JP4066925B2 - Power steering device with reduction gear - Google Patents

Description

  The present invention provides a steering input shaft driven by a steering motor via an electronic control unit so that rotation of a steering handle for steering a steering wheel of a vehicle such as an automobile is not mechanically transmitted. By-wire type power steering device with a reduction gear, especially a gear shift capable of changing a gear ratio according to an operating state between a steering output operating member that steers a steered wheel via a tie rod and the like and a steering input shaft The present invention relates to a power steering apparatus with a reduction gear provided with a speed reducer.

For a steering device used in an automobile or the like, the gear ratio between the steering wheel and the steering output actuating member is changed according to the operating state of the vehicle in order to give appropriate steering characteristics according to the operating state of the vehicle. Is desired. For example, in a rack-and-pinion type steering device, the input and output sun gears having different numbers of teeth are coupled to the input shaft connected to the steering handle and the pinion connected to the rack shaft. The planetary gears are engaged with the sun gears, and the planetary gears are coaxially coupled integrally and supported rotatably on a common gear carrier. A worm wheel is formed on the outer periphery of the gear carrier, and meshed with the worm wheel. There is one in which a reduction ratio from an input shaft to a pinion is changed by rotating a worm to be rotated by a motor (Patent Document 1). In this type of steering device, the total number of rotations of the input shaft with respect to the total stroke of the rack shaft is one rotation or more.
Japanese Patent Laid-Open No. 60-209362 (pages 3, 4 and 1 and 2).

  In a steer-by-wire power steering system, a steering motor that drives a steering input shaft (input shaft) in association with the rotation of the steering handle needs to detect the absolute rotation angle of the steering input shaft and perform feedback control. There is. However, since the rotation speed of the steering input shaft is one rotation or more as described above, if the rotation angle of the steering input shaft driven by the steering motor is detected as it is, the detected value of the rotation angle is determined every rotation. Returning to 0, the absolute rotation angle of the steering motor cannot be detected. Therefore, there is a problem that the technique of Patent Document 1 described above cannot be immediately applied to a steer-by-wire power steering apparatus as it is.

  The present invention adds a device to a transmission that transmits the rotation of a steering input shaft driven by a steering motor by changing a gear ratio to a steering output shaft that steers a steered wheel via a steering output actuating member. Therefore, it aims at solving such a problem.

  To this end, a power steering apparatus with a reduction gear according to the present invention has a steering input shaft and a steering output shaft that steers steering wheels via a steering output actuating member. In a power steering apparatus with a reduction gear that includes a transmission that changes a transmission ratio according to an operating state and transmits the transmission to a steering output shaft, a steering motor that rotationally drives a steering input shaft, and a steering angle of a steering handle And an electronic control device that feedback-controls the operation of the steering motor, and the transmission is an intermediate shaft that is provided coaxially with the steering output shaft by reducing the total number of rotations of the steering input shaft to one rotation or less. A speed reduction mechanism for transmitting to the vehicle, a planetary gear speed increasing mechanism for increasing the rotation of the intermediate shaft and changing the speed increasing ratio according to the operating state of the vehicle to transmit to the steering output shaft, and both mechanisms are housed. It shall consist of a casing and The gear speed increasing mechanism includes a speed increaser carrier that is coaxially fixed to the intermediate shaft and rotatably supported by the casing, and is coaxially fixed to the speed increaser carrier and is parallel to the intermediate shaft and separated by a predetermined distance in the radial direction. First and second speed-increasing planetary gears rotatably supported around the axis, a speed increaser input sun gear fixed to the intermediate shaft and meshing with the first speed-increasing planetary gear, and a second speed increasing fixed to the steering output shaft It consists of a gearbox output sun gear that meshes with a high-speed planetary gear, and the gear ratio control motor is rotated by a gear ratio control motor that is operated according to the operating state of the vehicle. A rotation angle sensor for detecting the rotation angle of the intermediate shaft is provided for feedback control.

  In the power steering apparatus with a reduction gear described in the previous section, the steering input shaft is arranged coaxially with the intermediate shaft, and the reduction mechanism is decelerated by being fixed coaxially with the reduction gear carrier fixed to the steering input shaft. The first and second reduction planetary gears that are supported on the machine carrier so as to be rotatable about an axis parallel to the steering input shaft and spaced apart by a predetermined distance in the radial direction, and the reduction machine fixed sun gear fixed to the casing and meshing with the first reduction planetary gear And a planetary gear reduction mechanism comprising a reduction gear output sun gear fixed to the intermediate shaft and meshing with the second reduction planetary gear.

