JP7494534B2 - Parts support structure - Google Patents

Description

This invention relates to a support structure for parts.

Patent Document 1 discloses a hydraulic control device having the following support structure as an example of a support structure for parts. That is, in this hydraulic control device, a valve spool (valve) arranged inside a valve case (valve body) is supported by the valve body so that it can slide back and forth. More specifically, the valve case has multiple inflow and outflow paths for hydraulic oil, and the valve spool is supported by the valve case via a positive gap. With a valve having this configuration, the hydraulic pressure of the hydraulic oil can be controlled according to the control position of the valve spool.

In addition, Patent Documents 2 and 3 disclose specific examples of the composition of negative thermal expansion materials having negative thermal expansion. Patent Document 4 discloses a method for manufacturing a negative thermal expansion material. Patent Document 5 discloses a technology for suppressing interfacial peeling due to heat by inserting a composite material having a low thermal expansion coefficient and a thermal conductivity at least 1/3 that of copper between an electronic device and a heat sink made of copper or the like. Furthermore, Patent Document 6 discloses a negative thermal expansion material made of nanoparticles having magnetic and ferroelectric properties and having a negative thermal expansion coefficient at a temperature below the magnetic transition temperature of the nanoparticles.

JP 2004-359995 A International Publication No. 2014/030293 JP 2017-048071 A JP 2017-048072 A JP 2017-008337 A JP 2010-029990 A

Patent Document 1 describes that the valve spool and the valve case are made of the same material to prevent a difference in thermal expansion coefficient between them. By adopting such a configuration, leakage of hydraulic oil caused by temperature-dependent changes in the gap between the two can be suppressed, and deterioration of hydraulic controllability can be suppressed.

However, in a support structure in which one part is supported by another, it may be necessary to select different metal materials from various viewpoints other than thermal expansion coefficient, such as cost or wear resistance.

The present invention was made in consideration of the above-mentioned problems, and its purpose is to make it possible to select different metal materials while reducing the adverse effects caused by differences in linear expansion coefficients in a support structure in which one part is supported by another part.

The support structure for a member according to a first aspect of the present invention includes a first part and a second part, and one of the first and second parts supports the other of the first and second parts . The first part is formed of a first metallic material and includes one or more elements. The second part is formed of a second metallic material having a base material with a higher linear expansion coefficient than the first metallic material and includes one or more elements . The first part faces the second part in a specific direction while being sandwiched by the second part with a positive, zero or negative gap therebetween . The second metallic material includes a base material and a negative thermal expansion material mixed into the base material . The negative thermal expansion material is mixed into the base material in an amount that reduces the temperature change of the dimensional difference between the dimensions of the first part and the dimensions of the second part in a specific direction at a location where the first part and the second part face each other with a gap therebetween, compared to a case where the negative thermal expansion material is not mixed in. The first part is a valve. The second part is a valve body that slidably supports the valve. The valve body includes a first opposing surface facing the valve via a positive gap, and the negative thermal expansion material is mixed into the base material only in a first peripheral portion, which is a portion of the valve body located around the first opposing surface.

The valve may be disposed within a valve body. The valve and the valve body may be provided in a hydraulic control device that controls the controlled hydraulic pressure of the hydraulic fluid according to the axial position of the valve.

The first peripheral portion may include a peripheral wall of the valve body located on the outer periphery of the valve.

The case may be a transaxle case that houses a rotating body that is a component of a transaxle mounted on a vehicle.

The support structure for a member according to the second aspect of the present invention includes a first part and a second part, and one of the first and second parts supports the other of the first and second parts. The first part is formed of a first metallic material and includes one or more elements. The second part is formed of a second metallic material having a base material with a linear expansion coefficient higher than that of the first metallic material and includes one or more elements. The first part faces the second part in a specific direction while being sandwiched by the second part with a positive, zero or negative gap therebetween. The second metallic material includes a base material and a negative thermal expansion material mixed into the base material. The negative thermal expansion material is mixed into the base material in an amount that reduces the temperature change of the dimensional difference between the dimensions of the first part and the dimensions of the second part in a specific direction at a location where the first part and the second part face each other with a gap, compared to a case in which the negative thermal expansion material is not mixed in. The first part includes, as a plurality of elements, a pair of bearings and a rotating body having a pair of shaft parts rotatably supported by the pair of bearings. The second part is a case that supports the pair of bearings. Each of the pair of bearings is sandwiched between the rotor and the case in the axial direction of the rotor. The case includes a pair of second opposing surfaces facing the pair of bearings with a negative gap therebetween. The negative thermal expansion material is mixed into the base material only in a second peripheral portion, which is a portion of the case located around the pair of second opposing surfaces.

The second peripheral portion may include a portion connecting the pair of second opposing surfaces.

A support structure for a member according to a third aspect of the present invention includes a first part and a second part, and one of the first and second parts supports the other of the first and second parts. The first part is formed of a first metallic material and is composed of one or more elements. The second part is formed of a second metallic material having a base material with a higher linear expansion coefficient than the first metallic material and is composed of one or more elements. The first part faces the second part in a specific direction while being sandwiched by the second part with a positive, zero or negative gap therebetween. The second metallic material is composed of a base material and a negative thermal expansion material mixed into the base material. The negative thermal expansion material is mixed into the base material in an amount that reduces the temperature change of the dimensional difference between the dimensions of the first part and the dimensions of the second part in a specific direction at a location where the first part and the second part face each other with a gap therebetween, compared to a case in which the negative thermal expansion material is not mixed in. The first part is a stator core of a rotating electric machine. The second part is a case that has an inner circumferential surface facing the outer circumferential surface of the stator core and houses the stator core. The case includes a support portion that supports the stator core at a position spaced from the inner circumferential surface. The case includes a third opposing surface that faces the outer circumferential surface of the stator core via a gap. The negative thermal expansion material is mixed into the base material only in a third peripheral portion that is a portion of the case located around the third opposing surface.
A support structure for a member according to a fourth aspect of the present invention includes a first part and a second part, and one of the first and second parts supports the other of the first and second parts. The first part is formed of a first metallic material and includes one or more elements. The second part is formed of a second metallic material having a base material with a higher linear expansion coefficient than the first metallic material and includes one or more elements. The first part faces the second part in a specific direction while being sandwiched by the second part with a positive, zero or negative gap therebetween. The second metallic material includes a base material and a negative thermal expansion material mixed into the base material. The negative thermal expansion material is mixed into the base material in an amount that reduces the temperature change of the dimensional difference between the dimensions of the first part and the dimensions of the second part in a specific direction at a location where the first part and the second part face each other with a gap therebetween, compared to a case where the negative thermal expansion material is not mixed in. The first part is a stator core of a rotating electric machine. The second part is a case that houses the stator core. The stator core is shrink-fitted to a peripheral wall of a case located on the outer periphery of the stator core. The case includes a third opposing surface facing the outer periphery of the stator core via a gap. The negative thermal expansion material is mixed into the base material only in a third peripheral portion, which is a portion of the case located around the third opposing surface.

The third peripheral portion may include a peripheral wall of the case located on the outer periphery of the stator core.

The first component may be a pump rotor of an oil pump. The second component may be a pump body that houses the pump rotor and supports the pump rotor so that it can rotate freely.

The pump body may include a fourth opposing surface that faces the pump rotor with a positive gap therebetween. The negative thermal expansion material may be mixed into the base material only in a fourth peripheral portion, which is a portion of the pump body that is located around the fourth opposing surface.

The fourth peripheral portion may include a wall portion of the pump body located on the outer periphery of the pump rotor.

When the negative thermal expansion material is mixed uniformly throughout the pump body, the mixing ratio of the negative thermal expansion material to the base material may be within a range in which the linear expansion coefficient of the second metal material is smaller than that of the first metal material within a specific range that reduces the difference in the linear expansion coefficients of the first metal material and the second metal material compared to when the mixing ratio is zero.

When the negative thermal expansion material is mixed uniformly throughout the second component, the mixing ratio of the negative thermal expansion material to the base material may be within a specific range that reduces the difference in the linear expansion coefficient between the first metal material and the second metal material compared to when the mixing ratio is zero.

The mixing ratio may be a value that makes the linear expansion coefficient of the second metal material equal to the linear expansion coefficient of the first metal material within a specific range.

