JPH1159450A - Electrically driven power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrically driven power steering device which can transmit large output even when a clutch mechanism is miniaturized. SOLUTION: In this electrically driven power steering device, first and second rotors 35, 36 rotatably arranged on an output shaft 8 respectively have driven bevel gears 52, 53 meshed with a driving bevel gear 34 arranged on an armature shaft 31 of an electric motor 6. Rotation of the electric motor 6 is transmitted to the driven bevel gears 52, 53 to cause rotation in the mutually opposite direction. A movable body 37 engaged with a helical spline 54 is arranged on the output shaft 8. The movable body 37 is arranged in a movable manner on the output shaft 8 to the sides of the first rotor 35 and the second rotor 36 by electromagnetic force of an electromagnetic solenoid 41 through a lever 40. A first clutch 38 is arranged between the movable body 37 and the first rotor 35 opposed thereto. A second clutch 39 is arranged between the movable body 37 and the second rotor 36 opposed thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a stub shaft connected to a steering wheel according to a rotating direction.
The present invention relates to an electric power steering apparatus that switches a rotation direction transmitted from an electric motor and transmits the rotation to a pinion shaft.

[0002]

2. Description of the Related Art As a prior art, Japanese Patent Application Laid-Open No. 6-29326 is known.
There is a “power steering device” described in Japanese Patent Application Laid-Open No. 6-206. This conventional apparatus includes one drive bevel gear driven by a drive mechanism and a pair of driven bevel gears meshing with the drive bevel gear, and each driven bevel gear is rotatable around the stub shaft and the pinion shaft, respectively. Supported. In addition, a movable body is provided so as to straddle both shafts of a stub shaft and a pinion shaft that face each other in the axial direction. The movable body is helically spline-coupled to one of the two shafts and straight spline-coupled to the other, and a clutch mechanism is provided between the movable body and the two driven gears.

According to this device, when a relative rotation is generated between the stub shaft and the pinion shaft according to the torsion of the torsion bar by the rotation torque of the steering wheel, the movable body moves in the axial direction according to the relative rotation direction. By moving, the clutch mechanism is connected between the steering wheel and one driven bevel gear rotatable in the same direction. At this time, the driven bevel gear is driven by the drive mechanism to rotate each driven bevel gear, so that one driven bevel gear and the movable body connected by the clutch mechanism rotate integrally, so that the driven bevel gear is driven through the movable body. As a result, the power of the drive mechanism is transmitted to the pinion shaft, and the steering assist force can be applied.

Another conventional device is disclosed in
There is an “electric power steering device” described in Japanese Patent No. 273165. This conventional device includes a forward bevel gear and a reverse bevel gear provided around a handle shaft,
A forward rotation clutch for intermittently connecting the handle shaft and the forward bevel gear, a reverse rotation clutch for intermittently connecting the handle shaft and the reverse bevel gear, and a drive bevel gear meshing with the forward bevel gear and the reverse bevel gear; A reduction gear device connected to the driving bevel gear, and an electric motor driving the reduction gear device,
The vehicle includes a torque sensor that detects a steering torque and a vehicle speed sensor that detects a vehicle speed, and controls the operation of an electric motor, a forward rotation clutch, and a reverse rotation clutch based on outputs of the torque sensor and the vehicle speed sensor. This conventional device is different from the former conventional device in that the clutch mechanism is operated based on the driver's steering force, while the output of the torque sensor is used to control the forward rotation clutch and the reverse rotation clutch. The only difference is the basic operation.

[0005]

The former prior art (JP-A-6-293266) has a structure in which a movable body is moved by a driver's steering force to connect a clutch mechanism. When suddenly switching left and right does not cause discomfort to the driver, considering that the direction of the steering assist force is switched by smoothly switching the clutch mechanism, for example, if the clutch mechanism is a ratchet type engagement clutch, Vibration at the time of clutch engagement / disconnection is directly transmitted to the steering wheel, which is not preferable. Therefore, it is conceivable to apply a friction clutch that has relatively few problems such as noise at the time of clutch engagement / disconnection and vibration directly transmitted to the steering wheel. However, when a friction clutch is used, it is necessary to obtain the pressing force for engaging the clutch plate by the moving force of the movable body, that is, the steering force of the driver.

However, in general, in a power steering apparatus, a steering assist force by an electric motor is applied so that steering can be performed with a steering force of about 5 Nm.
The amount of movement of the movable body caused by the steering force of the driver cannot be set so large. Therefore, since the pressing force for engaging the clutch plate cannot be increased only by the steering force of the driver, in order to obtain the required pressing force, a material having a high friction coefficient is used for the clutch plate, It is necessary to increase the outer diameter of the plate to increase the contact area. However, a material having a high coefficient of friction is naturally disadvantageous to wear of the friction contact surface, and has a problem in durability. further,
The method of increasing the outer diameter of the clutch plate in order to increase the contact area naturally has a problem that the size of the device is increased.

The latter prior art (JP-A-62-27316)
No. 5), for example, an electromagnetic clutch that operates based on the driver's steering torque can be employed, so that the pressing force (engaging force) of the clutch plate can be obtained by the magnetic force generated in the exciting coil of the electromagnetic clutch. it can. For this reason, if the current value to be supplied to the excitation coil and the number of turns of the excitation coil are increased, a clutch suitable for the output of the electric motor can be provided. However, the physical size of the electromagnetic clutch becomes large in order to perform all the clutch engaging force only by the attraction force of the electromagnetic clutch. Also, in this case (the latter conventional technology), there is no mention of a method of transmitting output other than the electromagnetic clutch, so if a high-output motor is to be adopted in the future, a method other than enlarging the electromagnetic clutch will be used. The fact was that there was no such thing. The present invention has been made based on the above circumstances, and an object of the present invention is to provide an electric power steering device capable of transmitting a large output even when a clutch mechanism is downsized.

[0008]

Means for Solving the Problems According to the present invention, there is provided a switching device for switching the one-way rotation output from the electric motor in the forward and reverse directions according to the rotation direction of the stub shaft, and transmitting the rotation. The apparatus includes a first rotating body and a second rotating body that rotate in opposite directions to each other by transmitting the rotation of the electric motor, and the first rotating body and the second rotating body according to the rotation direction of the stub shaft. Selecting means for selecting one of the rotating bodies, a clutch mechanism for drivingly connecting the one rotating body selected by the selecting means and the output shaft, and generating a load in the thrust direction of the output shaft by the output of the electric motor; Conversion means for converting the thrust load into an engagement force of the clutch mechanism.

In this case, since the engagement force of the clutch mechanism can be obtained by the thrust load generated by the output of the electric motor, the steering force of the driver changes the rotation direction of the electric motor with respect to the switching device (by the selection means). It is only necessary to provide a trigger for selecting one of the first rotating body and the second rotating body). This allows
Unlike the related art, it is not necessary to directly use the driver's steering force to obtain the engagement force of the clutch mechanism, so that the driver's steering force may be small. Also, since it is not necessary to carry all the engaging force of the clutch mechanism with the electromagnetic clutch, the power consumption can be reduced, the efficiency is high, and the engaging force of the clutch mechanism can be obtained by the output generated by the electric motor itself. Even if the clutch mechanism is miniaturized, a large output can be transmitted.

Since the output shaft is formed integrally with the pinion shaft, the switching device can be disposed on the steering shaft. as a result,
Compared to a configuration in which the output of the output shaft is transmitted to the rack shaft using a transmission member, the arrangement of the switching device is restricted, but the weight, size, and cost of the electric power steering device are reduced because the transmission member is not used. There is an advantage that can be provided.
The above-mentioned steering shaft is composed of a stub shaft and a pinion shaft connected by a torsion bar.

(3) A one-way clutch is provided in a transmission path for transmitting one-way rotation of the electric motor to the switching device. The safety that the rotation of the rack shaft can be performed by the manual steering operation can be provided.

The conversion means engages the helical spline with the output shaft or a cylindrical fixing member arranged concentrically with the output shaft, and the axial direction on the output shaft along the helical spline. The movable body receives the output of the electric motor and moves in a direction to increase the engagement force of the clutch mechanism. In this case, when one of the rotating bodies selected by the selection means and the output shaft are drivingly connected by the clutch mechanism in accordance with the rotation direction of the stub shaft, the helical spline engages with the output shaft or the cylindrical fixing member. The movable body can move on the output shaft along the helical spline by the output of the electric motor in a direction to increase the engaging force (pressing load) of the clutch mechanism. By utilizing the thrust load generated by the movement of the movable body, it is possible to reliably generate the engaging force of the clutch mechanism that transmits the output of the electric motor to the output shaft. The effect of claim 1 in which only a small force for switching is sufficient can be realized with a simple structure.

(Means of Claim 5) The clutch mechanism comprises a first
A first clutch disposed between the rotating body and the movable body,
It comprises a second clutch disposed between the second rotating body and the movable body, and the first clutch and the second clutch are both friction clutches. In this case, even if the switching device is provided on the steering shaft directly connected to the steering wheel, there are relatively few problems such as noise when the clutch is engaged / disengaged and vibration directly transmitted to the steering wheel, and the electric type is comfortable for the driver. A power steering device can be provided.

(Claim 6) The clutch mechanism may be a first clutch.
A first clutch disposed between the rotating body and the movable body,
The first clutch and the second clutch are each configured by combining a friction clutch and a meshing clutch, respectively, with a second clutch disposed between the second rotating body and the movable body. It is a composite clutch. In this case, even if the switching device is provided on the steering shaft directly connected to the steering wheel, problems such as noise when the clutch is disconnected and vibration directly transmitted to the steering wheel can be solved by the friction clutch, and the problem of the friction clutch can be solved. It is possible to compensate for the slippage of the clutch at the time of transmission of high power and the reduction of durability due to the wear of the friction surface by the reliable transmission of power by the meshing clutch. As a result, the clutch mechanism becomes more complicated than in the case of claim 5 described above.
There is an advantage that a durable electric power steering apparatus can be provided in which the clutch is smoothly connected and disconnected.

(7) A movable member is provided with a clutch releasing elastic member acting in a direction for releasing the first clutch and the second clutch when the electric motor is not driven. I have. In this case, when the driver suddenly switches the steering direction, the movable body can be moved by the action of the elastic member when one of the first clutch and the second clutch is released. The responsiveness can be improved, and the sense of delay in following the steering assist force can be eliminated. Further, even when the movable body vibrates in the axial direction due to vibration from the vehicle or the like in a stationary state where the electric motor is not driven, the generation of abnormal noise is prevented by the elastic member absorbing the vibration, and However, there is an advantage that wear and damage of the clutch due to contact with the first clutch and the second clutch can be prevented.

(Means of Claim 8) The selecting means is a moving means for moving the movable body in the axial direction according to a relative torsion angle between the stub shaft and the pinion shaft, and a relative means between the stub shaft and the pinion shaft. And switch means for controlling energization of the electric motor in accordance with the torsion angle. In this case, a relative twist is generated between the stub shaft and the pinion shaft due to the rotational torque of the steering wheel caused by the steering force of the driver, and the movable body is moved in the axial direction by the moving means according to the twist angle. In this way, while selecting either the first clutch or the second clutch, a trigger for pressing and engaging the clutch is created. Further, when the motor is driven by the switch means, the movable body that engages with the helical spline with the output shaft or the cylindrical fixed member is rotated by the output of the motor via the clutch on the selected one rotating body side, and the output shaft is rotated. While generating a load in the thrust direction, the clutch can be moved on the output shaft along the helical spline in a direction to increase the pressing load of the clutch. Since the movement of the movable body continues until the driving force of the output shaft and the reaction force from the rack shaft balance, the engagement force of the clutch that transmits the output of the electric motor to the output shaft using the thrust load due to the movement of the movable body. Can be reliably generated.

