JP2007001564A - Steer-by-wire system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the maneuverability of a vehicle, and to improve the lay-out performance of an engine part or the like by providing a compact steering mechanism. <P>SOLUTION: The steering angle of a steering wheel 10 is electrically detected, and the turning angle of a turning wheel is computed by a steering control driving device 30 on the basis of the detecting signal to turn the turning wheel with driving force of a steering actuator 1. The actuator 1 drives an electric motor 40 on the basis of the computed turning angle, and outputs oscillating rotation from a pitman arm 2 though a reduction gear, and moves a tie-rod arm 3 to turn the turning wheel. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention mechanically disconnects from the steering wheel to the steered wheel, electrically detects the steering angle of the steering wheel, calculates the steered angle of the steered wheel by the control device based on the detection signal, The present invention relates to a steer-by-wire system that steers a steered wheel with a driving force of a steer actuator.

  A steering system using steer-by-wire (SBW) that does not mechanically connect a steering wheel to a steered wheel has been proposed.

  This steering system electrically detects the steering angle of the steering wheel, and based on this detection signal, the control unit (ECU) calculates the turning angle of the steered wheel and drives an actuator that is mechanically independent from the steering wheel. The steering wheel is steered and driven.

  When such a steer-by-wire is adopted, the arrangement of various devices constituting the steering system, the degree of design freedom, and the like are expanded, and the overall steering system can be easily downsized.

  In patent document 1, it is a steer-by-wire, Comprising: A tie rod is linearly moved by rack and pinion type steering, and it is comprised so that a wheel may be steered independently on either side.

  In patent document 2, it is steer-by-wire, Comprising: A tie rod is linearly moved by a ball screw type, and it is comprised so that a wheel may be steered independently.

In Non-Patent Document 1, a so-called ball screw type steering mechanism using a pitman arm is also known.
Japanese Patent Publication No. 7-33142 JP 2001-310751 A Automobile Technology Handbook [Automobile Technology Association, 1991, 2nd volume, page 527, Fig. 8-1]

  However, in Patent Documents 1 and 2, in the method in which the tie rod is steered by linearly moving the actuator, the actuator becomes longer in the axial direction, which restricts other components such as the engine layout.

  Moreover, in patent document 1 and 2, when there was abnormality in an actuator, there also existed a problem which cannot steer normally.

  The present invention has been made in view of the circumstances as described above, and allows the left and right wheels to be steered independently, improving the motion performance of the vehicle, and at the same time providing a compact steering mechanism, An object of the present invention is to provide a steer-by-wire system that improves the layout of engine parts and the like and has a fail-safe function.

In order to achieve the above object, the steer-by-wire system according to the present invention mechanically disconnects from the input device to the steered wheels, and the control device controls the steering actuator according to the input of the input device. In the steer-by-wire system that steers the steered wheels by the driving force,
The steering actuator outputs a swinging and rotating motion, moves a tie rod arm, and steers the steered wheels.

  Preferably, a pair of the steering actuators are provided corresponding to the left and right steered wheels of the vehicle.

Preferably, the steering actuator has a housing fixed to the vehicle, and outputs the oscillating rotational motion from a pitman arm.
The tie rod arm has one end connected to the pitman arm and the other end connected to a knuckle arm.

  Furthermore, it is preferable to further include a fail-safe mechanism that mechanically transmits the driving force of one steering actuator to the other steering actuator.

  Further preferably, the swing rotation output shaft and the drive shaft of the electric motor are substantially orthogonal to each other via a worm reduction mechanism.

Further preferably, the oscillating rotation output shaft is driven by a planetary gear mechanism,
The planetary gear mechanism is
A fixed internal gear fixed to the housing;
An output shaft internal gear for driving the output shaft;
A revolving gear train that meshes with the fixed internal gear and the output shaft internal gear and revolves and rotates together;
An input carrier for revolving the revolution gear train,
It comprises. The input carrier is driven by a worm wheel.

Further preferably, the steering actuator outputs the rotation of the motor as the oscillating rotational motion through a reduction gear,
The speed reducer is
A sun gear rotating around the central axis;
A plurality of first planetary gears that revolve and rotate while meshing with the outer peripheral teeth of the sun gear,
A non-rotating first outer ring gear that meshes with the first planetary gear inscribed,
A plurality of second planetary gears having a different number of teeth from the first planetary gears and rotating and revolving integrally with the first planetary gears;
The first planetary gear includes a first outer ring gear that rotates while meshing with the second planetary gear while being inscribed, thereby outputting the oscillating rotational motion to the pitman arm.

