JP2008072907A - Working vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify an interlocking structure for automatic vehicle speed control in a working vehicle which can perform the automatic vehicle speed control for reducing the speed of a vehicle to constantly keep the driving of a working portion on the overload of an engine 6. <P>SOLUTION: An electric motor 170 is linked to a straight travel rotary shaft 105 of a straight travel HST type transmission mechanism 35 through a connection mechanism 171 of a system different from an operation system directed from a main transmission lever 77 to the straight travel rotary shaft 105. The linkage mechanism 171 has an interlock-switching means for permitting or canceling the interlock of the straight travel rotary shaft 105 to the electric motor 170. When the automatic vehicle speed control is not performed, the interlock-switching means is set to a canceling state for not preventing the operation of the straight travel rotary shaft 105. Before the vehicle speed of the travel machine frame is reduced during the performance of the automatic vehicle speed control, the interlock-switching means is set to a permission state for operating the straight travel rotary shaft 105 in a speed-reducing direction with the power of the electric motor 170. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a work vehicle such as a farm work machine such as a combine, and more particularly to a configuration for executing automobile speed control of the work vehicle.

  Conventionally, in a combine as a work vehicle, power from an engine mounted on a traveling machine body is appropriately shifted by a hydraulic drive means, and this shift output is transmitted to a working unit such as a mowing unit or a threshing unit and a traveling unit. It is configured to communicate separately. It is known to perform constant rotation control (isochronous control) that keeps the engine speed substantially constant even when the engine load fluctuates depending on the combine working state, crop conditions, and the like (for example, Patent Document 1). reference). Such constant rotation control is performed in a range where the engine load does not exceed a predetermined value.

  Patent Document 1 also discloses that control is performed so as to decelerate the vehicle speed of the traveling machine body when the engine load exceeds a predetermined value in order to avoid stopping the engine when the engine is overloaded.

In this case, the main speed change lever and the steering handle arranged in the control unit of the traveling machine body are interlocked and connected to the hydraulic drive means via a mechanical interlocking mechanism, and an electric motor is interposed in the mechanical interlocking mechanism. Has been. If the engine load is equal to or greater than a predetermined value, the hydraulic drive means is actuated in the deceleration direction by the drive of the electric motor regardless of the operation position of the main transmission lever, and as a result, the vehicle speed of the traveling machine body is reduced. It is configured as follows.
JP 2000-69838 A

  However, in the configuration of Patent Document 1, since the electric motor is interposed in a mechanical interlocking mechanism that interlocks and connects the main transmission lever, the steering handle, and the hydraulic drive means, the driving force of the electric motor is reduced to the machine. The structure for transmitting to the hydraulic drive means while being related to the mechanical interlocking mechanism has to be extremely complicated, and there is a problem that the number of parts increases and the manufacturing cost increases.

  Therefore, the present invention has a technical problem to provide a work vehicle that solves the above-described problems.

  In order to solve this technical problem, the invention according to claim 1 is a hydraulic drive means for shifting the power from the engine mounted on the traveling machine body, and the speed change output of the hydraulic drive means is increased or reduced. A speed change operation means, a load detection means for detecting the load of the engine in relation to the fuel supply means for the engine, and the vehicle speed of the traveling machine body is reduced when the engine is overloaded to eliminate the overload. Then, the work vehicle is provided with vehicle speed control means for executing vehicle speed control for returning and increasing the vehicle speed of the traveling machine body toward the original vehicle speed before deceleration, and the shift output of the hydraulic drive means is obtained. The adjusting unit for adjusting is associated with a speed change actuator via a linkage mechanism that is different from the operation system from the speed change operation means to the adjustment portion, and the linkage mechanism includes the adjustment mechanism. And an interlocking switching unit that allows or cancels the interlocking of the shift actuator and the speed change actuator, and when the vehicle speed control is not executed, the interlocking switching unit does not hinder the operation of the adjusting unit. Before the vehicle speed of the traveling machine body is decelerated during execution of the vehicle speed control, the interlock switching means is set to a permissible state in which the adjustment unit is operated in the deceleration direction by the power of the speed change actuator. It is what is comprised.

  According to a second aspect of the present invention, in the work vehicle according to the first aspect, in the case where the vehicle speed control means executes a control for returning and increasing the vehicle speed of the traveling machine body, the adjustment unit of the hydraulic drive means. The shift actuator is controlled so as to be driven stepwise when the motor is operated in the speed increasing direction.

  According to a third aspect of the present invention, in the work vehicle according to the first or second aspect, the linkage mechanism is configured to drive an adjustment member that can rotate integrally with a rotation shaft as the adjustment portion, and drive the speed change actuator. And a drive member that can turn about a pivot parallel to the turning shaft, and a linkage rod for turning the two members together, and the end of the linkage rod on the drive member side Is formed with a guide slot extending in the longitudinal direction of the linkage rod, and the linkage rod and the drive member are connected via a pivot pin inserted into the guide slot, The guide slot and the pivot pin constitute the interlocking switching means, and before the vehicle speed of the traveling machine body is decelerated during execution of the vehicle speed control, the pivot pin is driven by driving the speed change actuator. Is the guide groove Is that is configured to move to a position closer to the edge of the control member closer in.

  According to the configuration of the present invention, the adjustment unit for adjusting the shift output of the hydraulic drive means, the transmission actuator for operating the adjustment unit in the decelerating direction, the operation system from the shift operation means to the adjustment unit, Are linked via a separate linkage mechanism, so that the vehicle speed control is executed, but the operation system and the speed change actuator need not be directly linked. In other words, it is not necessary to interpose the speed change actuator in the operation system. For this reason, restrictions such as the layout of the transmission actuator and the linkage mechanism are remarkably reduced, and the degree of freedom in design is improved. As a result, the interlocking structure for vehicle speed control can be simplified and the number of parts can be reduced, which can contribute to the reduction of manufacturing costs.

  Further, the linkage mechanism has interlocking switching means for allowing or canceling the interlocking between the adjusting unit and the speed change actuator, and when the vehicle speed control is not being executed, the interlocking switching means It is set in a release state that does not hinder the operation of the adjusting unit, and before the vehicle speed of the traveling machine body is decelerated during execution of the vehicle speed control, the interlock switching means uses the power of the speed change actuator to move the adjusting unit in the deceleration direction. Since it is configured to be set in the permissible state to be operated, when the vehicle speed of the traveling machine body is decelerated during execution of the vehicle speed control, the power of the speed change actuator is transmitted through the linkage mechanism to the hydraulic type It is quickly transmitted to the adjusting part of the driving means.

  For this reason, when the vehicle speed control is executed, the time lag from when the speed change actuator is driven to when the traveling machine body starts a deceleration operation is extremely short, and if the engine is overloaded during the execution of the vehicle speed control. The traveling body can be quickly shifted to the deceleration operation. As a result, there is an effect that efficient vehicle speed control can be executed.

  The inventions according to claims 2 and 3 further embody the structure of the combine according to the invention according to claim 1, and in any of the inventions, the function and effect of claim 1 are surely produced.

  In particular, according to the invention of claim 2, when the vehicle speed control means performs the control for returning and increasing the vehicle speed of the traveling machine body, the vehicle speed control means operates the adjusting portion of the hydraulic drive means in the speed increasing direction. Therefore, the vehicle speed in the forward direction of the traveling vehicle body is gradually recovered and increased at a time instead of at once. For this reason, there exists an effect that the said traveling body is safe, without speeding up rapidly.

  Hereinafter, an embodiment embodying the present invention will be described with reference to the drawings (FIGS. 1 to 15) when applied to a normal combine as a work vehicle. 1 is a side view of the combine, FIG. 2 is a skeleton diagram showing a traveling drive system of the combine, FIG. 3 is a plan view of a control unit, FIG. 4 is a perspective view of a side column, and FIG. 5 is a main shift lever and a steering handle. FIG. 6 is a front view showing the relationship between the detent means, the linkage mechanism, and the electric motor. FIG. 7 is a sectional view taken along the line VII-VII in FIG. 8 to 11 are views showing the operation mode of the linkage mechanism, FIG. 8 is a view showing a state in which the straight advance detent rod is rotated in the forward speed increasing direction, and FIG. 9 is a pivot pin driven by the electric motor. FIG. 10 is a diagram showing a state where the sector gear and the relay arm are rotated to the maximum forced deceleration position by driving the electric motor, and FIG. 11 is a diagram showing the state of the electric motor. Return the sector gear and relay arm to the forward speed increase direction by driving. FIG. 12 is a functional block diagram of the controller, FIG. 13 is a control map showing the relationship between the vehicle speed and the deceleration amount of the traveling machine body, and FIG. 14 is a flowchart showing an example of the vehicle speed control. 15 is a time chart showing an example of vehicle speed control.

(1). First, a schematic structure of a combine will be described with reference to FIG.

  The ordinary combine in the embodiment includes a traveling machine body 1 supported by a pair of left and right traveling crawlers 2 as traveling portions. At the front part of the traveling machine body 1, a cutting part 3 for taking in planted cereal grains such as rice, wheat and soybeans is mounted by a single-acting hydraulic cylinder 4 so as to be adjustable up and down.

  A cabin-type control unit 5 is mounted on the front side of the traveling machine body 1 (in the embodiment, the front right side). Behind the control unit 5, a diesel engine 6 (see FIG. 2) as a power source and a grain tank 7 for storing the grain after threshing are arranged.

  On the other side of the traveling machine body 1 (left side in the embodiment), a threshing unit 8 for threshing the harvested cereals sent from the harvesting unit 3 is mounted. Below the threshing unit 8, a sorting unit 9 for performing swing sorting and wind sorting is arranged.

