JP4783352B2 - Rack and pinion type electric power steering system - Google Patents

Description

  The present invention relates to an electric power steering apparatus in which a steering assist force by an electric motor is applied to a steering system of an automobile or a vehicle. In particular, the assist is limited near a rack end (maximum turning angle) and an impact is applied at the rack end. The present invention relates to a control device for an electric power steering device that is not allowed to be generated.

  In the electric power steering apparatus, the electric motor generates an auxiliary torque corresponding to the magnitude of the steering torque, and transmits the auxiliary torque to the steering system to reduce the steering force that the driver steers.

  In a general electric power steering apparatus, a rack end is provided on a rack shaft and a housing end is provided on a rack housing portion that accommodates the rack shaft in order to prevent steering wheels from being steered beyond a certain level. The steering wheel is steered from the neutral position to the left and right by a rack end mechanism constituted by a housing end to a predetermined angle, so that the steering wheel has a maximum turning angle (hereinafter referred to as a rack end angle). When it reaches, the rack end and the housing end come into contact with each other in the left and right rack end mechanisms, and the steering wheel cannot be steered in the same direction beyond that.

  Therefore, even though the steering handle is steered to the vicinity of the rack end angle, a large steering torque is applied to the steering handle and the steering wheel cannot be steered when the rack end angle is reached. The person inputs a larger steering torque. In response to this steering torque, a large steering assist force is applied from the electric motor to the steering mechanism, so that a large impact is applied to the rack end mechanism and a large impact sound is generated, or components of the rack end mechanism are damaged. It may cause deformation. Further, due to the rotational kinetic energy due to the inertia moment of the motor, the rotation of the motor overshoots, causing a large impact to act on the components such as the rack gear, resulting in damage or deformation.

  As an apparatus for avoiding such a problem, for example, there is an apparatus disclosed in [Patent Document 1]. In the device described in [Patent Document 1], after the steering angle (operation amount) of the steering handle reaches a predetermined angle near the rack end angle, the target current value is decreased as the turning angle increases. By setting the target current value to zero when the turning angle reaches the rack end angle, a large impact is prevented from being applied to the rack end mechanism.

  However, in the device described in [Patent Document 1], when the steering handle is turned back in the opposite direction in the vicinity of the rack end angle, the target current value is limited until the turning angle becomes a predetermined angle or less. Therefore, a sufficient steering assist force according to the steering torque cannot be given to the steering system, the steering handle becomes heavy, the substantial rack end angle that can be operated by the driver is reduced, and it is mechanically provided. There is a problem that the steering handle cannot be cut to the specified rack end angle.

As a countermeasure, in the device described in [ Patent Document 2 ], the gain of the steering torque value T is obtained when the steering angle θ _{1 is} near the rack end angle and the motor rotational speed ω _M is the set value ω ₁ or more. Is to lower.
Further, the gain of the motor angular velocity feedback is increased only when the steering angle is greater than the steering angle (operation amount) near the rack end angle and is increased.
Japanese Patent Publication No. 6-4417 JP 2006-248252 A (see paragraphs [0038] and [0047])

However, in the technique of [Patent Document 2], when the driver further increases the steering handle when the rack end of one of the left and right rack shafts is in contact with the housing end of the housing, torque is increased. When the sensor detects the steering torque, an assist torque is generated in the direction of increasing the motor, and a stronger force is applied to the rack end and the housing end that are already in contact with each other. When the absolute value of the motor rotational speed ω is smaller than the set value | ω ₁ | or when the motor rotational speed ω hits the rack end at a high rotational speed, the motor rotates due to the kinetic energy due to the inertia moment of the motor. The problem of overshooting and generating a large impact on components such as rack gears cannot be solved. Therefore, even if the rack end and the housing end are in contact with each other and the operation is further increased, the motor and the reduction mechanism (worm gear, worm wheel, etc.) will not cause a problem in the mechanical soundness of the steering system due to the load. Gears), rack gears, pinion gears, bearings, housings, etc. need to be strengthened. Also, the motor may be overloaded and burned out.
Accordingly, an object of the present invention is to provide an electric power steering device that limits the assist in the vicinity of the rack end and does not apply an impact in order to solve the above problem.

In order to solve the above-mentioned problem, the invention according to claim 1 is directed to at least a steering torque generated by an input from an operating element, wherein an electric motor generates an auxiliary torque and transmits the auxiliary torque to a steering system of a front wheel. In a rack-and-pinion type electric power steering apparatus that steers the front wheels by displacing the rack shaft in the axial direction based on the torque and the auxiliary torque, between the operating sensor and the torque sensor that detects the steering torque, A rotation termination mechanism that regulates the maximum steering angle of the front wheels by regulating the maximum steering angle of the operating element by forming an operation termination is provided on the housing that houses the rack shaft between the torque sensor and the front wheels. a housing end which is provided with a rack end mechanism consisting of a rack end which is provided to the rack shaft, regulations by the rotation terminating mechanism In the state of the maximum turning angle that is characterized in that the side of the rack end and housing end corresponding thereto is configured so as not to contact.
The invention according to claim 2, in addition to the configuration of the invention according to claim 1, the rack end mechanism is characterized Rukoto used for positioning for issuing a center of movement of the rack shaft during assembly.

According to the rack and pinion type electric power steering apparatus according to claim 1 or claim 2 , when the operation element reaches the operation end, the rotation terminal mechanism prevents further operation by the operation element at the operation end. The torque sensor cannot detect a signal that generates further auxiliary torque by the electric motor in the blocked direction. Furthermore, in the state of the maximum turning angle regulated by the rotation termination mechanism, the rack end and the housing end on the corresponding side are not in contact with each other, so even if the motor overshoots, the rack end and the housing end And the detected torque detected by the torque sensor can be reduced.

The invention according to claim 3 is the rack-and-pinion type electric power steering device according to claim 1 or 2 , wherein the rotation termination mechanism has a speed reduction mechanism, and the operating element is restricted by the operation termination. The allowable rotation operation range is changed.

According to the third aspect of the present invention, since the rotation termination mechanism can change the allowable rotation operation range of the operation element by the speed reduction mechanism, the left and right steering angles (operation amount) of the same steering handle (operation element) as the conventional one are given to the driver. ) Can give a range.

The rotation terminal mechanism has an input shaft having an external gear to which rotation from the rotary shaft of the operating element is transmitted, and an internal gear that meshes with the external gear of the input shaft , and has a first protrusion on the outer peripheral side. A ring gear provided with a portion and an annular fixed portion surrounding the ring gear, and the external gear of the input shaft and the internal gear of the ring gear constitute a reduction mechanism, and on the inner peripheral side of the fixed portion, It is desirable to provide a second protrusion that abuts the first protrusion and restricts the rotation of the first protrusion.
This, in rotation terminating mechanism, the internal gear of the external gear and the ring gear of the input shaft, the relative rotational angle of the input shaft can reduce the rotational angle of the ring gear, the driver prior to the same steering wheel ( A left and right steering angle (operation amount) range in the operation element) can be given. Furthermore, the amount of operation of the steering handle corresponding to the rack end angle can be changed simply by exchanging the ring gear, and it can be applied to various types of vehicles.

The rotation termination mechanism includes a planetary gear speed reducer unit as a speed reduction mechanism, and a fixed portion that fixes an outer ring gear of the planetary gear speed reducer unit, and the first projecting portion on the planet carrier of the planetary gear speed reducer unit. The rotation from the rotary shaft of the operating element is transmitted to the sun gear of the planetary gear speed reducer unit, and the fixed portion or the outer ring gear is in contact with the first protruding portion to rotate the first protruding portion. It is preferable to provide the 2nd protrusion part to regulate.
In this end-of-rotation mechanism, the planetary gear reducer unit can reduce the rotation angle of the planet carrier relative to the rotation angle of the sun gear, so that the driver can use the same steering handle (operator) as the left and right steering angles. (Operation amount) range can be given. Furthermore, it can be arranged coaxially with the rotary shaft of the operation element, and a well-balanced rotation termination mechanism can be mounted, and the load applied to one planetary gear when the first protrusion and the second protrusion come into contact with each other. However, it is shared by the planet carrier and can withstand larger loads. Therefore, the rotation termination mechanism can be reduced in size accordingly.

In addition, the rotation termination mechanism includes a screw portion having a male screw, to which rotation from the rotation shaft of the operation element is transmitted, and an annular first pin fixed to the screw portion and provided with a first protrusion on the outer peripheral side. A second stopper having a stopper and a female screw that meshes with the threaded portion, disposed above the first stopper, and provided with a second projecting portion that contacts the first projecting portion on the lower surface side thereof; A third stopper having a female screw that meshes with the screw portion, disposed below the first stopper, and provided with a third protrusion on the upper surface side thereof that contacts the first protrusion; A guide member that prevents the rotation of the third stopper and moves the second and third stoppers along the axial direction of the screw portion, the screw portion, the second stopper, the third stopper, and It is desirable that the guide member constitutes a speed reduction mechanism .

