JP2011117786A - Torque detection device and power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique which enables accurate detection of a steering torque in a region where the steering torque applied to a steering wheel is small. <P>SOLUTION: A torque detection device detects the steering torque applied to the steering wheel of a vehicle. The device includes a plurality of torque sensors which output analog electric signals according to the steering torque with amplification factors different mutually, an A/D conversion unit which converts the analog electric signals output from the torque sensors in a plurality into digital values, and a torque operation unit which selects some torque sensor outputting the electric signal to be used out of the torque sensors in a plurality, according to the speed of the vehicle, (step 602) and calculates the torque, using the digital value (D1 or D2) obtained through conversion of the electric signal output from the selected torque sensor by the A/D conversion unit (step 604 or 606). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a torque detection device and a power steering device.

In recent years, a torque detection device suitable for a power steering device for reducing the steering force of a vehicle has been proposed.
For example, Patent Document 1 describes a torque detection device configured as follows. That is, the torque sensor described in Patent Document 1 includes a magnetostrictive torque sensor, an amplifying unit, an A / D conversion unit, a control unit, and the like, and the magnetostrictive torque sensor transmits a torque value applied to the steering shaft as an electrical analog signal. Convert to The amplifying unit amplifies the analog signal converted by the magnetostrictive torque sensor at three different amplification factors and outputs the analog signal. The A / D converter converts each analog signal amplified by the amplifier into a digital signal. The control unit inputs a plurality of digital signals converted by the A / D conversion unit, uses one of the digital signals for determination of excessive torque, and uses one of the digital signals for normal power steering device control. The other digital signal is used to adjust the analog signal when the torque value is zero.

JP 2000-355280 A

In order to improve the steering feeling during traveling when the speed of the vehicle is above a certain level, it is important to detect the steering torque with high accuracy in a region where the applied steering torque is small.
Therefore, it is desirable that all the steering torque applied to the steering wheel can be detected and that the steering torque in a region where the steering torque is small can be detected with high accuracy.

  For this purpose, the present invention is a torque detection device for detecting a steering torque applied to a steering wheel of a vehicle, and outputs a plurality of analog electrical signals corresponding to the steering torque at different amplification factors. Torque sensors, conversion means for converting analog electrical signals output from the plurality of torque sensors into digital values, and output from any torque sensor in the plurality of torque sensors according to the speed of the vehicle. Selecting means for selecting whether to use the electrical signal; and calculating means for calculating torque using a digital value output from the torque sensor selected by the selecting means and converted by the converting means. This is a featured torque detection device.

Here, the plurality of torque sensors include a first torque sensor and a second torque sensor having an amplification factor larger than the amplification factor of the first torque sensor, and the selection means includes When the vehicle speed is equal to or lower than a predetermined speed, the electric signal output from the first torque sensor is used. When the vehicle speed is higher than the predetermined speed, the electric signal is output from the second torque sensor. It is preferable to use an electrical signal.
The ratio between the amplification factor of the first torque sensor and the amplification factor of the second torque sensor is the maximum value of the steering torque to be detected by the first torque sensor and the second torque sensor. Is preferably determined based on a ratio to the maximum value of the steering torque that is assumed to be applied at a speed equal to or lower than the predetermined speed.

  From another point of view, the present invention provides a first rotating shaft connected to a vehicle steering wheel, a second rotating shaft connected to the first rotating shaft via a torsion bar, A plurality of torque sensors for outputting analog electrical signals corresponding to relative rotation angles between the first rotation shaft and the second rotation shaft at different amplification factors, and analog signals output from the plurality of torque sensors Conversion means for converting the electrical signal of the motor into a digital value, selection means for selecting which of the torque sensors in the plurality of torque sensors to use according to the speed of the vehicle, and the selection Calculating means for calculating torque using a digital value output from the torque sensor selected by the means and converted by the converting means, It is the location.

