Transmission manufacturing method

Abstract

To provide a transmission for a traveling vehicle, which enables a cam pin of a shifter to smoothly move in a guide groove of a shift drum.SOLUTION: A transmission is equipped with a shift drum 9 that is rotated according to operation of a shift operation tool 19, and is provided with a guide groove 90 bending in a circumferential direction of a surface of a drum, and a gear type transmission device 30 that has a cam pin 69a inserted in the guide groove, and whose shift stages are switched by shifters S1 and S2 moving by copying motion of the cam pin 69a due to rotations of the shift drum 9. An inside inner wall of a bending part of the guide groove 90 is formed by first end mill mechanical machining along an extending direction of the guide groove 90, and second end mill mechanical machining along an extending direction of the guide groove 90 expanding an inside inner wall curvature radius of the inside inner wall formed by the first end mill mechanical machining.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a transmission that switches gear stages using a shift drum.

Background Art

[0002] In the transmission disclosed in Patent Document 1, a shift drum is provided that is externally fitted to an operation shaft that rotates in conjunction with the operation of an operating tool for shifting. A linking pin (cam pin) of a shifter is inserted into a guide groove (guide groove) provided in the boss portion of the shift drum. When switching gear stages, the shifter is displaced by the rotation of the shift drum, and as a result, the gear stage is switched. The cam hole extends while bending into a shape suitable for switching gear stages. In the transmission disclosed in Patent Document 2, a moving member (an integrated member of a shift drum and a shift fork) is provided that is externally fitted so as to be movable along an operation shaft that rotates in conjunction with the operation of an operating tool for shifting. Since a linking pin (cam pin) inserted into a cam hole (guide groove) provided in the boss portion of the moving member is fixed to the operation shaft, when switching gear stages, the moving member moves by the rotation of the operation shaft, and as a result, the gear stage is switched. The cam hole of Patent Document 2 also extends while bending into a shape suitable for switching gear stages, similar to the guide groove of Patent Document 1.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] The guide grooves formed on the surface of the shifter's cam pin shift drum are formed to a constant width by circumferential machining strokes of an end mill. In gear shifting control, quicker shifting is achieved by making the shifter move quickly, but to achieve this, the bending angle of the guide groove's bends must be tight. When the bending angle of the bends is tight, when the cam pin is tilted relative to the guide groove, a locking condition occurs between the contact point between the cam pin and the inner and outer circumferential walls of the guide groove and the shifter's shifting point, resulting in a malfunction in the gear shifting operation.

[0005] In view of the above circumstances, the object of the present invention is to provide a transmission for a vehicle in which the cam pin of the shifter can move smoothly through the guide groove of the shift drum. [Means for solving the problem]

[0006] The transmission for a vehicle according to the present invention comprises a gear shifting device, a shift drum that rotates based on the operation of the gear shifting device and has a guide groove formed on its surface that is curved in the circumferential direction, a shifter having a cam pin inserted into the guide groove and moving by the tracking action of the cam pin due to the rotation of the shift drum, and a gear-type transmission device in which the gear stage is switched by the movement of the shifter. The aforementioned guide groove However, it includes an inner wall projection portion that indicates the minimum inner wall curvature radius at the bent portion of the guide groove, a flattened inner wall projection portion that is flattened by continuous end mill chamfering of the inner wall projection portion and the inner wall adjacent portion adjacent to the inner wall projection portion, and an outer inner wall portion that faces the flattened inner wall projection portion, wherein the ratio of the outer inner wall portion to the outer inner wall curvature radius is 2 to 1.5. moreover, According to the present invention, A method for manufacturing a transmission for a vehicle, comprising: a gear shifting device; a shift drum that rotates based on the operation of the gear shifting device and has a guide groove formed thereon that is curved along the circumferential direction of the drum surface; a shifter having a cam pin inserted into the guide groove and moving by the tracking motion of the cam pin due to the rotation of the shift drum; and a gear-type transmission that switches gears by the movement of the shifter, is described as follows: The process includes a first end mill machining step along the extension direction of the guide groove for forming the inner wall of the bent portion of the guide groove, and a second end mill machining step along the extension direction of the guide groove for increasing the radius of curvature of the inner wall formed by the first end mill machining step. In this case, it is preferable that the ratio of the radius of curvature of the outer inner wall of the bent portion to the radius of curvature of the inner wall of the inner wall is 2 or less.

