JP2008074315A - Vehicular suspension structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular suspension structure for suppressing the vibration transmitted from an engine to a vehicle cabin via an engine mounting part. <P>SOLUTION: In the suspension structure, a transmission path of the vibration transmitted to a body 14 from an engine 16 via a first bush 22, a second bush 24 and a third bush 26 forms a first transmission path, and a transmission path of the vibration transmitted to the body 14 from the engine 16 via a transmission unit 18, a drive shaft 20, a knuckle 30 and an absorber 38 forms a second transmission path. In this condition, the absorber 38 has the sliding resistance to be set so that, in a substantially entire range of the idling number of rotation, the vibration level of the vibration synthesizing the vibration to be transmitted from the engine 16 to the body 14 via the first transmission path with the vibration to be transmitted from the engine 16 to a body casing via the second transmission path is lower than the vibration level of the vibration to be transmitted from the engine 16 to the body 14 via the first transmission path. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a vehicle suspension structure, and more particularly to a vehicle suspension structure including an absorber interposed between a main body housing provided with a passenger cabin and a wheel support member for supporting a wheel.

  As the engine rotates, engine vibrations are transmitted to the vehicle cabin through various paths. When the engine vibration is transmitted to the vehicle cabin, the vehicle occupant feels the vibration. If such vibration transmitted to the vehicle cabin becomes large, it will be difficult to provide a comfortable vehicle environment for the passenger. Furthermore, there is a high possibility that the vehicle is stopped when the engine is idling. In this case, since there is no vibration of the vehicle cabin due to traveling of the vehicle, the occupant particularly feels vibration transmitted from the engine. Therefore, it is not preferable that the vibration of the engine is transmitted to the vehicle cabin particularly during idling.

One of the paths through which engine vibration is transmitted to the vehicle cabin is a path through which engine vibration is transmitted to the main body housing via the suspension device. For this reason, in Patent Document 1, a suspension device that suppresses the unsprung resonance frequencies of the front left and right wheels from overlapping by changing the unsprung resonance frequencies of the front wheels when the engine is idling. Has been proposed. In Patent Document 2, a friction member is provided between the rod guide and the piston rod to give a frictional resistance to the insertion / removal operation of the piston rod, and the friction member is pivoted with respect to the rod guide by a member made of a highly rigid material. There has been proposed a hydraulic shock absorber that advantageously reduces a wide range of vibrations including high frequency vibrations by biasing in the direction.
JP 2001-159443 A JP 2005-199861 A

  The engine is usually attached to the main body housing via an attachment portion having an elastic member such as a rubber bush. With the techniques described in Patent Document 1 and Patent Document 2 described above, it is difficult to suppress vibration transmitted from the engine to the main body housing via the engine mounting portion.

  This invention is made | formed in view of such a subject, The objective is to suppress the vibration transmitted to a vehicle passenger compartment from an engine via the attachment part of an engine.

  In order to solve the above problems, a vehicle suspension structure according to an aspect of the present invention is a vehicle suspension structure including an absorber interposed between a main body housing provided with a cabin and a wheel support member that supports a wheel. The absorber has a structure in which an engine unit including an engine and a transmission unit fixed to the engine is attached to a main body housing via an attachment portion, and the transmission unit is connected to a wheel support member via a drive shaft. In the vehicle having the first transmission path, the vibration transmission path transmitted from the engine to the main body casing via the mounting portion is used as the first transmission path, and the main body casing via the transmission unit, drive shaft, wheel support member, and absorber is provided. The transmission path of the transmitted vibration is the second transmission path In this case, the amplitude of the vibration transmitted from the engine to the main body housing through the first transmission path is substantially higher than the range of the idling speed range that can be set as the engine speed during idling. The sliding resistance is set such that the vibration amplitude obtained by combining the vibration transmitted to the main body casing and the vibration transmitted from the engine via the second transmission path to the main body casing has a lower value. According to this aspect, the vibration transmitted from the engine to the cabin through the first transmission path can be suppressed using the vibration transmitted from the engine to the cabin through the second transmission path.

