Speed reducer, vehicle, and electric vehicle

Abstract

To provide a frictional transmission type speed reducer which achieves high torque transmission efficiency, suppresses vibration and noise, and enables speed reduction at a high speed reduction ratio.SOLUTION: A speed reducer includes: a case; a sun roller which has a rotary shaft corresponding with a center axis and rotates around the axis of the rotary shaft relative to the case when rotation is input thereto; a plurality of intermediate rollers each of which has an outer peripheral surface pressed against the outer peripheral surface of the sun roller and rotates when receiving rotation of the sun roller; a plurality of support pins provided at the case and respectively supporting the intermediate rollers; a plurality of outer rollers each of which has an outer peripheral surface pressed against the outer peripheral surface of the intermediate roller and rotates when receiving rotation of the intermediate roller; and an outer ring which has an inner peripheral surface pressed against the outer peripheral surfaces of the outer rollers and rotates when receiving rotation of the outer rollers.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a speed reducer, a vehicle, and an electric vehicle.

Background Art

[0002] In recent years, as the rotation speed of motors for electric vehicles (EVs) has been increasing, the rotation speed of motors has come to be targeted at 50,000 revolutions per minute. In such a case, the speed reducer (drive system) combined with the motor is required to handle higher input rotation speeds, such as a higher reduction ratio than conventional ones.

[0003] As one way to handle such high input rotation speeds, a friction transmission type speed reducer is regarded as promising. In a friction transmission type speed reducer, since there is no gear meshing change, torque fluctuations and noise generation due to tooth impacts are small. Also, since lubrication failure at the gear tooth roots during high rotation does not occur, it is considered advantageous for high rotation.

[0004] For example, Patent Document 1 discloses a friction transmission type continuously variable transmission for vehicles in this way.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] There is a demand for a friction transmission type speed reducer that uses a high-speed motor, has high torque transmission efficiency, suppresses vibration and noise, and can achieve high reduction ratio reduction.

[0007] An object of the present invention is to provide a friction transmission type speed reducer that has high torque transmission efficiency, suppresses vibration and noise, and realizes high reduction ratio reduction.

Means for Solving the Problems

[0008] The speed reducer according to one aspect of the present invention includes a case, a sun roller having a rotation axis that coincides with a central axis and rotating around the axis of the rotation axis with respect to the case when rotation is input, and an outer peripheral surface that is pressed against the outer peripheral surface of the sun roller. A plurality of intermediate rollers that rotate by receiving the rotation of the sun roller, a plurality of support pins provided on the case and respectively supporting the plurality of intermediate rollers, and an outer peripheral surface that is pressed against the outer peripheral surfaces of the plurality of intermediate rollers. It has a plurality of outer rollers that rotate by receiving the rotation of the intermediate rollers, and an outer ring that has an inner peripheral surface pressed against the outer peripheral surface of the outer rollers and rotates by receiving the rotation of the outer rollers.

Effects of the Invention

[0009] According to the present invention, (1) Generate a high pressing load between friction surfaces during torque transmission when rotational torque is transmitted from the motor, (2) Make the pressing load proportional to the torque during torque transmission when rotational torque is transmitted from the motor, (3) Do not generate a speed difference within the friction contact surface during torque transmission when rotational torque is transmitted from the motor, (4) The pressing force of the friction surface is not received by the case during torque transmission when rotational torque is transmitted from the motor are satisfied, and a friction transmission type speed reducer that has high torque transmission efficiency, suppresses vibration and noise, and realizes high reduction ratio reduction can be provided.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

[0011] An electric vehicle 10 according to an embodiment will be described with reference to FIGS. 1 to 5.

[0012] FIG. 1 shows a schematic diagram of a vehicle 10a of the electric vehicle 10 (a vehicle for an electric vehicle) according to the present embodiment.

