JP5767035B2 - Speed control structure of work vehicle - Google Patents

Description

  The present invention brakes a wheel with a braking force according to an operation position of a speed change operation means for changing the output of the continuously variable transmission by changing the output of the continuously variable transmission and an operation pedal for automatically returning to the stepping release position. The output of the continuously variable transmission is preset by a shift operation tool by controlling the operation of the shift operation means based on a brake device, a pedal sensor for detecting the operation position of the operation pedal, and the output of the pedal sensor The present invention relates to a vehicle speed control structure for a work vehicle, which includes a control means for changing to a speed corresponding to the output of the pedal sensor in a shift range over the set speed and zero speed.

  In the vehicle speed control structure of the work vehicle as described above, the vehicle body brakes and stops when the operation pedal reaches the stop braking region beyond the boundary position between the shift braking region and the stop braking region, and exceeds the boundary position. There is one configured to start the vehicle body by returning to the speed change braking region (see, for example, Patent Document 1).

JP 2010-111353 A

  In the above configuration, in order to maintain the braking stop state of the vehicle body, it is necessary to hold the operation pedal in the stop braking region with a large pedaling force. When the pedal effort is reduced, the operation pedal is likely to return to the speed change braking region beyond the boundary position, and thus there is a possibility that the vehicle body is unexpectedly started.

  An object of the present invention is to prevent a possibility that the vehicle body starts unexpectedly due to a decrease in the depressing force on the operation pedal due to other operations in a state where the vehicle body is braked and stopped by depressing the operation pedal. is there.

According to a first aspect of the present invention, there is provided a shifting operation means for changing the output of the continuously variable transmission by changing the speed of the continuously variable transmission, and a wheel with a braking force corresponding to the operation position of the operation pedal that automatically returns to the stepping release position A brake device for braking, a pedal sensor for detecting an operation position of the operation pedal, and an operation of the shift operation means based on an output of the pedal sensor, thereby controlling an output of the continuously variable transmission with a shift operation tool. In a vehicle speed control structure for a work vehicle, comprising a control means for changing to a speed according to the output of the pedal sensor in a speed change range over a preset set speed and zero speed,
As the shift output setting data indicating the relationship between the operation position of the operation pedal and the output of the continuously variable transmission, the control means has a deceleration end position of the operation pedal at which the output of the continuously variable transmission becomes zero speed. First data set so that a stepping operation amount from the stepping release position is increased, and second data set so that a stepping operation amount from the stepping release position is reduced,
When the control means detects that the operation position of the operation pedal is a position on the stepping limit position side beyond the deceleration end position from the output of the pedal sensor during execution of the control operation based on the first data, Ri constructed from the execution state of the control operation based on the first data to switch to the execution state of the control operation based on the second data tare,
The deceleration end position of the second data is located in a brake release area that is an operation area of the pedal in which the operation of the brake device is released .

  According to the first aspect, during execution of the control operation based on the first data, the vehicle is braked and stopped by depressing the operation pedal to the operation position on the depressing limit position side exceeding the deceleration end position of the first data. Then, when the operation pedal exceeds the deceleration end position of the first data, the control means switches from the execution state of the control operation based on the first data to the execution state of the control operation based on the second data. The vehicle body will not start unless it passes through the deceleration end position of the first data and returns to the deceleration end position of the second data.

  Therefore, by performing other operations while the vehicle body is braked and stopped by depressing the operation pedal, the pedal force on the operation pedal is reduced, and the operation pedal is decelerated at the first data and at the end of the first data. Even when the vehicle has returned to the position, the vehicle body can be prevented from starting.

  Therefore, it is possible to prevent the vehicle body from starting unexpectedly due to a decrease in the depressing force on the operation pedal due to another operation in a state where the vehicle body is braked and stopped by the operation pedal depression.

According to a second aspect of the present invention , a wheel is operated with a braking force corresponding to an operation position of a speed change operation means for changing the output of the continuously variable transmission by changing the output of the continuously variable transmission and an operation pedal for automatically returning to the depression release position. A brake device for braking, a pedal sensor for detecting an operation position of the operation pedal, and an operation of the shift operation means based on an output of the pedal sensor, thereby controlling an output of the continuously variable transmission with a shift operation tool. In a vehicle speed control structure for a work vehicle, comprising a control means for changing to a speed according to the output of the pedal sensor in a speed change range over a preset set speed and zero speed,
As the shift output setting data indicating the relationship between the operation position of the operation pedal and the output of the continuously variable transmission, the control means has a deceleration end position of the operation pedal at which the output of the continuously variable transmission becomes zero speed. First data set so that a stepping operation amount from the stepping release position is increased, and second data set so that a stepping operation amount from the stepping release position is reduced,
When the control means detects that the operation position of the operation pedal is a position on the stepping limit position side beyond the deceleration end position from the output of the pedal sensor during execution of the control operation based on the first data, It is configured to switch from the execution state of the control operation based on the first data to the execution state of the control operation based on the second data,
In the first data and the second data, the speed increase associated with the movement of the operation pedal toward the depression release position side ends, and the output of the continuously variable transmission is the operation position of the operation pedal at which the set speed becomes the set speed. A certain acceleration end position is set such that the acceleration end position of the second data is smaller in the stepping operation amount from the depression release position than the acceleration end position of the first data.

  According to the second invention, in the first data, the output of the continuously variable transmission is changed by depressing the operation pedal between the acceleration end position (deceleration start position) and the deceleration end position of the first data. The second data acceleration end position (deceleration start position) set so that the stepping operation amount from the depression release position is smaller than the first data acceleration end position and the first data deceleration end position. The output of the continuously variable transmission changes when the operation pedal is depressed over the deceleration end position set so that the depression operation amount from the release position becomes small.

  Thereby, the change amount of the continuously variable transmission with respect to the change amount of the operation position of the operation pedal in the first data, and the change of the output of the continuously variable transmission device with respect to the change amount of the operation position of the operation pedal with the second data. The quantity can be similar or the same.

  Therefore, the operation feeling of the speed change operation by the operation pedal in the first data can be similar to or the same as the operation feeling of the speed change operation by the operation pedal in the second data, and the operability in the speed change operation by the operation pedal can be improved. Can be better.

