JP2016070295A - Speed change gear of work vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain a stable travel speed with the travel speed not changing even when stepping-in of an HST (Hydraulic Static Transmission) pedal changes in some degree.SOLUTION: In a work vehicle in which power is transmitted from an engine 4 to travel devices 2, 3 via an HST 11 and the HST 11 is shifted by stepping-in of a HST pedal 7b to change a travel speed, a speed change gear of the work vehicle shift-controls the HST 11 in plural stages in regard to stepping-in amounts of the HST pedal 7b. In addition, the speed change gear of the work vehicle is provided with a road travel mode M1 of steplessly shifting the HST 11 correspondingly to a stepping-in depth of the HST pedal 7b and a work travel mode M2 of shifting the HST 11 in plural stages, and can properly select between the travel modes by a mode switching means 32.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a transmission in a tractor for agriculture, construction, transportation, and other work vehicles.

Conventionally, a tractor provided with an HST (hydraulic continuously variable transmission) is known (for example, Patent Documents 1 and 2).
This tractor increases or decreases the traveling speed in the forward / rearward direction as the HST pedal is depressed, and the speed change operation is simplified by continuously variable transmission.

JP 2013-204783 A EP1177114B1

  A conventional work vehicle having an HST automatically shifts the traveling speed in accordance with the amount of depression of the HST pedal. However, if the depth of depression of the accelerator pedal fluctuates against the intention of the operator due to shaking of the vehicle body, the traveling speed However, there was a problem that the gears shifted in response to the movement of the accelerator pedal and the driving was jerky.

  Therefore, an object of the present invention is to maintain a stable traveling speed without changing the traveling speed even if the depression of the HST pedal is slightly varied in a work vehicle having an HST.

The problems of the present invention are solved by the following technical means.
According to the first aspect of the present invention, in a work vehicle in which power is transmitted from the engine 4 to the traveling devices 2 and 3 via the HST 11, and the HST 11 is shifted by stepping on the HST pedal 7b, the traveling speed is changed. A transmission for a work vehicle is characterized in that the HST 11 is shift-controlled to a plurality of stages with respect to the depression amount of 7b.

  The invention according to claim 2 is provided with a road traveling mode M1 for continuously shifting the HST 11 corresponding to the stepping depth of the HST pedal 7b and a work traveling mode M2 for shifting the HST 11 to a plurality of stages. The transmission for a work vehicle according to claim 1, wherein the traveling mode can be selected as appropriate.

  The invention according to claim 3 is provided with a brake pedal 7c that operates in preference to the operation of the HST pedal 7b, and when the brake pedal 7c is depressed, the hydraulic continuously variable transmission 11 is shifted to a plurality of stages and decelerated. A transmission for a work vehicle according to claim 1.

  According to the first aspect of the present invention, since the traveling speed does not fluctuate within the same shift stage even if the stepping depth of the HST pedal 7b slightly fluctuates during traveling with the depression of the HST pedal 7b, Since the traveling speed does not fluctuate even if the driver depresses the depth of the HST pedal 7b by the driver, the traveling speed does not fluctuate, so the vehicle can travel at a stable speed.

  In the invention according to claim 2, when traveling on a flat road, it is possible to smoothly shift according to the depression of the HST pedal 7b by traveling in the on-road traveling mode M1, and when traveling on a wasteland such as a farm field, By traveling in the work travel mode M2, the travel speed does not fluctuate even if the aircraft shakes.

  According to the third aspect of the present invention, in the case of running on a rough ground, even when the brake pedal 7c is depressed to stop, even if the body shakes, the running speed can be stopped without disturbance.

Side view of the tractor according to the first embodiment related to the present invention Plan view of the tractor of the same embodiment Configuration development diagram of transmission system of tractor of the same embodiment (A) Hydraulic circuit diagram of the hydraulic continuously variable transmission of the tractor of the embodiment, (b) Hydraulic circuit diagram of the hydraulic continuously variable transmission of the tractor of the second embodiment Input / output block diagram for explaining the control unit of the tractor of the embodiment The figure which shows the relationship between the depression amount of the HST pedal at the time of acceleration and the drive current value of the trunnion shaft The figure which shows the relationship between the depression amount of the HST pedal at the time of deceleration, and the drive current value of the trunnion shaft In order to show the positional relationship between the Hi-Lo switching lever and the steering handle in the tractor according to Embodiment 2 of the present invention, these are enlarged perspective views as seen from the work seat side. Input / output block diagram for explaining the control unit of the second tractor of the second embodiment Flowchart diagram of auto cruise mode in the second embodiment

  Hereinafter, a tractor according to an embodiment of the work vehicle of the present invention will be described with reference to the drawings. In the present 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.