In the power steering apparatus with a reduction gear described in the preceding paragraph , the reduction gear fixing and reduction gear output sun gear are internal gears in which the first and second reduction planetary gears are engaged from the inside, and the rotation angle sensor is the outer periphery of the reduction gear output sun gear. It is desirable to detect the rotation angle of the intermediate shaft that is fixed to this.

  As described above, according to the present invention, the speed reduction mechanism decelerates the total number of rotations of the steering input shaft that is rotationally driven by the steering motor to 1 rotation or less and transmits it to the intermediate shaft. By detecting the rotation angle with the rotation angle sensor, the absolute rotation angle of the steering input shaft can be immediately detected. Therefore, the electronic control unit can feedback control the operation of the steering motor by comparing the absolute rotation angle of the steering input shaft detected in this way with the steering angle of the steering wheel. Further, since the rotation of the intermediate shaft thus decelerated is accelerated by the planetary gear speed increasing mechanism and transmitted to the steering output shaft, the rotation angle of the steering output shaft is controlled by the steering wheel via the steering output operating member. It is an appropriate value for The planetary gear speed increasing mechanism operates the gear ratio control motor in accordance with the operating state of the vehicle and rotates the speed increaser carrier to change the speed increasing ratio and to perform appropriate steering according to the operating state of the vehicle. Characteristics can be given.

  According to the second aspect of the present invention, the planetary gear speed reduction mechanism and the planetary gear speed increasing mechanism are arranged coaxially with each other so that the steering input shaft is disposed coaxially with the intermediate shaft and the speed reduction mechanism is a planetary gear speed reduction mechanism. Since the device as a whole has a uniform shape close to a cylindrical shape, the mounting property on the vehicle is improved.

  The invention according to claim 3, wherein the reduction gear fixed and reduction gear output sun gear is an internal gear, and the rotation angle sensor detects the rotation angle of the intermediate shaft fixed to the outer periphery of the reduction gear output sun gear. According to this, since the rotation angle sensor detects the rotation angle of the intermediate shaft at the outer periphery of the reduction gear output sun gear away from the rotation axis of the intermediate shaft, the detection accuracy of the rotation angle is improved, and the structure for mounting the rotation angle sensor to the casing It will also be easy.

  Next, the best mode of the power steering apparatus with a reduction gear according to the present invention will be described with reference to FIGS. As shown in FIG. 1, the steering device with a reduction gear according to this embodiment includes a long and thin cylindrical housing 10, and a rack shaft (steering) in which a rack 12 is formed along the longitudinal direction in a part of the axial direction. An output actuating member 11 is guided and supported by the housing 10 so as to be movable in the axial direction, and both ends of the rack shaft 11 are connected to left and right front wheels (steering wheels) 15 via tie rods 14, respectively. The transmission 20 attached to one side of the housing 10 rotates the steering input shaft 22 (see FIG. 2, which is the output shaft of the steering motor 56 in the illustrated embodiment) driven by the steering motor 56. The pinion 13 that is decelerated and transmitted to the steering output shaft 24 and is coaxially fixed to the front end portion of the steering output shaft 24 that obliquely intersects the rack shaft 11 meshes with the rack 12, thereby It is designed to move in the axial direction.

  As shown in FIG. 1, the steering handle 50 is provided with a steering angle sensor 51 that detects the rotation angle, and a torque reaction force mechanism 52 that applies an appropriate torque reaction force according to the operating state to the steering handle 50. Yes. The electronic control unit 55 outputs a control amount calculated based on the rotation angle of the steering handle 50 detected by the steering angle sensor 51 to the steering motor 56 to rotationally drive the steering input shaft 22, and at the same time, a rotation angle described later. The rotation angle of the steering input shaft 22 detected by the sensor 57 is input, and the operation of the steering motor 56 is feedback-controlled.

  As illustrated in FIG. 2, the transmission 20 includes a casing 21 that is integrally fixed to the housing 10. The casing 21 is rotatably provided with a steering input shaft 22, an intermediate shaft 23, and a steering output shaft 24 that are coaxially arranged in series. A planetary gear reduction mechanism (a reduction mechanism) is provided between the steering input shaft 22 and the intermediate shaft 23. 30), and a planetary gear speed increasing mechanism 40 is provided between the intermediate shaft 23 and the steering output shaft 24, respectively.