According to a third invention, in the first or second invention,
The brake device is operated in the operation area of the operation pedal that extends from the operation position of the operation pedal located between the deceleration end position of the first data and the deceleration end position of the second data to the depression limit position. The braking operation area is set.

  According to the third invention, in the shifting operation by the operating pedal with the first data, the output of the continuously variable transmission changes in the shifting operation area of the operating pedal according to the stepping operation position of the operating pedal, When the pedal reaches the braking operation area, the braking device brakes in a state where the speed is reduced at the operation position of the operating pedal, so that the operability of the shifting operation by the operating pedal can be improved and the vehicle travels. The stop can be reliably performed while reducing the load on the braking device.

  In addition, in the speed change operation by the operation pedal with the second data, the output of the continuously variable transmission changes according to the stepping operation position of the operation pedal in the speed change operation area of the operation pedal, and the braking device does not brake. Therefore, the operability of the speed change operation by the operation pedal can be improved over the entire speed change operation region of the operation pedal.

It is the whole tractor side view. It is a whole top view of a tractor. It is a vertical side view which shows a transmission structure. It is a block diagram which shows a control structure. It is a figure which shows the relationship between the operation position of a brake pedal, and the output of a continuously variable transmission. It is a side view which shows the operation position of a brake pedal. It is a time chart which shows the relationship between the output of a continuously variable transmission, a forward clutch, and a reverse clutch. It is a flowchart of forward / reverse switching control.

  Hereinafter, an embodiment in which a vehicle speed control structure for a work vehicle according to the present invention is applied to a tractor that is an example of a work vehicle will be described with reference to the drawings as an example for carrying out the present invention.

  As shown in FIGS. 1 and 2, this tractor has a clutch housing 2 connected to the rear part of an engine 1 mounted on the front thereof, and a transmission case (hereinafter referred to as a T / M case) also serving as a frame. 3) is connected so as to extend from the rear part of the clutch housing 2 toward the rear part of the vehicle body. On the left and right sides of the engine 1, a pair of left and right front wheels 4 are disposed so as to be steerable and drivable. A pair of left and right rear wheels 5 are arranged on both left and right sides of the rear portion of the T / M case 3 so as to be drivable and brakeable. Above the T / M case 3, a steering wheel 6 for driving the front wheels, a driver's seat 7, and the like are arranged to form a boarding operation unit 8.

  As shown in FIG. 3, the power from the engine 1 is transmitted to the main transmission 11 through the main clutch 9 and a gear-type power distribution mechanism 10. Then, the power after the shift by the main transmission 11 is transmitted to the synchromesh sub-transmission 13 via the electrohydraulic control type forward / reverse switching device 12 as the driving power, and after the shift by the sub-transmission 13 Is transmitted to the left and right front wheels 4 via the electrohydraulic control type front wheel transmission 14 and the front wheel differential 15 as power for driving the front wheels, and for the rear wheels as power for driving the rear wheels. This is transmitted to the left and right rear wheels 5 via a differential 16 or the like. Further, the power (non-shifting power) from the engine 1 that has passed through the main transmission 11 is used as power for PTO for taking out the power via the electrohydraulic control type PTO clutch 17 and the synchromesh type PTO transmission 18. It is transmitted to the shaft 19.

  As shown in FIGS. 1 and 2, the rear part of the T / M case 3 has a pair of left and right which allows a working device (not shown) such as a rotary tiller and a plow connected to the rear part of the tractor to be lifted and lowered. The lift arms 20 and a pair of left and right lift cylinders 21 that swing and drive the corresponding lift arms 20 are provided. The right lift arm 20 is connected via a rolling cylinder 23 to a right lower link 22 that is connected to the lower right rear portion of the T / M case 3 so as to be able to swing up and down. The left lift arm 20 is connected to the lower link 22 on the left side of the T / M case 3 so as to be swingable up and down via a connecting rod 24 for connecting the working device. A single-acting hydraulic cylinder is adopted for the left and right lift cylinders 21, and a double-acting hydraulic cylinder is adopted for the rolling cylinder 23.

  That is, this tractor can raise and lower the working device connected to the rear part by the operation of the left and right lift cylinders 21 and can be rolled by the operation of the rolling cylinder 23. Further, when a driving type work device such as a rotary tiller is connected to the rear part, the work device can be driven by working power taken out from the PTO shaft 19.

  As shown in FIG. 4, the engine 1 operates with an accelerator cylinder 26 that operates a speed control lever 25 of a speed governor (not shown), and the output speed is set between an idling speed and a rated speed. Can be changed steplessly. The accelerator cylinder 26 is an electric cylinder. The operation of the accelerator cylinder 26 is controlled by a control operation of an accelerator control means 27A provided as a control program in an electronic control unit (hereinafter referred to as ECU) 27 that functions as a control means.

  The ECU 27 is configured using a microcomputer including a CPU and an EEPROM. The ECU 27 includes an output of a lever sensor 29 that detects the operating position of the accelerator lever 28, an output of a pedal sensor 31 that detects the operating position of the accelerator pedal 30, and an output of an engine sensor 32 that detects the output rotation speed of the engine 1. , Etc. are entered. Further, first engine speed setting data indicating the relationship between the operation position of the accelerator lever 28 and the output speed of the engine 1, and a second value indicating the relationship between the operation position of the accelerator pedal 30 and the output speed of the engine 1. Engine speed setting data, etc. are provided.

  As shown in FIGS. 1, 2, and 4, the accelerator lever 28 is configured as a position-holding type that swings back and forth, and is disposed on the lower right side of the steering wheel 6. The accelerator pedal 30 is configured in a self-returning type that automatically returns to the depression release position, and is provided at the right foot portion of the boarding operation unit 8. A rotary potentiometer is employed for the lever sensor 29 for the accelerator lever and the pedal sensor 31 for the accelerator pedal. The engine sensor 32 employs an electromagnetic pickup type rotation sensor. Map data, a relational expression, etc. are employable as 1st engine speed setting data and 2nd engine speed setting data.

