VEHICULAR ENGINE AND POWER TRAIN MOUNTING ARRANGEMENT

Abstract: A mounting arrangement for an automotive vehicle includes a transverse engine having a crankshaft an axis of which extends transversely to a longitudinal axis of the vehicle, a gear train (4) of a transmission having an axis (Z) which extends in parallel with the axis (X) of the engine crankshaft, and a differential gear unit having an axis (Y) which extends in parallel to the axes of the engine crankshaft and the transmission gear train. The axis of the engine crankshaft is located rearward of the axis of the transmission gear train and over the axis of the differential gear unit, and the axis of the differential gear unit is located rearward of the axis of the transmission gear train. Further, the engine has cylinders which are inclined forward.

Description: The invention relates to a power train arrangement for an automotive vehicle as indicated in the precharacterizing part of claim 1. A mounting arrangement for an automotive vehicle with transversely disposed engine, transmission and differential gear unit according to the preamble of claim 1 is known in the art as disclosed, for example, in DE-A-19 63 019. In the prior art arrangement according to US-A-4 223 569 and engine is disposed at the front of a front wheel or four wheel drive vehicle with an axis of an engine crankshaft extending transversely to a longitudinal axis of the vehicle. A torque converter is arranged adjacent to the engine with its axis being aligned with the axis of the engine crankshaft for a power transmission therefrom. At the front of the engine and the torque converter, a gear train of a transmission is disposed with its axis parallel to the axis of the engine crankshaft or the torque converter. An output power of the torque converter is transmitted to an input shaft of the transmission gear train by means of a sprocket-chain connection therebetween. Further, a differential gear unit is disposed at the rear of the transmission gear train and the engine with its axis being aligned with the axis of the transmission gear train for a power transmission therefrom. In the above-noted mounting arrangement, however, since the transmission gear train and the differential gear unit are transversely arranged with their axes being aligned with each other, a degree of freedom for mounting other vehicular components, such as various components of a suspension system, is so limited in a transverse or width direction of the vehicle. Further, when the above-noted mounting arrangement is applied to a four wheel drive vehicle, a transfer unit is further disposed adjacent to the differential gear unit with its axis being aligned with the axis of the differential gear unit for a power transmission therefrom. Accordingly, a location of the transfer unit is caused to be offset or deviated laterally from the lateral center of the vehicle. The transfer unit controls a power distribution to be transmitted to rear wheels through a propeller shaft and a rear wheel differential gear unit. The propeller shaft extends axially between the transfer unit and the rear wheel differential gear unit. As a result, the propeller shaft is inevitably offset or deviated laterally from the lateral center of the vehicle, so that no space for a brake pedal is provided at one lateral side of the vehicle due to existence of a floor projection or tunnel for accommodating the offset propeller shaft underneath a vehicle floor. Accordingly, a problem has been raised that the same layout of the foregoing vehicular components can not satisfy both right and left steering wheel vehicles due to no space of the brake pedal at the one lateral side of the vehicle. On the other hand, if the differential gear unit is disposed at the rear of the transmission gear train so as to arrange the propeller shaft to extend axially at the lateral center of the vehicle, a problem is raised that a weight distribution to front wheels increases to deteriorate controllability of the steering wheel as well as durability of front tires due to an inevitable forward location change of the engine, which location is far forward of axes of the front wheels, and due to a corresponding increased front overhang. Another mounting arrangement has been proposed, wherein the axis of the engine crankshaft is arranged above and forward of the axis of the transmission gear train, and the axis of the differential gear unit is arranged rearward of and level with the axis of the transmission gear train. In this arrangement, however, since the engine is still inevitably located considerably forward of the axes of the front wheels, a corresponding large weight distribution to the front wheels as well as the corresponding increased overhang are resulted. In addition, since the engine is located substantially over the transmission gear train, a higher engine hood line is resulted to narrow front visibility, and further, insufficient space for an engine oil pan is resulted. Therefore, it is the object of the invention to provide a power train arrangement of a vehicular engine that can increase a degree of freedom for mounting other vehicular components, such as, various components of a suspension system in a transverse or width direction of the vehicle. This object is solved by the features as claimed in the characterizing part of claim 1. In accordance with the invention a mounting arrangement of a vehicular engine and an associated power train is provided that, when applied to a four wheel drive vehicle, can prevent a lateral deviation