JP2010047158A - Vehicular steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive vehicular steering device capable of detecting an absolute rotation angle of a steering member with high accuracy. <P>SOLUTION: An electric power steering device 1 has a ball screw mechanism 25 for converting the rotation of a ball nut 36 driven by an electric motor 23 through a speed reduction mechanism 24 to the axial movement of a rack shaft 10; a resolver 41 for detecting a rotation angle of an output shaft 29 of the electric motor 23; an encoder 42 for detecting a rotation angle of a driven gear 38 of the speed reduction mechanism 24; and an absolute angle detection device 43 for detecting an absolute rotation angle of the steering member 2 based on the output of the resolver 41 and the encoder 42. When the least common multiple of the tooth number Zp of the drive gear 26 and the tooth number Zr of the driven gear 28 is made to LCM(Zp, Zr), the maximum value of the number of revolution of the steering member 2 is made to N, a stroke amount of the rack shaft 10 per one rotation of the steering member 2 is made to L and a lead of the screw shaft 37 of the ball screw mechanism 25 is made to R, an expression of LCM(Zp, Zr)>(N×L×Zr/R) is satisfied. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle steering apparatus.

A vehicle steering device may include a rotation angle detection device for detecting an absolute rotation angle of a steering member, and drive control of an electric motor may be performed using the detected absolute rotation angle (for example, Patent Documents). 1).
Further, in Patent Document 1, in order to obtain the absolute rotation angle of the steering member, the rotation angle detection device determines the rotation angle of the output shaft of the electric motor that drives the steered shaft that is linked to the steering member via a reduction gear. It has been proposed to detect.
JP 2005-53416 A

  However, in Patent Document 1, the multi-rotation rotation angle of the output shaft of the electric motor is reduced to a rotation angle (within one rotation) within the measurement range of the rotation angle detection device by the speed reducer. As a result, the resolution of the detected absolute rotation angle of the steering member is lowered, and the detection accuracy is deteriorated. Further, since a dedicated speed reducer is used for detecting the rotation angle, the structure becomes complicated. As a result, the vehicle steering device becomes expensive.

  Accordingly, an object of the present invention is to provide an inexpensive vehicle steering apparatus that can detect the absolute rotation angle of a steering member with high accuracy.

The vehicle steering apparatus (1) according to the present invention is a steerer that extends the rotation of a ball nut (36) driven by an electric motor (23) via a speed reduction mechanism (24, 24A) in the left-right direction (X) of the vehicle. A ball screw mechanism (25) for converting the axial movement of the shaft (10), a first angle detector (41) for detecting the rotation angle of the output shaft (29) of the electric motor, and a second angle detection And an absolute angle detector (43) for detecting the absolute rotation angle of the steering member (2) based on the outputs of the first and second angle detectors, and the speed reduction mechanism comprises: The second angle detection includes a driving body (26, 60) provided coaxially with the output shaft of the electric motor and a driven body (28, 61) provided coaxially with the ball nut. The device detects the rotation angle of the driven body, and the number of teeth Zp of the driving body LCM (Zp, Zr) is the least common multiple of the number of teeth Zr of the driven body, N is the number of rotations of the steering member corresponding to both stroke ends of the steered shaft, and When the stroke amount of the steered shaft is L and the lead of the screw shaft (37) of the ball screw mechanism is R, the following formula 1 is satisfied.
LCM (Zp, Zr)> (N × L × Zr / R) (Formula 1)
According to the present invention, since the above equation 1 is satisfied, the combination of the rotation angles detected by the first and second angle detectors and the absolute rotation angle of the steering member corresponding to both stroke ends of the steered shaft Correspond one-on-one. As a result, the absolute rotation angle of the steering member can be detected with high accuracy based on the combination of the outputs of the first and second angle detectors. In addition, since the above-described reduction mechanism and ball screw mechanism for transmitting the necessary power are originally used for detecting the absolute rotation angle of the steering member, conventional vehicle steering using a reduction gear dedicated to the detection of the absolute rotation angle. Compared with the device, the structure can be simplified. As a result, the vehicle steering device can be made inexpensive.