Further, when the steering assist force of the electric motor becomes sufficient, the relative twist angle between the stub shaft and the pinion shaft is eliminated, so that the movable body moves away from the selected clutch by the action of the moving means. While the pressing force is removed, the drive of the electric motor is stopped by the switch means, so that the clutch on the selected side, that is, the engaged side can be completely disengaged. The provision of this switch means that the motor does not need to be energized at all times, so that it has an excellent effect that power consumption can be suppressed, and the current supplied to the motor can be controlled by a microcomputer or the like. Accordingly, it is possible to apply a current for applying the minimum necessary steering assist force, and it is possible to obtain a further power saving effect. Further, by controlling the current supplied to the electric motor using detection signals from a vehicle speed sensor, a rotation speed sensor, an acceleration sensor, a raindrop detection sensor, a tire pressure sensor, a steering angle sensor, and the like mounted on the vehicle, higher altitude is achieved. In addition, it is possible to provide a power-saving electric power steering device.

The moving means is an electromagnet apparatus for moving the movable body by electromagnetic force based on a command from the switch means. In this case, there is a factor of cost increase due to the provision of the electromagnet device in the moving means, but the link between the switching means and the switching device can be performed only by a flexible lead wire for operating the electromagnet. As a result, a degree of freedom is provided between the switch means and the switching device. For example, the switch means can be disposed on the steering shaft, and the switching device and the electric motor can be disposed on the rack shaft. In addition to a large degree of freedom in installation in a small space engine room, there is no need to support a heavy electric motor with a steering shaft, so that there is an advantage that the support member for the steering shaft can be simplified. Needless to say, the electromagnet device generates only a small force that triggers the switching of the rotation direction, and can be made smaller than the electromagnet device for transmitting all the output of the electric motor in the prior art. It is the same as

(Means of Claim 10) The moving means is related to a helical spline formed on one of a shaft rotating in relation to the rotation of the stub shaft and a shaft rotating in relation to the rotation of the pinion shaft. And a sliding body that engages with the other while being rotatively restricted and axially movable, and moves the movable body based on the amount of movement of the sliding body. In this case, as compared with the configuration described in claim 9, there is an advantage that it is possible to provide an electric power steering device that is lightweight, small and inexpensive as much as there is no electromagnet device.

The switch means is a torque sensor for electrically detecting a relative twist angle between the stub shaft and the pinion shaft. In this case, the necessary minimum driving force can be generated from the electric motor only when the steering assist force is required, and unnecessary power consumption by the electric motor can be suppressed.

The switch means is a torque sensor that electrically amplifies the relative twist angle between the stub shaft and the pinion shaft and then electrically detects the relative twist angle. The relative torsion angle between the stub shaft and the pinion shaft is a play of the steering wheel for the driver, and increasing the relative torsion angle on the steering shaft requires the turning response of the vehicle to the rotation of the steering wheel. In general, the relative twist angle needs to be suppressed to a small value of about 2 to 5 degrees. To detect this minute displacement, the components of the torque sensor are required to have high dimensional accuracy, but according to the present invention, the relative twist angle is mechanically amplified and then electrically detected. With such a configuration, it is not necessary to require a very high degree of dimensional accuracy for the components of the torque sensor, and it is possible to provide an inexpensive switch means.

The switch means is a torque sensor for electrically detecting the amount of axial movement of the sliding body. In this case, since the torque sensor can be formed integrally with the moving means, a lightweight, small, and inexpensive switch means can be provided.

(Switching means) The switching means is a torque sensor for electrically detecting the amount of mechanical strain between the sliding body and the movable body generated in the moving means. In this case, since the torque sensor can be configured integrally with the moving means,
It is possible to provide a lightweight, small, and inexpensive switch means.

[0024]

Next, an electric power steering apparatus according to the present invention will be described with reference to the drawings. (First Embodiment) FIG. 1 is a cross-sectional view of a switching device used in an electric power steering device (hereinafter, referred to as the present device), and FIG. 2 is a schematic diagram showing an entire configuration of the present device. As shown in FIG. 2, the present device 1 applies a steering shaft 4 for transmitting a steering force of a steering wheel 2 to a wheel-side rack shaft 3, a torque sensor 5 disposed on the steering shaft 4, and a rack shaft 3. Motor 6 as a power source of the assisted steering force, a switching device 7 for switching the one-way rotation output from the motor 6 in the forward and reverse directions and transmitting the rotation, and a rack for transmitting the rotation transmitted via the switching device 7. It comprises an output shaft 8 for transmitting to the shaft 3 and the like.

The steering shaft 4 includes a stub shaft 9 and a pinion shaft 1 which are coaxially opposed to each other.
0 and a torsion bar 11 (see FIG. 3) for connecting the stub shaft 9 and the pinion shaft 10. The stub shaft 9 has one end connected to the steering wheel 2 and the other end rotatably supported by a bearing 13 (see FIG. 3) fixed to a cover 12 of the torque sensor 5. The pinion shaft 10 is provided with a pinion gear 14 on the other end side. The pinion gear 14 is engaged with and connected to a rack gear 15 formed on the rack shaft 3 (see FIG. 2), and one end side is fixed to a casing 16 of the torque sensor 5. It is rotatably supported by a bearing 17 (see FIG. 3). As shown in FIG. 3, the torsion bar 11 is inserted into a hollow portion 9a formed at the other end of the stub shaft 9 and a hollow portion 10a formed at one end of the pinion shaft 10, and each of the shafts 9, 10
Are prevented from rotating by pins 18 and 19.

The torque sensor 5 is a well-known non-contact type, which detects a force for steering the steering wheel 2 by the driver (steering force) and a torsion direction of the steering shaft 4 by a voltage. As shown in FIG. 3, the specific configuration of the torque sensor 5 is a cylindrical member 20, 21 made of a magnetic material disposed at the other end of the stub shaft 9 and the pinion shaft 10. An excitation coil 22 and a detection coil 23 for detecting a magnetic change, which are disposed on the outer periphery of an opposing portion facing the axial direction, and an excitation coil 24 for assuring temperature, which is disposed on an outer periphery of the cylindrical portion 21 of the pinion shaft 10. And a detection coil 25, each coil 2 for detecting a magnetic change.
A plate 26 made of a non-magnetic material is interposed between the coils 2 and 23 and the coils 24 and 25 for temperature assurance, and the coils 22 and 23 for detecting magnetic change and the coils 24 and 25 for temperature assurance.
Are separated to form a separate magnetic circuit.

The cylindrical portions 20 and 21 are formed with concavo-convex portions 20a and 21a, respectively, which face each other in the axial direction. The excitation coil 22 and the detection coil 23 for detecting a magnetic change, and the excitation coil 24 and the detection coil 25 for assuring temperature are fixed to the casing 16 so as to be concentric with the shaft centers of the shafts 9 and 10, respectively. I have. An AC voltage is applied to each of the excitation coils 22 and 24, and a magnetic circuit of the magnetic change detection coil 23 that passes through the concave and convex portions 20 a and 21 a of each of the cylindrical portions 20 and 21 and the pinion shaft 1.
An induced voltage is generated in the magnetic circuit of the temperature assurance detection coil 25 passing through the 0 cylindrical portion 21.

Here, the operation of the torque sensor 5 will be described. When the driver rotates the steering wheel 2, relative torsion occurs between the stub shaft 9 and the pinion shaft 10 due to the elastic deformation of the torsion bar 11 connecting the stub shaft 9 and the pinion shaft 10. As a result, the uneven portions 20 formed on the cylindrical portions 20 and 21 of the stub shaft 9 and the pinion shaft 10 are formed.
a, 21a change in magnetoresistance, and the induced voltage generated in the detection coil 23 for detecting magnetic change changes. Since the detection coil 25 for temperature assurance has no change in magnetic resistance, the induced voltage generated in the detection coil 25 does not change. However, since the resistance of each of the coils 22 to 25 changes due to the temperature change, it is necessary to detect the difference between the induced voltage change of the temperature assurance detection coil 25 and the induced voltage generated at the magnetic change detection coil 23. Thus, irrespective of the temperature change, the change in the steering force according to the relative twist between the stub shaft 9 and the pinion shaft 10 and the twist direction of the torsion bar 11 can be detected by the voltage.

As shown in FIG. 1, the motor 6 includes a cylindrical yoke 27, a plurality of permanent magnets 28 fixed to the inner peripheral surface of the yoke 27, and an armature arranged on the inner peripheral side of the permanent magnets 28. (Described below), and a known DC motor including a brush device (not shown) for supplying power to the armature. The armature includes an armature core 29 configured by laminating a plurality of thin steel plates, an armature coil 30 wound around the armature core 29, and an armature shaft 31 that supports the armature core 29. One end is rotatably supported by a bearing 33 fixed to the center case 32 of the switching device 7, and the other end is rotatably supported by a bearing (not shown). A drive bevel gear 34 for transmitting the rotation generated by the electric motor 6 is provided at one end of the armature shaft 31, and a rectifier electrically and mechanically coupled to the armature coil 30 on the outer periphery of the other end. A child (not shown) is provided. The electric motor 6
Rotates in one direction, and for the following description, it is assumed that the armature shaft 31 rotates clockwise when viewed from below in FIG.

The switching device 7 is, as shown in FIG.
The first rotating body 35 and the second rotating body 36 which rotate in the opposite directions by the rotation of the first rotating body 35 and the movable body 37 provided on the output shaft 8 so as to be movable in the axial direction (left-right direction in FIG. 1). A first clutch 38 provided between the movable body 37 and the first rotating body 35; a second clutch 39 provided between the movable body 37 and the second rotating body 36; Solenoid 41 for moving the movable body 37 in the axial direction through the
Etc. The output shaft 8 is provided with a pinion gear 42 on the other end side. The pinion gear 42 is engaged with and connected to the rack gear 43 of the rack shaft 3 (see FIG. 2), and a bearing 44 fixed to the center case 32 of the switching device 7. And a cover 4 fitted to the center case 32.
The axial thrust is regulated by a washer 47 while being rotatably supported by a bearing 46 fixed to the bearing 5. The output shaft 8 is connected to the electric motor 6 as shown in FIG.
Are arranged orthogonally to the armature shaft 31.

The first rotator 35 and the second rotator 36 are
Bearings 48, 4, 4, and 4 are disposed on the outer periphery of the output shaft 8 so as to face each other in the axial direction (the left-right direction in FIG. 1).
The axial thrust is regulated by washers 50 and 51 while being rotatably supported by 9. Also, the first
The rotating body 35 and the second rotating body 36 have driven gears 52 and 53, respectively, at the outer peripheral end thereof.
2, 53 are meshed with a drive bevel gear 34 provided on the armature shaft 31 to transmit the rotation of the armature. However, when the armature rotates clockwise, the first rotating body 35 rotates rightward when viewed from the left side in FIG. 1, and the second rotating body 36 rotates leftward (rightward when viewed from the right side in FIG. 1).

