JP7831927B2 - Rotating machinery and detection devices - Google Patents

Description

This invention relates to a rotating machine and a detection device.

Conventionally, magnetostrictive rotating devices or detection devices are known as rotating devices or detection devices capable of detecting forces applied to a shaft. For example, a strain detection device has been proposed that includes a magnetic layer fixed to the outer surface of a shaft and a detection coil for detecting changes in the permeability of the magnetic layer (see, for example, Patent Document 1).

Japanese Patent Application Publication No. 5-52679

In magnetostrictive rotating machinery or detection devices, the overall size of the device around the shaft tends to increase due to the need to arrange detection coils and other components. This invention addresses the miniaturization of rotating machinery or detection devices as one example of its problem-solving objectives.

The rotating device or detection apparatus of the present invention comprises a case, a shaft rotatably supported relative to the case, and a detection unit disposed on the outer or inner surface of the case. The case comprises a first case member, a second case member, and a connecting portion connecting the first and second case members. The detection unit is disposed between the shaft and the connecting portion.

This is a perspective view of a rotating device (detection device) according to an embodiment of the present invention. This is another perspective view of a rotating device (detection device) according to an embodiment of the present invention. This is a side view of a rotating device (detection device) according to an embodiment of the present invention. This is a cross-sectional view taken along line A-A in Figure 3 of a rotating device (detection device) according to an embodiment of the present invention. This figure shows an example of the usage state of a rotating device (detection device) according to an embodiment of the present invention.

In describing the embodiments of the present invention, for the sake of explanation, the direction of arrow a along the central axis (axis X) of the shaft 20 is referred to as one axial side, and the direction of arrow b along axis X is referred to as the other axial side. Here, the direction along axis X, i.e., the direction of arrows a and b, is referred to as the axial direction. In Figure 4, the direction of arrows cd, i.e., the direction perpendicular to the axial direction, is referred to as the radial direction, the direction of arrow c moving away from axis X is referred to as the outward or one radial side, and the direction of arrow d moving towards axis X is referred to as the inward or the other radial side.

Furthermore, the direction of arrow e (the front of the electric assist bicycle 2 in Figure 5) is referred to as the direction of travel, and the direction of arrow f (the rear of the electric assist bicycle 2 in Figure 5) is referred to as the direction of reversing. Additionally, when the electric assist bicycle 2 is mounted, the direction of arrow g, which aligns with the direction of gravity, is referred to as the upward direction of gravity, and the direction of arrow h, which aligns with the direction of gravity, is referred to as the downward direction of gravity.

The following describes an embodiment of the present invention with reference to the drawings. In this embodiment, the rotating device or detection device (hereinafter referred to as the rotating device 1) is a part of the drive unit 3 of the electric assist bicycle 2 (see Figure 5). Figure 1 is a perspective view showing the overall configuration of the rotating device 1 as seen from one side. Figure 2 is a perspective view showing the overall configuration of the rotating device 1 as seen from the other side. Figure 3 is a side view showing the configuration of one side of the rotating device 1. Figure 4 is a cross-sectional view showing the configuration of the rotating device 1 in the section A-A of Figure 3. Figure 5 is a diagram showing an example of the rotating device 1 in use, where the drive unit 3 including the rotating device 1 is mounted on the electric assist bicycle 2.

The rotating device 1 comprises a case 10, a shaft 20, and a detection unit 50 (see Figure 4). The case 10 includes a first case member 11, a second case member 12, and a connecting part 13 that connects the first case member 11 and the second case member 12. The second case member 12 is an egg-shaped cup when viewed from the other axial side (arrow b direction) and opens on one axial side (arrow a direction). The first case member 11 is an egg-shaped flat plate when viewed from one axial side (arrow a direction) and functions as a lid that closes the opening of the second case member 12 from one axial side. However, the shapes of the first case member 11 and the second case member 12 are not limited to being egg-shaped when viewed from one axial side (arrow a direction) and the other axial side (arrow b direction), but may be any shape.