Here, the plurality of torque sensors include a first torque sensor and a second torque sensor having an amplification factor larger than the amplification factor of the first torque sensor, and the selection means includes When the vehicle speed is equal to or lower than a predetermined speed, the electric signal output from the first torque sensor is used. When the vehicle speed is higher than the predetermined speed, the electric signal is output from the second torque sensor. It is preferable to use an electrical signal.
The ratio between the amplification factor of the first torque sensor and the amplification factor of the second torque sensor is the maximum value of the steering torque to be detected by the first torque sensor and the second torque sensor. Is preferably determined based on a ratio to the maximum value of the steering torque that is assumed to be applied at a speed equal to or lower than the predetermined speed.

  According to the present invention, it is possible to detect all of the steering torque applied to the steering wheel and to detect the steering torque in a region where the steering torque is small with higher accuracy than in the case where the present invention is not employed.

1 is a cross-sectional view of an electric power steering device to which a torque detection device according to an embodiment is applied. It is an enlarged view of the X section in FIG. It is a schematic block diagram of the main components of the torque detection apparatus which concerns on embodiment. It is the figure which looked at the torque detection apparatus from the Y direction in FIG. It is a figure which shows the state of the torque detection apparatus before a 1st rotating shaft and a 2nd rotating shaft displace relatively. FIG. 5 is a diagram showing a state where a magnet (first rotation shaft) is rotated counterclockwise with respect to a yoke (second rotation shaft) when viewed in FIG. 4. It is a figure which shows the state which the magnet rotated clockwise with respect to the yoke when it sees in FIG. It is a figure which shows the relationship between the relative angle of a magnet (1st rotating shaft) and a yoke (2nd rotating shaft), and the magnetic flux density which a 1st magnetic sensor and a 2nd magnetic sensor detect. It is a figure which shows the relationship between the electric torque which a 1st magnetic sensor and a 2nd magnetic sensor output, the magnetic flux density to detect, and the steering torque corresponding to this magnetic flux density. It is a flowchart which shows the procedure of the torque calculation process which a torque calculating part performs.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view of an electric power steering device (hereinafter simply referred to as “EPS device”) 100 to which a torque detection device 1 according to an embodiment is applied. FIG. 2 is an enlarged view of a portion X in FIG. FIG. 3 is a schematic configuration diagram of main components of the torque detection device 1 according to the embodiment. 4 is a diagram of the torque detection device 1 as viewed from the Y direction in FIG. 3 and 4, a bracket 60 described later is omitted.

  The torque detection device 1 detects a relative angle between the first rotation shaft 120 rotatably supported by the housing 110 and the second rotation shaft 130 also rotatably supported by the housing 110, and detects the first angle. This is a device for detecting the torque applied to one of the first rotating shaft 120 and the second rotating shaft 130 based on the relative angle between the rotating shaft 120 and the second rotating shaft 130.

The housing 110 is a member that is fixed to a main body frame (vehicle body) of a vehicle such as an automobile, and is configured such that the first housing 111 and the second housing 112 are coupled by, for example, a bolt.
The first rotating shaft 120 is a rotating shaft to which a steering wheel (not shown) is connected, and is rotatably supported by the first housing 111 via a bearing 113.

The second rotating shaft 130 is coaxially coupled to the first rotating shaft 120 via a torsion bar 140 and is rotatably supported by the second housing 112 via a bearing 114. A pinion 131 formed on the second rotating shaft 130 meshes with a rack (not shown) of a rack shaft (not shown) connected to the wheel. Then, the rotary motion of the second rotary shaft 130 is converted into a linear motion of the rack shaft through the pinion 131 and the rack, and the wheels are steered.
A worm wheel 150 is fixed to the second rotating shaft 130 by, for example, press fitting. The worm wheel 150 meshes with a worm gear 161 connected to the output shaft of the electric motor 160 fixed to the second housing 112.

  In the EPS device 100 configured as described above, the torque detection device 1 detects the steering torque T applied to the steering wheel based on the relative angle between the first rotation shaft 120 and the second rotation shaft 130. To do. The driving of the electric motor 160 is controlled based on the steering torque T detected by the torque detection device 1, and the torque generated by the electric motor 160 is transmitted to the second rotating shaft 130 via the worm gear 161 and the worm wheel 150. Thereby, the torque generated by the electric motor 160 assists the driver's steering force applied to the steering wheel.

