JP3589080B2 - Torque detector - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a torque detection device that detects a steering torque generated by operating a steering wheel, and is suitable as a torque detection device used in an electric power steering device that assists the steering torque with the driving force of an electric motor. .
[0002]
[Prior art]
Conventionally, as a torque detecting device used in the electric power steering device, for example, a torque detecting device shown in FIGS. 19 and 20 is known.
FIG. 19 is an explanatory view showing a structure of a steering mechanism of the electric power steering device including a partial cross section, and FIG. 20 is an electric configuration of a torque detection device provided in the steering mechanism shown in FIG. FIG. 4 is an explanatory diagram showing by a block.
First, the structure of the steering mechanism will be described with reference to FIG.
The steering mechanism 70 includes a hollow shaft 72 connected to a steering wheel (not shown) of the vehicle, and a lower portion of the shaft 72 is inserted into an upper portion 73 a of the housing 73. A shaft 74 is inserted through a lower portion 73b of the housing 73, and a pinion P that meshes with the rack R is attached to a lower portion of the shaft 74. The rack R is configured to transmit the rotational torque of a motor (not shown) that assists the steering force.
[0003]
A torsion bar 75 is housed inside the shaft 72, and the upper end of the torsion bar 75 is connected to the shaft 72 by a pin 76. The lower end of the torsion bar 75 is in spline engagement with the recess of the shaft 74.
A sensor ring 77 made of a magnetic material is provided at an intermediate portion of the shaft 72 located inside the housing 73, and a sensor ring 78 made of a magnetic material is provided on the shaft 74. I have. A sensor coil 79 is provided at a position facing the outer peripheral surfaces of the sensor rings 77 and 78 located inside the housing 73 with a predetermined gap from each of the sensor rings 77 and 78.
That is, the sensor unit 71 is configured by the sensor rings 77 and 78, the sensor coil 79, and the gap between the sensor rings 77 and 78 and the sensor coil 79.
[0004]
In the steering mechanism 70 having the above structure, when the steering torque is transmitted to the shaft 72 by operating the steering wheel, the torsion bar 75 is twisted to cause a relative displacement between the shaft 72 and the shaft 74, and the sensor ring 77, The overlap amount of 78 is displaced, and the inductance generated in the sensor coil 79 changes. The inductance is detected by an interface circuit unit (hereinafter, referred to as an I / F circuit unit) 80 provided in the housing 73, converted into a torque signal, and supplied to a microcomputer (hereinafter, referred to as a microcomputer) provided in the vehicle. Is output.
[0005]
Next, the operation of the I / F circuit unit 80 will be described with reference to FIG.
The DC current supplied from the power supply input is converted into a reference voltage by a regulator circuit 83 after an extra harmonic component is removed by a filter circuit 82. The oscillation circuit 84 generates a sine wave signal based on the reference voltage generated from the regulator circuit 83, and applies the sine wave signal to the sensor coil 79. Then, since a sine wave voltage proportional to the inductance of the sensor coil 79 is generated at both ends of the sensor coil 79, the AC component of the sine wave voltage is extracted by the DC cut circuit 85, and the amplitude of the AC component is further detected by the detection circuit 86. Is converted into a signal having a DC voltage proportional to the amplitude thereof, and is input to the addition circuit 87.
[0006]
The sine wave voltage generated at both ends of the sensor coil 79 is also input to the temperature compensation circuit 88, and is converted into a temperature drift signal indicating the amount by which the inductance of the sensor coil 79 drifts under the influence of temperature. Then, the temperature drift signal is input as a compensation signal to an addition circuit 87. The addition circuit 87 extracts the difference between the signal output from the detection circuit 86 and the compensation signal output from the temperature compensation circuit 88, and obtains the temperature drift signal. A torque component signal of only the torque component whose component has been canceled is output to the scaling circuit 89. Subsequently, the scaling circuit 89 converts the gain of the torque component signal. The gain-converted torque component signal is amplified by the output amplifier circuit 90, and further amplified as a torque signal to an A / D input port of a microcomputer (not shown). Is output.
[0007]
Then, the microcomputer calculates an assist amount by the electric motor based on the magnitude of the input torque signal, and outputs a drive signal corresponding to the calculated assist amount from the motor drive circuit to the electric motor. The torque is transmitted to the rack R (FIG. 19), and the steering torque is assisted.
Further, since the scaling circuit 89, the output amplifier circuit 90, and the like constituting the I / F circuit unit 80 are analog circuits, the output of the torque signal may fluctuate due to variations in the characteristics of the semiconductor elements. When such a change occurs, the assist amount calculated by the microcomputer changes, which may lead to a feeling of strangeness in the steering operation.
Therefore, conventionally, potentiometers 89a and 90a are provided in the scaling circuit 89 and the output amplifier circuit 90 so that the output of each circuit can be finely adjusted so that the above-mentioned uncomfortable feeling does not occur.
