Differential drive device and friction clutch

Abstract

To provide a differential drive device and a friction clutch capable of improving energy transmission efficiency.SOLUTION: A differential drive device comprises: a pair of rotors 21, 23 having a circumferential toothed part 21a, 23a with a different number of teeth, and supported to allow differential rotation and expansion of an axial distance between the rotors; a pair of gears 25, 27 with a different number of teeth, respectively meshing with the toothed parts 21a, 23a of the pair of rotors 21, 23, and supported to rotate integrally; and a drive unit 29 that expands the axial distance between the pair of rotors 21, 23 by the differential rotation of the pair of rotors, which can further improve energy transmission efficiency.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a gear-based differential drive and a friction clutch. [Background technology]

[0002] A differential drive actuator described in Patent Document 1 is a conventional differential drive device.

[0003] The differential drive actuator includes a first circular member having a first plurality of teeth and a second circular member disposed adjacent to the first circular member and having a second plurality of teeth that differs in number from the first plurality of teeth. The circular members are commonly driven by a pinion gear. The different numbers of teeth on the two circular members cause them to rotate at slightly different speeds. The circular members may also have complementary cam surfaces, cam recesses and balls, cams and cam followers, or threaded members that cause the circular members to translate axially or separate at different rotational speeds.

[0004] The axial translation of such a circular member can be used to actuate or move valves, dampers, plates, clutches, steering mechanisms, shutters, and a wide variety of other devices controlled or regulated by linear motion.

[0005] However, in such a differential drive actuator, the efficiency of energy transmission between the pinion gear and the circular member is low, and there is a limit to how small the electric motor that drives the pinion gear can be made. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-29586 Summary of the Invention [Problem to be solved by the invention]

[0007] The problem to be solved was the low efficiency of energy transmission. [Means for solving the problem]

[0008] The present invention comprises a pair of rotating bodies having toothed portions with different numbers of teeth arranged around them and supported so as to be able to rotate differentially and to expand the axial distance between them, a pair of gears with different numbers of teeth that are supported so as to be able to mesh with each of the toothed portions of the pair of rotating bodies and rotate together, and a drive unit that expands the axial distance between the pair of rotating bodies by the differential rotation of the pair of rotating bodies. [Effects of the Invention]

[0009] The present invention can increase the efficiency of energy transmission. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view of a friction clutch using a differential drive device according to an embodiment. [Figure 2] FIG. 2 is a simplified skeleton diagram of a differential drive device according to an embodiment for comparison. [Figure 3] FIG. 3 is a skeleton diagram of a differential drive device according to a comparative example. [Figure 4] FIG. 4 is a skeleton diagram of a differential drive device according to another comparative example. [Figure 5] Figure 5 is a chart comparing reduction ratios, etc. [Figure 6] FIG. 6 is a graph showing the relationship between the reduction ratio and the efficiency. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention achieves the object of enabling further improvement in energy transmission efficiency as follows.

[0012] The differential drive device of the present invention comprises a pair of rotating bodies having toothed portions with different numbers of teeth arranged around them and supported so as to be able to rotate differentially and to expand the axial distance between them, a pair of gears with different numbers of teeth that are supported so as to be able to mesh with each of the toothed portions of the pair of rotating bodies and rotate together, and a drive unit that expands the axial distance between the pair of rotating bodies by the differential rotation of the pair of rotating bodies.

[0013] The differential drive device is applied to a friction clutch, but can also be applied to actuate or move a wide variety of devices that are controlled or adjusted by linear motion, such as valves, dampers, plates, clutches, steering mechanisms, shutters, and the like, which are operated by expanding the axial distance between a pair of rotating bodies.

[0014] The pair of gears are idler gears, but can also be configured as pinion gears. The pair of gears are separate and fixed together, but can also be one piece.

[0015] The drive unit includes an electric motor that drives the pair of gears.

[0016] The electric motor includes a pinion gear that meshes with and interlocks the pair of gears.

[0017] The electric motor is a geared motor.

[0018] The drive unit includes a torque cam that generates a thrust force between the pair of rotors by the differential rotation.

[0019] The drive unit may be any unit capable of generating a thrust force, and may be a facing cam, a screw mechanism, or the like, instead of a torque cam.

[0020] The friction clutch uses the differential drive device and includes a friction member that is fastened by increasing the axial distance between the pair of rotors.

[0021] The friction member is made up of a friction plate, but it may be made up of any fastening member such as a cone clutch. [Example]

[0022] [Friction clutch] FIG. 1 is a cross-sectional view of a friction clutch using a differential drive device according to an embodiment.