  The accelerator control means 27A performs accelerator control based on the output of the lever sensor 29 for the accelerator lever, the output of the pedal sensor 31 for the accelerator pedal, the output of the engine sensor 32, and the like. Specifically, the operation of the accelerator lever 28 is performed based on the output of the lever sensor 29 for the accelerator lever, the output of the pedal sensor 31 for the accelerator pedal, the first engine speed setting data, and the second engine speed setting data. The set rotation speed corresponding to the position and the set rotation speed corresponding to the operation position of the accelerator pedal 30 are obtained, and the obtained set rotation speed by the accelerator lever 28 and the set rotation speed by the accelerator pedal 30 are compared. When the set rotational speed by the accelerator pedal 30 is equal to or lower than the set rotational speed by the accelerator lever 28, the set rotational speed by the accelerator lever 28 is adopted as the target rotational speed. Further, when the set rotational speed by the accelerator pedal 30 is higher than the set rotational speed by the accelerator lever 28, the set rotational speed by the accelerator pedal 30 is adopted as the target rotational speed. Then, the operation of the accelerator cylinder 26 is controlled so that the output of the engine sensor 32 matches the adopted target rotational speed (within the dead band width of the target rotational speed).

  As shown in FIG. 3, the main transmission 11 employs a hydraulic mechanical continuously variable transmission (hereinafter referred to as HMT) 33 which is an example of a continuously variable transmission A. The HMT 33 is configured by combining a hydrostatic continuously variable transmission (hereinafter referred to as HST) 34 and a planetary gear mechanism 35. The HST 34 includes an axial plunger type variable displacement pump 34A, an axial plunger type constant displacement motor 34B, and the like. The planetary gear mechanism 35 supports a sun gear 35A located at the center thereof, three planetary gears 35B distributed at equal intervals around the sun gear 35A and meshed with the sun gear 35A, and each planetary gear 35B rotatably supported. A planetary carrier 35C and an outer gear 35D that surrounds the planetary gears 35B in a state of meshing with the planetary gears 35B are provided. The power from the power distribution mechanism 10 is transmitted to the pump shaft 34Aa of the HST 34 and the planetary carrier 35C of the planetary gear mechanism 35. The HST 34 transmits the power after shifting by the HST 34 from the motor shaft 34Ba to the planetary gear mechanism 35. This is transmitted to the sun gear 35A. The planetary gear mechanism 35 combines the power from the engine 1 transmitted to the planetary carrier 35C and the power after shifting by the HST 34 transmitted to the sun gear 35A and transmits the resultant to the forward / reverse switching device 12.

  As shown in FIGS. 3 and 4, the HST 34 can change the power from the engine 1 by changing the swash plate angle of the variable displacement pump 34 </ b> A. The swash plate angle of the variable displacement pump 34 </ b> A can be changed steplessly by the operation of the transmission cylinder 36 provided in the T / M case 3. A double-acting hydraulic cylinder is adopted as the transmission cylinder 36. The operation of the shift cylinder 36 is controlled by the operation of a shift valve 37 that controls the flow of oil to the shift cylinder 36. An electromagnetic proportional valve is adopted as the speed change valve 37. The operation of the shift valve 37 is controlled by the control operation of the vehicle speed control means 27B provided in the ECU 27 as a control program.

  As shown in FIGS. 2 and 4, the ECU 27 includes a swash plate that detects the output of the lever sensor 39 that detects the operation position of the main transmission lever 38 as a transmission operation tool, and the swash plate angle of the variable displacement pump 34A. The output of the angle sensor 40 is input. Further, swash plate angle setting data indicating the relationship between the operation position of the main transmission lever 38 and the swash plate angle of the variable displacement pump 34A is provided.

  The main speed change lever 38 is configured to be a front and rear swinging position holding type and is provided on the front side of the armrest 41 provided on the right side of the driver seat 7. A rotary potentiometer is adopted for the lever sensor 39 and the swash plate angle sensor 40 for the main transmission lever. Map data, relational expressions, etc. can be adopted as the swash plate angle setting data.

  The vehicle speed control means 27B performs main shift control based on the output of the lever sensor 39 for the main shift lever, the output of the swash plate angle sensor 40, and the swash plate angle setting data. Specifically, the variable displacement pump 34A corresponding to the operation position of the main transmission lever 38 obtained based on the operation position of the main transmission lever 38 output from the lever sensor 39 for the main transmission lever and the swash plate angle setting data. The swash plate angle is set to the target swash plate angle, and the operation of the shift valve 37 is controlled so that the swash plate angle of the variable displacement pump 34A matches the target swash plate angle (contains within the dead zone width of the target swash plate angle). Then, the speed change cylinder 36 is operated.

  Although not shown, the swash plate angle setting data indicates the relationship between the operation position of the main transmission lever 38 and the swash plate angle of the variable displacement pump 34A, and when the operation position of the main transmission lever 38 is the zero speed position. Variable when the swash plate angle of the variable displacement pump 34A becomes the maximum angle in the reverse rotation direction, the operation position of the pump swash plate 34Ab becomes the reverse rotation maximum speed position, and the operation position of the main transmission lever 38 is the maximum speed position. The main transmission lever 38 is operated from the zero speed position so that the swash plate angle of the capacity pump 34A becomes the maximum angle in the forward rotation direction and the operation position of the pump swash plate 34Ab becomes the forward rotation highest speed position. The operation amount from the highest reverse rotation speed position of the pump swash plate 34Ab is set according to the amount.

  In the HMT 33, when the swash plate angle of the variable displacement pump 34A is the maximum angle in the reverse rotation direction (hereinafter referred to as the minimum swash plate angle of the variable displacement pump 34A), the combined output by the planetary gear mechanism 35 becomes zero speed. And the combined output by the planetary gear mechanism 35 is the fastest when the swash plate angle of the variable displacement pump 34A is the maximum angle in the forward rotation direction (hereinafter referred to as the maximum swash plate angle of the variable displacement pump 34A). Thus, the output is increased in accordance with the operation amount from the minimum swash plate angle of the variable displacement pump 34A (the reverse rotation fastest position of the pump swash plate 34Ab).

  That is, the speed change operation means B that changes the output of the HMT 33 by operating the pump swash plate 34Ab of the variable displacement pump 34A by the speed change cylinder 36, the speed change valve 37, and the like. The swash plate angle setting data is set so that a proportional relationship between the operation position of the main transmission lever 38 and the output of the HMT 33 is established.

