JP3672439B2 - Work vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention is provided with a hydraulic clutch and a synchromesh gear speed change mechanism that is operated to change speed by an actuator in series in a transmission system between an engine and a traveling wheel, and at the time of shifting, the hydraulic clutch is set prior to operation of the actuator. The present invention relates to a work vehicle including a control unit that performs a cutting operation and engages and operates a hydraulic clutch after completion of a shift by actuation of an actuator.
[0002]
[Prior art]
  As a work vehicle configured as described above, there is one disclosed in Japanese Patent Application Laid-Open No. 9-242871, and in this conventional example, a main transmission mechanism that is operated in four stages by hydraulic cylinders 11 and 12. A, a first sub-transmission mechanism B that is shifted in two steps by the hydraulic cylinder 13, and a second sub-shift that is shifted in two steps by the hydraulic cylinder 14.Mechanism D andThe hydraulic clutch 3 interposed in the transmission system, and a control device 25 for controlling the hydraulic cylinder and the hydraulic clutch 3 are provided. The control device 25 is interlocked with the start of operation of the hydraulic cylinder at the start of shifting. The hydraulic clutch 3 is disengaged and the gear clutch 3 is engaged when the gear shift is completed, so that the gear can be shifted without manually disengaging the main clutch 2.
[0003]
[Problems to be solved by the invention]
  Considering the speed change operation of the conventional speed change system, when the speed change is started, the shift member of the gear speed change system starts to be separated from one gear system by the driving force of the hydraulic cylinder. The hydraulic clutch is disengaged in conjunction with Next, the operation is started in the direction in which the predetermined shift member meshes with the gear system by the driving force of the hydraulic cylinder. In this operation, the occlusion is completed in a state where the rotation speeds of the shift member and the gear system are synchronized by a synchronizing member such as a synchronizer ring, and then the hydraulic clutch is engaged and operated. However, when the shift member is engaged with the gear system by the driving force of the hydraulic cylinder, it is difficult for the shift member to reach synchronous rotation due to the resistance caused by the strong contact between the shift fork or the like that operates the shift member and the shift member. In addition, when the temperature of the lubricating oil in the transmission case is low and the viscosity of the lubricating oil is high, not only is the shift member and the gear system difficult to reach a synchronized state, but smooth shifting operation may not be performed.
[0004]
  An object of the present invention is to make it possible to smoothly perform a speed change operation in a work vehicle including a gear speed change system operated by an actuator as described above, a hydraulic clutch that is operated to be turned off at the time of the speed change operation, and the speed change system. It is in.
[0005]
[Means for Solving the Problems]
  According to a first aspect of the present invention (Claim 1), as described at the beginning, a hydraulic clutch is provided in a transmission system between an engine and a traveling wheel, and a synchromesh gear transmission mechanism that is operated to change speed by an actuator. In a work vehicle equipped with a control means for connecting in series and operating the hydraulic clutch to be disengaged prior to the operation of the actuator at the time of shifting, and to engage and operate the hydraulic clutch after completion of the shifting by the operation of the actuator,The actuator is composed of a hydraulic cylinder, and is equipped with an oil temperature sensor that measures the temperature of hydraulic oil supplied to the hydraulic cylinder.If the operated speed change member does not end the speed change operation within the set time after the start of the speed change operation,The hydraulic cylinder only when the temperature measured by the oil temperature sensor is below the specified valueTemporarily reduce the shifting operation force fromHydraulic cylinderAfter temporarily operating in the reverse direction,Hydraulic cylinderThe control means of the control means is set so as to operate again in the speed change direction, and its operation and effect are as follows.
[0006]
  A second feature of the present invention (Claim 2) is that, in Claim 1, the actuator is composed of a double-acting hydraulic cylinder,This hydraulic cylinderWhen reducing the shifting operation force fromHydraulic pressureReducing the hydraulic oil pressure against the cylinder,Hydraulic cylinderWhen operating in the reverse direction, the control means is set to switch the supply / discharge direction of the hydraulic oil to / from the hydraulic cylinder, and its operation and effect are as follows.
