The present invention relates to an electric compressor having a compression mechanism, an electric motor and a motor driving circuit.
Japanese Patent Application Publication No. 2010-112261 discloses an electric compressor having a housing that accommodates therein a compression mechanism for compressing a refrigerant gas, an electric motor for driving the compression mechanism and a motor driving circuit for driving the electric motor. The motor driving circuit includes a circuit board and electronic components that are mounted on the circuit board.
The electric compressor further has a bus bar for supplying electric power from an external power supply to the circuit board. The bus bar is resin-molded integrally with a washer through which a bolt is inserted. The washer serves as a seat for the bolt. With the bolt inserted through the washer and screwed into a boss of the housing, the bus bar is fixed to the housing through resin. The resin ensures insulation between the bus bar and the housing.
An electromagnetic noise is generated from the electronic components, and there is a fear that motor driving circuit may malfunction when the electromagnetic noise transmitted to the bus bar. In order to prevent the transmission of the electromagnetic noise, a shield plate that can intercept the electromagnetic noise may be interposed between the electronic components and the bus bar. The shield plate and the bus bar are disposed in such a state that the insulation is secured. Accordingly, the malfunction of the motor driving circuit caused by the transmission of the electromagnetic noise to the bus bar is prevented because the electromagnetic noise generated from the electronic components is intercepted by the shield plate.
From the viewpoint of downsizing the electric compressor, the above shield plate is preferably molded integrally with the bus bar. In molding of the bus bar and the shield plate, each bus bar and the shield plate need to be held in place by a pair of mold members so as not to be displaced in the mold by the injection pressure of resin.
The shield plate may be held by the mold members with the surface of the shield plate on side thereof that is opposite from the bus bar placed in contact with a part of one of the mold members and the surface of the shield plate on the side on which the bus bar is provided placed in contact with a part of the other mold member where no bus bar is formed. In some case, however, the bus bar may not be held properly by the pair of mold members because part of one of the mold member is unable to be placed in contact with the surface of bus bar on the side thereof facing the shield plate due to the interference with the shield plate.
In such case, a hole may be formed through the shield plate, through which a part of the one of the mold members is inserted so as to be into contact with a part of the bus bar on the side thereof facing the shield plate. The other side of the bus bar is set into contact with a part of the other mold member, with the result that the bus bar is held by a pair of the mold members.
In the configuration in which the bus bar and the shield plate are integrally resin-molded, however, the bus bar is exposed through the hole and, consequently, the electromagnetic noise is transmitted from the electronic components through the hole to the bus bar. In addition, the aforementioned washer that is used to fix the bus bar to the housing increases the number of parts of the electric compressor.
The present invention, which has been made in light of the problems mentioned above, is directed to providing an electric compressor that prevents the transmission of an electromagnetic noise from electronic components to the bus bar while permitting to reduce the number of parts.