  According to the present invention, the steering actuator outputs a swinging rotary motion, moves the tie rod arm, and steers the steered wheels, so that the motion performance of the vehicle can be improved, and the compact A simple steering mechanism can be provided to improve the layout of engine parts and the like.

  Furthermore, the degree of freedom of the vehicle layout can be increased, the backlash when the planetary gear mechanism is used can be reduced, and the maneuverability can be improved while reducing the noise.

  Hereinafter, a steer-by-wire system according to an embodiment of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic plan view of a vehicle equipped with a steer-by-wire system according to a first embodiment of the present invention.

  In the present embodiment, generally, a tie rod arm 3 and a knuckle arm 4 are used by using a steering actuator 1 (rotary actuator) that rotates (swings) the pitman arm 2 without using a direct acting actuator. To move the front wheels (steering wheels). Further, by using a pair of steering actuators 1, the left and right front wheels are steered.

  Thus, the steering system using the steering actuator 1 eliminates the steering mechanism at the center of the vehicle, so that the layout of other components such as the engine is improved.

  Further, since the left and right steering can be performed independently by the pair of steering actuators 1, steering is performed by changing the tire angle so that the left and right cornering forces can be maximized, thereby improving the motion performance of the vehicle. be able to.

  FIG. 2A is a schematic plan view showing the relationship between the angle of the pitman arm and the angle of the front wheel.

  When the pair of left and right steering actuators 1 are rotated by the same angle, the left and right wheels approximately satisfy the Ackermann condition (a condition that passes through one point (near the rotation center of the vehicle) where each axle extends). If designed, it is easy to control and stable steering is possible.

  Furthermore, it is desirable that the movement of one steering actuator 1 is mechanically transmitted to the other steering actuator 1. Thereby, even if one steering actuator 1 breaks down, it can be set as the fail safe characteristic which can be steered.

  In addition, it is possible to provide a certain dead zone (a mechanism that does not transmit a small change in angle) in the connection mechanism so that the left and right wheels can be independently steered.

  FIG. 2B is a schematic plan view showing the positional relationship between the pitman arm and the front wheels according to a modification.

  FIG. 2C is a schematic front view showing the positional relationship between the pitman arm and the front wheels according to another modification.

  As a method for arranging the steering actuator 1, there is a method as shown in FIG. 2B in addition to FIG. 2A, and the steering actuator 1 is arranged in accordance with the layout of the seat, engine, and drive system. Selection of arrangement is possible.

  There is a combination of whether the tie rod arm 3 is rearward or frontward of the axle or alternate, and there is a combination of whether the steering actuator 1 is on the shaft side or on the opposite side of the tie rod arm 3, and further shown in FIG. As described above, there are combinations of three-dimensional arrangements of the steering actuator 1, and a large number (32 types) of the combinations are possible.

  In addition, since the left and right can be controlled independently, it is possible to actively change toe-in, toe-out (the front wheels are turned in the case of c) or the left-right turning angle ratio.

  For example, in a front-wheel drive vehicle, toe-in caused by the driving force and suspension elasticity can be actively corrected, the front wheel rolling resistance can be reduced, and fuel consumption can be improved.

  It is also possible to correct the bump steer that changes the angle of the front wheel due to the suspension stroke, and to change the turning angle ratio according to the cornering force of the left and right wheels to improve the turning performance.

  FIG. 3 is a schematic back view of the steer-by-wire system according to the first embodiment of the present invention. FIG. 3 is a front wheel steering device, as viewed from the rear.

  The steering input device 10 (steering wheel or joystick) and the steering actuator 1 that changes the steering angle of the steered wheels have a steer-by-wire configuration that is electrically connected. In order to change the angles of the right and left steered wheels, steered actuators (rotary actuators) are individually connected.

  The pair of steering actuators 1 are electrically driven by a steering control drive device 20 and controlled according to vehicle information such as an input angle of the steering input device 10, a torque signal, and a vehicle speed.

  Further, the steering control drive device 20 feeds back the road surface reaction force information obtained from the current signals and angle signals of the axial force sensor 21 and the steering actuator 1 to the anti-actuator actuator 11 in consideration of the vehicle information. Send appropriate information to the person.

