JP5974542B2 - Work vehicle - Google Patents

Description

  The present invention relates to a work vehicle that automatically changes gears in a continuously variable manner corresponding to pedal operation.

  The continuously variable work vehicle of Patent Document 1 includes a shift control device that includes a hydrostatic continuously variable transmission mechanism and that automatically shifts by trunnion operation control corresponding to a shift pedal operation. This shift control device switches the follow-up operation speed according to the deviation between the target position and the operation position for the trunnion operation at the time of shifting of the continuously variable transmission mechanism according to the map data. The shift control sensitivity can be set arbitrarily.

JP 2009-270607 A

  However, when the shift control sensitivity is set so that the following operation at the time of shifting of the continuously variable transmission mechanism becomes low speed, the work vehicle can suppress the shock due to sudden acceleration, but the stepped-on shift pedal is released. Even during operation, since the vehicle is gradually decelerated to the stop vehicle speed, there is a problem that it is difficult to respond by an emergency stop.

  An object of the present invention is to provide a continuously variable transmission having a speed change control system capable of responding to an emergency stop even when the speed change control sensitivity is set to a low sensitivity while ensuring a degree of freedom in setting speed change control sensitivity of the traveling vehicle speed. It is to provide a work vehicle of the type.

According to the first aspect of the present invention, there is provided a continuously variable transmission mechanism (11) that performs a stepless speed change operation in a vehicle speed range including a stop vehicle speed and transmits engine power to a traveling portion, and the continuously variable transmission mechanism (11) is moved forward and backward. for each running direction of advance and based on the pedal sensor (31) value for detecting the amount of depression of the shift pedal (7b) to the shift control to the target speed ratio, the continuously variable transmission mechanism (11) by the target speed ratio In a work vehicle including a control unit (P) for reaching a target vehicle speed ,
The continuously variable transmission mechanism (11) includes a sensitivity setting tool (9b) that speeds up or slows down the time until the gear ratio is changed to the target gear ratio,
Wherein the control unit (P) is a structure for defining the time to be shifted to the target gear ratio of the continuously variable transmission mechanism for the operation of the change pedal (7b) (11) with sensitivity setting device (9b), the sensitivity When the setting sensitivity by the setting tool (9b) is set to a lower sensitivity side than the predetermined standard sensitivity, the time to reach the target vehicle speed is delayed, and the setting sensitivity by the sensitivity setting tool (9b) is higher than the predetermined standard sensitivity. When set to the high sensitivity side, it is configured to increase the time to reach the target vehicle speed,
In no event the set sensitivity by the sensitivity setting device (9b) is set to the low sensitivity side of the predetermined normal sensitivity after depression of the change pedal (7b), stopping the depression of the change pedal (7b) again When the release operation for stopping the running is performed , the continuously variable transmission mechanism (11) is controlled to shift so that the vehicle speed is stopped at the standard sensitivity.
In no event the set sensitivity by the sensitivity setting device (9b) is set to the high sensitivity side of the predetermined normal sensitivity depression amount of the shift pedal (7b) is Mu said at depression of substantially less than 50% The speed change mechanism (11) is controlled with high sensitivity to increase the time required to reach the target vehicle speed. When the stepping operation of the speed change pedal (7b) is about 50% or more , the stepless speed change mechanism (11) A work vehicle is characterized in that the speed change mechanism (11) is speed-change controlled at the predetermined standard sensitivity to reach a target vehicle speed .

According to a second aspect of the present invention, the continuously variable transmission mechanism (11) includes an output variable hydraulic pump (21p) and a quantitative hydraulic motor (21m) that receives the output of the hydraulic pump (21p). The number of rotations output from the fixed hydraulic motor (21m) is changed by the amount of rotation of a trunnion shaft (21t) provided in the pump (21p).
A maximum speed setting dial (9a) for restricting the maximum speed when the speed change pedal (7b) is depressed to the maximum position is provided. When the maximum speed is restricted by the maximum speed setting dial (9a), the speed pedal (7b ) To the maximum position, the amount of rotation of the trunnion shaft (21t) is limited so that it can only reach the maximum speed regulated, and the lower limit value of the maximum speed setting range of the maximum speed setting dial (9a) Is configured to be approximately 50% of the upper limit value, and the lower limit value is configured to be correctable within a predetermined range,
A cruise control switch (9c) is provided for maintaining the rotational position of the trunnion shaft (21t) when the shift pedal (7b) is turned on even when the operation of the shift pedal (7b) is stopped. The work vehicle according to claim 1 , wherein the function of the cruise control switch (9c) is made effective even when high speed is restricted .

According to the first aspect of the present invention, the control unit shift-controls the continuously variable transmission mechanism to the target speed ratio based on the pedal sensor value for detecting the amount of depression of the speed change pedal in each of the forward and backward travel directions. To reach the target vehicle speed.
The sensitivity setting tool increases or decreases the time until the continuously variable transmission mechanism is shifted to the target gear ratio. The time required for shifting to the target gear ratio of the continuously variable transmission mechanism relative to the operation of the shift pedal is defined by the sensitivity setting tool. If the sensitivity set by the sensitivity setting tool is set to be lower than the predetermined standard sensitivity, the time until the target vehicle speed is reached is delayed. When the sensitivity set by the sensitivity setting tool is set on the higher sensitivity side than the predetermined standard sensitivity, the time required to reach the target vehicle speed is increased.
When the sensitivity set by the sensitivity setting tool is set to the lower sensitivity side than the standard sensitivity, if the release operation for stopping the travel by stopping the shift pedal is performed again after the shift pedal is depressed, it stops at the standard sensitivity. Shift control of the continuously variable transmission mechanism is performed so that the vehicle speed is reached.
Therefore, when the sensitivity setting tool that allows arbitrary sensitivity setting is set to a sensitivity lower than the specified standard sensitivity , the acceleration speed is gradually followed up to the vehicle speed corresponding to the depression while suppressing the acceleration shock in the operation of the shift pedal. Ru is. On the other hand, when the release operation for stopping the travel by stopping the depression of the shift pedal after the depression of the shift pedal is performed, the vehicle is promptly decelerated to the stop vehicle speed, so that it is possible to cope with a situation where a rapid deceleration is required.

When the sensitivity setting tool is set to a sensitivity higher than a predetermined standard sensitivity , and the stepping operation of the shift pedal is less than about 50%, the stepless speed change mechanism is controlled with high sensitivity to reach the target vehicle speed. Speed up the time. When the stepping amount of the shift pedal is approximately 50% or more, the continuously variable transmission mechanism is shift-controlled with a predetermined standard sensitivity to reach the target vehicle speed.
Therefore, in the case of a high sensitivity setting, when the operation of the shift pedal is small, the follow-up speed is quickly increased, and when the shift pedal is large, the normal follow-up speed is increased, which causes hunting of the engine rotation. Stable increase in speed is possible.