  The absorber has a resonance point near the lowest engine speed in the idling speed range and at a lower speed where the relationship between the amplitude of vibration transmitted from the engine to the main body housing through the second transmission path and the engine speed is within the range of idling speed. You may have the sliding resistance set to have. According to this aspect, it is possible to effectively cancel the vibration transmitted from the engine to the main body housing via the first transmission path using the vibration transmitted from the engine to the main body housing via the second transmission path. It becomes possible.

  According to the vehicle suspension structure of the present invention, it is possible to suppress vibration transmitted from the engine to the vehicle cabin via the engine mounting portion.

  Hereinafter, embodiments of the present invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the drawings.

  FIG. 1 is a diagram schematically illustrating a vehicle 10 provided with a suspension structure 12 according to the present embodiment. The vehicle 10 includes a suspension structure 12, a body 14, an engine 16, a transmission unit 18, a drive shaft 20, and the like. In FIG. 1, a figure schematically representing a spring indicates that the constituent element is an elastic member.

  A body 14 (not shown) that accommodates an occupant is integrally provided in the body 14 as a main body casing of the vehicle. The engine 16 generates engine torque that drives the wheels. In this embodiment, the engine 16 employs any internal combustion engine such as a reciprocating engine, a rotary engine, or a diesel engine. A motor that operates with electric power may be employed as the engine 16.

  The transmission unit 18 includes a transmission mechanism (not shown). This transmission mechanism shifts the drive of the engine 16 and transmits it to the drive shaft 20. For this reason, the transmission unit 18 is fixed to the engine 16. Thus, the engine 16 and the transmission unit 18 integrally form an engine unit 28.

  The engine 16 simultaneously generates vibration when generating engine torque. In order to suppress the vibration generated in the engine 16 from being transmitted to the vehicle cabin, the engine unit 28 is provided by a first bush 22, a second bush 24, and a third bush 26 each formed of rubber as an elastic member. It is attached to the body 14. Therefore, these bushes function as an attachment portion that is interposed between the engine unit 28 and the body 14 and attaches the engine unit 28 to the body 14.

  The suspension structure 12 includes a knuckle 30, a wheel 32, an absorber 38, a fourth bush 40, a lower arm 42, and a fifth bush 44. The wheel 32 has a wheel 36 and a tire 34. Since the tire 34 is usually formed of an elastic member such as rubber, the tire 34 is represented by a figure indicating that the tire 34 is an elastic member in FIG.

  The wheel 32 is supported by the knuckle 30 through a hub (not shown) so as to be rotatable about its central axis. Therefore, the knuckle 30 functions as a wheel support member that supports the wheel 32. The hub is connected to the transmission unit 18 by a drive shaft 20. Therefore, the knuckle 30 is connected to the transmission unit 18 via the drive shaft 20 so that vibration can be transmitted.

  The knuckle 30 is supported by the lower arm 42, and the lower arm 42 is supported by the body 14 via a fifth bush 44 formed of an elastic member such as rubber. Specifically, the lower arm 42 is formed in a C shape, and two end portions are provided with mounting holes formed so as to penetrate coaxially. The two end portions are arranged at the front and rear, and a rotation shaft is inserted into each mounting hole and fixed to the body 14 so that the lower arm 42 is supported so as to be rotatable with respect to the body 14 around the mounting hole. The The fifth bush 44 is provided in an annular shape, and is attached between the attachment hole of the lower arm 42 and the rotation shaft of the body 14.

  An absorber 38 is attached to the knuckle 30. In this embodiment, the absorber 38 is a hydraulic type. Note that a gas-filled type may be adopted as the absorber 38. The absorber 38 is fixed to the body 14 via a fourth bush 40 formed of an elastic member such as rubber.