  As shown in FIGS. 1 to 4, the forward / reverse switching device 12 includes a forward clutch 12A and a reverse clutch 12B that employ a multi-plate hydraulic clutch. Then, by controlling the operation of the forward / reverse switching valve 42 that controls the flow of oil to the forward clutch 12A and the reverse clutch 12B, the forward transmission that transmits the power from the HMT 33 to the auxiliary transmission 13 as the forward power. In this state, it is possible to switch to a reverse transmission state in which power from the HMT 33 is transmitted to the auxiliary transmission 13 as reverse power, and a transmission cut-off state in which transmission from the HMT 33 to the auxiliary transmission 13 is interrupted. The forward / reverse switching valve 42 is an electromagnetic control valve. The operation of the forward / reverse switching valve 42 is controlled by the control operation of the forward / reverse switching control means 27C provided in the ECU 27 as a control program.

  As shown in FIGS. 2 and 4, the ECU 27 receives an output of an FR sensor 44 that detects an operation position of the FR lever 43 for forward / reverse switching. The FR lever 43 is configured to be swingable back and forth so that the position can be switched between the forward position and the reverse position, and is disposed on the lower left side of the steering wheel 6. The FR sensor 44 is a micro switch for detecting a forward position that is switched to a closed state when the FR lever 43 is operated to a forward position, and a sensor for detecting a reverse position that is switched to a closed state when the FR lever 43 is operated to a backward position. A micro switch is provided.

  The forward / reverse switching control means 27 </ b> C performs forward / reverse switching control for switching the operating state of the forward / reverse switching device 12 based on the output of the FR sensor 44. In the forward / reverse switching control, basically, when the switching operation from the forward position to the reverse position of the FR lever 43 is detected based on the output of the FR sensor 44, the forward clutch 12A is depressurized and switched to the shut-off state. After the set time, the forward / reverse switching device 12 is switched to the reverse transmission state by controlling the operation of the forward / reverse switching valve 42 so that the reverse clutch 12B is boosted and switched to the transmission state. When the switching operation from the reverse position to the forward position of the FR lever 43 is detected based on the output of the FR sensor 44, the reverse clutch 12B is depressurized and switched to the shut-off state, and the forward clutch 12A is boosted after the set time. By controlling the operation of the forward / reverse switching valve 42 so as to switch to the transmission state, the forward / reverse switching device 12 is switched to the forward transmission state.

  As shown in FIG. 2, an auxiliary transmission lever 45 is provided at the left side of the driver's seat 7 in the boarding driver 8. Although not shown in the drawings, the sub-transmission device 13 is switched to one of a low speed gear for work, a high speed gear for work, and a fastest gear speed for movement according to the operation position of the sub-shift lever 45. In addition, the auxiliary transmission lever 45 is linked via a mechanical auxiliary transmission linkage mechanism.

  As shown in FIG. 3, the front wheel transmission 14 is driven by the power from the auxiliary transmission 13 so that the peripheral speed of the left and right front wheels 4 is synchronized with the peripheral speed of the left and right rear wheels 5 by the sliding operation of the shift member 46. To the left and right front wheels 4 and the power from the auxiliary transmission 13 to the left and right so that the peripheral speed of the left and right front wheels 4 is about twice that of the left and right rear wheels 5. It is possible to switch to the speed-up transmission state transmitted to the front wheels 4.

  Although not shown, the shift member 46 is a speed increasing switch that switches the front wheel transmission device 14 to the constant speed transmission state and the speed increasing transmission state by the operation of the front wheel transmission cylinder that employs a double-acting hydraulic cylinder. Slide into position. The operation of the front wheel transmission cylinder can be controlled by the operation of a front wheel transmission valve that controls the flow of oil to the front wheel transmission cylinder. An electromagnetic control valve is adopted as the front wheel shift valve. The operation of the front wheel shift valve is controlled by the control operation of the front wheel shift control means provided in the ECU 27 as a control program.

  The ECU 27 is supplied with the output of a steering angle sensor that detects the steering angle of the front wheels 4 and the output of a selection switch provided in the boarding operation unit 8. A rotary potentiometer is adopted as the steering angle sensor.

  The front wheel shift control means is configured to be able to execute front wheel shift control for switching the front wheel transmission device 14 between a constant speed transmission state and an acceleration transmission state based on the output of the steering angle sensor, and is selected by pressing a selection switch. Each time an ON signal is output from the switch, the front wheel shift selection state in which the front wheel shift control is executed and the front wheel shift selection release state in which the front wheel shift control is not executed are switched.

  Specifically, in the front wheel speed change control, when it is detected that the rudder angle of the front wheel 4 is less than a set angle (for example, 35 degrees) based on the output of the rudder angle sensor, the front wheel transmission 14 is transmitted at a constant speed. And when the steering angle of the front wheels 4 is detected to be greater than or equal to a set angle (for example, 35 degrees), the operation of the front wheel transmission valve is controlled so that the front wheel transmission 14 is in the speed increasing transmission state. To do.

  From this configuration, when it is desired to make the turning radius of the vehicle body smaller, for example, when the front wheel 4 is steered more than the set angle, the front wheel 4 is set by switching to the front wheel shift selection state by operating the selection switch. The front wheel transmission 14 can be automatically switched from the constant speed transmission state to the increased speed transmission state with steering beyond the angle, and the vehicle body can be turned with a turning radius smaller than that in the constant speed transmission state. Then, by returning the steering angle of the front wheels 4 to less than the set angle after the turn, the front wheel transmission 14 can be automatically returned from the speed increasing transmission state to the constant speed transmission state.

  As shown in FIGS. 1, 2, and 4, a pair of left and right brake pedals 47 are provided as operation pedals C at the right foot portion of the boarding operation unit 8. The left and right brake pedals 47 return and swing toward the depression release position by the action of the corresponding torsion springs 48. The left brake pedal 47 is linked to a left side brake 49 that brakes the left rear wheel 5 via a mechanical braking linkage mechanism 50. The right brake pedal 47 is linked to a right side brake 49 that brakes the right rear wheel 5 via a mechanical braking linkage mechanism 50. The left and right side brakes are multi-plate type.

