JP2008014403A - Transmission for tractor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission for a tractor, capable of relieving operator's burden while preventing sudden start of a working vehicle. <P>SOLUTION: The transmission 10 for the tractor 1 comprises a main gear shifter 20 consisting of multiple shift stages to be operated by a hydraulic control device based on an electric signal, and a sub gear shifter 60 consisting of shift stages to be shifted with mechanical operation. The gear ratio of the shift stages (the 10th, 11th and 11th stages) with the combination of the low speed stage of the sub gear shifter 60 with the maximum speed stage side of the main gear shifter 20 is overlapped with the gear ratio of the shift stages (the 13th, 14th and 15th stages) with the combination of the high speed stage of the sub gear shifter 60 with the minimum speed stage side of the main gear shifter 20. This reduces the shift operation of the sub gear shifter 60 during work in a speed region near a boundary between low-speed work and high-speed work to prevent the sudden start of the tractor 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a transmission of a tractor, and more specifically, a main transmission device including a multi-stage gear stage operated by a hydraulic device based on an electric signal, and high and low two-stage gear stages shifted by mechanical operation. It is related with the transmission of a tractor provided with the auxiliary transmission which consists of these.

  Conventionally, in the transmission of a working vehicle such as a tractor, in order to obtain a traveling speed (shift range) according to complicated work, the transmission has a large number of gears compared to a general vehicle such as an ordinary car. Is known (see, for example, Patent Document 1).

  In such a transmission, the engine output transmitted through the main clutch is branched into a traveling system and a PTO system. In the power transmission mechanism of the traveling system, a main transmission that performs multi-stage shifting, a multi-plate hydraulic clutch, a forward / reverse switching device, and a sub-transmission that performs high and low two-stage shifting are connected in series. The power shifted by each of these transmissions is transmitted to the rear wheels via the rear differential mechanism. In the present specification, the main transmission device and the auxiliary transmission device, which are generally called, are defined as the main transmission device, and the ultra-low speed switching device is defined as the auxiliary transmission device.

Japanese Patent No. 3583021

  By the way, in the transmission as described above, in a low-speed operation such as rotary tilling that travels at a relatively low speed, a low-speed region in which the sub-transmission device is in a low-speed stage is used. In high-speed work that travels, a high-speed region is used in which the auxiliary transmission is a high-speed stage.

  However, the high speed stage of the auxiliary transmission and the lowest speed stage of the main transmission are higher than the gear ratio (high speed stage in the low speed range) of the speed stage based on the combination of the low speed stage of the auxiliary transmission and the highest speed side of the main transmission. Since the gear ratio of the gear stage (low speed gear in the high speed range) is set to a higher speed range due to the combination on the side, when shifting from low speed work to high speed work, that is, the sub-transmission device is moved from the low speed stage to the high speed. When shifting to a stage, the work vehicle may start suddenly.

  Also, when shifting the auxiliary transmission from the low speed stage to the high speed stage, in the case of a vehicle that temporarily stops the work vehicle or requires a clutch operation, the speed range near the boundary between the low speed operation and the high speed operation is used. During this work, the above-described operation must be repeated, which increases the burden on the operator.

  Accordingly, an object of the present invention is to provide a transmission for a tractor that has a transmission ratio that overlaps between a low speed region and a high speed region, thereby solving the above-described problems.

The present invention according to claim 1 (see, for example, FIGS. 1 to 6), a main transmission (20) comprising a multi-stage shift stage operated by a hydraulic device (80) based on an electrical signal;
A sub-transmission device (60) composed of two high and low gears that are shifted by a mechanical operation.
In the transmission (10) of the tractor (1),
The gear ratio of the gear stage (for example, the tenth, eleventh and twelfth stages) by the combination of the low speed stage of the auxiliary transmission (60) and the highest speed stage of the main transmission (20), and the auxiliary transmission (60 ) And the transmission gear ratio (for example, thirteenth, fourteenth and fifteenth gears) of the combination of the main transmission (20) on the lowest gear side overlap each other.
The transmission (10) of the tractor (1) is characterized by this.

