JP2018000018A - Work vehicle - Google Patents

Abstract

An object of the present invention is to improve work stability in a field. A work vehicle (1) includes a work machine (4), an elevating section (41), an HCB, and a control section (3b). The working machine 4 is provided at the rear part of the machine body 2 and performs ground work. The lifting section 41 , HCB, lifts the working machine 4 with respect to the machine body 2 . When lowering the work implement 4, the control unit 3b selects a first mode in which the lowering speed of the work implement 4 is reduced at the reference height, and a mode in which the height of the work implement 4 that performs ground work with respect to the ground is constant. and a second mode of adjusting is performed on the lifting unit 41 and the HCB, and when the second mode is performed on the work implement 4 positioned above the first height as the reference height, The reference height is moved to a second height above the first height. [Selection drawing] Fig. 2

Description

  The present invention relates to a work vehicle.

  2. Description of the Related Art Conventionally, there is a work vehicle that travels while performing a predetermined ground work on a farm field or the like by mounting a ground work machine that can be moved up and down at the rear of the body. As such a work vehicle, for example, agriculture equipped with a DeSera control that reduces the descending speed of the ground work machine at a reference height with respect to the aircraft, and a depth control that maintains the ground work height of the work machine substantially constant A tractor for use is known (for example, see Patent Document 1).

JP 2005-167331 A

  However, the conventional work vehicle has room for further improvement in improving the work stability in the field. For example, in the conventional work vehicle, the reference height does not follow the change in the height of the ground during ground work.

  Therefore, when the ground level changes with respect to the work vehicle during ground work, such as when the aircraft sinks into the field, work is performed by the work implement landing before passing the reference height, that is, before decelerating. The work stability of the vehicle may be reduced.

  This invention is made | formed in view of the above, Comprising: It aims at providing the work vehicle which can improve the work stability in a farm field.

  In order to solve the above-described problems and achieve the object, the work vehicle according to claim 1 is provided at a rear portion of the machine body (2) and performs a ground work, and the work machine (4). And a first raising / lowering part (41, HCB) for raising and lowering the machine (2) and a lowering speed of the work machine (4) at a reference height when the work machine (4) is lowered. A control unit (3b) that causes the elevating unit (41, HCB) to execute a mode and a second mode in which the height of the work machine (4) that performs ground work is adjusted to be constant. And when the control unit (3b) executes the second mode for the work implement (4) located above the first height as the reference height, the reference unit (3b) The height is moved to a second height located above the first height. To.

  A work vehicle according to a second aspect is the work vehicle according to the first aspect, wherein the second height is an upper limit in a lifting range of the work implement (4).

  The work vehicle according to claim 3 is the work vehicle according to claim 1 or 2, wherein the elevating part (41, HCB) is rotatable about a predetermined rotation axis (AX1) with respect to the body (2). The control unit (3b) is provided on the basis of a rotation angle of the arm (43a) around the rotation axis (AX1). The height of the work machine (4) is detected.

  The work vehicle according to claim 4 is the work vehicle according to any one of claims 1 to 3, wherein the control unit (3b) is configured to move the reference height to the second height. When the work machine (4) executes the second mode below the first height, the reference height is returned to the first height.

  The work vehicle according to claim 5 is the work vehicle according to any one of claims 1 to 4, wherein the control unit (3b) is configured to move the reference height to the second height. When the control unit (3b) is turned off and restarted, the reference height is returned to the first height.

  According to the work vehicle of the first aspect, it is possible to avoid a situation in which the lowering speed of the work implement decreases below the height at which the work implement performs the ground work in the second mode. Therefore, hunting can be prevented and work stability in the field can be improved by suppressing the work machine from receiving an impact due to landing.

  According to the work vehicle of the second aspect, in addition to the effect of the invention of the first aspect, the reference point at which the lowering speed of the work machine decreases is positioned at the upper limit in the lifting range of the work machine. The lowering speed of the lowering is reduced in the entire stroke of the raising / lowering range (falling range). As a result, it is possible to prevent the work machine from receiving an impact due to landing regardless of the height of the work machine performing the ground work. Therefore, the work stability in the field can be further improved.

  According to the work vehicle of the third aspect, in addition to the effect of the invention of the first or second aspect, the sensor for detecting and setting the height of the work machine in the first mode and the second mode is shared. Can be realized. Therefore, the configuration of the work vehicle can be simplified and the production cost can be reduced.

  According to the work vehicle of the fourth aspect, in addition to the effect of the invention according to any one of the first to third aspects, the first mode is executed in conjunction with the amount of subsidence of the body relative to the field. It becomes possible. Therefore, the work stability in the field can be further improved.

  According to the work vehicle of the fifth aspect, in addition to the effect of the invention according to any one of the first to fourth aspects, the first height in the first mode every time the operator restarts the power supply. This makes it possible to avoid troublesome operations for setting. Therefore, the work efficiency of the worker can be improved.

FIG. 1 is a schematic side view of a tractor as a work vehicle. FIG. 2 is a functional block diagram of the tractor. FIG. 3 is a diagram showing a power transmission path of the tractor. FIG. 4 is a hydraulic circuit diagram of the tractor. FIG. 5A is a diagram (part 1) illustrating a method for moving a reference height. FIG. 5B is a diagram (part 2) illustrating a method for moving the reference height. FIG. 6 is a flowchart showing a processing procedure for changing the reference height.

<Overall configuration of work vehicle>
Hereinafter, the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by the following embodiment. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or that are substantially the same, that is, those in an equivalent range. Moreover, the component in the following embodiment can be combined suitably.

  A tractor 1 as a work vehicle according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic side view of a tractor 1 as a work vehicle according to an embodiment. FIG. 2 is a functional block diagram of the tractor 1. FIG. 3 is a diagram showing a power transmission path of the tractor 1. For easy understanding, the rear wheel 52 is seen through in FIG.

  In the following, for convenience of explanation, as shown in the figure, the three directions orthogonal to each other are respectively defined as the front-rear direction, the left-right direction, and the up-down direction, and the configuration of each part will be described according to this definition. The front-rear direction is the length direction of the tractor 1, the left-right direction is the width direction, and the up-down direction is the height direction. Among these, the front is the traveling direction of the tractor 1 during ground work, the left is the left-hand direction toward the front (front side of the paper in FIG. 1), and the right is the right-hand direction toward the front. The lower side is the direction in which gravity acts. In addition, these directions are defined for convenience in order to make the explanation easy to understand, and the present invention is not limited by these directions.

