GB2233085A

GB2233085A - Reducing electric power consumption of steering sensor system of vehicle

Info

Publication number: GB2233085A
Application number: GB9005242A
Authority: GB
Inventors: Saiichiro Oshita; Toyohiko Mouri; Tsutomu Takahashi
Original assignee: Fuji Jukogyo KK; Fuji Heavy Industries Ltd
Current assignee: Subaru Corp
Priority date: 1989-03-14
Filing date: 1990-03-08
Publication date: 1991-01-02
Also published as: DE4008105A1; JPH02240507A; GB9005242D0

Abstract

The electric power consumption of a steering sensor system for a vehicle having a microcomputer (27) for calculating the absolute steering angle in a normal operating mode in response to an output signal from a steering sensor (23) is reduced by changing the microcomputer from the normal operation mode to a stand-by mode of low electric power consumption on switching off the ignition switch, and the operation is changed from the stand-by mode to the normal operation mode during ignition switch-off in response to a trigger signal from a deviation detecting circuit (25) which responds to any deviation of the steering angle. Thus if the steering is turned while the ignition is off, the microcomputer is switched from stand-by to normal operation and the absolute value of the steering angle is not lost. The steering angle sensor may be an optical or magnetic rotary encoder or a potentiometer. <IMAGE>

Description

1 APPARATUS AND METHOD FOR REDUCING ELECTRIC POWER CONSUMPTION OF STEERING

SENSOR SYSTEM OF VEHICLE The present invention relates to an apparatus and a method for reducing electric power consumption of a steering sensor system of a vehicle and more particularly, to an analog type steering sensor for detecting a steering angle and a steering direction of a vehicle by utilizing a sinusoidal wave current.

Generally, the vehicle has various control systems for preventing rolling, and the steering angle sensor is equipped for detecting the steering angle and the steering direction. Figs. 1A to 1C show a steering system 1 with a conventional steering sensor 10. Referring to Fig. 1A, the steering system 1 comprises a steering gear box 2 and a steering column 5. The steering gear box 2 has both ends to which knuckle arms 4 are connected through tie-rod ends 3, respectively. The steering column 5 is a nollow struccure into which a steering shaft 50 is inserted. A column cover 8 which covers an upper portion of the steering column 5 is secured to a vehicle body by an attachment 9 and bolts (not shown). The steering shaft 53 has one end connected to the steering gear box 2 through a universal joint 6 and the other end connected to a steering wheel 7. The steering sensor 10 is mounted on an approximately lower portion of the steering column 5.

The steering sensor 10, as shown in Figs. 1B and 1C, comprises photo-interrupters 11, 12 and 13. The phase difference between the photointer rupte rs 11 and 12 is 900, and the interrupters 11 and 12 generate the sinusoidal wave output in dependency on the steering angle. And photo-interrupter 13 detects a neutral position of the steering shaft 50. The photointerrupters 11, 12 and 13 include light emitting portions lla, 12a and 13a such as light emitting diodes 2 and light receiving portions llb, 12b and 13b for receiving light from the light emitting portions lla, 12a and 13a, respectively. The steering shaft 50 is composed of three shaft portions 51, 52 and 53 having a large, a small and an intermediate diameter portions, respectively, and the intermediate diameter portion 53 connects to the large and small diameter portions 51 and 52. A steering disc 55, i.e. a code plate, is mounted on an outer periphery of the intermediate shaft portion 53, which rotates together with the shaft 50. The steering disc 55 is positioned between the light emitting portions lla and the light receiving portions llb, and provided with a plurality of slits 56 radially spaced with equal pitch!s, and a neutral slit 57 represents a neutral position of the steering wheel 7.

The conventional -steering system 1 described above utilizes an optical type rotary encoder as the steering sensor 10, for the light emitting portions and receiving. In another type of conventional steering system, a magnetic-type rotary encoder is utilized as a steering sensor in which Nand S-poles are alternatively provided on the outer periphery of a steering disc or a drum with an equdl circumferential pitch. A magnetic sensor such as a magnetic resistance element or a Hall element is secured to a portion opposing to and near the outer periphery of the disc or the drum. One example of these prior art systems is disclosed in the Japanese Utility Model Laid-open Publication No. 62-51214.