According to the invention according to claim 2, in addition to the effect of the invention according to claim 1, the lower limit value of the maximum speed setting range of the maximum speed setting dial is configured to be approximately 50% of the upper limit value, and the lower limit value is a predetermined value. Since the correction can be made within the range, even if the lower limit value shifts due to the individual characteristic difference of the continuously variable transmission mechanism (HST) or the oil temperature, it can be made as designed. Even if the maximum speed setting dial regulates the maximum speed, enabling the cruise control switch function enables the trunnion shaft for adjusting the output of the hydraulic pump of the continuously variable transmission mechanism even if the operation of the shift pedal is stopped. Can be maintained. Thereby, the versatility of vehicle speed control improves.

Plan view of the overall structure of the tractor Enlarged view of the shift setting section Configuration block diagram of traveling transmission system Configuration diagram of transmission system Internal configuration and hydraulic circuit diagram of hydrostatic continuously variable transmission mechanism Input / output block diagram of shift control system Flow chart of control processing example 1 Flow chart of control processing example 2 Flow chart of control processing example 3 Flowchart of control processing example 4 Flow chart of control processing example 5 Flowchart of control processing example 6 Characteristics of pedal operation and valve drive current Flowchart of control processing example 7 Characteristic diagram of maximum speed regulation example Flowchart of control processing example 8 Flowchart of control processing example 9 Flow chart of control processing example 10 Characteristic diagram of proportional solenoid drive current and vehicle speed shaft output speed Flowchart of control processing example 11 Flowchart of control processing example 12 Flowchart of control processing example 13 Flowchart of control processing example 14 Flowchart of control processing example 15 Flowchart of control processing example 16 Flowchart of control processing example 17 Flowchart of control processing example 18 Flowchart of control processing example 19 Flowchart of control processing example 20 Flowchart of control processing example 21 Flowchart of control processing example 22 Flowchart of control processing example 23 Flowchart of control processing example 24 Flowchart of control processing example 25 Flowchart of control processing example 26 Flow chart of control processing example 27 Change characteristics diagram of shift operation by sensitivity setting tool Flowchart of control processing example 28 Flowchart of control processing example 29 Flowchart of control processing example 30 Flowchart of control processing example 31

Embodiments specifically configured based on the above technical idea will be described below with reference to the drawings.
FIG. 1 is an overall configuration plan view of a tractor shown as an example of a work vehicle to which the present invention is applied. The work vehicle 1 supports the machine body by front and rear traveling wheels 2 and 3 so as to be able to work on the field, and performs work by attaching the work machine to the front part or the rear part of the machine body. Power is transmitted from the engine 4 mounted in the engine room at the front of the machine body to the traveling wheels 2 and 3. In the power transmission to the traveling wheels 2 and 3, the power shifted by the auxiliary transmission mechanism 12 (stepped transmission) and the continuously variable transmission mechanism 11 of the transmission 5 is continuously transmitted. In addition, power that is not continuously variable among the power input to the continuously variable transmission mechanism 11 is transmitted to the work power supply unit 6 that is abbreviated as PTO. The work power supply unit 6 includes a PTO mechanism 16a at the rear of the machine body and a PTO mechanism 16b at the lower center of the machine body.

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

As shown in an enlarged view in FIG. 2, a maximum speed setting dial 9a, a response control dial 9b, and a cruise control switch 9c are arranged in the shift setting unit 7h.
The maximum speed setting dial 9a determines the maximum speed of the vehicle body. When the maximum speed is determined, the maximum speed setting dial 9a is configured so that only the determined maximum speed can be obtained even when the shift pedal 7b is depressed to the maximum.

  As will be described later, the response control dial 9b is configured to shorten or speed up the arrival time to the target vehicle speed when stepping on the speed change pedal 7b and accelerating to the target vehicle speed.

  When the cruise control switch 9c is turned on, the speed at the time when the shift pedal 7b is turned on is maintained even if the operation of the shift pedal 7b is stopped. Specifically, the rotation position of the trunnion shaft 21t for adjusting the output of the hydraulic pump 21p of the continuously variable transmission mechanism 11 is maintained.

  As shown in the block diagram of FIG. 3, the traveling transmission system of the transmission 5 powers a hydrostatic continuously variable transmission mechanism 11 abbreviated as HST that receives engine power and an auxiliary transmission mechanism 12 that switches the vehicle speed range. They are arranged in series from the transmission upstream side to the downstream side, and are transmitted to the transmission mechanism 13 such as the rear wheel 3. The travel transmission system is provided with device operation sensors such as a rotation sensor 4r of the engine 4, an output rotation sensor 11r of the continuously variable transmission mechanism 11, an output rotation sensor 12r of the auxiliary transmission mechanism 12, and the like, and a shift operation tool such as the shift pedal 7b is provided. Based on this, the control unit P that controls the continuously variable transmission mechanism 11 constitutes a transmission system.

  As shown in the transmission system development diagram in FIG. 4, the transmission device 5 includes a traveling system device such as a continuously variable transmission mechanism 11, a sub-transmission mechanism 12, a rear wheel transmission mechanism 13, a 4WD switching unit 14 a that leads to the front wheel transmission mechanism 14. I have. The sub-transmission mechanism 12 that selects the vehicle speed range from the work speed to the road speed continuously shifts the vehicle speed range by the continuously variable transmission mechanism 11, and the transmission power is transmitted to the front and rear wheels 2 and 3. Of the power input from the engine 4 to the continuously variable transmission mechanism 11, power that is not continuously variable is configured to be able to operate the work machine from the rear and mid PTO mechanisms 16 a and 16 b via the PTO clutch 15. That is, the output shaft 21a from the engine 4 input to the continuously variable transmission mechanism 11 protrudes on the side opposite to the engine 4 (transmission device 5 side), and power is transmitted to the PTO clutch 15 through a plurality of gears. It is the composition which is. Thus, the rear PTO mechanism 16a and the mid PTO mechanism 16b are configured to rotate at a constant rotation.

