JP2008309175A - Transmission device for working vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission device for a working vehicle, enabling to contribute to improved operability of all kinds of working equipment including improved operability of vehicle speed control by actualizing the flexibility of stepwise set speed-change stages and improving a degree of freedom in arranging various kinds of operating tools on a cab. <P>SOLUTION: The transmission device for the working vehicle comprises a sub speed change part 38 for changing a driving speed zone for a travelling axle, a stepless speed change part 34 for steplessly changing the transmission ratio of the transmitting power, and a control part 90 for controlling the stepless speed change part 34 at a target transmission ratio and determining the target transmission ratio corresponding to a selected speed-change stage selected from a plurality of separately set speed-change stages. The control part 90 receives signals from speed increasing/reducing button switches B1, B2 to perform step-by-step increasing/reducing change processing of the selected speed-change stage corresponding to the speed increasing signal or the speed reducing signal and control the stepless speed change part 34 along the selected speed-change stage after changed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transmission for a work vehicle in which a continuously variable transmission is provided in a traveling transmission system and the vehicle speed is adjusted by the controller.

  As shown in Patent Document 1, by providing a continuously variable transmission mechanism, which is abbreviated as “HST transmission mechanism”, and a main transmission lever for operating the vehicle speed, the vehicle body is selected at a vehicle speed selected according to the lever position. 2. Description of the Related Art A transmission device for a work vehicle that travels is known.

This transmission can be switched to the vehicle speed intended by the operator in accordance with the operation of the main transmission lever via a control unit that drives and controls the trunnion shaft that adjusts the rotation ratio of the HST transmission mechanism.
JP 2002-250437 A

  However, since the work vehicle is configured to control the HST speed change mechanism so as to obtain a vehicle speed corresponding to the speed selected from the gear speed set by the lever guide of the main speed change lever, the position of the lever guide is set. It does not always match the optimum work vehicle speed intended by the operator, and there is a problem that unintentional work travel is forced. In addition, it is necessary to ensure the operability of the main shift lever for adjusting the vehicle speed, so that it is on the cab. However, in view of the arrangement of the operation tools for various work devices, a large number of operation tools are complicatedly arranged on the driver's cab, causing a decrease in operability.

  The problems to be solved include various improvements including improved operability of vehicle speed adjustment by making the stepped gears flexible and improving the degree of freedom of arrangement of various operating tools on the cab. An object of the present invention is to provide a transmission for a work vehicle that can contribute to an improvement in operability of the entire work equipment.

  The invention according to claim 1 is a sub-transmission unit that changes the driving speed band of the traveling axle, a continuously variable transmission unit that continuously changes the transmission ratio of the transmission power, and the continuously variable transmission unit as a target transmission ratio. And a control unit for determining a target transmission ratio corresponding to a selected shift stage selected from a plurality of separately set shift stages, wherein the control unit is a signal of an acceleration / deceleration button switch. In response to the acceleration signal or the deceleration signal, the selected shift speed is increased or decreased in increments of 1 and the continuously variable transmission is controlled along the changed selected shift speed. To do.

  The control unit controls the continuously variable transmission unit according to a target transmission ratio determined corresponding to a selected shift stage selected from a plurality of separately set shift stages, and an acceleration signal or a deceleration signal by an acceleration / deceleration button switch In response, the selected gear stage is increased or decreased in increments of one, and the continuously variable transmission is controlled by the target transmission ratio corresponding to the selected gear stage.

According to a second aspect of the present invention, in the configuration of the first aspect, the acceleration / deceleration button switch is configured integrally with a sub-transmission lever for shifting the sub-transmission unit.
The driving speed band is changed by the operation of the sub-shift lever, and the traveling vehicle speed of the work vehicle in the band is adjusted by selecting the gear position by the operation of the acceleration / deceleration button switch integrally disposed on the lever.

  According to the first aspect of the present invention, since the shift speed can be selected by the button switch, the vehicle speed can be set as intended by the operator without requiring the fixed shift speed to be handled by the operation lever. Operation at a vehicle speed that matches the operator's intention in the driving speed band is possible, and the freedom of placement is ensured by a compact shifting operation tool with an acceleration / deceleration button switch. Can be improved. In addition, since the change of the selected shift stage is processed in the control unit, it is easy to apply automatic shift control processing such as accelerator shift and memory shift.

  According to the second aspect of the present invention, in addition to the effect of the first aspect, the speed change operation is concentrated on the auxiliary speed change lever without requiring the operation of a plurality of levers when adjusting the vehicle speed, so that the operability can be improved. it can.

  Embodiments specifically configured based on the above technical idea will be described below with reference to the drawings. In this specification, the left and right directions in the forward direction of the work vehicle are referred to as left and right, respectively, the forward direction is referred to as front, and the reverse direction is referred to as rear.