  Vibration generated in the engine 16 is transmitted from the engine 16 to the body 14 via the first bush 22, the second bush 24, and the third bush 26. The vibration generated in the engine 16 is transmitted to the body 14 via the transmission unit 18, the drive shaft 20, the knuckle 30, the absorber 38, the fourth bush 40, the lower arm 42, and the fifth bush 44.

  FIG. 2 is a diagram schematically showing the vehicle 10 provided with the suspension structure 12 according to the present embodiment. In FIG. 2, M_p / p represents an engine unit equivalent mass that is the mass of the engine unit 28. M_sus represents a suspension equivalent mass which is a total mass of the knuckle 30, the wheel 32, the absorber 38, the fourth bush 40, the lower arm 42, and the fifth bush 44. K_p / p represents an engine unit support bush equivalent spring constant represented by one spring constant with the first bush 22, the second bush 24, and the third bush 26 as integral springs. K_strut represents a strut upper end bush equivalent spring constant that is a spring constant of the fourth bush 40. K_ab represents an absorber friction equivalent spring constant in which the sliding resistance due to friction of the absorber 38 is expressed as a spring constant. K_lwr represents a lower arm bush equivalent spring constant that is a spring constant of the fifth bush 44. K_d / s represents a drive shaft equivalent spring constant that is a spring constant of the drive shaft 20. K_tyre represents a tire equivalent spring constant that is a spring constant of the tire 34. F 0 represents vibration input by the engine 16.

  The sliding resistance due to friction of the absorber 38 acts in the direction of expansion when the absorber 38 contracts, and acts in the direction of contraction when the absorber 38 extends. Therefore, the nature of the spring is different from that of the spring that exerts an urging force according to the displacement from the reference position. However, the suspension structure 12 according to the present embodiment is intended to suppress the transmission of vibrations to the cabin during idling with a high frequency and a short amplitude, so that the sliding resistance due to the friction of the absorber 38 is approximated as a spring constant. Even so, a large error does not occur in the calculation of the amplitude of vibration. For this reason, in this embodiment, the sliding resistance due to the friction of the absorber 38 is approximated as a spring constant.

  In FIG. 2, the transmission path of vibration transmitted from the engine 16 to the body 14 via the first bush 22, the second bush 24, and the third bush 26 is defined as a first transmission path R1. In the first transmission path R1, vibration generated in the engine 16 is transmitted to the body 14 via the engine unit support bush equivalent spring constant K_p / p.

  A transmission path of vibration transmitted to the body 14 via the transmission unit 18, drive shaft 20, knuckle 30, absorber 38, fourth bush 40, lower arm 42, and fifth bush 44 is defined as a second transmission path R2. . In the second transmission path R2, vibrations generated in the engine 16 are a drive shaft equivalent spring constant K_d / s, a suspension equivalent spring constant M_sus, an absorber friction equivalent spring constant K_ab, a strut upper end bush equivalent spring constant K_strut, and a lower arm bush equivalent spring constant. It is transmitted to the body 14 via K_lwr.

  Here, in the second transmission path R2, the resonance angular frequency ωn that maximizes the second output F2 with respect to the input F0 is expressed by the following equation.

  In the second transmission path R2, if the absorber 38 does not slide during idling as in the prior art, the absorber 38 is treated as a rigid body in transmission of vibration during idling, and the absorber friction equivalent spring constant K_ab is infinite. Is approximated by As a result, K in Equation 1 is expressed by the following equation.

  Thus, in Equation 3, the resonance angular frequency ωn can be changed only by changing the strut upper end bush equivalent spring constant K_strut or the lower arm bush equivalent spring constant K_lwr. However, the degree of freedom for changing the strut upper end bush equivalent spring constant K_strut and the lower arm bush equivalent spring constant K_lwr is small considering the riding comfort during vehicle travel. On the other hand, in Equation 2, the resonance angular frequency ωn can be changed by changing the absorber friction equivalent spring constant K_ab. For this reason, the suspension structure 12 according to the present embodiment can change the resonance angular frequency ωn with a wide degree of freedom.

