Electronic control unit for car

Details Electronic control unit for car Electronic control unit for car

1998-08-26

2001-02-06

Wu, Daniel J. (Department: 2736)

Communications: electrical

Land vehicle alarms or indicators

Internal alarm or indicator responsive to a condition of the...

C340S635000, C714S053000, C714S055000

Reexamination Certificate

active

06184783

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an electronic control unit for a car (hereinafter referred to a “car electric control unit”).
Generally, a car electronic control unit is generally designed so as to be controlled by a microcomputer with the advance of its performance. In most cases, a car electronic control unit has such a circuit configuration in which the operation of the microcomputer is watched by a watchdog circuit for the purpose of fail safe at the time of running-away of a program in the microcomputer so that the microcomputer can be reset when the run-away state is detected.
Incidentally, a car electronic control unit generally has a function which stops such a microcomputer (that is, makes the microcomputer sleep) to thereby reduce consumed electric power when the microcomputer is not required to operate. However, if the microcomputer is made to sleep when the runaway state is watched by a built-in watchdog circuit, the electronic control unit resets the microcomputer to start on the basis of misjudgment that the microcomputer has stopped. That is, there arises a problem that the microcomputer starts to increase consumed electric power even in the case where the microcomputer is not required to operate. As a measure to solve such a problem, Japanese Utility Model Publication JP-3-34955(U) entitled “On-vehicle Appliance Control Circuit” proposes a circuit in which an electric source is supplied to a watchdog circuit only in the condition that the microcomputer is required to operate, for example, only when the ignition switch is in the on-state.
FIG. 6
is a functional block diagram showing operating functions of the car electronic control unit. The car electronic control unit has three basic functions as follows:
a seat belt lamp control function which turns a seat belt lamp
2
on/off only when an ignition switch
1
is in an on-state;
a key alarm function which concludes that an ignition key is left behind and sounds an alarm buzzer
5
when an ignition key sensor
4
detects the fact that the ignition key is left as it is inserted in a key cylinder in spite of the fact that the ignition switch
1
is in an off-state and the opened-state of a driver's seat door is detected on the basis of a signal from the door open/close detection sensor
3
; and
a room lamp turning-on function which turns-on a room lamp
8
while the door is opened or for several seconds (for example, 5 seconds) after the door is closed on the basis of signals from the door open/close detection sensor
3
and a timer
6
connected to the door open/close detection sensor
3
.
In addition to the above three basic functions, it has an additional function as follows.
A watchdog function which watches the operation, such as running-away, etc., of the control portion (microcomputer chip)
7
for controlling the operations of the aforementioned various functions.
In the seat belt lamp control function, the on-state of the ignition switch
1
is detected by a detection portion
11
in the control portion
7
and the seat belt lamp
2
is controlled to be turned on/off on the basis of the result of the detection. Specifically, as shown in
FIG. 7
, the ignition switch
1
has one end connected to a battery and the other end connected to a connection terminal
12
of the car electronic control unit. The connection terminal
12
is grounded through a resistor R
1
in the car electronic control unit and connected to a first input terminal I
1
of the control portion
7
through a resistor R
2
. A first output terminal Q
1
of the control portion
7
is connected to the base of an NPN-type first transistor Tr
1
through a resistor R
3
. The emitter of the first transistor Tr
1
is grounded, and the collector of the first transistor Tr
1
is connected to one end of the seat belt lamp
2
through a connection terminal I
3
. The other end of the seat belt lamp
2
is connected to the battery. A detection portion
11
in the control portion
7
performs on/off turning of the first transistor Tr
1
in accordance with the input state of the first input terminal I
1
to control the current in the seat belt lamp
2
to thereby control the turning on/off of the seat belt lamp
2
.
In the key alarm function, as shown in
FIG. 6
, a logical product AND among the off-state of the ignition switch
1
, the door opened-state detected by the door open/close detection sensor
3
and the key-presence state detected by the ignition key sensor
4
is detected by an AND circuit
21
to sound an alarm buzzer
5
. Specifically, one end of the door open/close detection sensor
3
is grounded, and the other end of the door open/close detection sensor
3
is connected to a connection terminal
22
of the car electronic control unit. The connection terminal
22
is connected to the battery through a resistor R
4
and connected to a second input terminal I
2
of the control portion
7
through a resistor R
5
. Further, one end of the ignition key sensor
4
is grounded, and the other end of the ignition key sensor
4
is connected to a connection terminal
23
of the car electronic control unit. The connection terminal
23
is connected to the battery through a resistor R
6
and connected to an input terminal I
3
of the control portion
7
through a resistor R
7
. Further, a second output terminal Q
2
of the control portion
7
is connected to the alarm buzzer
5
. The logical product AND among the off-state of the ignition switch
1
, the door opened-state detected by the door open/close detection sensor
3
and the key-presence state detected by the ignition key sensor
4
is detected by the AND circuit
21
in the control portion
7
to thereby control the sounding of the alarm buzzer
5
.
In the room lamp turning-on function, as shown in
FIG. 6
, the timer
6
counts time for several seconds (for example, 5 seconds) after the door open/close detection sensor
3
detects the door closed-state so that the room lamp
8
is turned on while the door open/close detection sensor
3
detects the fact that the door is in the opened-state or while an AND circuit
31
logically detects the fact that the count value of the timer
6
is within the time of several seconds (5 seconds). Specifically, as shown in
FIG. 7
, a third output terminal Q
3
of the control portion
7
is connected to the base of an NPN-type second transistor Tr
2
through a resistor R
8
. The emitter of the second transistor Tr
2
is grounded, and the collector of the second transistor Tr
2
is connected to one end of the room lamp
8
through a connection terminal
24
. The other end of the room lamp
8
is connected to the battery. The AND circuit
31
in the control portion
7
performs on/off turning of the second transistor Tr
2
in accordance with the door opened/closed state to control the current in the room lamp
8
to thereby control the turning on/off of the room lamp
8
.
In the watchdog function, as shown in
FIG. 6
, a watchdog circuit
41
is supplied with an electric source so as to operate when the ignition switch
1
is in the on-state. The watchdog circuit
41
receives a watchdog clear signal from a connection terminal WDO for reporting the internal operating state of the control portion
7
, so that the watchdog circuit
41
watches the operation of the control portion
7
on the basis of the watchdog clear signal. When the operation of the control portion
7
gets into an abnormal state such as running-away, etc., the watchdog circuit
41
sends a reset signal to a reset terminal RST of the control portion
7
. Specifically, as shown in
FIG. 7
, the watchdog circuit
41
is connected to a PNP-type transistor
43
(switching element) for switching the supply of a source current from an electric source (regulator)
42
. The base of the transistor
43
is connected to an NPN-type transistor
44
the connection of which to the ground is switched on/off on the basis of the on/off state of the ignition switch
1
.
FIG. 8
is a timing chart showing operations of respective parts. In the car electronic control unit, when

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