[0007] With this configuration, the radius of curvature of the inner inner wall, which indicates the degree of curvature of the inner inner wall in the bent portion (inflection portion) of the guide groove where a locking condition is likely to occur between the cam pin and the inner and outer circumferential walls of the guide groove and the shifter's shifting point, is increased, thus avoiding the locking condition. As a result, it becomes possible to optimize the movement of the shifter in the gear shifting control, achieving smooth gear shifting.

[0008] An appropriate ratio between the radius of curvature of the outer inner wall and the radius of curvature of the inner inner wall of the bent portion has been experimentally determined. In other words, the ratio between the radius of curvature of the outer inner wall of the bent portion and the radius of curvature of the inner inner wall of the bent portion is 2 or less, preferably 1.9 or less. For example, if the radius of curvature of the outer inner wall is 11 mm, the radius of curvature of the inner wall should be set to 5.5 to 7 mm, preferably 6 mm. In other words, the ratio between the radius of curvature of the outer inner wall and the radius of curvature of the inner inner wall of the bent portion should be set to approximately 2 to 1.5. Thus, in a preferred embodiment of the present invention, the ratio between the radius of curvature of the outer inner wall of the bent portion and the radius of curvature of the inner inner wall of the bent portion is 1.9 or less. [Brief explanation of the drawing]

[0009] [Figure 1] This is an overall side view of the multi-purpose vehicle. [Figure 2] This is a schematic diagram showing a plan view of the powertrain of a multi-purpose vehicle. [Figure 3] This is a plan view showing a gear-type transmission. [Figure 4] This is a plan view of the shifter and shift drum. [Figure 5] This is a plan view of the shift drum. [Figure 6] This is an unfolded view of the guide groove formed on the surface of the shift drum. [Modes for carrying out the invention]

[0010] In this specification, unless otherwise specified, "front" refers to the forward direction of the aircraft in the longitudinal direction (direction of travel), and "rear" refers to the rear direction of the aircraft in the longitudinal direction (direction of travel). Also, the left-right direction or lateral direction refers to the transverse direction of the aircraft (aircraft width direction) perpendicular to the longitudinal direction of the aircraft. "Up" or "down" refers to the positional relationship of the aircraft in the vertical direction (vertical direction), indicating the positional relationship based on the ground height.

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The multi-purpose vehicle shown in Figure 1 (an example of a "driving vehicle") is configured to be usable for a variety of purposes, such as transporting goods and recreation. The multi-purpose vehicle is equipped with a pair of left and right front wheels 11 as a driveable and steerable running device, and a pair of left and right rear wheels 12 as a driveable running device. In other words, the running body of the multi-purpose vehicle is configured to be able to move using the pair of left and right front wheels 11 and the pair of left and right rear wheels 12. In the center of the running body is a driver's compartment 13 where the operator sits and operates the vehicle. At the rear of the running body is a cargo bed 14 on which goods can be loaded. Below the cargo bed 14 on the running body is a drive unit 15.

[0012] The driver's unit 13 is protected by a frame-shaped lops frame 16. The driver's unit 13 is equipped with a driver's seat 17 in which the operator sits. The driver's unit 13 is also equipped with a steering handle 18 for steering the left and right front wheels 11, a gear shift lever 19 for shifting gears, an accelerator pedal 20 for changing the driving speed, a brake pedal 21 for braking the vehicle, a parking lever 22 for operating the parking brake, and the like. The drive unit 15 is equipped with a water-cooled gasoline engine (an example of an "engine"; hereinafter abbreviated as engine 23).

[0013] Figure 2 shows the powertrain of this multi-purpose vehicle. The powertrain includes an engine 23, a belt-type continuously variable transmission 29, and a non-synchronized transmission 24. Power from the engine 23 is shifted by the belt-type continuously variable transmission 29 and the transmission 24 and transmitted to the running gear.

