Transmission unit with parking lock function

Abstract

To compactly arrange and store many elements including a park lock mechanism.SOLUTION: A gear unit used in combination with a power source including a hollow output shaft includes a differential gear set sharing a rotation axis with the output shaft, a counter shaft fixedly including a first gear meshing with the output shaft and a second gear meshing with the differential gear set, the first gear and the second gear constituting a reduction gear set, a housing including an outer wall separating the differential gear set and the counter shaft from the outside, and a parking gear disposed on a side opposite to the first gear in an axial direction with respect to the second gear and fixed to the counter shaft.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The following disclosure relates to a gear unit that can be used as a two-shaft reduction gear in combination with a power source such as an electric motor having a hollow output shaft, and in particular to a reduction gear unit having a park lock function. [Background technology]

[0002] Technologies for propelling vehicles solely with electric motors, instead of internal combustion engines, are being actively investigated. Typically, torque generated by an electric motor is multiplied by a reduction gear set and output to the axles via a differential. To make the vehicle's drivetrain compact and easier to handle, the reduction gear set and differential are sometimes integrated into a single gear unit, which is then integrated with the electric motor. The differential may also be coaxial with the electric motor's output shaft, which is hollow to allow for easy extension of one of the axles.

[0003] The drive device as described above may also have a parking lock function. Patent Documents 1 and 2 disclose related techniques. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-95956 [Patent Document 2] International Publication No. 2020 / 067281 Summary of the Invention [Problem to be solved by the invention]

[0005] As can be easily understood, the drive unit includes a large number of elements as described above, and how to arrange and house them presents a technical problem. For example, if elements are added axially to the electric motor, the drive unit will naturally become longer in the axial direction, and the length of the axle must be reduced instead. This reduces the room for the axle to swing, adversely affecting the ride comfort of the vehicle. Increasing the dimensions in the vertical direction, avoiding the axial direction, raises the center of gravity and impairs the stability of the vehicle. The technology disclosed below has been devised to solve these problems. [Means for solving the problem]

[0006] According to one aspect, a gear unit used in combination with a power source having a hollow output shaft includes: a differential gear set that shares a rotation axis with the output shaft; a countershaft that fixedly includes a first gear that meshes with the output shaft and a second gear that meshes with the differential gear set, the first gear and the second gear forming a reduction gear set; a housing having an outer wall that separates the differential gear set and the countershaft from the outside; and a parking gear that is arranged axially opposite the first gear with respect to the second gear and is fixed to the countershaft.

[0007] Preferably, the gear unit further includes a parking lock device including a pawl journaled on the outer wall and engageable with the parking gear, and an actuator that swings the pawl to disengageably engage with the parking gear. More preferably, the pawl is disposed between the second gear and the outer wall. Or, even more preferably, the pawl is disposed between the actuator and the parking gear. Also preferably, the actuator includes a motor that generates rotation and a cam mechanism that converts the rotation into linear motion for swinging the pawl, the motor protruding from the outer wall. Or, preferably, the second gear and the parking gear are disposed in the same chamber within the housing. More preferably, the housing further includes a partition wall detachably coupled to the outer wall and enclosing the chamber, the partition wall including a bearing that rotatably supports the differential gear set. Also preferably, the partition wall includes an opening through which the parking gear can pass. [Effects of the Invention]

[0008] A compact gear unit is provided while incorporating a park lock mechanism. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of a gear unit coupled to a power source. [Figure 2] FIG. 2 is a plan view of the gear unit coupled to the power source. [Figure 3] FIG. 3 is a cross-sectional view of the gear unit as seen from below, taken along a plane passing through the differential shaft and the countershaft shaft. [Figure 4] FIG. 4 is a side view of the gear unit separated from the power source and viewed from the power source side, and is separated from the power source along line IV-IV. [Figure 5] 5 is a cross-sectional side view of the gear unit as seen from the opposite side to that of FIG. 4, taken along line VV of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Some exemplary embodiments are described below with reference to the accompanying drawings.

