JP4266934B2 - Working gear shifting structure - Google Patents

Description

  The present invention relates to a traveling speed change structure for a work vehicle.

  For example, as disclosed in Patent Document 1, the work vehicle includes a rotational speed detection unit that sets a reference rotational speed based on the rotational speed of the engine in a no-load state and detects the actual rotational speed of the engine, There is a configuration in which a traveling transmission is automatically operated to a high speed side and a low speed side based on an actual engine speed and a reference engine speed.

  In this case, the work vehicle is provided with an accelerator operating tool (for example, an accelerator lever or an accelerator pedal that is manually operated) that can set the engine speed, and the engine speed set by the accelerator operating tool is set. If the difference between the actual engine speed and the actual engine speed is small, it is determined that the load applied to the engine is small, and the traveling transmission is automatically operated to the high speed side. If the rotational speed difference from the engine speed is large, it is determined that the load applied to the engine is large, and the traveling transmission is automatically operated to the low speed side.

JP-A-3-163263 (Figs. 1, 2 and 3)

In a work vehicle, work traveling (relatively rarely operates the accelerator operating tool) that travels at a substantially constant speed while driving the working device, and the accelerator operating tool is relatively often operated. In many cases, the vehicle travels in various travel modes, such as on the road. Accordingly, there is room for improvement in terms of automatically and appropriately operating the transmission for a variety of travel modes.
SUMMARY OF THE INVENTION An object of the present invention is to provide a traveling transmission structure for a work vehicle so that a traveling transmission is automatically and appropriately operated in accordance with various traveling modes.

[I]
(Constitution)
A first feature of the present invention resides in the following structure in a traveling speed change structure for a work vehicle.
A traveling transmission, an accelerator operating tool for setting the engine speed, and a rotation speed detecting means for detecting the actual engine speed are provided. If the rotational speed difference between the engine rotational speed set by the accelerator operating tool and the actual engine rotational speed detected by the rotational speed detecting means is smaller than the first set value, the traveling transmission is made to operate at high speed. When the difference between the engine speed and the actual engine speed is greater than a second set value that is greater than the first set value, the travel transmission is operated to the low speed side. Automatic transmission means is provided. A changing means capable of changing the first and second set values is provided. In the changing means, the first operation position where the first set value can be changed to a smaller side and the larger side without changing the second set value, and the first and second set values can be changed simultaneously to the smaller side and the first set value can be changed. And a second operation position that can simultaneously change the first and second set values to the larger side.

(Function)
According to the first aspect of the present invention, an accelerator operating tool for setting the engine speed and an engine speed detecting means for detecting the actual engine speed are provided, and the engine set by the accelerator operating tool is provided. If the difference between the engine speed and the actual engine speed is small (less than the first set value), it is determined that the load on the engine is small, and the traveling transmission is automatically Operated on the high speed side. On the other hand, if the difference between the engine speed and the actual engine speed is large (greater than the second set value), it is determined that the load on the engine is large, and the traveling transmission is It is automatically operated to the low speed side.

In this case, according to the first feature of the present invention, the first and second set values are provided on the smaller side and larger according to various travel modes, provided with changing means capable of changing the first and second set values. Change to the side.
For example, if the first set value is changed to a larger side, if the difference between the engine speed and the actual engine speed does not become sufficiently large , the engine set speed and the actual engine speed the rotational speed difference is not greater than the first set value, the transmission for driving automatically be operated at a high speed side (in other words, the transmission device for traveling is easily operated in a high speed side). On the other hand, if the first set value is changed to a smaller side, the difference between the engine set speed and the actual engine speed will be slightly larger. Since the rotational speed difference becomes larger than the first set value, the traveling transmission is not automatically operated to the high speed side (in other words, the traveling transmission is difficult to operate to the high speed side).

For example, if the second set value is changed to a smaller side, the difference between the engine set speed and the actual engine speed becomes a little larger. Since the number difference becomes larger than the second set value, the traveling transmission is automatically operated to the low speed side (in other words, the traveling transmission is easily operated to the low speed side). On the other hand, if the second set value is changed to the larger side, if the difference between the engine speed and the actual engine speed does not become sufficiently large, the engine set speed and the actual engine speed. Is not greater than the second set value, the travel transmission is not automatically operated to the low speed side (in other words, the travel transmission is unlikely to be operated to the low speed side).
According to the first feature of the present invention, if the first set value is changed to a smaller side and a larger side without changing the second set value, the traveling transmission is automatically reduced in speed based on the second set value. The characteristic that the traveling transmission is automatically operated to the high speed side can be changed based on the first set value while maintaining the same characteristic that is operated to the high side. Such a state is suitable for, for example, a plowing work in which a work vehicle runs while pulling a plow or a subsoiler and digs up the work place in a work place that is relatively difficult to slide, such as a field.
According to the first feature of the present invention, the first and second set values are simultaneously changed to the smaller side or simultaneously changed to the larger side, whereby the traveling transmission is automatically set based on the first set value. Thus, the characteristic of operating on the high speed side and the characteristic of automatically operating the traveling transmission device on the low speed side based on the second set value can be simultaneously changed in the same direction. Such a state is suitable for, for example, a plowing work in which a work vehicle travels while pulling a rotary tiller and plows the work place in a relatively slippery work place such as a paddy field.

(The invention's effect)
According to the first feature of the present invention, in the traveling speed change structure of the work vehicle, the first and second set values are changed to a smaller side and a larger side according to various traveling modes, and the vehicle is used for traveling based on the first set value. By changing the characteristics of automatically operating the speed change device to the high speed side and the characteristics of automatically operating the speed change transmission device to the low speed side based on the second set value, various travel modes Accordingly, the traveling transmission can be configured to be automatically operated appropriately and the transmission performance of the work vehicle can be improved.
According to the first feature of the present invention, it is suitable for, for example, a plowing work in which a work vehicle runs while pulling a plow or a subsoiler and digs up the work place in a work place that is relatively difficult to slide, such as a field. As a result, the shifting performance of the work vehicle can be improved.
According to the first feature of the present invention, in a relatively slippery work place such as a paddy field, for example, a state where the work vehicle travels while pulling a rotary tiller and is suitable for a tilling work or the like for plowing the work place. As a result, the shifting performance of the work vehicle can be improved.

[II]
(Constitution)
The second feature of the present invention resides in the following structure in the traveling speed change structure for a work vehicle according to the first feature of the present invention.
The change rate of the first set value at the second operation position is set to be larger than the change rate of the first set value at the first operation position.

