EP1826389A1

EP1826389A1 - Internal Combustion Engine

Info

Publication number: EP1826389A1
Application number: EP07101110A
Authority: EP
Inventors: Masaki Yoneyama; Naoki Kono; Kohji Minami; Fumiaki Okubo; Hiroshi Kuribara
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 2006-02-28
Filing date: 2007-01-24
Publication date: 2007-08-29
Anticipated expiration: 2027-01-24
Also published as: EP1826389B1; DE602007004888D1; ES2339884T3

Abstract

To provide structure for avoiding the concentration of stress caused in the bolt hole in a circumference of the end of the bolt in a fastened part and to lighten the crankcase (2) in an internal combustion engine (1) provided with a fastening bolt for fastening upper and lower crankcases (2B) in a circumference of a crankshaft (11) and a bolt hole which is formed in the crankcase (2) and into which the fastening bolt is inserted and tightened. An opening is formed at an upper end of the bolt hole in the upper crankcase (2A), the end of the bolt hole is made to communicate with the opening, and the end of the fastening bolt is protruded into the opening in fitting the bolt.

Description

The present invention relates to a crankcase of an internal combustion engine, particularly relates to fastening structure of a part supporting a crankshaft in the crankcase.
Technique for making an opening at the end of a bolt hole and making the opening communicate with the bolt hole in fastening structure for fastening a crankcase and a crank cap in a circumference of a crankshaft is known (for example, refer to Patent document 1).
JP-A No. H10-122042
In a fastened part of a part rotatably supporting the crankshaft, a load applied to the crankshaft has a great effect upon the fastened part. In related art, as the end of a bolt remains inside the crankcase, stress concentrates in a bolt end circumference of the crankcase. Therefore, the rigidity of the crankcase is required to be increased, the weight of the crankcase necessarily increases, and it is difficult to lighten the crankcase.
The crankcase in the related art is equivalent to an upper crankcase in the invention and the crank cap in the related art is equivalent to a lower crankcase in the invention.
The invention is made to address the problem, the invention disclosed in Claim 1 is based upon an internal combustion engine provided with: a crankcase vertically partitioned; a crankshaft rotatably journalled to the crankcase; a fastening bolt for fastening upper and lower crankcases in a circumference of the crankcase; and a bolt hole which is formed in the crankcase and into which the fastening bolt is inserted and tightened, and is characterized in that an opening is formed at an upper end of the bolt hole in the upper crankcase, the end of the bolt hole communicates with the opening, and the end of the fastening bolt is protruded into the opening when the bolt is fastened.
The invention disclosed in Claim 2 is based upon the internal combustion engine disclosed in Claim 1, and is characterized in that a circumference of the end of the bolt hole is protruded into the opening of the crankcase.
The invention disclosed in Claim 3 is based upon the internal combustion engine disclosed in Claim 2, and is characterized in that an inside diameter of the bolt hole end circumference protruded part is made longer than a diameter of the bolt hole from the end of the part to the inside apart by predetermined distance, and no screw is formed.
The invention disclosed in Claim 4 is based upon the internal combustion engine disclosed in Claims 1 to 3, and is characterized in that the opening is formed in an arbitrary anomalous shape, and a V-type rib is formed at the edge of the opening with the end of the bolt hole in the center.
The invention disclosed in Claim 5 is based upon the internal combustion engine disclosed in Claims 1 to 4, and is characterized in that a cylinder block in which plural cylinders are arranged in parallel is arranged on the open upside of the crankcase, and the opening is formed in a crank journal wall partitioning space corresponding to the cylinder of the crankcase.
The invention disclosed in Claim 6 is based upon the internal combustion engine disclosed in Claim 1, and is characterized in that the opening is formed in a circle, and the opening is formed so that its diameter is equivalent to the double or less of a diameter of the bolt hole.
According to the invention disclosed in Claim 1, as the end of the bolt hole communicates with the opening and the end of the fastening bolt is protruded into the opening, the concentration of stress on the side of the bolt hole at the end of the bolt can be avoided. Therefore, as stress is dispersed in the whole fastened part of the bolt hole, the durability is enhanced and the crankcase can be lightened.
According to the invention disclosed in Claim 2, as the circumference of the end of the bolt hole is protruded into the opening of the crankcase, stress applied to the end of the bolt hole can be relieved by the protruded part and the rigidity of the crankcase is more enhanced. The fastened length of the bolt hole can be secured.
According to the invention disclosed in Claim 3, the protrusion of the bolt into the opening can be inhibited. Besides, the exposure of the edge of the termination of the bolt hole caused in working a screw can be prevented.
According to the invention disclosed in Claim 4, the opening can be formed in an arbitrary anomalous shape different from a normal shape such as a circle, hereby, the shape can be varied in accordance with the necessity of securing the rigidity of the crankcase, and the opening in the crankcase can be expanded at the maximum. In addition, the V-type rib is arranged at the peripheral edge of the opening, tensile stress applied to the periphery of the opening from the fastened part can be dispersed in the whole crankcase, and the lightening and securing the rigidity can be achieved.
According to the invention disclosed in Claim 5, as the opening provided to the crank journal wall functions for pressure relief between cylinders, pumping loss can be reduced and friction can be reduced.
According to the invention disclosed in Claim 6, as tensile stress applied to the circular opening can be uniformly received in the circumference of a circular part when the opening is formed in a circle and the inside diameter of the opening is set to the double or less, the reduction of the rigidity of the crankcase is possibly inhibited and the dispersion of the tensile stress is enabled.