The case 10 (first case member 11 and second case member 12) is formed from aluminum, magnesium, titanium, or an alloy containing at least one of these metals. Because these metals have relatively high internal losses (tanδ), vibrations in the case 10 can be dampened relatively quickly.

Because the case 10 is formed of the above-mentioned metal, vibrations that occur simultaneously with the strain of the case 10, and vibrations that become noise when detecting the strain of the case 10, can be attenuated relatively quickly in the detection unit 50 described later, enabling high-precision detection of strain. However, the first case member 11 and the second case member 12 may be formed of other metals, resins, etc. Furthermore, the first case member 11 and the second case member 12 may be formed of the same material, or they may be formed of different materials.

As shown in Figures 1, 2, and 4, the first case member 11 has a wall portion 11c that protrudes in the other axial direction (direction of arrow b), formed around the edge of the first case member 11. When the first case member 11 and the second case member 12 are connected, the end of the wall portion 11c in the other axial direction (direction of arrow b) is in contact with the end of the second case member 12 in one axial direction (direction of arrow a).

As shown in Figure 2, the second case member 12 has a roughly circular, cup-shaped motor housing 12m at its other axial end (in the direction of arrow b), as viewed from the other axial end (in the direction of arrow b). The motor housing 12m is positioned on the direction of travel side (in the direction of arrow e) of the through hole 12t (described later) and protrudes in the other axial direction (in the direction of arrow b). The motor housing 12m is the part that houses the motor (not shown) located inside the case 10.

As shown in Figures 1 and 2, the second case member 12 has a total of six roughly triangular flange portions 12a to 12f protruding from its outer surface. These flanges are located on the lower (arrow h) and upper (arrow g) sides in the direction of gravity in the retraction direction (arrow f), and on the upper (arrow g) side in the direction of gravity in the direction of gravity in the forward direction (arrow e), with one flange portion on each axial side (arrow a) and the other axial side (arrow b).

Case 10 is fixed to the electric assist bicycle 2 via flange portions 12a to 12f. However, the position, number, and shape of flange portions 12a to 12f are not limited to these; they may be in any position, number, and shape as long as they can be fixed to the electric assist bicycle 2. Furthermore, the means of fixing case 10 to the electric assist bicycle 2 does not necessarily have to be via flange portions 12a to 12f.

As shown in Figures 1 and 3, the first case member 11 and the second case member 12 are connected by seven connecting parts 13 (first connecting part 13a to seventh connecting part 13g) such as bolts in the portion where the wall portion 11c of the first case member 11 is formed. However, the number of connecting parts 13 is not limited to this and may be any number of two or more. In this embodiment, each connecting part 13 is a bolt, but is not limited to this. As shown in Figure 4, each connecting part 13 fixes the first case member 11 and the second case member 12 via a through hole 11h that penetrates the first case member 11 in the axial direction (arrow a direction) and a bottomed hole 12h formed on the end face of the second case member 12 toward the other axial side (arrow b direction) on one axial side (arrow a direction).

A circular through-hole 11t is formed in the first case member 11 on the side facing the retraction direction (direction of arrow f) and near the center in the direction of gravity. Furthermore, at the end of the second case member 12 on the other axial side (direction of arrow b), a circular through-hole 12t with a larger diameter than through-hole 11t is formed on the side facing the retraction direction (direction of arrow f) and near the center in the direction of gravity. As shown in Figure 4, through-holes 11t and 12t are in communication, and the shaft 20 passes through the case 10 via through-holes 11t and 12t.

The end 21 (Figure 4) of the shaft 20 on one axial side (direction of arrow a) protrudes outward from the case 10 (one axial side) through the through hole 11t of the first case member 11. The end 22 of the shaft 20 on the other axial side (direction of arrow b) protrudes outward from the case 10 (the other axial side) through the through hole 12t of the second case member 12.