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

  As shown in FIG. 5, the continuously variable transmission mechanism 11 includes an output variable hydraulic pump 21p driven by engine power and a fixed hydraulic motor 21m that receives the pump output. The hydraulic pump 21p is driven by being directly connected to the output shaft 21a from the engine 4. The hydraulic pump 21p has a trunnion shaft 21t for adjusting the output, and the angle of the swash plate 21s is changed by the rotation of the trunnion shaft 21t. The fixed hydraulic motor 21m is driven by the angular position of the swash plate 21s through the flow rate adjustment including the oil supply direction and output stop, and the forward / reverse variable speed rotation power including neutral output stop is transmitted from the output shaft 21b. Output. The trunnion angle control of the hydraulic pump 21p is configured to adjust the hydraulic oil flow rate by the drive current to the proportional solenoid valve 22 by the HST control of the servo mechanism. Since the adjustment of the hydraulic oil flow rate is performed by changing the duty ratio of the current, the trunnion shaft 21t rotates to the rotation position corresponding to the changed current value. A switching valve 22a is configured on the downstream side of the proportional solenoid valve 22. The switching valve 22a determines the rotational direction of the trunnion shaft 21t, that is, the forward / reverse direction of the output shaft 21b. Reference numeral P denotes a hydraulic circuit for power steering.

  As shown in the input / output block diagram of FIG. 6, the shift control system includes a pedal sensor 31 for the shift pedal 7b, a response control dial 9b as a sensitivity setting tool, a maximum speed setting dial 9a, and a forward or reverse position of the forward / reverse lever 7i. Each signal of the forward / reverse lever sensor 33, the cruise control switch 9c, the auxiliary transmission lever sensor 12p, the brake pedal sensor 34, the HST rotation sensor 11r, the engine rotation sensor 4r, the vehicle speed sensor 12r, etc. is input to the control unit P, The proportional solenoid valve 22 is configured to be capable of current control for each forward / backward direction based on table data corresponding to the dial position of the sensitivity setting tool 9b. When the vehicle is traveling, the forward / reverse lever 7i is used to select forward or reverse, and the shift pedal 7b is depressed to start traveling.

  By operating the forward / reverse lever 7i to the forward side, the output value to the proportional solenoid when the machine starts to move from the stopped state is output from the control unit P when the operation amount of the speed change pedal 7b becomes approximately 14%, and the body starts to move. The configuration. Conventionally, when the operation amount of the shift pedal 7b becomes approximately 20%, the structure is output from the control unit P and the body starts to move, so that the responsiveness is not good, but such a problem can be solved. When the forward / reverse lever 7i is operated to the reverse side, when the amount of operation of the speed change pedal 7b becomes approximately 11%, it is output from the control unit P and the body starts to move. By improving the responsiveness at the time of reverse travel, it becomes possible to promptly execute direction correction by repeating forward and backward travel.

  When the key switch is turned on and the power supply is energized to the controller P, if the forward / reverse lever 7i is operated either forward or backward, the vehicle does not travel even if the shift pedal 7b is depressed. And it is set as the structure which can drive | work by once operating the forward / reverse lever 7i to a neutral position, and then operating it forward or backward again.

  Thus, the continuously variable work vehicle has a continuously variable transmission mechanism 11 that shifts the vehicle speed range including the stop vehicle speed in a stepless manner and transmits engine power to the traveling units 2 and 3, and the continuously variable transmission mechanism. 11 is provided with a control system including a control unit P that performs gear shift control to a target gear ratio based on the depression amount of the shift pedal 7b in each of the forward and backward travel directions. The control unit P receives a sensitivity signal from the dial-type sensitivity setting tool 9b, and continuously shifts in response to the stepping operation of the shift pedal 7b corresponding to the dial position within a predetermined range from low sensitivity to high sensitivity centered on the standard sensitivity. The follow-up operation of the mechanism 11 can be adjusted gradually. Specifically, when the shift pedal 7b is depressed, the target vehicle speed is determined by the pedal sensor 31, and the trunnion shaft 21t is rotated to the target position so that the target vehicle speed is obtained, but the trunnion shaft 21t is rotated to the target position. Make the time to move faster or slower. Thereafter, the detection value from the vehicle speed sensor 12r is fed back, and when the vehicle speed is out of the target vehicle speed, the trunnion shaft 21t is rotated again and adjusted.

  As a specific speed change control by the speed change system, the case where the sensitivity setting tool 9b is set lower than the standard sensitivity will be described. In the case where the trunnion shaft 21t is returned to the neutral position by the release operation after the shift pedal 7b is depressed, If you return slowly, it will take time to slow down. Therefore, as shown in the flowchart of the control processing example 1 in FIG. 7, when the first processing step of deceleration determination (hereinafter abbreviated as “S1”) is applicable, the sensitivity setting tool 9b Only when the set sensitivity is lower than a predetermined standard sensitivity, the control processing (S2, S3) is performed in which the trunnion shaft 21t is rotated to control the shift so that the stop vehicle speed is the standard sensitivity.

  When the shift pedal 7b is depressed by the shift control, the control unit P shifts the continuously variable transmission mechanism 11 to the follow-up operation position based on the sensitivity set by the sensitivity setting tool 9b for each of the selected forward and backward travel directions. If the sensitivity is set to be lower than the standard sensitivity, when the shift pedal 7b is released from being depressed, the shift control is performed to the stop vehicle speed with the standard sensitivity. Therefore, when the sensitivity setting tool 9b that allows arbitrary sensitivity setting is set to a low sensitivity, the stepping operation of the shift pedal 7b is moderately followed up to the stepping-compatible vehicle speed while suppressing the acceleration shock. In addition, since the vehicle is promptly decelerated to the stop vehicle speed in response to the release operation of the shift pedal 7b, it is possible to cope with a situation where a rapid deceleration is required.

  Next, in the shift control when the sensitivity setting tool 9b is set to a higher sensitivity than the standard sensitivity, as shown in the flowchart of the control processing example 2 in FIG. 8, the depression amount of the shift pedal 7b is a predetermined reference value (for example, For the stepping-in operations (S11, S12) of approximately 50% or more, a control process (S13, S14) is performed that performs shift control with standard sensitivity at the time of forward acceleration or reverse acceleration.

  When the sensitivity setting tool 9b is set to high sensitivity by the above control process, if the stepping amount of the shift pedal 7b is less than the reference value, the continuously variable transmission mechanism 11 performs the shift control with high sensitivity by setting with the set operation sensitivity. If the amount of depression is equal to or greater than the reference value, the shift control is performed with the standard sensitivity. Therefore, in the case of a high sensitivity setting, when the operation of the shift pedal is small, the follow-up speed is quickly increased, and when the shift pedal is large, the normal follow-up speed is increased, which causes hunting of the engine rotation. Stable increase in speed is possible.