  A tractor 1 as a work vehicle according to the embodiment is a work vehicle that performs work on a farm field or the like. As shown in FIG. 1, a front wheel 51 provided as a steering wheel and a rear wheel provided as a drive wheel. And a travel control unit 3 (corresponding to the control means shown in FIG. 2) and the like. The power generated by the engine 7 mounted in the hood 6 at the front of the fuselage 2 is appropriately decelerated by the main transmission 40 (see FIG. 3) and the auxiliary transmission 140 (see FIG. 3). It is possible to communicate. The rear wheel 52 is driven by the power transmitted from the engine 7.

  Further, the tractor 1 can transmit the power generated by the engine 7 and decelerated by the main transmission 40 and the auxiliary transmission 140 to the front wheels 51 via the front wheel acceleration switching mechanism 172 (see FIG. 3). ing. When the front wheel acceleration switching mechanism 172 transmits power, the front wheel 51 and the rear wheel 52 are driven by the power transmitted from the engine 7. When the front wheel acceleration switching mechanism 172 interrupts the transmission of power, the two wheels including only the rear wheel 52 are driven by the power transmitted from the engine 7. That is, the tractor 1 can be switched between two-wheel drive and four-wheel drive. Further, a PTO (Power Take-Off) connecting device 8 to which the work machine 4 can be mounted is disposed at the rear of the machine body 2 of the tractor 1.

  Further, as shown in FIG. 1, a pilot seat 9 is provided at the center of the fuselage 2 of the tractor 1, and a front wheel 51 is steered in front of the pilot seat 9. A steering handle 10 used for the above is disposed. The steering handle 10 is disposed on the upper end side of a handle post 11 that rotatably supports the steering handle 10. Further, a pedal 9a (a clutch pedal, a brake pedal, an accelerator pedal, etc.) is provided below the handle post 11, that is, near the driver's feet when the driver is sitting on the cockpit 9.

  In addition, a cylinder case 41 a is provided behind the machine body 2. On both the left and right sides of the cylinder case 41a, lift arms 43a are provided so that the shaft center can rotate about the axis AX1 in the left-right direction. When the working oil is supplied to the cylinder 41 in the cylinder case 41a, the lift arm 43a is turned up around the axis AX1, and when the working oil is discharged from the cylinder 41, the lift arm 43a is turned down around the axis AX1. A lift arm sensor 4c that detects the rotation angle of the lift arm 43a is provided at the base of the lift arm 43a. The height of the work implement 4 is calculated based on the detection value of the lift arm sensor 4c.

  The lift arm 43a and the lower link 42 are connected by a lift rod 43b. The lift rod 43b includes a double-acting horizontal control hydraulic cylinder, and the left and right sides of the work implement 4 are raised and lowered by the expansion and contraction of the horizontal control hydraulic cylinder, and the cylinder length is detected by a stroke sensor (not shown). The In addition, an inclination sensor 4 a is provided in the vicinity of the cockpit 9 of the tractor 1.

  Thereby, the inclination control amount of the work machine 4 is calculated from the comparison between the detection value of the inclination sensor 4a and the detection value of the stroke sensor. The work implement lifting control unit 3b (see FIG. 2) drives the horizontal control hydraulic cylinder based on the calculated tilt control amount.

  In addition, in this embodiment, it has shown taking the case where the working machine 4 is a rotary tiller. The rotary cultivator as the work machine 4 includes a cultivating claw 45, a rotary cover 46a, and a rear cover 46b. The tilling claw 45 rotates by receiving power from the PTO shaft 8a and tills the soil. The rotary cover 46 a covers the top of the tilling claw 45. The rear cover 46b is provided at the rear part of the rotary cover 46a so as to be rotatable in the vertical direction.

  The work implement lifting control unit 3b changes the height of the work implement 4 by rotating the lift arm 43a based on the detection value of the plowing depth sensor 4b, and maintains the plowing depth at a set value. Specifically, when the rear cover 46b is lifted above a predetermined position, the work implement lifting control unit 3b moves the work implement 4 upward because the plowing depth is deeper than the set value. In addition, when the rear cover 46b is positioned below a predetermined position, the work implement lifting / lowering control unit 3b moves the work implement 4 downward because the plowing depth is shallower than the set value. Such movement of the work machine 4 in the vertical direction is executed based on the rotation angle of the lift arm 43a. Hereinafter, the control by the work implement lifting control unit 3b that maintains the plowing depth at the set value in this way may be referred to as “depth control”.

  Further, the tractor 1 performs so-called “decerer control” that reduces the descending speed of the work implement 4 near the ground so that the impact when the work implement 4 is grounded does not occur when the work implement 4 is lowered and landed. . In FIG. 1, an angular position around the axis AX1 of the lift arm 43a from which the work machine 4 starts to descend is shown as an upper position UP, and an example of an angular position where the work machine 4 performs ground work (cultivation) is shown as a lower position LP. Yes. Further, in FIG. 1, an angular position at which the lowering speed of the work implement 4 decreases at an angular position around the axis AX1 of the lift arm 43a is shown as a reference height DP (decerer position). When starting to descend from the upper position UP, the work machine 4 decreases the lowering speed at the reference height DP and lands at the lower position LP.

<How to change the reference height>
The work implement lifting control unit 3b included in the tractor 1 changes the height of the reference height DP in conjunction with the change in the height of the work implement 4 during ground work. Here, details of a method of changing the height of the reference height DP by the work implement lifting control unit 3b will be described with reference to FIGS. 5A and 5B. 5A and 5B are diagrams (part 1) and (part 2) for explaining a method of moving the reference height DP. 5A and 5B schematically show the working machine 4 including the lift arm 43a from the viewpoint of making the explanation easy to understand, and the angle range from the upper position UP to the lower position LP to the axis AX1 is more than actual. Exaggerated. In FIG. 5A, the work machine 4 located at the upper position UP and the reference height DP is indicated by a dotted line, and in FIG. 5B, the work machine 4 located at the reference height DP1 is indicated by a dotted line.