In this rotation termination mechanism, the rotation of the screw portion is converted into the vertical movement of the second and third stoppers, and the first protrusion of the first stopper is the second protrusion of the second stopper or the second stopper. Since the rotation angle of the screw part until it contacts with the third protrusion of the No. 3 stop is increased, the left and right steering angle (operation amount) range of the steering handle (operator) as in the conventional case is given to the driver. Can do.
Further, in this rotation end mechanism, the left and right steering angles of the steering handle can be set large, for example, can be set to 2 rotations or more (720 ° or more), and can be applied to vehicles other than automobiles. Therefore, the outer diameter of the rotary terminal mechanism can be made small, and the mountability to the vehicle can be further improved.

According to the present invention, when the operation element reaches the operation end, the rotation termination mechanism prevents further operation by the operation element at the operation end, so that the torque sensor is prevented from further assist torque by the electric motor. A signal that occurs in the direction cannot be detected. And even if an electric motor overshoots, it can be made to act in the direction which decreases the detection torque which a torque sensor detects.
Therefore, as in the case of the above-described prior art, in the state where the rack end and the housing end are in contact with each other, the case where the rack end is further increased by the operation element or the impact due to the overshoot of the rotation of the motor is considered. There is no need to increase the strength unnecessarily, and the weight can be reduced.

<< First Embodiment >>
A first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a configuration diagram of an electric power steering apparatus according to a first embodiment of the present invention.
FIG. 2 is a side view of the vicinity of the torque sensor and the pinion gear of the steering gear box in FIG.
As shown in FIG. 1, in the electric power steering apparatus 100A, a handle shaft 3a provided with a steering handle (operator) 3, a shaft 3c, and an input shaft 3d are connected by two universal joints 3b. The shaft 3d is connected to the pinion shaft 7 via the torsion bar 111, and the pinion gear 7a provided at the lower end of the pinion shaft 7 meshes with the rack gear 8a of the rack shaft 8 that can reciprocate in the vehicle width direction. The left and right front wheels 1L and 1R are connected to both ends of the rack shaft 8 via tie rods 9 and 9, respectively.

  The rack shaft 8 is supported by a rack guide 31 so as to be pushed from the opposite side of the rack gear 8 a to the pinion gear 7 a side and slidable in the left and right directions, and further urged by an adjustment bolt 32 via a compression spring 33. Thus, the rack gear 8a is pressed against the pinion gear 7a. Reference numeral 34 denotes a lock nut for preventing the adjustment bolt 32 from loosening.

The pinion shaft 7 passing through the torsion bar 111 from the input shaft 3d is supported by the steering gear box 10A via bearings 3e, 3f, and 3g at the upper, middle, and lower portions.
Rack ends 8 b and 8 b are provided at both ends of the rack shaft 8. Further, in the steering gear box 10A described above, a slide bearing 14 for sliding the rack shaft 8 freely in the axial direction is provided inside a rack housing portion 11A that accommodates the pinion gear 7a, the rack shaft 8, and the bearing 3g. Housing ends 11a and 11a are provided at the left and right ends.

However, these rack ends 8b, 8b and housing ends 11a, 11a are not provided for restricting the maximum turning angle as in the prior art, and the rack shaft 8 moves when the steering gear box 10A is assembled as a single item. It is only necessary for positioning to bring out the center.
Therefore, in the present embodiment, the maximum turning angle (rack end angle) is regulated in the amount of operation (steering angle) of the steering handle 3 that is full of left and right set by the rotation termination mechanism 6A described later. The rack end 8b and the rack housing 11a for positioning are provided with a margin so as not to contact at the maximum turning angle.
In the description of the present embodiment described below and the modifications 6B, 6B ′, 6C of the rotation termination mechanism of the present embodiment described later, and the second and third embodiments, “rack end angle” refers to the rotation termination angle. The maximum turning angle specified by the mechanism.
With this configuration, the electric power steering apparatus 100A can change the traveling direction of the vehicle when the steering handle 3 is operated. Here, the rack shaft 8, the rack gear 8a, and the tie rods 9 and 9 constitute a steering mechanism.

The electric power steering apparatus 100A includes an electric motor 4 that supplies an auxiliary steering force for reducing the steering force by the steering handle 3. A worm gear 5a provided on the output shaft of the electric motor 4 is connected to a pinion shaft. 7 is meshed with a worm wheel gear 5b.
That is, the worm gear 5a and the worm wheel gear 5b constitute a speed reduction mechanism 5A. The worm gear 5a, the worm wheel gear 5b, the pinion shaft 7, the rack shaft 8, the rack gear 8a, the tie rods 9, 9 and the like connected to the rotor of the motor 4 and the motor 4 constitute a steering system.

The electric motor 4 is a three-phase brushless motor including a stator (not shown) having a plurality of field coils and a rotor (not shown) that rotates inside the stator, and mechanically powers the electric power. This is converted to (P _M = ω _M T _M ).
Here, ω _M is an angular velocity of the electric motor 4, and T _M is a torque generated by the electric motor 4.

Here, varying the steering torque applied to the steering wheel 3 Ts, the coefficients of the assist amount A _H, which assists the booster has been generated torque of the motor 4 via a reduction mechanism, for example, as a function of vehicle speed VS k _A (VS). In this case, since A _H = k _A (VS) × Ts, the pinion torque Tp applied to the pinion shaft 7 is expressed by the following equation (1).
Tp = Ts + A _H
= Ts + k _A (VS) × Ts (1)
Thus, the steering torque Ts is expressed as the following equation (2).
Ts = Tp / (1 + k _A (VS)) (2)

Therefore, the steering torque Ts is reduced to 1 / {1 + k _A (VS)} times the pinion torque Tp (load). For example, if k _A (0) = 2 when the vehicle speed VS = 0, the steering torque Ts is controlled to be 1/3 lighter than the pinion torque Tp, and k _A when the vehicle speed VS = 100 km / h. If (100) = 0, the steering torque Ts becomes equal to the pinion torque Tp, and is controlled to feel the steering torque with a firm weight equivalent to that of manual steering. In other words, by controlling the steering torque Ts in accordance with the vehicle speed VS, a sense of responsiveness of a stable and stable steering torque is imparted lightly during low-speed traveling and firmly during high-speed traveling.

In addition, the electric power steering apparatus 100A includes an electric motor drive circuit 23 that drives the electric motor 4, a resolver 25, a torque sensor 110 that detects a pinion torque Tp applied to the pinion shaft 7, and a difference that amplifies the output of the torque sensor 110. a dynamic amplification circuit 21, a vehicle speed sensor S _V for detecting the speed of the vehicle (vehicle speed), the rotation terminating mechanism 6A for restricting the movement of the steering wheel 3 input to the torque sensor 110 in the rack end, the driving of the motor 4 A steering control ECU (Electric Control Unit) 200 is provided.

The electric motor drive circuit 23 includes a plurality of switching elements such as a three-phase FET bridge circuit, for example, and uses a DUTY (DUTY U, DUTY V, DUTY W) signal from the steering control ECU 200 (see FIG. 7). A rectangular wave voltage is generated and the electric motor 4 is driven.
The motor drive circuit 23 has a function of detecting a three-phase motor current I (IU, IV, IW) using a hall element (not shown).

The resolver 25 detects an electric motor rotation angle θ _m of the electric motor 4 and outputs an angle signal θ. For example, a magnetic sensor provided with a plurality of uneven portions at equal intervals in the circumferential direction is provided as a sensor for detecting a change in magnetoresistance. There is something close to the rotating body.
A vehicle speed sensor S _V is for detecting a vehicle speed as a pulse number per unit time, and outputs a vehicle speed signal VS.

(Torque sensor)
Next, the configuration of the torque sensor will be described with reference to FIGS. 3 is a cross-sectional view taken along arrow AA in FIG. 4A and 4B are diagrams for explaining the displacement of the upper floating portion, the lower floating portion, and the slider in a state where the steering torque is applied. FIG. 4A shows a neutral state, and FIG. 4B shows the pinion shaft when the left steering torque is applied. FIG. 4C shows a state in which the pinion shaft is rotated about 30 ° to the right by applying a right steering torque.
The torque sensor 110 detects the magnitude and direction of the steering torque Ts applied to the steering handle 3, and includes an input shaft 3d, a pinion in a lid portion 13A flanged on the rack housing portion 11A. It is assembled integrally with the shaft 7 and accommodated together with the bearings 3e and 3f.

  As shown in FIG. 2, the torque sensor 110 is rotatably supported by bearings 3e and 3f and a bearing (not shown) provided coaxially between the input shaft 3d and the pinion shaft 7, and the input shaft 3d. The pinion shaft 7 is connected by a torsion bar 111. The torque sensor 110 includes an upper idler portion 112 on the lower end side of the input shaft 3d connected to the pinion shaft 7 by a torsion bar 111, a lower idler portion 113 on the upper end side of the pinion shaft 7, an upper idler portion 112, and a lower portion. Pins 117A, 117A, 117B, and 117B (see FIG. 3) fixed to the respective outer peripheral surfaces of the idler 113, a slider 115, a first detection coil 114A, and a second detection coil 114B are configured. .

