JPH1178924A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device which has small number of components, has good assembling ability, and stably supplies steering auxiliary effort to a steering system even when a steering torque sensor fails. SOLUTION: An electric power steering device has two steering torque detecting means 12, 13 consisting of a steering torque sensor and a steering torque detector having a torque signal detector and a failure detecting means, and a control means 15 equipped with a switching means 20 which switches one steering torque detecting means 12 (or 13) to the other steering torque detecting means 13 (or 12) based on failure signals C1 , C2 from the failure detecting means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus for reducing the steering force of a driver by applying an auxiliary torque of an electric motor to a steering system, and in particular, to providing two steering torque detecting means having a failure detecting function. To an electric power steering device.

[0002]

2. Description of the Related Art A conventional electric power steering apparatus is
As disclosed in Japanese Utility Model Laid-Open Publication No. 6-65154, “Power steering device”, a plurality of torque sensors are provided, and a difference between torque signals detected by each of the torque sensors (for example, when two torque sensors are provided) is provided. When the difference between the torque signals is within a predetermined allowable range, an average value of the torque signals is output as a torque signal, and the torque signal is supplied to a booster to drive an electric motor to add an auxiliary torque to a steering system. What is composed is known.

On the other hand, when the difference between the torque signals is outside a predetermined allowable range, the motor is driven based on a torque signal from a torque sensor that outputs a minimum torque signal.

A conventional electric power steering apparatus includes a main torque sensor and a sub torque sensor, as disclosed in Japanese Patent Application Laid-Open No. 8-188166, entitled "Electric Power Steering Controller". The electric motor is driven based on the steering torque thus obtained, and the assist torque is assisted to the steering system.

On the other hand, the sub-torque sensor detects the voltage in conjunction with the main torque sensor, and the control unit detects an abnormality of the main torque sensor from the relationship between the main torque sensor and the sub-torque sensor.

[0006]

Problems to be Solved by the Invention
The electric power steering apparatus disclosed in Japanese Patent Application Laid-Open No. 8-188166 or Japanese Patent Application Laid-Open No. 8-188166 includes a plurality of torque sensors, but detects a failure of the torque sensor by comparing torque signals detected by the two torque sensors. Therefore, it was not possible to determine which of the two torque sensors had failed.

Therefore, when a failure occurs in any one of the two torque sensors, there is a problem that the operation of the device is stopped or an accurate torque signal cannot be obtained.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a steering feeling by detecting a steering torque with the other steering torque sensor even if one of the steering torque sensors fails. An object of the present invention is to provide an electric power steering device which does not affect the electric power steering.

[0009]

According to a first aspect of the present invention, there is provided an electric power steering apparatus comprising: a steering torque sensor and a steering torque detector having a failure detecting unit; The control means includes a switching means for switching to the other steering torque detecting means based on a failure signal from the failure detecting means when one of the steering torque detecting means determines its own failure. It is characterized by having.

[0010] The steering torque detecting means of the electric power steering apparatus according to the present invention comprises a set of a steering torque sensor and a steering torque detector having failure detecting means.
The control unit includes a switching unit that switches to the other steering torque detection unit based on a failure signal from the failure detection unit when one of the steering torque detection units determines its own failure. Therefore, even if one of the steering torque detecting means fails, the apparatus can be continuously operated based on the accurate steering torque by switching to the other steering torque detecting means.

According to a second aspect of the present invention, the steering torque detecting means of the electric power steering apparatus includes an operating element in which each set of the steering torque sensors is displaced in accordance with the steering torque, and an operation for converting the amount of displacement of the operating element into an electric signal. And a coil,
Moreover, the actuator is shared by two sets of steering torque sensors.

The steering torque detecting means according to the present invention comprises:
Since one actuator is shared by the pair of steering torque sensors,
Fewer parts required. Further, the assembly accuracy of the steering torque sensor is improved. Further, since the neutral point adjustment of the two sets of steering torque sensors can be performed simultaneously, the productivity is improved.

According to a third aspect of the present invention, the steering torque detecting means of the electric power steering apparatus includes an operating element in which each set of steering torque sensors is displaced in accordance with the steering torque, and an operation for converting the amount of displacement of the operating element into an electric signal. And a coil,
Moreover, the detection coils of the two sets of steering torque sensors are integrally combined.

The steering torque detecting means according to the present invention comprises:
Since the detection coils of the set are integrally combined, the steering torque sensor can be downsized, and the positional accuracy between the detection coils of the two systems of steering torque sensors can be increased. And one
When two operators are shared, the detection accuracy of the two systems of steering torque sensors can be further improved.

According to a fourth aspect of the present invention, the steering torque detecting means of the electric power steering apparatus is characterized in that the gains of the detection signals of the two sets of steering torque detecting means are different from each other.

The steering torque detecting means according to the present invention comprises:
Since the gains of the detection signals of the sets of steering torque detecting means are different from each other, even if the neutral point of one of the steering torque detecting means is shifted due to machining accuracy or the like, the gain of the steering torque detecting range should be set linearly. Can be.

According to a fifth aspect of the present invention, the steering torque detecting means of the electric power steering device includes an operating element in which each set of the steering torque sensors is displaced in accordance with the steering torque, and a detecting means for converting the amount of displacement of the operating element into an electric signal. A coil and a bobbin around which the detection coil is wound are provided, and a member having a different magnetic permeability from that of the bobbin is interposed between each set of bobbins.

The steering torque detecting means according to the present invention comprises:
Since a member with different magnetic permeability from the bobbin is interposed between the set of bobbins, interference of mutual magnetic fields between the detection coils wound around each bobbin is eliminated, and disturbance of magnetic flux generated between the detection coils is suppressed. can do. Therefore, the detection accuracy of the detection signal is increased. Further, since the two sets of bobbins can be made closer to each other, the combined structure of the two sets of steering torque detecting means can be reduced in size. Therefore, the degree of freedom of the arrangement of the steering torque detecting means is increased.

