JP7543243B2 - Lubrication structure for power transmission device - Google Patents

Description

The present invention relates to a power transmission device for a work vehicle.

Patent Document 1 shows a power transmission device in which a lubricating oil filter is installed in a tilted state with respect to the horizontal plane. This power transmission device structure prevents air from accumulating in the filter.

Patent No. 5875955

Patent document 1 does not disclose a configuration for efficiently discharging the air inside the filter to the outside. If air continues to accumulate inside the filter, there is a risk of air entrapment, so a mechanism for discharging the air inside the filter to the outside is required.

The lubrication structure of the power transmission device according to the first aspect of the present disclosure includes a power transmission device, an oil filter, a hydraulic pump, and an oil pipe. The power transmission device includes a first rotating element, a second rotating element, and a housing that houses the first rotating element and the second rotating element. The housing includes a first oil chamber for storing lubricating oil for lubricating the first rotating element, and a second oil chamber for storing lubricating oil for lubricating the second rotating element. The oil filter is connected to the housing and configured to purify the lubricating oil. The oil filter has an oil inlet for taking in the lubricating oil and an oil outlet for discharging the lubricating oil after purification. The hydraulic pump is configured to suck out the lubricating oil accumulated in the oil filter. The oil pipe connects the oil outlet and the hydraulic pump. The housing further includes an oil passage, a connection portion, and a partition wall. The oil passage extends from the first oil chamber toward the filter. The connection portion connects the oil passage and the oil inlet. The partition separates the connection space surrounded by the connection part and the oil filter from the second oil chamber. The partition includes a communication hole that connects the connection space to the second oil chamber vertically above the connection port where the oil passage connects to the connection part.

The configuration disclosed in this application allows the air that has accumulated in the filter to be efficiently discharged by providing a communication hole above the oil passage through which the lubricating oil flows.

FIG. 2 is a side view showing the entire tractor. FIG. 2 is a plan view showing the entire tractor. FIG. 2 is a skeleton diagram showing a power transmission device. FIG. 2 is a sectional front view showing the branch transmission mechanism. 4 is a cross-sectional side view showing a planetary gear mechanism, a reverse transmission mechanism, a first forward transmission mechanism, and a second forward transmission mechanism. FIG. FIG. 2 is a sectional front view showing the planetary gear mechanism. FIG. 4 is a sectional front view showing the reverse transmission mechanism. FIG. 2 is a left side view showing the appearance of the power transmission device. FIG. 2 is a rear view showing the appearance of the power transmission device. FIG. 10 is a partial cross-sectional view of the power transmission device taken along the line XI-XI' of FIG. 8. 10 is a partial cross-sectional view of the power transmission device taken along the line XII-XII' of FIG. 9. 13 is a partial cross-sectional view of the power transmission device taken along the line XIII-XIII' of FIG. 8 and FIG. 12. 14 is a partial cross-sectional view of the power transmission device taken along the line XIV-XIV' of FIG. 8 and FIG. 12. 10 is a partial cross-sectional view of the power transmission device taken along the line XV-XV' of FIG. 8. FIG. 16 is an enlarged view of area A in FIG. 15 . 10 is a partial cross-sectional view of the power transmission device taken along the line XVII-XVII' of FIG. 8. 18 is a partial cross-sectional view of the power transmission device taken along the line XVIII-XVIII' of FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the drawings showing embodiments thereof. In the drawings, the same reference numerals indicate corresponding or substantially identical components.
<Embodiment>
<Overall composition>

1 is a side view showing the entire tractor 1 according to an embodiment of the present invention. FIG. 2 is a plan view showing the entire tractor 1 according to an embodiment of the present invention. The tractor 1 is an example of a work vehicle. Referring to FIGS. 1 and 2, the tractor 1 according to an example of a work vehicle includes a pair of left and right steerable and drivable front wheels 2a, a pair of left and right drivable rear wheels 2b, an engine room 3 in which an engine 3a is housed at the front of the vehicle body, a driver's compartment 4 having a seat 4a at the rear of the vehicle body, and a vehicle body frame 5 supporting the engine room 3 and the driver's compartment 4. Furthermore, the tractor 1 includes a link mechanism 6 having a pair of left and right lift arms 6a that can be freely swung up and down and are provided on both sides of the rear end of the vehicle body frame 5, and a PTO shaft 7 that protrudes rearward from the rear end of the vehicle body frame 5. The front wheels 2a and rear wheels 2b are collectively referred to as the traveling device 2. In FIG. 2, the traveling device 2 is realized by wheels, but all or part of the traveling device 2 may be realized by crawlers.

The tractor 1 can be configured as a riding tiller by connecting a rotary tiller (not shown) to the rear of the vehicle body via a link mechanism 6 so that it can be raised and lowered freely, and by transmitting the output of the engine 3a to the rotary tiller from the PTO shaft 7. In addition, the tractor 1 can be configured as various riding work machines by connecting various work devices to the rear of the vehicle body so that they can be raised and lowered freely and driven.

