JP2023005474A - Power transmission device for work vehicle - Google Patents

Abstract

To suppress reduction in efficiency in switching a speed stage.SOLUTION: A power transmission device 8 includes: a planetary gear mechanism 30; a first shaft 38 that is a rotation shaft of a third gear 33 of the planetary gear mechanism; a second shaft 54 configured to transmit rotational force to a traveling device 2; and a third shaft 39 that is interposed between the first shaft and the second shaft. A reverse rotation transmission mechanism 40 is configured to transmit rotational force of the first shaft to the third shaft in order to drive the traveling device in a backward direction. A first forward rotation transmission mechanism 45 and a second forward rotation transmission mechanism 50 are respectively configured to transmit rotational force of the first shaft to the third shaft at a first speed transmission ratio and a second speed transmission ratio in order to drive the traveling device in a forward direction. The first forward rotation transmission mechanism and the second forward rotation transmission mechanism are provided between the reverse transmission mechanism and the planetary gear mechanism in an axial direction. An additional transmission mechanism 55 is configured to speed-change rotational force of the third shaft and transmit it to the second shaft.SELECTED DRAWING: Figure 3

Description

The present invention relates to a power transmission system for work vehicles.

Patent document 1 shows a power transmission device including a planetary gear mechanism driven by a hydraulic motor and a speed change mechanism having three speed stages.

JP 2012-40944 A

In the power transmission device of Patent Literature 1, it is required to suppress reduction in efficiency in switching between speed stages.

A power transmission device according to a first aspect of the present disclosure includes a planetary gear mechanism, a first shaft, a second shaft, a third shaft, a reverse transmission mechanism, a first forward rotation transmission mechanism, and a second forward rotation transmission mechanism. A transmission mechanism and an additional transmission mechanism are provided. The planetary gear mechanism has a sun gear, planetary gears and an internal gear. A first gear of the sun gear, the planetary gears and the internal gear is rotated by the engine. Among the sun gear, the planetary gear, and the internal gear, the second gear other than the first gear is rotated by the hydraulic motor of the hydraulic transmission driven by the engine. The first shaft is the rotation axis of the third gear other than the first gear and the second gear among the sun gear, the planetary gear, and the internal gear. The second shaft is configured to transmit rotational force to the travel gear. The third shaft is interposed between the first shaft and the second shaft. The reversing transmission mechanism is configured to transmit the rotational force of the first shaft to the third shaft in order to drive the traveling device in the reverse direction. The first forward transmission mechanism is provided between the reverse transmission mechanism and the planetary gear mechanism in the axial direction of the first shaft. The first forward rotation transmission mechanism transmits the rotational force of the first shaft to the third shaft at a first speed transmission ratio as a rotational force in a direction opposite to that of the reverse transmission mechanism in order to drive the traveling device in the forward direction. configured to The second forward transmission mechanism is provided axially between the reverse transmission mechanism and the planetary gear mechanism. In order to drive the traveling device in the forward direction, the second forward rotation transmission mechanism converts the rotational force of the first shaft into a rotational force in a direction opposite to that of the reverse transmission mechanism to a second speed transmission ratio that is smaller than the first speed transmission ratio. to the third shaft. The additional transmission mechanism is configured to change the speed of the rotational force of the third shaft and transmit it to the second shaft.

The configuration disclosed in the present application can reduce a decrease in efficiency in switching between speed stages during forward travel by providing the first forward rotation transmission mechanism and the second forward rotation transmission mechanism.

FIG. 1 is a side view showing the entire tractor. FIG. 2 is a plan view showing the entire tractor. FIG. 3 is a skeleton diagram showing a power transmission device. FIG. 4 is a cross-sectional front view showing the branch transmission mechanism. FIG. 5 is a cross-sectional side view showing the planetary gear mechanism, the reverse transmission mechanism, the first forward transmission mechanism, and the second forward transmission mechanism. FIG. 6 is a sectional front view showing a planetary gear mechanism. FIG. 7 is a cross-sectional front view showing a reversing transmission mechanism. FIG. 8 is a block diagram showing a shift operation device. FIG. 9 is a vehicle speed-efficiency diagram of the power transmission device according to the embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be specifically described with reference to the drawings showing its embodiments. In addition, the same reference numerals in the drawings indicate corresponding or substantially the same configurations.
<Embodiment>
<Overall composition>

FIG. 1 is a side view showing the entire tractor 1 according to an embodiment of the invention. FIG. 2 is a plan view showing the entire tractor 1 according to the embodiment of the invention. The tractor 1 is an example of a working vehicle. Referring to FIGS. 1 and 2, a tractor 1 according to an example of a work vehicle includes a pair of left and right front wheels 2a that can be steered and driven, a pair of left and right rear wheels 2b that can be driven, and an engine 3a provided at the front of the vehicle body. An engine compartment 3 to be accommodated, a driver's compartment 4 having a seat 4a provided at the rear of the vehicle body, and a vehicle body frame 5 supporting the engine compartment 3 and the driver's seat 4 are provided. Further, the tractor 1 includes a link mechanism 6 having a pair of left and right lift arms 6a arranged on both lateral sides of the rear end of the body frame 5 and capable of swinging up and down. A PTO shaft 7 protruding rearward of the vehicle body is provided. The front wheels 2a and the rear wheels 2b are collectively referred to as a travel device 2. As shown in FIG. In FIG. 2, the traveling device 2 is implemented by wheels, but all or part of the traveling device 2 may be implemented by crawlers.

