Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle subsystem or accessory control
Reexamination Certificate
2000-07-07
2001-11-06
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle subsystem or accessory control
C280S005510, C340S465000
Reexamination Certificate
active
06314355
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a steering angle detecting mechanism and, more particularly, a steering angle detecting mechanism in which supply of power is not interrupted in an off state of an ignition switch with reduced power consumption in the steering angle detecting mechanism.
2. Description of the Related Art
A steering angle detecting mechanism generally detects a steering angle of a steering wheel of a vehicle and comprises: a plurality of photocouplers each comprised of a light emitting element and a photodetecting element; a power source control unit for sequentially intermittently driving the plurality of photocouplers at predetermined intervals; and a micro control unit which drives the power source control unit, receives detection values outputted from the plurality of photocouplers, and calculates an absolute angle of a steering angle of the steering wheel from the detection values.
In this case, the plurality of photocouplers are arranged in positions where a light signal transmitted between the light emitting element and the photodetecting element changes according to the turn of the steering wheel, that is, positions where the turn state of the steering wheel can be detected. A change in the detection values of the plurality of photocouplers obtained according to the turn of the steering wheel is calculated by the micro control unit to thereby obtain the absolute angle of the steering angle of the steering wheel.
When the vehicle is not in use, that is, when the ignition switch is in an off state, since it is recognized that the steering wheel is not steered, the known steering angle detecting mechanism is switched to the standby mode at the same time the ignition switch is turned off. Although it is relatively rare, even in the inoperative state of the vehicle after the ignition switch is turned off, there is a case that the steering wheel is turned (operated). When the steering wheel is turned (operated) in the standby mode, the known steering angle detecting mechanism does not detect the steering angle of the turned (operated) steering wheel. When the ignition switch is turned on again and the steering angle detecting mechanism enters an normal operation mode, there is consequently an inconvenience such that a deviation occurs between the newly detected absolute angle of the steering angle and the actual absolute angle.
In order to solve the inconvenience, the following steering angle detecting mechanism is considered. When the ignition switch is turned off, the steering angle detecting mechanism is not switched to the standby mode but is maintained in the normal operation mode. In the normal operation mode, a plurality of photocouplers are driven at predetermined intervals and the absolute angle of the steering angle of the steering wheel is sequentially calculated on the basis of the detection values outputted from the plurality of photocouplers.
The newly devised steering angle detecting mechanism has, however, another inconvenience such that, since the mechanism is always set in the normal operation mode, the amount of consumption power of the vehicle-mounted power source (battery) when the vehicle is not used is large.
SUMMARY OF THE INVENTION
The present invention has been achieved in consideration of the technical background and its object is to provide a steering angle detecting mechanism capable of periodically detecting the steering angle of the steering wheel in a state where the power consumption is low when the ignition switch is off.
In order to achieve the object, according to the invention, there is provided a steering angle detecting mechanism comprising: a plurality of photocouplers for detecting a steering angle of a steering wheel; a timer circuit for setting time; a first power source control unit which is controlled by the set time of the timer circuit and intermittently drives one of the plurality of photocouplers; a second power source control unit for driving the rest of the plurality of photocouplers; a wake-up circuit for generating a wake-up signal when a detection value of the single photocoupler is different from the immediately preceding detection value of the single photocoupler; and a micro control unit which is switched between a sleep mode and a wake-up mode, wherein the micro control unit is switched to the sleep mode when an ignition switch is turned off, and to the wake-up mode for predetermined time when the wake-up signal is supplied, in the sleep mode, the micro control unit intermittently drives the single photocoupler at predetermined intervals and allows the wake-up circuit to generate the wake-up signal on the basis of the detection value of the single photocoupler, and in the wake-up mode, the micro control unit drives the plurality of photocouplers, detects a steering angle on the basis of detection values of the plurality of photocouplers, and stores the detection result.
In the construction, when the ignition switch is turned off, the micro control unit enters the sleep mode. In the sleep mode, one of the photocouplers is intermittently driven. When a detection value of the single photocoupler is the same as the previous detection value, the intermittent driving of the single photocoupler is repeated. Only when the detection value of the photocoupler is different from the immediately preceding detection value, the micro control unit is switched to the wake-up mode, drives all of the photocouplers, and obtains detection values of the photocouplers. After elapse of predetermined time, the micro control is again switched to the sleep mode. Consequently, the power consumption by the steering angle detecting mechanism can be largely reduced.
Preferably, in the steering angle detecting mechanism according to the invention, the interval at which the single photocoupler is intermittently driven is set in a range from 0.01 to 90 m sec.
When the interval of intermittently driving the single photocoupler is set shorter than 0.01 m sec, the driving time of the photocoupler becomes too short and a problem such that it is difficult to periodically detect the rotating timings of the steering wheel often occurs. On the other hand, when the interval of intermittent driving becomes longer than 90 m sec, a problem occurs such that it is difficult to accurately detect the rotational angle at the rotational speed level at which the steering wheel is rotated 6 times per second. It is therefore preferable to set the interval at which the single photocoupler is intermittently driven within the above range.
With the construction, the power consumption in the steering angle detecting mechanism can be reduced and the steering angle can be periodically detected with high reliability.
Further, in the steering angle detecting mechanism according to the invention, driving time of the single photocoupler is 0.005 m sec or longer and is set to 50% or lower of the interval at which the photocoupler is intermittently driven.
When the driving time of the single photocoupler is set to less than 0.005 m sec, the driving time is too short to make the photocoupler respond. A problem such that it is difficult to accurately detect the steering angle of the steering wheel occurs. When the driving time of the photocoupler is 50% or lower of the interval, the shorter the driving time is, the more the power consumption of the steering angle detecting mechanism can be reduced. Thus, it is desirable to set the driving time of the photocoupler within the range.
With such a construction, the power consumption can be reduced more than the half as compared with that of the conventional technique. The power which is larger than the power consumed to drive the circuits except for the photocouplers in the steering angle detecting mechanism can be reduced. Consequently, the effect of reduction in the power consumed by the steering angle detecting mechanism can be increased conspicuously and the steering angle can be detected periodically and accurately.
As a preferred embodiment of the construction, the in
Hoshi Toshiyuki
Kato Hironori
Mizuta Ken
Sanpei Yoshio
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Cuchlinski Jr. William A.
Hernandez Olga
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