  The left and right traveling crawlers 2 serving as traveling units include a plurality of driving wheels 11 and driven wheels 12 disposed at the front and rear ends of the longitudinal longitudinal track frame 10 below the traveling machine body 1 and a longitudinal middle portion of the track frame 10. The rolling wheel 13 arranged individually and the crawler belt 14 wound around the outer periphery of the wheels 11 to 13 are provided. The left and right crawler belts 14 are rotated around the wheels 11 to 13 by rotating the left and right drive wheels 11 with power from a drive output shaft 60 (see FIG. 2) that protrudes left and right outward from a mission case 30 described later. Is configured to be driven in rotation.

  The mowing unit 3 includes a rectangular tubular feeder house 15 that communicates with the front opening of the threshing unit 8, and a horizontally long bucket-shaped platform 16 that is connected to the front end of the feeder house 15. A lower surface portion of the feeder house 15 and a front end portion of the traveling machine body 1 are connected via a single-acting hydraulic cylinder 4.

  A lateral feed auger 17 is rotatably supported in the platform 16. A scraping reel 18 with a tine bar is disposed above the front portion of the lateral feed auger 17. A horizontally long clipper-shaped cutting blade 19 is disposed on the lower surface side of the platform 16. A pair of left and right weed bodies 20 project from the front portion of the platform 16.

  The planted cereals that have been pulled back by the scraping reel 18 are harvested by the cutting blade 19, and then collected in the vicinity of the central portion of the platform 16 by the rotational drive of the lateral feed auger 17. The collected cereal grains are sent to the threshing unit 8 via the chain conveyor 21 in the feeder house 15.

  In the handling room of the threshing unit 8, a front and rear longitudinal handling cylinder 22 for threshing the harvested cereal meal is built. Although not shown in detail, screw blades having a plurality of incisors are spirally wound around the outer peripheral surface of the handle 22. The harvested cereal mash that has been conveyed into the handling chamber is finely cut by each incisor of the handling cylinder 22.

  The sorting unit 9 disposed below the threshing unit 8 includes a swing sorting device 23 having a receiving net, a chaff sheave, and the like, and a wind sorting device 24 having a Kara fan or the like. The grains that have leaked from the receiving net are used as the first thing such as fine grains, the second thing such as the grain with branches, and the waste (swarf) by the swing sorting device 23 and the wind sorting device 24. Selected.

  After the sorting by the swing sorting device 23 and the wind sorting device 24, the first thing such as the fine particles collected in the first receiving bowl at the lower part of the traveling machine body 1 is the first conveyor 25 and the cereal conveyor (not shown). To the grain tank 7. A second thing such as a grain with a branch is returned to the handling room via the second conveyor 26, the reduction conveyor 27, and the like, and threshed again by the handling cylinder 22. The second item after the threshing is re-sorted by the sorting unit 9. The waste and the like are finely cut by a spreader 28 disposed below the rear portion of the threshing portion 8 and then discharged to the rear of the traveling machine body 1.

  The grain in the grain tank 7 is carried out to the loading platform of the transport truck (outside the traveling machine body 1) via the discharge auger 29 erected at the rear part of the traveling machine body 1.

(2). Next, the traveling drive system of the combine will be described with reference to FIG.

  In the ordinary combine according to the embodiment, the power from the engine 6 is appropriately shifted by the hydraulic drive means 31 in the mission case 30 and the right and left are output via the drive output shafts 60 projecting left and right outward from the mission case 30. It is configured to output to the drive wheel 11.

  In this case, in the transmission case 30, a hydraulic drive means 31 for shifting the power from the engine 6, a sub-transmission mechanism 32 having low speed, medium speed, high speed and neutral speed stages, and a pair of left and right A differential gear mechanism 33 having a planetary gear mechanism 51 and the like is incorporated.

  Power from the engine 6 is transmitted from the output shaft 34 of the engine 6 to the hydraulic drive means 31 via a pulley and a belt transmission system. The hydraulic drive means 31 includes a straight traveling HST transmission mechanism 35 including a first hydraulic pump 36 and a first hydraulic motor 37, and a turning HST transmission mechanism 38 including a second hydraulic pump 39 and a second hydraulic motor 40. It has.

  Power from the output shaft 34 toward the hydraulic drive means 31 is transmitted to the common pump shaft 41 of both the hydraulic pumps 36 and 39 outside the transmission case 30. In both the straight travel and turning HST transmission mechanisms 35 and 38, hydraulic oil is sent from the hydraulic pumps 36 and 39 to the hydraulic motors 37 and 40 by the power transmitted to the common pump shaft 41.

  In the straight traveling HST type transmission mechanism 35, the inclination angle of the rotary swash plate of the first hydraulic pump 36 is changed and adjusted in accordance with the shift position of a main transmission lever 77 (details will be described later) arranged in the control unit 5. Then, by changing the discharge direction and discharge amount of the hydraulic oil to the first hydraulic motor 37, the rotation direction and the rotation speed of the linear motor shaft 42 protruding from the first hydraulic motor 37 are arbitrarily adjusted. It is configured.

  The rotational power of the linear motor shaft 42 in the first hydraulic motor 37 is transmitted from the linear output gear 43 fixed to the linear motor shaft 42 to the auxiliary transmission mechanism 32 via the transmission gear mechanism 44. The rotational power of the linear motor shaft 42 is also branched and transmitted to the PTO shaft 46 having the clutch means 47 via the output gear 45. Although details are not shown, it is configured to drive working units such as the mowing unit 3 and the threshing unit 8 by the rotational power branched to the PTO shaft 46.

  The sub-transmission mechanism 32 is a conventionally known gear mechanism, and the rotation direction and the number of rotations of the linear motor shaft 42 are operated by operating a sub-transmission lever 78 (details will be described later) disposed in the control unit 5. The adjustment range is set so that it can be switched to four speed stages, low speed, medium speed, high speed, and neutral. A brake shaft 48 which is a component of the auxiliary transmission mechanism 32 is provided with a brake means 49 such as a wet multi-disc disk. In the embodiment, a vehicle speed sensor 197 such as a rotary encoder for detecting the vehicle speed of the traveling machine body 1 is provided in association with the brake shaft 48.

  The rotational power from the auxiliary transmission mechanism 32 is transmitted to the differential gear mechanism 33 from the auxiliary transmission output gear 50 fixed to the brake shaft 48. A pair of left and right planetary gear mechanisms 51, which are constituent elements of the differential gear mechanism 33, are formed symmetrically, and a pair of left and right carriers that rotatably support a plurality of planetary gears 53 on the same radius. 52. These two carriers 52 are arranged so as to oppose each other at an appropriate interval on the same axis.

  A center gear 55 is fixed to the center of the sun shaft 54 located between the left and right carriers 52. The center gear 55 meshes with the auxiliary transmission output gear 50 on the auxiliary transmission mechanism 32 side. Sun gears 56 are fixed to the left and right sides of the sun shaft 54 with the center gear 55 interposed therebetween. Each sun gear 56 meshes with each planetary gear 53 of the carrier 52 corresponding thereto. The left and right ends of the sun shaft 54 are rotatably supported by bearings (not shown) located at the rotation center of each carrier 52.

  A pair of left and right ring gears 57 having inner teeth on the inner peripheral surface and outer teeth on the outer peripheral surface are arranged concentrically with the sun shaft 54 so that the inner teeth mesh with the plurality of planetary gears 53. . Each ring gear 57 is pivotally supported by a carrier shaft 58 projecting left and right outward from the outer surface of the carrier 52 via a bearing (not shown).

  Rotational power from the auxiliary transmission output gear 50 in the auxiliary transmission mechanism 32 is transmitted to the left and right planetary gear mechanisms 51 via a center gear 55 fixed to the sun shaft 54. The rotational power transmitted to the left and right planetary gear mechanisms 51 is output from the carrier shaft 58 of each carrier 52 to the left and right drive output shafts 60 via the transmission gear mechanism 59.

  On the other hand, in the turning HST type transmission mechanism 38, the inclination angle of the rotary swash plate of the second hydraulic pump 39 according to the amount of turning operation of the steering handle 73 (details will be described later) arranged in the control unit 5. And adjusting the rotation direction and the rotation speed of the turning motor shaft 61 protruding from the second hydraulic motor 40 by changing the discharge direction and discharge amount of the hydraulic oil to the second hydraulic motor 40. Is configured to do.

  The rotational power of the turning motor shaft 61 in the second hydraulic motor 40 is transmitted from the turning output gear 62 fixed to the turning motor shaft 61 to the pair of left and right rotating gears 64 via the gear mechanism 63. The left rotation gear 64 meshes with the external teeth of the left ring gear 57 via the reverse rotation gear 65. The right rotation gear 64 directly meshes with the external teeth of the right ring gear 57. Accordingly, when the left ring gear 57 rotates forward at a predetermined rotational speed by the forward rotation of the second hydraulic motor 40, the right ring gear 57 rotates backward at the same rotational speed as the left ring gear 57.

  According to such a configuration, for example, if the driving of the turning HST transmission mechanism 38 is stopped, the left and right ring gears 57 are in a locked state (fixed state) in which they cannot rotate. At this time, the turning motor shaft 61 of the second hydraulic motor 40 is preferably locked (fixed) by a brake means 66 such as a wet multi-plate disk.

  When the straight HST transmission mechanism 35 is driven in a state where the driving of the turning HST transmission mechanism 38 is stopped, it is transmitted from the straight output gear 43 of the linear motor shaft 42 to the center gear 55 of the sun shaft 54. Rotational power is transmitted to the left and right sun gears 56 at the same rotational speed, and is output to the left and right drive output shafts 60 and thus to the drive wheels 11 at the same direction and the same rotational speed via the left and right planetary gears 53 and the carrier 52. . As a result, the traveling machine body 1 travels straight. In this case, the traveling machine body 1 moves forward when the linear motor shaft 42 is driven in the forward rotation direction, and the traveling machine body 1 moves backward when driven in the reverse rotation direction.

