Spacer and electric supercharger

A spacer is disposed between a rotor and a bearing of an electric supercharger to fix the rotor. The spacer has a tapered surface with a diameter decreasing toward the bearing in an outer circumferential surface of the spacer. An area of an end surface of the spacer on a rotor side is larger than an area of an end surface of the spacer on a bearing side. A balance correction part that corrects balance of the spacer is disposed inside a recess formed in the end surface. A region of the end surface located on an outer side of the recess relative to a central axis of the spacer constitutes a surface coming in contact with the rotor.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2016-202610 filed on Oct. 14, 2016 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a spacer and an electric supercharger, and relates to, for example, a spacer that is disposed between a rotor and a bearing of an electric supercharger to fix the rotor, and to an electric supercharger employing this spacer.

2. Description of Related Art

A typical electric supercharger supercharges intake air by rotating a rotor using magnetic force of a stator and thereby rotating a turbine fixed at a leading end of a shaft through the shaft. As disclosed in Japanese Patent Application Publication No. 2000-145469, such an electric supercharger has a spacer disposed between the rotor and the bearing to fix the rotor, and this spacer rotates with the rotor.

SUMMARY

Since the spacer rotates with the rotor, it is preferable that an unbalanced part of the spacer (i.e., a part with a manufacturing error that causes a deviation of the center of gravity of the spacer from the central axis of the spacer) be corrected during manufacturing.

Here, as shown inFIG. 3, a spacer101of JP 2000-145469 A has a conical shape with a diameter decreasing from the rotor side toward the bearing side as its basic form, and an end surface101aof the spacer101on the bearing side comes in contact with the bearing, while an end surface101bof the spacer101on the rotor side comes in contact with the rotor.

In the case where a balance correction part that corrects an unbalanced part is formed in the spacer101of JP 2000-145469 A, the correcting effect of this balance correction part depends on the radius of a portion, cut out from the spacer101to form the balance correction part, multiplied by the mass of that portion. However, designing the balance correction part is complicated by the fact that a circumferential surface101cof the spacer101is a tapered surface.

The area of the end surface101aof the spacer101is not large enough to form the balance correction part therein. Moreover, if the balance correction part is formed in the end surface101aof the spacer101, a burr of the balance correction part is formed in the end surface101a, which makes it difficult to secure the flatness required to appropriately bring the spacer101into contact with the bearing. Accordingly, it becomes difficult to appropriately fix (fasten) the spacer101to the rotor.

On the other hand, the area of the end surface101bof the spacer101is larger than the area of the end surface101aof the spacer101, and is large enough to form the balance correction part therein. Thus, the only location where the balance correction part can be formed is the end surface101bof the spacer101. However, if the balance correction part is formed in the end surface101bof the spacer101, a burr102is formed in the end surface101bas shown inFIG. 4, which makes it difficult to secure the flatness required to appropriately bring the spacer101into contact with the rotor. Thus, it becomes difficult to appropriately fix the spacer to the rotor.

The present disclosure realizes a spacer in which there is little deviation of the center of gravity of the spacer from the central axis of the spacer and which can be appropriately fixed to the rotor, and further realizes an electric supercharger.

A spacer according to an aspect of the present disclosure is a spacer that is disposed, to fix a rotor of an electric supercharger, between the rotor and a bearing disposed in a direction of a rotational axis of the rotor relative to the rotor, the spacer including a tapered surface with a diameter decreasing toward the bearing in an outer circumferential surface of the spacer, wherein: the area of an end surface of the spacer on a rotor side may be larger than the area of an end surface of the spacer on a bearing side; a balance correction part that corrects balance of the spacer may be disposed inside a recess formed in the end surface of the spacer on the rotor side; and, a region of the end surface located on an outer side of the recess relative to a central axis of the spacer may constitute a surface coming in contact with the rotor. This configuration makes it possible to correct the balance of the spacer and, at the same time, to appropriately bring the region of the end surface of the spacer on the rotor side located on the outer side of the recess relative to the central axis of the spacer into contact with the rotor. Thus, there is little deviation of the center of gravity of the spacer from the central axis of the spacer, so that the spacer can be appropriately fixed to the rotor.