[0019]

Embodiments of the present invention will be described with reference to the accompanying drawings. The drawings should be viewed in the direction of reference numerals. According to the present invention, two steering torque detecting means having a self-failure detecting function are provided, and even if a failure occurs in one of the steering torque detecting means, the other steering torque detecting means is switched to continue the assist torque to the steering system. It can be supplied.

FIG. 1 is an overall configuration diagram of an electric power steering apparatus according to the present invention. In FIG. 1, an electric power steering apparatus 1 includes a universal joint 3 a, a universal joint 3 a, a steering shaft 2 provided integrally with a steering wheel 17.
The manual steering force generating means (steering system) 6 is connected to the pinion 54a of the rack and pinion mechanism 5 provided in the gear box 4 via the connecting shaft 3 provided with the b.

A rack 7a meshing with the pinion 54a is provided.
The left and right front wheels 9 as steering wheels are connected to both ends via tie rods 8.

Thus, the steering wheel 1
At the time of steering, the front wheels 9 are rolled by manual steering via a normal rack and pinion type manual steering force generating means 6 to change the direction of the vehicle.

In order to reduce the steering force generated by the manual steering force generating means 6, an electric motor 10 for supplying an auxiliary torque is arranged coaxially with the rack shaft 7, and via a ball screw 11 provided coaxially with the rack shaft 7. To make it act on the rack shaft 7.

In the gear box 4, two steering torque detecting means 12 and a steering torque detecting means 13 for detecting the direction and magnitude of the driver's manual steering torque are arranged. The steering torque detecting means 12 and the steering torque detecting means 13 are provided. Provide the control means 15 with analog electric steering torque signals T ₁ and T ₂ corresponding to the steering torque detected by the control means 15.

The steering torque signal T ₁ detected by the steering torque detecting means 12 and the steering torque signal T ₂ corresponding to the same steering torque detected by the steering torque detecting means 13 are set to be equal (T ₁ = T ₂ ). I do.

The vehicle speed sensor 14 detects an electric pulse signal having a frequency corresponding to the speed of the vehicle, and provides a control unit 15 with a vehicle speed signal V.

The control means 15 comprises various arithmetic means, processing means, signal generating means, memory and the like based on a microprocessor, and a target current signal corresponding to the steering torque signal T ₁ or T ₂ corresponding to the vehicle speed signal V. (I _MS) generates the motor control signal corresponding to the target current signal (I _MS) and the deviation between the motor current signal I _MO corresponding to the motor current I _M which the motor current detecting means 19 has detected (negative feedback) V _O (for example, a mixed signal of an ON signal, an OFF signal, and a PWM signal)
Is generated, and the drive of the motor drive means 16 is controlled so that the deviation quickly becomes zero.

The control means 15 has a switching means.
Steering torque detecting means 12 or steering torque detecting means 13
If a failure occurs, the steering torque detecting means 12,
Switching between the steering torque detecting means 12 and 13 based on a failure signal supplied from the failure detecting means of 13, even if one of the steering torque detecting means 12 (or 13) fails, the other steering torque detecting means 13 (or 13). Alternatively, the control is switched to 12) so that the electric motor 10 is controlled to be continuously driven.

The motor driving means 16 is constituted by a bridge circuit composed of switching elements such as four power FETs (field effect transistors) and insulated gate bipolar transistors (IGBTs), and performs PWM based on the motor control signal V _O. outputs motor voltage V _M of (pulse width modulation), the motor 10 is PWM driven.

The motor current detecting means 19 converts the motor current I _M into a voltage using a resistor or a Hall element connected in series with the motor 10, detects the voltage, and detects a motor current signal I _MO corresponding to the motor current I _M. To the control means 15 (negative feedback).

FIG. 2 is a block diagram of a main part of the electric power steering apparatus according to the present invention. In FIG. 2, the electric power steering device 1 includes a steering torque detecting unit 1.
2, 13, a vehicle speed sensor 14, a control means 15, a motor driving means 16, and a motor current detecting means 19.

The steering torque detecting means 12, 13 will be described later in detail. Further, the vehicle speed means 14, the motor driving means 16 and the motor current detecting means 19 have been described with reference to FIG.

In FIG. 2, the control means 15 includes a switching means 20, a target current signal setting means 21, a deviation calculating means 22,
Drive control means 23 is provided.

The switching means 20 has an electronic switch or a switch function of software control.
Selecting one of the steering torque signal T ₂ supplied from the steering torque signal T ₁ and the steering torque detection means 13 is supplied from the selected steering torque signal T ₁ (or, T ₂₎ of the steering torque signal T Is supplied to the target current signal setting means 21.

Further, the switching means 20 changes the steering torque signal T ₁ to the steering torque signal T based on the failure signal C ₁ supplied from the steering torque detection means 12 or the failure signal C ₂ supplied from the steering torque detection means 13. ₂ (or, from the steering torque signal T ₂ steering torque signal T ₁₎ to perform the switching to.

For example, in the initial setting, the steering torque signal T ₁ is selected (indicated by a solid line). If the steering torque detecting means 12 fails for any reason, a failure signal is output from the steering torque detecting means 12. select the steering torque signal T ₂ by supplying the C ₁ to the switching means 20 (broken line).

In the initial setting, the steering torque signal T ₂ is selected (displayed by a broken line), and when the steering torque detection means 13 fails, the steering torque signal T ₁ is selected (displayed by a solid line). May be.