As shown in Figure 4, the first case member 11 is provided with a cylindrical projection 11d that protrudes axially (in the direction of arrow b) from the radially outer side (one radial side) of the through hole 11t. A first bearing 60 is positioned radially inner (the other radial side) of the projection 11d. The first bearing 60 is a ball bearing having an inner ring 61, an outer ring 62, and rolling elements. However, the first bearing 60 is not limited to a ball bearing; it may be various other types of bearings, such as a sleeve bearing.

The outer ring 62 of the first bearing 60 is inserted radially inward of the protrusion 11d. The inner ring 61 of the first bearing 60 is bonded or press-fitted to the outer circumferential surface (radially outer surface) of the shaft 20. As a result, the inner ring 61 of the first bearing 60 is fixed to the shaft 20 and rotates integrally with the shaft 20.

As shown in Figure 4, an output gear 80 is positioned near the end 22 on the other axial side (direction of arrow b) of the shaft 20. The output gear 80 is a gear that transmits the rotation of a motor (not shown) to the shaft 20. The output gear 80 is a component having a gear portion 81, a substantially cylindrical boss portion 82 coaxially mounted with the gear portion 81, having a smaller diameter than the gear portion 81 and protruding in the other axial direction (direction of arrow b), and an annular connecting portion 83 connecting the gear portion 81 and the boss portion 82. The output gear 80 is bonded or press-fitted to the outer circumferential surface (radially outer surface) of the shaft 20. As a result, the output gear 80 is fixed to the shaft 20 and rotates integrally with the shaft 20.

In the radial direction, a second bearing 70 is positioned outside the connection portion 83 of the output gear 80. The second bearing 70 has a larger diameter than the first bearing 60. The second bearing 70 is a ball bearing having an inner ring 71, an outer ring 72, and rolling elements. However, the second bearing 70 is not limited to a ball bearing; it may be various other types of bearings, such as a sleeve bearing.

The inner ring 71 of the second bearing 70 is bonded or press-fitted to the outer circumferential surface (radially outer surface) of the connection portion 83 of the output gear 80. This fixes the inner ring 71 of the second bearing 70 to the output gear 80, allowing it to rotate integrally with the shaft 20 and the output gear 80. The outer ring 72 of the second bearing 70 is fixed to the second case member 12 of the case 10 from the radially outer side and the other axial side (direction of arrow b). With this configuration, the shaft 20 is rotatably supported relative to the case 10.

As shown in Figures 1 and 3, the shaft 20 is positioned between the first connecting portion 13a and the second connecting portion 13b of the connecting portion 13. The first connecting portion 13a, the second connecting portion 13b, and the shaft 20 are arranged in a straight line in the direction of gravity, from the top in the direction of gravity, in the order of first connecting portion 13a, shaft 20, and second connecting portion 13b. In this embodiment, the distance between the shaft 20 and the first connecting portion 13a (X1 + Y1 in Figure 3) is equal to the distance between the shaft 20 and the second connecting portion 13b (X2 + Y2 in Figure 3). However, the distance between the shaft 20 and the first connecting portion 13a may differ from the distance between the shaft 20 and the second connecting portion 13b.

As shown in Figure 4, the first case member 11 of the case 10 has an outer surface 11a, which is the surface on one axial side (direction of arrow a), and an inner surface 11b, which is the surface on the other axial side (direction of arrow b). A detection unit 50 for detecting stress is arranged on the outer surface 11a of the first case member 11. However, the detection unit 50 may also be arranged on the inner surface 11b of the first case member 11.

As shown in Figure 4, the detection unit 50 is composed of a plurality of detection units (two in this embodiment), including a first detection unit 51 and a second detection unit 52. The detection unit 50 is positioned between the shaft 20 and the connecting unit 13. Specifically, the first detection unit 51 is positioned in the region between the shaft 20 and the first connecting unit 13a, and the second detection unit 52 is positioned in the region between the shaft 20 and the second connecting unit 13b. In other words, in an axial view, the shaft 20, the first detection unit 51, and the second detection unit 52 are positioned on a straight line connecting the first connecting unit 13a and the second connecting unit 13b. In other words, the shaft 20, the first detection unit 51, and the second detection unit 52 are arranged on a straight line connecting the first connecting unit 13a and the second connecting unit 13b within the plane of the outer surface 11a or the inner surface 11b, which is a plane extending in a direction intersecting the shaft 20, specifically, a plane extending in a direction perpendicular to the shaft 20.