  FIG. 3 is a diagram showing (second output F2) / (input F0) when the resonance angular frequency ωn is changed. In FIG. 3, the horizontal axis is the resonance angular frequency ωn, and the vertical axis is (second output F2) / (input F0), that is, the transmission rate of vibration in the second transmission path R2. In FIG. 3, a phase region is provided on the upper vertical axis for reference, and the phase change is also shown.

  Thus, by changing the absorber friction equivalent spring constant K_ab, the resonance angular frequency ωn, such as ωn1, ωn2, and ωn3, can be changed. In the example shown in FIG. 3, when the resonance angular frequency ωn is ωn2, the second output is resonated in an engine speed range that can be set as the engine speed during idling (hereinafter referred to as “idling speed range”). F2 increases. By changing the absorber friction equivalent spring constant K_ab, the resonance angular frequency ωn can be made larger than the idling rotational speed range as ωn1, and the resonant angular frequency ωn can be made larger than the idling rotational speed range as ωn1. Can also be reduced.

  When the resonance angular frequency ωn is higher than the idling rotational speed range, such as ωn1, the phase of the second output F2 remains zero in the idling rotational speed range, that is, remains in phase with the input F0. However, when the resonance angular frequency ωn is lower than the idling rotational speed range as in ωn3, the phase of the second output F2 is minus 180 °, that is, opposite to the input F0 in the idling rotational speed range. .

  FIG. 4A is a diagram showing a conventional vibration level of vibration transmitted to the body 14 when the input speed F0 is changed by changing the engine speed when a conventional absorber is employed. 4 (b) is a diagram showing the vibration level of vibration transmitted to the body 14 when the input speed F0 is changed by changing the engine speed when the absorber 38 according to the present embodiment is employed.

  4A and 4B, the horizontal axis represents the engine speed (rpm) and the vertical axis represents the vibration level (dB). The vibration level in FIGS. 4 (a) and 4 (b) refers to the amplitude expressed in dB (decibel). 4A and 4B, a line indicated by a two-dot chain line indicates the first output F1, and a line indicated by a broken line indicates the second output F2. A solid line indicates a vibration output (hereinafter referred to as “composite output”) F1 + F2 obtained by combining the first output F1 and the second output F2.

  As shown in FIG. 4A, in the conventional absorber, the combined output F1 + F2 has a larger value than the first output F1 over substantially the entire idling speed range. Therefore, the vibration level is worse than that of the first output F1 by the area Q1 indicated by the oblique lines.

  This is mainly because the second output F2 has a resonance point at an engine speed higher than the idling speed range, and the first output F1 and the second output F2 are in phase. . Since the first output F1 and the second output F2 have the same phase as described above, the second output F2 cannot cancel the first output F1, and conversely, the second output F2 is added to the first output F1. As a result, the combined output F1 + F2 has a high value.

  Further, the fact that the second output F2 has a resonance point in the vicinity of the highest engine speed in the idling speed range is one factor that causes the combined output F1 + F2 to have a high value. By placing the resonance point at such a location, the second output F2 becomes a high value in the idling rotational speed range. Therefore, the value of the second output F2 applied to the first output F1 in the idling rotation speed range is a high value, and the combined output F1 + F2 is a higher value.

  On the other hand, as shown in FIG. 4B, in the absorber 38 according to the present embodiment, the combined output F1 + F2 is smaller in value than the first output F1 in substantially the entire idling speed range. The sliding resistance is adjusted in advance. Since the absorber 38 has such a sliding resistance, in the example shown in FIG. 4B, the vibration level is improved as compared with the first output F1 by the region Q2 indicated by hatching.

  Specifically, as shown in FIG. 4B, the absorber 38 according to the present embodiment has a sliding resistance so that the resonance point is located at an engine speed at which the second output F2 is lower than the idling speed range. Is adjusted in advance. As a result, the first output F1 and the second output F2 are in opposite phases over substantially the entire idling speed range. Accordingly, the second output F2 can cancel the first output F1 in the idling rotation speed range, and the combined output F1 + F2 in the idling rotation speed range can be set to a low value.

