JPH0995247A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a magnetostrictive torque sensor to be used for the power steering control, and to improve the degree of freedom of design thereof. SOLUTION: Since a magnetostrictive torque sensor 12 is arranged remarkably close to a power steering control unit 8, even the faint signal from a detecting coil 40 can be transmitted to a power steering control unit 8 as a detecting signal through a signal line 44 without receiving the influence of noise. The magnetostrictive torque sensor 12 is thereby formed of a detecting coil 40 and an exciting coil 41, and other structure is arranged inside of the power steering control unit 8, or a software logic of the power steering control unit 8 is substituted for them. Volume of the magnetostrictive torque sensor 12 in the periphery of a steering shaft 10 is thereby reduced so as to facilitate the design. Furthermore, since the software logic can be substituted for a part thereof, the device can be miniaturized in total.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering device, and more particularly to an electric power steering device that detects a steering state using a magnetostrictive torque sensor.

[0002]

2. Description of the Related Art Conventionally, a general power steering device using an electric motor in an automobile is disclosed in Japanese Patent Laid-Open No. 5-25.
As shown in Nos. 4449-254451, an electric motor is provided on the shaft immediately below the steering wheel, a power steering control unit is provided in the dashboard to detect the torque applied to the steering shaft during steering, and the electric motor is driven according to the torque state. Steering is assisted by controlling the motor and transmitting the driving force to the steering shaft.

A magnetostrictive torque sensor is used as one of the torque sensors for detecting the torque generated on the steering shaft during steering. This magnetostrictive torque sensor does not have a torsion bar portion as compared with a torque sensor that detects a torsion angle due to a torsion bar, which is a typical one of other torque sensors. There was an advantage that you could get a feeling.

[0004]

However, the magnetostrictive torque sensor electrically captures the change in magnetic permeability caused by the distortion of the steering shaft, and the signal output from the coil for detection thereof is extremely weak. Therefore, if the weak signal as it is is transmitted from the magnetostrictive torque sensor to the power steering control unit via a long signal line, noise is likely to be generated, and the weak signal is transmitted at the position of the magnetostrictive torque sensor. It had to be amplified.
Along with this, in order to prevent the neutral point of steering from being shifted due to the influence of temperature, etc. being amplified, a mechanism (mechanical reversing switch) for neutral point correction processing and a neutral point correction processing The signal processing unit of was also provided in the magnetostrictive torque sensor.

Therefore, in addition to the magnetostriction detection coil, the excitation coil, and the excitation control unit, the steering shaft immediately below the steering wheel is provided with an amplification unit and a mechanism for correcting the neutral point and a signal processing unit. Since the torque sensor has to be arranged, the size of the torque sensor may be increased, and the arrangement may be difficult in design.

An object of the present invention is to reduce the size of the magnetostrictive torque sensor and improve the degree of freedom in design.

[0007]

Means for Solving the Problems and Effects of the Invention
The described invention is a rack bar that steers left and right wheels by moving left and right by a steering force from a steering shaft, a power steering control unit attached to a casing of the rack bar, and a control by the power steering control unit. The power steering control unit controls the drive unit according to the state of steering to move the rack bar left and right, thereby assisting the steering of the left and right wheels by the steering shaft. An electric power steering device, wherein a part of an amplification unit or an excitation control unit in a magnetostrictive torque sensor that is provided in the vicinity of a position for transmitting a steering force to the rack bar in the steering shaft and detects the steering state, or All of them are provided in the power steering control unit. That is an electric power steering system.

According to a second aspect of the present invention, the power steering control section itself also processes the detection signal amplified by the amplification section of the magnetostrictive torque sensor. It is an electric power steering device.

According to a third aspect of the present invention, the casing of the rack bar, the casing of the power steering control unit, or the casing of the magnetostrictive torque sensor is made of metal, and the casing between the magnetostrictive torque sensor and the power steering control unit is provided. The electric power steering apparatus according to claim 1 or 2, wherein the signal line passes through the inside of the metal casing.

