JP2006199125A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To hold down lowering of steering feeling due to meshing a rack and a pinion not contributing to the transmission of steering torque to the minimum in an electric power steering device including a plurality of motors. <P>SOLUTION: When the first and second pinions 28A, 28B provided on a sub-motor MA and a main motor MB, respectively, are meshed with the first and second racks 30A, 30B provided on a rack bar 29 to steer a wheel, a partly missing gear 30a is provided on the second rack 30B of the rack bar 20, whereby the main motor MB and the second pinion 28B are disengaged from the rack bar 29 to eliminate the influence of its inertia force and frictional force. Thus, a shock and noise when the rack bar 29 reaches the rack end to be instantaneously stopped can be reduced to prevent lowering of steering feeling. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electric steering apparatus in which a plurality of pinions are meshed with a rack provided on a rack bar, and the plurality of pinions are driven by respective motors to steer wheels.

When the two pinions provided on the main motor and sub motor are engaged with the rack provided on the rack bar, and the wheels are normally steered with the operating torque generated by the main motor. An electric steering device that drives a sub motor to compensate for a shortage of steering torque is described in Patent Document 1 below.
JP 2004-74831 A

  However, in such a two-motor type electric steering apparatus, when the main motor is started and the rack bar starts to move, the sub motor that is stopped by the steering torque of the main motor is driven from the outside. There is a problem that the smooth feeling of the rack bar is hindered by inertial force and frictional force, and the steering feeling and responsiveness are lowered.

  Also, when the rack bar moved by driving both or one of the main motor and sub motor reaches the rack end and stops, the two motors are instantaneously stopped against its inertial force, so one motor Compared with the electric steering device of the type, there is a problem that impact and noise at the rack end are increased and steering feeling is lowered.

  The present invention has been made in view of the above-described circumstances, and in an electric steering apparatus having a plurality of motors, a reduction in steering feeling due to the engagement of racks and pinions that do not contribute to transmission of steering torque is minimized. The purpose is to suppress it.

  In order to achieve the above object, according to the first aspect of the present invention, a plurality of pinions are meshed with a rack provided on the rack bar, and the plurality of pinions are driven by motors respectively corresponding to the wheels. In the electric steering apparatus for turning, an electric steering apparatus is proposed in which a missing tooth portion for releasing the engagement with at least one pinion is formed in the rack of the rack bar.

  According to the invention described in claim 2, in addition to the configuration of claim 1, two motors are provided, and when one motor generates steering torque, the pinion of the other motor is An electric steering device is proposed, which is opposed to the missing tooth portion.

  According to the invention described in claim 3, in addition to the configuration of claim 1, there is proposed an electric steering device characterized in that the missing tooth portion is provided at an end position of the rack.

  According to the invention described in claim 4, in addition to the configuration of claim 1, there is proposed an electric steering device characterized in that the missing tooth portion is provided at the center position of the rack.

  According to the invention described in claim 5, in addition to the structure of any one of claims 1 to 4, the driving time of the one motor is set shorter than that of the other motor. Or an electric steering device characterized in that the output is set to be small.

  The first and second pinions 28A and 28B of the embodiment correspond to the pinion of the present invention, and the first and second racks 30A and 30B of the embodiment correspond to the rack of the present invention. The main motor MB corresponds to the motor of the present invention.

  According to the configuration of the first aspect, when the wheels are steered by engaging the pinions respectively provided on the plurality of motors with the rack provided on the rack bar, the toothless portion is provided on the rack of the rack bar. At least one of the motor and the pinion can be separated from the rack bar, and the influence of the inertial force and frictional force can be eliminated to prevent the steering feeling from being lowered.

  According to the configuration of the second aspect, when one of the two motors generates the steering torque, the pinion of the other motor is opposed to the missing tooth portion of the rack. When the steering torque is not generated, the influence of the inertial force and frictional force can be eliminated to prevent the steering feeling from being lowered.

  According to the configuration of the third aspect, by providing the rack tooth-less portion at the rack end position, when the steering bar is cut to the limit position and the rack bar reaches the rack end, the other motor and pinion Since the connection with the rack bar is released, the inertial force acting on the rack bar can be reduced to minimize the occurrence of impact and noise, and the steering feeling can be prevented from being lowered.

  According to the configuration of the fourth aspect, by providing the rack tooth-less portion at the center position of the rack, when one motor is started at the start of turning the steering handle, the other motor, the pinion and the rack bar are connected. Therefore, the inertial force and frictional force acting on the rack bar can be reduced to prevent the steering feeling from being lowered and the steering response can be improved.

