JP3974386B2 - Reduction gear mechanism for electric drive - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reduction gear mechanism of an electric drive device.
[0002]
[Prior art]
For example, in a battery-assisted bicycle, an electric drive device for assisting the pedal effort is provided in connection with the pedal crankshaft to assist the pedal effort from the pedal. In this electric drive device, a drive shaft is constituted by a pedal crankshaft and a drive sleeve coaxial with the pedal crankshaft, a sprocket is fixed on the drive sleeve, and this is connected to a drive wheel (for example, a rear wheel) via a chain. The output shaft of the electric motor serving as auxiliary power is connected to the drive sleeve, and the output of the electric motor is transmitted to the rear wheel via the drive sleeve to give a rotational driving force. On the other hand, the pedal crankshaft connected to the pedal is also connected to the drive sleeve via a planetary gear mechanism or the like, and the rear wheel is driven to rotate via the drive sleeve by the pedal depression force. As a result, the pedal depression force and the driving force of the electric motor are fused on the driving sleeve, and the rear wheel is driven by the resultant force.
[0003]
The pedaling force applied to the pedal crankshaft is detected by torque detecting means. In accordance with the detected pedal force, the control circuit calculates the power to be assisted and drives the electric motor with a predetermined assist ratio.
[0004]
The electric motor is coupled to the drive shaft via a speed reduction mechanism. This reduction mechanism has, for example, a two-stage gear structure, and a first gear that meshes with the motor output shaft side is a first stage, and a second gear that is smaller in diameter than the first gear and provided integrally therewith is coaxial. The second stage is configured such that the second gear is connected to a large-diameter gear mounted on the drive shaft side. The intermediate shaft on which the integrally formed first gear and second gear are mounted is held in a casing that houses the electric motor.
[0005]
The rotation of the motor output shaft rotates the drive shaft via the large-diameter gear at a predetermined reduction ratio corresponding to the gear ratio between the first gear and the second gear integrated in two stages.
[0006]
[Problems to be solved by the invention]
However, in the conventional reduction mechanism, when trying to obtain a particularly large reduction ratio, the end of the intermediate shaft vibrates at the holding part on the casing side due to the vibration of the gears, generating unpleasant noise and causing deterioration. There was a problem of becoming.
[0007]
The present invention has been made in consideration of the above prior art, and an object of the present invention is to provide a reduction gear mechanism for an electric drive device that suppresses gear vibration and reduces noise generation.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, there is provided a reduction gear mechanism of an electric drive device provided with an intermediate shaft between a motor output shaft and a drive shaft and mounted on the intermediate shaft, and mounted on the intermediate shaft. A first gear that meshes with the gear on the motor output shaft side, a second gear that is smaller in diameter than the first gear and is integrally formed coaxially therewith, and that is mounted on the drive shaft and meshes with the second gear. In the reduction gear mechanism of the electric drive device comprising a large-diameter gear, the first gear and the second gear are helical gears having different torsion angles, and the directions of thrust forces by the helical gears are opposite to each other. The electric drive device is configured so that the resultant force is generated in a predetermined axial direction, and an intermediate shaft end portion in the predetermined axial direction is held by a resin material made of polybutyl terephthalate . A reduction gear mechanism is provided.
[0009]
According to this configuration, by using the helical gear, the meshing noise is reduced, and the helical gears of the first gear and the second gear on the common intermediate shaft are changed to change the shaft angle. If the direction in which the thrust force of the direction is applied is reversed, the thrust force due to the meshing of the gears is generated in the canceling direction, and each helical screw is applied so that the resultant force of the thrust force remaining after canceling acts in a certain direction. A gear is formed. As a result, the vibration generated from each of the two-stage integrated first gear and second gear is caused to cancel each other to reduce the vibration, and after canceling, the thrust force remains and acts in a fixed direction. By holding the shaft end in that direction with a resin material, vibration and noise can be effectively absorbed and reduced.
[0010]
In a preferred configuration example, an electric motor, its motor output shaft and the drive shaft are accommodated in a casing, and the casing includes a central housing and a left case and a right case sandwiching the central housing from both sides. It is formed of a resin material made of polybutyl terephthalate , the left case and the right case are formed of a metal material, and the intermediate shaft has one end held by the left case or the right case and the other end held by the central housing. It is characterized by that.