[0007]
[Action]
  First featureAccording to the present invention, when the speed change operation is not completed within the set time after the speed change member starts the speed change operation, the control means is configured to operate the hydraulic cylinder only when the temperature measured by the oil temperature sensor is equal to or lower than a predetermined value. The operating force of the engine is temporarily reduced and the hydraulic cylinder is operated in the opposite direction, so that the hydraulic oil temperature is low and the required driving force cannot be obtained from the hydraulic cylinder. Even when a member to be rotated synchronously, such as a synchronizer ring, does not reach the synchronized state, by operating the hydraulic cylinder again, the member to be rotated synchronously can be easily set to the synchronized rotational state to perform a shift.
[0008]
  According to the second feature,Double actingShifting with a hydraulic cylinder enables shifting operation with a small but powerful driving force, and even when reducing the hydraulic oil pressure to the hydraulic cylinder or switching the hydraulic oil supply / discharge direction to the hydraulic cylinder, It suffices to operate a control valve for controlling.
[0009]
〔The invention's effect〕
  Therefore,A work vehicle that can perform smooth and reliable shift operation with a simple improvement of the shift control mode even when the hydraulic oil temperature is low and the driving force of the hydraulic cylinder is insufficient has been rationally constructed.(Claim 1).Double actingShift operation is possible with the powerful driving force of the hydraulic cylinder.AndEven when shifting operations cannot be performed smoothlyBy lowering the hydraulic oil pressure to the hydraulic cylinder or switching the hydraulic oil supply / discharge direction to the hydraulic cylinderThe shift can be easily controlled (claim 2).
[0010]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the present invention will be described with reference to the drawings.
  As shown in FIG. 1, an engine E is mounted on the front portion of a vehicle body having a driving type front wheel 1 and a driving type rear wheel 2 (an example of a traveling wheel) configured to be steerable. A transmission case 4 to which power from the engine E is transmitted via the main clutch 3 is disposed at the rear of the vehicle body, and a pair of left and right driven up and down by a hydraulic cylinder (not shown) at the rear end upper position of the transmission case 4 An agricultural tractor as an example of a work vehicle is configured by including a lift arm 5 and disposing a driving unit at the center of the vehicle body.
[0011]
  As shown in FIGS. 1 and 2, the driving section includes a driving seat 6, a steering handle 7 is disposed at a position in front of the driving seat 6, and a swinging operation in the front-rear direction is performed near the steering handle 7. A freely moving forward / reverse switching lever 8 is disposed, a position lever 9 for controlling the swing angle of the lift arm 5 is disposed on the right side of the driver seat 6, and a shift lever for setting the traveling speed on the left side of the driver seat 6 10 (an example of a shift operation tool) is arranged. A clutch pedal 11 for disengaging the main clutch 3 by a stepping operation is arranged on the left side of the step, and a side for independently braking the left and right rear wheels 2 and 2 by a stepping operation on the right side of the step. Brake pedals 12 and 12 are arranged.
[0012]
  As shown in FIG. 3, the lever guide 13 for guiding the speed change lever 10 is branched from a main guide portion 13A formed in the longitudinal direction along the front-rear direction and a neutral position N intermediate the main guide portion 13A. A sub guide portion 13B is formed in parallel with the main guide portion 13A, an overdrive speed change range OD is disposed at the front end of the main guide portion 13A, and a parking brake (described later) is provided at the rear end of the main guide portion 13A. A parking position P for braking operation is arranged, a standard transmission range ST is arranged at the rear end portion of the sub guide portion 13B, and a creep transmission range CR is arranged at the front end portion of the sub guide portion 13B. In addition, each of the overdrive speed change range OD, the standard speed change range ST, and the creep speed change range CR has an operation range in which the speed change lever 10 can be slightly operated in the front-rear direction, and the speed change lever 10 is set in each operation range. The shift lever 10 is held at the central holding position n in the front-rear direction of the operation area. When the transmission lever 10 is operated forward from the holding position n, the speed increasing switch SwU operates the transmission lever 10. When the shift lever 10 is operated backward from the holding position n, the deceleration switch SwD is configured to detect the operation of the shift lever 10 and detects that the shift lever 10 is set to the parking position P. A parking switch SwP is provided.