The tractor 1 has a rotary tillage device (not shown) connected via a link mechanism 6 to the rear portion of the vehicle body so as to be vertically operable, and is configured to transmit the output of the engine 3a from the PTO shaft 7 to the rotary tillage device. Thus, a riding type cultivator can be constructed. In addition, the tractor 1 can constitute various riding-type working machines by connecting various working devices to the rear part of the vehicle body so as to be capable of being lifted and driven.

The vehicle body frame 5 includes a clutch housing 10 connected to the rear portion of the engine 3a, a continuously variable transmission case 20a having a front portion detachably connected to the rear portion of the clutch housing 10, and a rear portion of the continuously variable transmission case 20a. and a front wheel support frame 12 connected to the lower part of the engine 3a. The transmission case 11 includes a front transmission case 11a whose front part is detachably connected to the rear part of the continuously variable transmission case 20a, and a rear transmission case whose front part is detachably connected to the rear part of the front transmission case 11a. 11b. The vehicle body frame 5 includes a front wheel drive case 13 attached to a front wheel support frame 12, and supports a pair of left and right front wheels 2a through the front wheel drive case 13 so as to be drivable. The vehicle body frame 5 includes a pair of left and right rear wheel drive cases 14 arranged side by side on both sides of the rear transmission case 11b. 2b is drivably supported.

In the embodiment according to the present application, the front-rear direction (forward direction/rearward direction) of the tractor 1 means the front-rear direction (forward direction/rearward direction) as seen from the operator seated on the seat 4 a of the driver's seat 4 . The left direction, the right direction, and the width direction of the tractor 1 mean the left direction, the right direction, and the left and right direction, respectively, when viewed from the operator. The upward direction, the downward direction, and the height direction of the tractor 1 mean the upward direction, the downward direction, and the height direction as viewed from the operator. The front/rear/left/right (width)/up/down (height) directions of the tractor 1 correspond to the front/rear/left/right (width)/up/down (height) directions viewed from the operator.

FIG. 3 is a skeleton diagram showing the power transmission device 8 configured to transmit the driving force output by the engine 3a to the front wheels 2a and the rear wheels 2b. In FIG. 3, illustration of a power transmission system for transmitting the driving force output by the engine 3a to the PTO shaft 7 is omitted. As shown in FIG. 3, the power transmission device 8 transmits the driving force output from the engine 3a from the output shaft 3b to the hydraulic transmission mechanism 20 and the planetary gear mechanism 30 via the main clutch mechanism 15 and the branch transmission mechanism 16. configured as The power transmission device 8 transmits the driving force output from the first shaft 38 that outputs the rotational force of the planetary gear mechanism 30 to the reverse transmission mechanism 40 , the first forward rotation transmission mechanism 45 , and the second forward rotation transmission mechanism 50 . to the additional transmission mechanism 55 via one of the The power transmission device 8 further transmits power from the second shaft 54, which is the output shaft of the additional transmission mechanism 55, to the rear wheel differential mechanism 25, and from the second shaft 54 to the gear transmission mechanism 61, the front wheel transmission mechanism 70, and the rotary shaft. 27 to the front wheel differential mechanism 26 . That is, the second shaft 54 is configured to transmit rotational force to the travel device 2 . As described above, the power transmission device 8 includes the planetary gear mechanism 30, the first shaft 38, the second shaft 54, the reversing transmission mechanism 40, the first forward transmission mechanism 45, the second forward transmission mechanism 50, and the additional transmission mechanism. 55.

The hydraulic transmission mechanism 20 is housed in a continuously variable transmission case 20a connected to the front portion of the front transmission case 11a. The planetary gear mechanism 30, the reverse transmission mechanism 40, the first forward rotation transmission mechanism 45, and the second forward rotation transmission mechanism 50 are arranged in the front transmission case 11a. The additional transmission mechanism 55, the rear wheel differential mechanism 25 and the gear transmission mechanism 61 are arranged in the rear transmission case 11b. The branch transmission mechanism 16 is provided in the front portion of the continuously variable transmission case 20a. Each mechanism will be described in detail below.

As shown in FIGS. 3 and 4, the branch transmission mechanism 16 includes one engine-side gear 17 and a pair of transmission gears 18 and 19 rotatably provided inside a transmission mechanism case 16a connected to a continuously variable transmission case 20a. Prepare. The engine-side gear 17 is provided at the end of the output shaft 15a of the main clutch mechanism 15 so as to rotate integrally therewith. The engine-side gear 17 is rotatably supported around the output shaft 15a as a rotation axis. When the main clutch mechanism 15 is in the engaged state, the engine-side gear 17 is interlocked with the engine 3a side, and is rotationally driven by the driving force output from the output shaft 3b of the engine 3a. When the main clutch mechanism 15 is in the disengaged state, the engine-side gear 17 is not rotated by the engine 3a.