[0011]
According to this configuration, the right and left cases made of a metal material ensure sufficient casing strength, and the central housing is made of a resin material, so that weight reduction is achieved, and the central housing is made high by injection molding or the like. It can be formed easily and efficiently with accuracy, and the productivity of the electric drive device is increased. By using a thermosetting resin as an example, it is possible to sufficiently withstand high temperatures due to motor heat generation, and to improve water resistance and insulation.
[0012]
Using the resin material of the central housing of the casing, the end of the intermediate shaft is held with the resin material, and the axial force due to the thrust combined force of the helical gear is applied in the direction of the end of the casing. The resin material can effectively absorb the vibration and noise of the intermediate shaft and suppress the vibration and noise.
[0013]
In a further preferred configuration example, the electric drive device is an electric drive device for assisting pedal depression force of a battery-assisted bicycle.
[0014]
According to this configuration, by applying the structure of the present invention to the electric motor for assisting the pedaling force of the battery-assisted bicycle, particularly in a bicycle structure that is required to be reduced in size and weight, the weight can be reduced, thereby reducing the load. Cost reduction is achieved, and vibration and unpleasant noise are reduced, improving usability.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a side view of a battery-assisted bicycle equipped with an electric drive device according to an embodiment of the present invention.
[0016]
The battery-assisted bicycle 1 includes an electric drive device 4 according to the present invention mounted on the hanger portion 3 at the substantially center of the vehicle body frame 2, and a pedaling force for rotating the pedal crankshaft 6 by stepping on the pedal 5. The electric driving device 4 is combined with the power of an electric motor, which will be described later, and the rear wheel 7 is driven by the resultant force. As will be described later, the electric drive unit 4 has a sprocket on the drive shaft, and the rotation of the sprocket is transmitted to the rear wheel 7 by a chain 8 via a known free wheel.
[0017]
The electric drive device 4 is suspended and supported by a suspension bolt as will be described later with respect to a bracket 9 fixed (or integrally molded) to the vehicle body frame 2. Reference numeral 10 denotes a battery for driving the electric motor in the electric drive unit 4.
[0018]
FIG. 2 is a horizontal sectional view of the electric drive device according to the present invention.
The electric drive device 4 is configured by housing an electric motor 12 and a drive shaft 13 in a casing 11. The casing 11 is divided into three as will be described later, and includes a central housing 14 and a left case 15 and a right case 16 that sandwich the housing 11 from both sides. The electric motor 12 includes a motor output shaft 17, a rotor 18 fixed to the motor output shaft 17, and a stator 19 fixed in the casing 11 so as to face the outer periphery of the rotor 18. The drive shaft 13 includes a pedal crankshaft 6 (manpower input shaft) connected to the pedal 5 (FIG. 1) and a fusion sleeve 20 that is rotatably fitted on the outer periphery of the pedal crankshaft 6. A sprocket 21 is fixed on the fusion sleeve 20 and connected to the rear wheel 7 (FIG. 1) via the chain 8.
[0019]
A gear 22 is formed at the end of the motor output shaft 17. The first gear 24 of the intermediate shaft 23 meshes with the gear 22. A first gear 24 and a second gear 25 that is integral with the first gear 24 and smaller in diameter are mounted on the intermediate shaft 23. The second gear 25 meshes with a large-diameter gear 27 fixed to the fusion sleeve 20 via a ratchet 26. A reduction gear mechanism 72 (first reduction mechanism) is formed by such an intermediate shaft 23 and the two-stage integrated first and second gears 24 and 25 attached thereto. As a result, the rotational driving force of the electric motor 12 is decelerated by the reduction gear mechanism 72 and transmitted to the fusion sleeve 20 via the large-diameter gear 27 to drive the rear wheels.
[0020]
The pedal crankshaft 6 is connected to a planetary gear mechanism 29 (second reduction mechanism) via a ratchet 28. The planetary gear mechanism 29 is connected to the fusion sleeve 20, transmits the pedal depression force from the pedal crankshaft 6 to the fusion sleeve 20, and drives the rear wheels by the depression force.