Here, as the above-mentioned driving body and driven body, for example, a gear meshed with each other may be used, or a toothed pulley connected via a belt may be used.
In addition, although the alphanumeric characters in the parentheses indicate reference signs of corresponding components in the embodiments described later, the scope of the claims is not limited by these reference signs.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic diagram of a schematic configuration of an electric power steering apparatus as a vehicle steering apparatus according to a first embodiment of the present invention. Referring to FIG. 1, an electric power steering system (EPS) 1 includes a steering shaft 3 connected to a steering member 2 such as a steering wheel, and a first universal joint 4 attached to the steering shaft 3. An intermediate shaft 5 connected via a pin, a pinion shaft 7 connected to the intermediate shaft 5 via a second universal joint 6, and a rack tooth 9 meshing with a pinion tooth 8 provided near the end of the pinion shaft 7. And a rack shaft 10 as a turning shaft extending in the left-right direction X of the automobile.

  The pinion shaft 7 and the rack shaft 10 constitute a steering gear 11 composed of a rack and pinion mechanism. The rack shaft 10 is supported in a housing 13 fixed to the vehicle body 12 so as to be linearly reciprocable via a plurality of bearings (not shown). A pair of tie rods 14 are coupled to the rack shaft 10. Each tie rod 14 is connected to a corresponding steered wheel 16 via a corresponding knuckle arm 15.

When the steering member 2 is operated and the steering shaft 3 is rotated, this rotation is converted by the pinion teeth 8 and the rack teeth 9 into a linear motion of the rack shaft 10 along the left-right direction X of the automobile. Thereby, the turning of the steered wheels 16 is achieved.
The pinion shaft 7 is divided into an input shaft 17 connected to the steering member 2 and an output shaft 18 connected to the pinion teeth 8. The input shaft 17 and the output shaft 18 are connected to each other on the same axis via a torsion bar 19. When steering torque is input to the input shaft 17, the torsion bar 19 is elastically torsionally deformed, whereby the input shaft 17 and the output shaft 18 are rotated relative to each other.

  A torque sensor 20 that detects a steering torque based on the amount of relative rotational displacement between the input shaft 17 and the output shaft 18 via the torsion bar 19 is provided. A vehicle speed sensor 21 for detecting the vehicle speed is also provided. An ECU (Electronic Control Unit) 22 is provided as a control device. An electric motor 23 for generating a steering assist force, a reduction mechanism 24 that transmits and decelerates the output rotation of the electric motor 23, and a motion conversion that converts the output rotation of the reduction mechanism 24 into an axial movement of the rack shaft 10. A ball screw mechanism 25 as a mechanism is provided.

  Detection signals from the torque sensor 20 and the vehicle speed sensor 21 are input to the ECU 22. The ECU 22 controls the steering assisting electric motor 23 based on the torque detection result, the vehicle speed detection result, and the like. The output rotation of the electric motor 23 is decelerated by the speed reduction mechanism 24 and converted into linear movement by the ball screw mechanism 25. This linear movement is transmitted to the rack shaft 10. Thereby, steering is assisted.

FIG. 2 is an enlarged view of a main part of the electric power steering apparatus 1 of FIG. Referring to FIG. 2, the speed reduction mechanism 24 includes a drive gear 26 as a drive body driven by the electric motor 23, an intermediate gear 27 as an idle gear that meshes with the drive gear 26, and a driven gear that meshes with the intermediate gear 27. And a driven gear 28 as a body.
The drive gear 26, the intermediate gear 27, and the driven gear 28 are sequentially meshed to constitute a parallel shaft gear mechanism. The speed reduction mechanism 24 includes a first shaft 31 that supports the drive gear 26 and a second shaft 32 that supports the intermediate gear 27.