The pair of transmission gears 18 and 19 are arranged such that the rotation shafts 18a and 19a of the pair of transmission gears 18 and 19 are positioned at an arrangement height equal to or lower than the arrangement height of the rotation shaft 17a of the engine side gear 17, and are meshed with the engine side gear 17. positioned to match. The rotary shaft 18a of one transmission gear 18 is positioned at a lower height than the rotary shaft 19a of the other transmission gear 19. As shown in FIG. One of the transmission gears 18 is rotatably connected to the front end of a shaft 23 as an input shaft extending longitudinally of the vehicle body provided in a pump 21 that constitutes a hydraulic transmission mechanism 20 . The other transmission gear 18 is integrally rotatably connected to the extending end of an engine output introduction shaft 24 extending forward from the planetary gear mechanism 30 through the continuously variable transmission case 20a.

The branch transmission mechanism 16 is arranged on the front side of the vehicle body with respect to the hydraulic pump 21 and the hydraulic motor 22 that constitute the hydraulic transmission mechanism 20 . The hydraulic transmission mechanism 20 is a hydrostatic continuously variable transmission mechanism. The branch transmission mechanism 16 transmits the driving force output from the output shaft 3b by the engine 3a to the front side of the vehicle body with respect to the hydraulic transmission mechanism 20 by means of an engine-side gear 17 and a pair of transmission gears 18 and 19 on the hydraulic transmission mechanism 20 side and planetary gears. It is configured to branch to the gear mechanism 30 side. The branch transmission mechanism 16 transmits the driving force branched to the hydraulic transmission mechanism 20 side to the hydraulic transmission mechanism 20 through the pump shaft 23, and transmits the driving force branched to the planetary gear mechanism 30 side to the engine output introduction shaft. 24 to the planetary gear mechanism 30 .

The hydraulic transmission mechanism 20 is arranged in a continuously variable transmission case 20a provided in the front portion of the front transmission case 11a, and inside the continuously variable transmission case 20a so as to be positioned on the front side of the vehicle body with respect to the planetary gear mechanism 30. A hydraulic pump 21 and a hydraulic motor 22 are provided. The hydraulic pump 21 is a variable displacement type axial plunger type hydraulic pump. The hydraulic motor 22 is an axial plunger type hydraulic motor. The hydraulic transmission mechanism 20 can change the gear ratio by changing the angle of the swash plate of the hydraulic pump 21 . The hydraulic pump 21 is driven by the rotation of the engine 3a and outputs pressurized oil to the hydraulic motor 22 through an oil passage (not shown). Hydraulic motor 22 is thus driven by hydraulic pump 21 to rotate motor output shaft 28 .

5 is a cross-sectional view showing the planetary gear mechanism 30, the reverse transmission mechanism 40, the first forward transmission mechanism 45, and the second forward transmission mechanism 50. FIG. 6 is a cross-sectional side view showing the planetary gear mechanism 30. FIG. 5 and 6, the planetary gear mechanism 30 has a sun gear 31, a plurality of planetary gears 32, and an internal gear 33. As shown in FIG. The sun gear 31 is rotatably supported by the first support portion 30a of the front transmission case 11a via a bearing B1. The plurality of planetary gears 32 are distributed around the sun gear 31 at equal intervals. The internal gear 33 is configured to mesh with the three planetary gears 32 . Planetary gear mechanism 30 further comprises a carrier 35 and a first shaft 38 . A carrier 35 rotatably supports each planetary gear 32 via a support shaft 34 .

The carrier 35 is rotatably supported by the first boss portion 31a of the sun gear 31 via a pair of bearings B2. A support shaft 34 of each planetary gear 32 is connected to a carrier 35 . The planetary gear mechanism 30 further has a single annular support plate 36 . The support plate 36 connects the three support shafts 34 on the side of the planetary gear 32 opposite to the side where the carrier 35 is located. As shown in FIG. 6 , the support plate 36 prevents tilting of each support shaft 34 with respect to the carrier 35 and prevents the planetary gears 32 from tilting with respect to the sun gear 31 and the internal gear 33 . And the meshing state of the planetary gear 32 with the sun gear 31 is maintained in a normal state.

The sun gear 31 is integrated with the motor output shaft 28, which is the output shaft of the hydraulic transmission mechanism 20, by fitting the splines provided on the first boss portion 31a of the sun gear 31 and the motor output shaft 28, respectively. connected to rotate as

The engine output introduction shaft 24 is connected to an input gear 37 rotatably supported by the first support portion 30a of the front transmission case 11a via a bearing B5. The input gear 37 has a through hole through which the engine output introduction shaft 24 is passed. The engine output introduction shaft 24 and the input gear 49 are rotatably coupled together by spline fitting. The carrier 35 is formed with teeth configured to mesh with the input gear 49 on its outer periphery.

The boss portion 33a of the internal gear 33 is rotatably supported by the second support portion 30b of the front transmission case 11a via a bearing B3, and is rotatably supported by the second boss portion 31b of the sun gear 31 via a bearing B4. supported by A spline that meshes with a spline formed on the outer periphery of the first shaft 38 is formed on the inner periphery of the boss portion 33 a of the internal gear 33 . The engagement of these splines couples the internal gear 33 to rotate integrally with the first shaft 38 . The first shaft 38 is rotatably supported by the second support portion 30b of the front transmission case 11a via a bearing B6, and is rotatably supported by the third support portion 30c of the front transmission case 11a via a bearing B7. be done. The first shaft 38 has a central axis Ax1 and is rotatable around the central axis Ax1. Here, the direction along the central axis Ax1 is called the axial direction Dx.

