Support structure for vehicle differential mechanism

Abstract

To provide a support structure that effectively suppresses vibration of a differential mechanism without enlargement or complication.SOLUTION: There is provided a support structure for a vehicle differential mechanism that supports a differential mechanism 7, which outputs input torque in two different directions, at multiple locations of a frame member 10 of the vehicle, the structure comprising: a first support member 11 that connects a predetermined location of the differential mechanism 7 to the frame member 10; and a second support member 12 that connects another location whose distance from the center of gravity of the differential mechanism 7 is greater than that of the predetermined location to the frame member 10, where the second support member 12 is made of a material having a higher density than that of a material constituting the first support member 11.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a structure for supporting a differential mechanism used as a final reduction gear that transmits driving torque to left and right wheels and allows differential rotation of those wheels to a vehicle body.

Background Art

[0002] A structure for supporting this type of differential mechanism to a vehicle body is described in Patent Document 1. The support structure is a structure that supports the differential mechanism via elastic bodies at two locations in the front-rear direction of the vehicle body. Since the displacement amounts of the differential mechanism at those support locations are different, the ratio of the spring constants of those elastic bodies is configured to be constant for a first torque and a second torque transmitted to the differential mechanism at a specific rotational speed. Therefore, in the structure described in Patent Document 1, when the input rotational speed to the differential mechanism is a specific rotational speed and the torque is at a first value and a second value, the change in the ratio of the loads transmitted to the vehicle body via each elastic body is suppressed. As a result, it is said that vibrations transmitted to the vehicle body can be suppressed without increasing the spring constant of any one of the elastic bodies, such as increasing the spring constant when the displacement amount is small.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Since the differential mechanism described above transmits torque, it may vibrate in the rotational direction due to torque fluctuations. In that case, if the differential mechanism is configured such that a pinion gear is disposed between a pair of left and right side gears and the pinion gear is revolved by a ring gear, and the input shaft for rotating the ring gear is displaced from the center in the vehicle body width direction, the distances from the center of gravity of the differential mechanism to a plurality of support points that connect and support the differential mechanism to the vehicle body will be different. With such a structure, the displacement amounts at each support point accompanying the vibration will be different, and the support point far from the center of gravity will be displaced greatly. The support structure described in Patent Document 1 supports the differential mechanism via elastic bodies at two locations in the longitudinal direction of the vehicle, or specifies the spring constants of the elastic bodies at two support locations in the longitudinal direction of the vehicle among a plurality of support locations. Therefore, with such a structure, it is difficult to effectively suppress the vibration in the rotational direction centered on the input shaft.

[0005] This invention has been made against the background of the above circumstances, and an object thereof is to provide a support structure capable of effectively suppressing the vibration of a differential mechanism that may vibrate in the rotational direction centered on the center of gravity.

Means for Solving the Problems

[0006] In order to achieve the above object, this invention is a support structure for a vehicle differential mechanism that supports a differential mechanism that outputs the input torque in two different directions to a plurality of locations on a frame member of the vehicle, and includes a first support member that connects a predetermined location of the differential mechanism to the frame member, and a second support member that connects another location farther from the center of gravity of the differential mechanism than the predetermined location to the frame member, and the second support member is characterized in that it is made of a material having a higher density than the material constituting the first support member.

[0007] In this invention, the second support member may have a first connection portion connected to the differential mechanism and a second connection portion connected to the frame member, and the second connection portion may include an elastic member interposed between the second connection portion and the frame member.

[0008] In the present invention, the first support member may be made of an aluminum alloy, and the second support member may be made of (ductile) cast iron.

[0009] In the present invention, the differential mechanism has first and second torque output portions that are directed in opposite directions with respect to each other across the center of gravity, and the length by which the second torque output portion extends from the center of gravity is longer than the length by which the first torque output portion extends from the center of gravity, and the second support member may connect the second torque output portion to the frame member.

Advantages of the Invention

[0010] In the present invention, when torque is input, the differential mechanism vibrates in a direction of rotation about its center of gravity. In that case, although the amplitude or displacement amount tends to be larger at positions farther from the center of gravity than at positions closer to the center of gravity, since the second support member at a position farther from the center of gravity is made of a material with a higher density than the first support member at a position closer to the center of gravity and its mass and rigidity are large, displacement or vibration of the differential mechanism can be suppressed. That is, in order to suppress displacement or vibration of the differential mechanism, it is not necessary to increase the size of the second support member or to make its shape complicated to increase its rigidity, so the support structure of the differential mechanism can be made smaller or simpler.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0012] Next, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the embodiments described below are merely examples of implementing the present invention and do not limit the present invention.