The spacer may have a conical outer shape. The spacer may include a perforated portion, and the central axis of the spacer may be disposed on the rotational axis of the rotor.

In the above spacer, the balance correction part may be a weight adjustment part that is formed in the spacer so that the center of gravity of the spacer is located on the central axis of the spacer.

In the above spacer, the balance correction part may include an excavated portion formed in the spacer, and a burr resulting from formation of the excavated portion. The recess may be formed so as to have a diameter around the central axis of the spacer, and may have a depth that allows the recess to accommodate the burr of the balance correction part.

In the above spacer, the balance correction part may be a weight provided inside the recess.

An electric supercharger according to another aspect of the present disclosure is an electric supercharger in which a spacer is disposed, to fix a rotor, between the rotor and a bearing disposed in a direction of a rotational axis of the rotor relative to the rotor, the electric supercharger including: a housing that supports a shaft through the bearing and has an air flow passage; a turbine that is disposed inside the flow passage and fixed at a leading end of the shaft; and a stator that surrounds the rotor and is fixed to the housing, wherein: the area of an end surface of the spacer on a rotor side may be larger than the area of an end surface of the spacer on a bearing side; the spacer may have a tapered surface with a diameter decreasing toward the bearing in an outer circumferential surface of the spacer; a balance correction part that corrects balance of the spacer may be disposed inside a recess formed in the end surface of the spacer on the rotor side; and, a region of the end surface located on an outer side of the recess relative to a central axis of the spacer may constitute a surface coming in contact with the rotor. This configuration makes it possible to correct the balance of the spacer and, at the same time, to appropriately bring the region of the end surface of the spacer on the rotor side located on the outer side of the recess relative to the central axis of the spacer into contact with the rotor. Thus, there is little deviation of the center of gravity of the spacer from the central axis of the spacer, so that the spacer can be appropriately fixed to the rotor.

According to an aspect of the present disclosure, it is possible to realize a spacer in which there is little deviation of the center of gravity of the spacer from the central axis of the spacer and which can be appropriately fixed to the rotor, and to further realize an electric supercharger.

In the above electric supercharger, the spacer may have a conical outer shape. The spacer may include a perforated portion that extends through the spacer in a left-right direction of the electric supercharger, and the central axis of the spacer may be disposed on the rotational axis of the shaft.

In the above electric supercharger, the balance correction part may be a weight adjustment part that is formed in the spacer so that the center of gravity of the spacer is located on the central axis of the spacer.

In the above electric supercharger, the balance correction part may include an excavated portion formed in the spacer, and a burr resulting from formation of the excavated portion. The recess may be formed so as to have a diameter around the central axis of the spacer, and may have a depth that allows the recess to accommodate the burr of the balance correction part.

In the above electric supercharger, the balance correction part may be a weight provided inside the recess.

DETAILED DESCRIPTION OF EMBODIMENTS

A specific embodiment to which the present disclosure is applied will be described below in detail with reference to the drawings. However, the present disclosure is not limited to the following embodiment. To clarify the illustration, the following description and the drawings are simplified where appropriate.

First, the basic configuration of an electric supercharger of this embodiment will be described.FIG. 1is a sectional view schematically showing the electric supercharger of this embodiment. To clarify the illustration, an upper-lower direction and a left-right direction of the electric supercharger will be specified as indicated inFIG. 1for the following description, but these directions are changed as appropriate according to the form of use of the electric supercharger.

The electric supercharger1of this embodiment is suitable as a compressor of an air supply system of a fuel cell (FC) system, and as shown inFIG. 1, includes a housing2, a rotor3, and a stator4. Although the electric supercharger1of this embodiment is configured as a compressor of an air supply system of an FC system, the electric supercharger1can also be used as another type of compressor.

The housing2includes: a first housing part2awhere the rotor3, the stator4, etc. are housed; an air intake port2b; an exhaust port2cthrough which air taken in through the intake port2bis discharged; and a flow passage2dthat provides communication between the intake port2band the exhaust port2c.