According to a fourth aspect of the present invention, the power steering control section corrects the neutral point of the magnetostrictive torque sensor based on the data obtained in the power steering control. It is an electric power steering device.

According to a fifth aspect of the present invention, the power steering control section has a dead zone for power steering control in the vicinity of the neutral point of the magnetostrictive torque sensor. Is an electric power steering device.

In the electric power steering apparatus according to the first aspect of the present invention, the amplifying section or the exciting section of the magnetostrictive torque sensor is provided in the steering shaft in the vicinity of the position for transmitting the steering force to the rack bar and detects the steering state. Since a part or all of the control unit is provided in the power steering control unit, the magnetostrictive torque sensor does not become large, and the arrangement does not become difficult in terms of design.

Since the magnetostrictive torque sensor is provided in the vicinity of the position where the steering shaft transmits the steering force to the rack bar, the magnetostrictive torque sensor and the power steering control mounted on the rack bar casing are controlled. The parts are extremely close to each other in terms of distance. Therefore, by providing a part or all of the amplification section or the excitation control section of the magnetostrictive torque sensor in the power steering control section, a signal line is passed between the magnetostrictive torque sensor and the power steering control section. This signal line becomes extremely short, making it difficult for noise to travel.

Further, since the power steering control unit normally performs control processing by software logic according to a program, the program uses an actual detection signal amplified by the amplification unit of the magnetostrictive torque sensor. By including the processing for calculating the torque and other processing, the signal processing unit of the magnetostrictive torque sensor can be omitted, so the overall size can be reduced, the number of parts can be reduced, and the manufacturing cost can be reduced. it can.

Further, since the magnetostrictive torque sensor is provided in the vicinity of the position where the steering force is transmitted to the rack bar, the power steering control unit means the inside of the rack bar casing, the casing of the power steering control unit itself, or The signal line can be passed through the casing of the magnetostrictive torque sensor to signal-connect the magnetostrictive torque sensor and the power steering control unit. As a result, since the casing of the rack bar, the casing of the power steering controller, or the casing of the magnetostrictive torque sensor is usually made of metal, electromagnetic shielding becomes possible, and external noise is less likely to travel on the signal line.

Further, if the power steering control section is also configured to process the detection signal amplified by the amplification section of the magnetostrictive torque sensor, the power steering control section is obtained or used in the power steering control. Data is also available, based on that data,
The magnetostrictive torque sensor may be configured to perform neutral point correction. If the power steering control unit detects its own temperature, the power steering control unit and the magnetostrictive torque sensor are close in distance, so the temperature of the power steering control unit itself is regarded as the temperature of the magnetostrictive torque sensor. It is also possible to correct the neutral point.

By doing so, the conventional magnetostrictive torque sensor is provided with the mechanical reversing switch and the temperature sensor, and the neutral point of the detected value is obtained according to the reversing of the switch and the detected temperature. Unlike the above case, the magnetostrictive torque sensor does not need to have a mechanical reversing switch or a temperature sensor. If such a mechanical reversing switch or temperature sensor is not provided in the magnetostrictive torque sensor, the volume of the magnetostrictive torque sensor around the steering shaft becomes small, which facilitates the design.

Further, the power steering control section may perform power steering control having a dead zone near the neutral point of the magnetostrictive torque sensor. In the vicinity of the neutral point, due to mechanical play, temperature, etc., even if it is actually the neutral point, a signal as if steering had occurred may occur, and therefore power steering control is executed complicatedly. Can be prevented.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a partially cutaway explanatory view showing an electric power steering device 2. The electric power steering device 2 includes a rack bar 4, a motor unit 6, a power steering control unit 8, a steering shaft 10, and a magnetostrictive torque sensor 12.

The rack bar 4 has ball joints 4a and 4b formed at both ends thereof and is connected to tie rods 14 and 16 which are partially shown. The tie rods 14 and 16 are connected to knuckle arms of left and right wheels of an automobile (not shown), and the left and right movements of the rack bar 4 are reflected in the direction changes of the left and right wheels.