  As shown in FIG. 5A, the work implement 4 is supported by the lift arm 43a that rotates about the axis AX1, and starts to descend from the upper position UP toward the ground surface SE1 (see an arrow 240 in FIG. 5A). The work machine 4 decreases the descending speed at the reference height DP1, and gently lands on the ground SE1 at the lower position LP1. Thereby, the situation where the impact of landing on the ground SE1 of the work machine 4 can be avoided.

  Here, for example, when performing ground work in a field where the soil is soft and the tractor 1 is sinking in the field, the ground moves upward with respect to the body 2 (see the ground SE2 in FIG. 5A). For this reason, there is a possibility that the work implement 4 may land before passing the reference height DP1, that is, before decelerating. In FIG. 5A, a part of the work machine 4 that may collide with the ground SE2 without decelerating is indicated by hatching as a part BP.

  In such a case, a swaying or impact is applied to the machine body 2 due to the impact of the landing of the work machine 4, for example, a disturbance enters into the height detection information of the work machine in the depth control, and hunting that causes the work machine to move up and down unnecessarily. Happened, and work stability could be reduced. Further, when the work implement 4 is landed at a relatively high speed with the tilling pawl 45 rotated, there is a possibility that the driving force of the tilling pawl 45 will cause the tractor 1 to move forward, for example. It was.

  Therefore, in the tractor 1 according to the present embodiment, in the depth control, when the work implement 4 is positioned above the reference height DP1, the reference height DP is moved above the reference height DP1 (FIG. (See 5B arrow 243, reference height DP2). As a result, even when the work implement 4 is lowered from the upper position UP toward the ground SE2, the work implement 4 decelerates at the reference height DP2, so that a landing impact of the work implement 4 on the ground SE2 occurs. It can be avoided. Therefore, according to the tractor 1 according to the present embodiment, it is possible to avoid the impact when the work implement 4 lands by following the change in the height of the ground during the ground work, and to improve the work stability in the field. it can.

  Note that the change from the reference height DP1 to the reference height DP2 may be, for example, by changing the detection value by the lift arm sensor 4c by a predetermined angle (see angle θ1 in FIG. 5B) about the axis AX1. Thereby, the reference height DP can be changed by a simple process.

  Further, the reference height DP2 may be matched with the upper position UP. In this case, the work machine 4 starts to descend while being decelerated from the upper position UP. Such deceleration corresponds to reducing the lowering speed from the upper position UP of the work machine 4 than the lowering speed from the upper position UP when the reference height DP is located at the reference height DP1. Therefore, no matter how the height of the ground during the ground work changes, it is possible to avoid the impact when the work implement 4 lands following the change, and to improve the work stability in the field. The upper position UP is preferably the upper limit in the lifting range of the work implement 4.

  In addition, when the work implement 4 is positioned above the reference height DP1, the decelerator control is not performed (that is, turned off), and the work implement 4 is lowered from the upper position UP at a lower speed than when the deceler control is performed. Also good. Even if it does in this way, no matter how the height of the ground during ground work changes, the impact when the work machine 4 lands following the change is avoided, and the work stability in the field is improved. be able to.

  In the tractor 1 according to the embodiment, the height of the work implement 4 is set based on the lift arm 43a detected by the lift arm sensor 4c. This makes it possible to share a sensor for detecting and setting the height of the work machine 4 in the depth control and the decelerator control as the lift arm sensor 4c. Therefore, the configuration of the tractor 1 can be simplified and the production cost can be reduced.

  Note that a notification unit (not shown) for notifying the operator that the reference height DP1 has been changed to the reference height DP2 or the upper position UP, or that the decelerating control has been turned off is provided, for example, on the steering handle 10. It is good also as providing in the periphery, the meter panel 31, the operation panel 32, etc. Thereby, an operator's workability | operativity can be improved. The notification unit may be a display unit or a speaker of the mobile terminal MT described later.

  Further, in the tractor 1 according to the embodiment, the reference height DP may be returned to the height before the change (that is, the reference height DP1) according to the sinking amount of the body 2 into the field. Specifically, in FIG. 5B, after the reference height DP is changed to the reference height DP2, the amount of sinking of the airframe 2 into the field decreases (see the ground surface SE3 in FIG. 5B). Return to the reference height DP1. In this case, the work machine 4 does not land on the ground surface SE3 at the reference height DP1 (see the work machine 4 indicated by the dotted line in FIG. 5B). As a result, it is possible to avoid a situation where the work machine 4 is decelerated from above with respect to the ground, and the work efficiency can be improved. In the case of turning off the Desera control without moving the reference height DP1, if the amount of subsidence of the airframe 2 into the field is reduced, the Desaler control may be turned on again. Even in this case, it is preferable to notify the operator that the reference height DP2 has returned to the reference height DP1 or that the deceler control is turned on again in the notification unit.

  Note that it is preferable that the period during which the reference height DP is changed from the reference height DP1 and the setting of the decelerator control OFF is held until the power of the tractor 1 is turned off. That is, each time the tractor 1 is started, it is preferable that the reference height DP is set to the reference height DP1 or the deceler control is set to ON. Thereby, for example, if the reference height DP1 is set according to the state of the field with high work frequency, it becomes possible to avoid the troublesomeness of the operator setting the reference height DP1 every time work is performed. Workability can be improved.

  Further, it is preferable that the decelerating control is provided so as to be turned on / off by an operator. Such on / off is more preferably performed by, for example, a desera control on / off switch 330 (see FIG. 1) provided in the vicinity of the cockpit 9. Thereby, it becomes possible to change the descent state of the work implement 4 according to the preference of the worker, and convenience can be improved.

<Power transmission path>
Incidentally, the power of the engine 7 of the tractor 1 is transmitted to the rear wheels 52 via the main transmission 40, the forward / reverse hydraulic clutch 124, and the auxiliary transmission 140, as shown in FIG. The power of the engine 7 of the tractor 1 is also transmitted to the front wheels 51 via the main transmission 40, the forward / reverse hydraulic clutch 124, the auxiliary transmission 140, and the front wheel acceleration switching mechanism 172.

