JP2013001257A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power steering device capable of detecting the steering angle of a steering wheel even while suppressing sudden rise of costs.SOLUTION: When a shaft angle multiplier of an output side resolver 7 provided to a steering wheel side pinion shaft 2 is denoted by k, a shaft angle multiplier of a motor side resolver 13 provided to a motor side pinion shaft is denoted by k, and a rotation angle that the steering wheel side pinion shaft 2 is rotated via a rack shaft 3 when the motor side pinion shaft is rotated once is denoted by θ°, setting is performed to be values such that (θ/k)>(360/k) is satisfied and (θ/k)/(360/k) is not an integer. Thus, the combination of the value of an output side resolver output signal S2 and the value of a motor side resolver output signal S3 does not take the same value at different steering angles and the steering angle can be derived from both resolver output signals S2 and S3.

Description

  The present invention relates to a power steering apparatus.

  For example, as described in Patent Document 1, in a rack and pinion type power steering device in which a specific stroke changes according to a steering angle from a neutral position, a first resolver and a second resolver having different shaft angle multipliers are used as a handle shaft. A handle shaft rotation angle, which is a rotation angle within one rotation of the handle shaft, is obtained based on detection signals of both resolvers, and an output shaft of the electric motor that applies assist force to the output member of the steering gear is provided. A third resolver is provided to calculate the first and second derivative values of the motor rotation angle detected by the third resolver according to the handle shaft rotation angle, and to determine the direction and number of rotations in which the handle shaft is rotated from the neutral position. There has been proposed a technique for obtaining values based on positive / negative values and first-order differential values.

JP 2004-317296 A

  However, in the technique described in Patent Document 1, the rotation angle of the handle shaft is calculated using the change in the specific stroke based on the change in the rotation angle of the handle shaft. It could not be applied to a power steering device set to a constant value. Therefore, when it is necessary to detect the steering angle of the steered wheels in the power steering device in which the specific stroke of the rack and pinion mechanism is set to be constant, it is necessary to provide a relatively expensive so-called absolute type steering angle sensor. There was a problem that the cost would rise.

  The present invention has been made in view of such problems, and even when the specific stroke of the rack and pinion mechanism is constant, the steering angle of the steered wheels can be detected while suppressing the cost increase. It aims at providing a power steering device.

  The present invention constitutes a steering wheel side rack and pinion mechanism by meshing between a steering wheel side pinion shaft that rotates in accordance with a steering operation of the steering wheel and a steering wheel side rack tooth formed on the rack shaft, and a steering assist force. A motor-side rack and pinion mechanism having a specific stroke different from that of the steering wheel-side rack and pinion mechanism is formed by meshing between a motor-side pinion shaft that is rotationally driven by a motor that generates a motor and a motor-side rack tooth formed on the rack shaft. It is assumed that the power steering device.

In addition, every time the steering wheel side pinion shaft makes one rotation, a steering wheel side resolver that outputs a steering wheel side resolver output signal of k ₁ cycle, and every time the motor side pinion shaft makes one rotation, k ₂ cycles. When a rotation angle at which the steering wheel side pinion shaft rotates through the rack shaft when the motor side pinion shaft rotates once by the motor side resolver output signal and θ _a is rotated, (θ _a / K ₂ )> (360 / k ₁ ), and (θ _a / k ₂ ) / (360 / k ₁ ) is a non-integer value motor side resolver, and the steering wheel side A steering angle calculation unit that calculates the steering angle of the steered wheels based on the resolver output signal and the motor-side resolver output signal. That.

  According to the present invention, even when the specific stroke of the rack and pinion mechanism is constant, the steering angle of the steered wheels can be calculated based on the steering wheel side resolver output signal and the motor side resolver output signal. Increase in cost can be suppressed.

The figure which shows the outline of a power steering apparatus as the 1st Embodiment of this invention. FIG. 2 is a schematic cross-sectional view of the torque sensor shown in FIG. 1. Sectional drawing along the AA line of FIG. The functional block diagram of the electronic control apparatus shown in FIG. The figure which shows the relationship between the output side electrical angle and the motor side electrical angle, and the rotation position of an output shaft. The flowchart which shows the processing content of the angle position calculating part shown in FIG. The functional block diagram which shows the modification of the angular position calculating part in 1st Embodiment as 2nd Embodiment of this invention. The flowchart which shows the processing content of the angle position calculating part shown in FIG.