  The planetary gear speed reduction mechanism 30 has a carrier 31 fixed to the distal end portion of the steering input shaft 22, and a plurality of sets (for example, 3 sets) of first and second reduction planetary gears 33 fixed coaxially to each other. 34 is supported by the speed reducer carrier 31 so as to be rotatable around an axis parallel to the steering input shaft 22 and separated by a predetermined distance in the radial direction. Each first reduction planetary gear 33 is meshed with an internal reduction gear fixed sun gear 32 coaxially fixed to the casing 21 coaxially with the steering input shaft 22, and each second reduction planetary gear 34 is coaxial with the front end portion of the intermediate shaft 23. It is meshed from the inside with a fixed internal gear reducer output sun gear 35. The gear ratio of the first reduction planetary gear 33 to the reduction gear fixed sun gear 32 and the gear ratio of the second reduction planetary gear 34 to the reduction gear output sun gear 35 are smaller in the former gear ratio. The rotational speed of the shaft 22 is decelerated at a constant reduction ratio corresponding to the gear ratio and transmitted to the reduction gear output sun gear 35 and the intermediate shaft 23.

  The total number of rotations of the steering input shaft 22 corresponding to the entire stroke of the rack shaft 11 is one rotation or more as described above, but the above-described ratio of the respective teeth and the reduction ratio given thereby are the steering input shaft 22. Is set so that the total number of rotations is reduced to 1 rotation or less and transmitted to the reduction gear output sun gear 35 and the intermediate shaft 23. A pattern (for example, optical or magnetic) for detecting the rotation angle is provided along the circumferential direction on the outer peripheral surface of the internal gear reducer output sun gear 35, and this pattern is read on the casing 21 to reduce the speed reducer. A rotation angle sensor 57 that detects the rotation angle of the output sun gear 35 and the intermediate shaft 23 fixed to the output sun gear 35 is provided.

  The planetary gear speed increasing mechanism 40 has a speed increaser carrier 41 supported by the casing 21 so as to be coaxially rotatable between the intermediate shaft 23 and the steering output shaft 24, and are fixed coaxially to each other. A plurality of sets (for example, three sets) of first and second speed-up planetary gears 43 and 44 are supported by the speed-up gear carrier 41 so as to be rotatable about an axis parallel to the intermediate shaft 23 and separated by a predetermined distance in the radial direction. Yes. Each first speed increasing planetary gear 43 is engaged with an external gear speed increaser input sun gear 42 coaxially fixed to the rear end portion of the intermediate shaft 23, and each second speed increasing planetary gear 44 is engaged with the front end portion of the steering output shaft 24. Is meshed with an external gear reducer output sun gear 35 that is coaxially fixed to the shaft. A control driven gear 41 a formed coaxially on the outer periphery of the gearbox carrier 41 is meshed with a control drive gear 26 that is coaxially fixed to a gear ratio control input shaft 25 that is an output shaft of the gear ratio control motor 58. Are driven to rotate. The gear ratio control motor 58 is provided with a lock mechanism (not shown). As the steering motor 56 and the gear ratio control motor 58, for example, a brushless DC servo motor may be used.

  The ratio of the number of teeth of the first speed increase planetary gear 43 to the speed increaser input sun gear 42 and the ratio of the number of teeth of the second speed increase planetary gear 44 to the speed increaser output sun gear 45 are smaller in the former tooth number ratio. Therefore, in a state where the gear ratio control motor 58 is locked by the lock mechanism and the speed increaser carrier 41 is stopped, the rotational speed of the intermediate shaft 23 increases at a constant speed increase ratio corresponding to the gear ratio. It is accelerated and transmitted to the steering output shaft 24. When the speed increaser carrier 41 is rotated by the gear ratio control motor 58 after the lock is released, the speed increase ratio decreases if the rotation direction is the same as the rotation direction of the input shaft 23, and the speed increase ratio is the reverse. And the change of the speed increasing ratio is increased if the rotation speed of the carrier 31 is large.

  Next, the operation of the above-described embodiment will be described. When the steering handle 50 is rotated, the electronic control unit 55 outputs a control amount calculated based on the rotation angle of the steering handle 50 detected by the steering angle sensor 51 to the steering motor 56 to control the steering input shaft 22. The rotation angle sensor 57 detects the rotation angle of the reduction gear output sun gear 35 (and the intermediate shaft 23) reduced by the planetary gear reduction mechanism 30 by a predetermined reduction ratio. 55 receives the rotation angle of the reduction gear output sun gear 35 and feedback-controls the rotation of the steering input shaft 22 by the steering motor 56. The rotation of the steering input shaft 22 is decelerated at a constant reduction ratio by the planetary gear reduction mechanism 30 and transmitted to the intermediate shaft 23. The rotation of the intermediate shaft 23 changes the planetary gear whose speed increase ratio changes according to the operating state of the vehicle. The pinion 13, which is accelerated by the speed increasing mechanism 40 and transmitted to the steering output shaft 24 and rotates together with the steering output shaft 24, moves the rack shaft 11 in the axial direction via the rack 12, and moves to the left and right via the tie rods 14 at both ends. The front wheel 15 is steered.