  The upper floating portion 112 has floating pieces 112a and 112a that face each other. The lower floating portion 113 has a shape of a thick cylindrical body having a hollow portion 113a in the center, and the thin peripheral surface portions 113b and 113b are formed so that the side surfaces of the cylindrical body are thin on the opposite side surfaces. And the protruding peripheral surface portions 113c and 113c of the remaining side surface portions that are not thin.

  The upper floating portion 112 and the lower floating portion 113 are combined so that the floating piece 112a is stacked on the radially outer side of the thin peripheral surface portion 113b. At this time, there is a gap between the outer peripheral surface of the thin-walled peripheral surface portion 113b and the inner peripheral surface of the free-moving piece 112a, and a predetermined relative rotation angle, for example, −5 ° to + 5 ° can be rotated. With respect to the relative rotation beyond this, the circumferential end of the idler piece 112a and the circumferential end of the protruding peripheral surface portion 113c come into contact with each other so that the torsion bar 111 is not twisted any further.

  In addition, the diameter of the outer peripheral surface of the floating piece 112a of the upper floating portion 112 and the diameter of the outer peripheral surface of the protruding peripheral surface portion 113c of the lower floating portion 113 are the same. A cylindrical slider 115 covers the outer peripheral surfaces of the upper floating portion 112 and the lower floating portion 113 so as to be slidable. The slider 115 has longitudinally long holes 118A and 118A facing each other in the axial direction through which the pins 117A and 117A are inserted, and oblique long holes 118B and 118B through which the pins 117B and 117B are inserted facing each other. . The pins 117A, 117A, 117B, and 117B are combined with the torsion bar 111, the upper floating portion 112, and the lower floating portion 113, and then into the pin holes (not shown) through the long holes 118A and 118A and the oblique long holes 118B and 118B, respectively. Press fit to assemble.

The slider 115 is made of a magnetic core material. A first detection coil 114A and a second detection coil 114B, which are fixed to the inner peripheral surface of the lid portion 13A so as to face the outer peripheral surface of the slider 115 and surrounded by the yoke material, are arranged in two upper and lower stages.
Here, the pins 117A and 117A, the pins 117B and 117B, the long holes 118A and 118A, and the slanted long holes 118B and 118B constitute a cam mechanism, and when the upper floating portion 112 and the lower floating portion 113 are twisted, FIG. As shown, the slider 115 is guided in the long hole 118A and the slanted long hole 118B and moves up and down in the axial direction.

The vertical displacement of the slider 115 made of such a magnetic core causes a change in magnetic flux density around the first detection coil 114A and the second detection coil 114B, and the first detection coil 114A and the second detection coil. The inductance of 114B changes so that one becomes larger and the other becomes smaller, and the first detection coil 114A and the second detection coil 114B output torque detection voltages VT1 and VT2 as shown in FIG.
Torque detection voltages VT1, VT2 from the first detection coil 114A and the second detection coil 114B are amplified by the differential amplifier circuit 21, and a torque detection voltage (torque signal) VT3 is output to the steering control ECU.

(Rotation termination mechanism)
Next, the rotation termination mechanism 6A that restricts the movement of the steering handle 3 at the rack end angle at which the turning angle of the steering wheel reaches the maximum turning angle will be described with reference to FIG. FIG. 6 is a schematic plan sectional view of the rotation termination mechanism in the present embodiment. (A) shows a case where the steering handle is in a neutral position with respect to the left and right, (b) shows a full left steering state (“left rack end” state), and (c) shows a full state. The right steering state (the state of “right rack end”) is shown.

  As shown in FIG. 1, the rotation termination mechanism 6A is disposed closer to the steering handle 3 than the position where the torque sensor 110 is provided in the axial position of the input shaft 3d. As shown in FIG. A rotation stopper 41 of a substantially cylindrical body having a protruding portion 41a that protrudes a part of the outer peripheral surface on the radially outer side, fixed to the outer periphery, and fixed to the inner peripheral surface of the lid portion 13A. A stopper 40 is constituted by a substantially cylindrical fixed stopper 43 having a protruding portion 43a with a part of the inner peripheral surface protruding on the side. The rotation stopper 41 is rotatable to the left and right by about 180 ° as an allowable operation amount range (allowable rotation operation range) of the steering handle 3 on the inner peripheral side of the fixed stopper 43.

As shown in FIG. 6A, when the steering handle 3 is in the neutral position, the protruding portion 41a is positioned in the opposite direction to the protruding portion 43a by 180 °.
In the “left rack end” state in which the rack end 8b and the housing end 11a are in contact with each other as the rack shaft 8 is fully steered to the left as in the conventional configuration, as shown in FIG. Even if the protrusion 41 a abuts in the counterclockwise direction in the circumferential direction and the steering handle 3 is further rotated counterclockwise, no further rotation or operation force is transmitted to the torsion bar 111. When the reaction force of the load torque _TL from the road surface is applied, the torque is detected by the torque sensor 110, but when there is no reaction force, the torque is not detected. In particular, in this embodiment, the rack end 8b and the housing end 11a are prepared for positioning at the time of assembling the rack shaft 8, and the steering handle 3 with full left and right eyes regulated by the rotation end mechanism 6A is steered. The angle (operation amount) is set with a slight margin so that the rack end 8b and the housing end 11a do not contact each other. Therefore, even if the rotation of the motor 4 overshoots, the steering detected by the torque sensor 110 is detected. This acts in the direction of decreasing the torque Ts.

On the other hand, when the rack shaft 8 is fully steered to the right and the rack end 8b and the housing end 11a are in a “right rack end” state as in the conventional configuration, as shown in FIG. Even if the protruding portion 41a abuts the portion 43a in the clockwise direction in the circumferential direction and the steering handle 3 is further rotated clockwise, no further rotation or operating force is transmitted to the torsion bar 111. Since the rack end 8b and the housing end 11a are set with a slight margin as in the case of full left steering, even if the rotation of the motor 4 overshoots, the torque sensor 110 is set. Acts in the direction of decreasing the steering torque Ts detected.
6A, 6 </ b> B, and 6 </ b> C, it is assumed that the torsion bar 111 has a small twist amount.

(Steering control ECU)
Next, the steering control ECU will be described with reference to FIGS. FIG. 7 is a functional block diagram of the steering control ECU. FIG. 8A is a data table showing the relationship of the base signal to be output with respect to the torque signal that is an input in the base signal calculation unit, and FIG. It is a data table which shows the relationship of the compensation signal output with respect to the rotational speed of the electric motor which is the input in a damper compensation signal calculating part.
The steering control ECU 200 includes a microcomputer including a CPU, a ROM, a RAM, and the like and a program, and realizes the functions described in the functional block diagram of FIG.
The steering control ECU 200 includes a base signal calculation unit 220, an inertia compensation signal calculation unit 210, a damper compensation signal calculation unit 225, a Q axis (torque axis) PI control unit 240, and a D axis (magnetic pole axis) PI control unit 245. A two-axis three-phase conversion unit 260, a PWM conversion unit 270, a three-phase two-axis conversion unit 265, a motor speed calculation unit 280, and an excitation current generation unit 285.

The three-phase two-axis converter 265 detects the three-phase currents IU, IV, IW of the electric motor 4 detected by the electric motor drive circuit 23 with respect to the D axis that is the magnetic pole axis of the rotor of the electric motor 4 and the D axis. is intended to convert the two axes of the Q axis are electrically axis rotated 90 degrees, Q-axis current IQ is proportional to the generated torque T _M of the motor 4, D-axis current ID is proportional to the exciting current. Motor speed calculation unit 280, an angle signal θ differential operation to generate an angular velocity signal omega _M. The excitation current generation unit 285 generates a target signal of the excitation current “0” of the electric motor 4, but can perform field-weakening control by making the D-axis current and the Q-axis current substantially equal as necessary.

The base signal calculation unit 220 generates a base signal D _T that serves as a reference for the target signal IM of the output torque T _M ′ from the torque signal VT3 and the vehicle speed signal VS. This signal generation is performed by referring to the base table 220a previously set by experimental measurement or the like with the torque signal VT3 and the vehicle speed signal VS, and the base signal D stored in the base table 220a in FIG. The function of _T is shown. The base signal calculation unit 220 is provided with a dead band N1 in which the base signal _DT is set to zero when the value of the torque signal VT3 is small. When the value of the torque signal VT3 becomes larger than the dead band N1, the base signal calculation unit 220 is linear with the gain G1. It has an increasing characteristic. Further, the base signal calculation unit 220 has a characteristic that the output increases with the gain G2 at a predetermined torque value, and the output is saturated when the torque value further increases.