  Conversely, when the driving of the straight traveling HST transmission mechanism 35 is stopped, the sun shaft 54 and the left and right sun gears 56 are in a locked state (fixed state) where they cannot rotate. Also at this time, it is preferable to lock (fix) the linear motor shaft 42 of the first hydraulic motor 37 by the brake means 67 such as a wet multi-plate disk.

  When the turning HST transmission mechanism 38 is driven in a state where the driving of the straight traveling HST transmission mechanism 35 is stopped, the rotational power from the turning motor shaft 61 is transmitted via the left rotation gear 64 and the reverse rotation gear 65. The left ring gear 57 is rotated forward (reverse) at a predetermined rotational speed, while the right ring gear 57 is rotated reversely (forward) at the same rotational speed as the left ring gear 57 via the right rotational gear 64.

  The forward (reverse) direction rotational power transmitted to the left ring gear 57 rotates the left drive output shaft 60 and thus the left drive wheel 11 in the forward (reverse) direction via the left planetary gears 53 and the carrier 52. . The rotational power in the reverse (forward) direction transmitted to the right ring gear 57 rotates the right drive output shaft 60 and thus the right drive wheel 11 in the reverse (forward) direction via each planetary gear 53 and carrier 52 on the right side. .

  In other words, the rotational power from the turning HST transmission mechanism 38 is transmitted to the left and right planetary gear mechanisms 51 so as to apply rotational forces in opposite directions, and one of the drive wheels 11 of the left and right traveling crawlers 2 moves forward. The traveling machine body 1 spin-turns on the spot.

  Further, when the turning HST transmission mechanism 38 is driven while the straight traveling HST transmission mechanism 35 is driven, a difference occurs in the driving speed of the left and right traveling crawlers 2, and the traveling machine body 1 moves forward or backward. Turn left or right with a turning radius greater than the spin turn turning radius. The turning radius at this time is determined according to the difference in driving speed between the left and right traveling crawlers 2.

(3). Detailed structure in the control unit Next, the detailed structure in the control unit will be described with reference to FIGS. 3 and 4.

  A vertically long steering column 71 is erected in front of a control seat 70 disposed in the cabin-type control unit 5. A round steering handle 73 for changing the traveling (turning) direction and the turning speed of the traveling machine body 1 is attached to a handle shaft 72 (see FIG. 5) protruding upward from the steering column 71. In the embodiment, the rotatable range of the steering handle 73 is set to a size of about 135 ° to the left and right across the neutral position. Needless to say, when the hand is released from the steering handle 73, the steering handle 73 is automatically returned to the neutral position.

  A center panel body 74 having a liquid crystal display device 75 and the like is disposed inside a substantially annular handle wheel portion of the steering handle 73. The center panel body 74 is fixed only to the steering column 71 and is not connected to the steering handle 73. Therefore, even if the steering handle 73 is rotated, the center panel body 74 and the liquid crystal display device 75 are also operated. Does not move, and the screen is always easy to see from the operator.

  On one side of the control seat 70 (left side in the embodiment), a side panel body 76 that is long in the front-rear direction is disposed. On the side panel body 76, a main transmission lever 77, an auxiliary transmission lever 78, and a clutch lever 79 are arranged in order from the front.

  The main speed change lever 77 is used to move the traveling machine body 1 forward, stop, reverse and change its vehicle speed steplessly. The main transmission lever 77 according to the embodiment is configured to be able to tilt forward and backward along a guide groove 80 having a crank shape in plan view in the side panel body 76.

  Although details will be described later, when the main transmission lever 77 is tilted forward from a neutral (stopped) position in a substantially vertical posture, the traveling machine body 1 is configured to move forward by driving of the straight traveling HST transmission mechanism 35. . And it is comprised so that the advance speed of the traveling body 1 may become quick, so that the forward tilt angle of the main transmission lever 77 is large. On the contrary, when the main transmission lever 77 is tilted backward from the neutral position, the traveling machine body 1 is configured to move backward by driving the straight traveling HST transmission mechanism 35. And it is comprised so that the reverse speed of the traveling body 1 may become quick, so that the inclination angle to the back of the main transmission lever 77 is large.

  The sub-transmission lever 78 changes the sub-transmission mechanism 32 in the mission case 30 in accordance with the work state, thereby adjusting the output range of the hydraulic drive means 31 (the rotational direction and the rotational speed of the linear motor shaft 42). This is for setting and holding in four stages of low speed, medium speed, high speed and neutral. Similarly to the main transmission lever 77, the auxiliary transmission lever 78 is also configured to be tiltable back and forth.

  The clutch lever 79 serves as a single power transmission lever for the mowing unit 3 and a power transmission operation lever for the threshing unit 8, and is substantially L-shaped in plan view in the side panel body 76. The guide groove 81 is configured to be tiltable in the left and right and front and rear directions.

  When the clutch lever 79 of the embodiment is tilted to the left end position of the left and right groove portions 81a in the guide groove 81, both the mowing clutch and the threshing clutch (both not shown) are turned off, and the right end position (the front and rear groove portions 81b of the left and right groove portions 81b). When it is tilted to the rear end position), only the threshing clutch is engaged, and when it is tilted to the front end position of the front / rear groove 81b, both clutches are engaged.

  On the side panel body 76, various switches for operation and a plurality of dials for setting are also arranged. In the embodiment, the vehicle speed switch 82, the load factor setting dial 83, the automatic cutting height switch 84, the cutting height setting dial 85, and the automatic horizontal switch 86 are located in front of the main transmission lever 77 in the side panel body 76. , And an inclination setting dial 87 are arranged.

  The vehicle speed switch 82 is for operating on / off of the vehicle speed control that decelerates the vehicle speed when the engine 6 is overloaded and keeps the rotational drive of the mowing unit 3 and the threshing unit 8 constant. The load factor setting dial 83 is used to set and operate the set load factor LFa of the engine 6 during vehicle speed control. Although details will be described later, in the embodiment, when the load factor LF of the engine 6 is equal to or higher than the set load factor LFa, the vehicle speed in the forward direction of the traveling machine body 1 is set to be forcibly decelerated.

  Here, the engine load factor LF will be described. The engine load factor LF is defined as the ratio of the engine load during the cutting and threshing operation, with the engine load detected by the rack position sensor 200 described later as 100%. It is calculated. The engine load factor LF in the idling state becomes 0 (zero). The load factor setting dial 83 is configured to be able to arbitrarily adjust the set load factor LFa in the range of 70 to 100%.

  Although details will be described later, in the embodiment, when the set load factor LFa is determined, the corresponding return load factor LFb is automatically set. The return load factor LFb is a value (LFb (%) = LFa−α) smaller than the set load factor LFa by a predetermined rate. If the engine load factor LF becomes equal to or lower than the return load factor LFb during forced deceleration in the vehicle speed control, the vehicle speed in the forward direction of the traveling machine body 1 is directed toward the original vehicle speed corresponding to the forward tilting operation position of the main transmission lever 77. It is set to increase speed.

  The automatic cutting height switch 84 is for operating on / off of automatic cutting height control for maintaining the cutting unit 3 at a predetermined cutting height position. The cutting height setting dial 85 is used to set and operate the cutting height position during automatic cutting height control. The automatic horizontal switch 86 is for operating on / off of automatic horizontal control for maintaining the traveling machine body 1 in a horizontal horizontal posture. The tilt setting dial 87 is for setting and operating the left and right tilt angle of the traveling machine body 1.

  Further, a constant rotation control switch 88, an accelerator dial 89, a reel height adjustment dial 90, a reel speed change automatic switch 91, and the like are disposed at a position behind the main speed change lever 77 in the side panel body 76.

  The constant rotation control switch 88 is for operating on / off of constant rotation control for keeping the rotation speed of the engine 6 constant. The accelerator dial 89 is for adjusting the rotational speed of the engine 6. The reel height adjustment dial 90 is for adjusting the height position of the scraping reel 18 of the cutting unit 3. The reel speed change automatic switch 91 is for operating a mode for automatically adjusting the rotational speed of the scraping reel 18 in accordance with the vehicle speed of the traveling machine body 1.

  On the lower surface side of the control seat 70, a seat switch 92 for detecting whether an operator is sitting on the control seat 70 is disposed. On the lower surface side of the step plate 93 located between the control seat 70 and the steering handle 73, a pair of left and right step switches 94 for detecting whether or not the operator's feet are placed on the step plate 93 are provided. Has been placed.

  The seat switch 92 and both step switches 94 correspond to presence detecting means for detecting whether or not there is an operator in the control unit 5. When at least one of the seat switch 92 and the both step switches 94 is turned on and operated, the engine 6 is allowed to start and the power transmission from the engine 6 to the traveling unit and the working unit is permitted. Yes. Further, when all of the seat switch 92 and both step switches 94 are turned off, the driving of the engine 6 is stopped, or the power transmission from the engine 6 to the traveling unit and the working unit is automatically cut off. Is set to Note that at least one of the switches 92 and 94 may be provided.

(4). Connection structure between main transmission lever and steering handle and hydraulic drive means Next, a connection structure between the main transmission lever and steering handle and the hydraulic drive means will be described with reference to FIGS.

  A main speed change lever 77 as a speed change operation means is linked to a mechanical switching means 100 disposed in the steering column 71 via a relay link mechanism 95. Further, the handle shaft 72 of the steering handle 73 is also linked to the mechanical switching means 100.