[1]
FIG. 1 shows a transmission case 8 of a four-wheel drive agricultural tractor that is an example of a work vehicle. The power of the engine 1 is a forward clutch 5 or a reverse clutch 6, a cylindrical shaft 7, a first main transmission 10 (traveling). And the second main transmission 11, the auxiliary transmission 12, and the rear wheel differential device 13 are transmitted to the rear wheels 14. The power branched from immediately before the rear wheel differential device 13 is transmitted to the front wheel 19 through the transmission shaft 15, the hydraulic clutch type front wheel transmission device 16, the front wheel transmission shaft 17 and the front wheel differential device 18. The power of the engine 1 is transmitted to the PTO shaft 4 through the transmission shaft 2, the hydraulic multi-plate PTO clutch 3 and the PTO transmission 9.

  As shown in FIG. 1, the forward and reverse clutches 5 and 6 are hydraulic multi-plate types in which a friction plate (not shown) and a piston (not shown) are combined, and are operated to the transmission side by supplying hydraulic oil. Is done. When the forward clutch 5 is operated to the transmission side, the power of the engine 1 flows directly from the forward clutch 5 to the cylindrical shaft 7 and the airframe moves forward. When the reverse clutch 6 is operated to the transmission side, the power of the engine 1 is transmitted to the cylindrical shaft 7 in the reverse rotation state via the reverse clutch 6 and the transmission shaft 20 and the airframe moves backward.

  As shown in FIG. 1, the first main transmission 10 is a hydraulic clutch type in which four hydraulic multi-plate type first speed clutch 21, second speed clutch 22, third speed clutch 23 and fourth speed clutch 24 are arranged in parallel. The speed of the cylindrical shaft 7 is changed to the fourth speed by operating one of the first to fourth speed clutches 21 to 24 to the transmission side, and the transmission shaft 25 is shifted to the fourth speed. Is transmitted to.

  As shown in FIG. 1, the second main transmission 11 is configured as a hydraulic clutch type in which two hydraulic multi-plate low-speed clutches 26 and a high-speed clutch 27 are arranged in parallel. By operating one of the gears 27 to the transmission side, the power of the transmission shaft 25 is shifted in two stages and transmitted to the auxiliary transmission 12. The sub-transmission device 12 is configured in a synchromesh type for sliding the shift member 53 and can be shifted in two stages, and is mechanically operated by a transmission lever 28 shown in FIG.

[2]
Next, the hydraulic circuit for the forward and reverse clutches 5, 6 and the first and second main transmissions 10, 11 will be described.
As shown in FIG. 3, an electromagnetic proportional valve 35 for forward and reverse clutches 5 and 6 and pilot operated switching valves 36a and 37a and pilots for first-speed to fourth-speed clutches 21 to 24 are connected to an oil passage 30 from a pump 29. Operative switching valves 31a, 32a, 33a, 34a and electromagnetic proportional valves 38, 39 for the low speed and high speed clutches 26, 27 are connected.

  As shown in FIG. 3, a pilot operated switching valve 42 a for a hydraulic clutch 41 for differential lock operation in the front wheel differential device 18 and an oil pressure for differential lock operation in the rear wheel differential device 13 are provided in an oil path 40 branched from the oil path 30. A pilot operated switching valve 44a for the clutch 43 and pilot operated switching valves 47a and 48a for the standard clutch 45 and the speed increasing clutch 46 of the front wheel transmission 16 are connected. The switching valves 31a to 34a, 36a, 37a, 42a, 44a, 47a, 48a are urged to the oil discharge side (shutoff side) by springs, and are supplied to the supply side (transmission side) by supplying pilot pressure. Operated.

  As shown in FIG. 3, the pilot oil passage 50 branches from the oil passage 30 through the pressure reducing valve 49, and the pilot oil passage 50 is an operation portion of the switching valves 31 a to 34 a, 36 a, 37 a, 42 a, 44 a, 47 a, 48 a. The electromagnetic operation valves 31b, 32b, 33b, 34b, 36b, 37b, 42b, 44b, 47b, and 48b are connected to the operation unit. The electromagnetic operation valves 31b to 34b, 36b, 37b, 42b, 44b, 47b, and 48b are urged to the oil draining side (shut off side) by springs, and the electromagnetic operation valves 31b to 34b, 36b, 37b, 42b, 44b, When 47b and 48b are operated to the supply side, the pilot pressure is supplied to the operation portion of the switching valves 31a to 34a, 36a, 37a, 42a, 44a, 47a and 48a, and the switching valves 31a to 34a, 36a, 37a, 42a, 44a, 47a and 48a are operated on the supply side (transmission side).

[3]
Next, the structure of the operation part of the forward and reverse clutches 5 and 6 and the first and second main transmissions 10 and 11 will be described.
As shown in FIG. 3, an on-off valve 51 capable of draining the pilot pressure from the operation portion of the switching valves 36a, 37a is provided, and the on-off valve 51 is biased to the closing side by a spring, and the on-off valve 51 is opened. A clutch pedal 52 that is operated to the side is provided. As shown in FIG. 2, a forward / reverse lever 59 that can be operated to a forward position F, a reverse position R, and a neutral position N is provided at the base of the steering handle 58 of the front wheel 19.

  As shown in FIG. 2, the shift lever 28 is swingably supported around the horizontal axis of the maneuvering portion of the airframe, and the shift shaft 54, the shift lever 28, which slides the shift member 53 of the auxiliary transmission 12, Are mechanically linked by a linkage mechanism 55. By operating the shift lever 28 to the neutral position N, the low speed position L, and the high speed position H, the auxiliary transmission 12 (shift member 53) can be operated to the neutral position, the low speed position, and the high speed position. In addition, a position sensor 70 for detecting the operation position of the transmission lever 28 is provided.

  As shown in FIG. 2, a lock pin 56 that can be moved back and forth is provided on the lateral side of the speed change lever 28, and an operation button 57 for moving the lock pin 56 back and forth is provided above the speed change lever 28. . The lock pin 56 is urged to the protruding side (the right side of FIG. 2) by a spring (not shown) (the operation button 57 is also urged to the protruding side to the left side of FIG. 2), and is fixed. By engaging the lock pin 56 with the guide plate 60 of this part, the shift lever 28 is held at the neutral position N, the low speed position L, and the high speed position H. When the operation button 57 is pushed, the lock pin 56 is retracted, and the speed change lever 28 can be operated to the neutral position N, the low speed position L, and the high speed position H.

  As shown in FIG. 2, a shift-up button 61 and a shift-down button 62 are vertically arranged on the left side surface of the speed change lever 28. When the shift-up button 61 and the shift-down button 62 are pressed, they will be described later. 5], the first and second main transmissions 10, 11 are operated.