  In general, since the load on the road surface (road reaction force) varies depending on the traveling speed, the vehicle has a gain adjusted by the vehicle speed signal VS. The load is heaviest during stationary operation at zero vehicle speed, and the load is relatively light at medium and low speeds. For this reason, the base signal calculation unit 220 sets the gain (G1, G2) to be low and the dead zone N1 to be large as the vehicle speed VS increases and increases to increase the manual steering area and provide road surface information to the driver. To give. That is, a firm feeling of steering torque Ts is given as the vehicle speed VS increases. At this time, it is necessary to perform inertia compensation also in the manual steering region.

Returning to FIG. 7, the damper compensation signal calculation unit 225 is provided to compensate for the viscosity of the steering system and to have a steering damper function that compensates for a decrease in convergence when the vehicle travels at a high speed. , and the carried out by the angular velocity signal omega _M refers to the damper table 225a. (B) in FIG. 8 is a diagram showing a characteristic function of the damper table 225a, as the rotational speed omega _M of the electric motor 4 is increased to increase the compensation value I linearly, the compensation value is abruptly increased at a predetermined speed It has the characteristics to do.
Further, as the value of the vehicle speed signal VS is higher, the gain is increased to attenuate the output torque T _M ′ of the electric motor 4 according to the rotational speed of the electric motor 4, that is, the steering speed (steering rotational speed).
In other words, when the steering handle 3 is turned off, the electric current of the electric motor 4 is reduced, and when returning to the reverse, a large electric current is supplied to the electric motor 4. For example, if the rotational speed is increased when the steering handle 3 is increased, the rotational speed does not decrease immediately due to the inertia of the electric motor 4. To avoid this phenomenon, the damper compensation signal calculation unit 225 is provided with The current is increased and supplied, and the rotational speed when the steering handle 3 returns is controlled to be suppressed.

  In other words, when the steering wheel 3 is increased, the current to the electric motor 4 is reduced as the rotational speed of the steering wheel 3 is increased to increase the steering feeling of the steering wheel 3, and when the steering wheel 3 is returned, the electric motor 4 Increase the current to make it difficult to return. Due to this steering damper effect, the convergence of the steering wheel 3 can be improved and the vehicle characteristics can be stabilized.

Returning to FIG. 7 again, the adder 251 subtracts the output signal of the damper compensation signal calculator 225 from the output signal _DT of the base signal calculator 220 when the steering handle 3 is turned off. When returning the steering handle 3, the output signal of the damper compensation signal calculation unit 225 is added. The adder 250 adds the output signal of the adder 251 and the output signal of the inertia compensation signal calculation unit 210. The base signal calculation unit 220, the damper compensation signal calculation unit 225, and the adder 251 perform basic assist control.

The inertia compensation signal calculation unit 210 compensates for the influence of the inertia of the steering system, and the torque signal VT3 is calculated by referring to the inertia table 210a.
The inertia compensation signal calculation unit 210 compensates for a decrease in responsiveness due to the inertia of the rotor of the electric motor 4. In other words, when switching the rotation direction from the normal rotation to the reverse rotation or from the reverse rotation to the normal rotation, the electric motor 4 tries to maintain the state by inertia, so the rotation direction is not switched immediately. Therefore, the inertia compensation signal calculation unit 210 controls the rotation direction of the electric motor 4 to coincide with the timing at which the rotation direction of the steering handle 3 is switched. In this way, the inertia compensation signal calculation unit 210 improves the response delay of the steering due to the inertia (or viscosity) of the steering system and provides a clean steering feeling.
In addition, it is practical for vehicle characteristics such as front engine rear wheel drive (FF), front wheel rear wheel drive (FR), recreation vehicle (RV), and sedan, and steering characteristics that vary depending on vehicle conditions such as vehicle speed and road surface. Sufficient properties are imparted.

  The output signal IM of the adder 250 is a Q-axis current target signal that defines the torque of the electric motor 4, and the adder 252 subtracts the Q-axis current IQ from the output signal IM to generate a deviation signal IE. The Q-axis (torque axis) PI control unit 240 performs P (proportional) control and I (integral) control so that the deviation signal IE decreases. The adder 253 subtracts the D-axis current ID from the output signal of the exciting current generator 285. The D axis (magnetic pole axis) PI control unit 245 performs PI feedback control so that the output signal of the adder 253 decreases.

The 2-axis 3-phase converter 260 converts the 2-axis signal of the output signal VQ of the Q-axis (torque axis) PI control unit 240 and the output signal VD of the D-axis (magnetic pole axis) PI control unit 245 into 3-phase signals UU, UV , UW. The PWM converter 270 is a DUTY signal (DUTY U, DUTY V, DUTY W) which is an ON / OFF signal [PWM (Pulse Width Modulation) signal] with a pulse width proportional to the magnitude of the three-phase signals UU, UV, UW. Is generated.
Note that the biaxial three-phase converter 260 and the PWM converter 270 receive the angle signal θ of the electric motor 4 and output a signal corresponding to the magnetic pole position of the rotor.

(Operation and effect of rotation termination mechanism)
Next, the operation and effect of the rotation termination mechanism 6A in the present embodiment will be described with reference to FIGS.
The positional relationship between the rack shaft 8 and the rack housing portion 11A is as shown in FIG. 1 where there is no rotation termination mechanism 6A, and the housing end 11a at the right end of the rack housing portion 11A and the rack end 8b of the rack shaft 8 are in engagement contact. Or, conversely, when the left end housing end 11a of the rack housing portion 11A is in engagement with the rack end 8b of the rack shaft 8, if the steering handle 3 is further rotated to the right or left, In the electric power steering apparatus, a load larger than the load from the front wheels 1L, 1R is applied from the pinion shaft 7 to the rack shaft 8.
There are two reasons for this.

When the positional relationship between the rack shaft 8 and the rack housing portion 11A is not the end, that is, when the front wheels 1L, 1R are not fully turned to either the left or right, assuming that the load torque from the front wheels 1L, 1R is _TL , between the steering torque Ts and assist amount a _H and a pinion torque Tp, a relationship such as follows.
Ts + A _H = Tp = _TL (3)

However, the driver applies an operating force to the steering handle 3 in the direction in which the rack end 8b and the housing end 11a are in contact with the front wheels 1L and 1R fully turned to either the left or right. If it is present (added more), the load torque _TL applied from the front wheels 1L, 1R does not increase any more, but the torsion bar 111 is twisted more greatly, and the steering torque Ts in the torque sensor 110 is The steering control ECU 200 outputs a command to the motor drive circuit 23 to increase the current value. Then, by further increasing it as the steering torque Ts to the assist amount A _H is increased, the pinion gear 7a, via the rack gear 8a, torque is applied greater than the load torque T _L to the rack shaft 8.
Ts + A _H = Tp> T _L (4)

  In such a case, the electric motor 4, the worm gear 5a, the worm wheel gear 5b, the pinion gear 7a, the rack gear 8a, the bearings 3e, 3f, 3g, the rack end 8b, the rack housing portion 11A, and the normal load that does not reach the rack end angle. About 1.3 times the load.

Also, consider the moment when the rack end 8b and the housing end 11a come into contact. Now the rotation angular speed of the electric motor 4 omega _M, the rotational moment of inertia and I _M, the kinetic energy E _M as follows are stored in the electric motor 4.
EM = (1/2) · IM · ω _M ² (5)
This kinetic energy is absorbed by elastic deformation of the worm gear 5a, the worm wheel gear 5b, the pinion gear 7a, the rack gear 8a, the bearings 3e, 3f, 3g, the rack end 8b, the housing end 11a, and the like. It becomes as high as about 1.5 times the normal load that does not reach the corner.

These, by the steering torque Ts and shock load assist amount _{A H,} the electric motor 4, the worm gear 5a, the worm wheel gear 5b, the pinion gear 7a, the rack gear 8a, the bearings 3e, 3f, 3 g and the rack end 8b, usually the rack housing portion 11A In order to ensure the durability of these components, it is necessary to increase the size of the bearing, increase the size of the gear module to increase the size, There has been a problem that the weight of the component becomes large, such as increasing the thickness or providing reinforcing ribs. In electrical relation, the electric motor 4 may be overloaded and burned out.

However, according to the present embodiment, before the positioning rack end 8b and the housing end 11a come into contact with each other, the protrusions 41a and 43a are not applied so that the input shaft 3d cannot be further increased in the rotation termination mechanism 6A. The additional operating force from the steering handle 3 is not transmitted to the torsion bar 111. Since the torsion bar 111 does not occur a twist of more than twist due to the load torque T _L, between the steering torque Ts and assist amount A _H and a pinion torque Tp and the load torque T _L, the relationship of Equation (3) is maintained, further assist amount a _H from the electric motor 4 by turning-increasing does not occur. In addition, since the positioning rack end 8b and the housing end 11a are provided with a margin beyond the maximum turning angle (rack end angle), if the rotation of the motor 4 overshoots, the torque sensor 110 reducing the steering torque Ts to the detection, reducing the assist amount a _H. As a result, the following equation (6) is obtained.
Ts + A _H = Tp < _TL (6)
Become

Next, the behavior of the turning angle and the torque signal VT3 when the steering handle 3 is turned to the rack end angle will be described with reference to FIG.
(A) of FIG. 9 is a figure which shows the time transition of the operation amount of a steering handle, (b) is a figure which shows the time transition of the torque signal VT3 output from a torque sensor, (c) is actual figure. It is a figure which shows the time transition of the change of the turning angle of a front wheel.