The rotary encoder described above detects an amount of rotational displacement from a position before rotating, and the relative steering angle may be detected accordingly, but an absolute steering angle cannot be detected if only this type of the rotary encoder is utilized as the steering sensor.

In order to detect the absolute steering angle by the rotary encoder, the following process is necessary. When a starting position of the steering angle is zero, 3 i.e. at a neutral position, the position is set as the neutral position by the neutral slit 57 of the steering disc 55 or the rotary drum and by the photo-interrupter of the stationary side. The amount of the rotational displacement of the steering shaft against the neutral position as a reference is detected by counting pulses inputted from the rotary encoder by a microcomputer, thus obtaining the absolute steering angle and storing the same. In the next step, when pulses are input f rom the rotary encoder, the number of these pulses are counl.-ed and the amount of the displacement of the steering angle calculated by the counted pulses is added to the stored absolute steering angle. The obtained absolute steering angle is again stored as the absolute steering angle at that time. These counting, operating and storing processes must be continuously performed.

Accordingly, in a. case where a power source of the microcomputer is once switched of f by some reason, the memory of the absolute steering angle at that time is lost, the detection of the absolute steering angle is made impossible as far as the neutral position is reset even if the power source is again switched on. Therefore, it is required to maintain the connecting condition of the power source and the microcomputer in a parking time of a vehicle at which an ignition switch is off.

In addition, the steering wheel is rotated after the ignition switch is turned off, but such a case may occur. in such a case, it is necessary to detect the absolute steering angle by the manner that the microcomputer counts the pulses generated by the rotary encoder to calculate the amount of the displacement of the steering angle and adds the displacement to the stored absolute steering angle. The obtained absolute steering angle is newly stored. For this reason, it is required for the absolute steering angle detecting means to be always ready for starting operation even when the vehicle is 4 parked. Accordingly, a large amount of the electric power consumption is required even during parking and, hence, the battery may be consumed during a long parking time, thus being inconvenience.

An object of the present invention is to substantially eliminate the defects or drawbacks encountered in the prior art described above and to provide a method and an apparatus for reducing electric power consumption of a steering sensor system of a vehicle achieved by calculating an absolute steering angle of a steering wheel in a microcomputer responsive to the variation of an output signal from a steering sensor due to rotation of a steering shaft of the vehicle.

This and other objects can be achieved according to the present invention, in one aspect, by providing a method of reducing the electric power consumption of a steering sensor system for a vehicle having a microcomputer calculating an absolute steering angle in an usual operating mode responsive to an output signal from a steering sensor based on a rotation of a steering shaft of the vehicle, the method being characterized by the steps of alternating a mode of the microcomputer from a usual operation mode to a stand-by mode of low electric power consumption at a switch-off time of an ignition switch of the vehicle and rendering a steering angle deviation detection circuit operative, and changing the mode of the microcomputer from the stand-by mode to the usual operation mode in response to a trigger signal from the steering angle deviation detection circuit in dependency on the change of the steering angle.

In another aspect according to the present invention there is provided an apparatus for reducing electric power consumption of a steering sensor system for a vehicle having a microcomputer calculating an absolute steering angle in response to an output signal from a steering sensor based on a rotation of a steering shaft of the vehicle, the apparatus comprising deviation detection means for operating at a switch-off time of an ignition switch of the vehicle and transmitting a trigger signal to the microcomputer in response to the deviation of the steering angle and being characterized in that the microcomputer changes an operational mode from the usual operation mode to a stand-by mode of low electric power consumption at a switch-off time of the ignition switch, lo and the operation is changed from the stand-by mode to the usual operation mode in response to the trigger signal.

Further, according to the present invention descr:ibed above, the absolute steering angle is calculated from the output signal from the steering sensor by the microcomputer, and the operation of the microcomputer is changed to the stand-by mode of low electric power consumption in which the microcomputer is made inoperative at the "OFF" time of the ignition switch of the vehicle. In addition, a steering angle deviation detection circuit operates at the "OFF" time of the ignition switch of the vehicle and transmits the trigger signals at the deviation of the steering angle. The operation of the microcomputer is changed from the stand- by mode to the usual operation mode in response to the trigger signals from the steering angle deviation detection circuit. After a predetermined time elapses from the trailing edge of the trigger signal, the operation of the microcomputer is again transferred to the standby mode from the usual operation mode. Accordingly, the microcomputer can be accurately operated to detect the absolute steering angle when the steering wheel is operated at a parking time at which the ignition switch is turned off. Moreover, the stand-by mode with the low electric power consumption can be maintained during the parking time of the vehicle as far as the steering wheel is not operated. Thus, the electric power 6 consumption can be extremely reduced at the "OFF" time of the ignition switch and unnecessary consumption of the battery can be substantially eliminated.