A tractor will be described below as an example of a work vehicle.
1 is an overall side view, FIG. 2 is a plan view of the tractor of FIG. 1, FIG. 3 is a power diagram of the transmission of the tractor of FIG. 1, and FIG. 4 is a control block diagram of the transmission.

  The tractor shown in FIG. 1 to FIG. 3 includes front wheels 2 and 2 and rear wheels 3 and 3 at the front and rear portions of the fuselage, and the rotational power of the engine 5 mounted on the front of the fuselage is appropriately decelerated by the transmission 4 to The front wheels 2, 2 and the rear wheels 3, 3 are configured to communicate with each other.

  A steering handle 7 is supported on the handle post 6 at the center of the airframe, and a control seat 9 is provided behind the steering handle 7. Below the steering handle 7 is provided a forward / reverse switching lever 10 for switching the traveling direction of the airframe to the forward / backward direction. When the forward / reverse switching lever 10 is moved to the front side, the aircraft moves forward, and when it is moved backward, it moves backward. An accelerator lever 11 is provided on the opposite side of the forward / reverse switching lever 10 across the handle post 6, and an accelerator petal 15 and left and right brake petals 16 and 17 are disposed at the right corner of the step floor 13. A clutch pedal 19 is disposed at the left corner of the floor 13.

  Further, an auxiliary speed change button 21 that can be selected from 1st speed to 8th speed and which can be selected from among low speed, medium speed, high speed, and neutral positions is provided on the rear side. In addition, a PTO speed change lever 23 is provided at the rear thereof so that the 1st to 3rd speeds and the neutral position can be selected. Further, on the right side of the control seat 9, a position lever 24 for setting the height of a working machine (not shown), an automatic tilling depth lever 25 for automatically setting the tilling depth of the field, and behind these levers 24, 25 Is provided with a right-up switch 27 and a right-down switch 28, followed by an automatic horizontal switch 29 (on to keep the tractor's absolute horizontal position horizontal with respect to the horizontal plane of the earth, not horizontal with respect to the field scene). ) And a backup switch 30 (when the forward / reverse switching lever 10 is in the reverse position, the work machine raising link 31 raises the work machine) and a work machine (not shown) is located behind the machine body. The link 31 for connecting the two) is provided.

  FIG. 3 is a diagram showing a traveling transmission system of a tractor having a hydrostatic continuously variable transmission mechanism (forward / reverse continuously variable transmission mechanism) 34 according to this embodiment. The rotational power of the engine 5 is transmitted to the main clutch 32 that is operated by depressing the pedal-operated clutch pedal 19, and then transmitted from the hydrostatic continuously variable transmission mechanism input shaft 33 to the hydrostatic continuously variable transmission mechanism 34. . The hydrostatic continuously variable transmission mechanism 34 includes a hydraulic closed circuit 34c having a variable displacement hydraulic pump 34a and a constant displacement hydraulic motor 34b, and is introduced from an input shaft 33 of the hydrostatic continuously variable transmission mechanism 33. The hydraulic pump 34a is operated by motive power, and pressure oil corresponding to the inclination angle of the swash plate 34d provided in the hydraulic pump 34a is supplied from the hydraulic closed circuit 34c to the hydraulic motor 34b, and the travel output shaft 36 is supplied by the hydraulic motor 34b. To drive the power to the meshing transmission 38.

  The auxiliary transmission clutch 39 of the meshing transmission 38 is slidable to the left and right in FIG. 3, and when it is in the illustrated position, the power from the travel output shaft 36 is transmitted from the high-speed gear 42 via the gear 41 to the auxiliary transmission clutch. 39 is transmitted from the auxiliary transmission clutch 39 to the gear 45 of the transmission shaft 43, and the rotation of the transmission shaft 43 is driven through the deb unit 46 at the traveling speed of the auxiliary transmission high speed stage.

  Further, when the auxiliary transmission clutch 39 is moved to the right from the position shown in FIG. 3 and the auxiliary transmission clutch 39 is engaged with the gear 45 and the medium speed gear 47 of the transmission shaft 43, the power from the travel output shaft 36 is transmitted to the gear. 41 is transmitted from the gear 49 to the subtransmission clutch 39 through the gear 50, the gear 51, and the gear 47 sequentially, and further transmitted from the subtransmission clutch 39 to the gear 45 of the transmission shaft 43. The movement of the rear wheel 3 is driven at the traveling speed of the intermediate speed stage through the fat device 46.

