JPS6347533A - Leaf spring made of ceramic material and the like - Google Patents

Abstract

PURPOSE:To prevent the breakage of a leaf spring by making the center load supporting part of said leaf spring made of ceramic, etc. wider than both end supporting parts and reducing stress on the side end edge of the center part of said leaf spring. CONSTITUTION:A leaf spring 4 is formed into a rhomboid shape in which the board width of its center part is approx. 36mm while both side edge parts 9 are at an angle of approx. 30 deg. to an axial direction. When a load is applied to the leaf spring 4, the highest stress part is generated at the center part in the axial direction, while stresses in the vicinity of both side edge parts 9 are relatively low. That is, the stress values are, approx. 20-25kgf/mm<2> in a zone 6, approx. 25-30kgf/mm<2> in zones 7, and approx. 30kgf/mm<2> or more in a zone 8. Accordingly, any breakage starting from the side edge parts 9 of the center of the leaf spring 4 can hardly occur.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is applicable to ceramic materials such as alumina, zirconia, silicon nitride, silicon carbide, etc.), glass, special cements, and intermetallic compounds (such as TiAβ, Ti3AJ', N
! It relates to a leaf spring made of a brittle material such as 3Af, etc.).

<Conventional technology> Leaf springs made of ceramics, intermetallic compounds, glass, special cement, etc. can be used as leaf springs used in special environments, which are characterized by heat resistance, corrosion resistance, wear resistance, etc. However, all of them are brittle and highly sensitive to notches, so they often break early starting from minute racks in areas where stress is likely to concentrate, such as the edges. for example,
As shown in FIGS. 1 and 2, a rectangular leaf spring 1 made of silicon nitride, for example, is supported at both ends by a support member 2, and a load is applied to the central part of the spring 1 through a load member 3. When the leaf spring is used in a three-point bending method, stress concentration occurs particularly at both side edges 9 of the central part of the leaf spring, and the leaf spring is likely to break from that part. This trend is reflected in so-called ceramic materials (e.g. alumina, zirconia, silicon nitride, silicon carbide, etc.)
Glass, special cements, intermetallic compounds (e.g. TiAβ
,T)3A,! This tendency is clearly seen in brittle A and I materials such as 2, Ni3Δβ, etc.).

Conventionally, the corners of the side edges of the leaf springs are chamfered with flat or curved surfaces, and the roughness of the chamfered portions is made as small as possible to avoid such concentration of stress as much as possible. However, even with such chamfering, the stress at the corner is quite high, so the corner on the tension-responsive horn side tends to become the starting point of fracture.

In such three-point bending, it was conventionally thought that the stress component I was uniform along the width direction, but according to experiments conducted by the inventor, as shown in Fig. 2, When a rectangular leaf spring 1 is bent at three points, the load member 3 naturally
The highest stress occurs in the vicinity of , and it has been found that the stress in the center and in the vicinity of the side edges 9 is relatively high, particularly in the width direction. In this case, the material of the leaf spring 1 is silicon nitride, and its Young's modulus is 28,0OOffyf
The dimensions were 1.0trvn in thickness, 28.2m in width, and 62.48m in length. The width of the support member 2 and the load member 3 is 4mm, the distance between the inner ends of both support members 2 is 46mm, and the load applied to the load member 3 is 1mm.
It was 9f on 5th. The maximum stress value obtained was 33N.
It was gf/familiar 2.

Therefore, in such a rectangular leaf spring, the side edge 9
The stress becomes high, and furthermore, due to the stress concentration at the corner of the side edge 9, breakage from the corner becomes more likely to occur.

<Problems that the invention attempts to solve> In view of the problems of the prior art and the inventor's knowledge,
The main object of the invention is to provide a temporary spring from a brittle material with improved strength.

<Means for Solving the Problems> According to the present invention, this object is achieved by using a material made of ceramics, glass, intermetallic compounds, etc., which is supported at both ends and supports the cart approximately at its center. This can be achieved by providing a leaf spring made of a ceramic material or the like, in which the central load supporting portion is wider than the end supporting portions of the temporary spring made of the material. In particular, it is preferable that a straight line connecting the side edges of the end-supporting portions of the leaf spring and the side edges of the central load-supporting portion form an angle of 5° to 45° with respect to the axial direction of the leaf spring.

<Function> By doing so, the stress at the side edges of the central portion of the leaf spring becomes relatively small, and breakage of the leaf spring due to stress concentration can be prevented.

