Mounting structure of electric motor-driven compressor

The present invention relates to a mounting structure of an electric motor-driven compressor applied to a hybrid vehicle having an internal combustion engine (engine) and an electric motor for running the vehicle, and further relates to a method for mounting an electric motor-driven compressor.

US-A- 3 789 618 describes a mounting structure of an electric motor-driven compressor in a conventional motor vehicle having only an internal combustion engine for running the vehicle. The mounting structure comprises a compression mechanism for compressing fluid and a compressor electric motor integrated with said compression mechanism for driving said compression mechanism, wherein said compression mechanism can optionally be driven by only said electric motor. Said electric motor-driven compressor is mounted on the internal combustion engine in such a manner that said compressor electric motor is positioned closer to the centre of gravity of the internal combustion engine than said compression mechanism.

In recent years, to reduce exhaust gas discharged from an engine, research and development of a hybrid vehicle have been vigorously conducted. In response to this, research and development of refrigeration cycle for a vehicle such as an air conditioner for a vehicle suitable for the hybrid vehicle have been energetically conducted.

In a conventional type vehicle having only an engine as a power source, a driving force for a compressor for the refrigeration cycle thereof is supplied by the engine. However, the hybrid vehicle may have a following problem: since the engine stops in some running state, if the driving force is supplied only by the engine, the refrigeration cycle is also stopped when the compressor is stopped.

Therefore, it is desirable that the refrigeration cycle for the hybrid vehicle employs an electric motor-driven compressor having a built-in electric motor.

Regarding the hybrid vehicle, since the engine and the electric motor for running the vehicle are housed in an engine room, there is a little vacant space in the engine room in comparison with a conventional vehicle. Therefore, it is desirable that the electric motor-driven compressor is mounted on the engine.

However, since the vibration of the vehicle caused by the engine is acted on the compressor for the vehicle, if the conventional compressor supplied with the driving force only by the engine is simply replaced with the electric motor-driven compressor, the vibration of the vehicle probably might cause a damage to the electric motor-driven compressor (in particular, electric motor).

In this connection, there is a refrigeration cycle of a stay-at-home model such as a refrigerator, a home air conditioner or the like, as an example employing the electric motor-driven compressor in the refrigeration cycle. However, in these refrigeration cycles, a large vibration force like the vibration of the vehicle does not act on the electric motor-driven compressor in contrast to the refrigeration cycle for a vehicle. Therefore, the mounting structure of the electric motor-driven compressor in the refrigeration cycle of a stay-at-home model can not be applied to the electric motor-driven compressor for a vehicle.

The present invention is made in light of the foregoing problem, and it is an object of the present invention to provide a mounting structure of an electric motor-driven compressor for a vehicle taking into account the effect of the vibration of the vehicle.

This object is achieved by the mounting structure according to claim 1 and the method according to claim 4.

According to a mounting structure of an electric motor-driven compressor of the present invention, the electric motor-driven compressor is mounted on an internal combustion engine in such a manner that an electric motor is positioned closer to the center of gravity of the internal combustion engine than a compression mechanism.

Since the electric motor is positioned closer to the center of gravity in which the vibration of the internal combustion engine is small, a vibration force acting on the electric motor becomes small. Therefore, this prevents the electric motor from being damaged.

According to the present invention, a fixing portion of a motor housing is formed in a position deviated from a part corresponding to a stator core.

Therefore, the stator core is prevented from being greatly deformed in response to a deformation of a motor housing when a bolt is fastened.

According to another aspect of the present invention, the axial direction of an electric motor is parallel to a direction, which is parallel to a contact surface between the internal combustion engine and a fixing portion of an electric motor-driven compressor, and which has the smallest vibration force among directions parallel to the contact surface.

Accordingly, the vibration force applied to the electric motor becomes smaller, and the defective insulation of the electric motor can be prevented. Therefore, the reliability (durability) of the electric motor-driven compressor is improved.

Other features and advantages of the present invention will be appreciated, as well as methods of operation and the function of the related parts, from a study of the following detailed description, the appended claims, and the drawings, all of which form a part of this application. In the drawings: <ul id="ul0001" list-style="none" compact="compact"><li>FIG. 1 is a perspective view illustrating a mounting structure of an electric motor-driven compressor according to the present invention;</li><li>FIG. 2 is a schematic top plan view illustrating the mounting structure of the electric motor-driven compressor of the present invention when viewed from the top of a vehicle;</li><li>FIG. 3 is a schematic front view illustrating the mounting structure of the electric motor-driven compressor of the present invention when viewed from the front of the vehicle;</li><li>FIG. 4 is a graph showing measurement results of a vibration parallel to a crank shaft of an engine (lateral direction of the vehicle), measured at the compressor;</li><li>FIG. 5 is a graph showing measurement results of a vibration orthogonal to the crank shaft of the engine (vertical direction of the vehicle), measured at the compressor;</li><li>FIG. 6A is a partial cross-sectional view of an electric motor of the compressor;</li><li>FIG. 6B is a cross-sectional view taken along a line B-B in FIG. 6A; and</li><li>FIG. 7 is a schematic view showing a mounting state of an electric motor-driven compressor.</li></ul>

FIG. 1 is a perspective view illustrating a mounting structure of an electric motor-driven compressor applied to a hybrid vehicle having an internal combustion engine E and an electric motor M for running the vehicle (see FIGS. 2 and 3). In FIGS. 2 and 3, the reference numeral 30 represents a tire.