The rack bar 4 is slidably supported in the casing 18 in the left and right directions. A rotor 20 of the motor unit 6 is arranged in the casing 18, and a rotor shaft 22 thereof has a cylindrical shape, and the rack bar 4 slidably penetrates through the inside thereof. Further, the stator 24 of the motor unit 6 is arranged outside the rotor 20. This motor section 6
The rotation of the rotor 20 is controlled by the power steering control unit 8 via the current control power driver 54 (FIG. 4) in the power steering control unit 8.

A rotor shaft 22 that rotates integrally with the rotor 20 is connected to a ball nut 26 at the right end of FIG. The ball nut 26 is provided with a ball 28 and a spiral groove 30 formed in a part of the rack bar 4 and having a semicircular cross section.
Is fitted. Therefore, when the power steering control unit 8 controls the normal rotation / reverse rotation of the rotor 20, the ball nut 26 normally rotates / reverses via the rotor shaft 22,
An auxiliary moving force can be applied to the rack bar 4 in any left and right directions. As a result, power steering control can be executed.

As shown in the partially enlarged explanatory view of the electric power steering apparatus 2 of FIG. 2, the steering shaft 10 is shown.
Receives the steering force of a steering wheel (not shown) from the serration portion 32 on the input side, and the rack 3 formed on a part of the rack bar 4 at the pinion portion 34 on the output side.
6 to move the rack bar 4 left and right.

A magnetostrictive torque sensor 12 is provided on the steering shaft 10 intermediate between the serration portion 32 and the pinion portion 34 to detect the strain caused by steering of the steering wheel. The magnetostrictive torque sensor 1
In FIG. 2, only the detection coil 40 and the excitation coil 41 are arranged inside the casing 12 a of the magnetostrictive torque sensor 12.

Casing 12 of magnetostrictive torque sensor 12
“A” is made of an aluminum alloy and is integrally formed with the casing 18 of the rack bar 4 which is also made of an aluminum alloy. The casing 12a and the casing 18 extending from the magnetostrictive torque sensor 12 to the power steering control unit 8 on the casing 18 are provided with a line insertion hole 42, and the inside thereof is provided with a signal line from the detection coil 40 of the magnetostrictive torque sensor 12. An exciting current line 46 from the power steering control unit 8 and the power steering control unit 8 runs.

As shown in the schematic diagram of FIG. 3 and the block diagram of FIG. 4, the power steering controller 8 includes a microprocessor unit (MPU) 52 as a center, a current control power driver 54, a motor current control field effect transistor ( FET) 56, FET temperature sensor 58, power feeding system switch 60, power feeding voltage sensor 62, normal operation monitoring device 64, and RS232C interface (I / F) 66.

In the power steering control in the microprocessor unit 52, the detection signal from the magnetostrictive torque sensor 12 is subjected to arithmetic processing as a torque detection circuit to obtain a steering torque and a steering direction, and the steering torque and direction. In response to this, the current control power driver 54 is instructed about the direction of rotation of the motor unit 6 and the amount of torque.
The current control power driver 54 controls the rotation direction and the output torque of the motor unit 6 via the motor current control field effect transistor 56 based on the direction and the torque amount instructed by the microprocessor unit 52. During this power steering control, the microprocessor unit 52 operates from the rotational position sensor 68 to the rotational position of the motor unit 6 and from the current amount sensor 70 to the motor unit 6.
It monitors the actual amount of current flowing through.

In the power steering control,
Depending on the vehicle speed obtained from the vehicle speed sensor 72, various output patterns of the rotation direction and the torque amount of the motor unit 6 are adjusted based on the steering torque and the direction obtained from the signal of the magnetostrictive torque sensor 12, for example, at a low speed. The steering wheel 74 is controlled so that it can be steered more lightly when the vehicle is stationary, and the steering feeling is controlled so that the steering feeling can be enjoyed at medium and high speeds.

