TORQUE SENSOR FOR VEHICLE STEERING SYSTEM

Abstract

A torque sensor for a vehicle steering system having a power source, an oscillator and an offset voltage circuit part includes a current amplifier, first and second coils that are in series and connected at both ends thereof to output terminals of said current amplifier and said offset voltage circuit part, respectively, and first and second resistances that are in series and connected in parallel to said first and second coils. The torque sensor further includes first and second waveform selecting parts, first and second peak detectors, a first differential amplifier, and a first voltage-current converter.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is based on, and claims priority from, Korean Application Serial Number 10-2004-0104194, filed on Dec. 10, 2004, the disclosure of which is hereby incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to a torque sensor for a vehicle steering system adapted to prevent a distortion phenomenon of a torque detecting signal due to a temperature variation of a coil part of the torque sensor or the like.

BACKGROUND OF THE INVENTION

Generally, an Electronic Control Unit (ECU) of an Electrical Power Steering (EPS) system controls the steering of a vehicle by detecting steering torque according to the manipulation of a steering wheel of a driver through a torque sensor.

In the torque sensor of the EPS system, an output waveform of the torque detecting coil is sampled through a sampling pulse circuit.

The phase and amplitude of the output signal vary according to an impedance variation of the torque detecting coil. When a phase variation occurs due to environmental effect such as a temperature variation, or the like if a precise sampling of the signal is not executed, reliability of the torque sensor deteriorates by, for example, a distortion phenomenon of the torque detecting signal.

SUMMARY OF THE INVENTION

Embodiments of the present invention are provided to prevent a distortion phenomenon of a torque detecting signal caused by a variation of the amplitude and phase of an output signal of a coil part (temperature correcting coil and torque detecting coil) due to a temperature variation of the coil part of a torque sensor for a steering system or the like.

A torque sensor for a vehicle steering system includes a power source for supplying power. An oscillator oscillates by receiving a voltage from the power source. An offset voltage circuit part generates an offset voltage by using the voltage applied from the power source. A current amplifier outputs an offset voltage and an alternating current voltage, which is in-phase with a voltage outputted from the oscillator. A first and second coil are in series and connected at both ends thereof to output terminals of the current amplifier and the offset voltage circuit part. A first and second resistance are in series and connected in parallel to the first and second coil. A first and second waveform selecting part receive an alternating current voltage from a contact part of the first and second coil and from a contact part of the first and second resistance and then select and output a half-period of the alternating current voltage. A first and second peak detector detect a peak value of each output voltage of the first and second waveform selecting part. A first differential amplifier executes differential amplification by receiving voltages from the first and second peak detector. A first voltage-current converter outputs a torque signal by converting a voltage, which is outputted from the first differential amplifier, into a current.

The torque sensor further includes a third and fourth resistance that are in series and connected in parallel to the first and second coil. A third and fourth waveform selecting part receive an alternating current voltage from a contact part of the first and second coil and a contact part of the third and fourth resistance and then select and output a half-period of the alternating current voltage. A third and fourth peak detector detect a peak value of each output voltage of the third and fourth waveform selecting part. A second differential amplifier executes differential amplification by receiving voltages from the third and fourth peak detector. A second voltage-current converter outputs a fail-safe torque signal by converting a voltage, which is outputted from the second differential amplifier, into a current.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the nature and objects of the present invention, reference should be made to the following detailed description with the accompanying drawings, in which:

FIG. 1 is a block diagram of a torque sensor for a steering system according to an embodiment of the present invention;

FIG. 2 illustrates a waveform of an output voltage of an oscillator according to an embodiment of the present invention;

FIG. 3a illustrates a waveform of an output voltage of a current amplifier according to an embodiment of the present invention;

FIG. 3b illustrates a waveform of an output voltage of an offset voltage circuit part according to an embodiment of the present invention;

FIG. 4 illustrates a waveform of an output voltage of a first and second coil contact part according to an embodiment of the present invention;

FIG. 5 illustrates a waveform of an output voltage from a first and second waveform selecting part and a third and fourth waveform selecting part according to an embodiment of the present invention; and

FIG. 6 illustrates a waveform of an output voltage from a first and second peak detector and a third and fourth peak detector according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, an embodiment of the present invention is provided to prevent a distortion phenomenon of a torque detecting signal caused by a variation of a phase and amplitude of a signal outputted from a coil part (temperature correcting coil and torque detecting coil) due to a temperature variation of the coil part of a torque sensor for a steering system or the like. This is achieved by selecting a waveform and detecting a peak value after oscillating an oscillator via an applied voltage.