When the steering handle 3 is largely cut as shown in FIG. 9A and operated to near the rack end angle, the rack end 8b and the housing end 11a come into contact with each other as shown by the curve x1 in this embodiment. The torsion bar 111 has been twisted before, and at the time t1, an increase in the operation amount of the steering handle 3 is prevented by the rotation end mechanism 6A.
Then, as shown by the curve y1 in (b), the torque signal continues to increase until time t1 due to a large change in the operation amount of the steering handle 3 until time t1, but the increase in the operation amount of the steering handle 3 at time t1. Since the torque becomes zero, the torque signal stops increasing. As shown by the curve z1 in (c), the turning angle of the front wheels 1L and 1R slightly overshoots the rack end angle. Due to this overshoot, the torque signal VT3 decreases as shown by the curve y1 in (b). This overshoot is generated as a result of kinetic energy due to the moment of inertia of the electric motor 4.

On the other hand, in the prior art, as shown by the curve z2 in FIG. 9C, the rack end 8b and the housing end 11a come into contact with each other, so that the change (increase) in the turning angle is prevented. However, the amount of operation of the steering handle 3 as shown by the curve x2 in (a) increases and converges due to the influence of the steering wheel inertia moment caused by the operation of the steering handle 3 by the driver.
At this time, as indicated by the curve y2 in (b), the torque signal VT3 rapidly rises at the rack end angle, and the kinetic energy due to the moment of inertia of the motor 4 changes the impact force to the gears (worm gear 5a, worm wheel gear 5b). , Rack gear 8a, pinion gear 7a, etc.).
Therefore, conventionally, a collision between the rack end 8b and the housing end 11a occurs at the rack end angle as shown by the curve z2 in (c), and the torque signal VT3 further increases as shown in (b). The impact by kinetic energy is acting.

According to the present embodiment, as described above, the collision between the rack end 8b and the housing end 11a occurs when the steering handle 3 is increased in the vicinity of the rack end angle or in the large turning operation up to the rack end angle. Since this can be avoided, the pinion torque Tp can be reduced to the same level or less as the pinion torque Tp at the normal time when the rack end angle is not reached.
Therefore, it is possible to reduce loads that should be assumed in designing the electric motor 4, the worm gear 5a, the worm wheel gear 5b, the pinion gear 7a, the rack gear 8a, the bearings 3e, 3f, and 3g, the rack end 8b, and the rack housing portion 11A. In order to ensure the durability of the components, the size of the bearing is increased, the gear module is increased to increase the size, the rack housing portion 11A is thickened, reinforcing ribs are provided, etc. The problem that the weight of the parts becomes large is solved, and the component parts can be reduced in size and weight, and the mounting property to a vehicle, particularly the mounting property to a small vehicle is improved.
In addition, it is necessary to provide a sufficient current capacity so that the electric motor 4 does not burn out even when the operation is further increased in the rack end state, but this is alleviated and the electric motor 4 can be reduced in weight. .

《Modification of rotation termination mechanism》
The rotation termination mechanism in the present invention is not limited to that in the above-described embodiment, and for example, various modifications as described below are possible.
(First modification)
Next, a first modification of the rotation termination mechanism will be described with reference to FIG. FIG. 10 is a schematic plan sectional view of the rotation termination mechanism of this modification. (A) shows a case where the steering handle is in a neutral position with respect to the left and right, (b) shows a full left steering state (“left rack end” state), and (c) shows a full state. The right steering state (the state of “right rack end”) is shown.
The
As shown in FIG. 10, the rotation termination mechanism 6B includes an inner shaft 51 connected to the input shaft 3d, a rotation stopper 53 disposed on the outer side, and a fixed stopper 54 disposed on the outer side.

The inner shaft 51 is provided with an outer gear 51a, and a substantially cylindrical rotation stopper (ring gear) 53 having an inner gear 53a meshing with the outer gear 51a on the inner peripheral surface is eccentric with the inner shaft 51. Is provided. The number of teeth of the external gear 51a and the internal gear 53a is approximately 1: 3.
On the outer peripheral surface of the rotation stopper 53, a protruding portion (first protruding portion) 53b in which a part of the outer peripheral surface protrudes radially outward is provided. Moreover, it is fixed to the inner peripheral surface of the lid portion 13A, and has a projecting portion (second projecting portion) 54a that projects a part of the inner peripheral surface on the radially inner side. A fixed stopper 54 is provided, and the rotation stopper 53 and the fixed stopper 54 constitute a stopper 50.

The external gear 51a and the internal gear 53a constitute a speed reduction mechanism 55, and when the steering handle 3 is rotated approximately 540 ° to the left and right from the neutral state, the rotation stopper 53 is rotated approximately 180 ° to the left and right, respectively. Thus, the protrusion 53a comes into contact with the protrusion 54a from the circumferential direction.
Although not shown, the outer peripheral surface of the upper and lower end portions of the rotation stopper 53 has a cylindrical peripheral surface, and the entire inner peripheral surface provided on that portion and the upper and lower ends of the fixed stopper 54 is a cylindrical surface. A sliding bearing is constituted by a portion having a small diameter on the peripheral surface, and thereby the rotation stopper 53 can be rotated.

As shown in FIG. 10 (a), when the steering handle 3 is in the neutral position, the protruding portion 53a is positioned 180 ° opposite to the protruding portion 54a.
In the “left rack end” state in which the rack end 8b and the housing end 11a are in contact with each other when the rack shaft 8 is fully steered to the left, as shown in FIG. Even if the steering handle 3 is contacted counterclockwise and the steering handle 3 is further rotated counterclockwise, no further rotation or operating force is transmitted to the torsion bar 111. Conversely, in the “right rack end” state in which the rack end 8b and the housing end 11a are in contact with each other by the right steering with the rack shaft 8 full, as shown in (c), the protruding portion 53a is surrounded by the protruding portion 54a. Even if the steering handle 3 is contacted clockwise and the steering handle 3 is further rotated to the right, no further rotation or operating force is transmitted to the torsion bar 111.

  According to the rotation end mechanism 6B of this modification, the allowable operation amount range (allowable rotation operation range) from the rotation end mechanism 6A in the first embodiment to the rack end angle of the steering handle 3 is 540 ° to the left and right. Therefore, the amount of operation of the steering handle 3 in a normal vehicle can be set, which is convenient. Further, by replacing the rotation stopper (ring gear) 53 with a different number of teeth, for example, the allowable operation amount range can be set to a range of 450 ° or 600 °. That is, the operation amount of the steering handle corresponding to the rack end angle can be changed, and it is possible to cope with various vehicle types.

Also in this modified example, as in the first embodiment, even if the driver further increases the steering handle 3 when the rack shaft 8 is already in the rack end state, the rotation termination mechanism 6B is prevented from rotating. Thus, the additional operating force is not transmitted to the torsion bar 111. Further, between the steering torque Ts and assist amount A _H and a pinion torque Tp and the load torque T _L, remains the relationship in equation (3) or formula (6), comprising further from the electric motor 4 by turning-increasing assist amount _{A H} and the steering torque Ts is not generated.
Further, even in a large turning operation reaching the rack end, since the rack end 8b and the housing end 11a for regulating the rack end angle are not provided as in the conventional case, the collision is avoided.

  Therefore, it is possible to reduce loads that should be assumed in designing the electric motor 4, the worm gear 5a, the worm wheel gear 5b, the pinion gear 7a, the rack gear 8a, the bearings 3e, 3f, and 3g, the rack end 8b, and the rack housing portion 11A. In order to ensure the durability of the components, the size of the bearing is increased, the gear module is increased to increase the size, the rack housing portion 11A is thickened, reinforcing ribs are provided, etc. The problem that the weight of the parts becomes large is solved, and the component parts can be reduced in size and weight, and the mounting property to a vehicle, particularly the mounting property to a small vehicle is improved. Moreover, the current capacity can be increased and the electric motor 4 can be reduced in weight.

(Second modification)
Note that the speed reduction mechanism that decelerates the operation amount of about 540 ° left and right of the steering handle 3 to the rotation angle of about 180 ° left and right of the rotation stopper 53 is a combination of the external gear 51a and the internal gear 53a in the first modification. The speed reduction mechanism 55 is not limited to this.
Next, a rotation termination mechanism according to a second modification will be described with reference to FIG. FIG. 11 is a schematic perspective view of a rotation end mechanism of a second modification using a planetary gear reduction unit.
As shown in FIG. 11, a planetary carrier that connects the sun gear 56, the planetary gear 57 that meshes with the sun gear 56, revolves around the sun gear 56, the outer ring gear 58 having internal teeth that meshes with the planetary gear 57, and the planetary gear 57 shaft. A planetary gear reducer unit 59 composed of 57a may be used.

