Abstract:
An engine/transmission mounting arrangement in a front wheel drive vehicle including a bearing support at either end of the engine/transmission and an improved torque strut between the vehicle structure and the engine/transmission for restraining torsionally induced rolling movements of the engine/transmission. The improved torque strut having a substantial added mass to an end portion adjacent to the connection of the torque strut with the engine/transmission.

Description:
FIELD OF THE PRESENT INVENTION 
     This invention relates to a mounting arrangement for a transversely oriented engine/transmission for a front wheel drive type vehicle and more particularly to use of a torque strut member with a weighted end feature for inhibiting rotation or roll of the engine in it support mounts. 
     DESCRIPTION OF PRIOR ART 
     In recent times, there has been a major effort to increase fuel economy of automotive vehicles and there have been several technical trends developed to achieve increased fuel economy. One such trend is an increase in front-wheel-drive vehicles where the weight of the engine is placed over the traction wheels of the vehicle. Another trend to increase fuel economy is to provide smaller V-6 or straight line four-cylinder engines instead of the previously utilized V-8 engine. Still another trend is to make the vehicle smaller and lighter-weight. The comfort of the vehicle&#39;s occupants is very important in the effort to encourage car buyers to consider smaller and lighter vehicles. It is clear to those skilled in the art of vehicle engineering design that a major factor for maximizing occupant comfort is to minimize vibrations and noise, particularly those associated with the engine and transmission. 
     In front-wheel-drive vehicles, it is common engine and transmission mount practice to design the mounts to handle a torque reaction of the powertrain as well as supporting the assembly. The torque reaction comes from the action of the engine/transmission in the mounting arrangement and from the action of the entire powertrain at the differential or at the torque output to the driving wheels. It has been common practice to design the mounts to handle the torque reaction of both the engine/transmission and the differential (or powertrain output). Where the engine/transmission are mounted longitudinally in the vehicle (as opposed to being mounted transversely), the engine/transmission&#39;s torque reaction is in the vehicle&#39;s overall roll direction as defined as a moment about a generally longitudinal axis relative to the vehicle. On the other hand, the differential related torque reaction is in the vehicle&#39;s pitch direction as defined as a moment about a generally lateral axis relative to the vehicle. As a result, the two torque reaction effects are not additive and thus it is not difficult for the engine/transmission mounts to handle both torque reactions utilizing the spring rate of the engine/transmission cushion mounts. 
     When an engine/transmission of a vehicle is mounted transversely, the torque reaction of the engine/transmission is in the vehicle&#39;s pitch direction (moment about a laterally extending axis). The torque reaction of the differential is also in the vehicle&#39;s pitch direction. Thus, both torque reactions are additive and are directly coupled together acting upon the engine mounting arrangement. This effect imposes a very significant burden on the mounting arrangement since the resultant cumulative loads in the pitch direction includes both the engine/transmission&#39;s normal torque reaction and the differential&#39;s torque reaction which is effected by the effective transmission ratio and the axle ratio. 
     According to conventional practice and irrespective of the relative position of the engine and transmission in the vehicle, it is desirable for deriving a maximum benefit in isolating the vibration of the sprung mass including the powertrain and differential that the engine/transmission mounts be located adjacent to the points of minimum vibratory force in the powertrain system, i.e. node points. However, where a compact vehicle utilizes a transversely mounted engine of the type exhibiting relatively great vibration characteristics, e.g. an in-line four-cylinder, typically there is very little space available for conventional cushion mounting arrangements sized to effectively control pronounced powertrain vibrations as well as vertical motion or shake and any pitching motion. 
     The concerns identified above have been previously addressed and the combination engine/transmission mounting system disclosed in U.S. Pat. No. 4,901,814 to VonBroock, et al is known. VonBroock provides two engine mounts supporting an engine/transmission along three axes. The engine/transmission&#39;s torque reaction is resisted by two torque struts. In a preferred embodiment, one of the engine mounts is close to the center of gravity of the engine/transmission combination. A second engine mount is placed near an end of the engine of the engine/transmission combination. A support bracket in the form of a crescent shape extends in a fore and aft direction of the vehicle within the engine compartment. The bracket is positioned near the center of gravity of the engine/transmission combination. As explained in VonBroock, the torque struts are positioned close to the center of gravity of the engine/transmission combination. 
     The VonBroock engine/transmission mounting arrangement has several disadvantages. The first disadvantage is the need for a support bracket to be installed within the engine compartment where room is sparse. This is very undesirable especially in small compact vehicles. Secondly, the addition of the support bracket requires that the vehicles vehicle&#39;s forward wall including a dash panel which separates the engine compartment from the passenger compartment be reinforced to allow for attachment of the support bracket. Thirdly, the support bracket transmits vibrations of the engine/transmission to the passenger compartment in close proximity to the steering column of the vehicle. This is highly disadvantageous since this causes the vibrations to be amplified to the hands of the vehicle driver. 