[0013] As shown in FIG. 1, the vehicle 10a of the electric vehicle 10 includes a battery 12, an inverter 14, a motor 16, and a speed reducer 18 (a speed reducer for an electric vehicle). The battery 12 is used as a DC power source. The inverter 14 converts the DC power source from the battery 12 into an AC power source in order to drive the motor 16 driven by the AC power source. A speed reducer 18 that can be set to an appropriate reduction ratio is connected to the drive shaft of the motor 16. Then, the power reduced to a predetermined reduction ratio by the speed reducer 18 is transmitted to the wheels 22 via the drive shaft 20.

[0014] Note that the vehicle 10a may be rear-wheel drive, front-wheel drive, or all-wheel drive.

[0015] In the electric vehicle 10 shown in FIG. 1, the power decelerated by the speed reducer 18 is transmitted to the wheels 22 using the drive shaft 20. The vehicle 10a of the electric vehicle 10 may adopt a so-called in-wheel motor system in which, for example, the motor 16 and the speed reducer 18 are arranged on each wheel 22, and the wheels are directly driven from the speed reducer 18.

[0016] The speed reducer (roller type speed reducer) 18 according to the present embodiment will be described with reference to FIGS. 2 to 5.

[0017] FIG. 2 is a schematic front view of the speed reducer 18 according to the present embodiment. FIG. 3 is a schematic perspective view of the speed reducer 18 according to the present embodiment. FIG. 4 is a schematic exploded perspective view of the speed reducer 18 according to the present embodiment shown in FIGS. 2 and 3.

[0018] As shown in FIGS. 2 to 4, the speed reducer 18 includes a case (base) 30, a sun roller 32, a plurality of intermediate rollers 34, a plurality of outer rollers 36, a plurality of outer roller connectors 38, an outer ring 40, and a plurality of intermediate roller support pins (a plurality of support pins) 42.

[0019] The case 30 is formed as the exterior of the speed reducer 18. In FIGS. 2 to 4, only a part of the case 30 is shown. For simplicity of explanation, a part of the case 30 is formed, for example, in a flat plate shape. In the present embodiment, at least a part of the appearance of the case 30 is formed in a disk shape or a substantially disk shape.

[0020] The sun roller 32, the plurality of intermediate rollers 34, and the plurality of outer rollers 36 are preferably formed as substantially cylindrical rollers with their central axes (rotation axes) arranged parallel to each other to ensure the contact area and contact length with respect to each other.

[0021] The sun roller 32 receives rotation (driving force) from a motor 16 driven by electric power supplied from the battery 12. The sun roller 32 is rotatably supported about a predetermined rotation axis that coincides with the central axis with respect to the case 30 by a bearing (not shown). For this reason, when rotation is input, the sun roller 32 rotates about the axis of the rotation axis with respect to the case 30.

[0022] The case 30 is provided with an intermediate roller support pin 42 that rotatably supports an intermediate roller 34. The intermediate roller support pin 42 is fixed to and integrated with the case 30, for example. The intermediate roller support pin 42 is formed in a cylindrical or columnar shape. The central axis of the intermediate roller support pin 42 is arranged on a virtual axis parallel to the central axis of the sun roller 32 that penetrates the positions of the vertices of an equilateral triangle at a position equidistant from the central axis of the sun roller 32 in the case 30. In the present embodiment, three intermediate roller support pins 42 are provided on one surface of the flat plate portion of the case 30. The three intermediate roller support pins 42 are formed, for example, in a columnar shape with the same size and the same shape.

[0023] Note that, of the case 30, the rotation axis at the position where the central axis of the sun roller 32 is supported is the central axis of the speed reducer 18. In other words, the central axis of the sun roller 32 is the central axis of the speed reducer 18.

[0024] The number of intermediate roller support pins 42 may be four if the number of intermediate rollers 34 is four. If there are four or more intermediate roller support pins 42, the central axis of the intermediate roller support pin 42 is arranged on a virtual axis parallel to the central axis of the sun roller 32 that penetrates the positions of the vertices of a regular polygon at a position equidistant from the central axis of the sun roller 32 (the central axis of the speed reducer 18) in the case 30.

[0025] Then, the intermediate roller 34 is rotatably supported about the central axis of the intermediate roller support pin 42 as a rotation axis by a bearing (not shown) on the intermediate roller support pin 42. At this time, the central axis of the intermediate roller 34 coincides with the central axis of the intermediate roller support pin 42.