  According to the configuration of the fifth aspect, one of the motors is set to have a shorter driving time than the other motor, or the output is set to be smaller, so that one motor is driven by the steering torque generated by the other motor. When the motor is driven from the outside, the influence of the inertial force or frictional force of one of the motors on the steering feeling can be minimized.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples of the present invention shown in the accompanying drawings.

  1 to 7 show a first embodiment of the present invention. FIG. 1 is an overall perspective view of an electric power steering apparatus, FIG. 2 is an enlarged sectional view taken along line 2-2 of FIG. 1, and FIG. 4 is an enlarged cross-sectional view taken along line 4-4 of FIG. 1, FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. 1, FIG. FIG. 7 is an enlarged sectional view taken along line 7-7 in FIG.

  As shown in FIG. 1, the upper steering shaft 12 that rotates integrally with the steering handle 11 is protruded upward from the first reduction gear 16A via the upper universal joint 13, the lower steering shaft 14, and the lower universal joint 15. 1 pinion shaft 17A is connected. Tie rods 19 and 19 projecting from the left and right ends of the steering gear box 18 connected to the lower end of the first reduction gear 16A are connected to knuckles (not shown) of the left and right wheels WL and WR. A sub motor MA is supported on the first reduction gear 16A, and the operation of the sub motor MA is controlled by an electronic control unit U to which a signal from a steering torque sensor St housed in the first reduction gear 16A is input. The The steering gear box 18 is provided with a second reduction gear 16B, and the main motor MB supported by the second reduction gear 16B is also controlled by the electronic control unit U.

  As shown in FIGS. 2 and 3, the first reduction gear 16A includes a lower case 21 integrated with the steering gear box 18, an intermediate case 23 coupled to the upper surface thereof with bolts 22 ..., and bolts 24 ... on the upper surface thereof. The first pinion shaft 17A is rotatably supported by ball bearings 26 and 27 on the steering gear box 18 and the upper case 25. A first pinion 28A provided at the lower end of the first pinion shaft 17A meshes with a first rack 30A provided on a rack bar 29 supported inside the steering gear box 18 so as to be movable left and right. A pressing member 31 is slidably accommodated in a through hole 18 a formed in the steering gear box 18, and the pressing member 31 is attached to the rack bar 29 by a spring 33 disposed between the nut member 32 closing the through hole 18 a. By biasing toward the back surface, the first rack 30A can be correctly meshed with the first pinion 28A while suppressing the deflection of the rack bar 29.

  The rotation shaft 34 of the sub motor MA extending inside the first reduction gear 16A is rotatably supported by the lower case 21 by a pair of ball bearings 35 and 36. A worm 37 provided on the rotating shaft 34 of the sub motor MA meshes with a worm wheel 38 fixed to the first pinion shaft 17A.

  As shown in FIG. 4, the structure of the second speed reducer 16B is similar to the structure of the first speed reducer 16A, but the second speed reducer 16B does not include the upper case 25, and the steering gear box 18 and the middle The second pinion shaft 17B is supported by the case 23 via ball bearings 26 and 27. The second pinion 28B provided at the lower end of the second pinion shaft 17B meshes with the second rack 30B of the rack bar 29.

  The reference numerals of the constituent elements of the second speed reducer 16B are the same as those of the corresponding constituent elements of the first speed reducer 16A except for the first and second pinion shafts 17A and 17B and the first and second pinions 28A and 28B. The same code is used.

  Thus, when the sub motor MA is driven, the first pinion shaft 17A of the first reduction gear 16A rotates via the worm wheel 38 that meshes with the worm 37 provided on the rotation shaft 34, and meshes with the first pinion 28A. By driving the first rack 30A, the steering torque applied by the driver to the steering handle 11 is assisted by the sub motor MA.

  When the main motor MB is driven, the second pinion shaft 17B of the second reduction gear 16B rotates through the worm wheel 38 that meshes with the worm 37 provided on the rotation shaft 34, and meshes with the second pinion 28B. When the second rack 30B is driven, the steering torque applied by the driver to the steering handle 11 is assisted by the main motor MB.

  As shown in FIG. 5, of the first rack 30A and the second rack 30B formed on the rack bar 29, the toothless portion having no gear teeth at both ends of the second rack 30B meshed with the second pinion 28B. 30a and 30a are formed, and the second pinion 28B idles with respect to the second rack 30B when facing the missing tooth portions 30a and 30a.

  As is apparent from FIG. 1, the sub motor MA provided in the first speed reducer 16A is smaller and has a smaller output than the main motor MB provided in the second speed reducer 16B.