  When the auxiliary transmission clutch 39 further moves to the right side and engages with the gear 45 and the low speed gear 55 of the transmission shaft 43, the power from the travel output shaft 36 is transferred from the gear 49 to the gear 56 via the gear 41, and further from the gear 56. Is transmitted to the gear 57, transmitted from the gear 55 coaxial with the gear 57 to the sub-transmission clutch 39, and further transmitted from the sub-transmission clutch 39 to the gear 45 of the transmission shaft 43. The rear wheel 3 is driven at the traveling speed of the sub-speed stage.

  Even if the sliding position of the auxiliary transmission clutch 39 is on the left or right side, the output from the transmission shaft 43 is transmitted to the front wheel output shaft 61 via the gears 53, 59, 60, etc. in order. At this time, if the hydraulic clutch 63 is connected, the front wheel 2 is driven together with the rear wheel 3 via the differential device 65, and if the hydraulic clutch 64 is connected, the front wheel speed is increased. It becomes. The hydraulic clutch 63 and the hydraulic clutch 64 are not connected at the same time, and if the hydraulic clutch 63 and the hydraulic clutch 64 are not connected together, only the rear wheel 3 is driven.

  On the other hand, power input from the hydrostatic continuously variable transmission mechanism input shaft 33 to the variable displacement hydraulic pump 34a is transmitted from the pump output shaft 66 to the PTO drive system. The PTO drive system includes a PTO forward / reverse clutch 67 and a PTO auxiliary transmission clutch 68. When the tractor travels on the road, either one or both of the clutches 67 and 68 are in an unconnected state to drive the work machine. The PTO drive system is not driven.

  When working with the work implement in the field, the accelerator lever 11 is pulled toward the operator side (front side) and the engine speed is set to the rated speed, or a constant speed from the rated speed to the maximum speed. The hydraulic continuously variable transmission mechanism input shaft 33 and the pump output shaft 66 rotate at a constant rotational speed. The state shown in FIG. 3 is a neutral state, and the PTO shaft 69 directly connected to the pump output shaft 66 rotates together.

  When the PTO forward / reverse clutch 67 is slid in the left direction in the figure, the PTO forward / reverse clutch 67 meshes with the gear 70 and the gear 71 of the PTO shaft 69, so that the power of the PTO shaft 69 is the gear 70, the PTO forward / reverse clutch 67, and the gear 71. , The PTO transmission shaft 75 is driven through the gear 71a, the gear 72, the gear 74, the gear 78, the gear 77, and the gear 76 sequentially (PTO reverse rotation). When the PTO forward / reverse clutch 67 is slid in the right direction in the figure, the power of the PTO shaft 69 drives the PTO transmission shaft 75 through the gear 70, the PTO forward / reverse clutch 67, the gear 73, the gear 77, and the gear 76 sequentially. (PTO normal rotation).

  The power from the gear 78 interlocking with the driving of the gear 74 integrated with the gear 72 is also transmitted to the PTO transmission shaft 75, and when the PTO auxiliary transmission clutch 68 is in the position moved to the left most from the illustrated position, the gear 79 and the gear The gear dock 81 is engaged with the gear dock 83 provided in the PTO auxiliary transmission clutch 68 via 80, and the PTO first speed is obtained by the PTO drive shaft 84. When the PTO auxiliary transmission clutch 68 moves left or right from the illustrated position, power is transmitted to the PTO auxiliary transmission low speed gear 85 or the PTO auxiliary transmission high speed gear 86 that meshes in each case, and the gear 85, gear 68a. When the power is sequentially transmitted to the PTO drive shaft 84, the PTO second speed is obtained, and when the power is sequentially transmitted to the gear 86, the gear 68b and the PTO drive shaft 84, the PTO third speed is obtained.

  The tractor having the above-described configuration depresses the clutch pedal 19 when traveling on the road, and sets the auxiliary transmission lever 21 to a position suitable for traveling on the road (basically, the high-speed position may be set to the medium-speed position or the low-speed position). Next, the gear stage of the required speed is selected by the acceleration / deceleration button switches B1 and B2.

  Next, the forward / reverse switching lever 10 is moved forward or backward, and the engine pedal is increased by stepping on the accelerator pedal 15 while slowly releasing the clutch pedal 19 (with the main clutch 32 connected). At this time, even if the accelerator pedal 15 is fully depressed, the maximum speed is restricted to the position of the maximum gear position (8th speed) of the acceleration / deceleration button switches B1 and B2.

  Further, when working in the field, after depressing the clutch pedal 19, the sub-shift lever 21 is set to an appropriate position (basic is a low speed or medium speed position). Next, the speed change stage of the required speed is selected by the acceleration / deceleration button switches B1 and B2 according to the type of work, and the forward / reverse switching lever 10 is moved to the forward position. The accelerator lever 11 is moved to the pilot side (front side), and the engine speed is set to a rated speed or a maximum speed greater than the rated speed. Next, the clutch pedal 19 is moved forward (with the main clutch 32 connected). At this time, the engine speed is set between the rated speed and the maximum speed greater than or equal to the rated speed, but the working speed is restricted at the position selected by the acceleration / deceleration button switches B1 and B2.