[0023] As shown in Figure 1, friction clutch 1 is configured to set torque transmission between engine crankshaft 3 and transmission main shaft 5 by adjusting the engagement of friction members 7. This friction clutch 1 uses a differential drive device 8, which is configured to adjust the engagement of friction members 7.

[0024] First, the entire structure including the friction member 7 will be described.

[0025] The friction member 7 has a configuration in which inner plates and outer plates are arranged alternately in the axial direction, and the outer plates engage with the clutch housing 9 in the rotational direction, and the inner plates engage with the hub 11 in the rotational direction.

[0026] The clutch housing 9 is fixed to a flywheel 13 of the crankshaft 3, and the hub 11 is spline-engaged with the main shaft 5.

[0027] Therefore, the torque generated by the friction member 7 is transmitted from the crankshaft 3 to the main shaft 5.

[0028] A reaction force portion 9a is integrally provided with the clutch housing 9. The reaction force portion 9a is set at an end of the clutch housing 9 facing radially inward, and is positioned on one side of the friction member 7 in the axial direction.

[0029] A sleeve 15 is fitted onto the inner periphery of the reaction force portion 9a of the clutch housing 9. The sleeve 15 is loosely fitted onto the main shaft 5, and is integrally provided with a pressing portion 15a at one end, and has a stopper portion 17 fixed to the other end. The pressing portion 15a is arranged opposite to and in contact with the friction member 7, and a disc spring 19 is interposed between the pressing portion 15a and the reaction force portion 9a.

[0030] Therefore, the pressing portion 15a is biased against the reaction portion 9a by the set resilient force of the disc spring 19, and the friction member 7 is fastened.

[0031] The differential drive device 8 of the friction clutch 1 is configured to adjust the fastening force of the friction clutch 1. The differential drive device 8 includes a pair of rotating bodies 21, 23, a pair of idler gears 25, 27, and a drive unit 29. The drive unit 29 is configured to increase the axial distance between the pair of rotating bodies 21, 23 by differential rotation of the pair of rotating bodies 21, 23, and includes an electric motor 31 and a torque cam 33, and the electric motor 31 includes a pinion gear 35.

[0032] The pair of rotors 21, 23 have toothed portions 21a, 23a with different numbers of teeth arranged around their outer peripheries, and are supported to allow differential rotation and an expandable axial distance. The difference in the number of teeth between the toothed portions 21a, 23a is 1 to 3. It is difficult, according to common technical knowledge, for the difference in the number of teeth between the toothed portions 21a, 23a to exceed 3. The pair of rotors 21, 23 are configured so that their inner peripheries fit into the outer periphery of the sleeve 15, allowing for differential rotation and an expandable axial distance.

[0033] The torque cam 33 is provided between the pair of rotors 21, 23. The torque cam 33 is configured to generate a thrust force by the differential rotation between the pair of rotors 21, 23. The torque cam 33 is configured such that balls fit into cam grooves formed on the opposing surfaces of the pair of rotors 21, 23. When the pair of rotors 21, 23 rotate differentially, the balls are positioned in shallow portions of the cam grooves, and the distance between the pair of rotors 21, 23 can be expanded in the axial direction.

[0034] A thrust bearing 36 is interposed between one rotating body 21 and the reaction force portion 9a. A thrust bearing 37 is interposed between the other rotating body 23 and the stopper portion 17.

[0035] Therefore, when the distance between the pair of rotating bodies 21, 23 increases, the reaction force from the reaction force portion 9a is transmitted to the stopper portion 17 via the thrust bearing 36, one of the rotating bodies 21, the torque cam 33, the other rotating body 23, and the thrust bearing 37.

[0036] The transmission of this reaction force moves the sleeve 15 in the axial direction, and the pressing portion 15a moves axially toward the reaction portion 9a against the biasing force of the disc spring 19. The degree of axial movement of the pressing portion 15a is adjusted to reduce or eliminate the fastening force of the friction member 7. The degree of axial movement of the pressing portion 15a corresponds to the differential rotation of the pair of rotating bodies 21, 23.

[0037] The idler gears 25, 27 have different numbers of teeth corresponding to the difference in the number of teeth of the toothed portions 21a, 23a of the pair of rotating bodies 21, 23. The idler gears 25, 27 are configured to mesh with the toothed portions 21a, 23a of the pair of rotating bodies 21, 23, respectively. The idler gears 25, 27 are fastened to each other by bolts 39. This fastening allows the idler gears 25, 27 to rotate integrally.

[0038] The inner peripheries of the idler gears 25, 27 are rotatably supported on a fixed shaft 43 by bearings 41. A boss portion 45 that fits loosely on the fixed shaft 43 is formed on the inner periphery of the idler gear 27. The boss portion 45 is rotatably supported on the fixed shaft 43 by a bearing 47 at the end opposite to the bearing 41. A flange 43a at the outer end of the fixed shaft 43 is fastened and fixed to a transmission case 49 by bolts 51.