The planetary gear mechanism 30 has the above configuration. As a result, the driving force output from the engine 3a from the output shaft 3b is input to the input gear 37 via the engine-side gear 17, the transmission gear 19, and the engine output introduction shaft 24, whereby the driving force from the engine 3a Force is input to the carrier 35 without being subjected to the shifting action of the hydraulic transmission mechanism 20 . Further, the driving force output from the motor output shaft 28 by the hydraulic transmission mechanism 20 is input to the sun gear 31 . Then, the driving force from the hydraulic transmission mechanism 20 and the driving force from the engine 3a not affected by the transmission action of the hydraulic transmission mechanism 20 are synthesized, and the synthesized driving force is the reverse transmission mechanism 40 and the first forward rotation transmission mechanism. 45 and the first shaft 38 connected to the second forward rotation transmission mechanism 50 .

Therefore, the power transmission device 8 transfers the driving force output from the output shaft 3b of the engine 3a to the hydraulic transmission mechanism 20 side and the planetary gear through the branch transmission mechanism 16 at a location located on the front side of the vehicle body with respect to the hydraulic transmission mechanism 20. It branches off to the side of the mechanism 30 . The power transmission device 8 inputs the driving force branched to the hydraulic speed change mechanism 20 side to the hydraulic pump 21 of the hydraulic speed change mechanism 20 through the shaft 23 to drive the hydraulic pump 21 and the hydraulic motor 22 of the hydraulic speed change mechanism 20 . The motor output shaft is steplessly speed-changed regardless of whether the driving force is converted into the driving force in the forward rotation direction or the driving force in the reverse rotation direction by the speed change action. Output from 28. The power transmission device 8 inputs the driving force output from the motor output shaft 28 by the hydraulic transmission mechanism 20 to the sun gear 31 of the planetary gear mechanism 30, and branches the driving force to the planetary gear mechanism 30 side by the branch transmission mechanism 16. is input to the carrier 35 of the planetary gear mechanism 30 through the engine output introduction shaft 24 and the input gear 37, the driving force from the engine 3a and the driving force from the hydraulic transmission mechanism 20 are combined in the planetary gear mechanism 30, The combined driving force is output from the first shaft 38 to the reverse transmission mechanism 40 , the first forward rotation transmission mechanism 45 , and the second forward rotation transmission mechanism 50 .

Here, the planetary gear 32 rotated by the carrier 35 is called the first gear. The sun gear 31 rotated by the hydraulic motor 22 is called the second gear. The internal gear 33 rotating integrally with the first shaft 38 is called a third gear. At this time, it can be said that the first gear (planetary gear 32) of the sun gear 31, the planetary gear 32, and the internal gear 33 is rotated by the engine 3a. Among the sun gear 31, the planetary gear 32, and the internal gear 33, the second gear (sun gear 31) other than the first gear (planetary gear 32) is driven by the hydraulic motor 22 of the hydraulic transmission mechanism 20 driven by the engine 3a. It can be said that it is rotated. It can be said that the first shaft 38 is the rotating shaft of the third gear other than the first gear and the second gear among the sun gear 31 , the planetary gear 32 and the internal gear 33 .

Referring to FIG. 3 , the reverse transmission mechanism 40 includes a transmission gear 41 , a reverse gear 42 , a reverse output gear 43 and a reverse clutch 44 . The reversing transmission mechanism 40 is configured to transmit the rotational force of the first shaft 38 to the third shaft 39 in order to drive the traveling device 2 in the backward direction. The power transmission device 8 has a third shaft 39 . The third shaft 39 is interposed between the first shaft 38 and the second shaft 54 . The third shaft 39 is rotatably supported by the second support portion 30b of the front transmission case 11a via a bearing B8, and is rotatably supported by the third support portion 30c of the front transmission case 11a via a bearing B9. be done. The third shaft 39 has a central axis Ax3 and is rotatable around the central axis Ax3. Central axis Ax3 is substantially parallel to central axis Ax1. Therefore, the third shaft 39 extends in the axial direction Dx. The reverse clutch 44 is configured to connect and disconnect the first shaft 38 and the third shaft 39 via the reversing transmission mechanism 40 . A reverse clutch 44 is provided on the first shaft 38 . As shown in FIG. 7 , the transmission gear 41 is engaged with the reverse gear 42 , and the reverse gear 42 is meshed with the reverse output gear 43 . The transmission gear 41 does not mesh with the reverse output gear 43 . 7, illustration of a part of the configuration other than the transmission gear 41, the reverse gear 42, and the reverse output gear 43 in the power transmission device 8 is omitted.