The fault signals C ₁ and C ₂ are formed by, for example, different binary codes or different predetermined pulse numbers.
0 is a switch function of an electronic switch or a soft control to select the steering torque signal T ₂ (or the steering torque signal T ₁ ) when the failure signal C ₁ (or the failure signal C ₂ ) is supplied. Is configured to be switched.

The target current signal setting unit 21 includes a memory, such as a ROM in advance and the vehicle speed signal data V which is set based on experimental values or design values parameters and the steering torque signal data T and the target current signal data I _MS Corresponding data is stored, and the corresponding target current signal data I based on the vehicle speed signal V detected by the vehicle speed sensor 14 and the steering torque signal T (T ₁ , T ₂ ) detected by the steering torque sensor 12 (or 13). _MS is read out and the target current signal _IMS is supplied to the deviation calculating means 22.

The deviation calculation unit 22 includes a subtractor or subtraction function, and the target current signal I _MS supplied from the target current signal setting unit 21, a motor current signal I _MO supplied from the motor current detecting means 19 of the Deviation ΔI (= I _MS −I _MO )
And supplies the deviation signal ΔI to the drive control means 23.

The drive control means 23 includes a PID controller, a motor control signal generation means, etc.
After performing proportional (P), integral (I), and derivative (D) control on the deviation signal ΔI supplied from
A PWM motor control signal V _O corresponding to right steering or left steering of the steering wheel is generated based on a mixed signal obtained by mixing signals subjected to integral / derivative (PID) control, and the motor control signal V _O is _output to the motor driving means 16. To supply.

When the motor control signal V _O is generated, the motor 10 is driven via the motor driving means 16 and the motor 10
Is added to the steering system to reduce the driver's steering force.

FIG. 3 is a block diagram of a main part of the steering torque detecting means according to the present invention. In FIG. 3, the steering torque detecting means 12 includes a steering torque sensor 31 and a steering torque detector 32. The steering torque detecting means 13 has the same configuration as the steering torque detecting means 12. The pulse power supply 30 is provided with a pulse formed by dividing the reference clock of the control means 15 or a steering torque detector 32.
May be provided in the steering torque detecting means 12 and the steering torque detecting means 13, respectively, or may be shared by the steering torque detecting means 12 and the steering torque detecting means 13.

FIGS. 4A and 4B are diagrams showing an embodiment of a steering torque sensor according to the present invention. FIG. 4A is a basic configuration diagram of the steering torque sensor, and FIG. FIG. 2 shows a bridge circuit diagram formed by resistors.

In FIG. 4, the steering torque sensor 31 is
A core 31C (operator) made of a non-magnetic material (for example, aluminum) that is displaced in both directions (X1, X2) from the neutral point, and is disposed symmetrically in the displacement direction of the core 31C, and has an inductance corresponding to the displacement of the core 31C. There constructed from the detection coil 31A and the detection coil 31B varies differential, connect one end of the detection coil 31A and the detection coil 31B, connecting the other end of the detection coil 31A and the detection coil 31B to one end of the reference resistor R _F, respectively and ground and further connecting the other ends of the two reference resistance R _F (GND)
And a bridge circuit 3 shown in FIG.
5 is formed.

Further, a pulse power supply 30 (peak value V _I ) is applied between the connection between the detection coil 31A and the detection coil 31B and the connection between the two reference resistors R _F , and the detection coil 31A and the reference resistance R _F are applied. connection of R _F, and the detection coil 31
B and the reference resistor R _F connection parts are respectively connected to the detection terminals S1, S2
Take out as.

(B) In the equivalent circuit shown in FIG. 5, the inductances of the detection coils 31A and 31B are respectively L1 and L2.
Then, the bridge circuit 3 by applying the pulse power supply 30
5 detection terminals S1 and S2 are ground terminals (GN
Configure LR integrating circuit relative to the D), the detected voltage V _S1, V _S2 becomes the transient response voltage for pulse height V _I.
The detection voltage V _D of the detection terminals S1 and S2 is the detection voltage V
Deviation of _S1 and the V _S2 becomes (V _S1 -V _S2).

FIG. 5 shows a transient response voltage waveform diagram of the steering torque sensor according to the present invention. (A) shows the transient response voltage waveform when the duty of the falling waveform and the rising waveform of the pulse power supply are equal, and (b) shows the transient response voltage waveform when the duty of the falling waveform and the rising waveform of the pulse power supply are different. Show.

FIG. 7A shows that the period (T / 2) of the falling waveform of the pulse power supply is sufficiently longer than the time constant of the integrating circuit.
At time T / 2, the transient response voltage is set so as to reach 0 V. On the other hand, in FIG. 3B, the period (T1) of the falling waveform of the pulse power supply is set short so that the transient response voltage does not reach 0 V. Further, (a) view and (b) in FIG both periods of the rising waveform of the pulse power is sufficiently longer than the time constant of the integrating circuit, the transient response voltage at time T or time T2 is set to reach a peak value V _I I do.

The object on which the steering torque sensor 31 is mounted is displaced, and the core 31C shown in FIG.
If the displacement X1 is displaced toward the 1A side and the inductance L (inductance at the neutral point) of the detection coil 31A decreases to L1 with the displacement X1, for example, the inductance L of the detection coil 31B increases to L2, and the inductance becomes From the relationship of L1 <L2, the time constant (L1 / R _F ) of the transient response voltage V _S1 of the terminal S1 and the terminal S2 becomes smaller than the time constant (L2 / R _F ) of the transient response voltage V _S2 , as shown in FIG. falling and rising with respect to the pulse power of the transient response voltage V _S1 is faster with respect to the transient response voltage V _S2.