  The steering control drive device 20 also compensates for friction and inertia of the steering actuator 1 and performs control to change impedance such as apparent inertia of the steering system, thereby improving the driver's steering feeling and vehicle motion performance. Control can also be performed.

  The steering actuator 1 is fixed to the vehicle body 5. The vehicle control device 30 receives signals from the suspension sensor 31 and the hub sensor 32, controls the vehicle speed, wheel speed, yaw rate, etc., and sends signals such as the turning angle to the steering control drive device 20. .

  The pitman arm 2 is rotated about ± 60 ° by the steering actuator 1 as shown in FIG. 3, and the rotation is transmitted to the steered wheels through the link mechanism of the tie rod arm 3 and the knuckle arm 4 coupled to the ball joint. The steered angle changes by about −40 ° to + 33 °. The plus sign means the angle of the outer wheel in turning.

  The pair of steering actuators 1 having the same characteristics are arranged on the left and right, and the links are arranged symmetrically.

  The aforementioned angle of −40 to + 33 ° is designed so that the Ackermann condition is substantially satisfied when the left and right steering actuators 1 are operated at the same angle, whereby the left and right steering actuators 1 are the same. When the angle is rotated, normal steering and turning are possible.

  The angle of −40 to + 33 ° described above is a design parameter that varies depending on the minimum turning radius of the vehicle and the distance between wheels, and is merely an example.

  FIG. 4 is a cross-sectional view of the steering actuator (rotary actuator) of the steer-by-wire system according to the first embodiment of the present invention.

  In order to rotate the pitman arm, a very large torque is required. However, in order to reduce the size of the motor, it is necessary to obtain a large torque with a reduction ratio of about 1/200.

  In the present embodiment, a normal planetary speed reducer (2KH type) and a 3K type planetary speed reducer are combined to achieve a compact configuration.

  A deceleration part is demonstrated. The output of the electric motor 40 is connected to a first stage input sun gear 41 that is a normal planetary reduction mechanism, and is decelerated. The output is connected to the sun gear 42 of the next-stage 3K-type planetary reduction unit. Reference numeral 43 denotes a first stage planetary gear, and reference numeral 44 denotes a first stage output carrier.

  When the sun gear 42 rotates, the first outer ring gear 45 is fixed, so that the first planetary gear 46 revolves while rotating according to the gear ratio of the sun gear 42 and the first outer ring gear 45.

  The second planetary gear 47 moves integrally with the first planetary gear 46 via the elastic key 48.

  Since the number of teeth of the second planetary gear 47 is different from the number of teeth of the first planetary gear 46, the second outer ring gear 49 circumscribing the second planetary gear 47 is decelerated and rotated, and the second outer ring gear 49 The connected output shaft 50 rotates. Thereby, the pitman arm 2 can be swung and rotated.

  Here, the elastic key 48 is for preventing a large force from being applied to only one gear among the plurality of planetary gears, and is further used for reducing or eliminating backlash.

  Since the rotational phases of the first planetary gear 46 and the second planetary gear 47 can be twisted by the elasticity of the elastic key 48, the stresses of the plurality of gears on the circumference are averaged.

  When the rotational phase of a pair (or a plurality of pairs) of the first planetary gear 46 and the second planetary gear 47 is slightly shifted from the ideal value and connected by the elastic key 48, backlash can be reduced or eliminated. is there. Reduction / removal of backlash and elimination of play are effective in improving steering stability and reducing sound per tooth (rattle sound).

As shown in FIG. 5, which will be described later, the 3K type reduction ratio has the number of teeth of Z1 (input sun gear 41), Z2 (first planetary gear 46), Z3 (first outer ring gear 45), Z4 (second planetary gear). Gear 47), Z5 (second outer ring gear 49)
Reduction ratio = 2 * Z2 * Z5 / (Z2-Z4) / Z1
It becomes. If the difference between Z2 and Z4 is reduced, a very large reduction ratio can be obtained. In the present embodiment, the reduction ratio is 6.5 for the first stage, 37.1 for the 3K type of the second stage, and about 240 in total.

  Reference numeral 51 indicates a needle bearing, reference numeral 52 indicates a moment carrier pin, reference numeral 53 indicates a needle bearing, reference numeral 54 indicates a drive shaft of the electric motor, and reference numeral 55 indicates a needle bearing. , 56 indicates a fixed housing, 57 indicates a moment carrier, and 58 indicates a ball joint. The fail-safe mechanism will be described in detail later.

