Electricity: motive power systems – Periodic – repetitious or successive operations control of...
Reexamination Certificate
2000-05-30
2002-06-04
Fletcher, Marlon T. (Department: 2837)
Electricity: motive power systems
Periodic, repetitious or successive operations control of...
C318S444000, C318S445000
Reexamination Certificate
active
06400110
ABSTRACT:
BACKGOUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wiper control apparatus using a semiconductor switching element such as a MOSFET.
2. Description of the Prior Art
One of previously known wiper control apparatus is disclosed in JP-A-9-193748. In this wiper control apparatus, as seen from
FIG. 21
, when a combination switch
17
is set at an intermittent mode (INT), a driving circuit
20
turns on an interruption switch MOSFET
19
to start a motor
15
so that a wiper reciprocates once. Then, the terminals P and Q of a wiper switch
16
are connected to each other. Then, the driving circuit
20
turns off the interruption switch
19
to interrupt the power supply to the motor
15
. When the terminals P and Q of the wiper switch
16
are connected, a battery-voltage side terminal K and a ground side terminal J are connected to each other through a contact terminal T
1
and braking resistor
18
so that the motor
15
is braked. Thus, the wiper stops quickly.
However, the wiper control apparatus presents the following problems.
(1) When the wiper motor
15
generates an abnormal current as if it is locked, a large current continues to flow through a MOSFET
19
or resistor
18
. Therefore, the resistor
18
or MOSFET
19
may be excessively heated and burned. In order to avoid the burning, a countermeasure for setting a large current rating for the resistor
18
and MOSFET
19
and providing a radiator is required. This upsizes the apparatus and makes it expensive.
(2) When the plus terminal and minus terminal of a battery
11
are erroneously connected in a reverse direction, a large current continues to flow through the parasitic diode of the MOSFET
19
and the resistor
18
. Therefore, the resistor
18
and the MOSFET may be burned.
(3) For some time after the MOSFET
19
turns on, since the terminals P and Q of the wiper switch
16
remain connected, a tunneling current will flow through a passage of wiper switch
16
→resistor
18
→MOSFET
19
from the battery
11
. This leads to unnecessary dissipation of heat and noise.
(4) Setting the intermittent time and the after-wash wiping operation time after the washer has been operated is carried out in an analog manner using the charging/discharging theory of a capacitor. This leads to a large change in these times.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the problem of the conventional wiper control apparatus to provide a wiper control apparatus which is compact, reliable and surely operable using a semiconductor switch and a digital controller.
In order to attain the above object, in accordance with the first aspect of the present invention, there is provided a wiper control apparatus comprising:
a combination switch for setting an operation mode of a wiper at an intermittent wiper operation mode or a continuous wiper operation mode by means of position setting;
a wiper motor which is driven according to the operation mode set by the combination switch;
an autostop (AS) switch for producing a signal having a level varying according to a park position and other positions as the wiper motor rotates;
a first semiconductor switch element for on/off controlling energization of the wiper motor;
a controller for supplying a ON/OFF control signal to the first semiconductor switch element, wherein while the wiper operates in the operation mode set by the combination switch, if the level of the signal produced from the AS switch does not vary for a longer period than a prescribed abnormality detecting period owing to occurrence of abnormality of the wiper motor, the controller forcibly turns off the first semiconductor switch element.
In this configuration, when the abnormality of the wiper motor occurs, the controller monitors the duration of the abnormality to interrupt the energization. Therefore, the semiconductor switch element is not required to be excessively upsized, and hence can be down-sized and made inexpensive. In addition, the reliability of the entire wiper control apparatus inclusive of a driving circuit and a wiper motor is improved.
Preferably, after the abnormality is released, the controller decides that a set position of the combination switch has been changed and turns on the first semiconductor switch element to operate the wiper in the operation mode corresponding to the changed position. In this configuration, by position setting after the abnormality of the wiper motor has been released, the wiper operation can be resumed in the operation mode corresponding to the selected position.
Further, preferably, the controller is supplied with a driving voltage through an ignition switch from a battery, and after the abnormality is released, the controller detects re-energization successive to “off” of the ignition switch to turn on the semiconductor switch element and restores the operation of the wiper which had been set when the abnormality has occurred. In this configuration, by the turn off and re-energization of the ignition switch, the wiper operation stopped owing to occurrence of the abnormality can be restored.
In accordance with the second aspect of the present invention, there is provided a wiper control apparatus comprising:
a combination switch for setting an operation mode of a wiper at an intermittent wiper operation mode or a continuous wiper operation mode by means of position selection;
a wiper motor which is driven according to the operation mode set by the combination switch;
an autostop (AS) switch for producing a signal whose level varies according to a park position and other positions as the wiper motor rotates;
a first semiconductor switch element for on/off controlling energization of the wiper motor;
a controller for supplying an ON/OFF control signal to the first semiconductor switch element, wherein when an OFF position of the combination switch is set while the wiper operates, the controller maintains the “ON” of the first semiconductor switch element until the AS switch produces a signal having the level corresponding to the park position of the wiper. In this configuration, even when the combination switch is changed into the OFF position, the controller keeps the ON of the semiconductor switch element until the wiper returns to the park position, the wiper does not stop on the way.
In accordance with the third aspect of the present invention, there is provided a wiper control apparatus comprising:
a combination switch for setting an operation mode of a wiper at an intermittent wiper operation mode or a continuous wiper operation mode by means of position selection;
a wiper motor which is driven according to the operation mode set by the combination switch;
an autostop (AS) switch for producing a signal whose level varies according to a park position and other positions as the wiper motor rotates;
a first semiconductor switch element for on/off controlling energization of the wiper motor;
a second semiconductor switch element for turning on a closed circuit for braking the wiper motor by passing a reverse current through the wiper motor while energization of the wiper motor is off;
a controller for supplying a first ON/OFF control signal to the first semiconductor switch element and a second ON/OFF control signal to the second semiconductor switch element, wherein the controller provides a time delay td between rising edges or between trailing edges of the first control signal and the second control signal.
In this configuration, since the controller provides a time delay td between rising edges or between trailing edges of the first control signal and the second control signal, it is possible to prevent the first and second semiconductor switch elements from turning on simultaneously and a tunneling current from flowing, thus eliminating unnecessary dissipation of heat and noise.
Preferably, the first semiconductor switch element is an N-channel type MOSFET and the second semiconductor switch element is a P-type MOSFET. Therefore, these semiconductor switch elements can be down-sized and made inexpensive.
Kubota Kazuhiro
Yabe Hiroo
Armstrong Westerman & Hattori, LLP
Fletcher Marlon T.
Yazaki -Corporation
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