     It is desirable to provide a mounting arrangement for an engine/transmission combination suitable for a front-wheel-drive vehicle and which minimizes the generation of undesired vibration. It is desirable to provide an engine/transmission combination mounting arrangement which is simple and inexpensive. 
     SUMMARY OF THE INVENTION 
     The present invention concerns a combination engine and transmission mounting arrangement suitable for a vehicle with front wheel drive and a transversely mounted engine. The mounting arrangement provides a first bearing support which translationally and fixably supports the weight of a first end portion of the engine/transmission combination. A second bearing support is provided for translationally and fixably supporting an opposite second end portion of the engine/transmission combination. A first torque strut is provided having a first end connected to a vehicle structural member adjacent to a rear corner of the engine compartment. The opposite second end of the torque strut is connected to the engine/transmission combination generally adjacent the first end of the portion of the engine/transmission combination. A second torque strut is provided which is in vertical alignment with the first torque strut. The second torque strut has a first end connected to a structural member of the vehicle adjacent the rear corner of the engine compartment. A second end of the second torque strut is connected to the engine/transmission combination adjacent to but lower than where the first torque strut&#39;s second end attaches to the engine/transmission. 
     It is an object of the present invention to provide a combination engine/transmission mounting arrangement for an engine in a front-wheel drive and transverse mount vehicle. 
     It is another object of the present invention to provide a combination engine/transmission mounting arrangement for an engine in a front-wheel drive and transverse mount vehicle which minimizes powertrain vibrations. 
     The above noted and other objects of the present invention will be apparent to those skilled in the art from a review of the invention as it is provided in the accompanying drawings and detailed description of the preferred embodiment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an end schematic view of a combination engine/transmission mounting arrangement for an engine in a front-wheel drive and transverse engine mount vehicle according to the present invention illustrating the location of one bearing support and first and second torque struts; and 
     FIG. 2 is a top schematic view of a combination engine/transmission mounting arrangement as shown in FIG. 1 to illustrate the location of another bearing support; and 
     FIG. 3 is an exploded perspective view of a vehicle engine compartment and the combination engine/transmission showing the first bearing support for one end of the engine/transmission and the two torque struts and an associated shock absorber tower support of the vehicle. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the Figures, an engine/transmission mounting arrangement is shown for a vehicle with front-wheel drive and a transversely mounted engine. Specifically, the mounting arrangement  10  is provided within an engine compartment  12  of a vehicle  14 . The engine compartment  12  has a rear end wall or partition  11  and a passenger side comer  12 ′. An arrow  13  points in the forward direction or towards the front end of the vehicle. The passenger side corner  12 ′ is transversely or laterally located opposite to a driver side corner which is not shown but typically that corner is adjacent the steering wheel and column. A structural body or chassis member called a shock (absorber) tower  22  is located adjacent the rearward part of the passenger side comer  12 ′. The shock tower  22  mounts the upper end of a shock or McPherson strut suspension component (not shown). A structural member called a K frame  26  is located at a lower portion of the passenger side corner  12 ′. The K frame  26  is attached to the vehicle&#39;s frame rails and torque box. At the opposite drivers side comer, an identical structure is present. 
     A combination engine/transmission  30  is provided to power the vehicle  14 . Engine/transmission  30  has an engine block portion  32  with a lower portion covered by an oil pan or case  34 . Engine  30  has a crankshaft (not shown) that rotates about a rotational axis  38  which extends transversely to the longitudinal axis of the vehicle  14  parallel to the arrow  13 . The end of the crankshaft is attached to a sprocket or serpentine belt carrying wheel  42 . As shown, the engine/transmission  30  has four cylinders inline serviced by a four branch exhaust manifold  44 . A transmission  48  only partially shown in FIG. 3, is attached to a rearward and lower end portion of the engine block  32 . The transmission  48  includes a differential portion and a transaxle arrangement (not shown but common in the vehicle art) which connects to front wheels (not shown) of the vehicle. The differential and output transaxle extend in an axis which is normal to the vehicle&#39;s longitudinal axis or the arrowed line  13 . Thus, the differential and output transaxle axis extends laterally across the vehicle. 
     A first bearing support  54  for the combination engine/transmission is located in the engine compartment  10  adjacent shock tower  22 . The support  54  fixably supports the weight of one end portion of the engine/transmission  10  (and the included differential) and attaches to the engine/transmission  10  generally adjacent the engine block&#39;s first end  56 . The support  54  prevents lateral movements of the engine/transmission and also inhibits fore and aft or longitudinal translation of the end portion  56  of the engine. However, support  54  provides little if any resistance to torsional movements or engine rolling about the laterally extending roll axis (normal to the arrowed line  13 ). Ideally, the first bearing support  54  is positioned at or very near the engine&#39;s rotational center of reaction for the drive train assembly including engine  30 , transmission  48 , the differential, and the transaxles or final drive shafts. In practice, this location is typically not available due to other geometric constraints and assembly limitations. 