When the core 31C is displaced to the X1 side, the detection voltage V _D across the detection terminals S1 and S2 (= V _S1 −V _S2 )
Is detected with a polarity of minus (-) during the fall period of the pulse power supply and with a plus (+) polarity during the rise period of the pulse power supply.
When the core 31C is displaced toward the X2 side, the detection voltage V _D (= V _S1 −V _S2 ) has the opposite relationship to the above, the falling period of the pulse power source is plus (+), Is detected as minus (-).

As described above, the detection voltage V _D (= V _S1 −
V _S2 ), the displacement of X1 and X2 and the detection voltage V
_The direction of displacement can be detected by the sign of _D.

In FIG. 5, when the detection voltage V _D is detected during the falling period of the pulse power supply, the detection voltage V _D (= sign is negative) having the maximum absolute value at time t _M in FIG. V _DMAX-) can be detected, it can be detected to detect the voltage V _D at time T1 in (b) FIG. It should be _noted that by setting the time T1 to t _M in the diagram (b), the same detection voltage V _D (= V _DMAX− ) as in the diagram (a) can be detected.

In FIG. 7A, the detection voltage V _D can be detected during the rising period of the pulse power supply, and the detection voltage V _D having the maximum absolute value (the sign is plus) can be obtained.
_D (= V _{D MAX +} ) can be detected.

[0055] Thus, even in the amount of displacement of the core 31C is the same, by setting to detect the maximum value of the detection voltage V _D, constituting the steering torque sensor 31 with high sensitivity.

In FIG. 3, the steering torque detector 32 is
A torque signal detector 33 and a failure detecting means 34 are provided. The torque signal detector 33 detects the steering torque signal T based on the detection voltages V _S1 and V _S2 supplied from the steering torque sensor 31.
Detect ₁

The torque signal detector 33 outputs the voltages V _T1 and V _T2 corresponding to the detected voltages V _S1 and V _S2 to the failure detecting means 3.
4

FIG. 6 is a block diagram showing an embodiment of a torque signal detector according to the present invention. 6, the torque signal detector 33, a pulse generating circuit 45 supplies a pulse voltage V _I to the steering torque sensor 31, the high frequency contained in the pulse transient response voltage V _S1, V _S2 detected by the steering torque sensor 31 switching noise (N _S) 1-order CR low-pass filter 41A which is removed to output a pulse transient response voltage Va (V _S1, V _S2) of, 41B and the bottom of the pulse transient response voltage Va (V _S1, V _S2) bottom hold circuit 42A which holds and outputs the voltage VT _1, V _T2, 42B
And the difference between the bottom voltage V _T2 and the bottom voltage V _T1 (V _T2 −
V _T1 ) and amplifies by the gain G1 to obtain the deviation voltage Vb.
A differential amplifier 43 for outputting, by inverting the difference voltage Vb, the reference voltage (e.g., 2.5V) consist inverting amplifier 44 for detecting the torque detection voltage V _T which is shifted. The torque detection voltage _VT is the steering torque signal T ₁ shown in FIG. 2 (the steering torque signal T _{2 in} the case of the steering torque detection means 13), and the target current signal setting means 21 shown in FIG. Supplied to

FIG. 7 is a block waveform diagram of each of the torque signal detectors shown in FIG. (A) drawing the pulse voltage V _I output waveform of the pulse generating circuit 45, (b) drawing a pulse transient response voltage V _S1, V _S2 waveform detected by the bridge circuit of the steering torque sensor 31, the pulse voltage V _I fall and output circuit 45B of the pulse generating circuit 45 to rise (for example, switching transistors) includes switching noise N _S of.

(C) shows low-pass filters 41A and 41
It is a pulse transient response voltage Va (V _S1 , V _S2 ) waveform that has passed through B, and the switching noise N _S is removed.
(D) drawing represent a bottom voltage V _T1 and the bottom voltage V _T2 waveform, (e) drawing the deviation voltage V obtained by amplifying the deviation of the bottom voltage V _T2 and the bottom voltage V _T1 to (V _T2 -V _T1) only the gain G1
The b waveform is shown.

FIG. 7F shows a waveform of the torque detection voltage V _{T obtained} by inverting the deviation voltage Vb and shifting the reference voltage (for example, 2.5 V). When the torque (T) is 0, the torque detection voltage V _T is obtained. _T is a reference voltage (2.5 V) and changes linearly according to the direction and magnitude of the torque (T).

[0062] Thus, the torque signal detector 33 configured to detect a value corresponding to the torque acting on the steering torque sensor 31 (T) (absolute values and direction) in absolute value of the torque detection voltage V _T , for example, a torque when the (T) is applied to the left torque detection voltage V _T is reduced from 2.5V, the torque detection voltage V _T to act in the right direction in FIG. 7, such as to increase from 2.5V (f) The characteristic represented by the straight line shown in the figure is set.

[0063] Thus, by storing in a memory such as a ROM conversion table of pre-designed values and torque obtained based on the experimental value (T) and the torque detection voltage V _T as the data, a torque signal detector 33 detects Torque detection voltage V
_The torque (T) acting on the steering torque sensor 31 can be detected based on _T (absolute value).

[0064] Incidentally, the steering torque detector 32 driven by 5V power supply, for example, the torque detection voltage V _T with respect to the maximum value of the left steering 0.2V, the torque detection voltage V _T with respect to the maximum value of the rightward steering to 4.8V By setting, from 0.2V to 4.8
The torque detection voltage V _T in the range of V can be output as a steering torque signal T _1.

In FIG. 3, the failure detecting means 34 determines the failure of the steering torque detecting means 12 based on the bottom voltages V _T1 and V _T2 , and in the case of a failure, for example, a two-signal code or a predetermined number of pulses. and outputs a fault signal C _1.

FIG. 8 is a block diagram showing one embodiment of the failure detecting means according to the present invention. 8, the failure detection means 34 includes an average value calculation means 35, a comparison means 36, and a failure signal generation means 37.