Below, the torque detection apparatus 1 is explained in full detail.
The torque detection device 1 includes a magnet 10 attached to a first rotating shaft 120, a yoke 30 disposed in a magnetic field formed by the magnet 10, a magnetic sensor 40 that detects a magnetic flux density generated in the yoke 30, and a magnetic sensor. And a torque calculation unit 50 for calculating the steering torque T based on the output value from 40.

  The magnet 10 has a cylindrical shape, and as shown in FIG. 3, N poles and S poles are alternately arranged in the circumferential direction of the first rotating shaft 120 and are magnetized in the circumferential direction. The magnet 10 is attached to the first rotating shaft 120 via the collar 11. That is, the magnet 10 is fixed to the collar 11, and the collar 11 is fixed to the first rotation shaft 120. The magnet 10 rotates together with the first rotating shaft 120. The length of the magnet 10 in the axial direction of the first rotating shaft 120 is longer than the length of the yoke 30.

The yoke 30 is disposed outside the magnet 10 and is composed of a first yoke 31 and a second yoke 32. The first yoke 31 and the second yoke 32 are attached to the second rotating shaft 130.
The first yoke 31 includes a disk-shaped first annular portion 31a in which a hole having a diameter larger than the outer diameter of the magnet 10 is formed inside, and a first rotation from the first annular portion 31a. A plurality of first protrusions 31b formed to extend in the axial direction of the shaft 120. The second yoke 32 includes a disk-shaped second annular portion 32a in which a hole having a diameter larger than the outer diameter of the magnet 10 is formed inside, and a first rotation from the second annular portion 32a. A plurality of second protrusions 32b formed to extend in the axial direction of the shaft 120.

  The same number of first protrusions 31b and second protrusions 32b as the N poles and S poles of the magnet 10 are formed. That is, when the number of N poles and S poles of the magnet 10 is 12, for example, twelve first protrusions 31b and twelve second protrusions 32b are formed. The first protrusion 31b and the second protrusion 32b are opposed to the outer peripheral surface of the magnet 10 in the rotational radius direction of the first rotating shaft 120 as shown in FIGS. The surface of the first protrusion 31b and the second protrusion 32b facing the magnet 10 is a direction orthogonal to the rotation axis of the first rotation shaft 120. It is a rectangle when seen.

The first protrusions 31 b of the first yoke 31 and the second protrusions 32 b of the second yoke 32 are alternately arranged in the circumferential direction of the first rotating shaft 120.
In the torque detection device 1 according to the present embodiment, when the steering torque T is not applied to the steering wheel (torsion bar 140), that is, in the initial state where the torsion bar 140 is not twisted, FIG. As shown in FIG. 4, in the circumferential direction of the first rotating shaft 120, the boundary line between the north pole and the south pole of the magnet 10 coincides with the circumferential center of the first protrusion 31b when viewed in the clockwise direction. Are arranged to be. Further, when viewed in the clockwise direction, the boundary line between the S pole and the N pole of the magnet 10 and the center of the second protrusion 32b in the circumferential direction are arranged to coincide with each other. Further, when the steering torque T is applied to the torsion bar 140 and the torsion bar 140 is twisted, and the first protrusion 31b faces the north or south pole of the magnet 10, the second protrusion 32b The one protruding portion 31b faces a magnetic pole having a polarity different from the facing polarity.

As shown in FIG. 2, the yoke 30 includes a first yoke 31 and a second yoke 32 integrated by insert molding. The bracket 60 is also integrally formed when insert molding is performed. The bracket 60 includes a thin cylindrical axial portion 61 extending in the axial direction of the second rotary shaft 130 and a disk-shaped radial portion 62 extending from the axial portion 61 in the rotational radial direction of the second rotary shaft 130. And have. The axial portion 61 of the bracket 60 is press-fitted, welded, screwed, or caulked to the second rotating shaft 130, so that the axial portion 61 is fixed to the second rotating shaft 130. Thereby, the yoke 30 is also fixed to the second rotating shaft 130.
When forming the yoke 30, it is possible to suppress an increase in the number of types of components by using the same components as the first yoke 31 and the second yoke 32 and only changing the arrangement direction. It becomes.