  Next, the operation of the embodiment of the present invention having the above configuration will be described.

  When the steering torque sensor St detects the steering torque input to the steering handle 11 by the driver, the electronic control unit U causes the sub motor MA and the main motor MB to generate assist torque corresponding to the steering torque. At this time, the main motor MB is preferentially driven, and when the torque is insufficient even when the main motor MB generates the maximum assist torque, the sub motor MA is simultaneously driven so as to compensate for the shortage of the torque. That is, the main motor MB is always driven, and the sub motor MA is driven when the assist torque of the main motor MB is insufficient.

  When the vehicle collides and a large load is applied to the bumper from the front, and the engine in the engine room is pushed backward by the load and moves backward, the steering gear box 18 and the first reduction gear 16A disposed behind the engine. The second reduction gear 16B and the like also move backward. When the first speed reducer 16A moves backward in this way, the lower steering shaft 14 and the upper steering shaft 12 connected to the first pinion shaft 17A provided in the first speed reducer 16A are pushed backward, and the steering handle 11 is moved to the vehicle. There is a possibility of protruding into the room. In order to suppress the protrusion of the steering handle 11, it is desirable to make the clearance between the engine and the first reduction gear 16A as large as possible so that it is difficult to interfere with the first reduction gear 16A even if the engine moves backward.

  In this embodiment, the assist motor is separated into the sub motor MA and the main motor MB, and the sub motor MA provided in the first reduction gear 16A is made smaller than the main motor MB provided in the second reduction gear 16B. The expansion of the clearance makes it difficult for the first reduction gear 16 </ b> A to move backward during a collision, and the protrusion of the steering handle 11 into the vehicle interior can be minimized. Moreover, by reducing the size of the sub motor MA, the mass of the first speed reducer 16A including the sub motor MA is reduced, the inertia of the first speed reducer 16A moving backward due to the impact of the collision is reduced, and the protrusion of the steering handle 11 is further increased. It can be kept small.

  In addition, the resultant force of the assist torque generated by the main motor MB and the road surface reaction force acts on the meshing portion of the second pinion 28B and the second rack 30B driven by the main motor MB, while the sub motor MA A resultant force of the assist torque generated by the sub motor MA, the steering torque input by the driver to the steering handle 11, and the road surface reaction force acts on the meshing portion of the driven first pinion 28A and the first rack 30A. The durability of the meshing portion between the first pinion 28A and the first rack 30A may be reduced by the amount of the assist torque.

  However, by operating the main motor MB preferentially, the frequency with which the sub motor MA is operated is reduced, and the sub motor MA is made smaller than the main motor MB, and the generated assist torque is reduced. Therefore, the first pinion 28A and the first The lowering of the durability of the meshing portion with the rack 30A is prevented, and the durability of the meshing portion between the first pinion 28A and the first rack 30A and the durability of the meshing portion between the second pinion 28B and the second rack 30B are uniform. Can be

  By the way, in the case where the common rack bar 29 is driven by the sub motor MA and the main motor MB, the inertial force accompanying the movement of the rack bar 29, that is, the sub motor MA and the main motor MB are compared with those driven by the single motor. The sum of the inertial forces of the rotor and the first and second pinions 28A and 28B increases. Therefore, if the missing tooth portions 30a and 30a do not exist, steering is performed by driving both the sub motor MA and the main motor MB, or by driving only the main motor MB, and the rack bar 29 has a rack end in the horizontal direction. When the motor reaches the moment and stops instantaneously, a large impact or noise is generated by the inertial force.

  However, according to the present embodiment, immediately before the rack bar 29 reaches the rack end, the second pinion 28B of the main motor MB is opposed to the one missing tooth portion 30a of the second rack 30B, and the engagement is released. The inertial force of the rotor of the main motor MB and the second pinion 28B does not act on the rack bar 29, and the impact and noise when the rack bar 29 reaches the rack end are reduced. As a result, a decrease in steering feeling is suppressed, and a load applied to the gear teeth of the second rack 30B and the second pinion 28B is reduced.

  Further, when the second pinion 28B of the main motor MB is not opposed to the toothless portions 30a, 30a of the second rack 30B, that is, the first pinion 28A is engaged with the first rack 30A, and the second pinion 28B is second. When meshing with the rack 30B, if only the sub motor MA is driven, the friction force of the main motor MB becomes a load, and if only the main motor MB is driven, the friction force of the sub motor MA becomes a load. However, in the present embodiment, the main motor MB that operates frequently is enlarged and the sub motor MA that operates less frequently is reduced in size, so that energy loss caused by driving the stopped sub motor MA with the main motor MB is reduced. Steering feeling can be enhanced with a minimum.