[0026] The speed reducer 18 according to this embodiment has six outer rollers 36. In this embodiment, the plurality of outer rollers 36 are formed in three pairs. That is, the speed reducer 18 includes three outer roller portions 37 with two outer rollers 36 in one pair. The outer peripheral surfaces of the two outer rollers 36 of one outer roller portion 37 are each in contact with the outer peripheral surface of one intermediate roller 34.

[0027] Therefore, each outer roller portion 37 includes a first roller (outer roller) 36 that is pressed against the outer peripheral surface of the intermediate roller 34 and also pressed against the inner peripheral surface of the outer ring 40, and a second roller (outer roller) 36 that is circumferentially spaced apart from the first roller and is pressed against the outer peripheral surface of the intermediate roller 34 and also pressed against the inner peripheral surface of the outer ring 40. The first roller 36 and the second roller 36 are of the same size and have the same configuration.

[0028] A pair of outer rollers 36 of each outer roller portion 37 are supported in a separated state while being adjacent to each other by an outer roller coupler 38.

[0029] The outer roller coupler 38 includes a plate 38a and a pair of support pins 38b provided on the plate 38a.

[0030] The plate 38a is arranged parallel to the flat plate portion of the case 30 and is supported in contact with or spaced apart from the flat plate portion of the case 30. The pair of support pins 38b are formed in a cylindrical or columnar shape and are provided spaced apart on one surface side of the plate 38a. The pair of support pins 38b are, for example, fixed and integrated on one surface of the plate 38a. A pair of outer rollers (a first roller and a second roller) 36 are rotatably supported around the central axis of the pair of support pins 38b by bearings (not shown) respectively. The outer peripheral surfaces of the pair of outer rollers 36 supported in this way are spaced apart from each other. Therefore, the outer roller coupler 38 can connect the rotation axes of the first roller 36 and the second roller 36 of each outer roller portion 37 and rotate the first roller 36 and the second roller 36 in the same direction.

[0031] The inner peripheral surface of the outer ring 40 is formed so as to contact the outer peripheral surfaces of all three pairs of outer rollers 36. The central axis of the outer ring 40 is arranged parallel to the central axes of the sun roller 32, the plurality of intermediate rollers 34, and the plurality of outer rollers 36. Also, the central axis of the outer ring 40 is arranged to coincide with the central axis of the sun roller 32. The inner peripheral surface of the outer ring 40 is preferably formed to have an appropriate height along the central axis in order to ensure the contact area and contact length with the outer roller 36.

[0032] As shown in FIG. 4, when assembling the speed reducer 18, the sun roller 32, the intermediate roller 34, the outer roller portion 37 supported by the outer roller coupler 38, and the outer ring 40 are assembled to the case 30 in an appropriate order. When these components are formed with appropriate precision, simply by arranging the sun roller 32, the intermediate roller 34, the outer roller portion 37 supported by the outer roller coupler 38, and the outer ring 40 with respect to the case 30, the speed reducer 18 is formed with appropriate backlash and little play. For this reason, in the speed reducer 18, the central axis of the sun roller 32 is located at the position of the central axis of the speed reducer 18, the intermediate roller 34 is located outside the sun roller 32 along the radial direction with respect to the central axis of the sun roller 32, the outer roller portion 37 is located outside the intermediate roller 34 along the radial direction with respect to the central axis of the sun roller 32, and the outer ring 40 is located outside the outer roller portion 37 along the radial direction with respect to the central axis of the sun roller 32.

[0033] At this time, the intermediate roller 34 supported by the intermediate roller support pin 42 is arranged at an appropriate position while moving radially with respect to the central axis of the sun roller 32 between the sun roller 32 and the pair of outer rollers 36.