  As described above, when the planetary gear speed reduction mechanism is used, a compact reduction gear capable of high speed reduction is obtained, and thus the steering actuator 1 can be reduced in size and weight.

  This speed reduction mechanism is called a 3K type planetary gear speed reduction mechanism, and is a known structure (Mechanical Research (Yakkendo) vol 49, Noll, pages 1179 to 1181). Since the tooth surface contact surface pressure and stress are reduced only at the meshing portion with the outer ring gear (internal gear), the gear can be miniaturized. It can be seen that the number of components is also smaller than that of a normal planetary gear speed reduction mechanism (2KH type two-stage).

  The effect of applying this speed reduction mechanism to a steering device that requires a particularly small and compact size is great.

  Also, when used for steering, reverse operation (the pitman arm 2 rotates with respect to the input of axial force from the tie rod arm 3) for the vehicle's self-steering stability (restoration characteristics in the straight direction). Although it is desirable that the reverse operation efficiency is good, this speed reduction mechanism can satisfy such a condition by appropriately designing.

  FIG. 5 is a schematic diagram for explaining the balance between the 3K type and the normal type (2KH type) planetary gear speed reducers according to the first embodiment of the present invention.

  In the present embodiment, a 3K type reduction gear is used to reduce the size. This will be described. FIG. 5 is a diagram showing reaction forces received by the gear and the carrier in consideration of balance of forces in the reduction gear.

  In a normal planetary reduction gear (2KH type), the tangential force Fout received by the output gear Z3 and the tangential force Fin received by the input gear Z1 are the same (although the torque is multiplied by the reduction ratio).

  In this case, since the tooth surface stress of the input gear Z1 increases, it is necessary to reduce the reduction ratio to increase the diameter of Z1, or to increase the size of the device (Z3 is increased or lengthened in the axial direction). .

  Furthermore, since the reaction force received by the carrier is twice that of Fout, it is necessary to prepare a carrier having a high strength, so it is difficult to reduce the size of the apparatus.

  On the other hand, with the force received by the 3K type gear, the tangential force Frc of the gear Z2 and the tangential force Fin of the input gear are smaller than the tangential force Fout of the output stage as shown in the following equation.

Frc = (Z2 + Z4) ÷ (2 × Z2) × Fout
Fin = (Z2−Z4) ÷ (2 × Z2) × Fout
As can be seen from the equation, the tangential force of the input gear is ½ or less of Fout, and becomes a very small value depending on the difference between Z2 and Z4.

  Since the Fre part and Fout part where a large force is applied are in mesh with the internal gear and the external gear, the meshing rate is large, the root bending stress and the tooth surface pressure are small, which is advantageous for downsizing.

  The carriers generate moment loads Fml and Fm2 (values depending on the axial distance) due to the deviation of Fout and Rrc in the axial direction. However, since the values are small, the carrier can also be reduced in size.

  The 3K type provides a high reduction ratio and is very advantageous from the viewpoint of stress.

  However, the 3K type has a drawback that if the reduction ratio is increased too much, the tooth surfaces that receive a large force mesh at high speed, resulting in poor efficiency.

  Therefore, in the present embodiment, the first stage is decelerated using a normal planetary reduction gear (2KH type), and then the 3K type is used for deceleration.

  FIG. 6 shows the result of the reduction gear efficiency obtained from the energy balance with the efficiency of the pair of gears set to 98%.

  The gears of this device are spur gears, and the efficiency of a pair of gears can be made 98 to 99% when they are generally designed appropriately.

  The normal efficiency is the efficiency of a normal speed reducer, and the reverse efficiency is the efficiency when the speed reducer is used as a speed increaser.

  With a configuration of only 3K type, a simple and compact speed reducer can be obtained, but the efficiency is low at a high reduction ratio, and especially when the reduction ratio is 140 or more, the reverse efficiency is 0, that is, the reverse operation is impossible, and the steering mechanism. Is unusable.

  On the other hand, the configuration of the 3K type + normal planetary speed reducer (2KH type) of the present embodiment is slightly inferior to the multistage 2KH type planetary speed reducer, but can achieve almost the same efficiency. Reducer mass can be reduced to about half.

  FIG. 7 is a schematic plan view showing a fail-safe mechanism according to the first embodiment of the present invention.

  The left and right steering actuators 1 are connected by a fail-safe wire 60.

  The fail-safe wire 60 is a Bowden cable in which a wire 62 is passed through a cable sleeve 61 like a brake wire of a bicycle. It is connected.