When the reverse clutch 44 is switched to the engaged state, the driving force of the first shaft 38 is transmitted to the transmission gear 41, the reverse gear 42, the reverse output gear 43, and the third shaft 39 in this order. At this time, the third shaft 39 rotates to drive the front wheels 2a and the rear wheels 2b in the backward direction. Since the transmission gear 41 is rotatably supported by the first shaft 38 via the bearing B10, the transmission gear 41 is independent of the first shaft 38 when the reverse clutch 44 is switched to the disengagement state. to rotate. The reverse output gear 43 is formed integrally with the third shaft 39 . The transmission gear 41 is engaged with a reverse output gear 43 via a reverse gear 42 . Therefore, the transmission gear 41 , the reverse gear 42 , and the reverse output gear 43 rotate together with the third shaft 39 .

The first forward rotation transmission mechanism 45 includes a first transmission gear 46 , a first forward output gear 47 and a first forward clutch 48 . The first forward transmission mechanism 45 is provided between the reverse transmission mechanism 40 and the planetary gear mechanism 30 in the axial direction Dx of the first shaft 38 . In order to drive the traveling device 2 in the forward direction, the first forward transmission mechanism 45 converts the rotational force of the first shaft 38 into rotational force in the direction opposite to that of the reverse transmission mechanism 40, and rotates the third shaft at the first speed transmission ratio. 39. The first forward clutch 48 is configured to connect and disconnect the first shaft 38 and the third shaft 39 via the first forward rotation transmission mechanism 45 . A first forward clutch 48 is provided on the first shaft 38 .

When the first forward clutch 48 is switched to the engaged state, the driving force of the first shaft 38 is transmitted to the first transmission gear 46, the first forward output gear 47 and the third shaft 39 in this order. The third shaft 39 rotates to drive the front wheels 2a and the rear wheels 2b forward. The above-mentioned first speed transmission ratio is a value obtained by dividing the number of teeth of the first forward output gear 47 by the number of teeth of the first transmission gear 46 . The first transmission gear 46 is rotatably supported by the first shaft 38 via the needle bearing NB1. and rotate independently. The first forward output gear 47 is formed integrally with the third shaft 39 , is provided on the third shaft 39 , and is configured to rotate together with the third shaft 39 . A first transmission gear 46 is provided on the first shaft 38 and is engaged with a first forward output gear 47 . Therefore, the first transmission gear 46 and the first forward output gear 47 rotate together with the third shaft 39 .

The second forward rotation transmission mechanism 50 includes a second transmission gear 52 , a second forward output gear 51 and a second forward clutch 53 . The second forward transmission mechanism 50 is provided between the reverse transmission mechanism 40 and the planetary gear mechanism 30 in the axial direction Dx. More specifically, the second forward rotation transmission mechanism 50 is provided between the planetary gear mechanism 30 and the first forward rotation transmission mechanism 45 in the axial direction Dx. In order to drive the traveling device 2 in the forward direction, the second forward transmission mechanism 50 converts the rotational force of the first shaft 38 into a rotational force in the direction opposite to that of the reversal transmission mechanism 40 to a first speed transmission ratio smaller than the first speed transmission ratio. It is configured to transmit to the third shaft 39 at a two-speed transmission ratio. The second forward clutch 53 is configured to connect and disconnect the first shaft 38 and the third shaft 39 via the second forward rotation transmission mechanism 50 . A second forward clutch 53 is provided on the third shaft 39 . That is, the first forward clutch 48 and the second forward clutch 53 are provided on different shafts of the first shaft 38 and the third shaft 39 . When the second forward clutch 53 is switched to the engaged state, the driving force of the first shaft 38 is transmitted to the second transmission gear 52, the second forward output gear 51 and the third shaft 39 in this order. The third shaft 39 rotates to drive the front wheels 2a and the rear wheels 2b forward.

The second speed transmission ratio mentioned above is a value obtained by dividing the number of teeth of the second forward output gear 51 by the number of teeth of the second transmission gear 52 . Specifically, (1) the number of teeth of the first transmission gear 46 is smaller than the number of teeth of the second transmission gear 52, and (2) the second transmission ratio is smaller than the first transmission ratio. ) because the number of teeth of the first forward output gear 47 is greater than the number of teeth of the second forward output gear 51; However, either (1) or (2) may not be realized. Since the second forward output gear 51 is rotatably supported by the third shaft 39 via the needle bearing NB2, when the second forward clutch 53 is switched to the disengaged state, the second forward output gear 51 is shifted to the third It rotates independently of shaft 39 . Since the second transmission gear 52 is spline-fitted with the first shaft 38 , the second transmission gear 52 is provided on the first shaft 38 and configured to rotate together with the first shaft 38 . A second transmission gear 52 is provided on the third shaft 39 and engages with the second forward output gear 51 . Therefore, the second transmission gear 52 and the second forward output gear 51 rotate together with the first shaft 38 .

The reverse clutch 44, the first forward clutch 48, and the second forward clutch 53 include a cylinder, a piston, a rotation transmission source clutch disk, a rotation transmission destination clutch disk, and a rotation transmission source clutch disk and a rotation transmission destination clutch disk. A hydraulic clutch of known construction with springs urging the pistons apart. Therefore, detailed description of these clutches is omitted. In the second forward clutch 53, an oil passage 53c for hydraulically pressing a piston 53p pressed by a spring 53s from the opposite side is connected between the housing of the second forward clutch 53 and the second support portion of the front transmission case 11a. 30 b and is not provided in the third shaft 39 .