  1 to 6 are diagrams showing a first preferred embodiment of the present invention, in which FIG. 1 is a diagram showing an outline of a power steering device, and FIG. 2 is a sectional view showing an outline of a torque sensor in FIG. 3 is a cross-sectional view taken along line AA in FIG.

  In the power steering device shown in FIG. 1, when the steering wheel SW is rotated by the driver, the rotation of the steering wheel SW is transmitted to the steering wheel side pinion shaft 2 via the steering shaft 1, and the steering wheel The rotational motion of the side pinion shaft 2 is converted into the linear motion of the rack shaft 3, and the left and right steered wheels W1, W2 connected to both ends of the rack shaft 3 are steered. That is, the rack shaft 3 is formed with steering wheel side rack teeth (not shown) that mesh with the steering wheel side pinion shaft 2, and the steering wheel side rack teeth and the steering wheel side pinion shaft 2 are engaged with each other. A steering wheel side rack and pinion mechanism 4 for manual steering is configured.

  As shown in FIG. 2, the steering wheel side pinion shaft 2 is divided in the axial direction into an input shaft 2a on the steering wheel SW side and an output shaft 2b on the rack shaft 3 side. The input shaft 2a and the output shaft 2b are each formed in a hollow shape, and are coaxially connected to each other via a torsion bar 2c provided on the inner peripheral side of both the shafts 2a and 2b. In addition, although illustration is abbreviate | omitted, the axial direction both ends of the torsion bar 2c are each serration-coupled with the inner peripheral surface of both the shafts 2a and 2b so that relative rotation is impossible. As a result, the input shaft 2a and the output shaft 2b can rotate relative to each other with torsional deformation of the torsion bar 2c.

  On the outer peripheral side of the steering wheel side pinion shaft 2, there is provided a torque sensor housing 5 that is fixed to the vehicle body so as to surround the outer peripheral side of the steering wheel side pinion shaft 2, and the inner peripheral surface of the torque sensor housing 5 And an input side resolver 6 for detecting rotational displacement of the input shaft 2a is provided between the outer peripheral surface of the input shaft 2a. An output-side resolver 7 that detects the rotational position of the output shaft 2b is provided as a steering wheel-side resolver between the inner peripheral surface of the torque sensor housing 5 and the outer peripheral surface of the output shaft 2b. That is, by detecting the relative rotational displacement amount between the input shaft 2a and the output shaft 2b based on the torsional deformation of the torsion bar 2c by both the resolvers 6 and 7, the steering torque for rotating the steering wheel SW by the driver is detected. It is like that. In other words, the torque sensor TS for detecting the torque acting on the steering wheel side pinion shaft 2 is configured with both resolvers 6 and 7.

  Both resolvers 6 and 7 are of a known variable reluctance (VR) type in which a coil is provided only on the stator and no coil is provided on the rotor. The input-side resolver 6 is an outer peripheral surface of the input shaft 2. An annular input-side resolver rotor 6a that is integrally fitted to the input-side resolver rotor 6a. Input-side resolver stator 6b. On the other hand, the output-side resolver 7 has an annular output-side resolver rotor 7a that is integrally fitted to the outer peripheral surface of the output shaft 2b, and an outer peripheral side of the output-side resolver rotor 7a via a predetermined radial gap. And an annular output-side resolver stator 7 b that is inserted and fixed to the torque sensor housing 5.

In addition, the axial multiple angles of both resolvers 6 and 7 are set to be equal to each other, and in this embodiment, the axial multiple angles of both resolvers 6 and 7 are k ₁ respectively. That is, each time the input side resolver rotor 6a one rotation with the input shaft 2b, while the input side resolver output signal S1 of k ₁ cycle is output from the input side resolver stator 6b, together with the output side resolver rotor 7a and the output shaft 2b every time one rotation, k ₁ cycle of the output-side resolver output signal S2 is to be outputted from the output side resolver stator 7b.

  On the other hand, as shown in FIG. 3 in addition to FIG. 1, the rack shaft 3 is formed with motor side rack teeth 3 a different from the aforementioned steering wheel side rack teeth as motor side rack teeth. A motor side pinion shaft 9 that is driven by an electric motor M as an electric motor via a worm reduction mechanism 8 meshes with the teeth 3a as an electric motor side pinion shaft. That is, the motor side rack and pinion mechanism 10 that is an electric side rack and pinion mechanism is configured by the motor side rack teeth 3 a and the motor side pinion shaft 9. The specific stroke of the motor side rack and pinion mechanism 10 is different from that of the steering wheel side rack and pinion mechanism 4 in consideration of the characteristics of the electric motor M and the strength of the motor side rack teeth 3a.