Fig. 1 is a longitudinal section showing a part of an internal combustion engine 1 equivalent to one embodiment of the invention.
Fig. 2 is a top view showing a principal part of an upper crankcase 2A.
Fig. 3 is an enlarged longitudinal section showing its main part of the upper crankcase 2A.
Figs. 4A and 4B are explanatory drawings for explaining the effect of a bolt hole end circumference protruded part 32.

Fig. 1 is a partial longitudinal section showing an internal combustion engine 1 equivalent to one embodiment of the invention. The internal combustion engine is an in-line four-cylinder internal combustion engine and Fig. 1 shows a section of a bulkhead between cylinders. A crankcase 2 is vertically partitioned in two and is configured by an upper crankcase 2A and a lower crankcase 2B. A cylinder block 3, a cylinder head 4 and a cylinder head cover are connected to the upside of the upper crankcase 2A. The cylinder head cover is not shown. An oil pan 6 is connected to the bottom of the lower crankcase 2B.
A crankshaft supporting part 10 is formed on joined faces of the upper crankcase 2A and the lower crankcase 2B and a crankshaft 11 is rotatably supported in this part. A main gallery 12 and a lubricating oil passage 13 are provided under the crankshaft supporting part 10. Transmission shaft supporting structure 14 is provided to the rear of the crankcase 2. Camshaft supporting part 15 for driving an intake/exhaust valve is provided to an upper part of the cylinder head 4. A water jacket 17 is provided to inner circumferences of the cylinder block 3 and the cylinder head 4 and the cylinder bulkhead 16.
An upper crank journal wall 20A and a lower crank journal wall 20B are provided to the upper and lower crankcases 2A, 2B in parts corresponding to a crank journal corresponding part to the cylinder bulkhead 16. A journal bearing 21 is provided to the crankshaft supporting part 10 provided to the crank journal walls 20A, 20B. The upper crankcase 2A and the lower crankcase 2B are fastened by plural fastening bolts. The front and the rear of the crankshaft supporting part 10 are fastened by a front fastening bolt 22 and a rear fastening bolt 23 respectively particularly long.
In this embodiment, a large anomalous outline opening 24 that communicates space corresponding to adjacent cylinders is provided to the crank journal wall 20A of the upper crankcase 2A. The reason why the opening has the anomalous outline is that it does not have a circular outline formed by normal machining but is formed in an arbitrary shape if necessary. A small circular opening 25 having a circular section and piercing the plural crank journal walls 20A is formed at the back of the large anomalous outline opening 24 of the crank journal wall 20A of the upper crankcase 2A in parallel with the crankshaft 11 by drilling and others.
Fig. 2 is a top view showing a main part of the upper crankcase 2A. In Fig. 2, a cylinder block connected face 28 is shown. As described above, this internal combustion engine is the four-cylinder internal combustion engine and the crank journal walls 20A partitioning space corresponding to a cylinder 29 are provided in the upper crankcase 2A. In Fig. 2, the large anomalous outline opening 24 provided to the crank journal wall 20A, a front bolt hole 30 into which the front fastening bolt 22 is fitted and a rib 34 provided to an edge of the large anomalous outline opening 24 are seen.
