Leaf suspension

Abstract

A leaf suspension (10) is provided with a first leaf (11), a second leaf (12) adjacent to the first leaf (11), and a spacer (19) provided between the first leaf (11) and the second leaf (12). The second leaf (12) has an end (12a or 12b) that is a free end, and is restrained at an intermediate portion (12c). The spacer (19) is placed at a position of a node closest to the end (12a or 12b) among nodes that are present when natural vibration occurs in a portion from the intermediate portion (12c) to the end (12a or 12b).

Description

Leaf suspension

[0001] The present invention relates to a leaf suspension.

[0002] Patent Document 1 discloses a leaf spring suspension device that includes two upper and lower leaves and an auxiliary leaf provided below the upper and lower leaves.

[0003] Japanese Patent Application Laid-Open No. 2003-306019

[0004] When multiple leaves are stacked, vibrations are transmitted to each leaf in the stacking direction. Therefore, vibrations from the axle are transmitted to the leaf closest to the axle, and then reach the vehicle frame via the other leaves. Vibrations that reach the vehicle frame are one of the causes of noise generation.

[0005] An object of the present invention is to provide a leaf suspension that can suppress the transmission of vibration between a plurality of stacked leaves.

[0006] A leaf suspension according to one aspect of the present invention includes a first leaf, a second leaf adjacent to the first leaf, and a spacer provided between the first and second leaves. The second leaf has a free end and is constrained at an intermediate portion of the second leaf. The spacer is located at the node closest to the intermediate portion of the second leaf when a natural vibration occurs in the portion from the intermediate portion to the intermediate portion of the second leaf.

[0007] According to the leaf suspension, it is possible to suppress the transmission of vibration between the plurality of stacked leaves.

[0008] Fig. 1 is a perspective view showing an example of a leaf suspension according to an embodiment and its surrounding main components. Fig. 2 is a side view of the leaf suspension shown in Fig. 1. Fig. 3 is a diagram showing an example of a vibration mode in a leaf according to an embodiment. Fig. 4 is a diagram showing another example of a vibration mode in a leaf according to an embodiment.

[0009] Hereinafter, an embodiment will be described with reference to the drawings. In each drawing, FR and RR indicate the front and rear in the vehicle longitudinal direction, respectively. LH and RH indicate the left and right in the vehicle width direction, respectively. In addition, in the following description, the center of the vehicle in the vehicle width direction is referred to as the inner side in the vehicle width direction, and the side opposite the inner side in the vehicle width direction is referred to as the outer side in the vehicle width direction. The front and rear in the vehicle longitudinal direction, the front side and rear side in the vehicle longitudinal direction, the left and right in the vehicle width direction are simply referred to as "front," "rear," "front side," "rear side," "left side," and "right side," respectively. Furthermore, elements having the same function are assigned the same reference numerals, and redundant explanations will be omitted.

[0010] <Embodiment> Figure 1 is a perspective view showing an example of a leaf suspension 10 according to an embodiment and the main components surrounding it. As shown in Figure 1, the leaf suspension 10 is attached to each side of an axle 20 in the vehicle width direction. The axle 20 is a rear axle. That is, the axle 20 includes an axle shaft that drives rear wheels 23, and a differential gear 21 at its center that is connected to the axle shaft and a propeller shaft 22.

[0011] The leaf suspension 10 according to this embodiment includes multiple leaves (leaf springs). For ease of explanation, the following description will be given taking as an example a leaf suspension 10 including three leaves. The number of leaves is selected appropriately depending on the mechanical characteristics of each leaf and the expected load.

[0012] Figure 2 is a side view of the leaf suspension 10 shown in Figure 1. As shown in Figure 2, the leaf suspension 10 includes a first leaf 11, a second leaf 12, and a third leaf 13. Of the three leaves, leaf 11 is located at the top. Leaf 12 is located below leaf 11. Furthermore, leaf 13 is located below leaf 12.

