JPH01145266A - reduction gear - Google Patents

Abstract

PURPOSE:To obtain natural steering feeling by constituting both a clutch and a cam section to be concurrently rotated in such a way as to let no assisting force be transmitted to a pinion in a reduction gear suitable for an electric power steering device. CONSTITUTION:The sun gear 3 of No.1 planetary gear mechanism is fit onto the driving shaft 12 of an electric motor 10, and the sun gear 20 of No.2 planetary gear mechanism is fit onto a center rotating shaft 19 integrally provided for No.1 carrier 17 of the aforesaid planetary gear mechanism. In addition, the tip end of a center rotating shaft 27 provided integrally for No.2 carrier 25 of No.2 planetary gear is rotatably supported by the axial center section of a drum 28 so that the shaft 27 is formed with a square cam section 27a for letting a pair of clutches 26 in a half moon form be brought in contact with two side segments facing the cam section 27a by spring S force. Thence, a pressure plate 24 is provided between No.2 carrier 25 and a drum section 28, and a disc spring 32 is provided for the clutch 26 side of the pressure plate 24 so as to be energized the direction in which the clutch 26 is brought in to contact with the drum 28.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a speed reduction device most suitable for use in, for example, an electric power steering device.

(Prior art) As a device used in an electric power steering device, the fourth
．． The device shown in FIG. 5 is conventionally known.

In this conventional device, an input shaft 2 is connected to a handle l, and a pinion 3 is connected to this input shaft 2. This pinion 3 is engaged with a rack 4, and both ends of this rack 4 are connected to a side rod 5 and a knuckle arm 6.
It is linked to the wheels 7 via.

A torque sensor 8 is provided on the input shaft 2, and output signals from the torque sensor 8 and the vehicle speed sensor S are input to the control device 9.

The control device 9 is electrically connected to an electric motor 10, and the electric motor 10 is linked to a pinion 11 via a reduction gear device A, and the pinion 11 is engaged with the rack 4.

The specific configuration of the speed reduction device A is as shown in FIG. 4.

That is, when the electric motor 10 is driven and the output shaft 12 rotates, the sun gear 13 fitted to the output shaft 12 rotates.

Further, a ring gear 15 is fixed to the inner periphery of the casing 14 of this reduction gear A, and a planetary gear 16 is interposed between this ring gear 15 and the sun gear 13. Furthermore, this planetary gear 16 is rotatably supported by a support shaft provided on the first carrier 17.

Therefore, when the sun gear 13 rotates as described above,
While rotating, the planetary gear 16 revolves around the sun gear 13 and rotates the first carrier 17.

A central rotating shaft 19 is provided at the center of the first carrier 17 on the side opposite to the supporting shaft 18, and a sun gear 20 is fixed to this central rotating shaft 19. A planetary gear 2 is provided between this sun gear 20 and the ring gear 15.
1, and the planetary gear 21 is rotatably supported by a support shaft 23 of a second carrier 22.

Therefore, when the first carrier 17 rotates as described above, the sun gear 20 fixed to the first carrier 17
rotates, so as in the case above.

The planetary gear 21 revolves while rotating, and the second carrier 22
Rotate.

The second carrier 22 is provided with a cylindrical portion 22a at the center of the shaft opposite to the support shaft 23, and the pinion 11 is fitted into the cylindrical portion 22a.
It is formed to rotate integrally with the carrier 22.

Therefore, if the second carrier 22 rotates as described above,
The rotational force is transmitted to the pinion 11 and moves the rack 4, so that the steering force is power assisted.

Furthermore, the rotation of the drive shaft 12 is decelerated in the process of being transmitted from the first carrier 17 to the second carrier 22.

(Problems to be Solved by the Present Invention) In the conventional device as described above, the input shaft 2 provided on the handle 1 is connected to the electric motor 10 via the rack 4 and the speed reducer A. When the assist force by the electric motor 10 is transmitted to the rack 4, the assist force acts on the steering even when the steering wheel 1 is operated within a small range, so there is a problem that the steering wheel 1 turns too much.