  Note that the accelerator pedal 11 is used instead of the accelerator pedal 15 when the work implement is used in the field. Further, when traveling on the road, the accelerator pedal 15 is used and the accelerator lever 11 is not used. When driving on the road, the accelerator pedal 15 can be operated in the same way as when driving a car, and the engine rotation must be kept constant when working in the field. . Therefore, the accelerator lever 11 is operated during the work, and even if the hand is released from the accelerator lever 11 during the work, it does not return to the original position. Therefore, it is possible to maintain a constant engine speed by maintaining the operated accelerator position.

  FIG. 5 shows a left side view of the airframe near the handle post 6 and the control seat. 6 and 7 are plan views of the transmission case 91 (FIGS. 6A and 7A) and a plan view of the hydrostatic continuously variable transmission mechanism 34 housed in the transmission case 91. FIG. The figure (FIG.6 (b), FIG.7 (b)) is shown. FIG. 8 shows a side view of the transmission case 91 as viewed from the direction of arrow A in FIG. As shown in FIGS. 5 to 8, a link mechanism 95 that connects the hydraulic cylinder 93 that rotates the trunnion shaft 92 of the hydrostatic continuously variable transmission mechanism 34 and the trunnion shaft 92 that protrudes outside the transmission case 91 is provided. It is attached to the outer wall portion of the transmission case 91.

  The other end of the arm 95a having one end rotatably connected to the tip of the piston rod 93a of the cylinder 93 is rotatably supported on the outer wall of the transmission case 91, and the other end of the arm 95a is supported on the other end. One end of a rod 95b provided in a direction orthogonal to the longitudinal direction of the arm 95a is rotatably provided, and the other end of the rod 95b is substantially parallel to the arm 95a via a rotatable short arm 95c. The end of the rod 95d, whose length can be adjusted in the direction, is pivotally connected. The other end of the rod 95d whose length can be adjusted is rotatably connected to one end of a short arm 95e, and a boss 95f is fixed to the other end of the short arm 95e.

  The boss 95f is fixed to the shaft 95q with a bolt 95p. The shaft 95q is rotatably supported with respect to the transmission case 91, and a plate 95g is fixed to one end of the shaft 95q. The other end of the plate 95g is rotatably connected to a link arm 95h via a pin 95r, and the link arm 95h is rotatably connected to a cam 95j integrated with the trunnion shaft 92. Here, the cam 95j is fixed to the boss 95s, and the boss 95s is fixed to the trunnion shaft 92 by a bolt 95t.

  The plate 95g and the link arm 95h are connected by a pin 95r, and the connecting portion by the pin 95r has an arc-shaped elongated hole 95k1 of a fan-like member 95k fixed to the transmission case 91 with a shaft 95q as a pivot. Since the pin 95r is slidable only in the long hole 95k1, the rotation range of the cam 95j is also restricted within the range interlocked with the sliding of the pin 95r.

  By the link mechanism 95, the operation of the hydraulic cylinder 93 is interlocked with the arm 95a, the rod 95d, etc., and the cam 95j rotates together with the trunnion shaft 92. Further, the cam 95j is rotated by the cylinder 93 while the side surface of the cam 95j is in contact with the side surface of the roller 95m supported by the transmission case 91.

  6 shows a state in which the trunnion shaft 92 faces the swash plate 34d of the hydraulic pump 34a of the hydrostatic continuously variable transmission mechanism 34 toward the vehicle forward side, and is a plan view of the transmission case 91 in FIG. FIG. 7A) and a plan view of the hydrostatic continuously variable transmission mechanism 34 housed in the transmission case 91 (FIG. 7B) show the hydraulic pressure of the hydrostatic continuously variable transmission mechanism 34. The state where the swash plate 34d of the pump 34a is directed to the neutral position is shown, and the position where the roller 95m fits into the recess 95j1 of the cam 95j is the neutral position of the trunnion shaft 92. The roller 95m is pressed by a spring from the x direction in FIG. 9 shows a plan view of the transmission case 91 (FIG. 9A) and a plan view of the hydrostatic continuously variable transmission mechanism 34 housed in the transmission case 91 (FIG. 9B). The state shows a state in which the swash plate 34d of the hydraulic pump 34a of the hydrostatic continuously variable transmission mechanism 34 is disposed facing backward.