The average value calculation means 35 is constituted by an arithmetic circuit having an average value calculation function, and the average value V _H ｛= (V _{T1) of the} bottom voltages V _T1 and V _T2 supplied from the torque signal detector 33.
+ V _{T 2} ) / 2}, and compares the average signal V _H with the comparing means 3
6

[0068] Comparison means 36, for example constituted by the window comparator, the average value signal V _H which is supplied from the average value calculating means 35, compares the reference range values V _TK set in advance, the average value signal V _H is If it exceeds the reference range value V _TK , for example, an H-level failure determination signal H _O is supplied to the failure signal generation means 37.

The reference range value V _TK is, for example, an average value V _H ｛= (V _T1 +) of the bottom voltages V _T1 and V _T2 shown in FIG.
V _T2 ) / 2}, for example, a value obtained by adding an allowable value to 2.5 V.

The method of detecting a failure is not limited to the method described above. For example, whether the bottom voltages V _T1 and V _T2 are within allowable values (for example, 0.2 V ≦ V _T1 , V _T2 ≦ 4.8 V) Alternatively, it may be detected based on whether or not.

The fault signal generating means 37 is composed of a memory such as a ROM, for example, and stores fault signal data of a binary code in advance, and receives the H level fault determination signal H _O from the comparing means 36. , and outputs a fault signal C _1.

It should be noted that the failure detecting means 34 is
You may comprise so that it may be built in.

The structure of the steering torque detecting means 13 is the same as that of the steering torque detecting means 12, and a description thereof will be omitted. Also, the steering torque detecting unit 13 sets the binarization code data of the failed signal C ₂ to the fault signal C ₁ and different values.

As described above, the steering torque detecting means 12 of the electric power steering apparatus 1 according to the present invention includes two sets of the steering torque sensor 31 and the steering torque detector 32 having the failure detecting means 34. Make up,
The control means 15 includes a switching means 20 for switching to the other steering torque detecting means 13 based on the failure signal C ₁ from the failure detecting means 34 when one of the steering torque detecting means 12 determines its own failure. Therefore, even if one of the steering torque detecting means 12 is out of order, it is possible to switch to the other steering torque detecting means 13 and to continue operating the device.

FIG. 9 is a structural view of a main part of the electric power steering apparatus according to the present invention, and shows an assembled state in which a part around the gear box 4, the electric motor 10, and the ball screw 11 shown in FIG.

FIG. 10 is a sectional view taken along line 10-10 of FIG. The electric power steering device 1 rotatably supports a movable housing 51 in a fixed housing (corresponding to the gear box shown in FIG. 1) 4, rotatably supports an input shaft 52 in the movable housing 51, and An output shaft 54 is coupled to the fixed housing 4 via a coupling 53, and the output shaft 54 is rotatably supported by the fixed housing 4. The rotation center of the movable housing 51 and the rotation center of the input shaft 52 are eccentric to each other.

The movable housing 51 is a composite housing in which an upper movable housing 55 and a lower movable housing 56 are concentrically overlapped and bolted together. The input shaft 52 is
A first shaft 57 connected in series to the steering wheel 17 (see FIG. 1) via a universal joint or the like.
And a torsion bar 58 and a second shaft 59. Specifically, the input shaft 52 is configured such that the torsion bar 58 is inserted into the tubular first shaft 57 and the upper part of the torsion bar 58 is moved to the first position.
And a lower portion of the torsion bar 58 is serrated to an upper portion of the second shaft 59. The torsion bar 58 is a member that literally generates a torsion angle with respect to the torque, and generates a relative torsional displacement between the first shaft 57 and the second shaft 59. The output shaft 54 has a pinion 54a forming a part of the rack-and-pinion mechanism 5, and the pinion 54a
It is engaged with the rack 7a of the rack shaft 7. In the figure,
Reference numeral 91 denotes a rack guide, and S denotes an axis of a worm shaft described later.

Incidentally, the movable housing 51 is provided with two sets of steering torque detecting means 12 and 13 shown in FIG. In FIGS. 10 and 11, only the detection coils 31A and 31B of the steering torque sensor 31 and the core 31C forming the actuator are shown among the components of the steering torque detection means 12 and 13. Steering torque detecting means 12,
13 is a first shaft 57 connected by a torsion bar 58.
The steering torque of the steering system (corresponding to the manual steering force generating means 6 shown in FIG. 1) is detected by detecting the relative torsional displacement between the steering shaft and the second shaft 59.

FIG. 11 is a sectional view of a steering torque sensor according to the present invention. Here, for convenience of explanation, FIGS.
The steering torque sensor 31 of the steering torque detecting means 12 shown in FIG.
This will be described as "first steering torque sensor 31a", and the steering torque sensor 31 of the steering torque detecting means 13 will be described as "second steering torque sensor 31b".
Also, the detection coil 31 of the first steering torque sensor 31a
A and 31B are referred to as “first coil 31Aa” and “first coil 31Ba”, respectively, and the second steering torque sensor 31b
Are referred to as the “second coil 31”.
Ab "and" the second coil 31Bb ".

The upper movable housing 55 has a substantially cylindrical bobbin 61 integrally formed therein. Bobbin 61
Is divided into upper and lower two stages, and one of the first coils 31A is arranged in the upper stage.
a, and the other first coil 31Ba is wound on the lower stage. Moreover, the bobbin 61 is formed by further winding one of the second coils 31Ab around the outer periphery of the upper first coil 31Aa, and further winding the other second coil 31Bb around the outer periphery of the lower first coil 31Ba. is there.

The steering torque detecting means 12 (see FIG. 2) having the first coils 31Aa and 31Ba
Of the second coils 31Ab, 31Bb
(See FIG. 2)
Connect to terminal 63a of coupler 63. The first and second couplers 62 and 63 are formed integrally with the upper movable housing 55.