The vehicle body frame 5 includes a clutch housing 10 connected to the rear of the engine 3a, a continuously variable transmission case 20a whose front part is detachably connected to the rear of the clutch housing 10, a transmission case 11 connected to the rear 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 of the continuously variable transmission case 20a, and a rear transmission case 11b whose front part is detachably connected to the rear of the front transmission case 11a. The vehicle body frame 5 includes a front wheel drive case 13 attached to the front wheel support frame 12, and supports a pair of left and right front wheels 2a drivably via the front wheel drive case 13. The vehicle frame 5 has a pair of left and right rear wheel drive cases 14 arranged sideways on either side of the rear transmission case 11b, and supports the pair of left and right rear wheels 2b so that they can be driven via the pair of left and right rear wheel drive cases 14. In the following embodiments, the transmission case 11 (front transmission case 11a and rear transmission case 11b) may be referred to as the housing 11.

In the embodiment of the present application, the front-rear direction (front direction/rear direction) of the tractor 1 means the front-rear direction (front direction/rear direction) as seen by an operator seated in the seat 4a of the driver's seat 4. The left direction, right direction, and width direction of the tractor 1 mean the left direction, right direction, left and right directions, respectively, as seen by the operator. The up direction, down direction, and height direction of the tractor 1 mean the up direction, down direction, and height direction as seen by the operator. The front-rear/left-right (width)/up-down (height) directions of the tractor 1 respectively correspond to the front-rear/left-right (width)/up-down (height) directions as seen by the operator.

3 is a skeleton diagram showing a 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, the power transmission system that transmits 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 is configured to transmit the driving force output by the engine 3a from the output shaft 3b to the hydrostatic speed change mechanism 20 and the planetary gear mechanism 30 via the main clutch mechanism 15 and the branch transmission mechanism 16. The power transmission device 8 is configured to transmit the driving force output from the first shaft 38 that outputs the rotational force of the planetary gear mechanism 30 to the additional speed change mechanism 55 via one of the reverse transmission mechanism 40, the first forward transmission mechanism 45, and the second forward transmission mechanism 50. The power transmission device 8 is further configured to transmit power from the second shaft 54, which is the output shaft of the additional speed change mechanism 55, to the rear wheel differential mechanism 25, and from the second shaft 54 to the front wheel differential mechanism 26 via the gear transmission mechanism 61, the front wheel transmission mechanism 70, and the rotating shaft 27. In other words, the second shaft 54 is configured to transmit rotational force to the traveling 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 reverse transmission mechanism 40, the first forward transmission mechanism 45, the second forward transmission mechanism 50, and the additional speed change mechanism 55.

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

As shown in Figures 3 and 4, the branch transmission mechanism 16 includes an engine side gear 17 and a pair of transmission gears 18, 19 rotatably provided inside a transmission mechanism case 16a connected to a continuously variable transmission case 20a. The engine side gear 17 is provided at the end of the output shaft 15a of the main clutch mechanism 15 so as to be rotatable as one unit. The engine side gear 17 is supported so as to be rotatable with the output shaft 15a as the rotation axis. When the main clutch mechanism 15 is in a connected state, the engine side gear 17 is linked to the engine 3a side, and is rotated by the driving force output from the output shaft 3b of the engine 3a. When the main clutch mechanism 15 is in a disconnected state, the engine side gear 17 is not rotated by the engine 3a.

The pair of transmission gears 18, 19 are arranged such that the rotating shafts 18a, 19a of the pair of transmission gears 18, 19 are positioned at a height equal to or lower than the rotating shaft 17a of the engine side gear 17 and are in mesh with the engine side gear 17. The rotating shaft 18a of one transmission gear 18 is positioned at a height lower than the rotating shaft 19a of the other transmission gear 19. One transmission gear 18 is rotatably connected as one unit to the front end of a shaft 23 serving as an input shaft in the fore-and-aft direction of the vehicle body, which is provided in a hydraulic pump 21 constituting the hydraulic speed change mechanism 20. The other transmission gear 18 is rotatably connected as one unit to the extending end of an engine output introduction shaft 24 that extends from the planetary gear mechanism 30 toward the front of the vehicle body, penetrating the continuously variable speed change case 20a.

The branch transmission mechanism 16 is disposed on the vehicle body front side with respect to the hydraulic pump 21 and 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 is configured to branch the driving force output from the output shaft 3b of the engine 3a to the hydraulic transmission mechanism 20 side and the planetary gear mechanism 30 side by the engine side gear 17 and a pair of transmission gears 18, 19 on the vehicle body front side of the hydraulic transmission mechanism 20. The branch transmission mechanism 16 is configured to transmit the driving force branched to the hydraulic transmission mechanism 20 side to the hydraulic transmission mechanism 20 by the shaft 23, and to transmit the driving force branched to the planetary gear mechanism 30 side to the planetary gear mechanism 30 by the engine output introduction shaft 24.