     In a preferred arrangement, the first bearing support  54  uses hydro-bushings  58  which include a sleeve of elastomeric material to dampen and isolate vibration. The engine block  32  has a surface raised platform  60  and a tapped aperture  62  to be connected to the bearing support  54  by an appropriate threaded fastener. The first bearing support  54  is connected by a plurality of bolts  55  to the right side rail  57  of the vehicle  14 . 
     As revealed in FIG. 2, the opposite end portion  70  of the engine/transmission  10  is vertically supported by a second bearing support  74 . In a similar manner to the other bearing support  54 , the second bearing support  74  has an elastomeric sleeve construction to isolate the vehicle from vibrations of the motor/transmission  10 . The second bearing support  74  also fixably supports the weight of the other end portion of the engine /transmission  10  (and included differential) in three directions but is not designed to inhibit rotation of the engine/transmission  10 . The second bearing support  74  is connected at the left (or driver side) rail of the vehicle (not shown) at about the same height as the first bearing support  54 . A bracket (not shown) extends vertically downward from the second bearing support  74  to a position generally adjacent to the second end portion of the engine/transmission  10 . As mentioned previously, a line through the bearing mounts  54  and  74  is generally coincident with the axis of torque reaction of the drive train which includes both the contribution of the engine/transmission  10  and the powertrain output (or differential, transaxle, and drive shafts). The engine/transmission  10  is mounted within the vehicle  14  such that its rotational axis  38  extends substantially transversely of the vehicle and normal to the major or longitudinal axis of the vehicle which is parallel to line  13 . 
     An “L” frame assembly  78  with two parallel and spaced arms is mounted to shock tower  22  as shown in FIG.  3 . The arms of the frame assembly  78  have aligned bores  80  therethrough for a bolt  82 . A first torque strut  84  has a first end  86  and a second end  88 . The first end  86  carries an elastomeric isolating bushing  90  which is oriented for connection by bolt  82  to the L frame assembly  78  attached to the shock tower  22 . The opposite second end  88  of the torque strut  84  carries an elastomeric isolating bushing  92  oriented generally parallel with the rotational axis  38  of engine/transmission  10 . The second end  88  is connected by a bolt  93  to a strut bracket  94  carried at an upper location on the engine. The first torque strut  84  torsionally restrains the engine/transmission  10  while the bushings  90  and  92  isolate engine vibrations from transmittal to the vehicle. 
     A second torque strut  100  extends parallel to the first torque strut  84  and is generally vertically aligned therewith. The second torque strut  100  has a first end  102  and a second end  104 . The first end  102  carries an elastomeric isolating bushing  106  and is connected to the K frame  26  by bolt  108 . The pivotal axis of the bushing  106  and bolt  108  is generally parallel with the rotational axis  38  of the engine/transmission. The strut&#39;s second end  104  carries an elastomeric isolating bushing  110  and is connected to the engine block  32  via a bracket  112  which is fastened to the side of the engine block  32  and/or oil pan  34  by a plurality of bolts  114  which thread into an aperture  116 . Bracket  112  is also used to mount an air conditioning compressor (not shown) to the engine. Due to packaging restraints, the second torque strut  100  is longer than the first strut  84 . 
     In operation, the first bearing support  54  and second bearing support  74  support the weight of the engine/transmission  10  in the vertical direction and also prevent movement in the fore and aft direction and in the lateral direction. Torsional forces which would cause rocking or roll of the engine/transmission are inhibited by the first and second torque struts  84  and  100 . The isolation of the engine from the vehicle by the elastomeric bushings in the torque struts  84 ,  100  further inhibits transmission of vibrations to the shock tower  22  and K frame  26 . The attachment of the torque struts to the shock tower  22  and K frame  26  on the passenger side of the vehicle rather than the drivers side further isolate vibrations from the steering wheel of the vehicle located remotely from the passenger side. 
     Ideally, the two torque struts  84  and  100  should extend tangentially to an arc which describes the torsional axis of reaction of the power train with the strut&#39;s second ends  88  and  104  respectively connected to the engine/transmission  10  along a vertical plane  125  which intersects the torsional axis of reaction of the engine/transmission, differential, transaxle, and half-shafts. However, due to packaging constraints on the engine as shown, the actual connection of the second strut&#39;s end  104  in extended forward from plane  125 . 
     The ends  88 ,  104  of torque struts  84  and  100  have masses  103 ,  105  integrally connected thereto. Adding masses  103  and  105  tend to move the center of percussion of the torque struts generally coterminous with their bolted connections with the engine block  30 . In further detail, bushing  106  of end  102  of the second torque strut  100  has a high dynamic rate to prevent rigid body torque strut resonance in the longitudinal direction of the second torque strut  100 . The elastomeric bushing at the second end  104  of strut  100  has a lower dynamic rate isolator to provide isolation between the engine  30  and the K frame  18 . Typically, the bushing  106  will have a dynamic rate that is approximately 9-15 times and preferably 10-12 times higher than the dynamic rate of the bushing  110 .