<Example> FIG. 3 is a plan view of a temporary spring according to the invention.

This leaf spring 4 is made of silicon nitride like the leaf spring shown in FIG. 2, and has the same spring constant (
32.5 KIf/mm), the board width at the center is about 36 m, and both side edges 9 are about 30 m in the axial direction.
The leaf spring 4 had a diamond shape forming an angle of 1.5 m.The total length of this leaf spring 4 was 62.4 m.

When a cart similar to that described above with reference to FIGS. 1 and 2 was added to this leaf spring 4, a stress distribution as shown in FIG. 3 was obtained. That is, the highest stress occurs at the center in the axial direction as before, but unlike the above, the stress in the vicinity of both side edges 9 is kept relatively low. The specific stress values are 20KJf/m2 or less in region 5, 20 to 25Kgf/m2 in region 6, 25 to 30 to 3f/rrvn in region 7, and 3f/rrvn in region 8. It's 30
9'('/rrvn1 or more. Therefore, breakage starting from the central side edge 9 of the leaf spring 4 is unlikely to occur.

In addition, the maximum stress value in this example is 34 f/#2
Met.

In this way, by forming the leaf spring so that the center part is wider than the supporting parts at both ends, it is possible not only to prevent breakage due to stress concentration, but also to reduce the area of high stress parts. The effect of improving reliability in terms of strength is also reduced by 1q. In addition, in the case of this embodiment, the first
The area is approximately 36% smaller than the rectangular leaf spring shown in FIG. 2 and FIG. 2, and material costs can be saved. Particularly in the case of brittle materials such as ceramics, the reliability of strength tends to decrease as the effective volume and effective area become larger, and reducing the effective volume and effective area leads to improved strength reliability.

4 to 9 show different embodiments of the present invention. In the embodiment shown in FIGS. 4 and 5, the axial ends 10 and the central side edges 11 are cut away. In the embodiment shown in FIGS. 6 and 7, parallel portions 12 are provided on both supports to increase the stability of the supports. For the embodiments shown in FIGS. 5 and 7,
Since both side edges 11 are cut off, the stability of the load point portion is enhanced. In the embodiment shown in FIGS. 8 and 9, the side edges 13 are each curved outwardly to form a rhombus.

10 to 12 illustrate the method for measuring the angle θ that determines the characteristics of the rhombus shape as described above. For example, in the case of the embodiment shown in FIG. 7, the method shown in FIG. As shown in FIG.
As shown in Figure 1, when a similar embodiment is applied to four-point bending, the axis of the straight line 14 connecting the side edge of the support part and the side edge of the load part adjacent to the support part In the case of the embodiment shown in FIG. 8, as shown in FIG. 12, the angle with respect to the direction of 15 is 0. The angle of the straight line 14 connecting the lines with respect to the direction of the axis 15 is θ.

In general, if O is small, the stress at the side edges becomes high as in conventional rectangular leaf springs, which poses a problem in the strength of the same portions, which is not preferable. Conversely, when θ becomes 45° or more, the widths of the two isolated relatively high stress regions 7 formed on both sides of the central portion in FIG. Stress concentration in the area becomes a problem. Therefore, it is generally preferable that the angle 0 be in the range of 5° to 45°, and most preferably in the range of 10' to 30'.

<Effects of the Invention> As described above, according to the present invention, by appropriately determining the shape of the temporary spring made of brittle material, it is possible to not only prevent breakage due to stress concentration, but also increase the general strength. The effect is extremely large because materials can be saved.

[Brief explanation of drawings]

Figure 1 is a side view showing the loading area of the three-point bending method. FIG. 2 is a plan view showing a conventional rectangular leaf spring and its stress distribution under the three-point bending method. FIG. FIG. 4 to 9 are plan views showing different embodiments of the leaf spring according to the present invention. FIGS. 10 to 12 show three-point bending or FIG. 3 is a plan view showing a procedure for measuring an angle θ representing the shape characteristics of two types of temporary springs under four-point bending.

Claims (2)

[Claims] (1) A leaf spring made of a material such as ceramics, glass, cement, or an intermetallic compound that is supported at both ends and supports the load at approximately the center thereof, the center being closer to the support portions at both ends. A leaf spring made of a ceramic material or the like, characterized by a load-supporting portion having a wide width. (2) A straight line connecting the side edges of the both end support portions of the leaf spring and the side edge of the central load support portion forms an angle of 5° to 45° with respect to the axial direction of the leaf spring. A leaf spring made of a ceramic material or the like according to claim 1.