As shown inFIG. 1, the rotor3includes a magnet3a, a tubular body3b, and end plates3c. The magnet3ahas a cylindrical shape with a perforated portion extending through the magnet3ain a left-right direction of the rotor3. The tubular body3bhas a cylindrical shape with a perforated portion extending through the tubular body3bin the left-right direction of the rotor3, and the magnet3ais press-fitted inside the perforated portion of the tubular body3bso that a compressive stress is applied to the magnet3a. The end plates3ceach have a perforated portion with an inside diameter substantially equal to that of the perforated portion of the magnet3a, and are fitted inside the perforated portion of the tubular body3bso as to sandwich the magnet3afrom a left-right direction of the magnet3a.

A shaft5extending in the left-right direction of the electric supercharger1is passed through the perforated portions of the magnet3aand the end plates3cof the rotor3. In a state where the rotor3is housed inside the first housing part2aof the housing2, the rotor3is rotatably supported on the housing2through the shaft5.

In this embodiment, the shaft5is passed through washers6, spacers7, and bearings8so that the rotor3is sandwiched from the left-right direction of the electric supercharger1. Thus, the spacer7is disposed between the rotor3and the bearing8that is disposed in an extension direction of a rotational axis AX2of the shaft5(i.e., a rotational axis of the rotor3) relative to the rotor3. The shaft5is rotatably supported on the housing2through the bearings8. Accordingly, the rotor3is rotatably supported on the housing2through the shaft5. The specific shape of the spacer7will be described later.

Moreover, the shaft5is passed through a preloading spring9and a seal material10so that the rotor3, the left and right washers6, the left and right spacers7, and the left and right bearings8are sandwiched from the left-right direction of the electric supercharger1. The rotor3, the left and right washers6, the left and right spacers7, the left and right bearings8, and the seal material10are pressed into a flange5aformed on the shaft5by a restoring force of the preloading spring9that is compressed as a nut11is screwed on a right end of the shaft5. Thus, the rotor3, the left and right washers6, the left and right spacers7, the left and right bearings8, and the seal material10are fixed to the shaft5.

A resolver12that detects a rotation angle of the rotor3is provided at a right-side portion of the shaft5. Although the resolver12is housed inside a second housing part2eformed inside the housing2in this embodiment, the arrangement of the resolver12is not limited.

A left-side portion of the shaft5(a portion of the shaft5on the left side of the flange5a) protrudes into the flow passage2dof the housing2. The left-side portion of the shaft5is passed through a turbine13that is disposed inside the flow passage2dof the housing2, and a nut14is screwed on a left end of the shaft5so as to fix the turbine13between the nut14and the flange5aof the shaft5. Thus, when the shaft5rotates, air suctioned through the intake port2bof the housing2is compressed by the turbine13and discharged through the exhaust port2cof the housing2, and this air is then supplied to an FC stack, for example.

The stator4is disposed so as to surround the rotor3, and is fixed to the housing2in a state where the stator4is housed inside the first housing part2aof the housing2. The stator4includes a stator core4aand a stator coil4b. The stator core4ais composed of a stack of a plurality of magnetic steel sheets4c, and the rotor3extends through the inside of the stator core4a. The stator core4ais fixed to the housing2with a bolt15. The stator coil4bis wound around predetermined teeth formed in the stator core4a.

Next, the configuration of the spacer7in the electric supercharger1of this embodiment will be described.FIG. 2is a sectional view schematically showing the spacer in the electric supercharger of this embodiment. While the spacer7disposed on the left side of the rotor3will be described as a representative, the spacer7disposed on the right side has an equivalent configuration.

As shown inFIG. 2, the spacer7of this embodiment includes a perforated portion7aextending through the spacer7in the left-right direction of the electric supercharger1, and a central axis AX1of the spacer7is disposed on the rotational axis AX2of the shaft5.

The spacer7has a conical outer shape with a diameter decreasing toward the bearing8as its basic form. Accordingly, the spacer7has a tapered surface with a diameter decreasing toward the bearing8in an outer circumferential surface of the spacer7. The area of an end surface7cof the spacer7on the rotor3side is larger than the area of an end surface7bof the spacer7on the bearing8side. For example, the outside diameter of the end surface7bof the spacer7is substantially equal to the outside diameter of an inner ring of the bearing8, and the outside diameter of the end surface7cof the spacer7is substantially equal to the outside diameters of the rotor3and the washer6.

