JP4996432B2 - Independent suspension of work vehicle - Google Patents

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”.

  In the suspension configured as described above, when the expansion / contraction operation of the cylinder is controlled using the control device, it is conceivable to use various control modes in accordance with the traveling of the work vehicle and the work content. When the suspension is controlled by a control device capable of control based on a plurality of control modes, it is necessary to select and execute an appropriate control mode in accordance with the travel of the work vehicle and the work content. However, setting and changing the mode and height according to the running state and the work content are troublesome, and the mode change may be forgotten when the running state or the work content changes.

  Accordingly, an object of the present invention is to provide a stand-alone suspension for a work vehicle that can select a desired control mode and perform control based on the control mode.

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

In claim 1, as the control mode, at least an automatic mode for automatically maintaining the vehicle height at a preset height, and a manual mode for maintaining the vehicle height at a height set by the vehicle height setting means. And a vehicle body horizontal mode for adjusting the vehicle height so that the vehicle body is horizontal. In the automatic mode and the vehicle body horizontal mode, the traveling speed detected by the traveling speed detecting means for detecting the traveling speed of the work vehicle is A road driving mode in a non-zero state and a work mode for adjusting the vehicle height to a vehicle height corresponding to a work machine mounted on the work vehicle are selected, and one of the control modes is selected. A control unit that performs control based on the control mode; and a mode switching unit that issues an instruction to switch the control mode selected by the control unit. The control unit includes the mode switching unit. Based on the information relating to the instruction by, it switches the control mode selected, the control unit, when performing the control based on the manual mode, the work on the basis of information relating to the detection by said running speed detecting means When it is determined that the vehicle is traveling at a predetermined traveling speed or more, the suspension is a stand-alone suspension for a working vehicle that switches the selected control mode from the manual mode to the automatic mode .

According to a second aspect of the present invention, in the stand-alone suspension of the work vehicle according to the first aspect , the work vehicle includes a work machine detection unit that detects that the work machine is mounted on the work vehicle, and the control unit detects the work machine detection. When it is determined that a work implement is mounted on the work vehicle based on information relating to detection by the means, the control mode to be selected is switched from the road travel mode to the work mode.

According to a third aspect of the present invention, in the stand-alone suspension of the work vehicle according to the first or second aspect, the display unit displays information related to the control performed by the control unit.

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

The control mode includes at least an automatic mode for automatically maintaining the vehicle height at a preset height and a manual mode for maintaining the vehicle height at a height set by the vehicle height setting means. And a vehicle body horizontal mode for adjusting the vehicle height so that the vehicle body is horizontal. In the automatic mode and the vehicle body horizontal mode, the traveling speed detected by the traveling speed detecting means for detecting the traveling speed of the work vehicle is A road driving mode in a non-zero state and a work mode for adjusting the vehicle height to a vehicle height corresponding to a work machine mounted on the work vehicle are selected, and one of the control modes is selected. A control unit that performs control based on the control mode; and a mode switching unit that issues an instruction to switch the control mode selected by the control unit, the control unit being controlled by the mode switching unit. Based on the information relating to the instruction, by switching the control mode to be selected, select any of the control modes, it is possible to perform control based on the control mode. In addition, each control mode can be switched instantaneously with a simple operation, and the operability of the work vehicle can be improved.

In addition, the control unit determines that the work vehicle is traveling at a predetermined traveling speed or more based on information related to detection by the traveling speed detecting unit when performing control based on the manual mode. In this case, since the control mode to be selected is switched from the manual mode to the automatic mode, it is possible to automatically switch from the manual mode to the automatic mode when the traveling speed of the work vehicle exceeds a predetermined traveling speed. It becomes. As a result, when the tractor travels at a high speed, the tractor can be maintained in a stable posture regardless of an instruction from the mode switching means.

According to a second aspect of the present invention, in the independent suspension for the working vehicle according to the first aspect, the working vehicle includes a working machine detection unit that detects that the working machine is mounted on the working vehicle, and the control unit detects the working machine detection. When it is determined that the work machine is attached to the work vehicle based on the information related to the detection by the means, the work machine is attached to the work vehicle by switching the control mode to be selected from the road mode to the work mode. In this case, the control mode to be selected can be automatically switched from the road traveling mode to the work mode. This eliminates the need for complicated manual operation and allows the control mode to be reliably switched to the work mode.

According to a third aspect of the present invention, in the independent suspension of the work vehicle according to the first or second aspect, the information related to the control by the control unit is provided by including a display unit that displays information related to the control performed by the control unit. Can be easily confirmed by the operator.

  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.

  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 is a display unit that displays information about 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 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 is a working machine mounting device that supports a working machine such as a rotary so as to 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 71 in such a direction that the elevating cylinder rod 72b can extend and retract toward the rear.

  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. The center part of the front wheels 85 is connected to the output side of the final reduction gears 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. 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 third oil passage 300, a second oil passage 200, a control mechanism 400, and the like.

  The first oil passage 100 is connected to suspension cylinders 94 and 94 provided on the left and right sides of the tractor 1, respectively, and the suspension cylinders 94 and 94 are connected to each other. 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 connects the first oil passage 100 and the transmission case 31 in communication. 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 other end of the second oil passage 200 is connected to the transmission case 31. The second oil passage 200 is mainly composed of a hydraulic pump 201, a suction filter 202, a flow direction switching means 203, a pressure compensation flow control valve 204, an unloading oil passage 205, an unloading electromagnetic valve 206, a relief oil passage 207, a relief. The valve 208 and the like communicate with each other. In the following description, for convenience of explanation, the transmission case 31 side in the second oil passage 200 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 201 pumps hydraulic oil using the rotational power of the engine 10. The hydraulic pump 201 is provided in the middle of the second oil passage 200. The hydraulic pump 201 is driven by the power of the engine 10. When the hydraulic pump 201 is driven, the hydraulic oil in the transmission case 31 is sucked up from one end of the second oil passage 200 on the transmission case 31 side, and is pumped to the other end on the first oil passage 100 side.