In the accompanying drawings:

Fig. 1A is a schematic perspective view of a steering system having a steering sensor for a vehicle; Fig. 1B is a front view of the steering sensor shown in Fig. 1A; Fig. 1C is a side view of the steering sensor shown in Fig. 1A; Fig. 2 is a block diagram representing a circuit for detecting displacement of steering angle according to the present invention; is Fig. 3 is a circuit arrangement of a deviation detecting circuit of the circuit means shown in Fig. 2; Fig. 4 is a time chart for showing the operation according to the present invention; and Fig. 5 is a flowchart for showing the operation according to the present invention.

A preferred embodiment according.-to the present invention will be described hereunder- with reference to the accompanying drawings. A steering sensor. to be utilized for the embodiment is of a structure substantially identical to that shown in Figs. 1A to 1C, which is same as the above described conventional steering sensor.

Namely, a steering sensor 10 utilized for the present embodiment is of a two-phase output type of an incremental rotary encoder. Such an incremental rotary encoder comprises a steering disk 55 secured to a steering shaft 50, light emitting portions lla, 12a and 13a and light receiving portions llb, 12b and 13b secured to a steering column 5. The steering disk on which a plurality of slits 56 are circumferentially formed by a same pitch and a neutral slit 57 representing a neutral 7 position of a steering wheel 7 is formed, and is disposedbetween the light emitting portions lla, 12a and 13a and the light receiving portions llb, 12b, and 13b. Each of the light receiving portions llb, 12b receives an output from the corresponding light emitting portions lla, 12a pass through the slit, so as to generate an analog signal dependent on an amount of the received light. Accordingly, each of the light receiving portions llb, 12b generates a sinusoidal analog output for one pitch of the slit. The obtained sinusoidal analog output are shaped to pulses to be counted by a counter of a microcomputer 27 in a control unit C. A neutral pulse generated at the neutral position in the same manner by means of the light emitting and receiving portions 13a, 13b and the neutral slit 57. Therefore, an amount of the rotation angle displacement of the steering shaft 50 from the neutral position is detected by the counted pulses and the neutral pulse. Two pairs of the light emitting portions and the light receiving portions are arranged to shift the phase and the rotation direction of the steering shaft 50 is detected in response to the output order of the two kinds of phase- shifted outputs.

It is desirble to utilize the microcomputer 27 of the type provided with a mode of low electric power consumption which is so-called a stand-by mode in which power sources of memories are cut except a necessary memory for the absolute steering angle. The microcomputer 27 changes the processing mode from an operation mode to stand-by mode, when an ignition switch is turned off and again changes to the usual operation mode in response to an electric signal from the hardware.

Furthermore, whenever the pulse is inputted, the microcomputer 27 adds an increment or decrement of the steering angle corresponding to one pitch of the pulse to the previously stored absolute steering angle to calculate a new absolute steering angle and then stores the new angle.

These operations are continued. The 8 microcomputer 27 is equipped with a signal processing circuit and a gate circuit. The signal processing circuit forms pulses by the A/D conversion or wave shaping of the analog output such as sinusoidal waves from the steering sensor. The gate circuit decides the steering direction based on the order of inputs of the two-phase output signals as above described. In 'the stand-by mode, the microcomputer 27 equipped with these circuits is under an inoperative condition. According to the present invention, the microcomputer 27 of the type described above is set to the standby mode when the ignition switch is turned off. At the same time, a steering angle deviation detecting circuit 20 starts the operation, so as to transmit a trigger signal to the microcomputer 27 when the steering angle changes. The microcomputer 27 is switched on to carry out the usual operation mode when the steering angle deviation detecting circuit transmits the trigger signal to thereby detect the absolute steering angle. The microcomputer 27 returns again to the stand-by mode, when a predetermined time has elapsed after no deviation of the steering angle is detected.

The steering angle deviation detecting circuit 20 in the control unit C will be described hereunder with reference to Figs. 2 and 3 in more details.

