Motor assembly of X2Y RFI attenuation capacitors for motor radio frequency interference (RFI) and electromagnetic compatibility (EMC) suppression

A connector structure for a brush motor includes a connector body 10 associated with the motor, an X2Y capacitor structure 20, a positive power terminal connection structure 14 associated, a negative power terminal connection structure 14′ and a ground connection structure 16. The positive power terminal connection structure is electrically connected with the capacitor structure and is constructed and arranged to electrically engage a positive power terminal 18 of the motor. The negative power terminal connection structure 14′ is electrically connected with the capacitor structure and is constructed and arranged to electrically engage a negative power terminal of the motor. The ground connection structure 16 is electrically connected with the capacitor structure and is constructed and arranged to be electrically connected with a ground mass. The X2Y capacitor structure provides RFI suppression.

FIELD OF THE INVENTION

The invention relates to suppression of RFI for brush motors for automotive applications based on X2Y technology.

BACKGROUND OF THE INVENTION

Motor RFI Suppression is commonly completed by the use of a multitude wire wound inductors in series with the brushes and a film or ceramic capacitor in parallel to the power supply source.

An improved RFI suppression package, based on new technology of the X2Y component, is needed. Details of the X2Y can be found at http://www.x2y.com. An X2Y component is a four terminal device with unique architecture. X2Y is based on a standard bypass capacitor as a foundation provided with additional “reference” electrodes and two side terminations, called G1(ground) and G2, which are attached to the reference electrodes. Inserting parallel reference electrodes inside the bypass capacitor by dividing an unbalanced single end device, a balanced device is created. A balanced device is composed of two nominally identical halves.

The main benefits of balance are:Two tight tolerance “Y” capacitors (1–2.5%);Temperature variation effects elimination;Voltage vs. capacitor variation becomes equalized line-to-line.

FIG. 1shows a conventional X2Y component or capacitor11where two side terminations (G1and G2) attached to the reference electrodes results in acquiring one package consisting of the three capacitors. Cx is a capacitor between power lines and Cy is a capacitor between one power line and ground. The X2Y configuration is similar to a dual rectangular coaxial structure. An internal Faraday cage forms a shielded container for each conductor (+Bat and −Bat) inside the capacitor. At high frequency, the circuit noise in each capacitor will choose the low impedance path of the shield and opposing noise current will be cancelled. Inside the X2Y component, every other layer within the single component body is in opposition to cancel the magnetic fields. The components circuit inside operates simultaneously in multi-modes (Common and Differential Mode Noise Coupling).

X2Y components reduce Electro-magnetic Interference (EMI) by means of field cancellation. By contrast, standard components are using capacitance to shunt noise or inductors to block noise with high impedance.

X2Y components are in by-pass and effectively filtering only the noise. Because they are in by-pass X2Y components do not heat up like standard components.

The way the X2Y component is attached and placed can have major effects on how well it performs. Some special study and experimental research have been done to get maximum broadband filtering performance.

There is a need to provide an X2Y capacitor in a motor connector for Radio Frequency Interference (RFI) suppression.

SUMMARY OF THE INVENTION

An object of the invention is to fulfill the need referred to above. In accordance with the principles of the present invention, this objective is achieved by providing a connector structure for a brush motor. The connector structure includes a connector body associated with the motor. An X2Y capacitor structure is provided. A positive power terminal connection structure is associated with the connector body and is electrically connected with the capacitor structure and is constructed and arranged to electrically engage a positive power terminal of the motor. A negative power terminal connection structure is also associated with the connector body. The negative power terminal connection structure is electrically connected with the capacitor structure and is constructed and arranged to electrically engage a negative power terminal of the motor. A ground connection structure is electrically connected with the capacitor structure and is constructed and arranged to be electrically connected with a ground mass.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT

The present invention utilizes the X2Y technology to for motor RFI suppression. The mechanical assembly of such a balanced line electromagnetic interference (EMI) chip is not intuitive to meet the requirements of automotive environments and low cost assembly. The embodiment details a mechanical structure to package a capacitor into a motor connector body and utilizes low cost assembly techniques and components. The X2Y capacitor is small in size relative to the components of the assembly and is difficult to fit without utilizing tradition printed circuit board techniques. The X2Y capacitor is relatively new to the motor industry and the details of the incorporating the X2Y capacitor into a motor connector are described below.FIG. 2is a circuit diagram showing the electrical position of a X2Y capacitor20relative to a motor13in accordance with the invention.