  In this case, the input shaft 3d drives the sun gear 56, the planet carrier 57a corresponds to the rotation stopper 53, and has, for example, a projecting portion (first projecting portion) 57b projecting radially outward. The outer ring gear 58 corresponds to the fixed stopper 54 and is fixed to the lid portion 13A so that the outer edge side of the end face edge 58a of the outer ring gear 58 protrudes in the axial direction so as not to interfere with the planetary gear 57, for example. A second projecting portion) 58b is formed and engaged with the projecting portion 57b. If the number of teeth a of the sun gear and the number of teeth c of the outer ring gear are selected as 1: 2, the rotation angle of the planet carrier 57a is reduced to 1/3 with respect to the rotation angle of the sun gear 56, and the first embodiment is reduced. As in the first modification, the rotation angle of the planet carrier 57a (rotation stopper 53) is set to approximately 180 ° to the left and right with respect to the allowable operation amount range (allowable rotation operation range) of the steering handle 3 approximately 540 ° to the left and right. it can.

In the example shown in FIG. 11, the protruding portion 57b is provided radially outward from the planet carrier 57a. However, the protruding portion 57b is not limited thereto, and is protruded in the axial direction (upward in FIG. 11). The protruding portion 57b may be provided, and the protruding portion 58b may be provided so as to protrude radially inward from the end surface edge portion 58a of the outer ring gear 58.
Further, the protruding portion 58b may be provided to protrude radially inward from the inner peripheral surface of the lid portion 13A so as to engage with the protruding portion 57b.
By using a planetary gear speed reducer unit as the speed reduction mechanism 55, the rotation end mechanism can be coaxial with the central axis of the lid portion 13A, and the radial direction of the rotation end mechanism portion can be reduced. Further, since the load applied to the projecting portion 57b when the projecting portion 57b comes into contact with the projecting portion 58b is shared by each planetary gear 57 by the planetary carrier 57a, in the case of the rotation termination mechanism 6B of the second modification example. Can withstand larger loads. Accordingly, the rotation termination mechanism 6B ′ can be reduced in size.

(Third Modification)
Next, a third modification of the rotation termination mechanism will be described with reference to FIGS. FIG. 12 is a schematic plan sectional view of the rotation termination mechanism of this modification. (A) shows a case where the steering handle is in a neutral position with respect to the left and right, (b) shows a full left steering state (“left rack end” state), and (c) shows a full state. The right steering state (the state of “right rack end”) is shown. FIGS. 13A and 13B are perspective views individually showing elements constituting the rotation terminal mechanism of the third modification, wherein FIG. 13A is an external perspective view of the upper stopper, and FIG. 13B is a rotation stopper fixed to the screw portion. FIG. 3C is an external perspective view of the lower stopper, and FIG. 4D is an external perspective view of the guide member.
As shown in FIG. 13, the rotation end mechanism 6C includes a screw portion 61 having a male screw 61a cut on the outer periphery of the input shaft 3d, and a substantially cylindrical rotation stopper (welded to the axial center of the screw portion 61). The first stopper 62 includes an upper stopper (second stopper) 63, a lower stopper (third stopper) 65, and a guide member 67 disposed above and below the rotation stopper 62.

The rotation stopper 62 has a substantially cylindrical shape as shown in FIG. 13B, and has a protruding portion (first protruding portion) 62a in which a part of the outer peripheral surface protrudes radially outward. Have.
Incidentally, the radially outermost end of the protrusion 62 a is made smaller than the diameter of the inner peripheral surface of the guide member 67.
As shown in FIGS. 13A and 13C, the upper stopper 63 and the lower stopper 65 have a substantially cylindrical body, and have an internal thread 63a that matches the external thread 61a on the inner peripheral side. It has a guide piece 63b and a protruding portion (second protruding portion) 63c that are opposed to each other and project a part of the outer peripheral surface radially outward. The guide piece 63b and the projecting portion 63c engage with a guide hole 67b extending in the axial direction, which will be described later, of the guide member 67, and the upper stopper 63 is guided to the guide hole 67b by the left and right rotation of the screw portion 61, so Move to.
The guide piece 63b is flush with the cylindrical body portion of the upper stopper 63 with the same axial thickness, but the protruding portion 63c protrudes downward in the axial direction as shown in FIG. .
The lower stopper 65 is the same as the upper stopper 63 as it is, and is just upside down, and has the same configuration as the upper stopper 63. The protrusion 65c of the lower stopper 65 corresponds to the third protrusion described in the claims.
The rotation stopper 62, the upper stopper 63, and the lower stopper 65 constitute a stopper 60.

  The guide member 67 is a combination of members 67A and 67B obtained by dividing the cylindrical body in half in the axial direction. Each of the members 67A and 67B has a serration 67a extending in the axial direction on the outer peripheral surface and a center in the circumferential direction. And a guide hole 67b extending in the axial direction. The serration 67a meshes with a serration (not shown) provided on the inner peripheral surface of the lid portion 13A to fix the guide member 67 so as not to move in the circumferential direction within the lid portion 13A.

  Since the guide member 67 has a divided structure in this way, the outer diameters on both axial sides of the screw portion 61 are made smaller than the inner diameters of the threads of the female screws 63a and 65b of the upper stopper 63 and the lower stopper 65. The screw pieces 61 can be combined from above and below, and then the guide pieces 63b and 65b and the protrusions 63c and 65c can be fitted into the guide holes 67b of the respective members 67A and 67B to be assembled into an integral guide member 67. Thereafter, the guide member 67 is press-fitted and fixed to the inner peripheral surface of the lid portion 13A.

The male screw 61a, the female screw 63a, and the female screw 65a constitute a speed reduction mechanism. When the steering handle 3 is rotated about 540 ° left and right from the neutral state, the rotation stopper 62 is rotated about 540 ° left and right. The upper stopper 63 and the lower stopper 65 move in the axial direction by the same amount, for example, move upward in the case of left turning and move downward in the case of right turning. When the rotation stopper 62 is rotated approximately 540 ° to the left and right, the protrusion 62a is in contact with the protrusion 65c when turning left, and the protrusion 62a is in contact with the protrusion 63c from the circumferential direction when turning right. It comes to touch.
That is, as in the first modification of the first embodiment, the allowable operation amount range (allowable rotation operation range) of the steering handle 3 can be ensured to be approximately 540 ° on the left and right. Furthermore, without increasing the outer shape of the rotation termination mechanism 6C, for example, the allowable operation amount range can be set to two rotations (720 °) to the left and right, and can be applied to vehicles other than automobiles.

  FIG. 12A shows that when the steering handle 3 is in the neutral position, the protrusion 62a is positioned in the center in the axial direction with respect to the protrusions 63c and 65c. In (b), in a state of “left rack end” in which the rack end 8b and the housing end 11a are in contact with each other when the rack shaft 8 is fully steered to the left, the protrusion 62a is opposite to the protrusion 65c as viewed from above in the circumferential direction. This shows a state in which no further rotation or operating force is transmitted to the torsion bar 111 even if the steering wheel 3 is in contact with clockwise and the steering handle 3 is further rotated counterclockwise. In (c), on the contrary, in the “right rack end” state in which the rack end 8b and the housing end 11a are in contact with each other when the rack shaft 8 is fully steered to the right, the protruding portion 62a is seen from above in the circumferential direction. Thus, even if the steering handle 3 is rotated clockwise and the steering handle 3 is further rotated to the right, no further rotation or operation force is transmitted to the torsion bar 111.

Also in this modified example, as in the first embodiment, even if the driver further increases the steering handle 3 when the rack shaft 8 is already in the rack end state, the rotation termination mechanism 6C is prevented from rotating. Thus, the additional operating force is not transmitted to the torsion bar 111. Further, between the steering torque Ts and assist amount A _H and a pinion torque Tp and the load torque T _L, remains the relationship in equation (3) or formula (6), comprising further from the electric motor 4 by turning-increasing assist amount _{A H} and the steering torque Ts is not generated.
Further, even in a large turning operation reaching the rack end, since the rack end 8b and the housing end 11a for regulating the rack end angle are not provided as in the conventional case, the collision is avoided.

  As a result, as in the first embodiment, the design of the motor 4, the worm gear 5a, the worm wheel gear 5b, the pinion gear 7a, the rack gear 8a, the bearings 3e, 3f, and 3g, the rack end 8b, and the rack housing portion 11A is assumed. In order to reduce the load that should be achieved and to ensure the durability of these components in the past, the bearing size is increased, the gear module is increased to increase the size, and the thickness of the rack housing portion 11A is increased. The problem of increasing the weight of the component parts, such as increasing the thickness or providing reinforcing ribs, is solved, the component parts can be reduced in size and weight, and the mountability on a vehicle, particularly the mountability on a small vehicle is improved. Moreover, the current capacity can be increased and the electric motor 4 can be reduced in weight.

  The conductive power steering apparatus 100A in the first embodiment is such that the pinion shaft 7 is assisted and driven by the electric motor 4 via the speed reduction mechanism 5A, but is not limited thereto. The torque sensor converts the torsion angle of the torsion bar 111 into the vertical displacement amount of the slider 115, detects the displacement amount by the detection coils 114A and 114B, and outputs the torque signal VT3. Is not to be done.