According to the present invention, as described above, the second metal material having a base material with a higher linear expansion coefficient than the first metal material is composed of the base material and a negative thermal expansion material mixed into the base material. The negative thermal expansion material is mixed into the base material in an amount that reduces the temperature change in the dimensional difference between the dimensions of the first part and the second part in a specific direction at a location where the first part and the second part face each other, compared to when the negative thermal expansion material is not mixed in. This makes it possible to select different metal materials while reducing the adverse effects caused by the difference in linear expansion coefficients in a support structure in which one part is supported by the other part.

1 is a cross-sectional view showing an example of a support structure according to a first embodiment, in which a valve is slidably supported by a valve body; 1 is a graph showing a relationship between the mixing ratio R of the negative thermal expansion material to the base material of the second metallic material and the linear expansion coefficient. 5 is a graph for explaining the effect of the component support structure according to the first embodiment. 13 is a graph for explaining the effect of selecting a range W3 in the modification of the first embodiment. FIG. 1 is a schematic diagram showing an example in which a negative thermal expansion material is partially mixed into a valve body. 11 is a cross-sectional view showing a specific example of a support structure according to a second embodiment in which a pair of bearings, which rotatably support a rotating body, are supported by a case. FIG. 13 is a graph for explaining the effect of the component support structure according to the second embodiment. FIG. 7 is a schematic diagram showing an example in which a negative thermal expansion material is partially mixed into the transaxle case shown in FIG. 6 . 13 is a cross-sectional view showing a specific example of a support structure according to a third embodiment in which a stator core of a rotating electric machine is supported by a case via a fastener. FIG. 10 is a view of a stator core in a transaxle case as viewed from the axial direction of the rotating shaft shown in FIG. 9 . FIG. 11 is a graph for explaining three setting examples 1 to 3 of the gap C3 and their effects. FIG. 10 is a schematic diagram showing an example in which a negative thermal expansion material is partially mixed into the transaxle case shown in FIG. 13 is a cross-sectional view showing a specific example of a support structure according to a fourth embodiment in which a stator core of a rotating electric machine is supported by a case by utilizing shrink fitting. FIG. 13 is a cross-sectional view showing a specific example of a support structure according to a fifth embodiment, in which a pump rotor of an oil pump is rotatably supported by a pump body that houses the pump rotor. FIG. FIG. 15 is a schematic diagram showing an example in which a negative thermal expansion material is partially mixed into the pump body shown in FIG. 14 .

In the embodiments and variations described below, elements common to each figure are given the same reference numerals, and duplicate explanations are omitted or simplified. Furthermore, when the number, quantity, amount, range, etc. of each element is mentioned in the embodiments described below, the invention is not limited to the mentioned number, unless otherwise specified or clearly specified in principle. Furthermore, the structures, etc. described in the embodiments described below are not necessarily essential to the invention, unless otherwise specified or clearly specified in principle.

1. First embodiment
A first embodiment of the present invention and its modified examples will be described with reference to Figures 1 to 5. In this embodiment, a "support structure for slidably supporting a valve by a valve body" will be described as one aspect of the "support structure for a component" according to the present invention.

1-1. Example of a support structure for a component Fig. 1 is a cross-sectional view showing an example of a support structure according to the first embodiment in which a valve is slidably supported by a valve body. Fig. 1 shows a hydraulic control device 10. The hydraulic control device 10 includes a valve body 12 and a valve (valve spool) 14 arranged inside the valve body 12. The hydraulic control device 10 is mounted on, for example, a vehicle, and more specifically, is typically mounted on a power train.

As shown in FIG. 1, the valve body 12 has a cylindrical internal space 12a extending in the axial direction (up and down on the page), and both axial ends of the internal space 12a are closed. A number of ports 16 (six, for example) are formed on the inner circumferential surface of the valve body 12 at predetermined intervals in the axial direction. Return springs 18 are disposed on both ends of the internal space 12a. The valve 14 is biased from both sides toward the center of the internal space 12a by these return springs 18.

The valve 14 is formed in a rod shape and has multiple (three, for example) lands (large diameter portions) 20 for opening and closing the four ports 16 on the central side of the internal space 12a. The hydraulic pressure of the hydraulic oil selectively supplied to the internal space 12a from two ports 16 located on both ends of the internal space 12a acts on the lands 20 of the valve 14. By adjusting the hydraulic pressure from these two ports 16, the axial position of the valve 14 changes, and the open/closed state of the four ports 16 on the central side changes. As a result, the control hydraulic pressure of a device (not shown) that receives a supply of hydraulic oil from the hydraulic control device 10 is changed.

The hydraulic control device 10 having the above-mentioned configuration employs a support structure that slidably supports the valve 14 by the valve body 12. Note that in this embodiment, the hydraulic control device 10 is described as an example of a device equipped with such a support structure, but this support structure may also be employed in valves and valve bodies that are equipped for purposes other than hydraulic control.

In the example of the hydraulic control device 10, the valve 14 corresponds to an example of the "first part" according to the present invention, and the valve body 12 corresponds to an example of the "second part" according to the present invention. More specifically, in this example, the outer peripheral surface 20a of the land 20 faces the inner peripheral surface 12b of the valve body 12 in a state where they are sandwiched with a "positive gap C1" in the radial direction of the valve 14 (corresponding to an example of the "specific direction" according to the present invention). In addition, in the example of the hydraulic control device 10, the valve 14 (first part) faces the valve body (second part) with the gap C1 in the entire circumferential direction of the valve 14.

In addition, in other examples of the support structure in which the valve is slidably supported by the valve body, the inner circumferential surface of the valve and the outer circumferential surface of the valve body may face each other, as opposed to the example shown in Figure 1.

1-2. Example of setting the mixing ratio R of negative thermal expansion material The valve 14, which corresponds to the "first part", is made of iron (more specifically, an iron-based material), which is an example of the "first metal material". The valve body 12, which corresponds to the "second part", is made of a "second metal material" whose base material is, for example, aluminum (or an aluminum alloy). The second metal material may be another metal material such as a magnesium alloy. The linear expansion coefficient of iron (first metal material) is about 11.7 [ppm/°C], and that of aluminum (base material of the second metal material) is 23 [ppm/°C]. That is, the valve body 12 is made of a second metal material having a base material with a linear expansion coefficient higher than that of the material of the valve 14 (first metal material).

In addition, the second metal material is composed of aluminum, which is a base material, and a negative thermal expansion material mixed into the base material. The negative thermal expansion material has negative thermal expansion. Negative thermal expansion means that the volume of a material decreases as the temperature increases, as opposed to a normal material whose volume increases as the temperature increases. Specific examples of negative thermal expansion materials applicable to the support structure according to the present invention are not particularly limited, but include, for example, Sm _0.78 Y _0.22 S (a compound obtained by replacing some of the samarium atoms of samarium monosulfide SmS with yttrium atoms), β-eucryptite (LiAlSiO ₄ ), zirconium tungstate (ZrW ₂ O ₈ ), bismuth-nickel oxide (Bi _0.95 La _0.05 NiO ₃ ), or lead-vanadium oxide (Pb _0.76 La _0.04 Bi _0.20 VO ₃ ). The linear expansion coefficients [ppm/° C.] of the negative thermal expansion materials exemplified here are as follows:
Sm _0.78 Y _0.22 S: -65
β-eucryptite (LiAlSiO ₄ ): −7.6
Zirconium tungstate (ZrW ₂ O ₈ ): -9
Bismuth-nickel oxide (Bi _0.95 La _0.05 NiO ₃ ): -82
Lead-vanadium oxide (Pb _0.76 La _0.04 Bi _0.20 VO ₃ ): -590

2(A) to 2(C) are graphs each showing a schematic relationship between the mixing ratio R of the negative thermal expansion material in the base material of the second metal material and the linear expansion coefficient. The relationship between the linear expansion coefficient of the second metal material mixed with the negative thermal expansion material as described above and the mixing ratio R [vol %] can be roughly represented by the characteristics shown in any of Figs. 2(A) to 2(C) (a straight line, a downward convex curve, or an upward convex curve). The following explanation will be given using Fig. 2(A) as an example, but the same applies to Fig. 2(B) or Fig. 2(C). The mixing ratio R may be specified in wt %. Also, the position of the linear expansion coefficient of zero in Figs. 2(A) to 2(C) is an example, and although it will be lower than the value α1, it will differ depending on the specific example of the negative thermal expansion material.