The movable body 37 engages with a helical spline 54 provided on the outer periphery of the output shaft 8 between the first rotating body 35 and the second rotating body 36, and the helical spline 5
4 is provided so as to be movable on the output shaft 8. The movable body 37 includes a bearing 48 that supports the first rotating body 35.
1, while being pressed rightward in FIG. 1 by a spring 55 disposed via a washer, and by a spring 56 disposed via a washer between the bearing 49 supporting the second rotating body 36. 1 is pressed to the left. The two springs 55 and 56 are substantially the same so that the movable body 37 can be stopped substantially at the center of the first rotating body 35 and the second rotating body 36 when the switching device 7 is not operating. A load (pressing force) is applied. The first clutch 38
The first clutch 35 is constituted by friction pads 57 and 58 disposed on the opposing portions of the first rotating body 35 and the movable body 37, and the second clutch 39 is provided between the second rotating body 36 and the movable body 37. Are constituted by the friction pads 59 and 60 arranged at the opposed portions of the first and second members. The first clutch 38 and the second clutch 3
When the switching device 7 is not operated, the movable member 37 is evenly pressed from both sides in the axial direction by the springs 55 and 56 (the friction pads 57 and 58 and the friction pads 59 and 60 are released). Both are separated).

The electromagnetic solenoid 41 is, as shown in FIG.
A solenoid yoke 61 and a solenoid cover 62 forming a magnetic frame, a first coil 63 and a second coil 64 disposed inside the magnetic frame, and hollow portions of both coils 63 and 64 are movably disposed. The switching device 7 is disposed adjacent to the switching device 7. When the first coil 63 or the second coil 64 is energized, the electromagnetic solenoid 41 energizes the first coil 63
Alternatively, the plunger 65 moves toward the energized first coil 63 or the second coil 64 by receiving the magnetic force generated in the second coil 64, and the movement of the plunger 65 is transmitted to the movable body 37 through the lever 40. Accordingly, the movable body 37 can be moved in the axial direction. The energization of the first coil 63 and the second coil 64 is controlled by an electronic control unit (hereinafter, referred to as an ECU) (not shown) based on the voltage signal of the torque sensor 5. The lever 40 is disposed in the center case 32 and the solenoid yoke 61 through a long hole 32 a provided in the center case 32 and a long hole 61 a provided in the solenoid yoke 61, and one end of the lever 40 is located at the center of the plunger 65. The other end is connected to the concave portion of the movable body 37, and is swingably supported by the center case 32 by the support pin 66.

Next, an operation of switching the rotation direction of the electric motor 6 according to the rotation direction of the stub shaft 9 will be described. As an example, when the driver rotates the steering wheel 2 in a direction to turn the output shaft 8 to the right when viewed from the left side of FIG. 1, a voltage signal corresponding to the torsion direction of the torsion bar 11 is detected by the torque sensor 5, Based on the voltage signal, a current flows through the first coil 63 of the electromagnetic solenoid 41 according to a command from the ECU. Thereby, the plunger 65 is attracted to the right side in FIG. 1 by the magnetic force generated in the first coil 63, and the movement of the plunger 65 causes the lever 40 to press the movable body 37 to the left side in FIG. The spring 55 is bent to bring the friction pads 57 and 58 constituting the first clutch 38 into contact with each other.

On the other hand, a voltage signal corresponding to the steering force of the steering wheel 2 is detected by the torque sensor 5, and the electric motor 6 is energized by a command from the ECU based on the voltage signal. Thus, when the armature rotates in one direction (to the right as viewed from below in FIG. 1), the rotation of the armature is transmitted through the first rotating body 35 and the second rotating body 35 through driven driven gears 52 and 53 which mesh with the driving bevel gear 34, respectively. The first rotator 35 rotates clockwise as viewed from the left side in FIG. 1, and the second rotator 36 rotates left. First rotating body 35
Since the friction pad 57 is in contact with the friction pad 58 provided on the movable body 37, the rotation of the first rotating body 35 is transmitted to the movable body 37 via the first clutch 38.
The movable body 37 includes a helical spline 54 of the output shaft 8.
Therefore, while rotating in the same direction (right rotation) as the first rotating body 35, the user tries to move on the output shaft 8 along the helical spline 54 to the left side in FIG. By further moving the movable body 37 in the axial direction, the friction pads 57 and 58 are continuously pressed until the reaction force from the rack shaft 3 and the torque of the first rotating body 35 are balanced.

Here, the conditions for engaging the first clutch 38 using the output torque generated by the electric motor 6 itself will be described below. Torque of first rotating body 35 transmitted from electric motor 6: T Both friction pads 57, 58 constituting first clutch 38.
Average diameter of contact: R Friction coefficient between both friction pads 57 and 58: μ1 Mesh radius of helical spline 54 provided on output shaft 8 with movable body 37: r Helical spline 54 provided on output shaft 8 and movable body 37 And the torsion angle of the helical spline 54 provided on the output shaft 8 is θ. The pressing force F with which the movable body 37 presses the friction pads 57 and 58 is as follows: F = (tan θ−μ2) T / r The torque t that can be transmitted by the first clutch 38 is as follows: t = μ1 FR = μ1

In order to engage the friction pads 57 and 58 using the output torque T generated from the electric motor 6 itself, the following relationship may be satisfied. Torque T of first rotating body 35 ≦ torque t that can be transmitted by first clutch 38, that is, T ≦ μ1 · R · (tan θ−μ2) · T / r From this relationship, the following equation is obtained. r ≦ μ1 · R · (tan θ−μ2)...,...,..., in the present embodiment, for example, r = 10 (mm), R = 22
(mm), θ = 50 (deg), μ1 = 0.5, and μ2 = 0.1, the above equation holds. Thereby, if a friction coefficient exists between the friction pads 57 and 58 constituting the first clutch 38 by the attraction force of the electromagnetic solenoid 41 (that is, if the friction pads 57 and 58 are in contact), The first clutch 38 can be engaged using the output torque generated from the electric motor 6 itself. The second clutch 39 is also designed with the same specifications as the first clutch 38.

When the reaction force from the rack shaft 3 and the torque of the first rotating body 35 are balanced, the output torque of the electric motor 6 is reduced through the first rotating body 35 and the movable body 37 connected by the first clutch 38. Transmitted to the output shaft 8,
, A right-turn steering assist force is applied. Further, when the driver increases the steering force of the steering wheel 2, the current supplied to the electric motor 6 is increased by the voltage signal based on the steering force from the torque sensor 5, and the output of the electric motor 6 is increased. When the output of the electric motor 6 increases, the torque of the first rotating body 35 increases, and the movable body 37 further attempts to move to the left side in FIG. 1, so that the engaging force of the first clutch 38 (both friction pads 57 , 58). This movable body 37
With the further movement, the friction pads 57 and 58 are further pressed until the reaction force from the rack shaft 3 and the torque of the first rotating body 35 are balanced. And rack shaft 3
When the reaction force from the motor and the torque of the first rotating body 35 are balanced, the output torque of the electric motor 6 is transmitted to the output shaft 8 through the first rotating body 35 and the movable body 37 connected by the first clutch 38. Thus, the output shaft 8 is provided with a further steering assisting force of clockwise rotation.

Thereafter, when the driver stops the steering operation and releases the steering force, the current supplied to the motor 6 is interrupted by the voltage signal based on the release of the steering force from the torque sensor 5, and the output of the motor 6 stops. . As the output of the motor 6 stops, the torque of the first rotating body 35 disappears.
The pressing force for moving the movable body 37 to the left side in FIG. 1 via the helical spline 54 is eliminated. Further, since the voltage signal based on the torsion direction from the torque sensor 5 disappears due to the release of the steering force, the current supplied to the first coil 63 is cut off, and the magnetic force disappears. As a result, the suction force of the electromagnetic solenoid 41 for sucking the plunger 65, that is, the pressing force for moving the movable body 37 to the left side in FIG.
Is pushed back to the right in FIG. 1, and the first clutch 38 is released.

When the driver turns the steering wheel 2 in a direction in which the output shaft 8 is turned to the left as viewed from the left side of FIG.
An electric current flows through the second coil 64 according to a command from the CU, and the second clutch 39 is engaged, so that the output torque of the electric motor 6 is applied to the output shaft 8 through the second rotating body 36 and the movable body 37. The transmitted power is transmitted to the output shaft 8 to apply a left-handed steering assist force. Since the basic operation principle is the same as the case where the output shaft 8 is turned to the right, the description is omitted.

(Effects of the First Embodiment) In this embodiment, the steering assist force applied to the output shaft 8 is not proportional to the driver's steering force. 6
Can increase the pressing force of the clutch mechanism (the first clutch 38 or the second clutch 39) so as to balance the reaction force from the rack shaft 3 with its own driving force. As a result, the driver can increase the steering assist force without increasing the steering force. That is, since it is not necessary to directly use the driver's steering force to obtain the engagement force of the clutch mechanism as in the related art, the driver's steering force may be small. In addition, since it is not necessary for the electromagnetic clutch to bear all the engaging force of the clutch mechanism, the power consumption can be reduced, the efficiency is high, and the engaging force of the clutch mechanism can be obtained by the output generated by the electric motor 6 itself. Even if the clutch mechanism is downsized, a large output can be transmitted.

(Second Embodiment) FIG. 4 is a sectional view of a switching device used in the present device. As shown in FIG. 5, the present device 70 is applied to a steering shaft 73 for transmitting the steering force of the steering wheel 71 to the wheel side rack shaft 72, a torque sensor 74 disposed on the steering shaft 73, and the rack shaft 72. Motor 75, which is a power source of the assisted steering force, a switching device 76 for switching the one-way rotation output from the motor 75 in the forward and reverse directions and transmitting the rotation, and a rack for transmitting the rotation transmitted via the switching device 76. It comprises an output shaft 77 for transmitting to the shaft 72 and the like.

The steering shaft 73 includes a stub shaft 78 and a pinion shaft 79 which are coaxially opposed to each other, and a stub shaft 78 and a pinion shaft 7.
9 comprises a torsion bar 80 (see FIG. 6). The stub shaft 78 has one end connected to the steering wheel 71 and the other end rotatably supported by a bearing 82 (see FIG. 6) fixed to a sensor case 81 of the torque sensor 74. Pinion shaft 79
Is provided with a pinion gear 83 on the other end side, the pinion gear 83 is engaged with and connected to a rack gear 84 formed on the rack shaft 72 (see FIG. 5), and one end side is fixed to the sensor case 81 of the torque sensor 74. 8
5 (see FIG. 6) so as to be rotatable. The torsion bar 80 is, as shown in FIG.
8 is inserted into a hollow portion 78a formed on the other end of the pinion shaft 8 and a hollow portion 79a formed on one end of the pinion shaft 79.
It is stopped by 87.