The hydraulic transmission mechanism 20 includes a continuously variable transmission case 20a provided in front of the front transmission case 11a, and a hydraulic pump 21 and a hydraulic motor 22 arranged inside the continuously variable transmission case 20a so as to be positioned on the vehicle body front side with respect to the planetary gear mechanism 30. The hydraulic pump 21 is a variable capacity, 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). The hydraulic motor 22 is thus driven by the hydraulic pump 21 to rotate the motor output shaft 28.

Figure 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. Figure 6 is a cross-sectional side view showing the planetary gear mechanism 30. Referring to Figures 5 and 6, the planetary gear mechanism 30 has a sun gear 31, a plurality of planetary gears 32, and an internal gear 33. 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 positioned at equal intervals around the sun gear 31. The internal gear 33 is configured to mesh with the three planetary gears 32. The planetary gear mechanism 30 further includes a carrier 35 and a first shaft 38. The carrier 35 rotatably supports each planetary gear 32 via a support shaft 34.

The carrier 35 is supported rotatably relative to the sun gear 31 via a pair of bearings B2 on the first boss portion 31a of the sun gear 31. The support shaft 34 of each planetary gear 32 is connected to the carrier 35. The planetary gear mechanism 30 further has an annular support plate 36. The support plate 36 connects the three support shafts 34 on the side opposite to the side where the carrier 35 is located relative to the planetary gear 32. As shown in FIG. 6, the support plate 36 prevents the support shafts 34 from tilting relative to the carrier 35, and maintains the sun gear 31 and the meshing state of the planetary gear 32 with the sun gear 31 in a normal state so that the planetary gear 32 does not tilt relative to the sun gear 31 and the internal gear 33.

By engaging the splines on the first boss portion 31a of the sun gear 31 with the splines on the motor output shaft 28, the sun gear 31 is connected to rotate integrally with the motor output shaft 28, which is the output shaft of the hydraulic transmission mechanism 20.

The engine output introduction shaft 24 is connected to an input gear 37 that is rotatably supported via a bearing B5 on the first support portion 30a of the front transmission case 11a. The input gear 37 has a through hole therein through which the engine output introduction shaft 24 passes, and the through hole and the outer periphery of the engine output introduction shaft 24 are provided with splines that mesh with each other. The engine output introduction shaft 24 and the input gear 49 are rotatably connected as a single unit by a spline fit. The carrier 35 has teeth formed on its outer periphery that are configured to mesh with the input gear 49.

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. The inner circumference of the boss portion 33a of the internal gear 33 is formed with a spline that meshes with a spline formed on the outer circumference of the first shaft 38. The internal gear 33 is connected to the first shaft 38 so as to rotate integrally with the first shaft 38 by the engagement of these splines. 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. 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, so that the driving force from the engine 3a is input to the carrier 35 without being subjected to the speed change action of the hydraulic speed change mechanism 20. Furthermore, the driving force output from the motor output shaft 28 by the hydraulic speed change mechanism 20 is input to the sun gear 31. Then, the driving force from the hydraulic speed change mechanism 20 and the driving force from the engine 3a that is not subjected to the speed change action of the hydraulic speed change mechanism 20 are combined, and the combined driving force is output to the first shaft 38 connected to the reverse transmission mechanism 40, the first forward transmission mechanism 45, and the second forward transmission mechanism 50.

Therefore, the power transmission device 8 branches the driving force output from the engine 3a through the output shaft 3b to the hydraulic transmission mechanism 20 side and the planetary gear mechanism 30 side by the branch transmission mechanism 16 at a location located on the vehicle body front side with respect to the hydraulic transmission mechanism 20. The power transmission device 8 then inputs the driving force branched to the hydraulic transmission mechanism 20 side to the hydraulic pump 21 of the hydraulic transmission mechanism 20 through the shaft 23, converts it to a driving force in the forward rotation direction and a driving force in the reverse rotation direction by the speed change action of the hydraulic pump 21 and the hydraulic motor 22 of the hydraulic transmission mechanism 20, and outputs it from the motor output shaft 28 with stepless speed change regardless of whether it is converted to a driving force in the forward rotation direction or the reverse rotation direction. The power transmission device 8 inputs the driving force output from the motor output shaft 28 of the hydraulic speed change mechanism 20 to the sun gear 31 of the planetary gear mechanism 30, and inputs the driving force branched to the planetary gear mechanism 30 side by the branch transmission mechanism 16 to the carrier 35 of the planetary gear mechanism 30 via the engine output introduction shaft 24 and the input gear 37. In the planetary gear mechanism 30, the driving force from the engine 3a and the driving force from the hydraulic speed change mechanism 20 are combined, and the combined driving force is output from the first shaft 38 to the reverse transmission mechanism 40, the first forward transmission mechanism 45, and the second forward 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 the third gear. In this case, it can be said that the first gear (planetary gear 32) of the sun gear 31, planetary gear 32, and internal gear 33 is rotated by the engine 3a. It can be said that the second gear (sun gear 31) other than the first gear (planetary gear 32) of the sun gear 31, planetary gear 32, and internal gear 33 is rotated by the hydraulic motor 22 of the hydraulic speed change mechanism 20 driven by the engine 3a. It can be said that the first shaft 38 is the rotation axis of the third gear other than the first gear and the second gear of the sun gear 31, planetary gear 32, and internal gear 33.