The mechanical switching means 100 of the embodiment includes:
1. When the steering handle 73 is rotated to a position other than the neutral position while the main speed change lever 77 is tilted to a position other than the neutral position, the traveling machine body 1 moves to the left with a smaller turning radius as the rotation operation amount increases. Alternatively, the vehicle speed of the traveling machine body 1 (turning speed when moving forward and backward) decreases as the turning radius decreases and the turning radius decreases.
2. Even when the main transmission lever 77 is tilted in either the forward or backward direction, the turning operation direction of the steering handle 73 coincides with the turning direction of the traveling machine body 1 (the steering handle 73 is turned to the right). If it is turned, the traveling machine body 1 turns to the right, and if the steering handle 73 is turned to the left, the traveling machine body 1 turns to the left)
3. If the main transmission lever 77 is in the neutral position, it does not function even if the steering handle 73 is operated.
In order to execute various operations, the operating force from the main transmission lever 77 and the steering handle 73 is appropriately converted and transmitted to the vertically long double shaft 101 that is rotatably arranged at the lower end of the steering column 71. Is configured to do.

  The mechanical switching means 100 itself is not directly related to the present invention and will not be described in detail. However, if necessary, refer to Japanese Patent Application Laid-Open No. 2002-274421.

  The double shaft 101 associated with the mechanical switching means 100 is formed in a vertically long concentric shape by a straight-moving outer cylinder shaft 102 and a turning inner shaft 103 that can be rotated independently of each other. The rectilinear outer cylinder shaft 102 is linked to a rectilinear rotation shaft 105 protruding forward from the front surface of the mission case 30 via a rectilinear link mechanism 104. On the other hand, the turning inner shaft 103 is coupled to a turning rotation shaft 107 protruding forward from the front surface of the mission case 30 via a turning link mechanism 106.

  Here, the rectilinear rotation shaft 105 is for adjusting the inclination angle of the rotary swash plate of the first hydraulic pump 36 in the rectilinear HST transmission mechanism 35, and the shift output of the rectilinear HST transmission mechanism 35. Functions as an adjustment unit that adjusts The turning shaft 107 for turning is used to adjust the inclination angle of the rotary swash plate of the second hydraulic pump 39 in the turning HST transmission mechanism 38, and adjusts the shift output of the turning HST transmission mechanism 38. Functions as a control unit.

  The straight-travel link mechanism 104 is a straight-travel link projectingly provided on a lateral support shaft 110 and a straight-travel outer cylinder shaft 102 that are rotatably inserted into a support tube 109 fixed to the upper surface of the mission case 30 via a bracket 108. A straight relay rod 113 that connects the rotary arm 111 and the first straight swing arm 112 fixed to one end (right end in the embodiment) of the horizontal support shaft 110 and the other end of the horizontal support shaft 110 (the embodiment). In this case, a linearly-moving interlocking rod 116 that connects a linearly-moving second swinging arm 114 fixed to the left end) and a linearly-moving operating arm 115 attached to the linearly-rotating shaft 105 is provided.

  One end portion (front end portion in the embodiment) of the rectilinear relay rod 113 is pivotally attached to a rectilinear pivot arm 111 on the rectilinear outer cylinder shaft 102 side so as to be pivotable by a longitudinal pivot pin 117. Yes. The other end portion (rear end portion in the embodiment) of the rectilinear relay rod 113 is pivoted to the first rectilinear swing arm 112 on the side support shaft 110 side via a pivot pin 118 that is laterally directed laterally. It is worn.

  One end portion (upper end portion in the embodiment) of the straight interlocking rod 116 is pivotally attached to the second straight swing arm 114 on the side of the lateral support shaft 110 so as to be rotatable by left and right laterally attached pivot pins 119. Yes. The other end portion (lower end portion in the embodiment) of the rectilinear interlocking rod 116 is pivotally attached to a rectilinear operation arm 115 on the rectilinear rotation shaft 105 side via a pivoting pin 120 that is oriented in the front-rear and lateral directions. ing.

  When the main transmission lever 77 is tilted forward from the neutral position, the mechanical switching means 100 moves the outer cylinder shaft 102 for rectilinear movement and the pivot arm 111 for rectilinear movement around the inner shaft 103 for rotation through the relay link mechanism 95. By integrally rotating in the direction of the arrow SA, the straight traveling relay rod 113 is pulled forward (moved), and the first straight swing arm 112, the lateral support shaft 110, and the second straight swing. The arm 114 rotates integrally in the direction of the arrow SB around the lateral support shaft 110.

  Then, when the second swing arm 114 for rectilinear movement lifts the interlocking rod 116 for rectilinear movement by the rotational movement in the direction of the arrow SB, the operation arm 115 for rectilinear movement, and hence the rotation shaft 105 for rectilinear advance, moves in the direction of the arrow SC (forward increase It rotates in the speed direction (or the reverse deceleration direction, see FIGS. 5 and 8). As a result, the traveling machine body 1 performs the forward movement in proportion to the forward tilting operation amount of the main transmission lever 77.

  On the other hand, when the main transmission lever 77 is tilted backward from the neutral position, the mechanical switching means 100 moves the straight cylinder shaft 102 and the straight rotation arm 111 in the direction of the arrow SD via the relay link mechanism 95. By rotating integrally, the rectilinear relay rod 113 moves rearward, and the first rectilinear swing arm 112, the lateral support shaft 110, and the second rectilinear swing arm 114 are opposite to the previous arrows. Rotates integrally in the SE direction.

  Then, when the second rectilinear swing arm 114 pushes down the rectilinear interlocking rod 116 by the rotational movement in the arrow SE direction, the rectilinear operation arm 115 and hence the rectilinear pivot shaft 105 are moved in the arrow SF direction (reverse increase). It rotates in the speed direction (or forward deceleration direction, see FIGS. 5 and 8). As a result, the traveling machine body 1 performs the reverse operation in proportion to the backward tilting operation amount of the main transmission lever 77.

  On the other hand, the turning link mechanism 106 includes a turning cylinder 121 that is rotatably fitted to a projecting portion of the lateral support shaft 110 from the support cylinder 109, and a turning turning arm that protrudes from the turning inner shaft 103. 122 and a pivot rod 124 for pivoting that connects the first pivot arm 123 for pivoting provided on the rotating cylinder 121 and a substantially L-shaped first rotating arm for protruding that is provided on the rotating cylinder 121. 2 is provided with a turning interlocking rod 127 that connects a swing arm 125 and a turning operation arm 126 attached to the turning shaft 107 for turning.

  One end portion (front end portion in the embodiment) of the turning relay rod 124 is pivotally attached to the turning rotation arm 122 on the turning inner shaft 103 side so as to be turnable by a longitudinally attached pivot pin 128. . The other end portion (rear end portion in the embodiment) of the turning relay rod 124 pivots to the turning first swing arm 123 on the turning cylinder 121 side via a pivot pin 129 that is laterally laterally oriented. It is worn.

  One end portion (upper end portion in the embodiment) of the turning interlocking rod 127 is pivotally attached to the second swinging arm 125 for turning on the side of the turning cylinder 121 so as to be turnable by a pivoting pin 130 facing left and right laterally. Yes. The other end portion (the lower end portion in the embodiment) of the turning interlocking rod 127 is pivotally attached to the turning operation arm 126 on the turning turning shaft 107 side via a pivoting pin 131 that is oriented in the front-rear and lateral directions. ing.

  For example, when the steering handle 73 is turned to the left with the main speed change lever 77 tilted forward, the mechanical switching means 100 is connected to the turning inner shaft 102 and the turning turning arm via the handle shaft 72. By rotating 122 in the direction of the arrow TA, the turning relay rod 124 is pulled forward, and the first turning arm 123 for turning, the turning cylinder 121 and the second turning arm 125 for turning are moved. It rotates integrally in the direction of arrow TB around the horizontal support shaft 110.

  Then, the second swing arm 125 for turning pulls up the turning interlocking rod 127 by turning movement in the direction of arrow TB, so that the turning operation arm 126 and consequently the turning shaft 107 for turning turn in the direction of arrow TC (forward leftward rotation). Rotate in the turning direction (see FIG. 5). As a result, the traveling machine body 1 performs a left turn operation in proportion to the amount of leftward turning operation of the steering handle 73.

  In this case, the linear movement link mechanism 104 causes the linear movement rotation shaft 105 to move in the direction of the arrow SF (forward deceleration direction) in proportion to the amount of rotation of the steering handle 73 in the left direction by the action of the mechanical switching means 100. ), And the forward turning speed of the traveling machine body 1 is decelerated corresponding to the turning radius at that time.

  On the other hand, when the steering handle 73 is rotated to the right with the main transmission lever 77 tilted forward, the mechanical switching means 100 is connected to the turning inner shaft 103 and the turning rotation via the handle shaft 72. By rotating the moving arm 122 integrally in the direction of the arrow TD, the turning relay rod 124 moves rearward, and the first turning arm 123 for turning, the turning cylinder 121, and the second turning arm for turning. 125 rotates integrally in the direction of the arrow TE opposite to the previous one.

  Then, the turning swing arm 125 pushes down the turning interlocking rod 127 by the turning movement in the direction of the arrow TE, so that the turning operation arm 126 and the turning turning shaft 107 are moved in the direction of the arrow TF (forward right). It rotates in the turning direction (see FIG. 5). As a result, the traveling machine body 1 performs a right turn operation in proportion to the amount of turning operation of the steering handle 73 in the right direction.

  Also in this case, the linear link mechanism 104 causes the linear rotation shaft 105 to move in the direction of the arrow SF (forward deceleration) in proportion to the amount of rotation of the steering handle 73 in the right direction by the action of the mechanical switching means 100. The forward turning speed of the traveling machine body 1 is decelerated corresponding to the turning radius at that time.