FIG. 37 shows a change characteristic diagram of the shift operation by the sensitivity setting tool 9b. The vertical axis is the operation amount (depression amount) of the shift pedal 7b, and the horizontal axis is the elapsed time for the trunnion shaft 21t to move.
When the shift pedal 7b is depressed, the target vehicle speed is determined according to the depression operation amount (%). The rotation amount of the trunnion shaft 21t of the continuously variable transmission mechanism 11 is determined in accordance with the target vehicle speed, and the rotation direction from the neutral position of the trunnion shaft 21t is determined by the operation of the forward / reverse lever 7i. The

  A state where the shift pedal 7b is depressed 50% will be described. A symbol Tb indicates a sensitivity range set by the sensitivity setting tool 9b. When the sensitivity is adjusted, the rotational speed of the trunnion shaft 21t changes, and when the rotational speed of the trunnion shaft 21t changes, the time required to reach the target speed changes. However, even if the trunnion shaft 21t rotates to the target position, the time for reaching the target vehicle speed may change due to the influence of a load or the like.

  The minimum position (low sensitivity control) of the dial range of the sensitivity setting tool 9b is point F, and the maximum position (high sensitivity control) of the dial range is point E. The middle position of the dial range (standard sensitivity control) is point D. Between the point F and the point E, the sensitivity may be changed steplessly, or the sensitivity may be changed stepwise.

  When the dial range of the sensitivity setting tool 9b is set to the intermediate position (standard sensitivity control), the trunnion shaft 21t becomes the target rotation position at the elapsed time T2 along the line L1. When the dial range of the sensitivity setting tool 9b is set to the minimum position (low sensitivity control), the trunnion shaft 21t becomes the target rotation position at the elapsed time T3 along the line L3. When the dial range of the sensitivity setting tool 9b is set to the maximum position (high sensitivity control), the trunnion shaft 21t becomes the target rotation position at the elapsed time T1 along the line L2. However, in this embodiment, only when the dial range of the sensitivity setting tool 9b is set to the position of the point E of the maximum position (high sensitivity control), the point is changed to the point E1, and the elapsed time T1 along the line L4. The trunnion shaft 21t is set to the target rotation position at / 2.

  The point F of the minimum position (low sensitivity control) of the dial range of the sensitivity setting tool 9b is an acceleration that does not damage the lawn even if the tractor travels on the lawn or runs on the lawn. It is set to be. When running on snowy roads, low-sensitivity control is used to make the wheels less slippery. Further, the point E of the maximum position (high sensitivity control) of the dial range of the sensitivity setting tool 9b is set to be the limit of acceleration of the tractor (vibration generation, etc.). The line L4 when it is changed from the point E to the point E1 is accelerated twice as fast as the line L2 (may be between about 1.5 times and 2 times). It is often used for traveling when a large load is expected, such as when towing a vehicle. This is because we want to accelerate at an early stage. Thus, although the trunnion shaft 21t is at the target position at a high speed, since the load is applied, the acceleration of the tractor itself is slowed down, so that vibration due to the acceleration does not occur, and even if a large load is applied, a certain amount Acceleration performance can be obtained. And, with respect to the arrival time T1 / 2 of the trunnion shaft 21t to the target rotation position, the arrival time to the target vehicle speed is less than the time T1 / 2 because of the load even if the trunnion shaft 21t is controlled by the line L4. Be late. In addition, relatively high-sensitivity control is used when a front loader is attached to the front of the aircraft to perform scooping work such as earth and sand. This is because the front loader work repeats forwards and backwards many times in a short time, so it is desirable to increase work efficiency. Also, when traveling on the road, relatively high sensitivity control is used to move quickly.

  When the depressing amount of the shift pedal 7b exceeds 50% and the sensitivity setting of the sensitivity setting tool 9b exceeds the standard sensitivity (point D) and is set to the high sensitivity side (between point D and point E1) Are configured to be controlled by the standard sensitivity line L1. For example, when the depression amount of the speed change pedal 7b is 100%, the sensitivity setting of the sensitivity setting tool 9b is normally set between the sensitivity range Ta (point I (low sensitivity control) and point H (high sensitivity control)). However, it can be set only within the sensitivity range Tc (point I (low sensitivity control) and point G (standard sensitivity control)), thereby preventing sudden acceleration and engine stall.

Next, shift control at the time of brake operation in forward travel will be described.
Conventionally, when the output to the proportional solenoid valve 22 is gradually reduced in response to the operation of both the left and right brake pedals 7c, the output to the proportional solenoid valve 22 continues even when the vehicle speed is almost stopped. In this case, since the vehicle may travel at a slow speed by releasing the depression of the brake pedal 7c, in order to eliminate such an unstable state, as shown in the flowchart of the control processing example 3 in FIG. When it is determined that both the brake pedals 7c are depressed simultaneously (S21), when the vehicle speed becomes a predetermined threshold value near the stop speed (for example, 0.5 km / h) or less, the proportional solenoid valve 22 is turned on. A control process (S22, S23) for immediately turning off the output is configured.

  As a result of the above control process, the trunnion shaft 21t of the continuously variable transmission mechanism 11 returns to the neutral position and the rotation output is stopped when the deceleration operation corresponding to the brake operation decelerates to a substantially stopped state with a predetermined threshold. When the foot is released from the brake pedal 7c, the stop state can be safely maintained.

  As for the shift control at the time of reverse side deceleration, as shown in the flowchart of the control processing example 4 in FIG. 10, only when the proportional solenoid valve 22 is driven backward (S31) at the time of deceleration (S32), the sensitivity setting tool. A control process (S33) is performed in which the timing of changing the drive current of the proportional solenoid valve 22 preset by the range of 9b is decelerated by table data that is delayed for a certain time (for example, 10 ms) in all ranges.

  In general, for a continuously variable transmission mechanism that has an orifice on the reverse side of the continuously variable transmission mechanism and easily generates brake pressure, and has a characteristic that the deceleration on the reverse side is severe, the control process described above determines the timing of the deceleration operation during reverse travel. Due to the delay, the traveling feeling on the reverse side can be improved compared to the deceleration on the forward side.

  Further, regarding the shift control when operating the forward / reverse lever 7i during deceleration on the reverse side, as shown in the flowchart of the control processing example 5 in FIG. 11, when the proportional solenoid valve 22 is decelerating on the reverse side (S41, In S42), a control process (S43, S44) is applied to apply the same table data as the forward side for the subsequent reverse side deceleration operation when the forward / reverse lever 7i, which is also abbreviated as a linear lever, is operated on the forward side in the reverse direction. With this configuration, when the forward / reverse lever 7i is operated to move forward while stepping on the speed change pedal 7b during reverse travel, deceleration control is performed in the same way as during forward travel. Therefore, the driving feeling can be improved.

Next, special sensitivity setting by the sensitivity setting tool will be described.
The sensitivity setting tool 9b associates a dial range for setting sensitivity with a sensitivity range from the minimum to the maximum, and a predetermined special sensitivity (for example, for example) exceeding the maximum sensitivity at the dial position on one side which becomes the maximum sensitivity. The sensitivity is set to a scale that can be set.