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 reverse transmission mechanism 40 is configured to transmit the rotational force of the first shaft 38 to the third shaft 39 to drive the traveling device 2 in the reverse direction. The power transmission device 8 includes 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. The third shaft 39 has a central axis Ax3 and is rotatable around the central axis Ax3. The central axis Ax3 is substantially parallel to the central axis Ax1. Thus, 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 reverse transmission mechanism 40. The reverse clutch 44 is provided on the first shaft 38. As shown in FIG. 7, the transmission gear 41 engages with the reverse gear 42, and the reverse gear 42 meshes with the reverse output gear 43. The transmission gear 41 does not mesh with the reverse output gear 43. Note that in FIG. 7, some components in the power transmission device 8 other than the transmission gear 41, the reverse gear 42, and the reverse output gear 43 are not shown.

When the reverse clutch 44 is switched to an engagement state, the driving force of the first shaft 38 is transmitted in the order of the transmission gear 41, the reverse gear 42, the reverse output gear 43, and the third shaft 39. At this time, the third shaft 39 rotates so as to drive the front wheels 2a and the rear wheels 2b in the reverse direction. Since the transmission gear 41 is rotatably supported by the first shaft 38 via the bearing B10, when the reverse clutch 44 is switched to a disengagement state, the transmission gear 41 rotates independently of the first shaft 38. The reverse output gear 43 is formed integrally with the third shaft 39. The transmission gear 41 is engaged with the reverse output gear 43 via the 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 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. The first forward transmission mechanism 45 is configured to transmit the rotational force of the first shaft 38 to the third shaft 39 at a first speed transmission ratio as a rotational force in the opposite direction to that of the reverse transmission mechanism 40 in order to drive the traveling device 2 in the forward direction. The first forward clutch 48 is configured to connect and disconnect the first shaft 38 and the third shaft 39 via the first forward transmission mechanism 45. The first forward clutch 48 is provided on the first shaft 38.

When the first forward clutch 48 is switched to the on state, the driving force of the first shaft 38 is transmitted in the order of the first transmission gear 46, the first forward output gear 47, and the third shaft 39. The third shaft 39 rotates to drive the front wheels 2a and the rear wheels 2b in the forward direction. 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. Since the first transmission gear 46 is rotatably supported by the first shaft 38 via a needle bearing NB1, when the first forward clutch 48 is switched to the off state, the first transmission gear 46 rotates independently of the first shaft 38. 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. The first transmission gear 46 is provided on the first shaft 38 and engages with the 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 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 transmission mechanism 50 is provided between the planetary gear mechanism 30 and the first forward transmission mechanism 45 in the axial direction Dx. The second forward transmission mechanism 50 is configured to transmit the rotational force of the first shaft 38 to the third shaft 39 at a second transmission ratio smaller than the first transmission ratio as a rotational force in the opposite direction to that of the reverse transmission mechanism 40 in order to drive the traveling device 2 in the forward direction. The second forward clutch 53 is configured to couple and release the first shaft 38 and the third shaft 39 via the second forward transmission mechanism 50. The second forward clutch 53 is provided on the third shaft 39. In other words, 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 in the order of the second transmission gear 52, the second forward output gear 51, and the third shaft 39. The third shaft 39 rotates to drive the front wheels 2a and the rear wheels 2b in the forward direction.

The second speed transmission ratio described above is the 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. The second speed transmission ratio is smaller than the first speed transmission ratio, specifically, by (1) the number of teeth of the first transmission gear 46 being smaller than the number of teeth of the second transmission gear 52, and (2) the number of teeth of the first forward output gear 47 being 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 off state, the second forward output gear 51 rotates independently of the third shaft 39. Since the second transmission gear 52 is spline-fitted with the first shaft 38, it is provided on the first shaft 38 and configured to rotate together with the first shaft 38. The 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 are hydraulic clutches having a well-known configuration including a cylinder, a piston, a rotation transmission source clutch disc, a rotation transmission destination clutch disc, and a spring that presses the piston to separate the rotation transmission source clutch disc and the rotation transmission destination clutch disc. For this reason, detailed descriptions of these clutches are omitted. In the second forward clutch 53, an oil passage 53c for hydraulically pressing the piston 53p pressed by the spring 53s from the opposite side is provided in the housing of the second forward clutch 53 and the second support part 30b of the front transmission case 11a, but is not provided in the third shaft 39.