[0039] The electric motor 31 is configured to drive the pair of idler gears 25, 27. The electric motor 31 is a geared motor, and is provided with a pinion gear 35 on the output shaft 31b of a gearbox 31a. The gearbox 31a is a reduction mechanism using, for example, planetary gears. The pinion gear 35 meshes with the idler gear 25, and meshes and interlocks the pair of idler gears 25, 27.

[0040] [Action and effect] When the electric motor 31 is not energized or is slightly energized to maintain the rotational position, there is no differential rotation between the pair of rotating bodies 21, 23, and the friction member 7 is fastened by the biasing force of the disc spring 19.

[0041] When the electric motor 31 is energized, the rotation at a reduced speed is transmitted from the gear box 31a to the pinion gear 35 via the output shaft 31b.

[0042] The idler gear 25 rotates via the reduced rotation of the pinion gear 35, and the idler gear 27 rotates integrally therewith.

[0043] The integral rotation of these idler gears 25, 27 causes the pair of rotors 21, 23 to rotate in mesh with each other through the teeth 21a, 23a.

[0044] This meshing rotation causes the pair of rotors 21, 23 to rotate differentially in accordance with the difference in the number of teeth, and the fastening force of the friction member 7 is adjusted to be smaller depending on the degree of axial movement of the pressing portion 15a as described above.

[0045] By adjusting the engagement of the friction members 7 by such reduced rotation, the transmission efficiency of the differential drive device 8 can be made relatively high, and as a result, the electric motor 31 can be made smaller.

[0046] Fig. 2 is a simplified skeleton diagram of a differential drive device according to an embodiment for comparison. Fig. 3 is a skeleton diagram of a differential drive device according to a comparative example. Fig. 4 is a skeleton diagram of a differential drive device according to another comparative example. Fig. 5 is a table comparing reduction ratios, etc. Fig. 6 is a graph showing the relationship between reduction ratio and efficiency.

[0047] In the skeleton diagrams of FIGS. 2 to 4, components that are the same as or correspond to those in FIG. 1 are given the same reference numerals, and duplicated explanations will be omitted.

[0048] The differential drive device 8A in Fig. 2 is substantially the same as that in Fig. 1, but in order to compare transmission efficiency, the idler gears 25, 27 in Fig. 1 are omitted and a skeleton diagram is shown of a pair of pinion gears 25A, 27A that mesh with the toothed portions 21a, 23a of the pair of rotating bodies 21, 23. As in the case of the idler gears 25, 27, the pair of pinion gears 25A, 27A mesh with a difference in the number of teeth that corresponds to the difference in the number of teeth of the toothed portions 21a, 23a of the pair of rotating bodies 21, 23, which is one to three.

[0049] In the differential drive device 8B according to the comparative example of Figure 3, the pinion gear 25B that meshes with the toothed portions 21a, 23a of the pair of rotating bodies 21, 23 is single, unlike the differential drive device 8A, and the single pinion gear 25B simultaneously meshes with the toothed portions 21a, 23a of the pair of rotating bodies 21, 23 which have a difference in the number of teeth of one to three.

[0050] The differential drive device 8C according to another comparative example in FIG. 4 uses a general gear reduction mechanism, and corresponds to a device in which the rotor 23 in FIG. 1 is omitted, the pinion gear 25C meshes with the tooth portion 21a of the rotor 21, and a torque cam 33 is interposed between the stopper portion 17 and the rotor 21.

[0051] 1, the differential drive device 8A in Fig. 2 causes differential rotation of the pair of rotors 21, 23 due to rotational input from pinion gears 25A, 27A. This differential rotation operates torque cam 33, expanding the gap between the pair of rotors 21, 23 in the axial direction, and functions in the same way as in Fig. 1.

[0052] 1, the differential drive device 8B in Fig. 3 differs from the differential drive device 8 in Fig. 1 in that the rotational input from the pinion gear 25B causes the pair of rotors 21, 23 to rotate differentially. This differential rotation activates the torque cam 33, which expands the gap between the pair of rotors 21, 23 in the axial direction, thus functioning in the same way.

[0053] 1, the differential drive device 8C in Fig. 4 differs from the differential drive device 8 in Fig. 1 in that the rotational input from the pinion gear 25C causes the rotor 21 to rotate differentially relative to the stopper portion 17. This differential rotation causes the torque cam 33 to operate, expanding the gap between the rotor 21 and the stopper portion 17 in the axial direction, thereby functioning in the same way.

