JP2013154789A - Support structure of power plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce idling vibration by restraining vehicle body vibration caused by the roll resonance of a power plant at an idling time, in a vehicle of an FF system mounted with a few-cylinder engine.SOLUTION: On assumption that a vehicle 1 of a front engine and a front drive system in which a power plant 2 formed by connecting an engine 3 and a transmission 4 to each other is elastically supported by a vehicle body through engine mounts 5 to 7, in the engine 3, a primary explosion frequency in idling speed is in such a range of being around the roll resonance of the power plant 2, and vibration transmissibility becomes larger than one, and an elastic roll shaft A2 of a power plant 2 is arranged at an predetermined distance offset to a vehicle front side from a torque roll axis A1 of the power plant 2.

Description

  The present invention relates to a structure for supporting a power plant including an engine, a transmission, and the like. In particular, the present invention relates to a power plant support structure in an FF vehicle that is disposed horizontally with respect to the front-rear direction of the vehicle.

  Conventionally, as a support structure for this type of power plant, an engine mount that supports the left and right sides of the power plant is arranged on or near the vertical plane including the torque roll shaft of the power plant, and the torque reaction force of the power plant is arranged. An engine mount for absorbing is disposed in front of or behind the power plant.

  Generally, this type of power plant support structure is configured so that the torque roll shaft and the elastic roll shaft of the power plant coincide with each other in plan view. When the roll vibration force is generated in the engine, the vertical vibration is reduced and the vertical vibration is difficult to be excited.

  Here, the torque roll shaft and the elastic roll shaft will be briefly described. When the engine is exploded and torque is applied to the crankshaft, the power plant tries to be rotated by the reaction force, and the rotation shaft at that time is the torque roll shaft. Further, when the power plant is elastically supported by the engine mount, the power plant can be elastically rotated, but the rotation axis at that time is the elastic roll shaft. The elastic roll shaft is determined by the arrangement of each engine mount, the elastic coefficient, and the like. The torque roll shaft passes through the center of gravity of the power plant.

  In Patent Document 1, the left and right engine mount positions are arranged slightly ahead of the vertical plane including the inertia main shaft (inertial main shaft close to the torque roll shaft), and the spring constant of the rear engine mount is determined from the spring constant of the front engine mount. In the plan view, the main axis of inertia of the power plant and the elastic roll axis are made to coincide with each other. According to this power plant support structure, the two-node bending vibration of the vehicle body is suppressed, and the engine roll vibration and the vertical vibration are decoupled.

  Patent Document 2 discloses a configuration in which at least one of the left and right engine mounts is offset from the inertial main shaft of the power plant (inertial main shaft close to the torque roll shaft) at the rear of the vehicle. In this power plant support structure, the engine roll vibration and the vertical vibration are coupled to excite the vertical vibration, thereby suppressing the two-node bending vibration of the vehicle body.

  Patent Document 3 discloses a configuration in which left and right engine mount positions are arranged on the vehicle rear side with respect to an inertia main shaft (an inertia main shaft close to a torque roll shaft). In this power plant support structure, the two-node bending vibration of the vehicle body and the pitching during acceleration / deceleration of the vehicle are suppressed in a well-balanced manner.

Japanese Patent Laid-Open No. 11-28937 Japanese Patent Laid-Open No. 2005-319979 Japanese Patent Laid-Open No. 11-11159

  In recent years, as fuel efficiency competition progresses in the automobile industry, there is an expectation for automobiles equipped with a small cylinder engine (for example, a two-cylinder engine) with little mechanical loss. However, a 2-cylinder engine (or a single-cylinder engine) has a larger displacement per cylinder than a 3-cylinder engine and the like, and vibration input from the engine to the vehicle body increases. Further, in a small cylinder engine, the combustion frequency (combustion angle period 720 ° CA / reciprocal of time corresponding to the number of cylinders n) is low, and idling occurs near the roll resonance frequency of the elastically mounted power plant. There is a concern that the vibration during idling deteriorates.

  The techniques disclosed in Patent Literatures 1 to 3 are for suppressing the two-node bending resonance of the vehicle body, which is a region where the resonance frequency is relatively high (about 20 Hz to 27 Hz), and the region where the resonance frequency is lower than that. The roll resonance (engine roll resonance) of the power plant that is (about 12 to 17 Hz) cannot be suppressed. Therefore, the effect of suppressing idle vibration cannot be expected for a vehicle having a low combustion frequency and fearing the occurrence of roll resonance of the power plant during idling, such as an automobile equipped with a small cylinder engine.

  The present invention was devised in view of such problems, and in an FF vehicle equipped with a small cylinder engine, idle vibration can be reduced by suppressing vehicle body vibration due to power plant roll resonance during idling. It aims at providing the support structure of a power plant.