[0008]
[Problems to be solved by the invention]
However, the torque to be detected may vary from one sensor unit 71 to another due to variations in the mechanical processing accuracy of the sensor rings 77 and 78 and the sensor coil 79 or variations in material characteristics.
That is, conventionally, since there is a characteristic difference in the sensor unit 71, the assist amount calculated by the microcomputer is different for each electric power steering device even if the applied steering torque is the same. The rings could have been different.
[0009]
Therefore, an object of the present invention is to eliminate a variation in steering feeling caused by a characteristic difference of a sensor unit that detects torque.
[0010]
Means for Solving the Problems, Functions and Effects of the Invention
To achieve the above object, according to the first aspect of the present invention, a steering torque generated by operating a steering wheel connected to a steering mechanism is provided. With a sensor coil whose inductance changes according to Sensor section And an interface circuit for detecting the inductance and outputting a torque signal having a cycle corresponding to the detected inductance, and a micro circuit for calculating the steering torque based on the torque signal output from the interface circuit. And a computer, operated by the microcomputer. A torque detection device that drives the electric motor by a drive signal corresponding to the steering torque and detects the steering torque to function the electric power steering device that supplements the steering torque by the driving force of the electric motor. By applying a reference sine wave voltage to the single interface circuit unit before being assembled to the electric power steering apparatus, a deviation amount of the cycle of the torque signal due to a temperature change when the interface circuit unit is a single unit. And an inductance difference due to a temperature change of a sensor coil of the single sensor unit before being assembled to the electric power steering device; and attaching the sensor unit and the interface circuit unit to the electric power steering device; Rewriting characteristic difference data indicating a characteristic difference including a deviation amount of a cycle of a torque signal at normal temperature output from the interface circuit unit in a state where a predetermined steering torque is generated by operating a wheel at a predetermined reference angle. The microcomputer is provided with characteristic difference data storage means for storing the data as possible. Relative steering torque, the characteristic difference data stored in the characteristic difference data storage means The technical means of performing the correction corresponding to is adopted.
[0011]
The characteristic difference data storage unit stores characteristic difference data indicating a characteristic difference of a sensor unit that detects a steering torque generated by operating a steering wheel connected to the steering mechanism.
The correction means corresponds to the characteristic difference data stored in the characteristic difference data storage means with respect to the steering torque calculated by the steering torque calculation means for calculating the steering torque based on the output of the sensor unit. Make corrections.
Therefore, since the calculated steering torque can be prevented from being varied due to the characteristic difference of the sensor unit, it is possible to eliminate the situation where the steering feeling varies even in the same vehicle type.
[0013]
In particular, the claims 2 In the invention described in (1), since the rewriting means for rewriting each characteristic difference data stored in the characteristic difference data storage means is provided, for example, the characteristics of the sensor unit change due to aging, and the characteristic difference changes. Even in such a case, the characteristic difference data can be rewritten, so that the calculated steering torque can be corrected in accordance with the rewritten characteristic difference data. The situation where the feeling varies can be eliminated.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a torque detection device of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory view showing the structure of the steering mechanism including a partial cross section. FIG. 2A is an explanatory diagram showing the electric configuration of the electric power steering apparatus having the steering mechanism shown in FIG. 1 by blocks, and FIG. 2B is a diagram showing the structure of the EEPROM 29 shown in FIG. FIG. 4 is an explanatory diagram showing stored contents.
[0015]
As shown in FIG. 1, the steering mechanism 60 has substantially the same structure as the conventional steering mechanism 70 shown in FIG. 19, and is different in that an I / F circuit section 80 is not provided in this embodiment. The I / F circuit unit is provided in an electronic control unit (hereinafter, referred to as an ECU) 100 provided in the vehicle, as indicated by reference numeral 50 in FIG. The I / F circuit unit 50 is connected to the microcomputer 20, and the microcomputer 20 is connected to a motor drive circuit 102 that drives the electric motor M. Further, the ECU 100 is provided with an EEPROM 29, and the EEPROM 29 is connected to the microcomputer 20. The EEPROM 29 stores various types of data described later used for correcting the torque value when the microcomputer 20 calculates the torque value.
[0016]
Next, an electrical configuration of the sensor unit 71, the I / F circuit unit 50, and the microcomputer 20 will be described with reference to FIG.
The sensor unit 71 is configured by a magnetic circuit including a sensor coil 79, sensor rings 77 and 78 (FIG. 1), and a gap between the sensor coil 79 and the sensor rings 77 and 78.
The I / F circuit unit 50 includes a torque detection circuit 51 for detecting torque, and a failure detection circuit 56 for detecting an abnormality of the torque detection circuit 51.