  Although illustration is omitted, the left brake linking mechanism 50 links the left brake pedal 47 and the left side brake 49 via a crank arm and a push-pull rod so that the left brake pedal 47 is braked. When the operation region is depressed, the left side brake 49 is applied to the left rear wheel 5 with a braking force corresponding to the depression amount of the left brake pedal 47 in the braking operation region. is there. The right brake linking mechanism 50 links the right brake pedal 47 and the right side brake 49 via a crank arm and a push-pull rod so that the right brake pedal 47 is depressed to the braking operation region. In this case, the right side brake 49 is configured to act on the right rear wheel 5 with a braking force corresponding to the stepping operation amount of the right brake pedal 47 in the braking operation region.

  From this configuration, the left brake pedal 47 can be depressed to the braking operation region alone, whereby the left rear wheel 5 can be braked by the left side brake 49, and conversely, the right brake pedal 47 can be independently operated. The right rear wheel 5 can be braked by the right side brake 49 by depressing to the braking operation area. Further, the left and right rear wheels 5 can be simultaneously braked with the same braking force by the left and right side brakes 49 by simultaneously depressing the left and right brake pedals 47 to the braking operation region with the same operation amount.

  In other words, when turning the steering wheel 6 in the turning direction, the left or right brake pedal 47 corresponding to the rear wheel 5 on the inside of the turning is stepped on to the braking operation region alone, and the turning at that time The state can be switched from the turning state by the turning operation of the steering wheel 6 to the braking turning state in which the rear wheel 5 inside the turning is braked, and the turning radius of the vehicle body can be reduced. Further, the left and right side brakes 49 can be used as a braking device D for deceleration stop by simultaneously depressing the left and right brake pedals 47 to the braking operation region.

  Although not shown in the drawings, the left and right brake pedals 47 are provided with a connection mechanism that can be switched between a connection state that prevents the single operation and a connection release state that allows the single operation. As a result, the left and right brake pedals 47 can be switched between a state in which switching to the braking turning state by their single operation is possible and a state in which switching to the braking turning state is prevented.

  Further, the boarding operation unit 8 is equipped with a holding mechanism that enables the left brake pedal 47 that has been depressed to the braking operation region to be engaged and maintained in the braking operation region. Thus, after the left and right brake pedals 47 are connected to each other by the connecting mechanism, the left and right brake pedals 47 are engaged and held in the braking operation region by operating the holding mechanism and then stepping on the left and right brake pedals 47. The brake pedal 47 can be held at the stepping position in the braking operation area at that time, whereby the left and right side brakes 49 are set to the depression operation amount of the left and right brake pedals 47 in the braking operation area at that time. The braking state in which the left and right rear wheels 5 are braked with the corresponding braking force can be maintained. That is, the left and right side brakes 49 can be made to function as parking brakes by the holding mechanism.

  As shown in FIG. 4, the left and right brake pedals 47 include a single pedal sensor 51 that detects a both-step operation position that is an operation position when both the left and right brake pedals 47 are operated. It is linked via a link mechanism 52 configured to transmit only the amount of both stepping operations from the depression release position when the stepping operation of 47 is performed to the pedal sensor 51.

  The pedal sensor 51 employs a rotary potentiometer, and the pedal sensor 51 detects the amount of both stepping operations from the depressing release position of the left and right brake pedals 47 as the both stepping operation positions of the left and right brake pedals 47.

  In the link mechanism 52, the left and right contact members 52A provided on the upper side in the stepping direction of the left and right brake pedals 47 are operated by a tension spring (not shown), so that at least the arm portion of the left or right brake pedal 47 is provided. 47A is configured to maintain a state where it comes into contact with the upper side of the stepping direction. Thus, when both the left and right brake pedals 47 are not depressed, the contact member 52A is received by the left and right brake pedals 47 located at the depression release position, so that the brake pedal 47 is brought into the depression release position. When the left and right brake pedals 47 are operated by depressing one of the left and right brake pedals 47, the contact member 52A is received by the other brake pedal 47 located at the depressing release position and positioned at the reference position. The contact member 52A is configured to contact and follow the left and right brake pedals 47 by the action of the tension spring only when the left and right brake pedals 47 are both depressed. Then, the amount of follow-up movement from the reference position of the contact member 52A at this time is transmitted to the pedal sensor 51 as the amount of both stepping operations from the depression release position of the left and right brake pedals 47.

  As shown in FIGS. 4 and 5, the pedal sensor 51 outputs the detected position of both the left and right brake pedals 47 to the ECU 27. The ECU 27 includes shift output setting data indicating the relationship between the stepping operation positions of the left and right brake pedals 47 and the output of the HMT 33. Map data, relational expressions, and the like can be employed as the shift output setting data. The shift output setting data is used for both forward and reverse travel. However, the shift output setting data may include forward-only shift output setting data and reverse-only shift output setting data.

  In the ECU 27, the vehicle speed control unit 27B sets the swash plate angle of the variable displacement pump 34A set corresponding to the operation position of the main transmission lever 38, the output of the swash plate angle sensor 40, and the output of the pedal sensor 51 for the brake pedal. And pedal shift control based on the shift output setting data. Specifically, the set output (set speed) of the HMT 33 corresponding to the operation position of the main transmission lever 38 is obtained from the set swash plate angle of the variable displacement pump 34A set corresponding to the operation position of the main transmission lever 38. The shift output setting data is corrected so that the set output becomes the maximum output (maximum speed) corresponding to the depression release position a of the left and right brake pedals 47 in the shift output setting data. Then, based on both the stepping operation positions of the left and right brake pedals 47 output by the pedal sensor 51 for the brake pedal and the corrected shift output setting data, the HMT 33 corresponding to the both stepping operation positions of the left and right brake pedals 47 is selected. The output (output speed) is obtained, the obtained output of the HMT 33 is set as the target output (target speed), and the target swash plate angle of the variable displacement pump 34A corresponding to the target output for obtaining this target output as the output of the HMT 33 is obtained. The shift cylinder 36 is operated by controlling the operation of the shift valve 37 so that the swash plate angle of the variable displacement pump 34A matches the determined target swash plate angle (within the dead zone width of the target swash plate angle).