Stub shaft 78 and pinion shaft 7
9 has an inner diameter of a cylindrical portion 78 b provided on the stub shaft 78 and a pinion shaft 79.
A needle bearing 88 is disposed between the shaft 78 and the outer diameter of the inner cylindrical portion 79b provided to improve the coaxiality between the shafts 78 and 79. Further, a mechanical stopper that regulates the torsion angle of the torsion bar 80 is configured by the cylindrical portion 78b provided on the stub shaft 78 and the outer cylindrical portion 79c provided on the pinion shaft 79. This mechanical stopper has a well-known structure, and as shown in FIG. 7 (A sectional view of FIG. 6),
9, a cylindrical portion 78b of the stub shaft 78 is fitted on the inner periphery of the outer cylindrical portion 79c, and a parallel surface 79d provided on the inner periphery of the outer cylindrical portion 79c and an inclined surface 7 provided on the outer periphery of the cylindrical portion 78b.
8c. This allows
When the driver rotates the steering wheel 71 to twist the torsion bar 80, and the torsion angle becomes the above θ, the parallel surface 79d of the outer tubular portion 79c and the tubular portion 78
b, the gap between the inclined surface 78c and the parallel surface 79c is eliminated.
d and the inclined surface 78c are in contact with each other, and have a function of preventing the torsion bar 80 from being twisted more than the angle,
The torsion bar 80 secures the torsional durability.

The torque sensor 74 is a well-known non-contact type, which detects a force for steering the steering wheel 71 by the driver (steering force) and a torsion direction of the steering shaft 73 by a voltage. As shown in FIG. 6, the torque sensor 74 includes a sensor shaft 89 that rotates by transmitting the rotation of the stub shaft 78 and a sensor shaft 9 that rotates by transmitting the rotation of the pinion shaft 79.
0, excitation coil 91 and detection coil 9 for detecting magnetic change
2. It is composed of an excitation coil 93 for temperature assurance, a detection coil 94 and the like.

The sensor shaft 89 is connected to the stub shaft 7.
8, and is rotatably supported by a bearing 96 provided in a coil case 95 fitted in the sensor case 81, and has a spur gear fixed on a shaft of a stub shaft 78 on its shaft. A spur gear 98 is formed to mesh with the stub 97 and increase the rotation of the stub shaft 78. The sensor shaft 90 is arranged in parallel with the pinion shaft 79, and is arranged coaxially opposite to the sensor shaft 89, and is rotatably supported by a bearing 99 fixed to a coil case 95. Meshes with a spur gear 100 disposed on the axis of the pinion shaft 79, and
A spur gear 101 is formed to increase the speed of rotation. At each end of the sensor shaft 89 and the sensor shaft 90, there are provided cylindrical portions 102 and 103 made of a magnetic material, respectively. 103a are formed.

The coils 91 and 92 for detecting a magnetic change are:
The two cylindrical portions 102 and 103 are arranged on the outer periphery of the opposed portions facing each other in the axial direction, and are fixed to the coil case 95 so as to be concentric with the axis centers of the sensor shafts 89 and 90. The reference numeral 94 is arranged on the outer periphery of the cylindrical portion 102 and is fixed to the coil case 95 so as to be concentric with the axial center of each of the sensor shafts 89 and 90. Further, each coil 91, 92 for detecting a magnetic change and each coil 93 for temperature assurance,
A non-magnetic plate 104 is interposed between the coils 94 and 94 to separate the coils 91 and 92 for detecting magnetic change and the coils 93 and 94 for temperature assurance so as to form separate magnetic circuits. ing. An AC voltage is applied to each of the exciting coils 91 and 93, and the uneven portions 102 of the cylindrical portions 102 and 103 are applied.
a, a magnetic circuit of a magnetic change detecting detection coil 92 passing through 103a, and a temperature assurance detection coil 94 passing through the cylinder 102;
An induced voltage is generated in each of the magnetic circuits. The operation of the torque sensor 74 is the same as that of the first embodiment, and the description thereof is omitted.

As shown in FIG. 4, the electric motor 75 includes a cylindrical yoke 105, a plurality of permanent magnets 106 fixed to the inner peripheral surface of the yoke 105, and an armature disposed on the inner peripheral side of the permanent magnets 106. (Described below), and a known DC motor including a brush device (not shown) for supplying power to the armature. The armature has an armature core 107 formed by stacking a plurality of thin steel plates,
An armature coil 108 wound around the armature core 107 and an armature shaft 109 for supporting the armature core 107 are provided.
09 is rotatably supported by a bearing 111 fixed to the center case 110 of the switching device 76, and the other end is rotatably supported by a bearing (not shown). One end of the armature shaft 109 has a motor 7
Driving sun gear 112 for transmitting the rotation generated 5
Is formed on the tip side of the driving sun gear 112 (FIG. 4).
(On the lower side) is provided with a small diameter portion 109a. A commutator (not shown) electrically and mechanically coupled to the armature coil 108 is provided on the outer periphery of the other end of the armature shaft 109. The electric motor 7
5 rotates in one direction, and for the following description, it is assumed that the armature shaft 109 rotates clockwise when viewed from below in FIG.

Next, the structure of the switching device 76 for switching the rotation direction of the electric motor 75 in accordance with the rotation direction of the stub shaft 78 will be described with reference to FIG. An output shaft 77 that transmits the rotation of the electric motor 75 to the rack shaft 72 is arranged coaxially with the armature shaft 109 of the electric motor 75,
A pinion gear 113 provided on the other end side is engaged with and connected to the rack gear 114 of the rack shaft 72 (see FIG. 5). The output shaft 77 is provided with a bearing 115 at the inner diameter of a cylindrical concave portion provided at one end (the upper end in FIG. 4), and through the bearing 115, an armature shaft 109.
While being rotatably supported by the small-diameter portion 109a, and rotatably supported by a bearing 118 fixed to a cover 117 fitted to the clutch case 116, while being provided with an axial thrust regulated by a washer 119. I have.

An idle bevel gear 121 rotatably supported by a bearing 120 housed in a bearing holding portion 116a of the clutch case 116 is provided on the inner periphery of the clutch case 116. On the output shaft 77, a first rotating body 124 and a second rotating body 125 having bevel gears 122 and 123 facing the axial direction of the output shaft 77 while meshing with the idle bevel gear 121 are arranged. . The first rotating body 124 is rotatably supported on the output shaft 77 by a bearing 126 while applying axial thrust to the washer 12.
7 and are arranged. Similarly, the second rotating body 125 is rotatably supported on the output shaft 77 by the bearing 128, and also receives the axial thrust by the washer 1.
29, and are arranged.

The first rotating body 124 has a side surface 12
A plurality of pins 130 are fixed to 4a. This pin 1
30 are arranged at equal intervals in the circumferential direction of the side surface portion 124a,
It protrudes toward the electric motor 75 (upward in FIG. 4) in parallel with the output shaft 77. A planetary gear 132 is rotatably supported on the outer periphery of the pin 130 via a bearing 131. The planetary gear 132 meshes with the driving sun gear 112 formed on the axis of the armature shaft 109, and the internal gear 133 formed on the inner peripheral surface of the center case 110.
(Internal teeth). Therefore, the planetary gear reduction mechanism is disposed between the electric motor 75 and the first rotating body 124, and the rotation of the armature is reduced and transmitted to the first rotating body 124 by the planetary gear reduction mechanism. Is done. The first rotating body 124 rotates rightward as viewed from below in FIG. 4 due to the right rotation of the armature, and the second rotating body 1
25 rotates counterclockwise through the idle bevel gear 121 as viewed from below in FIG.

On the outer peripheral portion of the output shaft 77, the first rotating body 1
A helical spline 134 is formed between the second rotating body 125 and the second rotating body 125, and the first movable body 135 and the second movable body 136 engage with the helical spline 134,
Each of the output shafts 77 along the helical spline 134
It is movably arranged on the top. This first movable body 13
5 and the second movable body 136 are respectively connected to the first rotating body 12
4 and the second rotator 125, and the first movable member 135 and the first rotator 124 are provided with the first
Of the second movable body 13
A second clutch 138 is provided at a portion where the second rotating body 125 faces the second rotating body 125.

The first clutch 137 is connected to the first rotating body 1
24, a plurality of friction plates 13 which directly
7a, and a plurality of friction plates 137b that are directly spline-engaged with the first movable body 135.
37a and friction plates 137b are alternately arranged, and the friction plates 137a and 137b come into contact with each other and frictionally engage with each other, so that the first rotating body 124 and the first movable body 13
5 and the friction plates 137a and 137b are separated from each other so that the first rotating body 124 and the first movable body 1 are separated from each other.
35 can be separated. Second clutch 138
Consists of a plurality of friction plates 138a directly spline-engaged with the second rotating body 125 and a plurality of friction plates 138b directly spline-engaged with the second movable body 136. The friction plate 138a and the friction plate 138b Are alternately arranged, and the friction plates 138a and 138b are brought into contact with each other and frictionally engaged with each other, so that the second rotating body 125
And the second movable body 136, and each friction plate 13
8a and 138b are separated from each other,
5 and the second movable body 136 can be separated.

The first movable body 135 is connected to the output shaft 77
The helical spline 134 is pressed downward in FIG.
The downward movement is restricted by the end face of the. Similarly, the second movable body 136 is restricted from moving upward by the end face of the helical spline 134 while being pressed upward in FIG. 4 by a spring 140 regulated by a washer against the output shaft 77. Thus, when the switching device 76 is not operated, the friction plate groups 137a and 137b constituting the first clutch 137 and the second clutch 13
8, the friction plate groups 138a and 138b are released, and the first clutch 137 and the second clutch 13
8 has been released.

First rotating body 124 and second rotating body 125
Are provided with a first coil 141 and a second coil 142, each constituting an electromagnetic solenoid.
A ring 144 made of a conductor that supplies a current to the first coil 141 via an annular insulator 143 is provided on an outer peripheral portion of the first rotating body 124.
A ring 146 made of a conductor for supplying a current to the second coil 142 via an annular insulator 145 is provided on the outer peripheral portion of the ring. Each ring 144, 146 is the first
Are electrically connected to the terminals of the coil 141 and the second coil 142.

The outer periphery of the first rotating body 124 and the outer periphery of the second rotating body 125 are respectively provided with an insulating case 147,
148 are provided. A brush 149 that slides on the outer peripheral surface of the ring 144 and a spring 150 that presses the brush 149 against the ring 144 are provided in the case 147. A brush 151 that comes into contact with the brush 151 and a spring 152 that presses the brush 151 against the ring 146 are provided. Note that the first coil 141 and the second coil 14
The power supply to the power supply 2 is controlled by an ECU (not shown) based on the voltage signal of the torque sensor 74.

Next, the operation of this embodiment will be described.
When the driver rotates the steering wheel 71 and a voltage signal corresponding to the torsion direction of the torsion bar 80 is detected by the torque sensor 74, the first coil 141 is supplied to the first coil 141 by a command from the ECU based on the voltage signal. Current is applied. Thereby, the first movable body 135 is moved by the magnetic force generated in the first coil 141 so that the spring 1
The first clutch 137 is lightly engaged while the friction plate group 137a and 137b constituting the first clutch 137 come into contact with each other while being sucked toward the first rotating body 124 (upward in FIG. 4) while bending the 39. I do.