  The sensitivity setting tool (9b) proportionally distributes the sensitivity range from the minimum to the maximum corresponding to the dial range for setting the sensitivity. As described above, the dial position (point E) of the maximum sensitivity. Is set as another sensitivity (point E1) outside the above sensitivity range. As shown in FIG. 37, this content is when the depression amount of the speed change pedal 7b is up to 50%.

  As described above, the point E at the maximum position (high sensitivity control) in the dial range is changed to the sensitivity of the point E1, and in this case, the speed of the trunnion shaft 21t is controlled to be approximately twice as fast. By doing so, the time for reaching the target position of the trunnion shaft 21t is controlled to be halved.

  Specific control when the dial position of the sensitivity setting tool 9b configured as described above is set to the maximum sensitivity position at one end of the dial range is as follows. As shown in the flowchart of the control processing example 6 in FIG. When 22 is forward / reverse drive (S51), if the dial position of the sensitivity setting tool 9b is the maximum sensitivity position, the control is performed so that the set sensitivity is twice the maximum sensitivity by setting the 1-bit scale unit to 2 bits. The process (S52, S53) is configured.

  By the above control process, the sensitivity setting tool 9b can set the sensitivity not only by the sensitivity range from the minimum to the maximum and the dial range corresponding to the sensitivity range, but also by setting a higher specific sensitivity at the maximum sensitivity dial position. Therefore, it is possible to cope with a wide range of work by the speed change operation with the sensitivity in the normal range and the speed change operation with the special sensitivity exceeding it.

Next, control processing corresponding to individual characteristics of the device will be described.
Generally, regarding the operation of the continuously variable transmission mechanism 11, the work vehicle has an individual difference in the amount of depression of the speed change pedal 7 b when the machine starts to move due to the individual difference in relation to the drive current of the proportional solenoid valve 22 for controlling the operation. Occurs. With respect to such a problem, by performing the operation control with the valve driving current calculated based on the individual characteristics, it is possible to share the shifting operation corresponding to the pedal operation.

  Specifically, as shown in the characteristic diagram of the pedal operation and the valve drive current in FIG. 13, when the machine starts to move from the stopped state, the output value to the proportional solenoid valve 22 of B is stopped from the state in which the machine is moving. When measuring, the output value to the proportional solenoid valve 22 of C, and the output value to the proportional solenoid valve 22 of the saturation A when the speed becomes the upper limit even when the output increases are measured and stored as individual characteristics in the EEPROM. The continuously variable transmission mechanism 11 is controlled by an output value calculated from these three points according to the operation amount of the shift pedal 7b.

  As shown in the flowchart of the control processing example 7 in FIG. 14, the control of the continuously variable transmission mechanism 11 based on the above characteristic difference is performed according to the detection of the pedal operation in the case of traveling by the shift pedal 7b (S61). By configuring the control process for calculating the valve drive current (S62, S63), it is possible to absorb variations due to individual differences and enable the same operation in any machine.

  Next, the shift control in the case of receiving a high load is controlled in the same manner as the maximum speed restriction example shown in the characteristic diagram of FIG. 15 in which the output to the proportional solenoid is restricted to a range of 60% or less by the maximum speed setting dial 9a. That is, as shown in the flowchart of the control processing example 8 in FIG. 16, in the case of traveling by the shift pedal 7b (S71), when a decrease in the engine speed is detected due to an increase in load, the output to the proportional solenoid valve 22 is detected. The control process (S72, S73) for applying the restriction is configured.

  By controlling the valve drive current in the work that is likely to be loaded by the above control process, the work can be continued smoothly without an engine stall. Therefore, the continuously variable transmission mechanism 11 is loaded on a steep uphill. It is possible to avoid a situation that causes danger by performing the stall.

  Next, the deceleration control at the time of returning the pedal during forward travel will be described. As shown in the flowchart of the control processing example 9 in FIG. 17, in the case of travel by the speed change pedal 7b (S81), the speed change pedal 7b at the time of forward travel. After the end of the forward deceleration output at the time of stopping by the return operation (S82), the control process for repeating the constant period (for example, 2s) five times for the reverse side output to the proportional solenoid valve 22 for a certain time (for example, 50ms) By configuring (S83), even if the foot is decelerated by moving away from the speed change pedal 7b during forward traveling, the situation where the trunnion does not return to the neutral position and operates at a low speed can be eliminated and the stop state can be maintained safely. .

  Next, when the depression amount of the shift pedal 7b is small (for example, the depression amount is 25% or less), the shift control reflecting the sensitivity by the sensitivity setting tool 9b is proportional as shown in the flowchart of the control processing example 10 in FIG. Only within a small range of output to the solenoid valve 22 (S91), by constructing a control process (S92, S93) that further delays a fixed time (for example, 10 ms) for shifting except forward acceleration, The running shock during reverse acceleration / deceleration is alleviated, and the running feeling can be improved.

Next, an adjustment mode control process for storing the characteristics of the continuously variable transmission mechanism 11 will be described.
The characteristics of the continuously variable transmission mechanism 11 are shown in FIG. 19 from the start point B to the saturation point A for each of the forward side and the reverse side, as shown in the characteristic diagram of the drive current of the proportional solenoid and the output speed of the vehicle speed shaft. After the rotation speed reaches the upper limit due to an increase in current, the current reaches a stop point C due to a decrease in current, and the current, rotation speed characteristics, and maximum output have a certain variation width depending on the components involved in the supply pressure.

  In order to control the continuously variable transmission mechanism 11 having the above characteristics, the proportional solenoid drive current is gradually increased in the adjustment mode (S101) as shown in the flowchart of the control processing example 11 in FIG. A control process for storing the output value B when the detection of the vehicle speed pulse is started (S102, S103) is configured, and the stored output value B is used as a start operation point and applied to the shift control in the normal mode.

  That is, in the normal mode, starting the output to the proportional solenoid valve 22 from the stored output value B in response to the depression of the shift pedal 7b, the running operation is started in response to the pedal operation. It is possible to suppress mottling that does not start easily even if you step on.

  Further, as shown in the flowchart of the control processing example 12 in FIG. 21, in the adjustment mode (S111), the proportional solenoid drive current is gradually decreased from the saturated state where the output rotational speed becomes the upper limit, and the vehicle speed shaft rotation is performed. A control process (S112, S113) for storing the output value I1 when the number is detected to be equal to or less than a threshold value (for example, 95% of the saturation speed) is configured. By restricting the output value in the normal mode with the memorized output value I1 as an upper limit, it is possible to avoid a situation in which the vehicle speed is exceeded, especially for a small machine having a high reduction ratio, depending on the type of this machine.