  As shown in FIGS. 5 and 6, the shift output setting data includes first data and second data. The first data is that the output of the HMT 33 is set to the maximum output (the operation position of the main transmission lever 38) until the left and right brake pedals 47 reach the preset deceleration start position (acceleration end position) b from the depression release position a. The output of the HMT 33 is from the maximum output to the minimum output in inverse proportion to the amount of stepping on both the left and right brake pedals 47 until the deceleration end position c is exceeded after reaching the deceleration start position b. The relationship between the stepping operation positions of the left and right brake pedals 47 and the output of the HMT 33 is set so as to change between (zero speed) (see the solid line in FIG. 5). The second data is that the output of the HMT 33 is maintained at the minimum output until the left and right brake pedals 47 return to the preset acceleration start position (deceleration end position) e from the depression limit position d, and the acceleration start position e The output of the HMT 33 changes between the minimum output and the maximum output in inverse proportion to the stepping operation amount of the left and right brake pedals 47 until returning to less than the preset acceleration end position f after returning to In addition, the relationship between the stepping operation positions of the left and right brake pedals 47 and the output of the HMT 33 is set (see the broken line in FIG. 5).

  The deceleration start position b is set to an operation position where the amount of both stepping operations from the depression release position a of the left and right brake pedals 47 is larger than the acceleration end position f, and the acceleration start position e is the deceleration end position c. In addition, the operation position is set at a position where the amount of both stepping operations from the depression release position a of the left and right brake pedals 47 is smaller.

  Further, the difference in the amount of both stepping operations from the depression release position a of the left and right brake pedals 47 between the deceleration start position b and the acceleration end position f is determined between the deceleration end position c and the acceleration start position e. The left and right brake pedals 47 between the deceleration start position b and the deceleration end position c of the first data are made smaller than the difference in the amount of both stepping operations from the depression release position a of the left and right brake pedals 47 in FIG. The amount of change in the output of the HMT 33 relative to the amount of both stepping operations is the amount of change in the output of the HMT 33 relative to the amount of both stepping operations of the left and right brake pedals 47 between the acceleration start position e and the acceleration end position f of the second data. It is set to be smaller than this.

  The vehicle speed control means 27B changes the shift output setting data from the first data to the second data as the depressing operation position of the left and right brake pedals 47 exceeds the deceleration end position c in the pedal shift control based on the first data. The pedal shift control based on the second data is performed by switching. Further, in the pedal shift control based on the second data, the shift output setting data is switched from the second data to the first data as the operation position of both the left and right brake pedals 47 returns to less than the acceleration end position f. Pedal shift control based on the first data is performed.

  The operation areas of the left and right brake pedals 47 include a brake release area for maintaining the left and right side brakes 49 in a brake release state regardless of the depression operation of the left and right brake pedals 47, and a depression operation amount of the left and right brake pedals 47. The larger the braking force acting on the corresponding rear wheel 5 of the left and right side brakes 49 is, the smaller the amount of depression of the left and right brake pedals 47 is, the more the braking force acting on the corresponding rear wheel 5 of the left and right side brakes 49 is. And a braking operation area which becomes smaller. The boundary position g between the braking release area and the braking operation area is located between the deceleration end position c and the acceleration start position e, and the deceleration end in the shift operation area of the left and right brake pedals 47 in the first data is completed. The area portion on the position side overlaps with the braking operation area, and the shift operation area of the left and right brake pedals 47 in the second data is not overlapped with the braking operation area.

  With this configuration, when the left and right brake pedals 47 are both depressed in a traveling state in which the main transmission lever 38 is operated to an arbitrary operation position for traveling and the left and right brake pedals 47 are depressed to the release position a. The vehicle speed control means 27B executes the pedal shift control based on the first data, and the left and right side brakes 49 are controlled by the braking force corresponding to the amount of both stepping operations in the braking operation area of the left and right brake pedals 47. The rear wheel 5 is braked.

  As a result, the vehicle speed control means 27B maintains the output of the HMT 33 at a set speed corresponding to the operation position of the main speed change lever 38 until the left and right brake pedals 47 reach from the depression release position a to the deceleration start position b. In addition, since the left and right side brakes 49 do not brake the left and right rear wheels 5, the vehicle speed can be set to the accelerator lever 28, the main speed change lever 38, and the sub speed change lever regardless of the stepping operation of the left and right brake pedals 47. The set speed obtained based on the 45 operation positions can be made constant.

  In addition, the vehicle speed control means 27B responds to both the stepping operation positions of the left and right brake pedals 47 until the left and right brake pedals 47 exceed the boundary position g between the braking release area and the braking operation area from the deceleration start position b. Since the output of the HMT 33 is changed and the left and right side brakes 49 do not brake the left and right rear wheels 5, the vehicle speed is set to the set speed and the left and right brake pedals 47 by pressing both the left and right brake pedals 47. Can be changed between the speed obtained by depressing to the boundary position g.

  Further, until the left and right brake pedals 47 exceed the deceleration end position c from the boundary position g, the vehicle speed control means 27B changes the output of the HMT 33 according to the both stepping operation positions of the left and right brake pedals 47, and Since the left and right side brakes 49 brake the left and right rear wheels 5 with a braking force corresponding to the amount of both stepping operations in the braking operation area of the left and right brake pedals 47, the vehicle speed is bounded by the left and right brake pedals 47. The speed can be changed between the speed obtained when the pedal is depressed to the position g and the zero speed, and the vehicle body is braked and stopped when the left and right brake pedals 47 reach or end at the deceleration end position c. be able to.

  When the left and right brake pedals 47 exceed the deceleration end position c, the vehicle speed control means 27B switches from a state where the pedal shift control based on the first data is executed to a state where the pedal shift control based on the second data is executed. The vehicle speed control means 27B maintains the output of the HMT 33 at zero speed until the left and right brake pedals 47 return from the depression limit position d beyond the deceleration end position c to the boundary position g after passing through the deceleration end position c. In this state, the left and right side brakes 49 brake the left and right rear wheels 5 with a braking force corresponding to the amount of both stepping operations in the braking operation area of the left and right brake pedals 47, so that the left and right brake pedals 47 decelerate. The vehicle body can be maintained in the braking stop state even if the pedaling force on the left and right brake pedals 47 is weakened so as to be closer to the boundary position g than the end position c.