On the other hand, a voltage signal corresponding to the steering force of the steering wheel 71 is detected by the torque sensor 74,
The electric motor 75 is energized by a command from the ECU based on the voltage signal. Accordingly, when the armature rotates in one direction (right rotation when viewed from below in FIG. 4), the rotation of the armature is transmitted to the first rotating body 124 via the planetary gear reduction mechanism, and further, the first rotating body is rotated. 124 is the first
Is transmitted to the first movable body 135 via the clutch 137. Since the first movable body 135 is engaged with the helical spline 134 of the output shaft 77, the first movable body 135 rotates in the same direction (clockwise rotation) as the first rotator 124, and moves along the helical spline 134 along the output shaft. Attempt to move upward on FIG. By further moving the first movable body 135 in the axial direction, the friction plate group 137a constituting the first clutch 137 until the reaction force from the rack shaft 72 and the torque of the first rotating body 124 are balanced. 137
Continue to press b. When the reaction force from the rack shaft 72 and the torque of the first rotating body 124 are balanced, the first rotating body 124 connected by the first clutch 137 and the first rotating body 124
The output torque of the electric motor 75 is transmitted to the output shaft 77 through the movable body 135, and a right-turn steering assist force is applied to the output shaft 77.

Thereafter, when the driver stops the steering operation and releases the steering force, the current supplied to the motor 75 is cut off by the voltage signal based on the release of the steering force from the torque sensor 74, and the output of the motor 75 is stopped. I do. Electric motor 7
With the stop of the output of No. 5, the torque of the first rotating body 124 is lost, so that there is no pressing force for moving the first movable body 135 through the helical spline 134 upward in FIG. Further, since the release of the steering force eliminates the voltage signal based on the torsion direction from the torque sensor 74, the current supplied to the first coil 141 is cut off, and the magnetic force disappears. As a result, the first force is
Is pushed back to the initial position (the position shown in FIG. 4), and the first clutch 137 is released. In addition,
When the second coil 142 is energized by a command from the ECU, the second movable body 136 is attracted and the second clutch 138 is engaged, so that the output torque of the electric motor 75 is reduced by the first rotation. Idle bevel gear 12 from body 124
1 to the second rotating body 125, and further transmitted to the output shaft 77 through the second movable body 136 connected to the second rotating body 125 by the second clutch 138.
A left-handed steering assist force is applied to the output shaft 77.

(Effect of Second Embodiment) In this embodiment, the first
Effects similar to those of the embodiment: It is possible for the driver to increase the steering assist force without increasing the steering force. Also,
Since it is not necessary for the electromagnetic clutch to bear all the engaging forces of the clutch mechanisms (the first clutch 137 and the second clutch 138), power consumption can be reduced, the power consumption is reduced, and the output generated by the electric motor 75 itself is reduced. Since it is possible to obtain the engaging force of the clutch mechanism, it is possible to obtain｝ that enables transmission of a large output even if the clutch mechanism is downsized, and the output shaft 77 and the armature shaft 109 of the electric motor 75 are coaxial. Since it is arranged and the electromagnetic solenoid is incorporated in the switching device 76, there is an advantage that it is possible to provide a relatively lightweight, small, and inexpensive electric power steering device. In the clutch mechanism described in the first embodiment, a friction pad having a high friction coefficient is used in order to satisfy μ1 = 0.5 in the equation. Therefore, a clutch mechanism can be configured by stacking a plurality of plate members (friction plate group) having a friction coefficient of about 0.1. As a result, a relatively inexpensive plate member can be manufactured.

Further, the torque sensor 7 described in this embodiment
4 is a configuration in which the relative torsion angle between the stub shaft 78 and the pinion shaft 79 is mechanically amplified and then electrically detected, so that it is not necessary to require a very high degree of dimensional accuracy for the sensor components. Inexpensive torque sensor 74 can be provided. That is, the relative torsion angle between the stub shaft 78 and the pinion shaft 79 corresponds to the play of the steering wheel 71 for the driver, and increasing the relative torsion angle on the steering shaft 73 requires the steering wheel 71 to rotate. In general, the relative torsion angle needs to be suppressed to a small value of about 2 to 5 degrees in order to reduce the turning response of the vehicle to the rotation of the vehicle. For this reason, in the torque sensor 5 described in the first embodiment, a high dimensional accuracy is required for the sensor components in order to detect a minute displacement, and therefore, the torque sensor 5 is more expensive than the torque sensor 74 of the present embodiment.

(Third Embodiment) FIG. 8 is a sectional view of a switching device used in this device. As shown in FIG. 9, the present device 160 is a steering shaft 1 that transmits a steering force of a steering wheel 161 to a wheel-side rack shaft 162.
63, an electric motor 164 that is a power source of the steering assist force applied to the rack shaft 162, a switching device 165 that switches the one-way rotation output from the electric motor 164 in the forward and reverse directions and transmits the rotation, and the switching device 165. It is composed of a torque sensor 166 (see FIG. 8) and the like arranged adjacent to each other. The steering shaft 163 includes a stub shaft 167 and a pinion shaft 168 that are coaxially opposed to each other, and a torsion bar 169 (see FIG. 8) that connects the stub shaft 167 and the pinion shaft 168.

The stub shaft 167 has one end connected to the steering wheel 161 and the other end connected to the switching device 16.
5, while being rotatably supported by a bearing 171 fixed to the clutch cover 170, the axial thrust is regulated by a washer 172 (see FIG. 8). The pinion shaft 168 is provided with a pinion gear 173 at the other end, and the pinion gear 173 is engaged with and connected to a rack gear 174 formed on the rack shaft 162 (see FIG. 9), and a bearing 176 having one end fixed to the clutch case 175. And bearing 1 fixed to clutch case 177
The axial thrust is regulated by washers 179 and 180 while being rotatably supported by 78 (see FIG. 8). The clutch cover 170 and the clutch case 1
75 and 177 are fitted so that the stub shaft 167 and the pinion shaft 168 are arranged coaxially.

As shown in FIG. 8, one end of the torsion bar 169 is inserted into a hollow portion 167a formed on the other end of the stub shaft 167, and the helical spline 1
The other end is inserted into a hollow portion 168 a formed at one end of the pinion shaft 168.
The torsion bar 169 is provided with a pin 181 that penetrates and engages in the radial direction, and the pin 181 is inserted into a long hole 168 b formed in the pinion shaft 168, so that the torsion bar 169 is attached to the pinion shaft 168. 169 is supported so as to be movable in the axial direction (vertical direction in FIG. 8) in the elongated hole 168b while restricting the rotation. Also,
Recesses are formed at both ends of the torsion bar 169, and springs 182 and 183 are provided between the one recess and the stub shaft 167 and between the other recess and the pinion shaft 168, respectively. Thereby, the torsion bar 169 is connected to both shafts 167 and 16.
Pressed by springs 182 and 183 from the eighth side, the steering shaft 163 is supported so as not to easily move in the axial direction even if it vibrates.

As shown in FIG. 8, the motor 164 includes a cylindrical yoke 184, a plurality of permanent magnets 185 fixed to the inner peripheral surface of the yoke 184, and an armature disposed on the inner peripheral side of the permanent magnet 185. (Described below), and a known DC motor including a brush device (not shown) for supplying power to the armature. The armature has an armature core 18 formed by laminating a plurality of thin steel plates.
6, an armature coil 187 wound around the armature core 186, and an armature shaft 188 supporting the armature core 186. One end of the armature shaft 188 is rotatably supported by a bearing 190 fixed to a center case 189. The other end is rotatably supported by a bearing (not shown). An armature gear 191 for transmitting the rotation generated by the electric motor 164 is formed at one end of the armature shaft 188, and the armature shaft 188 is electrically and mechanically coupled to the armature coil 187 at the other end of the armature shaft 188. A commutator (not shown) is provided. The electric motor 164 rotates in one direction, and for the following description, it is assumed that the armature shaft 188 rotates clockwise when viewed from above in FIG. 8 (B in the figure).

Next, the switching device 1 for switching the rotation direction of the electric motor 164 according to the rotation direction of the stub shaft 167.
65 will be described. In this embodiment, the motor 1
The output shaft that transmits the rotation of the shaft 64 to the rack shaft 162 is the pinion shaft 168 itself, and the output shaft and the pinion shaft 168 are integrated. Pinion shaft 1
68, a first rotating body 1 having a spur gear 192
93 and a second rotating body 195 having a spur gear 194 are arranged to face each other in the axial direction. First rotating body 193
Is rotatably supported by a clutch case 177 by a bearing 196, and the second rotating body 195 is rotatably supported by the clutch case 175 by a bearing 197.

On the outer peripheral portion of the pinion shaft 168,
Helical splines 198 and 199 are formed, and the first movable body 200 and the second movable body 200 that can move on the pinion shaft 168 by engaging with the helical splines 198 and 199 are formed.
Of the first rotating body 193 and the second rotating body 195 are disposed. Further, a multi-plate plate group constituting the first clutch 202 is provided at an opposing portion between the first rotating body 193 and the first movable body 200, and the second rotating body 195 and the second movable body 200 A group of multiple plates constituting the second clutch 203 is provided at a portion facing the body 201. Note that the first clutch 202 and the second clutch 203 have the same configuration as in the second embodiment.

The first movable body 200 is provided with a spring 227 fixed to a pinion shaft 168 by a washer.
8, the movement in the axial direction is restricted by the end face of the helical spline 198. Similarly, the second movable body 201 has a spring 22 fixed to a pinion shaft 168 by a washer.
8, the downward movement of the helical spline 199 is restricted by the end face of the helical spline 199 while being pressed downward in FIG. 8. As a result, the multi-plate group forming the first clutch 202 and the multi-plate group forming the second clutch 203 are released, and the first clutch 202 and the second clutch 203 are released. .

A pin 181 that penetrates the torsion bar 169 passes through a slot 168 b of the pinion shaft 168 at an opposing portion of the pinion shaft 168 between the first movable body 200 and the second movable body 201. 16
8 protrudes outward from the outer diameter of the first movable body 200.
And a third movable body 204 disposed at a portion opposite to the second movable body 201. This third movable body 204
The transmission member 20 is attached to the movable iron core 205 of the torque sensor 166 disposed on the outer periphery of the clutch cases 175 and 177.
6 are connected. The transmission member 206 is disposed in a recess formed on the outer peripheral portion of the third movable body 204 via a hard ball 207 for a bearing.

The torque sensor 166 of this embodiment is a known differential transformer type electromagnetic sensor, and as shown in FIG.
A first excitation coil 208 and a first detection coil 209 for detecting a magnetic change, a second excitation coil 210 and a second detection coil 21 for detecting a magnetic change are provided on an outer peripheral portion of the movable iron core 205.
1 is arranged. Each of the coils 208 to 211 is inserted into the coil case 212 so as to be concentric with the movable iron core 205. Further, the coil cases 212 are fitted so as to be concentric with each other, while the clutch cases 175, 1
77 is fixed to the outer peripheral portion. Each excitation coil 208,
An AC voltage is applied to each of the detection coils 210, and each of the detection coils 20 has a magnetic circuit including the movable iron core 205.
An induced voltage is generated at 9, 211. This allows
When the movable core 205 moves in the axial direction, the induced voltage of one of the detection coils 209 and 211 increases and the induced voltage of the other decreases due to a change in the magnetic circuit. Using this voltage change, the amount of movement of the movable core 205 can be extracted as a voltage signal.