[0013]
  As shown in FIGS. 4 and 5, the base end portion of the speed change lever 10 is provided with a bifurcated fork-like member 14, and the fork-like member 14 is fitted to a laterally rotating shaft 15 and has a front-rear posture. A vine-wound spring 17 that supports the shift lever 10 so as to be swingable around the support shaft 16 and urges the shift lever 10 from the main guide portion 13A side to the side where the sub guide portion 13B is formed around the support shaft 16 is provided. Yes. Further, a fan-shaped cam member 18 is provided on the vehicle body side, and a concave portion 18A corresponding to the overdrive speed change range OD, creep speed change range CR, neutral position N, standard speed change range ST, and parking position P with respect to the cam member 18 is provided. And a roller 20 engaged with each concave portion by the urging force of the spring 19 is provided at a swinging end of an arm 21 supported so as to be swingable with respect to the speed change lever 10 so that the speed change lever 10 is overdriven. An urging mechanism F that can be held at the holding position n of each of the shift range OD, the standard shift range ST, and the creep shift range CR, and that can be biased and held at the neutral position N and the parking position P, further rotates. A potentiometer-type lever sensor LS for determining the operation position of the transmission lever 10 from the rotation amount of the shaft 15 is provided. In each of the overdrive speed range OD, the creep speed range CR, and the standard speed range ST, the concave portion 18A has a gentle slope so that the speed increasing switch SwU and the speed reducing switch SwD can be operated by the speed change lever 10. Has been.
[0014]
  As shown in FIG. 6, a first arm 23 provided on the rotating shaft 15 and an operation arm 24 for creep shifting are connected via a first rod 25, and a second arm 26 provided on the rotating shaft 15 An overdrive speed change operation arm 27 is linked through a pair of second rods 28 and 28 and a swingable intermediate arm 29, and a third arm 30 provided on the rotary shaft 15 and an operation wire 31 are connected. The parking brake is linked. As shown in FIG. 7, the parking brake protrudes into the transmission case by the urging force of the compression spring 32 with respect to the side wall of the transmission case 4 and engages with the gear G of the traveling system in the transmission case. A lock member 33 is provided, and an operation piece 34 that contacts the flange-like portion 33B on the outer end side of the lock member 33 and operates the lock member 33 in the disengagement direction is provided around the support shaft 35. The operation wire 31 is connected to the end of a switching arm 36 for operating the operation piece 34. When the shift lever 10 is set to the shift range, the lock member 33 is set to the non-engagement position (non-braking state / off) by the operation force from the operation wire 31, and the shift lever 10 is set to the parking position P. In this case, the operation wire 31 is relaxed, and the position where the lock member 33 engages with the gear G (braking position / on) is set by the urging force of the compression spring 32. As a result, the front and rear wheels 1 and 2 are held in the locked state. It has become a thing.
[0015]
  As shown in FIG. 6, when the shift lever 10 is set to the overdrive shift range OD, the overdrive transmission mechanism Tod (described later) is set to be turned on and the creep transmission mechanism Tcr (described later) is set to the on state. However, since the third transmission mechanism T3 (described later) arranged at the top of the transmission of the creep transmission mechanism is set to the neutral position, the power from the overdrive transmission mechanism is transmitted to the traveling system. . Further, when the speed change lever 10 is set to the creep speed change range CR, the overdrive speed change mechanism Tod is set to the cut-off state, and at the same time, the third speed change mechanism T3 is set to the transmission state, so that the creep speed change mechanism Tcr Power is transmitted to the traveling system. When the shift lever 10 is set to the neutral position N, the overdrive transmission mechanism Tod and the creep transmission mechanism Tcr are both held at the neutral position, and no power is transmitted to the traveling system. Further, when the transmission lever 10 is set to the standard transmission range ST, a mechanical linkage is formed so that the creep transmission mechanism Tcr is set to the standard position while the overdrive transmission mechanism Tod is turned off. In this way, the transmission operation mechanism is configured by a system that mechanically sets the transmission state of the creep transmission device Tcr and sets the transmission state of the overdrive transmission mechanism Tod by the operation force of the transmission lever 10.