  The power plant support structure according to the present invention is based on the premise that the power plant in which the engine and the transmission are connected to each other is elastically supported by the vehicle body via an engine mount in a front engine / front drive type vehicle. Is included in the range (amplification region) where the primary explosion frequency at the idle rotation speed is in the vicinity of the roll resonance frequency of the power plant and the vibration transmissibility is greater than 1. The elastic roll shaft of the power plant is offset from the torque roll shaft of the power plant by a predetermined distance on the vehicle front side.

  Desirably, the engine in which the primary explosion frequency at the idle speed is in the vicinity of the roll resonance frequency of the power plant and the vibration transmissibility is greater than 1 is a two-cylinder engine.

  According to the power plant support structure having the above-described configuration, the elastic roll shaft of the power plant is offset from the torque roll shaft of the power plant by a predetermined distance to the front side of the vehicle. The vertical inertia force is generated by the force, and the pitching vibration excited by the roll vibration force on the vehicle body and the pinching vibration excited by the vertical inertia force on the vehicle body are in a mutually canceling relationship. Thus, the generation of vehicle body vibration due to roll resonance of the power plant is prevented, and in a vehicle equipped with an engine having a low combustion frequency, idle vibration caused by roll resonance of the power plant can be reliably suppressed during idling.

  According to the power plant support structure of the present invention, the engine in which the primary explosion frequency at the idling speed is in the vicinity of the roll resonance frequency of the power plant and the vibration transmissibility is greater than 1 is mounted. In the vehicle, vehicle vibration during idling can be suppressed.

It is a top view which shows the support structure of the power plant which concerns on embodiment of this invention. It is a left view which shows the support structure of the power plant which concerns on embodiment of this invention. It is explanatory drawing for demonstrating the pitching vibration of a vehicle. It is a top view which shows the support structure of the power plant which concerns on other embodiment of this invention.

  Hereinafter, a power plant support structure according to an embodiment of the present invention will be described with reference to the drawings. Note that “front” added to the coordinate axes in the figure indicates the front of the vehicle, “right” indicates the right side of the vehicle, and “upper” indicates the upper side of the vehicle.

  FIG. 1 is a plan view showing a power plant support structure in a vehicle 1 of a front engine / front drive system. The power plant 2 is configured by connecting a two-cylinder engine 3 and a transmission 4 and is disposed laterally with respect to the longitudinal direction of the vehicle. That is, the power plant 2 is arranged such that the crankshaft (not shown) of the engine 3 is directed in a direction substantially perpendicular to the vehicle front-rear direction (vehicle width direction). The transmission 4 is disposed on the left side of the engine 3. In the figure, “G” indicates the center of gravity of the power plant 2, “A 1” indicates the torque roll axis of the power plant 2, and “A 2” indicates the elastic roll axis of the power plant 2.

  The power plant 2 is elastically supported by three engine mounts 5 to 7 installed on a body frame 8 (vehicle body) of the vehicle 1, that is, a left engine mount 5, a right engine mount 6, and a rear engine mount 7. The body frame 8 shown in FIG. 1 includes left and right side members 8a and 8b extending in the front-rear direction of the vehicle, and a cross member 8c constructed between the side members 8a and 8b. The left and right engine mounts 5 and 6 are provided on the left and right side members 8a and 8b, respectively, and the rear engine mount 7 is provided on the cross member 8c. The rear engine mount 7 is mainly for absorbing the torque reaction force of the power plant 2, and is disposed behind the power plant 2. In the present embodiment, a so-called torque rod that includes a rod member is employed.

  The engine 3 is a two-cylinder engine in which the primary explosion frequency at the idle speed is in the vicinity of the roll resonance frequency of the power plant 2 and the vibration transmissibility is greater than 1.

  The left engine mount 5 and the right engine mount 6 mainly support the static load of the power plant 2, and both of them have a predetermined distance ΔI (about the predetermined distance ΔI from the vertical plane including the torque roll axis A 1 of the power plant 2. (It will be described in detail later.) It is disposed at a position offset to the front side of the vehicle. Thus, the elastic roll shaft A2 of the power plant 2 is offset from the torque roll shaft A1 of the power plant 2 by a predetermined distance from the vehicle front side by ΔI. The offset arrangement of the elastic roll axis A2 of the power plant 2 with respect to the torque roll axis A1 is maintained so that the elastic roll axis A2 and the torque roll axis A1 are overlapped when viewed from the front of the vehicle.