  When the steering handle 73 is turned left and right with the main transmission lever 77 tilted rearward, the operations of the turning link mechanism 106 and the straight traveling link mechanism 104 are opposite to those described above. That is, the operation of both link mechanisms 106 and 104 during forward left turn is the same as that during reverse right turn, while the operation of both link mechanisms 106 and 104 during forward right turn is the same as that during reverse left turn. Is set to

  As shown in FIGS. 6 and 7, the rectilinear rotation shaft 105 has a rectilinear detent for holding the rotary swash plate of the first hydraulic pump 36 in the neutral position when the main transmission lever 77 is in the neutral position. Means 132 are attached. Similarly, a turning detent means 133 for holding the rotating swash plate of the second hydraulic pump 39 in the neutral position when the steering handle 73 is in the neutral position is attached to the turning shaft 107 for turning. Yes.

  As is clear from FIG. 6, the straight detent means 132 and the turning detent means 133 are arranged symmetrically and basically have the same configuration. In the straight detent means 132, a substantially cylindrical boss member 134 is fitted on the straight rotation shaft 105 as an adjustment portion of the straight HST transmission mechanism 35 so as to rotate integrally ( (See FIG. 7). A midway portion of the straight advance detent rod 135 formed in a substantially Y-plate shape is fixed to the front end portion of the straight advance rotation shaft 105 with a nut 136.

  A corner portion of a neutral holding arm 138 formed in a substantially L-shape is pivotally supported by a pivot shaft 137 projecting from a position near the left and right center of the mission case 30. A neutral holding roller 139 that is in contact with a neutral holding cam surface 135a formed on the upper end surface of the straight advance detent rod 135 is rotatably attached to the tip of the lateral arm portion 138a of the neutral holding arm 138. The neutral holding roller 139 is configured to always press and contact the neutral holding cam surface 135a of the straight advance detent rod 135 by the elastic biasing force of the biasing spring 140. The urging spring 140 according to the embodiment is mounted between the vertical arm portion 138b of the neutral holding arm 138 for straight movement and the vertical arm portion 158b (details will be described later) of the neutral holding arm 158 for turning. Has been.

  On the other hand, a corner portion of a substantially L-shaped straight advance operation arm 115 and a stopper plate 142 are fixed to a cylindrical member 141 that is rotatably fitted in the middle portion of the boss member 134. In the rectilinear operation arm 115, the distal end of the lateral arm portion 115a is pivotally attached to the other end portion (lower end portion in the embodiment) of the rectilinear interlocking rod 116 by a pivoting pin 120 that is front-rear and laterally oriented. . The vertical arm 115b of the straight operation arm 115 extends so as to overlap the vertical hook 135b of the straight detent rod 135 in a front view.

  A torsion spring 143 as return biasing means is fitted on the outer peripheral portion of the cylindrical member 141. Both end portions of the torsion spring 143 extend downward while intersecting, and sandwich the vertical arm portion 115b of the straight advance operation arm 115 and the vertical flange portion 135b of the straight advance detent rod 135.

  It should be noted that a pair of stopper receivers for restricting the rotation of the rectilinear detent rod 135 and the rectilinear operation arm 115 about the rectilinear rotation shaft 105 are provided on the left and right sides of the vertical rod portion 135b of the rectilinear detent rod 135. 144 is arranged. These stopper receivers 144 are fixed to the lower part of the front surface of the stopper plate 142. When the contact body 145 projecting rearward from the vertical flange 135b hits each stopper receiving body 144, the straight detent bar 135 and the straight operation arm 115 do not rotate more than a predetermined angle around the straight rotation shaft 105. So that it is regulated.

  A main shift position sensor 147 serving as a saddle position detecting means having a sensing arm 148 that can be turned up and down is attached to the bracket 146 disposed on the front side of the mission case 30. The main shift position sensor 147 is configured so that the rotation position (rotation angle) of the straight travel detent rod 135 is determined based on the rotation angle of the sensing arm 148 by contact with the operating pin 149 provided at the upper end of the straight travel detent rod 135. ), And a potentiometer type that detects the tilt angle of the rotary swash plate in the first hydraulic pump 36 and the tilt operation amount of the main transmission lever 77.

  In the turning detent means 133, a substantially cylindrical boss member (not shown) is fitted on the turning rotation shaft 107 as the adjusting portion of the turning HST transmission mechanism 38 so as to rotate integrally. Has been. A midway portion of the turning detent rod 155 formed in a substantially Y-plate shape is fixed to the distal end portion of the turning shaft 107 for turning by a nut 156.

  A corner portion of a neutral holding arm 158 formed in a substantially L-shape is pivotally supported by a pivot shaft 157 projecting from a position near the left and right center in the mission case 30. A neutral holding roller 159 that is in contact with a neutral holding cam surface 155a formed on the upper end surface of the turning detent rod 155 is rotatably attached to the tip of the lateral arm portion 158a of the neutral holding arm 158. The neutral holding roller 159 is configured to always press and contact the neutral holding cam surface 155a of the turning detent rod 155 by the elastic biasing force of the biasing spring 140.

  On the other hand, a corner portion of a substantially L-shaped turning operation arm 126 and a stopper plate 162 are fixed to a cylindrical member (not shown) that is rotatably fitted in the middle portion of the boss member. . In the turning operation arm 126, the distal end of the horizontal arm portion 126a is pivotally attached to the other end portion (the lower end portion in the embodiment) of the turning interlocking rod 127 with a pivoting pin 131 that is oriented in the front-rear and lateral directions. . The vertical arm portion 126b of the turning operation arm 126 extends so as to overlap the vertical hook portion 155b of the turning detent rod 155 in a front view.

  A torsion spring 163 as return biasing means is fitted on the outer peripheral portion of a cylindrical member (not shown). Both end portions of the torsion spring 163 extend downward while intersecting, and sandwich the vertical arm portion 126b of the turning operation arm 126 and the vertical hook portion 155b of the turning detent rod 155.

  Note that a pair of stopper receivers for restricting the turning of the turning detent rod 155 and the turning operation arm 126 about the turning rotary shaft 107 are provided on the left and right sides of the vertical rod portion 155b of the turning detent rod 155. 164 is arranged. These stopper receivers 164 are fixed to the lower part of the front surface of the stopper plate 162. When the contact body 165 projecting rearward from the vertical flange portion 155b hits each stopper receiving body 164, the turning detent rod 155 and the turning operation arm 126 do not turn around the turning shaft 107 for turning more than a predetermined angle. So that it is regulated.

(5). Next, an interlocking structure between the electric motor and the hydraulic drive means will be described with reference to FIGS.

  An electric motor 170 as a speed change actuator is connected to an operation system (relay link mechanism 95) from the main speed change lever 77 toward the straight movement turning shaft 105 on the straight movement turning shaft 105 which is an adjustment portion of the straight advance HST transmission mechanism 35. The mechanical switching means 100 and the straight traveling link mechanism 104) are associated with each other via a link system 171 of a different system.

  In the embodiment, an electric motor 170 capable of forward and reverse rotation as a speed change actuator is screwed to the back side of the bracket plate 169 fixed to the support cylinder 109 on the mission case 30. A pinion gear 173 as a drive side gear is fixed to the motor output shaft 172 of the electric motor 170. On the other hand, at a position below the electric motor 170 on the back surface of the bracket plate 169, a sector gear 174 as a driven gear is rotated by a pivot 175 extending in parallel with the rectilinear pivot 105 and the pivot pivot 107. It is pivotally attached. By engaging both the gears 173 and 174, the rotational driving force from the electric motor 170 can be transmitted to the rectilinear rotation shaft 105 via the linkage mechanism 171.

  The linkage mechanism 171 includes a vertical rod portion 135b of a straight detent rod 135 as an adjustment member, a relay arm 176 as a drive member fixed to the sector gear 174 and its pivot 175, a vertical rod portion 135b and a relay arm 176. And a connecting rod 177 for rotating in conjunction with each other.

  In the embodiment, the vertical hook 135b of the straight detent bar 135 extends longer than the vertical bar 155b of the turning detent bar 155. A lower end portion of the vertical flange portion 135b of the straight traveling detent rod 135 is pivotally attached to one end portion of the linkage rod 177 by a longitudinally attached pivot pin 178.

  A guide slot 179 extending in the longitudinal direction is formed at the other end of the linkage rod 177 on the relay arm 176 side. The other end of the linkage rod 177 and the relay arm 176 are connected via a pivot pin 180 inserted in the guide slot 179. The combination of the pivot pin 180 on the relay arm 176 side and the guide slot 179 of the linkage rod 177 corresponds to an interlocking switching unit that allows or cancels the interlocking of the linear shaft 105 and the electric motor 170. Is.

  The relay arm 176 and the sector gear 174 are driven by the rotation of the pinion gear 173 by the electric motor 170 from the initial position shown in FIGS. 6 and 8 (the standby position when the vehicle speed control is not executed) to the maximum shown in FIG. In the range up to the forced deceleration position, it is configured to be rotatable around the pivot 175.

  As shown in FIGS. 6 to 11, a gear position sensor 182 as a gear position detecting means having a sensing arm 183 that can be turned up and down is attached to the bracket plate 169 fixed to the support cylinder 109 on the mission case 30. It has been. This gear position sensor 182 is a potentiometer that detects the position of the sector gear 174 from the rotation angle of the sensing arm 183 caused by contact with the operation pin 185 of the rotation plate 184 fixed to the pivot 175 separately from the relay arm 176. Of the formula.

  A pair of stopper shafts 181 for restricting the rotation of the sector gear 174 around the pivot 175 is disposed on the left and right sides of the sector gear 174 in the bracket plate 169. The sector gear 174 is regulated so that the sector gear 174 and the relay arm 176 do not rotate beyond the range of the initial position to the maximum forced deceleration position around the pivot 175 by the side edge of the rotation direction in the sector gear 174 hitting each stopper shaft 181. ing.