The magnetic sensor 40 includes a first magnetic sensor 41 and a second magnetic sensor 42.
The first magnetic sensor 41 and the second magnetic sensor 42 are respectively fixed to the housing 110, and the first annular portion 31 a and the first annular portion 31 a of the first yoke 31 are arranged in the axial direction of the first rotating shaft 120. It arrange | positions between the 2nd ring parts 32a of the two yokes 32. FIG. The first magnetic sensor 41 and the second magnetic sensor 42 are arranged at different positions in the circumferential direction of the first rotating shaft 120.

  The first magnetic sensor 41 and the second magnetic sensor 42 detect a magnetic flux density between the first yoke 31 and the second yoke 32, and an electric signal (for example, a voltage) proportional to the detected magnetic flux density. Signal) and output, for example, a Hall IC. Then, the first magnetic sensor 41 multiplies the value obtained by converting the detected magnetic flux density into an electric signal by a coefficient γ1 and outputs the result as an electric signal E1. That is, the first magnetic sensor 41 amplifies a value obtained by converting the detected magnetic flux density into an electric signal with an amplification factor γ1, and outputs the amplified signal as an electric signal E1. Further, the second magnetic sensor 42 multiplies the value obtained by converting the detected magnetic flux density into an electric signal by a coefficient γ2, and outputs the result as an electric signal E2. That is, the second magnetic sensor 42 amplifies a value obtained by converting the detected magnetic flux density into an electric signal with an amplification factor γ2, and outputs the amplified electric signal E2.

In this embodiment, γ2 is set to a larger value than γ1. That is, the first magnetic sensor 41 and the second magnetic sensor 42 detect the same magnetic flux density, and the second magnetic sensor 42 detects γ2 / γ1 (a value larger than 1) of the output value E1 of the first magnetic sensor 41. ) Output double value.
Moreover, the range of the magnitude | size of the electric signal which the 1st magnetic sensor 41 and the 2nd magnetic sensor 42 output is the same. Therefore, the range of the magnetic flux density detected by the second magnetic sensor 42 is γ1 / γ2 (a value smaller than 1) times the range of the magnetic flux density detected by the first magnetic sensor 41.
The first magnetic sensor 41 and the second magnetic sensor 42 each detect a magnetic flux density at a predetermined cycle, and output an electric signal having a value proportional to the detected magnetic flux density.

The outputs of the first magnetic sensor 41 and the second magnetic sensor 42 of the torque detection device 1 configured as described above will be described.
FIG. 5 is a diagram illustrating a state of the torque detection device 1 before the first rotation shaft 120 and the second rotation shaft 130 are relatively displaced. FIG. 5A shows the relationship between the magnet 10 and the yoke 30 as viewed in the Y direction in FIG. FIG. 5B is a view of the magnet 10 and the yoke 30 as viewed in the Z direction in FIG.

  When the steering torque T is not applied to the steering wheel, that is, in the initial state where the torsion bar 140 is not twisted, as shown in FIGS. 4 and 5A, the circumferential direction of the first rotating shaft 120 , The circumferential center of the first protrusion 31b and the second protrusion 32b, which are the protrusions of the yoke 30, coincides with the boundary line between the N pole and the S pole of the magnet 10. In such a case, the same number of lines of magnetic force enter and exit from each of the first and second protrusions 31b and 32b from the N and S poles of the magnet 10. Therefore, there is no magnetic flux density difference between the first annular portion 31a of the first yoke 31 and the second annular portion 32a of the second yoke 32, so that the first magnetic sensor 41 and the first magnetic sensor 41 The magnetic flux density detected by the second magnetic sensor 42 is zero.