  3, the main transmission 40 includes a Hi-Lo transmission mechanism 60 and a main transmission mechanism 90, and the Hi-Lo transmission mechanism 60 further includes a first Hi-Lo transmission mechanism 61 and a second Hi-Lo transmission mechanism. The main transmission mechanism 90 includes a first main transmission mechanism 91 and a second main transmission mechanism 101.

  Among these, the 1st Hi-Lo speed change mechanism 61 has the 1st Hi-Lo speed change Lo side gear 63 and the 1st Hi-Lo speed change Hi side gear 64 from which the number of teeth differs. The gears 63 and 64 are a main transmission input shaft first gear 54 and a main transmission that are fixed to a main transmission input shaft 53 that is an input shaft when the power output from the engine 7 is input to the main transmission 40. The gear is engaged with the device input shaft second gear 55. That is, the first Hi-Lo speed change Lo side gear 63 is engaged with the main transmission input shaft first gear 54, and the first Hi-Lo speed change Hi side gear 64 is engaged with the main transmission input shaft second gear 55.

  Further, the first Hi-Lo transmission mechanism 61 includes a first Hi-Lo transmission clutch 62 and a first Hi-Lo transmission output gear 65. The first Hi-Lo shift clutch 62 includes a clutch that switches between the first Hi-Lo shift Lo side gear 63 and the first Hi-Lo shift output gear 65, the first Hi-Lo shift Hi side gear 64, and the first Hi-Lo shift. And a clutch for switching between on and off of the output gear 65. Therefore, the first Hi-Lo speed change clutch 62 is between the first Hi-Lo speed change Lo side gear 63 and the first Hi-Lo speed change Hi side gear 64 and the first Hi-Lo speed change output gear 65. Thus, it is possible to transmit power. Further, the first Hi-Lo speed change output gear 65 is fixed to a main speed change mechanism first intermediate shaft 81 capable of transmitting power between the first Hi-Lo speed change mechanism 61 and the first main speed change mechanism 91. Engage with the intermediate shaft gear 82.

  Similarly, the second Hi-Lo speed change mechanism 71 has a second Hi-Lo speed change Lo side gear 73 and a second Hi-Lo speed change Hi side gear 74 with different number of teeth, and the second Hi-Lo speed change Lo side gear 73 is The main transmission input shaft first gear 54 meshes, and the second Hi-Lo shift Hi side gear 74 meshes with the main transmission input shaft second gear 55.

  The second Hi-Lo transmission mechanism 71 has a second Hi-Lo transmission clutch 72 and a second Hi-Lo transmission output gear 75. The second Hi-Lo shift clutch 72 includes a clutch for switching between the second Hi-Lo shift Lo side gear 73 and the second Hi-Lo shift output gear 75, the second Hi-Lo shift Hi side gear 74, and the second Hi-Lo shift. A clutch that switches between on and off with the output gear 75. For this reason, the second Hi-Lo shift clutch 72 is between the second Hi-Lo shift Lo side gear 73 and the second Hi-Lo shift Hi side gear 74 and the second Hi-Lo shift output gear 75. Thus, it is possible to transmit power. Further, the second Hi-Lo speed change output gear 75 is fixed to a main speed change mechanism second intermediate shaft 85 capable of transmitting power between the second Hi-Lo speed change mechanism 71 and the second main speed change mechanism 101. The intermediate shaft gear 86 meshes with the intermediate shaft gear 86.

  Here, the second Hi-Lo shift output gear 75 has a different number of teeth from the first Hi-Lo shift output gear 65, and the second intermediate shaft gear 86 also has a different number of teeth from the first intermediate shaft gear 82. ing. For this reason, the transmission ratio between the second Hi-Lo transmission output gear 75 and the second intermediate shaft gear 86 is different from the transmission ratio between the first Hi-Lo transmission output gear 65 and the first intermediate shaft gear 82. ing.

  The main transmission mechanism 90 has a main transmission mechanism output shaft first gear 111 and a main transmission mechanism output shaft second gear 112 fixed to a main transmission mechanism output shaft 110 that is an output shaft of the main transmission mechanism 90. The main transmission mechanism 91 includes a first main transmission first gear 93 that meshes with the main transmission mechanism output shaft first gear 111, and a first main transmission second gear 94 that meshes with the main transmission mechanism output shaft second gear 112. Have

  Further, the first main speed change mechanism 91 transmits the power transmitted from the main speed change mechanism first intermediate shaft 81 to one of the first main speed change first gear 93 and the first main speed change second gear 94. A first main transmission shifter 92 capable of transmission is provided. For this reason, the power transmitted from the main transmission mechanism first intermediate shaft 81 to the first main transmission mechanism 91 is transmitted through the first main transmission first gear 93 and the main transmission mechanism output shaft first gear 111, or The transmission can be transmitted to the main transmission mechanism output shaft 110 from any one of the transmission paths via the first main transmission second gear 94 and the main transmission mechanism output shaft second gear 112.

  Similarly, the second main transmission mechanism 101 includes a second main transmission first gear 103 that meshes with the main transmission mechanism output shaft first gear 111 and a second main transmission second gear that meshes with the main transmission mechanism output shaft second gear 112. 104 and a second main transmission shifter 102. For this reason, the power transmitted from the main transmission mechanism second intermediate shaft 85 to the second main transmission mechanism 101 is transmitted through the second main transmission first gear 103 and the main transmission mechanism output shaft first gear 111, or The transmission can be made to the main transmission mechanism output shaft 110 from any one of the transmission paths via the second main transmission second gear 104 and the main transmission mechanism output shaft second gear 112.

  Of the gears included in the main transmission mechanism 90, the first main transmission first gear 93 and the first main transmission second gear 94, the second main transmission first gear 103 and the second main transmission second gear 104, The transmission mechanism output shaft first gear 111 and the main transmission mechanism output shaft second gear 112 have different numbers of teeth. Therefore, the transmission ratio between the first main transmission first gear 93 and the main transmission mechanism output shaft first gear 111 and the first main transmission second gear 94 and the main transmission mechanism output shaft second gear 112 are between. This is different from the transmission ratio.