or offset of a location of a propeller shaft from the lateral centre of the vehicle, that can minimize a weight distribution to front wheels as well as a front overhang while satisfying other requirements, and that can allow a lower engine hood line while satisfying other requirements. The present invention will be understood more fully from the detailed description given hereinbelow and from the accompanying drawings of the preferred embodiment of the invention, which are given by way of example only, and are not intended to be limitative of the present invention. In the drawings: Fig. 1 is a schematic diagram viewing from a left side of a vehicle and showing relative locations of vehicular components according to a preferred embodiment of the present invention; Fig. 2 is a schematic plan view of Fig. 1; and Fig. 3 is a graph showing resonance frequencies derived by the preferred embodiment of Fig. 1 and the background art, relative to engine revolution speed and secondary engine vibration frequency. DESCRIPTION OF THE PREFERRED EMBODIMENT Now, a mounting arrangement of an engine and an associated power train for an automotive vehicle according to a preferred embodiment of the present invention will be described hereinbelow with reference to Figs. 1 and 2. Figs. 1 and 2 respectively show a front side of a four wheel drive vehicle. At a front and left side of a ladder type sub-frame 2 is mounted a gear train 4 of a transmission with its axis Z extending transversely to a longitudial axis of the vehicle or extending in a width direction of the vehicle. An oil pump 6 is further provided underneath the transmission gear train 4. A reference numeral 8 designates a radiator which is arranged forward of the sub-frame 2. A differential gear unit 10 is mounted rearward of the transmission gear train 4 at a left side of the vehicle with its axis Y extending in parallel with the axis Z of the transmission gear train 4. The differential gear unit 4 is connected to the transmission gear train 4 through an idler gear unit 12 for a power transmission from the transmission gear train 4. An engine 14 is disposed with an axis X of an engine crankshaft extending in parallel with the axes Y and Z of the respective differential gear unit 10 and transmission gear train 4. The axis X of the engine crankshaft is located rearward of the axis Z of the transmission gear train 4 and above the axis Y of the differential gear unit 10 substantially in a vertical direction. The engine 14 is a six-cylinder in-line type engine with the cylinders 16 inclined forward and is supported by the sub-frame 2 through four engine mountings 18 one of which is illustrated in detail in a circle in Fig. 1 as an example. An engine oil pan 20 is fixed to a slanted rear end or lower end of a cylinder block. Space for the engine oil pan 20 is sufficiently ensured due to the forward inclined arrangement of the engine cylinders 16. Reference numerals 22 and 24 respectively show a lower link and a tension rod of a suspension unit which is provided at both lateral sides of the sub-frame 2. A torque converter 26 is provided on the left of the engine 14 with its axis being aligned with the axis X of the engine crankshaft for a power transmission from the latter. The torque converter 26 and the transmission gear train 4 are connected through, for example, a sprocket-chain connection 27 therebetween. A transfer unit 28 is further disposed on the right of the differential gear unit 10 with its axis being aligned with the axis Y of the differential gear unit 10 for a power transmission from the latter. The transfer unit 28 controls a power distribution to be transmitted to rear wheels through a propeller shaft 30 and a rear wheel differential gear unit (not shown). As seen from Fig. 2, the propeller shaft 30 extends axially rearward from the transfer unit 28 at the lateral center of the vehicle. Reference numerals 32 and 34 respectively denote a brake pedal and an accelerator pedal, and reference numerals 36 and 38 denote a rack-and-pinion steering gear of a steering mechanism. In the preferred embodiment as described above, since the axes X, Y and Z of the engine crankshaft, the differential gear unit 10 and the transmission gear train 4 are arranged in parallel with one another, a degree of freedom for the layout in the width direction of the vehicle is increased. Accordingly, the layout of, for example, the lower link 22 and the tension rod 24 of the suspension system becomes more flexible. Further, an engine having a larger number of cylinders, such as, an eight-cylinder in-line type engine can be easily installed. Further, since the transfer unit 28 can be arranged at the lateral center of the vehicle, the propeller shaft 30 can also be arranged to extend axially rearward from the transfer unit 28 at the lateral center of the vehicle. Accordingly, sufficient space for the brake pedal 32 and the accelerator pedal 34 is ensured at both lateral sides of the vehicle. Further, since the axis X of the engine crankshaft is located rearward of the axis Z of the transmission gear train 4, a weight distribution to front wheels is made less in comparison with the aforementioned background art to improve controllability of the steering wheel as well as the durability of the front tires. Still further, the rearward location of the axis X of the engine crankshaft relative to the axis Z of the transmission gear train 4 allows the engine cylinders 16 to be inclined forward in view of the front overhang, so that a lower engine hood line is successfully