JP2003329524A - Torque detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that, in a torque detector for detecting a torque by detecting an impedance change generated in a magnetic coil surrounding a magnetic body, the impedance is hard to adjust, and that its detection accuracy is unsatisfactory. <P>SOLUTION: A first rotation angle sensor 6 and a second rotation angle sensor 7 surround an input shaft 2 and an output shaft 3. When a sine-wave output S1 and a cosine-wave output C1 from the sensor 6 and a sine-wave output S2 and a cosine-wave output C2 from the sensor 7 are used so as to compute S1 C1-C1 S2, a sine waveform changed by an angle of twist Δθ between both sensors 6, 7 is obtained without depending on the rotation angles of the sensors 6, 7, and the torque is detected. On the basis of a comparison of an input voltage with an output voltage of the sensor 6 (or 7), a rotation angle (a relative position) of the input shaft 2 (or the output shaft 3) is detected. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque detecting device, and is used, for example, in a torque detecting device for detecting a torque applied to a steering shaft in an electric power steering device of an automobile.

[0002]

2. Description of the Related Art Generally, in an electric power steering apparatus, a magnetic body is provided on an input shaft and an output shaft connected through a torsion bar, and impedance change generated in an electromagnetic coil surrounding the magnetic body is detected. The torque is detected, and the assist force of the electric motor is adjusted according to the detected torque. However, there is a problem that the impedance adjustment is complicated and the detection accuracy is poor. In addition, there is a problem that steering angle information cannot be obtained.

Therefore, a rotation angle sensor for detecting the rotational position is provided on each of the input and output shafts, and the differential angle between the input and output shafts is detected using the outputs of these rotation angle sensors. There is provided a torque detection device for detecting torque (for example, Japanese Patent Laid-Open No. 2001-194251,
And Japanese Patent Laid-Open No. 2001-272204).

[0004]

However, the torque detecting device of the above publication has a drawback in that the input side rotor and the output side rotor need a means for converting the rotational angle output into an angle. For example, sin θ, cos θ for rotation angle θ
Two rotation angle sensors (generally resolvers) capable of outputting analog signals are used, and the sin θ signal and the cos θ signal from each rotation angle sensor are input to a control unit such as a microcomputer. The torque difference may be detected based on the angle difference between the two sensors. In this case, generally, the rotation of each rotation angle sensor is calculated using the equation tan ^-1 (sin θ / cos θ). The angles θ1 and θ2 are obtained, and the difference (θ1 −θ2) is obtained.

However, the control unit such as the microcomputer is
Since there is a limit to the resolution when capturing the θ and cos θ signals, there are drawbacks that the torque resolution cannot be obtained and that the control load of the microcomputer becomes high. By the way, in the electric power steering apparatus, in addition to the magnitude of the torque applied to the steering member such as the steering wheel, it is necessary to detect the direction of the torque, that is, the left or right direction of steering.

For example, in the torque detecting device proposed in Japanese Patent Laid-Open No. 2000-352502, the rotation angle of the input shaft is compared with the rotation angle of the output shaft, and the torque is increased in the direction in which the input shaft is ahead. It is decided that it has been added. On the other hand, on the steering shaft of the running vehicle, along with the normal torque (steering torque) applied from the input shaft on the steering wheel side in response to the steering operation, the road surface reaction force applied to the steering wheel is output by the steering mechanism side. It acts as input torque from the shaft (hereinafter referred to as reverse input torque).

Such a reverse input torque transmits information from the road surface to the driver and is an important element.
The reverse input torque in a frequency range higher than necessary causes a problem that the driver feels uncomfortable or anxious in the form of steering wheel vibration. The present invention has been made in view of the above problems, and an object of the present invention is to provide a torque detection device having a high torque resolution and capable of reducing a control load. Another object of the present invention is to provide a torque detection device capable of determining from which side of the input member and the output member the torque is input.