[0014] As shown in Figure 2, the engine 23 is positioned with its crankshaft facing sideways to the machine. The engine 23 is equipped with a main output shaft 25 integrated with the crankshaft and a secondary output shaft 26 integrated with the crankshaft. The output of the main output shaft 25 is input to a belt-type continuously variable transmission mechanism 29. The output of the secondary output shaft 26 drives a generator 28, which consists of an alternator and the like.

[0015] The transmission 24 that inputs the output of the belt-type continuously variable transmission mechanism 29 includes a gear-type transmission 30, a rear-wheel differential mechanism 31 capable of creating a speed difference between the left and right rear wheels 12, a front-wheel differential mechanism 32 capable of creating a speed difference between the left and right front wheels 11, an intermediate transmission device 34 that transmits the output from the gear-type transmission 30 to the rear-wheel differential mechanism 31 and the front-wheel differential mechanism 32, and the like.

[0016] The belt-type continuously variable transmission mechanism 29 includes a drive pulley 37 attached to a drive shaft 36 that can be interlockingly connected to the main output shaft 25 of the engine 23 via a centrifugal clutch, a driven pulley 38 positioned behind the drive pulley 37, and an endless belt 39 wound around the drive pulley 37 and the driven pulley 38.

[0017] The belt-type continuously variable transmission mechanism 29 is configured such that the winding diameters of the drive pulley 37 and the driven pulley 38 change according to the rotational speed of the engine 23, thereby enabling the power of the engine 23 to be continuously variable and output to the gear-type transmission 30.

[0018] The gear-type transmission 30 inputs the power of the belt-type continuously variable transmission mechanism 29 from an input shaft 40 that rotates integrally with the driven pulley 38, shifts the power input from the input shaft 40, and can output it to a final gear 41 interlockingly connected to the rear-wheel 12 side and a power take-off shaft 42 that can be interlockingly connected to the front-wheel 11 side.

[0019] The rear-wheel differential mechanism 31 outputs the power input from the final gear 4 to the left and right rear wheels 12 via rear-wheel drive shafts 43 extending along the left-right direction of the vehicle body.

[0020] The left and right front wheels 11 and the left and right rear wheels 12 are each provided with a brake device 50 composed of a disc brake mechanism. Each brake device 50 is interlockingly connected to a brake pedal 21 (see FIG. 1) via a master cylinder (not shown).

[0021] As shown in Figures 2 and 3, the gear-type transmission 30 is equipped with an input shaft 40, a transmission shaft 51, a relay shaft 52, and a transmission shaft 53 as shafts for transmitting power. The input shaft 40, the transmission shaft 51, the relay shaft 52, and the transmission shaft 53 are rotatably supported within the transmission case 33.

[0022] The input shaft 40 is fixedly supported so that the forward first-speed drive gear 55 of the forward first-speed gear mechanism 54, the forward second-speed drive gear 57 of the forward second-speed gear mechanism 56, and the reverse drive gear 59 of the reverse gear mechanism 58 rotate integrally with the input shaft 40.

[0023] As shown in Figure 3, the transmission shaft 51 supports the forward first-speed driven gear 60, which constitutes the gear shift of the forward first-speed gear mechanism 54, the forward second-speed driven gear 61, which constitutes the gear shift of the forward second-speed gear mechanism 56, and the reverse driven gear 62, which constitutes the gear shift of the reverse gear mechanism 58, in a manner that allows them to rotate relative to each other. The forward first-speed driven gear 60 is always meshed with the forward first-speed drive gear 55. The forward second-speed driven gear 61 is always meshed with the forward second-speed drive gear 57. The reverse driven gear 62 is always meshed with the reverse drive gear 59 via the reverse gear 63 (see Figure 2).