  The suction filter 202 removes impurities mixed in the hydraulic oil. The suction filter 202 is provided at one end of the second oil passage 200 on the transmission case 31 side. The working oil sucked from one end of the second oil passage 200 on the transmission case 31 side is removed of impurities when passing through the suction filter 202.

  The flow direction switching means 203 switches the direction in which the hydraulic oil can flow in the second oil passage 200 or blocks the flow of hydraulic oil. The flow direction switching means 203 is provided in the middle of the second oil passage 200. The flow direction switching means 203 is mainly composed of an ascending solenoid valve 203a, a descending solenoid valve 203b, and the like.

  The ascending solenoid valve 203a is a valve that operates by electromagnetic force. The ascending solenoid valve 203 a is provided in the middle of the second oil passage 200 and downstream of the hydraulic pump 201.

  The descending solenoid valve 203b is a valve that operates by electromagnetic force. The descending solenoid valve 203b is provided in the middle of the second oil passage 200 and downstream of the ascending solenoid valve 203a.

  The pressure-compensated flow control valve 204 keeps the flow rate of the hydraulic oil passing toward one side constant. The pressure compensation flow control valve 204 is provided in the middle of the second oil passage 200 and between the ascending solenoid valve 203a and the descending solenoid valve 203b. The pressure compensation type flow control valve 204 mainly includes a check valve 204a, a throttle 204b, a spool (not shown), and the like.

  When the hydraulic oil flows from the upstream side to the downstream side of the second oil passage 200, the hydraulic oil passes through the check valve 204 a of the pressure compensation type flow control valve 204. When hydraulic fluid flows from the downstream side to the upstream side of the second oil passage 200, the spool moves due to the pressure difference before and after the throttle 204b, and the oil passage area in the pressure compensation flow control valve 204 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 type flow rate control valve 204 in this way, it becomes possible to keep the flow rate of the hydraulic oil constant even if the pressure difference before and after the throttle 204b fluctuates.

  The unloading oil passage 205 connects the middle portion of the second oil passage 200 and the transmission case 31 in communication. One end of the unloading oil passage 205 is in the middle of the second oil passage 200 and is connected in communication between the hydraulic pump 201 and the lift solenoid valve 203a. The other end of the unloading oil passage 205 is connected to the transmission case 31.

  The unloading electromagnetic valve 206 is a valve that is closed by electromagnetic force. The unloading electromagnetic valve 206 is provided in the middle of the unloading oil passage 205.

  The relief oil passage 207 connects the middle portion of the second oil passage 200 and the transmission case 31 in communication. One end of the relief oil passage 207 is in the middle of the second oil passage 200 and is connected in communication between the hydraulic pump 201 and the lift solenoid valve 203a. The other end of the relief oil passage 207 is connected to the transmission case 31.

  The relief valve 208 is a valve that opens when a pressure exceeding a preset pressure is applied. The relief valve 208 is provided in the middle of the relief oil passage 207. When the pressure in the second oil passage 200 (between the hydraulic pump 201 and the lift solenoid valve 203a) is equal to or lower than the pressure preset in the relief valve 208, the relief valve 208 is closed and the relief oil passage 207 is shut off. The When the pressure in the second oil passage 200 (between the hydraulic pump 201 and the lift electromagnetic valve 203a) exceeds the pressure preset in the relief valve 208 due to an abnormality occurring in the suspension hydraulic circuit 95, the relief valve 208 is When opened, the relief oil passage 207 is communicated, and the hydraulic oil in the second oil passage 200 is allowed to flow out to the transmission case 31, thereby preventing the suspension hydraulic circuit 95 from being damaged.

  The third oil passage 300 is branched from the first oil passage 100 and communicates with the first oil passage 100. 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 third oil passage 300 mainly communicates with the accumulator 301, the third oil passage cutoff valve 302, and the like.

  The accumulator 301 absorbs the impact transmitted through the hydraulic oil. The accumulators 301 and 301 are connected to the other end of the third oil passage 300 branched into two from the branch point 300a.

  The third oil passage cutoff valve 302 is a valve that is closed by electromagnetic force. The third oil passage cutoff valve 302 is provided in the middle of the third oil passage 300 and is provided between one end where the third oil passage 300 is connected to the first oil passage 100 and the branch point 300a.

  When the third oil passage shut-off valve 302 is opened and the third oil passage 300 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 third oil passage 300. Is transmitted to the accumulators 301 and 301 through the hydraulic oil and absorbed by the accumulators 301 and 301.

  Note that the number of accumulators 301 used in the suspension hydraulic circuit 95 may be one or three or more as long as a capacity sufficient to perform a function of absorbing an impact is ensured.

  The control mechanism 400 operates an electromagnetic valve or the like 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 machine body angle detection unit 403, a work implement detection unit 404, a vehicle height setting unit 411, a control unit 450, and the like.

  The position sensor 401 is an expansion / contraction amount detecting means for detecting the extension amount (or contraction 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 (or the amount by which the suspension cylinder rods 94b and 94b are extended from the reference position A). Here, the “reference position A” is a position serving as a reference for determining the expansion and contraction of the suspension cylinder rods 94b and 94b. In the present embodiment, the position at the approximate center of the stroke range in which the suspension cylinder rods 94b and 94b can expand and contract is defined as "reference position A". Further, the independent suspension 90 according to the present embodiment is configured such that the body of the tractor 1 is substantially parallel to the ground when the suspension cylinder rods 94b and 94b are at the reference position A.

  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 airframe angle detection means 403 detects the inclination of the airframe of the tractor 1 in the front-rear direction. The airframe angle detection means is provided in the tractor 1 and detects the inclination of the airframe of the tractor 1 with respect to the horizontal in the front-rear direction. The airframe angle detection means 403 can be constituted by an acceleration sensor, a pendulum type tilt sensor, or the like.

