Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle diagnosis or maintenance indication
Reexamination Certificate
2000-08-24
2002-03-12
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle diagnosis or maintenance indication
C714S024000, C123S333000, C123S478000, C303S084200, C303S115400
Reexamination Certificate
active
06356821
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to an electronic control unit (ECU) for a vehicle such as a car and the like, and more particularly to an electronic control unit of a safety control system for a vehicle having simple structure and high reliability.
BACKGROUND OF THE INVENTION
In the safety control system of a vehicle such as an antilock brake system (ABS) and the like, the electronic control unit (ECU) having one or more microcomputers therein is used. In the electronic control unit, results of operation including arithmetic operation by the microcomputers are used for controlling various actuators and the like, and thereby running performance, braking performance and the like are improved.
In such electronic control unit, when, for example, a microcomputer therein becomes out of order and outputs incorrect operation result or incorrect control data, there is a possibility that serious influence on an operation of the vehicle, such as abnormal driving, abnormal braking and the like occurs. Therefore, conventionally, the electronic control unit comprises a fail-safe mechanism for preventing occurrence of such abnormal control.
FIG. 5
schematically shows an example of a structure of a conventional electronic control unit. As shown in
FIG. 5
, the electronic control unit comprises a duplicate structure of a pair of microcomputers
51
and
52
. An input signal
50
is commonly supplied to both of the microcomputers
51
and
52
. The microcomputers
51
and
52
comprise watchdog pulse monitoring circuits
53
and
54
, and mutual communication and monitoring circuits
55
and
56
. Each of the watchdog pulse monitoring circuits
53
and
54
mutually monitors watchdog pulses outputted from the other microcomputer and decides if the watchdog pulses have a predetermined constant period, that is, if on-time and off-time of each watchdog pulse are respectively within predetermined time ranges. Thereby, each of the watchdog pulse monitoring circuits
53
and
54
monitors abnormal run of a CPU not shown in the drawing of the other microcomputer. Also, mutual communication and monitoring circuits
53
and
54
mutually send and receive the contents of random access memories (RAM's) (not shown in the drawing) which are included in the microcomputers
51
and
52
and which store result of operation of CPU's in the microcomputers
51
and
52
, and compare the contents of the RAM's mutually to detect abnormal condition of the microcomputers. Also, there is provided a comparing circuit
57
which compares operation results outputted from both microcomputers
51
and
52
. When the operation results do not coincide, it is determined that there is any fault in operational function and the like of a processing system including the microcomputers
51
and
52
, and the comparing circuit
57
outputs a fault signal indicating that there is a fault condition in the processing system. In response to the output of the fault signal, operation of the processing system is halted if necessary, thereby securing reliability.
FIG. 6
illustrates another example of a structure of a conventional electronic control unit. The electronic control unit shown in
FIG. 6
comprises a microcomputer
61
and a fail-safe microcomputer, that is, a sub-processing unit,
62
. The microcomputer
61
accepts an input signal
60
, performs necessary processing operation on the input signal
60
, and supplies the result of the processing operation as an output signal
65
. The fail-safe microcomputer
62
accepts the input signal
60
and performs simple processing operation on the input signal
60
. The output of the microcomputer
61
is supplied via a pre-driver
64
to one or more actuators and the like not shown in the drawing as a control signal. The fail-safe microcomputer
62
comprises an output monitoring circuit or block
63
which monitors the condition of the output signal
65
from the microcomputer
61
. When the output monitoring circuit
63
detects abnormal condition of the output signal
65
, the output monitoring circuit
63
controls the pre-driver
64
such that the driver output from the pre-driver
64
is disabled or turned off.
In Japanese patent laid-open publication No. 7-52784, an anti-skid controller is disclosed as a vehicle safety apparatus. The anti-skid controller disclosed in this publication has a structure in which a wheel speed operation value obtained by an operation of a main processor itself is compared with a wheel speed operation value from a sub-processor received via a data transferring means are compared with each other to decide if the anti-skid controller operates normally. However, the technical idea of this prior art structure is basically the same as that of the duplicated structure including a plurality of microcomputers shown in
FIG. 5
, FIG.
6
and the like.
Also, in an anti-skid controller disclosed in Japanese patent laid-open publication No. 7-40828, there are provided a plurality of processors. In this anti-skid controller, operation results of these plurality of processors are compared and, based on the result of the comparison, malfunction is detected. However, the technical idea of this prior art structure is also basically the same as that of the duplicated structure including a plurality of microcomputers shown in
FIG. 5
, FIG.
6
and the like.
In this way, in each of the conventional electronic control units mentioned above, a duplicated structure comprising two microcomputers is used and, therefore, it is difficult to decrease cost and circuit scale of the electronic control unit.
This is because, a duplicated microcomputer system having fail-safe function requires relatively high performance microcomputers. Therefore, usually, each of the microcomputers is constituted of a 16 bit or 8 bit microcomputer which is relatively expensive among various electronic components of the electronic control unit. As a result thereof, when the duplicated microcomputer system is constituted of such 16 bit or 8 bit microcomputers, cost and size of the electronic control unit itself are also greatly influenced by the microcomputers.
Recently, a method of diagnosis has been improved, and an electronic control unit is proposed in which the diagnosis is performed by using 4 bit microcomputer. For example, Japanese patent laid-open publication No. 7-17337 discloses an electronic control unit having such structure. In the electronic control unit disclosed in this publication, to detect abnormal condition of a processing system thereof, a main CPU is constituted of a 16 bit microcomputer and a sub CPU is constituted of an 8 bit microcomputer, thereby a structure of the electronic control unit is simplified. However, even in this structure, it is necessary to use two microcomputers and it is difficult to decrease cost and circuit scale of the electronic control unit.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to obviate the disadvantages of the conventional electronic control unit for a vehicle.
It is another object of the present invention to provide an electronic control unit for a vehicle which has high reliability but which has small circuit scale and is less expensive.
It is still another object of the present invention to provide an electronic control unit for a vehicle which has high reliability but which has simple structure and small size.
It is still another object of the present invention to provide an electronic control unit for a vehicle in which diagnosis of a microcomputer in the electronic control unit can be performed by using a simple and low cost structure.
It is still another object of the present invention to provide an electronic control unit for a vehicle which has simple structure and low cost, but which can realize equal reliability with that of the conventional system having duplicated microcomputers.
According to an aspect of the present invention, there is provided an electronic control unit which receives an input signal from outside and performs data processing on the
Cuchlinski Jr. William A.
NEC Corporation
To Tuan C
Whitham Curtis & Christofferson, PC
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