  Next, a second embodiment of the present invention will be described with reference to FIG.

  In the first embodiment, two missing teeth 30a and 30a are provided at both ends of the second rack 30B. However, in the second embodiment, one missing tooth 30a is provided at the center of the second rack 30B. Yes, when the steering handle 11 is in the neutral position, the second pinion 28B faces the tooth missing portion 30a. At the moment when the steering handle 11 starts to be turned from the neutral position, only the sub motor MA operates and the main motor MB is in a stopped state. Accordingly, if the missing tooth portion 30a does not exist, when the sub motor MA is activated and the rack bar 29 is moved through the first pinion 28A and the first rack 30A, the second rack 30B and the second pinion 28B are used. Thus, a frictional force is generated by driving the main motor MB from the outside. In addition, since the inertial force of the rotor of the main motor MB and the second pinion 28B acts on the rack bar 29, the response time from when the sub motor MA is started until the rack bar 29 starts moving increases.

  However, according to this embodiment, since the second pinion 28B is opposed to the toothless portion 30a of the second rack 30B at the moment when the sub motor MA is started by operating the steering handle 11 from the neutral position, the main motor MB The rotor and the second pinion 28B are not driven by an external force to reduce the frictional force, and the inertial force of the rotor of the main motor MB and the second pinion 28B does not act on the rack bar 29. Will improve. Then, the rack bar 29 starts moving, the static friction changes to dynamic friction, and the rack bar 29 becomes easy to move, so the second pinion 28B meshes with the second rack 30B, so the rack bar 29 moves smoothly. Start.

  Next, a third embodiment of the present invention will be described with reference to FIG.

  In the third embodiment, two missing teeth 30a and 30a are provided at both ends of the first rack 30A, and one missing tooth 30a is provided at the center of the second rack 30B. According to the third embodiment, for the same reason as in the first embodiment, the teeth of the first pinion 30A of the sub motor MA and the one missing tooth portion 30a of the first rack 30A immediately before the rack bar 29 reaches the rack end. Since the coupling is released, the inertial force of the rotor of the sub motor MA and the first pinion 28A does not act on the rack bar 29, and the impact and noise when the rack bar 29 reaches the rack end are reduced. Similarly to the second embodiment, when the sub motor MA is started with the steering handle 11 in the neutral position, the frictional force is reduced because the second pinion 28B is opposed to the toothless portion 30a of the second rack 30B. In addition, since the inertial force of the rotor of the main motor MB and the second pinion 28B does not act on the rack bar 29, the response name is improved.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the present invention described in the claims. It is.

  For example, in the embodiment, a small motor is used for the sub motor MA and a large motor is used for the main motor MB, but the size relationship is arbitrary.

Overall perspective view of electric power steering device 2-2 line enlarged sectional view of FIG. 3-3 sectional view of FIG. Sectional view taken along line 4-4 in FIG. Sectional view along line 5-5 in FIG. Action explanatory diagram with rack end 7-7 enlarged sectional view of line 7-7 The figure corresponding to the said FIG. 5 which concerns on 2nd Example. The figure corresponding to the said FIG. 5 which concerns on 3rd Example.

Explanation of symbols

28A 1st pinion (pinion)
28B Second Pinion (Pinion)
29 rack bar 30A first rack (rack)
30B 2nd rack (rack)
30a Missing tooth part MA Sub motor (motor)
MB main motor (motor)
WL wheel WR wheel

Claims (5)

A plurality of pinions (28A, 28B) are meshed with racks (30A, 30B) provided on the rack bar (29), and the plurality of pinions (28A, 28B) are driven by corresponding motors (MA, MB), respectively. In the electric steering device that steers the wheels (WL, WR),
An electric steering device characterized in that a rack (30B) of the rack bar (29) is formed with a missing tooth portion (30a) for releasing the engagement with at least one pinion (28B).   Two motors (MA, MB) are provided, and when one motor (MA) generates steering torque, the pinion (28B) of the other motor (MB) is opposed to the tooth missing portion (30a). The electric steering apparatus according to claim 1, wherein:   The electric steering apparatus according to claim 1, wherein the tooth missing portion (30a) is provided at an end position of the rack (30B).   The electric steering device according to claim 1, wherein the tooth missing portion (30a) is provided at a center position of the rack (30B). The motor according to any one of claims 1 to 4, wherein the one motor (MA) is set to have a shorter driving time or a smaller output than the other motor (MB). The electric steering device according to claim 1.

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