  When the electric motor M is driven and controlled by an ECU 14 to be described later, and the output shaft 12 of the electric motor M rotates, the rotation is transmitted to the motor-side pinion shaft 9 via the worm reduction mechanism 8 and the motor side. The rotation of the pinion shaft 9 is converted into a linear motion by the motor side rack and pinion mechanism 10, and the output of the electric motor M is transmitted to the rack shaft 3 as a steering assist force. In addition, the code | symbol 11 of FIG. 3 has shown the worm housing which accommodates the worm reduction mechanism 8. FIG.

  Further, the motor-side pinion shaft 9 is provided with a motor-side resolver 13 that detects the rotational displacement of the motor-side pinion shaft 9 as an electric motor-side resolver. The motor-side resolver 13 includes an annular motor-side resolver rotor 13a that is integrally fitted to the outer peripheral surface of the motor-side pinion shaft 9 on the side opposite to the rack shaft 3, and the motor-side resolver rotor 13b. An annular motor-side resolver stator 13b that is extrapolated to the outer peripheral side through a predetermined radial gap and fixed to the worm housing 11, and a coil is provided only on the motor-side resolver stator 13b. The motor side resolver rotor 13a is of a known variable reluctance (VR) type in which no coil is provided.

In the present embodiment, the shaft angle multiplier of the motor side resolver 13 is k ₂ . That is, the motor-side resolver 13 outputs a motor-side resolver output signal S3 having a period of k ₂ every time the motor-side resolver rotor 13a rotates together with the motor-side pinion shaft 9.

  As shown in FIG. 1, in addition to the motor-side resolver output signal S3, the input-side resolver output signal S1 and the output-side resolver output signal S2 are taken into an electronic control unit (hereinafter abbreviated as ECU) 14. Details of the ECU 14 are shown in FIG. 4 as a functional block diagram.

As shown in FIG. 4, the ECU 14 includes an input-side electrical angle calculation unit 15 that calculates an input-side electrical angle θ _e1 according to the rotational position of the input shaft 2 a based on the input-side resolver output signal S1, and an output-side resolver output. Based on the signal S2, the output-side electrical angle calculator 16 that calculates the output-side electrical angle θ _e2 corresponding to the rotational position of the output shaft 2b, and the rotational position of the motor-side pinion shaft 9 based on the motor-side resolver output signal S3. The motor-side electrical angle computing unit 17 that computes the corresponding motor-side electrical angle θ _e3 , and the difference between the input-side electrical angle θ _e1 and the output-side electrical angle θ _e2 , that is, the twist amount of the torsion bar 2 c, Based on the torque calculator 18 for calculating the steering torque T acting on the pinion shaft 2, the output-side electrical angle θ _e2 , the motor-side electrical angle θ _e3, and the steering torque T, the rotational position θ _SW of the steering wheel SW The steering wheel SW returns due to the friction of the steering system when the steering wheel SW is switched back based on the angular position calculation unit 19 that calculates the steering angle θ _W of the steered wheels W1 and W2 and the rotational position θ _SW of the steering wheel SW. A steering return control unit 20 that outputs a steering return control command signal S4 for suppressing deterioration of the steering performance, and a steering assist torque that is generated by the electric motor M according to the steering torque T, the steering angle θ _W , and the steering return control command signal S4. And an inverter 22 that supplies three-phase AC power to the electric motor M based on the motor drive command signal S5.

Further, the angular position calculation unit 19 calculates the absolute rotational position θ _p of the output shaft 2b based on the output side electrical angle θ _e2 and the motor side electrical angle θ _e3 as described later, A steering wheel position calculation unit 24 for calculating the absolute rotation position θ _SW of the steering wheel SW by adding or subtracting the torsion amount of the torsion bar 2c obtained from the steering torque T to or from the rotation position θ _p of the output shaft 2b; And a rudder angle calculation unit 25 for calculating an absolute rudder angle θ _W of the steered wheels W1 and W2 based on the rotational position θ _p of the output shaft 2b. Since the steered wheels W1 and W2 are connected to the rack shaft 3 via a link mechanism (not shown), the steering angle θ _W can be uniquely determined from the rotational position θ _p of the output shaft 2b. .