[0024] A cylindrical first boss member 64 is fixedly supported on the transmission shaft 51 between the forward first-speed driven gear 60 and the reverse driven gear 62, so as to rotate integrally with the transmission shaft 51. A first transmission gear 65 is fixedly supported on the transmission shaft 51 so as to rotate integrally with the transmission shaft 51. A cylindrical second boss member 66 is fixedly supported on the transmission shaft 51 between the first transmission gear 65 and the forward second-speed driven gear 61, so as to rotate integrally with the transmission shaft 51.

[0025] The outer circumference of the first boss member 64 is provided with a first constant-meshing spline 67 having multiple external teeth in the circumferential direction. The outer circumference of the second boss member 66 is provided with a second constant-meshing spline 68 having multiple external teeth in the circumferential direction.

[0026] Multiple (for example, three) spline mechanisms 70 are provided on the gear shift shaft 51. A spline mechanism 70 is provided for each gear mechanism 54, 56, and 58. Each spline mechanism 70 is provided with an outer spline 71 and an inner spline 72 that can mesh with the outer spline 71.

[0027] A shifter consisting of shift sleeves 73 and 74 and shift forks 69 and 75 is used to switch the gear ratio of the gear-type transmission 30. The fork portions 69b and 75b of the shift forks 69 and 75 are sandwiched in central grooves 73a and 74a formed on the circumferential surfaces of the shift sleeves 73 and 74, and are able to move integrally. In this embodiment, two shifters are used, namely a first shifter S1 and a second shifter S2. The first shifter S1 consists of a first shift fork 69 and a first shift sleeve 73, and the second shifter S2 consists of a second shift fork 75 and a second shift sleeve 74.

[0028] Specifically, the spline mechanism 70 of the forward first-speed gear mechanism 54 is equipped with an outer spline 71 of the forward first-speed driven gear 60 and an inner spline 72 on one end of the first shift sleeve 73 that can mesh with the outer spline 71 of the forward first-speed driven gear 60. The spline mechanism 70 of the reverse gear mechanism 58 is equipped with an outer spline 71 of the reverse driven gear 62 and an inner spline 72 on the other end of the first shift sleeve 73 that can mesh with the outer spline 71 of the reverse driven gear 62. The spline mechanism 70 of the forward second-speed gear mechanism 56 is equipped with an outer spline 71 of the forward second-speed driven gear 61 and an inner spline 72 on one end of the second shift sleeve 74 that can mesh with the outer spline 71 of the forward second-speed driven gear 61.

[0029] The first constant-engagement spline 67 of the first boss member 64 is constantly engaged with the inner spline 72 of the first shift sleeve 73. The first shift sleeve 73 is slidable along the axial direction X of the gear shift shaft 51 by a first shift fork 69 which is linked to the gear shift operating device 19. This allows the inner spline 72 of the first shift sleeve 73 to engage with the outer spline 71 of the forward first-speed driven gear 60 or the outer spline 71 of the reverse driven gear 62.

[0030] The inner spline 72 of the second shift sleeve 74 is constantly engaged with the second constant-engagement spline 68 of the second boss member 66. The second shift sleeve 74 is slidable along the axial direction X of the gear shift shaft 51 by a second shift fork 75 which is linked to the gear shift operating device 19. This allows the inner spline 72 of the second shift sleeve 74 to engage with the outer spline 71 of the forward second-speed driven gear 61.

[0031] The relay shaft 52 is fixedly supported so that the first driven gear 76, which is always meshed with the first transmission gear 65, and the second transmission gear 77 rotate together with the relay shaft 52.

[0032] As shown in Figure 4, the first shift fork 69 and the second shift fork 75 are fitted onto a common sliding shaft 78. The first shift fork 69 and the second shift fork 75 are supported so as to be slidable along the axial direction X by the sliding shaft 78 and the gear shift shaft 51. The gear of the gear-type transmission 30 is switched by the movement of the first shift fork 69 and the second shift fork 75 along the axial direction X based on the operation of the gear shifting device 19.

[0033] Figure 4 shows a shift drum 9 that moves the first shifter S1 and the second shifter S2. The shift drum 9 has shaft portions 9a at both ends and is supported by the transmission case 33 so as to be rotatable around the pivot axis PR. The shift drum 9 is linked to the gear shifting device 19 via a linkage mechanism 79 and rotates in response to the operation of the gear shifting device 19, thereby switching the gear of the gear-type transmission 30.

