JP2009120128A - Independent suspension for work vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an independent suspension for a work vehicle, disabling a suspension function. <P>SOLUTION: This independent suspension includes: a suspension cylinder 94 supporting a front wheel 85; a first oil passage 100 communicatingly connected with the suspension cylinder 94; an accumulator 201 absorbing shock; a second oil passage 200 communicatingly connecting the first oil passage 100 with the accumulator 201; a second oil passage shutoff valve 202 arranged in the middle of the second oil passage 200 and shutting off a hydraulic fluid flow in the second oil passage 200; a suspension lock changing-over switch 403 outputting an instruction to shut off the hydraulic fluid flow in the second oil passage 200 by the second oil passage shutoff valve 202; and a control section 450 shutting off the hydraulic fluid flow in the second oil passage 200 by the second oil passage shutoff valve 202 according to the instruction output from the suspension lock changing-over switch 403. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a stand-alone suspension used in a work vehicle used for farm work, construction, transportation work, and the like.

Conventionally, a technique related to a stand-alone suspension of 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 front suspension of a tractor.
JP 2002-137613 A

In the configuration disclosed in Patent Document 1 described above, the impact that the front wheel of the tractor receives from the unevenness of the ground during traveling or working can be transmitted and absorbed to the accumulator via the cylinders, ports, etc. constituting the suspension. it can.
In other words, the cylinder expands and contracts due to an impact that the front wheels of the tractor receive from the unevenness of the ground during running or working. The cylinder is connected in communication with the accumulator through an oil passage or the like constituting the port or a hydraulic circuit, and an impact received by the cylinder by hydraulic oil filled in the hydraulic circuit is transmitted to the accumulator and absorbed. Is done. Such a function of absorbing an impact by the suspension is hereinafter simply referred to as a “suspension function”.

However, such a configuration is disadvantageous in that the suspension vibrates unnecessarily when work is performed using a work machine such as a loader or a backhoe, and workability is deteriorated.
That is, when work is performed using a work machine such as a loader or a backhoe, the load applied to the front wheels of the tractor greatly varies due to excavation and transportation of earth and sand. Due to the fluctuation of the load, the cylinder constituting the suspension is unnecessarily expanded and contracted, resulting in deterioration of workability such as deterioration of ride comfort and handling stability of the operator and reduction of work accuracy.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a stand-alone suspension for a work vehicle that can invalidate the suspension function when working with a loader, a backhoe, or the like that does not require a suspension function.

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

  That is, in claim 1, a hydraulic cylinder that supports a wheel to be movable up and down, a first oil passage that is connected to the hydraulic cylinder, an accumulator that absorbs an impact applied to the hydraulic cylinder, and the first oil passage And a second oil passage that connects the accumulator and a second oil passage shut-off valve that is provided in the middle of the second oil passage and that can shut off the flow of hydraulic oil in the second oil passage. An instruction switch for instructing to shut off the flow of hydraulic oil in the second oil passage by the second oil passage shut-off valve, and the second oil passage shut-off valve according to the instruction of the instruction switch. And a controller that blocks the flow of hydraulic oil in the passage.

In Claim 2, it comprises traveling speed detection means for detecting the traveling speed of the work vehicle,
Based on the information related to the detection by the travel speed detection means, the control unit, when the travel speed of the work vehicle is equal to or greater than a predetermined value, controls the second oil passage shut-off valve regardless of an instruction of the instruction switch. The flow of hydraulic oil in the second oil passage is not blocked.

In Claim 3, the hydraulic cylinder which supports a wheel so that raising and lowering is possible, the 1st oil passage connected to the hydraulic cylinder, the accumulator which absorbs the impact added to the hydraulic cylinder,
A second oil passage that connects the first oil passage and the accumulator, and a second oil passage that is provided in a middle portion of the second oil passage and is capable of blocking a flow of hydraulic oil in the second oil passage. An oil passage shut-off valve, work state detection means for detecting a work state of the work vehicle, and the second oil passage shut-off valve based on information related to detection of the work state by the work state detection means. And a controller that blocks the flow of hydraulic oil in the passage.

  According to a fourth aspect of the present invention, there is provided vibration detecting means for detecting the frequency of expansion and contraction of the hydraulic cylinder, and the control section is configured such that the frequency is equal to or greater than a predetermined value based on information relating to detection by the vibration detecting means. In this case, the flow of hydraulic oil in the second oil passage is shut off by the second oil passage cutoff valve.

  According to a fifth aspect of the present invention, the control unit includes a display unit that displays whether the flow of hydraulic oil in the second oil passage is blocked.

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

  According to the configuration of the first aspect, the flow of the hydraulic oil in the second oil passage can be shut off by the second oil passage shut-off valve according to the instruction of the instruction switch, and the suspension function of the work vehicle can be invalidated. It becomes possible.

  According to the second aspect of the present invention, when the traveling speed of the work vehicle exceeds a predetermined value, the flow of the hydraulic oil in the second oil passage is caused by the second oil passage shut-off valve regardless of the instruction of the instruction switch. The suspension function of the work vehicle can be made effective without blocking.

  According to the third aspect of the present invention, when the work vehicle is in a working state, the second oil passage shut-off valve can shut off the flow of hydraulic oil in the second oil passage, and the suspension function of the work vehicle can be achieved. Can be disabled.

  By configuring as in the fourth aspect, it is possible to prevent the abnormal vibration caused by the expansion and contraction of the hydraulic cylinder in the work vehicle.

  By configuring as in claim 5, the operator of the work vehicle can check at a glance whether the suspension function of the work vehicle is valid or invalid.

  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 1 which is one Embodiment of the working vehicle which concerns on this invention is demonstrated using FIG.1 and FIG.2.
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 arrow X direction in FIG. 1 will be described as the forward direction of the tractor 1, and the arrow Y direction in FIG. 2 will be described as the left direction of the tractor 1.

  The tractor 1 is equipped with various work machines (rotary, front loader, etc.), and performs various operations using the work machines that are installed. The tractor 1 mainly includes a body frame 5, an engine 10, a clutch 20, a transmission 30, a rear axle mechanism 40, a cabin 50, a hydraulic lifting mechanism 70, a front axle mechanism 80, and the like. Further, the tractor 1 in this embodiment is equipped with a front loader 60 which is a working machine.

  The body frame 5 is a member that becomes a skeleton of the tractor 1. The body frame 5 is a substantially box-shaped member formed by using a plurality of substantially rectangular plate-shaped members.

The engine 10 generates rotational power that drives the wheels of the tractor 1. The engine 10 is fixed to a midway part in the front-rear direction of the body frame 5. The rotational power generated by the engine 10 is output from an output shaft (not shown) provided in the engine 10.
A bonnet 11 that is a member covering the engine 10 is disposed above the engine 10.

