POWER PLANT STRUCTURE FOR MOTOR VEHICLE

Abstract: A power plant structure for four wheel drive cars is disclosed. A clutch part (18) comprises a housing (22) receiving a clutch (20) coaxially connected to the engine (10). A transmission part (40) comprises a transmission (42) in a case (44). A transfer part (54) comprises a transfer (60) and differentials (56,58) in a transfer case (62). In order to increase the rigidity of the power plant: the transmission part (40) and transfer part (54) are arranged in paralell with and beside the engine (10) and the clutch part (18); the transfer part (54) is below the transmission part (40); and the clutch housing (22), the transmission case (44), and the transfer case (62) constitute a monolithic housing construction secured to the engine (10).

Description: The present invention relates in general to an automotive power plant structure which, for producing drive power and transmitting the power to driven wheels, comprises an engine part, a clutch part, a transmission part, and a transfer part, and more particularly, the present invention relates to a low noise level automotive power plant structure which has a high rigidity in construction to reduce noise induced by the vibration thereof. In conventional techniques, there are provided power plant structures of a type which is adopted in four wheel drive cars, see for example DE-A-3 506 727. This type of power plant structure is essentially composed of an engine part, a clutch part, a transmission part, and a transfer part. The engine part is transversely mounted on an engine mounting frame of a vehicle body. The clutch part comprises a clutch and a clutch housing for receiving the clutch. The clutch is coaxially connected to a crankshaft of the engine part. The transmission part comprises a transmission and a transmission case for receiving the transmission. The transmission case is secured to the clutch housing and an input shaft of the transmission is coaxially connected to an output shaft of the clutch. The transfer part comprises a differential unit, a transfer, and a transfer case. The transfer case receives the differential unit and the transfer. The transfer case is secured to a side face of the clutch housing. The differential unit comprises center and front differentials which transfer the drive power from the transmission to front and rear driving axles. However, the conventional power plant structure as mentioned hereinabove has a drawback which will be described in the following. The power plant is generally too long because of the aligned arrangement of the transmission part relative to the clutch part and the engine part. That is, in this power plant, the transmission part, the clutch part, and the engine part are arranged in tandem. This elongated structure tends to provide the power plant with insufficient rigidity. Furthermore, since the transmission case and the transfer case are not directly secured to the stoutly built engine part but to the clutch housing, the insufficient rigidity of the power plant becomes marked. Low rigidity lowers the fundamental frequency of the power plant, the fundamental frequency being the frequency of vibration, at the lowest level, of the normal mode. That is, when the engine runs, the transmission case and the transfer case tend to vibrate easily. Particularly, when the engine runs at a high speed, there arises an unpleasant noise induced by resonance due to the vibration of the power plant. Recently, the occurrence of this noise has become severe because the fundamental frequency has decreased with the advance of high speed and high power engines. Therefore, it would be desirable to be able to provide a power plant structure which is free of the above-mentioned drawbacks and which comprises an engine (usually with a cylinder block, a bearing cap support housing, and an oil pan), for four wheel drive cars. The present invention provides a power plant structure for a motor vehicle, comprising: an engine having a crankshaft; a clutch which is coaxial with the crankshaft; a transmission which is arranged substantially parallel to the crankshaft and alongside the engine and the clutch; and a transfer part which comprises differentials and a transfer and which is arranged substantially parallel to the crankshaft and alongside the engine and the clutch; characterised in that: a monolithic integral housing structure has three portions respectively consisting of a clutch housing in which the clutch is received, a transmission case in which the transmission is received, and a transfer case in which the transfer and the differentials are received; and the clutch housing, the transmission case, and the transfer case of the integral housing structure are each directly mounted on the engine. Preferred features of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings, in which: Fig. 1 is a rear vertically sectional, but partially cutaway, view of a power plant structure of the present invention; Fig. 2 is an expanded sectional view of the power plant structure of the invention; Fig. 3 is a front view of the power plant structure, showing cover parts; and Fig. 4 is a graph showing a characteristic of the fundamental frequency of the power plant. Referring to Figs. 1 to 4, particularly Figs. 1 and 2, there is shown a power plant structure of the present invention for a four wheel drive car. As is best shown in Fig. 2, the power plant structure comprises an internal combustion engine part 10, a clutch part 18, a transmission part 40, and a transfer part 54. As will become apparent as the description proceeds, housings or cases for the clutch part 18, transmission part 40, and transfer part 54 are integral in construction and respectively secured to the engine part 10. The engine part 10 is transversely mounted on an engine mounting frame (not shown) of a motor vehicle. The engine part 10 comprises a cylinder block 12, a bearing cap support housing 13, and an oil