Viewed from the axial direction, the distance between the shaft 20 and the detection unit 50 is greater than the distance between the connecting unit 13 and the detection unit 50. Specifically, viewed from the axial direction, the distance between the shaft 20 and the first detection unit 51 (the distance Y1 between the center of the shaft 20 and the center of the first strain sensor 31 in Figure 3) is greater than the distance between the first connecting unit 13a and the first detection unit 51 (the distance X1 between the center of the first connecting unit 13a and the center of the first strain sensor 31 in Figure 3). Furthermore, the distance between the shaft 20 and the second detection unit 52 (the distance Y2 between the center of the shaft 20 and the center of the second strain sensor 32 in Figure 3) is greater than the distance between the second connecting unit 13b and the second detection unit 52 (the distance X2 between the center of the second connecting unit 13b and the center of the second strain sensor 32 in Figure 3).

In this embodiment, the distance Y1 between the shaft 20 and the first detection unit 51, viewed from the axial direction, is equal to the distance Y2 between the shaft 20 and the second detection unit 52. However, the distance Y1 between the shaft 20 and the first detection unit 51, viewed from the axial direction, may be different from the distance Y2 between the shaft 20 and the second detection unit 52.

As shown in Figure 4, the first detection unit 51 includes a first strain sensor 31 attached to the outer surface 11a of the first case member 11, and the portion of the outer surface 11a of the first case member 11 to which the first strain sensor 31 is attached (first deformation portion 41). The second detection unit 52 includes a second strain sensor 32 attached to the outer surface 11a of the first case member 11, and the portion of the outer surface 11a of the first case member 11 to which the second strain sensor 32 is attached (second deformation portion 42).

The first deformable portion 41 and the second deformable portion 42 are capable of elastic or plastic deformation. Furthermore, the first deformable portion 41 and the second deformable portion 42 may be formed from a material (such as a shape-memory material) that restores to its original shape under certain conditions after deformation. The entire first case member 11, including the first deformable portion 41 and the second deformable portion 42, may be integrally formed from the same material, or the first deformable portion 41 and the second deformable portion 42 may be formed from a different material than the other parts of the first case member 11. Note that the first deformable portion 41 and the second deformable portion 42 only need to be capable of elastic or plastic deformation; they do not need to be more easily deformable than the other parts of the first case member 11.

On the outer surface 11a of the first case member 11, the region between the shaft 20 and the connecting portion 13 (including the first deformable portion 41 and the second deformable portion 42, and the surrounding areas of the first and second deformable portions 41 and 42) is formed as a smooth surface without ribs, recesses, protrusions, etc. This smooth surface is a deformable surface (vibrating surface) that can bend in the axial direction (arrow ab direction) due to stress applied to the first case member 11, resulting in an uneven surface.

The first strain sensor 31 and the second strain sensor 32 are sensors that detect the strain in the first deformation section 41 and the second deformation section 42, respectively. Typically, the first strain sensor 31 and the second strain sensor 32 are strain gauges. When the first strain sensor 31 and the second strain sensor 32 are strain gauges, they are mounted on the outer surface 11a of the first case member 11 such that the orientation of the grid (gauge) (typically the longitudinal direction of the strain gauge) is aligned with the straight line connecting the first detection section 51 and the second detection section 52 (aligned with the direction of gravity).

When the first strain sensor 31 and the second strain sensor 32 are strain gauges, the strain in the first deformation section 41 and the second deformation section 42 is detected as a change in resistance. Note that the first strain sensor 31 and the second strain sensor 32 are not limited to strain gauges; they may be piezoelectric elements or other various sensors.