<< Second Embodiment >>
Next, an electric power steering apparatus according to a second embodiment of the present invention will be described with reference to FIG.
FIG. 14 is a configuration diagram of an electric power steering apparatus according to the second embodiment of the present invention. The electric power steering apparatus 100B of this embodiment is of a type in which the rack shaft 8 is assisted and driven by the electric motor 4 via the ball screw 5c.
In the first embodiment, instead of the electric motor 4 driving the pinion shaft 7 via the worm gear 5a and the worm wheel gear 5b, in the present embodiment, the electric motor 4 is constituted by the worm gear 5a and the worm wheel gear 5b. The difference is that the speed reduction mechanism 5B and the ball screw 5c are driven, and the rotational motion of the ball screw 5c is directly converted into the linear motion of the rack shaft 8 for driving.
Further, in this embodiment, the torque sensor 120 using a magnetostrictive film is different from the torque sensor 110 in the first embodiment.
The same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.
Since the arrangement of the speed reduction mechanism 5B is different from that of the first embodiment, the rack housing portion 11B and the lid portion 13B of the steering gear box 10B of the present embodiment are different in shape from the first embodiment but have substantially the same functions. It is.

  The torque sensor 120 has the same configuration as that described in FIG. 1 and FIG. 2 of Japanese Patent Application Laid-Open No. 2006-322952. A magnetostrictive material having a magnetostriction constant of 2 is formed at two locations in the axial direction by plating, vapor deposition or the like, with a predetermined film thickness, for example, 30 microns or less, and with a predetermined axial interval over the entire circumference in the circumferential direction. A first magnetostrictive film 121A and a second magnetostrictive film 121B are configured. Moreover, in order to obtain magnetic anisotropies in opposite directions, they are applied by heating to high temperature heating with a predetermined torque applied to the input shaft 3d, returning to room temperature, and removing the torque. As a result, even when no torsional torque is applied to the magnetostrictive films 121A and 121B, tensile stress is always applied, and tensile strain is applied. Therefore, hysteresis in the inverse magnetostrictive characteristics is reduced. Further, unlike the torque sensor 110 in the first embodiment, since the torsion bar 111 is not provided and the twist does not occur, the steering angle of the steering handle 3 and the turning angle of the front wheels 1L and 1R are twisted. There will be no difference. As a result, the range of the turning angle corresponding to the allowable operation amount range determined by the rotation termination mechanism 6 is also substantially widened.

An exciting coil (not shown) in the torque sensor 120 is arranged in common with the first and second magnetostrictive films 121A and 121B via a minute gap, and a minute gap is formed at a circumferential position 90 ° away from the exciting coil in the circumferential direction. The first detection coil 124A is arranged for the first magnetostrictive film 121A, and the second detection coil 124B is arranged for the second magnetostrictive film 121B.
In the torque sensor 120, when a torque is applied to the input shaft 3d, the torque is also applied to the first and second magnetostrictive films 121A and 121B, and the first and second magnetostrictive films 121A and 121B are inversely magnetostrictive according to the torque. An effect is produced. When a high-frequency AC voltage (excitation voltage) is supplied from an excitation voltage supply source (not shown) to the above-described excitation coil, a change in the magnetic field due to the inverse magnetostriction effect based on the torque applied to the first and second magnetostrictive films 121A and 121B is obtained. Changes in impedance or induced voltage can be detected by the first and second detection coils 124A and 124B, respectively. At this time, since the tensile stress is always applied to the first and second magnetostrictive films 121A and 121B in addition to the torsional torque of the input shaft 3d, a characteristic with low hysteresis is obtained, and this impedance or induced voltage is obtained. From this change, the torque applied to the input shaft 3d can be detected.
The signal voltages VT1, VT2 output from the first and second detection coils 124A, 124B, respectively, are input to the differential amplifier circuit 21, amplified, and input to the steering control ECU 200 as the torque signal VT3.

Also in the present embodiment, the rotation termination device 6 is disposed closer to the steering handle 3 than the position where the torque sensor 120 is provided at the axial position of the input shaft 3d.
In FIG. 14, the rotation termination mechanism 6 is a representative representation of the rotation termination mechanisms 6A, 6B, 6C, and any of the rotation termination mechanisms 6A, 6B, 6C may be combined.

Also in this embodiment, as in the first embodiment and its modification, even if the driver further increases the steering handle 3 from the rack end 8 already in the rack end state, The rotation operation is blocked and the additional operating force is not transmitted to the first and second magnetostrictive films 121A and 121B of the torque sensor 120. Further, between the steering torque Ts and assist amount A _H and a pinion torque Tp and the load torque T _L, remains the relationship in equation (3) or formula (6), comprising further from the electric motor 4 by turning-increasing assist amount _{A H} and the steering torque Ts is not generated.
Further, even in a large turning operation that reaches the rack end, the collision is avoided because the rack end 8b and the housing end 11a that restrict the rack end angle are not provided as in the prior art.

  Therefore, it is possible to reduce loads that should be assumed in designing the electric motor 4, the worm gear 5a, the worm wheel gear 5b, the pinion gear 7a, the rack gear 8a, the bearings 3e, 3f, and 3g, the rack end 8b, and the rack housing portion 11A. In order to ensure the durability of the components, the size of the bearing is increased, the gear module is increased to increase the size, the rack housing portion 11A is thickened, reinforcing ribs are provided, etc. The problem that the weight of the parts becomes large is solved, and the component parts can be reduced in size and weight, and the mounting property to a vehicle, particularly the mounting property to a small vehicle is improved. Moreover, the current capacity can be increased and the electric motor 4 can be reduced in weight.

<< Third Embodiment >>
Next, an electric power steering apparatus according to a third embodiment of the present invention will be described with reference to FIG.
FIG. 15 is a configuration diagram of an electric power steering apparatus according to the third embodiment of the present invention. The electric power steering apparatus 100C of this embodiment is of a type in which the handle shaft 3a is assisted and driven by the electric motor 4 via the worm gear 5a and the worm wheel gear 5b.
In the first embodiment, instead of the electric motor 4 driving the pinion shaft 7 via the worm gear 5a and the worm wheel gear 5b, in the present embodiment, the electric motor 4 is constituted by the worm gear 5a and the worm wheel gear 5b. The difference is that the handle shaft 3a is driven via the speed reduction mechanism 5A.
Further, in this embodiment, the torque sensor 120 using a magnetostrictive film is different from the torque sensor 110 in the first embodiment.

  As shown in FIG. 15, the electric power steering apparatus 100 </ b> C has a space between the column housing 15 that houses the handle shaft 3 a of the steering handle 3 and the pinion shaft 7 that protrudes above the lid portion 13 </ b> C of the steering gear box 10 </ b> C. The shaft 3c is connected to the two universal joints 3b.

The column housing 15 accommodates a bearing 3e disposed under the seal 3h provided at the upper end thereof, and the rotation termination mechanism 6, the torque sensor 120, the bearing 3i, the worm wheel gear 5b, and the bearing 3j are disposed below the bearing 3e. The output shaft 3k which is the lower end of the handle shaft 3a extending downward from the lower end of the column housing 15 is connected to the universal joint 3b. A pinion gear 7 a provided at the lower end of the pinion shaft 7 meshes with a rack gear 8 a of the rack shaft 8 that can reciprocate in the vehicle width direction, and both ends of the rack shaft 8 are connected to left and right via tie rods 9, 9. The front wheels 1L and 1R are connected.
The same components as those in the first embodiment and the second embodiment are denoted by the same reference numerals, and redundant description is omitted.
Since the arrangement of the speed reduction mechanism 5A is different from that of the first embodiment, the rack housing portion 11C and the lid portion 13C of the steering gear box 10C of the present embodiment are different in shape from the first embodiment but have substantially the same functions. It is. However, the rotation termination mechanism 6 is not disposed in the lid portion 13C, and the holding function of the rotation termination mechanism 6 as in the first and second embodiments is unnecessary.

  Further, the torque sensor 120 in this embodiment is housed in the column housing 15, and the first and second magnetostrictive films 121A and 121B are formed on the outer peripheral surface of the handle shaft 3a, and the first and second magnetostrictive films 121A and 121A are formed. The only difference from the second embodiment is that an exciting coil (not shown) and first and second detection coils 124A and 124B are arranged in 121B via a minute gap, and the torque sensor in the second embodiment is essentially different. The configuration is the same as 120.

Also in the present embodiment, the rotation terminal device 6 is disposed closer to the steering handle 3 than the position where the torque sensor 120 is provided in the axial position of the handle shaft 3a.
In FIG. 15, the rotation termination mechanism 6 is a representative representation of the rotation termination mechanisms 6A, 6B, 6C described above, and any of the rotation termination mechanisms 6A, 6B, 6C may be combined.