A bearing 2 is provided on the outer periphery of the second rotating body 195.
A first drive shaft 215 having a spur gear 214 meshing with the spur gear 194 is provided while being rotatably supported by the clutch case 175 by 13. In addition, a clutch case 177 is provided on an outer peripheral portion of the first rotating body 193.
The clutch case 177 and the center case 18 are supported by bearings (not shown) stored in a bearing holding portion 216 provided in the
9 and a second drive shaft 219 having a spur gear 218 meshing with the spur gear 192 while being rotatably supported by the second drive shaft 219. Further, spur gears 220 and 221 are provided at the end of the first drive shaft 215 and the end of the second drive shaft 219, respectively, and mesh with each other.

The second drive shaft 21 located between the bearing holder 216 provided on the clutch case 177 and the bearing holder 217 provided on the center case 189 is opposed to the second drive shaft 21.
9 is provided on the outer diameter portion of the outer peripheral portion of the second drive shaft 2 with the spur gear 222 meshing with the armature gear 191 and transmitting the rotation from the armature gear 191 to the inner diameter portion.
A clutch outer 223 that accommodates a roller-type one-way clutch that blocks the rotation from 19 is provided. This one-way clutch is, as shown in FIG.
A plurality of wedge-shaped cam chambers 224 are formed on the inner peripheral surface of the cylinder 23, and a cylindrical roller 225 and a spring 226 pressing the cylindrical roller 225 are provided in each cam chamber 224, and a second drive shaft 219 is provided. 10, the roller 225 rolls on the outer peripheral surface of the second drive shaft 219 and the clutch idles. Conversely, when the clutch outer 223 rotates leftward (in the direction of the arrow) in FIG.
9 and the inner peripheral surface of the cam chamber 224, so that the clutch outer 223 and the second drive shaft 219 are engaged.
Are configured to rotate integrally and to transmit each other's rotation.

The positional relationship between the spur gears will be described with reference to FIG. 10. The spur gear 218 provided on the second drive shaft 219 is formed by a spur gear 192 formed on the outer periphery of the first rotating body 193. And the first drive shaft 2
Spur gear 214 provided on the second rotating body 19
5 meshes with a spur gear 194 formed on the outer peripheral portion. Further, a spur gear 221 provided at the end of the second drive shaft 219 (in FIG. 10, appears to overlap the spur gear 218 in the axial direction with the same number of teeth as the spur gear 218) is provided at the end of the first drive shaft 215. The spur gear 220 provided in the section (FIG. 1)
At 0, the spur gear 214 looks axially overlapped with the same number of teeth as the spur gear 214).

As a result, when the armature gear 191 rotates clockwise (in the direction of the arrow), the spur gear 222 meshing with the armature gear 191 rotates counterclockwise, and the rotation of the spur gear 222 is transmitted via the one-way clutch to the second drive shaft. 219, and the second drive shaft 219 rotates left. As a result, the spur gear 192 meshing with the spur gear 218 provided on the second drive shaft 219 rotates clockwise, and the first rotating body 193 having the spur gear 192 rotates clockwise (in the direction of the arrow). In addition, the spur gear 220 meshing with the spur gear 221 provided at the end of the second drive shaft 219 rotates clockwise, and the first drive shaft 215 having the spur gear 220 rotates clockwise, so that the The spur gear 194 that meshes with the spur gear 214 provided on the first drive shaft 215 rotates counterclockwise, and the second spur gear 194 having the spur gear 194 is rotated.
Is rotated left (in the direction of the arrow).

Next, an operation of switching the rotation direction of the electric motor 164 according to the rotation direction of the stub shaft 167 will be described with reference to FIG. As an example, a case in which the driver rotates the steering wheel 161 in a direction in which the stub shaft 167 is turned to the right when viewed from above in FIG. The torsion bar 169 engages the helical spline 167b with the stub shaft 167, and the pin 181 with the pinion shaft 168.
Stub shaft 16
7 moves on the steering shaft 163 according to the twist angle between the pinion shaft 168 and the pinion shaft 168. In this embodiment,
Since the helical spline 167b shown in FIG. 8 is twisted rightward, the torsion bar 169 moves while flexing the spring 183 in the downward direction.

With the movement of the torsion bar 169,
The third movable body 204 connected to the torsion bar 169 via the pin 181 also moves in the axis-down direction. Thus, the spring 227 is flexed via the first movable body 200 and the multiple plate group forming the first clutch 202 is brought into contact with the first clutch 202 to lightly engage the first clutch 202. In the torque sensor 166, the third movable body 2
As the movable iron core 205 connected via the hard sphere 207 and the transmission member 206 to the axis 04 moves in the axial direction to change the magnetic circuit, the induced voltage generated in the second detection coil 211 increases, The induced voltage generated in one detection coil 209 decreases. This voltage change is caused by the torsion bar 1
A torsion torque between the stub shaft 167 and the pinion shaft 168 that moves the torsion bar 169 while bending the spring 183 in proportion to the amount of movement of the pin 69;
That is, it is proportional to the steering force of the driver. Based on the voltage signal of the torque sensor 166 corresponding to the driver's steering force, the ECU
When a current flows through the electric motor 164 in response to a command from the first rotating body 193, the first rotating body 193 rotates clockwise due to the right rotation of the armature, and the second rotating body 195 rotates leftward.

The first rotating body 193 includes the first clutch 2
Since the first movable body 200 is connected to the first movable body 200 via the second movable body 02, the right rotation output is transmitted from the first rotating body 193 to the first movable body 200. Since the first movable body 200 is in helical spline engagement with the pinion shaft 168, when the right rotation output is transmitted from the first rotating body 193, the first movable body 200 will further move in the axis-downward direction in FIG. And Due to the further movement of the first movable body 200, the multi-plate plate group forming the first clutch 202 is kept pressed until the reaction force from the rack shaft 162 and the torque of the first rotating body 193 are balanced. And the rack shaft 16
When the reaction force from 2 and the torque of the first rotating body 193 are balanced, a right-turn steering assist force is applied to the pinion shaft 168.

Thereafter, when the driver stops the steering operation and releases the steering force, the current supplied to the motor 164 is interrupted by the voltage signal based on the cancellation of the steering force from the torque sensor 166, and the output of the motor 164 stops. . When the output of the electric motor 164 stops, the torque of the first rotating body 193 disappears, so that there is no pressing force for moving the first movable body 200 via the helical spline 198 in the axially downward direction in FIG. Further, with the release of the steering force, the torsion bar 169 is pushed back in the axial direction of FIG. 8 by the reaction force of the spring 183, so that the multi-plate plate group constituting the first clutch 202 is opened, and the first clutch 202 is opened. Rotating body 1
93 and the first movable body 200 are separated. When the driver rotates the steering wheel 161 in a direction in which the stub shaft 167 is turned to the left as viewed from the upper side of FIG. 8 (B view), the torsion bar 169 moves in the axial direction and the second By engaging the clutch 203, the second rotating body 195 and the second movable body 201
And the pinion shaft 168 is provided with a left-handed steering assist force. The basic operation principle is the same as when the above-described pinion shaft 168 is turned clockwise.

(Effect of Third Embodiment) In this embodiment, the first
The same effect as the embodiment can be obtained, and the first movable body 200 for lightly engaging the first clutch 202 and the second clutch 203 with respect to the first embodiment and the second embodiment. In addition, there is no need to use an electromagnet device as a moving unit for moving the second movable body 201. Further, since the output shaft of the switching device 165 is integrated with the pinion shaft 168, the switching device 1 is mounted on the steering shaft 163.
The torque sensor 166 can be configured integrally with the moving means while the 65 is arranged. As a result, a lightweight, compact and inexpensive electric power steering device can be provided.

(Fourth Embodiment) FIG. 11 is a sectional view of a switching device used in this device. As shown in FIG. 12, the device 230 includes a steering shaft 233 that transmits the steering force of the steering wheel 231 to the wheel-side rack shaft 232, an electric motor 234 that is a power source of a steering assist force applied to the rack shaft 232, The switching device 235 includes a switching device 235 for switching the rotation in one direction output from the motor 234 in the forward and reverse directions and transmitting the rotation, a torsional sliding device 236, and the like. The steering shaft 233 includes a stub shaft 237 and a pinion shaft 238 that are coaxially opposed to each other, and a torsion bar 239 that connects the stub shaft 237 and the pinion shaft 238.

The stub shaft 237 has one end connected to the steering wheel 231 and the other end rotatably supported by a bearing 241 fixed to the slider cover 240 (see FIG. 11). Pinion shaft 238
Is provided with a pinion gear 242 on the other end side, and this pinion gear 242 is engaged with and connected to a rack gear 243 formed on the rack shaft 232 (see FIG. 12).
Bearing 245 having one end fixed to slider cover 244
(See FIG. 11). The slider cover 240 and the slider cover 244 are fixed to the outer peripheral portion of the clutch case 247 while being fitted to the slider case 246 such that the stub shaft 237 and the pinion shaft 238 are coaxially arranged.
As shown in FIG. 11, the torsion bar 239 includes a hollow portion 237a formed on the other end of the stub shaft 237 and a hollow portion 23 formed on one end of the pinion shaft 238.
8a, each shaft 237, 238 respectively
Are prevented from rotating by pins 248 and 249.

The slider 250 of the torsional sliding device 236 is provided on the outer periphery of the opposing portion between the stub shaft 237 and the pinion shaft 238. This slider 250
The straight spline 237b formed on the outer diameter portion on the other end side of the stub shaft 237 and the helical spline 238b formed on the outer diameter portion on one end side of the pinion shaft 238 are engaged with each other. Therefore, this slider 250
When the driver rotates the steering wheel 231 to cause a twist between the stub shaft 237 and the pinion shaft 238, the driver can move on the steering shaft 233. Specifically, the helical spline 238b of the pinion shaft 238 shown in FIG. When the stub shaft 237 is twisted to the left with respect to the pinion shaft 238, the stub shaft 237 moves to the right on the steering shaft 233.

As shown in FIG. 11, the electric motor 234 includes a cylindrical yoke 251, a plurality of permanent magnets 252 fixed to the inner peripheral surface of the yoke 251, and an armature disposed on the inner peripheral side of the permanent magnet 252. (Described below), and a known DC motor including a brush device (not shown) for supplying power to the armature. The armature is an armature core 25 formed by stacking a plurality of thin steel plates.
3, an armature coil 254 wound around the armature core 253, and an armature shaft 255 for supporting the armature core 253. One end of the armature shaft 255 is rotatably supported by a bearing 256 fixed to a clutch case 247. The other end is rotatably supported by a bearing (not shown). A drive bevel gear 257 for transmitting the rotation generated by the electric motor 234 is formed at one end of the armature shaft 255, and the armature shaft 255 is electrically and mechanically coupled to the armature coil 254 on the other end. A commutator (not shown) is provided. Note that the electric motor 234 rotates in one direction, and for the following description, it is assumed that the armature shaft 255 rotates left when viewed from below in FIG.