The area of the end surface7bof the spacer7is not large enough to form a balance correction part to be described later therein, while the area of the end surface7cof the spacer7is large enough to form the balance correction part to be described later therein. Thus, the spacer7of this embodiment has such a shape that the balance correction part can be formed only in the end surface7cof the spacer7.

Although the spacer7of this embodiment has a conical shape with the diameter decreasing toward the bearing8as its basic form, the spacer7may have any shape, provided that the spacer7has a tapered surface in a part of the outer circumferential surface and that the area of the end surface7cof the spacer7is larger than the area of the end surface7bof the spacer7.

The shaft5is passed through the perforated portion7aof the spacer7, and the spacer7is fixed to the rotor3through the washers6by an axial force that is exerted as the nut11is screwed. Thus, the spacer7rotates with the rotor3around the shaft5.

A recess7dis formed in the end surface7cof the spacer7. A balance correction part7ementioned above is disposed inside the recess7d. The balance correction part7eis a weight adjustment part that is formed in the spacer7so that the center of gravity of the spacer7is located substantially on the central axis AX1of the spacer7. For example, the balance correction part7eincludes an excavated portion7fformed in the spacer7, and a burr7gresulting from formation of the excavated portion7f. For example, the recess7dis formed so as to have a diameter R1around the central axis AX1of the spacer7, and has a depth D1that allows the recess7dto accommodate the burr7gof the balance correction part7e. Alternatively, the balance correction part7emay be a weight or the like provided inside the recess7d. A single or a plurality of balance correction parts7emay be provided.

Of the end surface7cof the spacer7, a region7hlocated on an outer side of the recess7drelative to the central axis AX1constitutes a surface coming in contact with the rotor3. The area and the like of the region7hof the end surface7cof the spacer7are set so that a surface pressure acting on the region7hwhen the spacer7is fixed to the rotor3does not exceed an allowable surface pressure of the region7h.

In this embodiment, the balance correction part7eis formed inside the recess7dof the spacer7. Thus, the burr7gof the balance correction part7eis accommodated inside the recess7dof the spacer7and does not protrude toward the rotor3beyond the region7hof the end surface7cof the spacer7. Accordingly, the region7hof the end surface7cof the spacer7can be appropriately brought into contact with the rotor3. Thus, according to the spacer7of this embodiment, the balance of the spacer7is corrected and, at the same time, the part of the spacer7coming in contact with the rotor3is highly flat. According to the spacer7of this embodiment, therefore, there is little deviation of the center of gravity of the spacer7from the central axis AX1of the spacer7, so that the spacer7can be appropriately fixed to the rotor3.

In this case, a fixing torque T with which the spacer7is fixed to the rotor3can be expressed by <Formula 1> below. Here, the axial force exerted by screwing the nut11is N, the diameter of a point of application at which this axial force acts intensively in the region7hof the end surface7cof the spacer7is R2, and the coefficient of friction of the region7hof the end surface7cof the spacer7is μ.
T=N×μ×(R2/2)   <Formula 1>

Even if the recess7dis not formed in the end surface7cof the spacer7(i.e., even if the end surface7cof the spacer7is substantially flat), it is practically impossible to form a perfectly flat surface, so that the position of contact between the end surface7cof the spacer7and the rotor3cannot be stabilized. Thus, depending on the manufacturing error of the spacer7, the spacer7may come in contact with the rotor3at a position closer to the central axis AX1in the end surface7cof the spacer7, or may come in contact with the rotor3at a position farther from the central axis AX1in the end surface7cof the spacer7.

In the spacer7of this embodiment, however, the surface coming in contact with the rotor3is limited to the region7hthat is located on the outer side of the recess7din the end surface7c, i.e., the recess7ddoes not come in contact with the rotor3, so that the position of contact with the rotor3can be stabilized. Moreover, since the fixing torque T depends on the diameter R2of the point of application of the axial force, the spacer7can be fixed to the rotor3with a higher fixing torque than if a region located on an inner side of the region7hin the end surface7ccomes in contact with the rotor3.

The present disclosure is not limited to the above embodiment but can be appropriately modified within the scope of the gist of the disclosure.