FIG. 1 is a side view of the overall configuration of a tractor as an example of a work vehicle according to the present invention, and FIG. 2 is a plan view of the overall configuration of the tractor.
As shown in FIGS. 1 and 2, the tractor 1 supports the machine body by front and rear traveling wheels 2 and 3 so as to be able to work on the field, and performs work by attaching the work machine to the front part or the rear part of the machine body. Power is transmitted from the engine 4 mounted in the engine room 4a in the front of the machine body to the traveling wheels 2 and 3. In the power transmission to the traveling wheels 2 and 3, the power shifted by the auxiliary transmission mechanism 12 (stepped transmission) of the transmission 5 and the hydraulic continuously variable transmission (HST) 11 is continuously transmitted. Further, of the power input to the hydraulic continuously variable transmission 11, power that is not continuously variable is transmitted to the work power supply unit 6 that is abbreviated as PTO. The work power supply unit 6 includes a PTO mechanism 16a at the rear of the machine body and a PTO mechanism 16b at the lower center of the machine body.

  In addition, various operation devices are provided centering on the work seat 7, and the steering handle 7a, the HST pedal 7b, and the left and right set brake pedals 7c (used as a left brake pedal and a right brake pedal by releasing the connection) are used for driving operation. Sub-shift lever 7d, 4WD lever 7e for switching between rear wheel drive and four-wheel drive, emergency stop switch 7f for emergency stop of engine, blinker switch 7g, auto cruise switch 7h, rear and mid PTO levers for working machine operation 8a, 8b, a position lever 8c for determining the ascending / descending position of the working machine mounted, a forward / reverse lever 7i, a throttle lever 7j for setting the engine speed, two external hydraulic levers 8d for driving another hydraulic device, etc. It is configured with. The sub transmission lever 7d performs a gear shifting operation of the stepped sub transmission mechanism 12 shown in FIG.

  Further, when the auto-cruise switch 7h is turned on, the auto-cruise mode is set, and the vehicle speed at the time of the on-state is maintained even if the foot is released from the HST pedal 7b. Specifically, in the auto cruise mode, the rotational position of the trunnion shaft 21t for adjusting the output of the hydraulic pump 21p of the continuously variable transmission 11 is maintained.

  In the traveling transmission system of the transmission 5, the hydrostatic continuously variable transmission 11 called HST receiving engine power and the subtransmission mechanism 12 for switching the vehicle speed range are arranged in series from the power transmission upstream side to the downstream side. The power is transmitted to the transmission mechanism 13 such as the rear wheel 3.

  The travel transmission system is provided with device operation sensors such as a rotation sensor 4r of the engine 4 and a vehicle speed sensor 12r, and the HST 11 is controlled based on the output from the HST pedal depression amount detection sensor 31 for detecting the depression amount of the HST pedal 7b. A transmission system is constituted by the control unit 100 to be controlled.

  Further, the tractor 1 of the present embodiment is provided with a mode switching switch 32 that gives an instruction to switch between road traveling and work traveling, and the mode switching result by the mode switching switch 32 is output to the control unit 100. The

  As shown in the transmission system development diagram in FIG. 3, the transmission 5 includes traveling system equipment such as a HWD 11, a sub-transmission mechanism 12, a rear wheel transmission mechanism 13, a 4WD switching unit 14 a extending to the front wheel transmission mechanism 14.

Each vehicle speed range by the subtransmission mechanism 12 that selects the vehicle speed range from the working speed to the road speed is continuously variable at the HST 11, and this shift power is transmitted to the front and rear wheels 2 and 3.
Of the power input from the engine 4 to the HST 11, power that is not continuously variable is configured to be able to operate the work machine from the rear and mid PTO mechanisms 16 a and 16 b via the PTO clutch 15. That is, the output shaft 21a from the engine 4 input to the hydraulic continuously variable transmission 11 protrudes on the opposite side (transmission device 5 side) from the engine 4, and power is supplied to the PTO clutch 15 via a plurality of gears. It is the structure that is being transmitted. Thus, the rear PTO mechanism 16a and the mid PTO mechanism 16b are configured to rotate at a constant rotation.