pan 14. Detailed description of the support housing 13 can be referred to US-A-4,497,292. The cylinder block 12 is formed with a plurality (four in the illustrated embodiment) of aligned cylinder bores and securely mounted on a top surface of the bearing cap support housing 13 with interposal of a suitable sealing member or gasket therebetween. Mounting portions 16a,16b are integrally formed on respective major side faces of the cylinder block 12 and the bearing cap support housing 13, the major side faces facing rearward of the vehicle. The mounting portions 16a,16b directly mount thereon both the transmission case 44 and the transfer case 62. As is seen from Fig. 2, the mounting portions 16a,16b are aligned perpendicular to a front face 10a of the engine part 10. The front face 10a is the face through and from which a crankshaft of the engine part 10 projects outward. The clutch part 18 comprises a clutch 20 and a clutch housing 22 which receives the clutch 20. The clutch housing 22 is secured at a flange portion 17 thereof to the front face 10a of the engine part 10 by means of a plurality of bolts. The clutch 20 comprises a flywheel 24 equipped at a periphery thereof with a ring gear 26, a clutch disc 28, a pressure plate 29, and a clutch cover 30. The clutch 20 is arranged concentric with the crankshaft of the engine part 10. Designated by numeral 32 is an output shaft of the clutch 20. The transmission part 40 is arranged beside the engine part 10 and the clutch part 18. The transmission part 40 comprises a transmission 42 and a transmission case 44 for receiving the transmission 42. The transmission part 40 is arranged in such a manner that a main shaft 46 and a counter shaft 48 of the transmission 42 are parallel to the crankshaft and the clutch output shaft 32. The main shaft 46 is connected to the clutch output shaft 32 through a drive chain 34 to transfer a drive force from the output shaft 32 to the main shaft 46. A front part of the transmission case 44 is positioned beside an upper part of the clutch housing 22. The transmission case 44 is securely connected, at a flange portion 50a integrally formed on a rear side portion thereof, by means of a plurality of bolts, to a mounting portion 16a which is integrally formed on the side face of the cylinder block 12. This arrangement of the transmission case 44 relative to the clutch housing 12 and the engine part 10 can considerably reduce the length of the power plant structure as compared with the conventional power plant structures, thereby enhancing the rigidity thereof. The transfer part 54 comprises a transfer 60, a center differential 56, a front differential 58, and a transfer case 62. The transfer case 62 receives the transfer 60 and the differentials 56 and 58. A front part of the transfer case 62 is positioned beside a lower part of the clutch housing 22. The transfer case 62 is securely connected, at a flange portion 50b integrally formed on a rear side portion thereof, by means of a plurality of bolts, to a mounting portion 16b which is integrally formed on a side face of the bearing cap support housing 13. The transfer case 62 is positioned below the transmission case 44. The clutch housing 22, the transmission case 44 and the transfer case 62 form a monolithic housing structure which is securely connected to the front and side faces of the engine part 10, these two faces meeting at generally right angles. This configuration considerably enhances the rigidity of the power plant structure. When assembly of the power plant is intended, the clutch 20 coaxially connected to the engine part 10 is inserted into the clutch housing 22 which forms the monolithic structure with the transmission case 44 and the transfer case 62. Thereafter, the engine part 10 is secured to the clutch housing 22, the transmission case 44, and the transfer case 62. If the sizes and the weights of both the transmission case 40 and the transfer case 62 are reduced, the rigidity of the power plant structure can be enhanced. Therefore, in order to enhance the rigidity, the transmission 42 is arranged in such a manner that the main shaft 46 is positioned as close as possible to the clutch housing 22. That is, the distance W between an axis ℓ1 of the crankshaft and an axis ℓ2 of the main shaft 46 is minimized. This arrangement, however, makes the flange portion 50a,50b project into an imaginary extension 23 of the clutch housing 22. Therefore, the flange portion 50a,50b interfere with insertion of the clutch 20 into the clutch housing 22. To eliminate this interference, a notch 52 is provided in the flange portion 50a,50b. In assembly, the clutch 20 connected to the engine part 10 is put into the notch 52 at its ring gear 26. Then, the clutch 20 is inserted, along the axis ℓ1, without any abutment of the ring gear 26 against the flange portion 50a,50b, into the clutch housing 22. The length L of the notch 52 is made somewhat greater than a distance S which is the thickness of the clutch 20. Referring to Figs. 2 and 3, a front case cover 36 is provided to cover front faces of the transmission case 44 and the transfer case 62, and a portion of the clutch housing 22. A chain cover 38 is mounted on the front case cover 36 to cover the drive chain 34 which transmits the drive force from the output shaft 32 to the main shaft 46. An oil bath 66 is provided between the front case cover 36 and the chain cover 38 to lubricate the drive chain 34. A rear case cover 64 covers a rear face of the transfer case 62. As mentioned hereinabove, this unique construction of the power plant structure is effective in considerably enhancing the rigidity thereof. As the rigidity increases, the fundamental frequency of the power plant increases, too. Accordingly, with the present invention, the vibration of the power plant structure can be considerably reduced and particularly, when the engine runs at a high speed, noise induced by resonance can be suppressed or at least minimized.

