POWER PLANT STRUCTURE FOR MOTOR VEHICLE

Abstract: Herein disclosed in a power plant structure which generally includes an engine part and a transmission part. In order to increase the rigidity of the power plant structure, the cylinder block of the engine is tightly connected by bolts to a mounting portion integrally formed on a transmission case. For more assured rigidity, a ladder beam structure is tightly disposed between the cylinder block and the mounting portion.

Description: Background of the Invention 1. Field of the Invention The present invention relates in general to an automotive power plant structure which, for producing a drive power and transmitting the power to driven wheels, consists of an engine part and a transmission 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 engine noise emitted therefrom. 2. Description of the Prior Art Japanese Utility Model First Provisional Publication No. 58.53826 shows an internal combustion engine which is constructed rigid for reducing noise emitted therefrom. This prior art engine has a unique construction practically applied thereto. That is, the engine comprises a cylinder block having a lower skirt section which is bulged outwardly and extends downwardly to define thereinside an upper part of a crankcase. A plurality of main bearing bulkheads are parallelly aligned and disposed inside of the skirt section. Each bulkhead is formed with a bearing section. A ladder beam structure is securely connected to the bottom portion of the cylinder block and includes a plurality of main bearing cap sections each having both ends integrally connected to respective side beam sections. Each bearing cap section is secured at its top portion onto each bearing bulkhead by means of cap bolts so as to associate with the bearing section of the bulkhead thereby forming a cylindrical bore in which the journal of a crankshaft is rotatably supported. An oil pan is secured to the bottom portion of the ladder beam structure. With the construction as described hereinabove, the rigidity of the bearing cap sections is increased and the vibration of the skirt section is reduced. Thus, the engine noise can be reduced to a certain low level. US-A-43 39 964 and DE-A-29 13 076 disclose power plant structures to be used in particular in motor cycles. Said prior art power plant structures include an engine having a cylinder block and a transmission having a transmission case. Said transmission case has a mounting portion to which the lower portion of said cylinder block is mounted and secured by connecting means or are constructed, at least partly as an integral housing. Summary of the Invention It is an object of the present invention to provide an automotive power plant structure which is constructed to achieve much more assured noise reduction as compared with the above-mentioned conventional engine construction. According to the present invention, there is provided a power plant structure which comprises an engine including a cylinder block, a transmission including a transmission case, a mounting portion integrally formed on the transmission case to mount thereon the cylinder block, connecting means, such as bolts, for securely connecting the cylinder block to the mounting portion, which is formed with a recess portion, constituting a part of an oil pan of the engine upon mounting of the engine onto the mounting portion. Brief Description of the Drawings The features and advantages of the power plant structure of the present invention will be more appreciated from the following description when taken in conjunction with the accompanying drawings, in which: Fig. 1 is a front vertical sectional view of a power plant structure of an embodiment of the present invention; Fig. 2 is a side view of the power plant structure of the embodiment, which is taken from the direction of the arrow "11" of Fig. 1; Fig. 3 is a perspective view of a ladder beam structure which is practically applied to the power plant structure of the present invention. Detailed Description of the Invention Referring to Figs 1 to 3, particularly Fig. 1, there is shown a power plant structure of an embodiment of the present invention, which is generally designated by reference "A". The power plant structure "A" comprises generally an internal combustion engine part and a transmission part which are rigidly connected with each other in a manner as will be described hereinafter. The engine part comprises a cylinder block 10 which is formed with a plurality (four in the illustrated embodiment) of cylinder barrels 10a each of which defines therein a cylinder bore (no numeral). The cylinder block 10 includes a skirt section 12 which is bulged outwardly and extends downwardly to define thereinside an upper part of a crankcase (no numeral). The skirt section 12 is integrally connected through a lower block deck 10b with the cylinder barrels 10a. A plurality of main bearing bulkheads 14 are parallelly aligned and disposed inside of the skirt section 12. Each bearing bulkhead 14 is located below and connected to a position between the adjacent two cylinder barrels 10a. The bearing bulkhead 14 is integrally connected at its top part with the lower block deck 10b and at its side parts with the inner walls of the skirt section 12. Each bearing bulkhead 14 is provided at its bottom central portion with a bearing section 14a for rotatably receiving the journal of a crankshaft (not shown). A ladder beam structure 16 is securely connected to the bottom part of the cylinder block 10, which, as is shown in Fig. 3, includes a plurality of main bearing cap sections 18 each having both ends integrally connected to respective side beam sections 20 and 22. Each bearing cap section 18 is secured at its top portion onto each bearing bulkhead 14 by means of cap bolts 24 (see Fig. 1) so as to associate with the bearing section of the bulkhead 14, thereby forming a cylindrical bore 26 in which the journal of the crankshaft (not shown) is rotatably received. The ladder beam structure 16 is sealingly seated on a bank of a recessed portion 30 which is integrally formed on a transmission case 28 of the transmission part. The recessed portion 30 comprises a continuous side wall 30a which is shaped to match with the bottom portion of the ladder beam structure 16 and a bottom wall 30b which is shaped to serve as a part of the upper wall of the transmission case 28. A plurality of bolts 32 are used for rigidly connecting the ladder beam structure 16 and the bank of the recessed portion 30 with an interposal of a suitable sealing member or gasket (not shown) therebetween. With this, it will be appreciated that the recessed portion 30 serves also as an oil pan for the engine part. Designated by numerals 34, 36 and 38 are gears which are installed in the transmission case 28, and designated by numeral 40 is an under cover of the transmission case 28. As is seen in Fig. 2, the side wall 30a of the recessed portion 30 is formed with an oil draining hole which is plugged by a drain plug 42. A rear cover 44 is provided at a rear side of the power plant structure for housing therein a known gear mechanism by which the drive power of the crankshaft is transmitted to the gears 34, 36 and 38 in the transmission case 28. Designated by numeral 46 is a front cover fixed to a front side of the cylinder block 10. Because of the provision of the ladder beam structure 16, the rigidity of the bearing cap sections 18 is increased and the vibration of the cylinder block skirt section 12 is suppressed or at least minimized. In addition, since the ladder beam structure 16 is rigidly connected or tightly bolted to the recessed portion 30 of the transmission case 28, the rigidity of the ladder beam structure 16 of itself is also increased thereby suppressing or at least minimizing vibration of its lower part. Furthermore, since the engine part is rigidly connected through the ladder beam structure 16 to the transmission part, the substantial sectional area of the engine part is enlarged increasing the geometrical (second) moment of inertia of the same. Thus, the rigidity of the engine against a torsional stress and that against a bending stress are increased. This unique construction of the power plant structure is effective in reducing the engine noise of frequency ranging from about 200 Hz to about 3 KHz. In addition, since the engine part and the transmission part are compactly assembled in the above-mentioned manner, the whole surface area (viz., the noise emitting area) of the power plant structure including these two parts is considerably reduced thereby much more effectively reducing the noise.