The main oscillation circuit 52 constitutes an LR oscillation circuit by its own resistance and the inductance generated in the sensor coil 79, and oscillates a pulse signal having a cycle corresponding to the inductance generated in the sensor coil 79. The pulse signal oscillated from the main oscillation circuit 52 is shaped by a pulse shaping circuit 53, and the shaped pulse signal is input to the timer input 20a of the microcomputer 20 as a torque signal T.
[0017]
The temperature detection circuit 54 extracts a DC component from the AC / DC superimposed signal generated in the sensor coil 79, adds necessary scaling to the extracted DC component, and outputs a signal obtained by adding this scaling to a temperature characteristic signal (hereinafter, a temperature characteristic signal). ) To the A / D input 20b of the microcomputer 20 and the differential amplifier 65. Further, the torque detection circuit 51 is provided with a temperature sensor 55 for detecting a circuit temperature of the I / F circuit section 50, and a circuit temperature signal th detected by the temperature sensor 55 is supplied to the A / D converter of the microcomputer 20. Output to input 20c.
In the present embodiment, a thermistor is used as the temperature sensor 55.
[0018]
The fail detection circuit 56 includes a sub-oscillation circuit 57 having substantially the same configuration as the main oscillation circuit 52 included in the torque detection circuit 51. Similarly to the main oscillation circuit 52, the sub oscillation circuit 57 forms an LR oscillation circuit by its own resistance and the inductance of the sensor coil 79, and outputs a pulse signal having a cycle corresponding to the inductance of the sensor coil 79. It oscillates at the oscillation timing of the main oscillation circuit 52.
[0019]
The signal oscillated from the sub-oscillation circuit 57 is shaped by the pulse shaping circuit 58, and the shaped signal is output to the timer input 20d of the microcomputer 20 as the monitor 1 signal.
Further, the fail detection circuit 56 includes a temperature detection circuit 59 having substantially the same configuration as the temperature detection circuit 54 provided in the torque detection circuit 51. The temperature detection circuit 59 extracts a DC component from the AC / DC superimposed signal generated in the sensor coil 79, adds necessary scaling to the extracted DC component, and outputs a signal obtained by adding the scaling to the differential amplifier circuit 65. . The output from the differential amplifier circuit 65 is input to the A / D input 20e of the microcomputer 20 as a monitor 2 signal.
[0020]
Here, a main flow from steering operation to assisting steering torque will be described.
When the steering wheel is operated, the torsion bar 75 (FIG. 1) is twisted, causing a relative displacement between the shaft 72 and the shaft 74, displacing the overlap amount of the sensor rings 77 and 78, and displacing the sensor coil 79. Changes in inductance. The main oscillation circuit 52 oscillates a pulse signal having a cycle corresponding to the inductance, and the pulse signal is input to the timer input 20a of the microcomputer 20 as a torque signal T after being shaped by a pulse shaping circuit 53.
Then, the microcomputer 20 calculates a torque value based on the cycle of the received torque signal T. Subsequently, the torque value is output to the motor drive circuit 102 (FIG. 2A), and the motor drive circuit 102 outputs a drive signal corresponding to the torque value to the electric motor M. Then, the electric motor M rotates, and the rotation torque is transmitted to the rack R (FIG. 1), and the steering torque is assisted.
[0021]
Further, the microcomputer 20 corrects the torque signal T based on the temperature change of the sensor unit 71 using the taken temperature characteristic signal Vt, and uses the circuit temperature signal th to correct the torque signal T based on the temperature change of the I / F circuit unit 50. Is corrected.
Further, the microcomputer 20 monitors the torque signal T and the monitor 1 signal, and determines that an abnormality has occurred in the main oscillation circuit 52 when a predetermined difference occurs between the two signals. The determination is made based on, for example, whether or not a value (2B-A) obtained by subtracting the period A of the torque signal from a value obtained by doubling the pulse width B of the monitor 1 signal exceeds a predetermined value C.
Further, the microcomputer 20 monitors the voltage V2 of the monitor 2 signal, and determines that an abnormality has occurred in the temperature detection circuit 54 when the voltage V2 is out of a predetermined range. The determination is made based on, for example, whether or not the voltage V2 is out of the range of VB ≦ V2 ≦ VA.
[0022]
Next, features of the torque detection device according to the present embodiment will be described with reference to FIGS.
The torque detecting device according to the present embodiment corrects not only the variation of the torque signal T due to the temperature change and the assembly error of the sensor unit 71 and the I / F circuit unit 50, but also the torque signal T due to the characteristic difference of the sensor unit 71. Is characterized in that it is possible to correct the variation in the steering feeling and to eliminate the variation in the steering feeling for the same vehicle type.
It should be noted that various deviation amounts acquired in each process described below are stored in the EEPROM 29 (FIG. 2B) provided in the ECU 100.