The torque sensor according to the embodiment of the present invention includes a power source (E) for supplying power. An oscillator 2 oscillates by receiving a voltage from power source (E). An offset voltage circuit, part 6 generates an offset voltage (V_offset) by using the voltage applied from power source (E). A current amplifier 4 outputs an offset voltage (V_offset) and an alternating current (AC) voltage, which is in-phase with a voltage outputted from oscillator 2. A first and second coil (L1, L2) are in series and are connected at both ends thereof to output terminals of current amplifier 4 and offset voltage circuit part 6. A first and second resistance (R1, R2) are in series and are connected in parallel to first and second coil (L1, L2). A first and second waveform selecting part 8a, 8a′ receive an alternating current (AC) voltage from a contact part (A) of first and second coil (L1, L2) and from a contact part (B) of first and second resistance (R1, R2) and then select and output a half-period of the AC voltage. A first and second peak detector 10a, 10a′ detect a peak value of each output voltage of first and second waveform selecting part 8a, 8a′. A first differential amplifier 12a performs differential amplification by receiving voltages outputted through first and second peak detector 10a,10a′. A first voltage-current converter 14a outputs a torque signal (Ts) by converting a voltage, which is outputted from first differential amplifier 12a, into a current.

The torque sensor according to the embodiment of the present invention is configured to detect a fail-safe torque.

A third and fourth resistance (R1′, R2′) are in series and connected in parallel to first and second coil (L1, L2). A third and fourth waveform selecting part 8b, 8b′ receive an AC voltage from contact part (A) of first and second coil (L1, L2) and a contact part (B′) of third and fourth resistance (R1′, R2′) and then select and output a half-period of the AC voltage. A third and fourth peak detector 10b, 10b′ detect a peak value of each output voltage of third and fourth waveform selecting part 8b, 8b′. A second differential amplifier 12b executes differential amplification by receiving voltages outputted through third and fourth peak detector 10b, 10b′. A second voltage-current converter 14b outputs a torque signal (Ts′) by converting a voltage, which is outputted from second differential amplifier 12b, into a current. The fail-safe torque is required to make a steering by using torque detecting signal (Ts′) when an abnormality of torque detecting signal (Ts) or the like occurs.

First and second waveform selecting part 8a, 8a′ and third and fourth waveform selecting part 8b, 8b′ can preferably be half-wave rectifier circuits.

The operation of the torque sensor according to the embodiment of the present invention will now be described with reference to drawings.

As illustrated in FIG. 1, when the power is provided from power source (E) to oscillator 2, an oscillating voltage of oscillator 2 is applied to current amplifier 4. An output waveform (Va) of oscillator 2 is illustrated in FIG. 2.

Current amplifier 4 outputs a direct current (DC) voltage (V_offset) and an AC voltage (Vb), which is in-phase with an output voltage of oscillator 2, into a temperature correcting coil (L1, first coil) (see FIG. 3a). Simultaneously, a DC voltage (V_offset) is inputted into a torque detecting coil (L2, second coil) through offset voltage circuit part 6 generating the offset voltage (V_offset) by using the power from power source (E) (see FIG. 3b).

Temperature correcting coil (L1, first coil) and torque detecting coil (L2, second coil) are connected in series between an output terminal of current amplifier 4 and an output terminal of offset voltage circuit part 6. An amplitude of an AC voltage of a contact part (A) between temperature correcting coil (L1) and torque detecting coil (L2) varies according to the difference between inductance of temperature correcting coil (L1) and inductance of torque detecting coil (L2) (see FIG. 4).

First and second resistance (R1, R2) are connected in parallel to temperature correcting coil (L1) and torque detecting coil (L2). If the values of first and second resistance (R1, R2) are identical to each other, only the DC voltage (V_offset) is applied into contact part (B). In case third and fourth resistance (R3, R4) have an identical value, the voltage of contact part (B′) and the voltage of contact part (B) are identical.