  The work machine detection means 404 detects that a work machine such as a rotary tiller, a fertilizer spreader, or a front loader is attached to the tractor 1. The work machine detection means 404 is provided in the attachment part of the work machine. For example, when the work machine is mounted via the hydraulic lifting mechanism 70, the work machine detection means 404 is provided at the rear end of the top link 77 or the lower link 76, and when the front loader is mounted, the machine frame 5 Provided at the bracket 61 mounting portion. The work machine detection means 404 can be configured by a contact sensor, a switch, or the like.

  The vehicle height setting means 411 instructs the amount of expansion / contraction from the reference position of the suspension cylinder rods 94b and 94b. The vehicle height setting means 411 is provided near 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. The vehicle height setting means 411 is constituted by a dial-like switch or the like, and can be steplessly instructed by the operator to extend and retract the suspension cylinder rods 94b and 94b from the reference position.

  The control unit 450 controls the operation of the flow direction switching means 203, the unloading electromagnetic valve 206, etc. based on various input information. 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 flow direction switching means 203, the unloading electromagnetic valve 206, and the like.

  The control unit 450 is connected to the position sensors 401 and 401, and can detect the detection of the amount of expansion / contraction of the suspension cylinder rods 94b and 94b by the position sensors 401 and 401 as a detection signal. The control unit 450 is connected to the traveling speed detection unit 402 and can receive detection of the rotational 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 airframe angle detection unit 403, and can detect the detection of the tilt of the tractor 1 in the front-rear direction by the airframe angle detection unit 403 as a detection signal. The control unit 450 is connected to the work implement detection unit 404 and can receive detection of the attachment of the work implement by the work implement detection unit 404 as a detection signal. The control unit 450 is connected to the vehicle height setting means 411, and can receive information relating to the instruction of the amount of expansion / contraction from the reference position of the suspension cylinder rods 94b and 94b by the vehicle height setting means 411 as a detection signal. The control unit 450 is connected to the meter panel 53, and can transmit a signal related to information on control by the control unit 450 to the meter panel 53.

  The control unit 450 has an automatic mode, a manual mode, a machine body horizontal mode, and the like as control modes for controlling the operation of the flow direction switching means 203, the unloading electromagnetic valve 206, and the like. Below, the control based on each said control mode by the control part 450 is demonstrated.

  First, control based on the automatic mode of the control unit 450 will be described with reference to FIGS. 4 to 6. The automatic mode is a control mode in which the vehicle height of the front part of the tractor 1 is maintained at a predetermined height.

  The control unit 450 receives the detection of the amount of expansion / contraction from the reference position A of the suspension cylinder rods 94b and 94b by the position sensors 401 and 401 as a detection signal. Based on the detection signal, the controller 450 calculates an average value of the amount of expansion / contraction from the reference position A of the suspension cylinder rods 94b and 94b (average expansion / contraction amount EM) (FIG. 4, S110). The reason why the average expansion / contraction amount EM is calculated is that the suspension cylinders 94 and 94 are connected to each other, and the expansion / contraction amounts of the two suspension cylinders 94 and 94 do not always match.

  Based on the average expansion / contraction amount EM, the control unit 450 controls operations of the ascending electromagnetic valve 203a, the descending electromagnetic valve 203b, the unloading electromagnetic valve 206, and the like so that the average expansion / contraction amount EM is within the set range. That is, control is performed so that the average expansion / contraction amount EM is positioned within the set range (−L ≦ EM ≦ + L). This setting range can be arbitrarily set by a setting machine (not shown), and the set value L is a value that the tractor 1 does not hunt due to, for example, small unevenness or vibration. That is, the set range is a dead zone.

  As shown in FIG. 4, the controller 450 determines whether or not the average expansion / contraction amount EM is greater than + L (S120). As shown in FIG. 5, the average expansion / contraction amount EM is a value larger than + L (the vehicle height at the front of the body of the tractor 1 is a set value that is higher than the vehicle height when the suspension cylinder rods 94b and 94b are at the reference position A). In the case where it is longer than L, the control unit 450 transmits a signal related to the operation of the lowering electromagnetic valve 203b to the lowering electromagnetic valve 203b (FIG. 4, S130). The descending solenoid valve 203b is actuated by the signal, and the downstream side and the upstream side of the descending solenoid valve 203b in the second oil passage 200 are communicated. When the second oil passage 200 is communicated by the descending solenoid valve 203b, the hydraulic oil in the suspension cylinders 94, 94, the first oil passage 100, and the third oil passage 300 is lowered by the descending solenoid valve 203b and the pressure compensation type flow control valve 204. And it returns to the transmission case 31 via the raising solenoid valve 203a. As a result, the hydraulic oil in the suspension cylinders 94 and 94 can flow out, and the suspension cylinder rods 94b and 94b can be contracted.

When it is determined that the average expansion / contraction amount EM is not a value larger than + L (FIG. 4, S120), the control unit 450 determines whether the average expansion / contraction amount EM is a value smaller than A + L (FIG. 4, S140).
As shown in FIG. 6, the average amount of expansion / contraction EM is less than -L (the vehicle height at the front of the fuselage 1 is set higher than the vehicle height when the suspension cylinder rods 94b and 94b are at the reference position A). In the case where it is contracted by the value L or more, the controller 450 transmits signals related to the operation of the ascending solenoid valve 203a and the unloading solenoid valve 206 to the ascending solenoid valve 203a and the unloading solenoid valve 206, respectively (FIG. 4, S150). ). The rising solenoid valve 203a is actuated by the signal to communicate the upstream side and the downstream side of the raising solenoid valve 203a in the second oil passage 200, and the unloading solenoid valve 206 is actuated, and the inside of the unloading oil passage 205 Shut off the flow of hydraulic oil. When the second oil passage 200 is communicated by the ascending solenoid valve 203a, the hydraulic oil sucked from the transmission case 31 by driving the hydraulic pump 201 passes through the ascending solenoid valve 203a, the pressure compensation flow control valve 204, and the descending solenoid valve 203b. To the first oil passage 100. As a result, hydraulic oil can be pumped into the suspension cylinders 94 and 94, and the suspension cylinder rods 94b and 94b can be extended.