The linear expansion coefficients α1, α2, and α3 in FIG. 2 correspond to the linear expansion coefficients of the first metallic material, the base material of the second metallic material, and the negative thermal expansion material, respectively. That is, when the mixing ratio R is 0%, the linear expansion coefficient of the second metallic material is equal to the linear expansion coefficient α2 of the base material. Also, when the mixing ratio R is 100%, the linear expansion coefficient of the second metallic material is equal to the linear expansion coefficient α3 of the negative thermal expansion material. And as the mixing ratio R increases from 0%, the linear expansion coefficient of the second metallic material decreases.

The mixing ratio R1 in FIG. 2 corresponds to the value of the mixing ratio R when the linear expansion coefficient of the second metallic material is equal to the linear expansion coefficient α1 of the first metallic material. In addition, the linear expansion coefficient α4 corresponds to the value of the linear expansion coefficient when the difference (absolute value) of the linear expansion coefficient α1 between the second metallic material and the first metallic material is equal to the difference Δα between the base material of the second metallic material (mixing ratio R is zero) and the first metallic material when the linear expansion coefficient of the second metallic material is lower than the linear expansion coefficient α1 of the first metallic material due to the high mixing ratio R. And the mixing ratio R2 corresponds to the value of the mixing ratio R when the second metallic material has a linear expansion coefficient α4 on the side where the mixing ratio R is higher than the mixing ratio R1.

In addition, the specific range W1 of the mixing ratio R shown in FIG. 2 is a range of the mixing ratio R where the mixing ratio R is higher than 0% and lower than R2. When the mixing ratio R is within this specific range W1, the "difference in the linear expansion coefficient between the first metal material and the second metal material" is smaller than when the mixing ratio R is zero.

In this embodiment, the material of the valve body 12 (second metal material) corresponding to the "second part" is determined to have a mixing ratio R1 within the above-mentioned specific range W1. More specifically, in this embodiment, as an example, the negative thermal expansion material is mixed uniformly into the base material of the entire valve body 12 at a mixing ratio R1. The valve body 12 mixed with the negative thermal expansion material in this manner can be manufactured, for example, by casting. More specifically, for example, before the molten aluminum base material is poured into a mold for molding the valve body 12, a necessary amount of negative thermal expansion material is added to the molten aluminum to mix the negative thermal expansion material into the entire volume of the valve body 12 at a mixing ratio R1.

When the mixing ratio R1 is selected when the negative thermal expansion material is mixed uniformly into the entire valve body 12, the valve body 12 has a linear expansion coefficient equivalent to the linear expansion coefficient α1 of the first metal material (iron) of the valve 14. As a result, when the temperature of the hydraulic control device 10 changes, the valve body 12 expands or contracts with the same thermal expansion characteristics as the valve 14. This means that the temperature change of the dimensional difference between the dimension L11 of the valve 14 and the dimension L21 of the valve body 12 in the radial direction of the valve 14 at the location where the valve 14 and the valve body 12 face each other through the positive gap C1 (see FIG. 1) (in other words, the temperature change of the gap C1) is smaller than when the negative thermal expansion material is not mixed (when the mixing ratio R is zero).

Therefore, in other words, in this embodiment, the negative thermal expansion material is mixed into the base material in an amount that reduces the temperature change in the dimensional difference between dimensions L11 and L21 in the radial direction (specific direction; see FIG. 5(B) below) of the valve 14 at the location where the valve 14 (first part) and the valve body 12 (second part) face each other with the gap C1 in between, compared to when the negative thermal expansion material is not mixed in.

1-3. Effects As described above, in the valve body 12 provided in the hydraulic control device 10 of this embodiment, the negative thermal expansion material is uniformly mixed into the entire part (aluminum) at a mixing ratio R1 included in the specific range W1. Figure 3 is a graph for explaining the effects of the support structure for a part according to the first embodiment. The dashed line in Figure 3 corresponds to a comparative example in which the mixing ratio R is zero, and the solid line corresponds to the hydraulic control device 10 of this embodiment.

In the comparative example shown in FIG. 3, the valve body is made of the second metal material consisting only of the base material (aluminum). Therefore, when the temperature of the hydraulic control device 10 rises, this valve body expands more than the valve 14, which is made of the first metal material (iron). Therefore, the gap C1 between the valve body and the valve 14 increases at a large rate with increasing temperature, as shown by the dashed line.

In contrast, according to this embodiment, the valve body 12 has the same thermal expansion characteristics as the valve 14, so that the gap C1 increases with increasing temperature at a gentler rate than in the comparative example, as shown by the solid line. That is, the change in the gap C1 accompanying temperature changes (in other words, the temperature change in the dimensional difference between the dimensions L11 and L21 shown in FIG. 1) can be suppressed compared to the comparative example. As a result, leakage of hydraulic oil through the gap C1 at high temperatures can be suppressed compared to the comparative example, so the accuracy of hydraulic control by the hydraulic control device 10 can be improved. In addition, wear and galling of the valve 14 can be easily suppressed, eliminating the need for measures such as applying a coating treatment to the surface of the valve 14, and reducing the manufacturing cost of the valve 14.

1-4. Modifications (other settings of the mixing ratio R)
In the above-described first embodiment, the negative thermal expansion material is mixed into the base material at a mixing ratio R1. However, the mixing ratio R is not necessarily limited to the mixing ratio R1 as long as it is within the specific range W1 shown in FIG. 2. Specifically, any value within the range W2 (0<R<R1) lower than the mixing ratio R1 may be selected as the mixing ratio R. In this range W2, the difference in the linear expansion coefficient between the second metal material and the first metal material is larger than in the example of the mixing ratio R1, but the difference can be made smaller than in the example (comparative example) where the mixing ratio R is zero. Therefore, even when the range W2 is selected, the effect of suppressing the change in the gap C1 due to the temperature change can be obtained compared to the comparative example. And, as the mixing ratio R approaches the mixing ratio R1 within the range W2, the difference in the linear expansion coefficient between the second metal material and the first metal material can be made smaller, so that the effect of suppressing the change in the gap C1 is enhanced.

Also, any value within range W3 (R1<R<R2) higher than mixing ratio R1 may be selected as mixing ratio R. Even in this range W3, the difference in linear expansion coefficient between the second metal material and the first metal material is larger compared to the example of mixing ratio R1, but the difference can be made smaller compared to the example (comparative example) where mixing ratio R is zero. Therefore, even when range W3 is selected, the effect of suppressing changes in gap C1 due to temperature changes can be obtained compared to the comparative example. And, as mixing ratio R approaches mixing ratio R1 within range W3, the difference in linear expansion coefficient between the second metal material and the first metal material can be made smaller, so the effect of suppressing changes in gap C1 is enhanced.

When a mixing ratio R within range W3 is selected in the example of the hydraulic control device 10, the effect described below with reference to FIG. 4 can be obtained. FIGS. 4(A) and 4(B) are graphs for explaining the effect of selecting range W3 in a modified example of embodiment 1. Note that the vertical positions on the page of each waveform of the temperature characteristic of gap C1 in FIG. 4(B) are merely examples, and change depending on the initial setting of gap C1. The same is true for FIG. 3 described above.

There is a relationship between the viscosity of the hydraulic oil of the hydraulic control device 10 and the temperature as shown in FIG. 4(A). That is, the viscosity of the hydraulic oil is high at low temperatures and decreases as the temperature increases. For this reason, if it is assumed that the gap C1 is constant regardless of temperature, the higher the temperature and the lower the viscosity, the easier it is for the hydraulic oil to leak through the gap C1. On the other hand, when the mixing ratio R within the range W3 is selected, the linear expansion coefficient of the second metal material is lower than the linear expansion coefficient α1 of the first metal material. As a result, when the temperature of the hydraulic control device 10 rises, the valve 14 (first part) located on the inner side expands more than the valve body 12 (second part) on the outer side, in contrast to the comparative example. For this reason, as shown in FIG. 4(B), a characteristic is obtained in which the gap C1 becomes smaller as the temperature increases. In other words, the gap C1 can be changed so that the hydraulic oil is less likely to leak out as the temperature increases. Therefore, if the gap C1 becomes smaller at high temperatures due to such a characteristic, the hydraulic oil is less likely to leak out through the gap C1 even if the viscosity is lowered. As described above, when range W3 is selected, hydraulic oil is less likely to leak through gap C1 at high temperatures compared to when mixing ratio R1 or range W2 is selected, and the accuracy of hydraulic control can be more effectively improved.