  FIG. 10 is a diagram showing the arrangement of shift switches 10a and 10b provided at the base of the forward / reverse switching lever 10 and the operation mode thereof. 10A and 10C, the forward shift switch 10a and the reverse shift switch 10b provided at the base of the forward / reverse switching lever 10 when the forward / reverse switching lever 10 is in the forward position and the reverse position are operated. FIG. 10B is a layout diagram when the forward / reverse switching lever 10 is in the neutral position and does not come into contact with either the forward shift switch 10a or the reverse shift switch 10b.

  When the forward / reverse switching lever 10 is tilted forward from the neutral position so that the forward shift switch 10a of the forward / reverse switching lever 10 is operated, it is ready to move in the forward direction, and the reverse shift switch 10b of the forward / reverse switching lever 10 is operated. Thus, when the forward / reverse switching lever 10 is tilted backward from the neutral position, preparation for moving in the backward direction is made. It should be noted that acceleration in the forward and reverse directions of the vehicle is only performed by the acceleration / deceleration button switches B1 and B2.

  Further, since an EEPROM 90a for storing the target speed by the acceleration / deceleration button switches B1 and B2 is arranged in the controller 90, first, a value to be shifted by operating one of the acceleration / deceleration button switches B1 and B2. Output value (T), the value (A) of the minimum vehicle speed instruction position by the acceleration / deceleration button switches B1 and B2, and the value (B) of the maximum vehicle speed instruction position are stored in the EEPROM 90a.

Next, the controller 90 calculates the first value as an output ratio to the hydraulic cylinder 93 with respect to the total stroke amount of the trunnion shaft turning hydraulic cylinder 93 corresponding to the turning angle of the trunnion shaft 92 by the following equation (1). .
Output ratio to hydraulic cylinder = (TA) / (AB) (1)

  In this way, the hydraulic cylinder 93 is operated according to the first value obtained by the above equation (1). The magnitude of the detected value of the trunnion shaft position sensor 92a obtained at that time is the same as that of the trunnion shaft position sensor 92a. Corresponding to a detection range, for example, any voltage value between 0 and 5 volts. Therefore, the detection value of the trunnion axis position sensor 92a is transmitted to the controller 90, and the controller 90 obtains the magnitude of the detection value of the trunnion axis position sensor 92a as a ratio to the magnitude of the entire detection range of the trunnion axis position sensor 92a. This is the second value. The controller 90 controls the obtained second value to be equal to the first value, and when the first value and the second value are equal, the electromagnetic valve (not shown) of the trunnion shaft rotating hydraulic cylinder 93 is shown. (The oil in the cylinder 93 does not leak out and the cylinder piston is held at the position where the output is stopped).

  A trunnion shaft position sensor 92a (FIG. 6) that detects the rotation position of the trunnion shaft 92 by the operation of the trunnion shaft rotation hydraulic cylinder 93 is configured to detect the degree of rotation of the rotation shaft 93d. The trunnion shaft position sensor 92a is coupled to the other end of an arm 93c having one end rotatably provided on the opposite side of the connecting portion of the arm 95e at the tip of the rod 95d. Thereby, the trunnion shaft position sensor 92a detects the movement (position) of the trunnion shaft 92. The position sensor 92a of the trunnion shaft 92 includes a stopper 93e provided at the maximum extension setting position on the forward side of the piston rod 93a of the trunnion shaft rotating hydraulic cylinder 93 and a stopper 93f (FIG. 8) provided at the minimum shortening setting position on the reverse side. Each set position is set as a reference value that allows the trunnion shaft 92 to rotate. The position where the roller 95m fits into the recess 95jl of the cam 95j is the neutral position of the trunnion shaft 92, and this is also set as the reference value. Each set position detected by the trunnion axis position sensor 92a is stored in a memory (EEPROM) 90a of the controller 90 as a reference position.

  Further, detection of a trunnion shaft position sensor 92a contacting the stopper 93e provided at the maximum extension setting position on the forward side of the piston rod 93a of the hydraulic cylinder 93 for turning the trunnion shaft and the stopper 93f provided at the minimum shortening setting position on the reverse side. Since the rotation range of the trunnion shaft rotation hydraulic cylinder 93 can be controlled using the position as a reference position, the dimensions of the link mechanism 95 for associating the rotation angle of the trunnion shaft 92 of the hydrostatic continuously variable transmission mechanism 34 are as follows. Errors and the like can be absorbed.

  A switch for entering a mode for adjusting the reference value of the position sensor 92a of the rotational position of the trunnion shaft 92 is provided on the operation panel of the control seat 9. This switch is covered with a cover and is included in the switch group. The names are arranged to be similar to each other so that switches for adjusting the reference values of the respective position sensors can be easily identified. The reason is that, when there are a large number of sensors to be adjusted, a switch having a similar name is attached to the switch group in the adjustment mode so as to prevent the switch from entering the adjustment mode.