[0008]

Means for Solving the Problems and Effects of the Invention In order to achieve the above object, the invention according to claim 1 has an input member and an output member which are coaxially and relatively rotatably connected to each other via a torsion bar. Torque detection including first and second rotation angle sensors provided and a torque calculation unit that calculates torque based on sine wave output and cosine wave output obtained from the first and second rotation angle sensors, respectively In the device, the torque calculation unit may calculate a product of a sine wave output of the first rotation angle sensor and a cosine wave output of the second rotation angle sensor, a cosine wave output of the first rotation angle sensor, and a second rotation angle. It is characterized in that the torque is calculated based on the difference between the product of the angle sensor and the output of the sine wave.

The present invention has the following operational effects. That is, assuming that the rotation angle of the input member is θ and the output member is displaced from the input member by the twist angle of Δθ, the sine wave output S1 and the cosine wave output C1 obtained from the first rotation angle sensor are They are represented by Esin θ and Ecos θ, respectively (E: voltage amplitude). On the other hand, the sine wave output S2 and the cosine wave output C2 obtained from the second rotation angle sensor are represented by Esin (θ-Δθ) and Ecos (θ-Δθ), respectively.

Here, S1 · C2−C1 · S2 = Esin θ × Ecos (θ−Δθ) −Ecos θ × Esin (θ−Δθ) = 0.5E ² [sin (2 θ−Δθ) + sin (Δθ) ] −0.5E ² [sin (2 θ−Δθ) −sin (Δθ)] = E ² sin (Δθ), which does not depend on the rotation angle θ of the input member, and is determined by the twist angle Δθ of the output member with respect to the input member. A varying sin waveform can be obtained, and the torque is detected based on the phase angle difference (that is, the twist angle Δθ) thus obtained.

In the conventional torque sensor, since the sine wave output and the cosine wave output of each rotation angle sensor are input to the control unit such as a microcomputer to detect the torque, the torque resolution is limited and the control load of the microcomputer is limited. However, in the present invention, the above formula (S1 · C2-C1 ·
Since the torque may be calculated based on S2) and the calculation result may be output to the control unit such as a microcomputer, the torque resolution can be increased and the control load of the control unit can be reduced.

According to a second aspect of the present invention, in the first aspect, the rotation angle of at least one of the input member and the output member is calculated based on the output from at least one of the first and second rotation angle sensors. It is characterized by further comprising a rotation angle calculation unit. In the present invention, the rotation angle, which is an essential function of the rotation angle sensor, can be detected by an absolute value. The rotation angle can be easily detected by using the main elements of the torque detection device, and downsizing and cost reduction can be achieved by reducing the number of parts.

According to a third aspect of the present invention, in the first or second aspect, the angular velocity or the angular acceleration of each of the input member and the output member is based on the rotation angle detected by the first and second rotation angle sensors. And a relationship between the angular velocities or the angular accelerations calculated by the calculating means is used to determine whether the torque is due to an input from the input member side or an input from the output member side. It is characterized by further comprising a determination means. In the present invention, it is possible to determine whether the torque is due to the input from the input member side or the input from the output member side. Therefore, for example, when the present torque detection device is applied to an electric power steering device of a vehicle, it is determined whether the torque is due to an input from a steering member or an input from a steering mechanism, and steering is performed based on the determination result. It is possible to drive and control the auxiliary motor.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a schematic configuration of an electric power steering device (EPS) including a torque detection device according to an embodiment of the present invention. Referring to FIG. 1, the electric power steering apparatus 1 includes an input shaft 2 as an input member connected to a steering member such as a steering wheel (not shown), and an output member connected to a steering mechanism such as a rack and pinion mechanism. Output shaft 3 and a torsion bar 4 connecting the input shaft 2 and the output shaft 3 coaxially with each other so as to be relatively rotatable. The input shaft 2, the torsion bar 4, and the output shaft 3 constitute a steering shaft 11.