The reverse clutch 44, the first forward clutch 48, and the second forward clutch 53 are switched between their engaged and disengaged states by the shift lever or switch on the driver's seat 4, and an electronic circuit (not shown) controls the opening and closing of a control valve that controls whether or not hydraulic oil is supplied to one of the reverse clutch 44, the first forward clutch 48, and the second forward clutch 53 corresponding to the operation of the shift lever or switch. The electronic circuit controls the reverse clutch 44, the first forward clutch 48, and the second forward clutch 53 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. In other words, the electronic circuit controls one of the reverse clutch 44, the first forward clutch 48, and the second forward clutch 53 to be engaged and the remaining clutch to be disengaged, or controls all of the reverse clutch 44, the first forward clutch 48, and the second forward clutch 53 to be disengaged.

The additional transmission mechanism 55 is configured to change 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 connected to the third shaft 39 via a joint JT so as to rotate together with the fourth shaft 39a, a first gear 57 and a second gear 59 provided on the fourth shaft 39a so as to rotate together with the first gear 57, a low-speed gear 56 provided on the second shaft 54 so as to rotate relatively thereto while meshing with the first gear 57, a high-speed gear 58 provided on the second shaft 54 so as to rotate relatively thereto while meshing with the second gear 59, and a transmission cylinder shaft 60 provided on the second shaft 54 so as to rotate together with the first gear 57 and the second gear 59. 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 splined inner wall that fits with the spline 54s. The fourth shaft 39a may be formed integrally with the third shaft 39. The transmission cylinder shaft 60 has a first engagement portion that can engage with the high-speed gear 58 on a portion other than the inner surface, and a second engagement portion that can engage with the low-speed gear 56 on a portion other than the inner surface.

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 engages with the boss of the low-speed gear 56, the driving force transmitted from the reverse transmission mechanism 40, the first forward transmission mechanism 45, or the second forward 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. In this case, the low-speed state is achieved regardless of whether the driving force is transmitted from the reverse transmission mechanism 40, the first forward transmission mechanism 45, or the second forward transmission mechanism 50. 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 engages with the high-speed gear 58, the driving force transmitted from any of the reverse transmission mechanism 40, the first forward transmission mechanism 45, and the second forward transmission mechanism 50 is transmitted to the second shaft 54 via the second gear 59, the high-speed gear 58, and the transmission cylinder shaft 60. In this case, the high-speed state is achieved regardless of whether the driving force is transmitted from the reverse transmission mechanism 40, the first forward transmission mechanism 45, or the second forward transmission mechanism 50.

The lubrication structure 9 of the power transmission device 8 will be described below. FIG. 8 is a left side view showing the appearance of the power transmission device 8. FIG. 9 is a rear view showing the appearance of the power transmission device 8. Referring to FIG. 8 and FIG. 9, the lubrication structure 9 includes two oil filters 79 and 80 connected to the transmission case 11 and configured to purify the lubricating oil for lubricating the rotating elements of the power transmission device 8. More specifically, the oil filter 79 is an HST filter. The oil filter 80 is a suction filter. Both the oil filters 79 and 80 have a substantially cylindrical shape. As shown in FIG. 9, the oil filter 79 is disposed so that the central axis of the cylinder faces approximately in the horizontal direction D _H , while the central axis of the cylinder of the oil filter 80 is inclined by an angle α from the horizontal direction D _H. Although α is preferably 90 degrees, it may be inclined at the maximum possible angle in relation to the minimum ground clearance and a connection portion 91 (described later). The oil filter 80 is disposed so that its tip faces downward. Fig. 10 is a perspective view of the oil filter 80. Referring to Fig. 10, the oil filter 80 has a plurality of oil inlets 81 that take in lubricating oil and an oil outlet 82 that discharges the lubricating oil. The oil inlets 81 are provided around the oil outlet 82.