Claims: A power plant structure including an engine having a clyinder block (10) with a lower skirt (12) and a transmission having a transmission case (28), said transmission case (28) having a mounting portion (30) to which the lower skirt (12) of said cylinder block (10) is mounted and secured by connecting means (16,24,32), characterized in that said mounting portion (30) is formed with a recess portion comprising a partition wall (30b) by which an interior of said cylinder block (10) and an interior of said transmission case (28) are separated and in that said recess portion constitutes part of an oil pan of said engine. A power plant structure as claimed in claim 1, in which said mounting portion (30) of said transmission case (28) is shaped to match with the lower skirt (12) of said cylinder block (10). A power plant structure as claimed in claim 2, in which said connecting means (16,24,32) comprises a plurality of connecting bolts (24,32). A power plant structure as claimed in claim 3, characterized in that said connecting means (16,24,32) includes a ladder beam structure (16) which is tightly disposed between the lower skirt (12) of said cylinder block (10) and said mounting portion (30) of said transmission case (28), said ladder beam structure (16) being so constructed and arranged as to increase the rigidity of said lower skirt (12) and said mounting portion (30). A power plant structure as claimed in claim 4, in which said ladder beam structure (16) comprises: a plurality of main bearing cap sections (18) which are spaced from one another; and two side beam sections (20,22) between which said main bearing cap sections (18) are arranged in such a manner that longitudinal both ends of each main bearing cap section (18) are integrally connected to said side beam sections (20,22) respectively. A power plant structure as claimed in claim 5, in which each main bearing cap section (18) is secured by bolts (24) at its top portion onto each bearing bulk head (14) which is formed in the lower skirt (12) of said cylinder block (10). A power plant structure as claimed in claim 6, in which said lower skirt (12) of the cylinder block which is bulged outwardly and extends downward from a major part of said cylinder block (10) to define there inside an upper part of a crank case. A power plant structure as claimed in claim 7, in which said mounting portion (30) of the transmission case (28) comprises: a continuous side wall (30a) shaped to match a bottom portion of said ladder beam structure (16); and said partition wall (30b) shaped to serve as a part of an upper wall of said transmission case (28), whereby said recess portion serves as the oil pan of said engine.

Inventors: HAYASHI, YOSHIMASA C/O NISSAN MOTOR CO.,LTD., TAMAZAWA, TSUYOSHI C/O NISSAN MOTOR CO.,LTD.
Applicants: NISSAN MOTOR CO., LTD.
Application year: 1988
Main classification: F02B61
IPC codes: F02F7, F02B61, F02F1