Next, the switching device 2 for switching the rotation direction of the electric motor 234 according to the rotation direction of the stub shaft 237.
The structure of No. 35 will be described. The output shaft 258 of the switching device 235 is disposed orthogonal to the armature shaft 255 of the electric motor 234, and has a bearing 259 fixed to the clutch case 247 and a bearing 261 fixed to the clutch cover 260 fitted to the clutch case 247. The axial thrust is regulated by the washer 262 while being rotatably supported by the shaft. On the output shaft 258, driven bevel gears 263, 26 meshing with the drive bevel gear 257, respectively.
The first rotator 265 and the second rotator 266 having the four rotators 4 are disposed so as to face each other in the axial direction (the left-right direction in FIG. 11). The first rotator 265 and the second rotator 266 are
Bearings 267, 268 respectively arranged on the output shaft 258
, And the axial thrust is regulated by the washers 269 and 270. The first
When the armature rotates counterclockwise, the rotating body 265 of FIG.
Is rotated rightward when viewed from the left side, and the second rotating body 266 is arranged to rotate leftward.

Helical splines 271 and 272 are formed on the outer periphery of the output shaft 258, and the first movable body 273 and the second movable body 273 are engaged with the helical splines 271 and 272.
Movable body 274 is disposed. The first movable body 273 and the second movable body 274 are disposed at opposing portions of the first rotating body 265 and the second rotating body 266, respectively, and output shafts 258 along helical splines 271 and 272.
It is provided movably on the top. Also, the first rotating body 2
A multi-plate plate group constituting the first clutch 275 is disposed at a portion where the first movable body 65 and the first movable body 273 face each other.
The opposing portion between the rotating body 266 and the second movable body 274 includes
A multi-plate group forming the second clutch 276 is provided. The first clutch 275 and the second clutch 276 have the same configuration as in the second embodiment.

The first movable body 273 is the first rotating body 26
While being pressed to the left in FIG. 11 by a spring 277 disposed between the bearing 267 and the bearing 267 that supports the shaft 5, the movement of the helical spline 271 in the axial left direction is restricted by the end face of the helical spline 271. Similarly, the second movable body 274 is
While being pressed rightward in FIG. 11 by a spring 278 disposed between the bearing 268 supporting the second rotating body 266 via a washer, the movement of the helical spline 272 in the axial right direction is restricted by the end face. ing. This allows
The multi-plate group forming the first clutch 275 and the multi-plate group forming the second clutch 276 are released, and the clutches 275 and 276 are released.

The first movable body 273 and the second movable body 274
A third movable body 279 is disposed between the first movable body and the third movable body. Further, the third movable body 279 is provided with a clutch case 247.
Lever 280 disposed through a long hole 247a provided in the slider case 246 and a long hole 246a provided in the slider case 246.
Is connected to the slider 250. Lever 280 is provided at both ends with locking portions 280 a and 280 b having a concave shape when viewed from the axial direction (left-right direction) of FIG. 11, and one locking portion 280 a is provided in a concave portion of The slider 250 is engaged with the other locking portion 280b.
Of the support pin 2 in the clutch case 247.
At 81, it is swingably supported. Also, the lever 28
A plurality of strain gauges 282 for detecting the strain generated in the lever 280 are provided at the base of one of the locking portions 280a.

At one end of the output shaft 258, a spur gear 283 is formed, and the idle gear 2 meshing with the spur gear 283 is formed.
84 is rotatably supported by a bearing 285 fixed to the clutch cover 260. Furthermore, idle gear 2
Reference numeral 84 meshes with a spur gear 286 provided on the pinion shaft 238. As a result, the rotation torque generated by the electric motor 234 is transmitted to the output shaft 258 via the switching device 235, and the rotation of the output shaft 258 is transmitted to the spur gear 283 → idle gear 284 → spur gear 286. Pinion shaft 23 with spur gear 286
8 is transmitted.

Next, an operation of switching the rotation direction of the electric motor 234 according to the rotation direction of the stub shaft 237 will be described with reference to FIG. As an example, a case where the driver rotates the steering wheel 231 in a direction in which the stub shaft 237 is turned to the right when viewed from the left side in FIG. 11 will be described. In this case, the slider 250 on the steering shaft 233 moves to the left on the steering shaft 233 as described above. With the movement of the slider 250, the lever 280 that operates with the support pin 281 as a fulcrum moves through the first movable body 2 via the third movable body 279.
73 is pressed to the right while flexing the spring 277. By moving the first movable body 273 to the right side, the multi-plate plates constituting the first clutch 275 are brought into contact with each other to lightly engage the first clutch 275, while the distortion generated in the lever 280 is reduced. Detected by gauge 282,
The motor 23 outputs a signal from an amplifier (not shown) that outputs a voltage proportional to the amount of distortion according to a command from the ECU.
Current is passed through 4, and the armature starts rotating to the left.

The left rotation of the armature drives the bevel gear 257
Transmitted to the driven gears 263 and 264 through
A first rotating body 265 having a driven gear 263 is shown in FIG.
1 rotates to the right as viewed from the left, and the second rotating body 266 having the driven bevel gear 264 starts to rotate to the left. Since the first rotating body 265 is connected to the first movable body 273 via the first clutch 275, the right rotation output is transmitted from the first rotating body 265 to the first movable body 273. You. Since the first movable body 273 is in helical spline engagement with the output shaft 258, when the right rotation output is transmitted from the first rotating body 265, the first movable body 273 further moves to the right side in FIG. I do. The further movement of the first movable body 273 causes the first clutch 27 to move until the reaction force from the rack shaft 232 and the torque of the first rotating body 265 are balanced.
5 is continuously pressed. And
Reaction force from rack shaft 232 and first rotating body 265
When the torque is balanced, the clockwise output is transmitted to the output shaft 258, and the clockwise steering assist force is applied to the pinion shaft 238 from the output shaft 258 via the idle gear 284.

Thereafter, when the driver stops the steering operation and releases the steering force, the current supplied to the motor 234 is cut off by the signal based on the cancellation of the steering force from the amplifier, and the output of the motor 234 stops. When the output of the electric motor 234 is stopped, the torque of the first rotating body 265 is lost, so that the first movable body 2 is connected via the helical spline 271.
There is no pressing force to move 73 to the right in FIG. Further, with the release of the steering force, the slider 250 returns to the initial position (the position shown in FIG. 11), so that the multi-plate group forming the first clutch 275 is released, and the first clutch 275 is released.
Of the rotating body 265 and the first movable body 273 are separated. The stub shaft 23 is viewed from the left side of FIG.
When the driver turns the steering wheel 2
31 is rotated, the slider 250 moves to the right on the steering shaft 233 and engages the second clutch 276 via the lever 280, so that the second rotating body 266 and the second movable body 274 are connected via a second clutch 276. Thereby, the output shaft 2
The output of left rotation is transmitted to 58, and a left rotation steering assist force is applied to the pinion shaft 238 from the output shaft 258 via the idle gear 284. This basic operating principle is
This is the same as turning the stub shaft 237 to the right.

(Effect of Fourth Embodiment) In the present embodiment, the first
The same effect as that of the third embodiment can be obtained, and, similarly to the third embodiment, a first movable body 273 for lightly engaging the first clutch 275 and the second clutch 276.
Further, it is not necessary to use an electromagnet device as a moving unit for moving the second movable body 274. Also, the first clutch 2
75 and the output shaft 25 on which the second clutch 276 is disposed
8 is not hollow, it is easy to secure the strength of the output shaft 258. As a result, a lightweight, compact and inexpensive electric power steering device can be provided.

(Fifth Embodiment) FIG. 13 is a sectional view of a switching device used in this device. This apparatus is a modification of the second embodiment, and the schematic configuration of the entire apparatus is the same as that of FIG. As shown in FIG. 13, the electric motor 290 includes a cylindrical yoke 291, a plurality of permanent magnets 292 fixed to the inner peripheral surface of the yoke 291,
2 is a well-known DC motor that includes an armature (described below) disposed on the inner peripheral side of the motor 2 and a brush device (not shown) for supplying power to the armature.

The armature includes an armature core 293 formed by laminating a plurality of thin steel plates, an armature coil 294 wound around the armature core 293, and an armature shaft 295 for supporting the armature core 293.
The armature shaft 295 has one end rotatably supported by a bearing 297 fixed to the center case 296 and the other end rotatably supported by a bearing (not shown). A driving sun gear 298 for transmitting the rotation generated by the electric motor 290 is formed at one end of the armature shaft 295.
A small-diameter portion 299 is provided on the distal end side (the lower side in FIG. 13) with respect to FIG. A commutator (not shown) electrically and mechanically coupled to the armature coil 294 is provided on the outer periphery of the other end of the armature shaft 295. Note that the electric motor 290 rotates in one direction, and for the following description, it is assumed that the armature shaft 295 rotates clockwise when viewed from below in FIG.

Next, the structure of the switching device for switching the rotation direction of the electric motor 290 according to the rotation direction of the stub shaft will be described. The output shaft 300 that transmits the rotation of the electric motor 290 to the rack shaft is arranged coaxially with the armature shaft 295 of the electric motor 290, and passes through a bearing 301 provided in a cylindrical recess formed at the other end of the output shaft 300. While being rotatably supported by a small-diameter portion 299 of the armature shaft 295 and rotatably supported by a bearing 304 fixed to a clutch cover 303 fitted to the clutch case 302, while axially thrusting the washer 30.
5 regulations. The clutch case 302 is coaxially fitted to the center case 296, and is disposed so that the armature shaft 295 and the output shaft 300 are coaxial. At the other end of the output shaft 300, a flange 306 is integrally formed on the outer periphery.
A support pin 308 having a first planetary gear 307 meshing with the driving sun gear 298 is rotatably supported via a bearing 309. Note that a plurality of the support pins 308 and the first planetary gears 307 are arranged at equal intervals in the circumferential direction of the flange portion 306.

First rotating body 311 having internal gear 310 meshing with first planetary gear 307 for internal teeth
Are rotatably supported coaxially with the output shaft 300 by a bearing 312 pressed into the clutch case 302. A second planetary gear 313 is formed at an end of the support pin 308 (an end opposite to the first planetary gear 307).
The second planetary gear 313 is in external mesh with a second sun gear 315 formed on the second rotating body 314.
The second rotating body 314 is arranged on the outer periphery of the output shaft 300 and is rotatably supported coaxially with the output shaft 300 by a bearing 316 pressed into the clutch case 302. The first coil 31 forming an electromagnetic solenoid is press-fitted and fixed to the inner periphery of the clutch case 302 on the outer periphery of the first rotor 311 and the second rotor 314, respectively.
7 and a second coil 318 are provided. These coils 317 and 318 are electrically connected to a power supply device through lead wires (not shown).

The inner peripheral surfaces of both ends of the clutch case 302
A first helical spline 319 and a second helical spline 320 are formed, respectively. The first helical spline 319 is engaged with the first helical spline 319, and the axial direction of the output shaft 300 along the first helical spline 319. Movable body 321 movable in the axial direction of the output shaft 300 along the second helical spline 320 while being engaged with the second movable body 321 Are disposed so as to sandwich the first rotating body 311 and the second rotating body 314.

First rotating body 311 and first movable body 321
And a claw portion 32 constituting the first clutch
3 and 324 are provided, and similarly, pawl portions 325 and 326 constituting a second clutch are provided at a portion where the second rotating body 314 and the second movable body 322 are opposed to each other. The first movable body 321 is restricted from moving upward by the end surface of the center case 296 while being pushed upward in FIG. 13 by the spring 327 against the first coil 317. Similarly, while the second movable body 322 is pressed against the second coil 318 by the spring 328 in the downward direction in FIG. 13, the downward movement is restricted by the end face of the clutch cover 303. As a result, the pawl portions 323 and 324 constituting the first clutch and the pawl portions 325 and 326 constituting the second clutch are released, and the respective clutches are released.