The drive gear 26 is a bevel gear and is formed in a substantially cylindrical shape from metal, for example, steel. A plurality of power transmission gear teeth are formed on the outer periphery of the drive gear 26. The drive gear 26 and the first shaft 31 are fixed to each other so that they can rotate together. Specifically, the drive gear 26 and the first shaft 31 are integrally formed as a single component by a single member.
The drive gear 26 is rotatably supported by the housing 13 via the first shaft 31 and a pair of bearings in a both-end supported state. The drive gear 26 is disposed coaxially with the first shaft 31 and the output shaft 29 of the electric motor 23. The first shaft 31 is connected to the output shaft 29 of the electric motor 23 via a shaft coupling 33.

  The intermediate gear 27 is a helical gear, and is formed in a substantially cylindrical shape by a synthetic resin member, for example. A plurality of power transmission gear teeth are formed on the outer periphery of the intermediate gear 27. The intermediate gear 27 and the second shaft 32 are fixed to each other so that they can rotate together. The intermediate gear 27 may be formed of metal, for example, steel, and the intermediate gear 27 and the second shaft 32 may be integrally formed as a single component by a single member. Further, the intermediate gear 27 is rotatably supported by the housing 13 via the second shaft 32 and a pair of bearings in a both-end supported state.

The driven gear 28 is a bevel gear, and is formed in an annular shape from metal, for example, steel. A plurality of power transmission gear teeth are formed on the outer periphery of the driven gear 28.
The driven gear 28 and a ball nut 36 (to be described later) of the ball screw mechanism 25 are fixed to each other so that they can rotate together. The driven gear 28 is rotatably supported by the housing 13 via a ball nut 36 and a pair of bearings in a both-sided state.

  The ball screw mechanism 25 includes a ball nut 36 having a spiral ball rolling groove on the inner peripheral surface, and a screw shaft 37 formed on a part of the rack shaft 10 and having a spiral ball rolling groove on the outer peripheral surface. And a plurality of balls 38 that roll in a track formed so that the ball rolling groove of the screw shaft 37 and the ball rolling groove of the ball nut 36 are opposed to each other. Each ball 38 is infinitely circulated by a circulation path that connects one end and the other end of the ball rolling groove of the ball nut 36.

  The ball nut 36 is rotatably supported by the housing 13 via a pair of bearings. Further, the ball nut 36 is restricted from moving relative to the housing 13 in the axial direction S3 of the rack shaft 10. The ball nut 36 and the driven gear 28 are disposed concentrically with each other, and are fixed to each other so as to rotate together. The ball nut 36 is driven by the driven gear 28.

The screw shaft 37 is driven by a ball nut 36 via a plurality of balls 38 and functions as a linear moving member. The screw shaft 37 is integrally formed with the rack shaft 10 from a single material.
The rack shaft 10, the screw shaft 37, the ball nut 36, and the driven gear 28 are disposed concentrically with each other. The ball nut 36 of the ball screw mechanism 25 is driven by the electric motor 23 via the speed reduction mechanism 24, and thereby rotates around the central axis of the rack shaft 10. Accordingly, the rotation of the ball nut 36 is converted into a linear movement of the screw shaft 37 in the axial direction of the rack shaft 10.

  Thus, the rotation center axis of the output shaft 29 of the electric motor 23 and the rotation center axis of the drive gear 26 are arranged concentrically with each other. At the same time, the rotation center axis of the drive gear 26, the rotation center axis of the intermediate gear 27, and the rotation center axis of the driven gear 28 are arranged in parallel to each other. Further, the output shaft 29 of the electric motor 23 is arranged in parallel to the axial direction S3 of the rack shaft 10. A predetermined distance is separated between the output shaft 29 of the electric motor 23 and the rack shaft 10. The predetermined distance is set to a minimum value corresponding to the outer shape of the electric motor 23 or a value approximate to this value. Thereby, the enlargement of the driven gear 28 can be suppressed while realizing a required reduction ratio. As a result, the external shape of the steering gear 11, the speed reduction mechanism 24, and the ball screw mechanism 25 can be reduced in size.