  As shown in FIG. 2, whichever of the 7-segment shift display 64 for displaying the shift positions (1st to 8th) of the first and second main transmissions 10 and 11 and the forward and reverse clutches 5 and 6 is the transmission side. The control unit is provided with a neutral lamp 67 indicating that the forward lamp 65 and the reverse lamp 66, the shift lever 28 or the forward / backward lever 59 are operated to the neutral position N. As shown in FIG. 3, a pressure sensor 74 that detects the operating pressure of the forward and reverse clutches 5 and 6 is provided, and the forward and reverse lamps 65 and 66 are turned on by detection of the pressure sensor 74. An artificially operated setting switch 68 is provided. The setting switch 68 includes a manual mode position shown in FIG. 2, a travel mode position pushed in the D1 direction, and a load mode position pushed in the D2 direction. It is configured to be operable at three positions.

[4]
Next, the operation of the forward / reverse lever 59 will be described with reference to FIG.
When the forward / reverse lever 59 is operated to the forward position F (step S1), an operation current is supplied to the electromagnetic operation valve 36b, the switching valve 36a is operated to the supply side, and the forward clutch 5 is operated to the transmission side (step S2). The forward lamp 65 is lit (step S3). When the forward / reverse lever 59 is operated to the reverse position R (step S1), an operation current is supplied to the electromagnetic operation valve 37b, the switching valve 37a is operated to the supply side, and the reverse clutch 6 is operated to the transmission side (step S4). The reverse lamp 66 is turned on (step S5), and the buzzer 71 shown in FIG. 2 is intermittently operated (step S6).

  When the forward / reverse lever 59 is operated to the neutral position N (step S1), the operation current to the electromagnetic operation valves 36b and 37b is cut off, and the switching valves 36a and 37a are operated to the oil drain side, and the forward and reverse clutches 5 and 6 are operated. Is operated to the shut-off side (step S7), and the neutral lamp 67 is turned on (step S8). When the clutch pedal 52 is depressed, the on-off valve 51 is operated to the open side, the switching valves 36a and 37a are operated to the oil drain side, the forward and reverse clutches 5 and 6 are operated to the cutoff side, and the neutral lamp 67 is lit. . When both the forward and reverse clutches 5 and 6 are operated to the cut-off side in this way, the power is cut off in the forward and reverse clutches 5 and 6 and the airframe stops.

[5]
Next, a state where the setting switch 68 is pushed to the manual mode position will be described with reference to FIG.
When the setting switch 68 is pushed to the manual mode position, the manual mode is set. As shown in FIG. 1, the first main transmission 10 can shift to 4 speeds, and the second main transmission 11 can shift to 2 speeds. Therefore, the first and second main transmissions 10 and 11 can shift to 8 speeds. The speed can be changed. With the low speed clutch 26 operated to the transmission side, the 1st to 4th clutches 21 to 24 correspond to the 1st to 4th shift positions, and the high speed clutch 27 is operated to the transmission side, The first to fourth speed clutches 21 to 24 correspond to the shift positions of the fifth speed to the eighth speed.

  As shown in FIGS. 2 and 3, each of the 1st to 4th speed clutches 21 to 24 and the low speed and high speed clutches 26 and 27 are provided with pressure sensors 63 and 74 for detecting the operating pressure. , 74 are detected, and the current shift positions (first to eighth gears) of the first and second main transmissions 10 and 11 are detected, and the detected shift positions are displayed on the shift display unit 64.

  In the above state, it is assumed that the up-shift button 61 or the down-shift button 62 is pressed (steps S11 and S12). In this case, as shown by a solid line A1 (time point B1) in FIG. 6, when the shift-up button 61 is pressed (step S11), the 1st to 4th clutches 21 that are one speed higher than the current shift position are located. To 24 are started to be operated to the transmission side by the electromagnetic operation valves 31b to 34b (step S13). When the downshift button 62 is pressed (step S12), the first to fourth speed clutches 21 to 24, which are one step lower than the current shift position, are started to be operated to the transmission side by the electromagnetic operation valves 31b to 34b. (Step S14).

  When the speed change lever 28 is operated to the low speed position L or the high speed position H (step S15), it is operated to the transmission side almost simultaneously with steps S13 and S14, as indicated by a solid line A2 (time point B1) in FIG. The operating pressure of the low speed or high speed clutch 26, 27 is operated from the operating pressure P2 in the transmission state to the predetermined low pressure P3 by the electromagnetic proportional valves 38, 39 (step S16). In this case, when operating from the fourth speed shift position to the fifth speed shift position, the operating pressure of the low speed clutch 26 is operated to zero, and the operating pressure of the high speed clutch 27 is operated from zero to the predetermined low pressure P3. Conversely, when operating from the fifth speed shift position to the fourth speed shift position, the operating pressure of the high speed clutch 27 is operated to zero, and the operating pressure of the low speed clutch 26 is operated from zero to the predetermined low pressure P3.

  As shown by a solid line A1 (time point B2 to time point B3) in FIG. 6, the operating pressures of the first to fourth speed clutches 21 to 24 on the first-stage high speed side or the first-stage low speed side are transmitted by electromagnetic operation valves 31b to 34b. The operating pressure P1 is started. At the same time, as indicated by a one-dot chain line A3 in FIG. 6 (from time B2 to time B3), the operating pressures of the first to fourth speed clutches 21 to 24 before the push-up operation of the shift up button 61 or the shift down button 62 are electromagnetic. The operating valves 31b to 34b start to be operated from the operating pressure P1 in the transmission state to zero (step S17).

  When the speed change lever 28 is operated to the low speed position L or the high speed position H (step S18), the operating pressure of the low speed or high speed clutches 26, 27 is changed as shown by the solid line A2 (time point B3 to time point B4) in FIG. The electromagnetic proportional valves 38 and 39 are gradually operated from the predetermined low pressure P3 to the pressure increasing side (step S19). As a result, the power of the first-speed to fourth-speed clutches 21 to 24 on the first-stage high-speed side or the first-stage low-speed side starts to be transmitted via the low-speed or high-speed clutches 26 and 27. When the pressure sensor 63 detects that the operating pressure of the low-speed or high-speed clutches 26 and 27 has reached the operating pressure P2 in the transmission state, as shown at time B4 of the solid line A2 in FIG. 6 (step S20), a shift is performed. It is determined that the speed change operation by pressing the up button 61 or the shift down button 62 is completed, the speed change position after the speed change operation is displayed on the speed change display section 64 (step S21), and the buzzer 71 is activated only once. The operator is notified of the end of the speed change operation (step S22). As a result, the process proceeds to step S11, and a speed change operation by the next pressing operation of the upshift button 61 or the downshift button 62 becomes possible.