(Example of partial mixing in the valve body)
Figures 5(A) and 5(B) are schematic diagrams showing an example in which a negative thermal expansion material is partially mixed into the valve body 12. Figure 5(B) is a cross-sectional view taken along the line X1-X1 of Figure 5(A). Note that in Figure 5(A), the illustration of the configuration around the valve body 12 is simplified in a schematic manner. This also applies to Figures 8, 12, and 15 described below.

The inner peripheral surface 12b of the valve body 12 facing the valve 14 through the positive gap C1 is referred to as the "first opposing surface." The portion of the valve body 12 located around this first opposing surface is referred to as the "first peripheral portion." In the valve body 12 described in the first embodiment, the negative thermal expansion material is mixed not only in the first peripheral portion but also in the entire valve body 12 so that it is uniformly mixed into the base material at a mixing ratio R1. Unlike this example, the negative thermal expansion material may be mixed only in the first peripheral portion, as in the example shown in FIG. 5. The first peripheral portion is the peripheral wall 12c of the valve body 12 located on the outer periphery of the valve 14.

More specifically, the negative thermal expansion material may be mixed uniformly into the base material in the first peripheral portion at any mixing ratio R within a specific range W1, for example. This makes it possible to bring the linear expansion coefficient of the valve body 12 closer to that of the valve 14, targeting the portion that has a large effect on the temperature change of the dimensional difference between dimensions L11 and L21 shown in FIG. 1 (temperature change of gap C1).

In addition, the negative thermal expansion material does not necessarily have to be mixed uniformly into the base material in the first peripheral portion at any mixing ratio R within the specific range W1, so long as it is mixed into the base material in an amount that reduces the temperature change of the above-mentioned dimensional difference compared to when the negative thermal expansion material is not mixed in. In other words, the negative thermal expansion material may be mixed into the base material in the first peripheral portion at different mixing ratios R (including zero) depending on the location within the first peripheral portion. Specifically, for example, the negative thermal expansion material may be mixed into a certain portion of the first peripheral portion at a higher mixing ratio R regardless of whether it is inside or outside the specific range W1, and may not be mixed into another portion of the first peripheral portion.

In addition, the "first peripheral portion" may be determined as appropriate according to the support structure of the target component as a portion located around the first opposing surface, instead of the example setting shown in FIG. 5, and necessary to obtain the effect of suppressing the temperature change in the gap C1 (the temperature change due to the above-mentioned dimensional difference) caused by the inclusion of the negative thermal expansion material. This also applies to FIGS. 8, 12, and 15 described below.

The valve body 12 (second part) partially mixed with the negative thermal expansion material as described above can be manufactured, for example, using a three-dimensional molding machine. This also applies to the examples shown in Figures 8, 12, and 15 described below.

In addition, the negative thermal expansion material may be mixed into some or all of the portions of the valve body 12 other than the first peripheral portion such that the mixing ratio R decreases continuously (or stepwise) toward zero as the distance from the first peripheral portion increases. The valve body 12 according to such an example may also be manufactured using, for example, a three-dimensional molding machine.

2. Second embodiment
Next, a second embodiment of the present invention and its modified example will be described with reference to Figures 6 to 8. In this embodiment, a "support structure in which a pair of bearings, which rotatably support a rotating body, are supported by a case" will be described as another aspect of the "support structure for a component" according to the present invention.

2-1. Example of a support structure for a part Fig. 6 is a cross-sectional view showing a specific example of a support structure according to the second embodiment in which a pair of bearings that rotatably support a rotor are supported by a case. Fig. 6 shows an example of an internal structure of a transaxle case 30 included in a power train mounted on a vehicle. A differential device (differential gear) 32 is housed in the transaxle case 30. The differential device 32 includes a differential gear case 34. The differential gear case 34 is a rotor, and is generally made of an iron-based material (e.g., cast iron), and rotates integrally with a ring gear 36. The differential device 32 is connected to a drive shaft 38 that transmits driving force to the wheels.

The differential gear case 34 has a pair of shaft portions (cylindrical shaft portions) 34a formed cylindrically so as to cover the outer periphery of each drive shaft 38. The pair of shaft portions 34a are rotatably supported by a pair of bearings 40. The bearings 40 are, for example, tapered roller bearings, but may be other rolling bearings such as angular ball bearings. The pair of bearings 40 are supported by the transaxle case 30. More specifically, the transaxle case 30 has bearing support holes 30a that support each bearing 40. The bearings 40 are fixed by press-fitting into the bearing support holes 30a.

Each of the pair of bearings 40 is sandwiched between the differential gear case 34 and the transaxle case 30 (via shims 42, described below) in the axial direction D of the rotating shaft of the differential gear case 34. More specifically, the transaxle case 30 is divided into two pieces in the left-right direction of the paper in FIG. 6, and is assembled so that the pair of bearings 40 and the differential gear case 34 are sandwiched (via shims 42) from both left-right sides.

In the example shown in FIG. 6, a ring-shaped shim 42 is interposed between one of the pair of bearings 40 (the right side of the paper in FIG. 6) and the transaxle case 30 facing it. A number of shims 42 of different thicknesses are prepared, and a shim 42 of an appropriate thickness is selected to absorb the dimensional variations in the differential gear case 34, the bearings 40, and the transaxle case 30 in the axial direction D when assembling the transaxle case 30. By interposing the shim 42 selected in this way between one of the bearings 40 and the transaxle case 30 (two pieces of the transaxle case 30), a desired preload (axial load) can be applied to each of the pair of bearings 40 in the axial direction D. The use of preload can increase the support rigidity of the differential gear case 34.

In the example shown in FIG. 6, a pair of bearings 40, a differential gear case 34, and a shim 42 made of iron (more specifically, an iron-based material), which is an example of a first metallic material, correspond to an example of a "first part consisting of multiple elements" according to the present invention. The first metallic materials constituting the pair of bearings 40, the differential gear case 34, and the shim 42 may be the same or different. In addition, by using the above-mentioned pressurization, the shim 42 (first part) faces the transaxle case 30 (second part) with a "negative gap C2" around the bearing 40 on the right side of the paper, and the bearing 40 (first part) faces the transaxle case 30 (second part) with a "negative gap C2" around the bearing 40 on the left side of the paper.

The presence of the shim 42 is not necessarily required to apply pressure to the pair of bearings 40 by sandwiching the pair of bearings 40 between the differential gear case 34 and the transaxle case 30. If the shim 42 is not used, the pair of bearings 40 and the differential gear case 34 correspond to the "first part."

On the other hand, the transaxle case 30 formed from the second metal material corresponds to an example of the "second part" and "case" according to the present invention. The base material of the second metal material is, for example, aluminum (or an aluminum alloy). The second metal part may also be, for example, a magnesium alloy.

In the example shown in FIG. 6, the transaxle case 30, which is one element, corresponds to the "second part", but the "second part" may also be composed of multiple elements, just like the "first part". In addition, the rotating body (constituent part of the transaxle) housed in the "transaxle case" as the "second part" is not limited to the differential gear case 34 as long as it is rotatably supported by a pair of bearings, and may be, for example, the rotor of an electric motor. Furthermore, the "case" as the "second part" is not limited to the transaxle case 30 as long as it supports a pair of bearings, and may be, for example, a case supporting a pair of bearings that supports the rotating shaft of an electric motor (not a component part of the transaxle).

2-2. Example of Setting the Mixing Ratio of Negative Thermal Expansion Material In this embodiment, the base material (aluminum) of the transaxle case 30 is mixed with a negative thermal expansion material. The mixing ratio R can be selected from within a specific range W, as in the first embodiment and its modified examples, and an example of this is the mixing ratio R1. In this embodiment, the negative thermal expansion material is mixed into the base material at a uniform mixing ratio R1 for the entire transaxle case 30, as an example. That is, in this embodiment, the negative thermal expansion material is mixed into the base material in an amount that reduces the temperature change of the dimensional difference between the dimension L12 of the first part and the dimension L22 of the second part in the axial direction D (specific direction) at the location where the shim 42 or the bearing 40 (first part) and the transaxle case 30 (second part) face each other via the gap C2, compared to when the negative thermal expansion material is not mixed.

2-3. Effects As described above, the transaxle case 30 supporting the pair of bearings 40 is mixed with a negative thermal expansion material in the base material (aluminum) at a mixing ratio R1. This allows the transaxle case 30 to have a linear expansion coefficient equivalent to that of the bearing 40 made of iron. As a result, for the same reason as in the first embodiment, the change in the gap C2 due to temperature change (the above-mentioned temperature change in the dimensional difference) can be effectively suppressed compared to the comparative example in which the mixing ratio R is zero. Furthermore, even if a value other than the mixing ratio R1 is selected within the specific range W1, the effect of suppressing the change in the gap C2 due to temperature change compared to the comparative example can be obtained.