Here, the relationship between the rotational position of the output shaft 2b, the output side electrical angle θ _e2 and the motor side electrical angle θ _e3 is shown in FIG. Note that 0 ° on the horizontal axis in FIG. 5 means that the output shaft 2b is in the neutral position, that is, the position where the steered wheels W1 and W2 are directed straight. Further, in FIG. 5, only the region where the horizontal axis is positive (for example, the right steering region) is illustrated, but it goes without saying that the output-side electrical angle is also obtained in the region where the horizontal axis is negative (for example, the left steering region). θ _e2 and the motor-side electrical angle θ _e3 change with the same period as in the illustrated region in accordance with the change in the rotational position of the output shaft 2b.

In the example shown in FIG. 5, the shaft angle multiplier k ₁ of the output side resolver 7 is 15, the shaft angle multiplier k ₂ of the motor side resolver 13 is 2, and the specific stroke of the steering wheel side rack and pinion mechanism 4 (rack for one rotation of the output shaft 2b). axial movement of the shaft 3) S ₁ 45mm / rev, the ratio stroke (axial direction movement amount of the rack shaft 3 with respect to one revolution of the motor-side pinion shaft 9 of the motor-side rack-and-pinion mechanism 10) S ₂ to 55 mm / rev, The rotation angle n of the lock-to-lock of the steering wheel SW is 1080 ° (3 rotations). That is, the output shaft 2b can rotate 540 ° from the neutral position to the left and right sides.

As shown in FIG. 5, the output-side electrical angle θ _e2 and the motor-side electrical angle θ _e3 are both set to 0 ° when the rotational position of the output shaft 2b is 0 °, and the output side Since the shaft multiple angle of the resolver 7 is set to k ₁ as described above, one cycle (360 °) of the output-side electrical angle θ _e2 is (360 / k ₁ ) ° as the rotational displacement amount of the output shaft 2b. It corresponds. In other words, the output side electrical angle θ _e2 takes the same value every time the output shaft 2b rotates by (360 / k ₁ ) °.

Further, as described above, the specific stroke S _{1 of} the motor side rack and pinion mechanism 10 is different from the specific stroke S _{2 of the} steering wheel side rack and pinion mechanism 4, and one rotation of the motor side pinion shaft 9 is output. This corresponds to (S ₂ / S ₁ ) rotation of the shaft 2b. That is, when the motor-side pinion shaft 9 is rotated once, the output shaft 2b rotates (360 · (S ₂ / S ₁ )) °. When this (360 · (S ₂ / S ₁ )) ° is expressed as θ _a for convenience, one period (360 °) of the motor-side electrical angle θ _e3 is the rotational displacement amount of the output shaft 2b (θ _a / k ₂ ) °. In other words, the motor-side electrical angle θ _e3 takes the same value and the same value every time the output shaft 2b rotates by (θ _a / k ₂ ) °.

In the present embodiment, the ratio stroke of shaft angle multiplier k _1, the shaft angle multiplier k ₂ ratio stroke S ₁ of the steering wheel-side rack-and-pinion mechanism 4, motor-side rack and pinion mechanism 10 of the motor-side resolver 13 on the output side resolver 7 S ₂ is set so as to satisfy the relationship of the following expressions (1) and (2).

(Θ _a / k ₂ )> (360 / k ₁ ) (1)
(Θ _a / k ₂ ) / (360 / k ₁ ) ≠ N (N is an integer) (2)
As a result, as shown in FIG. 5, when the output shaft 2b rotates in the positive direction from the neutral position, when the motor-side electrical angle θ _e3 becomes 0 ° in one cycle, the output shaft 2b the output electrical angle theta _e2 in the rotary position theta _c of not become 0 °, the rotational position of the output shaft 2b of the output side electrical angle theta _e2 just before the rotational position theta _c and its rotational position theta _c becomes 0 ° An angle difference I is generated between This angular difference I is accumulated and becomes larger as the rotational position of the output shaft 2b rotates in the positive direction from the neutral position.