The clutch 20 transmits rotational power generated by the engine 10. The clutch 20 is disposed at the rear part of the engine 10. The clutch 20 is connected to the output shaft of the engine 10 and transmits the rotational power of the engine 10 transmitted from the output shaft to a transmission shaft (not shown) connected to the clutch 20.
Further, the clutch 20 can disconnect the output shaft of the engine 10 and the transmission shaft of the clutch 20. When the connection between the output shaft of the engine 10 and the transmission shaft of the clutch 20 is released, the transmission of rotational power from the output shaft of the engine 10 to the transmission shaft of the clutch 20 is cut off.

The transmission 30 shifts (decelerates) the input rotational power. The transmission 30 is fixed to the rear end portion of the body frame 5. The transmission 30 includes a transmission case 31 that is a substantially box-shaped member, and a plurality of gears (not shown) arranged in the transmission case 31.
The transmission 30 is connected to the transmission shaft of the clutch 20, and the rotational power transmitted from the transmission shaft of the clutch 20 is changed by the plurality of gears.

  Further, a PTO shaft 32 protrudes rearward from the substantially central portion of the rear surface of the transmission case 31. One end of the PTO shaft 32 is connected to a plurality of gears arranged in the transmission case 31, and rotates by rotational power changed by the transmission 30.

  In addition to the transmission that uses only gears for the transmission in this embodiment, the hydraulic pressure generated by driving the hydraulic pump is converted to rotational force by the hydraulic motor, and the gear ratio is continuously changed by friction. It is also possible to use what is to be used.

  The rear axle mechanism 40 supports the tractor 1 by the rear wheels 42 and 42 and transmits the rotational power changed by the transmission 30 to the rear wheels 42 and 42. The rear axle mechanism 40 mainly includes a rear axle 41, a rear wheel 42, and the like.

  The rear axles 41 and 41 are rotated by the rotational power changed by the transmission 30. One end of each of the rear axles 41 and 41 is connected to the transmission 30 and protrudes from the left side surface and the right side surface of the transmission case 31 toward the left direction and the right direction, respectively.

  The rear wheels 42 and 42 support the tractor 1 and transmit the driving force of the tractor 1 to the ground. The central portions of the rear wheels 42 and 42 are fixed to the other ends of the rear axles 41 and 41, respectively, and the rear wheels 42 and 42 are also rotated by the rotation of the rear axles 41 and 41. The tractor 1 can move forward or backward by rotating the rear wheels 42.

  The cabin 50 covers a space where an operator of the tractor 1 gets on. The cabin 50 includes a seat 51, a steering handle 52, a meter panel 53, a clutch pedal 54, a left brake pedal 55L, a right brake pedal 55R, and the like.

  The seat 51 is seated by an operator. The seat 51 is disposed at the rear part in the cabin 50.

  The steering handle 52 is operated by the operator to steer the tractor 1. The steering handle 52 is a substantially ring-shaped member, and is disposed at a position that is a front portion in the cabin 50 and can be operated by an operator seated on the seat 51. The steering handle 52 is connected to a steering mechanism (not shown), and the front wheels 85 and 85 of the tractor 1 are steered by operating the steering handle 52.

  The meter panel 53 displays information related to the tractor 1. The meter panel 53 is disposed in front of the seat 51. The meter panel 53 is a display unit that can display various information such as the traveling speed of the tractor 1, the rotational speed of the engine 10, and the remaining amount of fuel.

  The clutch pedal 54 is for operating the clutch 20. The clutch pedal 54 is disposed on the lower left side of the steering handle 52. The clutch pedal 54 is connected to the clutch 20. When the operator operates the clutch pedal 54 (depresses the clutch pedal 54), the clutch 20 disconnects the output shaft of the engine 10 and the transmission shaft of the clutch 20.

The left brake pedal 55L and the right brake pedal 55R are for performing an operation for braking the tractor 1.
The left brake pedal 55L is disposed on the lower right side of the steering handle 52. The left brake pedal 55L is connected to a left rear axle braking mechanism (not shown) that brakes the rear axle 41 on the left side of the tractor 1. When the left brake pedal 55L is operated by the operator (the left brake pedal 55L is depressed), the left rear axle 41 of the tractor 1 is braked by the left rear axle braking mechanism, and consequently the left rear wheel 42 of the tractor 1 is braked. The
The right brake pedal 55R is disposed on the lower right side of the steering handle 52 and on the right side of the left brake pedal 55L. The right brake pedal 55R is connected to a right rear axle braking mechanism (not shown) that brakes the rear axle 41 on the right side of the tractor 1. When the right brake pedal 55R is operated by the operator (the right brake pedal 55R is depressed), the right rear axle braking mechanism brakes the rear axle 41 on the right side of the tractor 1, and consequently the right rear wheel 42 of the tractor 1 is braked. The

Further, fenders 56 and 56 are provided outside the cabin 50.
The fenders 56 and 56 are respectively fixed to the left side surface and the right side surface of the cabin 50 so as to cover from the front end of the outer periphery of the rear wheels 42 and 42 through the upper end to the rear of the upper end.

  The front loader 60 is attached to the front portion of the tractor 1 and is used for operations such as earth and sand transport and excavation. The front loader 60 mainly includes a bracket 61, a bucket lift arm 62, a bucket lift cylinder 63, an intermediate link 64, a bucket cylinder 65, a bucket link 66, a bucket 67, and the like.

  The bracket 61 supports the front loader 60. The brackets 61 and 61 are respectively disposed on the left and right sides of the bonnet 11, and the lower ends of the brackets 61 and 61 are respectively fixed to the left and right sides of the body frame 5.

  The bucket lift arm 62 is a plate-like member formed by bending upward and downward from a straight line connecting the front and rear center portions. The rear end portions of the bucket lift arms 62 and 62 are supported on the upper ends of the brackets 61 and 61 so as to be vertically rotatable.

The bucket lift cylinder 63 is a hydraulic cylinder including a bucket lift cylinder body 63a and a bucket lift cylinder rod 63b slidably inserted into the bucket lift cylinder body 63a.
The end portions of the bucket lift cylinders 63, 63 on the bucket lift cylinder main bodies 63a, 63a side are supported by the substantially vertical central portions of the brackets 61, 61 so as to be vertically rotatable.
Ends of the bucket lift cylinders 63 and 63 on the bucket lift cylinder rods 63b and 63b side are supported by the middle portions of the bucket lift arms 62 and 62 so as to be vertically rotatable.

  The intermediate link 64 is a substantially triangular plate member. The lower ends of the intermediate links 64 and 64 are respectively supported by the front portions of the bucket lift arms 62 and 62 so as to be pivotable back and forth.