Voltages of contact parts (A, B) of first and second coil (L1, L2) and first and second resistance (R1, R2) are applied to first waveform selecting part 8a and second waveform selecting part 8a′, respectively. A signal waveform (Vd) outputted through first and second waveform selecting part 8a, 8a′ is shown in FIG. 5. As shown in FIG. 5, a signal outputted through first and second waveform selecting part 8a, 8a′ (half-wave rectifier circuits) is a signal that has selected only a half-period of the applied AC voltage.

In reference to FIG. 6, the output signal from first and second waveform selecting part 8a and 8a′ is applied into first and second peak detecting part 10a, 10a′, respectively, to detect a peak value (Vp) of the applied AC signal (Vd1-Vd3). For overcoming a discordance with a sampling pulse generating circuit which conventionally occurs according to a variation of an amplitude and phase of coils (L1, L2) due to a temperature variation or the like, a rectification conversion of an AC signal from oscillator 2 and a detection of a peak value of the rectified signal are pre-executed in the embodiment of the present invention.

A differential amplification is produced in the voltage supplied to first differential amplifier 12a from first and second peak detecting part 10a, 10a′ and then the differential amplified signal is outputted as a torque detecting signal (Ts) through first voltage-current converter 14a. The outputted torque detecting signal is inputted into an Electronic Control Unit (ECU, not shown), thus a steering force is obtained by operating a motor according to torque detecting signal (Ts).

In the fail-safe torque detecting sensor according to the embodiment of the present invention, operations of third and fourth waveform selecting part 8b, 8b′, third and fourth peak detecting part 10b, 10b′, second differential amplifier 12b, and second voltage-current converter 14b are identical to that of the main circuit of torque detecting sensor described above. Therefore, fail-safe torque detecting signal (Ts′) is employed to detect a torque in a fail-safe torque detecting sensor in case of an abnormality of main torque detecting signal (Ts) or the like.

In order to prevent a distortion phenomenon of the outputted torque detecting signal even in case a phase and amplitude vary due to a temperature variation of the coil part (temperature correcting coil and torque detecting coil) of the torque sensor or the like, a rectification conversion through waveform selecting parts of the rectifier circuit and a peak value of a signal converted into rectification are detected after oscillating oscillator 2 by using the power supplied from power source (E).

The technical concept is not limited to the embodiment of the present invention and should be determined by a logical interpretation within the scope of claims of the present invention.

As apparent from the foregoing, there is an advantage in the torque sensor for a vehicle steering system in that a distortion phenomenon of a torque detecting signal according to the phase variation in the coil part due to a temperature variation or the like is prevented.

Claims

1. A torque sensor for a vehicle steering system, comprising:

a power source that supplies power;

an oscillator that oscillates by receiving a voltage from said power source;

an offset voltage circuit part that generates an offset voltage by using said voltage supplied from said power source;

a current amplifier that outputs an alternating current voltage which is in-phase with a voltage outputted from said oscillator;

first and second coils that are in series and connected at both ends thereof to output terminals of said current amplifier and said offset voltage circuit part, respectively;

first and second resistances that are in series and connected in parallel to said first and second coils;

first and second waveform selecting parts that receive an alternating current voltage from a contact part of said first and second resistances and from a contact part of said first and second coils, respectively, and then select and output a half-period of said alternating current voltage;

first and second peak detectors that detect a peak value of each output voltage of said first and second waveform selecting parts;

a first differential amplifier that executes differential amplification by receiving voltages outputted through said first and second peak detectors;

a first voltage-current converter that outputs a torque signal by converting a voltage, which is outputted from said first differential amplifier, into a current; and

third and fourth resistances being in series and connected in parallel to said first and second coils;

third and fourth waveform selecting parts that receive an alternating current voltage from a contact part of said third and fourth resistances and from a contact part of said first and second coils, respectively, and then select and output a half-period of said alternating current voltage;

third and fourth peak detectors that detect a peak value of each output voltage of said third and fourth waveform selecting parts;

a second differential amplifier that executes differential amplification by receiving voltages outputted through said third and fourth peak detectors; and a second voltage-current converter that outputs a fail-safe torque signal by converting a voltage, which is outputted from said second differential amplifier, into a current.

2. (canceled)

3. The torque sensor as defined in claim 1, wherein each of said first, second, third and fourth waveform selecting parts include a half-wave rectifier circuit.

4. (canceled)