[0016]
  The transmission case 4 has a transmission system shown in FIG. That is, the first speed change mechanism T1 including four sets of gears and two sets of synchromesh type shift members 41 and 42 so as to shift the power transmitted from the engine E through the main clutch 3 in four stages. The hydraulic clutch C disposed at the lower transmission of the first transmission mechanism T1, the two gears disposed at the lower transmission of the hydraulic clutch C, and one synchromesh type shift member 43 so as to shift the power in two stages. And a second sub-transmission mechanism T2 including a reverse gear system and a synchromesh-type shift member 44 for transmitting the power of the second transmission mechanism T2 in a normal rotation state and a reverse rotation state. A third speed machine including an advance transmission mechanism Tfr and two sets of gears and one synchromesh type shift member 45 arranged below the transmission of the forward / reverse transmission mechanism Tfr so as to change the power in two stages. T3, an overdrive transmission mechanism Tod that includes a pair of gear systems that are arranged on the lower side of the transmission to obtain a high-speed transmission state and a synchromesh type shift member 46, and a third transmission that is arranged on the lower side of the transmission of the third transmission mechanism T3. A creep transmission mechanism Tcr provided with a state in which the speed change state from the mechanism T3 is transmitted as it is, a set of gears that decelerate greatly, and a constant mesh type shift member 47 is provided. The power from this transmission system is transmitted to the rear wheel 2 via the differential 48 for the rear wheel 2 and is driven in such a manner that the peripheral speed of the front wheel 1 is matched with the peripheral speed of the rear wheel 2. The front wheel 1 is transmitted to the front wheel 1 via the front wheel speed increasing device 49 and the front wheel drive shaft 50 that can be switched to a speed increasing drive state in which the peripheral speed of the front wheel 1 is made higher than the peripheral speed of the rear wheel 2. The traveling transmission system is configured so that The front wheel speed increasing device 49 is formed with an operating system so that the front wheel 1 is switched to the speed increasing drive state when the front wheel 1 is operated to be larger than a preset steering angle. By switching, the turning radius of the vehicle body is reduced.
[0017]
  The first transmission mechanism T1 and the second transmission mechanism T2 constitute a main transmission TM that shifts the forward travel speed to eight stages. The TM includes three shift members 41, 42, and 43. A first hydraulic cylinder P1, a second hydraulic cylinder P2, and a third hydraulic cylinder P3 (an example of an actuator) that operate each of them are provided, and the shift member 44 of the forward / reverse transmission mechanism Tfr is mechanically linked to the forward / reverse switching lever 8. The third speed change mechanism T3 includes a fourth hydraulic cylinder P4 (an example of an actuator) that operates the shift member 45, and the shift member 46 of the overdrive speed change mechanism Tod is linked to the operation arm 27 for overdrive speed change. The shift member 47 of the creep transmission mechanism Tcr is linked to the operation arm 24 for creep transmission.
[0018]
  As shown in FIG. 9, a hydraulic system for controlling each of the hydraulic cylinders and the hydraulic clutch C is configured. That is, the first, second, and fourth hydraulic cylinders P1, P2, and P4 are configured as a double-acting type in which the shift members 41, 42, and 45 can be set at both operation ends and a neutral position (the publication number is given). The three hydraulic cylinders P3 have a double-acting type in which the shift member 43 can be set at both operation ends, and control these hydraulic cylinders P1, P2, P3, and P4. An oil passage system is formed for supplying hydraulic oil from the hydraulic pump 51 driven by the engine E to the seven electromagnetically operated cylinder control valves V1, V1, V2, V2, V3, V4, and V4. In addition, an oil passage system for supplying hydraulic oil from the hydraulic pump 51 to the hydraulic clutch C through a pilot-operated on-off valve Vc is formed, and the hydraulic clutch C is formed by an electromagnetic proportional pressure control valve Vp. Entering Oil passage is formed for adjusting the pressure of time, oil passage system is formed to supply the hydraulic oil to the pilot oil passage 53 via the orifice 52. Further, an oil passage for operating the on-off valve Vc is formed by the pressure of the pilot oil passage 53, and a system for reducing the pressure with respect to the pilot oil passage 53 via five check valves 54 is provided. Yes. Four of the five check valves 54 are mechanically opened / closed when the hydraulic cylinders P1, P2, P3, P4 are operated, and the other check valve 54 is opened / closed when the forward / reverse switching lever 8 is operated. The pilot oil passage 53 is provided with a pressure sensor 55 so as to be operated.