[0013] The differential mechanism in the present invention is mounted on a vehicle and functions to cause differential rotation of two output members. An example thereof is a mechanism used as a final reduction gear that distributes and transmits the torque transmitted from a driving force source to left and right wheels. FIG. 1 is a schematic diagram showing an example thereof, and the example shown here is an example used as a front differential that transmits torque to the front wheels of a four-wheel drive vehicle. That is, the vehicle 1 includes a driving force source 2 composed of an engine or an engine and a motor, and a transmission 3 and a transfer 4 are sequentially connected to the output side thereof. The transfer 4 is a well-known mechanism that distributes and transmits the torque output from the driving force source 2 to the front propeller shaft 5 side and the rear propeller shaft 6 side. The front propeller shaft 5 extends through the side portion of the driving force source 2 and is disposed on the front side of the vehicle 1, and the tip end thereof is connected to a front differential 7 that is a differential mechanism in the embodiment of the present invention.

[0014] The front differential 7 has a conventionally known configuration. Although not particularly shown, a pinion gear that meshes with these is disposed between the left and right side gears, and a ring gear is attached to a differential carrier that holds the pinion gear. The ring gear is configured to input torque from the front propeller shaft 5. As schematically shown in FIG. 2, boss portions 8l and 8r that house integral rotating shafts of the left and right side gears are provided on both the left and right sides of the differential case 9. The front differential 7 is disposed offset from the center in the vehicle width direction in order to avoid interference with the drive power source 2. Therefore, while the left boss portion 8l slightly protrudes from the differential case 9, the right boss portion 8r extends greatly to the right so as to cross under the drive power source 2. Accordingly, the left boss portion 8l corresponds to the first torque output portion in the embodiment of the present invention, and the right boss portion 8r corresponds to the second torque output portion in the embodiment of the present invention.

[0015] The front differential 7 is connected and supported at two locations with respect to the vehicle body. That is, the front differential 7 is disposed near a front cross member (hereinafter simply referred to as a cross member) 10 that is a frame member constituting a part of the vehicle body frame. The front differential 7 is attached to the cross member 10 by a first support bracket (hereinafter simply referred to as a bracket) 11 that connects the differential case 9 and the cross member 10, and a second support bracket (hereinafter simply referred to as a bracket) 12 that connects the right boss portion 8r and the cross member 10. The center of gravity of the front differential 7 is near the center of the differential case 9. Therefore, the first bracket 11 is provided at a position closer to the center of gravity than the second bracket 12. The shapes or structures of these brackets 11 and 12 are substantially the same as those conventionally known. They are directly connected to the front differential 7 by fixing bolts (not shown) and are connected to the cross member 10 via mounts (not shown). Note that the first bracket 11 corresponds to the first support member in the embodiment of the present invention, and the second bracket 12 corresponds to the second support member in the embodiment of the present invention.

[0016] Figure 3 shows the second bracket 12, and bolt holes 13 for connecting to the front differential 7 are provided at two locations, above and below, at one end in the longitudinal direction (the right side in Figure 3). These bolt holes correspond to the first connecting portion in the embodiment of the present invention. A cylindrical boss portion 14 is formed at the opposite end (the left side in Figure 3), and a mount cushion 15 is inserted therein. The mount cushion 15 corresponds to the elastic member in the embodiment of this invention, and a through hole for passing a bolt (not shown) for connecting to the cross member 10 is formed along the central axis. This cylindrical boss portion 14 corresponds to the second connecting portion in the embodiment of this invention.

[0017] The first bracket 11 also has the same configuration as the above-described second bracket 12, and dimensions such as the wall thickness and width of each part are set so as to have the required compressive and tensile strengths, and rigidity against bending and torsion. The first bracket 11, which is close to the center of gravity, is made of a light alloy such as an aluminum alloy. On the other hand, the second bracket 12, which is far from the center of gravity, is made of a material with a higher density than the material of the first bracket 11 (for example, cast iron such as ductile cast iron). Therefore, the second bracket 12 is heavier than when it is made of the same material as the first bracket 11, and when ensuring the strength or rigidity such as torsion and bending when made of the same material as the first bracket 11, the so-called reinforcing portions such as ribs can be reduced, and the dimensions of each part including the plate thickness can be small.