When the steering torque T is input to the steering wheel and the torsion bar 140 is twisted, the relative position in the circumferential direction between the magnet 10 and the yoke 30 changes.
FIG. 6 is a diagram illustrating a state in which the magnet 10 (first rotating shaft 120) rotates counterclockwise with respect to the yoke 30 (second rotating shaft 130) when viewed in FIG. FIG. 7 is a diagram illustrating a state in which the magnet 10 is rotated in the clockwise direction with respect to the yoke 30 when viewed in FIG. 4. In each figure, (a) is the figure which looked at the relationship between the magnet 10 and the yoke 30 from the Y direction in FIG. (B) is the figure which looked at the magnet 10 and the yoke 30 in the Z direction in (a).
8 shows the relative angle between the magnet 10 (first rotating shaft 120) and the yoke 30 (second rotating shaft 130), and the magnetic flux density detected by the first magnetic sensor 41 and the second magnetic sensor 42. It is a figure which shows the relationship.

  As shown in FIGS. 6 and 7, when the torsion bar 140 is twisted, the circumferential center of the first protrusion 31 b and the second protrusion 32 b of the yoke 30 in the circumferential direction of the first rotating shaft 120. And the boundary line between the N pole and S pole of the magnet 10 does not match. That is, compared with the initial state, the area | region where either magnetic pole of the magnet 10 opposes the 1st projection part 31b and the 2nd projection part 32b of the yoke 30 increases.

  More specifically, in the state of FIG. 6, the first protrusion 31 b of the first yoke 31 has an increased area facing the N pole of the magnet 10, and the second protrusion of the second yoke 32. In the portion 32b, a region facing the south pole of the magnet 10 is increased. For this reason, the magnetic lines of force from the N pole of the magnet 10 toward the first protrusion 31b are larger than the magnetic lines of force from the first protrusion 31b toward the S pole of the magnet 10. Moreover, the magnetic force line which goes to the S pole of the magnet 10 from the 2nd protrusion part 32b increases more than the magnetic force line which goes to the 2nd protrusion part 32b from the N pole of the magnet 10. As a result, the magnetic flux density from the first annular portion 31a of the first yoke 31 toward the second annular portion 32a of the second yoke 32 increases.

  When the direction from the first annular portion 31a of the first yoke 31 toward the second annular portion 32a of the second yoke 32 is a plus direction, when viewed from the initial state in FIG. As the magnet 10 (first rotating shaft 120) rotates in the clockwise direction with respect to the yoke 30 (second rotating shaft 130), the first magnetic sensor 41 and the second magnetic sensor 42 detect. The magnetic flux density increases in the positive direction.

  Further, in the state of FIG. 7, the first protrusion 31 b of the first yoke 31 has an increased area facing the south pole of the magnet 10, and the second protrusion 32 b of the second yoke 32 is The region facing the north pole of the magnet 10 increases. Therefore, the magnetic lines of force from the first protrusion 31b toward the S pole of the magnet 10 are larger than the magnetic lines of force from the N pole of the magnet 10 toward the first protrusion 31b. Further, the magnetic lines of force from the N pole of the magnet 10 toward the second protrusion 32b are larger than the magnetic lines of force from the second protrusion 32b toward the S pole of the magnet 10. As a result, the magnetic flux density from the second annular portion 32a of the second yoke 32 toward the first annular portion 31a of the first yoke 31 increases. Therefore, as viewed in FIG. 4 from the initial state, the magnet 10 (first rotating shaft 120) rotates counterclockwise with respect to the yoke 30 (second rotating shaft 130). The magnetic flux density detected by the first magnetic sensor 41 and the second magnetic sensor 42 increases in the negative direction.

  FIG. 8 shows a change in magnetic flux density when the first rotating shaft 120 and the second rotating shaft 130 are relatively rotated by one magnetic pole (α degree) in both directions. The first magnetic sensor 41 and the second magnetic sensor 42 are proportional to the twist angle of the torsion bar 140 by allowing the torsion bar 140 to be twisted by 1/3 × α degrees in both directions. Magnetic flux density can be detected. In other words, the first magnetic sensor 41 and the second magnetic sensor 42 can detect a magnetic flux density proportional to the steering torque T applied to the steering wheel.

  The first magnetic sensor 41 and the second magnetic sensor 42 detect the magnetic flux density between the first yoke 31 and the second yoke 32, and generate an electric signal having a value proportional to the detected magnetic flux density. The signals are converted and output at amplification rates γ1 and γ2, respectively. FIG. 9 is a diagram showing the relationship between the electrical signals output from the first magnetic sensor 41 and the second magnetic sensor 42, the detected magnetic flux density, and the steering torque T corresponding to the magnetic flux density.