[0019]
  When the hydraulic cylinders P1, P2, P3, and P4 start to operate, the corresponding check valve 54 is opened to reduce the pressure in the pilot oil passage 53, thereby switching the on-off valve Vc to the drain position and disengaging the hydraulic clutch C. Thus, the shift is performed by the operation of the hydraulic cylinder at the timing when the hydraulic clutch C is in the disengaged state. Thereafter, when the operation of the hydraulic cylinder is completed, the check valve 54 is returned to the closed state. As a result, the on-off valve Vc is operated to the hydraulic oil supply position, and the pressure of the hydraulic oil supplied thereby is adjusted by the control valve Vp. It is sent to the hydraulic clutch C, and the hydraulic clutch C reaches the engaged state, and it is not necessary to manually disengage the main clutch 3 at the time of shifting. Similarly, when the forward / reverse switching lever 8 is operated, the corresponding check valve 54 is opened to reduce the pressure in the pilot oil passage 53, thereby switching the on-off valve Vc to the drain position and disengaging the hydraulic clutch C. The shift is performed in the operated state, and then the check valve 54 is returned to the closed state when the operation of the forward / reverse switching lever 8 is completed. As a result, the on-off valve Vc is operated to the hydraulic oil supply position and the operation supplied thereby. The oil pressure is adjusted by the control valve Vp and sent to the hydraulic clutch C, and the hydraulic clutch C reaches the engaged state. Further, when the speed change operation is performed in this manner, the pressure in the pilot oil passage 53 rises after decreasing, and when this change in pressure is detected by an electric switch type pressure sensor 55, a control device (described later). However, by adjusting the current to the electromagnetic solenoid of the control valve Vp, the hydraulic clutch C is boosted while adjusting the supply pressure of the hydraulic oil supplied to the hydraulic clutch C according to a predetermined characteristic, and a shock is generated. It enters smoothly and switches to a state.
[0020]
  As described above, when the hydraulic cylinder starts to operate, the hydraulic clutch C is released immediately before the start of the operation of the shift member due to the mechanical clearance of the member linked to the hydraulic cylinder and the elastic distortion of the shift system. In this state, the shift member can be operated with the hydraulic cylinder in the state in which the hydraulic clutch C is disengaged, so that the shift can be performed without manually operating the main clutch 3. Further, when the shift by the shift member is completed, the shift power can be transmitted by returning the hydraulic clutch C to the engaged state.
[0021]
  As shown in FIG. 10, a key switch 62 for starting and stopping the engine E and supplying and stopping electric power to an electric device provided in the vehicle body with respect to a control device 61 (an example of control means) including a microprocessor. The pressure sensor 55, the three speed increasing switches SwU, the three speed reducing switches SwD, the parking switch SwP, the lever sensor LS, and the forward / reverse sensor for detecting the operation position of the forward / reverse switching lever 8. 63, a system for inputting a signal from the main clutch sensor 64 for determining the state of the main clutch 3, and the seven cylinder control valves V1, V1, V2, V2, V3, V4, V4, and the pressure A system for outputting a control signal to the control valve Vp and the shift display device D arranged on the meter panel at the front position of the driver seat 6 is formed.