Furthermore, when the speed reduction device A receives an input from the rack 4 side due to the self-lining torque that causes the tires 7 to return to the straight running state after steering, the above input torque is transmitted to the speed reduction device A and the electric motor 10. Therefore, there was a problem in that the return of the handle l was difficult due to the added friction loss.

Further, the torque caused by steering and the above-mentioned self-lining torque after steering are transmitted from the rack 4 side to the electric motor 10 via the reduction gear device A, but if the electric motor 10 fails and locks, the electric motor 10 does not rotate, there is a problem in that it is impossible to perform the above-mentioned manual steering or return steering using self-lining torque.

An object of the present invention is to provide an excellent speed reduction device as described below.

(1) Even when the steering wheel is operated within a small range, the steering wheel can be operated with the same feeling as manual operation.

(2) After steering, the self-lining makes it easy for the tires to return to a straight running state.

(3) If the electric motor malfunctions and locks up, a fail-safe function operates and manual steering is possible.

(Means for Solving Problems) The present invention is based on the following configuration and is an improvement thereof.

That is, the present invention is based on a sun gear that rotates integrally with the drive shaft of an electric motor, a ring gear located outside the sun gear, and a ring gear that rotates around the sun gear between the sun gear and the ring gear. This is a speed reduction device in which a casing houses a planetary gear that revolves and a carrier that rotates as the planetary gear revolves and transmits rotational force to a pinion shaft.

Based on the above configuration, the present invention provides a central rotating shaft on one side of the carrier, that is, the pinion shaft, forms a cam portion on this central rotating shaft, and connects the central rotating shaft and the pinion shaft. A pressure plate fixed to the drum and the casing is provided between the drum and the casing, a central rotating shaft is inserted into the drum, and a pair of clutches are connected to the cam between the inner circumference of the drum and the outer circumference of the cam. A spring is applied to the clutches to apply a force in a direction to bring them into contact with the cam portion, and when no rotational force is applied to the cam portion, the clutches are placed in contact with the outer periphery of the two. A gap is formed between the clutch and the drum, and a spring member is provided between the clutch and the pressure plate that acts in the direction of pressing the clutch against the drum to bring the clutch into contact with the drum and apply rotational force to the cam. If this occurs, the cam part and clutch are prevented from rotating together, the clutch and drum are integrated, and the drum and pinion shaft are connected.
Only when the rotational force from the drive shaft side of the electric motor is large is it transmitted to the pinion shaft, and if the electric motor is locked, the connection between the clutch and the drum is automatically released, and normal manual steering is no longer possible. It is characterized by a structure that allows it to be carried out.

(Operation of the present invention) With the above configuration, when the assist force from the electric motor is transmitted to the pinion, when the operating range of the handle is small and therefore the assist force from the electric motor is small, the assist force is transmitted to the pinion shaft. will no longer be transmitted.

Further, when the tires try to return to the straight-ahead state after steering, the torque transmitted from the pinion shaft side is no longer transmitted to the transmission gear and the electric motor.

Furthermore, even if the electric motor fails and locks, the torque transmitted from the pinion shaft side will no longer be transmitted to the electric motor, similarly to the above.

(Effects of the Invention) According to the speed reduction device of the present invention, when the assist force from the electric motor is transmitted to the rack, when the operating range of the handle is small and therefore the assist force from the electric motor is small, the assist force is transmitted to the pinion. Since it is not transmitted to the shaft, a natural steering feel can be obtained with manual steering.

Further, when the tires try to return to the straight-ahead state after steering, the torque transmitted from the pinion shaft side is no longer transmitted to the transmission gear and the electric motor, so the return performance of the steering wheel is improved.

Furthermore, if the electric motor fails and becomes locked, the coupling between the clutch and the drum is automatically released mechanically, and similarly to the above, the torque transmitted from the pinion shaft side is no longer transmitted to the electric motor. Therefore, normal manual steering becomes possible.

(Embodiment of the present invention) In the reduction gear device A of the embodiment shown in FIGS. 1 to 3, a sun gear 13 is fitted onto a drive shaft 12 of an electric motor 10. Further, on the inner circumference of the casing 29 near the electric motor 10,
A ring gear 15 is provided.