[0023]
FIG. 4 is an explanatory diagram showing the flow of processing from the microcomputer 20 taking in the torque signal T, performing the above-described corrections, and calculating the torque value. FIGS. 5 to 7 are explanatory diagrams showing details of the processing performed in each block shown in FIG.
FIGS. 8 to 10 are flowcharts showing the flow of processing executed by the microcomputer 20 in real time. FIG. 8 is a flowchart showing a flow of a torque signal calculation performed based on the torque signal T, and FIG. 9 is a flowchart showing a flow of a temperature characteristic signal calculation performed based on the temperature characteristic signal Vt. 9 is a flowchart showing a flow of a circuit temperature calculation executed based on the circuit temperature signal th.
[0024]
FIG. 11 to FIG. 16 are flowcharts showing the flow of processing performed to acquire in advance data used when executing each processing shown in FIG. 8 to FIG. FIGS. 11 to 13 are flowcharts showing the flow of processing for acquiring data before assembling the I / F circuit unit 50 and the sensor unit 71 to an actual vehicle.
FIG. 11 is a flowchart showing a flow of a process for acquiring data such as a deviation amount of a torque signal due to a temperature change in the case of the I / F circuit unit 50 alone, and FIG. FIG. 13 is a flowchart showing a flow of a process for obtaining data such as a deviation amount of a temperature characteristic signal due to a temperature change at the time of FIG. It is a flowchart which shows.
[0025]
FIG. 14 to FIG. 16 are flowcharts showing a flow of a process of acquiring data after assembling the I / F circuit unit 50 and the sensor unit 71 to an actual vehicle.
FIG. 14 is a flowchart showing a flow of a process for obtaining torque signal data at normal temperature, and FIG. 15 is a flowchart showing a flow of a process for obtaining temperature characteristic signal data at normal temperature. 16 is a flowchart showing a flow of processing for calculating a coefficient for inductance correction.
[0026]
[Before assembly]
First, a process of acquiring data before assembling the I / F circuit unit 50 and the sensor unit 71 to an actual vehicle will be described with reference to FIGS.
First, a process for acquiring data such as a deviation amount of a torque signal due to a temperature change when the I / F circuit unit 50 alone is described with reference to FIG.
This processing is performed by the I / F circuit unit 50 separately from the sensor unit 71 when the I / F circuit unit 50 is completed. For example, a temperature aging process or a burn-in inspection of the I / F circuit unit 50 is performed. This is performed under a constant temperature environment in the process. This process is performed by applying a reference sine wave voltage to the I / F circuit unit 50 and loading the torque signal T output from the I / F circuit unit 50 into the microcomputer.
[0027]
First, a torque signal (hereinafter, referred to as a torque signal T (20)) output from the I / F circuit unit 50 placed at an ambient temperature of 20 ° C. is taken in (step (hereinafter abbreviated as S) 401), and The shift amount of the cycle of the received torque signal T (20) (hereinafter referred to as shift amount T (20)) is calculated, and the shift amount T (20) is stored in a memory (for example, a memory built in a microcomputer). (S403). Further, the deviation amount T (20) is also stored in the EEPROM 29 (FIG. 2B). The shift amount T (20) stored in the EEPROM 29 is used for calculation in a later-described torque signal circuit section offset correction (S101 in FIG. 8, and 21 in FIGS. 4 and 5).
Subsequently, a torque signal when the ambient temperature is 80 ° C. (hereinafter, referred to as a torque signal T (80)) is fetched (S405), and a shift amount of the cycle of the fetched torque signal T (80) (hereinafter, shift amount). T (80)) is stored in the memory (S407).
[0028]
Then, a value K1 obtained by subtracting the difference T (20) from the difference T (80) stored in the memory (T (80) -T (20)) by the temperature difference 60 (80-20) is obtained. The calculation is performed (S409). That is, the shift amount K1 of the cycle per 1 ° C. is obtained. Subsequently, the deviation amount K1 is stored in the EEPROM 29 (S411). This deviation amount K1 is used for calculation in later-described torque signal circuit section inclination correction (S103 in FIG. 8, and 22 in FIGS. 4 and 5).
[0029]
Next, a flow of a process for acquiring data such as a deviation amount of a temperature characteristic signal due to a temperature change in the case of the I / F circuit unit 50 alone will be described with reference to FIG.
This processing is also performed under the same environment as the processing for obtaining the amount of deviation of the cycle of the torque signal T described above.