[0034] Also, at this time, between the outer peripheral surface of the sun roller 32 and the outer peripheral surface of the intermediate roller 34, between the outer peripheral surface of the intermediate roller 34 and the outer peripheral surface of the outer roller 36, and between the outer peripheral surface of the outer roller 36 and the inner peripheral surface of the outer ring 40, they are in linear contact parallel to the central axis of the sun roller 32, respectively. The central axes of the sun roller 32, the intermediate roller 34, the outer roller 36, and the outer ring 40 are parallel to each other. Also, the central axis (rotation axis) of the sun roller 32 and the central axis (rotation axis) of the outer ring 40 coincide.

[0035] By forming the speed reducer 18 in this manner, a pressing load can be generated linearly parallel to the central axis of the sun roller 32 between the inner peripheral surface of the outer ring 40 and the outer peripheral surface of the outer roller 36, between the outer peripheral surface of the outer roller 36 and the outer peripheral surface of the intermediate roller 34, and further between the outer peripheral surface of the intermediate roller 34 and the outer peripheral surface of the sun roller 32. Therefore, the inner peripheral surface of the outer ring 40 and the outer peripheral surface of the outer roller 36, the outer peripheral surface of the outer roller 36 and the outer peripheral surface of the intermediate roller 34, and further the outer peripheral surface of the intermediate roller 34 and the outer peripheral surface of the sun roller 32 are respectively pressed.

[0036] When assembling the speed reducer 18, it is also possible to perform shrink fitting by slightly thermally expanding the outer ring 40 and then incorporating it outside the outer roller 36. In this case, an initial applied pressure can be generated between the inner peripheral surface of the outer ring 40 and the outer peripheral surface of the outer roller 36. And a pressing load can be generated linearly parallel to the central axis of the sun roller 32 between the inner peripheral surface of the outer ring 40 and the outer peripheral surface of the outer roller 36, between the outer peripheral surface of the outer roller 36 and the outer peripheral surface of the intermediate roller 34, and further between the outer peripheral surface of the intermediate roller 34 and the outer peripheral surface of the sun roller 32.

[0037] The operation of the speed reducer 18 according to this embodiment will be described with reference to FIG. 5.

[0038] When rotational torque is input from the motor 16 to the shaft portion 32a of the sun roller 32 on the central axis of the sun roller 32, the speed reducer 18 rotates at that position in a state where the central axis of the sun roller 32 coincides with the central axis of the speed reducer 18. Then, torque is transmitted from the sun roller 32, the intermediate roller 34 and the outer roller 36 rotate substantially at that position, and the outer ring 40 rotates about the axis of the central axis of the sun roller 32. In this embodiment, the rotation direction of the sun roller 32 and the rotation direction of the outer ring 40 are the same direction.

[0039] When rotational torque is input from the motor 16 to the sun roller 32 during torque transmission, a force acts so as to enter between the outer peripheral surface that becomes the friction surface of the intermediate roller 34 according to the rotational direction, the outer peripheral surface that becomes the friction surface of the sun roller 32, and the outer peripheral surfaces that become the friction surfaces of the pair of outer rollers 36. At this time, a force continues to act in the normal direction of the linear contact surface parallel to the central axis of the sun roller 32 between the outer peripheral surface of the sun roller 32 and the outer peripheral surface of the intermediate roller 34. A force continues to act in the normal direction of the linear contact surface parallel to the central axis of the sun roller 32 between the outer peripheral surface of the intermediate roller 34 and the outer peripheral surfaces of the pair of outer rollers 36. Further, a force continues to act in the normal direction of the linear contact surface parallel to the central axis of the sun roller 32 between the outer peripheral surfaces of the pair of outer rollers 36 and the inner peripheral surface that becomes the friction surface of the outer ring 40. These three normal directions are parallel to one plane (virtual plane) parallel to the flat plate portion of the case 30. At this time, the outer peripheral surface of the intermediate roller 34 abuts on the outer peripheral surface of the sun roller 32 and the outer peripheral surfaces of the pair of outer rollers 36 at one linear location parallel to the central axis of the sun roller 32, respectively. For this reason, the intermediate roller 34 rotates substantially in that position while being linearly supported in three locations spaced apart from each other with respect to the sun roller 32 and the pair of outer rollers 36 in a direction parallel to the central axis of the sun roller 32. For this reason, when rotational torque is input from the motor 16 to the sun roller 32, the sun roller 32, the intermediate roller 34, and the outer roller 36 are balanced within the outer ring 40 in the speed reducer 18 according to the present embodiment. Therefore, when the speed reducer 18 is operating, a large load is prevented from being applied to the intermediate roller support pin 42 that supports the intermediate roller 34. For this reason, the speed reducer 18 according to the present embodiment prevents a large load from being applied to the case 30 of the speed reducer 18.