Figure 11 is a partial cross-sectional view of the power transmission device 8 taken along the line XI-XI' in Figure 8. Referring to Figure 11, the power transmission device 8 includes a housing 11 (transmission case 11). The housing 11 houses the above-mentioned rotating elements such as the gears and the rotating shaft. The housing 11 includes a first oil chamber R1 and a second oil chamber R2. The first oil chamber R1 and the second oil chamber R2 are separated by a first partition wall 66. The first oil chamber R1 houses the additional speed change mechanism 55, the gear transmission mechanism 61, the front wheel transmission mechanism 70, and the second drive shaft 64 that transmits the driving force to the PTO shaft 7. The power transmission device 8 includes a second reduction mechanism 63 that is connected to the hydraulic pump 21 via a transmission mechanism (not shown) and transmits the driving force to the second drive shaft 64. The second reduction mechanism 63 includes a small diameter gear 63A and a large diameter gear 63B. The number of teeth of the large diameter gear 63B is greater than the number of teeth of the small diameter gear 63A. The large diameter gear 63B is provided on the second drive shaft 64. In FIG. 11, most of the second drive shaft 64 and the large diameter gear 63B are provided above the XI-XI' cross section, and are therefore illustrated by dashed lines. The second oil chamber R2 accommodates the planetary gear mechanism 30, the reverse transmission mechanism 40, the first forward transmission mechanism 45, the second forward transmission mechanism 50, and the second reduction mechanism 63 that reduces the rotational speed of the second drive shaft 64. The planetary gear mechanism 30, the reverse transmission mechanism 40, the first forward transmission mechanism 45, and the second forward transmission mechanism 50 correspond to the first reduction mechanism 65 that reduces the rotational speed of the first drive shaft 71 that transmits the driving force to the traveling device.

At least one of the rotating elements of the additional speed change mechanism 55, the gear transmission mechanism 61, the front wheel transmission mechanism 70, and the second drive shaft 64 is called the first rotating element. At least one of the rotating elements of the planetary gear mechanism 30, the reverse transmission mechanism 40, the first forward rotation transmission mechanism 45, the second forward rotation transmission mechanism 50, and the second reduction mechanism 63 is called the second rotating element. For example, if a rotating element that rotates at the same rotation speed as the rotation of the first shaft 38 is called the second rotating element, and a rotating element that rotates at the same rotation speed as the rotation of the third shaft 39 that rotates accordingly is called the first rotating element, when the first rotating element rotates, the second rotating element also rotates, and the rotation speed of the second rotating element is faster than the rotation speed of the first rotating element. In addition, if the second drive shaft 64 is the first rotating element, and the rotating elements of the second reduction mechanism 63 excluding the large diameter gear 63B are the second rotating elements, when the first rotating element rotates, the second rotating element also rotates, and the rotation speed of the second rotating element is faster than the rotation speed of the first rotating element.

Figure 12 is a partial cross-sectional view of the power transmission device 8 taken along the XII-XII' cross section of Figure 9. Referring to Figures 11 and 12, the housing 11 further includes an oil passage 90 extending from the first oil chamber R1 toward the oil filter 80, and a connection portion 91 connecting the oil passage 90 and the oil inlet 81. The lubricating oil in the first oil chamber R1 flows into the oil passage mainly from the oil intake INL through the path indicated by the arrow in Figure 12. The oil intake INL is provided behind the 2-wheel/4-wheel drive switching clutch 72, which is configured to connect and disconnect the gear transmission mechanism 61 and the rotating shaft 27 of the front wheel transmission mechanism 70. The space from the oil intake INL to the oil passage 90 is partitioned by covers 96 and 97. The cover 96 prevents air bubbles generated by the 2-wheel/4-wheel drive switching clutch 72 stirring the lubricating oil from flowing into the oil passage 90. In addition, the front wheel transmission mechanism 70 has a slower rotational speed than the first reduction gear mechanism 65 and is located lower than the additional speed change mechanism 55 and the gear transmission mechanism 61, so it is difficult for air bubbles mixed with the lubricating oil to enter through the oil intake port INL. The cover 97 prevents air bubbles generated by the lubricating oil being stirred by the rotation of the rotating shaft 27 and the rotating members connected to the rotating shaft 27 from flowing into the oil passage 90.

13 is a partial cross-sectional view of the power transmission device taken along the XIII-XIII' cut plane of FIG. 8 and FIG. 12. As shown in FIG. 13, the cover 97 is provided below the rotating shaft 27. The arrows shown in FIG. 12, which are indicated by dotted lines below the cover 97, indicate that the cover 97 is below the cover 97. FIG. 14 is a partial cross-sectional view of the power transmission device taken along the XIV-XIV' cut plane of FIG. 8 and FIG. 12. Referring to FIG. 13 and FIG. 14, the oil passage 90 is partitioned from the other internal spaces of the housing 11. In particular, as shown in FIG. 14, the second oil chamber R2 and the oil passage 90 are partitioned by the second partition wall 98. This prevents the lubricating oil foamed by the second rotating element, which has a high rotation speed, from flowing into the oil passage 90.

Figure 15 is a partial cross-sectional view of the power transmission device 8 taken along the XIV-XV' cut surface of Figure 8. Referring to Figure 15, the housing 11 further includes a partition wall 93 that separates the connection space 92 surrounded by the connection portion 91 and the oil filter 80 from the second oil chamber R2. The partition wall 93 includes a communication hole 95 that communicates the connection space 92 with the second oil chamber R2 vertically above the connection port 94 where the oil passage 90 connects to the connection portion 91. The opening size of the communication hole 95 is smaller than the opening size of the connection port 94. Figure 16 is an enlarged view of region A in Figure 15. Referring to Figure 16, the lubrication structure 9 further includes a flow rate adjustment screw 99 that is screwed into the communication hole 95. The communication hole 95 includes a screw groove 95S for screwing in the flow rate adjustment screw 99.