  The torque calculation unit 50 is an arithmetic logic operation circuit including a CPU, a ROM, a RAM, a backup RAM, and the like. In the torque calculation unit 50, electrical signals E1 and E2, which are analog signals output from the first magnetic sensor 41 and the second magnetic sensor 42, are converted into digital signals by A / D conversion units (not shown), respectively. The obtained digital values D1 and D2 are obtained. The torque calculation unit 50 calculates the steering torque T using the digital value (D1 or D2) based on the output value from either the first magnetic sensor 41 or the second magnetic sensor 42. In addition to selecting whether to calculate T, the steering torque T is calculated using a digital value (D1 or D2) based on the output value from the selected sensor, and the calculated steering torque T is output.

  The torque calculation unit 50 is realized by, for example, an electronic control unit (hereinafter simply referred to as “ECU”) that is provided outside the housing 110 and also has a function of controlling the electric motor 160 of the EPS device 100. In such a case, the ECU controls the A / D converter that converts the analog signals output from the first magnetic sensor 41 and the second magnetic sensor 42 into digital signals, the torque calculator 50, and the electric motor 160. A motor control unit (not shown). Then, the ECU stores the digital values D1 and D2 converted by the A / D conversion unit in the RAM, and calculates the steering torque T by the torque calculation unit 50 based on the stored digital values D1 or D2. Then, the ECU calculates a target auxiliary torque based on the calculated steering torque T, calculates a target current required for the electric motor 160 to supply the target auxiliary torque, and based on the calculated target current. A series of EPS control processes for controlling the operation of the electric motor 160, such as performing feedback control and generating a signal for controlling the electric motor 160, is executed.

  When the torque calculator 50 selects the output value from the first magnetic sensor 41 or the second magnetic sensor 42 when calculating the steering torque T, the torque detector 1 Is based on the speed V of the vehicle on which the EPS device 100 to which is applied is mounted. More specifically, when the speed V is equal to or lower than the predetermined speed VT, based on the output value from the first magnetic sensor 41, when the speed V is higher than the predetermined speed VT, Based on the output value from the second magnetic sensor 42.

  Here, in the EPS device 100, the range of the steering torque T to be detected by the torque detection device 1 is determined in consideration of the assumed range of the steering torque T or the range of the steering torque T whose performance should be guaranteed. Thus, the magnetic flux density between the first yoke 31 and the second yoke 32 (the relative rotational angle between the first rotating shaft 120 and the second rotating shaft 130) and the magnetic force for detecting the magnetic flux density. The relationship with the electrical signal output from the sensor is determined.

  Therefore, for example, when only the first magnetic sensor 41 is used, the electric signal E1 output from the first magnetic sensor 41 is converted into a digital signal by the A / D converter based on the digital value D1. When performing the EPS control process, it is necessary to match the maximum value Emax of the electric signal E1 to the maximum steering torque T assumed or the maximum steering torque T whose performance should be guaranteed. Therefore, when only the first magnetic sensor 41 is used, the digital signal assigned to the region where the detected torque is small is also limited, and the quantization error is limited. Then, due to the characteristics of the EPS apparatus 100, the area where the detected torque is, for example, 1/4 or less of the maximum steering torque Tmax adjusted to the maximum value Emax of the electric signal E1 is mounted. This is when the vehicle is traveling at a certain speed (for example, 30 km / h although it depends on the specifications of the vehicle). As a result, improvement in torque detection accuracy in a region where the detected torque is small, which is important for improving the steering feeling when the vehicle on which the EPS device 100 is mounted is traveling at a certain speed or higher, is suppressed. .

  Therefore, in the present embodiment, in addition to the first magnetic sensor 41, a second magnetic sensor 42 having an amplification factor γ2 larger than the amplification factor γ1 of the first magnetic sensor 41 is provided, and the speed V is When the speed is larger than the predetermined speed VT, the torque calculation unit 50 calculates the steering torque T based on the output value from the second magnetic sensor 42 having a large amplification factor. Thereby, when based on the output value from the 2nd magnetic sensor 42, compared with the case based on the output value from the 1st magnetic sensor 41, the detection torque per bit is γ1 / γ2 (γ1 / γ2). Is a value smaller than 1), and the torque detection accuracy can be improved.