The bucket cylinder 65 is a hydraulic cylinder including a bucket cylinder body 65a and a bucket cylinder rod 65b slidably inserted into the bucket cylinder body 65a.
The end portions of the bucket cylinders 65 and 65 on the bucket cylinder main body 65a and 65a side are supported by the substantially front and rear central portions of the bucket lift arms 62 and 62 so as to be vertically rotatable.
Ends of the bucket cylinders 65 and 65 on the bucket cylinder rods 65b and 65b side are respectively supported by upper and rear portions of the intermediate links 64 and 64 so as to be vertically rotatable.

  The bucket link 66 has a round bar shape. The rear ends of the bucket links 66 and 66 are supported on the upper front portions of the intermediate links 64 and 64, respectively, so as to be vertically rotatable.

  The bucket 67 serves as a working unit for the front loader 60. The lower portion of the rear surface of the bucket 67 is supported by the front ends of the bucket lift arms 62 and 62 so as to be vertically rotatable. The upper part of the rear surface of the bucket 67 is supported by the front ends of the bucket links 66 and 66 so as to be vertically rotatable.

In the front loader 60 configured as described above, the front side (bucket 67 side) of the front loader 60 can be moved up and down by extending and retracting the bucket lift cylinder rods 63b and 63b by an operation unit (not shown).
Further, the bucket 67 can be rotated up and down with respect to the bucket lift arms 62 and 62 by expanding and contracting the bucket cylinder rods 65b and 65b by an operation unit (not shown).
By combining the above operation and the forward / backward movement of the tractor 1, it is possible to carry out operations such as earth and sand transport and excavation using the front loader 60.

  The hydraulic lifting mechanism 70 supports a working machine such as a rotary so that it can be lifted and lowered. The hydraulic lifting mechanism 70 mainly includes an upper cover 71, a lifting cylinder 72, a lift arm 73, lift rods 74L and 74R, a lift rod cylinder 75, a lower link 76, a top link 77, and the like.

  The upper cover 71 is a substantially box-shaped member. The upper cover 71 is disposed on the transmission case 31.

The lift cylinder 72 is a hydraulic cylinder including a lift cylinder body 72a and a lift cylinder rod 72b slidably inserted into the lift cylinder body 72a.
The elevating cylinder body 72a is disposed in the upper cover in such a direction that the elevating cylinder rod 72b can be expanded and contracted rearward.

The lift arms 73 and 73 are plate-like members. One end (front end) of the lift arms 73 and 73 is fixed to both ends of one lift arm shaft 73a inserted into a hole penetrating the left side surface and the right side surface of the upper cover 71, respectively.
One end of a rod-like connecting member 73b is fixed at a substantially central portion of the lift arm shaft 73a perpendicularly to the lift arm shaft 73a. The other end of the connecting member 73b is connected to the end of the elevating cylinder rod 72b.
The lift cylinder 72 expands and contracts the lift cylinder rod 72b by hydraulic pressure to rotate the lift arm shaft 73a via the connecting member 73b, and as a result, the other ends (rear ends) of the lift arms 73 and 73 are moved up and down.

The lift rods 74L and 74R connect the lift arms 73 and 73 to the lower links 76 and 76, respectively. The lift rods 74L and 74R are substantially rod-shaped members.
One end (upper end) of the lift rod 74L is connected to the rear end of the left lift arm 73 of the tractor 1.
One end (upper end) of the lift rod 74R is connected to the rear end of the right lift arm 73 of the tractor 1.

The lift rod cylinder 75 is a hydraulic cylinder including a lift rod cylinder body 75a and a lift rod cylinder rod 75b slidably inserted into the lift rod cylinder body 75a. The lift rod cylinder 75 is provided in the middle of the lift rod 74L.
When the lift rod cylinder 75 extends and contracts the lift rod cylinder rod 75b by hydraulic pressure, the lift rod 74L can be expanded and contracted in the longitudinal direction.

The lower links 76 and 76 support work machines mounted on the tractor 1. The lower links 76 and 76 are plate-like members, and one ends (front ends) of the lower links 76 and 76 are supported by the rear portion of the left side surface and the rear portion of the right side surface of the transmission case 31 so as to be vertically rotatable.
The middle part of the lower link 76 on the left side of the tractor 1 is connected to the lower end of the lift rod 74L.
The middle part of the lower link 76 on the right side of the tractor 1 is connected to the lower end of the lift rod 74R.

  The top link 77 supports a work machine attached to the tractor 1. One end (front end) of the top link 77 is supported by the upper cover 71 through the top link bracket 77a so as to be vertically rotatable.

By connecting the rear ends of the lower links 76 and 76 and the rear end of the top link 77 to a work machine such as a rotary machine, the work machine is mounted on the tractor 1 via the hydraulic lifting mechanism 70.
The lifting cylinder 72 extends and retracts the lifting cylinder rod 72b, so that the rear ends of the lower links 76 and 76 are lifted up and down via the lift arms 73 and 73, the lift rods 74L and 74R, and the work attached to the tractor 1 The machine is moved up and down.
The lift rod cylinder 75 extends and contracts the lift rod cylinder rod 75 b, so that the lower link 76 on the left side of the tractor 1 is lifted and lowered independently of the lower link 76 on the right side of the tractor 1. As a result, it is possible to change the horizontal inclination of the work implement mounted on the tractor 1 via the hydraulic lifting mechanism 70.

  Further, by connecting the working machine mounted on the tractor 1 and the PTO shaft 32 using a universal joint or the like, the rotational power can be transmitted to the working machine.

  The front axle mechanism 80 supports the tractor 1 with the front wheels 85 and 85 and transmits the rotational power changed by the transmission 30 to the front wheels 85 and 85. The front axle mechanism 80 mainly includes a center case 81, a differential device 82, a front wheel drive shaft 83, a final reduction gear 84, a front wheel 85, an independent suspension 90, and the like.

  The center case 81 is a box-shaped member and is fixed to the front portion of the body frame 5 and the lower portion of the body frame 5.

  The differential device 82 distributes rotational power. The differential device 82 is disposed in the center case 81. The rotational power changed by the transmission 30 is transmitted to the differential device 82 via a propulsion shaft (not shown). The rotational power transmitted from the transmission 30 is distributed by the differential device 82 in both the left and right directions of the tractor 1.

  The front wheel drive shafts 83 and 83 transmit rotational power. One ends of the front wheel drive shafts 83 and 83 are connected to the differential device 82 and project from the left side surface and the right side surface of the center case 81 toward the left direction and the right direction, respectively.

  The final reduction gears 84 and 84 decelerate and output the input rotational power. The final reduction gears 84 and 84 are constituted by a planetary gear mechanism or the like. The input sides of the final reduction gears 84 and 84 are connected to the other ends of the front wheel drive shafts 83 and 83 via universal joints 83a and 83a, respectively.