[0040] Further, according to the present embodiment, when rotational torque is input from the motor 16 to the sun roller 32, the speed reducer 18 can generate a high pressing load on each of the friction surfaces between the outer peripheral surface of the sun roller 32 and the outer peripheral surface of the intermediate roller 34, between the outer peripheral surface of the intermediate roller 34 and the outer peripheral surface of the outer roller 36, and between the outer peripheral surface of the outer roller 36 and the inner peripheral surface of the outer ring 40.

[0041] When rotational torque is input from the motor 16 to the sun roller 32, the outer peripheral surface of the intermediate roller 34 rotates smoothly with respect to the outer peripheral surface of the sun roller 32. Also, the outer peripheral surface of the outer roller 36 rotates smoothly with respect to the outer peripheral surface of the intermediate roller 34. And the inner peripheral surface of the outer ring 40 rotates smoothly with respect to the outer peripheral surface of the outer roller 36. For this reason, in the speed reducer 18 according to the present embodiment, between the outer peripheral surface of the sun roller 32 and the outer peripheral surface of the intermediate roller 34, and between the outer peripheral surface of the intermediate roller 34 and the outer peripheral surfaces of the pair of outer rollers 36 (the outer peripheral surface of the first roller 36 and the outer peripheral surface of the second roller 36), and between the outer peripheral surfaces of the pair of outer rollers 36 (the outer peripheral surface of the first roller 36 and the outer peripheral surface of the second roller 36) and the inner peripheral surface of the outer ring 40, pressing loads proportional to the torque can be generated respectively. Therefore, by using the speed reducer 18 according to the present embodiment, when rotational torque is input from the motor 16 to the sun roller 32, the pressing load between the sun roller 32 and the intermediate roller 34, the pressing load between the intermediate roller 34 and the outer roller 36, and the pressing load between the outer roller 36 and the outer ring 40 can be transmitted in order from the sun roller 32 to the outer ring 40 so as to be proportional to the torque respectively. Therefore, by using the speed reducer 18 according to the present embodiment, the pressing load can be transmitted in order from the sun roller 32 to the outer ring 40 so as to be proportional to the torque respectively during torque transmission from the motor 16.

[0042] Also, when rotation is input to the sun roller 32 during torque transmission from the motor 16, the moving speed (circumferential speed) of the outer peripheral surface of the sun roller 32 and the moving speed (circumferential speed) of the outer peripheral surface of the intermediate roller 34 are the same or substantially the same, and the moving speed (circumferential speed) of the outer peripheral surface of the intermediate roller 34 and the moving speed (circumferential speed) of the outer peripheral surface of the outer roller 36 (the outer peripheral surface of the first roller 36 and the outer peripheral surface of the second roller 36) are the same or substantially the same, and the moving speed (circumferential speed) of the outer peripheral surface of the outer roller 36 (the outer peripheral surface of the first roller 36 and the outer peripheral surface of the second roller 36) and the moving speed (circumferential speed) of the outer peripheral surface of the outer ring 40 are the same or substantially the same. Therefore, in the speed reducer 18 according to the present embodiment, no speed difference or almost no speed difference occurs in the circumferential speeds of the outer peripheral surface of the sun roller 32, the outer peripheral surface of the intermediate roller 34, the outer peripheral surface of the outer roller 36 (the outer peripheral surface of the first roller 36 and the outer peripheral surface of the second roller 36), and the inner peripheral surface of the outer ring 40. Therefore, in the speed reducer 18 according to the present embodiment, since the circumferential speed of the outer peripheral surface of the sun roller 32 and the circumferential speed of the inner peripheral surface of the outer ring 40 are equal, the outer ring 40 is decelerated by the ratio of their diameters with respect to the sun roller 32.