When the transmission lever 28 is operated to the neutral position N, the sub-transmission device 12 (shift member 53) is operated to the neutral position, so that the airframe is stopped. When the shift-up button 61 or the shift-down button 62 is pushed and operated in the state where the shift lever 28 is operated to the neutral position N (steps S11 and S12), the first and second main transmissions 10 and 11 (1 The high-speed to fourth-speed clutches 21 to 24, the low-speed and high-speed clutches 26 and 27) are operated to the first-stage high-speed side or the first-stage low-speed side (steps S13, S14, and S17). 64 (step S21), the buzzer 71 is activated only once (step S22).
In this case, since the aircraft is stopped, the operation to the predetermined low pressure P3 of the operating pressure of the low speed or high speed clutch 26, 27 and the operation to the operating pressure P2 in the transmission state are not performed as in steps S16 and S19. .

[6]
Next, a state in which the first and second main transmissions 10, 11 are automatically operated to the high speed side when the setting switch 68 is pushed to the travel mode position will be described with reference to FIG.
When the setting switch 68 is pushed to the travel mode position, a travel mode assuming road travel is set. As shown in FIGS. 1 and 2, a hand accelerator lever 73 (corresponding to an accelerator operating tool) capable of artificially setting the accelerator opening of the engine 1 to an arbitrary position is provided, and the operation position of the hand accelerator lever 73 is provided. A potentiometer type opening degree sensor 75 for detecting the engine speed is provided, and a rotation speed sensor 72 (corresponding to a rotation speed detection means) for detecting the actual rotation speed N2 of the engine 1 is provided. The rotational speed and opening of the engine 1 in a no-load state (a state in which the forward and reverse clutches 5 and 6 are operated to the cutoff side and the PTO clutch 3 is operated to the cutoff side and no load is applied to the engine 1). The relationship with the detection value of the sensor 75 (the operation position of the hand accelerator lever 73) is obtained in advance, and the engine 1 in the no-load state is determined by the detection value of the opening sensor 75 (the operation position of the hand accelerator lever 73). Is determined as the set rotational speed N1 of the engine 1.

  As described in [5], the timer starts counting in the state where the first and second main transmissions 10 and 11 are operated by the up-shift button 61 or the down-shift button 62 (step S31). The set rotational speed N1 of the engine 1 is detected (step S32), and the actual rotational speed N2 of the engine 1 is detected (step S33). Thereby, the set rotational speed N1 of the engine 1 is equal to or higher than the first predetermined rotational speed N4 (eg, 1200 rpm) (step S34), and the rotational speed difference between the set rotational speed N1 of the engine 1 and the actual rotational speed N2 of the engine 1 is set. The value N3 (for example, 100 rpm) or less (step S37), and the state where the hand accelerator lever 73 is not operated (step S38) is maintained for a set time (for example, 2 seconds) (step S39) (in this case, The set rotational speed N1 of the engine 1 is a fourth predetermined rotational speed N7 (for example, 2400 rpm) or higher (step S35), and the actual rotational speed N2 of the engine 1 is a fifth predetermined rotational speed N8 (for example, 2300 rpm) or higher (step S36). Then, the process proceeds from step 34 to step S38, bypassing step S37).

  As described above, when the states of steps S34, S37, and S38 are maintained for a set time (for example, 2 seconds) (step S39), steps S13, S16, S17, and S19 to S22 of FIG. The first and second main transmissions 10, 11 are operated to the first high speed side (step S45). When the set rotational speed N1 of the engine 1 detected in step S32 is equal to or higher than the first predetermined rotational speed N4 (for example, 1200 rpm) and lower than the second predetermined rotational speed N5 (for example, 1400 rpm) (step S41), the step of FIG. S13, S16, S17, and S19 to S22 are performed only once (steps S42 and S45). In this case, when the first and second main transmissions 10 and 11 have reached the eighth speed position (step S40), steps S13, S16, S17, and S19 to S22 of FIG. 5 are not performed.

  As described above, after the first and second main transmissions 10 and 11 are operated to the first high speed side (steps S42 and S45), the states of steps S34, S37, and S38 are set to a set time (for example, 2 seconds). When the engine speed is maintained for a long time (step S39), the set rotational speed N1 of the engine 1 detected in step S32 is equal to or higher than the second predetermined rotational speed N5 (for example, 1400 rpm) and lower than the third predetermined rotational speed N6 (for example, 1600 rpm). If present (step S41), steps S13, S16, S17, S19 to S22 of FIG. 5 are performed, and the first and second main transmissions 10, 11 are operated to the first high speed side (steps S43, S45). (The first and second main transmissions 10, 11 are operated to the two-stage high speed side with respect to the aforementioned steps S42, S45). In this case, if the first and second main transmissions 10 and 11 have reached the eighth speed position (step S40), steps S13, S16, S17, and S19 to S22 of FIG. 5 are not performed.

  As described above, after the first and second main transmissions 10 and 11 are operated to the first high speed side (steps S41, S43, and S45), the states of steps S34, S37, and S38 are further set for a set time (for example, 2 seconds). ) (Step S39), if the set rotational speed N1 of the engine 1 detected in step S32 is equal to or higher than a third predetermined rotational speed N6 (for example, 1600 rpm) (step S41), FIG. Steps S13, S16, S17, and S19 to S22 are performed, and the first and second main transmissions 10 and 11 are operated to the first-speed side (steps S44 and S45) (in contrast to the aforementioned steps S42 and S45) Thus, the first and second main transmissions 10 and 11 are operated to the three-speed side). In this case, when the first and second main transmissions 10 and 11 have reached the eighth speed position (step S40), steps S13, S16, S17, and S19 to S22 of FIG. 5 are not performed.

[7]
Next, a state in which the first and second main transmissions 10, 11 are automatically operated to the low speed side when the setting switch 68 is pushed to the travel mode position will be described with reference to FIG.
As described in [6] above, in the state where the first and second main transmissions 10 and 11 are automatically operated to the high speed side, the timer starts counting (step S51), and the set rotation of the engine 1 is started. The number N1 is detected (step S52), and the actual engine speed N2 is detected (step S53). Accordingly, the set rotational speed N1 of the engine 1 is equal to or lower than the sixth predetermined rotational speed N9 (for example, 1000 rpm) (step S54), and the actual rotational speed N2 of the engine 1 is equal to or lower than the seventh predetermined rotational speed N10 (for example, 2300 rpm) (step S55). ) Assume that the state where the hand accelerator lever 73 is not operated (step S56) is maintained for a set time (for example, 0.75 seconds) (step S57).

  As described above, when the states of steps S54, S55, and S56 are maintained for a set time (for example, 0.75 seconds) (step S57), steps S14, S16, S17, and S19 to S22 of FIG. 5 are performed. Thus, the first and second main transmissions 10 and 11 are operated to the first low speed side (step S59). As described above, after the first and second main transmissions 10 and 11 are operated to the first low speed side (step S59), the states of steps S54, S55, and S56 are further set at a set time (for example, 0.75 seconds). If maintained for a long time (step S57), steps S14, S16, S17, S19 to S22 of FIG. 5 are performed, and the first and second main transmissions 10, 11 are operated to the first-stage low speed side ( Step S59).

