Vehicle-mounted noise filter

Abstract

Disclosed is a vehicle-mounted noise filter capable of suppressing electric field coupling between a pair of capacitors in the FM radio band, thereby allowing the intrinsic noise attenuation performance of a noise filter circuit to be exerted even in the FM radio band. The vehicle-mounted noise filter comprises a ground plate (1), a coil (2), a pair of capacitors (3a, 3b), and a conductive shielding plate (4). The ground plate (1) is grounded in a vehicle body. A lead wire is wound around the coil (2). The pair of capacitors (3a, 3b) are disposed such that the coil (2) is interposed therebetween, and are electrically connected to the coil (2) and the ground plate (1) so as to form a pi-type filter circuit. The conductive shielding plate (4) is grounded in the ground plate (1) and is disposed between the pair of capacitors (3a, 3b) so as to shield the electric field coupling between the pair of capacitors (3a, 3b).

Description

technical field [0001] The present invention relates to an on-vehicle noise filter, and more particularly to an on-vehicle noise filter capable of improving noise attenuation performance even in the FM radio band (very high frequency band). Background technique [0002] Various types of noise filters have been developed for removing noise of in-vehicle electrical components. For example, anti-fog wires and radio antennas are often located together on the same rear window of the vehicle. In this case, a noise filter is connected in series with the wiring for supplying power to the anti-fog wire in order to prevent, for example, AM radio from being adversely affected by noise superimposed on the wiring. [0003] In consideration of installation space and influence on vehicle performance, an in-vehicle noise filter needs to be small in size and light in weight. For example, Patent Document 1 discloses a noise filter capable of achieving size reduction and heat radiation reduc...

AI Technical Summary

Problems solved by technology

The working speed of ECU has become faster and correspondingly, the frequency of occurrence of noise has increased and the frequency of noise has become higher, also causing adverse effects on FM radio

[0005] By using a conventional noise filter such as that disclosed in Patent Document 1, a sufficient amount of noise suppression can be obtained for the AM radio band, however, a sufficient amount of noise suppression cannot usually be obtained for the FM radio band

This is because input side noise cannot pass through the filter circuit but directly leaks to the output side due to the influence of electric field coupling between the input terminal and output terminal of the noise filter, which prevents obtaining a sufficient amount of noise attenuation

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