Actuator incorporating a casing having a motor mounting structure

An actuator includes an electric motor having a shaft, an output member coupled to the shaft, a casing having a wall, a mounting structure, and a tubular body sleeved around the shaft and coupling the mounting structure to the wall. The motor is mounted to the casing via the mounting structure.

FIELD OF THE INVENTION

This invention generally relates to a casing for an electric motor and specifically to a casing having a motor mounting structure and an actuator incorporating such a casing.

BACKGROUND OF THE INVENTION

Many devices employ an actuator incorporating an electric motor. The motor is usually mounted in a casing of an actuator by a motor mount. In a known actuator, a bracket and screws are used to mount the motor in the casing. In another known actuator, two elastomeric dampers are disposed between the ends of the motor and the casing to isolate the casing from vibrations generated by the motor. Such motor mounts can reduce the audible noise level of the actuator. However, as the bracket and the dampers are separately formed from the casing, assembling steps are required in the manufacturing process and additional sources of failure may be introduced.

Thus, there is a desire for an improved actuator that can overcome the above described shortcomings. Specifically, there is a desire for a low noise actuator with few components, reliable performance, and a simple manufacturing process.

SUMMARY OF THE INVENTION

Accordingly, in one aspect thereof, the present invention provides an actuator, comprising: a motor having a shaft; an output member coupled to the shaft; and a casing accommodating the motor and having a first casing part and a second casing part, the first casing part comprising a base and a mounting structure for mounting the motor to the casing, wherein the mounting structure is fixed to a first edge portion of the base by a connecting structure such that the mounting structure is cantilevered above the base.

Preferably, the connecting structure connects the mounting structure to the first edge portion of the base via a wall extending along the first edge portion of the base.

Preferably, the mounting structure comprises an abutment plate and a sleeve extending from the abutment plate, the motor being a press fit in the sleeve with an end plate of the motor abutting the abutment plate and the shaft extending through the abutment plate.

Preferably, the connecting structure extends from a side of the abutment plate remote from the sleeve.

Preferably, the sleeve has a free end and a supporting rib connects the free end of the sleeve to a second edge portion of the base.

Preferably, the connecting structure comprises a tubular body sleeved around the shaft of the motor, and the tubular body has a window formed in a circumferential surface thereof.

Preferably, an interlock structure is formed between the second casing part and the tubular body.

Preferably, the motor comprises a housing having a cut-out formed therein; and the second casing part comprises a projection engaged with the cut-out in the housing.

Preferably, the first casing part, connecting structure and mounting structure are integrally formed as a single monolithic structure.

Preferably, at least one opening is formed in the circumferential surface of the sleeve.

Preferably, the abutment plate comprises a non-flat abutment surface axially contacting the motor; and the sleeve extends in the axial direction of the motor from the abutment surface.

Preferably, the abutment surface has a V-shaped rib, and the motor contacts the abutment surface only at the tip of the V-shaped rib.

Preferably, the tubular body and the mounting structure are integrally formed as a monolithic structure.

Preferably, the tubular body and the mounting structure are separately formed and assembled to each other.

Preferably, the sleeve has a continuous circumferential surface.

In a second aspect thereof, the present invention provides a casing for an actuator, comprising: a wall; a mounting structure for mounting a motor having a shaft to the casing; and a damper disposed between the mounting structure and the wall, the damper integrally extending from the wall such that the damper and the wall form a monolithic member.

Preferably, the damper comprises a tubular body for sleeving the shaft of the motor.

Preferably, the tubular body extends from the wall in an axial direction of the motor.

DETAILED DESCRIPTION OF THE VARIOUS EMBODIMENTS

FIG. 1illustrates an actuator10incorporating a casing12in accordance with a preferred embodiment of the present invention.FIG. 2is a partial plan view of the actuator10.FIG. 3is a sectional view of the actuator10taken along line A-A inFIG. 2. By way of example, the actuator10is suitable for such applications as those used in the HVAC system of a vehicle. The actuator10comprises the casing12, an electric motor14, and a gear transmission (not shown) for transmitting the rotation of the motor14to an output member (not shown). The motor14, the gear transmission, and the output member are received in the casing12.

Also referring toFIG. 4, the motor14is preferably a DC motor and comprises a shaft16and a housing18with two flat end plates20and22that are substantially perpendicular to the shaft16. A worm24is provided on the shaft16. The gear transmission comprises a worm wheel26(shown inFIG. 3) engaged with the worm24. To clearly show the structure of the casing12, the output member and other components of the gear transmission are not shown in the figures. Two cylindrical bosses28and30protrude axially from the end plates20and22, respectively, and accommodate bearings for supporting the shaft16. A flange32extends axially from the end plate22of the housing18remote from the worm24. A cut-out33is formed in the flange32.

In accordance with the preferred embodiment, the casing12is made of plastic, e.g., polypropylene, and includes a first casing part34and a second casing part36coupled to each other.FIGS. 5 and 6illustrate the first casing part34viewed from different angles.FIG. 7illustrates the second casing part36. The first casing part34includes a first base38and a first side wall39. The second casing part36includes a second base40and a second side wall41. The motor14is mounted to the casing12via a mounting structure42. Preferably, the mounting structure42and the first casing part34are integrally formed as a monolithic structure, i.e. it may be a single piece injection molding. The mounting structure42comprises an abutment plate43and a sleeve44axially extending from the abutment plate43.