[0011] It should be noted that the drawings are not necessarily drawn to scale, and therefore the dimensional relationships between the drawings are not limited to those shown. In the drawings, directions are conveniently indicated by arrows F, A, R, L, U, and D. In normal use, these correspond to the front, rear, right, left, top, and bottom of the vehicle, respectively, but the device can also be used in other ways, for example, by being reversed left and right, up and down, or facing in a different direction, or even tilted.

[0012] The gear unit 1 according to this embodiment is a reduction gear unit equipped with a parking lock device 7, and is used in combination with a power source 3 such as an electric motor equipped with a hollow output shaft 5. Of course, it is not limited to an electric motor, and may also be combined with an internal combustion engine or a so-called hybrid system.

[0013] 1 and 2 in combination with Fig. 3, the gear unit 1 is accommodated in a housing that is detachably coupled to a power source 3, and the housing also includes an outer wall 11, a partition wall 13, and a cover 15 that are detachably coupled to each other. The housing may, of course, further include other elements.

[0014] One end of the output shaft 5 extends beyond the cover 15 into the gear unit 1. The end is provided with gear teeth for meshing or is attached separately. The output shaft 5 is hollow, and its interior is a cylindrical cavity 5T sized to allow the right axle to pass through.

[0015] The gear unit 1 includes a differential gear set 21 and a countershaft 31 that mesh with each other within a housing.

[0016] The differential gear set 21 shares a rotation axis X with the output shaft 5 and is rotatable about the rotation axis X. The countershaft 31 is rotatable about a counter axis C that is different from but parallel to the rotation axis X and is meshed with both the output shaft 5 and the differential gear set 21. The differential gear set 21 receives torque via the countershaft 31 and distributes the torque differentially to both axles via side gears 27R, 27L. The right axle is coupled to the side gear 27R through the cavity 5T, and the left axle is coupled to the left side gear 27L through an opening in the outer wall 11.

[0017] The differential gear set 21 includes a differential case 23 that is, for example, substantially cylindrical around the axis X. Bosses protrude from both ends of the differential case 23, and the differential case 23 is rotatably supported by a housing at both bosses. The differential case 23 includes gear teeth 25 fixed to its outer periphery, for example, and meshes with the countershaft 31 via the gear teeth 25. The gear teeth 25 are preferably helical gears, and may be directly engraved on the differential case 23 or may be a separate element that is coupled to the differential case 23.

[0018] The differential gear set 21 may be, for example, a bevel gear type as shown in the example shown in the figure, and includes a pinion shaft fixed to the differential case 23 and a pinion gear rotatably supported thereon, with side gears 27R, 27L meshing with the pinion gear to differentially distribute torque. Of course, other types such as a face gear type or a planetary gear type may be used instead of the bevel gear type. The differential gear set 21 may also be equipped with a differential limiting mechanism or a differential locking mechanism.

[0019] The countershaft 31 is fixedly provided with a large-diameter first gear 33 and a smaller-diameter second gear 35, both of which are preferably helical gears. The first gear 33 meshes with the output shaft 5, and the second gear 35 meshes with the gear teeth 25 of the differential gear set 21. Due to the difference in diameter between the first gear 33 and the second gear 35, the combination of these gears forms a reduction gear set, thereby amplifying the torque of the output shaft 5 and transmitting it to the differential gear set 21. The first gear 33 may be, for example, a disk-shaped one about the counter axis C, with gear teeth engraved on its outer periphery. It may be integral with the countershaft 31, or for manufacturing convenience, it may be fabricated separately and then coupled to the countershaft 31. For coupling, for example, a spline connection, a lug connection, welding, or a press fit may be used. Meanwhile, the second gear 35 may be formed integrally with the countershaft 31, or it may be fabricated separately and then coupled to the shaft. 3, since no particular element is interposed between the first gear 33 and the second gear 35, the first gear 33 and the second gear 35 can be arranged as close as possible to each other, which is advantageous for reducing the dimensions of the gear unit 1 in the directions of the axes C and X.

