JP6644409B2 - Power unit support structure - Google Patents

Description

  The present invention relates to a power unit support structure that couples an engine, a transmission, and a differential and supports a power unit that is disposed in a front-rear direction in an engine room of a vehicle.

  BACKGROUND ART Conventionally, in order to reduce the weight of a power unit in a cab-over type vehicle such as an automobile, an engine, a transmission, and a differential device are combined into a unit, and the unit is vertically installed in an engine room at a front portion of the vehicle in a front-rear direction. ing. In addition, in this type of front engine / front drive (FF) type vertical power unit structure, cushioning mounts support the side or front of the differential to reduce the effect of tire rotational reaction. Has been proposed (for example, see Patent Document 1).

Japanese Patent No. 29297794 (see paragraphs 0012 to 0021 and FIGS. 1 to 4)

  Meanwhile, in the case of a structure in which an engine, a transmission, and a differential device are combined and vertically arranged in an engine room in the front-rear direction as in Patent Literature 1, as shown in FIG. Generally, E is supported by a front mount FM and a rear mount RM having resiliency, and a tire drive reaction force is absorbed by the front mount FM, and an engine drive reaction force is absorbed by the rear mount RM. . In addition, in FIG. 3, T is a transmission.

  As shown in FIG. 3, in the case of a vertical power unit in which the engine E, the transmission T, and the differential device D are combined, since the center of gravity G1 of the engine E is normally in the upper position, the center of gravity G1 of the engine E is The angle α formed by the inertia main axis Ia of the unit connecting the transmission T and the combined center of gravity G2 of the differential gear D with the elastic main axis Ea becomes large, so that the vibration during traveling becomes large, which causes a reduction in NV performance.

Here, the angle between the torque roll axis Ta, which is the axis of the unit when the torque is generated about the crankshaft, and the inertia main axis Ia is β, and the relationship between the torque roll axis Ta and the inertia main axis Ia is the inertia. The main axis Ia is the X axis, the axis perpendicular to the X axis is the Z axis, the roll inertia moment in the X axis direction is Ix, the yaw inertia moment in the Z axis direction is Iz, and the angle formed by the inertia main axis Ia and the crankshaft axis is γ. As
tanβ = (Ix / Iz) · tanγ (1 formula)
The torque roll axis can be calculated from this (Equation 1). Note that, in the case of a vertical power unit in which the engine E, the transmission T, and the differential device D are combined, the angle β becomes smaller because Iz >> Ix usually holds.

  As described above, in the vertical type power unit as shown in FIG. 3, in order to absorb a large vibration caused by the large angle α, both mounts FM and RM, particularly the rear mount RM, have a soft spring characteristic with a small spring constant. It is common to adopt one.

  However, if a soft spring characteristic having a small spring constant is adopted as the mounts FM and RM, there is a disadvantage that the durability of the mounts FM and RM is reduced and the life is shortened. Further, a tire driving reaction force is added to the driving reaction force of the engine as a problem peculiar to the vertical type unit. However, there is a problem that the tire FM cannot sufficiently be absorbed by the mount FM having a small spring constant.

  The present invention makes it possible to use a mount having a large spring constant and a hard spring characteristic as a mount for supporting a so-called vertical-type power unit in which an engine, a transmission, and a differential device are coupled, thereby extending the life of the mount. The purpose is to.

In order to achieve the above object, the power unit support structure of the present invention is a power unit support structure that supports a power unit in which an engine, a transmission, and a differential device are coupled and arranged in a front-rear direction in an engine room of a vehicle. A front mount and a rear mount that respectively support the differential device and the engine, and a main shaft of inertia of a unit that connects a center of gravity of the engine to a combined center of gravity of the transmission and the differential device; and a crankshaft of the engine. The rear mount is used to support the engine in a slanted state so that the torque roll axis, which is the axis of the unit when torque is generated, coincides with the axis .

According to the present invention, an inertia main axis of a unit that connects a center of gravity of an engine with a combined center of gravity of a transmission and a differential, and a torque roll axis that is an axis of the unit when torque is generated around an engine crankshaft. By supporting the engine in a slanted state by the rear mount so that the two parts coincide with each other, the center of gravity of the engine can be lowered, and the inertia main shaft can be brought closer to the torque roll shaft. The front mount and the rear mount that support each can adopt hard spring characteristics with a large spring constant, which can extend the life of the mount, and reduce the tire driving reaction force peculiar to the vertical type power unit. It can be sufficiently absorbed.