Fig. 3 is an enlarged longitudinal section showing a main part of the upper crankcase 2A and shows the circumference of bolt holes 30, 31 in front of and at the back of the crankshaft supporting part 10 provided to the upper crank journal wall 20A. The front bolt hole 30 is a bolt hole into which the front fastening bolt 22 is screwed and the rear bolt hole 31 is a bolt hole into which the rear fastening bolt 23 is screwed. An upper end of the front bolt hole 30 communicates with the large anomalous outline opening 24, the circumference of the upper end of the front bolt hole 30 is protruded into the large anomalous outline opening 24, and a bolt hole end circumference protruded part 32 is formed. In the bolt hole end circumference protruded part 32, an extended diameter part 33 the inside diameter of which is slightly extended, compared with the diameter of the bolt hole is formed from the end to the inside apart by predetermined distance, and no screw is formed in the extended diameter part 33. A V-type rib 34 is formed at the edge of the large anomalous outline opening 24 with the upper end of the front bolt hole 30 in the center. The end of the front fastening bolt 22 fitted into the front bolt hole 30 is protruded into the large anomalous outline opening 24 as shown in Fig. 1.
As described above, the small circular opening 25 having the circular section is formed in the crank journal wall 20A of the upper crankcase 2A by drilling and others and the end of the rear bolt hole 31 communicates with the small circular opening 25. The end of the rear fastening bolt 23 screwed into the rear bolt hole 31 is protruded into the small circular opening 25 as shown in Fig. 1. It is optimum that the inside diameter of the small circular opening has length equivalent to 1.3 times of the inside diameter of the bolt hole, however, it is desirable that the inside diameter has double or shorter length at the maximum. This reason is that an upper limit of the dimension of the inside diameter is set to avoid the deterioration of the rigidity of the crankcase.
Figs. 4 are explanatory drawings for explaining the effect of the bolt hole end circumference protruded part 32 in the invention. Fig. 4(a) shows that part in the invention, the protruded part 32 is formed in the circumference of the end of the bolt hole 30 in the crank journal wall 20A, and the end of the fastening bolt 22 is protruded into the opening 24. Fig. 4(b) shows the above-mentioned part in related art of the invention, no protruded part is formed in a circumference of the end of a bolt hole 030 in a crank journal wall 020A, and the end of a fastening bolt 022 remains in the bolt hole 030. As shown in Fig. 4(b), when no protruded part is formed in the circumference of the end of the bolt hole, tensile stress T is caused in the crank journal wall in the vicinity of the fastening bolt in assembling an internal combustion engine. In the meantime, as shown in Fig. 4(a), when the protruded part 32 is formed in the circumference of the end of the bolt hole, stress in the crank journal wall 20A in the vicinity of the fastening bolt in assembling the internal combustion engine is compressive stress C. It is generally known that the fatigue strength of structure is enhanced by compressive stress. Further, as tensile force F acts on the fastening bolt 22 by the vibration of the crankshaft when the internal combustion engine is driven, larger compressive stress is produced in the vicinity of the bolt hole in the crank journal wall 20A in the case that the protruded part 32 is formed in the circumference of the end of the bolt hole and the fatigue strength of the crank journal wall 20A is increased.
As described in detail above, as this embodiment has the above-mentioned configuration, the following effect is produced.