Further, the pawl portions 323, 32 of the first clutch
First rotating body 311 and first movable body 32 on the inner diameter side
A pair of friction plates 329 and 330 constituting a third clutch are disposed in a portion facing the first clutch. The friction plate 330 provided on the first movable body 321 is pressed downward by a spring 331 in FIG. 13 while being restricted from rotating by a key groove portion provided on the first movable body 321, and the first clutch is disengaged. The downward movement is regulated by the washer 332 so that the gap between the friction plates 329 and 330 is smaller than the gap between the claw portions 323 and 324. Similarly, a pair of friction plates 333 and 334 constituting a fourth clutch are disposed at the opposed portion between the second rotating body 314 and the second movable body 322 on the inner diameter side of the claw portions 325 and 326. Have been. Second movable body 322
The friction plate 334 provided in the second movable body 32
13 is pressed downward by the spring 335 in FIG. 13 while the rotation is restricted by the key groove portion provided in the second clutch 2. The downward movement is regulated by the washer 336 so that the distance becomes smaller.

Next, an operation of switching the rotation direction of the electric motor 290 according to the rotation direction of the stub shaft will be described. When a current is passed to, for example, the first coil 317 from a torque sensor (not shown, for example, described in FIG. 6) by a driver's steering operation based on a voltage signal based on the torsion direction of the stub shaft and the pinion shaft,
Due to the magnetic force generated in the first coil 317, the spring 3
27 and the first movable body 3 while flexing the spring 331.
The third clutch is lightly engaged by bringing both friction plates 329 and 330 constituting the third clutch into contact with each other (at this time, the pawl portion 32 constituting the first clutch).
3 and 324 are not engaged).

Here, when the electric motor 290 is driven, the first planetary gear 307 is driven by the clockwise rotation of the driving sun gear 298.
, The first rotating body 311 having the internal gear 310 is about to rotate to the left. As a result, the first rotating body 311 is connected to the first movable body 32 via the third clutch.
1 to transmit torque. The first movable body 321 further flexes the springs 327 and 331 along the first helical spline 319 of the clutch case 302 by the rotational force transmitted from the first rotary body 311, and It moves to the side 311 and presses both friction plates 329 and 330 until the reaction force from the rack shaft and the torque of the output shaft 300 are balanced.

The reaction force from the rack shaft and the output shaft 300
When the torque of the first rotating body 311 having the internal gear 310 is completely balanced with the clutch case 302,
, The rotation of the driving sun gear 298 is transmitted while being decelerated while rotating the output shaft 300 to the right. When the reaction force from the rack shaft and the torque of the output shaft 300 are not balanced, the first movable body 321 is further moved.
Moves, and the friction plates 329 and 330 constituting the third clutch gradually restrict the rotation of the first rotating body 311 rotating leftward (while applying the brake). Claw portions 323, 3 constituting one clutch
24 is engaged. By the engagement of the pawl portions 323 and 324, the first rotating body 3 having the internal gear 310
11 is completely engaged with the clutch case 302 and its rotation is restricted, so that the right rotation of the drive sun gear 298
It is transmitted at a reduced speed while rotating 00 to the right.

When there is no torsion, energization of the first coil 317 is interrupted by the voltage signal from the torque sensor, and the first movable body 321 is moved to the initial position (FIG. 13) by the force of the springs 327 and 331. Position shown)
To release each clutch. On the other hand, when an electric current is applied to the second coil 318, the rotation of the second rotating body 314, which is about to rotate clockwise, is restricted in the same manner as described above, and the clockwise rotation of the driving sun gear 298 causes the output shaft 30 to rotate.
0 is transmitted while decelerating while rotating counterclockwise.
The rotation direction of 90 can be switched according to the rotation direction of the stub shaft.

(Effect of Fifth Embodiment) In this embodiment, the first
Since the same effect as that of the embodiment can be obtained and the electromagnet device is not built in the rotating body, a brush device for electrically connecting to the electromagnet device required in the second embodiment is not required. In addition, the same effect as the second embodiment (the output shaft 300
And the armature shaft 295 are arranged coaxially,
Since the electromagnetic solenoid can be incorporated in the switching device, it is possible to obtain a relatively lightweight, small, and inexpensive electric power steering device). Also, in this embodiment, unlike the other embodiments, a friction clutch is used when the reaction force from the rack shaft is small, and when the reaction force is large, the output of the electric motor 290 is transmitted by reliably engaging with the pawl clutch. Used in combination. this is,
When the rotation of the steering wheel is suddenly switched between left and right, which is a problem of the meshing clutch, the meshing of the clutch can be performed smoothly so that vibration, noise, abrasion of the claws, breakage of the claws, etc. do not occur when the clutch is disconnected. In order to ensure the durability of the friction clutch, the transmission can be transmitted reliably by the meshing clutch at the time of high output. There are advantages that can be provided.

(Modification) In the above embodiment, the pinion shaft and the rack shaft, and the output shaft and the rack shaft are engaged by the rack-and-pinion method, but other methods (for example, ball screw method, worm Roller method,
Needless to say, a worm pin method can be used instead. The configuration of each component in the above embodiments is not limited, and an electric power steering device that can easily transmit high output without increasing the size of the clutch, which is the subject, can be provided even in a combination of the embodiments. .

[Brief description of the drawings]

FIG. 1 is a sectional view of a switching device used in the present apparatus (first embodiment).

FIG. 2 is a schematic diagram showing an overall configuration of the present apparatus (first embodiment).

FIG. 3 is a sectional view of a torque sensor used in the present apparatus (first embodiment).

FIG. 4 is a sectional view of a switching device used in the present device (second embodiment).

FIG. 5 is a schematic diagram showing an overall configuration of the present apparatus (second embodiment).

FIG. 6 is a sectional view of a torque sensor used in the present apparatus (second embodiment).

FIG. 7 is a sectional view taken along line A of FIG. 6 (second embodiment).

FIG. 8 is a sectional view of a switching device used in the present device (third embodiment).

FIG. 9 is a schematic diagram showing an overall configuration of the present apparatus (third embodiment).

FIG. 10 is a plan view showing a positional relationship between spur gears (third embodiment).

FIG. 11 is a sectional view of a switching device used in the present device (fourth embodiment).

FIG. 12 is a schematic diagram showing the entire configuration of the present apparatus (fourth embodiment);
Example).

FIG. 13 is a sectional view of a switching device used in the present device (fifth embodiment).

[Description of Signs] (First Embodiment) 1 This device (electric power steering device) 2 Steering wheel 3 Rack shaft 5 Torque sensor (switch means) 6 Electric motor 7 Switching device 8 Output shaft 9 Stub shaft 10 Pinion shaft 11 Torsion Bar 35 First rotating body 36 Second rotating body 37 Movable body (conversion means) 38 First clutch (clutch mechanism) 39 Second clutch (clutch mechanism) 41 Electromagnetic solenoid (moving means / electromagnet device) 54 Helical Spline 55 Spring (elastic member for releasing clutch) 56 Spring (elastic member for releasing clutch) (third embodiment) 223 Clutch outer (one-way clutch) 224 Cam chamber (one-way clutch) 225 Roller (one-way clutch) 226 Spring (one-way clutch) ( Fourth embodiment) 250 slider (sliding body)

Claims (14)

[Claims] A stub shaft connected to a steering wheel; a rack shaft connected to wheels; a pinion shaft connected to the rack shaft; a torsion bar connecting the stub shaft and the pinion shaft; An electric motor that is a power source of a steering assist force applied to the rack shaft; and a switching device that transmits the one-directional rotation output from the electric motor in a forward / reverse direction according to the rotation direction of the stub shaft, and An output shaft for transmitting the rotation transmitted via the switching device to the rack shaft, wherein the switching device is provided rotatably about the output shaft, A first rotator and a second rotator to which rotation of an electric motor is transmitted and rotate in opposite directions to each other; Selecting means for selecting one of the first rotating body and the second rotating body in accordance with the rotation direction of the shaft; and the one rotating body selected by the selecting means and the output A clutch mechanism that drives and connects the shaft to the motor; and a conversion unit that generates a load in the thrust direction of the output shaft by the output of the electric motor, and converts the thrust load into an engagement force of the clutch mechanism. Electric power steering device. 2. An electric power steering apparatus according to claim 1, wherein said output shaft is formed integrally with said pinion shaft. 3. The electric power steering apparatus according to claim 1, wherein a one-way clutch is provided in a transmission path for transmitting one-way rotation of the electric motor to the switching device. 4. The conversion means engages a helical spline with the output shaft or a cylindrical fixing member disposed concentrically with the output shaft, and axially moves on the output shaft along the helical spline. The electric motor according to any one of claims 1 to 3, further comprising a movable movable body, wherein the movable body moves in a direction to increase an engagement force of the clutch mechanism in response to an output of the electric motor. Power steering device. 5. The clutch mechanism according to claim 1, wherein the first clutch is disposed between the first rotating body and the movable body, and the first clutch is disposed between the second rotating body and the movable body. The electric power steering apparatus according to claim 4, comprising a second clutch, wherein the first clutch and the second clutch are both friction clutches. 6. The clutch mechanism, wherein: a first clutch disposed between the first rotating body and the movable body; and a first clutch disposed between the second rotating body and the movable body. 5. The clutch according to claim 4, wherein the clutch is composed of a second clutch, and the first clutch and the second clutch are each a composite clutch configured by combining a friction clutch and a meshing clutch. Electric power steering device. 7. The movable body is provided with a clutch releasing elastic member that acts in a direction to release the first clutch and the second clutch when the electric motor is not driven and at rest. 7. The method according to claim 4, wherein
4. An electric power steering device according to any one of the above. 8. A moving means for moving the movable body in an axial direction according to a relative torsion angle between the stub shaft and the pinion shaft; And switch means for controlling energization of the electric motor in accordance with a typical torsion angle.
4. An electric power steering device according to any one of the above. 9. An electric power steering apparatus according to claim 8, wherein said moving means is an electromagnet apparatus for moving said movable body by electromagnetic force based on a command from said switch means. 10. The moving means engages a helical spline formed on one of a shaft that rotates in connection with the rotation of the stub shaft and a shaft that rotates in connection with the rotation of the pinion shaft. 9. The electric type according to claim 8, further comprising a sliding body that is movably engaged in the axial direction while being restricted in rotation, and that moves the movable body based on a moving amount of the sliding body. Power steering device. 11. The apparatus according to claim 8, wherein said switch means is a torque sensor for electrically detecting a relative torsion angle between said stub shaft and said pinion shaft. Electric power steering device. 12. A switch according to claim 8, wherein said switch means is a torque sensor for mechanically amplifying a relative torsion angle between said stub shaft and said pinion shaft and then electrically detecting said twist angle. 10. The electric power steering device according to any one of items 10 to 10. 13. An electric power steering apparatus according to claim 10, wherein said switch means is a torque sensor for electrically detecting an axial movement amount of said sliding body. 14. An electric motor according to claim 10, wherein said switch means is a torque sensor for electrically detecting an amount of mechanical strain between said sliding body and said movable body generated in said moving means. Power steering device.