  As described above, when the electric motor 170 is associated with the rectilinear rotation shaft 105 via the linkage mechanism 171 different from the operation system from the main transmission lever 77, the operation system and the electric motor 170 are associated with each other. And do not need to be linked directly. In other words, it is not necessary to provide the electric motor 170 in the operation system.

  For this reason, restrictions such as the layout of the electric motor 170 and the linkage mechanism 171 are remarkably reduced, and the degree of freedom in designing an interlocking structure for vehicle speed control is improved. As a result, the interlocking structure can be simplified and the number of parts can be reduced, which can contribute to the reduction of manufacturing costs.

  When the straight detent rod 135 is in the neutral position and the sector gear 174 and the relay arm 176 are in the initial position (see FIG. 6), that is, when the main transmission lever 77 is in the neutral position and the traveling machine body 1 is stopped. Is set such that the pivot pin 180 fixed to the relay arm 176 is positioned at the longitudinal center of the guide slot 179 in the linkage rod 177.

  When the vehicle speed switch 82 is in the off state (vehicle speed control is not executed), the interlocking switching means composed of the pivot pin 180 and the guide groove hole 179 rotates the rotation shaft 105 for rectilinear movement and the main operation. The release lever 77 is set in a release state that does not prevent the tilting operation of the transmission lever 77.

  In other words, when the vehicle speed switch 82 is in the off state, the sector gear 174 and the relay arm 176 are always held at the initial positions. In this state, the relay arm can be operated even if the main transmission lever 77 is tilted in any direction. The long diameter dimension of the guide slot 179 is set so that the pivot support pin 180 on the 176 side does not hit both edges in the longitudinal direction of the guide slot 179. That is, when the main speed change lever 77 is tilted when the vehicle speed control is not being executed, the pivot pin 180 on the relay arm 176 side slides within the guide groove hole 179 of the linkage rod 177, but the guide groove The hole 179 becomes idle without being caught on both edges in the longitudinal direction, and the presence of the linkage mechanism 171 does not hinder the tilting operation of the main transmission lever 77.

  When the main transmission lever 77 is tilted forward from the neutral position, the linear operation arm 115 rotates in the arrow SC direction (forward acceleration direction) via the linear link mechanism 104. Since the vertical arm 115b of the straight operation arm 115 is sandwiched together with the vertical hook 135b of the straight detent rod 135 at both ends of the torsion spring 143, it is fixed to the straight detent rod 135 and this. The rectilinear rotation shaft 105 also rotates in the arrow SC direction (forward acceleration direction) (see FIG. 8). As a result, the vehicle speed in the forward direction of the traveling machine body 1 is increased.

  When the detent rod 135 for rectilinear movement rotates in the direction of the arrow SC (forward speed increasing direction) around the rectilinear rotation shaft 105, the linkage rod 177 is directed obliquely upward to the pivot pin 180 on the relay arm 176 side. Be pushed to. For this reason, the pivot pin 180 slides relatively toward the lower edge of the guide slot 179 in the linkage rod 177 (the edge near the vertical flange 135b) (see FIG. 8).

  At this time, depending on the forward tilting operation amount of the main speed change lever 77, a large gap is opened between the pivot pin 180 and the lower edge portion of the guide slot 179 (see gap D in FIG. 8). If the gap D is large, when the deceleration control is executed, the movement time is increased by the size of the gap D until the pivot pin 180 hits the lower edge of the guide slot 179 by driving the electric motor 170. For this reason (because a time lag occurs), it is considered that the efficiency of the deceleration control is not so good.

  Therefore, in the embodiment, the distance between the pivot pin 180 and the lower edge portion of the guide slot 179 is determined by the controller 190 described later from the detection information of the main shift position sensor 147 and the detection information of the gear position sensor 182 at this time. (Gap D) is obtained.

  Then, the electric motor 170 is operated based on the calculation result, and the sector gear 174 and the relay arm 176 are rotated in the direction of the arrow RE by the rotational drive of the pinion gear 173 by the electric motor 170 to guide the pivot pin 180. It is set in an allowable state in which it is slid so as to be as close as possible to the lower edge of the slot 179 (see FIG. 9). The distance between the pivot pin 180 and the lower edge of the guide slot 179 after the slide movement is set to such a size that a slight gap (for example, several mm) is opened.

  When the vehicle speed switch 82 is in the on state (vehicle speed control is being executed), when the pinion gear 173 is driven to rotate by the electric motor 170, the relay arm 176 and the sector gear 174 are further rotated in the direction of the arrow RE. (Refer to FIG. 10) The pivot pin 180 on the relay arm 176 side hits the lower edge of the guide slot 179 in the linkage rod 177, and pushes the linkage rod 177 in the direction of an arrow DOWN that is inclined downward toward the straight detent rod 135. Then, the straight travel detent rod 135 and thus the straight travel rotation shaft 105 are rotated in the direction of the arrow SF (forward deceleration direction). As a result, the vehicle speed in the forward direction of the traveling machine body 1 is automatically reduced.

  In this case, before the pivot pin 180 hits the lower edge of the guide slot 179 (before the vehicle speed of the traveling machine body 1 is reduced), the pivot pin 180 is below the guide slot 179 by driving the electric motor 170. Since it is moved and held near the edge, when the relay arm 176 and the sector gear 174 are further rotated in the direction of the arrow RE, the power of the electric motor 170 is transmitted via the linkage mechanism 171. The straight detent rod 135 and thus the straight traveling pivot shaft 105 are quickly transmitted. For this reason, the time lag from when the electric motor 170 is driven to when the traveling machine body 1 starts the deceleration operation becomes extremely short. Therefore, if the engine 6 is overloaded during the execution of the vehicle speed control, it is possible to quickly shift to the deceleration operation of the traveling machine body 1 and to execute the efficient vehicle speed control.

  In the embodiment, when the relay arm 176 and the sector gear 174 are rotated to the maximum forced deceleration position, the straight advance detent rod 135 returns to the neutral position (see FIG. 10), and the straight advance rotary shaft 105 and the first The rotary swash plate of the hydraulic pump 36 is configured to move to the neutral position. For this reason, when the engine 6 is overloaded during the execution of the vehicle speed control, the traveling machine body 1 can be decelerated to a state where it substantially stops.

  According to such a configuration, when the engine 6 is overloaded, the straight drive HST transmission mechanism 35 and the power from the engine 6 are not used for the forward movement of the traveling machine body 1, and the reaping unit 3 and the threshing unit 8 are driven to rotate. Therefore, even with an ordinary combine with a heavy load fluctuation, clogging of the cutting part 3, reduction in rotation of the threshing part 8, and engine stop can be reliably suppressed, and the effectiveness of vehicle speed control (stable Improved).

  The vertical flange 135b of the straight detent rod 135 and the vertical arm 115b of the linear operation arm 115 are sandwiched together at both ends of the torsion spring 143, but the elastic restoring force of the torsion spring 143 is linear. This is much smaller than the force for moving the straight link mechanism 104 including the operation arm 115.

  For this reason, when the vehicle speed in the forward direction of the traveling machine body 1 is decelerated during execution of the vehicle speed control, the straight detent rod 135 (and hence the straight rotation shaft 105) rotates in the direction of the arrow SF (forward deceleration direction). However, the straight advance operation arm 115 is held at a position corresponding to the forward tilt operation position of the main transmission lever 77 (see FIG. 10).

  Therefore, the rotational force of the straight travel detent rod 135 in the direction of the arrow SF (forward / deceleration direction) does not propagate to the main speed change lever 77 via the straight travel link mechanism 104 and the mechanical switching means 100, and the vehicle speed control is executed. Whenever the traveling machine body 1 is forcibly decelerated, there is no inconvenience that the main transmission lever 77 moves freely in front of the eyes.

  After the vehicle speed in the forward direction of the traveling machine body 1 is decelerated during the execution of the vehicle speed control, the relay arm 176 and the sector gear 174 are returned and rotated in the direction of the arrow BA by the rotational drive of the pinion gear 173 by the electric motor 170. The pivot pin 180 on the relay arm 176 side slides in the guide slot 179 of the linkage rod 177 and moves away from the lower edge of the guide slot 179 (see FIG. 11).

  As a result, there is room for the elastic restoring force of the torsion spring 143 to act as much as the pivot pin 180 moves away from the lower edge of the guide slot 179. With this elastic restoring force, the vertical arm in the straight operation arm 115 is provided. To the position of the section 115, the straight detent rod 135 and, therefore, the rectilinear rotation shaft 105 returns and rotates at a moderate speed to return to the state shown in FIG.

  In this case, the linkage rod 177 is pushed in the upward arrow UP direction toward the pivot pin 180 on the relay arm 176 side by the return rotation of the straight detent rod 135 in the arrow SC direction, and a slight gap is formed. Needless to say, the lower edge of the guide slot 179 approaches the pivot pin 180 to the extent that it opens.

  In the embodiment, the electric motor 170 is set to rotate the pinion gear 173 stepwise by an appropriate angle step by step, and thus rotate the relay arm 176 and the sector gear 174 stepwise in the direction of the arrow BA. For example, after the electric motor 170 rotates the pinion gear 173 by an appropriate angle, a cycle of waiting for a time TM (for example, 0.5 seconds) is repeated.

  Then, if the pivot pin 180 on the relay arm 176 side is separated from the lower edge portion of the guide slot 179, the elastic restoring force of the torsion spring 143 returns and rotates the straight detent rod 135 and hence the straight rotation shaft 105. . That is, following the stepwise rotation of the relay arm 176 and the sector gear 174 in the direction of the arrow BA, the straight-ahead detent rod 135 and the straight-ahead rotation shaft 105 return and rotate in the direction of the arrow SC. As a result, the vehicle speed in the forward direction of the traveling machine body 1 is gradually increased to return, not at a stroke.