According to a second aspect of the present invention (see, for example, FIGS. 2 to 5), the main transmission (20) has 12 stages.
A transmission (10) of a tractor (1) according to claim 1.

  In addition, although the code | symbol in the said parenthesis is for contrast with drawing, it does not have any influence on description of a claim by this.

  According to the first aspect of the present invention, the speed ratio of the speed change stage by the combination of the low speed stage of the auxiliary transmission and the maximum speed stage side of the main transmission, the high speed stage of the auxiliary transmission, and the minimum speed stage of the main transmission. Since the gear ratio of the gear stage by the combination on the side is overlapped, the gear stage by the combination of the low speed stage of the auxiliary transmission and the highest speed stage side of the main transmission is different from the high speed stage of the auxiliary transmission. The speed range is higher than that of the combination of the main transmission on the lowest speed side, and the speed range of the low speed work area and the high speed work area is increased. As a result, it is possible to reduce the speed change operation of the subtransmission device during work in the speed range near the boundary between the low speed work and the high speed work, and to reduce the burden on the operator.

  Also, when shifting the sub-transmission device from the low-speed stage to the high-speed stage, the sub-transmission that is set lower than the speed set by the combination of the low-speed stage of the sub-transmission apparatus and the highest speed stage side of the main transmission. The work vehicle can be started from a low speed by the speed set by the combination of the high speed of the device and the minimum speed of the main transmission, and the work vehicle can be prevented from starting suddenly. .

  According to the second aspect of the present invention, since the main transmission is composed of 12 shift stages, the number of shift stages by the combination of the main transmission and the sub-transmission is 24, and the low speed work area and the high speed work area are In either case, a speed more suitable for work can be set.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, a tractor 1 as a working vehicle, which is an example of an embodiment of the present invention, is an airframe 5 supported by a pair of front wheels 6 and 6 and rear wheels 4 and 4 arranged on the left and right. The airframe 5 is provided with a bonnet 2 in which an engine 7 (see FIG. 2) is housed inside at a front portion. Further, a mission case 3 fixed to the airframe 5 integrally is disposed at the lower part of the airframe 5.

  The transmission case 3 includes a front main transmission 20A, a hydraulic clutch 30 that intermittently transmits power output from the front main transmission 20A and transmitted to the downstream side, and a downstream side of the hydraulic clutch 30. A transmission having a connected forward / reverse switching device 40, a rear main transmission device 20B connected to the downstream side of the forward / reverse switching device 40, a sub-transmission device 60 disposed downstream of the rear transmission device 20B, and the like. 10 is arranged to constitute a traveling drive system. The front main transmission 20A and the rear main transmission 20B constitute the main transmission 20, which will be described in detail later.

  As shown in FIG. 2, the power from the engine 7 is transmitted through a main clutch 11, an output shaft 12, an output gear 13 fixed to the output shaft 12, and an input gear 15 meshing with the output gear 13. The input gear 15 is transmitted to the fixed input shaft 16. A plurality of gears 16a, 16b, 16c, and 16d having different numbers of teeth are integrally fixed to the input shaft 16.

  In the transmission case 3, there is a PTO main transmission unit 75 disposed adjacent to the input shaft 16, and a PTO rotation switching device 76 for rotating the PTO shaft forward and backward on the downstream side of the PTO main transmission unit 75. It arrange | positions and it is comprised so that motive power can be output to a working machine (not shown) via a PTO axis | shaft.

  The front main transmission 20A of the main transmission 20 includes a transmission shaft 21 that is rotatably supported with respect to the transmission case 3. The transmission shaft 21 includes the gears 16a, 16b, 16c, and 16d. Gears 22a, 22b, 22c, and 22d having different numbers of teeth that are always meshed with each other are rotatably supported. A shift member 23 that can selectively engage and disengage with the gears 22a and 22b by a synchromesh method is provided between the gear 22a and the gear 22b, and a synchronizer between the gear 22c and the gear 22d. Shift members 25 that can be selectively engaged with and disengaged from the gears 22c and 22d by a mesh system are arranged so as to be movable in the axial direction of the transmission shaft 21, respectively.