  Thereby, even when one of the steering actuators 1 breaks down and does not generate output torque, the movement of the other actuator is transmitted and the left and right wheels are normally steered.

  The fail-safe wire 60 is adjusted so that there is a slight play when the steering actuator 1 is operating normally, and the left and right steering actuators 1 can output a certain amount of independent output. ing.

  Returning to FIG. 4, the failsafe wire 60 will be described.

  The fail safe wire 60 is a Bowden wire in which a wire 62 passes through a cable sleeve 61 and can transmit a tensile force. One end of the cable sleeve 61 is attached to a side of the steering actuator 1. Yes.

  The wire 62 is wound around a pulley formed on the outer periphery of the moment carrier of the 3K-type reduction part. In the illustrated example, it is wound around a moment carrier / wire pulley 63.

  A pair of wires 62 are output as shown in FIG. 7 so that tension is generated in each of the right rotation and the left rotation.

  The opposite end of the cable sleeve 61 is similarly attached to the steering actuator 1 on the opposite side, with the relationship between right rotation and left rotation reversed.

  Usually, the moment carrier (63) rotates with the revolution of the first and second planetary gears 46 and 47, and aims to eliminate the inclination of the gear due to the moment.

  However, since the output shaft 50 can be rotated by rotating the moment carrier (63), this is used for the fail-safe wire 60. A fail-safe mechanism can be provided without adding extra parts.

The rotation of the moment carrier (63) is 3K type
Carrier to output shaft reduction ratio = Z2 × Z5 / (Z2−Z4) / (Z1 + Z2)
Is output at a reduction ratio of.

  From the relationship between the reduction ratio, the turning radius of the pitman arm 2 and the pulley radius, the generated tension of the wire with respect to the pitman arm thrust is determined.

  In the present embodiment, the ratio of the wire tension to the pitman arm thrust (tension ratio) is about 2/5.

  The cable sleeve 61 can be made thinner as the wire tension is smaller. However, if the tension ratio is too small, the wire length becomes longer and the pulley becomes larger (the shaft length increases). About / 5 is desirable.

  A cable adjuster 64 is provided to adjust the slack of the wire 62. In the present embodiment, when the cable adjuster 64 is screwed, the wire is slackened. For left and right independent control, it is desirable to provide a certain amount of slack (about 1 to 5 degrees in terms of pitman arm angle).

  As described above, the pair of steering actuators 1 are connected by the mechanical connection mechanism (fail-safe mechanism).

  As a result, even if one of the steering actuators 1 breaks down and the output becomes impossible, the movement of the other steering actuator 1 is transmitted, so that a serious situation such as inability to steer is not caused. A fail-safe configuration can be obtained.

  Further, as a mechanical connection mechanism, a relay rod may be used as in a conventional pitman arm type steering, but it is preferable to use a wire (Borden cable) or hydraulic pressure, thereby laying out other parts. The pair of steering actuators 1 can be connected without sacrificing performance.

  In addition, this invention is not limited to embodiment mentioned above, A various deformation | transformation is possible.

  In the above-described embodiment, the electric motor 40 is a DC brushless motor, and a resolver type angle sensor is built in the motor, and torque, speed, and position are controlled by the steering control drive device 30. Is made. Further, the torque of the pitman arm 2 is estimated by detecting the current.

  Since it is greatly decelerated by the reduction gear, the output torque of the electric motor 40 is relatively small and 2N. m with an output torque of about 400 m. A large torque of m can be output. It can be applied to a passenger car of about 1.5 tons.

  The output shaft 50 uses a needle bearing 55 and a ball bearing 59 to support a large reaction force that the pitman arm 2 receives from the tie rod arm 3, and is designed so that no extra force acts on the gear.

  Next, FIG. 8 is a cross-sectional view of the steering actuator (rotary actuator) of the steer-by-wire system according to a modification of the first embodiment of the present invention.

  In this modification, a plurality of strain gauges 70 are attached to the housing 56 to replace the shaft force sensor 21 (FIG. 3).

  The above-described shaft force sensor 21 in FIG. 3 is attached to the tie rod arm 3 which is a movable part, and care must be taken so that the wiring is not cut. When the sensor (strain gauge 70) is attached to the housing 56, the sensor (strain gauge 70) does not move, so there is no such concern, and a highly reliable load measurement can be performed.

  Note that the position where the strain gauge 70 is affixed is appropriately selected as shown in FIG. 8 in order to perform highly accurate measurement.