  Further, in order to regulate the output when the oil temperature rises, in the same manner as described above, the output value I2 when the vehicle speed shaft rotational speed is detected to be equal to or less than a threshold value (for example, 85% of the saturation rotational speed point) in the adjustment mode. Is stored in memory. By applying this memorized output value I2 as the upper limit when the hydraulic oil temperature rise is regulated (for example, 105 ° C.) in the normal mode, the load on the continuously variable transmission mechanism 11 is reduced, and there is no effect due to the oil temperature rise. Damage to the step transmission mechanism 11 can be prevented.

  Next, the deceleration control corresponding to the oil temperature will be described. As shown in the flowchart of the control processing example 13 in FIG. 22, the forward deceleration output end (S121) when stopping by the return operation of the shift pedal 7b during forward traveling is performed. Later, only when the oil temperature becomes equal to or higher than a threshold value (for example, 70 ° C.), a control process for intermittent output (for example, intermittent output of 50 ms at a cycle of 2 s) to the reverse proportional solenoid valve 22 (S122, S123) By solving this problem, when the vehicle is decelerated with the foot off the speed change pedal 7b, the trunnion shaft 21t moves backward and the problem of the low oil temperature that causes a slow reverse operation can be solved and the stop state can be maintained safely. it can.

  Further, as shown in the flowchart of the control processing example 14 in FIG. 23, in the adjustment mode (S131), as shown in FIG. 19 above, the characteristic diagram of the drive current of the proportional solenoid and the output speed of the vehicle speed shaft is shown. Then, a control process (S132, S133) for memorizing the output value C when the detection of the vehicle speed pulse is completed by gradually reducing the proportional solenoid drive current is configured, and the memorized output value C is set as the stop operation point. And applied to the shift control in the normal mode.

  That is, when the output to the proportional solenoid is reduced by releasing the depression of the shift pedal 7b in the normal mode, the output to the proportional solenoid valve 22 is turned off at the time of the output value C by the memory, thereby corresponding to the pedal operation. Thus, since the running is stopped, it is possible to suppress mottling that does not easily stop even when the shift pedal 7b is released.

  Next, the control process corresponding to the sub-shift will be described. As shown in the flowchart of the control process example 15 in FIG. 24, the proportional solenoid valve 22 is operated when the position of the sub-shift lever 7d is the working speed L as the stall guard function (S141). The control process (S142, S143) which makes the upper limit value of output to the value when the maximum vehicle speed becomes 95% is configured. Due to the above control processing, in the position of the working speed L applied to high load work such as a loader, even if it receives an excessive load, it becomes difficult to stall due to the upper limit restriction of the drive current of the proportional solenoid, and the accuracy of the stall guard function is improved. be able to.

  The maximum speed setting dial 9a is configured such that the lower limit of the setting range is approximately 50% of the upper limit setting value. In the range set by the maximum speed setting dial 9a, the operation amount of the maximum speed setting dial 9a and the actual maximum maximum speed are set by proportional distribution. Thereby, the operation amount of the dial and the actual upper limit of the maximum speed restriction can be operated with the same operation feeling. If the maximum speed limit is set to 95% of the maximum vehicle speed, the maximum speed limit is set to 47.5%, so that the dial operation amount and the actual maximum speed limit limit Can be operated with the same operation feeling.

  In addition, since the maximum speed setting dial 9a has a difference between where electrical output starts and where it actually starts operation, the maximum speed lower limit value and upper limit value are set based on the actual operation start point. It is configured to do.

  Further, when the upper limit of the maximum speed restriction is set to 95% by the maximum speed setting dial 9a, the actual vehicle speed may become a value other than 95% and shift. At this time, the automatic correction (auto tuning) is adopted. Specifically, the D / A value at the upper limit position of the maximum speed restriction of the dial is configured to match the vehicle speed pulse value when the actual vehicle speed is 95%. As a result, the maximum speed setting dial 9a can be appropriately set from the lowest speed lower limit value to the upper limit value.

  When an emergency stop condition occurs during the automatic correction (auto tuning), the control operation is stopped and the automatic correction (auto tuning) is stopped. The emergency stop conditions include key switch position detection, brake switch on / off detection, forward / reverse lever neutral position detection, sub-shift neutral position detection, and the like. Thereby, an emergency stop can be enabled. Regarding the neutral position detection of the forward / reverse lever, the operation of the forward / reverse lever to the opposite side before operation (from the forward side to the reverse side via the neutral position and from the reverse side to the forward side via the neutral position) The control operation is stopped and automatic correction (auto tuning) is stopped. This is because it cannot be determined whether the operation is normal or emergency stop.

  Regarding the handling of the lower limit value of the maximum speed, as shown in the flowchart of the control processing example 16 in FIG. 25, when the maximum speed setting dial 9a is operated (S151), the lower limit value of the setting range can be corrected by the external communication device. For example, the control processing (S152, S153) is configured so that it can be corrected within a predetermined range (a range of approximately ± 10%). That is, the lower limit value of the maximum speed setting range can be corrected within a range of approximately 40% to 60% of the upper limit setting value. Even if an external communication device is not used, the correction may be made, for example, with a dial (not shown) provided on the apparatus side. After such correction, the maximum speed is set with the maximum speed setting dial 9a. By such control processing, even if the lower limit value shifts due to the difference in individual characteristics of HST or the oil temperature, correction can be performed by using an external communication device such as a checker or the dial on this machine. When the maximum vehicle speed by the high-speed setting dial 9a is set to the lower limit, the design value can be achieved.

  As described above, the lower limit of the maximum speed setting range can be corrected within the range of approximately 40% to 60% of the upper limit setting value, but it is set by correcting separately on the forward side and the reverse side. You may comprise. In this case, a forward-side setting dial and a backward-side setting dial may be provided on the apparatus side, or an external checker may be connected to the apparatus and set.

  Even when the maximum speed is restricted by the maximum speed setting dial 9a, the function of the cruise control switch 9c described above is effective. That is, even if the operation of the shift pedal 7b is stopped, the rotation position of the trunnion shaft 21t for adjusting the output of the hydraulic pump 21p of the continuously variable transmission mechanism 11 is maintained. Thereby, the versatility of vehicle speed control improves.

  Next, the upper limit of the output value in consideration of the hysteresis of the proportional solenoid will be described. The output value when the proportional solenoid drive current is gradually decreased from the saturated state where the output speed is the upper limit by the adjustment mode, and the vehicle speed shaft speed is detected to be less than a threshold value (for example, 85% of the saturated speed). (For example, 150) is stored, and when the oil temperature sensor exceeds a specified value (for example, 105 ° C.) (S161) as shown in the flowchart of the control processing example 17 in FIG. The output value in the normal mode is regulated by setting a slightly small value (for example, 149) as the upper limit of the output value (S163a), and after returning the shift pedal 7b by 50% or more, the stored value is set to the upper limit of the output value (S162, S162). Restriction is applied as S163b).