First, a temperature characteristic signal (hereinafter referred to as a temperature characteristic signal Vt (20)) output from the I / F circuit 50 when the ambient temperature is 20 ° C. is captured (S501), and the captured temperature characteristic signal Vt (20) is acquired. (Hereinafter, referred to as a deviation amount Vt (20)), and the deviation amount Vt (20) is stored in a memory (S503). Further, the deviation amount Vt (20) is also stored in the EEPROM 29 (FIG. 2B). The deviation amount Vt (20) stored in the EEPROM 29 is used in the calculation in the temperature correction signal circuit offset correction (S201 in FIG. 9 and 26 in FIGS. 4 and 5) described later. Subsequently, a temperature characteristic signal when the ambient temperature is 80 ° C. (hereinafter, referred to as a temperature characteristic signal Vt (80)) is captured (S505), and a voltage deviation amount of the captured temperature characteristic signal Vt (80) (hereinafter, referred to as S50). , The deviation amount Vt (80)) is stored in the EEPROM 29 (S507).
[0030]
Then, a value K2 obtained by subtracting the difference Vt (20) from the difference Vt (80) stored in the memory (Vt (80) -Vt (20)) by the temperature difference 60 (80-20) is obtained. The calculation is performed (S509). That is, the shift amount K2 per 1 ° C. is obtained.
Subsequently, the deviation amount K2 is stored in the EEPROM 29 (S511). The deviation amount K2 is used for an arithmetic process in a later-described temperature characteristic signal circuit portion inclination correction (S203 in FIG. 9, and 27 in FIGS. 4 and 5).
[0031]
Next, a flow of processing for acquiring an inductance difference due to a characteristic difference of the sensor unit 71 will be described with reference to FIG.
This processing is also performed under the same environment as the processing for obtaining the amount of deviation of the cycle of the torque signal T described above. First, the inductance L1 of the sensor coil 79 at an ambient temperature of 20 ° C. is detected (S901), and the detected inductance L1 is stored in a memory (S903). Subsequently, the inductance difference ΔL is calculated by subtracting the reference inductance L0 from the inductance L1 (S905), and the calculated inductance difference ΔL is stored in the EEPROM 29 (FIG. 2B) (S907). This inductance difference ΔL is used for calculation in a torque signal sensor section characteristic difference correction (S112 in FIG. 8, and 36 in FIGS. 4 and 6) described later.
[0032]
[After assembly]
Next, a process for obtaining reference data for correcting an assembly error when the sensor unit 71 and the I / F circuit 50 are assembled in an actual vehicle will be described with reference to FIGS.
The following processes are performed in an inspection process in a factory at normal temperature (10 ° C. to 20 ° C.) when the vehicle is shipped, for example. The following processes are performed in a state where the sensor unit 71 and the I / F circuit unit 50 are assembled in an actual vehicle, the steering is steered by a predetermined reference angle, and a predetermined steering torque is generated.
[0033]
First, a flow of a process of acquiring torque signal data will be described with reference to FIG.
In the above state, the normal-temperature torque signal T (c) output from the I / F circuit unit 50 is fetched (S601), and the cycle amount of the fetched torque signal T (c) is shifted (hereinafter, the shift amount T3 (c). ) Is calculated, and the deviation amount T3 (c) is stored in the EEPROM 29 (FIG. 2B) (S603). The deviation amount T3 (c) is used for the calculation in the torque signal sensor unit offset correction (S107 in FIG. 8, 31 in FIGS. 4 and 6).
[0034]
Next, a flow of processing for acquiring temperature characteristic signal data will be described with reference to FIG.
This process is also performed in the same state as the torque signal data acquisition process (FIG. 14). The temperature characteristic signal Vt (c) at normal temperature output from the I / F circuit unit 50 is fetched (S701), and the voltage deviation amount of the fetched temperature characteristic signal Vt (c) (hereinafter, deviation amount Vt3 (c)) Is calculated, and the deviation amount Vt3 (c) is stored in the EEPROM 29 (FIG. 2B) (S703). This deviation amount Vt3 (c) is used for the calculation in the temperature characteristic signal sensor unit offset correction (S207 in FIG. 9, 34 in FIGS. 4 and 6).
[0035]
Next, a flow of a coefficient calculation process for inductance correction will be described with reference to FIG.
This process is also performed in the same state as the torque signal data acquisition process (FIG. 14). The product (K5 × Vt3 (c)) of the constant K5 and the deviation amount Vt3 (c) obtained in the temperature characteristic signal data acquisition processing (FIG. 15) described above is added to the torque signal data acquisition processing (FIG. 14). A coefficient T7 is calculated by adding the shift amount T3 (c) calculated in S603) (S801), and the coefficient T7 is stored in the EEPROM 29 (FIG. 2B) (S803). This coefficient T7 is used for calculation in torque signal sensor section inductance correction (S109 in FIG. 8, 32 in FIGS. 4 and 6) described later.
[0036]
[Flow of torque value calculation]
Next, the microcomputer 20 fetches the torque signal T from the I / F circuit unit 50 and corrects the fetched torque signal T using the various displacement amounts stored in the EEPROM 29 in the above-described processing. The flow for calculating an accurate torque value will be described with reference to FIGS. 4 to 6 and FIGS.