  The hydraulic clutch 30 is configured by a hydraulic clutch disposed between the front main transmission 20A and the forward / reverse switching device 40, and the output of the front main transmission 20A is supplied to the forward / reverse switching device 40 by supplying hydraulic pressure. When the hydraulic pressure is cut off, the output of the front main transmission 20A is not transmitted to the forward / reverse switching device 40, and the power transmission of the travel drive system is cut off.

  The forward / reverse switching device 40 includes an intermediate shaft 42 and a transmission shaft 45 that are rotatably supported by the transmission case 3 in parallel with the input shaft 41. An intermediate gear 42a that meshes with the gear 41a is integrally fixed to the intermediate shaft 42.

  The input shaft 41 is connected to the transmission shaft 21 via the hydraulic clutch 30 and rotates together with the transmission shaft 21 when the hydraulic clutch 30 is in the engaged state. Gears 41 a and 41 b with different numbers of teeth are integrally fixed to the input shaft 41.

  A gear 45b meshing with the gear 41b and a gear 45a meshing with the gear 42a are rotatably supported on the transmission shaft 45. Between the gear 45b and the gear 45a, a shift member 47 that is selectively engageable and disengageable with the gears 45a and 45b by a synchromesh method is disposed so as to be movable in the axial direction of the transmission shaft 45. Yes.

  The rear main transmission 20B of the main transmission 20 includes the latter half of the transmission shaft 45 described above and a transmission shaft 51 that is rotatably supported by the transmission case 3.

  A gear 26a that meshes with the gear 28a is rotatably supported at the rear half of the transmission shaft 45, and gears 26b and 26c having different numbers of teeth are fixed integrally. Further, a shift member 27 that can be engaged with and disengaged from the gear 26a by a synchromesh method is disposed in the vicinity of the gear 26a so as to be movable in the axial direction of the transmission shaft 45.

  The transmission shaft 51 is integrally fixed with the gear 28a, and a gear 28b meshing with the gear 26b and a gear 28c meshing with the gear 26c are supported rotatably. Between the gear 28b and the gear 28c, a shift member 29 that can be selectively engaged and disengaged with the gears 28b and 28c by a synchromesh method is disposed so as to be movable in the axial direction of the transmission shaft 51. Yes.

  A gear 51 a and a gear 51 b are integrally fixed to the rear half of the transmission shaft 51, and the gear 51 a meshes with the gear 55 a and the gear 51 b meshes with the gear 57, respectively. The transmission shaft 55 is rotatably supported with respect to the transmission case 3 so as to be located on the same axis as the transmission shaft 45. On the transmission shaft 55, a gear integrally formed by the gear 55a and a gear 55b having a smaller diameter than the gear 55a and a gear 57 meshing with the gear 51b are rotatably supported. Further, a gear 56 is integrally fixed to the transmission shaft 55, and a gear 58 in which a small diameter gear and a large diameter gear are integrally formed is disposed.

  The auxiliary transmission 60 includes an output shaft 61 that is rotatably supported by the transmission case in parallel with the transmission shaft 51 and the transmission shaft 55. On the output shaft 61, a gear 61a meshing with the gear 55b and a gear 61b meshing with the gear 57 are rotatably supported. Between the gear 61a and the gear 61b, a shift member 62 that can be selectively engaged with and disengaged from the gears 61a and 61b by a synchromesh method is disposed so as to be movable in the axial direction of the output shaft 61. Yes. A gear 63 that meshes with the gear 58 is integrally fixed to the output shaft 61.

  The output shaft 61 is connected to the rear wheels 4 and 4 through a differential gear 71 and the like, so that the tractor 1 can be driven. The rotation of the gear 58 is transmitted to the gear 56 through the transmission shaft 55, and the rotation of the gear 58 and the gear 56 is transmitted to the quick turn device 72. The rotation output from the quick turn device 72 is transmitted to the front wheels 6 and 6 through the differential gear 73 and the like, so that the tractor 1 can be driven.

