ELECTRONIC CONTROL APPARATUS FOR USE IN AUTOMOBILE

Abstract: An electronic control apparatus for use in an automobile has a base (14) of a good thermal conductivity having one side disposed in contact with engine cooling water. Semiconductor devices (8, 9, 10, 22, 90) are disposed on the other side of the base so that the semi­ conductor devices are maintained at the temperature of the engine cooling water, whereby the influence of high ambient air temperature to the semiconductor devices is reduced.

Description: BACKGROUND OF THE INVENTION The present invention relates to an electronic control apparatus for use in an automobile and comprises: a first cooling water passage formed in a wall of an intake manifold of an engine and having an opening which opens to atmosphere, a base mounted on said intake manifold so as to cover said opening of said first cooling water passage, said base having one side in which a second cooling water passage for circulation of the cooling water is formed and the other side on which semiconductor devices are disposed, said base being made of a material having a good thermal conductivity and an enclosure fixed to said base to hermetically cover said semiconductor devices. In general, a typical electronic control apparatus for use in an automobile is disposed in a driver's or passenger's compartment and is connected by a considerably long wire harness to sensors, actuators or the like which are mounted in an engine compartment and on an internal combustion engine. For this reason, external noise which may enter the wire harness has been a problem. To solve the problem, such an electronic control apparatus may be provided in the engine compartment so that the wire harness can be made as short as possible. However, if the electronic control apparatus is provided in the engine compartment, the temperature in the engine compartment raises a serious problem. More specifically, the air temperature in the engine compartment can be maintained at a considerably low temperature when an automobile is running since fresh air flows into the engine compartment. However, when the automobile is stopped after its high-speed running, air stagnates in the engine compartment and heated by the heat of the internal combustion engine, with the result that the air temperature in the engine compartment rises to a high level. If the electronic control apparatus for an automobile is exposed to such a high temperature for a long time, then a problem occurs that semiconductor devices which constitute a part of the electronic control apparatus cannot maintain their normal functions. For this reason, it is necessary to cool the electronic control apparatus for an automobile. As a cooling method, Japanese Patent Unexamined Publication No. 50-58987 proposes a method of cooling an electronic control apparatus for an automobile by using gasoline supplied to an internal combustion engine. However, when gasoline is used as a cooling medium as described above, the following problems will be encountered: (1) Since gasoline is introduced into the electronic control apparatus for an automobile, it is necessary to design a special sealed structure for anti-leak purposes. If a leakage of gasoline should occur, possibility of fire is extremely high; (2) Since gasoline is intended to absorb the heat generated in the electronic control apparatus for an automobile, the temperature of gasoline rises, so that vapor bubbles are easily produced, with the result that a vapor lock may occur in fuel injection valves. GB-A-2 183 304 describes an electronically controlled fuel-injection pump having a pump control unit which is mounted on a pump body 1. The electronic components of the control unit are cooled by fuel oil which passes through a cooling passage formed between heat transfer plates. Fuel oil flows to cool electronic components of the control unit. The heat transfer plate supports a circuit board of the control unit. Staggered ribs are disposed on the plate and act to prevent the fuel oil from lying stagnant in the cooling passage. JP-A-57-212345 describes an electronic control circuit for measuring the cooling water temperature which is disposed at a cooling water path of the internal combustion engine. However, the cooling water is not intended to cool the circuit temperature, but the temperature of the cooling water is to be detected. Moreover, the thermal conduction between the cooling water passage and the electronic circuit of the control system is considerably tedious as heat has to pass a housing, a flange-like portion and a wall of the cooling water path before being dissipated. SUMMARY OF THE INVENTION It is an object of the present invention to provide an electronic control apparatus suitable for use in an automobile which is provided with a cooling structure capable of solving problems such as danger of fire and a vapor lock in a fuel injection valve. This object is solved in accordance with the features of the independent claim 1. Dependent claims 2 to 4 are directed on preferred embodiments of the present invention. In the electronic control apparatus according to the present invention, the engine cooling water flows through the first and second cooling water passage to maintain the temperature of the base and hence the temperature of the semiconductor devices at the temperature of the engine cooling water, whereby the influence of high-temperature air can be reduced. The above and other objects, features and advantages of the present invention will become more apparent from the following description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram of the electronic control apparatus; Fig. 2 is a fragmentary sectional view of an internal combustion engine on which an embodiment of the electronic control apparatus of the invention is mounted, Fig. 3 is a graphic illustration of the temperature characteristic of the electronic control apparatus. DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described hereinunder with reference to the accompanying drawings. Fig. 1 is a block diagram showing the arrangement of essential circuit parts of an exemplified electronic control apparatus suitable for use in an automobile. The electronic control apparatus, which is represented generally by reference numeral 1, comprises e.g. a temperature sensor 6, a knock sensor 7, an input unit 8, an arithmetic unit 9 constituted by a ROM, a