  11 a is a charge pump of HST 11 and is housed in a transmission case surrounding the transmission 5. The rear PTO mechanism 16a drives a rotary, a snowplow, a mower, and the like attached to the rear part of the machine body. The mid PTO mechanism 16b drives a mower, a snow remover, a road cleaning machine, and the like that are attached to the lower part of the machine body between the front wheel 2 and the rear wheel 3.

  As shown in the hydraulic circuit diagram of FIG. 4A, the HST 11 includes a variable output hydraulic pump 21p driven by engine power and a fixed hydraulic motor 21m that receives the pump output.

  The hydraulic pump 21p is driven by being directly connected to the output shaft 21a from the engine 4. The hydraulic pump 21p is provided with a trunnion shaft 21t for adjusting the output, and the angle of the swash plate 21s is changed by the rotation of the trunnion shaft 21t. The fixed hydraulic motor 21m is driven by the angular position of the swash plate 21s through the flow rate adjustment including the oil supply direction and output stop, and the forward / reverse variable speed rotation power including neutral output stop is transmitted from the output shaft 21b. Output.

  The trunnion angle control of the hydraulic pump 21p is configured such that the hydraulic oil flow rate is adjusted by the drive current to the proportional solenoid valve (including the trunnion forward solenoid and trunnion reverse solenoid) 22 by HST control of the servo mechanism.

  That is, as shown in FIG. 5, the control unit 100 is instructed by the mode changeover switch 32 to change the rotation angle of the trunnion shaft 21t of the HST 11 with respect to the depression amount detected by the depression amount detection sensor 31 of the HST pedal. Control according to the mode.

  Since the adjustment of the hydraulic oil flow rate is performed by changing the duty ratio of the current, the trunnion shaft 21t rotates to the rotation position corresponding to the changed current value. In addition, a switching valve 22a is configured on the downstream side of the proportional solenoid valve 22. This switching valve 22a detects forward / backward switching of the forward / reverse lever 7i by the forward / reverse lever switch 33, and rotates the trunnion shaft 21t. The moving direction, that is, the forward / reverse direction of the output shaft 21b is determined. Reference numeral P denotes a hydraulic circuit for power steering.

Next, in FIG. 6, the relationship between the depression amount of the HST pedal and the operation of the trunnion shaft will be described.
When the operator operates the mode changeover switch 32 to set the road traveling mode M1, the output is sent to the control unit 100, and the correspondence relationship for the road traveling mode M1 stored in the memory 110 is read. This mode is suitable when traveling on the road.

  When the operator depresses the HST pedal 7b, the control unit 100 reads from the memory 110 the amount of change in the operating angle of the trunnion shaft 21t of the HST 11 with respect to the depressing amount detected by the HST pedal depressing amount detection sensor 31. Control is performed with the duty ratio of the current according to the issued road driving mode M1.

  By setting this mode, as indicated by line L2 in FIG. 6, the duty ratio of the drive current for rotating the trunnion shaft 21t changes according to the degree of depression of the HST pedal 7b, and the adjustment of the traveling speed of the tractor 1 is easy. It is suitable for traveling on a flat road while adjusting the speed.

  The drive current for rotating the trunnion shaft 21t controls the proportional solenoid valve 22 of FIG. By controlling this proportional solenoid valve 22, the amount of hydraulic oil increases or decreases, and the rotational speed of the trunnion shaft 21t changes. The switching valve 22a is a valve that determines the rotational direction of the trunnion shaft 21t, that is, the rotational direction (forward and backward) of the swash plate 21s.

  A line L1 indicates a target value of the rotation angle of the trunnion shaft 21t with respect to the depression amount of the HST pedal 7b. A target value of the driving current in the road traveling mode M1 corresponding to the line L1 is indicated by a line L2. In this way, by controlling the proportional solenoid valve 22 by changing the drive current, the rotational speed of the trunnion shaft 21t changes. In the line L2, the target speed is reached while the acceleration gradually increases with the amount of change in acceleration per unit time. On the other hand, in the line L3b, the trunnion shaft 21t rotates at a constant speed. Therefore, the amount of change in acceleration per unit time reaches the target speed at a constant acceleration. The rotational speed of the trunnion shaft 21t of the line L3a is the highest speed (maximum capability of the proportional solenoid valve 22 and the hydraulic circuit), and the rotational speed of the trunnion shaft 21t of the line L3a is 70% of the highest speed.