The torque calculation unit 50 changes the calculation formula used when calculating the torque, depending on which of the first magnetic sensor 41 and the second magnetic sensor 42 is used.
For example, in the case of detecting a torque within a range of ± Tmax that is twice the Tmax with a voltage signal of 0 to Emax output from the first magnetic sensor 41, the electrical signal output from the first magnetic sensor 41 The digital signal D1 obtained by converting E1 by the A / D conversion unit is calculated by substituting it into the following equation (1).
T = ((2 × Tmax) / Emax) × D1−Tmax (1)

Further, a torque signal in the range of ± (Tmax × (γ1 / γ2)), which is twice the range of (Tmax × (γ1 / γ2)), is detected by a voltage signal of 0 to Emax output from the second magnetic sensor 42. In this case, the calculation is performed by substituting the digital signal D2 obtained by converting the electrical signal E2 output from the second magnetic sensor 42 by the A / D converter into the following equation (2).
T = ((2 × Tmax × (γ1 / γ2)) / Emax) × D2−Tmax × (γ1 / γ2) (2)

Hereinafter, the torque calculation process performed by the torque calculation unit 50 will be described using a flowchart.
FIG. 10 is a flowchart illustrating a procedure of torque calculation processing performed by the torque calculation unit 50. The torque calculation unit 50 performs this torque calculation process at a predetermined cycle, for example.
The torque calculator 50 first reads the speed V (step 601). This is a process of reading, as a speed V, a value that is input in advance from a speed sensor (not shown) that is mounted on the vehicle and detects the speed of the vehicle and stored in a predetermined area of the RAM.
Thereafter, the torque calculation unit 50 determines whether or not the speed V read in step 601 is equal to or lower than a predetermined speed VT (step 602). If an affirmative determination is made in step 602, the digital value D1 input from the first magnetic sensor 41 and converted into a digital signal by the A / D converter is read from the RAM (step 603). Thereafter, the steering torque T is calculated by substituting the digital value D1 read in step 603 into the above-described equation (1) (step 604).

On the other hand, if a negative determination is made in step 602, the digital value D2 input from the second magnetic sensor 42 and converted into a digital signal by the A / D converter is read from the RAM (step 605). Thereafter, the steering torque T is calculated by substituting the digital value D2 read in step 605 into the above-described equation (2) (step 606).
Then, the torque calculation unit 50 outputs the steering torque T calculated in Step 604 or Step 606 to a part where the EPS control process is performed (Step 607).

The torque calculation unit 50 calculates the steering torque T based on the detection value of the first magnetic sensor 41 or the second magnetic sensor 42 in this way. Then, the calculated steering torque T is output as a detection value of the torque detection device 1 toward a portion where EPS control processing is performed.
Therefore, according to the torque detection device 1 according to the present embodiment, the steering torque T applied at a speed higher than the predetermined speed VT is more increased than the configuration in which the detection is performed using only the first magnetic sensor 41. It can be detected with high accuracy. Therefore, the steering feeling at a speed higher than the predetermined speed VT can be improved.

  The magnetic sensor 40 of the torque detection device 1 configured as described above includes two magnetic sensors, ie, a first magnetic sensor 41 and a second magnetic sensor 42 having different amplification factors. You may be comprised from three or more different magnetic sensors. And by providing the number of speeds that will be the threshold for the number of magnetic sensors and selecting the magnetic sensor to be used according to the speed, it is possible to improve the torque detection accuracy in a wider range of speeds and to detect the torque per bit. The steering torque T can be detected more finely.

  Further, the torque detection device 1 described above includes two magnetic sensors having different amplification factors. However, the present invention is not limited to such a mode, and includes only one magnetic sensor and outputs an output signal from the magnetic sensor as A / A plurality of amplifiers that amplify at different amplification factors may be provided at the front stage of the D conversion unit, and the steering torque T may be selected based on the output from which amplifier according to the speed.