[0018] Therefore, by configuring the second bracket 12 such that the material is changed to a high-density metal material and the dimensions of each part are maintained at the dimensions when made of the same material as the first bracket 11, the support strength or support rigidity at a location far from the center of gravity in the front differential 7 is increased. As a result, even if torque is input to the front differential 7 and rotational vibration occurs, the so-called mass effect and rigidity effect that suppress displacement or amplitude at a location far from the center of gravity are improved, and the vibration of the front differential 7 can be effectively suppressed. The results of an experiment (simulation) conducted by the inventors to confirm the effects of this invention are shown in FIG. 4.

[0019] FIG. 4 is a diagram showing the results of measuring the sound pressure sensitivity (dB) at specific predetermined frequencies from 50 Hz to 100 Hz for the example of the present invention and a comparative example. The example of the present invention is an example in which a bracket having the same structure and shape as the conventional bracket is made of cast iron, and the comparative example is a conventional bracket made of an aluminum alloy, and the structure and shape are the same as those of the example of the present invention. These brackets were used to support the front differential 7 with the vehicle body (cross member 10) as shown in FIG. 2, and a predetermined torque was input to transmit the torque, thereby causing vibration in the front differential 7. The measurement results for the example of the present invention are shown by line A in FIG. 4, and the measurement results for the comparative example are shown by line B in FIG. 4.

[0020] As shown by the frames in FIG. 4 respectively, in each of a predetermined range centered around approximately 65 Hz, a predetermined range centered around approximately 75 Hz, and a predetermined range centered around approximately 85 Hz, the sound pressure sensitivity shows a maximum value. However, in any of these ranges, the sound pressure sensitivity in the example of the present invention is smaller than that in the comparative example, and it was confirmed that the vibration suppression effect is excellent according to the example of the present invention. Note that at frequencies outside these ranges, the sound pressure sensitivity according to the example of the present invention may exceed that of the comparative example, but since the sound pressure sensitivity at those frequencies is originally small, there is no particular problem in terms of the vibration suppression effect.

[0021] As described above, according to the embodiment of the present invention, the vibration of the front differential 7 can be effectively suppressed without increasing the size of the bracket 12 at a location far from the center of gravity of the front differential 7 or making the structure complex. Also, differently, when the same vibration suppression effect as the conventional one is sufficient, the bracket 12 in the direction far from the center of gravity of the front differential 7 can be made smaller, or the structure or shape can be made simpler.

[0022] Note that the present invention is not limited to the above-described embodiment, and the structure or shape of the differential mechanism is not limited to that shown in the above embodiment. Similarly, the structures and shapes of the brackets 11 and 12, and further their attachment positions may be appropriately changed and selected within the scope of the present invention. Furthermore, the metal material only needs to have a high density for the material of the support member in the direction far from the center of gravity of the differential mechanism, and is not limited to aluminum alloy and cast iron.

Explanation of Reference Numerals

[0023] 1 Vehicle 2 Driving Force Source 3 Transmission 4 Transfer 5 Front Propeller Shaft 6 Rear Propeller Shaft 7 Front Differential (Differential Mechanism) 8l, 8r Boss Portions 9 Differential Case 10 Cross Member 11 First Support Bracket (Bracket) 12 Second Support Bracket (Bracket) 13 Bolt Hole 14 Boss Portion 15 Mount Cushion

Claims

1. A support structure for a differential mechanism of a vehicle that supports an input torque output in two different directions at a plurality of locations on a frame member of the vehicle, comprising: a first support member that connects a predetermined location of the differential mechanism to the frame member; a second support member that connects another location, which is farther from the center of gravity of the differential mechanism than the predetermined location, to the frame member; and the second support member is made of a material having a higher density than the material constituting the first support member. A support structure for a differential mechanism of a vehicle, characterized by the above.

2. The support structure for a differential mechanism of a vehicle according to claim 1, comprising: the second support member having a first connection portion connected to the differential mechanism and a second connection portion connected to the frame member; and the second connection portion is provided with an elastic member interposed between the second connection portion and the frame member. A support structure for a differential mechanism of a vehicle, characterized by the above.

3. The support structure for a differential mechanism of a vehicle according to claim 1 or 2, comprising: the first support member is made of an aluminum alloy; the second support member is made of cast iron. A support structure for a differential mechanism of a vehicle, characterized by the above.

4. The support structure for a differential mechanism of a vehicle according to claim 1 or 2, comprising: the differential mechanism has first and second torque output portions directed in opposite directions with respect to the center of gravity; the length by which the second torque output portion extends from the center of gravity is longer than the length by which the first torque output portion extends from the center of gravity; and the second support member connects the second torque output portion to the frame member. A support structure for a differential mechanism of a vehicle, characterized by the above.

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