[0020] 3 and 5, the countershaft 31 further includes a fixed parking gear 37 that constitutes the parking lock device 7. Needless to say, the parking gear 37 is located axially outward of the first gear 33 and the second gear 35, or on the axially opposite side of the second gear 35 from the first gear 33, and near the end farthest from the power source 3. That is, the parking gear 37 can be located very close to the outer wall 11 and between a bearing 39L (described below) and the second gear 35. As can be easily seen from FIG. 3, such an arrangement does not affect the axial dimension of the gear unit 1 (the width direction in the illustrated example), and is therefore advantageous for making the gear unit 1 compact. The parking gear 37 is also disk-shaped, but its periphery is engraved with locking teeth that are different from the gear teeth. The parking gear 37 may be integral with the countershaft 31, but for ease of assembly, it can be a separate piece and fixed to the countershaft 31 by press-fitting, spline connection, or the like.

[0021] Referring mainly to FIG. 5, the parking lock device 7 further includes a pole 43 that engages with the parking gear 37 and an actuator 45 that drives the pole 43.

[0022] The pole 43 is axially supported on the outer wall 11 and swings about its axis to engage with the parking gear 37, immobilizing the countershaft 31. The pole 43 is located between the second gear 35 and the outer wall 11, and between the actuator 45 and the parking gear 37. Although not shown in the figure, the fulcrum of the pole 43 may further include a spring biased in a direction to encourage disengagement.

[0023] The actuator 45 can be a device that directly applies a rotational force to the axis of the pole 43, or an electric device that generates linear motion along the operating axis L. As such an electric device, a fluid pressure device such as hydraulic or pneumatic pressure can be used, or a combination of a motor and a cam mechanism as described below can be used.

[0024] In the illustrated example, the actuator 45 includes a motor 47, a spindle 49 having a thread on its outer periphery, a spindle nut 51 fitted to the spindle 49 for linear movement, and a cone 53 that follows the spindle nut 51 and acts on the pawl 43. The motor 47 generates controlled rotational motion around the operating axis L. When the spindle 49 is driven by the motor 47 and rotates around the operating axis L, the spindle nut 51 is guided by the thread and causes linear movement along the operating axis L. In other words, the combination of the spindle 49 and the spindle nut 51 forms a kind of cam mechanism. For example, by using a coil spring 55 to press the cone 53 against the spindle nut 51, the cone 53 follows the spindle nut 51. The outer surface of the cone 53 is appropriately profiled, and the pawl 43 swings in a controllable manner when pressed by this outer surface. Such an actuator 45 is compact in the radial direction, although not in the axial direction, and is therefore advantageous for making the gear unit 1 compact. In particular, when the operating axis L is oriented in a direction perpendicular to the axes C and X, as in the illustrated example, it is advantageous to make the gear unit 1 compact in the direction of the axes C and X.

[0025] 1, 2, and 3, the housing includes, for example, an outer wall 11, a partition wall 13, and a cover 15. These are detachably coupled to each other to house and support the above-mentioned elements. The cover 15 may also serve as a cover for the power source 3.

[0026] The outer wall 11 is sized to isolate the differential gear set 21 and the countershaft 31 from the outside. The entire wall 11 may be integrally formed, for example by casting, or may be further divided into multiple parts. The outer wall 11 may generally be shaped like two adjacent pots joined to each other, each containing the differential gear set 21 and the countershaft 31, although of course they are spatially connected to each other internally.

[0027] The portion of the side wall of the outer wall 11 corresponding to the bottom of the pot, i.e., the portion corresponding to the countershaft 31, is closed and has an opening in the portion corresponding to the differential gear set 21. The left axle is coupled to the side gear 27L through this opening. A seal member is usually fitted into this opening to create a liquid-tight seal between the axle and the outer wall 11. In addition to the opening, the outer wall 11 may also have several through holes for the purpose of introducing lubricating oil, for example.

[0028] The outer wall 11 also has a cylindrical portion protruding in the direction of arrow F along these pot-shaped portions, and this portion houses and secures the actuator 45. As best shown in FIG. 5, the pole 43 is journaled on the outer wall 11 adjacent to this portion. The portion housing the actuator 45 can be located very close to the side wall. As shown in FIG. 2, its side surface is generally flush with the side wall in a plan view, and does not protrude beyond the side wall in the direction of arrow L. This is advantageous for limiting the dimensions of the gear unit 1 in the directions of axes C and X. On the other hand, the portion may protrude to some extent in the direction of arrow F, and a motor 47 and a connector 9 for electrically connecting the motor 47 can be disposed in this portion. The connector 9 is exposed to the outside, for example, in the direction of arrow R. This arrangement provides convenient access to the connector 9 from the outside and facilitates the task of connecting the connector 9 to a harness. Furthermore, as can be easily understood from, for example, FIGS. 1 and 4, when used in the illustrated manner, the connector 9 is located at the highest position of the gear unit 1. Such a position is less susceptible to mud and foreign objects kicked up from the ground, and is therefore advantageous in preventing malfunctions.