The torque detecting device 5 detects the steering torque based on the relative rotational displacement amount between the input shaft 2 and the output shaft 3 via the torsion bar 4. The torque detection device 5 is
First and second resolvers 6, 7 as rotation angle sensors provided around the input shaft 2 and the output shaft 3, respectively.
And signals from these first and second resolvers 6 and 7 (sine wave outputs S1 and S2 and cosine wave output C1, which will be described later).
The torque calculation unit 12a calculates the torque based on C2).

The torque calculator 12a is included in the processing circuit 12, and the processing circuit 12 includes the input shaft 2 and the output shaft 3.
Rotation angle calculation units 12b and 12c for detecting the respective rotation angles (absolute positions) of the. Rotation angle calculator 1
2b is a voltage of the input shaft 2 based on a comparison between the voltage on the primary side of the first resolver 6 (one of the orthogonal input voltages, e11 for example) and the voltage on the secondary side (for example, sine wave output S1). Detects the rotation angle (absolute position). Similarly, the rotation angle calculation unit 12c compares the voltage on the primary side of the second resolver 7 (one of the orthogonal input voltages, for example, e21) with the voltage on the secondary side (for example, sine wave output S2). Based on this, the rotation angle (absolute position) of the output shaft 3 is detected.

The torque detection signal from the torque calculation unit 12a and the rotation angle detection signals from the rotation angle calculation units 12b and 12c are given to the control unit 8. The control unit 8 controls the voltage applied to the electric motor 10 for assisting steering via the driver 9 based on the torque detection signal, the rotation angle detection signal, the vehicle speed detection signal, and the like. The rotation of a rotating shaft (not shown) of the electric motor 10 is transmitted to the output shaft 3 via a reduction mechanism such as a worm gear mechanism to assist steering.

Each of the first resolvers 6 is an annular rotor (rotor) 1 which is attached to an input shaft 2 so as to rotate integrally therewith.
3 and an annular stator (stator) 15 that surrounds the rotor 13 and is fixed to the housing 14 of the electric power steering apparatus 1, for example. The second resolver 7 has the same configuration as the first resolver 6, but differs from the first resolver 6 in that its rotor 13 is fixedly rotatably attached to the output shaft 3.

Referring to FIG. 2A, the rotor 13 and the stator 15 of the first resolver 6 are electrically connected to each other by 90 degrees.
Two coils 13a, 13b and 15a, 15 that are offset from each other
b is arranged. For example, with the rotor 13 as the primary side, a sine wave input e11 and a cosine wave input e12 (corresponding to input voltages that are orthogonal to each other) are applied to the coils 13a and 13b to excite them, and the coils 15 of the stator 15 on the secondary side
sine wave output S1 from a and 15b respectively as output voltage
And the cosine wave output C1.

Similarly, referring to FIG. 2B, in the second resolver 7, for example, the rotor 13 is used as the primary side of each coil 1
A sine wave input e21 and a cosine wave input e22 (corresponding to input voltages that are orthogonal to each other) are applied to the coils 3a and 13b to excite them, and the coils 15a and 15 of the stator 15 serving as the secondary side are excited.
A sine wave output S2 and a cosine wave output C2 are taken out from each of b as output voltages. In each resolver 6 and 7, the stator 15 may be the primary side and the rotor 13 may be the secondary side.

Next, the torque calculation unit 12 of the processing circuit 12
The processing in a will be described. That is, the rotation angle of the rotor 13 of the first resolver 6 is θ, and the second resolver 7 is
If the rotor 13 of the first resolver 6 is deviated from the rotor 13 of the first resolver 6 by a twist angle of Δθ, two orthogonal (phase difference 90 °) outputs (voltages) obtained from the first resolver 6, that is, Sine wave output S1 and cosine wave output C1
Are represented by E sin θ and Ecos θ, respectively.