The front wheels 85 and 85 support the tractor 1 and transmit the driving force of the tractor 1 to the ground. Central portions of the front wheels 85 and 85 are connected to the output side of the final reduction gears 84 and 84. The rotational power changed by the transmission 30 is transmitted to the final reduction gears 84 and 84 via the differential device 82 and the front wheel drive shafts 83 and 83. Is transmitted to. The rotational power transmitted to the final reduction gears 84 and 84 is decelerated by the final reduction gears 84 and 84 and then transmitted to the front wheels 85 and 85, and the front wheels 85 and 85 are rotated. The tractor 1 can move forward or backward by rotating the front wheels 85.

  Hereinafter, an independent suspension 90 which is an embodiment of an independent suspension for a work vehicle according to the present invention will be described with reference to FIGS.

The independent suspensions 90 and 90 reduce the impact that the tractor 1 receives from the ground via the front wheels 85 and 85. The independent suspension 90 mainly includes an upper arm 91, a lower arm 92, a joint 93, a suspension cylinder 94, a suspension hydraulic circuit 95, and the like.
In the tractor 1 according to this embodiment, independent suspensions 90 and 90 (excluding the suspension hydraulic circuit 95) having the same structure are provided symmetrically on the left and right sides of the center case 81. Hereinafter, only one (left side) independent suspension 90 will be described, and description of the other (right side) independent suspension 90 will be omitted.

  The upper arm 91 is a member that supports the joint 93. One end of the upper arm 91 is supported on the left side surface of the body frame 5 via an upper arm bracket 91a so as to be vertically rotatable.

  The lower arm 92 is a member that supports the joint 93. One end of the lower arm 92 is supported by the lower left portion of the center case 81 so as to be rotatable up and down.

The joint 93 supports the final reduction gear 84.
The upper part of the joint 93 is supported by the other end of the upper arm 91 so as to be able to rotate back and forth and up and down.
The lower part of the joint 93 is supported by the other end of the lower arm 92 so as to be pivotable back and forth and up and down.
A final reduction gear 84 is rotatably provided on the left side surface of the joint 93.
By configuring as described above, the front wheel 85 is supported by the body frame 5 and the center case 81 of the tractor 1 through the final reduction gear 84, the joint 93, the upper arm 91, and the lower arm 92 so as to be vertically rotatable.

The suspension cylinder 94 is a hydraulic cylinder including a suspension cylinder body 94a and a suspension cylinder rod 94b slidably inserted into the suspension cylinder body 94a.
The end of the suspension cylinder 94 on the suspension cylinder body 94a side is supported on the left side surface of the machine body frame 5 so as to be vertically rotatable via a cylinder bracket 94c.
An end portion of the suspension cylinder 94 on the suspension cylinder rod 94b side is supported by a midway portion of the lower arm 92 so as to be vertically rotatable.

  The suspension hydraulic circuit 95 controls the flow of hydraulic oil in the independent suspension 90. The suspension hydraulic circuit 95 mainly includes a first oil passage 100, a second oil passage 200, a third oil passage 300, a control mechanism 400, and the like.

  The first oil passage 100 connects suspension cylinders 94, 94 provided on the left and right sides of the tractor 1. The first oil passage 100 mainly includes a stop valve 101, a pressure extraction port 102, an overload oil passage 103, an overload valve 104, and the like.

  The stop valve 101 can shut off the oil passage. The stop valves 101 and 101 are provided in the middle of the first oil passage 100 and in the vicinity of the suspension cylinders 94 and 94, respectively. During maintenance of the suspension cylinders 94 and 94, the stop valves 101 and 101 are closed to block the communication of the first oil passage 100, and the hydraulic oil in the first oil passage 100 can be prevented from flowing out.

  The pressure extraction port 102 is for extracting the pressure in the first oil passage 100. The pressure extraction port 102 is provided in the middle of the first oil passage 100 and between the stop valves 101 and 101. When a failure occurs, the pressure in the first oil passage 100 can be confirmed by connecting a pressure gauge 102a to the pressure extraction port 102 as shown in FIG.

The overload oil passage 103 communicates the first oil passage 100 and the transmission case 31.
The transmission case 31 is one of the members constituting the transmission 30 and at the same time is an oil tank that stores hydraulic oil used in the suspension hydraulic circuit 95.
One end of the overload oil passage 103 is in the middle of the first oil passage 100 and is connected in communication between the stop valves 101 and 101. The other end of the overload oil passage 103 is connected to the transmission case 31.

The overload valve 104 is a valve that opens when a pressure exceeding a preset pressure is applied. The overload valve 104 is provided in the middle of the overload oil passage 103.
When the pressure in the first oil passage 100 is equal to or lower than the pressure preset in the overload valve 104, the overload valve 104 is closed and the overload oil passage 103 is shut off.
When the pressure in the first oil passage 100 exceeds the pressure set in advance in the overload valve 104 due to an excessive load applied to the suspension cylinders 94 and 94, the overload valve 104 is opened to perform overload. The oil passage 103 is communicated, and the hydraulic oil in the first oil passage 100 is allowed to flow out to the transmission case 31 so that the suspension hydraulic circuit 95 can be prevented from being damaged.

  The second oil passage 200 branches from the first oil passage 100 and communicates therewith. One end of the second oil passage 200 is in the middle of the first oil passage 100 and is connected in communication between the stop valves 101 and 101. The second oil passage mainly communicates with the accumulator 201, the second oil passage cutoff valve 202, and the like.

  The accumulator 201 absorbs the impact transmitted through the hydraulic oil. The accumulators 201 and 201 are connected to the other ends of the second oil passages 200 branched into two from the branch point 200a.

  The second oil passage cutoff valve 202 is a valve that is closed by electromagnetic force. The second oil passage shut-off valve 202 is provided in the middle of the second oil passage 200 and is provided between one end where the second oil passage 200 is connected to the first oil passage 100 and the branch point 200a.

  When the second oil passage shut-off valve 202 is opened and the second oil passage 200 is communicated, the impact received by the front wheels 85 and 85 from the ground is within the suspension cylinders 94 and 94, the first oil passage 100, and the second oil passage 200. Is transmitted to the accumulators 201 and 201 through the hydraulic oil and absorbed by the accumulators 201 and 201.

  Note that the number of accumulators 201 used in the suspension hydraulic circuit 95 may be one or three or more, and it is sufficient if a capacity sufficient to perform a function of absorbing an impact is ensured.

The third oil passage 300 connects the first oil passage 100 and the transmission case 31 in communication. One end of the third oil passage 300 is in the middle of the first oil passage 100 and is connected in communication between the stop valves 101 and 101. The other end of the third oil passage 300 is connected to the transmission case 31. The third oil passage 300 is mainly composed of a hydraulic pump 301, a suction filter 302, an ascending solenoid valve 303, a descending solenoid valve 304, a pressure compensation flow control valve 305, an unloading oil passage 306, an unloading solenoid valve 307, and a relief oil. The passage 308 communicates with the relief valve 309 and the like.
In the following description, for convenience of explanation, the transmission case 31 side in the third oil passage 300 is defined as the upstream side, and the first oil passage 100 side is defined as the downstream side, and the following description is performed based on the definition.