  The electric power steering apparatus 1 of the present embodiment detects a rotation angle of a resolver 41 as a first angle detector that detects a rotation angle of an output shaft 29 of an electric motor 23 and a driven gear 28 as a driven body. And an absolute angle detector 43 that detects the absolute rotation angle of the steering member 2 based on the outputs of the resolver 41 and the encoder 42.

Here, the absolute rotation angle of the steering member 2 is a predetermined reference rotation angle position, for example, a rotation angle position with respect to the rotation angle position of the steering member 2 when the steering member 2 is in a neutral state. The absolute rotation angle of the steering member 2 includes the rotation angle position of the steering member 2 when the steering member 2 makes multiple rotations (360 ° or more).
The rotation angle of the output shaft 29 is a predetermined reference rotation angle position, for example, a rotation angle position with respect to the rotation angle position of the output shaft 29 when the steering member 2 is in a neutral state. The rotation angle of the output shaft 29 indicates the rotation angle position of the output shaft 29 when the output shaft 29 rotates within the range of one rotation (less than 360 °). When the output shaft 29 rotates many times, the rotation angle of the output shaft 29 changes periodically every time the output shaft 29 rotates once.

  The rotation angle of the driven gear 28 is a rotation angle position with respect to a predetermined reference rotation angle position, for example, a rotation angle position of the driven gear 28 when the steering member 2 is in a neutral state. The rotation angle of the driven gear 28 indicates the rotation angle position of the driven gear 28 when the driven gear 28 rotates within the range of one rotation (less than 360 °). When the driven gear 28 makes multiple rotations, the rotation angle of the driven gear 28 changes periodically every time the driven gear 28 makes one rotation.

The resolver 41 detects the rotation angle of the output shaft 29 in order to control the energization of the electric motor 23.
The electric motor 23 includes a motor housing 45, an output shaft 29 rotatably supported by the motor housing 45, a rotor 46 including a permanent magnet that rotates along with the output shaft 29, and a plurality of coils. And a stator 47 fixed to 45. The stator 47 and the rotor 46 constitute a brushless motor. In such an electric motor 23, the excitation timing of the stator 47 is controlled according to the position of the magnetic pole of the rotor 46 with respect to the stator 47.

  The resolver 41 is disposed inside the motor housing 45. The resolver 41 includes an annular resolver stator 49 as a fixed portion, and an annular resolver rotor 50 as a movable portion and as a detection rotor. The resolver 41 can detect the rotation angle of the resolver rotor 50 with respect to the resolver stator 49 and outputs the rotation angle of the output shaft 29. The resolver 41 is an absolute displacement sensor that detects a rotation angle within one rotation.

  The encoder 42 is an absolute magnetic displacement sensor that detects a rotation angle within one rotation. The encoder 42 has a fixed portion 52 and an annular movable portion 53 as a detection rotor. The fixed part 52 includes, for example, a magnetoresistive element. The movable part 53 includes a magnet. Depending on the relative position between the fixed portion 52 and the movable portion 53, the output signal from the fixed portion 52 is different. The movable portion 53 is fixed to the driven gear 28 so as to be able to rotate along with the driven gear 28. The fixed part 52 is fixed to the housing 13. The encoder 42 can detect the rotation angle of the movable portion 53 with respect to the fixed portion 52 and outputs the rotation angle of the driven gear 28.

  In the present embodiment, the least common multiple of the number of teeth Zp of the drive gear 26 and the number of teeth Zr of the driven gear 28 is LCM (Zp, Zr), and the number of rotations of the steering member 2 corresponding to both stroke ends of the rack shaft 10 is determined. When N is N, the stroke amount of the rack shaft 10 per rotation of the steering member 2 is L, and the lead of the screw shaft 37 of the ball screw mechanism 25 is R, Equation 1: LCM (Zp, Zr)> (N × L × Zr / R).