Switching between the on state and the disengagement state of each of the reverse clutch 44, the first forward clutch 48, and the second forward clutch 53 is input by a shift lever or switch on the driver's seat 4, and an electronic circuit (not shown) is operated. , the reverse clutch 44 corresponding to the operation of the shift lever or the switch, the first forward clutch 48, and the second forward clutch 53. Control. The electronic circuit controls so that two or more of the reverse clutch 44, the first forward clutch 48, and the second forward clutch 53 are not engaged at the same time. That is, the electronic circuit either engages one of the reverse clutch 44, the first forward clutch 48, and the second forward clutch 53, and disengages the remaining clutches. 44, the first forward clutch 48, and the second forward clutch 53 are all disengaged.

The additional transmission mechanism 55 is configured to change the speed of the rotational force of the third shaft 39 and transmit it to the second shaft 54 . As shown in FIG. 3, the additional transmission mechanism 55 includes a fourth shaft 39a that is rotatably connected to the third shaft 39 via a joint JT, and a first gear that is rotatably provided on the fourth shaft 39a. 57 and a second gear 59; It comprises a high-speed gear 58 which is relatively rotatable, and a transmission tube shaft 60 which is rotatably mounted on the second shaft 54 . The first gear 57 and the second gear 59 are rotatable together with the third shaft 39 . The second shaft 54 has a spline 54s for engaging with the transmission cylinder shaft 60 . The inner surface of the transmission cylinder shaft 60 has a spline inner wall that fits with the spline 54s. In addition, the fourth shaft 39 a may be formed integrally with the third shaft 39 . The transmission cylinder shaft 60 has a first engaging portion that can be engaged with the high-speed gear 58 except for the inner surface, and a second engaging portion that can be engaged with the low-speed gear 56 except for the inner surface.

In the additional transmission mechanism 55, when the transmission cylinder shaft 60 is moved in the axial direction of the fourth shaft 39a by a shift fork (not shown) and the transmission cylinder shaft 60 is engaged with the boss portion of the low speed gear 56, the reverse transmission mechanism 40, The driving force transmitted from either the first forward rotation transmission mechanism 45 or the second forward rotation transmission mechanism 50 is transmitted to the second shaft 54 via the first gear 57, the low speed gear 56, and the transmission cylinder shaft 60. be done. In this case, even if the driving force is transmitted from any one of the reverse transmission mechanism 40, the first forward transmission mechanism 45, and the second forward rotation transmission mechanism 50, the low speed state occurs. In the additional transmission mechanism 55, when the transmission cylinder shaft 60 is moved in the axial direction of the fourth shaft 39a by a shift fork (not shown) and the transmission cylinder shaft 60 is engaged with the high-speed gear 58, the reverse transmission mechanism 40 and the first forward gear 58 are engaged. The driving force transmitted from either the forward rotation transmission mechanism 45 or the second forward rotation transmission mechanism 50 is transmitted to the second shaft 54 via the second gear 59 , the high speed gear 58 and the transmission tube shaft 60 . In this case, regardless of which of the reverse transmission mechanism 40, the first forward transmission mechanism 45, and the second forward rotation transmission mechanism 50, the driving force is transmitted, the high speed state is established.

FIG. 8 is a block diagram showing a shift operation device 80 that shifts the power transmission device 8. As shown in FIG. As shown in FIG. 8, a shift operation device 80 for shifting the power transmission device 8 includes a shift operation portion 29, which is a cylinder for changing the direction of the swash plate of the hydraulic pump 21 of the hydraulic transmission mechanism 20, and a first forward clutch. 48, a control device 81 linked to the second forward clutch 53 and the reverse clutch 44, a shift lever 82, a shift detection sensor 83 that detects the operating position of the shift lever 82, and an engine rotation sensor 84 that detects the output speed of the engine 3a. , the forward/reverse lever 85, the forward/reverse detection sensor 86 for detecting the operating position of the forward/reverse lever 85, and the transmission cylinder shaft 60, with which of the boss portion of the low-speed gear 56 or the boss portion of the high-speed gear 58 to engage. A switching lever 87 for selection and a switching detection sensor 88 for detecting the operating position of the switching lever 87 are provided. As shown in FIG. 2, the shift lever 82 is provided on a lever support 91 connected to the front of an armrest 90 installed on the lateral side of the seat 4a of the driver's seat 4 so as to be capable of swinging back and forth. .

The shift detection sensor 83 is composed of a rotary potentiometer whose rotary operation part is interlocked with the shift lever 82 . The forward/reverse detection sensor 86 is composed of a rotary potentiometer in which the forward/reverse lever 85 is interlocked with a rotary operation portion. The control device 81 is composed of a microcomputer, and includes a travel speed change control circuit 89A and a forward/reverse control circuit 89B. The switching detection sensor 88 is composed of a rotary potentiometer in which a rotary operation part is interlocked with the switching lever 87 .