If the FET temperature sensor 58 determines that the motor current control field effect transistor 56 is overheated, or if the power supply voltage sensor 62 determines that the power supply to the battery B is insufficient. The microprocessor unit 52 stops the power steering control, turns off the power supply system switch 60, and stops the power supply to the current control power driver 54.
When the normal operation monitoring device 64 determines that the microprocessor unit 52 itself is abnormal, the normal operation monitoring device 64 turns off the power supply system switch 60 to stop the power supply to the current control power driver 54. To do.
The RS232C interface 66 is provided for communication processing with other control devices and the like. The exciting coil 41 of the magnetostrictive torque sensor 12 is supplied with an exciting current through an exciting current line 46 by an exciting controller (not shown) arranged in the power steering controller 8.

As described above, the microprocessor unit 52 also has a built-in amplifier for the detection signal from the detection coil 40 of the magnetostrictive torque sensor 12, and amplifies the detection signal from the detection coil 40. The steering torque and the steering direction are obtained by converting into a digital value and performing arithmetic processing as a torque detection circuit. As shown in FIGS. 3 and 4, the microprocessor unit 52 obtains data from the other control device via the RS232C interface 66 or the vehicle speed or the rotational position of the motor unit 6 for power steering control. Further, the temperature data of the field effect transistor 56 for controlling the motor current, which is a part of the power steering controller 8, is also obtained from the FET temperature sensor 58. Therefore, the neutral point of the detection signal from the magnetostrictive torque sensor 12 can be determined based on these data.

In addition to the detecting coil 40 and the exciting coil 41, a torque detecting circuit, a temperature sensor, or a mechanical reversing switch is provided in the casing 12a as in the conventional case.
Unlike the case where the detected signal is amplified by the torque detection circuit and the neutral point of the detected value is obtained according to the temperature detected by the reversal of the mechanical reversing switch or the temperature sensor, the inside of the casing 12a is Only the detection coil 40 and the excitation coil 41 are required. For this reason, it is not necessary to arrange anything other than the detection coil 40 and the excitation coil 41 in the casing 12a of the magnetostrictive torque sensor 12, and the magnetostrictive torque sensor 12 around the steering shaft 10 is eliminated.
The volume is small and the design is easy. Furthermore, since the magnetostrictive torque sensor 12 has no internal electronic circuit,
The casing 12a itself may be cheaper than the conventional one.

In the electric power steering apparatus 2, the magnetostrictive torque sensor 12 is provided in the vicinity of the pinion portion 34 which contacts the rack 36 formed in a part of the rack bar 4 and transmits the steering operation. Therefore, the rack bar 4
The magnetostrictive torque sensor 12 exists at a position very close to the power steering control unit 8 provided in the casing 18.

Therefore, even a weak signal from the detection coil 40 can be transmitted to the power steering controller 8 through the signal line 44 with almost no noise. Further, in particular, in the electric power steering apparatus 2, the line insertion hole 42 that penetrates the signal line 44 that transmits the weak signal of the detection coil 40 through the casings 12a and 18 made of aluminum alloy.
The power steering controller 8 is inserted through the inside without going outside. Therefore, the electromagnetic shielding effect of the casings 12a and 18 can almost completely block noise from the outside.

Also, in the power steering control section 8, the signal processing section for the calculation processing of the detection signal of the magnetostrictive torque sensor 12 becomes unnecessary by changing the software logic, and it is not necessary to increase the size. . For this reason, the size can be reduced overall, the degree of freedom in designing an automobile can be increased, and the cost can be reduced.

[Others] The power steering control unit 8 has determined the neutral point of steering, but in the vicinity of the neutral point,
A slight torque change unrelated to steering may occur due to mechanical play between the pinion portion 34 and the rack 36, temperature, or the like. When such a torque change occurs, the power steering control may be complicatedly executed. Therefore, in the vicinity of the neutral point, there is a dead zone in the power steering control according to the calculated steering torque, and the complicated control processing is performed. May be prevented.