  When the controller 450 determines that the average expansion / contraction amount EM is not smaller than -L (FIG. 4, S120), that is, when the average expansion / contraction amount EM is within the set range, the descending solenoid valve 203b and the ascending solenoid valve 203a. And the transmission of the signal relating to the operation of the unloading electromagnetic valve 206 is stopped (FIG. 4, S160), and the flow of the hydraulic oil in the second oil passage 200 is again interrupted by the ascending electromagnetic valve 203a, and the unloading electromagnetic valve The inside of the unloading oil passage 205 is communicated by 206.

  When the control unit 450 performs control based on the automatic mode, the control unit 450 transmits a signal indicating that control based on the automatic mode is performed to the meter panel 53, and indicates that the meter panel 53 is performing control based on the automatic mode. Is displayed. The control unit 450 calculates the actual vehicle height of the front part of the body of the tractor 1 based on the average expansion / contraction amount EM. The control unit 450 transmits a signal related to the vehicle height information to the meter panel 53 and causes the meter panel 53 to display the actual vehicle height of the front part of the body of the tractor 1.

  As described above, when the control unit 450 performs control based on the automatic mode, the vehicle height of the front of the body of the tractor 1 is set to a predetermined height (when the suspension cylinder rods 94b and 94b are at the reference position A). The height). As a result, when the load applied to the front part of the tractor 1 changes when the work machine of the tractor 1 is detached or when the load applied to the body changes during the work, the vehicle in the front part of the tractor 1 The height can be kept constant, and the tractor 1 can be kept in a stable posture. Further, the operator can check the current control mode and the vehicle height of the front part of the tractor 1 by the display on the meter panel 53.

  Hereinafter, the control based on the manual mode of the control unit 450 will be described with reference to FIGS. The manual mode is a control mode in which the vehicle height at the front of the body of the tractor 1 is maintained at a height set by the operator as needed.

  The control unit 450 calculates the average expansion / contraction amount EM as in the case of performing control based on the automatic mode (S201 in FIG. 7).

  The control unit 450 receives the detection of the rotational speed of the rear axle 41 of the tractor 1 by the traveling speed detection means 402 as a detection signal. The controller 450 calculates the traveling speed V of the tractor 1 based on the detection signal (S202 in FIG. 7). 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. In the present embodiment, the traveling speed V of the tractor 1 is calculated based on the rotational speed of one rear axle 41 of the tractor 1. However, the rotational speeds of the two rear axles 41 and 41 are detected and the rotational speeds are detected. It is also possible to calculate the traveling speed V of the tractor 1 from the average value.

  The control unit 450 receives, as a detection signal, information related to the instruction of the amount of expansion / contraction from the reference position of the suspension cylinder rod 94b / 94b by the vehicle height setting means 411. Specifically, the vehicle height setting means 411 sets the amount of expansion / contraction of the suspension cylinder rods 94b / 94b as a percentage of the stroke range in which the suspension cylinder rods 94b / 94b can expand / contract from the reference position A (from + 100% with the reference position set to 0%). It is possible to indicate steplessly (up to -100%).

  The control unit 450 calculates the indicated expansion / contraction amount EP based on the detection signal from the vehicle height setting means 411 (S203 in FIG. 7). The instruction extension / contraction amount EP is an extension / contraction amount from the reference position of the suspension cylinder rods 94b and 94b indicated by the operator operating the vehicle height setting means 411.

  As shown in FIG. 7, the controller 450 determines whether or not the traveling speed V is zero (S210).

  When the traveling speed V is zero (the tractor 1 is stopped), the control unit 450 performs stop-time control (from S211 to S215) described below.

  When the traveling speed V is zero, the control unit 450 transmits a signal related to the operation of the third oil passage cutoff valve 302 to the third oil passage cutoff valve 302 (S211).

  The third oil passage shut-off valve 302 is actuated by a signal relating to the operation of the third oil passage shut-off valve 302 transmitted by the control unit 450, and the flow of hydraulic oil in the third oil passage 300 is shut off (FIGS. 9 and 9). 10). When the flow of the hydraulic oil in the third oil passage 300 is shut off by the third oil passage shut-off valve 302, the communication between the suspension cylinders 94 and 94 and the accumulators 301 and 301 is shut off. As a result, the suspension function of the tractor 1 is stopped.

  Next, the control unit 450 determines whether or not the average expansion / contraction amount EM is larger than the instruction expansion / contraction amount EP (FIG. 7, S212).

  When the average expansion / contraction amount EM is larger than the instruction expansion / contraction amount EP, as shown in FIG. 9, the control unit 450 transmits a signal related to the operation of the lowering electromagnetic valve 203b to the lowering electromagnetic valve 203b (FIG. 7, S213).

  The descending solenoid valve 203b is actuated by a signal relating to the actuation of the descending solenoid valve 203b transmitted by the control unit 450, and the downstream side and the upstream side of the descending solenoid valve 203b in the second oil passage 200 are communicated. When the second oil passage 200 is communicated by the descending solenoid valve 203b, the hydraulic oil in the suspension cylinders 94, 94 and the first oil passage 100 is moved to the descending solenoid valve 203b, the pressure compensation flow control valve 204, and the ascending solenoid valve 203a. To the transmission case 31. As a result, the hydraulic oil in the suspension cylinders 94 and 94 can flow out, and the suspension cylinder rods 94b and 94b can be contracted.

  When the control unit 450 operates the descending electromagnetic valve 203b to make the average expansion / contraction amount EM coincide with the instruction expansion / contraction amount EP, the control unit 450 stops transmission of a signal related to the operation of the descending electromagnetic valve 203b, and again the second electromagnetic valve 203b performs the second operation. The flow of hydraulic oil in the oil passage 200 is blocked (FIG. 7, S216).

