulator oil passage 69 can be shut off.
In the hydraulic circuit according to the present embodiment, two accumulators 68 are provided, but the present invention is not limited to this. That is, one or three or more accumulators 68 used in the hydraulic circuit may be used as long as they have sufficient capacity to sufficiently perform a function such as shock absorption as a suspension.

  The first oil passage 50 is connected to the transmission case 12 by an overload oil passage 71 branched from a middle portion of the first oil passage 50. An overload valve 72 is disposed in the middle of the overload oil passage 71 and normally shuts off the overload oil passage 71. The overload valve 72 allows the first oil passage 50 and the transmission case 12 to communicate with each other when an excessive load is applied to the suspension cylinder 27 and a pressure exceeding the pressure set in advance in the overload valve 72 is generated in the circuit. The hydraulic oil in the first oil passage 50 is returned to the mission case 12 to prevent circuit breakage and the like.

Stop valves 73 and 73 are provided on the first oil passage 50 and in the vicinity of the suspension cylinders 27 and 27. During maintenance of the suspension cylinders 27 and 27, the first oil passage 50 can be shut off by closing the stop valves 73 and 73.
A pressure take-out port is provided in the middle of the first oil passage 50. When a failure occurs, a pressure gauge 74 can be attached to check the pressure.

The suspension cylinders 27 and 27 are provided with position sensors 101 and 101, respectively. The position sensor 101 is position detection means for detecting the amount of extension of the rod of the suspension cylinder 27. That is, the position sensor 101 constantly detects the amount (or the amount of contraction) that the rod of the suspension cylinder 27 has extended (or contracted) from the reference position, and based on the amount, the cylinder position changed due to leakage from a valve or the like is detected. It can be corrected.
By displaying the extension amount of the rod of the suspension cylinder 27 detected by the position sensor 101 on an output device such as a monitor, the current extension amount of the suspension cylinder 27 can be confirmed. Further, by connecting the position sensor 101 to a control means for controlling an electromagnetic valve provided in the hydraulic circuit, the position sensor 101 is automatically based on the program stored in the control means in advance and the amount of extension of the position sensor 101. It is also possible to control the solenoid valve.

  The operation of the hydraulic circuit configured as described above will be described below.

First, the operation of the hydraulic circuit in the state shown in FIG. 3 will be described.
When the tractor 1 is working or running, the hydraulic circuit is in a state as shown in FIG. 3 (hereinafter referred to as “normal state”).

  In the normal state, the second oil passage 51 is blocked by the hydraulic oil flow direction switching means 52. In this case, the hydraulic oil sucked up and pumped from the mission case 12 by the hydraulic pump 60 is returned to the mission case 12 again via the unloading electromagnetic valve 62.

The first oil passage 50 is connected in communication with accumulators 68 and 68. Thereby, the impact applied to the suspension cylinders 27 and 27 is absorbed by the accumulators 68 and 68.
The first oil passage 50 connects the suspension cylinders 27 and 27 in communication with each other. That is, when one suspension cylinder 27 is contracted, the excess oil flows into the other and the other extends. Thereby, the wheel swinging action in the tractor in which wheels are provided on the left and right of one axle case, and the center part of the axle case is pivotally mounted on the fuselage frame so that the left and right wheels can swing vertically. Similarly, the left and right wheels can be swung up and down with respect to each other.
That is, it is possible to improve the riding comfort and handling stability of the tractor 1 by absorbing the impact received by the tractor 1 from the road surface by the accumulator while swinging the front wheels 3 and 3 up and down.

Next, the operation of the hydraulic circuit in the state shown in FIG.
When hydraulic fluid is pumped into the suspension cylinder 27 and the vehicle height ahead of the machine body is raised, the hydraulic circuit is in a state as shown in FIG. 4A (hereinafter referred to as “rise state”).