The traveling shift control circuit 89A detects the output speed of the engine 3a in a state where the accelerator is set based on the information detected by the engine rotation sensor 84, and operates the shift lever based on the information detected by the shift detection sensor 83. 82 is determined, and based on the detected output speed of the engine 3a and the determined operating position of the shift lever 82, hydraulic shifting is performed so that the vehicle speed corresponding to the operating position of the shift lever 82 appears. The mechanism 20 is gear-shift-controlled via the gear-shift operation unit 29 . Further, the travel speed change control circuit 89A can change whether the transmission tube shaft 60 is engaged with the boss portion of the low speed gear 56 or the boss portion of the high speed gear 58 based on the information detected by the switching detection sensor 88. is. Specifically, when the low-speed gear 56 is engaged, the speed range realized by the power transmission device 8 is mainly intended for work traveling, so the switching lever 87 is set in the direction to set it. manipulated. When the high-speed gear 58 is engaged, the speed range realized by the power transmission device 8 is mainly intended for traveling on farm roads, so the switching lever 87 is operated in the direction to set it.

The forward/reverse control circuit 89B determines the operation position of the forward/reverse lever 85 based on the information detected by the forward/reverse detection sensor 86, and determines the operation position of the forward/reverse lever 85 based on the result of this determination. The reverse transmission mechanism 40, the first forward rotation transmission mechanism 45, and the second forward rotation transmission mechanism 50 are switched and controlled so as to be in the operating state.
<Functions and effects of the embodiment>

FIG. 9 is a vehicle speed-efficiency diagram of the power transmission device 8 according to the embodiment. In FIG. 9, "work Lo" is the vehicle speed-efficiency line when the drive force is output to the third shaft 39 by the first forward rotation transmission mechanism 45 when the switching lever 87 is switched to the work travel mode. Represents correspondence. "Work Lo" represents the correspondence relationship between the vehicle speed and the efficiency line when the drive force is output to the third shaft 39 by the first forward rotation transmission mechanism 45 when the switching lever 87 is switched to the work travel mode. . “Work Hi” represents the vehicle speed-efficiency relationship when the driving force is output to the third shaft 39 by the second forward rotation transmission mechanism 50 when the switching lever 87 is switched to the work travel mode. “Travel Lo” represents the vehicle speed-efficiency relationship when the drive force is output to the third shaft 39 by the first forward rotation transmission mechanism 45 when the switching lever 87 is switched to the farm road travel. “Traveling Hi” represents the relationship between vehicle speed and efficiency when the driving force is output to the third shaft 39 by the second forward rotation transmission mechanism 50 when the switching lever 87 is switched to the farm road travelling.

FIG. 9 also shows the vehicle speed-efficiency line of the power transmission device according to JP-A-2012-040944. In the power transmission device according to Japanese Unexamined Patent Application Publication No. 2012-040944, in the auxiliary transmission mechanism corresponding to the additional transmission mechanism 55 of the embodiment, the transmission cylinder shaft is engaged with one of three stages of high speed gear, medium speed gear and low speed gear. configured to fit together. “Conventional Lo” in FIG. 9 represents the vehicle speed-efficiency correspondence relationship when the transmission cylinder shaft in the power transmission device according to Japanese Patent Application Laid-Open No. 2012-040944 is engaged with the low-speed gear. “Conventional Mid” in FIG. 9 represents the vehicle speed-efficiency correspondence relationship when the transmission cylinder shaft in the power transmission device according to Japanese Patent Application Laid-Open No. 2012-040944 is engaged with the medium speed gear. "Conventional Hi" in FIG. 9 represents the vehicle speed-efficiency correspondence relationship when the transmission cylinder shaft in the power transmission device according to Japanese Patent Application Laid-Open No. 2012-040944 is engaged with the high-speed gear.

Referring to FIG. 9, in the conventional power transmission device, efficiency decreases when switching between low speed gear and medium speed gear, and when switching between medium speed gear and high speed gear. 8 is capable of shifting in four stages, so that the reduction in efficiency at the time of switching can be suppressed more than before. More specifically, when the transmission tube shaft 60 is engaged with the low-speed gear 56, the efficiency when switching from the first forward rotation transmission mechanism 45 to the second forward rotation transmission mechanism 50 and the second forward rotation transmission mechanism The difference from the maximum efficiency when the rotational force of the first shaft 38 is transmitted to the third shaft 39 by means of 50 is suppressed compared to the conventional case. When the transmission cylinder shaft 60 is engaged with the high-speed gear 58, the efficiency when switching from the first forward rotation transmission mechanism 45 to the second forward rotation transmission mechanism 50, The difference from the maximum efficiency when the rotational force of is transmitted to the third shaft 39 is suppressed as compared with the conventional art.

Furthermore, it is necessary to stop the tractor 1 before switching gears by the additional transmission mechanism 55 using the switching lever 87 . Work travel includes rotary plowing, plowing, and fertilizing work. With the conventional power transmission device, the tractor 1 is stopped at the start of work, and in the case of rotary plowing (or plowing), the tractor 1 is set to a low gear, For fertilizing (or plowing) it should be set to medium gear. When driving on farm roads, it is necessary to set the gear to high speed. Furthermore, in the case of plowing, there is a loss of efficiency in either low or medium gear. In the power transmission device 8 according to the present embodiment, the tractor 1 is stopped at the start of work and the transmission tube shaft 60 is rotated at a low speed in any of the rotary plowing, plowing, and fertilizing work. The switching lever 87 may be set for work travel in which the gear 56 is engaged. Such an operation is easier for the user to understand than the conventional one, and facilitates the operation.