  As described above, the main transmission 40 that can transmit the power input from the engine 7 side to the output side by changing the gear ratio by the first Hi-Lo shift clutch 62 or the first main transmission shifter 92 is By changing the transmission path and changing the transmission gear ratio, an 8-speed gear stage is provided. In other words, the main transmission 40 switches the input from the main transmission input shaft first gear 54 or the main transmission input shaft second gear 55 (second speed), the first intermediate shaft gear 82, or the second intermediate shaft. The output from the gear 86 can be switched (second speed), and the output from the main transmission mechanism output shaft first gear 111 or the main transmission mechanism output shaft second gear 112 can be switched (second speed). For this reason, the main transmission 40 has a gear stage of 2nd speed × 2nd speed × 2nd speed = 8th speed. The eighth gear is assigned from the first gear to the eighth gear from the gear stage having a large reduction ratio from the main transmission input shaft 53 to the main transmission mechanism output shaft 110 toward the gear stage having a small reduction ratio. .

  A main transmission mechanism output shaft 110 that is an output shaft of the main transmission 40 is connected to a forward / reverse input shaft 121 that is an input shaft of a forward / reverse switching mechanism 120 including a forward / reverse hydraulic clutch 124. A forward / reverse input first gear 122 and a forward / reverse input second gear 123 are fixed to the forward / reverse input shaft 121, and among these, the forward / reverse input second gear 123 is provided by the forward / reverse switching mechanism 120. The counter gear 134 fixed to the counter shaft 133 is engaged with the counter gear 134.

  The forward / reverse switching mechanism 120 has a forward / reverse output first gear 131 that meshes with the forward / reverse input first gear 122 and a forward / reverse output second gear 132 that meshes with the counter gear 134. Further, the forward / reverse switching mechanism 120 uses the power transmitted to the forward / reverse output first gear 131 or the forward / reverse output second gear 132 as either the forward / reverse output first gear 131 or the forward / reverse output second gear 132. From one side, it has a forward / reverse hydraulic clutch 124 that can transmit to a forward / reverse output shaft 130 that is an output shaft of the forward / reverse switching mechanism 120.

  The forward / reverse hydraulic clutch 124 is used for switching between forward and reverse movement of the rear wheel 52 by the power transmitted from the engine 7 and for transmitting and blocking the power transmitted from the engine 7 to the rear wheel 52. . The forward / reverse hydraulic clutch 124 includes a clutch that switches between the first and second output gears 131 and 130, and a clutch that switches between the second and second output gears 132 and 130. Thus, the gear connected to the forward / reverse output shaft 130 can be switched. The forward / reverse output first gear 131 side clutch and the forward / reverse output second gear 132 side clutch of the forward / reverse hydraulic clutch 124 operate by supplying hydraulic oil.

  Here, in the power transmission path from the forward / reverse input shaft 121 to the forward / reverse output shaft 130, the forward / reverse output first gear 131 directly meshes with the forward / reverse input first gear 122, whereas the forward / reverse output The second gear 132 meshes with the forward / reverse input second gear 123 via the counter gear 134. For this reason, in the forward / reverse output first gear 131 and the forward / reverse output second gear 132, the rotation directions are opposite to each other. As a result, when the power transmission path to the forward / reverse output shaft 130 is switched by the forward / reverse hydraulic clutch 124, the forward / reverse output first gear 131 side and the forward / reverse output second gear 132 side are switched. In the case of switching, the rotational directions of the power transmitted to the forward / reverse output shaft 130 are opposite to each other.

  When the forward / reverse switching lever is operated to the forward position, the forward / reverse hydraulic clutch 124 switches the power transmission path to the forward / reverse output shaft 130 to the forward / reverse output first gear 131 side, that is, the front side, and advances the rear wheel 52 forward. Rotate in the direction. When the forward / reverse switching lever is operated to the reverse position, the forward / backward hydraulic clutch 124 switches to the forward / reverse output second gear 132 side, that is, the rear side, and rotates the rear wheel 52 in the reverse direction. Further, the forward / reverse hydraulic clutch 124 cuts off transmission of power transmitted from the engine 7 to the rear wheel 52 when both clutches cut off transmission of power based on the pedal operation of the clutch pedal, etc. The rear wheel 52 is restricted from rotating by the power from the engine 7.

  The forward / reverse output shaft 130 of the forward / reverse switching mechanism 120 is connected to a sub-transmission input shaft 141 that is an input shaft of the sub-transmission device 140, and the sub-transmission input shaft 141 has sub-transmission inputs having different numbers of teeth. The first gear 142 and the auxiliary transmission input second gear 143 are fixed.

  The sub-transmission device 140 includes a sub-transmission first gear 145 that meshes with the sub-transmission input first gear 142, and a sub-transmission second gear 146 that meshes with the sub-transmission input second gear 143. Further, the sub-transmission device 140 transmits the power transmitted to the sub-transmission first gear 145 and the sub-transmission second gear 146 from either the sub-transmission first gear 145 or the sub-transmission second gear 146. A sub-shift first shifter 144 that can be transmitted to a sub-shift output shaft 150 that is an output shaft of the device 140 is provided. Further, the sub-transmission device 140 transmits power transmitted to a gear having a different number of teeth between the front gear and the rear gear to any one of the gears having a different number of teeth between the front gear and the rear gear. On the other hand, a sub-transmission second shifter 171 that can be transmitted to the sub-transmission output shaft 150 that is the output shaft of the sub-transmission device 140 is provided.

  Here, the transmission ratio between the auxiliary transmission input first gear 142 and the auxiliary transmission first gear 145 and the transmission ratio between the auxiliary transmission input second gear 143 and the auxiliary transmission second gear 146 are different from each other. Yes. Therefore, when the transmission path of power to the auxiliary transmission output shaft 150 is switched between the auxiliary transmission first gear 145 side and the auxiliary transmission second gear 146 side by the auxiliary transmission first shifter 144, the auxiliary transmission input shaft The transmission gear ratio between 141 and the auxiliary transmission output shaft 150 changes. In addition, when the auxiliary transmission second shifter 171 is used to switch between the front gear and the rear gear, the transmission ratio between the auxiliary transmission input shaft 141 and the auxiliary transmission output shaft 150 changes. As described above, the sub-transmission device 140 has four-speed gear stages having different gear ratios and can be switched.