On the other hand, the two orthogonal outputs (voltages) obtained from the second resolver 7, that is, the sine wave output S2 and the cosine wave output C2, are E sin (θ-Δθ) and Eco, respectively.
It is represented by s (θ-Δθ). However, each coil 17,1
Since the maximum values of the signal amplitude of 8 are substantially equal, this is approximated by E. Here, S1 · C2−C1 · S2 = Esin θ × Ecos (θ−Δθ) −Ecos θ × Esin (θ−Δθ) = 0.5E ² [sin (2 θ−Δθ) + sin (Δθ)] − 0 .5E ² [sin (2θ−Δθ) −sin (Δθ)] = E ² sin (Δθ), which does not depend on the rotation angle θ of the rotor but changes with the twist angle Δθ between the rotors (Fig. 3 (Reference) can be obtained, and the torque can be detected based on the obtained phase angle difference (that is, the twist angle Δθ).

On the other hand, the rotation angle calculation unit 12b detects the angle based on the equation θ = tan ⁻¹ (S1 / C1) using the two orthogonal voltages S1 and C1 obtained by the first resolver 6. θ is extracted as an absolute value, and the rotation angle of the input shaft 2 is detected by this. Similarly, the rotation detector 12
c detects the rotation angle of the output shaft 3. Rotation angle calculation unit 12
Only one of b and 12c may be provided. As described above, according to the present embodiment, the twist angle Δ of the output member with respect to the input member does not depend on the rotation angle θ of the input member.
A sin waveform varying with θ can be obtained, and the torque is detected based on the phase angle difference (that is, the twist angle Δθ) thus obtained. Further, it is very easy to detect the rotation angle (absolute position), which is the original function of the resolver.

Conventionally, in this type of torque sensor,
After inputting the sine wave output and the cosine wave output of each rotation angle sensor to a control unit such as a microcomputer and obtaining the rotation angle of each rotation angle sensor in the control unit, the torque was detected based on these differences. However, there is a problem that the torque resolution is limited and the control load of the microcomputer is large. On the contrary,
In the present embodiment, the torque calculation unit 12a of the processing circuit 12 is
Is the product of the sine wave output S1 of the first resolver 6 and the cosine wave output C1 of the second resolver 7, and the cosine wave output C1 of the first resolver 6 and the sine wave output S1 of the second resolver 7. The difference (S1 · C2−C1 · S2) from the product is calculated, the torque is calculated based on the difference, and the calculation result is output to the control unit 8. Therefore, the torque resolution can be increased and the control load of the control unit 8 including, for example, a microcomputer can be reduced.

Particularly in a column coaxial type electric power steering apparatus, great effects can be obtained.
This is because a conventional impedance change detection type torque sensor has an axial dimension of about 40 mm, and a general resolver for detecting a rotation angle has an axial dimension of about 15 mm.
Therefore, if a conventional torque sensor and a resolver for detecting the rotation angle are arranged coaxially with the steering column in an attempt to detect both the torque and the rotation angle, about 5
Although the axial dimension of 5 mm is required, in the present embodiment in which the torque detection and the rotation angle detection are achieved by using two resolvers, the axial dimension of about 30 mm is sufficient, and the size can be significantly reduced and parts can be achieved. It is possible to expect a significant cost reduction due to the integration.

Next, FIG. 4 is a control section for determining whether the torque is due to the input from the input shaft 2 or the input from the output shaft 3 by using the torque detecting device 1 of the above-described embodiment. 8 is a flowchart showing the flow of processing of No. 8. In step S1, the control unit 8 that has read the torque detection signal from the processing circuit 12 and the rotation angle detection signals θ ₁ and θ ₂ of the input shaft 2 and the output shaft 3 determines whether or not torque is generated. The determination is made (step S2).

When torque is generated, the input shaft 2
And the angular velocity θ of each of the output shafts 3 ₁’, Θ₂’Calculate
(Step S3), the absolute value of the angular velocity of the input shaft 2 |
θ₁Is the absolute value of the angular velocity of the output shaft 3 | θ₂’|
Greater than or equal (| θ₁′ │ ≧ │θ₂’|
Indicates that the torque is input to the input shaft 2 (that is, the positive input).
It is determined to be due (steps S4 and S5). Again
Absolute value of angular velocity of force axis 3 | θ₂’| Is the angular velocity of the input shaft 2.
Absolute value of | θ ₁’| Greater than (| θ₁’| <|
θ₂The torque from the output shaft 3 (ie,
(Reverse input) is determined (steps S4, S
6).