  When the operator operates the mode changeover switch 32 to set the work travel mode M2, the setting is sent to the control unit 100, and the correspondence relationship for the work travel mode M2 stored in the memory 110 is read out. It is. This mode is suitable when, for example, plowing work is performed on a farm field.

  When the worker depresses the HST pedal 7b, the control unit 100 drives the trunnion shaft 21t of the hydraulic continuously variable transmission 11 with respect to the depression amount (L1) detected by the HST pedal depression amount detection sensor 31. Is controlled according to the work travel mode M2 read from the memory 110.

  By setting this mode, as shown in FIG. 6, when the depression of the HST pedal 7b is started, the duty ratio of the drive current of the trunnion shaft 21t is increased to 40%. That is, when the amount of depression of the HST pedal 7b is up to 30%, the rotational speed of the trunnion shaft 21t until the target speed is reached is controlled with the duty ratio of the drive current of the proportional solenoid valve 22 being 40%. As a result, the rotation speed of the trunnion shaft 21t rotates at 40% of the maximum speed. With the amount of change in acceleration per unit time, the target speed is reached at a constant acceleration, but the acceleration value is small. Since the amount of depression of the HST pedal 7b is small, the vehicle can travel safely by slowly reaching the target speed.

  Further, when the depression amount of the HST pedal 7b is 30% to 60% of the whole, the rotational speed of the trunnion shaft 21t until the target speed is reached is controlled by the duty ratio of the drive current of the proportional solenoid valve 22 at 70%. .

  Further, when the depression amount of the HST pedal 7b is 60% to 100% of the whole, the rotational speed of the trunnion shaft 21t until the target speed is reached is controlled by the duty ratio of the drive current of the proportional solenoid valve 22 at 100%. . As a result, the target speed is reached at a constant acceleration with the amount of change in acceleration per unit time, but the acceleration value is large. Since the amount of depression of the HST pedal 7b is large, the driving intended by the driver can be achieved by reaching the target speed in a short time.

  By the way, controlling the duty ratio of the drive current of the proportional solenoid valve 22 at 100% is to maximize the capability of the proportional solenoid valve and the hydraulic circuit, so the rotational speed of the trunnion shaft 21t is the fastest. It becomes.

  As described above, since the speed is changed in three steps without being sensitive to the depression amount of the HST pedal 7b, it is easy to maintain the set speed even if the degree of depression of the HST pedal 7b slightly changes due to shaking of the airframe. Therefore, for example, it is a mode suitable for work traveling on a farm field.

  During deceleration, as shown in FIG. 7, the duty ratio of the drive current of the trunnion shaft 21t is controlled at 70% until the depression amount of the HST pedal 7b reaches 30%, and the depression amount of the HST pedal 7b is reduced to 30% or less. Then, when the duty ratio of the drive current of the trunnion shaft 21t is controlled at 40% and the depression amount of the HST pedal 7b becomes 0%, the drive current of the proportional solenoid valve 22 is not passed. At this time, the trunnion shaft 21t is in a neutral position.

Next, the 2nd tractor 200 as an example of the work vehicle of this invention is demonstrated.
First, the configuration of the second tractor 200 will be described. The components described in the first embodiment with reference to FIGS. 1 to 3 are substantially the same, and thus have substantially the same function. Constituent elements are denoted by the same reference numerals, and description thereof is omitted.

  Moreover, in HST11 of the said Embodiment 1, although the hydraulic motor was demonstrated as the fixed hydraulic motor 21m (refer FIG. 4 (a)) without the swash plate, in 2nd HST11b of this Embodiment 2, the hydraulic motor was demonstrated. 4B, a variable hydraulic motor 121m provided with a swash plate 121s is provided. The second HST 11b of the second embodiment is configured so that the output of the variable hydraulic motor 121m can be switched between two stages of high speed and low speed, and this is called two-stage switching of the variable hydraulic motor 121m having the swash plate 121s. .