  An auxiliary transmission output gear 151 is fixed to the auxiliary transmission output shaft 150, and the auxiliary transmission output gear 151 meshes with a rear wheel differential 155 that is a differential gear for the rear wheel 52. The rear wheel differential 155 is configured to be able to transmit power to a rear wheel drive shaft 156 connected to the rear wheel 52, whereby the power output from the auxiliary transmission 140 is transmitted to the rear wheel 52. Can be transmitted.

  As shown in FIG. 3, the tractor 1 includes a PTO output mechanism 160 that transmits power generated by the engine 7 to the PTO shaft 8 a of the PTO coupling device 8. The PTO output mechanism 160 can receive power from the main transmission input shaft second gear 55 of the main transmission input shaft 53, and switches between transmission and interruption of power to the PTO shaft 8a side. It has a clutch 161 and a PTO transmission 162 that shifts when power is transmitted to the PTO shaft 8a.

  Further, as shown in FIG. 3, the tractor 1 includes a front wheel side power transmission mechanism 170 including a front wheel acceleration switching mechanism 172 that transmits power generated by the engine 7 to the front wheel 51 side. The front wheel side power transmission mechanism 170 is capable of receiving power from the auxiliary transmission device 140 and performs switching of the rotational speed when transmitting the power received from the auxiliary transmission device 140 to the front wheel 51 side. A front wheel acceleration switching mechanism 172 that switches between transmission and interruption of power to the front wheel 51 is provided.

  The front wheel acceleration switching mechanism 172 is neutral when the two wheels are driven, that is, when the power to the front wheels 51 is cut off. The front wheel acceleration switching mechanism 172 connects a rear clutch when driving four wheels, that is, when transmitting power to the front wheel 51 side, and connects a front clutch when increasing the front wheel speed.

  Further, the front wheel side power transmission mechanism 170 has a rotational speed and a rotation direction (according to the rotation of the rear wheel 52) of the rear wheel side power transmission gear 173 disposed on the rear output side of the front wheel acceleration switching mechanism 172. A vehicle speed sensor 211 (corresponding to vehicle speed detection means) for detecting information) is provided. The vehicle speed sensor 211 detects the rotation speed and the rotation direction of the rear wheel side power transmission gear 173 as an output shaft portion output from the front wheel speed increase switching mechanism 172 of the front wheel side power transmission mechanism 170, thereby Information corresponding to rotation is detected. In the present embodiment, the vehicle speed sensor 211 may be arranged anywhere as long as it can detect information according to the rotation of the rear wheel 52, and may detect the rotation speed and rotation direction of any member.

  The front wheel side power transmission gear 180 disposed on the output side of the front wheel side power transmission mechanism 170 meshes with a front wheel differential 181 that is a differential gear for the front wheel 51, and the front wheel differential 181 is connected to the front wheel 51. Power is transmitted to the front wheel drive shaft 183 via a vertical shaft 182 and the like. As a result, the power output from the front wheel side power transmission mechanism 170 can be transmitted to the front wheel 51.

<Control device>
As shown in FIG. 2, the travel control unit 3 includes an engine control unit 3 a that controls the engine 7 and the like, a work machine lifting control unit 3 b that lifts and lowers the work machine 4 mounted on the PTO coupling device 8, and a meter panel 31. In addition, it is connected to the operation panel 32 and the like via the communication unit 318 so as to be able to communicate with each other alternately. The communication unit 318 is a communication line such as a CAN (Controller Area Network). Further, the tractor 1 is provided with a GPS control device (not shown) that acquires position information of the tractor 1 by GPS (Global Positioning System). The GPS control device can acquire position information on the earth by acquiring GPS coordinates at predetermined time intervals via a GPS antenna 317 (see FIG. 1) provided above the airframe 2. Note that the above CAN includes not only wired communication but also wireless communication. Further, the communication unit 318 is provided so as to be able to communicate with a mobile terminal MT such as a tablet PC, a smartphone, or a personal computer. The mobile terminal MT according to the present embodiment has a built-in GPSMTa.

  The engine control unit 3a injects into the cylinder of the engine 7 based on the engine exhaust temperature, the engine speed, the pressure of the engine lubricating oil, the temperature of the cooling water of the engine 7, the fuel supply pressure, the accelerator operation amount, and the like. Outputs a signal to operate the injector.

  The work implement lifting / lowering control unit 3b receives a signal from the tilling depth sensor 4b, a signal from the lift arm sensor 4c, a raising position restriction signal from the raising position restriction dial 312 and a lowering speed setting signal from the lowering speed adjustment dial 313. Is done. The work implement lifting / lowering control unit 3b outputs a work implement lifting / lowering signal to the work implement raising solenoid 314 and the work implement lowering solenoid 315 to operate the cylinder 41.

  The traveling control unit 3 controls the traveling of the tractor 1 by controlling the main transmission 40, the auxiliary transmission 140, the forward / reverse switching mechanism 120, the PTO output mechanism 160, and the front wheel side power transmission mechanism 170. For example, when the brake depression detection switch 25 detects the pedal operation of the brake pedal by the operator and the vehicle speed sensor 211 detects the rotation of the auxiliary transmission input first gear 142, the traveling control unit 3 stops or substantially stops the body 2 Thus, the hydraulic pressure to the front or rear clutch of the forward / reverse hydraulic clutch 124 is controlled. The travel control unit 3 receives the travel speed of the airframe 2 from the vehicle speed sensor 211, the temperature of the mission oil, the detection result of the brake depression detection switch 25, and the like from the oil temperature sensor 320.

  The traveling control unit 3 receives the detection result of the forward clutch pressure sensor 230 a that detects the hydraulic pressure of the clutch on the first gear 131 side in the forward / reverse hydraulic clutch 124 in the forward / reverse hydraulic clutch 124, and A reverse clutch pressure sensor for controlling the hydraulic pressure of the clutch on the 2-gear 132 side is connected to output such a control signal.