The following description will be made in accordance with the flow shown in FIGS.
[Torque signal circuit offset correction 21]
The microcomputer 20 fetches the torque signal T output from the I / F circuit unit 50 into the timer input 20a, calculates the cycle T (t), and calculates the shift amount stored in the EEPROM 29 in the cycle T (t). The period T1 is calculated by correction for adding T (20) (S101 in FIG. 8).
[0037]
[Conversion from voltage to temperature 24]
On the other hand, the microcomputer 20 takes in the circuit temperature signal th output from the I / F circuit section 50 in the A / D input 20c in the circuit temperature calculation of FIG. 10, and converts the voltage of the circuit temperature signal th into a circuit corresponding to the voltage. The temperature is converted into a temperature (hereinafter, referred to as a circuit temperature tc0) (S301 in FIG. 10). This conversion is performed using map data in which the voltage th and the temperature tc0 are associated with each other, as indicated by reference numeral 24 in FIG.
[100 weighted average 25]
Subsequently, the microcomputer 20 calculates the weighted circuit temperature tc using the weighted average of the 100 temperatures tc0 (S303 in FIG. 10).
[Torque signal circuit inclination correction 22]
Then, the microcomputer 20 performs a correction by multiplying the deviation amount K1 stored in the EEPROM 29 by the weighted circuit temperature tc calculated in S303 of the circuit temperature calculation in the torque signal calculation of FIG. Tc is calculated, and the cycle T2 is calculated by correction of adding the cycle T1 calculated in S101 to K1 · tc (S103 in FIG. 8).
[0038]
[Temperature signal circuit part offset correction 26]
On the other hand, the microcomputer 20 takes in the temperature characteristic signal Vt output from the I / F circuit unit 50 into the A / D input 20b in the temperature characteristic signal calculation of FIG. 9 and stores it in the EEPROM 29 in the voltage Vt of the temperature characteristic signal Vt. The voltage Vt1 is calculated by the correction for adding the deviation amount Vt (20) (S201 in FIG. 9).
[Temperature signal circuit part inclination correction 27]
Subsequently, the microcomputer 20 performs a correction of multiplying the deviation amount K2 stored in the EEPROM 29 by the weighted circuit temperature tc calculated in S303 of the circuit temperature calculation, calculates K2 · tc, and calculates K2 · tc. Calculate the voltage Vt2 by correcting the voltage Vt1 calculated in S201 to tc (S203 in FIG. 9).
[0039]
[Torque signal circuit nonlinear correction 23]
Then, in the torque signal calculation of FIG. 8, in a nonlinear region where the circuit temperature th exceeds a predetermined value, for example, 100 ° C., the microcomputer 20 adds the offset amount ΔT2 corresponding to the weighted circuit temperature tc to the cycle T2, and Is calculated to perform nonlinear correction of the torque signal circuit section (S105 in FIG. 8). The calculation of the offset amount ΔT2 is performed using map data in which ΔT2 and tc are associated with each other, as shown at 23 in FIG.
[Temperature signal circuit part inclination correction 27]
On the other hand, the microcomputer 20 adds the offset amount ΔVt2 corresponding to the weighted circuit temperature tc to the voltage Vt2 in a nonlinear region where the circuit temperature th exceeds a predetermined value, for example, 100 ° C. in the temperature characteristic signal calculation of FIG. The non-linear correction of the temperature characteristic signal circuit portion is performed by calculating Vt3 (S205 in FIG. 9). The calculation of the offset amount ΔVt2 is performed using map data in which ΔVt2 and tc are associated with each other, as shown at 28 in FIG.
[0040]
[Torque signal sensor section offset correction 31]
Then, the microcomputer 20 calculates the cycle T4 by adding the shift amount T3 (c) stored in the EEPROM 29 to the cycle T3 calculated in S105 in the torque signal calculation in FIG. 8 (S107 in FIG. 8).
[Torque signal sensor section inductance correction 32]
Subsequently, the microcomputer 20 calculates a shift amount K7 with respect to the shift amount T7 stored in the EEPROM 29, and calculates a cycle T5 by multiplying the shift amount K7 by the cycle T4 calculated in S107 (S109 in FIG. 8). ). The calculation of the shift amount K7 is performed using map data in which K7 and T7 are associated with each other, as indicated by 32 in FIG.
[0041]
[Temperature signal sensor part offset correction 34]
On the other hand, the microcomputer 20 calculates the voltage Vt4 by adding the shift amount Vt3 (c) stored in the EEPROM 29 to the voltage Vt3 calculated in S205 in the temperature characteristic signal calculation in FIG. 9 (S207 in FIG. 9).