  The two-stage switching between the low speed side and the high speed side is performed by rotating the swash plate 121s by the trunnion shaft 121t on the variable hydraulic motor 121m side. The operating angle of the trunnion shaft 121t is switched by the stage switching valve 122. And the Hi-Lo switching lever 210 which instruct | indicates switching of the stage switching valve 122 is arrange | positioned in the downward vicinity of the steering handle 7a (refer FIG. 8).

  That is, since the mechanism for instructing the switching of the stage switching valve 122 is not a push type switch but a lever type, the position of the lever can be easily confirmed during operation. Further, since the Hi-Lo switching lever 210 is disposed in the vicinity of the lower portion of the steering handle 7a, the switching operation can be performed quickly and easily, the shift loss is small, and the work efficiency is improved. From the above, according to this configuration, the operational feeling is better than the conventional one, and the operability is improved.

In the second embodiment, when the Hi-Lo switching lever 210 is operated upward, it is switched to Hi, and when it is operated downward, it is switched to Lo.
In the second embodiment, while the auto-cruise switch 7h (see FIGS. 2 and 9) is in the ON state, the Hi-Lo switching lever 210 also functions to instruct increase / decrease of the vehicle speed in the auto-cruise mode. ing. Thereby, the number of switches can be reduced.

Here, FIG. 8 is an enlarged perspective view of the Hi-Lo switching lever 210 and the steering handle 7a as viewed from the work seat 7 side in order to show the positional relationship between the Hi-Lo switching lever 210 and the steering handle 7a.
Further, the memory 110 of the second embodiment has a function of storing the vehicle speed in addition to the function described in the first embodiment.

The second tractor 200 according to the second embodiment is provided with a memory return switch 220 (see FIG. 9) for instructing whether or not to shift to the vehicle speed stored in the memory 110.
In addition to the functions of the control unit 100 described in the first embodiment, the control unit 100 ′ (see FIG. 8) of the second embodiment includes a Hi-Lo switching lever 210, an auto cruise switch 7h, and a memory. In addition to having a function of receiving each output from the return switch 220, the operation of the stage switching valve 122 is also controlled.

Here, FIG. 9 is an input / output block diagram illustrating the control unit 100 ′ of the second tractor 200 of the present embodiment.
With the above configuration, the control unit 100 ′ (see FIG. 8) according to the second embodiment allows the Hi-Lo switching lever 210 to perform the first operation while the auto-cruise mode is on according to an instruction from the auto-cruise switch 7h. An instruction to increase or decrease the rotational speed of the variable hydraulic motor 121m of the second HST 11b is accepted as an instruction to increase or decrease the vehicle speed in the auto cruise mode.

  In addition, when the auto cruise mode is switched from the on state to the off state by the auto cruise switch 7h, the control unit 100 ′ stores the vehicle speed of the traveling vehicle body immediately before being switched in the auto cruise mode in the memory 110 (see FIG. 9). Let After that, the control unit 100 ′ receives the vehicle speed shift instruction from the memory return switch 220 after the auto cruise mode is switched to the on state by the auto cruise switch 7 h by the operator's operation. The vehicle speed is shifted to the previous vehicle speed stored in the memory 110.

The control operation by the control unit 100 ′ will be further described mainly with reference to FIG.
Here, FIG. 10 is a flowchart of the auto-cruise mode in the present embodiment.

  As shown in FIG. 10, when the auto-cruise switch 7h is turned on by the operator, the control unit 100 ′ proceeds to step S20 through step S10, and the HST pedal 7b at the time when the ON signal from the auto-cruise switch 7h is received. Is received from the HST pedal depression amount detection sensor 31, and an output signal is sent to the proportional solenoid valve 22 in order to travel while maintaining the corresponding vehicle speed, and the second HST 11b (see FIG. 4 (b)). The rotation amount of the trunnion shaft 21t of the hydraulic pump 21p is controlled to be constant (see step S20).