[0021]
The planetary gear mechanism 29 includes a carrier 30 that is driven in one direction by a ratchet 28, a planetary gear 31 that is rotatable about the carrier 30, a ring gear 71 that is fixed to the casing on the outer peripheral side of the planetary gear 31, The sun gear 32 is fixed to the fusion sleeve 20 on the inner peripheral side of the planetary gear 31. The rotational force of the pedal crankshaft 6 revolves and rotates the planetary gear 31 through the carrier 30 from the ratchet 28, rotates the sun gear 32, and transmits the rotational force due to the pedaling force to the fusion sleeve 20 to transmit the rear wheel to the rear wheel. To drive.
[0022]
The central housing 14 of the casing 11 divided into three is formed by injection molding of a resin material such as PBT (polybutyl terephthalate). The left case 15 and the right case 16 sandwiching the central housing 11 are formed of an ADC (aluminum die cast alloy) material.
[0023]
The casing 11 is assembled by connecting the left case 15 and the right case 16 with fastening bolts 33 at a plurality of locations (for example, 5 locations). In this example, the fastening bolt 33 is inserted from the left case 15 side, and is screwed into a female screw portion formed in the right case 16 so that both the cases 15 and 16 are fastened and joined.
[0024]
The casing 11 is fixed and held on a vehicle body bracket 9 fixed to the vehicle body frame by suspension bolts 34 at a plurality of locations (for example, three locations). In this case, as shown in the drawing, the width between the body brackets 9 disposed in the respective suspension portions is narrower than the width of the casing 11, so that a collar 35 serving as a spacer is attached to the suspension bolt 34 and the suspension bolt 34 and this are screwed. The right and left cases 15 and 16 are fastened and fixed by the mating nut 36.
[0025]
The end portion of the pedal crankshaft 6 and the end portion of the fusion sleeve 20 constituting the drive shaft 13 are supported by the left case 15 and the right case 16 via bearings 37 and 38, respectively. The drive shaft 13 is stably and firmly held by supporting the bearing portions of the drive shaft 13 on the left and right cases 15 and 16 made of a metal material having a high strength as described above.
[0026]
The left end of the motor output shaft 17 of the electric motor 12 is supported on the left case 15 via a bearing 39. In this example, the bearing 40 that holds the right end of the motor output shaft 17 is provided in the central housing 14 made of resin. In this case, an arc-shaped metal convex wall (not shown) is provided integrally with the right case 16 so as to hold the bearing 40 at a plurality of locations along the outer peripheral surface of the bearing 40 and protrudes toward the central housing side. By fixing and holding the bearing 40 by the convex wall, the bearing 40 is stably and firmly fixed and held as in the case where the bearing 40 is held in a case made of a metal material. Further, there is no positional deviation due to molding error or deformation of the resin material. A notch (not shown) is provided in the resin material of the central housing 11 where such a convex wall is disposed so as not to prevent insertion of the convex wall from the right case 16 made of a metal material.
[0027]
As will be described later, the inside of the casing 11 includes a motor chamber that houses the electric motor 12, a speed reducer chamber that houses the reduction gear 25, the planetary gear mechanism 29, and the like, and a motor control circuit board (not connected) that is energized by an FET or the like. It is divided into a control room that accommodates (shown).
[0028]
As described later, annular projections 45 and 55 are provided on the dividing surface between the central housing 14 and the left and right cases 15 and 16 of the casing 11 divided into three, along the peripheral edge of the central housing side, as will be described later. Annular grooves 44 and 54 into which the annular protrusions 45 and 55 are fitted are formed on the mating surfaces of the left and right cases. As a result, the sealing performance of the casing 11 is ensured, and the center housing 14 that is a casing divided body and the left and right cases 15 and 16 can be aligned, and the drive shaft 13 and the motor output shaft that are disposed across the dividing surface. 17 axis alignment is possible.
[0029]
In the above configuration, in the present invention, the intermediate shaft 23 is provided between the motor output shaft 17 and the drive shaft 13, and the reduction gear mechanism 72 of the electric drive device mounted on the intermediate shaft 23 is provided on the intermediate shaft 23. A first gear 24 that is engaged with the gear 22 on the motor output shaft 17 side, a second gear 25 that is smaller than the first gear 24 and is integrally formed coaxially therewith, and the drive shaft 13. In the reduction gear mechanism 72 of the electric drive device comprising the large-diameter gear 27 that is mounted and meshed with the second gear 25, the first gear 24 and the second gear 25 are helical gears having different torsion angles, The directions of thrust forces by the helical gears are opposite to each other, and the resultant force is generated toward the central housing side.