  In this case, as described above, even if the first and second main transmissions 10 and 11 are repeatedly operated to the first stage low speed side, as described in [5] and [6] above, the upshift button 61 or When the first and second main transmissions 10 and 11 have been operated by pressing the downshift button 62 (step S58), steps S14, S16, S17, and S19 to S22 in FIG. Not done.

  As shown in FIG. 9, when the clutch pedal 52 is depressed, the on-off valve 51 is operated to the open side, the switching valves 36a and 37a are operated to the oil drain side, and the forward and reverse clutches 5 and 6 are moved to the cutoff side. When operated (step S71), the timer starts counting (step S72), the operating pressures of the forward and reverse clutches 5 and 6 are detected (step S73), and as shown in FIG. 1 and FIG. The rotational speed of the cylindrical shaft 7 is detected by the rotational speed sensor 69 provided on the lower side of the reverse clutches 5 and 6 (step S74).

  As a result, the operating pressure of the forward and reverse clutches 5 and 6 is zero (step S75), and the rotational speed of the cylindrical shaft 7 is equal to or lower than the eighth predetermined rotational speed N11 (for example, 1000 rpm) (step S76). If maintained for (for example, 0.75 seconds) (step S77), it is determined that the aircraft has stopped or the velocity of the aircraft has become extremely low, and the first and second main transmissions 10, 11 are It is automatically operated to the fifth speed shift position (step S78).

[8]
Next, a state in which the first and second main transmissions 10 and 11 are automatically operated to the low speed side in a state where the setting switch 68 is pushed to the load mode position will be described with reference to FIGS. explain.
When the setting switch 68 is pushed to the load mode position, the load mode is set. The shift lever 28 is operated to the low speed position L or the high speed position H (step S91), the forward / reverse lever 59 is operated to the forward position F (step S92), the engine 1 is operating (step S93), and the front wheel 19 The steering angle is within the range of the right and left set angles from the straight-ahead position (step S94) (the aircraft is not turning slightly), and the hand accelerator lever 73 is not operated (step S95). (For example, the state in which the change speed of the set rotational speed N1 of the engine 1 is within a range of ± 50 rpm / 100 milliseconds), the operating pressure of the low speed or high speed clutch 26, 27 is the operating pressure P2 in the transmission state ( Step S96), a shift operation by pressing the up-shift button 61 or the down-shift button 62 described in [5] above, or a change in [8] and [9] described later. Operation and is in the state it is finished (step S97), the process proceeds to step S101.

  When the process proceeds to step S101, a deceleration-side count number KD and an acceleration-side count number KU, which will be described later, are reset, a set rotational speed N1 of the engine 1 is detected (step S102), and an actual rotational speed N2 of the engine 1 is detected. Is detected (step S103), and the actual change speed V1 of the rotational speed N2 of the engine 1 is detected (step S104). Accordingly, when the set rotational speed N1 of the engine 1 is equal to or higher than the ninth predetermined rotational speed N12 (for example, 1300 rpm) (step S105) and smaller than the tenth predetermined rotational speed N13 (for example, 1600 rpm) (step S106), the process proceeds to step S107. To do.

  In step S107, the rotational speed difference between the set rotational speed N1 of the engine 1 and the actual rotational speed N2 of the engine 1 is equal to or greater than the second set value N14, and the change speed V1 is a predetermined change speed V11 (for example, 10 rpm / 200 milliseconds). ) Hereinafter (step S108), if the shift positions of the first and second main transmissions 10, 11 are not the lower limit position E2 of [11] described later (step S109), the process proceeds to step S110.

In this case, the difference in rotational speed between the set rotational speed N1 of the engine 1 and the actual rotational speed N2 of the engine 1 becomes equal to or larger than the second set value N14 (step S107), and the actual rotational speed N2 of the engine 1 is reduced. It shows the state to do.
If the change speed V1 is a positive value, it means that the actual engine speed N2 is increasing. If the change speed V1 is a negative value, the actual engine speed N2 is reduced. It means that As a result, the change speed V1 falls below a predetermined change speed V11 (for example, 10 rpm / 200 milliseconds) (step S108), and the actual engine speed N2 hardly changes (the change speed V1 is a positive value). ) Or a state in which the actual rotational speed N2 of the engine 1 decreases (change speed V1 is a negative value).

  When the process proceeds to step S110 as described above, the count number K1 is set based on the difference between the predetermined change speed V11 and the change speed V1 (steps S111, S112, S113, S114). As shown in FIG. 14, “0”, “V12 (negative value)” and “V13 (negative value smaller than V12)” are set with respect to the predetermined change speed V11, and 0 at the predetermined change speed V11 or less. As described above, four regions of less than 0, V12 or more, less than V12, V13 or more, and less than V13 are set, and the count number K1 is “0”, “KK1”, “KK2”, “ KK3 ". In this case, the magnitude relationship is 0 <KK1 <KK2 <KK3.

Next, when the rotational speed difference between the set rotational speed N1 of the engine 1 and the actual rotational speed N2 of the engine 1 is equal to or greater than a third set value N15 (for example, 1.5 times the second set value N14) (step S115). ), The count number K2 is set to “KK4” (KK4 is larger than KK3) (step S116), and the difference between the rotational speed N1 of the engine 1 and the actual rotational speed N2 of the engine 1 is set to the third setting. If it is less than the value N15 (for example, 1.5 times the second set value N14) (step S115), the count number K2 is set to “0” (step S117).
When the count numbers K1 and K2 are set as described above, the count numbers K1 and K2 are added to the count number KD on the deceleration side (step S118).

  By repeating steps S102 to S118 as described above, the count numbers K1 and K2 are added to the count number KD on the deceleration side, the count number KD on the deceleration side increases, and the count number KD on the deceleration side 5 reaches the deceleration-side set count KD1 (step S119), steps S14, S16, S17, and S19 to S22 of FIG. 5 are performed, and the first and second main transmissions 10, 11 are moved to the low speed side by one stage. It is operated (step S120).

  In this case, in the standard state, it takes about 0.75 seconds for the deceleration-side count KD to reach the deceleration-side set count KD1. As the change speed V1 becomes smaller than the predetermined change speed V11 as in steps S112, S113, and S114, the count number K1 is set to be larger. As in steps S115 and S116, the actual rotational speed N2 of the engine 1 is set. When the value greatly decreases, the count number K2 is set to a large value, and the count number KD on the deceleration side quickly reaches the set count KD1 on the deceleration side, so that the first and second main transmissions 10, 11 are slowed down by one stage. The operation timing to the side becomes earlier.