More specifically, referring to the example shown in FIG. 5, in the example shown in FIG. 5, the shaft double angle k ₁ of the output side resolver 7 is 15, the shaft double angle k ₂ of the motor side resolver 13 is 2, and the steering wheel side Since the specific stroke S ₁ of the rack and pinion mechanism 4 is 45 mm / rev and the specific stroke S ₂ of the motor side rack and pinion mechanism 10 is 55 mm / rev, (θ _a / k ₂ ) / (360 / k ₁ ) ≈9 In the process in which the output shaft 2b rotates in the positive direction from the neutral position, every time the motor-side electrical angle θ _e3 cycles, 0.17 cycles of the output-side electrical angle θ _e2 (the output shaft 2b The angle difference I of about 4 ° in the rotation direction of (4) is accumulated. That is, on the condition that (θ _a / k ₂ ) / (360 / k ₁ ) is a non-integer value, in other words, (θ _a / k ₂ ) is not divisible by (360 / k ₁ ), the angle difference I will occur.

As a result, in the process in which the output shaft 2b rotates in the positive or negative direction from the neutral position within the range of the lock-to-lock, the combination of the output-side electrical angle θ _e2 and the motor-side electrical angle θ _e3 differs. Therefore, the rotational position of the output shaft 2b can be derived from the output-side electrical angle θ _e2 and the motor-side electrical angle θ _e3 .

That is, the pinion position calculation unit 23 shown in FIG. 4 stores a map showing a correspondence relationship between the combination of the output side electrical angle θ _e2 and the motor side electrical angle θ _e3 and the rotational position of the output shaft 2b. By referring to the map, the rotational position of the output shaft 2b is derived from the output-side electrical angle θ _e2 and the motor-side electrical angle θ _e3 .

By the way, the output shaft 2b is rattled in the rotation direction due to the backlash of the steering wheel side rack and pinion mechanism 4, so that the rotation position of the output shaft 2b and the motor side pinion are caused by the shakiness of the output shaft 2b. The relative relationship with the rotational position of the shaft 9 may deviate from the normal relative relationship. Thereby, the rotational position of the output shaft 2b is not in the range of the cycle of the motor-side electrical angle θ _e3 corresponding to the actual rotational position, but in the range of the cycle of the motor-side electrical angle θ _e3 adjacent to the cycle. There is a risk of erroneous detection. Therefore, the angle difference I accumulated for each cycle of the motor-side electrical angle θ _e3 is made larger than the backlash amount θ _b of the steering wheel-side rack and pinion mechanism 4 in the rotation direction of the output shaft 2b. It is preferable to prevent such erroneous detection. Note that the backlash amount θ _b of the steering wheel side rack and pinion mechanism 4 in the present embodiment is 1 °.

However, the accumulation of the angle difference I as described above within the range of the rotation angle n ° of the lock-to-lock, that is, I · n / (θ _a / k ₂ ) is one cycle of the output side electrical angle θ _e2 , that is, ( 360 / k ₁ ), the rotational position of the output shaft 2b is not within the range of the period of the output electrical angle θ _e2 corresponding to the actual rotational position, but instead of the output electrical angle θ _e2 . There is a possibility that it is erroneously detected as being within the range of another period.

Therefore, in the present embodiment, the backlash of the output-side shaft angle multiplier k ₁ of the resolver 7, the shaft angle multiplier k ₂ of the motor-side resolver 13, the lock-to-lock of the steering wheel SW rotation angle n, the steering wheel-side rack-and-pinion mechanism 4 The quantity θ _b is set so as to satisfy the relationship of the following expression (3).

360 / k ₁ > θ _b · n / (θ _a / k ₂ ) (3)
As a result, the angle difference I is made larger than the backlash amount θ _b of the steering wheel side rack and pinion mechanism 4 and the angle difference I is accumulated within the range of the rotation angle n of the lock-to-lock, that is, I N / (θ _a / k ₂ ) can be made smaller than one cycle of the output-side electrical angle θ _e2 , that is, (360 / k ₁ ) °, and the rotational position of the output shaft 2b is as described above. False detection can be suppressed.

Next, the processing contents of the angular position calculation unit 19 in the present embodiment will be described with reference to the flowchart of FIG. First, the angular position calculation unit 19 reads the output-side electrical angle θ _e2 from the output-side electrical angle calculation unit 16 and the motor-side electrical angle θ _e3 from the motor-side electrical angle calculation unit 17 (steps S1 and S2). Based on the output-side electrical angle θ _e2 and the motor-side electrical angle θ _e3 , the rotational position θ _p of the output shaft 2b is calculated using the map stored in the pinion position calculation unit 23 (step S3).