[0030]
FIG. 3 is a side view as seen from the inner surface side (right side) of the left case 15 constituting the casing 11, and FIG. 4 is a cross-sectional configuration diagram of the AA portion thereof.
[0031]
A partition wall 43 that partitions the periphery of the motor chamber 41 and the control chamber 42 and the two chambers is formed on the inner surface side of the left case 15. The partition wall 43 between the motor chamber 41 and the control chamber 42 is formed with an opening 51 through which a signal cable, a power cable and the like are inserted. A continuous annular groove 44 surrounding each of the motor chamber 41 and the control chamber 42 is formed along the partition wall 43 on the mating surface with the central housing 14. An annular projection 45 (FIG. 5) which is also continuous and provided in the central housing 14 described later is fitted into the annular groove 44. As a result, the motor chamber 41 and the control chamber 42 are sealed, and alignment with the central housing 14 (FIGS. 2 and 5) is performed.
[0032]
Fastening attachment holes 46 are formed at five locations along the outer peripheral edge of the left case 15, and the aforementioned fastening bolts 33 (FIG. 2) are inserted therethrough. Further, suspension brackets 47 are provided at three positions so as to protrude from the outer peripheral edge of the left case 15, and suspension attachment holes 48 are formed respectively. The above-described suspension bolts 34 (FIG. 2) are inserted into these suspension mounting holes 48.
[0033]
The pedal crankshaft 6 is inserted into the pedal crankshaft insertion hole 49 via the bearing 37 shown in FIG. Further, the end portion of the motor output shaft 17 is supported by the motor bearing portion 50 through the bearing 39 of FIG.
[0034]
The control chamber 42 accommodates a printed circuit board (not shown) on which, for example, six FETs (not shown) are mounted in a line. These six FETs are in thermal contact with the inner surface of the left case 15 through a heat sink (not shown) made of a metal material to dissipate heat. The heat sink may be formed integrally with the case material on the inner surface of the left case 15. The six FETs are pressed against the inner wall surface of the case from the inside of the case by, for example, a common pressing plate (not shown). The presser plate is tightened from the outside of the case with screws (not shown) through, for example, two through holes 53 provided in the case to press-contact each FET to the inner wall surface of the case. Reference numeral 52 denotes a dent for screw head escape of six screws for fixing the FET to the heat sink.
[0035]
FIG. 5 is a cross-sectional configuration diagram of the central housing 14.
On the left and right side surfaces of the central housing 14, there are respectively an annular protrusion 45 fitted in the annular groove 44 of the left case 15 and an annular protrusion 55 fitted in an annular groove 54 of the right case 16 shown in FIGS. It is formed. Fastening bolt insertion holes 56 are formed along the peripheral edge of the central housing 14 at five positions corresponding to the aforementioned fastening mounting holes 46 (FIG. 3).
[0036]
The interior of the central housing 14 is separated by a partition wall 57 into a motor chamber 41, a control chamber 42 (see FIG. 3), and a reducer chamber 58. The motor chamber 41 houses the electric motor 12 as described above, and the control chamber 42 houses a printed circuit board to which an FET or the like is bonded. The reduction gear chamber 58 houses the reduction gear mechanism 72 and the planetary gear mechanism 29 shown in FIG. The left end portion of the intermediate shaft 23 (FIG. 2) of the reduction gear mechanism 72 is fitted and supported in a bearing recess 59 formed in the reduction gear chamber 58. A pedal crankshaft insertion hole 62 is formed in the left partition wall forming the speed reducer chamber 58, and the pedal crankshaft 6 (FIG. 2) is inserted therethrough.
[0037]
A motor output shaft insertion hole 60 is formed in the right wall portion of the partition wall 57 forming the motor chamber 41, and the motor output shaft 17 is inserted through the bearing 40 (FIG. 2) as described above. Reference numeral 61 denotes a bearing fitting portion.
[0038]
6 is a view of the right case 16 as viewed from the inner surface side (left side), and FIG. 7 is a cross-sectional configuration diagram of the CC portion of FIG.