In addition, the present embodiment, which utilizes a pair of pressurized bearings 40, provides the following effects. FIG. 7 is a graph for explaining the effects of the component support structure of embodiment 2. In a comparative example in which the mixing ratio R is zero, if the pressurization of the pair of bearings 40 is ensured at an appropriate value P1 when the transaxle case 30 is at a high temperature, the following problem occurs. That is, as shown by the dashed line in FIG. 7, the lower the temperature, the higher the pressurization becomes excessively high due to the difference in the linear expansion coefficient between iron (bearings) and aluminum (differential gear case). Conversely, if an appropriate pressurization is applied at low temperatures in this comparative example, the pressurization becomes insufficient at high temperatures.

In contrast, according to the present embodiment, which uses the second metal material mixed with a negative thermal expansion material at a mixing ratio R1, the change in the gap C2 due to temperature change can be effectively suppressed as described above. This leads to the ability to reduce the change in preload relative to temperature change, as represented by the solid line in FIG. 7. More specifically, since the preload setting can be lowered at low temperatures compared to the comparative example, it is possible to maintain good bearing life, bearing loss, and shaft support rigidity.

2-4. Modifications (other settings of the mixing ratio R)
Also with respect to the support structure described in the second embodiment, any value within the range W2 or W3 (see FIG. 2) may be selected as the mixing ratio R instead of the mixing ratio R1.

(Example of partial mixing in transaxle case)
Fig. 8 is a schematic diagram showing an example in which a negative thermal expansion material is partially mixed into the transaxle case 30 shown in Fig. 6. As shown in Fig. 8, the wall surfaces 30b of the transaxle case 30 facing a pair of bearings (in Fig. 8, which uses a shim 42, the right side of the paper is the shim 42 and the left side of the paper is the bearing 40) via a negative gap C2 are referred to as a "pair of second opposing surfaces". The portions of the transaxle case 30 located around the second opposing surfaces are referred to as a "second surrounding portion".

In the example shown in FIG. 8, the negative thermal expansion material is mixed into the base material only in the second peripheral portion. The second peripheral portion is the portion 30c that connects the pair of second opposing surfaces (wall surfaces 30b). More specifically, the negative thermal expansion material may be mixed uniformly into the base material in the second peripheral portion at any mixing ratio R within a specific range W1, for example. This makes it possible to bring the linear expansion coefficient of the transaxle case 30 closer to those of the iron-based bearing 40, differential gear case 34, and shim 42, targeting the portions that have a large effect on the temperature change of the dimensional difference between dimensions L12 and L22 shown in FIG. 6 (temperature change of gap C2).

Also, similar to the example of the hydraulic control device 10 described above, the negative thermal expansion material does not necessarily have to be mixed uniformly into the base material in the second peripheral portion at any mixing ratio R within the specific range W1, so long as it is mixed into the base material in an amount that reduces the temperature change of the above-mentioned dimensional difference compared to when the negative thermal expansion material is not mixed in. In other words, the negative thermal expansion material may be mixed into the base material in the second peripheral portion at different mixing ratios R (including zero) depending on the location within the second peripheral portion. Specifically, for example, the negative thermal expansion material may be mixed into a certain portion of the second peripheral portion at a higher mixing ratio R regardless of whether it is inside or outside the specific range W1, and may not be mixed into another portion of the second peripheral portion.

Furthermore, negative thermal expansion material may be mixed into some or all of the portions of the transaxle case 30 other than the second peripheral portion such that the mixing ratio R decreases continuously (or stepwise) toward zero, for example, as it moves away from the second peripheral portion.

3. Third embodiment
Next, a third embodiment of the present invention and a modification thereof will be described with reference to FIGS.

3-1. Example of a Support Structure for a Component In this embodiment, a "support structure in which a stator core of a rotating electrical machine is supported by a case via a fastener" will be described as another aspect of the "support structure for a component" according to the present invention.

Figure 9 is a cross-sectional view showing a specific example of a support structure according to embodiment 3 in which the stator core of a rotating electric machine is supported by a case via a fastener. Figure 9 shows an example of the internal structure of a transaxle case 50 included in a power train mounted on a vehicle. The transaxle case 50 houses a rotating electric machine 52. A rotating electric machine is one that has at least one of the functions of an electric motor and a generator. The rotating electric machine 52 includes a rotor 56 that rotates integrally with the rotating shaft 54, a stator core 58 located on the outer periphery of the rotor 56, and a stator coil 60 wound around the stator core 58.

The stator core 58 corresponds to an example of the "first part" according to the present invention, and is formed from a first metallic material. The first metallic material is a magnetic material, an example of which is iron (more specifically, an iron-based magnetic material). More specifically, the stator core 58 is formed, for example, by laminating electromagnetic steel sheets whose base material is iron.

10 is a view of the stator core 58 in the transaxle case 50 viewed from the axial direction of the rotating shaft 54 shown in FIG. 9. As shown in FIG. 10, the transaxle case 50 is provided with a plurality of (three, for example) support portions (e.g., boss portions) 50a for supporting the stator core 58. Through holes 58b corresponding to these support portions 50a are formed in the outer peripheral surface 58a of the stator core 58. The stator core 58 is supported by the support portions 50a of the transaxle case 50 via fasteners such as bolts (not shown) inserted into the through holes 58b. The transaxle case 50 also has an inner peripheral surface 50b facing the outer peripheral surface 58a of the stator core 58. In FIG. 10, the peripheral wall 50c including the inner peripheral surface 50b of the transaxle case 50 is represented by a two-dot chain line. Each support portion 50a is provided at a position away from the inner peripheral surface 50b.

The transaxle case 50 having the above-mentioned configuration corresponds to an example of the "second part" according to the present invention. The transaxle case 50 is formed from a second metal material. The inner peripheral surface 50b of the transaxle case 50 faces the outer peripheral surface 58a of the stator core 58 through a "gap C3". A specific example of setting the gap C3 will be described later with reference to Figures 11(A) to 11(C). The base material of the second metal material is, for example, aluminum (or an aluminum alloy). The second metal material may also be, for example, a magnesium alloy. The case formed from the second metal material and housing the stator core may be a case of a rotating electric machine used for other purposes other than a transaxle case.

3-2. Example of Setting the Mixing Ratio of Negative Thermal Expansion Material In this embodiment, the base material (aluminum) of the transaxle case 50 is mixed with a negative thermal expansion material. The mixing ratio R can be selected from within a specific range W, as in the first embodiment and its modified examples, and an example of this is the mixing ratio R1. In this embodiment, the negative thermal expansion material is mixed into the base material at a uniform mixing ratio R1 for the entire transaxle case 50, as an example. That is, in this embodiment, the negative thermal expansion material is mixed into the base material in an amount that reduces the temperature change of the dimensional difference between the dimension L13 of the first part and the dimension L23 of the second part in the radial direction (specific direction) of the stator core 58 at the location where the stator core 58 (first part) and the transaxle case 50 (second part) face each other with the gap C3 in between, compared to when the negative thermal expansion material is not mixed.

3-3. Effects As described above, the transaxle case 50 is mixed with a negative thermal expansion material in the base material (aluminum) at a mixing ratio R1. This allows the transaxle case 50 to have a linear expansion coefficient equivalent to that of the stator core 58 made of iron (electromagnetic steel sheet). As a result, for the same reason as in the first embodiment, the change in the gap C3 due to temperature change (the above-mentioned temperature change in the dimensional difference) can be effectively suppressed compared to the comparative example in which the mixing ratio R is zero. Furthermore, even if a value other than the mixing ratio R1 is selected within the specific range W1, the effect of suppressing the change in the gap C3 due to temperature change compared to the comparative example can be obtained.

As described above, the effect of effectively suppressing changes in gap C3 due to temperature changes leads to the following effects in relation to the setting of gap C3. Figures 11(A) to 11(C) are graphs that explain three setting examples 1 to 3 of gap C3 and their effects.