The first coils 31Aa, 31Ba and the second
The coils 31Ab and 31Bb are shared by one core 31.
The amount of displacement of the C (operator) in the axial direction is independently converted into an electric signal. In other words, the first steering torque sensor 31a and the second steering torque sensor 31b share one annular core 31C.
C is integrally attached to the outer periphery of the slider 64.
For this reason, the first and second steering torque sensors 31a, 31b
Can be adjusted at the same time.

The substantially cylindrical slider 64 has a first shaft 5
7 and the second shaft 59. Slider 6
The connecting structure 4 forms an inclined groove 64a and a vertically long straight groove 64b on the slider 64, and engages the inclined groove 64a with the pin 57a of the first shaft 57.
b is engaged with the pin 59a of the second shaft 59.
For this reason, the slider 64 with the core 31 </ b> C
It can be displaced in the axial direction according to the relative torsional displacement of the second shaft 59 and the shaft 7. In the drawing, reference numeral 65 denotes a return spring for resiliently pushing the slider 64 in the axial direction.

With the above structure, when the slider 64 is displaced in the axial direction, the core 31C is also displaced in the axial direction. Core 3
The first coils 31Aa and 31B correspond to the displacement amount of 1C.
a and the inductances of the second coils 31Ab and 31Bb change differentially.

The first coil 31A is attached to the movable housing 51.
a, 31Ba and the second coils 31Ab, 31Bb are attached.
The 1Ba and the second coils 31Ab and 31Bb can be integrally assembled around the input shaft 52 that rotates.

FIG. 12 is a sectional view taken along line 12-12 of FIG. 10, and the second shaft is located at a position eccentric by a distance L in the direction opposite to the worm shaft 33 with respect to the rotation center O of the movable housing 51 in plan view. This indicates that 59 rotation centers A have been set. It should be noted that only the second shaft 59 is shown for the input shaft 52, and the first and second steering torque sensors 31 related thereto are shown.
a, 31b, the first shaft 57, and the torsion bar 58 are omitted.

The electric power steering apparatus 1 has a variable steering angle ratio control mechanism 70.
(1) The steering angle ratio is changed by changing the rotation center A of the input shaft 52 by rotating the movable housing 51 via the worm gear mechanism 72 by the steering angle ratio control motor 71, and (2) The displacement amount of the rotation center A of the input shaft 52 is detected by a displacement sensor 74, and the steering angle ratio control electric motor 71 is controlled based on the detection signal so that the steering angle ratio control is stably performed. . Note that the steering angle ratio is a ratio of the steering angle of the steered wheels to the steering angle of the steering wheel 17 (see FIG. 1). Hereinafter, the variable steering angle ratio control mechanism 70 will be described with reference to FIGS.

The worm gear mechanism 72 includes a worm shaft 73 connected to an output shaft 71a of a steering angle ratio control motor 71,
Wheel 5 that meshes with worm 73a of worm shaft 73
6a. The wheel 56a is a tooth formed on an outer peripheral portion of the lower movable housing 56. Displacement sensor 74
Is for indirectly detecting the amount of displacement of the axis A of the input shaft 52 by detecting the amount of change in the cam surface 56b formed on the outer peripheral portion of the lower movable housing 56.
The detection end 74a in contact with 6b is composed of a potentiometer that moves forward and backward.

FIG. 13 is an exploded perspective view around the coupling according to the present invention. The coupling 53 includes a second shaft 59
An upper flange 81 integrally formed at a lower end of the lower flange 83, a lower flange 83 connected to the upper flange 81 via a plurality of balls 82, and a lower extension of the lower flange 83 connected to a connection hole 54b of the output shaft 54. And a connecting shaft 84. Specifically, the coupling 53 forms a connecting groove 81a having a tapered side sectional view at the lower end surface of the upper flange 81, and a connecting groove 83a having a tapered side sectional view at the upper end surface of the lower flange 83, These connecting grooves 81a,
.. Are arranged in a row on a connecting groove 8a.
The upper and lower flanges 81 and 83 are connected by contacting the tapered surfaces 1a and 83a. For this reason, the coupling 53 is connected to the second shaft 59 so as to be relatively movable in the direction perpendicular to the axis and not to rotate relatively.

The connecting hole 54b is located eccentrically from the output shaft 54, and the connecting shaft 84 is located eccentrically from the second shaft 59. The connecting hole 54b and the connecting shaft 84 are rotatably connected to each other. It was done. In the figure, reference numeral 85 denotes a plate-shaped ball retainer.

Next, the variable steering angle ratio control mechanism 70 having the above configuration
Will be described with reference to FIGS. 13 and 14. FIG.
In 3, when the second shaft 59 rotates, the connection shaft 84 rotates around the rotation center B of the output shaft 54 by the action of the balls 82 of the coupling 53. Therefore, the rotation of the second shaft 59 is transmitted to the output shaft 54.

FIG. 14 shows a worm gear mechanism according to the present invention,
FIG. 4 is an explanatory diagram of a relationship between a lower movable housing and a second shaft. When the worm shaft 73 is rotated forward and backward, the lower movable housing 56 is rotated forward and backward within the range of the rotation angle θ. Since the rotation center A of the second shaft 59 is eccentric from the rotation center O of the lower movable housing 56, it is displaced in the range of A _{1 to} A _{2 in accordance} with the rotation angle θ of the lower movable housing 56.