Referring to Fig. 2, reference numeral 21 designates a switching circuit for supplying a power to a constant voltage circuit 22 at the "OFF" time of an ignition switch IG. Reference numeral 23 designates a sensor circuit such as the rotary encoder for the steering sensor adapted to transmit the analog signal as the sinusoidal waves. However, a steering sensor for generating a signal of such as square waves may be utilized. The steering angle deviation detecting circuit 20 of Fig. 2 is further equipped with an amplifying circuit 24, a deviation detecting circuit 25, a i 9 monastable multi-circuit 26, the microcomputer 27, and a constant voltage circuit 28 for the microcomputer 27.

In the circuit described above, the signal output from the sensor circuit 23 is, as described before, input into the microcomputer 27 by a steering angle input circuit 29 under the "OW condition of the ignition switch IG. The output signal is then pulsed and the pulse is counted by the counter to calculate the amount of deviation of the steering angle. The calculated amount is added to the stored absolute steering angle to obtain and store a new absolute steering angle. These operations are continued to detect the absolute steering angle.

The microcomputer 27 is switched into the stand-by mode when the ignition switch IG is switched to "OFF" and the operation of the microcomputer 27 stops. Under these conditions, the switching circuit 21 is changed to be the condition in which the power is supplied to the constant voltage circuit 22 and, hence, the steering angle deviation detecting circuit 20 is made operative.

The sensor circuit 23 transmits no output signal when the steering wheel 7 is not rotated under the operation mode of the steering angle deviation detecting circuit, so that the microcomputer 27 can maintain the stand-by mode. However, when the steering wheel 7 is rotated, the sensor circuit 23 generates output signals of sinusoidal waves, which are then amplified in the amplifying circuit 24 and then input into the deviation detecting circuit 25.

As shown by the time chart of Fig. 4, the deviation detecting circuit 25 generates an "OW signal when the deviation of the input signal reaches a predetermined amount and turns the "OW signal to the "OFF" condition when the deviation of the steering angle stops. The monostable multi-circuit 26 generates a pulse (a trigger signal) having predetermined time intervals to the microcomputer 27 in response to the "OW signal from the deviation detecting circuit 25.

The operation of the microcomputer 27 is changed to the usual operation mode from the stand-by mode in response to the input of the trigger signal from the monostable multi-circuit 26. The microcomputer then carries out the detection of the absolute steering angle as shown in the flowchart of Fig. 5 (steps S100, S101) in response to the output signals from the steering sensor of the sensor circuit 23 through the steering signal input circuit 29. In steps S102 and S103 in the flowchart of Fig. 5, the microcomputer 27 again returns to the stand-by mode in a case where the predetermined time is elapsed after the detection of no steering angle deviation. No deviation of the steering angle is decided at the condition where the steering angle calculated by the ste p S101 is equal to the steering angle calculated in the last routine.

As shown in the flowchart of Fig. 5, the steps are not limited to a case where the microcomputer returns to the stand-by mode. The operation of the microcomputer may be made so as to return the stand-by mode f rom the usual operation mode 'as a predetermined time elapses after the leading edge or trailing edge of the trigger signal from the monostable multi-circuit 26. As described above, the operation of the microcomputer is changed to the usual operation mode only at the time when the trigger signals are input from- the steering angle deviation detecting circuit during the "OFF" condition of the ignition switch IG, whereas the operation of the microcomputer returns to the stand-by mode when the predetermined conditions such as described above are satisfied. These operations are continued, whereby the deviation of the steering angle caused at parking time of the vehicle can be accurately read out and detect the absolute steering angle and the stand-by condition can be maintained during at a time of no deviation of the 11 steering angle. Thus, the reduction of the electric power consumption during the parking time of the vehicle can be achieved and unnecessary consumption of the battery can be eliminated.

It will be easily understood that the operation of the microcomputer 27 is changed to the usual operation mode when the ignition switch is turned on and the switching circuit 27 is simultaneously changed to make the steering angle deviation detecting circuit inoperative.

In the foregoing embodiment, the optical steering angle sensor is referred to, but a magnetic detection type or potensiometer type sensor may be utilized as far as such sens6r can-detect the steering angle.

Further, though the microcomputer detects the steering angle by counting the pulses corresponding to the sinusoidal wave signal output from the steering angle sensor, the microcomputer may directly converts the sinusoidal wave signal into the digital value to calculate the steering angle in higher resolution.