  In order to perform feedback control by the electronic control unit 55, it is necessary to detect the absolute rotation angle of the steering input shaft 22, but the total number of rotations of the steering input shaft 22 with respect to the entire stroke of the rack shaft 11 is one rotation or more. Therefore, if the rotation angle of the steering input shaft 22 is detected as it is, the detection value of the rotation angle returns to 0 every rotation, and the absolute rotation angle cannot be detected. However, in the above-described embodiment, the rotation angle sensor 57 detects the rotation angle of the reduction gear output sun gear 35 and the intermediate shaft 23 that are decelerated so that the total number of rotations of the steering input shaft 22 is 1 rotation or less. The detection value of the rotation angle detected by the rotation angle sensor 57 does not return to 0, and the absolute rotation angle of the steering input shaft 22 is detected by dividing this detection value by the reduction ratio of the planetary gear reduction mechanism 30. can do. The electronic control unit 55 compares the absolute rotation angle of the steering input shaft 22 detected by the rotation angle sensor 57 with the steering angle of the steering handle 50 detected by the steering angle sensor 51 in this way. The rotation of 22 is feedback controlled.

  Since the rotation of the intermediate shaft 23 thus decelerated is accelerated by the planetary gear speed increasing mechanism 40 and transmitted to the steering output shaft 24, the rotation angle of the steering output shaft 24 is via the pinion 13 and the rack shaft 11. Thus, the steering wheel 15 is an appropriate value for steering.

  The electronic control unit 55 determines whether or not to control the speed increasing ratio of the planetary gear speed increasing mechanism 40 based on the operation state of the vehicle detected by various sensors such as a vehicle speed sensor, a yaw rate sensor, and a lateral acceleration sensor. If it is determined that the speed ratio control is to be performed, the lock mechanism of the gear ratio control motor 58 is released, and the gear ratio control motor 58 is operated according to the detected operating state of the vehicle, so that the gear ratio control is performed. The speed increase ratio is changed by rotating the speed increaser carrier 41 via the input shaft 25 and the control drive gear 26. As a result, appropriate steering characteristics according to the operating state of the vehicle such as the vehicle speed, yaw rate and lateral acceleration can be obtained.

  In the above-described embodiment, the steering input shaft 22 is coaxially arranged with the intermediate shaft 23, and the first and second reduction planetary gears 33 and 34 that are coaxially fixed to each other are the reduction gear carrier 31 that is fixed to the steering input shaft 22. The first reduction planetary gear 33 is engaged with the reduction gear fixed sun gear 32, and the second reduction planetary gear 34 is engaged with the reduction gear output sun gear 35 fixed to the intermediate shaft 23 by the planetary gear reduction mechanism 30. The rotation of the steering input shaft 22 is decelerated and transmitted to the intermediate shaft 23. In this way, the planetary gear speed reduction mechanism 30 is arranged coaxially with the planetary gear speed increasing mechanism 40, and the transmission 20 as a whole. Since it becomes an orderly shape close to a cylindrical shape and there is no portion that protrudes partially on one side in the radial direction, the mountability to the vehicle is improved. However, the present invention is not limited to this, and can be implemented using a reduction mechanism 30 other than the planetary gear type.

  In the above-described embodiment, the reduction gear fixed and reduction gear output sun gears 32 and 35 are internal gears with which the first and second reduction planetary gears 33 and 34 are engaged from the inside, and the rotation angle sensor 57 is the reduction gear output sun gear 35. The rotation angle sensor 57 detects the rotation angle of the intermediate shaft 23 by approaching the outer periphery of the intermediate shaft 23. In this way, the rotation angle sensor 57 is located on the outer periphery of the reduction gear output sun gear 35 away from the rotation axis of the intermediate shaft 23. Since the rotation angle is detected, the detection accuracy of the rotation angle is improved, and the mounting structure of the rotation angle sensor 57 to the casing 21 is simplified. However, the present invention is not limited to this, and the reduction gear fixing and reduction gear output sun gears 32 and 35 can be implemented as external gears.

  In this type of steer-by-wire type steering device, the rotation of the steering handle 50 is not mechanically transmitted to the steering input shaft 22, so that the steering wheel 15 can be steered if the steering motor 56 is locked due to failure. There is a problem of disappearing. However, according to the above-described embodiment, in the case of such a failure, the absolute rotation angle of the steering input shaft 22 detected by the rotation angle sensor 57 and the steering angle of the steering handle 50 detected by the steering angle sensor 51 are determined. Since an abnormality occurs in the comparison result, the electronic control unit 55 detects such an abnormality and operates the gear ratio control motor 58 in accordance with the steering angle of the steering handle 50 detected by the steering angle sensor 51. By switching the control of the gear ratio control motor 58, the problem that the steering wheel 15 cannot be steered is solved. That is, according to this embodiment, a fail-safe function for locking the steering motor 56 can be provided.