  Next, the operation of the tractor 1 will be described.

  For example, the rotation output from the engine 7 is transmitted to the input gear 15 via the main clutch 11, the output shaft 12, the output gear 13 fixed to the output shaft 12, and the input gear 15 meshing with the output gear 13. Is transmitted to the input shaft 16 which is fixed. The rotation transmitted to the input shaft 16 is transmitted to the front main transmission 20A via a plurality of gears 16a, 16b, 16c and 16d having different numbers of teeth.

  In the front main transmission 20A, when the shift member 23 is in the neutral position separated from the gear 22a and the gear 22b, the gears 22a and 22b are idle with respect to the transmission shaft 21, respectively. When the shift member 23 is engaged with the gear 22a (or gear 22b), the shift member 23 rotates together with the engaged gear 22a (or gear 22b) to rotate the transmission shaft 21.

  Further, when the shift member 25 is in the neutral position separated from the gear 22c and the gear 22d, the gears 22c and 22d are idle with respect to the transmission shaft 21, respectively. When the shift member 25 is engaged with the gear 22c (or gear 22d), the shift member 25 rotates together with the engaged gear 22c (or gear 22d) to rotate the transmission shaft 21.

  That is, the front main transmission 20A is synchronized with the gears 16a, 16b, 16c, 16d, the gears 22a, 22b, 22c, 22d that are always meshed with the gears 16a, 16b, 16c, 16d, and the shift members 23, 25. It is composed of mesh type synchronous mesh gear transmission, and gears 16a and gear 22a, gears 16b and gear 22b, gears 16c and gear 22c, gears 16d and gear 22d, and gears of four stages with different transmission ratios. A stage is set.

  Here, for example, when the hydraulic clutch 30 is in the engaged state, the rotation of the transmission shaft 21 is transmitted to the forward / reverse switching device 40 via the input shaft 41.

  In the forward / reverse switching device 40, when the shift member 47 is in the neutral position separated from the gears 45a and 45b, the gears 45a and 45b idle with respect to the transmission shaft 45, respectively. When the shift member 47 is engaged with the gear 45a (or 45b), the shift member 47 rotates together with the engaged gear 45a (or 45b) to rotate the transmission shaft 45.

  At this time, when the rotation of the gear 45a is transmitted to the transmission shaft 45 and when the rotation of the gear 45b is transmitted to the transmission shaft 45, the rotation direction transmitted to the transmission shaft 45 is reversed by the action of the intermediate gear 42a. . That is, if the rotation transmitted to the transmission shaft 45 via the gear 45b is the rotation in the forward direction of the tractor 1, the rotation transmitted to the transmission shaft 45 via the gear 45a is the rotation in the backward direction of the tractor 1. Thus, the forward / backward switching of the tractor 1 can be performed.

  In the rear main transmission 20B to which the rotation is transmitted by the transmission shaft 45, the gear 26a is idle with respect to the transmission shaft 45 when the shift member 27 is in the neutral position where it is detached from the gear 26a. When the shift member 27 is engaged with the gear 26a, the shift member 27 rotates together with the engaged gear 26a to rotate the transmission shaft 51.

  When the shift member 29 is in the neutral position separated from the gears 28 b and 28 c, the gears 28 b and 28 c are idle with respect to the transmission shaft 51. When the shift member 29 is engaged with the gear 28b (or the gear 28c), the shift member 29 rotates together with the engaged gear 28b (or the gear 28c) to rotate the transmission shaft 51.

  That is, the rear main transmission 20B includes a gear 26a, a gear 28a that always meshes with the gear 26a, a shift member 27 and gears 26b and 26c, and gears 28b and 28c that always mesh with these gears 26b and 26c. The member 29 includes a synchromesh type synchronous mesh gear transmission, and the gears 26a and 28a, the gears 26b and 28b, and the gears 26c and 28c are meshed so that three speeds with different transmission ratios are obtained. Is set. Thereby, in the main transmission 20 constituted by the front main transmission 20A and the rear main transmission 20B, twelve shift stages having different transmission ratios are set.