Returning to FIG. 13, the description will be continued. Second axis 5
The eccentric distance from the rotation center A of the output shaft 54 to the rotation center B of the output shaft 54 is a, and the rotation center B of the output shaft 54 is
The eccentric distance to the point of action C is denoted by b. When the rotation center A of the second shaft 59 is displaced in the range of A _{1 to} A ₂ , the eccentric distance a changes correspondingly. On the other hand, the output shaft 5
The rotation center B of No. 4 does not change. If the eccentric distance a changes, the rotation angle of the output shaft 54 changes with respect to the rotation angle of the second shaft 59. As a result, the steering angle ratio changes.

Next, a modification of the steering torque sensor 3 will be described with reference to FIGS. The same components as those in the above embodiment are denoted by the same reference numerals, and description thereof will be omitted. FIG. 15 is a cross-sectional view of a steering torque sensor (first modified example) according to the present invention. The first and second steering torque sensors 31a and 31b of the first modified example have four coils (first and second coils).
Coils 31Aa, 31Ba and a second coil 31Ab,
31Bb) are piled up and down in four stages, and an annular core 31C (first
It is characterized in that two cores 31Ca and two second cores 31Cb) are provided above and below.

Specifically, one cylindrical bobbin 61 is divided into four upper and lower stages, and the first coil 31Aa, the first coil
Coil 31Ba, second coil 31Ab, second coil 31
It is wound on each stage in the order of Bb. The slider 64
First core 31C for first coils 31Aa, 31Ba
a and second cores 31Cb for the second coils 31Ab and 31Bb are mounted in two upper and lower stages. The shapes, dimensions and materials of the two cores 31Ca and 31CbB are the same.

FIG. 16 is a sectional view of a steering torque sensor (second modification) according to the present invention. The first and second steering torque sensors 31a and 31b of the second modification have a configuration obtained by further modifying the first modification of FIG.
1Aa, a clearance (gap) [delta] ₁ between the 31Ba and the first cores 31Ca, a second coil 31Ab, and a gap [delta] ₂ between the 31Bb and second core 31Cb, characterized in that changed. For example, the outer diameter of the first core 31Ca, by setting smaller than the outer diameter of the second core 31Cb, the gap [delta] ₁ is greater than the gap [delta] _2. Gain of the detection signal of the second torque sensor 31b clearance [delta] ₁ is large is smaller than the gain of the detection signal of the first torque sensor 31a.

FIG. 19 is a characteristic diagram of the steering force-steering torque signal of the steering torque detecting means using the steering torque sensor shown in FIG. (A) is a characteristic diagram of two steering torque sensors having the same steering force-steering torque signal T (gain of the detection signal), and (b) is a two steering torque sensor having different steering force-steering torque signal T characteristics. FIG. In addition,
The T ₂ characteristics of (a) and (b) indicate the deviation from the center value (2.5 V) generated due to the processing accuracy of the steering torque sensor (the steering force is 0 and the steering torque signal T is 2.5 V + Δ).
T).

(A) In the figure, the T ₁ characteristic indicates that the steering force is 0.
Steering torque signal T in (neutral point) is the center value 2.5V, by the steering torque detection range of steering force -T _M (e.g., counterclockwise steering) from + T _M (e.g., clockwise steering) , Change linearly.

On the other hand, the T ₂ characteristic indicates that the steering force is 0 (neutral point).
And the steering torque signal T has a center value of 2.5 V + ΔT,
Until the steering force F _A is changed linearly (linear), since the steering force F _A above steering torque signal T is saturated,
Affects steering feeling.

In order to eliminate the influence of the steering feeling due to the saturation of the steering torque signal T, the T ₂ characteristic in FIG.
The gain of the detection signal as the second torque sensor 31b shown in FIG. 16 is lower than the first torque sensor 31a, set to the steering force becomes linear (linear) by the steering torque detection range from -T _M + T _M I do.

FIG. 17 is a sectional view of a steering torque sensor (third modification) according to the present invention. The first and second steering torque sensors 31a and 31b of the third modification have a configuration obtained by further modifying the first modification of FIG.
A member 92 having a different magnetic permeability is interposed between Ba and the second coil 31Ab. Specifically, the bobbin 61 is divided into upper and lower parts, and members 92 having different magnetic permeability are interposed between the divided parts. The members having different magnetic permeability may be air layers.

FIG. 18 is a sectional view of a steering torque sensor (fourth modification) according to the present invention. The steering torque sensor 3 of the fourth embodiment has a configuration obtained by further modifying the third embodiment of FIG. 17 described above, and includes a first coil 31Ba and a second coil 31A.
b, a plurality of members 92A having different magnetic permeability from each other,
92B and 92C are interposed.

In this embodiment, the number of the microprocessors constituting the control means is one. However, the present invention is applied to an electric power steering device using one microprocessor for each of the main control device and the sub control device. Can also be applied.

Further, in this embodiment, the transient response voltage of the pulse power supply is detected by using the detection coil and the resistor in the steering torque sensor. However, the primary coil is driven by the AC power supply using the differential transformer. Alternatively, the differential output of the secondary coil may be detected.

[0105]

As described above, the steering torque detecting means of the electric power steering apparatus according to the first aspect is constituted by two sets of a steering torque sensor and a steering torque detector having a failure detecting means. In addition, the control means
When one of the steering torque detecting means determines its own failure, there is provided switching means for switching to the other steering torque detecting means based on a failure signal from the failure detecting means. Also, since the device can be switched to the other steering torque detecting means and the device can be continuously operated, the steering assist force can be stably supplied to the steering system even if the steering torque sensor fails.

In the steering torque detecting means of the electric power steering apparatus according to the second aspect, one actuator is commonly used for two sets of steering torque sensors, so that the number of parts can be reduced. For this reason, the assembling accuracy of the steering torque sensor can be improved, and the neutral point adjustment of the two sets of steering torque sensors can be performed simultaneously, so that the productivity can be improved.

