Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1999-12-30
2001-02-06
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C073S204220, C073S118040
Reexamination Certificate
active
06182639
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermal-type airflow meter suitable for measuring the flow rate of air taken into an internal combustion engine, and more particularly to a thermal-type airflow meter, which comprises a housing for protectingly accommodating an electronic circuit therein and a sub-air passage.
2. Description of the Related Art
JP-A 3-233168 discloses an example of prior art thermal-type airflow meters. In this prior art, a housing part for protecting an electronic circuit therein and a sub-air passage part are arranged in the same plane to be made one body. Further, there is also proposed an airflow meter, in which a housing and a sub-air passage are plastic-molded as a unitary body.
However, the prior art as mentioned above needs to be improved in the following respects:
(1) A member in which a housing and a sub-air passage are formed should be suitably shaped for assembly by means of insertion technology (that is, should have proper dimensions to match an inserting hole);
(2) The relative positioning of a housing and a sub-air passage should never vary. That is, after the sub-air passage has been fixedly attached to a member in which a main air passage is formed, the attached position of the subair passage should never vary;
(3) The deformation of an airflow meter due to the environmental operating conditions as small as possible, and the durability and reliability thereof should be sufficient; and
(4) There should be freedom in designing the shape of a sub-air passage, and further even if it has the complicated shape, it can be easily manufactured.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a thermal-type airflow meter which can measure the flow rate of air with high accuracy and has excellent durability and reliability against the operating environment. Further, the present invention provides an intake air system for an internal combustion engine and a control system therefor, which is high in its control ability and reliability.
A thermal-type airflow meter according to a feature of the present invention has a sub-air passage which accommodates a flow rate measuring part including a heating resistor, and a housing which is arranged next to the sub-air passage, and which accommodates therein an electronic control unit for controlling the heating of the flow rate measuring part. The sub-air passage and the housing are plastic-molded separately, then fixedly attached to each other and put on a flat metallic base member which is mechanically strong in its longitudinal direction. The sub-air passage and the housing are fixed on the metallic base member.
Preferably, adhesion among the sub-air passage, the housing and the metallic base member is provided via a face which belongs in common to two of the aforesaid members that come into contact with each other.
According to another feature of the present invention, a thermal-type airflow meter has a sub-air passage with at least one bent portion, through which flows a part of the air in a main air passage that functions as an intake air passage of an internal combustion engine. A heating resistor arranged within the sub-air passage and an electronic circuit electrically connected to the heating resistor produce a signal indicative of an air flow rate, based on the heat radiated by the heating resistor. A housing which accommodates and protects electronic circuit is composed of a frame part surrounding the electronic circuit, a connector part with connector terminals for electrically connecting the electronic circuit with external devices, and fixing mounts for fixedly supporting the heating resistor on the opposite side to the connector part with respect to the frame part. All of the latter parts are plastic-molded as one body, as is a member for forming the sub-air passage. At least the frame part of the housing and the sub-air passage member are formed in a flat shape and fixedly arranged on a flat metallic base member in the longitudinal direction thereof, so as to locate the heating resistor in the sub-air passage.
According further to another feature of the present invention, a housing which accommodates and protects the electronic circuit comprises a frame part surrounding the electronic circuit, a connector part with connector terminals for electrically connecting the electronic circuit with external devices, and fixing mounts for fixedly supporting the heating resistor on the opposite side to the connector part with respect to the frame part. All of these parts are plastic-molded as one body, as is a member for forming the sub-air passage. At least the frame part of the housing and the sub-air passage member are formed in a flat shape and fixedly arranged on a flat metallic base member in the longitudinal direction thereof. A cover is provided for covering an opposite side of the metallic base member to the frame part, which cover is fixed both to the housing and the sub-air passage member, so that the frame part is covered by the metallic base member on one side and by the cover on the opposite side, thereby forming a closed compartment for accommodating therein the electronic circuit.
The thermal-type airflow meter according to the present invention can be attached to a part of a body of an air cleaner. Further, an intake air system for a combustion engine performs the fuel control using such an airflow meter.
According to the present invention, since the housing and the sub-air passage member are separately plastic-molded, the longitudinal dimension of both can be shortened, so that the initial dimensional change of those members during molding can be suppressed. The housing and the sub-air passage adhere to each other, and both are fixedly mounted on a mechanically strong metallic base member to suppress the dimensional change during assembling and aging.
In this manner, dimensional accuracy can be secured and the influence of the dimensional change on the measuring accuracy can be reduced, so that accurate measurement of the air flow rate can be achieved. Further, each member is fixed to more than one other member. (That is, it is held to at least two members which are separate from each other.) Accordingly, the incidence of separation or removal of two members is significantly reduced, with the result that the durability and reliability of the airflow meter is much improved.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.
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Igarashi Shinya
Kozawa Masayuki
Takasago Akira
Tsutsui Mitsukuni
Uchiyama Kaoru
Castro Arnold
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
Hitachi , Ltd.
Yuen Henry C.
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