  The gear 51a that is integrally fixed to the transmission shaft 51 is transmitted to the auxiliary transmission 60 through the integrally formed gears 55a and 55b, and similarly, the gear 51b is transmitted through the gear 57, respectively. .

  In the auxiliary transmission 60, when the shift member 62 is in the neutral position separated from the gear 61a and the gear 61b, the gears 61a and 61b idle with respect to the output shaft 61, respectively. When the shift member 62 is engaged with the gear 61a (or gear 61b), the shift member 62 rotates with the engaged gear 61a (or gear 61b) to rotate the output shaft 61.

  That is, the sub-transmission device 60 includes gears 55b and 57, gears 61a and 61b that are always meshed with the gears 55b and 57, and a synchromesh type synchronous mesh gear transmission that includes the shift member 62. Two gear stages having different transmission ratios are set by the meshing of the gear 61a, the gear 57, and the gear 61b.

  Then, the rotation of the output shaft 61 is transmitted to the rear wheels 4 and 4 via the differential gear 71. In the four-wheel drive state, the rotation of the output shaft 61 is transmitted to the front wheels 6 and 6 through the gear 63, the gear 58, the transmission shaft 55, the gear 56, the quick turn device 72, the differential gear 73, and the like. Is done. Thereby, the tractor 1 is driven to travel.

  Next, the hydraulic control device (hydraulic device) 80 related to the main transmission 20 and the hydraulic clutch 30 of the tractor 1 will be described.

  As shown in FIG. 3, the hydraulic oil discharged from the oil pump 81 is used for traveling operation, and controls the main transmission 20 and the hydraulic clutch 30 by hydraulic pressure via a check valve 82. 80.

  The temperature and pressure of the pressure oil flowing into the hydraulic control device 80 are detected by the oil temperature sensor 83 and the hydraulic sensor 84 and fed back to the electrical control device 140, which will be described in detail later. The filters 85 and 87 are disposed between the check valve 82 and the hydraulic sensor 84.

  Part of the pressure oil that has passed through the filter 85 is supplied to the proportional pressure control solenoid valve 86. The proportional pressure control solenoid valve 86 is regulated by an operation based on an electric signal, and the regulated pressure oil is sent to the hydraulic clutch 30 via a filter 91 and a shuttle valve 92, and the front main transmission device. 20A and the forward / reverse switching device 40 are connected.

  The solenoid valve 101 controls the hydraulic actuator 102 for displacing the position of the shift member 27 of the rear main transmission 20B. The shift piston 103 of the hydraulic actuator 102 expands and contracts by the pressure oil supplied from the solenoid valve 101, and the stop position is held by the pin 105. The check valve 107 is released when the shift piston 103 moves and the pin 105 moves from the notch portion of the shift piston 103 to the shaft portion, and reduces the hydraulic pressure supplied to the hydraulic clutch 30 so that the hydraulic clutch 30 Perform the cutting operation.

  The solenoid valve 111 and the solenoid valve 112 control the hydraulic actuator 113 for displacing the position of the shift member 29 of the rear main transmission 20B. The shift piston 115 of the hydraulic actuator 113 expands and contracts by the pressure oil supplied from the solenoid valves 111 and 112, and the stop position is held by the pin 116. The check valve 117 is released when the shift piston 115 moves and the pin 116 moves from the notch portion of the shift piston 115 to the shaft portion, and the hydraulic pressure supplied to the hydraulic clutch 30 is reduced, so that the hydraulic clutch 30 Perform the cutting operation.

  The solenoid valve 121 and the solenoid valve 122 control the hydraulic actuator 123 for displacing the position of the shift member 23 of the front main transmission 20A. The shift piston 125 of the hydraulic actuator 123 expands and contracts by the pressure oil supplied from the solenoid valves 121 and 122, and the stop position is held by the pin 126. The check valve 127 is released when the shift piston 125 moves and the pin 126 moves from the notch portion of the shift piston 125 to the shaft portion, and the hydraulic pressure supplied to the hydraulic clutch 30 is reduced, and Perform the cutting operation.