With reference toFIG. 3, a motor connector body10is shown including an X2Y capacitor mounting assembly, generally indicated at12, in accordance with the principles of the invention. The assembly12includes three conductive components manufactured by a sheet metal forming operation and a conventional X2Y capacitor20. The three conductive components include a positive power terminal connection component14, a negative power terminal connection component14′ and a ground connection component16.

FIG. 7shows a power connection component14that is substantially identical to component14′. The positive and negative power terminal connection components14,14′ are each preferably a stamped component that surrounds the associated power terminal. Thus, component14surrounds the positive power terminal18and component14′ surrounds the negative power terminal30(FIG. 6). The power terminal connection components14,14′ have a mechanical interference spring connection and/or solder connection to the associated terminal18,30and have a mechanical or solder connection to the X2Y capacitor20. In the illustrated embodiment, each component14,14′ includes a main body22bent to have an upstanding portion24. The body22includes first spring structure26constructed and arranged to resiliently engage an associated terminal18,30. The upstanding portion24includes a second spring structure28constructed and arranged to resiliently engage the generally rectangular X2Y capacitor20in space25between the two components14and14′ (FIG. 6). Components14,14′ are preferably made of a conductive material capable of carrying low currents such as phosphor bronze or beryllium copper or copper or brass.

The components14,14′ are preferably mechanically fit onto the motor connector10and held thereon by the means of an interference clip on the component14,14′ or by a clip on the connector10. Surrounding the positive and negative power terminals with component14and component14′, respectively, prevents noise from bypassing the X2Y capacitor20and suppresses noise in the nearest proximity to the noise source (motor's brushes).

With reference toFIG. 3–5, the ground connection component16is preferably a stamped component that surrounds, without contacting, both the positive and negative power connection components,14,14′. Component16has a mechanical interference spring connection and/or solder connection to the X2Y capacitor20. In the illustrated embodiment, the component16includes a main body that is stamped into a generally U-shaped configuration defining two opposing sides32,34joined by a central portion35. Each side32,34includes spring structure36in the form of a plurality of spring tabs37. The component16is constructed and arranged so that it can be placed over a portion of the motor connector10with the spring structure36engaging a portion of the connector10. The small spring tabs37provide an overall low inductance multiple ground connection to the ground mass and reduces parasitic inductance of that connection. The ground connection can be made to the end cap, stator or motor mounting flange. The multiple parallel connections to ground reduce the total inductance between the X2Y capacitor20and ground.

In the embodiment, the central portion35of the component16includes an opening40for receiving the component14,14′ and the X2Y capacitor20. To provide ground contact with the X2Y capacitor, the central portion35includes opposing spring contacts44that extend into the opening and resiliently contact ground areas46(FIG. 6) of the X2Y capacitor20. Of course, instead of or in combination with the spring contacts44, a solder connection can be made in two places with the X2Y capacitor20. Component16is preferably made of a conductive material capable of carrying low currents such as phosphor bronze or beryllium copper or copper or brass. The component16is mechanically fit onto the motor connector10and is held on by the means of an interference clip on the component16or clip on the connector10.

A function of the component16is to bypass High Frequency such as, for example, 70 MHz-108 MHz noise. Therefore, the area of the ground connection has to be large to minimize total impedance of component16. The X2Y capacitor20connects to the component16at two points via contacts44in order to decrease internal X2Y inductance. All connections should be as short and wide as possible to reduce impedance.

Components14,14′ and component16form a mechanical socket that permits ease of assembly of the X2Y capacitor20.

Utilizing stampings for the circuit connections and incorporating them into the motor connector10is a feature of the embodiment. The assembly can be assembled using automation or manual assembly utilizing low cost components.

This invention can be use on any motor with a multitude of poles, and brushes and will be placed near the input power source.