  The travel control unit 3 includes information indicating ON / OFF from the clutch automatic cutoff setting switch 28, a detection result from the main shift lever position sensor 210 that detects an operation position of the main shift lever, and an operation position of the sub shift lever. And a detection result from the forward / reverse lever position sensor 27 for detecting the operation position of the forward / reverse switching lever.

  The traveling control unit 3 includes a forward switching solenoid 261 that operates the clutch on the forward / reverse output first gear 131 side in the forward / backward hydraulic clutch 124, a reverse switching solenoid 262 that operates the clutch on the forward / reverse output second gear 132 side, A forward / reverse pressure boosting solenoid 265 for controlling the hydraulic pressure when the forward / reverse hydraulic clutch 124 is operated to reduce a shock at the time of switching between forward and reverse is connected to output these control signals.

  The traveling control unit 3 also operates a first main transmission first solenoid 251 that operates the first main transmission shifter 92 to the side where the main transmission mechanism first intermediate shaft 81 and the first main transmission first gear 93 are connected. The first main transmission second solenoid 252 that is operated to the side where the main transmission mechanism first intermediate shaft 81 and the first main transmission second gear 94 are connected is connected to output these control signals. The travel control unit 3 includes a second main transmission first solenoid 255 that operates the second main transmission shifter 102 on the side where the main transmission mechanism second intermediate shaft 85 and the second main transmission first gear 103 are connected, A second main transmission second solenoid 256 that is operated on the side where the second intermediate shaft 85 of the transmission mechanism and the second main transmission second gear 104 are connected is connected to output these control signals.

  The travel control unit 3 also includes a first Lo-side solenoid 242 that operates a clutch on the first Hi-Lo shift Lo side gear 63 side, and a clutch on the first Hi-Lo shift Hi side gear 64 side in the first Hi-Lo shift clutch 62. Is connected to the first Hi-side solenoid 241 for operating the control signal and outputs these control signals. The traveling control unit 3 operates the second Lo-side solenoid 246 that operates the second Hi-Lo shift Lo side gear 73 side clutch, and the second Hi-Lo shift Hi side gear 74 side clutch in the second Hi-Lo shift clutch 72. The second Hi side solenoid 245 to be connected is connected to output these control signals.

  The travel control unit 3 is connected to a 4WD solenoid 325 and a front wheel acceleration solenoid 326 that operate the front wheel acceleration switching mechanism 172, and a PTO clutch solenoid 327 that operates the PTO clutch 161, and outputs these control signals. To do.

  When controlling the tractor 1, for example, the traveling control unit 3 reads the computer program into a memory incorporated in the processing unit based on the detection result of the main shift lever position sensor 210 or the like. The travel control of the tractor 1 is performed by controlling the actuators such as the first Hi-side solenoid 241 according to the result of the calculation. At that time, the processing unit appropriately stores a numerical value in the middle of the calculation in the storage unit, and retrieves the stored numerical value and executes the calculation.

<Hydraulic circuit of work vehicle>
Next, the hydraulic circuit of the tractor 1 will be described with reference to FIG. FIG. 4 is a hydraulic circuit diagram of the tractor 1. The tractor 1 has a hydraulic circuit HCA and a hydraulic circuit HCB. The hydraulic circuit HCA and the hydraulic circuit HCB are hydraulically supplied using lubricating oil with the inside of the transmission case as a tank port T by a pump PM driven by the engine 7.

  As shown in FIG. 4, the hydraulic circuit HCA includes a first main transmission valve 190, a second main transmission valve 191, and a reverser valve 192. The first main transmission valve 190 switches the first Hi-Lo transmission clutch 62 and the first main transmission shifter 92. The second main transmission valve 191 switches the second Hi-Lo transmission clutch 72 and the second main transmission shifter 102. The reverser valve 192 switches the forward / reverse hydraulic clutch 124.

<Hydraulic circuit for raising and lowering work equipment>
As shown in FIG. 4, a cylinder 41 is connected to the hydraulic circuit HCB. By changing the flow of oil in the hydraulic circuit HCB, the cylinder 41 expands and contracts to raise and lower the work implement 4. That is, the hydraulic circuit HCB and the cylinder 41 are elevating units that elevate the work implement 4 relative to the machine body 2. As shown in FIG. 4, the hydraulic circuit HCB includes a work implement ascending solenoid 314, a work implement descending solenoid 315, a descending pilot valve 413, a descending main valve 414, an ascending main valve 415, an ascending pilot valve 417, And a check valve 418.

  Pressure oil sent out from the pump PM is supplied to the hydraulic circuit HCB via a pressure reducing circuit, a filter, or the like. The work implement lifting / lowering control unit 3b switches the lowering main valve 414 and the rising main valve 415 by outputting a work implement raising / lowering signal to the work implement raising solenoid 314 and the work implement lowering solenoid 315.

  For example, when the lift pilot valve 417 is switched from the oil chamber 417a having a check valve to the oil chamber 417b having a throttle by the work implement lift solenoid 314, the lift main valve 415 is opened. Thereby, the pressure oil from the pump PM is supplied to the cylinder 41 (see FIG. 1) side, the cylinder 41 is extended, and the work machine 4 is raised. When the rising main valve 415 returns to the state shown in FIG. 4, the pressure oil sent to the cylinder 41 is restricted from flowing out to the hydraulic circuit HCB side by the check valve 418, and the position of the lift arm 43 a is maintained. Is done.

  When the lowering pilot valve 413 is switched from the oil chamber 413a having the check valve to the oil chamber 413b having the throttle by the work implement lowering solenoid 315, the lowering main valve 414 is opened. Thereby, the oil pushed out from the cylinder 41 by the dead weight of the work machine 4 is discharged to the tank port T, the cylinder 41 is contracted, and the work machine 4 is lowered.

  The work implement lowering solenoid 315 is a proportional solenoid, and the lowering pilot valve 413 can change the flow rate of oil passing through the lowering pilot valve 413 by adjusting the throttle of the oil chamber 413b with the proportional solenoid. it can. Further, the lowering speed of the work machine 4 changes according to the flow rate of the oil passing through the lowering pilot valve 413. For example, if the throttle opening of the oil chamber 413b is increased, the flow rate of oil passing through the descending pilot valve 413 per unit time increases, and the descending speed of the work implement 4 increases. On the other hand, if the throttle opening of the oil chamber 413b is reduced, the flow rate of the oil passing through the descending pilot valve 413 per unit time decreases, and the descending speed of the work implement 4 increases.