It is a side view of one Embodiment of the support structure of the power unit which concerns on this invention. It is an operation explanatory view of one embodiment. It is operation | movement explanatory drawing of a prior art example.

  One embodiment of a power unit support structure according to the present invention will be described in detail with reference to FIGS.

  As shown in FIG. 1, a power unit U according to the present embodiment includes an engine E, a transmission T, and a differential device D which are connected to an engine room below a seat 2 installed in a cabin of a cab-over type vehicle 1. It is a vertical structure of a front engine / front drive (FF) type arranged in the direction.

  As shown in FIG. 2, the differential device D and the engine E are supported by a front mount FM and a rear mount RM, respectively. In particular, the rear mount RM is the same as that of the conventional engine E shown by a dashed line in FIG. The engine E is supported in a state where the center of gravity of the engine E is lowered by slanting from the position. At this time, the main axis of inertia IA of the unit U connecting the center of gravity G1 of the engine E and the combined center of gravity G2 of the transmission T and the differential device D is set to the torque roll axis Ta determined by the angle β obtained by the calculation of the above (Equation 1). The engine E is slanted so as to match.

  In this manner, when the engine E is slanted and supported by the rear mount RM, the center of gravity G1 of the engine can be lowered from the state of the dashed line in FIG. 2 to the state of the solid line, and the main shaft of inertia in the roll direction and the crankshaft axis. IA can be made to substantially match, and as a result, the main inertia axis IA can be made to substantially match with the crankshaft axis and the torque roll axis Ta.

  Therefore, according to the above-described embodiment, the angle β formed by the two axes Ta and IA becomes zero due to the coincidence between the torque roll axis Ta and the inertia main axis IA, and the angle α1 formed by the inertia main axis IA with the elastic main axis Ea is also shown in FIG. 2 is much smaller than the angle α in the conventional structure shown by the one-dot chain line (α1 <α), the tire driving reaction force can be received by the front and rear long-span mounts FM and RM, and the front mount FM Without increasing the position of the rear mount RM or the position of the rear mount RM, it is possible to maximize the engine room and the occupant accommodation space below the seat 2 of the vehicle 1.

  Further, the vibration can be greatly suppressed by the coincidence between the torque roll axis Ta and the inertia main axis IA, the NV performance (noise vibration performance) of the vehicle 1 can be improved, and both mounts FM and RM have a large spring constant and are hard. The use of spring characteristics can extend the life of the mounts FM and RM.

  Further, by matching the torque roll axis Ta, the inertia main axis IA, and the crankshaft axis, the elastic main axis Ea can be disassembled by disassembling the six degrees of freedom of the roll direction elastic axis, the yaw direction elastic axis, and the pitch direction elastic axis, The rigid resonance frequency can be reduced while the rigid resonance of the power unit U is not coupled. As a result, the idling rotational speed of the vehicle 1 can be reduced to achieve low fuel consumption.

  The present invention is not limited to the above-described embodiment, and various changes other than those described above can be made without departing from the gist of the present invention. For example, in the above embodiment, the engine E is slanted so that the main axis of inertia IA coincides with the torque roll axis Ta. However, the main axis of inertia IA does not necessarily need to coincide with the torque roll axis Ta, and The engine E may be slanted so that the angle β formed with the roll axis Ta is reduced.

  Further, in the above-described embodiment, an example in which the present invention is applied to a small cab-over type vehicle has been described. However, the present invention is not limited to a small vehicle, but may be applied to other vehicles that need to be expanded such as occupant accommodation spaces. Can be applied.

DESCRIPTION OF SYMBOLS 1 ... Vehicle E ... Engine T ... Transmission D ... Differential device IA ... Inertial spindle FM ... Front mount RM ... Rear mount

Claims (1)

In a power unit supporting structure in which an engine, a transmission and a differential device are combined and a power unit is disposed in a front-rear direction in an engine room of a vehicle,
A front mount and a rear mount supporting the differential and the engine, respectively.
The inertia main axis of the unit connecting the center of gravity of the engine with the combined center of gravity of the transmission and the differential gear coincides with the torque roll axis, which is the axis of the unit when torque is generated around the crankshaft of the engine. A support structure for the power unit, wherein the engine is supported in a slanted state by the rear mount.

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