  Further, the relationship between the axial force of the tie rod arm 3 and the strain amount of the strain gauge 70 changes depending on the angle of the pitman arm 2, but it may be calculated by calculating the relationship in advance.

  Next, FIG. 9 is a cross-sectional view of a steering actuator (rotary actuator) of a steer-by-wire system according to another modification of the first embodiment of the present invention.

  In this modification, a traction drive speed reducer 80 (for example, a planetary roller speed reducer) is used as the first stage speed reducer instead of the gear mechanism.

Since the reduction ratio of the steering actuator 1 is as large as 240, the first-stage input shaft rotation speed is as high as 3000 to 5000 min ⁻¹ . For this reason, noise becomes a problem when gears are used.

  In FIG. 4 described above, in order to cope with this, the tooth surface is polished only in the first stage, or a device using a resin gear is devised.

  However, when higher silence is required, the first stage is the traction drive speed reducer 80 (for example, a planetary roller speed reducer) as in this modification. There is no meshing, and high quietness is obtained due to rolling contact.

  In FIG. 9, a planetary roller speed reducer is used as the traction drive speed reducer 80. In addition, a traction drive speed reducer using a wedge effect can be used.

  Further, the output shaft 50 uses a resolver 90 (output shaft angle sensor) as a rotation angle sensor.

  The resolver 90 is a so-called 3X resolver and can detect an absolute angle in a 120 ° range. The absolute angular position of the 60 ° pitman arm 2 can be known, and the control reliability is improved.

  In this modification, a traction drive speed reducer 80 is used, and even if there is a change in the reduction ratio of the traction drive (change due to slip or dimensional change due to temperature), this resolver 90 can correct it. It is.

  In such a configuration, when considering the pair of steering actuators 1, the number of angle sensors (the angle sensor (resolver) inside the electric motor 40 and the output angle sensor) is four in total.

  Accordingly, it is possible to determine the abnormality of the sensor based on majority logic, and it is possible to adopt a fail-safe configuration that enables steering even if any one of the sensors fails.

(Second Embodiment)
FIG. 12 is a sectional view of a pitman arm type steering actuator (rotary actuator) of a steer-by-wire system according to a conventional example.

  In the conventional example of FIG. 12, the rotation of the electric motor 201 is reduced by the wave gear reduction device 203, and the swing rotation output is obtained by the pitman arm 209. Since the drive shaft 202 and the output shaft 207 of the electric motor 201 are coaxial, and the output shaft 207 also includes an angle sensor 208 (resolver), the configuration is long in the axial direction. If it is long in the axial direction, a problem arises due to interference with the engine and driving parts when mounted on the vehicle. Reference numeral 204 denotes a wave generator, reference numeral 205 denotes a circular spline, and reference numeral 206 denotes a flex spline.

  In addition, the pitman arm actuator has a large reduction ratio in order to obtain a large torque, and the electric motor rotates at a high speed, but there is also a problem that a gear meshing sound is generated.

  In the conventional example of FIG. 12, a wave gear reduction device 203 without backlash is used. Although there is no problem of backlash, there is a case where tooth skipping (ratcheting phenomenon) occurs with respect to an impact load. Once tooth skipping occurs, there is also a problem that load resistance is lowered and stable running becomes impossible.

  On the other hand, in the planetary gear mechanism of the above-described first embodiment (FIG. 4), although a phenomenon such as tooth skipping or tooth loss does not occur, it is difficult to reduce backlash.

  That is, in the planetary gear mechanism of the first embodiment (FIG. 4) described above, there are three correlated meshes (the meshing of the input sun gear 42 and the first stage planetary gear 43, the first stage planetary gear 43 and the first gear It is necessary to simultaneously adjust the meshing with the outer ring gear 45 and the meshing of the second planetary gear 47 and the second outer ring gear 49 of the output shaft 50 to reduce the backlash, which makes it difficult to reduce the backlash.

  In contrast, in the present embodiment, the electric motor and the output shaft are generally orthogonalized by using a worm reduction mechanism to prevent the actuator from becoming vertically long. Further, since the worm speed reduction mechanism is based on sliding contact, there is no meshing noise as in the gear mechanism, which is advantageous in terms of noise. The worm reduction mechanism is also widely used in electric power steering devices, and can obtain a high reduction ratio (about 1:20) with high efficiency (80% or more).