  An example of specific numerical values is as follows. That is, the number of teeth Zp of the drive gear 26 is 19 (sheets). The number of teeth of the driven gear 28 is Zr = 64 (sheets). These least common multiple LCM (Zp, Zr) = 1216. The number of rotations N of the steering member 2 corresponding to between both stroke ends of the rack shaft 10 is 2.93 (rotation). Stroke amount L of the rack shaft 10 per rotation of the steering member 2 = 53.7 (mm). The lead R of the screw shaft 37 of the ball screw mechanism 25 is 8.5 (mm). Value (N × L × Zr / R) = 1184.6 on the right side of Equation 1 above. Therefore, LCM (Zp, Zr)> (N × L × Zr / R) is satisfied.

  The relationship between the combination of the rotation angles of the output shaft 29 and the driven gear 28 and the above equation 1 will be specifically described. The drive gear 26 and the driven gear 28 are interlocked with each other. Accordingly, the combination of the rotation angle of the drive gear 26 detected by the resolver 41 and the rotation angle of the driven gear 28 detected by the encoder 42 corresponds to, for example, that the driven gear 28 rotates at a predetermined rotation speed. Fluctuates periodically.

  The predetermined rotation speed of the driven gear 28 described above (a value corresponding to the period of change when the combination of the values described above changes with respect to the rotation of the driven gear 28) is, for example, the left side of the above equation 1 [minimum It corresponds to a value obtained by dividing the common multiple LCM (Zp, Zr)] by the value Zr. On the other hand, the value obtained by dividing the right side of Equation 1 above by the value Zr corresponds to the rotation speed of the driven gear 28 corresponding to the distance between both stroke ends of the rack shaft 10 (corresponding to the entire operation angle range of the steering member 2). .

Therefore, when satisfying the above formula 1, the same combination does not appear in the combination of both the outputs of the resolver 41 and the encoder 42 when the steering member 2 is rotated in the entire operation angle range. The absolute angle detection device 43 can accurately detect the absolute rotation angle of the steering member 2.
A resolver 41 and an encoder 42 are connected to the absolute angle detection device 43, and the output of the resolver 41 and the output of the encoder 42 are input. The absolute angle detection device 43 calculates the absolute rotation angle of the steering member 2 based on the rotation angle of the output shaft 29 detected by the resolver 41 and the rotation angle of the driven gear 28 detected by the encoder 42.

The absolute angle detection device 43 is realized by a program and a CPU for executing the program. Specifically, the absolute angle detection device 43 is configured integrally with the ECU 22, and the program of the absolute angle detection device 43 is stored in the ROM of the ECU 22. The CPU of the absolute angle detection device 43 is also used by the CPU of the ECU 22.
FIG. 3 is a graph showing the relationship between the rotation angle of the driven gear 28 and the output shaft 29 as the outputs of the resolver 41 and the encoder 42 shown in FIG. 1 and the absolute rotation angle of the steering member 2. The horizontal axis of the graph of FIG. 3 shows the absolute rotation angle of the steering member 2. The vertical axis of the graph of FIG. 3 shows the rotation angle (0 to 360 °) of the driven gear 28 and the output shaft 29. 2 and 3, for example, when the rotation angle of the output shaft 29 takes the value A1 and the rotation angle of the driven gear 28 takes the value B1, the absolute rotation angle of the steering member 2 is determined by the value C1. . When the rotation angle of the output shaft 29 takes the value A1 and the rotation angle of the driven gear 28 takes the value B2, the absolute rotation angle of the steering member 2 is determined to be the value C2.

  Thus, there are many combinations of the rotation angle value of the output shaft 29 and the rotation angle value of the driven gear 28. The absolute rotation angle of the steering member 2 is uniquely determined for each of the many combinations. The relationship between the value of the rotation angle of the output shaft 29 and the value of the rotation angle of the driven gear 28 and the relationship of the absolute rotation angle of the steering member 2 are determined in advance and stored in the absolute angle detection device 43 as a data table. ing. This data table is compared with the combination of the rotation angle value of the output shaft 29 and the rotation angle value of the driven gear 28. Thereby, the absolute rotation angle of the steering member 2 can be determined from the combination of the rotation angle value of the output shaft 29 and the rotation angle value of the driven gear 28.