Next, the steering angle calculation unit 25 calculates the steering angle θ _W of the steered wheels W1, W2 based on the rotational position θ _p of the output shaft 2b (step S4), and information on the steering angle θ _W is obtained from the steering assist control unit. and outputs 21 (step S5), and the steering wheel position calculating unit 24, the rotational position theta _SW of the steering wheel SW is calculated as described above on the basis of the rotational position theta _p of the output shaft 2b (step S6), and its Information on the rotational position θ _SW of the steering wheel SW is output to the steering return control unit 20 and another control system (see FIG. 4) (step S7). Other control systems mentioned here include, for example, a driving support system such as a parking support system and a vehicle attitude control system. More specifically, the rear view monitor in the parking support system predicts the vehicle. Used to display a route.

Then, as described above, the steering return control unit 20 shown in FIG. 4 outputs the steering return control command signal S4 for suppressing the deterioration of the returnability of the steering wheel SW based on the rotational position θ _SW of the steering wheel SW. The steering assist control unit 21 sets a steering assist torque to be generated by the electric motor M according to the steering torque T, the steering angle θ _W , and the steering return control command signal S4, and outputs the motor drive command to the control unit 21. The signal S5 is output to the inverter 22. As a result, the output shaft 12 of the electric motor M is rotationally driven with the electric power supplied from the inverter 22, and the rotational driving force is transmitted to the rack shaft 3 as a steering assist force.

Therefore, according to the present embodiment, even if the specific stroke of the steering wheel side rack and pinion mechanism 4 is constant, the absolute angular position θ _p of the output shaft 2b within the lock-to-lock range, and hence the rotation The steering angle θ _W of the steered wheels W1 and W2 can be calculated based on the output side resolver output signal S2 and the motor side resolver output signal S3 without using a dedicated rudder angle sensor, so that an increase in cost can be suppressed.

Moreover, since the steering angle θ _W of the steered wheels W1 and W2 is calculated using the output side resolver 7 used as the torque sensor TS, the cost increase can be more effectively suppressed. Can do.

  FIG. 7 is a functional block diagram showing a modification of the angular position calculation unit 19 in the first embodiment described above as the second embodiment of the present invention. In FIG. 7, the same reference numerals are assigned to the same or corresponding parts as those in the first embodiment described above.

The angular position calculation unit 26 in the second embodiment shown in FIG. 7 determines the rotational position of the output shaft 2b when an ignition switch (not shown) is turned on and the ECU 14 is switched from the power-off state to the power-on state. An initial rotational position calculator 27 that calculates the initial rotational position θ ₀ based on the output-side electrical angle θ _e2 and the motor-side electrical angle θ _e3 , and the rotational displacement amount Δθ _p of the output shaft 2b from the initial rotational position θ ₀ are output. A rotational displacement amount calculation unit 28 that counts based on the side electrical angle θ _e2 , and a first pinion position calculation that calculates the rotational position θ _p of the output shaft 2 b by adding the rotational displacement amount Δθ _p to the initial rotational position θ _0. Apart from the unit 29 and the first pinion position calculation unit 29, a second pinion position calculation unit for calculating the rotational position θ _p ′ of the output shaft 2b based on the output side electrical angle θ _e2 and the motor side electrical angle θ _e3 30 and the first pinio By comparing and the rotational position theta _p of the output shaft 2b which is operated rotational position theta _p of the output shaft 2b which is calculated by the second pinion position calculating unit 30 'by the position calculating unit 29, the first pinion position calculating section comprises the rotational position of the output shaft 2b which is calculated at 29 theta _p and the abnormality determining unit 31 to determine the presence or absence of abnormality of the rotational position theta _p 'of the output shaft 2b which is calculated by the second pinion position calculating section 30, the This is different from the first embodiment described above. Other parts are the same as those in the first embodiment described above.

That is, as shown in the flowchart of FIG. 8, the angular position calculation unit 26 in the present embodiment starts with the initial rotation position when an unillustrated ignition switch is turned on and the ECU 14 changes from the power-off state to the power-on state. The computing unit 27 reads the output-side electrical angle θ _e2 and the motor-side electrical angle θ _e3 (steps S11 and S12), and rotates the output shaft 2b based on the output-side electrical angle θ _e2 and the motor-side electrical angle θ _e3. The position is calculated as the initial rotational position θ ₀ (step S13). The initial rotation position calculation unit 27 calculates the initial rotation position θ ₀ by the same calculation method as the pinion position calculation unit 23 of the first embodiment described above.