If the gap C3 can be maintained at substantially zero with respect to temperature changes, the outer peripheral surface 58a of the stator core 58 can be kept in stable and appropriate contact with the inner peripheral surface 50b of the transaxle case 50. This is effective in improving the heat dissipation performance of the stator core 58. On the other hand, if the gap C3 is set large on the negative side, the force (pressure) with which the transaxle case 50 tightens the stator core 58 becomes excessive, and there is a concern that the efficiency of the rotating electric machine 52 will decrease due to distortion of the stator core 58.

In the setting of Comparative Example 1 (mixing ratio R = 0) shown in Figure 11 (A), a negative gap C3 is set so that it is not excessively large in the low temperature range. With this setting, when the temperature rises, the gap C3 becomes positive and the stator core moves away from the transaxle case. As a result, the heat dissipation performance of the stator core decreases.

In contrast, according to the configuration of this embodiment, in which the temperature change of the gap C3 can be suppressed by mixing in a negative thermal expansion material, setting example 1 can be adopted. According to setting example 1, as shown in FIG. 11(A), the setting of the gap C3 at low temperatures is the same as that of comparative example 1, but even if a temperature change occurs, the gap C3 can be maintained substantially near zero (more specifically, near zero on the negative side where contact between the stator core 58 and the transaxle case 50 is ensured). As a result, the heat dissipation effect of the stator core 58 using the transaxle case 50 can be obtained well over a wide temperature range.

Next, in Comparative Example 2 (mixing ratio R = 0) shown in FIG. 11 (B), a design concept is adopted in which a heat dissipation effect is obtained even at high temperatures by setting a negative gap C3 over a wide temperature range. However, with this setting, the negative gap C3 becomes excessively large at low temperatures. As a result, there is concern that the efficiency of the rotating electric machine may decrease due to distortion of the stator core. In contrast, with Setting Example 2 of this embodiment, the negative gap C3 is set to the same value as in Comparative Example 2 at high temperatures, while the efficiency decrease of the rotating electric machine caused by the negative gap C3 becoming excessive at low temperatures can be suppressed. In other words, the heat dissipation effect can be ensured over a wide temperature range, while the efficiency decrease of the rotating electric machine due to the decrease in pressure at low temperatures can be suppressed.

Next, in Comparative Example 3 (mixing ratio R = 0) shown in FIG. 11 (C), the highest priority is given to avoiding a decrease in the efficiency of the rotating electric machine, and a design concept is adopted in which the stator core does not come into contact with the transaxle case in each temperature range. However, this setting does not allow for improvement in heat dissipation performance using the transaxle case. In contrast, according to Setting Example 3 of this embodiment, a setting is obtained in which the gap C3 at low temperatures is equivalent to zero on the positive side, while the expansion of the gap C3 with increasing temperature is suppressed. This prevents a decrease in the efficiency of the rotating electric machine, while preventing the air layer that functions as a heat insulating layer between the stator core 58 and the transaxle case 50 from becoming larger with increasing temperature. Therefore, compared to Comparative Example 3, a setting is obtained that can increase the heat dissipation effect to the transaxle case 50 and avoid a decrease in the efficiency of the rotating electric machine.

3-4. Modifications (other settings of the mixing ratio R)
Also with respect to the support structure described in the third embodiment, any value within the range W2 or W3 (see FIG. 2) may be selected as the mixing ratio R instead of the mixing ratio R1.

(Example of partial mixing in transaxle case)
12(A) and 12(B) are schematic diagrams showing an example in which a negative thermal expansion material is partially mixed into the transaxle case 50 shown in FIG. 9. FIG. 12(B) is a cross-sectional view taken along the line X2-X2 of FIG. 12(A). As shown in FIGS. 12(A) and 12(B), the inner peripheral surface 50b of the transaxle case 50 facing the outer peripheral surface 58a of the stator core 58 via a gap C3 is referred to as the "third opposing surface." The portion of the transaxle case 50 located around this third opposing surface is referred to as the "third surrounding portion."

In the example shown in FIG. 12, the negative thermal expansion material is mixed into the base material only in the third peripheral portion. The third peripheral portion is the peripheral wall 50c of the transaxle case 50 located on the outer periphery side of the stator core 58. More specifically, the negative thermal expansion material may be mixed uniformly into the base material in the third peripheral portion at any mixing ratio R within a specific range W1, for example. This makes it possible to bring the linear expansion coefficient of the transaxle case 50 closer to that of the stator core 58, targeting the portion that has a large effect on the temperature change of the dimensional difference between dimensions L13 and L23 shown in FIG. 9 (temperature change of gap C3).

More preferably, the third peripheral portion into which the negative thermal expansion material is mixed may include a peripheral wall 50c located on the outer periphery of the stator core 58, as well as a side wall 50d shown in FIG. 12(A). The side wall 50d is a wall portion of the transaxle case 50 located on both ends of the rotating shaft 54. When the side wall 50d is also included in the third peripheral portion, the surface of the side wall 50d facing the stator core 58 also corresponds to the "third opposing surface."

Also, similar to the examples of the hydraulic control device 10 and the transaxle case 30 described above, the negative thermal expansion material does not necessarily have to be mixed uniformly into the base material in the third peripheral portion at any mixing ratio R within the specific range W1, so long as it is mixed into the base material in an amount that reduces the temperature change of the above-mentioned dimensional difference compared to when the negative thermal expansion material is not mixed in. In other words, the negative thermal expansion material may be mixed into the base material in different mixing ratios R (including zero) depending on the location within the third peripheral portion. Specifically, for example, the negative thermal expansion material may be mixed into a certain portion of the third peripheral portion at a higher mixing ratio R regardless of whether it is inside or outside the specific range W1, and may not be mixed into another portion of the third peripheral portion.

Furthermore, negative thermal expansion material may be mixed into some or all of the portions of the transaxle case 50 other than the third peripheral portion such that the mixing ratio R decreases continuously (or stepwise) toward zero, for example, as it moves away from the third peripheral portion.

4. Fourth embodiment
Next, a fourth embodiment of the present invention and its modification will be described with reference to FIG.

4-1. Example of a Support Structure for a Component In this embodiment, a "support structure in which a stator core of a rotating electrical machine is supported by a case using shrink fitting" will be described as another aspect of the "support structure for a component" according to the present invention.

Figure 13 is a cross-sectional view showing a specific example of a support structure according to embodiment 4, in which the stator core of a rotating electric machine is supported by a case using shrink fitting. The configuration shown in Figure 13 is the same as the configuration shown in Figure 9, except for the points described below.

Specifically, in the example shown in FIG. 13, the rotating electric machine 72 housed in the transaxle case 70 includes a stator core 74 as well as a rotor 56 and a stator coil 60. In addition, in this embodiment, the stator core 74 (first part) is shrink-fitted to the peripheral wall 70c of the transaxle case 70 (second part) located on the outer periphery side of the stator core 74. Therefore, the gap C4 between the outer periphery surface 74a and the inner periphery surface 70b of the stator core 74 is a negative gap. Thus, in this embodiment, the stator core 74 is supported by the transaxle case 70 via the negative gap C4.

4-2. Example of Setting the Mixing Ratio of Negative Thermal Expansion Material In this embodiment, the base material (aluminum) of the transaxle case 70 is mixed with a negative thermal expansion material. The mixing ratio R can be selected from within the specific range W as in the first embodiment and its modified examples, and an example of this is the mixing ratio R1. In this embodiment, the negative thermal expansion material is mixed into the base material at a uniform mixing ratio R1 for the entire transaxle case 70 as an example. That is, in this embodiment, the negative thermal expansion material is mixed into the base material in an amount that reduces the temperature change of the dimensional difference between the dimension of the first part (similar to the dimension L13 in FIG. 10) and the dimension of the second part (similar to the dimension L23 in FIG. 10) in the radial direction (specific direction) of the stator core 74 at the location where the stator core 74 (first part) and the transaxle case 70 (second part) face each other with the gap C4 in between, compared to when the negative thermal expansion material is not mixed.

4-3. Effects As described above, the transaxle case 70 is mixed with a negative thermal expansion material in the base material (aluminum) at a mixing ratio R1. This allows the transaxle case 70 to have a linear expansion coefficient equivalent to that of the stator core 74 made of iron (electromagnetic steel sheet). As a result, for the same reason as in the first embodiment, the change in the gap C4 due to temperature change (the above-mentioned temperature change in the dimensional difference) can be effectively suppressed compared to the comparative example in which the mixing ratio R is zero. Furthermore, even if a value other than the mixing ratio R1 is selected within the specific range W1, the effect of being able to suppress the change in the gap C4 due to temperature change compared to the comparative example can be obtained.