  Referring to FIG. 2, ECU 22 includes a microcomputer and the like. This microcomputer includes a CPU, a RAM, a ROM, and the like. In addition, the microcomputer has a built-in timer, and controls the electric motor 23, for example, based on a program or data stored in a ROM or the like. The ECU 22 is connected to the absolute angle detection device 43 and controls the electric motor 23 based on the output of the absolute angle detection device 43.

For example, the ECU 22 has a return control function for improving the steering performance when the steering member 2 returns. Alternatively, the ECU 22 has a convergence control function (damping control) that prevents the steering wheel from rotating beyond a predetermined neutral position when the steering member 2 returns. Which of the return control function and the convergence control function is determined according to the characteristics of the vehicle.
The return control is performed in a vehicle having a small force (referred to as “self-aligning torque”) in which the wheel tries to return in the straight direction, that is, a vehicle in which the steering wheel returns poorly. For example, when the absolute rotation angle is within a predetermined range (for example, a position away from the neutral position by a predetermined angle), and when the steering torque is within the predetermined range (for example, the steering torque is not more than a predetermined value), The electric motor 23 is driven so that the steering member 2 returns to the neutral position.

Since the steering member 2 quickly returns to the neutral position by the return control, it is possible to prevent the steering angle (residual steering angle) from increasing when the steering wheel stops without returning to the neutral position.
In addition, the convergence control is performed in a vehicle having a large self-aligning torque, that is, a vehicle with a tight steering wheel return. Based on the absolute rotation angle of the steering member 2, the handle is prevented from rotating beyond a predetermined neutral position.

  As described above with reference to FIG. 2, the electric power steering apparatus 1 as the vehicle steering apparatus of the present embodiment rotates the ball nut 36 driven by the electric motor 23 via the speed reduction mechanism 24. A ball screw mechanism 25 that converts the axial movement of the rack shaft 10 as a steered shaft extending in the left-right direction X, and a resolver 41 as a first angle detector that detects the rotation angle of the output shaft 29 of the electric motor 23. And an encoder 42 as a second angle detector, and an absolute angle detector 43 that detects the absolute rotation angle of the steering member 2 based on the output of the resolver 41 and the output of the encoder 42. The speed reduction mechanism 24 includes a drive gear 26 as a drive body provided coaxially with the output shaft 29 of the electric motor 23 and a driven gear 28 as a driven body provided coaxially with the ball nut 36. . The encoder 42 detects the rotation angle of the driven gear 28.

  In this configuration, the least common multiple of the number of teeth Zp of the drive gear 26 and the number of teeth Zr of the driven gear 28 is LCM (Zp, Zr), and the number of rotations of the steering member 2 corresponding to both stroke ends of the rack shaft 10 is N. When the stroke amount of the rack shaft 10 per rotation of the steering member 2 is L and the lead of the screw shaft 37 of the ball screw mechanism 25 is R, Formula 1: LCM (Zp, Zr)> (N × L × Zr / R).

  According to the present embodiment, since the above Expression 1 is satisfied, the combination of the rotation angle detected by the resolver 41 and the encoder 42 and the absolute rotation angle of the steering member 2 corresponding to both stroke ends of the rack shaft 10 are obtained. One-to-one correspondence. As a result, the absolute rotation angle of the steering member 2 can be detected with high accuracy based on the combination of the output of the resolver 41 and the output of the encoder 42. In addition, since the above-described reduction mechanism 24 and the ball screw mechanism 25 for power transmission that are necessary for detecting the absolute rotation angle of the steering member 2 are used, the conventional reduction mechanism dedicated to the detection of the absolute rotation angle is used. Compared with a vehicle steering device, the structure can be simplified. As a result, the vehicle steering device 1 can be made inexpensive.

Further, since the absolute rotation angle of the steering member 2 is detected based on the output of the resolver 41 and the output of the encoder 42, the steering member 2 is used to detect the absolute rotation angle of the steering member 2. The conventional angle detector provided can be eliminated or simplified.
The resolver 41 detects the relative rotation angle of the rotor with respect to the stator and controls the absolute rotation angle (absolute steering angle) of the output shaft 29 for controlling the energization of the electric motor 23 composed of a brushless motor. I also use it. Thereby, the structure can be simplified.