A plurality of planetary gears 6 are brought into contact between the sun gear 13 and ring gear 15 as described above, and these planetary gears 16 are connected to a support shaft 18 provided on the first carrier 17.
It is rotatably supported.

A center rotating shaft 19 is formed on the opposite side of the first carrier 17 from the planetary gear 16, and a sun gear 20 is fixed to the center rotating shaft 19. The leading end of the central rotating shaft 18 projects from the sun gear 20, and the projecting end is rotatably inserted into the shaft center of the second carrier 25.

Further, a plurality of support shafts 23 are provided on the sun gear 20 side of the second carrier 25, and the support shafts 23 rotatably support the planet gear 21. The ring gear 15 is fixed to the inner circumference of the ring gear 15.

A central rotating shaft 27 is formed on the opposite side of the second carrier 25 from the planetary gear 21, and its tip protrudes toward the drum 28 side.
It is rotatably inserted into the center of the shaft of 8. Further, a rectangular cam portion 27a is formed on the central rotating shaft 27, and a pair of half-moon-shaped clutches 26 are formed on two opposing sides of the cam portion 27a.
is in contact with A spring S is provided in the space where the two clutches 26 face each other, and this spring S fixes both ends to the clutch 26, and also connects the clutch 28 to the inner cam portion 27.
It acts in the direction of pressing the two opposing sides of a, respectively. A gap e is usually formed between the outer periphery of the clutch 26 and the drum 28.

Further, a pressure plate 24 fixed to the inside of the casing 2S is provided between the second carrier 25 and the drum 2B,
A disc spring 32, which is a spring member of the present invention, is provided on the clutch 26 side of the pressure plate 24. The disc spring 32 acts in a direction to bring the clutch 26 into contact with the drum 28.

In this way, the central rotating shaft 27 is rotated through the cam portion 27a.
, is linked to the drum 28 via the clutch 2B, but a pin hole 30 is formed on the opposite side of the drum 28 from the clutch 26, and a knock pin 30a is installed in this pin hole 30 to connect the drum 28 to the pinion shaft 31. are combined. A pinion 11 is formed on the pinion shaft 31, and the pinion 11 is engaged with the rack 4.

Therefore, when the electric motor 10 is driven, the sun gear 13
rotates, and as the sun gear 13 rotates, the planetary gears 16 rotate while revolving around the sun gear 13.

If the planetary gear 16 revolves around the sun gear 13, the first
As the carrier 17 rotates, the central rotating shaft 19 of the first carrier 17 rotates, and the sun gear 20 fixed to the central rotating shaft 18 rotates.

When the sun gear 20 rotates as described above, the planetary gear 21 meshed with it rotates and revolves around the sun gear 20, and the second carrier 25 rotates accordingly. When the second carrier 25 rotates, a cam portion 27a formed on the central rotating shaft 27, which is integral with the second carrier 25, rotates in the direction of the arrow shown in FIG.

At this time, since the pair of clutches 26 are pressed against the cam portion 27a by the spring S, they tend to rotate together with the rotation of the cam portion 27a.

However, since the clutch 28 is in pressure contact with the drum 28 by a disk spring 32 provided on the side thereof, the rotation thereof is prevented. In other words, since the pressure force exerted by the disc spring 32 is slightly larger than the spring force of the spring S, the cam portion 2
Even if 7a moves in the rotational direction, the clutch 26
The cam portion 27a presses the clutch 26 against the inner periphery of the drum 28 against the spring S without rotating together with the clutch 27a.

When the central rotating shaft 27 and the drum 28 are thus integrated via the clutch 28, the pinion 11 of the pinion shaft 31 connected to the drum 28 rotates, and the rack 4 is moved.

However, the rotational force of the electric motor 10 is low, and the cam portion 2
When the rotational torque of 7a is small, the spring force of the disc spring 32 is set so that the clutch 26 and the cam portion 27a rotate together, so the clutch 2B and the drum 28 are not coupled. Therefore, in this case, clutch 2
6 and the drum 28 are not integrated, and the output of the electric motor 10 is not transmitted to the pinion shaft 31.