  When the average expansion / contraction amount EM is not larger than the instruction expansion / contraction amount EP, the control unit 450 determines whether or not the average expansion / contraction amount EM is a value smaller than the instruction expansion / contraction amount EP (FIG. 7, S214).

  When the average expansion / contraction amount EM is smaller than the instruction expansion / contraction amount EP, as shown in FIG. 10, the control unit 450 sends a signal related to the operation of the ascending solenoid valve 203 a and the unloading solenoid valve 206, as shown in FIG. Each is transmitted to the electromagnetic valve 206. (FIG. 7, S215). The rising solenoid valve 203a is actuated by the signal to communicate the upstream side and the downstream side of the raising solenoid valve 203a in the second oil passage 200, and the unloading solenoid valve 206 is actuated, and the inside of the unloading oil passage 205 Shut off the flow of hydraulic oil. When the second oil passage 200 is communicated by the ascending solenoid valve 203a, the hydraulic oil sucked from the transmission case 31 by driving the hydraulic pump 201 passes through the ascending solenoid valve 203a, the pressure compensation flow control valve 204, and the descending solenoid valve 203b. To the first oil passage 100. As a result, hydraulic oil can be pumped into the suspension cylinders 94 and 94, and the suspension cylinder rods 94b and 94b can be extended.

  When the control unit 450 operates the rising electromagnetic valve 203a to make the average expansion / contraction amount EM coincide with the instruction expansion / contraction amount EP, the control unit 450 stops transmission of a signal related to the operation of the rising electromagnetic valve 203a, and again starts the second electromagnetic valve 203a. The flow of hydraulic oil in the oil passage 200 is blocked (FIG. 7, S216).

  By the control of the control unit 450 as described above, the height of the vehicle front portion of the tractor 1 is set as needed by the operator (the height when the extension amount of the suspension cylinder rods 94b and 94b is the indicated extension amount EP). ) Can be maintained. Thereby, when the tractor 1 is stopped, it becomes possible to adjust the vehicle height of the front part of the body of the tractor 1 to a height at which it is easy to attach and detach the work implement or perform maintenance. In addition, the suspension function is stopped by shutting off the third oil passage 300, and it is possible to prevent the suspension cylinders 94 and 94 from being unexpectedly expanded and contracted when performing attachment / detachment or maintenance of the work implement. Thereby, it becomes possible to improve workability | operativity, such as attachment or detachment of a working machine, or a maintenance.

  If the traveling speed V is not zero, as shown in FIG. 8, the controller 450 determines whether or not the traveling speed V is equal to or lower than the reference traveling speed VT (S220). The reference travel speed VT is a predetermined travel speed value stored in the controller 450 in advance, and can be changed by setting means (not shown).

  When the traveling speed V is equal to or lower than the reference traveling speed VT (when the tractor 1 is traveling at the reference traveling speed VT or lower), the control unit 450 performs low-speed control (from S221 to S224) described below.

  When the traveling speed V is less than or equal to the reference traveling speed VT, the control unit 450 determines whether the average expansion / contraction amount EM is greater than the limit instruction expansion / contraction amount EPR (S221).

  Here, the limit instruction expansion / contraction amount EPR is an expansion / contraction amount calculated by multiplying the instruction expansion / contraction amount EP by a predetermined coefficient α (0 <α <1) stored in the control unit 450 in advance. When the tractor 1 is traveling at a reference traveling speed VT or less, the controller 450 has a range of expansion / contraction amount that can be instructed by the vehicle height setting means 411 (difference between the maximum value and the minimum value of the limit instruction expansion / contraction amount EPR). When the travel speed V is zero, the range of expansion / contraction amount that can be instructed (the difference between the maximum value and the minimum value of the instruction expansion / contraction amount EP) is limited. For example, when α = 0.6, the expansion / contraction amount that can be instructed by the vehicle height setting means 411 is + 100% to −100% with the reference position being 0% in the control at the time of stop, whereas the control at low speed is performed In this case, the reference position is set to 0% and limited from + 60% to -60%. By providing such a restriction, the range of the vehicle height that can be set when the tractor 1 is traveling at the reference traveling speed VT or less is set to the range of the vehicle height that can be set when the tractor 1 is stopped. Also make it smaller.

  When the average expansion / contraction amount EM is larger than the limit instruction expansion / contraction amount EPR, as shown in FIG. 11, the control unit 450 transmits a signal related to the operation of the lowering electromagnetic valve 203b to the lowering electromagnetic valve 203b (FIG. 8, S222). The descending solenoid valve 203b is actuated by the signal, and the downstream side and the upstream side of the descending solenoid valve 203b in the second oil passage 200 are communicated. When the second oil passage 200 is communicated by the descending solenoid valve 203b, the hydraulic oil in the suspension cylinders 94, 94, the first oil passage 100, and the third oil passage 300 is lowered by the descending solenoid valve 203b and the pressure compensation type flow control valve 204. And it returns to the transmission case 31 via the raising solenoid valve 203a. As a result, the hydraulic oil in the suspension cylinders 94 and 94 can flow out, and the suspension cylinder rods 94b and 94b can be contracted.

  When the control unit 450 operates the lower electromagnetic valve 203b to make the average expansion / contraction amount EM coincide with the limit instruction expansion / contraction amount EPR, the control unit 450 stops transmission of a signal related to the operation of the lower electromagnetic valve 203b, and the lower electromagnetic valve 203b again performs the first operation. The flow of hydraulic oil in the two oil passage 200 is blocked (FIG. 8, S2225).

  When the average expansion / contraction amount EM is larger than the restriction instruction expansion / contraction amount EPR, the control unit 450 determines whether or not the average expansion / contraction amount EM is a value smaller than the restriction instruction expansion / contraction amount EPR (FIG. 8, S223).