According to the present embodiment, similarly to the first embodiment and the modification thereof, even if the driver further operates the steering handle 3 after the rack shaft 8 is already in the rack end state, the rotation end mechanism 6B. Thus, the rotational operation is prevented, and the additional operating force is not transmitted to the first and second magnetostrictive films 121A and 121B of the torque sensor 120. Further, between the steering torque Ts and assist amount A _H and a pinion torque Tp and the load torque T _L, remains the relationship in equation (3) or formula (6), comprising further from the electric motor 4 by turning-increasing assist amount _{A H} and the steering torque Ts is not generated.
Further, even in a large turning operation reaching the rack end, since the rack end 8b and the housing end 11a for regulating the rack end angle are not provided as in the conventional case, the collision is avoided.
In particular, since the rotation end mechanism 6 is provided at the hand of the steering handle 3, it is easy to adjust the center alignment of the handle shaft 3a of the steering handle 3 and the center of the rotation end mechanism 6.

  Therefore, it is possible to reduce loads that should be assumed in designing the electric motor 4, the worm gear 5a, the worm wheel gear 5b, the pinion gear 7a, the rack gear 8a, the bearings 3e, 3f, and 3g, the rack end 8b, and the rack housing portion 11A. In order to ensure the durability of the components, the size of the bearing is increased, the gear module is increased to increase the size, the rack housing portion 11A is thickened, reinforcing ribs are provided, etc. The problem that the weight of the parts becomes large is solved, and the component parts can be reduced in size and weight, and the mounting property to a vehicle, particularly the mounting property to a small vehicle is improved. Moreover, the current capacity can be increased and the electric motor 4 can be reduced in weight.

It is a lineblock diagram of the electric power steering device concerning a 1st embodiment of the present invention. FIG. 2 is a side view of the vicinity of a torque sensor and a pinion gear of the steering gear box in FIG. 1. It is a detailed block diagram of a torque sensor, and is an AA arrow sectional view in FIG. It is a figure explaining the displacement of an upper floating part, a lower floating part, and a slider in the state where steering torque was added, (a) shows a neutral state, (b) shows the state where left steering torque is applied, c) is a diagram showing a state in which the right steering torque is applied. It is a figure explaining the voltage output signals VT1 and VT2 from a torque sensor, and the torque detection voltage (torque signal) VT3 amplified by the differential amplifier circuit. It is a typical plane sectional view of a rotation termination mechanism in this embodiment, (a) is a figure showing a case where a steering handle is in a neutral position with respect to the left and right, (b) is a left steering full of It is a figure which shows a state (state of "left rack end"), (c) is a figure which shows the right steering state (state of "right rack end") full. It is a functional block diagram of steering control ECU. (A) is a data table which shows the relationship of the base signal output with respect to the torque signal which is the input in a base signal calculating part, (b) is with respect to the rotational speed of the electric motor which is the input in a damper compensation signal calculating part. It is a data table which shows the relationship of the compensation signal to output. (A) is a figure which shows the time transition of the operation amount of a steering handle, (b) is a figure which shows the time transition of the torque signal VT3 output from a torque sensor, (c) is an actual front wheel rotation. It is a figure which shows the time transition of the change of a steering angle. It is a typical plane sectional view of the rotation termination mechanism of the 1st modification, (a) is a bell showing the case where a steering handle is in a neutral position with respect to right and left, and (b) is full. It is a figure which shows the left steering state (state of "left rack end"), (c) is a figure which shows the right steering state (state of "right rack end") full. It is a typical perspective view of the rotation termination mechanism of the 2nd modification using a planetary gear reduction unit. It is a typical plane sectional view of the rotation termination mechanism of the 3rd modification, (a) is a bell showing the case where a steering handle is in a neutral position with respect to right and left, and (b) is full. The left steering state ("left rack end" state) is a bell, and (c) is a diagram showing the full right steering state ("right rack end" state). It is the perspective view which showed separately the element which comprises the rotation termination mechanism of a 3rd modification, (a) is the external perspective view of an upper stopper, (b) is the external perspective view of the rotation stopper fixed to the screw part. (C) is an external perspective view of a lower stopper, (d) is an external perspective view of a guide member. It is a block diagram of the electric power steering apparatus which concerns on the 2nd Embodiment of this invention. It is a block diagram of the electric power steering apparatus which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

1L, 1R Front wheel 3 Steering handle (operator)
3a Handle shaft 3d Input shaft 4 Motor 5A, 5B Deceleration mechanism 5a Worm gear 5b Worm wheel gear 6A, 6B, 6B ', 6C Rotation termination mechanism 7 Pinion shaft 7a Pinion gear 8 Rack shaft 8a Rack gear 8b Rack end 9 Tie rod 10A, 10B, 10C Steering gear box 11A, 11B, 11C Rack housing part 11a Housing end 13A, 13B, 13C Lid part 21 Differential amplifier circuit 23 Motor drive circuit 40 Stopper 41 Rotation stopper 41a, 43a Projection part 43 Fixed stopper 51 Inner shaft (input shaft) )
51a External gear 53 Rotation stopper (ring gear)
53a Internal gear 53b Protruding part (first projecting part)
54 fixed stopper 54a protrusion (second protrusion)
55 Deceleration mechanism 56 Sun gear 57 Planetary gear 57a Planetary carrier 57b Protruding part (first projecting part)
58 Outer ring gear 58b Protruding part (second projecting part)
59 Planetary gear reducer unit (reduction mechanism)
61 Screw part 62 Rotation stopper (first stopper)
62a protrusion (first protrusion)
63 Upper stopper (second stopper)
63c Protrusion (second protrusion)
65 Lower stopper (third stopper)
65c Protruding part (third projecting part)
100A, 100B, 100C Electric power steering device 110, 120 Torque sensor 111 Torsion bar 200 Steering control ECU

Claims (7)

At least, the electric motor generates an auxiliary torque according to the steering torque generated by the input from the operation element, transmits the auxiliary torque to the steering system of the front wheels, and the rack shaft is axially driven based on the steering torque and the auxiliary torque. In the rack and pinion type electric power steering apparatus that steers the front wheel by displacing the front wheel,
Rotation that regulates the maximum turning angle of the front wheel by forming an operation end of the operation element between the torque sensor that detects the steering torque and the operation element to restrict the maximum steering angle of the operation element. While providing a termination mechanism,
A rack end mechanism comprising a housing end provided in a housing for housing the rack shaft, and a rack end provided in the rack shaft, between the torque sensor and the front wheel;
The rack-and-pinion type electric power steering apparatus, wherein the rack end and the housing end on the side corresponding to the maximum turning angle regulated by the rotation end mechanism are not in contact with each other.   The rack-and-pinion type electric power steering apparatus according to claim 1, wherein the rack end mechanism is used for positioning for providing a center of movement of the rack shaft during assembly.   The rack-and-pinion electric motor according to claim 1 or 2, wherein the rotation end mechanism includes a speed reduction mechanism, and changes an allowable rotation operation range of the operation element regulated by the operation end. Power steering device. The rotation termination mechanism is
An input shaft having an external gear to which rotation from the rotation shaft of the operating element is transmitted;
A ring gear having an internal gear that meshes with an external gear of the input shaft, and having a first protrusion on the outer peripheral side;
An annular fixed portion surrounding the ring gear;
Consists of
The external gear of the input shaft and the internal gear of the ring gear constitute the speed reduction mechanism,
The second projecting portion that contacts the first projecting portion and regulates the rotation of the first projecting portion is provided on the inner peripheral side of the fixed portion. Rack and pinion type electric power steering device. The rotation termination mechanism is
A planetary gear speed reducer unit as the speed reduction mechanism;
A fixed portion for fixing the outer ring gear of the planetary gear speed reducer unit,
Providing a first protrusion on the planet carrier of the planetary gear reducer unit;
The rotation from the rotary shaft of the operating element is transmitted to the sun gear of the planetary gear reducer unit,
4. The second projecting portion according to claim 3, wherein the fixed portion or the outer ring gear is provided with a second projecting portion that abuts on the first projecting portion and restricts rotation of the first projecting portion. Rack and pinion type electric power steering device. The rotation termination mechanism is
A screw portion having a male screw to which rotation from the rotary shaft of the operating element is transmitted;
An annular first stopper fixed to the screw portion and provided with a first protrusion on the outer peripheral side;
A second stopper having a female screw that meshes with the threaded portion, disposed above the first stopper, and provided with a second projecting portion that contacts the first projecting portion on the lower surface thereof;
A third stopper having a female screw that meshes with the threaded portion, disposed below the first stopper, and provided with a third projecting portion that contacts the first projecting portion on the upper surface thereof;
A guide member that prevents the rotation of the second and third stoppers and moves the second and third stoppers along the axial direction of the screw portion;
Consisting of
The rack-and-pinion type electric power steering apparatus according to claim 3, wherein the screw portion, the second stopper, the third stopper, and the guide member constitute the speed reduction mechanism .   The rack and pinion type electric power steering device according to any one of claims 1 to 6, wherein the torque sensor is a magnetostrictive torque sensor.

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