  The solenoid valve 131 and the solenoid valve 132 control the hydraulic actuator 133 for displacing the position of the shift member 25 of the front main transmission 20A. The shift piston 135 of the hydraulic actuator 133 expands and contracts by the pressure oil supplied from the solenoid valves 131 and 132, and the stop position is held by the pin 136. The check valve 137 is released when the shift piston 135 moves and the pin 136 moves from the notch portion of the shift piston 135 to the shaft portion, and the hydraulic pressure supplied to the hydraulic clutch 30 is reduced, so that the hydraulic clutch 30 Perform the cutting operation.

  Next, the operation of the hydraulic control device 80 will be described.

  When pressure oil is supplied from the solenoid valve 101 to the hydraulic actuator 102 based on the speed change operation from the main speed change operation switch 151, the shift piston 103 extends, and the shift member 27 of the rear main speed change device 20B is connected to the transmission shaft 45. Move along. Accordingly, for example, when the shift piston 103 of the hydraulic actuator 102 is in the extended position, the shift member 27 of the rear main transmission 20B is engaged with the gear 26a, and when the shift piston 103 is in the contracted position, the shift member 27 is moved to the neutral position. Position so that the position.

  Further, when pressure oil is supplied from the solenoid valve 111 to the hydraulic actuator 113 based on the speed change operation from the main speed change operation switch 151, the shift piston 115 extends and pressure oil is supplied from the solenoid valve 112 to the hydraulic actuator 113. Then, the shift piston 115 contracts, and the shift member 29 of the rear main transmission 20B is moved along the transmission shaft 45. Thus, for example, when the shift piston 115 of the hydraulic actuator 113 is in the extended position, the shift member 29 of the rear main transmission 20B is engaged with the gear 28b, and when the shift piston 115 is in the contracted position, the shift member 29 is It meshes with the gear 28c. As shown in FIG. 3, when the shift piston 115 is in the intermediate position, the shift member 29 is positioned at a neutral position that does not mesh with the gears 28b and 28c.

  Further, the shift piston 125 of the hydraulic actuator 123 moves the shift member 23 of the front main transmission 20A by the same action as the shift piston 115 of the hydraulic actuator 113. Further, the shift member 25 of the front main transmission 20A is also moved by the same action with respect to the shift piston 135 of the hydraulic actuator 133.

  As shown in FIG. 4, the control device 140 has a first speed solenoid valve 122, a second speed solenoid valve 121, a third speed solenoid valve 132, a fourth speed solenoid valve 131, a low speed solenoid valve 111, and a medium speed solenoid on the output side. A valve 112, a high-speed solenoid valve 101, and a proportional pressure control solenoid valve 86 are connected. Further, on the input side of the control device 140, there are a main transmission operation switch 151, an engine rotation sensor 152, an axle rotation sensor 153, a hydraulic sensor 84, an oil temperature sensor 83, a forward / reverse sensor 154, a hydraulic clutch sensor 155, and an auxiliary transmission sensor. 156 is connected.

  Then, the control device 140 outputs data from the main transmission operation switch 151, the engine rotation sensor 152, the axle rotation sensor 153, the hydraulic sensor 84, the oil temperature sensor 83, the forward / reverse sensor 154, the hydraulic clutch sensor 155, and the auxiliary transmission sensor 156. 1-speed solenoid valve 122, 2-speed solenoid valve 121, 3-speed solenoid valve 132, 4-speed solenoid valve 131, low speed solenoid valve 111, medium speed solenoid valve 112, high speed solenoid valve 101 and proportional pressure control solenoid. The operation of the valve 86 is controlled. Thereby, the shift operation of the shift member 23 and the shift member 25 of the front main transmission 20A, the shift member 27 and the shift member 29 of the rear main transmission 20B, and the hydraulic clutch 30 are performed, and the shift operation of the main transmission 20 is performed. And the on / off operation of the hydraulic clutch 30 is performed.