In this embodiment, the shaft 20 is the crankshaft of the electric assist bicycle 2. When a pedal (not shown) attached to one end 21 on one axial side (direction of arrow a) of the shaft 20 is pressed, the end on one axial side (direction of arrow a) of the shaft 20 tends to tilt downward in the direction of gravity. In this case, due to the principle of leverage, the other end 22 on the other axial side (direction of arrow b) of the shaft 20 tends to tilt upward in the direction of gravity (direction of arrow g). Conversely, when a pedal (not shown) attached to the other end 22 on the other axial side (direction of arrow b) of the shaft 20 is pressed, the other end 22 on the other axial side (direction of arrow a) of the shaft 20 tends to tilt downward in the direction of gravity (direction of arrow h). In this case, due to the principle of leverage, the other end 21 on one axial side (direction of arrow a) of the shaft 20 tends to tilt upward in the direction of gravity (direction of arrow g). Thus, when the pedal is pressed, the shaft 20 presses the first bearing 60 radially (downward in the direction of gravity (arrow h direction) or upward in the direction of gravity (arrow g direction)), generating stress in the first case member 11 into which the first bearing 60 is inserted, corresponding to the force applied to the pedal.

Here, the first case member 11 is fixed to the second case member by the first connecting portion 13a and the second connecting portion 13b. Furthermore, since the first connecting portion 13a, the second connecting portion 13b, and the shaft 20 are arranged linearly in the direction of gravity, the stress applied to the first case member 11 by the shaft 20 is concentrated on the straight line connecting the first connecting portion 13a, the shaft 20, and the second connecting portion 13b. The first deformation portion 41 and the second deformation portion 42 are positioned on the straight line connecting the first connecting portion 13a, the shaft 20, and the second connecting portion 13b. Since the first strain sensor 31 and the second strain sensor 32 are attached to the first deformation portion 41 and the second deformation portion 42, respectively, the first strain sensor 31 and the second strain sensor 32 can detect the stress as strain.

The force applied to the pedals (pedaling force) is calculated based on the stress detected by the first strain sensor 31 and the second strain sensor 32. The output of the motor (not shown) of the electric assist bicycle 2 can be adjusted according to the calculated pedaling force. If the calculated pedaling force is smaller than a predetermined threshold, it is considered that little assistance is needed, and the motor output is reduced. Conversely, if the calculated pedaling force is larger than the predetermined threshold, it is considered that more assistance is needed, and the motor output is increased. Because the rotating device 1 in this embodiment has a simple structure in which the detection unit 50 is directly positioned on the case 10, the overall device can be made smaller.

Ideally, when calculating the pedaling force, only the stress generated in the first case member 11 when one end 21 of the shaft 20 (in the direction of arrow a) tilts upward in the direction of gravity (in the direction of arrow g) or downward in the direction of gravity (in the direction of arrow h) should be detected. However, if the detection unit 50 is positioned close to the shaft 20, even when one end 21 of the shaft 20 tilts in a direction other than the direction of gravity, strain may occur in the detection unit 50, and this may be detected (as noise) by the detection unit 50. This is because the area around the shaft 20 in the first case member 11 is far from the connecting part 13 fixed to the second case member 12, making it easily deformable and prone to strain due to stress.

In this embodiment of the rotating device 1, the distances Y1 and Y2 between the shaft 20 and the detection unit 50 are greater than the distances X1 and X2 between the connecting unit 13 and the detection unit 50. That is, the detection unit 50 is positioned closer to the connecting unit 13 than to the shaft 20. As a result, the rotating device 1 according to this embodiment suppresses noise generation and can accurately detect the stress generated in the first case member 11 when the end 21 on one axial side (direction of arrow a) of the shaft 20 tilts in the direction of gravity. Therefore, the rotating device 1 according to this embodiment can accurately calculate the pedaling force.

The rotating device and detection device of the present invention have been described above with reference to preferred embodiments. However, the rotating device and detection device of the present invention are not limited to the configurations of the above embodiments. For example, the rotating device 1 according to the above embodiment is used in an electric assist bicycle, but the rotating device and detection device of the present invention are not limited to those used in electric assist bicycles and can be applied to any device that needs to detect stress on a shaft that is rotatably supported with respect to a case.