[0043] These contents are the same not only when the sun roller 32 receives the driving force from the motor 16 and rotates in the direction shown in FIG. 5, but also when it rotates in the direction opposite to the direction shown in FIG. 5. In this case, the outer ring 40 rotates in the direction opposite to the direction shown in FIG. 5 due to the transmission of power.

[0044] Therefore, according to the present embodiment, (1) generating a high pressing load between each friction surface in the speed reducer 18 during torque transmission when rotational torque is transmitted from the motor 16 to the speed reducer 18; (2) making the pressing load proportional to the torque during torque transmission when rotational torque is transmitted from the motor 16 to the speed reducer 18; (3) not generating a speed difference within the friction contact surface during torque transmission when rotational torque is transmitted from the motor 16 to the speed reducer 18; (4) not receiving the pressing force of the friction surface by the case 30 during torque transmission when rotational torque is transmitted from the motor 16 to the speed reducer 18; A speed reducer 18 that satisfies all of the above is provided. According to this embodiment, for example, by using a high-speed motor 16, it is possible to provide a friction transmission type speed reducer 18 that has high torque transmission efficiency, little vibration and noise, and realizes high reduction ratio reduction.

[0045] Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist thereof at the implementation stage. Also, the respective embodiments may be implemented in appropriate combination, and in that case, the combined effects can be obtained. Furthermore, the above-described embodiment includes various inventions, and various inventions can be extracted by combinations selected from a plurality of disclosed constituent elements. For example, even if some constituent elements are deleted from all the constituent elements shown in the embodiment, if the problem can be solved and the effect can be obtained, the configuration from which these constituent elements are deleted can be extracted as an invention.

Explanation of Reference Numerals

[0046] 10... Electric vehicle, 10a... Vehicle, 12... Battery, 14... Inverter, 16... Motor, 18... Speed reducer, 20... Drive shaft, 22... Wheel, 30... Case, 32... Sun roller, 32a... Shaft portion, 34... Intermediate roller, 36... Outer roller, 37... Outer roller portion, 38... Outer roller coupler, 38a... Plate, 38b... Support pin, 40... Outer ring, 42... Intermediate roller support pin.

Claims

1. A case, a sun roller having a rotation axis that coincides with a central axis and that rotates about the axis of the rotation axis with respect to the case when rotation is input, a plurality of intermediate rollers having an outer peripheral surface that is pressed against the outer peripheral surface of the sun roller and that rotate by receiving the rotation of the sun roller, a plurality of support pins provided on the case and respectively supporting the plurality of intermediate rollers, a plurality of outer rollers having an outer peripheral surface that is pressed against the outer peripheral surfaces of the plurality of intermediate rollers and that rotate by receiving the rotation of the intermediate rollers, an outer ring having an inner peripheral surface that is pressed against the outer peripheral surface of the outer roller and that rotates by receiving the rotation of the outer roller and having a speed reducer.

2. The support pin is formed in a cylindrical shape or a columnar shape, and a central axis of the support pin is disposed at a position equidistant from the central axis of the sun roller in the case, The speed reducer according to claim 1.

3. Each of the plurality of outer rollers has a first roller that is pressed against the outer peripheral surface of the intermediate roller and that is pressed against the inner peripheral surface of the outer ring, and a second roller that is circumferentially spaced apart from the first roller, that is pressed against the outer peripheral surface of the intermediate roller, and that is pressed against the inner peripheral surface of the outer ring, and includes The speed reducer has a coupler that connects a rotation axis of the first roller and a rotation axis of the second roller and rotates the first roller and the second roller in the same direction, The speed reducer according to claim 1 or claim 2.

4. The speed reducer according to claim 1 or claim 2, a motor that inputs a driving force to the sun roller of the speed reducer, and a battery that supplies electric power for driving the motor and having a vehicle.

5. An electric vehicle including the vehicle according to claim 4.

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