attained. Further, since the relative location of the engine 14 as described above as well as the forward inclined arrangement of the engine cylinders 16 allow the cylinder block of the engine 14 to be fixedly connected to a casing of the transmission gear train 4 and to a casing of the differential gear unit 10 in addition to a secure connection to a casing of the torque converter 26, a connection rigidity of the engine 14 with the foregoing associated components becomes large enough to shift a resonance frequecy out of a frequency band of a secondary engine vibration derived by a practical engine revolution speed range, which is illustrated in Fig. 3. In Fig. 3, a point A shows a resonance frequency derived in the aforementioned preferred embodiment, and a point B shows a resonance frequency derived in the aforementioned background art in which the axis of the engine crankshaft is arranged above and forward of the axis of the transmission gear train, and the axis of the differential gear unit is arranged rearward of and level with the axis of the transmission gear train. As clearly seen from Fig. 3, the point B of the background art is set within the practical engine revolution speed range, while the point A of the preferred embodiment is set out of the practical engine revolution speed range. It is to be appreciated that in place of the in-line cylinder type engine, other types of engines, such as, a V-type engine having forward and rearward inclined cylinders may be employed as shown by dotted lines in Figs. 1 and 2. The V-type engine can be installed in the normal posture or in a posture with the forward inclined cylinders more inclined forward or with the rearward inclined cylinders more inclined rearward according to a relative engine layout with other vehicular components. When the V-type engine is installed in place of the in-line cylinder type engine, though the rearward inclined cylinders 16 inevitably approach close to a dash panel 40, the degree of freedom for the layout in the width direction of the vehicle is sufficiently large as mentioned above to allow the V-type engine to be installed in a predetermined limited lateral space with the cylinders not interfering with a booster of a brake mechanism, such as, a Master vac 42. Accordingly, the engine can be arranged as close to the dash panel 40 as possible to provide the minimum front overhang. Further, the lateral space for the Master vac 42 is sufficiently' provided at both lateral sides of the engine 14 to allow either a right or left steering wheel with the same layout of the engine. Still further, assuming that the vehicle is hit from front with the engine displaced rearward, the engine is supported evenly on large dimentions of the dash panel 40 with no interference with the Master vac 42, resulting in minimum deformation of the dash panel 40. For example, the present invention may also be applicable to a manual transmission vehicle in place of the automatic transmission vehicle as in the preferred embodiment. In this case, the torque converter 26 may be replaced by a manually operated clutch unit. Further, the present invention may also be applicable to a front-engine front-drive vehicle in place of the four wheel drive vehicle as in the preferred embodiment.

Claims: A power train arrangement mounted in a front engine compartment of an automotive vehicle having a longitudinal axis, comprising: a transverse engine (14) including an engine block and a cylinder head (16), said cylinder head (16) being disposed forward of said engine block with respect to the forward travel direction of the automotive vehicle, the transverse engine (14) being transversely mounted in the front engine compartment and having a crankshaft with a cranckshaft axis (X) extending transversely to the longitudinal axis of the vehicle; a transmission gear train (4) drivingly connected to said cranckshaft and having an axis of rotation (Z) extending in parallel to and below the cranckshaft axis ; a differential gear unit (10) drivingly connected to said transmission gear train (4) and having an axis of rotation (Y) extending in parallel to and below said cranckshaft axis; a transfer unit (28) drivingly connected to said differential gear unit (10), characterized in that said transverse engine (14) is inclined about said cranckshaft axis (X) in a forward travel direction of the automotive vehicle, said axis of rotation (Z) of said transmission gear train (4) is disposed forward of said crankshaft axis (X) with respect to the forward travel direction of the automotive vehicle, and said axis of rotation (Y) of said differential gear unit (10) is disposed rearward of said cranckshaft axis (X) with respect to the forward travel direction of the automotive vehicle; and in that the transfer unit (28) has an axis of rotation in alignment with said axis of rotation (Y) of said differential gear unit (10). A power train arrangement as claimed in claim 1, characterized in that a torque converter (26) drivingly connected to said crankshaft has an axis of rotation in alignment with said crankshaft axis (X). A power train arrangement as claimed in claim 1 or 2, characterized in that a propeller shaft (3) drivingly connected to said transfer unit (28) extends rearward from said transfer unit (28), with respect to the forward travel of the automotive vehicle.

Inventors: FUKUDA, NOBUYOSHI, ISHIDA, YOSHIYUKI, NAKA, ATSUYUKI, OSAKO, JUNJI, SAGARA, KIYOSHI
Applicants: NISSAN MOTOR CO., LTD.
Application year: 1990
Main classification: B60K5
IPC codes: B60K5, B60K17