[0029] 1, although the parking lock device 7 protrudes forward, the entire gear unit 1 is within the range of the power source 3 when viewed from the side. In particular, when the power source 3 is projected onto a plane perpendicular to the rotation axis X and the counter axis C, the differential gear set 21, counter shaft 31, housing, pole 43, and cam mechanism, excluding the motor 47 and connector 9, are located within the range of the projection. In other words, it is clear that the gear unit 1 is compact at least in the vertical and longitudinal directions.

[0030] Referring to FIG. 4 in combination with FIGS. 1 to 3, the housing preferably includes a partition wall 13, which supports at least the differential gear set 21. For support, the outer wall 11 includes a left bearing 29L, and the partition wall 13 includes a right bearing 29R, each of which is fitted with, for example, a roller bearing, and which rotatably supports a boss portion of the differential gear set 21. To provide a stronger support, the periphery of the partition wall 13 may extend to the periphery of the housing, and its entire periphery may be sandwiched and fixed between the outer wall 11 and the cover 15. The countershaft 31 may also be supported by the partition wall 13, but it may also be supported by the cover 15 instead of the partition wall 13. In either case, the countershaft 31 extends beyond the partition wall 13 into the space 59 enclosed by the partition wall 13 and the cover 15, where it is coupled with the first gear 33 and meshes with the output shaft 5.

[0031] The partition wall 13 is coupled to the outer wall 11 to enclose a chamber 57. The differential gear set 21, the second gear 35, the parking gear 37, and the pawl 43 are housed within the chamber 57. The first gear 33 is located outside the chamber 57, in a space 59 enclosed by the partition wall 13 and the cover 15. The space 59 is not isolated from the chamber 57, and the partition wall 13 has an opening 41 therethrough to at least allow fluid communication between the two. The opening 41 allows the passage of lubricating oil; for example, lubricating oil splashed up by the first gear 33 passes through the opening 41 and reaches each element of the gear unit 1. The opening 41 may also be sized to allow the parking gear 37 to pass through. As will be described later, this is advantageous for assembling the gear unit 1.

[0032] The cover 15 contacts the right end of the partition wall 13 and is coupled to the outer wall 11 with the partition wall 13 sandwiched between them. The cover 15 has an opening through which the output shaft 5 is pulled out, but the portion corresponding to the countershaft 31 is closed, thereby effectively isolating the interior of the gear unit 1 from the power source 3. A seal member may be provided around the output shaft 5, making the interior of the gear unit 1 liquid-tight from the power source 3. This helps to separate the lubricating oil for the gear unit 1 from the lubricating oil for the power source 3. A bearing 39R may be formed in the cover 15 at a portion corresponding to the countershaft 31. The outer wall 11 may be provided with a corresponding bearing 39L, which supports both ends of the countershaft 31. Needless to say, a ball bearing or the like may be provided between the bearings 39R and 39L and the countershaft 31. Furthermore, the hub portions of the parking gear 37 and the first gear 33 may be abutted against the inner races of the respective ball bearings to support them in the axial direction.