[Conversion from voltage to temperature 44]
Subsequently, the microcomputer 20 converts the voltage Vt4 calculated in S207 into a temperature Vts (S209 in FIG. 9). This conversion is performed using map data in which the voltage Vt4 and the temperature Vts are associated with each other, as indicated by 44 in FIG.
[100 weighted average 45]
Subsequently, the microcomputer 20 calculates the circuit temperature Vtsa weighted using the weighted average of the 100 temperatures Vts (S303 in FIG. 10).
[0042]
[Torque signal sensor temperature correction 33]
Then, in the torque signal calculation of FIG. 8, the microcomputer 20 calculates the deviation ΔT5 of the inductance ΔT5 with respect to the temperature of the sensor coil 79 with respect to the weighted circuit temperature Vtsa calculated in S211 of the temperature characteristic signal calculation. The cycle T6 is calculated by adding the cycle T5 calculated in S109 to the deviation amount ΔT5 (S111 in FIG. 8).
[0043]
[Torque signal sensor section characteristic difference correction 36]
Subsequently, the microcomputer 20 reads the inductance difference ΔL stored in the EEPROM 29, calculates a correction coefficient K8 corresponding to the inductance difference ΔL using the map data indicated by 36 in FIG. 6, and calculates the cycle calculated in S111. The cycle T7 is calculated by multiplying T6 by the correction coefficient K8 (S112 in FIG. 8).
In this way, by performing the characteristic difference correction of the torque signal sensor unit, it is possible to eliminate the deviation of the cycle of the torque signal T due to the characteristic difference of the sensor unit 71.
[0044]
[Conversion from cycle to torque 41, torque value 42, 100 weighted average 43]
Then, the microcomputer 20 converts the cycle T7 calculated in S112 into a torque corresponding to the cycle T7, and calculates a torque value tq100 (S113 in FIG. 8). This conversion is performed using map data in which the cycle T7 and the torque tq100 are associated with each other, as indicated by 41 in FIG. Subsequently, the microcomputer 20 performs weighting by performing weighted averaging processing on the tq100 calculated in S113 (S115).
The weighted tq100 is sent to the motor drive circuit 102 (FIG. 2A), and the motor drive circuit 102 supplies a drive signal of a cycle corresponding to tq100 to the electric motor M. As a result, the electric motor M rotates, the rotational torque of the electric motor M is transmitted to the rack R (FIG. 1), and the steering torque is assisted.
The microcomputer 20, the EEPROM 29, and the I / F circuit unit 50 described above correspond to the torque detection device of the present invention.
[0045]
As described above, if the torque detecting device of the present embodiment is used, the deviation of the cycle of the torque signal T due to the characteristic difference of the sensor unit 71 can be eliminated by the torque signal sensor unit characteristic difference correction 36 (S112). In addition, variations in characteristics of the sensor unit 71 and the I / F circuit unit 50 due to a change in environmental temperature, processing accuracy, an assembly error, and the like can be eliminated by the above various correction processes.
Therefore, it is possible to eliminate a situation in which the steering feeling is different in the same vehicle type in which the torque detecting device is mounted.
In addition, since the correction processing can be automatically executed by software in accordance with the magnitude of the variation, it is not necessary to adjust individual analog circuits.
[0046]
Next, a torque detecting device according to a second embodiment of the present invention will be described with reference to FIGS.
The inductance of the sensor coil 79 of the sensor unit 71 may change with aging.
Therefore, for example, the configuration is such that the inductance difference ΔL can be rewritten at the time of vehicle inspection. FIG. 17 is a flowchart showing the flow of the rewriting process, and FIG. 18 is an explanatory diagram showing a steering mechanism to which the torque detection device according to the second embodiment is applied.
[0047]
As shown in FIG. 18, a detection terminal 62 for detecting the inductance of the sensor coil 79 is provided at the right end of the drawing of the steering mechanism 61, and a measuring instrument is connected to the detection terminal 62 at the time of vehicle inspection or the like. Then, the inductance L1 of the sensor coil 79 is detected. Then, the inductance difference ΔL is obtained by the flow shown in FIG.
The inductance L1 of the sensor coil 79 is detected (S921), the inductance L1 is stored in a memory (S923), and the reference inductance L0 is subtracted from the inductance L1 to obtain an inductance difference ΔL (S925). (S927).
As described above, if the torque detecting device of the second embodiment is used, even when the inductance of the sensor coil 79 changes due to aging, the inductance difference ΔL can be rewritten to the latest data. Therefore, the secular change of the steering feeling can be suppressed.
[0048]
In the above embodiments, the inductance difference ΔL is used to correct the characteristic difference of the sensor unit 71, but the difference of the impedance Z of the sensor unit 71 can be used as ΔZ. The conditions such as the ambient temperature at the time of acquiring various data before and after assembling are not limited to the above-mentioned conditions, but can be changed.