The first casing part34of the casing12also includes connecting structure, optionally in the form of a tubular body50, between the abutment plate43and the side wall39for coupling the mounting structure42to the side wall39of the casing12. The connecting structure preferably functions as a damper to reduce the transmission of vibrations from the motor to the casing. Preferably, the tubular body50, the abutment plate43, and the side wall39are integrally formed as a monolithic structure. A through hole52is formed in the abutment plate43. The axial end of the tubular body50remote from the abutment plate43is closed by an end wall54extending from the side wall39.

As can be seen inFIG. 3, the sleeve44is spaced from the first base38to prevent or mitigate motor vibrations being transferred to the first base. The connecting structure fixes the mounting structure to an edge portion of the first base in a cantilever manner, such that the mounting structure is suspended above the first base. Preferably, the connecting structure is fixed to the edge portion by a wall that extends from the edge portion, although it could be directly connected. The optional rib48braces the free end of the sleeve to a second edge portion of the first base, directly or via a portion of a wall.

Optionally, a rib48is formed on the first casing part34and supports the free end of the sleeve44. In this embodiment, several openings49are formed in the circumferential surface of the sleeve44so that the entire circumferential surface of the sleeve44is not a continuous surface. By this configuration, material usage for the mounting structure42is reduced.

The motor14is inserted into the sleeve44and mounted to the sleeve44in a tight manner such as by an interference fit or press fit. The end plate20of the housing18of the motor14abuts against the abutment plate43. The flange32of the housing18abuts against a locking member46formed on the second base40of the second casing part36. Thus, the housing18of the motor14is axially positioned between the abutment plate43and the locking member46. The locking member46locates in a cut-out33formed in an edge of the motor housing18, forming an interlock mechanism to prevent the motor from turning within the sleeve44. The motor shaft16extends into the tubular body50via the through hole52. The tubular body50is sleeved around the worm24on the shaft16without contacting the worm so that the shaft16can rotate freely within the tubular body50. The free end56of the shaft16reaches and is axially supported by the end wall54. The flat end plate20of the housing18of the motor14abuts against the axial abutment plate43of the casing12. The boss28extending from the end plate20extends into and is radially supported by the tubular body50.

A notch58is formed in the side wall39outside the end wall54of the tubular body50of the first casing part34, and a corresponding ridge60is formed on the side wall41of the second casing part36of casing12. The notch58and the ridge60engage with each other to circumferentially position the second casing part36relative to the first casing part34. Furthermore, the end wall54of the tubular body50and the side walls39and41of the casing12provide a stiff support for the tubular body50, which is beneficial in diminishing the noise and/or vibration of the casing12while the motor14is in operation. A window62is formed in the circumferential surface of the tubular body50so that the worm24on the shaft16is exposed and engaged with the worm wheel26.

Preferably, a projection64extends from the outer surface of the tubular body50in the first casing part34and a corresponding slot66is formed in the second casing part36. When the first casing part34and the second casing part36are assembled together, the projection64is engaged with the slot66to form an interlock structure, thereby reducing or substantially eliminating the tipping of the mounting structure42during the operation of the motor14.

In accordance with another embodiment of the present invention as illustrated inFIG. 8, the sleeve44of the mounting structure42has no opening formed in the circumferential surface thereof, so that the entire circumferential surface of the sleeve44is a continuous surface. The sleeve44has an L-shaped portion70integrally extending from the base38of the first casing part34and an arcuate portion72connecting two circumferential ends of the L-shaped portion70. The motor14is mounted to the sleeve44by an interference fit. Alternatively, the sleeve44may be rectangular in shape.

In accordance with an embodiment of the present invention, the tubular body50and the mounting structure42may be separately formed and assembled to each other.

In accordance with yet another embodiment, as illustrated inFIG. 9, the inner surface74of the abutment plate43of the mounting structure42facing the motor14is a convex surface so that gaps76are formed between the end plate20of the motor14and portions of the surface74remote from the shaft16. As the contact area between the abutment plate43and the end plate20is reduced, less vibration is transmitted from the motor14to the casing12of the actuator10.

In accordance with a further embodiment as illustrated inFIG. 10, the inner surface74, which is also referred to as abutment surface, of the abutment plate43on the mounting structure42is a flat surface with a V-shaped rib78extending therefrom. The end plate20of the motor14contacts the abutment plate43only at the tip of the V-shaped rib78, which reduces the contact area between the abutment plate43and the end plate20. Thus, less vibrations generated by the motor14are transmitted to the casing12.

In accordance with a preferred embodiment of the present invention, the tubular body50is made of a filled polypropylene and is arranged to link the mounting structure42to the side wall39of the casing12. The tubular body50acts as a damper to reduce the amount of motor vibration transmitted to the casing12. The mounting structure42, the tubular body50and the rest of the first casing34can be formed as a monolithic structure. Therefore, the manufacturing process is simple, the cost of the actuator is reduced, and the reliability is improved.

In the description and claims of the present application, each of the verbs “comprise”, “include”, “contain” and “have”, and variations thereof, are used in an inclusive sense, to specify the presence of the stated item or feature but do not preclude the presence of additional items or features.

For example, the inner surface74of the abutment plate43may be other shapes, such as concave, convex, wavy or bumpy, as long as the contact area is reduced to diminish the transmission of vibrations. Also, the damper may take a form other than tubular.