When the initial rotational position θ ₀ is calculated in this way, the rotational displacement amount calculation unit 28 substitutes 0 for the rotational displacement amount Δθ _p (step S14), and starts counting the rotational displacement amount Δθ _p ( step S15), and thereafter, calculates a rotational position theta _p of the output shaft 2b by first pinion position calculating unit 26 adds the amount of rotational displacement [Delta] [theta] _p at the initial rotational position theta ₀ (step S16).

Then, the steering angle calculation unit 25 calculates the steering angle θ _W of the steered wheels W1 and W2 based on the rotational position θ _p of the output shaft 2b (step S17), and information on the steering angle θ _W is steering assist controlled. The steering wheel position calculation unit 24 calculates the rotation position θ SW of the steering wheel _SW as described above based on the rotation position θ _p of the output shaft 2b (step S19). Information on the rotational position θ _SW of the steering wheel SW is output to the steering return control unit 20 and other control systems (step S20).

Next, in step S21, it is determined whether or not the steering torque T is zero. If the steering torque T is not zero, the process returns to step S16 because the steering operation is being performed by the driver, and the rotational position of the output shaft 2b. While calculating θ _p again, when the steering torque T is zero, that is, when the driver is not performing the steering operation, the second pinion position calculating unit 30 performs the output-side electrical angle θ _e2 and the motor-side electrical angle θ. Load _e3 respectively (step S22, S23), their computes the rotation position theta _p 'of the output shaft 2b on the basis of the output side electrical angle theta _e2 and the motor-side electrical angle theta _e3 (step S24). The second pinion position calculation unit 30 calculates the rotational position θ _p ′ of the output shaft 2b by the same calculation method as the pinion position calculation unit 23 of the first embodiment described above.

In step S25, the rotation position θ _p of the output shaft 2b calculated by the first pinion position calculation unit 29 and the rotation position θ _p ′ of the output shaft 2b calculated by the second pinion position calculation unit 30 are calculated. The abnormality determination unit 31 determines whether or not the absolute value of the difference (| θ _p −θ _p ′ |) is smaller than a predetermined abnormality determination threshold A. If the condition of | θ _p −θ _p ′ | <A is satisfied in step S25, the rotational position θ _p of the output shaft 2b calculated by the first pinion position calculating unit 29 and the second pinion position calculating unit 30 It is determined that there is no abnormality in the rotational position θ _p ′ of the output shaft 2b calculated in step S1, and the rotational position θ _p ′ is substituted for the initial rotational position θ ₀ of the output shaft 2b (step S26). Return to.

On the other hand, if the condition | θ _p −θ _p ′ | <A is not satisfied in step S25, the rotation position θ _p of the output shaft 2b calculated by the first pinion position calculation unit 29 and the second pinion position calculation unit It is determined that an abnormality has occurred in at least one of the rotational positions θ _p ′ of the output shaft 2b calculated in 30, and an abnormality detection signal S6 is output from the abnormality determination unit 31 to the steering assist control unit 21; The calculation process in the angular position calculation unit 26 is terminated. When the abnormality detection signal S6 is input from the abnormality determination unit 31, the steering assist control unit 21 gradually reduces the steering assist torque applied to the rack shaft 3 with time, and stops the steering assist by the electric motor M. To do.

Therefore, according to the present embodiment, substantially the same effect as that of the first embodiment described above can be obtained, and the rotational position θ _p of the output shaft 2b calculated by the first pinion position calculation unit 29 and the first position By detecting an abnormality in the rotational position θ _p ′ of the output shaft 2b calculated by the 2-pinion position calculation unit 30, the abnormality determination unit 31 can improve the reliability of the power steering apparatus.

  Here, it is the technical idea grasped | ascertained from each embodiment mentioned above, Comprising: It describes below with the effect about what was described in the claim.

  (1) The steering wheel side pinion shaft is configured by connecting the input shaft on the steering wheel side and the output shaft on the rack shaft side via a torsion bar, and detects the rotational displacement of the input shaft. A side resolver is provided on the input shaft, and an output side resolver for detecting rotational displacement of the output shaft is provided on the output shaft as the steering wheel side resolver, and output signals of the input side resolver and the output side resolver The power steering device according to (1), further comprising: a torque calculation unit that calculates a steering torque that acts on the steering wheel side pinion shaft.

  According to the technical idea described in (1), the steering angle of the steered wheels is detected using the output-side resolver for detecting the steering torque, which is advantageous in terms of cost.