  The hydraulic pump 301 pumps hydraulic oil using the rotational power of the engine 10. The hydraulic pump 301 is provided in the middle of the third oil passage 300. The hydraulic pump 301 is driven by the power of the engine 10. When the hydraulic pump 301 is driven, the hydraulic oil in the transmission case 31 is sucked up from one end on the transmission case 31 side of the third oil passage 300 and is pumped to the other end on the first oil passage 100 side.

  The suction filter 302 removes impurities mixed in the hydraulic oil. The suction filter 302 is provided at one end of the third oil passage 300 on the transmission case 31 side. Impurities are removed from the hydraulic oil sucked from one end of the third oil passage 300 on the transmission case 31 side when passing through the suction filter 302.

  The ascending solenoid valve 303 is a valve that operates by electromagnetic force. The ascending solenoid valve 303 is provided in the middle of the third oil passage 300 and downstream of the hydraulic pump 301.

  The descending solenoid valve 304 is a valve that operates by electromagnetic force. The descending solenoid valve 304 is provided in the middle of the third oil passage 300 and downstream of the ascending solenoid valve 303.

  The pressure-compensated flow control valve 305 keeps the flow rate of the hydraulic oil passing toward one side constant. The pressure compensation flow control valve 305 is provided in the middle of the third oil passage 300 and between the ascending solenoid valve 303 and the descending solenoid valve 304. The pressure compensation flow control valve 305 mainly includes a check valve 305a, a throttle 305b, a spool (not shown), and the like.

When the hydraulic oil flows from the upstream side to the downstream side of the third oil passage 300, the hydraulic oil passes through the check valve 305 a of the pressure compensation type flow control valve 305.
When the hydraulic oil flows from the downstream side to the upstream side of the third oil passage 300, the spool moves due to the pressure difference before and after the throttle 305b, and the oil passage area in the pressure compensation type flow control valve 305 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. By operating the pressure compensation flow control valve 305 in this way, the flow rate of the hydraulic oil can be kept constant even if the pressure difference before and after the throttle 305b fluctuates.

  The unloading oil passage 306 connects the middle portion of the third oil passage 300 and the transmission case 31 in communication. One end of the unloading oil passage 306 is in the middle of the third oil passage 300 and is connected in communication between the hydraulic pump 301 and the lift solenoid valve 303. The other end of the unloading oil passage 306 is connected to the transmission case 31.

  The unloading electromagnetic valve 307 is a valve that is closed by electromagnetic force. The unloading electromagnetic valve 307 is provided in the middle of the unloading oil passage 306.

  The relief oil passage 308 connects the middle portion of the third oil passage 300 and the transmission case 31 in communication. One end of the relief oil passage 308 is in the middle of the third oil passage 300 and is connected in communication between the hydraulic pump 301 and the lift solenoid valve 303. The other end of the relief oil passage 308 is connected to the transmission case 31.

The relief valve 309 is a valve that opens when a pressure exceeding a preset pressure is applied. The relief valve 309 is provided in the middle of the relief oil passage 308.
When the pressure in the third oil passage 300 (between the hydraulic pump 301 and the lift solenoid valve 303) is equal to or lower than the pressure preset in the relief valve 309, the relief valve 309 is closed and the relief oil passage 308 is shut off. The
When the pressure in the third oil passage 300 (between the hydraulic pump 301 and the lift solenoid valve 303) exceeds the pressure preset in the relief valve 309 due to an abnormality occurring in the suspension hydraulic circuit 95, the relief valve 309 is When opened, the relief oil passage 308 is communicated, and the hydraulic oil in the third oil passage 300 is allowed to flow out to the transmission case 31, thereby preventing the suspension hydraulic circuit 95 from being damaged.

  The control mechanism 400 operates an electromagnetic valve provided in the suspension hydraulic circuit 95 based on various input signals. The control mechanism 400 mainly includes a position sensor 401, a traveling speed detection unit 402, a suspension lock changeover switch 403, a control unit 450, and the like.

  The position sensor 401 detects the extension amount of the suspension cylinder rod 94b. The position sensors 401 and 401 are provided in the suspension cylinders 94 and 94, respectively. The position sensors 401 and 401 detect the amount of extension (or contraction) of the suspension cylinder rods 94b and 94b from the reference position.

  The traveling speed detection means 402 detects the traveling speed of the tractor 1. Specifically, the traveling speed detection means 402 is provided in the vicinity of the rear axle 41 of the tractor 1 and detects the rotational speed of the rear axle 41.

The suspension lock changeover switch 403 is an instruction means for giving an instruction to interrupt or circulate the flow of hydraulic oil in the second oil passage 200 by the second oil passage cutoff valve 202. The suspension lock changeover switch 403 is provided around the seat 51 in the cabin 50. The vicinity of the seat 51 is a position that can be operated by an operator sitting on the seat 51 and operating the tractor 1.
An operation portion (a portion operated by the operator) 403a of the suspension lock changeover switch 403 is a position (hereinafter referred to as this position) where the suspension function is invalidated (the second oil passage 200 is shut off by the second oil passage cutoff valve 202). (Referred to as “lock position A”), a position that makes the suspension function effective (the second oil passage shut-off valve 202 does not shut off the second oil passage 200) (hereinafter, this position is referred to as “lock release position B”). And can be switched to either

  The suspension lock changeover switch 403 can be configured by various switches such as a toggle switch, a push button switch, a slide switch, a touch panel, and the like.

The control unit 450 controls the operation of the second oil passage shut-off valve 202 based on information related to detection of the traveling speed of the tractor 1 by the traveling speed detection means 402 and information related to the position of the operation unit 403a of the suspension lock switch 403. To do.
Specifically, the control unit 450 may be configured such that a CPU, ROM, RAM, HDD, or the like is connected by a bus, or may be configured by a one-chip LSI or the like.
The control unit 450 stores various programs and data for controlling the operation of the second oil passage cutoff valve 202.

The controller 450 is connected to the position sensors 401 and 401, and can detect the detection of the extension amount of the suspension cylinder rod 94b by the position sensors 401 and 401 as a detection signal.
The control unit 450 is connected to the ascending electromagnetic valve 303 and can transmit a signal related to the control of the operation of the ascending electromagnetic valve 303 to the ascending electromagnetic valve 303.
The control unit 450 is connected to the descending solenoid valve 304 and can transmit a signal related to the control of the operation of the descending solenoid valve 304 to the descending solenoid valve 304.
The controller 450 is connected to the unloading solenoid valve 307 and can transmit a signal related to the control of the operation of the unloading solenoid valve 307 to the unloading solenoid valve 307.