  The final return rotation position of the straight detent rod 135 is the original position corresponding to the forward tilt operation position of the main transmission lever 77. Therefore, finally, the vehicle speed in the forward direction of the traveling machine body 1 is increased stepwise to the original vehicle speed corresponding to the forward tilt operation position of the main transmission lever 77.

  According to this configuration, the operator does not need to repeat the forward tilting operation of the main transmission lever 77 in order to restore the vehicle speed after the vehicle speed in the forward direction of the traveling machine body 1 is forcibly decelerated by the vehicle speed control. For this reason, the operation frequency of the main transmission lever 77 can be reduced, and the operation burden on the operator can be reduced.

  Further, since the electric motor 170 is driven stepwise when the rectilinear rotation shaft 135 is rotated in the direction of the arrow SC, the vehicle speed in the forward direction of the traveling machine body 1 corresponds to the forward tilt operation position of the main transmission lever 77. It can be gradually increased toward the original vehicle speed. For this reason, the traveling machine body 1 is safe without speeding up rapidly. In addition, since the return vehicle speed does not exceed the speed corresponding to the forward tilting operation position of the main transmission lever 77, it is possible to reliably avoid the possibility that the vehicle speed will become abnormally high, and to ensure sufficient safety.

  In the embodiment, even when the vehicle speed control is being executed, the main transmission lever 77 is tilted backward to move the straight detent rod 135 and the straight rotation shaft 105 in the direction of the arrow SF (reverse acceleration direction). ) (When the traveling machine body 1 is retracted), the electric motor 170 is configured not to be driven.

(6). Configuration of Control Unit Next, a configuration for executing vehicle speed control and the like of the traveling aircraft will be described with reference to FIGS. 12 and 13.

  Although not shown in detail, a controller 190 such as a microcomputer as vehicle speed control means mounted on the traveling machine body 1 is a central processing unit 191 (CPU) for executing various arithmetic processes and controls, a control program and data. Read-only memory 192 (ROM) for storing data, read / write memory 193 (RAM) as needed to temporarily store control programs and data, clocks as timer functions, input / output devices (sensors, actuators, etc.) ) And an input / output interface (not shown) for exchanging data.

  In the ROM 192 of the controller 190, a detection value V (vehicle speed of the traveling vehicle body 1) of a vehicle speed sensor 197 provided in association with the brake shaft 48 (see FIG. 2) and vehicle speed control execution for the vehicle speed V are executed. A relational expression or a control map showing a relationship with the deceleration amount vr at the time is stored in advance.

  An example of the relational expression in this case is vr = A × V. Here, A is a proportionality constant. FIG. 13 shows a case where such a relational expression is used as a control map. In FIG. 13, the vehicle speed V of the traveling machine body 1 is taken on the horizontal axis, and the deceleration amount vr is taken on the vertical axis.

  As shown in FIG. 13, the proportionality constant A is a value greater than 0 and 1 or less (0 <A ≦ 1), and the relationship between the vehicle speed V and the deceleration amount vr is expressed by a straight line having a positive slope. Yes. In other words, the vehicle speed V and the deceleration amount vr have a relationship that the deceleration amount vr increases (decelerates greatly) as the vehicle speed V increases (increases). Since 0 <A ≦ 1, the deceleration amount vr does not exceed the vehicle speed V. In other words, the traveling machine body 1 does not decelerate excessively when the vehicle speed control is executed. Note that data of a pair of the vehicle speed V and the corresponding deceleration amount vr may be stored in the ROM 192 of the controller 190 as a table map.

  The input interface of the controller 190 includes, for example, an automobile speed switch 82, a load factor setting dial 83, an automatic cutting height switch 84, a cutting height setting dial 85, an automatic horizontal switch 86, an inclination setting dial 87, a constant rotation control switch 88, Accelerator dial 89, reel height adjustment dial 90, reel shift automatic switch 91, main shift position sensor 147, sub-shift lever 78, cutting clutch sensor for detecting the on / off state of the cutting clutch for power transmission to the cutting unit 3 194, In order to detect the rotational speed of the threshing clutch sensor 195, the gear position sensor 182, the seat switch 92, the left and right step switches 94, and the engine 6 for detecting the on / off state of the power threshing clutch for the threshing unit 8. Engine rotation sensor 196, vehicle speed sensor 97, a rack position sensor 200 as a load detection means for detecting the fuel supply amount from the rack position of the fuel injection pump 199 with an electronic governor 198 as a fuel supply means, a power switch 201 for turning on and off the power of the entire combine, and the like. It is connected.

  On the other hand, the output interface of the controller 140 includes, for example, an electronic governor 198 that adjusts and controls the load (output) of the engine 6, and a rack actuator that adjusts the rack position of the fuel injection pump 199 so that the rotational speed of the engine 6 becomes a predetermined value. 202, an electric motor 170 as a speed change actuator, a liquid crystal display device 75, and the like are connected.

(7). Next, an example of vehicle speed control will be described with reference to FIGS. 14 and 15.

The controller 190 as vehicle speed control means is
1. When the engine load factor LF obtained from the detection information of the rack position sensor 200 becomes equal to or greater than the set load factor LFa, the rectilinear rotation shaft 105 of the rectilinear HST transmission mechanism 35 is moved in the direction of the arrow SF (forward) through the linkage mechanism 171. Drive the electric motor 170 to rotate in the deceleration direction),
2. 1 above. When the engine load factor LF is larger than the return load factor LFb and smaller than the set load factor LFa (LFb <LF <LFa), the straight rotation shaft 105 of the straight traveling HST transmission mechanism 35 is temporarily executed. To maintain the vehicle speed of the traveling aircraft 1 in the state at that time,
3. When the engine load factor LF becomes equal to or less than the return load factor LFb, the electric motor is configured such that the rectilinear rotation shaft 105 returns and rotates in the direction of the arrow SC (forward acceleration direction) toward the original state via the linkage mechanism 171. 170 is driven stepwise, and as a result, the rotational drive of the mowing unit 3 and the threshing unit 8 is kept constant.
The vehicle speed control is executed.

  Here, it is assumed that the vehicle speed switch 82 is set to the on state. Further, it is assumed that the set load factor LFa is preset by the load factor setting dial 83 and stored in the RAM 193 of the controller 190 together with the return load factor LFb.

  First, following the start of the vehicle speed control, it is determined whether or not the cutting clutch is engaged based on the detection information of the cutting clutch sensor 194 (step S1). When it is determined that the mowing clutch is in the disengaged state (S1: NO), it means that the combine is not performing the mowing and threshing operation, and the process returns as it is.

  When it is determined that the mowing clutch is in the engaged state (S1: YES), it means that power is transmitted to at least the mowing unit 3, and the mowing and threshing operation is being executed or is in a ready state. Accordingly, it is next determined whether or not at least one of the sheet switch 92 and the left and right step switches 94 is in the on state (step S2). When it is determined that the seat switch 92 and both the left and right step switches 94 are all turned off (S2: NO), it means that there is no operator in the control unit 5, and thus the traveling machine body 1 is automatically in this state. In order to avoid executing the vehicle speed control for increasing or decreasing speed, the process returns as it is.

  When it is determined that at least one of the seat switch 92 and the left and right step switches 94 is in the on state (S2: YES), it means that there is an operator in the control unit 5, and then the main shift position sensor 147 Based on the detected information, it is determined whether or not the main transmission lever 77 is tilted forward (step S3). When it is determined that the main transmission lever 77 is not tilted forward (i.e., neutral or backward) (S3: NO), the traveling machine body 1 is stopped or moved backward, and this state It is unlikely that you will be mowing and threshing, so you will return.

  When it is determined that the main transmission lever 77 is tilted forward (S3: YES), the traveling machine body 1 is moving forward, and there is no hindrance to the execution of the vehicle speed control. A set load factor LFa that is a set value of the load factor setting dial 83, a return load factor LFb, a detected value of the vehicle speed sensor 197 (vehicle speed V of the traveling machine body 1), and a detected value of the rack position sensor 200 (engine load) Is read (step S4), and the current engine load factor LF is calculated based on the engine load (step S5).

  Next, it is determined whether or not the current engine load factor LF is equal to or greater than the set load factor LFa read in step S4 (step S6). When it is determined that the current engine load factor LF is smaller than the set load factor LFa (S6: NO), the load applied to the mowing unit 3, the threshing unit 8, and the engine 6 is small, and there is no problem in the mowing and threshing operation. Because there is, return as it is.

  When it is determined that the current engine load factor LF is equal to or greater than the set load factor LFa (S6: YES, refer to time T1 in FIG. 15 (the engine load factor at this time is LF1)), for example, a large amount of harvested cereals For example, the cutting part 3 and the threshing part 8 and thus the engine 6 are heavily loaded. If the mowing and threshing operation is continued in such a state, the engine 6 may stop due to overload (engine stop).

  Therefore, in this case, the vehicle speed V at the time of execution of the vehicle speed control is calculated from the vehicle speed V (indicated as V1 in FIG. 15) read at step S4 and the relational expression or control map stored in advance in the ROM 192 of the controller 190. A deceleration amount vr (= A × V) is calculated (step S7). Then, by driving the electric motor 170, the rectilinear rotation shaft 105 of the rectilinear HST transmission mechanism 35 is rotated in the direction of arrow SF (forward deceleration direction) via the linkage mechanism 171, so that the traveling direction of the traveling machine body 1 is increased. The vehicle speed V is decelerated by a deceleration amount vr in a predetermined time (denoted as V2 in FIG. 15), and the engine load factor LF is appropriately reduced in conjunction with this (step S8).