Referring to FIG. 8, the lubrication structure 9 further includes a hydraulic pump 73 and an oil pipe 75. The hydraulic pump 73 is configured to suck out the lubricating oil accumulated in the oil filter 80. The oil pipe 75 connects the oil outlet 82 and the hydraulic pump 73. FIG. 17 is a partial cross-sectional view of the power transmission device 8 taken along the XVII-XVII' section of FIG. 8. FIG. 18 is a partial cross-sectional view of the power transmission device 8 taken along the XVIII-XVIII' section of FIG. 8. Referring to FIGS. 17 and 18, the connection part 91 is provided so as to surround the oil pipe 75. Referring to FIGS. 15 to 17, the oil filter 80 includes a filter body 84 configured to remove impurities from the lubricating oil. The filter body 84 is connected to the connection port 94 via the oil inlet 81 and to the oil pipe 75 via the oil outlet 82. The oil filter 80 further includes a filter housing 83 that houses the filter body 84 and extends in the extension direction D- _E . The extension direction D _-E corresponds to the height direction of the approximately cylindrical shape of the oil filter 80. With reference to Figures 8 and 18, the lubrication structure 9 further includes an additional oil pipe 77 connected to the oil pipe 75. With reference to Figure 8, the additional oil pipe 77 extends obliquely downward from the oil pipe 75. A pipe connected to another hydraulic pump (not shown) that supplies pilot oil is connected to a connection port 78 of the additional oil pipe 77.

The filter housing 83 includes a housing base end 85 including the oil inlet 81 and the oil outlet 82 described above, a housing end 86 opposite to the housing base end 85 with respect to the extension direction D _E , a filter inner side surface 83IS facing the filter body 84, and a filter outer side surface 83OS surrounding the filter inner side surface 83IS on the opposite side to the filter inner side surface 83IS. The upper end of the filter inner side surface 83IS in the vertical direction D _V rises in the vertical direction D _V from the housing end portion 86 toward the housing base end portion 85. In other words, the upper end of the oil filter 80 in the vertical direction D _V falls in the vertical direction D _V as it moves away from the connection portion 91. The connection portion 91 faces the connection space 92 and has an inner side surface 91IS that is connected to a surface 93OS of the partition wall 93 facing the connection space 92. The upper end of the inner surface 91IS in the vertical direction _DV rises from the oil filter 80 toward the partition wall 93.
<Actions and Effects of the Embodiments>

The lubrication structure 9 according to the embodiment described above has the following features. (1) Oil is supplied to the oil filter 80 from the first oil chamber R1, which houses rotating members with a slow rotation speed, via an oil passage 90 that is separated from the first oil chamber R1 and the second oil chamber R2, which houses rotating members with a fast rotation speed. As a result, lubricating oil with a low air content flows into the oil filter 80. This prevents air entrainment.

(2) The upper end of the oil filter 80 in the vertical direction _DV decreases as it moves away from the connection portion 91. In other words, the upper end of the filter inner surface 83IS in the vertical direction _DV increases in _{the vertical direction DV from} the housing end portion 86 toward the housing base end portion 85. For this reason, even if lubricating oil containing air flows in from the oil inlet 81, the air is easily discharged to the outside.

(3) The filter housing 83 includes an oil outlet 82 that communicates between the filter body 84 and the oil pipe 75, and an oil inlet 81 that communicates between the connection port 94 of the oil passage 90 and the filter body 84. The oil inlet 81 is provided around the oil outlet 82. In other words, the connection portion 91 is provided so as to surround the oil pipe 75. For this reason, the lubricating oil flows in from below the oil pipe 75, and air tends to be discharged from above the oil pipe 75. For this reason, even if lubricating oil containing air flows in from the oil inlet 81, the air tends to be discharged to the connection portion 91.

(4) The upper end of the inner surface 91IS of the connection portion 91 in the vertical direction _DV rises from the oil filter 80 toward the partition wall 93. For this reason, even if air is discharged into the connection space 92 formed by the connection portion 91, the air tends to flow along the inner surface 91IS of the connection portion 91 toward the partition wall 93.

(5) The partition wall 93 includes a communication hole 95 that communicates the connection space 92 and the second oil chamber R2 above the connection port 94 of the oil passage 90 in the vertical direction _DV . Therefore, air that has flowed toward the partition wall 93 is discharged from the communication hole 95 to the second oil chamber R2. The lubrication structure 9 further includes a flow rate adjustment screw 99 that is screwed into the communication hole 95. Therefore, it is possible to adjust the flow rate to an optimum level so that the air accumulated in the connection space 92 is discharged to the second oil chamber R2 while preventing the lubricating oil in the second oil chamber R2, which contains a large amount of air, from flowing into the connection space 92.