[0034] As shown in Figure 5, the shift drum 9 is a cylindrical body, and two guide grooves 90, namely a first guide groove 91 and a second guide groove 92, are formed on its surface along the circumferential direction. The cam pin 69a of the first shift fork 69 is inserted into the first guide groove 91, and the cam pin 75a of the second shift fork 75 is inserted into the second guide groove 92.

[0035] Figure 6 is an unfolded view of the guide groove 90. The guide groove 90 extends circumferentially while being displaced from side to side in the direction of the rotation axis PR, and as a result forms a bent line. Due to the shape of the bent portion BP, the shifters (first shifter S1 and second shifter S2) move along the axial direction X. In other words, the position of the shifters is determined by the rotation angle of the shift drum 9, and the gear shift is performed.

[0036] The guide groove 90 is formed by machining using an end mill. In end mill machining, relative feed is performed between the end mill and the shift drum 9 along the extension direction of the virtual guide groove to be formed. In the machining that forms this guide groove 90, an end mill having a diameter that matches the width of the guide groove 90 is used, and the bent guide groove 90 is formed by a combination of the lateral feed of the end mill and the rotation of the shift drum 9. In this end mill machining (first end mill machining), in the bent portion of the bent section BP (the portion around the bending point), the machining trajectory of the inner part of the end mill, which is closer to the bending center, is shorter than the machining trajectory of the outer part of the end mill, which is further from the bending center. In other words, the outer part of the end mill makes a wide turn, while the inner part of the end mill makes a narrow turn, so the trajectory inside the bending center (the radius of curvature of the inner inner wall, which is the peripheral wall on the bending center side, shown as "r1" in Figure 6) is smaller than the radius of curvature of the outer inner wall (shown as "r2" in Figure 6). Therefore, in this state, this inner wall becomes a protrusion in the guide groove 90, preventing the smooth passage of the cam pins 69a and 75a through the guide groove 90. This causes the shifter to lock up between the contact points between the cam pins 69a and 75a and the outer peripheral wall of the bent portion BP, the contact points between the cam pins 69a and 75a and the inner peripheral wall of the bent portion BP, and the contact points between the fork portions 69b and 75b of the shift forks 69 and 75 and the peripheral walls of the central grooves 73a and 74a of the shift sleeves 73 and 74.

[0037] To resolve this issue, additional end mill machining (second end mill machining) is performed on at least the bent portion of the bent section BP so that the radius of curvature of the inner wall approaches the radius of curvature of the outer wall. This additional second end mill machining makes the ratio of the radius of curvature of the outer wall of the bent section to the radius of curvature of the inner wall of the bent section approximately 2 or less, preferably 1.9 to 1.5. For example, if the radius of curvature of the outer wall is 11 mm, the radius of curvature of the inner wall is set to 5.5 to 7 mm, preferably 6 mm.

[0038] Next, the gear shifting will be explained in detail with reference to Figures 3 and 4. When the gear shifting device 19 is operated to the forward first gear position, the shift drum 9 rotates, and the first shift sleeve 73 is slid toward the forward first gear driven gear 60 by the first shift fork 69, and the forward first gear driven gear 60 and the first boss member 64 (gear shift shaft 51) are linked together by the first shift sleeve 73. At this time, the second shift sleeve 74 is not linked together with the forward second gear driven gear 61. As a result, the gear-type transmission 30 is in a state where it outputs forward first gear power. In this state, when the accelerator pedal 20 is pressed down, the vehicle is driven in forward first gear.

[0039] When the gear shifting device 19 is operated to the forward second gear position, the shift drum 9 rotates, and the second shift sleeve 74 slides toward the forward second gear driven gear 61 by the second shift fork 75. The second shift sleeve 74 then connects the forward second gear driven gear 61 and the second boss member 66 (gear shift shaft 51) in conjunction. At this time, the first shift sleeve 73 is not connected to the forward first gear driven gear 60 or the reverse gear driven gear 62. As a result, the gear-type transmission 30 is in a state where it can output forward second gear power. In this state, when the accelerator pedal 20 is pressed, the vehicle is driven in forward second gear.