  In addition, the torque detection device 1 described above has a magnet 10 and a yoke 30 that change the magnetic flux density according to the relative angle between the first rotation shaft 120 and the second rotation shaft 130, and steering according to the detected magnetic flux density. Although the magnetic sensor which outputs the voltage according to the torque T is used, it is not limited to this aspect in particular. For example, the torque detection device 1 has two coils, a mechanism that changes the inductance of these two coils in accordance with the operation of the steering wheel, and a voltage that corresponds to the steering torque T based on the change in these inductances. A configuration including a torque detection circuit for outputting may also be used. In such a configuration, a plurality of amplifiers that amplify the output signal from the torque detection circuit with different amplification factors are provided, and it is selected which of the amplifiers calculates the steering torque T according to the speed. May be.

DESCRIPTION OF SYMBOLS 1 ... Torque detection apparatus, 10 ... Magnet, 30 ... Yoke, 31 ... 1st yoke, 32 ... 2nd yoke, 40 ... Magnetic sensor, 41 ... 1st magnetic sensor, 42 ... 2nd magnetic sensor, 50 DESCRIPTION OF SYMBOLS ... Torque calculation part, 60 ... Bracket, 100 ... Electric power steering device (EPS device), 110 ... Housing, 120 ... First rotating shaft, 130 ... Second rotating shaft, 140 ... Torsion bar, 150 ... Worm wheel, 160 ... Electric motor

Claims (6)

A torque detection device for detecting a steering torque applied to a steering wheel of a vehicle,
A plurality of torque sensors for outputting analog electrical signals corresponding to the steering torque at different amplification factors;
Conversion means for converting analog electrical signals output from the plurality of torque sensors into digital values;
Selection means for selecting which of the torque sensors in the plurality of torque sensors to use the electrical signal according to the speed of the vehicle;
Calculating means for calculating torque using a digital value output from the torque sensor selected by the selecting means and converted by the converting means;
A torque detection device comprising: The plurality of torque sensors include a first torque sensor and a second torque sensor having an amplification factor larger than the amplification factor of the first torque sensor,
The selection means uses an electrical signal output from the first torque sensor when the speed of the vehicle is equal to or lower than a predetermined speed, and the second means when the speed is higher than the predetermined speed. The torque detection device according to claim 1, wherein an electric signal output from the torque sensor is used.   The ratio between the amplification factor of the first torque sensor and the amplification factor of the second torque sensor is selected by the second torque sensor and the maximum value of the steering torque to be detected by the first torque sensor. The torque detection device according to claim 2, wherein the torque detection device is determined based on a ratio to a maximum value of the steering torque assumed to be applied at a speed equal to or less than the predetermined speed. A first axis of rotation coupled to a vehicle steering wheel;
A second rotating shaft coupled to the first rotating shaft via a torsion bar;
A plurality of torque sensors for outputting analog electrical signals corresponding to relative rotation angles between the first rotating shaft and the second rotating shaft at different amplification factors;
Conversion means for converting analog electrical signals output from the plurality of torque sensors into digital values;
Selection means for selecting which of the torque sensors in the plurality of torque sensors to use the electrical signal according to the speed of the vehicle;
Calculating means for calculating torque using a digital value output from the torque sensor selected by the selecting means and converted by the converting means;
A power steering apparatus comprising: The plurality of torque sensors include a first torque sensor and a second torque sensor having an amplification factor larger than the amplification factor of the first torque sensor,
The selection means uses an electrical signal output from the first torque sensor when the speed of the vehicle is equal to or lower than a predetermined speed, and the second means when the speed is higher than the predetermined speed. The power steering apparatus according to claim 4, wherein an electric signal output from the torque sensor is used.   The ratio between the amplification factor of the first torque sensor and the amplification factor of the second torque sensor is selected by the second torque sensor and the maximum value of the steering torque to be detected by the first torque sensor. 6. The power steering device according to claim 5, wherein the power steering device is determined based on a ratio to a maximum value of the steering torque that is assumed to be applied at or below the predetermined speed.

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