  Further, although the operation positions of the gear positions are from 1st to 8th speed, the hydraulic cylinder 93 is operated by the control of the controller 90 with the operation position of each gear position as the target position, and the trunnion shaft 92 is controlled to rotate.

  The control output to the hydraulic cylinder 93 when the hydraulic cylinder 93 is operated by the controller 90 to control the rotation of the trunnion shaft 92 is a pulse output, and the pulse cycle is changed according to the deviation between the target position and the current position. It can be. That is, when the deviation is large, the pulse output cycle is shortened to make the operation of the trunnion shaft turning hydraulic cylinder 93 relatively fast, and when the deviation is small, the pulse output cycle is made long and the trunnion shaft turning hydraulic cylinder is made. The operation of 93 is made relatively slow.

  If the control output to the target position of the trunnion shaft turning hydraulic cylinder 93 is a continuous output instead of a pulse output, when the trunnion shaft 92 is operated, the operating speed of the hydraulic cylinder 93 is too fast and the vehicle traveling speed is suddenly accelerated or suddenly increased. Although the vehicle may be decelerated, the vehicle can be smoothly accelerated and decelerated by using the control output as a pulse output.

  At this time, the difference in operation speed can be reduced by changing the pulse on time or changing the pulse cycle on the expansion side and the contraction side of the piston rod 93a of the trunnion shaft turning hydraulic cylinder 93. This is because the piston (not shown) that bisects the oil chamber inside the cylinder at the end of the rod 93a traversing the hydraulic cylinder 93 is divided into the side where the piston rod 93a is located (extended side) and the side where the piston rod 93a is not located (contracted). This is to adjust the oil chamber cross-sectional area on the side).

  The engine is started by depressing the clutch pedal 19 and turning the clutch switch 97 (FIG. 4) on (clutch disengagement) and setting the forward / reverse switching lever 10 to neutral, but when the hydraulic cylinder 93 is not neutral immediately after engine startup. There is. This is because if the engine 5 is turned off during forward travel, the trunnion shaft turning hydraulic cylinder 93 may stop operating in a state other than the neutral position.

  Therefore, when the trunnion shaft turning hydraulic cylinder 93 is not in the neutral position, an output is made to return the hydraulic cylinder 93 to the neutral position, and the warning buzzer is continuously sounded until the hydraulic cylinder 93 returns to the neutral position. As a configuration, driving safety is enhanced.

  Further, when the engine is started, if the trunnion shaft turning hydraulic cylinder 93 is in a position other than the neutral position, continuous output is used instead of pulse output in order to increase the operating speed of the hydraulic cylinder 93 in order to quickly return to the neutral position.

  When the engine is started, the forward / reverse switching lever 10 is always in the neutral position, but if the clutch pedal 19 is returned and the main clutch 32 is engaged, the vehicle may start. For this purpose, as described above, the hydraulic cylinder 93 is operated with continuous output instead of pulse output, so that the trunnion shaft rotating hydraulic cylinder 93 is quickly returned to the neutral position when the engine is started. At this time, an alarm buzzer is sounded to alert the operator.

  Further, when the forward / reverse switching lever 10 is set to neutral in the traveling state during forward or reverse travel, when the clutch pedal 19 is not depressed (the main clutch 32 is turned on and the clutch switch 97 is turned off), the hydraulic cylinder 93 outputs a pulse ( When the clutch pedal 19 is depressed (the main clutch 32 is disengaged and the clutch switch 97 is engaged), the hydraulic cylinder 93 returns to neutral with continuous output (fast). Also, when the clutch pedal 19 is depressed (the main clutch 32 is disengaged and the clutch switch 97 is engaged) and the forward / reverse switching lever 10 moves forward or backward and the speed change target is changed by the acceleration / deceleration button switches B1 and B2, continuous output (fast) To the target position.

  As described above, when the control output to the target position of the trunnion shaft rotating hydraulic cylinder 93 is a pulse output and the pulse cycle is changed according to the deviation between the target position and the current position, the position sensor 92a of the trunnion shaft 92 is used. If the value of does not change significantly, increase the ON time ratio within a predetermined period (pulse period) consisting of ON / OFF of the pulse output and increase the ON time (increase the pulse output) It is good also as a structure which correct | amends.

  This is because, for example, when the temperature of the lubricating oil is low and the trunnion shaft turning hydraulic cylinder 93 does not operate in a pulse cycle with a short on time, the on time within the predetermined pulse cycle is made longer to turn the trunnion shaft. This is because the hydraulic cylinder 93 needs to be corrected to increase the operation output.