  Further, until the left and right brake pedals 47 return from the boundary position g to the acceleration start position e, the vehicle speed control means 27B keeps the vehicle speed at zero by setting the output of the HMT 33 to zero. Even if the left and right side brakes 49 release the braking of the left and right rear wheels 5 by reducing the pedaling force on the left and right brake pedals 47 so that 47 is closer to the acceleration start position e than the boundary position g, the vehicle body is stopped. It becomes possible to maintain.

  Further, until the left and right brake pedals 47 return from the acceleration start position e to the acceleration end position f, the vehicle speed control means 27B changes the output of the HMT 33 according to the both stepping operation positions of the left and right brake pedals 47. Thus, the left and right side brakes 49 do not brake the left and right rear wheels 5, so that the vehicle speed can be changed between the zero speed and the set speed by depressing both the left and right brake pedals 47.

  When the left and right brake pedals 47 exceed the acceleration end position f, the vehicle speed control means 27B switches from the state in which the pedal shift control based on the second data is executed to the state in which the pedal shift control based on the first data is executed. Instead, as described above, between the left and right brake pedals 47 from the depression release position “a” to the deceleration start position “b”, the vehicle speed is kept constant at the set speed regardless of the depressing operation of both the left and right brake pedals 47. Can do.

  That is, the left and right brake pedals 47 can be used as shift pedals that change the vehicle speed between zero speed and a set speed, thereby facilitating a shift operation.

  In the state where the left and right brake pedals 47 are both depressed to the operation position on the depressing limit position side exceeding the deceleration end position c and the vehicle body is braked and stopped, the left and right brake pedals 47 pass the deceleration end position c. Since the vehicle body does not start unless it returns to the acceleration start position e, the left and right brake pedals 47 are caused by other operations when the vehicle body is braked and stopped by both stepping operations of the left and right brake pedals 47. Even when the pedaling force decreases and the left and right brake pedals 47 return to between the deceleration end position c and the acceleration start position e, the vehicle body can be prevented from starting.

  Moreover, while the vehicle speed control means 27B is executing the pedal shift control based on the first data, the left and right brake pedals 47 do not switch to the pedal shift control based on the second data unless the left and right brake pedals 47 exceed the deceleration end position c. While the brake pedal 47 of the left and right is being stepped on both the deceleration start position b and the deceleration end position c, there is no change in the relationship between the both pedal operation positions of the left and right brake pedals 47 and the vehicle speed. Therefore, while the vehicle speed control means 27B is executing the pedal shift control based on the second data, the pedal shift control based on the first data is performed as long as the left and right brake pedals 47 do not exceed the acceleration end position f. By not switching to the left and right, while the left and right brake pedals 47 are both depressed between the deceleration start position b and the deceleration end position c, Both stepping operation position and without change occurs in the relationship between vehicle speed Rekipedaru 47, since the operation feeling becomes constant, such inching operation of repeating and stopping vehicle starting is facilitated.

  As shown in FIGS. 4, 7 and 8, the forward / reverse switching control means 27C is command means E for instructing the forward / reverse switching by the forward / reverse switching device 12 functioning as the transmission switching means E during high speed traveling. When the operating state of the forward / reverse switching device 12 is switched based on the output of a certain FR sensor 44, the energy absorbed by the forward clutch 12A and the reverse clutch 12B becomes excessive, and the forward clutch 12A and the reverse clutch 12B burn out. Therefore, in the forward / reverse switching control, the following control operation is performed in order to avoid the occurrence of burning.

  First, it is determined whether or not the switching operation of the FR lever 43 to the forward position or the reverse position is detected based on the output of the FR sensor 44 [Step # 1]. If the switching operation is not detected, Step # 1 is performed. When the switching operation is detected, the output speed of the HMT 33 (the input speed to the forward / reverse switching device 12) is calculated based on the output of the engine sensor 32 and the output of the swash plate angle sensor 40 [Step # 2]. Then, it is determined whether or not the output speed of the HMT 33 exceeds a preset speed for forward / reverse switching (for example, 15 Km / h) that is set in advance to prevent burning (step # 3).

  If the set speed for preventing burnout has not been exceeded, the forward clutch 12A or the reverse clutch 12B not corresponding to the operation position of the FR lever 43 is depressurized and switched to the shut-off state, and the FR lever 43 is operated after the set time. Clutch pressure switching control is performed to control the operation of the forward / reverse switching valve 42 so that the forward clutch 12A or the reverse clutch 12B corresponding to the position is boosted and switched to the transmission state [Step # 4]. When the is finished, the forward / reverse switching control is finished.

  When the set speed for preventing burnout is exceeded, the speed reduction control for controlling the operation of the speed change valve 37 so that the swash plate angle of the variable displacement pump 34A is reduced by the operation of the speed change cylinder 36 and the output speed of the HMT 33 is lowered. [Step # 5], the output speed of the HMT 33 is calculated based on the output of the engine sensor 32 and the output of the swash plate angle sensor 40 [Step # 6], and a timer (not shown) provided in the ECU 27 is calculated. To measure the time from the start of the deceleration control [Step # 7].

  Next, it is determined whether or not the output speed of the HMT 33 has reached the set speed for preventing burnout [Step # 8]. When the set speed for preventing burnout has been reached, the deceleration control is terminated and the output of the HMT 33 is set. The speed is maintained at the set speed for preventing burnout [Step # 9], and the clutch pressure switching control is started [Step # 10], and the time is counted from the start of the clutch pressure switching control by a timer [Step # 11]. ].

  If the set speed for preventing burnout has not been reached in step # 8, it is determined whether or not the first set time has elapsed since the start of the deceleration control [step # 12]. Returning to step # 8, if the time has elapsed, the process proceeds to step # 9 to maintain the output speed of the HMT 33 at the speed at that time.