In the steering torque detecting means of the electric power steering apparatus according to the third aspect, since the two sets of detecting coils are integrally combined, the steering torque sensor can be reduced in size and the position between the two systems of steering torque sensors can be reduced. Accuracy can be improved. In addition, the detection accuracy of the two systems of steering torque sensors can be further improved by sharing one actuator.

The steering torque detecting means of the electric power steering apparatus according to claim 4 makes the gains of the detection signals of the two sets of steering torque detecting means different from each other, and the neutral point of one of the steering torque detecting means is changed depending on machining accuracy or the like. Even in the case of deviation, the gain of the steering torque detection range can be set linearly, so that it is possible to prevent a decrease in steering feeling.

In the steering torque detecting means of the electric power steering apparatus according to the fifth aspect, since a member having a different magnetic permeability from the bobbin is interposed between the two sets of bobbins, mutual detection between the detecting coils wound on the respective bobbins is performed. The disturbance of the magnetic field generated between the detection coils can be suppressed by eliminating the interference of the magnetic field.
Therefore, the detection accuracy of the detection signal is increased. Further, since the two sets of bobbins can be made closer to each other, the combined structure of the two sets of steering torque detecting means can be reduced in size. Therefore, the degree of freedom of the arrangement of the steering torque detecting means is increased.

Accordingly, it is possible to provide an electric power steering apparatus which has a small number of parts, is excellent in assemblability, and can stably supply a steering assist force to the steering system even if the steering torque sensor fails.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an electric power steering device according to the present invention.

FIG. 2 is a block diagram of a main part of an electric power steering apparatus according to the present invention.

FIG. 3 is a block diagram of a main part of a steering torque detecting unit according to the present invention.

FIG. 4 is a configuration diagram of an embodiment of a steering torque sensor according to the present invention.

FIG. 5 is a transient response voltage waveform diagram of the steering torque sensor according to the present invention.

FIG. 6 is a block diagram of a torque signal detector according to an embodiment of the present invention.

FIG. 7 is a block waveform diagram of each torque signal detector shown in FIG. 6;

FIG. 8 is a block diagram showing an embodiment of a failure detecting means according to the present invention.

FIG. 9 is a configuration diagram of a main part of an electric power steering device according to the present invention.

FIG. 10 is a sectional view taken along line 10-10 of FIG. 9;

FIG. 11 is a sectional view of a steering torque sensor according to the present invention.

FIG. 12 is a sectional view taken along line 12-12 of FIG. 10;

FIG. 13 is an exploded perspective view around a coupling according to the present invention.

FIG. 14 is an explanatory diagram showing a relationship between a worm gear mechanism, a lower movable housing, and a second shaft according to the present invention.

FIG. 15 is a cross-sectional view of a steering torque sensor (first modification) according to the present invention.

FIG. 16 is a cross-sectional view of a steering torque sensor (second modification) according to the present invention.

FIG. 17 is a sectional view of a steering torque sensor (third modification) according to the present invention.

FIG. 18 is a sectional view of a steering torque sensor (fourth modification) according to the present invention.

19 is a characteristic diagram of a steering force-steering torque signal characteristic of a steering torque detecting unit using the steering torque sensor shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electric power steering device, 2 ... Steering shaft, 3 ... Connection shaft, 4 ... Gear box, 5 ... Rack and pinion mechanism, 6 ... Manual steering force generation means, 7 ... Rack shaft, 8 ... Tie rod, 9 ... Left and right Front wheel, 10 ... electric motor,
11 ... ball screw, 12, 13 ... steering torque detecting means,
14 vehicle speed sensor, 15 control means, 16 motor drive means, 17 steering wheel, 19 motor current detection means, 20 switching means, 21 target current signal setting means, 22 deviation calculation means, 23 drive Control means, 31
(31a, 31b) ... steering torque sensor, 31A (31
Aa, 31Ab), 31B (31Ba, 31Bb) ... detection coil, 31C ... core (operator), 32 ... steering torque detector, 33 ... torque signal detection means, 34 ... failure detection means, 35 ... average value calculation means, 36: comparison means, 37: failure signal generation means, 92, 92A to 92C: members having different magnetic permeability.

Claims (5)

[Claims] An electric motor for applying an auxiliary torque to a steering system, a steering torque detecting means for detecting a steering torque of the steering system, and controlling the driving of the electric motor based on at least a steering torque signal from the steering torque detecting means. An electric power steering device comprising: a control unit that outputs a motor control signal to be driven; and a motor drive unit that drives the motor based on the motor control signal. The steering torque detection unit includes: a steering torque sensor; And a steering torque detector having
And a control unit configured to switch to the other steering torque detection unit based on a failure signal from the failure detection unit when one of the steering torque detection units determines its own failure. An electric power steering device, comprising: 2. The steering torque sensor of each of the above sets, comprising: an operating element that is displaced in accordance with a steering torque; and a detection coil that converts an amount of displacement of the operating element into an electric signal. The electric power steering apparatus according to claim 1, wherein the power steering apparatus is shared by two sets of steering torque sensors. 3. The steering torque sensor of each of the above sets includes an operator that is displaced in accordance with a steering torque, and a detection coil that converts an amount of displacement of the operator into an electric signal. 2. The electric power steering apparatus according to claim 1, wherein the detection coils of the steering torque sensor are integrally combined. 4. The electric power steering apparatus according to claim 1, wherein said two sets of steering torque detecting means have different gains of detection signals. 5. The steering torque sensor of each set includes an operator that is displaced in accordance with a steering torque, a detection coil that converts an amount of displacement of the operator into an electric signal, and a bobbin that winds the detection coil. 2. The electric power steering apparatus according to claim 1, wherein a member having a different magnetic permeability from the bobbin is interposed between each pair of bobbins.