In addition, according to this embodiment, similar to the effect of setting the pressure of the bearing 40 in embodiment 2 (see FIG. 7), the change in shrink fitting pressure (the pressure that the stator core 74 receives from the transaxle case 70 due to shrink fitting) with respect to temperature changes can be reduced. More specifically, since the shrink fitting pressure can be lowered at low temperatures compared to the comparative example (mixture ratio R=0), distortion of the stator core 74 caused by high shrink fitting pressure can be suppressed, thereby suppressing a decrease in efficiency of the rotating electric machine 72. On the other hand, at high temperatures, the heat dissipation performance from the stator core 74 to the transaxle case 70 can also be improved, similar to setting examples 1 and 2 shown in FIGS. 11(A) and 11(B).

4-4. Modifications (other settings of the mixing ratio R)
Also with respect to the support structure described in the fourth embodiment, any value within the range W2 or W3 (see FIG. 2) may be selected as the mixing ratio R instead of the mixing ratio R1.

(Other examples of contaminating sites)
Even in the support structure described in embodiment 4, which utilizes shrink fitting to support the stator core 74, the mixing location may be determined as in the example described with reference to Figures 12 and 12(B).

5. Fifth embodiment
Next, a fifth embodiment of the present invention will be described with reference to FIGS.

5-1. Example of a Support Structure for a Component In this embodiment, as another aspect of the "support structure for a component" according to the present invention, a "support structure that rotatably supports a pump rotor of an oil pump by a pump body that houses the pump rotor" will be described.

Figure 14 is a cross-sectional view showing a specific example of a support structure according to embodiment 5, in which a pump rotor of an oil pump is rotatably supported by a pump body that houses the pump rotor. Figure 14 shows an example of the internal structure of a transaxle case 80 included in a power train mounted on a vehicle. A rotating electric machine 82 is housed in the transaxle case 80. An oil pump 88 is disposed on one end side of a rotating shaft 86 that rotates integrally with a rotor 84 of the rotating electric machine 82.

The oil pump 88 includes a pump rotor 90 and a pump body 92. The pump body 92 is formed with a cylindrical, concave pump rotor housing hole 92a that houses the pump rotor 90. The pump rotor 90 is rotatably supported by the pump body 92 (more specifically, by the pump rotor housing hole 92a). The pump rotor 90 is driven to rotate by a pump drive shaft 94 inserted inside the rotating shaft 86.

More specifically, the oil pump 88 is, as an example, a known internal gear type trochoid pump. The pump rotor 90 is composed of an inner rotor 96 with star-shaped external teeth and an outer rotor 98 formed in a cylindrical shape. The outer rotor 98 is formed with an inner rotor accommodation chamber (not shown) that accommodates the inner rotor 96 rotatably. This inner rotor accommodation chamber is formed with star-shaped internal teeth that mesh with the external teeth of the inner rotor 96 and have a different number of teeth than the external teeth. The inner rotor accommodation chamber is also connected to a side wall 92a1 of the pump rotor accommodation hole 92a of the pump body 92. The side wall 92a1 is formed with an oil intake port and an oil discharge port (both not shown) that communicate with the inner rotor accommodation chamber. The above-mentioned pump drive shaft 94 drives the inner rotor 96 to rotate. The center of rotation of the inner rotor 96 and the center of rotation of the outer rotor 98 are eccentric to each other. The outer rotor 98 rotates in the same direction as the inner rotor 96 while being eccentric to the inner rotor 96 as the inner rotor 96 rotates. The oil sucked into the inner rotor chamber from the oil intake port is discharged from the oil discharge port by utilizing the change in volume of the inner rotor chamber caused by the change in the gap between the outer and inner teeth that occurs while the two rotors 96, 98 are rotating. The end of the inner rotor chamber located opposite the side wall 92a1 is closed by a plate 100.

In the example of the oil pump 88 shown in FIG. 14, the pump rotor 90 corresponds to an example of the "first part" according to the present invention, and the pump body 92 corresponds to an example of the "second part" according to the present invention. The pump rotor 90 is made of iron (more specifically, an iron-based material), which is an example of the first metal material, and the base material of the pump body 92 is aluminum (or an aluminum alloy). The second metal material may be, for example, a magnesium alloy. The outer peripheral surface 98a of the outer rotor 98 included in the pump rotor 90 faces the inner peripheral surface 92a2 of the pump body 92 located on the outer peripheral side of the outer peripheral surface 98a through a small positive gap C5. The side wall 92a1 of the pump body 92 faces the side wall 90a of the pump rotor 90 through a small positive gap C5'.

5-2. Example of Setting the Mixing Ratio of Negative Thermal Expansion Material In this embodiment, the base material (aluminum) of the pump body 92 is mixed with a negative thermal expansion material. The mixing ratio R can be selected from within a specific range W, as in the first embodiment and its modified examples, and an example of this is the mixing ratio R1. In this embodiment, the negative thermal expansion material is mixed into the base material at a uniform mixing ratio R1 for the entire pump body 92, as an example. That is, in this embodiment, the negative thermal expansion material is mixed into the base material in an amount that reduces the temperature change of the dimensional difference in a specific direction at the location where the pump rotor 90 (first part) and the pump body 92 (second part) face each other via the gap C5, compared to the case where the negative thermal expansion material is not mixed. The dimensional difference in this example corresponds to the dimensional difference between the dimension L14 of the first part and the dimension L24 of the second part in the radial direction (specific direction) of the pump rotor 90, and the dimensional difference between the dimension L14' of the first part and the dimension L24' of the second part in the width direction (specific direction) of the pump rotor 90, as shown in Figure 14.

5-3. Effects As described above, the pump body 92 that rotatably supports the pump rotor 90 is mixed with a negative thermal expansion material in the base material (aluminum) at a mixing ratio R1. This allows the pump body 92 to have a linear expansion coefficient equivalent to that of the pump rotor 90 made of iron. As a result, for the same reason as in the first embodiment, the change in the gaps C5 and C5' due to temperature changes (the temperature change of the above-mentioned two dimensional differences) can be effectively suppressed compared to the comparative example in which the mixing ratio R is zero. Furthermore, even if a value other than the mixing ratio R1 is selected within the specific range W1, the effect of suppressing the change in the gaps C5 and C5' due to temperature changes can be obtained compared to the comparative example.

Furthermore, in the example of oil pump 88, if an amount of oil that leaks through gaps C5 and C5' without heading toward the oil discharge port increases, the volumetric efficiency of oil pump 88 decreases. In the comparative example in which the mixing ratio R is zero, the gaps C5 and C5' become large at high temperatures, and the volumetric efficiency is likely to decrease. In contrast, according to the oil pump 88 of this embodiment, the effect of effectively suppressing the changes in gaps C5 and C5' that accompany temperature changes is obtained, and therefore the volumetric efficiency at high temperatures can be increased.

5-4. Modifications (other settings of the mixing ratio R)
With respect to the support structure described in the fifth embodiment, instead of the mixing ratio R1, any value within the ranges W2 or W3 (see FIG. 2) may be selected as the mixing ratio R. In addition, with this support structure as well, by selecting the range W3, the effects described with reference to FIGS. 4A and 4B in the first embodiment can be obtained. That is, compared to the case where the mixing ratio R1 or the range W2 is selected, it is possible to make it difficult for the hydraulic oil to leak through the gaps C5 and C5' at high temperatures when the viscosity of the hydraulic oil is low, and the volumetric efficiency of the oil pump 88 can be more effectively improved.

(Example of partial mixing in the pump body)
15(A) and 15(B) are schematic diagrams showing an example in which a negative thermal expansion material is partially mixed into the pump body 92 shown in FIG. 14. FIG. 15(B) is a view of the oil pump 88 as seen from the direction of the arrow X3 in FIG. 15(A). As shown in FIG. 15(A), the inner peripheral surface 92a2 and the surface of the side wall 92a1 of the pump body 92 facing the pump rotor 90 through the gaps C5 and C5' are respectively referred to as "fourth opposing surfaces". The portions of the pump body 92 located around these fourth opposing surfaces are referred to as "fourth surrounding portions".

In the example shown in FIG. 15, the negative thermal expansion material is mixed into the base material only for the fourth peripheral portion. The fourth peripheral portion is a wall portion 92b of the pump body 92 located on the outer periphery side of the pump rotor 90. More specifically, this wall portion 92b is specified as a ring-shaped portion having a predetermined width in the radial direction of the pump rotor 90 from the inner periphery surface 92a2.