  When the average expansion / contraction amount EM is smaller than the limit instruction expansion / contraction amount EPR, as shown in FIG. 12, the control unit 450 outputs a signal related to the operation of the ascending solenoid valve 203 a and the unloading solenoid valve 206 as shown in FIG. Each is transmitted to the electromagnetic valve 206 (FIG. 8, S224). The rising solenoid valve 203a is actuated by the signal to communicate the upstream side and the downstream side of the raising solenoid valve 203a in the second oil passage 200, and the unloading solenoid valve 206 is actuated, and the inside of the unloading oil passage 205 Shut off the flow of hydraulic oil. When the second oil passage 200 is communicated by the ascending solenoid valve 203a, the hydraulic oil sucked from the transmission case 31 by driving the hydraulic pump 201 passes through the ascending solenoid valve 203a, the pressure compensation flow control valve 204, and the descending solenoid valve 203b. To the first oil passage 100. As a result, hydraulic oil can be pumped into the suspension cylinders 94 and 94, and the suspension cylinder rods 94b and 94b can be extended.

  When the control unit 450 operates the ascending electromagnetic valve 203a to make the average expansion / contraction amount EM coincide with the limit instruction expansion / contraction amount EPR, the control unit 450 stops transmission of a signal related to the operation of the ascending electromagnetic valve 203a. The flow of hydraulic oil in the two oil passage 200 is blocked (FIG. 8, S2225).

  By the control of the control unit 450 as described above, the vehicle height at the front part of the body of the tractor 1 can be adjusted to the vehicle height according to the preference of the operator, and work by the tractor 1 can be performed. At this time, by limiting the range of the amount of expansion / contraction that can be instructed by the vehicle height setting means 411, the range of the vehicle height at the front of the body of the tractor 1 that can be set is smaller than when the tractor 1 is stopped. . As a result, when the vehicle is traveling at the reference traveling speed VT or less, it is possible to prevent the vehicle height from changing greatly, and to improve the ride comfort of the operator and the stability of the body of the tractor 1.

  When the traveling speed V is equal to or higher than the reference traveling speed VT (when the tractor 1 is traveling at the reference traveling speed VT or higher), the control unit 450 ends the control based on the manual mode and starts the control based on the automatic mode ( FIG. 8, S230). As a result, when the tractor 1 travels at a reference travel speed VT or higher (high speed), the control unit 450 automatically starts control based on the automatic mode, and takes a stable posture regardless of an instruction from the vehicle height setting means 411. It becomes possible to travel.

  When the control unit 450 performs control based on the manual mode, the control unit 450 transmits a signal indicating that control based on the manual mode is performed to the meter panel 53, and indicates that the meter panel 53 is performing control based on the manual mode. Is displayed. The control unit 450 transmits information related to the instruction from the vehicle height setting means 411 to the meter panel 53 as a signal, and the content of the instruction by the vehicle height setting means 411 is sent to the meter panel 53 as a percentage (from + 100% to- Display up to 100%). The control unit 450 calculates the actual vehicle height of the front part of the body of the tractor 1 based on the average expansion / contraction amount EM. The control unit 450 transmits a signal related to the vehicle height information to the meter panel 53 and causes the meter panel 53 to display the actual vehicle height of the front part of the body of the tractor 1. The operator can confirm the current control mode, the content of the instruction by the vehicle height setting means 411, and the vehicle height of the front part of the tractor 1 by the display on the meter panel 53.

  Hereinafter, the control based on the aircraft horizontal mode of the control unit 450 will be described with reference to FIGS. 13 to 15. The airframe horizontal mode is a control mode in which the tractor 1 is tilted substantially horizontally before and after the airframe.

  The control unit 450 receives, as a detection signal, detection of the inclination of the tractor 1 with respect to the horizontal in the front-rear direction of the tractor 1 by the aircraft angle detection means 403. The control unit 450 calculates an inclination angle δ with respect to the horizontal in the front-rear direction of the body of the tractor 1 based on the detection signal. The inclination angle δ is defined as “positive” when the body of the tractor 1 is tilted forward and “negative” when tilted forward.

  The control unit 450 controls operations of the ascending solenoid valve 203a, the descending solenoid valve 203b, the unloading solenoid valve 206, and the like so that the inclination angle δ is within the set range. That is, control is performed so that the inclination angle δ falls within the set range (−θ ≦ δ ≦ θ). This set value θ can be arbitrarily set by a setting device (not shown). The set value θ is a value that the tractor 1 does not hunt due to, for example, small unevenness or vibration of the ground. That is, the set range is a dead zone.

  As shown in FIG. 13, the control unit 450 determines whether or not the inclination angle δ is larger than the set value θ (S310).

  When the inclination angle δ is larger than the set value θ (the body of the tractor 1 is tilted forward), the control unit 450 transmits a signal related to the operation of the lowering electromagnetic valve 203b to the lowering electromagnetic valve 203b (S320). The descending solenoid valve 203b is actuated by the signal, and the downstream side and the upstream side of the descending solenoid valve 203b in the second oil passage 200 are communicated. As shown in FIG. 14, when the second oil passage 200 is communicated by the descending solenoid valve 203b, the hydraulic oil in the suspension cylinders 94, 94, the first oil passage 100, and the third oil passage 300 is lowered by the descending solenoid valve 203b, It is returned to the transmission case 31 via the pressure compensation flow control valve 204 and the ascending electromagnetic valve 203a. As a result, the hydraulic oil in the suspension cylinders 94 and 94 can flow out, and the suspension cylinder rods 94b and 94b can be contracted.

  When the airframe of the tractor 1 becomes horizontal by operating the descending electromagnetic valve 203b, the control unit 450 stops transmission of a signal related to the operation of the descending electromagnetic valve 203b (FIG. 13, S350), and again the first operation is performed by the descending electromagnetic valve 203b. The flow of hydraulic oil in the two oil passage 200 is blocked.