  Further, in the planetary gear mechanism according to the present embodiment, the input sun gear is eliminated from the planetary gear mechanism of the first embodiment (FIG. 4) described above, and the revolution of the planetary gear is used as the input. The occurrence of backlash has been changed from three to two to facilitate backlash adjustment.

  FIG. 10A is a cross-sectional view of the steering actuator (rotary actuator) of the steer-by-wire system according to the second embodiment of the present invention, and FIG. 10B includes a cross-section of the steering actuator (rotary actuator). It is a perspective view. In FIG. 10 (b), the output shaft is sectioned, and the housing and fine parts are not drawn.

  The output shaft 110 and the drive shaft (worm 101) of the electric motor 100 are substantially orthogonal to each other via a worm reduction mechanism.

  The planetary gear mechanism meshes with the fixed internal gear 105 fixed to the housing 120, the output shaft internal gear 108 that drives the output shaft 110, the fixed internal gear 105, and the output shaft internal gear 108, and is integrated. Revolving and rotating revolving gear train (first planetary gear 106 and second planetary gear 107), and input carrier 102 (worm wheel) revolving these revolving gear trains (first planetary gear 106 and second planetary gear 107). And.

  The electric motor 100 is disposed in a direction orthogonal to the output shaft 110 via a worm reduction mechanism. With such a layout, the electric motor 100 is arranged in the lateral (width) direction of the vehicle, and the layout is close to that of the conventional rack and pinion system, and there is little interference with other components such as the engine layout.

  The rotation of the electric motor 100 is decelerated by the worm 101 and transmitted to the worm wheel 102. The first planetary gear 106 and the second planetary gear 107 revolve by the carrier pin 103 attached to the worm wheel 102. The first planetary gear 106 and the second planetary gear 107 are connected by a key 104.

  Since the second planetary gear 107 meshes with the fixed internal gear 105 fixed to the housing 120, when the second planetary gear 107 revolves with the carrier pin 103, the second planetary gear 107 is fixed to the fixed internal gear 105. Rotate according to the number ratio of teeth.

  Since the first planetary gear 106 rotates and revolves in the same manner as the second planetary gear 107, the output shaft internal gear 108 rotates to match the rotation and revolution and is decelerated.

  This mechanism does not have a central pinion (sun gear) as an input, compared to the planetary gear mechanism of the first embodiment (FIG. 4) described above. Since no backlash occurs at the pinion part, there are three to two places where the backlash adjustment is necessary (the second planetary gear 107 and the fixed internal gear 105, and the first planetary gear 106 and the output shaft internal gear 108). And less. Since the meshing of the gears is only the meshing of the internal gears and the external gears, the stress is smaller than that of the conventional mechanism and the size can be reduced.

  As described above, according to the present embodiment, the degree of freedom of the vehicle layout can be increased, the backlash when the planetary gear mechanism is used can be reduced, and the maneuverability can be improved while reducing the noise. .

  FIG. 11 is a schematic diagram for explaining the backlash adjustment mechanism.

  In the present embodiment, the following method is adopted as the backlash adjustment mechanism.

  As shown in FIG. 11, the first and second planetary gears 106 and 107 are internal gears (fixed internal gears) with the PCD of the first and second planetary gears 106 and 107 being variable by elastic deformation of the carrier 109. The gear 105 and the output shaft internal gear 108) are pressed against each other.

  Since the configuration is such that no pinion gear is provided, such backlash can be removed.

  In addition, this invention is not limited to embodiment mentioned above, A various deformation | transformation is possible.

1 is a schematic plan view of a vehicle equipped with a steer-by-wire system according to a first embodiment of the present invention. (A) is a schematic plan view showing the relationship between the angle of the pitman arm and the angle of the front wheel. (B) is a schematic plan view showing the positional relationship between the pitman arm and the front wheels according to a modification. (C) is a schematic front view showing the positional relationship between the pitman arm and the front wheels according to another modification. It is a back surface schematic diagram of the steer-by-wire system which concerns on 1st Embodiment of this invention. It is sectional drawing of the actuator for steering (rotary actuator) of the steer-by-wire system which concerns on 1st Embodiment of this invention. FIG. 4 is a schematic diagram illustrating a balance between 3K type and normal type (2KH type) planetary gear speed reducers according to the first embodiment of the present invention. It is the result of obtaining the efficiency of the speed reducer from the energy balance with the efficiency of the pair of gears being 98%. 1 is a schematic plan view illustrating a fail-safe mechanism according to a first embodiment of the present invention. It is sectional drawing of the steering actuator (rotary actuator) of the steer-by-wire system which concerns on the modification of 1st Embodiment of this invention. It is sectional drawing of the steering actuator (rotary actuator) of the steer-by-wire system which concerns on the other modification of 1st Embodiment of this invention. (A) is sectional drawing of the steering actuator (rotary actuator) of the steer-by-wire system which concerns on 2nd Embodiment of this invention, (b) is a perspective view containing the cross section of the steering actuator (rotary actuator). It is. It is a schematic diagram for demonstrating a backlash adjustment mechanism. It is sectional drawing of the actuator for a pitman arm type steering (rotary actuator) of the steer-by-wire system which concerns on a prior art example.