  In the hydraulic circuit in the normal state as shown in FIG. 3, when the rising solenoid valve 54 and the unloading solenoid valve 62 are switched, the rising state is as shown in FIG.

  In the raised state, the hydraulic oil can flow from the mission case 12 toward the first oil passage 50. In this case, the hydraulic oil in the mission case 12 is sucked by the hydraulic pump 60 and is pumped to the first oil passage 50 via the ascending solenoid valve 54, the check valve 67, and the descending solenoid valve 55.

  As a result, the hydraulic oil flows into the suspension cylinders 27 and 27, and the suspension cylinders 27 and 27 extend. That is, the vehicle height in front of the fuselage of the tractor 1 in which the suspension mechanism 20 is disposed increases.

  In the raised state, the working oil in the suspension cylinder 27 flows into the transmission case 12 through the overload valve 72 and the vehicle height in front of the machine body is lowered, or when the work machine is mounted in front of the machine body. It is used to raise the vehicle height ahead of the fuselage when improving.

  The switching to the lifted state is automatically performed when the solenoid valve and the position sensors 101 and 101 in the hydraulic circuit are connected to the control means, and the suspension cylinders 27 and 27 are contracted below the position preset in the control means. There are a method of switching to the above, a method of providing a switch for operating an electromagnetic valve in the hydraulic circuit, and a method of manually operating and switching the switch.

Next, the operation of the hydraulic circuit in the state shown in FIG.
When the hydraulic oil in the suspension cylinder 27 is returned to the mission case 12 and the vehicle height in front of the fuselage is lowered, the hydraulic circuit is referred to as a state as shown in FIG. ).

  In the normal state hydraulic circuit as shown in FIG. 3, when the lowering electromagnetic valve 55 is switched, the lowering state as shown in FIG.

In the lowered state, the hydraulic oil can flow from the first oil passage 50 toward the mission case 12. In this case, the hydraulic oil in the suspension cylinder 27 and the first oil passage 50 flows out to the transmission case 12 via the descending electromagnetic valve 55 and the throttle 66.
In this case, the flow rate of the hydraulic oil flowing out to the mission case 12 is kept constant by the pressure compensation type flow control valve 53.

As a result, the hydraulic oil in the suspension cylinders 27 and 27 flows out to the transmission case 12 via the first oil passage 50 and the second oil passage 51, and the suspension cylinders 27 and 27 are contracted. In other words, the vehicle height in front of the tractor 1 where the suspension mechanism 20 is disposed is lowered.
Further, since the flow rate of the hydraulic oil flowing out to the mission case 12 is kept constant by the pressure compensation type flow control valve 53, the vehicle height is prevented from abruptly descending and the vehicle height is lowered at a constant speed. Can do.

  The lowered state is used for lowering the vehicle height in front of the aircraft when lowering the vehicle height that has been raised due to the elevated state or when controlling the attitude of the aircraft when climbing up.

  For switching to the lowered state, a method for automatically switching by a control means connected to a solenoid valve in the hydraulic circuit or a switch for operating the solenoid valve in the hydraulic circuit are provided, and the switch is operated manually. Then, there is a method of switching.

In the normal state hydraulic circuit shown in FIG. 3, the suspension function can be stopped (hereinafter referred to as “suspension lock state”) by switching the suspension lock switching electromagnetic valve 70. That is, by switching the suspension lock switching electromagnetic valve 70, the accumulators 68 and 68 and the first oil passage 50 are shut off, and the shock absorbing function of the accumulators 68 and 68 can be stopped.
In the suspension lock state, a load applied to the front wheels 3 and 3 is increased by performing a brake operation while the tractor 1 is traveling, and a state where the front of the machine body is lowered (sunk) can be prevented. In loader work or the like, the suspension lock state may be easier to work, and in this case, the suspension can be locked by an operator's operation.