  If the inclination angle δ is not greater than the set value θ, the control unit 450 determines whether the inclination angle δ is less than the set value −θ (FIG. 13, S330).

  When the inclination angle δ is smaller than the set value −θ (the body of the tractor 1 is tilted forward and downward), the control unit 450 sends signals related to the operation of the ascending solenoid valve 203a and the unloading solenoid valve 206 to the ascending solenoid valve. It transmits to 203a and the unloading solenoid valve 206, respectively (FIG. 13, S340). The rising solenoid valve 203a is actuated by the signal to communicate the upstream side and the downstream side of the raising solenoid valve 203a in the second oil passage 200, and the unloading solenoid valve 206 is actuated, and the inside of the unloading oil passage 205 Shut off the flow of hydraulic oil. As shown in FIG. 15, when the second oil passage 200 is communicated by the ascending solenoid valve 203a, the hydraulic fluid sucked up from the transmission case 31 by the drive of the hydraulic pump 201 becomes the ascending solenoid valve 203a, the pressure compensation type flow control valve. The pressure is fed to the first oil passage 100 via 204 and the descending electromagnetic valve 203b. As a result, hydraulic oil can be pumped into the suspension cylinders 94 and 94, and the suspension cylinder rods 94b and 94b can be extended.

  When the airframe of the tractor 1 becomes horizontal by operating the ascending electromagnetic valve 203a, the control unit 450 stops transmission of a signal related to the operation of the ascending electromagnetic valve 203a (FIG. 13, S350), and the ascending electromagnetic valve 203a again performs the first operation. The flow of hydraulic oil in the two oil passage 200 is blocked.

  In addition, when the ground of the tractor 1 cannot be leveled within the stroke range in which the suspension cylinder rods 94b and 94b can extend and contract, such as when the ground is greatly inclined, the control unit 450 performs control based on the body horizontal mode. Cancel.

  When performing control based on the aircraft horizontal mode, the control unit 450 transmits a signal indicating that control based on the aircraft horizontal mode is being performed to the meter panel 53, and performs control based on the aircraft horizontal mode on the meter panel 53. Is displayed. The control unit 450 calculates the actual vehicle height of the front part of the body of the tractor 1 based on the average expansion / contraction amount EM. The control unit 450 transmits a signal related to the vehicle height information to the meter panel 53 and causes the meter panel 53 to display the actual vehicle height of the front part of the body of the tractor 1.

  As described above, when the control unit 450 performs control based on the aircraft horizontal mode, it is possible to keep the tilt of the tractor 1 before and after the aircraft horizontal. Thereby, it becomes possible to improve workability such as ride comfort and safety of the operator and work accuracy. Further, the operator can check the current control mode and the vehicle height of the front part of the tractor 1 by the display on the meter panel 53.

  Hereinafter, a method of switching the above-described control mode (automatic mode, manual mode, aircraft horizontal mode) will be described with reference to FIG.

  The control mechanism 400 includes mode switching means 412. The mode switching means 412 instructs to switch the control mode. The mode switching means 412 is provided near the seat 51 in the cabin 50. The mode switching unit 412 can be configured by various switches such as a toggle switch, a push button switch, and a slide switch, a touch panel, and the like.

  The control unit 450 is connected to the mode switching unit 412 and can receive, as a detection signal, information related to an instruction to switch the control mode by the mode switching unit 412.

  The control unit 450 switches the control mode each time the mode switching unit 412 is operated by the operator. Specifically, when the mode switching unit 412 is operated while the control unit 450 performs control based on the manual mode, the control unit 450 switches the control mode from the manual mode to the automatic mode. When the mode switching unit 412 is operated while the control unit 450 performs control based on the automatic mode, the control unit 450 switches the control mode from the automatic mode to the machine body horizontal mode. When the mode switching unit 412 is operated while the control unit 450 performs control based on the aircraft horizontal mode, the control unit 450 switches the control mode from the aircraft horizontal mode to the manual mode.

  As described above, when the control unit 450 performs control based on the manual mode and the travel speed V becomes equal to or higher than the reference travel speed VT, the control unit 450 switches the control mode from the manual mode to the automatic mode. .

  The automatic mode and the aircraft horizontal mode further have a road traveling mode and a work mode, respectively. The control based on the road running mode by the control unit 450 conforms to the automatic mode and the aircraft horizontal mode described above, and will not be described below.

  The work mode is a control mode in which the vehicle height of the front part of the tractor 1 is adjusted based on the type of work machine attached to the tractor 1. For example, when the work implement is mounted via the hydraulic elevating mechanism 70, the work implement detection means 404 provided at the rear end of the top link 77 or the lower link 76 detects the attachment of the work implement, and the control unit 450 performs the detection. Such a signal is transmitted as a detection signal. The control unit 450 controls the vehicle height at the front of the tractor 1 so that the vehicle height corresponds to the working machine attached to the rear of the vehicle. Specifically, when the work machine is mounted on the rear part of the tractor 1, the work can be efficiently performed by lowering the vehicle height at the front part of the machine and increasing the load applied to the front wheels 85 and 85. . When the front loader 60 is mounted, the work machine detection means 404 provided in the bracket 61 mounting portion of the machine body frame 5 detects the mounting of the front loader 60, and the control unit 450 uses the signal related to the detection as a detection signal. Send. The control unit 450 controls the vehicle height of the front part of the tractor 1 to be a vehicle height corresponding to the work machine (front loader 60) attached to the front part of the machine body. Specifically, when a work machine is mounted on the front part of the tractor 1, it is possible to work more efficiently by raising the vehicle height of the front part of the tractor and moving the center of gravity to the rear part of the tractor 1. The road driving mode and the work mode can be switched manually using the mode switching means 412 or other switching switches.

  Each time the control unit 450 switches the control mode, the control unit 450 causes the meter panel 53 to display which mode is the currently selected control mode.