Explanation of symbols

1 Steering actuator (rotary actuator)
2 Pitman arm 3 Tie rod arm 4 Knuckle arm 5 Car body 10 Steering input device (steering wheel)
DESCRIPTION OF SYMBOLS 11 Reaction force actuator 20 Steering control drive device 21 Axial force sensor 30 Vehicle control device 31 Suspension sensor 32 Hub sensor 40 Electric motor 41 First stage input sun gear 42 Sun gear 43 First stage planetary gear 44 First stage output carrier 45 First Outer ring gear 46 First planetary gear 47 Second planetary gear 48 Elastic key 49 Second outer ring gear 50 Output shaft 51 Needle bearing 52 Moment carrier pin 53 Needle bearing 54 Drive shaft 55 Needle bearing 56 Housing 57 Moment carrier 58 Ball joint 59 Ball bearing 60 Fail-safe wire 61 Cable sleeve 62 Wire 63 Moment carrier / wire pulley 64 Cable adjuster 70 Strain gauge 80 Traction drive reducer (for example, planetary roller reducer)
90 resolver (output shaft angle sensor)
100 Electric motor 101 Worm 102 Input carrier (worm wheel)
103 carrier pin 104 key 105 fixed internal gear 106 first planetary gear 107 second planetary gear 108 output shaft internal gear 109 carrier 110 output shaft 111 pitman arm 120 housing 201 electric motor 202 drive shaft 203 wave gear reduction device 204 wave generator 205 Circular spline 206 Flex spline 207 Output shaft 208 Angle sensor (resolver)
209 Pitman Arm

Claims (7)

In the steer-by-wire system in which the input device to the steered wheel are mechanically disconnected, the control device controls the steered actuator according to the input of the input device, and the steered wheel is steered by its driving force.
The steer-by-wire system, wherein the steering actuator outputs a swinging and rotating motion, moves a tie rod arm, and steers the steered wheels.   The steer-by-wire system according to claim 1, wherein a pair of the steering actuators are provided corresponding to the left and right steered wheels of the vehicle. The steering actuator has a housing fixed to the vehicle, and outputs the oscillating rotational motion from a pitman arm.
The steer-by-wire system according to claim 1 or 2, wherein the tie rod arm has one end connected to the pitman arm and the other end connected to a knuckle arm.   The steer-by-wire system according to claim 2 or 3, further comprising a fail-safe mechanism that mechanically transmits the driving force of one steering actuator to the other steering actuator.   5. The steer-by-wire system according to claim 1, wherein the swing rotation output shaft and the drive shaft of the electric motor are substantially orthogonal to each other via a worm reduction mechanism. The swing rotation output shaft is driven by a planetary gear mechanism,
The planetary gear mechanism is
A fixed internal gear fixed to the housing;
An output shaft internal gear for driving the output shaft;
A revolving gear train that meshes with the fixed internal gear and the output shaft internal gear and revolves and rotates together;
An input carrier for revolving the revolution gear train,
The steer-by-wire system according to claim 5, comprising: The steering actuator outputs the rotation of the motor through the speed reducer as the oscillating rotational motion,
The speed reducer is
A sun gear rotating around the central axis;
A plurality of first planetary gears that revolve and rotate while meshing with the outer peripheral teeth of the sun gear,
A non-rotating first outer ring gear that meshes with the first planetary gear inscribed,
A plurality of second planetary gears having a different number of teeth from the first planetary gears and rotating and revolving integrally with the first planetary gears;
2. A first outer ring gear that rotates in mesh with the second planetary gear while inscribed therein, and thereby outputs the oscillating rotational motion to the pitman arm. The steer-by-wire system according to any one of 4.

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