Conversely, if there is no difference between the predetermined change speed V11 and the change speed V1 as in step S111, the count number K1 is set to “0”, and the actual engine speed N2 of the engine 1 as in steps S115 and S117. Is not decreased so much, the count number K2 is set to “0”, so that the count number KD on the deceleration side reaches the set count KD1 on the deceleration side later, and 1 of the first and second main transmissions 10, 11 The operation timing to the low speed side is delayed.
When the change speed V1 becomes larger than the predetermined change speed V11 (for example, 10 rpm / 200 milliseconds) as in step S108, it is determined that the actual rotational speed N2 of the engine 1 is increasing, and the process proceeds to step S101. The count number KD on the deceleration side is reset.

  In step S105, in a state where the set rotational speed N1 of the engine 1 is smaller than the ninth predetermined rotational speed N12 (for example, 1300 rpm), the actual rotational speed N2 of the engine 1 crosses the eleventh predetermined rotational speed N21 (for example, 1500 rpm). If it has decreased (step S121), steps S14, S16, S17, and S19 to S22 of FIG. 5 are performed regardless of the count number KD on the deceleration side, and the first and second main transmissions 10 and 11 are moved to the first stage. It is operated to the low speed side (step S122).

As shown in FIG. 2, there is provided a dial operation type sensitivity adjustment switch 76 (corresponding to the changing means) which can be manually operated, as shown in [10] described later and solid lines A4 and A5 in FIG. The first setting value N16 (see [9] described later) and the second setting value N14 are set and changed by the sensitivity adjustment switch 76.
Thus, as described above, when the rotational speed difference between the set rotational speed N1 of the engine 1 and the actual rotational speed N2 of the engine 1 becomes equal to or larger than the second set value N14 ("operation region toward low speed side"), The first and second main transmissions 10 and 11 are operated to the first-stage low speed side, and the difference in rotational speed between the set rotational speed N1 of the engine 1 and the actual rotational speed N2 of the engine 1 is the first and second. If it is between the set values N16 and N14 (“standard area”), the first and second main transmissions 10 and 11 are not operated on either the low speed side or the high speed side.

[9]
Next, a state in which the first and second main transmissions 10 and 11 are automatically operated to the high speed side when the setting switch 68 is pushed to the load mode position will be described with reference to FIGS. 11 and 15. To do.
In step S106 of the previous item [8], when the set rotational speed N1 of the engine 1 is equal to or higher than a tenth predetermined rotational speed N13 (for example, 1600 rpm), the shift positions of the first and second main transmissions 10 and 11 will be described later. If it is not the limit position E3 on the high speed side of [11] (step S131), the process proceeds to step S132.

  When the routine proceeds to step S132, a rotational speed difference between the set rotational speed N1 of the engine 1 and the actual rotational speed N2 of the engine 1 is detected, and the set rotational speed N1 of the engine 1 and the actual rotational speed N2 of the engine 1 are detected. When the rotational speed difference is equal to or smaller than the first set value N16, it is determined that the actual rotational speed N2 of the engine 1 is increasing. In this case, as shown in [10] described later and a solid line A5 in FIG. 13, a first set value N16 (see “operation area to high speed side”) is set. When the rotational speed difference between the set rotational speed N1 of the engine 1 and the actual rotational speed N2 of the engine 1 is equal to or less than the first set value N16 (step S132), the set rotational speed N1 of the engine 1 and the actual engine 1 The count number K3 is set (steps S135, S136, and S137) based on the rotation speed difference from the rotation speed N2 (step S133).

  As shown in FIG. 16, N17, N19, and N20 are set for the rotation speed N18 corresponding to the first set value N16, and the relationship is such that N17 <N18 <N19 <N20. . Thereby, five areas of N20 or more, less than N20, N19 or more, less than N19, N18 or more, less than N18, N17 or more, and less than N17 are set. Thus, the count number K3 is set to “KK6”, “KK7”, and “KK8” (steps S135, S136, and S137) depending on which region the actual rotational speed N2 of the engine 1 enters (step S133). In this case, “KK6”, “KK7”, and “KK8” are positive values and have a relationship of magnitude of KK6 <KK7 <KK8.

  When the rotational speed difference between the set rotational speed N1 of the engine 1 and the actual rotational speed N2 of the engine 1 is larger than the first set value N16 (step S132), the actual rotational speed N2 of the engine 1 is less than N18 and greater than or equal to N17. (Step S134), the count number K3 is set to “−KK5” (Step S138). In this case, “−KK5” is a negative value.

  When the count number K3 is set in this way, the count number K3 is added to the count number KU on the speed increasing side (step S139). In this case, when the count numbers K3 “KK6”, “KK7”, and “KK8” are added to the count number KU on the speed increasing side, the count number KU on the speed increasing side increases, and the count number on the speed increasing side count number KU. When K3 “−KK5” is added, the count number KU on the speed increasing side decreases.

  By repeating steps S102 to S139 as described above, the count number K3 is added to the count number KU on the acceleration side, and the count number KU on the acceleration side is increased, and the count number on the acceleration side is increased. When KU reaches the set count KU1 on the speed increasing side (step S140), steps S13, S16, S17, S19 to S22 of FIG. 5 are performed, and the first and second main transmissions 10, 11 are one-stage high speed. (Step S141).

  In this case, in a standard state, it takes about 2.0 seconds for the speed-up count number KU to reach the speed-up side set count KU1. As in steps S135, S136, and S137, as the actual engine speed N2 becomes larger than the engine speed N18 corresponding to the first set value N16 (the engine 1 set engine speed N1 and the actual engine 1 engine speed). As the rotational speed difference from N2 becomes smaller than the first set value N16), the count number K3 is set to be larger. Thereby, the count number KU on the speed increasing side reaches the speed increasing side set count KU1 earlier, and the operation timing of the first and second main transmissions 10, 11 to the first speed side becomes earlier.

Conversely, as shown in step S138, when the actual engine speed N2 is smaller than the engine speed N18 corresponding to the first set value N16 (the engine 1 set engine speed N1 and the actual engine 1 engine speed N2). Since the count number K3 is set to a negative value “−KK5”, the speed-up side count number KU is slower than the speed-up side set count KU1. As a result, the operation timing of the first and second main transmissions 10, 11 to the one-stage high speed side is delayed.
When the actual rotational speed N2 of the engine 1 is smaller than N17 (see FIG. 16) as in step S134, it is determined that the actual rotational speed N2 of the engine 1 has not increased, and the process proceeds to step S101 and increases. The count number KU on the fast side is reset.

As shown in the previous item [8] and FIG. 2, the sensitivity adjustment switch 76 sets and changes the first set value N16 and the second set value N14 (see the previous item [8]).
As a result, as described above, when the rotational speed difference between the set rotational speed N1 of the engine 1 and the actual rotational speed N2 of the engine 1 becomes equal to or less than the first set value N16 ("operation region to the high speed side"), The first and second main transmissions 10 and 11 are operated to the first high speed side, and the difference in rotational speed between the set rotational speed N1 of the engine 1 and the actual rotational speed N2 of the engine 1 is the first and second. If it is between the set values N16 and N14 (“standard area”), the first and second main transmissions 10 and 11 are not operated on either the low speed side or the high speed side.