[0013] The leaf 11 extends in the longitudinal direction of the vehicle from the front end 11a to the rear end 11b. As shown in the example, an eye 16a may be formed at the front end 11a, and an eye 16b may be formed at the rear end 11b. A bushing 17 is attached to the inside of each of the eyes 16a and 16b. The bushing 17 is formed in a cylindrical shape with a through hole. A shaft (not shown) is inserted into a bracket (not shown) provided on a vehicle body frame (not shown) and is inserted into the through hole of the front bushing 17. A shaft (not shown) is inserted into a shackle 25 and is inserted into the through hole of the rear bushing 17.

[0014] The leaf 12 extends in the longitudinal direction of the vehicle from a front end 12 a to a rear end 12 b. Both the front end 12 a and the rear end 12 b are free ends. The length of the leaf 12 in the longitudinal direction of the vehicle is equal to or less than the length of the leaf 11 in the same direction.

[0015] The leaf 13 extends in the longitudinal direction of the vehicle from a front end 13 a to a rear end 13 b. Both the front end 13 a and the rear end 13 b are provided as free ends. The length of the leaf 13 in the longitudinal direction of the vehicle is equal to or less than the length of the leaf 12 in the same direction.

[0016] The leaf 11 includes an intermediate portion 11c located between the front end 11a and the rear end 11b. Similarly, the leaf 12 includes an intermediate portion 12c located between the front end 12a and the rear end 12b. The leaf 13 includes an intermediate portion 13c located between the front end 13a and the rear end 13b. These intermediate portions 11c, 12c, and 13c are aligned at the same position in the vehicle fore-and-aft direction and are restrained to the axle 20 by the clamp portion 14.

[0017] The clamping portion 14 has a base plate 14a, an intermediate plate 14b, and a U-bolt 15. The intermediate portions 11c, 12c, and 13c of each leaf are located between the intermediate plate 14b and the base plate 14a. The U-bolt 15 is inserted through the intermediate plate 14b and the base plate 14a with the axle 20 sandwiched between them and fastened with a nut (not shown). With this fastening, the axle 20 is sandwiched and restrained between the U-bolt 15 and the intermediate plate 14b. The intermediate portions 11c, 12c, and 13c are also sandwiched and restrained between the intermediate plate 14b and the base plate 14a.

[0018] 2, the leaf suspension 10 includes a clip band 18. The clip band 18 flexibly bundles, for example, the leaves 11 and 12. The clip band 18 prevents the leaf 12 from shifting in the vehicle width direction relative to the leaf 11.

[0019] Furthermore, the leaf suspension 10 according to this embodiment includes a spacer (silencer) 19. The spacer 19 is provided between the leaf 11 and the leaf 12. The spacer 19 is made of a material such as resin or rubber. The spacer 19 is located at the node closest to the end of the leaf 12 when natural vibration occurs in the portion from the intermediate portion 12c to the end. The end here refers to at least one of the front end 12a and the rear end 12b.

[0020] The position of the spacer 19 will be described by taking an example in which the spacer 19 is provided behind the intermediate portions 11c and 12c. Fig. 3 is a diagram showing an example of a vibration mode of the leaf 12. Fig. 4 is a diagram showing another example of a vibration mode of the leaf 12.

[0021] As described above, the leaf suspension 10 is fixed to the axle 20 by the clamp 14. The axle 20 also includes a differential gear 21. While the propeller shaft 22 (see FIG. 1) rotates, the rotation causes the differential gear 21 to vibrate. The vibrations of the differential gear 21 are transmitted to the leaf suspension 10 via the axle 20, and are then transmitted to a vehicle body frame (not shown) connected to the leaf suspension 10. In this series of vibration transmissions, one of the leaves of the leaf suspension 10 may resonate, generating unwanted noise. In other words, the source of the vibration in this case is the differential gear 21.