[0040] When the gear shifting device 19 is operated to the reverse position, the shift drum 9 rotates, and the first shift sleeve 73 slides toward the reverse driven gear 62 by the first shift fork 69. The first shift sleeve 73 then connects the reverse driven gear 62 to the first boss member 64 (gear shift shaft 51). At this time, the second shift sleeve 74 is not connected to the forward second gear driven gear 61. As a result, the transmission 24 outputs reverse power. In this state, when the accelerator pedal 20 is pressed, the vehicle moves in reverse.

[0041] [Another embodiment] (1) In the above-described embodiment, the gear shifting device 19 and the shift drum 9 of the gear-type transmission 30 were mechanically connected by a linkage mechanism 79 such as a link mechanism and capable of transmitting the operating displacement, but it is also possible to use a drive-by-wire system. When a drive-by-wire system is used, a drive signal is sent to the actuator of the shift drum 9 based on a detection signal from an operation detector that detects the amount of operation of the gear shifting device 19, causing the shift drum 9 to rotate and the gear to be switched.

[0042] (2) In the above-described embodiment, the shifter was configured such that the shift forks 69 and 75 were engaged and connected to the central grooves 73a and 74a of the shift sleeves 73 and 74, but the configuration is not limited to this. For example, the shift sleeves 73 and 74 and the shift forks 69 and 75 may be integrally formed. Furthermore, the shifter may be a further divided component.

[0043] (3) In the embodiment described above, a belt-type continuously variable transmission mechanism 29 was provided, but a hydraulic continuously variable transmission mechanism may be used, or the continuously variable transmission mechanism may be omitted and a simple main clutch mechanism may be used.

[0044] (4) In the embodiment described above, the running gear consisted of a pair of left and right front wheels 11 and a pair of left and right rear wheels 12, but it may also be configured as a three-wheeled or two-wheeled type. [Industrial applicability]

[0045] The present invention is applicable to a vehicle equipped with a gear-type transmission that switches gears using a shift drum. [Explanation of symbols]

[0046] 9: Shift drum 9a:Shaft part 19: Gear shifter 29: Belt-type continuously variable transmission 30: Gear-type transmission 51: Gear shift shaft 52: Relay axis 53: Transmission shaft 54: Forward single-speed gear mechanism (gear shift) 56: Forward two-speed gear mechanism (gear shift) 58: Reverse gear mechanism (gear shift) 69: First shift fork (shift fork) 69a: Cam pin 69b: Fork section 79: Interlocking Mechanism 90: Guide groove 91: First guide groove 92: Second guide groove BP: Bent part PR: Rotating axis S1: First Shifter S2: Second Shifter X: Axial direction

Claims

1. Gear shifting mechanism, A shift drum that rotates in response to the operation of the aforementioned gear shifting device and has a guide groove formed along the circumferential direction of the drum surface, A shifter having a cam pin inserted into the guide groove, and moving by the tracking motion of the cam pin due to the rotation of the shift drum, A method for manufacturing a transmission for a vehicle, comprising a gear-type transmission in which the gear position is switched by the movement of the shifter, A first end mill machining step along the extension direction of the guide groove to form the inner and outer inner walls of the bent portion of the guide groove, The device comprises a second end mill machining step along the extension direction of the guide groove for increasing the radius of curvature of the inner wall formed by the first end mill machining step, The first end mill machining step and the second end mill machining step are performed using relative feed between the end mill and the shift drum. A method for manufacturing a transmission, wherein in the second end mill machining step, the inner inner wall radius is brought close to the outer inner wall radius such that the ratio of the outer inner wall radius of curvature to the inner inner wall radius of curvature of the inner inner wall is 2 or less.

2. The method for manufacturing a transmission according to claim 1, wherein the ratio of the radius of curvature of the outer inner wall to the radius of curvature of the inner inner wall is 2 to 1.5.

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