Further, since both the resolver 41 and the encoder 42 for detecting the absolute rotation angle of the steering member 2 are separated from the steering shaft 3 and the steering member 2, in order to absorb the impact in the vicinity of the steering shaft 3 and the steering member 2. It is easy to secure the space.
For example, referring to FIG. 1, a steering column 55 that rotatably supports the steering shaft 3 is configured to absorb impact energy in the event of a vehicle collision. The steering member 2 and at least a part of the steering shaft 3 and the steering column 55 are held on the vehicle body via the bracket 56 with a predetermined holding force. In the event of a vehicle collision, when the steering member 2 and at least a part of the steering shaft 3 and the steering column 55 receive an impact force that exceeds a predetermined holding force, the steering member 2 can move relative to the vehicle body toward the front of the vehicle. ing. The amount of movement of the steering member 2 when absorbing shock can be increased.

Moreover, the following modifications can be considered about this embodiment. In the following description, the difference from the above-described embodiment will be mainly illustrated, and this point will be mainly described. Although explanation is omitted about other composition, it is the same as that of the above-mentioned embodiment, and attaches the same numerals.
For example, FIG. 4 is an enlarged view of a main part of a schematic configuration of an electric power steering apparatus 1 as a vehicle steering apparatus according to a second embodiment of the present invention. The electric power steering apparatus 1 according to the second embodiment has a speed reduction mechanism 24A shown in FIG. 4 instead of the speed reduction mechanism 24 shown in FIG. The speed reduction mechanism 24 of FIG. 2 and the speed reduction mechanism 24A of FIG. 4 are different in the following points, and the other configurations are the same.

The speed reduction mechanism 24A has a driving pulley 60 as a driving body and a driven pulley 61 as a driven body in FIG. 4 instead of the driving gear 26 and the driven gear 28 in FIG. The speed reduction mechanism 24A has an endless toothed belt 62 as a power transmission member in FIG. 4 instead of the intermediate gear 27 in FIG.
The drive pulley 60 is fixed so as to be able to rotate along with the first shaft 31. The drive pulley 60 is a toothed pulley. A plurality of power transmission teeth are formed on the outer periphery of the drive pulley 60. The driven pulley 61 is fixed so as to be able to rotate along with the ball nut 36. The driven pulley 61 is a toothed pulley. A plurality of teeth for power transmission are formed on the outer periphery of the driven pulley 61. The toothed belt 62 has a plurality of power transmission teeth.

  The toothed belt 62 is wound around the drive pulley 60 and the driven pulley 61. The teeth of the drive pulley 60 and the teeth of the toothed belt 62 mesh with each other. The teeth of the driven pulley 61 and the teeth of the toothed belt 62 mesh with each other. Thereby, the drive pulley 60 and the driven pulley 61 are connected so as to be able to be interlocked and transmit power. As a result, the rotation of the drive pulley 60 is decelerated and output as the rotation of the driven pulley 61.

The encoder 42 detects the rotation angle of the driven pulley 61. The movable portion 53 of the encoder 42 is fixed so as to rotate along with the driven pulley 61.
In the present embodiment, the number of teeth of the toothed drive pulley 60 is used instead of the number of teeth of the drive gear, and the number of teeth of the toothed driven pulley 61 is used instead of the number of teeth of the driven gear. When satisfied, Formula 1 is satisfied.

Therefore, the effect described in the first embodiment, that is, the absolute rotation angle of the steering member 2 is detected with high accuracy, and the manufacturing cost of the electric power steering apparatus 1 can be reduced.
In the first embodiment described above, the intermediate gear 27 may be eliminated. In this case, the drive gear 26 and the driven gear 28 mesh directly. The gears 26, 27, and 28 are bevel gears. However, the present invention is not limited to this. For example, spur gears, bevel gears, and hypoid gears may be used. In the second embodiment described above, it is also conceivable to use a chain (not shown) instead of the toothed belt 62 as the power transmission member. In short, the speed reduction mechanism described above may include a pair of gears that mesh with each other directly or via an idle gear, or a pair of toothed pulleys that interlock with each other via a power transmission member. Further, the number of teeth in the above-described formula 1 is the number of gear teeth of a gear or the number of teeth for power transmission of a toothed pulley.