[0039]
A partition wall 63 that forms a reduction gear chamber 58 is provided along the outer peripheral edge of the right case 16. A continuous annular groove 54 is formed along the mating surface of the partition wall 63 with the central housing 14. An annular protrusion 55 on the central housing 14 side is fitted into the annular groove 54, and the seal of the reduction gear chamber 58 and the alignment of the central housing 14 and the right case 16 are performed.
[0040]
As in the case of the left case 15, suspension brackets 64 are provided at three locations on the outer peripheral edge of the right case 16, and suspension attachment holes 65 through which the suspension bolts 34 (FIG. 2) are inserted are formed.
[0041]
Corresponding to the fastening holes 46 (FIG. 3) of the left case 15 through which the five fastening bolts 33 (FIG. 2) are respectively inserted and the fastening bolt insertion holes 56 of the central housing 14 aligned therewith, the right case 16 Fastening screw holes 66 are formed at five positions on the peripheral edge. The fastening bolt 33 is screwed into the fastening screw hole 66.
[0042]
The right end portion of the intermediate shaft 23 (FIG. 2) is fitted and supported in a bearing recess 67 formed on the inner surface of the right case 16.
[0043]
A drive shaft insertion hole 68 is opened through the right case 16, and the drive shaft 13 including the pedal crankshaft 6 and the fusion sleeve 20 shown in FIG. Reference numeral 69 denotes a bearing fitting portion that holds the bearing 38 (FIG. 2).
[0044]
The right case 16 is formed of an aluminum die-cast alloy (ADC material) formed in the same manner as the left case 15 described above, and forms an integral casing 11 (FIG. 2) with the resin central housing 14 sandwiched from the left and right. To do.
[0045]
FIG. 8 is an explanatory diagram of the main configuration of the reduction gear mechanism according to the present invention.
A gear 22 composed of a helical gear is formed at the end of the motor output shaft 17. A first gear 24 formed of a helical gear meshing with the gear 22 and a second gear 25 integrated therewith are mounted on the intermediate shaft 23 via a sleeve 70. The second gear 25 is a helical gear similar to the first gear 24, and a large-diameter gear 27, which is also a helical gear meshing with the helical gear, is attached to the fusion sleeve 20 via the ratchet 26. Is done. The fusion sleeve 20 constitutes the drive shaft 13 together with the pedal crankshaft 6 as described above.
[0046]
The upper end of the intermediate shaft 23 is fixed and held in an intermediate shaft support recess 67 of the right case 16 made of an aluminum alloy, and the lower end of the intermediate shaft 23 is inserted in an intermediate shaft support recess 59 of the central housing 14 made of a resin material. And is held fixed. A sleeve 70 is attached to the intermediate shaft 23. On this sleeve 70, the 1st gear 24 and the 2nd gear 25 which consist of a helical gear of 2 steps | paragraphs integral are attached with respect to the intermediate shaft 23 so that rotation is possible.
[0047]
The helical gears of the first gear 24 and the second gear 25 have the axial thrust direction of the helical gear of the first gear 24 in the axial direction of the helical gear of the second gear 25. The teeth of each helical gear are formed so that the thrust force is canceled out in the direction opposite to the direction of the force. Further, the helical gear of the first gear 24 is twisted so that the thrust force of the resultant resultant force of the canceled first gear 24 and the remaining thrust force of the second gear 25 acts on the central housing 14 side. The angle of the helical gear of the second gear 25 is different from that of the helical gear (for example, the twist angle of the first gear 24 is 26 ° and the twist angle of the second gear 25 is 16 °). As a result, both the helical gear and the intermediate shaft 23 receive thrust toward the central housing made of resin material, and the intermediate shaft 23 is held by the resin material recess 59, so that vibration and noise are effectively absorbed. And noise due to vibration is reduced.
[0048]
【The invention's effect】
As described above, in the present invention, by using a helical gear, the meshing noise is reduced and the twist angle of the helical gears of the first gear and the second gear on the common intermediate shaft is changed. By reversing the direction in which the axial thrust force acts, the thrust force generated by the meshing of the gears is generated in the canceling direction, and the resultant force of the remaining thrust force canceling is applied in a fixed direction. Each helical gear is formed. As a result, the vibration generated from each of the two-stage integrated first gear and second gear is caused to cancel each other to reduce the vibration, and after canceling, the thrust force remains and acts in a fixed direction. By holding the shaft end in that direction with a resin material, vibration and noise can be effectively absorbed and reduced.