When the controller 450 does not transmit a signal related to the operation of the ascending solenoid valve 303 to the ascending solenoid valve 303, the ascending solenoid valve 303 communicates the downstream side of the ascending solenoid valve 303 and the transmission case 31, and the upstream of the ascending solenoid valve 303. Cut off the flow of hydraulic fluid from the side.
At this time, the control unit 450 does not transmit a signal related to the operation of the unloading solenoid valve 307 to the unloading solenoid valve 307, and the unloading oil passage 306 is formed in the middle of the third oil passage 300, the transmission case 31, Connect the communication.
As a result, the hydraulic oil sucked up from the transmission case 31 by driving the hydraulic pump 301 is returned to the transmission case 31 again through the unloading oil passage 306.

When the controller 450 does not transmit a signal related to the operation of the lowering solenoid valve 304 to the lowering solenoid valve 304, the lowering solenoid valve 304 blocks the flow of hydraulic oil from the downstream side to the upstream side of the lowering solenoid valve 304, and the upstream side The hydraulic oil is circulated only from the downstream to the downstream side.
At this time, the control unit 450 transmits a signal related to the operation of the ascending solenoid valve 303 to the ascending solenoid valve 303 to operate the ascending solenoid valve 303 so that the upstream side and the downstream side of the ascending solenoid valve 303 communicate with each other. When the part 450 transmits a signal related to the operation of the unloading solenoid valve 307 to the unloading solenoid valve 307 to operate the unloading solenoid valve 307 and shut off the unloading oil passage 306, the hydraulic pump 301 is driven. The hydraulic oil sucked up from the transmission case 31 is pumped to the first oil passage 100 through the ascending solenoid valve 303, the pressure compensation flow control valve 305, and the descending solenoid valve 304. As a result, hydraulic oil is pumped to the suspension cylinders 94 and 94, and the vehicle height in front of the tractor 1 can be raised.

  The controller 450 does not transmit a signal related to the operation of the ascending solenoid valve 303 to the ascending solenoid valve 303 but transmits a signal related to the operation of the descending solenoid valve 304 to the descending solenoid valve 304 to operate the descending solenoid valve 304 and descend When the downstream side and the upstream side of the solenoid valve 304 communicate with each other, the hydraulic oil in the first oil passage 100 and the second oil passage 200 passes through the lowering solenoid valve 304, the pressure compensation flow control valve 305, and the raising solenoid valve 303. Returned to the transmission case 31. As a result, the hydraulic oil in the suspension cylinders 94 and 94 can flow out, and the vehicle height in front of the tractor 1 can be lowered.

  Hereinafter, an embodiment of the control mode of the independent suspension of the work vehicle according to the present invention will be described with reference to FIGS.

As shown in FIG. 3, the control unit 450 is connected to the traveling speed detection unit 402 and can receive detection of the rotation speed of the rear axle 41 of the tractor 1 by the traveling speed detection unit 402 as a detection signal.
The control unit 450 is connected to the suspension lock changeover switch 403, and can receive information relating to the position of the operation unit 403a of the suspension lock changeover switch 403 as a detection signal.
The control unit 450 is connected to the second oil passage cutoff valve 202 and can transmit a signal related to the control of the operation of the second oil passage cutoff valve 202 to the second oil passage cutoff valve 202.
The controller 450 is connected to the meter panel 53, and can transmit a signal related to the operation information of the second oil passage cutoff valve 202 to the meter panel 53.

  The controller 450 constantly calculates the traveling speed V of the tractor 1 based on the detection signal of the rotational speed of the rear axle 41 of the tractor 1 received from the traveling speed detection means 402. Specifically, the traveling speed V of the tractor 1 is calculated based on the rotation speed of the rear axle 41 and the diameter (or radius) of the rear wheel 42 stored in advance in the control unit 450.

  The control unit 450 receives information related to the position of the operation unit 403a of the suspension lock changeover switch 403 as a detection signal, and determines the content of the detection signal (FIG. 4, S110).

When the control unit 450 receives from the suspension lock changeover switch 403 a detection signal indicating that the position of the operation unit 403a of the suspension lock changeover switch 403 is the lock release position B (hereinafter referred to as “detection signal S”), A signal indicating that the second oil passage shut-off valve 202 is not operating (hereinafter referred to as “display signal D1”) is transmitted to the meter panel 53 (FIG. 4, S140). At this time, the control unit 450 does not transmit a signal (hereinafter referred to as “control signal C”) to activate the second oil passage cutoff valve 202 to the second oil passage cutoff valve 202.
Since the second oil passage shut-off valve 202 communicates with the second oil passage 200, the suspension function is effective.
Based on the display signal D1, the meter panel 53 displays that the second oil passage shut-off valve 202 is not operating, that is, displays that the suspension function is effective.

  As shown in FIG. 5A, the controller 450 detects from the suspension lock changeover switch 403 to a detection signal (hereinafter referred to as “detection signal L”) that the position of the operation portion 403a of the suspension lock changeover switch 403 is the lock position A. ) Is compared, the magnitude relationship between the traveling speed V of the tractor 1 and the reference traveling speed VT which is a predetermined value is compared (S120 in FIG. 4). The reference travel speed VT is a constant travel speed value stored in advance in the control unit 450.

When the controller 450 determines that the travel speed V is less than the reference travel speed VT, the control unit 450 transmits a control signal C to the second oil passage shut-off valve 202 and indicates that the second oil passage shut-off valve 202 is operating. A signal (hereinafter referred to as “display signal D2”) is transmitted to the meter panel 53 (FIG. 4, S130).
The second oil passage shut-off valve 202 is actuated by the control signal C and shuts off the flow of hydraulic oil in the second oil passage 200.
When the flow of the hydraulic oil in the second oil passage 200 is blocked, the communication between the suspension cylinders 94 and 94 and the accumulators 201 and 201 is blocked, and the suspension function becomes invalid.
Based on the display signal D2, the meter panel 53 displays that the second oil passage shutoff valve 202 is operating, that is, indicates that the suspension function is invalid.

As shown in FIG. 5B, when the controller 450 determines in S120 that the traveling speed V is equal to or higher than the reference traveling speed VT, the controller 450 transmits a display signal D1 to the meter panel 53 (S140). At this time, the controller 450 does not transmit the control signal C to the second oil passage cutoff valve 202.
Since the second oil passage shut-off valve 202 communicates with the second oil passage 200, the suspension function is effective.
Based on the display signal D1, the meter panel 53 displays that the second oil passage shut-off valve 202 is not operating, that is, displays that the suspension function is effective.

In this embodiment, the traveling speed detection unit 402 detects the rotational speed of the rear axle 41, and the control unit 450 calculates the traveling speed V of the tractor 1 based on the detected rotational speed. The present invention is not limited to this.
For example, the traveling speed detecting means may be a ground sensor or the like and directly detects the traveling speed V of the tractor 1. Further, the traveling speed detection means may detect the rotational speed of the engine 10 and the reduction ratio of the tractor 1, and the control unit 450 may calculate the traveling speed V of the tractor 1 based on the rotational speed and the reduction ratio. . That is, the traveling speed detection means according to the present invention may be any means as long as the control unit 450 detects information for obtaining the traveling speed V of the tractor 1.