  Thereafter, when the operator operates the Hi-Lo switching lever 210, the control unit 100 ′ accepts an instruction from the Hi-Lo switching lever 210 as an instruction to increase or decrease the vehicle speed in the auto-cruise mode. , And an output signal is sent to the stage switching valve 122 to maintain the vehicle speed after the slight increase / decrease operation. That is, for example, when the operator switches the Hi-Lo switching lever 210 to the “Hi” side, the control unit 100 ′ rotates the trunnion shaft 121t on the variable hydraulic motor 121m side in a direction in which the vehicle speed slightly increases. Therefore, a command is issued to the stage switching valve 122 and the process proceeds to step S50.

  If the operator does not operate the Hi-Lo switching lever 210 (see step S30), the process proceeds to step S50 while maintaining the vehicle speed when the ON signal from the auto cruise switch 7h is received (see step S45). .

  If the ON signal from the memory return switch 220 is not received in step S50, the control unit 100 ′ proceeds to step S60, determines whether or not the auto cruise switch 7h has been switched from ON to OFF, and turns OFF. When it is determined that the vehicle has been switched, the process proceeds to step S70, and the vehicle speed immediately before the auto cruise switch 7h is switched from ON to OFF is stored in the memory 110.

When the control unit 100 ′ determines in step S60 that the auto cruise switch 7h has not been switched from ON to OFF, the control unit 100 ′ returns to immediately before step S30.
Thereafter, when the operator turns on the auto-cruise switch 7h again while traveling in the auto-cruise mode, the process proceeds to step S80 if it is determined through steps S10 to S50 that the memory return switch 220 is turned on. . Then, it is determined whether or not the vehicle speed immediately before the auto cruise switch 7h is switched from ON to OFF is stored in the memory 110. When it is determined that the vehicle speed is stored, the auto cruise switch 7h is switched from ON to OFF. The vehicle speed is changed to the vehicle speed immediately before switching (step S90), and then the process returns to immediately before step S30.

  In step S80, when it is determined whether or not the vehicle speed immediately before the auto cruise switch 7h is switched from ON to OFF is stored in the memory 110, if it is determined that the vehicle speed is not stored, immediately before step S50. Return to.

  As a result, when working in the auto cruise mode at a certain work place, then traveling on the road and working in the auto cruise mode again at the next work place, the previous work place is turned on by turning on the memory return switch. This is convenient for the operator.

  In the above-described embodiment, the configuration has been described in which the Hi-Lo switching lever 210 is switched to Hi when it is operated upward, and is switched to Lo when the Hi-Lo switching lever 210 is operated downward. In the case of “Hi”, a lamp (not shown) arranged on the meter panel (not shown) may be turned on, and in the case of “Lo”, the lamp arranged on the meter panel may be turned off. Thereby, in addition to the above effect, the lamp is lit with “Hi”, so that the operator can be alerted to the speed.

  Further, in the above-described embodiment, the configuration has been described in which the Hi-Lo switching lever 210 is switched to Hi when operated upward, and switched to Lo when operated downward, but is not limited to this, for example, “Hi” after engine startup. Thus, the configuration may be such that the operator operates “Hi-Lo switching lever 210” to become “Lo”.

  In the above-described embodiment, a configuration has been described in which the Hi-Lo switching lever 210 is switched to Hi when operated upward, and is switched to Lo when operated downward. However, the present invention is not limited to this. For example, the Hi-Lo switching lever 210 is moved up and down. When operated in either direction, it is possible to switch between “Hi” and “Lo”. When switched to “Hi”, a lamp (not shown) arranged on the meter panel (not shown) is turned on and set to “Lo”. When switched, the lamp arranged on the meter panel may be turned off. Thereby, the operator can distinguish between “Hi” and “Lo”.

  In the above-described embodiment, a configuration has been described in which the Hi-Lo switching lever 210 is switched to Hi when operated upward, and is switched to Lo when operated downward. However, the present invention is not limited to this. For example, the Hi-Lo switching lever 210 is moved up and down. When operated in either direction, it is possible to switch between “Hi” and “Lo”. When switched to “Lo”, a lamp (not shown) arranged on the meter panel (not shown) is turned on and set to “Hi”. When switched, the lamp arranged on the meter panel may be turned off. Thereby, the operator can distinguish between “Hi” and “Lo”. Further, in this configuration, after the engine is started, “Hi” may be set and “Lo” may be set when the operator operates the Hi-Lo switching lever 210.