[0022]
  As shown in the figure, the shift display device D includes a light emitting diode type display 66 for displaying a gear number, and a forward movement indicating that the forward / reverse switching mechanism Tfr is set to the forward movement state by the letter “F”. A ramp 67, a reverse ramp 68 indicated by a letter "R" indicating that the forward / reverse switching mechanism Tfr is set to the reverse state, the shift lever 10 being set to the neutral position N, and the main transmission. When the two hydraulic cylinders P1 and P2 of TM and the hydraulic cylinder P4 of the third transmission mechanism T3 are set to the neutral position, the neutral lamp 69 indicating the neutral state with the letter “N” and the transmission lever 10 are parked. The parking lamp 70 indicating that the position P is set by the letter “P”, and the overdrive indicating that the overdrive transmission mechanism Tod is in the transmission state by the letters “overdrive”. Eve ramp 71, a standard ramp 72 indicating that the creep transmission mechanism Tcr is in the standard transmission state by a letter “standard”, and a creep lamp 73 indicating that the creep transmission mechanism Tcr is in a transmission state by a letter “creep” The shift control by the controller 61 will be described below.
[0023]
  As shown in the flowchart of FIG. 11, when the key switch 62 is turned on and the control is started together with the start of the engine E, a shift control routine (# 200 step) is executed, and when the shift range is changed by operating the shift lever 10 based on the signal from the lever sensor LS (step # 101), the initial state setting routine (# 300) is executed. Step) is executed, and then the display operation for displaying the shift state on the shift display device D is continuously performed until reset (steps # 102 and # 103). In the display operation, any one of the overdrive lamp 71, the standard lamp 72, and the creep lamp 73 is turned on based on the setting state of the shift lever 10, and the shift stage set in the main transmission TM is displayed on the display 66. When the shift lever 10 is set to the neutral position N, the neutral lamp 69 is lit, and the forward lamp 67 or the reverse lamp 68 is lit based on the set position of the forward / reverse switching mechanism Tfr. It has become.
[0024]
  The control operation of the shift control routine (step # 200) is set as shown in the flowchart of FIG. 12, and in this control, the forward / reverse sensor 63 detects that the forward / reverse switching mechanism Tfr is in a position other than neutral. When the lever sensor LS detects that the creep transmission mechanism Tfr is not in the creep state and the main clutch sensor 64 detects that the main clutch 3 is in the engaged state (# 201- Step # 203), when the speed increasing switch SwU is turned on, the speed change target is increased by one step, and when the speed reduction switch SwD is turned on, the speed change target is decreased by one step to obtain this speed change target. The hydraulic cylinders P1, P2, and P4 of the TM and the third transmission mechanism T3 are operated (sequential transmission mode, # 204 to # 208 steps). Flop).
[0025]
  When the forward / reverse switching mechanism Tfr is in the neutral position, the main clutch 3 is disengaged when the forward / reverse sensor 63 detects that the creep transmission mechanism Tcr is in the creep state transmission state. When it is detected by the main clutch sensor 64 (steps # 201 to # 203), when the speed increasing switch SwU is turned on, the ON time continues for a predetermined interval (shorter than 1 second). Every time), the shift target is increased by one step, and conversely, when the deceleration switch SwD is turned on, the shift target is increased every predetermined interval (short time of 1 second or less) within the time that the ON time continues. The speed is lowered by one step, and the speed is changed by the operation of one of the hydraulic cylinders P1, P2, P4 of the main transmission TM and the third speed change mechanism T3 so as to obtain this speed change target. Cormorants control mode is set (continuous transmission mode, # 209 to # 212 steps # 208 steps).
[0026]
  Further, in this shift control, by operating the shift lever 10 in the standard shift range ST, the main transmission TM and the third shift mechanism T3 can be combined to make a 16-speed shift, and the shift lever 10 is moved to the overdrive shift range. By shifting at OD, it is possible to shift in 8 steps in the same way, and by shifting the shift lever 10 in the creep shift range CR, it is possible to shift in 16 steps (shifting only 8 steps in the main transmission TM). May be configured). When the shift lever 10 is operated at the standard shift ST, the standard lamp 72 is lit and at the same time the shift stage is displayed on the display 66. When the shift lever 10 is operated in the overdrive shift range OD, the overdrive lamp 71 is displayed. At the same time as is lit, the gear stage is displayed on the display 66, and when the shift lever 10 is operated in the creep gear shift range CR, the creep stage 73 is lit and at the same time the gear stage is displayed on the display 66.