As described above, the independent suspension 90 of the tractor 1 of this embodiment is
A suspension cylinder 94 that supports the front wheel 85 to be movable up and down;
A first oil passage 100 communicated with the suspension cylinder 94;
An accumulator 201 for absorbing an impact applied to the suspension cylinder 94;
A second oil passage 200 that connects the first oil passage 100 and the accumulator 201 in communication,
A second oil passage shut-off valve 202 provided in the middle of the second oil passage 200 and capable of shutting off the flow of hydraulic oil in the second oil passage 200;
A suspension lock changeover switch 403 for giving an instruction to shut off the flow of hydraulic oil in the second oil passage 200 by the second oil passage cutoff valve 202;
A controller 450 that shuts off the flow of hydraulic oil in the second oil passage 200 by the second oil passage shut-off valve 202 in accordance with an instruction of the suspension lock changeover switch 403;
It comprises.
With this configuration, the hydraulic oil flow in the second oil passage 200 can be shut off by the second oil passage shut-off valve 202 in accordance with the instruction of the suspension lock changeover switch 403, and the suspension function of the tractor 1 is invalidated. It becomes possible to make it.
Furthermore, by disabling the suspension function during work of a loader, backhoe, etc., it becomes possible to improve workability such as improvement of ride comfort and handling stability of the operator and work accuracy.

Further, the independent suspension 90 of the tractor 1 of this embodiment is
A traveling speed detecting means 402 for detecting the traveling speed V of the tractor 1 is provided;
The control unit 450
Based on the information relating to the detection by the traveling speed detecting means 402, when the traveling speed V of the tractor 1 is equal to or higher than a predetermined value (reference traveling speed VT), the second oil passage shut-off valve regardless of the instruction of the suspension lock changeover switch 403. 202 does not block the flow of hydraulic oil in the second oil passage 200.
With this configuration, when the traveling speed V of the tractor 1 becomes equal to or higher than a predetermined value (reference traveling speed VT), the second oil passage shutoff valve 202 causes the second oil passage shut-off valve 202 to perform the second operation regardless of the instruction of the suspension lock changeover switch 403. The suspension function of the tractor 1 can be made effective without interrupting the flow of hydraulic oil in the oil passage 200.
As a result, when the traveling speed of the tractor 1 increases during movement, the suspension function can be automatically enabled and the ride comfort and handling stability of the operator can be improved without operating the suspension lock switch 403. It becomes possible to make it.

Hereinafter, the control mechanism 500 will be described with reference to FIGS.
The control mechanism 500 is another embodiment of the control mechanism 400. Basically, members having substantially the same configuration as the control mechanism 400 are given the same member numbers, and description thereof is omitted.
Note that the control mechanism 500 is a control mechanism that is used when work is performed by the rotational power of the PTO shaft 32 (for example, when rotary tillage work is performed).

  As shown in FIG. 6, the control mechanism 500 mainly includes a position sensor 401, a PTO rotation detection unit 501, a vibration detection unit 502, a control unit 450, and the like.

The PTO rotation detection unit 501 is a work state detection unit that detects that the PTO shaft 32 is rotating. The PTO rotation detection means 501 is provided in the vicinity of the PTO shaft 32 and detects whether or not the PTO shaft 32 is rotating.
Note that the PTO rotation detecting means 501 is not limited to detecting that the PTO shaft 32 is rotating directly as in the present embodiment, but may be a lever or a switch for operating switching of rotation or stop of the PTO shaft 32. It may be detected that the PTO shaft 32 is rotating by detecting the operation.

  The vibration detection means 502 and 502 detect the vibration frequency of the object. The vibration detection means 502 and 502 are provided in the suspension cylinders 94 and 94, respectively. The vibration detectors 502 and 502 detect the frequency F of the expansion and contraction motion of the suspension cylinder rods 94b and 94b.

The control unit 450 is connected to the PTO rotation detection unit 501 and can receive detection of rotation of the PTO shaft 32 by the PTO rotation detection unit 501 as a detection signal.
The control unit 450 is connected to the vibration detection means 502/502, and can receive the frequency F of the expansion / contraction motion of the suspension cylinder rod 94b by the vibration detection means 502/502 as a detection signal.
The control unit 450 is connected to the second oil passage cutoff valve 202 and can transmit a signal related to the control of the operation of the second oil passage cutoff valve 202 to the second oil passage cutoff valve 202.
The controller 450 is connected to the meter panel 53, and can transmit a signal related to the operation information of the second oil passage cutoff valve 202 to the meter panel 53.

  The controller 450 determines whether a detection signal (hereinafter referred to as “detection signal R”) indicating that the PTO shaft 32 is rotating is received from the PTO rotation detection means 501 (FIG. 7, S210).

When receiving the detection signal R, the control unit 450 transmits the control signal C to the second oil passage cutoff valve 202 and transmits the display signal D2 to the meter panel 53 (FIG. 7, S220).
The second oil passage shut-off valve 202 is actuated by the control signal C and shuts off the flow of hydraulic oil in the second oil passage 200.
When the flow of the hydraulic oil in the second oil passage 200 is blocked, the communication between the suspension cylinders 94 and 94 and the accumulators 201 and 201 is blocked, and the suspension function becomes invalid.
Based on the display signal D2, the meter panel 53 displays that the second oil passage shutoff valve 202 is operating, that is, indicates that the suspension function is invalid.

As shown in FIG. 8A, when the control unit 450 has not received the detection signal R, the frequency F and a reference frequency FT that is a predetermined value based on the detection signal received from the vibration detection means 502/502. Are compared (FIG. 7, S230). The reference frequency FT is a constant frequency value stored in the controller 450 in advance.
In this embodiment, the controller 450 determines the frequency of the suspension cylinder rods 94b and 94b calculated based on the detection signals received from the two vibration detection means 502 and 502 as the frequency F when compared with the reference frequency FT. Although the average value of the frequency of the telescopic motion is used, the present invention is not limited to this, and the frequency of one of the suspension cylinder rods 94b can be used as the frequency F.

When the control unit 450 determines that the frequency F is equal to or higher than the reference frequency FT, the control unit 450 transmits a control signal C to the second oil passage cutoff valve 202 and transmits a display signal D2 to the meter panel 53 (S220).
When the flow of the hydraulic oil in the second oil passage 200 is blocked, the communication between the suspension cylinders 94 and 94 and the accumulators 201 and 201 is blocked, and the suspension function becomes invalid.
Based on the display signal D2, the meter panel 53 displays that the second oil passage shutoff valve 202 is operating, that is, indicates that the suspension function is invalid.