RAM and a CPU, and an output unit 10. The input unit 8 is arranged to receive, through input wires, the output signals of a cooling water temperature sensor 2 for detecting the temperature of engine cooling water in an internal combustion engine, an engine speed sensor 3 for detecting the rotational speed of the internal combustion engine, an air flow sensor 4 for detecting the intake flow of air into the internal combustion engine, and an idle switch 5 for detecting the engine when in an idle state. An output unit 10 outputs control signals, through output wires, to valves 11 for effecting various kinds of compensation, to fuel injection valves 12 and to an ignition device 13. The electronic control apparatus 1 has a mechanical construction shown in Fig 2, according to the invention. Referring to Fig. 2, reference numeral 14 denotes a base made of a material having a good thermal conductivity such as aluminum. A cooling water passage 15 is formed in the bottom of the base 14. When the base 14 is mounted on the intake manifold 29, the passage 15 communicates with a cooling water passage 30 formed in the wall of the intake manifold 30. Fig. 2 shows a part of an engine on which an embodiment of the electronic control apparatus 1 is mounted. As shown, the electronic control apparatus 1 is mounted on the top side of the intake manifold 29 in which the cooling water passage 30 is formed. This cooling water passage 30 communicates with a water passage 31 which is formed in the engine E. The water is circulated through the water passages 30 and 31 by means of a water pump (not shown). An opening 32 is formed in a portion of the top wall of the water passage 30 formed in the intake manifold 29. The base 14 is mounted on the intake manifold 29 in such a manner that the base 14 covers the opening 32. Accordingly, the temperature of the base 14 is maintained at the temperature of the water by the effect of the water which flows through the water passage 30. Semiconductor devices are disposed on the other side of the base 14 and are directly or indirectly fixed to the base 14. According to the embodiment shown in Fig. 1, the semiconductors of the block 1 are fixed to a ceramic board 20 which in turn is fixed to the base 14. The input unit 8 and the output unit 10 are disposed on the surface of the ceramic board 20 which faces a space 21 between the ceramic board 20 and the base 14, while the arithmetic unit 9 is disposed on the other side of the ceramic board 20. In addition, on this side of the board 20, there may be disposed a storage device including a data ROM, a RAM and the like. The reason why the storage device is disposed on the side of the base body 14 opposite to the space 21 is that the storage device can be easily replaced by another one. An output transistor may be fixed to another ceramic board which is fixed to the base 14. Furthermore, the temperature sensor 6, e.g. being of the thermistor-type is fixed to the ceramic board 20, while the knock sensor 7 is directly fixed to the base 14. An enclosure 23 is fixed to the surface of the base 14 opposite to the closure plate 17. A liquid-tight seal ring can be interposed between the enclosure 23 and the base 14. The operation of the electronic control apparatus 1 having the above-described construction will be described hereinunder with reference to Fig. 3. While an automobile is running, air flows through an engine compartment. Accordingly, during the running of the automobile, the temperature of the air, the temperature of the water and the temperature of the electronic control apparatus 1 are kept substantially constant, as shown by lines T A , T W and T S in Fig. 5, respectively. When the automobile is stopped at time point t 0 , however, the temperature of the water and ambient temperature (or air temperature) within the engine compartment start to rise. Subsequently, when time t R is reached, the ambient temperature exceeds the temperature of the water. The temperature of the electronic control apparatus 1 essentially follows the temperature rise of the water until the temperature of the electronic control apparatus 1 generally coincides with the water temperature, by means of the communication of water between the cooling water passages 15 and 30 and 31. Accordingly, the electronic control apparatus 1 is not greatly influenced by ambient air of high temperature. It is to be noted that the water temperature is normally maintained at about 80°C and rises at times to a maximum of 130°C, whereas the ambient air temperature frequently rises to a far higher temperature. Accordingly, in accordance with the present invention, it is possible to sufficiently reduce the influence of the ambient temperature to the electronic control apparatus. Although the temperature sensor 6 is provided on the base 14, the water temperature sensor 2 may be provided in place of the temperature sensor 6. The vibration of the internal combustion engine can be detected by the knock sensor 7.

Claims: An electronic control apparatus for use in an automobile, comprising: a) a first cooling water passage formed in a wall of an intake manifold (29) of an engine and having an opening (32) which opens to atmosphere; b) a base (14) mounted on said intake manifold so as to cover said opening of said first cooling water passage, said base having one side in which a second cooling water passage (15) for circulation of the cooling water is formed and the other side on which semiconductor devices are disposed, said base being made of a material having a good thermal conductivity; and c) an enclosure (23) fixed to said base to hermetically cover said semiconductor devices. An electronic control apparatus according to claim 1, wherein a temperature sensor (6) is disposed on said base. An electronic control apparatus according to claim 1, wherein a knock sensor (7) is disposed on said base. An electronic control apparatus according to claim 1, wherein a board (20) for carrying said semiconductor devices is disposed between said base and said enclosure, input and output units (8, 10) being disposed between said board and said base, and an arithmetic unit (9) and a data storage device (90) being disposed between said board and said enclosure.

Inventors: KASHIMURA, YUICHI, SUDA, SEIJI, WATANABE, SHIZUHISA
Applicants: HITACHI, LTD.
Application year: 1988
Main classification: F02D41
IPC codes: B60R16, F02D35, F02D41, F01P3