  When the oil temperature sensor rises in the state where the shift pedal 7b is depressed by the above control processing, when the output value is restricted by the memorized value, and when the shift pedal 7b is depressed again, the memorized value is obtained. When the output value is restricted, the actual vehicle speed can be made almost the same by adjusting the output value to compensate for the hysteresis of the proportional solenoid. The problem of deviation in actual vehicle speed due to hysteresis can be solved.

  As shown in the flowchart of the control processing example 18 in FIG. 27, the upper limit restriction during reverse travel is such that the proportional solenoid drive current is gradually decreased from the saturated state in the reverse adjustment mode (S171), and the vehicle speed shaft rotational speed is reduced. The output value when the threshold value (for example, 80% of the saturation speed) is detected is stored in memory (S172, S173), and this stored value is regulated as the upper limit of the output value when the forward / reverse lever 7i is moving backward in the normal mode. By applying the upper limit, the upper limit is imposed at the output point at which the vehicle speed shaft rotational speed actually drops, so that it is possible to suppress the vehicle speed from being exceeded during reverse travel.

  Regarding the characteristic adjustment of the continuously variable transmission mechanism 11, as shown in the flowchart of the control processing example 19 in FIG. 28, in the adjustment mode (S181), the current value to the proportional solenoid is gradually increased or decreased from the saturation point. In this case, the output current value is sequentially changed (S182, S183) by a fixed value (for example, 1) at a fixed interval (for example, every 500 ms), so that the output current value is changed more than every second. Since it does not take much time to adjust the characteristics of the step transmission mechanism 11, a smooth shipping process in a factory can be realized.

  As for the detection of the vehicle speed shaft rotational speed, as shown in the flowchart of the control processing example 20 in FIG. 29, in the adjustment mode (S191), the current value to the proportional solenoid is raised to the saturation point and the vehicle speed shaft rotational speed at that time is determined. At the time of detection, the average value of the vehicle speed shaft rotation speed is calculated (S193) by sampling (S192) at a fixed number of times (for example, 30 times) at a fixed interval (for example, 100 ms), thereby affecting the influence of variations due to high rotation. Therefore, it is possible to detect the correct rotational speed of the vehicle and to improve the accuracy of the oil temperature control and the vehicle speed regulation by model according to the design value.

  Regarding the handling of the difference in the reduction ratio of the traveling transmission system, as shown in the flowchart of the control processing example 21 in FIG. 30, the transmission reduction ratio is proportional to the small type that is different from the large type (S201, S202). By setting the maximum output (saturation point) to the solenoid to the value at which the maximum vehicle speed reaches 95% (S203), the difference in reduction ratio is compensated to make the maximum vehicle speed equal to that of the large model and the HST output shaft Control can be handled in common.

In addition to the control processing described above, the following control processing can be configured.
As for the load control, as shown in the flowchart of the control processing example 22 in FIG. 31, when the load control switch is on and the sub-transmission 12 is “work” (S211, S212), the operation amount of the maximum speed setting dial 9a. By configuring the control process (S213) to provide an upper limit value (for example, 95%), the upper limit is set at the highest speed for high load work such as loader work so that the trunnion angle is not opened to the maximum. , Work interruptions due to engine stalls can be avoided.

  As shown in the flowchart of the control processing example 23 in FIG. 32, the deceleration control by returning the shift pedal 7b during forward travel (stopping the release of the stepping operation) is stopped by returning the shift pedal 7b during the forward travel (depressing the stepping operation). After completion of forward deceleration output (S221), the proportional solenoid valve 22 repeats the output to the reverse side and forward side five times each time (for example, 50 ms) (S222, S223), and then the output is turned off (S224). The control processing is performed. As a result, even if the foot is decelerated from the speed change pedal 7b during forward travel, the situation where the trunnion shaft 21t does not return to the neutral position and operates at a low speed can be eliminated and the stop state can be maintained safely.

  As for the control corresponding to the temperature rise of the hydraulic oil, as shown in the flowchart of the control processing example 24 in FIG. 33, in the case of traveling by the shift pedal 7b (S231), the oil temperature rises and a threshold value (for example, 105 ° C.) When the maximum speed is exceeded, a control process (S232, S233) is performed to perform a predetermined restriction (for example, 10%) on the upper limit speed by the maximum speed setting dial 9a. By controlling the output to the proportional solenoid valve 22 and removing the load by the above control process, HST burnout due to an increase in the oil temperature can be prevented.

  As for another deceleration control by returning the shift pedal 7b (depressing the stepping operation) during forward traveling, as shown in the flowchart of the control processing example 25 in FIG. 34, the operation for returning (depressing the stepping operation) of the shift pedal 7b during forward traveling is performed. When the vehicle speed becomes less than a threshold value (for example, 0.1 to 0.2 km / h) after the end of the forward deceleration output at the time of stopping due to (S241), a certain period of time (for example, the proportional solenoid valve 22 on the reverse side) , 50 ms) driving is repeated five times at a constant cycle (for example, 2 s) (S242, S243), and the above-mentioned repetition is continued in a range where the vehicle speed after deceleration is equal to or higher than the threshold (S244). As a result, even if the foot is released from the speed change pedal 7b and the vehicle is decelerated during forward travel, the trunnion shaft 21t does not return to the neutral position and does not return at a slow speed, and can be stopped safely. State can be maintained.

  In the maximum speed setting dial 9a, the upper limit that can be set is restricted by the position of the auxiliary transmission lever 7d, and when the position is the working speed L, the upper limit is restricted to 60%. As shown in the flowchart of the control processing example 26 in FIG. 35, if the position of the auxiliary transmission lever 7d is the working speed L as the stall guard function (S251), the upper limit of the maximum speed setting dial 9a is set to 50% when the engine speed is reduced. By configuring the control processing (S252, S253) to be switched, it is possible to limit the upper limit at the time of high negative due to loader work or the like, so that the accuracy of the stall guard function can be improved.

  As for the upper limit restriction when the oil temperature rises, as shown in the flowchart of the control processing example 27 in FIG. 36, when the oil temperature sensor exceeds a specified value (eg, 105 ° C.) (S261), the output to the proportional solenoid Control processing for reducing the output value by a fixed value every predetermined time (for example, 500 ms) when changing to a stored value (for example, 85%) for the upper limit of the value (S262, S263) With this configuration, if the current value is suddenly changed by regulation, the trunnion returns too much, resulting in an excessive decrease in the vehicle speed. By mitigating the change, an excessive decrease in the vehicle speed can be avoided.