As shown in FIG. 8B, when the control unit 450 determines that the frequency F is less than the reference frequency FT, the control unit 450 transmits a display signal D1 to the meter panel 53 (FIG. 7, S240). At this time, the controller 450 does not transmit the control signal C to the second oil passage cutoff valve 202.
Since the second oil passage shut-off valve 202 communicates with the second oil passage 200, the suspension function is effective.
Based on the display signal D1, the meter panel 53 displays that the second oil passage shut-off valve 202 is not operating, that is, displays that the suspension function is effective.

In the present embodiment, the PTO rotation detection unit 501 is used as the work state detection unit according to the present invention, but the present invention is not limited to this.
For example, whether or not a work machine is mounted on the tractor 1 is detected by a sensor provided on a portion (lower link 76 or top link 77) connected to the work machine of the hydraulic lifting mechanism 70, and the work machine is mounted on the tractor 1. It is also possible to adopt a configuration in which the detection signal R is transmitted to the control unit 450 when it is in the state.
That is, the work state detecting means according to the present invention may be any means that can detect whether or not the tractor 1 is in the work state. The “working state” is a state in which the tractor 1 is performing a work such as a tilling work or a loader work using some work machine, or a state in which the tractor 1 is ready to perform the work.

As described above, the independent suspension 90 of the tractor 1 of this embodiment is
A suspension cylinder 94 that supports the front wheel 85 to be movable up and down;
A first oil passage 100 communicated with the suspension cylinder 94;
An accumulator 201 for absorbing an impact applied to the suspension cylinder 94;
A second oil passage 200 that connects the first oil passage 100 and the accumulator 201 in communication,
A second oil passage shut-off valve 202 provided in the middle of the second oil passage 200 and capable of shutting off the flow of hydraulic oil in the second oil passage 200;
PTO rotation detection means 501 for detecting the working state of the tractor 1,
A control unit 450 that shuts off the flow of hydraulic oil in the second oil passage 200 by the second oil passage shut-off valve 202 based on information relating to the detection of the work state by the PTO rotation detection means 501;
It comprises.
With this configuration, when the tractor 1 is in a working state, the second oil passage shutoff valve 202 can block the flow of hydraulic oil in the second oil passage 200, and the suspension function of the tractor 1 can be improved. It can be disabled.
Accordingly, it is possible to omit a complicated switching operation by automatically switching the suspension function between valid and invalid. Further, since there is no manual switching operation, it is possible to prevent the switching operation from being mistaken.

Further, the independent suspension 90 of the tractor 1 of this embodiment is
A vibration detecting means 502 for detecting the expansion and contraction frequency of the suspension cylinder 94;
The control unit 450
Based on the information related to the detection by the vibration detection means 502, when the frequency F is equal to or higher than a predetermined value (reference frequency FT), the flow of hydraulic oil in the second oil passage 200 is caused by the second oil passage shut-off valve 202. Is to shut off.
With this configuration, it is possible to prevent the tractor 1 from generating abnormal vibration due to expansion and contraction of the suspension cylinder 94.
This makes it possible to improve the ride comfort and handling stability of the operator.

Further, the independent suspension 90 of the tractor 1 of this embodiment is
The meter panel 53 which displays whether the flow of the hydraulic oil in the 2nd oil path 200 is interrupted | blocked by the control part 450 is comprised.
With this configuration, the operator of the tractor 1 can confirm at a glance whether the suspension function of the tractor 1 is valid or invalid.

  The display unit according to the present invention is not limited to the meter panel 53 in the present embodiment, and can be configured using a monitor, a light, a sound generator, or the like independent of the meter panel 53.

BRIEF DESCRIPTION OF THE DRAWINGS The whole side view which showed the whole structure of the tractor which concerns on one Embodiment of this invention. The front enlarged view which similarly shows the front axle mechanism of a tractor. The schematic diagram which similarly shows the suspension hydraulic circuit of a tractor. The flowchart which shows the outline | summary of control of an independent type suspension. The schematic diagram which shows the suspension hydraulic circuit of the tractor which concerns on one Embodiment of this invention. The schematic diagram which shows the suspension hydraulic circuit of the tractor which concerns on another one Embodiment of this invention. The flowchart which shows the outline | summary of control of an independent type suspension. The schematic diagram which shows the suspension hydraulic circuit of the tractor which concerns on another one Embodiment of this invention.

Explanation of symbols

1 Tractor 90 Independent suspension 94 Suspension cylinder (hydraulic cylinder)
DESCRIPTION OF SYMBOLS 100 1st oil path 200 2nd oil path 201 Accumulator 202 2nd oil path shut-off valve 403 Suspension lock changeover switch (indication switch)
450 Controller

Claims (5)

A hydraulic cylinder that supports the wheels to be movable up and down;
A first oil passage communicating with the hydraulic cylinder;
An accumulator for absorbing an impact applied to the hydraulic cylinder;
A second oil passage that connects the first oil passage and the accumulator;
A second oil passage shut-off valve provided in the middle of the second oil passage and capable of shutting off the flow of hydraulic oil in the second oil passage;
An instruction switch for giving an instruction to shut off the flow of hydraulic oil in the second oil passage by the second oil passage cutoff valve;
A control unit that shuts off a flow of hydraulic oil in the second oil passage by the second oil passage shut-off valve according to an instruction of the instruction switch;
A stand-alone suspension for a work vehicle. Comprising travel speed detecting means for detecting the travel speed of the work vehicle;
The controller is
Based on the information relating to the detection by the traveling speed detecting means, when the traveling speed of the work vehicle is equal to or higher than a predetermined value, the second oil passage shut-off valve is connected to the second oil passage in the second oil passage regardless of the instruction of the instruction switch. The independent suspension for a work vehicle according to claim 1, wherein the flow of hydraulic oil is not blocked. A hydraulic cylinder that supports the wheels to be movable up and down;
A first oil passage communicating with the hydraulic cylinder;
An accumulator for absorbing an impact applied to the hydraulic cylinder;
A second oil passage that connects the first oil passage and the accumulator;
A second oil passage shut-off valve provided in the middle of the second oil passage and capable of shutting off the flow of hydraulic oil in the second oil passage;
Work state detection means for detecting the work state of the work vehicle;
A control unit that shuts off the flow of hydraulic oil in the second oil passage by the second oil passage shut-off valve based on information relating to detection of the work state by the work state detection means;
A stand-alone suspension for a work vehicle. Comprising vibration detecting means for detecting the frequency of expansion and contraction of the hydraulic cylinder;
The controller is
The flow of hydraulic oil in the second oil passage is shut off by the second oil passage shut-off valve when the frequency is equal to or greater than a predetermined value based on information relating to detection by the vibration detecting means. The independent suspension of the working vehicle according to any one of claims 3 to 4.   The independence of the work vehicle according to any one of claims 1 to 4, further comprising a display unit that displays whether or not the flow of hydraulic oil in the second oil passage is blocked by the control unit. Mold suspension.

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