The above-described inductance difference ΔL corresponds to the characteristic difference data of the present invention, the EEPROM 29 corresponds to the characteristic difference data storage means, and S901 to S907 of FIG. 13 executed by the microcomputer 20 function as the characteristic difference data storage means of the present invention. . In addition, S112 of FIG. 8 executed by the microcomputer 20 functions as a correction unit of the present invention, and S921 to S927 of FIG. 17 function as a rewriting unit.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a structure of a steering mechanism including a partial cross section that functions by a torque detection device according to an embodiment of the present invention.
FIG. 2A is an explanatory diagram showing an electric configuration of an electric power steering device having the steering mechanism shown in FIG. 1 by blocks, and FIG. 2B is a diagram showing FIG. 2A; FIG. 4 is an explanatory diagram showing storage contents of an EEPROM 29 shown in FIG.
FIG. 3 is an explanatory diagram showing the electrical configuration of a sensor unit 71, an I / F circuit unit 50, and a microcomputer 20 by blocks.
FIG. 4 is an explanatory diagram showing, in a block diagram, a flow of processing until a microcomputer 20 takes in a torque signal T, performs each of the above-described corrections, and calculates a torque value.
FIG. 5 is an explanatory diagram showing details of processing performed in each block shown in FIG. 4;
FIG. 6 is an explanatory diagram showing details of processing performed in each block shown in FIG. 4;
FIG. 7 is an explanatory diagram showing details of processing performed in each block shown in FIG. 4;
FIG. 8 is a flowchart showing a flow of a torque signal calculation executed based on the torque signal T.
FIG. 9 is a flowchart illustrating a flow of a temperature characteristic signal calculation performed based on the temperature characteristic signal Vt.
FIG. 10 is a flowchart showing a flow of a circuit temperature calculation executed based on a circuit temperature signal th.
FIG. 11 is a flowchart illustrating a flow of a process for acquiring data such as a deviation amount of a torque signal due to a temperature change when the I / F circuit unit 50 is alone.
FIG. 12 is a flowchart illustrating a flow of a process for acquiring data such as a deviation amount of a temperature characteristic signal due to a temperature change in the case of the I / F circuit unit 50 alone.
FIG. 13 is a flowchart illustrating a flow of a process for acquiring an inductance difference due to a characteristic difference of the sensor unit 71.
FIG. 14
5 is a flowchart showing a flow of a process for obtaining torque signal data at a normal temperature.
FIG. 15 is a flowchart illustrating a flow of processing for acquiring temperature characteristic signal data at normal temperature.
FIG. 16 is a flowchart illustrating a flow of a process for calculating a coefficient for inductance correction.
FIG. 17 is a flowchart showing a flow of processing for rewriting the inductance difference ΔL in the second embodiment of the present invention.
FIG. 18 is an explanatory diagram showing a steering mechanism to which the torque detection device according to the second embodiment of the present invention is applied.
FIG. 19 is an explanatory view showing a structure of a steering mechanism of a conventional electric power steering apparatus including a partial cross section.
20 is an explanatory diagram showing in block form an electric configuration of a torque detection device provided in the steering mechanism shown in FIG. 19;
[Explanation of symbols]
20 microcomputer
29 EEPROM (characteristic difference data storage means)
50 I / F circuit section
71 Sensor section
77,78 sensor ring
79 Sensor coil

Claims (2)

A sensor unit having a sensor coil whose inductance changes according to a steering torque generated by an operation of a steering wheel connected to a steering mechanism, and a sensor that detects the inductance and outputs a torque signal having a cycle corresponding to the detected inductance. An interface circuit section for outputting, and a microcomputer for calculating the steering torque based on the torque signal output from the interface circuit section, and a drive signal corresponding to the steering torque calculated by the microcomputer . A torque detection device that drives the electric motor and detects the steering torque to function an electric power steering device that supplements the steering torque with the driving force of the electric motor.
By applying a reference sine wave voltage to the single interface circuit unit before being assembled to the electric power steering apparatus, a deviation amount of the cycle of the torque signal due to a temperature change when the interface circuit unit is a single unit. And an inductance difference due to a temperature change of a sensor coil of the single sensor unit before being assembled to the electric power steering device; and attaching the sensor unit and the interface circuit unit to the electric power steering device; When the wheel is operated at a predetermined reference angle to generate a predetermined steering torque, characteristic difference data indicating a characteristic difference including a deviation amount of a cycle of a torque signal at normal temperature output from the interface circuit unit can be rewritten. Characteristic difference data storage means for storing the
The microcomputer according to claim 1, wherein the microcomputer performs a correction corresponding to the characteristic difference data stored in the characteristic difference data storage unit on the calculated steering torque . 2. The torque detecting device according to claim 1, further comprising rewriting means for rewriting the characteristic difference data stored in the characteristic difference data storage means .

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