[0027]
  The control operation of the initial state setting routine (# 300 step) is set as shown in the flowchart of FIG. 13. In this control, when the speed change range after the change of the speed change lever 10 is the overdrive speed range OD, the control operation is performed. Set the speed change target of the transmission TM to the lowest speed, and if the speed change range after the change of the speed change lever 10 is the creep speed change range CR, set the speed change target of the main transmission TM to the highest speed, Further, the hydraulic cylinder is controlled so as to reveal this shift stage to perform a shift operation (steps # 301 to # 305).
[0028]
  Further, in this tractor, the control operation in the # 208 step is set so as to perform a reliable shift when the shift members 41, 42, 43, 45 are operated to the transmission side of the hydraulic cylinders P1 to P4. That is, as shown in the flowchart of FIG. 14, at the start of shifting, first, the corresponding hydraulic cylinder is controlled by operating the corresponding cylinder control valve so as to shift the transmission member in the transmission state to the neutral side, and the pilot oil passage Confirm that the pressure sensor 55 has been turned off as the pressure of 53 decreases.(When the steps # 501 and # 502, the main transmission TM, and the third transmission mechanism T3 are in a neutral state, this processing is not performed). Next, the operation of the corresponding hydraulic cylinder is started by operating the corresponding cylinder control valve so that the shift member to be set in the transmission state is operated toward the transmission side, and the hydraulic oil at the start time is started. When the oil temperature is measured by an oil temperature sensor and the oil temperature is high enough to neglect the viscosity of the hydraulic oil, the current value for the electromagnetic solenoid of the control valve Vp after the pressure sensor 55 reaches the ON state. Is controlled in accordance with predetermined characteristics to smoothly increase the pressure of the hydraulic oil supplied to the hydraulic clutch C and switch to the transmission state without generating a shock (steps # 503 to # 506).
[0029]
On the other hand, when the hydraulic oil temperature is low and the hydraulic oil viscosity is high, the timer (which consists of software) is counted almost simultaneously with the cylinder operation as described above. When it is detected that the pressure sensor 55 has been switched to the ON state within the time set by this timer (a value of several seconds or less), the shift member operates to the proper transmission position and the pilot oil passage 53 indicates that the pressure of the valve 53 has increased and the on-off valve Vc has been switched to the open state, so that the current supplied to the electromagnetic solenoid of the control valve Vp is controlled according to a predetermined characteristic and supplied to the hydraulic clutch C. The oil pressure is raised smoothly and no shock is generated. (Steps # 507 to # 509, # 506), and when the hydraulic cylinder is operated to the side that operates the shift member to the transmission side in this way, the pressure is set within the time set by the timer. When the sensor 55 is not switched to the ON state (when the shift member is not operated to the proper transmission position), the hydraulic oil supplied to the hydraulic cylinder by the operation of the cylinder valve is set to a state that can be discharged, or By operating the hydraulic cylinder in the reverse direction by operating the cylinder valve, the operating force is released for a preset time, and then the hydraulic cylinder is started to operate on the transmission side by operating the cylinder valve, as described above. At the same time, the timer (configured by software) starts counting and detects that the pressure sensor 55 has been switched on within the time set by this timer. In this case, the shift member operates to an appropriate transmission position, and the pressure in the pilot oil passage 53 increases, indicating that the on-off valve Vc is switched to the open state. The current value is controlled in accordance with a predetermined characteristic to smoothly increase the pressure of the hydraulic oil supplied to the hydraulic clutch C and switch to the transmission state without generating a shock (steps # 510 to # 514, # 506). When the shift member is not operated to the proper transmission position within the time set by the timer, the hydraulic cylinder is operated to return the shift member to the neutral position by operating the cylinder valve, and the display 66 is flashed. It is informed that the shift is impossible (steps # 515 and # 516).
[0030]
  As described above, according to the present invention, when shifting is performed in a low-temperature environment in the hydraulic cylinder, the shift member is not smoothly operated due to the viscosity of the lubricating oil stored in the transmission case 4 or is in contact with the shift member. If the shift member is difficult to rotate synchronously with the gear transmission system due to the resistance from the shift fork and the appropriate shift is not performed within the set time, after canceling the shift operation force and temporarily interrupting the shift operation, Since the speed change operation is performed again, the influence of the resistance due to the viscosity of the lubricating oil is reduced, and the resistance that acts on the shift member when the operating force is released is reduced to facilitate the synchronous rotation, thereby smoothly Thus, a reliable speed change operation can be performed.