  In the above-described embodiment, the control drive gear 26 and the control driven gear 41a that drive the gearbox carrier 41 of the planetary gear speed increasing mechanism 40 are spur gears (or helical gears), but worms and worm wheels are used. Therefore, the gear ratio control input shaft 25 cannot be reversely driven from the gear box carrier 41 side, so that the gear ratio control motor 58 is provided. A locking mechanism is not required.

  In the above-described embodiment, the gear ratio control motor 58 is described as being controlled by the electronic control device 55, but the gear ratio control motor 58 is controlled by an electronic control device different from the electronic control device 55. May be.

It is explanatory drawing which shows the whole structure of best embodiment of the power steering device with a reduction gear by this invention. It is explanatory drawing which shows the transmission of embodiment shown in FIG. 1, and its surrounding structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Steering output action member (rack shaft), 15 ... Steering wheel (front wheel), 20 ... Transmission, 21 ... Casing, 22 ... Steering input shaft, 23 ... Intermediate shaft, 24 ... Steering output shaft, 30 ... Deceleration mechanism (Planetary gear reduction mechanism), 31 ... reduction gear carrier, 32 ... reduction gear fixed sun gear, 33 ... first reduction planetary gear, 34 ... second reduction planetary gear, 35 ... reduction gear output sun gear, 40 ... planetary gear speed increase mechanism, 41 ... gearbox carrier, 42 gearbox input sun gear, 43 ... first gearbox planetary gear, 44 ... second gearbox planetary gear, 45 ... gearbox output sun gear, 50 ... steering handle, 55 ... electronic control unit, 56 ... Steering motor, 57... Rotation angle sensor, 58... Gear ratio control motor.

Claims (3)

A steering input shaft and a steering output shaft that steers the steering wheel via a steering output operating member; and changing the speed ratio of the rotation of the steering input shaft in accordance with the operating state of the vehicle, the steering output shaft In a power steering apparatus with a reduction gear comprising a transmission for transmitting to
A steering motor that rotationally drives the steering input shaft, and an electronic control unit that feedback-controls the operation of the steering motor based on a steering angle of a steering handle;
The transmission includes a speed reduction mechanism that reduces the total number of rotations of the steering input shaft to 1 rotation or less and transmits it to an intermediate shaft that is provided coaxially with the steering output shaft, and accelerates the rotation of the intermediate shaft. And a planetary gear speed increasing mechanism for changing the speed increasing ratio according to the operating state of the vehicle and transmitting it to the steering output shaft, and a casing for housing both mechanisms,
The planetary gear speed increasing mechanism includes a speed increaser carrier rotatably supported on the casing coaxially with the intermediate shaft, and a radius parallel to the intermediate shaft and fixed to the speed increaser carrier. First and second speed-up planetary gears rotatably supported about an axis separated by a predetermined distance in the direction, a speed-up gear input sun gear fixed to the intermediate shaft and meshed with the first speed-up planetary gear, and the steering The speed-up gear output sun gear is fixed to the output shaft and meshes with the second speed-up planetary gear. Let's change the speed ratio,
A power steering apparatus with a reduction gear, wherein the casing is provided with a rotation angle sensor for detecting a rotation angle of the intermediate shaft for the feedback control. The power steering apparatus with a reduction gear according to claim 1, wherein the steering input shaft is coaxially disposed with the intermediate shaft, and the reduction mechanism is coaxial with a reduction gear carrier fixed to the steering input shaft. First and second reduction planetary gears fixedly supported by the reduction gear carrier so as to be rotatable about an axis parallel to the steering input shaft and spaced apart by a predetermined distance in the radial direction, and fixed to the casing to the first A planetary gear reduction mechanism comprising a reduction gear fixed sun gear that meshes with a first reduction planetary gear and a reduction gear output sun gear that is fixed to the intermediate shaft and meshes with the second reduction planetary gear. apparatus. In the power steering apparatus with reduction gear as claimed in 請 Motomeko 2, wherein the reduction gear fixed and reduction gear output sun gear and internal gear of the first and second reduction planetary gear is engaged from the inside, the rotation angle sensor A power steering apparatus with a reduction gear, wherein the rotation angle of the intermediate shaft fixed to the outer circumference of the reduction gear output sun gear is detected.

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