As described above, the hydraulic circuit of the independent suspension for work vehicle according to the present embodiment includes the first oil passage 50 that connects the suspension cylinders 27 and 27 respectively provided on the left and right independent suspensions 23 and 23, and the first oil passage 50. A second oil passage 51 configured by a single oil passage that connects the oil passage 50 and the transmission case 12 in communication, and a hydraulic oil distribution direction switching means 52 that switches a distribution direction of the hydraulic oil to a middle portion of the second oil passage 51. Are provided.
As a result, the hydraulic oil is pumped from the mission case 12 to the first oil passage 50 and the hydraulic oil is discharged from the first oil passage 50 to the mission case 12. Can be done through. That is, hydraulic oil can be pumped and discharged without using a plurality of oil passages, and the hydraulic circuit can be configured simply. As a result, it is possible to save space in the hydraulic circuit and reduce production costs by reducing the number of parts.

In addition, the hydraulic circuit of the independent suspension for the work vehicle according to the present embodiment has the lift solenoid valve 54 that allows the hydraulic oil flow direction switching means 52 to flow from the transmission case 12 toward the first oil passage 50. And a descending electromagnetic valve 55 that is disposed between the ascending solenoid valve 54 and the first oil passage 50 and allows the hydraulic oil to flow from the first oil passage 50 toward the transmission case 12. is there.
As a result, the hydraulic oil is pumped from the mission case 12 to the first oil passage 50 and the hydraulic oil is discharged from the first oil passage 50 to the mission case 12. Can be done through. That is, hydraulic oil can be pumped and discharged without using a plurality of oil passages, and the hydraulic circuit can be configured simply. As a result, it is possible to reduce the number of parts and the cost.

Further, the hydraulic circuit of the independent suspension for the work vehicle according to the present embodiment is disposed between the ascending solenoid valve 54 and the descending solenoid valve 55, and the hydraulic fluid flowing out from the first oil passage 50 to the transmission case 12. The pressure compensation type flow control valve 53 for keeping the flow rate constant is provided.
Thereby, it is possible to prevent the vehicle height of the tractor 1 from being rapidly lowered and to be stably lowered at a constant speed.

The whole side view showing the whole composition of the tractor concerning one example of the present invention. The front enlarged view which similarly shows the suspension mechanism of a tractor. The hydraulic circuit diagram which shows the normal state of the suspension of a tractor similarly. (A) The hydraulic circuit diagram which similarly shows the rising state of the suspension of the tractor, (b) The hydraulic circuit diagram which similarly shows the falling state of the suspension of the tractor.

Explanation of symbols

1 Tractor 12 Mission Case 20 Suspension Mechanism 21 Center Case 23 Suspension 27 Suspension Cylinder (Hydraulic Cylinder)
50 First oil passage 51 Second oil passage 52 Hydraulic oil flow direction switching means 53 Pressure compensated flow control valve (outflow flow control means)
54 Solenoid valve (inflow permitting means)
55 Lowering solenoid valve (outflow permission means)

Claims (3)

A first oil passage that connects and connects hydraulic cylinders respectively provided to left and right independent suspensions;
A second oil passage constituted by a single oil passage connecting the first oil passage and the oil tank in communication;
Hydraulic oil flow direction switching means for switching the flow direction of the hydraulic oil in the middle of the second oil path;
A hydraulic circuit for an independent suspension mechanism for a work vehicle comprising: The hydraulic oil flow direction switching means,
Inflow permission means for allowing hydraulic oil to flow from the oil tank toward the first oil passage;
An outflow permission means that is disposed between the inflow permission means and the first oil passage, and allows the working oil to flow from the first oil passage toward the oil tank;
The hydraulic circuit of the independent suspension mechanism for work vehicles according to claim 1 constituted by the above. The outflow flow rate control means which is arrange | positioned between the said inflow permission means and the said outflow permission means, and maintains the flow volume of the hydraulic fluid which flows into the said oil tank from the said 1st oil path is comprised. Hydraulic circuit of independent suspension mechanism for work vehicles.

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