In the above-mentioned flow, whether the input is the normal input or the reverse input is judged based on the comparison of the absolute values of the angular velocities of the input shaft 2 and the output shaft 3 | θ ₁ '| and | θ ₂ ' | Not limited to, the absolute value of the angular acceleration of the input shaft 2 and the output shaft 3 | θ
It is also possible to determine whether the input is a positive input or a reverse input based on the comparison of the magnitudes of ₁ ″ | and | θ ₂ ″ |. That is, when the absolute value of the angular acceleration | θ ₁ ″ | of the input shaft ₂ is greater than or equal to the absolute value of the angular acceleration | θ ₂ ″ | of the output shaft 3 (| θ ₁ ″ | ≧ | θ ₂ '' | the), it is determined that due to the input torque from the input shaft 2 (i.e., positive input), in the case of the reverse _{(| θ 1 '' | <} | θ 2 ''
|) Is determined to be due to reverse input.

The present invention is not limited to the above-mentioned embodiments, and for example, the rotation angle calculation units 12b and 12c.
May be abolished. Further, various modifications can be made within the scope of the claims of the present invention, such as applying the present torque detection device to a general rotary machine.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an electric power steering device to which a torque detection device according to an embodiment of the present invention is applied.

2A and 2B are schematic diagrams of a resolver that is a first and a second rotation angle sensor.

FIG. 3 is a diagram showing a relationship between torque and detection output.

FIG. 4 is a flowchart showing a flow of arithmetic processing according to another embodiment of the present invention.

[Explanation of symbols]

1 Electric Power Steering Device 2 Input Shaft (Input Member) 3 Output Shaft (Output Member) 4 Torsion Bar 5 Torque Detecting Device 6 First Resolver (First Rotation Angle Sensor) 7 Second Resolver (Second Rotation Angle) Sensor 8 Control unit (calculating unit, determining unit) 9 Driver 10 Electric motor 11 Steering shaft 12 Processing circuit 12a Torque calculation unit 12b, 12c Rotation angle calculation unit 13 Rotor 13a, 13b Coil 15a, 15b Coil 15 Stator S1, S2 Sine Wave output C1, C2 Cosine wave output e11, e21 Sine wave input e12, e22 Cosine wave input θ, θ ₁ , θ ₂ Rotation angle Δθ Twist angle (torque) θ ₁ ′, θ ₂ ′ Angular velocity θ ₁ ″, θ ₂ '' Angular acceleration

Continued front page    (72) Inventor Masahiko Sakamaki             3-5-8 Minamisenba, Chuo-ku, Osaka-shi, Osaka               Koyo Seiko Co., Ltd. F-term (reference) 3D033 CA28 DB05

Claims (3)

[Claims] 1. A first rotation angle sensor and a second rotation angle sensor respectively provided on an input member and an output member coaxially rotatably coupled to each other via a torsion bar, and a first rotation angle sensor and a second rotation angle sensor. In a torque detection device including a torque calculation unit that calculates a torque based on a sine wave output and a cosine wave output obtained from each, the torque calculation unit includes a sine wave output of the first rotation angle sensor and a second rotation angle sensor. The torque is calculated based on the difference between the product of the cosine wave output of the rotation angle sensor and the product of the cosine wave output of the first rotation angle sensor and the sine wave output of the second rotation angle sensor. Torque detection device. 2. A rotation angle calculation unit for calculating a rotation angle of at least one of an input member and an output member based on an output from at least one of the first and second rotation angle sensors. A torque detection device comprising: 3. The rotation angle detected by the first and second rotation angle sensors according to claim 1,
Based on the calculation means for calculating the angular velocities or the angular accelerations of the input member and the output member and the relationship between the angular velocities or the angular accelerations calculated by the calculation means, the torque may be input from the input member side. And a determination means for determining whether the input is from the output member side.