(2) an initial rotational position computing unit that computes an initial rotational position of the steering wheel side pinion shaft based on the steering wheel side resolver output signal and the motor side resolver output signal;
A rotational displacement amount computing unit for computing a rotational displacement amount from the initial rotational position of the steering wheel side pinion shaft based on the steering wheel side resolver output signal;
A first pinion position calculator that calculates the rotational position of the steering wheel side pinion shaft by adding the rotational displacement amount to the initial rotational position;
A second pinion position calculation unit that calculates the rotational position of the steering wheel side pinion shaft separately from the first pinion position calculation unit based on the steering wheel side resolver output signal and the motor side resolver output signal;
By comparing the rotation position of the steering wheel side pinion shaft calculated by the first pinion position calculation unit with the rotation position of the steering wheel side pinion shaft calculated by the second pinion position calculation unit, the first pinion An abnormality determining unit that determines whether there is an abnormality in the rotational position of the steering wheel side pinion shaft calculated by the position calculating unit and the rotational position of the steering wheel side pinion shaft calculated by the second pinion position calculating unit;
(1) The power steering device according to (1).

  According to the technical idea described in (2), the rotational position of the steering wheel side pinion shaft calculated by the first pinion position calculating unit and the steering wheel side pinion shaft calculated by the second pinion position calculating unit. The reliability of the power steering apparatus can be improved by determining the presence / absence of an abnormality in the rotational position using the abnormality determination unit.

  (3) When the steering torque calculation result in the torque calculation unit is zero, the abnormality determination unit calculates the rotation position of the steering wheel side pinion shaft and the second pinion position calculated by the first pinion position calculation unit. By comparing the rotation position of the steering wheel side pinion shaft calculated by the calculation unit, the rotation position of the steering wheel side pinion shaft calculated by the first pinion position calculation unit and the second pinion position calculation unit are calculated. The power steering device according to (2), wherein the presence or absence of an abnormality in the rotational position of the steering wheel side pinion shaft is determined.

  According to the technical idea described in (3), when the steering torque T is zero, that is, when the steering operation by the driver is not performed and the steering assist is not performed, the processing by the abnormality determination unit is performed. Therefore, the process in the abnormality determination unit and the process for the steering assist are performed at different timings, and the load on the arithmetic processing unit can be reduced.

2 ... Steering wheel side pinion shaft 3 ... Rack shaft 3a ... Motor side rack teeth (motor side rack teeth)
4. Steering wheel side rack and pinion mechanism 7. Output side resolver (steering wheel side resolver)
9. Motor side pinion shaft (motor side pinion shaft)
10. Motor side rack and pinion mechanism (motor side rack and pinion mechanism)
13. Motor side resolver (motor side resolver)
25 ... Rudder angle calculation unit SW ... Steering wheel M ... Electric motor (electric motor)

Claims (2)

A steering wheel side pinion shaft that rotates in accordance with the steering operation of the steering wheel;
An electric motor that generates steering assist force;
A motor-side pinion shaft that is rotationally driven by the motor;
A steering wheel side rack tooth that meshes with the steering wheel side pinion shaft and constitutes a steering wheel side rack and pinion mechanism, and a motor side that meshes with the motor side pinion shaft and has a specific stroke different from that of the steering wheel side rack and pinion mechanism A rack shaft that has motor-side rack teeth that constitute a rack and pinion mechanism, converts the rotation of the steering wheel side pinion shaft and the motor side pinion shaft into a linear motion, and transmits it to the steered wheels;
And the steering wheel side resolver the steering wheel side pinion shaft and outputs a steering wheel-side resolver output signal of the k ₁ cycle every time one rotation,
Together with the motor side pinion shaft and outputs a motor-side resolver output signal of the k ₂ cycles every time one rotation, the motor side pinion shaft via the rack shaft when brought into one revolution the steering wheel side pinion shaft (Θ _a / k ₂ )> (360 / k ₁ ) and (θ _a / k ₂ ) / (360 / k ₁ ) is a non-integer value when the rotation angle is θ _a °. A motor-side resolver configured to be
A steering angle calculation unit that calculates the steering angle of the steered wheels based on the steering wheel side resolver output signal and the motor side resolver output signal;
A power steering device comprising: When the rotation angle of the lock-to-lock of the steering wheel is n ° and the backlash amount of the steering wheel side rack and pinion mechanism in the rotation direction of the steering wheel side pinion shaft is θ _b °, the steering wheel side resolver is , (360 / k ₁ )> (θ _b · n / (θ _a / k ₂ )) is satisfied.

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