However, the speed at which the trunnion shaft rotating hydraulic cylinder 93 moves to the target position (depending on the pulse on time) can be changed in accordance with the position of the auxiliary transmission lever 21.
This is because if the sub-transmission device selects the low speed stage, even if the hydraulic cylinder 93 is brought to the target position as quickly as possible, it will not be suddenly accelerated or decelerated. If it is selected, if the movement to the target position of the trunnion shaft turning hydraulic cylinder 93 is quickly performed, the vehicle is suddenly accelerated or decelerated. In this case, the moving speed to the target position of the hydraulic cylinder 93 is comparatively delayed. . Thus, the response of the hydraulic cylinder 93 is improved even when traveling at a low speed.

  Further, the hydraulic cylinder 93 is controlled to expand and contract in accordance with the speed change target by the acceleration / deceleration button switches B1 and B2 and the state of the forward / reverse switching lever shift switches 10a and 10b. A sensor 11a (FIG. 4) may be provided to change the operating speed (by changing the pulse on time) of the trunnion shaft turning hydraulic cylinder 93 according to the position of the throttle sensor 11a.

  With the above configuration, when the engine speed is low, the response of the operation speed of the trunnion shaft rotating hydraulic cylinder 93 is improved, and when the engine speed is high, the target speed can be changed with good feeling.

  Further, by providing a headland control mode switch that can increase the traveling speed when traveling backward as compared with the traveling speed when traveling forward, the maneuverability at the headland is improved. In headlands (corner corners), there are times when forward and reverse are repeated to change the direction of the vehicle, but in that case, if the traveling speed is slower than the traveling speed when moving forward, You may feel that turning performance is not good. Therefore, when traveling on a headland, the headland control mode is set in which the traveling speed at the time of reverse traveling is made faster than the traveling speed at the time of forward movement, and the switch that can be selected by this mode, for example, tilling of the field during reverse traveling Work efficiency can be improved.

  For example, when the speed change target at the time of forward movement is the third speed, the signal is input to the controller 90, and the controller 90 controls the hydraulic cylinder 93 so that the trunnion shaft 92 is in a position to output the third speed. When moving backward, the controller 90 controls the hydraulic cylinder 93 so that, for example, the trunnion shaft 92 is in a position for producing the fourth speed or the fifth speed even if the speed change target is the third speed.

  However, it is desirable that the headland control mode is selected only at the rotary work speed (for example, only at the sub-shifting low speed) because there is an unexpected problem if the vehicle moves fast when backing up on the road.

Next, shift control by the acceleration / deceleration button switches B1 and B2 will be described.
As shown in the perspective view of the main part of FIG. 11, the sub-transmission lever 21 has an L-shaped lever guide with “low speed” (first speed of operation) P1 and “medium speed” (operation 2). Speed) P2 and “road on road” P3 shift positions can be selected, and acceleration / deceleration button switches B1 and B2 are provided in the vicinity of the grip 21g so that the operator can operate the button with the thumb while holding the grip 21g with the left hand. In this way, the grip 21g is arranged on the right side surface.

  As shown in the control block diagram of FIG. 12, the control unit 90 of the transmission 4 controls the hydrostatic continuously variable transmission mechanism 34 as a continuously variable transmission unit to a target transmission ratio by means of trunnion control outputs 93x and 93y. The target transmission ratio is determined in correspondence with a selected shift stage selected by a shift operation unit from a plurality of shift stages set separately. The control unit 90 receives signals from the acceleration button switch B1 and the deceleration button switch B2 serving as a speed change operation unit for changing the selected gear position, and in accordance with the acceleration signal or the deceleration signal based on the data stored in the EEPROM 90a. The control unit 90 performs an increase / decrease change process for the selected shift stage in increments of one.

  By configuring the control unit 90 in this way, the continuously variable transmission unit 34 is controlled in accordance with a target transmission ratio determined corresponding to a selected shift stage selected from a plurality of separately set shift stages, and acceleration / deceleration is performed. When the speed increasing signal or the speed reducing signal from the button switches B1 and B2 is received, the selected shift speed is increased or decreased one by one, and the continuously variable transmission 34 is controlled by the target transmission ratio corresponding to the selected shift speed. In addition, since the change of the selected shift stage is processed in the control unit, it is easy to apply automatic shift control processing such as accelerator shift and memory shift.

  The acceleration / deceleration button switches B1 and B2 are disposed integrally with the auxiliary transmission lever 21 for changing the speed of the auxiliary transmission unit 38, so that the driving speed band is changed by the operation of the auxiliary transmission lever 21. By operating the acceleration / deceleration button switches B1 and B2 that are integrally disposed in the vehicle 21, the traveling vehicle speed of the work vehicle is adjusted at the vehicle speed corresponding to the selected gear position in the vehicle speed band. Therefore, when the vehicle speed is adjusted, the shifting operation is concentrated on the sub-shifting lever 21 without requiring an operation for a plurality of levers, so that the operability can be improved.