In this application, the words "comprise" and their derivatives are open-ended terms that describe the presence of elements and do not exclude the presence of other elements not listed. This also applies to the words "have," "include," and their derivatives.

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

Ordinal numbers such as "first" and "second" are merely terms used to identify a configuration and have no other meaning (such as a particular order). For example, the presence of a "first element" does not imply the presence of a "second element," and the presence of a "second element" does not imply the presence of a "first element."

Words expressing degree, such as "substantially," "about," and "approximately," can mean a reasonable deviation that does not significantly change the final result, unless otherwise specified in the embodiment. All numerical values described in this application can 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 A only, B only, and both A and B.

In view of the above disclosure, it is clear that various changes and modifications of the present invention are possible. Therefore, the present invention may be implemented in a manner different from the specific disclosure of this application without departing from the spirit of the present invention.

Claims (14)

a power transmission device comprising a first rotating element, a second rotating element, and a housing that houses the first rotating element and the second rotating element, the housing including a first oil chamber for storing a lubricating oil for lubricating the first rotating element, and a second oil chamber for storing a lubricating oil for lubricating the second rotating element;
an oil filter connected to the housing, configured to purify the lubricating oil, the oil filter having an oil inlet for taking in the lubricating oil and an oil outlet for discharging the purified lubricating oil;
a hydraulic pump configured to suck out lubricating oil accumulated in the oil filter;
an oil pipe connecting the oil outlet and the hydraulic pump;
Equipped with
The housing includes:
an oil passage extending from the first oil chamber toward the oil filter;
a connection portion that connects the oil passage and the oil inlet;
a partition wall that separates a connection space surrounded by the connection portion and the oil filter from the second oil chamber;
Further comprising:
The partition wall includes a communication hole that communicates the connection space and the second oil chamber vertically above a connection port at which the oil passage is connected to the connection portion.
Lubrication structure for power transmission devices.
2. The lubrication structure according to claim 1, wherein the upper end of the oil filter in the vertical direction descends in the vertical direction as it moves away from the connection portion.
The oil filter is
a filter body configured to remove impurities from the lubricating oil;
a filter housing that houses the filter body and extends in an extension direction;
Including,
The filter housing includes:
a housing base end portion including an oil outlet port communicating between the filter body and the oil pipe and an oil inlet port communicating between the connection port and the filter body;
a housing end portion opposite the housing base end portion with respect to the extension direction;
an inner filter surface facing the filter body;
a filter outer surface surrounding the filter inner surface opposite the filter inner surface;
Including,
The upper end of the filter inner surface in the vertical direction rises in the vertical direction from the distal end of the housing toward the proximal end of the housing.
The lubrication structure according to claim 1 or 2.
The lubrication structure according to claim 3 , wherein the oil inlet is provided around the oil outlet.
The lubrication structure according to claim 4 , wherein the connection portion is provided so as to surround the oil pipe.
the connection portion has an inner surface facing the connection space and connected to a surface of the partition wall facing the connection space,
6. The lubrication structure according to claim 2, wherein the upper end of the inner surface in the vertical direction rises from the oil filter toward the partition wall.
When the first rotating element rotates, the second rotating element also rotates;
The rotation speed of the second rotating element is faster than the rotation speed of the first rotating element.
The lubrication structure according to any one of claims 1 to 6.
the power transmission device includes a first reduction mechanism that reduces the rotation speed of a first drive shaft that transmits driving force to a traveling device, and a second reduction mechanism that reduces the rotation speed of a second drive shaft that transmits driving force to a power take-off shaft,
the second oil chamber accommodates the first reduction mechanism and the second reduction mechanism,
The second rotating element is one rotating element of the second reduction mechanism.
A lubrication structure according to any one of claims 1 to 7.
The power transmission device further includes the first reduction mechanism and a front wheel transmission mechanism for transmitting driving force to a front traveling device,
the first oil chamber accommodates the front wheel transmission mechanism,
The first rotating element is one rotating element of the front wheel transmission mechanism.
The lubrication structure according to claim 8.
The first oil chamber and the second oil chamber are separated by a first partition wall.
The lubrication structure according to any one of claims 1 to 9.
The second oil chamber and the oil passage are partitioned by a second partition wall.
The lubrication structure according to any one of claims 1 to 10.
The size of the opening of the communication hole is smaller than the size of the opening of the connection port.
A lubrication structure according to any one of claims 1 to 11.
Further comprising a flow rate adjusting screw screwed into the communication hole.
A lubrication structure according to any one of claims 1 to 12.
The communication hole includes a thread groove for screwing in the flow rate adjusting screw.
The lubrication structure according to claim 13.

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