(1) Generally, when the end of the fastening bolt remains on the way of the bolt hole, the concentration of stress is caused in a boundary between a part in which the fastening bolt is fitted and a part in which the fastening bolt is not fitted in the circumference of the bolt hole. In this embodiment, as the ends of the bolt holes 30, 31 are made to communicate with the openings 24, 25 provided to the crank journal wall 20A and the ends of the fastening bolts 22, 23 are protruded into the openings, the concentration of stress in the circumferences of the bolt holes 30, 31 at the ends of the bolts can be avoided. Therefore, as the stress is dispersed in the whole fastened parts of the bolt holes, the durability is enhanced and the crankcase can be lightened.
(2) As the circumference of the end of the bolt hole 30 is protruded into the opening 24 in the crank journal wall, stress applied to the end of the bolt hole can be relieved by the protruded part and the rigidity of the crankcase is more enhanced. The fastened length of the bolt hole can be secured.
(3) In the protruded part 32 of the bolt hole end circumference, as the extended diameter part 33 the inside diameter of which is longer than the diameter of the bolt hole is formed from the end to the inside apart by the predetermined distance and no screw is formed there, the protrusion of the bolt into the opening 24 in the crank journal wall can be inhibited. Besides, the exposure of the acute-angled edge of the termination of the bolt hole caused in working a screw can be prevented.
(4) The opening 24 in the crank journal wall is not necessarily required to have a normal shape such as a round shape but can be formed in an arbitrary anomalous shape, hereby, the shape can be varied in accordance with the necessity of securing the rigidity of the crankcase, and the opening in the crank journal wall can be expanded at the maximum. Besides, the V-type rib 34 is arranged at the peripheral edge of the opening with the end of the bolt hole in the center, tensile stress applied to the opening from the fastened part can be dispersed in the whole crankcase, and lightening and securing the rigidity can be achieved.
(5) As the openings 24, 25 provided to the crank journal wall function for pressure relief between cylinders, pumping loss can be reduced and friction can be reduced.
(6) When the circular opening 25 is provided to the crank journal wall, tensile stress applied to the opening can be uniformly received in the circumference of the circular part, as the inside diameter of the opening is set to the double or less, the reduction of the rigidity of the crankcase is possibly inhibited, and the dispersion of the tensile stress is enabled.
(7) In the above-mentioned embodiment, the opening is provided to the crank journal wall, however, a position of the opening is not limited to the crank journal wall.

1: Internal combustion engine,
2: Crankcase,
2A: Upper crankcase,
2B: Lower crankcase,
3: Cylinder block,
10: Crankshaft supporting part,
11: Crankshaft,
16: Cylinder bulkhead,
20: Crank journal wall,
21: Journal bearing,
22: Front fastening bolt,
23: Rear fastening bolt,
24: large anomalous outline opening,
25: Small circular opening,
29: Space corresponding to cylinder,
30: Front bolt hole,
31: Rear bolt hole,
32: Bolt hole end circumference protruded part,
33: Extended diameter part,
34: Rib

Claims

An internal combustion engine comprising:
a crankcase (2) vertically partitioned in two;

a crankshaft (11) rotatably journalled to the crankcase;

a fastening bolt that fastens the upper and lower crankcases (2A, 2B) in a circumference of the crankshaft (11); and

a bolt hole which is formed in the crankcase (2) and into which the fastening bolt is inserted and tightened,
wherein the internal combustion engine (1) further includes an opening formed at an upper end of the bolt hole in the upper crankcase (2A),
the end of the bolt hole communicates with the opening, and
when the bolt is fastened, an end of the fastening bolt is protruded into the opening.
The internal combustion engine according to Claim 1,
wherein a circumference of the end of the bolt hole is protruded into the opening of the crankcase (2).
The internal combustion engine (1) according to any of the preceding claims,
wherein an inside diameter of the bolt hole end circumference protruded part is made longer than a diameter of the bolt hole from the end of the part to the inside apart by predetermined distance, and
no screw is formed.
The internal combustion engine according to any of the preceding claims,
wherein the opening is formed in an arbitrary anomalous shape, and
a V-type rib is formed at the edge of the opening with the end of the bolt hole in the center.
The internal combustion engine (1) according to any of the preceding claims,
wherein a cylinder block (3) in which a plurality of cylinders are arranged in parallel is arranged on the open upside of the crankcase (2), and
the opening is formed in a crank journal wall (20) partitioning space corresponding to the cylinder of the crankcase (2).
The internal combustion engine according to any of the preceding claims,
wherein the opening is formed in a circle, and
the opening is formed so that its diameter is equivalent to the double or less of a diameter of the bolt hole.