Claims: A power plant structure for a motor vehicle, comprising: an engine (10) having a crankshaft; a clutch (20) which is coaxial with the crankshaft; a transmission (42) which is arranged substantially parallel to the crankshaft and alongside the engine (10) and the clutch (20); and a transfer part (54) which comprises differentials (56,58) and a transfer (60) and which is arranged substantially parallel to the crankshaft and alongside the engine (10) and the clutch (20); characterised in that: a monolithic integral housing structure has three portions respectively consisting of a clutch housing (22) in which the clutch (20) is received, a transmission case (44) in which the transmission (42) is received, and a transfer case (62) in which the transfer (60) and the differentials (56,58) are received; and the clutch housing (22), the transmission case (44), and the transfer case (62) of the integral housing structure are each directly mounted on the engine (10). A power plant structure as claimed in claim 1, in which the clutch housing (22) is directly secured to the front end face of the engine (10), being the face through and from which the crankshaft of the engine (10) projects outward. A power plant structure as claimed in claim 2, including a front case cover (36) to cover front end faces of the transmission case (44), the transfer case (62), and a part of the clutch housing (22). A power plant structure as claimed in claim 2 or 3, including a rear case cover (64) to cover a rear end face of the transfer case (62). A power plant structure as claimed in any preceding claim, including a chain cover (38) which covers a drive chain (34) which transmits a drive force from an output shaft (32) of the clutch (20) to an input shaft (46) of the transmission (42). A power plant structure as claimed in claim 5, in which the input shaft (46) of the transmission (42) is parallel to the crankshaft and the output shaft (32) of the clutch (20). A power plant structure as claimed in claim 5 or 6, when dependent on claim 3, including an oil bath (66) which is provided between the chain cover (38) and a part of the front case cover (36). A power plant structure as claimed in any preceding claim, in which a mounting portion (16a,16b) is integrally formed on the engine (10) and directly mounts thereon both the transmission case (44) and the transfer case (62) of the integral housing structure. A power plant structure as claimed in claim 8, in which the transmission case (44) is positioned beside an upper part of the clutch housing (22) and is securely connected, at a flange portion (50a) integrally formed on a rear side portion thereof, to an upper part (16a) of the said mounting portion, the said rear side portion of transmission case facing the said upper part (16a) of the mounting portion. A power plant structure as claimed in claim 8 or 9, in which the transfer case (62) is positioned beside a lower part of the clutch housing (22) and below the transmission case (44) and is directly securely connected, at a flange portion (50b) integrally formed on a rear side portion thereof, to a lower part (16b) of the said mounting portion, the said rear side portion of the transfer case (62) facing the said lower part (16b) of the mounting portion. A power plant structure as claimed in claim 9 or 10, in which the said flange portion (50a;50b) has a notch (52) preventing the clutch (20) from abutting against the said flange portion when the clutch is being inserted into the clutch housing (22). A power plant structure as claimed in claim 11, in which the notch (52) has a length (L) which is greater than thickness (S) of the clutch (20). A power plant structure as claimed in any of claims 10 to 12, when dependent on claim 9, in which the said upper and lower parts (16a,16b) of the mounting portion are integrally formed on side faces of a cylinder block (12) and of a bearing cap support housing (13), respectively, the side faces facing rearward when the power plant structure is mounted in the motor vehicle. A power plant structure as claimed in any of claims 8 to 13, when dependent on claim 2, in which the said mounting portion (16a,16b) is perpendicular to the front end face of the engine (10). A power plant structure as claimed in any preceding claim, in which the clutch housing (22), the transmission case (44), and the transfer case (62) are mounted on the engine (10) by means of a plurality of connecting bolts.

Inventors: HIRABAYASHI, YUJI, KANETOSHI, KAZUHIKO
Applicants: NISSAN MOTOR CO., LTD.
Application year: 1990
Main classification: F02B61
IPC codes: F02B61, B60K5, B60K17