In the rotating device 1 according to the above embodiment, the detection unit 50 is located on the outer surface 11a of the first case member 11. However, in the rotating device and detection device of the present invention, the detection unit may be located on the inner surface of the first case member. When the detection unit is located on the inner surface of the first case member, the strain sensor and wiring can be housed inside the case, resulting in a more durable configuration.

In the rotating device 1 according to the above embodiment, the detection unit 50 is composed of two detection units, including a first detection unit 51 and a second detection unit 52. However, in the rotating device and detection device of the present invention, there may be one detection unit or three or more detection units. When there is only one detection unit, for example, in the rotating device 1 according to the above embodiment, the second detection unit 52 may not exist, and only the first detection unit 51 may exist. Conversely, in the rotating device 1 according to the above embodiment, the first detection unit 51 may not exist, and only the second detection unit 52 may exist. Furthermore, when there are three or more detection units, for example, a total of four detection units may be arranged, two between the first connecting unit and the shaft, and two between the second connecting unit and the shaft. Additionally, an additional detection unit may be provided on the second case member of the case.

In the rotating device 1 according to the above embodiment, the connecting portion 13 and the shaft 20 are arranged in line with respect to gravity. However, in the rotating device and detection device of the present invention, the connecting portion and the shaft may be arranged in line with respect to gravity inclined. The degree of inclination may be, for example, 30° or less, 20° or less, 10° or less, or 5° or less.

In the rotating device 1 according to the above embodiment, the shaft 20, the first detection unit 51, and the second detection unit 52 are arranged on a straight line connecting the first connecting unit 13a and the second connecting unit 13b. However, in the rotating device and detection apparatus of the present invention, the connecting unit, shaft, and detection unit do not necessarily have to be arranged in a strictly straight line. For example, the detection unit may be positioned slightly offset from the straight line connecting the connecting unit and the shaft in the direction of travel or the direction of reversal.

Furthermore, those skilled in the art can modify the sensor device of the present invention as appropriate and change various combinations of its components in accordance with conventionally known knowledge. As long as such modifications still possess the configuration of the present invention, they are, of course, included within the scope of the present invention.

1…Rotating device (detection device), 10…Case, 11…First case member, 11a…Outer surface, 11b…Inner surface, 12…Second case member, 13…Connecting part, 13a…First connecting part, 13b…Second connecting part, 20…Shaft, 50…Detection part, 51…First detection part, 52…Second detection part.

Claims (5)

The case and,
A shaft rotatably supported in relation to the aforementioned case,
The case has a detection unit disposed on the outer or inner surface,
The aforementioned case is,
First case component,
The second case component,
It comprises a connecting portion that connects the first case member and the second case member,
The detection unit is positioned between the shaft and the connecting portion.
A rotating device in which, when viewed from the axial direction of the shaft, the distance between the shaft and the detection unit is greater than the distance between the connecting unit and the detection unit . The case and,
A shaft rotatably supported in relation to the aforementioned case,
The case has a detection unit disposed on the outer or inner surface,
The aforementioned case is,
First case component,
The second case component,
It comprises a connecting portion that connects the first case member and the second case member,
The detection unit is positioned between the shaft and the connecting portion.
The aforementioned connecting portion has a plurality of connecting portions, including a first connecting portion and a second connecting portion.
The aforementioned detection unit is a rotating device having a plurality of detection units, including a first detection unit and a second detection unit. The rotating device according to claim 2 , wherein the first detection unit and the second detection unit are arranged in the first case member. The rotating device according to claim 2 , wherein the shaft, the first detection unit, and the second detection unit are arranged on a straight line connecting the first connecting unit and the second connecting unit when viewed from the axial direction of the shaft. The rotating device according to any one of claims 1 to 4, wherein the connecting portion and the shaft are arranged in line with the direction of gravity.