As used herein, "comprising" and its derivatives are open-ended terms describing the presence of elements and do not exclude the presence of other elements not listed. This also applies to the words "having", "including" and their derivatives.

The terms "member", "part", "element", "body" and "structure" can have multiple meanings such as single part and multiple parts.

Ordinal numbers such as "first" and "second" are merely terms to identify configurations and have no other meaning (eg, a particular order, etc.). For example, the presence of a "first element" does not imply the existence of a "second element", nor does the presence of a "second element" imply the existence of a "first element". does not imply that

Words such as "substantially," "about," and "approximately," expressing degrees, can mean a reasonable amount of deviation such that the end result does not change significantly, unless the embodiment specifically states otherwise. . All numerical values set forth in this application may be interpreted to include words such as "substantially," "about," and "approximately."

In this application, the phrase "at least one of A and B" should be interpreted to include only A, only B, and both A and B.

Obviously, many variations and modifications of the present invention are possible in view of the above disclosure. Accordingly, the present invention may be practiced otherwise than as specifically disclosed herein without departing from the spirit of the invention.

Claims (12)

a sun gear, a planetary gear, and an internal gear, wherein a first gear among the sun gear, the planetary gear, and the internal gear is rotated by an engine, and the sun gear, the planetary gear, and the a planetary gear mechanism in which a second gear other than the first gear among internal gears is rotated by a hydraulic motor of a hydraulic transmission mechanism driven by the engine;
a first shaft that is a rotation axis of a third gear other than the first gear and the second gear among the sun gear, the planetary gear, and the internal gear;
a second shaft configured to transmit rotational force to the travel device;
a third shaft interposed between the first shaft and the second shaft;
a reverse transmission mechanism configured to transmit the rotational force of the first shaft to the third shaft in order to drive the traveling device in the backward direction;
provided between the reversing transmission mechanism and the planetary gear mechanism in the axial direction of the first shaft, and for driving the traveling device in the forward direction, the rotational force of the first shaft is transferred to the reversing transmission mechanism; a first forward rotation transmission mechanism configured to transmit a rotational force in the opposite direction to the third shaft at a first speed transmission ratio;
provided between the reversing transmission mechanism and the planetary gear mechanism in the axial direction, and for driving the traveling device in the forward direction, rotating the first shaft in a direction opposite to that of the reversing transmission mechanism; a second forward rotation transmission mechanism configured to transmit rotational force to the third shaft at a second speed transmission ratio that is smaller than the first speed transmission ratio;
an additional speed change mechanism configured to change the speed of the rotational force of the third shaft and transmit it to the second shaft;
comprising
Work vehicle power transmission.
The second forward transmission mechanism is provided between the planetary gear mechanism and the first forward transmission mechanism in the axial direction,
The power transmission device according to claim 1.
the reversing transmission mechanism comprises a reverse clutch configured to connect and disconnect the first shaft and the third shaft via the reversing transmission mechanism;
The first forward rotation transmission mechanism includes a first forward clutch configured to connect and disconnect the first shaft and the third shaft via the first forward rotation transmission mechanism,
The second forward rotation transmission mechanism includes a second forward clutch configured to connect and disconnect the first shaft and the third shaft via the second forward rotation transmission mechanism,
The reverse clutch is provided on the first shaft,
The first forward clutch and the second forward clutch are provided on different shafts from among the first shaft and the third shaft,
The power transmission device according to claim 1 or 2.
The first forward clutch is provided on the first shaft,
the second forward clutch is provided on the third shaft;
The power transmission device according to claim 3.
The first forward rotation transmission mechanism includes:
a first forward output gear mounted on said third shaft and configured to rotate with said third shaft;
a first transmission gear mounted on the first shaft and engaged with the forward output gear;
with
The second forward rotation transmission mechanism is
a second transmission gear mounted on the first shaft and configured to rotate with the first shaft;
a second forward output gear mounted on the third shaft and engaged with the second transmission gear;
The number of teeth of the first transmission gear is less than the number of teeth of the second transmission gear,
The power transmission device according to claim 4.
The second transmission gear is spline-fitted with the first shaft,
The power transmission device according to claim 5.
7. The power transmission device according to claim 5, wherein said first transmission gear is rotatably supported on said first shaft via a needle bearing.
The number of teeth of the first forward output gear is greater than the number of teeth of the second forward output gear,
The power transmission device according to any one of claims 5 to 7.
The first forward output gear is integrally formed with the third shaft,
The power transmission device according to claim 8.
10. The power transmission device according to any one of claims 5 to 9, wherein said second forward output gear is rotatably supported on said third shaft via a needle bearing.
11. The power transmission device according to any one of claims 1 to 10, wherein said additional transmission mechanism performs only two-stage speed switching.
The additional transmission mechanism is
a first gear and a second gear rotatable together with the third shaft;
a low-speed gear provided rotatably relative to the second shaft while meshing with the first gear;
a high-speed gear provided rotatably relative to the second shaft while meshing with the second gear;
a transmission tube shaft provided rotatably integrally with the second shaft;
with
The transmission cylinder shaft has a first engaging portion that can be engaged with the high-speed gear and a second engaging portion that can be engaged with the low-speed gear,
A power transmission device according to any one of claims 1 to 11.

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