  Thus, the work implement lifting control unit 3b (see FIG. 2) can arbitrarily change the opening degree of the lowering pilot valve 413 by the work implement lowering solenoid 315 that is a proportional solenoid. Therefore, the lowering speed of the work machine 4 can be arbitrarily changed.

  As shown in FIG. 4, a return valve 419 is provided between the hydraulic circuit HCB and the cylinder 41. The return valve 419 has a throttle that can be manually changed, and the amount of oil returned from the cylinder 41 to the tank port T per unit time can be adjusted by the operator setting the throttle amount. It is possible to do. Therefore, the return valve 419 can also arbitrarily change the lowering speed of the work implement 4 and can improve the convenience for the operator.

<Processing procedure to change the reference height>
Next, a processing procedure according to the reference height DP changing method executed by the tractor 1 will be described with reference to FIG. FIG. 6 is a flowchart showing a processing procedure for changing the reference height DP.

  As shown in FIG. 6, when the depth control (second mode) is turned on and the work machine 4 starts ground work (step S201), the decelerating control (first mode) is turned on (step S202), and the reference The height DP is set to the reference height DP1 (first height) (step S203). Note that step S202 and step S203 may be executed prior to step S201, for example, when the tractor 1 is started.

  Subsequently, the work implement lifting control unit 3b determines whether or not the work implement 4 is higher than the reference height DP1 (step S204). When the work machine 4 is higher than the reference height DP1 (step S204, Yes), the reference height DP is moved to the reference height DP2 (second height) (step S205), and the processes after step S206 are executed. To do. When the work machine 4 is not higher than the reference height DP1 (No at Step S204), the processes after Step S206 are executed.

  Subsequently, the work implement lifting control unit 3b determines whether or not the ground work of the work implement 4 has been completed (step S206). Step S206 may be determined by, for example, turning off the depth control or stopping the engine 7 of the tractor 1. When the ground work of the work machine 4 is finished (step S206, Yes), the process is finished. When the ground work of the work machine 4 is not completed (No at Step S206), it is determined whether the reference height DP is the reference height DP2 (Step S207).

  When the reference height DP is the reference height DP2 (step S207, Yes), it is determined whether or not the work machine 4 is lower than the reference height DP1 (step S208). In step S207, when the reference height DP is not the reference height DP2, that is, the reference height DP1 (No in step S207), the processes after step S204 are repeated.

  In step S208, when the work machine 4 is lower than the reference height DP1 (step S208, Yes), the reference height DP is returned to the reference height DP1 (step S209), and the processes after step S206 are repeated. In step S208, when the work machine 4 is not lower than the reference height DP1 (No in step S208), the processes after step S206 are repeated.

  As described above, the work vehicle according to one aspect of the embodiment includes a work machine, an elevating unit, and a control unit. The work machine is provided at the rear of the machine body and performs ground work. The elevating unit moves the working machine up and down relative to the machine body. The control unit adjusts the first mode for decreasing the descent speed of the work implement at the reference height when the work implement is lowered, and the second mode for adjusting the height relative to the ground of the work implement performing the ground work to be constant. When the second mode is executed for the work implement positioned above the first height as the reference height, the reference height is set to the first height. It is moved to a second height located above the height.

  As a result, it is possible to avoid a situation in which the lowering speed of the work implement decreases below the height at which the work implement performs the ground work in the second mode. Therefore, hunting can be prevented and work stability in the field can be improved by suppressing the work machine from receiving an impact due to landing.

  In the above-described embodiment, the case where the working machine performs the rotary tilling work has been described as an example. However, the working machine is not limited to this, and the working machine may perform a trencher, a side coating work, a scraping work, or a plow work. Moreover, in embodiment mentioned above, the case where the work vehicle was a tractor was demonstrated as an example. However, the work vehicle is not limited to this, and may be a civil engineering work vehicle, a rice transplanter, or the like.

  Further effects and modifications can be easily derived by those skilled in the art. Thus, the broader aspects of the present invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications can be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

DESCRIPTION OF SYMBOLS 1 Tractor 2 Airframe 3 Travel control part 3a Engine control part 3b Work machine raising / lowering control part 4 Work machine 4c Lift arm sensor 7 Engine 8 PTO coupling device 8a PTO shaft 9 Pilot seat 10 Steering handle 11 Handle post 31 Meter panel 32 Operation panel 40 Main transmission 41 Cylinder 41a Cylinder case 42 Lower link 43a Lift arm 43b Lift rod 45 Tillage claw 46a Rotary cover 46b Rear cover 51 Front wheel 52 Rear wheel 413 Down pilot valve 414 Down main valve 415 Up main valve 417 Up pilot valve 418 Check valve 419 Return valve HCA, HCB Hydraulic circuit PM pump T Tank port

Claims (5)

A work machine provided at the rear of the machine body for performing ground work;
An elevating unit for elevating the working machine relative to the machine body;
A first mode in which the lowering speed of the work implement is decreased at a reference height when the work implement is lowered, and a first mode in which the height of the work implement performing ground work is adjusted to be constant with respect to the ground. A control unit that executes the mode of 2 on the lifting unit,
The controller is
When the second mode is executed for the work implement positioned above the first height as the reference height, the reference height is set to be higher than the first height. A working vehicle characterized by being moved to a height of The second height is
The work vehicle according to claim 1, wherein the work vehicle is an upper limit in a lifting range of the work implement. The elevating part is
The machine body is provided so as to be rotatable around a predetermined rotation axis, and has an arm for raising and lowering the working machine,
The controller is
The work vehicle according to claim 1, wherein the height of the work implement is detected based on a rotation angle of the arm around the rotation axis. The controller is
When the work implement executes the second mode below the first height after the reference height has moved to the second height, the reference height is set to the first height. The work vehicle according to any one of claims 1 to 3, wherein the work vehicle is returned to. The controller is
The reference height is returned to the first height when the control unit is powered off and restarted after the reference height moves to the second height. The work vehicle according to any one of 1 to 4.

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