  The sensitivity setting tool 9b is configured as shown in the flowchart of the control processing example 28 in FIG. If the sub-shift is in the high speed position (S281) and the trunnion shaft 21t is in the speed increasing direction (S282), the setting value of the sensitivity setting tool 9b is ignored and the movement of the trunnion shaft 21t is always delayed by 20 ms (S283). To do. As a result, it is possible to suppress a decrease in engine speed when a load is applied, and to prevent the running performance from deteriorating.

  Further, as shown in the flowchart of the control processing example 29 in FIG. 39, the sub-shift is in the high speed position (S291), and the shift pedal 7b is depressed by a predetermined amount or more (50% or more) and the output to the proportional solenoid is large. Yes (S292), at the time of forward / reverse acceleration (S293), and when the setting value of the sensitivity setting tool 9b is set to the more sensitive side than the median value (S294), the setting value of the sensitivity setting tool 9b Is configured to control the movement of the trunnion shaft 21t with a value corresponding to the median. As a result, a decrease in engine speed when a load is applied can be suppressed, and the vehicle can travel at an appropriate acceleration according to the depression of the shift pedal 7b.

  In addition, when the load control is activated and the proportional solenoid controls the movement of the trunnion shaft 21t to the target rotation position on the deceleration side, the rotation of the trunnion shaft 21t is the most regardless of the setting of the sensitivity setting tool 9b. It is configured to rotate at a high speed. Thereby, the effect of preventing engine stall can be enhanced.

  A control processing example 30 shown in FIG. 40 shows a control processing example based on the relationship between traveling and oil temperature other than the automatic cruise traveling by the cruise control switch 9c. When the cruise control switch 9c is off and the vehicle is not in an automatic cruise traveling (S301), and the oil temperature of the continuously variable transmission mechanism (HST) 11 shows an abnormal value (S302), the sensitivity setting tool 9b Regardless of the setting, the setting value of the sensitivity setting tool 9b controls the movement of the trunnion shaft 21t with a value corresponding to the most insensitive. Thereby, the load of the continuously variable transmission mechanism (HST) 11 can be reduced and a failure can be prevented.

  A control processing example 31 shown in FIG. 41 shows a control processing example based on the relationship between traveling and oil temperature other than the automatic cruise traveling by the cruise control switch 9c. When the cruise control switch 9c is turned off and the vehicle is not traveling automatically (S401), and the oil temperature of the continuously variable transmission mechanism (HST) 11 shows an abnormal value (S402), the highest speed setting dial Regardless of the setting of 9a, the maximum speed is controlled by a value corresponding to the lower limit value of the maximum speed setting dial 9a. Thereby, the load of the continuously variable transmission mechanism (HST) 11 can be reduced and a failure can be prevented.

1 Working vehicle 4 Engine 5 Transmission 7b Shift pedal 7c Brake pedal 7d Sub-shift lever 9a Maximum speed setting dial 9b Sensitivity setting tool (response control dial)
9c Cruise control switch 11 continuously variable transmission mechanism 12 auxiliary transmission mechanism 12p auxiliary transmission lever sensor 13 transmission mechanism 21p hydraulic pump 21m fixed hydraulic motor 21t trunnion shaft 22 proportional solenoid valve
31 Pedal sensor 33 Forward / reverse lever sensor A Saturation output value B Start output value C Stop output value P Control unit

Claims (2)

A continuously variable transmission mechanism (11) that performs a stepless speed change operation in the vehicle speed range including the stop vehicle speed to transmit the engine power to the traveling portion, and a speed change pedal for each of the forward and backward travel directions in the continuously variable transmission mechanism (11). pedal sensor (31) to shift control to the target gear ratio based on the value, the control unit to reach the target vehicle speed by a continuously variable transmission mechanism (11) to the target speed ratio for detecting the amount of depression of (7b) ( P),
The continuously variable transmission mechanism (11) includes a sensitivity setting tool (9b) that speeds up or slows down the time until the gear ratio is changed to the target gear ratio,
Wherein the control unit (P) is a structure for defining the time to be shifted to the target gear ratio of the continuously variable transmission mechanism for the operation of the change pedal (7b) (11) with sensitivity setting device (9b), the sensitivity When the setting sensitivity by the setting tool (9b) is set to a lower sensitivity side than the predetermined standard sensitivity, the time to reach the target vehicle speed is delayed, and the setting sensitivity by the sensitivity setting tool (9b) is higher than the predetermined standard sensitivity. When set to the high sensitivity side, it is configured to increase the time to reach the target vehicle speed,
In no event the set sensitivity by the sensitivity setting device (9b) is set to the low sensitivity side than a predetermined normal sensitivity after depression of the shift pedal (7b), stopping the depression of the shift pedal (7b) again When the release operation for stopping the running is performed , the continuously variable transmission mechanism (11) is controlled to shift so that the vehicle speed is stopped at the standard sensitivity.
In no event the set sensitivity by the sensitivity setting device (9b) is set to the high sensitivity side of the predetermined normal sensitivity depression amount of the shift pedal (7b) is Mu said at depression of substantially less than 50% The speed change mechanism (11) is controlled with high sensitivity to increase the time required to reach the target vehicle speed. When the stepping operation of the speed change pedal (7b) is about 50% or more , the stepless speed change mechanism (11) A work vehicle characterized in that the speed change mechanism (11) is speed-controlled with the predetermined standard sensitivity to reach a target vehicle speed . The continuously variable transmission mechanism (11) includes a variable output hydraulic pump (21p) and a quantitative hydraulic motor (21m) that receives the output of the hydraulic pump (21p), and a trunnion provided in the hydraulic pump (21p). The number of rotations output from the fixed hydraulic motor (21m) is changed by the amount of rotation of the shaft (21t),
A maximum speed setting dial (9a) for restricting the maximum speed when the speed change pedal (7b) is depressed to the maximum position is provided. When the maximum speed is restricted by the maximum speed setting dial (9a), the speed pedal (7b ) To the maximum position, the amount of rotation of the trunnion shaft (21t) is limited so that it can only reach the maximum speed regulated, and the lower limit value of the maximum speed setting range of the maximum speed setting dial (9a) Is configured to be approximately 50% of the upper limit value, and the lower limit value is configured to be correctable within a predetermined range,
A cruise control switch (9c) is provided for maintaining the rotational position of the trunnion shaft (21t) when the shift pedal (7b) is turned on even when the operation of the shift pedal (7b) is stopped. The work vehicle according to claim 1 , wherein the function of the cruise control switch (9c) is made effective even during high speed regulation .

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