Signal line 44 and exciting current line 46
Is the line insertion hole 42 of the casing 18 of the rack bar 4.
The casing of the power steering control unit 8 is partially extended to be connected to the casing 12a of the magnetostrictive torque sensor 12, and a line insertion hole is formed in a portion of the casing of the power steering control unit 8. It may be formed and the signal line 44 and the exciting current line 46 may be inserted therein. In addition, a part of the casing 12a of the magnetostrictive torque sensor 12 is extended to the power steering control unit 8, and the casing 12 of the magnetostrictive torque sensor 12 is extended.
It is also possible to form a line insertion hole in a part of a and insert the signal line 44 and the exciting current line 46 therethrough.

Furthermore, the signal line 44 and the exciting current line 46 may be independent through holes, that is, dedicated through holes for each line. Further, when a temperature sensor is provided near the magnetostrictive torque sensor 12 in order to perform torque detection that requires a particularly high accuracy, the signal line of the temperature sensor may be inserted through any of the above insertion holes. .

[Brief description of drawings]

FIG. 1 is a partially cutaway explanatory view showing an electric power steering device.

FIG. 2 is a partially enlarged explanatory diagram thereof.

FIG. 3 is a schematic diagram of an electric power steering device.

FIG. 4 is a block diagram of an electric power steering device.

[Explanation of symbols]

2 ... Electric power steering device 4 ... Rack bar 4a, 4b ... Ball joint 6 ... Motor part 8 ... Power steering control part 10 ... Steering shaft 12 ... Magnetostrictive torque sensor 12a, 18 ... Casing 14, 16 ... Tie rod 20 ... Rotor 22 ... Rotor shaft 24 ... Stator 26 ... Ball nut 32 ... Serration part 34 ... Pinion part 36 ... Rack 40 ... Detection coil 41 ... Excitation coil 42 ... Line insertion hole 44 ...
Signal line 46 ... Excitation current line 52 ... Microprocessor unit 54 ... Current control power driver 56 ... Motor current control field effect transistor 58 ... FET temperature sensor 60 ... Power supply system switch 62 ... Power supply voltage sensor 64 ... Normal operation monitoring Device 66 ... RS232C interface 68 ... Rotation position sensor 70 ... Current amount sensor 72 ... Vehicle speed sensor 74 ... Steering wheel

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirotaka Umeda 1203 Shimoda, Naka Ushiyama, Kasugai, Aichi Prefecture

Claims (5)

[Claims] 1. A rack bar for steering left and right wheels by moving left and right by a steering force from a steering shaft, a power steering control unit attached to a casing of the rack bar, and a control by the power steering control unit. The power steering control unit controls the drive unit according to the state of steering to move the rack bar left and right, thereby assisting the steering of the left and right wheels by the steering shaft. An electric power steering apparatus, comprising: a steering shaft, a portion of an amplification unit or an excitation control unit of a magnetostrictive torque sensor that is provided near a position for transmitting a steering force to the rack bar and detects the steering state, or All are provided in the power steering controller An electric power steering device. 2. The electric power steering apparatus according to claim 1, wherein the power steering control unit itself also processes the detection signal amplified by the amplification unit of the magnetostrictive torque sensor. 3. The casing of the rack bar, the casing of the power steering control unit or the casing of the magnetostrictive torque sensor is made of metal, and a signal line between the magnetostrictive torque sensor and the power steering control unit is
The electric power steering apparatus according to claim 1 or 2, wherein the electric power steering apparatus passes through the inside of the metal casing. 4. The electric power steering apparatus according to claim 2, wherein the power steering control unit corrects the neutral point of the magnetostrictive torque sensor based on the data obtained in the power steering control. 5. The electric power steering apparatus according to claim 1, wherein the power steering control section has a dead zone for power steering control near a neutral point of the magnetostrictive torque sensor.