  According to the power plant support structure thus configured, it is possible to suppress vehicle vibration during idling. That is, as shown in FIG. 2, the elastic roll shaft A2 of the power plant 2 is offset from the torque roll shaft A1 of the power plant 2 by a predetermined distance by ΔI to the front side of the vehicle. And the vertical vibration come to be coupled. That is, the vertical inertia force F is generated by the roll vibration force T1 around the elastic roll axis A2. Then, when the offset amount ΔI of the elastic roll axis A2 of the power plant 2 is a predetermined value, the pitching vibration shown in FIG. The pinching vibration shown in 3 (b), in which the vertical inertia force F is excited with respect to the vehicle body of the vehicle 1, has a reverse phase and the same amplitude, and constantly cancels out. Thereby, generation | occurrence | production of the vehicle body vibration by roll resonance of the power plant 2 is prevented. As a result, in a vehicle equipped with the two-cylinder engine 3 having a low combustion frequency, idle vibration caused by roll resonance of the power plant 2 can be reliably suppressed during idling. In FIG. 3, “C” indicates the position of a pitching vibration node.

  The offset amount ΔI (the predetermined distance ΔI) of the elastic roll shaft A2 of the power plant 2 can be obtained by experiments. That is, a plurality of level values (for example, ΔIx = 0 mm, 5 mm, 10 mm, 15 mm, 20,...) Are set in advance as the offset amount ΔIx of the elastic roll axis A2 of the power plant 2, and idle operation is performed for each level value. Go and measure the floor vibration value of the car body. Then, the range of the offset amount ΔIx having a large vibration reduction effect is obtained from the relationship between the obtained vehicle body floor vibration value and the offset amount ΔIx, and the range of the offset amount ΔIx that is clearly judged to have the reduction effect (for example, the offset amount ΔIx) = 0 mm, the range of the offset amount ΔIx where the vibration level is lower by 5 dB or more can be set as the predetermined distance ΔI.

<Other embodiments>
In the embodiment described above, the left and right engine mounts 5 and 6 are powered by the elastic roll shaft A2 of the power plant 2 so as to be offset from the torque roll shaft A1 of the power plant 2 by a predetermined distance ΔI toward the vehicle front side. Although it has been offset from the vertical plane including the torque roll axis A1 of the plant 2 by a predetermined distance ΔI to the front side of the vehicle, the elastic roll axis A2 of the power plant 2 is more than the torque roll axis A1 of the power plant 2 by other configurations. Alternatively, it may be offset by a predetermined distance on the vehicle front side by ΔI.

  For example, as in the vehicle 1A shown in FIG. 4, the left and right engine mounts 5 and 6 are disposed on the vertical plane including the torque roll axis A1 of the power plant 2 while the left and right sides are disposed on the vehicle front side of the power plant 2. A cross member 8d is further installed between the members 8a and 8b, and a front engine mount 9 (torque rod) for elastically supporting the power plant 2 is provided on the cross member 8d. The spring constants of the front and rear engine mounts 7 and 9 are appropriately set. By defining, the elastic roll axis A2 of the power plant 2 can be offset to the vehicle front side by ΔI from the torque roll axis A1 of the power plant 2 by a predetermined distance. Even with such a configuration, the same effects as those of the above-described embodiment can be obtained. In addition, about the structure similar to the vehicle 1 demonstrated based on FIG. 1, the same code | symbol is attached | subjected in FIG.

  In the above-described embodiment, a two-cylinder engine has been described as an example of the engine 3 constituting the power plant 2. However, the engine 3 has an explosion primary frequency at the idle rotation speed of the roll of the power plant 2. A single-cylinder engine or a three-cylinder engine may be used as long as it is in the vicinity of the resonance frequency and within a range where the vibration transmissibility is greater than 1.

  The present invention can be applied to, for example, a power plant support structure for an FF vehicle equipped with a two-cylinder engine.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Power plant 3 Engine 4 Transmission 5 Left engine mount 6 Right engine mount 7 Rear engine mount 9 Front engine mount A1 Torque roll shaft A2 Elastic roll shaft

Claims (2)

In a front engine / front drive type vehicle, in a power plant support structure in which a power plant formed by connecting an engine and a transmission is elastically supported by a vehicle body via an engine mount,
The engine includes an explosion primary frequency at an idle rotation speed in the vicinity of a roll resonance frequency of a power plant and a vibration transmissibility larger than 1.
The power plant support structure is characterized in that the elastic roll shaft of the power plant is offset from the torque roll shaft of the power plant by a predetermined distance on the vehicle front side. The power plant support structure according to claim 1,
A power plant in which the primary explosion frequency at the idle speed is in the vicinity of the roll resonance frequency of the power plant and the vibration transmissibility is greater than 1 is a two-cylinder engine. Support structure.