  In addition, the auxiliary transmission lever 21 is provided with an automatic transmission switch B3 on the rear side. The automatic shift switch B3 is used when switching to the automatic shift mode, that is, the accelerator shift. The accelerator shift can be performed with an excellent feeling by continuously changing the vehicle speed by the continuously variable transmission unit 34.

  The accelerator shift is provided with an accelerator sensor for detecting the accelerator opening and an engine rotation sensor, and as shown in the shift relationship diagram of FIG. 13, shift control for changing the trunnion target according to the relationship between the accelerator sensor and the engine rotation sensor. Configure. For example, according to the rank R of the accelerator opening, the gear shifts only up to the gear range within the range (fourth speed in the figure), and when the actual engine speed exceeds the change line L, the trunnion is shifted to the first shift position. To change. Such a shift process enables a shift without a sense of incongruity.

Also, the “road running” position of the sub-shift lever is set to be the same as “high speed”, and the target of the trunnion arm is set to a lower speed than the number of speeds at “high speed”. For example, as shown in the speed change relationship diagram of FIG. 14, the “high speed” 8-speed shift range is set to 4 steps for “running on the road”, and the trunnion is divided into 4 steps according to the relationship between the accelerator opening and the engine speed. The shift control is appropriately changed to the target.
With the shift control described above, since there is no need for a small number of shift stages when traveling on the road, it is possible to reduce the shift feeling (not shock) that occurs when the trunnion target changes.

  In addition, since the conventional lever-type shift operating tool is configured by providing a key groove at the shift position, the limit is 8 to 10 in relation to the lever stroke and the distance between the key grooves or the layout. However, the number of gears that can be instructed by the acceleration / deceleration button switches B1 and B2 can be freely set as in the example (8th and 5th gears) shown in the development diagram of the gears in FIG. It is possible to meet the needs of users and work, so versatility can be increased.

It is a left view of the tractor of one Example of this invention. It is a top view of the tractor of FIG. It is a power diagram of the transmission of the tractor of FIG. It is a control block diagram of the transmission of the tractor of FIG. FIG. 2 is a left side view of the airframe in the vicinity of the steering wheel post and the control seat of the tractor of FIG. 1. FIG. 6 is a plan view (FIG. 6A) of the transmission case of the forward tractor in FIG. 1 and a plan view (FIG. 6B) of the hydrostatic continuously variable transmission mechanism housed in the transmission case. is there. FIG. 7 is a plan view of the transmission case of the tractor in the neutral state of FIG. 1 (FIG. 7A) and a plan view of the hydrostatic continuously variable transmission mechanism housed in the transmission case (FIG. 7B). is there. It is the side view of the transmission case seen from the arrow A direction of Fig.7 (a). FIG. 9 is a plan view (FIG. 9A) of the transmission case of the reverse tractor in FIG. 1 and a plan view of the hydrostatic continuously variable transmission mechanism housed in the transmission case (FIG. 9B). is there. The forward / reverse switching lever of the tractor in FIG. 1 is in the forward position (FIG. 10 (a)), neutral position (FIG. 10 (b)), or reverse position (FIG. 10 (c)). It is a figure which shows arrangement | positioning of the shift switch provided in the base part, and its operation | movement aspect. It is a principal part perspective view of an operation part. It is a control block diagram of a transmission. FIG. 6 is a shift relationship diagram for an accelerator shift. FIG. 5 is a speed change relationship diagram of “road running”. FIG.

Explanation of symbols

2 Front wheel 3 Rear wheel 4 Transmission 5 Engine 10 Forward / reverse switching lever 11 Accelerator lever 11a Throttle sensor 15 Accelerator pedal 19 Clutch pedal 21 Sub transmission lever 21g Grip 34 Hydrostatic continuously variable transmission mechanism (continuously variable transmission)
38 Transmission (sub transmission)
90 control unit 93x, 93y trunnion control output B1 acceleration button switch B2 deceleration button switch B3 automatic transmission switch

Claims (2)

The sub-transmission unit (38) for changing the driving speed band of the traveling axle, the continuously variable transmission unit (34) for changing the transmission ratio of the transmission power continuously, and the continuously variable transmission unit (34) as a target transmission ratio. And a control unit (90) for determining a target transmission ratio corresponding to a selected shift stage selected from a plurality of separately set shift stages,
In response to the signal from the acceleration / deceleration button switch (B1, B2), the control unit (90) increases / decreases the selected shift stage in increments of 1 according to the acceleration signal or deceleration signal. A continuously variable transmission unit (34) is controlled along a subsequent selected shift stage.   The work vehicle according to claim 1, wherein the acceleration / deceleration button switch (B1, B2) is integrally formed with an auxiliary transmission lever (21) for shifting the auxiliary transmission unit (34). Transmission device.

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