  After the start of the clutch pressure switching control, whether or not the clutch pressure of the booster forward clutch 12A or the reverse clutch 12B has reached the set pressure based on the output of the forward pressure sensor 53 or the output of the reverse pressure sensor 54 [Step # 13], and when the clutch pressure on the booster side reaches the set pressure, the swash plate angle of the variable displacement pump 34A is increased by the operation of the shift cylinder 36, and the output speed of the HMT 33 becomes the main shift lever. The speed increase control is performed to control the operation of the shift valve 37 so as to increase to a set speed corresponding to the operation position 38 [step # 14].

  If the clutch pressure on the boost side has not reached the set pressure, it is determined whether or not the second set time has elapsed since the start of the clutch pressure switching control [step # 15]. Returning to step # 13, when the time has elapsed, the routine proceeds to step # 14, where acceleration control is performed.

  Then, it is determined whether or not the clutch pressure switching control is finished [Step # 16], and the forward / reverse switching control is finished when the clutch pressure switching control and the speed increasing control are finished.

  That is, when the output speed of the HMT 33 when switching between forward and backward based on the operation of the FR lever 43 is a speed that can be reduced to the set speed for preventing burning during the first set time by the deceleration control. Can avoid burning of the forward clutch 12A and the reverse clutch 12B without causing the driver to feel uncomfortable due to the long forward / reverse switching time. Further, even if the output speed of the HMT 33 cannot be reduced to the setting speed for preventing burnout during the first setting time by the deceleration control, the driver feels uncomfortable because the switching time for forward / reverse travel becomes long. Without making it feel, burning of the forward clutch 12A and the reverse clutch 12B can be suppressed.

  In this tractor, the engine sensor 32, the swash plate angle sensor 40, and the like constitute detection means G that detects the output speed of the HMT 33, which is the rotational speed in the transmission system including the forward / reverse switching device 12. In addition, the HMT 33 functions as a transmission means H that changes the rotational speed of the transmission system including the forward / reverse switching device 12 when switching between forward and backward by the operation of the forward / reverse switching device 12.

    [Another embodiment]

[1] As the continuously variable transmission A, a hydrostatic continuously variable transmission or a belt-type continuously variable transmission can be employed.

[2] As the speed change operation means B, an electric cylinder or the like can be employed.

[3] The operating pedal C may be a single equipped brake pedal. The braking device D may be a single device, or may be configured to brake the front wheels 4 or both the front wheels 4 and the rear wheels 5.

[4] The pedal sensor 51 may be provided corresponding to each of the left and right brake pedals 47.

[5] A switch or the like may be employed as the shift operation tool 38.

[6] The first data and the second data may be set so that the acceleration end positions b and f are the same position.

[7] The operation area of the operation pedal C from the deceleration end position e of the second data to the depression limit position d may be set as a braking operation area in which the braking device D is operated.

The vehicle speed control structure of a work vehicle according to the present invention can be applied to a tractor including a continuously variable transmission, a riding rice transplanter, a combine, a riding mower, and the like.
Etc.

5 Wheel 27 Control means 38 Shifting operation tool 51 Pedal sensor A Continuously variable transmission B Shifting operation means C Operation pedal D Braking device a Depressing release position b Speed increasing end position (first data)
c Deceleration end position (first data)
d Depression limit position e Deceleration end position (second data)
f Speed increasing end position (second data)

Claims (3)

Shifting operation means for changing the output of the continuously variable transmission by shifting the continuously variable transmission, a braking device for braking the wheel with a braking force according to the operation position of the operation pedal that automatically returns to the depression release position, A pedal sensor for detecting an operation position of the operation pedal, and a set speed that is set in advance by using a speed change operation tool by controlling the operation of the speed change operation means based on the output of the pedal sensor. In a vehicle speed control structure for a work vehicle, comprising a control means for changing to a speed according to the output of the pedal sensor in a shift range over zero speed,
As the shift output setting data indicating the relationship between the operation position of the operation pedal and the output of the continuously variable transmission, the control means has a deceleration end position of the operation pedal at which the output of the continuously variable transmission becomes zero speed. First data set so that a stepping operation amount from the stepping release position is increased, and second data set so that a stepping operation amount from the stepping release position is reduced,
When the control means detects that the operation position of the operation pedal is a position on the stepping limit position side beyond the deceleration end position from the output of the pedal sensor during execution of the control operation based on the first data, Ri constructed from the execution state of the control operation based on the first data to switch to the execution state of the control operation based on the second data tare,
A vehicle speed control structure for a work vehicle in which the deceleration end position of the second data is located in a brake release region that is an operation region of the pedal from which the operation of the brake device is released . Shifting operation means for changing the output of the continuously variable transmission by shifting the continuously variable transmission, a braking device for braking the wheel with a braking force according to the operation position of the operation pedal that automatically returns to the depression release position, A pedal sensor for detecting an operation position of the operation pedal, and a set speed that is set in advance by using a speed change operation tool by controlling the operation of the speed change operation means based on the output of the pedal sensor. In a vehicle speed control structure for a work vehicle, comprising a control means for changing to a speed according to the output of the pedal sensor in a shift range over zero speed,
As the shift output setting data indicating the relationship between the operation position of the operation pedal and the output of the continuously variable transmission, the control means has a deceleration end position of the operation pedal at which the output of the continuously variable transmission becomes zero speed. First data set so that a stepping operation amount from the stepping release position is increased, and second data set so that a stepping operation amount from the stepping release position is reduced,
When the control means detects that the operation position of the operation pedal is a position on the stepping limit position side beyond the deceleration end position from the output of the pedal sensor during execution of the control operation based on the first data, It is configured to switch from the execution state of the control operation based on the first data to the execution state of the control operation based on the second data,
In the first data and the second data, the speed increase associated with the movement of the operation pedal toward the depression release position side ends, and the output of the continuously variable transmission is the operation position of the operation pedal at which the set speed becomes the set speed. certain speed increasing end position, the second the speed increasing end position data Ru set tare as depression amount decreases from the depression release position than the speed increasing end position of the first data created Speed control structure for industrial vehicles.   The brake device is operated in the operation area of the operation pedal that extends from the operation position of the operation pedal located between the deceleration end position of the first data and the deceleration end position of the second data to the depression limit position. The vehicle speed control structure for a work vehicle according to claim 1, wherein the vehicle speed control structure is set in a braking operation area to be operated.

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