  If controlled in this way, if the vehicle speed V in the forward direction of the traveling machine body 1 is high, the engine load factor LF can be quickly lowered by greatly decelerating. If the vehicle speed V is low, the deceleration amount vr can be kept as small as possible to maintain the rotation of the cutting part and the threshing part, and thus maintain the efficiency of the cutting and threshing work. Therefore, it is possible to execute an appropriate vehicle speed control corresponding to the vehicle speed at that time, and to contribute to the efficiency of the cutting and threshing work.

  After the vehicle speed V in the forward direction of the traveling machine body 1 is decelerated by the deceleration amount vr, the detected value of the vehicle speed sensor 197 (vehicle speed V of the traveling machine body 1) and the detected value (engine load) of the rack position sensor 200 are again obtained. Reading (step S9), the current engine load factor LF is calculated based on the engine load (step S10).

  And it is discriminate | determined whether the engine load factor LF calculated | required by step S10 is below the reset load factor LFb read by step S4 (step S11). When it is determined that the engine load factor LF is greater than the return load factor LFb (S11: NO), it is then determined again whether or not the current engine load factor LF is greater than or equal to the set load factor LFa (step S12). .

  When it is determined that the engine load factor LF is equal to or higher than the set load factor LFa (S12: YES, refer to the time point T3 in FIG. 15), it means that the engine load has not yet decreased. Is newly calculated from the vehicle speed V at the time when the vehicle speed is read in and the relational expression or control map stored in advance in the ROM 192 of the controller 190 (step A). S13).

  Next, when the electric motor 170 is driven, the rectilinear rotation shaft 105 of the rectilinear HST transmission mechanism 35 is rotated in the direction of arrow SF (forward / deceleration direction) via the linkage mechanism 171, so that the traveling direction of the traveling machine body 1 is increased. The vehicle speed V is decelerated by the deceleration amount vr over a predetermined time, and in conjunction with this, the engine load factor LF is reduced again as appropriate (step S14). Then, the process returns to step S9. That is, as is clear from the series of steps S9 to S14, the forced deceleration operation of the traveling machine body 1 is repeated until the engine load factor LF becomes equal to or less than the set load factor LFa.

  By controlling in this way, the engine load factor LF can be reliably reduced by repeating the forced deceleration operation. Therefore, even in the case of a normal combine with a heavy load fluctuation, the cutting portion 3 is clogged, the threshing portion 8 is reduced in rotation, and the engine. It is effective in suppressing stops and can improve the effectiveness (stability) of vehicle speed control.

  When it is determined in step S12 that the engine load factor LF is smaller than the set load factor LFa (S12: NO), the engine load factor LF is larger than the return load factor LFb and smaller than the set load factor LFa. Therefore (LFb <LF <LFa, see time point T4 in FIG. 15), then, the rectilinear rotation shaft 105 of the rectilinear HST transmission mechanism 35 is held in position, and the vehicle speed V of the traveling machine body 1 is determined at that time (step The vehicle speed V read in S9 is maintained at the state indicated by V3 in FIG. 15 (step S16). Then return.

  With this control, if the engine load factor LF is larger than the return load factor LFb and smaller than the set load factor LFa when the vehicle speed control is executed, the traveling vehicle body 1 maintains the predetermined vehicle speed V at that time. I will run. Accordingly, fluctuations in the vehicle speed during execution of the vehicle speed control are suppressed as much as possible, and deterioration of the riding comfort during the execution of the control can be suppressed.

  Now, returning to step S11, when it is determined that the engine load factor LF is equal to or lower than the return load factor LFb (S11: YES), the engine load is sufficiently reduced, and the cutting and threshing operation is not hindered. This means that the process proceeds to step S15.

  In step S15, by the stepwise driving of the electric motor 170, the rectilinear rotation shaft 105 of the rectilinear HST transmission mechanism 35 is rotated stepwise in the direction of the arrow SC (forward deceleration direction), and the traveling machine body 1 is rotated. The vehicle speed V in the forward direction is gradually returned and increased toward the original vehicle speed V1 corresponding to the forward tilting operation position of the main transmission lever 77 (see after time T5 in FIG. 15), and then the process returns.

  In the embodiment, the electric motor 170 is referred to as a return speed increase corresponding to the speed increase amount corresponding to the rotation of the pinion gear 173 by an appropriate angle, and standby (vehicle speed holding) for a time TM (for example, 0.5 seconds). By repeating the cycle, the vehicle speed V in the forward direction of the traveling machine body 1 is set to be gradually increased (stepwise) toward the original vehicle speed V1.

  If such control is employed, the vehicle speed in the forward direction of the traveling machine body 1 is gradually increased and returned, not at a stretch. Therefore, the traveling machine body 1 is safe without being suddenly increased in speed.

(8). Others The present invention is not limited to the above-described embodiment, and can be embodied in various forms. For example, the present invention is not limited to the conventional combine as described above, but can be widely applied to various work vehicles such as agricultural machines such as a self-propelled self-removing combine and a tractor and special work vehicles such as a crane truck. . Moreover, although all the engines employ | adopted for the above-mentioned embodiment were a diesel type thing, a gasoline type engine may be sufficient. In this case, the fuel injection pump is arranged at the position of the throttle valve for fuel adjustment in the carburetor. As a means for adjusting the movement position of the throttle valve, an actuator such as an electromagnetic solenoid that rotates a valve operating shaft attached to the throttle valve may be employed. The movement position detecting means of the throttle valve (corresponding to the load detecting means described in the claims) may be a rotation angle sensor such as a potentiometer that detects the rotation angle of the throttle valve.

  In addition, the structure of each part is not limited to embodiment of illustration, A various change is possible in the range which does not deviate from the meaning of this invention.

It is a top view of a combine. It is a skeleton figure which shows the traveling drive system of a combine. It is a top view of a control part. It is a perspective view of a side column. It is explanatory drawing which shows typically the connection relation of a main speed-change lever, a steering handle, and a hydraulic drive means. It is a front view which shows the relationship between a detent means, a linkage mechanism, and an electric motor. FIG. 7 is a side sectional view taken along line VII-VII in FIG. 6. It is a figure which shows the state which rotated the detent rod for rectilinear advance in the forward acceleration direction. It is a figure which shows the state which made the pivot pin approach the lower edge part of a guide slot by the drive of an electric motor. It is a figure which shows the state which rotated the sector gear and the relay arm to the maximum forced deceleration position by the drive of the electric motor. It is a figure which shows the state which returned and rotated the sector gear and the relay arm in the forward acceleration direction by the drive of the electric motor. It is a functional block diagram of a controller. It is a figure of the control map which shows the relationship between the vehicle speed of a traveling body, and the deceleration amount. It is a flowchart which shows an example of vehicle speed control. It is a time chart which shows an example of vehicle speed control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Traveling machine body 2 Traveling crawler 5 Steering part 6 Engine 31 Hydraulic drive means 35 HST transmission mechanism for rectilinear advance 38 HST transmission mechanism for turning 77 Main shift lever 82 as gear shift operation means Automobile speed switch 100 Mechanical switching means 104 Straight advance Link mechanism 105 Straight rotation shaft 106 Swing link mechanism 107 Swing rotation shaft 115 Straight operation arm 116 Straight travel interlocking rod 132 Straight travel detent means 133 Turning detent means 135 Straight travel detent fence 135b As an adjustment member Vertical shaft portion 170 Electric motor 171 as a speed change actuator 173 Link mechanism 173 Sector gear 176 Sector gear 176 Relay arm 177 Link rod 179 Guide groove hole 180 Pivot pin 190 Controller as vehicle speed control means 198 Fuel injection pump 200 as fuel supply means Negative Rack position sensor as load detection means

Claims (3)

Related to hydraulic drive means for shifting power from an engine mounted on a traveling machine body, shift operation means for increasing / decreasing a shift output of the hydraulic drive means, and fuel supply means for the engine Load detecting means for detecting the load of the engine and decelerating the vehicle speed of the traveling vehicle body when the engine is overloaded, and when the overload is eliminated, the vehicle speed of the traveling vehicle body is directed toward the original vehicle speed before deceleration. A work vehicle equipped with vehicle speed control means for executing vehicle speed control to increase the return speed,
The adjustment unit for adjusting the shift output of the hydraulic drive means is associated with a shift actuator via a linkage mechanism that is separate from the operation system from the shift operation means toward the adjustment unit, The linkage mechanism includes interlocking switching means that allows or cancels the interlocking between the adjusting portion and the speed change actuator,
When the vehicle speed control is not being performed, the interlocking switching unit is set to a release state that does not interfere with the operation of the adjustment unit, and before the vehicle speed of the traveling machine body is decelerated during the execution of the vehicle speed control, A work vehicle configured such that the interlock switching unit is set in an allowable state in which the adjusting unit is operated in a deceleration direction by the power of the speed change actuator.   When the vehicle speed control means executes control for returning and increasing the vehicle speed of the traveling machine body, the vehicle speed control means gradually drives the speed change actuator when operating the adjusting portion of the hydraulic drive means in the speed increasing direction. The work vehicle according to claim 1, wherein the work vehicle is controlled so as to perform the following. The linkage mechanism includes an adjustment member that can rotate integrally with a rotation shaft as the adjustment portion, a drive member that can rotate about a pivot parallel to the rotation shaft by driving the speed change actuator, A linkage rod for rotating both the members in conjunction with each other;
A guide slot extending in the longitudinal direction of the linkage rod is formed at the end of the linkage rod on the drive member side, and the linkage rod and the drive member are pivots inserted into the guide slot. It is connected via a support pin, the guide slot and the pivot pin constitute the interlocking switching means,
Before the vehicle speed of the traveling machine body is decelerated during execution of the vehicle speed control, the pivot pin is moved to a position close to the edge of the guide slot near the adjustment member by driving the speed change actuator. The work vehicle according to claim 1, wherein the work vehicle is set so as to perform.

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