  Furthermore, as shown in FIG. 4B, the absorber 38 according to the present embodiment has a sliding resistance adjusted in advance so that the second output F2 has a resonance point near the lowest engine speed in the idling speed range. Has been. By placing the resonance point at such a location, the second output F2 can be made high in the idling rotational speed range. For this reason, in the idling rotation speed range, the second output F2 can be canceled with a large value, and the combined output F1 + F2 can be reduced.

  The present invention is not limited to the above-described embodiment, and an appropriate combination of the elements of the embodiment is also effective as an embodiment of the present invention. Various modifications such as design changes can be added to the embodiments based on the knowledge of those skilled in the art, and embodiments to which such modifications are added can be included in the scope of the present invention. Here are some examples.

  In a modification, the sliding resistance of the absorber 38 using the vibration transmissibility in the first transmission path R1 instead of the first output F1, and using the vibration transmissibility in the second transmission path R2 instead of the second output F2. decide. In this modified example, the vibration transmission rate from the engine 16 to the body 14 in the first transmission path R1 is larger than the vibration transmission rate from the engine 16 in the first transmission path R1 to the body 14 in almost the entire idling speed range. The absorber 38 has a sliding resistance set so that the vibration transmission rate to the body 14 is lower.

  Also in this modification, in order to achieve the sliding resistance as described above, the vibration transmission rate from the engine 16 to the body 14 in the second transmission path R2 is near and low in the lowest engine speed in the idling speed range. The absorber 38 has a sliding resistance set so as to have a resonance point at the rotational speed. Thus, even if the vibration transmissibility is used, vibration transmitted from the engine 16 to the body 14 during idling can be suppressed.

It is a figure showing typically a vehicle provided with a suspension structure concerning this embodiment. It is a figure which shows still more typically the vehicle provided with the suspension structure which concerns on this embodiment. It is a figure which shows (2nd output F2) / (input F0) when changing resonance angular frequency (omega) n. (A) is a figure which shows the conventional vibration level of the vibration transmitted to a body when changing engine speed and changing input F0 in the case of employ | adopting the conventional absorber, (b). FIG. 5 is a diagram showing the vibration level of vibration transmitted to the body when the input speed F0 is changed by changing the engine speed when the absorber according to the present embodiment is employed.

Explanation of symbols

  10 vehicle, 12 suspension structure, 14 body, 16 engine, 18 transmission unit, 20 drive shaft, 22 first bush, 24 second bush, 26 third bush, 28 engine unit, 30 knuckle, 32 wheels, 34 tire, 36 Wheel, 38 absorber, 40 fourth bush, 42 lower arm, 44 fifth bush.

Claims (2)

A suspension structure for a vehicle including an absorber interposed between a main body housing provided with a cabin and a wheel support member for supporting a wheel,
The absorber is
In a vehicle having a structure in which an engine unit including an engine and a transmission unit fixed to the engine is attached to a main body housing via an attachment portion, and the transmission is connected to a wheel support member via a drive shaft,
A transmission path of vibration transmitted from the engine to the main body casing via the mounting portion is defined as a first transmission path, and is transmitted from the engine to the main body casing via the transmission unit, the drive shaft, the wheel support member, and the absorber. When the vibration transmission path is the second transmission path, the amplitude of vibration transmitted from the engine to the main body housing via the first transmission path in substantially the entire idling speed range that can be set as the engine speed during idling. Rather, the amplitude of the vibration obtained by combining the vibration transmitted from the engine via the first transmission path to the main body casing and the vibration transmitted from the engine via the second transmission path to the main body casing is lower. A suspension structure for a vehicle having a sliding resistance set as described above.   The absorber has a resonance point where the relationship between the amplitude of the vibration transmitted from the engine to the main body housing through the second transmission path and the engine speed is near the lowest engine speed and the lower engine speed in the idling engine speed range. The vehicle suspension structure according to claim 1, wherein the vehicle has a sliding resistance set to have

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