[0022] 3 shows a state in which a third-order natural vibration occurs in the portion of the leaf 12 from the intermediate portion 12c to the rear end 12b. As described above, the intermediate portion 12c is constrained. Therefore, as shown in FIG. 3, the rear portion 12d of the intermediate portion 12c (see FIGS. 3 and 4) acts as a fixed end, and the rear end 12b acts as a free end.

[0023] The spacer 19 according to this embodiment is located at the node closest to the rear end 12 b among the nodes when natural vibration occurs in the portion from the intermediate portion 12 c to the rear end 12 b of the leaf 12. That is, in this embodiment, nodal mounting of the spacer 19 is applied to the leaf suspension 10.

[0024] For example, as shown in Fig. 3, the spacer 19 is located at node N3, which is the closest to the rear end 12b, among multiple nodes that occur when a third-order natural vibration is assumed. Alternatively, as shown in Fig. 4, the spacer 19 is located at node N2, which is the closest to the rear end 12b, among multiple nodes that occur when a second-order natural vibration is assumed. In either case, the spacer 19 is located at a position where a node of the natural vibration occurs.

[0025] The effects of the leaf suspension 10 according to this embodiment will now be described.

[0026] (1) The leaf suspension 10 includes a first leaf 11, a second leaf 12 adjacent to the first leaf 11, and a spacer 19 disposed between the first and second leaves 11 and 12. The leaf 12 has a rear end 12b, which is a free end, and is constrained by an intermediate portion 12c of the leaf 12. The spacer 19 is located at the node closest to the rear end 12b when natural vibration occurs in the portion of the leaf 12 from the intermediate portion 12c to the rear end 12b. Therefore, the leaf suspension 10 can reduce the transmission rate of vibration caused by the resonance from the leaf 12 to the leaf 11, even when the leaf 12 resonates due to vibration from the axle 20. In other words, it is possible to suppress vibration transmission between the stacked leaves. The spacer 19 may also be located at the node closest to the front end 12a when natural vibration occurs in the portion of the leaf 12 from the intermediate portion 12c to the front end 12a, which is a free end. The same effect as described above can be achieved in this case.

[0027] (2) In the leaf suspension 10, the spacer 19 is positioned at the node closest to the rear end 12b of the leaf 12 when a natural vibration of 400 to 460 Hz occurs in the portion of the leaf 12 from the intermediate portion 12c to the rear end 12b. When the differential gear 21 generates vibrations that induce a humming noise, the frequency is generally said to be 400 to 460 Hz. The frequency of this humming noise corresponds to the frequency of the 11th harmonic that occurs when the propeller shaft rotates at 2200 to 2500 rpm. By positioning the spacer 19 at the node when a natural vibration of 400 to 460 Hz occurs, transmission of the vibration of the leaf 12 to the leaf 11 during resonance can be more efficiently suppressed, thereby suppressing noise at the above frequency. The spacer 19 may also be positioned at the node closest to the front end 12a of the leaf 12 when a natural vibration of 400 to 460 Hz occurs in the portion of the leaf 12 from the intermediate portion 12c to the front end 12a. In this case, the same effect as above can be obtained.

[0028] (3) For example, the spacer 19 is positioned within a range of 77 to 87% of the length L1 from the intermediate portion 12c (rear portion 12d of the intermediate portion 12c) to the rear end 12b. The length L2 shown in FIG. 2 indicates a range of 77 to 87% of the length L1. By positioning the spacer 19 within a range of 77 to 87% of the length L1, it is possible to suppress transmission of vibration of the leaf 12 during resonance to the leaf 11, thereby suppressing noise at the above-mentioned frequency. The spacer 19 may also be positioned within a range of 77 to 87% of the length L1 from the front portion of the intermediate portion 12c to the front end 12a. Even in this case, the same effect as described above can be obtained.

[0029] (4) The spacer 19 may be a so-called silencer. In other words, the spacer 19 may also function as a member for suppressing impact noise during vibration. This makes it possible to suppress the transmission of vibration during resonance while also suppressing the generation of impact noise between the leaves due to shocks during driving.