  In the above-described embodiment, a configuration has been described in which the Hi-Lo switching lever 210 is switched to Hi when operated upward, and is switched to Lo when operated downward. However, the present invention is not limited to this. For example, the Hi-Lo switching lever 210 is moved up and down. Even if the operation is performed in either direction, “Hi” and “Lo” can be switched, and the Hi-Lo switching lever 210 is not switched unless the “up” and “down” positions are held for a certain period of time. good.

  In the above embodiment, while the auto-cruise switch 7h (see FIGS. 2 and 9) is in the ON state, the Hi-Lo switching lever 210 also functions as an instruction to increase or decrease the vehicle speed in the auto-cruise mode. However, the present invention is not limited to this. For example, in the auto-cruise mode, even if the Hi-Lo switching lever 210 is operated in the vertical direction, the vehicle speed cannot be switched between “Hi” and “Lo”. There may be.

  Further, in the above embodiment, the configuration for performing “ON” and “OFF” of the auto cruise mode using the auto cruise switch 7h (see FIGS. 2 and 9) has been described. During the cruise mode, the auto-cruise mode can be canceled by long-pressing the Hi-Lo switching lever 210 in one direction, and then the vehicle speed “Hi” is operated by operating the Hi-Lo switching lever 210 in the vertical direction. , “Lo” can be switched.

  In the second embodiment, the second tractor 200 in which the new configuration and function described in the second embodiment are further added to the configuration and function of the tractor 1 described in the first embodiment. However, the tractor which is an example of the work vehicle of the present invention is not limited to this, and includes, for example, the configuration and function newly described in the second embodiment, and the configuration and function described in the first embodiment. For example, by storing in advance the relationship between the depression amount of the HST pedal and the trunnion operation amount in accordance with various work modes, there is no third or configuration that enables traveling control suitable for the various work modes. May be a tractor.

  Moreover, in the said embodiment, although demonstrated taking the agricultural tractor as an example, it is not restricted to this, For example, it may be a tractor for construction or transportation, or it is not limited to a tractor, for example, Other work vehicles may be used.

  The HST pedal 7b of the above embodiment is an example of the shift instruction tool of the present invention, and the HST pedal depression amount detection sensor 31 of the present embodiment is an example of the shift operation amount detection sensor of the present invention.

  In the above-described embodiment, the configuration using the HST pedal 7b as an example of the shift instruction tool of the present invention has been described. However, the present invention is not limited to this. For example, a lever-type shift instruction tool may be used.

  As described above, according to the tractor 1 of the present embodiment, when the work travel mode M2 is set, the trunnion shaft 21t adapted to the travel speed can be obtained without paying attention to the degree of depression of the HST pedal 7b during the work travel. Therefore, the speed adjustment can be performed easily and appropriately. That is, it is not necessary to concentrate attention on the depression and depressing of the HST pedal 7b, and excessive depression during fine adjustment is eliminated, thereby reducing worker fatigue.

  In the second embodiment, the configuration in which the mechanism for instructing the switching of the stage switching valve 122 is a lever type has been described. However, the configuration is not limited to this, and for example, a push type configuration may be used.

  The present invention is useful as a work vehicle such as a tractor for agriculture, construction, and transportation.

2 Front wheels (traveling device)
3 Rear wheels (travel device)
4 Engine 7b HST pedal 7c Brake pedal 11 HST (Hydraulic continuously variable transmission)
32 Mode change means (mode change switch)
M1 Road driving mode M2 Work driving mode

Claims (3)

  Power is transmitted from the engine (4) to the travel devices (2) and (3) via the HST (11), and the HST (11) is shifted by depressing the HST pedal (7b) to change the travel speed. In a vehicle, a transmission for a work vehicle, wherein the HST (11) is shift-controlled to a plurality of stages with respect to an amount of depression of the HST pedal (7b).   A road travel mode (M1) for continuously shifting the HST (11) and a work travel mode (M2) for shifting the HST (11) to a plurality of stages are provided in accordance with the stepping depth of the HST pedal (7b). The transmission device for a work vehicle according to claim 1, wherein the travel mode can be appropriately selected by means (32).   A brake pedal (7c) that operates in preference to the operation of the HST pedal (7b) is provided, and when the brake pedal (7c) is depressed, the hydraulic continuously variable transmission (11) is shifted to a plurality of stages and decelerated. The work vehicle transmission according to claim 1, wherein the work vehicle has a transmission.

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