More specifically, the negative thermal expansion material may be mixed uniformly into the base material in the fourth peripheral portion at any mixing ratio R within the specific range W1. This makes it possible to bring the linear expansion coefficient of the pump body 92 closer to that of the pump rotor 90, targeting the areas that have a large effect on the temperature change of the gaps C5 and C5'.

More preferably, the fourth peripheral portion into which the negative thermal expansion material is mixed may include wall portion 92c in addition to wall portion 92b described above. More specifically, wall portion 92c is a portion included in side wall 92a1, and is specified as a disk-shaped portion having a predetermined width from the surface of side wall 92a1 in the axial direction of pump rotor 90.

Also, similar to the examples of the hydraulic control device 10 and the transaxle cases 30, 50, and 70 described above, the negative thermal expansion material does not necessarily have to be mixed uniformly into the base material in the fourth peripheral portion at any mixing ratio R within the specific range W1, so long as it is mixed into the base material in an amount that reduces the temperature change of the above-mentioned dimensional difference compared to when the negative thermal expansion material is not mixed in. In other words, the negative thermal expansion material may be mixed into the base material in the fourth peripheral portion at different mixing ratios R (including zero) depending on the location within the fourth peripheral portion. Specifically, for example, the negative thermal expansion material may be mixed into a certain portion of the fourth peripheral portion at a higher mixing ratio R regardless of whether it is inside or outside the specific range W1, and may not be mixed into another portion of the third peripheral portion.

Furthermore, negative thermal expansion material may be mixed into some or all of the portions of the pump body 92 other than the fourth peripheral portion such that the mixing ratio R decreases continuously (or in stages), for example toward zero, as the distance from the fourth peripheral portion increases.

The examples and other modifications described in each embodiment described above may be combined as appropriate within the scope of what is possible in combinations other than those explicitly stated, and may be modified in various ways without departing from the spirit of the present invention.

10 Hydraulic control device 12 Valve body 12b Inner circumferential surface of valve body (first opposing surface)
12c: peripheral wall of valve body (first peripheral portion)
14 Valve 20 Valve land 20a Outer circumferential surface of land 30 Transaxle case 20b Wall surface of transaxle case (pair of second opposing surfaces)
30c: A portion (second peripheral portion) connecting a pair of second opposing surfaces (wall surfaces 30b)
34 Differential gear case 40 Bearing 42 Shim 50, 70, 80 Transaxle case 50b, 70b Inner peripheral surface of transaxle case (third opposing surface)
50c, 70c Transaxle case peripheral wall (third peripheral portion)
50d Side wall of transaxle case (third peripheral portion)
58, 74 Stator core of rotating electric machine 88 Oil pump 90 Pump rotor 92 Pump body 92a1 Side wall of pump body (fourth opposing surface)
92a2 Inner circumferential surface of pump rotor receiving hole of pump body (fourth opposing surface)
92b, 92c: Wall portion (fourth peripheral portion) of the pump body 92
98 Pump rotor outer rotor

Claims (9)

a first part formed of a first metallic material and consisting of one or more elements;
a second part formed of a second metallic material having a base material with a linear expansion coefficient higher than that of the first metallic material, the second part being made of one or more elements;
a support structure for supporting one of the first and second components, the support structure comprising:
The first part faces the second part in a specific direction in a state where the first part is sandwiched by the second part with a positive, zero or negative gap therebetween,
the second metallic material includes the base material and a negative thermal expansion material mixed in the base material,
the negative thermal expansion material is mixed into the base material in an amount that reduces a temperature change in a dimensional difference between a dimension of the first component and a dimension of the second component in the specific direction at a location where the first component and the second component face each other with the gap therebetween, compared to a case in which the negative thermal expansion material is not mixed in ;
the first component is a valve;
the second component is a valve body that slidably supports the valve,
The valve body includes a first opposing surface facing the valve via the positive gap,
The negative thermal expansion material is mixed into the base material only in a first peripheral portion, which is a portion of the valve body located around the first opposing surface.
A support structure for a part, comprising: The component support structure according to claim 1 , wherein the first peripheral portion includes a peripheral wall of the valve body located on an outer periphery side of the valve. The valve is disposed within the valve body;
3. The component support structure according to claim 1, wherein the valve and the valve body are provided in a hydraulic control device that controls a controlled hydraulic pressure of hydraulic oil in accordance with an axial position of the valve. a first part formed of a first metallic material and consisting of one or more elements;
a second part formed of a second metallic material having a base material with a linear expansion coefficient higher than that of the first metallic material, the second part being made of one or more elements;
a support structure for supporting one of the first and second components, the support structure comprising:
The first part faces the second part in a specific direction in a state where the first part is sandwiched by the second part with a positive, zero or negative gap therebetween,
the second metallic material includes the base material and a negative thermal expansion material mixed in the base material,
the negative thermal expansion material is mixed into the base material in an amount that reduces a temperature change in a dimensional difference between a dimension of the first component and a dimension of the second component in the specific direction at a location where the first component and the second component face each other with the gap therebetween, compared to a case in which the negative thermal expansion material is not mixed in;
the first part includes, as the plurality of elements, a pair of bearings and a rotating body having a pair of shaft portions rotatably supported by the pair of bearings;
the second component is a case that supports the pair of bearings,
Each of the pair of bearings is sandwiched between the rotor and the case in an axial direction of the rotor,
the case includes a pair of second opposing surfaces facing the pair of bearings with the negative gap therebetween,
A component support structure, characterized in that the negative thermal expansion material is mixed into the base material only in a second peripheral portion, which is a portion of the case located around the pair of second opposing surfaces. The component support structure according to claim 4 , wherein the second peripheral portion includes a portion connecting the pair of second opposing surfaces. 6. The component support structure according to claim 4, wherein the case is a transaxle case that houses the rotating body, which is a component of a transaxle mounted on a vehicle. a first part formed of a first metallic material and consisting of one or more elements;
a second part formed of a second metallic material having a base material with a linear expansion coefficient higher than that of the first metallic material, the second part being made of one or more elements;
a support structure for supporting one of the first and second components, the support structure comprising:
The first part faces the second part in a specific direction in a state where the first part is sandwiched by the second part with a positive, zero or negative gap therebetween,
the second metallic material includes the base material and a negative thermal expansion material mixed in the base material,
the negative thermal expansion material is mixed into the base material in an amount that reduces a temperature change in a dimensional difference between a dimension of the first component and a dimension of the second component in the specific direction at a location where the first component and the second component face each other with the gap therebetween, compared to a case in which the negative thermal expansion material is not mixed in;
the first component is a stator core of a rotating electrical machine,
the second component is a case that has an inner circumferential surface facing an outer circumferential surface of the stator core and accommodates the stator core,
the case includes a support portion that supports the stator core at a position spaced from the inner circumferential surface,
the case includes a third opposing surface facing an outer circumferential surface of the stator core with the gap therebetween,
a negative thermal expansion material is mixed into the base material only in a third peripheral portion, which is a portion of the case positioned around the third opposing surface. a first part formed from a first metallic material and consisting of one or more elements;
a second part formed of a second metallic material having a base material with a linear expansion coefficient higher than that of the first metallic material, the second part being made of one or more elements;
a support structure for supporting one of the first and second components, the support structure comprising:
The first part faces the second part in a specific direction in a state where the first part is sandwiched by the second part with a positive, zero or negative gap therebetween,
the second metallic material includes the base material and a negative thermal expansion material mixed in the base material,
the negative thermal expansion material is mixed into the base material in an amount that reduces a temperature change in a dimensional difference between a dimension of the first component and a dimension of the second component in the specific direction at a location where the first component and the second component face each other with the gap therebetween, compared to a case in which the negative thermal expansion material is not mixed in;
the first component is a stator core of a rotating electrical machine,
the second component is a case that houses the stator core,
The stator core is shrink-fitted to a peripheral wall of the case located on an outer circumferential side of the stator core,
the case includes a third opposing surface facing an outer circumferential surface of the stator core with the gap therebetween,
The negative thermal expansion material is mixed into the base material only in a third peripheral portion, which is a portion of the case located around the third opposing surface.
A support structure for a part, comprising: The component support structure according to claim 7 or 8 , wherein the third peripheral portion includes a peripheral wall of the case located on an outer periphery side of the stator core.

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