[0030] (5) As described above, the intermediate portion 12c of the leaf 12 is attached to the axle 20, which includes the differential gear 21, together with the leaf 11. Therefore, an increase in the whine noise of the differential gear 21 can be suppressed.

[0031] <Modification> A leaf suspension according to a modification includes N leaves, and the Kth and K+1st leaves, counting from the uppermost leaf, are configured as in the above embodiment. Here, N is an integer equal to or greater than 2, and K is an integer equal to or greater than 1 and equal to or less than N-1. When N is 3 or greater, K can be multiple. For example, when N=5, K is one or more of 1, 2, 3, and 4. In the leaf suspension according to the modification, the Kth and K+1st leaves correspond to leaves 11 and 12, respectively, in the above embodiment. That is, the K+1st leaf has a free front or rear end and is constrained at its middle. A spacer 19 is provided between the Kth leaf (the first leaf) and the K+1st leaf (the second leaf). The spacer 19 is positioned at the node closest to the front or rear end of the K+1st leaf when a natural vibration occurs in the portion from the middle to the front or rear end of the K+1st leaf. Therefore, the leaf suspension according to the modification can achieve the same effect as the effect (1) above.

[0032] In a modified example, the spacer 19 may be located at the node closest to the front or rear end of the (K+1)th leaf when a natural vibration of 400 to 460 Hz occurs in the portion from the middle to the front or rear end of the (K+1)th leaf. In this case, the same effect as that of (2) above can be obtained.

[0033] In addition, the spacer 19 in the modified example may be located in a range of 77 to 87% of the length L1 from the rear of the intermediate portion of the (K+1)th leaf to the rear end, starting from the intermediate portion. Alternatively, the spacer 19 may be located in a range of 77 to 87% of the length L1 from the front of the intermediate portion of the (K+1)th leaf to the front end, starting from the front of the intermediate portion. In this case, the same effect as that of (3) above can be obtained.

[0034] In a modified example, the spacer 19 may be a so-called silencer. In this case, the same effect as that of (4) above can be obtained. Also, the middle portion of the (K+1)th leaf may be attached to an axle equipped with a differential gear together with the Kth leaf. In this case, the same effect as that of (5) above can be obtained.

[0035] 1 to 4 correspond to the above-described modified example when N = 3 and K = 1. When K includes 1, the two leaves closest to the body frame are provided with spacers 19 arranged in the predetermined positions, and therefore vibrations transmitted to the body frame can be more effectively suppressed than when K does not include 1.

[0036] The above-described embodiments and modifications are merely examples described to facilitate understanding of the invention. The technical scope of the invention is not limited to the specific technical matters disclosed in the above-described embodiments and modifications, but also includes various modifications, changes, alternative technologies, etc. that can be easily derived therefrom.

[0037] 10 Leaf suspension, 11 Leaf (first leaf), 12 Leaf (second leaf), 12a Front end, 12b Rear end, 12c Middle portion, 19 Spacer

Claims

1. A leaf suspension comprising: a first leaf; a second leaf having a free end adjacent to the first leaf; and a spacer provided between the first leaf and the second leaf, wherein the second leaf is constrained at a middle portion of the second leaf, and the spacer is located at the position of a node closest to the end portion when a natural vibration occurs in the portion of the second leaf from the middle portion to the end portion.

2. A leaf suspension as described in claim 1, wherein the spacer is located at the node closest to the end of the second leaf when a natural vibration of 400 to 460 Hz occurs in the portion from the middle to the end of the second leaf.

3. A leaf suspension according to claim 2, wherein the spacer is positioned within a range of 77 to 87% of the length from the intermediate portion to the end portion, starting from the intermediate portion.

4. A leaf suspension according to any one of claims 1 to 3, wherein the spacer is a silencer.

5. A leaf suspension according to any one of claims 1 to 3, wherein the intermediate portion of the second leaf is attached together with the first leaf to an axle having a differential gear.

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