[10]
Next, the setting of the first set value N16 (see the previous item [9]) and the second set value N14 (see the previous item [8]) by the sensitivity adjustment switch 76 will be described.
As shown in FIG. 13, by operating the sensitivity adjustment switch 76, the first set value N16 (solid line A5) and the second set value N14 (solid line A4) are set, and the first set value N16 (solid line). The “high-speed operation area”, “standard area”, and “low-speed operation area” are set by A5) and the second set value N14 (solid line A4).

  As a result, as described in the preceding paragraphs [8] and [9], when the rotational speed difference between the set rotational speed N1 of the engine 1 and the actual rotational speed N2 of the engine 1 becomes equal to or larger than the second set value N14 (“low speed side The first and second main transmissions 10 and 11 are operated to the first-stage low speed side. When the rotational speed difference between the set rotational speed N1 of the engine 1 and the actual rotational speed N2 of the engine 1 is between the first and second set values N16 and N14 (“standard range”), the first and second The main transmissions 10, 11 are not operated on either the low speed side or the high speed side. When the rotational speed difference between the set rotational speed N1 of the engine 1 and the actual rotational speed N2 of the engine 1 becomes equal to or smaller than the first set value N16 (“operation region toward the high speed side”), the first and second main transmissions 10 , 11 are operated to the one-stage high speed side.

As shown in FIG. 13, when the sensitivity adjustment switch 76 is operated within the operation range H1, the first set value N16 is maintained at “N33”, and the second set value N14 is maintained at “N35”. Yes.
As shown in FIG. 13, when the sensitivity adjustment switch 76 is operated within the operation range H2 (corresponding to the first operation position) , the second set value N14 is maintained unchanged from “N35”, and the second 1 The set value N16 is linearly changed corresponding to the operation position of the sensitivity adjustment switch 76 within a small range of “N33” and “N34”. In this case, the relationship is N33 <N34 <N35 (corresponding to a state in which the first set value N16 is changed to a smaller side and a larger side without changing the second set value N14).

As shown in FIG. 13, when the sensitivity adjustment switch 76 is operated in the operation range H3 (corresponding to the second operation position) , the first adjustment value N16 is in the range of “N31” and “N33”, and the sensitivity adjustment switch Corresponding to the operation position 76, it is changed linearly. In this case, the relationship is N31 <N33, and the difference between “N31” and “N33” is larger than the difference between “N33” and “N34” (operation range). The rate of change of the first set value N16 (solid line A5) in the operating range H3 is larger than the rate of change of the first set value N16 (solid line A5) at H2) (first and second) The setting values N16 and N14 can be changed simultaneously to the smaller side, and the first and second setting values N16 and N14 can be changed simultaneously to the larger side).

  As shown in FIG. 13, when the sensitivity adjustment switch 76 is operated within the operation range H4, the first set value N16 is set to “0”. As described above, when the sensitivity adjustment switch 76 is operated to the operation range H4 and the first set value N16 is set to [0], the first and second main transmissions 10 as described in [9] above. , 11 is not operated on the high speed side.

  As shown in FIG. 13, when the sensitivity adjustment switch 76 is operated in the operation ranges H3 and H4, the second set value N14 corresponds to the operation position of the sensitivity adjustment switch 76 in the range of “N32” and “N35”. Change linearly. In this case, the relationship is 0 <N31 <N32 <N33 <N34 <N35. Compared to the difference between “N33” and “N34” and the difference between “N31” and “N33”, The difference between “N32” and “N35” is large (the rate of change of the first set value N16 (solid line A5) in the operation range H2 and the first set value N16 (solid line A5) in the operation range H3. ), The change rate of the second set value N14 (solid line A4) in the operation ranges H3 and H4 is larger) (the first and second set values N16 and N14 are made smaller). It can be changed at the same time, and the first and second set values N16 and N14 can be changed simultaneously to the larger side).

[11]
As described in [8] and [9] above, when the first and second main transmissions 10 and 11 are automatically operated to the low speed side and the high speed side when the load mode is set, And the second main transmissions 10, 11 are set within the range of the low speed side and high speed side limit positions E2, E3 (for example, the low speed side and high speed side limit positions E2, E3, the low speed side and the high speed side). It is operated in the range of three shift positions at an intermediate position between the limit positions E2 and E3 (steps S109 and S131).

  In this case, as described in [8] and [9], the shift positions of the first and second main transmissions 10 and 11 when the setting switch 68 is pushed to the load mode position are within the automatic shift range. It is set as the limit position E3 on the high speed side. Therefore, as described in [5] above, in the state where the setting switch 68 is pushed to the manual mode position, the shift-up button 61 or the shift-down button 62 is pushed to operate the first and second main transmissions 10. , 11 are operated to the desired shift position, and the setting switch 68 is pushed to the load mode position, so that the automatic shift range (high-speed limit position E3) can be arbitrarily set to the low speed side and the high speed side. it can. When the limit position E3 on the high speed side of the automatic transmission range is set in this way, the limit position E2 on the low speed side of the automatic transmission range is set accordingly.

[12]
Next, the operation of the auxiliary transmission 12 using the transmission lever 28 will be described.
When the transmission lever 28 is operated to the neutral position N, the sub transmission 12 (shift member 53) is operated to the neutral position, and when the transmission lever 28 is operated to the low speed position L, the sub transmission 12 (shift member 53) is moved to the low speed position. When the shift lever 28 is operated to the high speed position H, the auxiliary transmission 12 (shift member 53) is operated to the high speed position.

  For example, when the forward / reverse lever 59 is operated to the forward position F (the forward clutch 5 is operated to the transmission side and the reverse clutch 6 is operated to the disengagement side), the transmission lever 28 is moved to the low speed position L (high speed position H). In the operating state (the state in which the speed change lever 28 is held at the low speed position L (high speed position H) by the operation button 57 and the lock pin 56), the operation pin 57 is pressed to operate the lock pin 56 to the guide plate 60. When the retraction operation is performed, the switching valve 36a is operated to the oil discharge side by the electromagnetic operation valve 36b, and the forward clutch 5 is operated to the cutoff side.

  As a result, the shift lever 28 is operated from the low speed position L (high speed position H) to the neutral position N and the high speed position H (low speed position L) while the operation button 57 is pressed, and the operation button 57 is returned. The shift lever 28 is held at the neutral position N and the high speed position H (low speed position L) by the lock pin 56.