Therefore, when the rotational force of the electric motor 10 is large, the output of the electric motor 10 is
1. It is transmitted to the wheels 7 via the rack 4. However, when the rotational force of the electric motor 10 is small, the electric motor 10
output is not transmitted to the pinion shaft 31. for that,
When the steering wheel l is operated within a small range, the assist force does not act on the steering, so there is no problem of the steering wheel l being turned too much, and the driver does not experience an unnatural steering sensation.

Further, the side surface of the clutch 26 is brought into contact with the drum 28 by the spring force of the disc spring 32. Although the spring force of the disc spring 32 is larger than the spring force of the spring S as described above, There is not enough power to combine it with 26. Moreover, since a gap is maintained between the outer periphery of the clutch 26 and the drum 28, when there is no output from the electric motor 10 and the pinion shaft 31 receives input from the rack 4 side via the pinion 11, the clutch 28 and the drum 28 slide. Therefore, the pinion shaft 31 and the clutch 26 are not coupled, and input from the rack 4 side is not transmitted to the central rotating shaft 27 of the reduction gear.

Therefore, when the tires try to return to the straight running state after steering and the reduction gear receives input from the rack 4 side, the transmission gear and the electric motor 10 do not rotate, and the rotation of these gears causes loss is eliminated, and the return performance of the handle l is improved.

In addition, if the electric motor 10 breaks down and locks,
This eliminates the rotational torque of the cam portion 27a.

The clutch 2B is connected to the cam portion 2 by the spring force of the spring S.
7a side, and a gap is maintained between the outer periphery of the clutch 26 and the drum 28. Therefore, clutch 2
6 and the drum 28 is mechanically and automatically released, and similarly to the above, the torque transmitted from the pinion shaft side is no longer transmitted to the electric motor. Therefore, normal manual steering becomes possible.

In the above embodiment, the cam portion 27a is rectangular, the clutch 26 is half-moon shaped, and the disc spring is a plate spring. It may be configured using the shape and members of.

[Brief explanation of the drawing]

Drawings 1 to 3 show embodiments of this invention.
The figure is a cross-sectional view, Figure 2 is an enlarged cross-sectional view of main parts showing the relative relationship between the cam part, clutch, and drum in the cross section taken along the line 4.5 shows a conventional speed reduction device. FIG. 4 is a sectional view, and FIG. 5 is an explanatory diagram of an example in which this speed reduction device is used in electric power steering. IO...Electric motor, 12...Drive shaft, 13...
Sun gear, 15...Ring gear, 16...Planetary gear, 17.22...Carrier, 24...Pressure plate, 26...Clutch, 27...Center rotating shaft, 27a
... cam part, 28 ... drum, 31 ... pinion shaft, 32 ... disc spring which is the spring member of this invention, S.
...Spring, e...gap.

Claims (1)

[Claims] A sun gear that rotates integrally with the drive shaft of the electric motor, a ring gear located outside the sun gear, a planetary gear that is located between the sun gear and the ring gear and revolves around the sun gear while rotating, and the revolution of the planetary gear. In a reduction gear device in which a carrier that rotates with the rotation and transmits rotational force to a pinion shaft is housed in a casing, a central rotating shaft is provided on one side of the carrier, that is, the pinion shaft, and a cam is attached to this central rotating shaft. A pressure plate fixed to the drum and the casing is provided between the central rotating shaft and the pinion shaft, and the central rotating shaft is inserted into the drum, and the inner periphery of the drum and the cam part are A pair of clutches are placed opposite to each other with a cam section in between, and a spring is applied to each clutch to apply a force in the direction of contacting the cam section, so that rotational force is applied to the cam section. If not, a gap is formed between the outer periphery of the clutch and the drum, and a spring member is provided between the clutch and the pressure plate that acts in the direction of pressing the clutch against the drum. is brought into contact with the drum, and when a rotational force is applied to the cam part, the cam part and the clutch are prevented from rotating together, the clutch and the drum are integrated, and the drum and the pinion shaft are connected,
Only when the rotational force from the drive shaft side of the electric motor is large is it transmitted to the pinion shaft, and if the electric motor is locked, the connection between the clutch and the drum is automatically released, and normal manual steering is no longer possible. A deceleration device configured to allow this.