Moreover, although each above-mentioned embodiment demonstrated the case where the electric motor 23 was a brushless motor, not only this but motors other than a brushless motor, for example, a DC motor, may be sufficient.
Moreover, it is also conceivable to use an angle detector different from the angle detector for energization control of the electric motor 23 as the first angle detector. Further, the first angle detector is not limited to the resolver 41, and for example, a known configuration such as a magnetic displacement sensor, a potentiometer, a photoelectric displacement sensor, or the like can be used. Further, the second angle detector is not limited to the magnetic encoder 42, and a known configuration such as a resolver, a potentiometer, a photoelectric displacement sensor, or the like can be used.

  In the above-described embodiment, the example in which the present invention is applied to the electric power steering apparatus 1 that outputs the output of the electric motor 23 as the steering assist force has been described, but the present invention is not limited thereto. For example, a transmission ratio variable mechanism that includes a transmission ratio variable mechanism capable of changing a ratio of a steered wheel turning angle to a steering angle of a steering member, and that uses an output of an electric motor to drive the transmission ratio variable mechanism, is used for vehicle steering Even if the present invention is applied to a device, a steer-by-wire type vehicle steering device in which the mechanical connection between the steering member and the steered wheel is released and the steered wheel is steered by the output of the electric motor, etc. Good. In addition, various changes can be made within the scope of the matters described in the claims.

It is a mimetic diagram of a schematic structure of a steering device for vehicles of a 1st embodiment of the present invention. It is an enlarged view of the principal part of FIG. It is a graph which shows the relationship between the output shaft shown in FIG. 1, the rotation angle of a driven gear, and the absolute rotation angle of a steering member. It is an enlarged view of the principal part of schematic structure of the steering apparatus for vehicles of the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electric power steering device (vehicle steering device), 2 ... Steering member, 10 ... Rack shaft (steering shaft), 23 ... Electric motor, 24, 24A ... Deceleration mechanism, 25 ... Ball screw mechanism, 26 ... Drive gear (Driving body), 28 ... driven gear (driven body), 29 ... output shaft of electric motor, 36 ... ball nut, 37 ... screw shaft, 41 ... resolver (first angle detector), 42 ... encoder (second) Angle detector), 43 ... absolute angle detector, 60 ... driving pulley (driving body), 61 ... driven pulley (driven body), L ... stroke amount of rack shaft per rotation of steering member, N ... rack shaft The number of rotations of the steering member corresponding to between both stroke ends, R ... lead of the screw shaft. X: Left-right direction of vehicle, Zp: Number of teeth of driving body, Zr: Number of teeth of driven body.

Claims (1)

A ball screw mechanism that converts rotation of a ball nut driven by an electric motor through a speed reduction mechanism into axial movement of a steered shaft extending in the left-right direction of the vehicle;
A first angle detector for detecting a rotation angle of the output shaft of the electric motor;
A second angle detector;
An absolute angle detector that detects the absolute rotation angle of the steering member based on the outputs of the first and second angle detectors,
The speed reduction mechanism includes a driving body provided coaxially with the output shaft of the electric motor, and a driven body provided coaxially with the ball nut.
The second angle detector detects a rotation angle of the driven body,
The least common multiple of the number of teeth Zp of the driving body and the number of teeth Zr of the driven body is LCM (Zp, Zr), the number of rotations of the steering member corresponding to both stroke ends of the steered shaft is N, and A steering apparatus for a vehicle that satisfies the following formula 1 where L is a stroke amount of the steered shaft per rotation of the steering member and R is a lead of the screw shaft of the ball screw mechanism.
LCM (Zp, Zr)> N × L × Zr / R Formula 1

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