As shown in FIG. 1 to FIG. 3, an electric motor-driven compressor 10 for a vehicle refrigeration cycle comprises a scroll type compression mechanism 11 for sucking and compressing refrigerant and an electric motor 12 for driving the compression mechanism.

In the housing of the electric motor 12, as shown in FIG. 1, four bolt holes (fixing portions) 13 for fixing the electric motor-driven compressor 10 to a part of the engine E are formed on a housing of the electric motor 12, and the electric motor-driven compressor 10 is fixed to the engine by inserting the through bolts 132 (see FIG. 6B) into female thread holes (not shown) made in crank case of the engine E through the bolt holes 13.

The electric motor-driven compressor 10 is fixed to the engine E such that the electric motor 12 is positioned closer to the center of gravity G of the engine E than the compression mechanism 11 and that the axial direction L₁ of the electric motor 12 corresponds with the direction L₂ of the crank shaft of the engine E. Therefore, the axial direction L₁ of the electric motor 12 is parallel to the direction L₂ of the crank shaft of the engine E. The axial direction L₁ of the electric motor 12 is the axial direction of a rotor (armature) in the electric motor 12, and is parallel to a motor shaft of the electric motor 12.

It is generally known that the electric motor 12 includes a rotor (armature), a stator and the like. Therefore, the electric motor 12 is generally heavier than the compression mechanism 11. Therefore, usually, the center of gravity G₁ of the electric motor-driven compressor 10 locates closer to the electric motor 12 than the compression mechanism 11. On the other hand, the vibration of the engine E becomes smaller as the position is closer to the center of gravity G of the engine E.

Therefore, if the electric motor 12 is positioned closer to the center of gravity G of the engine E than the compression mechanism 11, the vibration of the electric motor 12 is reduced, and a vibration force applied to the electric motor 12 is reduced. Thus, the electric motor 12 is prevented from being damaged by the vibration of the engine E.

The main reason for the damage of the electric motor 12 is that the winding of the rotor or the stator is shifted and cause the insulation failure. Therefore, inventors studied a relationship between the vibration direction and the damage of the electric motor 12, and discovered that when the vibration force is applied to the electric motor 12 in its axial direction, the winding was further shifted and cause the insulation failure than when the vibration force is applied to the electric motor 12 in its radial direction.

As understood from FIGS 4 and 5, the vibration force applied to the winding of the electric motor 12 is reduced, and the insulation failure is prevented since the direction L₂ of the crank shaft of the engine E, in which the vibration (vibration force) of the engine E is small, corresponds with the axial direction L₁ of the electric motor 12. Therefore, the reliability (durability) of the electric motor 12 (electric motor-driven compressor 10) is improved.

As shown in FIG. 6A, the electric motor 12 includes an approximate cylindrical-shped stator core 121, a coil 122 wound on the stator core 121, a magnet rotor 123 made of a permanent magnet and rotates in the stator core 121, and a motor housing 124 for housing the stator core 121, the coil 122 and the magnet rotor 123.

The stator core 121 is made by laminating thin magnetic materials such as silicon steel sheets.

The stator core 121 is pressed and fixed in the inner periphery of the motor housing 124 by a shrink fit (tight fit), and the magnet rotor 123 is rotatably supported in the motor housing 124 via a bearing 125 disposed on a shaft 126.

Furthermore, stays 131 having bolt holes 131 are integrally formed with the motor housing 124 such that each bolt hole 13 is positioned at an area deviated from an area corresponding to the stator core 121 of the motor housing 124 (the area designated by X in FIG. 6A).

Accordingly, the stator core 121 is prevented from being greatly deformed as the motor housing 124 is deformed when the bolts 132 are fastened. Therefore, the defective problems such as peeling or breakage of the silicon steel sheets constituting the stator core 121.

In the above described embodiment, the direction L₂ of the crank shaft corresponds with (parallel with) the axial direction L₁ of the electric motor 12. However, there may be a case in a vehicle of some type or size where it is difficult to mount the electric motor-driven compressor 10 on the engine E in a state in which the direction L₂ of the crank shaft corresponds with the axial direction L₁ of the electric motor 12.

In that case, the electric motor-driven compressor 10 may be fixed to the engine E such that the axial direction L₁ of the electric motor 12 is positioned parallel to a direction, which is parallel to a contact surface 13a between the engine E and bolt holes 13, and which has the smallest vibration force among directions parallel to the contact surface 13a.

The electric motor-driven compressor 10 according to the above described embodiment is driven only by the electric motor 12.

Furthermore, in the above described embodiment, the bolts 132 are provided such that they pass through the motor housing 124 in the radial direction of the magnet rotor 123 as shown in FIG. 6B. However, as shown in FIG. 7, the bolt holes 13 (stays 131) may be formed only in the engine block side of the motor housing 124.

In this case, since the fastening force is not applied to the motor housing 124, the stator core 121 is hardly deformed.

Although the present invention has been described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. The scope of the present invention is defined in the appended claims.