[0033] The bearing structure described above allows the counter shaft C, the rotation shaft X, and the operating shaft L to assume a specific positional relationship. As can be seen from FIGS. 2 and 3, the parking lock device 7 can be disposed near the side wall of the housing, avoiding the relatively large-diameter first gear 33 and the differential gear set 21. In this case, as can be seen from FIG. 5, for example, the operating shaft L of the actuator 45 is located very close to the counter shaft C. This helps to reduce the dimensions of the gear unit 1, particularly in the height direction. To further reduce the height direction, the counter shaft C may be offset downward with respect to the rotation shaft X. Referring mainly to FIGS. 4 and 5, considering a reference plane S including the rotation shaft X (a horizontal plane when the gear unit 1 is used in the illustrated mode), the counter shaft C may have an offset O1 with respect to this reference plane S. Then, the offset O2 of the operating shaft L with respect to the reference plane S (the offset O1 and the offset O2 are in opposite directions with respect to the reference plane S) can be reduced by the amount of the offset O1. This lowers the position of the actuator 45, thereby helping to reduce the height of the gear unit 1. Furthermore, by having the offset O1, the first gear 33 is the lowest of all the rotating elements, and its outer periphery sweeps the lowest point inside the housing, which is advantageous for splashing up and circulating all of the lubricating oil inside the housing.

[0034] The assembly process of the gear unit 1 is, for example, as follows.

[0035] First, the first gear 33 and parking gear 37 are coupled to the countershaft 31, which includes the second gear 35. The assembled countershaft 31 is passed through the opening 41 and combined with the partition wall 13. In parallel, the differential gear set 21 is assembled and fitted into the bearing 29R of the partition wall 13 together with a roller bearing. By moving the entire countershaft 31 slightly sideways, the second gear 35 meshes with the gear teeth 25 of the differential gear set 21.

[0036] In parallel, each component of the actuator 45 is successively assembled into the outer wall 11. The pole 43, together with the return spring, is also assembled inside the outer wall 11. These are then combined together into the above-mentioned assembly.

[0037] The cover 15 is connected to these assemblies, and then the output shaft 5 is connected. The first gear 33 is a helical gear, so it is twisted as it meshes with the output shaft 5. At this stage, all of the gears in the gear unit 1 are meshed, so the first gear 33 can be rotated by rotating any of the gear elements. For example, by inserting a collet jig into the left side gear 27L and turning it slightly, the first gear 33 can be rotated, and therefore the output shaft 5 can be meshed with it.

[0038] Although several embodiments have been described, modifications or variations of the embodiments can be made based on the above disclosure. [Industrial Applicability]

[0039] A compact gear unit is provided while incorporating a park lock mechanism. [Explanation of symbols]

[0040] 1 gear unit 3 Power source 5 Output shaft 5T cavity 7 Park lock device 9 Connectors 11 Exterior Wall 13 Bulkhead 15 Cover 21 Differential gear set 23 Differential case 25 gear teeth 27R, 27L side gear 29R, 29L, 39R, 39L bearings 31 Countershaft 33 First Gear 35 Second Gear 37 Parking Gear 41 Aperture 43 Paul 45 Actuator 47 Motor 49 Spindle 51 Spindle nut 53 Corn 55 Spring Room 57 59 Space C Counter shaft L Actuation axis X rotation axis S reference plane O1, O2 offset

Claims

1. A gear unit used in combination with a power source having a hollow output shaft, a differential gear set that shares a rotation axis with the output shaft; a counter shaft fixedly provided with a first gear meshing with the output shaft and a second gear meshing with the differential gear set, the first gear and the second gear constituting a reduction gear set; a housing having an outer wall that separates the differential gear set and the countershaft from the outside; a parking gear disposed on the axially opposite side of the first gear with respect to the second gear and fixed to the counter shaft; A gear unit equipped with

2. a parking lock device including a pole pivotally supported on the outer wall and engageable with the parking gear, and an actuator that swings the pole to disengageably engage with the parking gear, The gear unit of claim 1 further comprising:

3. The gear unit of claim 2 , wherein the pawl is disposed between the second gear and the outer wall.

4. The gear unit of claim 2 , wherein the pawl is disposed between the actuator and the parking gear.

5. 3. The gear unit according to claim 2, wherein the actuator comprises a motor that generates rotation and a cam mechanism that converts the rotation into linear motion for swinging the pole, the motor protruding from the outer wall.

6. The gear unit of claim 1 , wherein the second gear and the parking gear are disposed within the same chamber in the housing.

7. 7. The gear unit of claim 6, wherein the housing further comprises a partition wall detachably coupled to the outer wall to enclose the chamber, the partition wall comprising bearings for rotatably supporting the differential gear set.

8. The gear unit of claim 7 , wherein the partition has an opening through which the parking gear can pass.

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