  In this case, when the operation button 57 is returned at the neutral position N of the shift lever 28, the switching valve 36a is operated to the supply side by the electromagnetic operation valve 36b, and the forward clutch 5 is immediately operated to the transmission side by the electromagnetic proportional valve 35. The When the operation button 57 is returned at the high speed position H (low speed position L) of the speed change lever 28, the switching valve 36a is operated to the supply side by the electromagnetic operation valve 36b, and the forward clutch 5 is gradually transmitted by the electromagnetic proportional valve 35. Operated on the side.

  In a state where the forward / reverse lever 59 is operated to the reverse position R (a state where the reverse clutch 6 is operated to the transmission side and the forward clutch 5 is operated to the disengagement side), the operation button 57 of the speed change lever 28 is depressed as described above. When the push and return operations are performed, the reverse clutch 6 is operated to the disengagement side and the transmission side as described above.

[First Alternative Embodiment of the Invention]
In the above-mentioned [Best Mode for Carrying Out the Invention], as shown in [10] and FIG. 13, when the sensitivity adjustment switch 76 is operated within the operation range H4, the first set value N16 is “0”. The first set value N16 (solid line A5) in the operation range H3 may be linearly extended to “0” as it is (for example, a diagram of the operation range H4). The left edge of page 13 is “0”). Thereby, even if the sensitivity adjustment switch 76 is operated in the operation range H4, the “operation area toward the high speed side” is set.

[Second Embodiment of the Invention]
In the above-mentioned [Best Mode for Carrying Out the Invention], the first and second set values N16 and N14 are set by one sensitivity adjustment switch 76 as described in [10] above. Instead, the first and second sensitivity adjustment switches 76 for setting and changing the first set value N16 and the sensitivity adjustment switches 76 for setting and changing the second set value N14 are separately provided. The setting values N16 and N14 may be set and changed independently.

[Third Another Embodiment of the Invention]
In the above-mentioned [Best Mode for Carrying Out the Invention] [First Alternative Embodiment of the Invention] [Second Alternative Embodiment of the Invention], it is described in [8], [9], [10], and [11] above. The operation in the load mode may be performed in the same manner also in the travel mode described in [6] and [7].

[Fourth Embodiment of the Invention]
In the above-mentioned [Best Mode for Carrying Out the Invention] [First Alternative Embodiment of the Invention] [Second Alternative Embodiment of the Invention] [Third Alternative Embodiment of the Invention] Like the second main transmission 11, the transmission 12 includes a hydraulic multi-plate low-speed clutch (not shown) and a high-speed clutch (not shown) arranged in parallel. An electromagnetic proportional valve (not shown) may be provided for each high speed clutch. If comprised in this way, the 1st-2nd main transmission apparatus 10 and 11 and the subtransmission apparatus 12 will set the 1st-16th speed shift position, and push the upshift button 61 and the downshift button 62 will be pushed. By operating, the first and second main transmissions 10 and 11 and the auxiliary transmission 12 are configured to be operated to the 1st to 16th speed shift positions.

[Fifth Embodiment of the Invention]
[Best Mode for Carrying Out the Invention] [First Alternative Embodiment] [Second Alternative Embodiment] [Third Alternative Embodiment] [Fourth Embodiment] In another embodiment, the first and second main transmissions 10 and 11 shown in FIG. 1 are configured as a hydraulic clutch type, but the first and second main transmissions 10 and 11 are similar to the auxiliary transmission 12. A shift member (not shown) may be configured to be a gear transmission type that slides, and the shift member may be configured to slide by a hydraulic cylinder (not shown).
The work vehicle in which the first and second main transmissions 10 and 11 are configured to be capable of shifting to 10 stages or 6 stages, and the auxiliary transmission 12 is configured to be capable of shifting to 3 stages of a high speed position, a medium speed position, and a low speed position. The present invention can also be applied to a working vehicle in which the first and second main transmissions 10, 11 are configured as hydrostatic or belt-type continuously variable transmissions.

Schematic diagram showing the transmission system of the mission case The figure which shows the linkage state of a shift lever, a shift up button, a shift down button, a setting lever, and each part Hydraulic circuit diagram of forward and reverse clutches, first and second main transmissions, etc. Diagram showing the flow of control when operating the forward / reverse lever The figure which shows the flow of control at the time of pushing and operating a shift up button and a shift down button in manual mode The figure which shows the state of the 1st-4th speed clutch at the time of pushing and operating a shift up button and a shift down button in manual mode, a low speed, and a high speed clutch The figure which shows the flow of control in the state in which the 1st and 2nd main transmission is automatically operated by the high speed side in driving | running | working mode. The figure which shows the flow of control in the state in which the 1st and 2nd main transmission is automatically operated by the low speed side in driving | running | working mode. The figure which shows the flow of control in the state in which the 1st and 2nd main transmission is automatically operated to the 5th gear position in driving mode. The figure which shows the flow of the first half of control in the state in which the 1st and 2nd main transmission is automatically operated by the low speed side and the high speed side in load mode. The figure which shows the flow of the second half of the control in the state in which the 1st and 2nd main transmission is automatically operated by the low speed side and the high speed side in load mode. The figure which shows the flow of control in the state in which the 1st and 2nd main transmission is automatically operated to the low speed side in load mode. The figure which shows the relationship between the operation position of a sensitivity adjustment switch, and the 1st and 2nd setting value. The figure which shows the state near the predetermined change speed in load mode The figure which shows the flow of control in the state in which the 1st and 2nd main transmission is automatically operated by the high speed side in load mode. The figure which shows the state of the rotation speed corresponding to the engine setting rotation speed, 1st setting value, and 1st setting value in load mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 10 Transmission for driving | running | working 72 Rotational speed detection means 73 Accelerator operating tool 76 Change means
H2 operation range (first operation position)
H3 operation range (second operation position)
N1 Engine set speed N2 Actual engine speed N14 Second set value N16 First set value

Claims (2)

A traveling transmission, an accelerator operating tool for setting the engine speed, and a rotation speed detecting means for detecting the actual engine speed;
If the difference in engine speed set by the accelerator operating tool and the actual engine speed detected by the engine speed detecting means is smaller than the first set value, the shift for traveling is performed. operating the device in high-speed side, the rotational speed difference between the rotation speed of the set speed and the actual engine of the engine, when larger than the second set value larger than the first set value, for the running With automatic transmission means for operating the transmission to the low speed side,
E Bei change means capable of changing the first and second set value,
The change means allows the first operation position to change the first set value to a smaller side and a larger side without changing the second set value, and simultaneously changes the first and second set values to a smaller side. A traveling speed change structure for a work vehicle comprising a second operation position that is capable of simultaneously changing the first and second set values to a larger side . 2. The traveling speed change structure for a work vehicle according to claim 1, wherein a change rate of the first set value at the second operation position is set larger than a change rate of the first set value at the first operation position .

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