[0031]
  In the present invention, it is possible not only to set one of the overdrive speed change mechanism Tod and the creep speed change mechanism Tcr to the transmission state by operating the single speed change lever 10, Just by operating the main transmission device TM one step or continuously, the main transmission device TM can be operated one step or continuously by simply operating the speed change lever 10 to the deceleration position. Therefore, the speed change operation is simple and easy, and the side where the speed change lever 10 is operated to the overdrive speed range OD is set to the front side of the vehicle body with reference to the standard speed range CR. Since the side where the shift lever 10 is operated to the creep shift range CR is set to the rear side of the vehicle body with reference to the standard shift range CR, the direction of increase / decrease of the traveling speed and the operation of the shift lever 10 are set. Further, the shift lever 10 is held at the holding position n by the biasing force of the biasing mechanism F in any of the shift ranges of the standard shift range CR, the overdrive shift range OD, and the creep shift range CR. If the shift lever 10 is operated forward with respect to the holding position n, the traveling speed is increased, and the shifting operation is performed by reducing the traveling speed by operating the shift lever 10 in the opposite direction. Is difficult to occur.
[0032]
  Implementation aboveIs provided with an oil temperature sensor (not shown) for measuring the temperature of the hydraulic oil supplied to the hydraulic cylinders P1 to P4, and a temperature signal from the oil temperature sensor is input to the control device 61. And formingThe cylinder control routine is shown in FIG.The control shown in the flowchart is performed.
[Brief description of the drawings]
[FIG. 1] Whole side view of an agricultural tractor
[Fig. 2] Plan view of rear part of agricultural tractor
[Fig. 3] Plan view of lever guide
FIG. 4 is a side view of a shift lever support structure.
FIG. 5 is a front view of a shift lever support structure.
FIG. 6 is a side view showing the linkage of the shift lever.
FIG. 7 is a longitudinal sectional view showing a parking brake.
FIG. 8 is a schematic diagram of a traveling transmission system.
FIG. 9 is a hydraulic circuit diagram for traveling speed change.
FIG. 10 is a block circuit diagram of a control system.
FIG. 11 is a flowchart of the main control operation.
FIG. 12 is a flowchart of a shift control routine.
FIG. 13 is a flowchart of an initial state setting routine.
FIG. 14 is a flowchart of a cylinder control routine.
[Explanation of symbols]
  1, 2 running wheels
  61 Control means
  C Hydraulic clutch
  E engine
  P1 to P4 Actuator
  T1-T3 gear transmission mechanism

Claims (2)

The transmission system between the engine and the traveling wheel is provided with a hydraulic clutch and a synchromesh gear transmission mechanism that is operated by the actuator in series, and at the time of shifting, the hydraulic clutch is operated before the operation of the actuator. A work vehicle comprising a control means for engaging and operating a hydraulic clutch after the end of a shift by actuation of an actuator;
The actuator includes a hydraulic cylinder, and includes an oil temperature sensor that measures the temperature of hydraulic oil supplied to the hydraulic cylinder. If the speed change operation is not completed within this period, the speed change operation force from the hydraulic cylinder is temporarily reduced or the hydraulic cylinder is temporarily stopped only in a situation where the temperature measured by the oil temperature sensor is equal to or lower than a predetermined value. A working vehicle in which the control mode of the control means is set so that the hydraulic cylinder is operated again in the speed change direction after being operated in the reverse direction. The actuator is composed of a double-acting hydraulic cylinder, and when the shifting operation force from the hydraulic cylinder is reduced, the hydraulic oil pressure on the hydraulic cylinder is reduced and the hydraulic cylinder is operated in the reverse direction. The work vehicle according to claim 1, wherein the control mode of the control means is set so as to switch the supply / discharge direction of the hydraulic oil to / from the hydraulic cylinder.

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