[Brief description of the drawings]
FIG. 1 is an overall view of a battery-assisted bicycle to which an electric drive device of the present invention is applied.
FIG. 2 is a horizontal sectional configuration diagram of the electric drive device according to the embodiment of the present invention.
FIG. 3 is an inner surface view of a left case of the electric drive device of FIG. 2;
4 is a cross-sectional configuration view taken along the line BB in FIG. 3;
5 is a cross-sectional configuration diagram of a central housing of the electric drive device of FIG. 2;
6 is an inner surface view of a right case of the electric drive device of FIG. 2. FIG.
7 is a cross-sectional configuration diagram taken along the line CC of FIG. 6;
FIG. 8 is a configuration explanatory view of a reduction gear mechanism of the present invention.
[Explanation of symbols]
1: battery-assisted bicycle, 2: body frame 3: hanger part, 4: electric drive device,
5: Pedal, 6: Pedal crankshaft, 7: Rear wheel, 8: Chain,
9: bracket, 10: battery, 11: casing, 12: electric motor,
13: Drive shaft, 14: Central housing, 15: Left case, 16: Right case,
17: Motor output shaft, 18: Rotor, 19: Stator,
20: Fusion sleeve, 21: Sprocket, 22: Gear,
23: intermediate shaft, 24: first gear, 25: second gear, 26: ratchet,
27: Large-diameter gear, 28: Ratchet, 29: Planetary gear mechanism, 30: Carrier,
31: Planetary gear, 32: Sun gear, 33: Fastening bolt, 34: Suspension bolt,
35: collar, 36: nut, 37: bearing, 38: bearing,
39: Bearing, 40: Bearing, 41: Motor room, 42: Control room,
43: partition wall, 44: annular groove, 45: annular projection, 46: mounting hole for fastening,
47: Suspension bracket, 48: Suspension mounting hole, 49: Pedal crankshaft insertion hole,
50: Motor bearing, 51: Opening, 52: Recess,
53: Presser plate mounting through-hole, 54: annular groove, 55: annular projection,
56: Fastening bolt insertion hole, 57: Partition wall, 58: Reducer chamber,
59: Recess for supporting the intermediate shaft, 60: Motor output shaft insertion hole,
61: Bearing fitting portion, 62: Pedal crankshaft insertion hole, 63: Partition wall,
64: suspension bracket, 65: mounting hole for suspension, 66: screw hole for fastening,
67: Recess for supporting the intermediate shaft, 68: Drive shaft insertion hole, 69: Bearing fitting portion,
70: Sleeve, 71: Ring gear, 72: Reduction gear mechanism.

Claims (3)

  An intermediate shaft is provided between the motor output shaft and the drive shaft, and is a reduction gear mechanism of an electric drive device mounted on the intermediate shaft. The reduction gear mechanism is mounted on the intermediate shaft and meshes with a gear on the motor output shaft side. Deceleration of an electric drive device comprising one gear, a second gear having a smaller diameter than that of the first gear and coaxially formed therewith, and a large-diameter gear mounted on the drive shaft and meshing with the second gear In the gear mechanism, the first gear and the second gear are helical gears having different torsion angles. The directions of the thrust forces of the helical gears are opposite to each other, and the resultant force is directed to a predetermined axial direction. A reduction gear mechanism for an electric drive device, wherein the intermediate shaft end portion in the predetermined axial direction is held by a resin material made of polybutyl terephthalate. An electric motor, its motor output shaft, and the drive shaft are accommodated in a casing. The casing includes a central housing and a left case and a right case sandwiching the central housing from both sides, and the central housing is made of polybutyl terephthalate. The left case and the right case are made of a metal material, and the intermediate shaft has one end held by the left case or the right case and the other end held by the central housing. The reduction gear mechanism of the electric drive device according to claim 1.   The reduction gear mechanism of the electric drive device according to claim 2, wherein the electric drive device is an electric drive device for assisting pedal depression force of an electric assist bicycle.

Images