  As described above, in the transmission 10 of the tractor 1, as shown in FIG. 5, the combination of the gears of the four stages of the front main transmission 20 </ b> A, the three stages of the rear main transmission 20 </ b> B, and the two stages of the auxiliary transmission 60. A total of 24 shifts can be realized.

  In these charts of FIG. 5, in the front main transmission 20A, the gear 16a and the gear 22a are engaged in the first stage, the gear 16b and the gear 22b are engaged in the second stage, and the gear 16c and the gear 22c. And the gear 16d and gear 22d are in the fourth stage. In the rear main transmission 20B, the gear 26c and the gear 28c are in the first stage, and the gears 26b and 28c. Is in the second stage, and the gear 26a and the gear 28a are in the third stage.

  Further, in the transmission 10, as shown in FIG. 6, the speed corresponding to each stage number is set by the combination of gears shown in FIG. 5, and the tractor 1 can travel at the speed corresponding to each stage number. It is possible.

  Here, in the present embodiment, among the speeds corresponding to the number of stages, the 10th, 11th and 12th stages and the 13th, 14th and 15th stages are set to overlap. As a result, it is possible to travel at a speed that is more suitable for work in the low-speed work using the low speed stage of the sub-transmission device 60, and to start from a lower speed even in the high-speed work that uses the high speed stage of the sub-transmission device 60. It becomes possible. That is, it is possible to increase the speed range of the low speed work area and the high speed work area and reduce the speed change operation of the auxiliary transmission 60.

  As described above, according to the present invention, the transmission 10 of the tractor 1 shifts gears (10th, 11th, and 12th) according to the combination of the low speed stage of the auxiliary transmission 60 and the highest speed stage side of the main transmission 20. The ratio and the gear ratio of the shift speeds (13th, 14th and 15th speeds) based on the combination of the high speed stage of the auxiliary transmission 60 and the lowest speed stage side of the main transmission 20 are overlapped. The combination of the low speed stage and the maximum speed stage side of the main transmission 20 is the higher speed stage than the speed stage of the combination of the high speed stage of the auxiliary transmission 60 and the minimum speed side of the main transmission 20. The speed range of the low speed work area and the high speed work area is increased. As a result, it is possible to reduce the speed change operation of the auxiliary transmission 60 during work in a speed range near the boundary between the low speed work and the high speed work, and to reduce the burden on the operator.

  In addition, when the auxiliary transmission 60 is shifted from the low speed stage to the high speed stage, it is set lower than the speed setting speed of the combination of the low speed stage of the auxiliary transmission 60 and the highest speed stage side of the main transmission 20. The tractor 1 can be started from a low speed by the set speed of the shift stage by the combination of the high speed stage of the auxiliary transmission 60 and the minimum speed stage side of the main transmission 20, and the working vehicle can start suddenly. Can be prevented.

  In addition, since the main transmission 20 is composed of 12 shift stages, the shift stage by the combination of the main transmission 20 and the sub-transmission apparatus 60 is 24, and it is more effective in both the low speed work area and the high speed work area. A speed suitable for the work can be set.

A side view of a tractor. The schematic diagram which shows the transmission system of a tractor. The hydraulic circuit diagram which shows the hydraulic system of the main transmission of a tractor and a hydraulic clutch. The block diagram of a control apparatus. A chart listing the combinations of each tractor gear. The chart which shows the speed by the combination of each gear of a tractor.

Explanation of symbols

1 Tractor 10 Transmission 20 Main Transmission 60 Sub Transmission 80 Hydraulic Device (Hydraulic Control Device)

Claims (2)

A main transmission comprising a multi-stage shift stage operated by a hydraulic device based on an electrical signal;
A sub-transmission device comprising two high and low gears that are shifted by a mechanical operation.
In tractor transmission,
The speed ratio of the shift stage based on the combination of the low speed stage of the auxiliary transmission and the maximum speed stage of the main transmission, and the shift stage of the combination of the high speed stage of the auxiliary transmission and the minimum speed side of the main transmission The gear ratio of
Tractor transmission characterized by that. The main transmission is composed of 12 stages.
The tractor transmission according to claim 1.

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