Furthermore, in the foregoing embodiment, the amplifying circuit 24 and the deviation detection circuit 25 are equipped for the detection of the steering angle deviation because the output signals from the steering angle sensor are analog output of such as sinusoidal waves. However, in a case where the output signal from the steering angle sensor is of square wave outputr the amplifying circuit 24 and the deviation detecting circuit 25 may be eliminated. In this case,, the square wave output signals from the sensor circuit 23 are directly input into the monostable multi-circuit 26, which then transmits the trigger signals with predetermined time interval every leading edge of the square output signal to thereby change the operation of the microcomputer 27 from the standby mode to the usual operation mode.

As described hereinbefore, according to the present invention, in the steering angle sensor for the vehicle is i 12 of the type in which the absolute steering angle is calculated from the output signal from the steering sensor by the microcomputer, the operation of the microcomouter is changed to the stand-by mode of low electric power consumption in which the microcomputer becomes inoperative at the "OFF" time of the ignition switch. The steering angle deviation detecting citcuit 20 operates at the "OFF" time of the ignition switch for transmitting the trigger signals at the deviation of the steering angle. The operation of the microcomputer is changed from the stand-by mode to the usual operation mode in response to the trigger signals from the steering angle deviation detecting circuit 20. After the predetermined time elapses from such as the detection of the no steering angle deviation, the operation of the microcomputer is again transferred to the stand-by mode from the usual operation mode. Accordingly, the microcomputer can be accurately operated to detect the absolute steering angle when the steering wheel is operated at the parking time at which the ignition switch is made off. Moreover, the stand-by mode of low electric power consumption can be maintained during the parking time of the vehicle as far as the steering wheel is not operated. Thus, the electric power consumption-can be largely reduced when the ignition switch is off and unnecessary consumption of the battery can be substantially eliminated.

13

Claims

CLAIMS:

1 A method of reducing electric power consumption of a steering sensor system for a vehicle having a microcomputer calculating an absolute steering angle in an usual operation mode in response to an output signal from a steering sensor based on a rotation of a steering shaft of the vehicle, comprising the steps of: altering a mode of the microcomputer from the usual operation mode to a stand-by mode of low electric power consumption at a switch-off time of an ignition switch of the vehicle and rendering operative a steering angle deviation detecting circuit; and changing the mode of the microcomputer from the stand-by mode to the usual operation mode in response to a trigger signal from the steering angle deviation detecting circuit in dependence on the deviation of the steering angle.

2. The method according to claim 1, further comprising the step of: returning the mode of the microcomputer f rom the usual operation mode to the stand-by mode when a predetermined time is elapsed after no deviation of the steering angle is detected.

The method according to claim 1, wherein: the changing step includes generating a deviation detecting signal during the deviation of steering angle and producing the trigger signal to the microcomputer in response to the deviation detecting signal so as to change the mode.

4. The method according to claim 1, further comprising the step of: returning the mode of the microcomputer from the usual operation mode to the stand-by mode when a 1 14 A predetermined time is elapsed from an edge of the trigger signal.

5. An apparatus for reducing electric power consumption of a steering sensor system for a vehicle having a microcomputer calculating an absolute steering angle in an usual operation mode in response to an output signal from a steering sensor based on a rotation of a steering shaft of the vehicle, comprising: deviation detecting means responsive to the deviation of the steering angle for operating at a switch-off time of an ignition switch of the vehicle and for transmitting a trigger signal to the microcomputer; said microcomputer carrying out the operation in a manner that the operation of the microcomputer is changed from the usual operation mode to a stand-by mode of lo w electric power consumption at a switch-off time of the ignition switch and the operation is changed from the stand-by mode to the usual operation mode in response to the trigger signal.

6. A method of reducing electric power consumption of a steering sensor system substantially as hereinbefore described with reference to Figures 2 to 5.

7. An apparatus for reducing electric power consumption of a steering sensor system for a vehicle substantially as hereinbefore described with reference to and as shown in figures 2 to 5.

Published 1990 at The, Pa:lentOfiP,,ne.Sta-te Fnuse.66'71 High Holborn, LondonWC1R4TR Further copies mkv be obtained from The Pat,-n'O.'fice Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printel by Multiplex techiliques lW, St Mary Cray, Kent, Con. P87