  As described above, the control unit 450 switches the control mode based on the instruction from the mode switching unit 412, so that each control mode can be switched instantaneously with a simple operation. Thereby, the operability of the tractor 1 can be improved. Further, when the traveling speed V becomes equal to or higher than the reference traveling speed VT, the manual mode can be automatically switched to the automatic mode. When the tractor 1 travels at a high speed, the tractor regardless of the instruction from the mode switching means 412. 1 can be maintained in a stable posture. In addition, the control unit 450 automatically switches the control mode from the road running mode to the work mode, so that it is possible to reliably switch to the work mode without forgetting operation or mistakes. Further, the operator can confirm the current control mode by displaying on the meter panel 53 and can surely switch to the desired control mode by operating the mode switching means 412.

  As described above, the independent suspension 90 of the present embodiment has at least the automatic mode for maintaining the vehicle height at a predetermined height as the control mode and the manual mode for maintaining the vehicle height at the height set by the vehicle height setting means 411. And a vehicle body horizontal mode for adjusting the vehicle height so that the vehicle body is horizontal. The automatic mode and the vehicle body horizontal mode correspond to a road traveling mode and a vehicle height depending on a work machine mounted on the tractor 1. A control unit 450 that selects one of the control modes and performs control based on the control mode, and a control mode that the control unit 450 selects. Mode switching means 412 for issuing an instruction to switch between, and the control unit 450 switches the control mode to be selected based on information relating to the instruction by the mode switching means 412. Is shall. With this configuration, it is possible to select an arbitrary control mode and perform control based on the control mode. In addition, each control mode can be switched instantaneously with a simple operation, and the operability of the tractor 1 can be improved.

  In addition, the independent suspension 90 of this embodiment includes a work machine detection unit 404 that detects that the work machine is mounted on the tractor 1, and the control unit 450 includes information related to detection by the work machine detection unit 404. When it is determined that the work machine is mounted on the tractor 1 on the basis, the control mode to be selected is switched from the road running mode to the work mode. With this configuration, when the work machine is mounted on the tractor 1, the control mode to be selected can be automatically switched from the road travel mode to the work mode. This eliminates the need for complicated manual operation and allows the control mode to be reliably switched to the work mode.

  In addition, the independent suspension 90 of this embodiment includes a traveling speed detection unit 402 that detects the traveling speed V of the tractor 1, and the control unit 450 detects the traveling speed when performing control based on the manual mode. When it is determined that the tractor 1 is traveling at a reference traveling speed VT or higher, which is a predetermined traveling speed, based on information relating to detection by the means 402, the control mode to be selected is switched from the manual mode to the automatic mode. is there. With this configuration, when the traveling speed V of the tractor 1 becomes equal to or higher than the reference traveling speed VT, it is possible to automatically switch from the manual mode to the automatic mode. As a result, when the tractor 1 travels at a high speed, the tractor 1 can be maintained in a stable posture regardless of an instruction from the mode switching means 412.

  In addition, the independent suspension 90 of this embodiment includes a meter panel 53 that displays information related to control performed by the control unit 450. With this configuration, an operator can easily confirm information related to control by the control unit.

  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.

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

  In the present embodiment, the control unit 450 has an automatic mode, a manual mode, and an aircraft horizontal mode as control modes. However, the present invention is not limited to this, and the control unit 450 has a larger number of control modes. It may be a thing.

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 the control based on automatic mode. The schematic diagram which shows the suspension hydraulic circuit in the control based on automatic mode. The schematic diagram which shows the suspension hydraulic circuit in the control based on automatic mode. The flowchart which shows the outline | summary of the control based on manual mode. The flowchart which shows the outline | summary of the control based on manual mode. The schematic diagram which shows the suspension hydraulic circuit in the control based on manual mode. The schematic diagram which shows the suspension hydraulic circuit in the control based on manual mode. The schematic diagram which shows the suspension hydraulic circuit in the control based on manual mode. The schematic diagram which shows the suspension hydraulic circuit in the control based on manual mode. The flowchart which shows the outline | summary of the control based on body horizontal mode. The schematic diagram which shows the suspension hydraulic circuit in the control based on a body horizontal mode. The schematic diagram which shows the suspension hydraulic circuit in the control based on a body horizontal mode.

1 Tractor 53 Meter panel 70 Hydraulic lifting mechanism (work machine mounting device)
90 Independent suspension 94 Suspension cylinder (hydraulic cylinder)
402 Traveling speed detection means 404 Work implement detection means 411 Vehicle height setting means 412 Mode switching means 450 Controller

Claims (3)

As the control mode, at least the automatic mode for automatically maintaining the vehicle height at a preset height, the manual mode for maintaining the vehicle height at the height set by the operator using the vehicle height setting means , A vehicle body horizontal mode for adjusting the vehicle height so that the automatic mode and the vehicle body horizontal mode are on the road in a state where the traveling speed detected by the traveling speed detecting means for detecting the traveling speed of the work vehicle is not zero. A travel mode and a work mode for adjusting the vehicle height to a vehicle height corresponding to a work machine mounted on the work vehicle, selecting any one of the control modes, and based on the control mode A control unit for performing control, and mode switching means for issuing an instruction to switch the control mode selected by the control unit, wherein the control unit is information related to the instruction by the mode switching means. Based on, it switches the control mode selected, the control unit, when performing the control based on the manual mode, the traveling speed the work vehicle is in a predetermined on the basis of the information relating to the detection by said running speed detecting means An independent suspension for a work vehicle, characterized in that, when it is determined that the vehicle is traveling, the control mode to be selected is switched from the manual mode to the automatic mode . 2. The stand-alone suspension for a work vehicle according to claim 1, further comprising work machine detection means for detecting that a work machine is mounted on the work vehicle, wherein the control unit is information related to detection by the work machine detection means. When the work vehicle is determined to be mounted on the work vehicle based on the above, the selected suspension control mode is switched from the road travel mode to the work mode. 3. The independent suspension for a work vehicle according to claim 1, further comprising a display unit that displays information related to control performed by the control unit.

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