[0054] Although differential drive units 8A, 8B, and 8C all provide reduced differential rotation, when the diameters and numbers of teeth of the rotors 21 are standardized and compared, the relationship shown in Figure 5 is obtained. In other words, the reduction ratio decreases in the order of differential drive units 8B, 8A, and 8C, with differential drive unit 8A having a relatively medium reduction ratio.

[0055] In terms of the size of the differential drive devices 8A, 8B, and 8C, the differential drive device 8C is large in proportion to the reduction ratio, but the differential drive devices 8A and 8B can be made small because they can obtain a large reduction ratio.

[0056] In terms of transmission efficiency, the differential drive devices 8A and 8B function as paradox gear mechanisms, and the relationship between transmission efficiency and reduction ratio is on the curve shown in FIG.

[0057] Both of the differential drive devices 8A and 8B can achieve a large reduction ratio in a small space.

[0058] In the differential drive device 8B, the difference in the number of teeth between the toothed portions 21a, 23a of the pair of rotors 21, 23 is at most three. As a result, the reduction ratio of the differential drive device 8B will not be less than about 50:1. In other words, it will be 80:1, 200:1, etc.

[0059] On the other hand, differential drive device 8A has the same basic structure as differential drive device 8B, and the relationship between transmission efficiency and reduction ratio is on the curve in Figure 6. Furthermore, differential drive device 8A allows for the tooth number difference between toothed portions 21a, 23a of the pair of rotors 21, 23 to be freely set, and the reduction ratio can be set to approximately 50:1 or less. In other words, it can be set to 20:1, for example.

[0060] For example, if the torque required to release the friction member 7 is 50 Nm when applied to the same friction clutch, and if the efficiency of the differential drive device 8B is 100%, then an electric motor capable of outputting 50 ÷ 200 = 0.25 Nm will be sufficient, even if the reduction ratio is 200:1.

[0061] However, as shown in FIG. 6, the efficiency of the differential drive device 8B drops to about 7% when the reduction ratio is 200:1, so an electric motor capable of outputting 0.25 Nm ÷ 0.07 ≒ 3.57 Nm is required.

[0062] In contrast, the differential drive unit 8A can achieve a reduction ratio of, for example, 20:1 by setting the difference in the number of teeth between the toothed portions 21a, 23a of the pair of rotors 21, 23. The efficiency of a reduction ratio of 20:1 is as high as 45%, as shown in Figure 6. If used with a reduction ratio of 20:1, an electric motor capable of outputting 0.25 Nm (0.25 Nm ÷ 0.45 ≒ 0.556 Nm) is sufficient to obtain an output of 0.25 Nm.

[0063] Furthermore, even if the electric motor 31 is a geared motor as in the embodiment and the reduction ratio of the gearbox 31a is set to 10:1 to achieve a reduction ratio of 200:1, the transmission efficiency of the gearbox 31a of this planetary reduction mechanism is 85%. Therefore, to obtain an output of 0.25 Nm, an electric motor that can output 0.25 Nm ÷ 0.45 ÷ 0.85 = 0.653 Nm is sufficient.

[0064] In other words, the differential drive device 8A can use an electric motor 31 with a torque output that is one-fifth or less of that of the differential drive device 8B, and although it is a geared motor, it can use an electric motor 31 that is small and has low energy consumption. [Explanation of symbols]

[0065] 1 Friction clutch 7 Friction materials 8 Differential drive unit 21, 23 Pair of rotating bodies 21a, 23a Teeth 25, 27 Idler gear (pair of gears) 29 Drive unit 31 Electric motor (geared motor) 33 Torque Cam 35 Pinion gear

Claims

1. a pair of rotors having circumferentially arranged toothed portions with different numbers of teeth, and supported so as to be capable of differential rotation and so as to allow an axial distance therebetween to be expanded; a pair of gears with different numbers of teeth that are supported so as to be meshed with the toothed portions of the pair of rotors and rotate together; a drive unit that increases the axial distance between the pair of rotors by differential rotation of the pair of rotors; A differential drive device comprising:

2. 2. The differential drive device of claim 1, The drive unit includes an electric motor that drives the pair of gears. Differential drive.

3. 3. The differential drive device of claim 2, The electric motor includes a pinion gear that meshes with and interlocks the pair of gears. Differential drive.

4. 3. The differential drive device of claim 2, The electric motor is a geared motor. Differential drive.

5. The differential drive device according to any one of claims 1 to 4, the drive unit includes a torque cam that generates a thrust force between the pair of rotors by the differential rotation, Differential drive.

6. A friction clutch using the differential drive device of claim 5, A friction member is provided which is fastened by increasing the axial distance between the pair of rotating bodies. Friction clutch.

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