JPH08200380A - Crankshaft support structure for internal combustion engine - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] The amount of bending deformation of the crankshaft is small, the bending stress of the crankshaft is alleviated, and in conventional engines the diameter of the crankpin and crank journal of the crankshaft is small. Provided is a crankshaft support structure for an internal combustion engine, which can maintain an equivalent stress level even if it is lightweight and can reduce friction loss. A two-piece structure having a journal support portion 12 for supporting a journal surface of a crankshaft and a thrust support portion 13 for supporting a side surface of a crankshaft web are provided. The divided metal crank bearings 6 and 7 are fitted to the bearing portion of the cylinder block through the groove portions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved crankshaft support structure for an internal combustion engine.

[0002]

2. Description of the Related Art Improving the support rigidity of a crankshaft is effective not only for reducing stress on the crankshaft but also for reducing engine vibration noise, and many proposals have been made. One example is a ladder frame, that is, a cylinder. There are a lower beam in which a block is vertically divided into two parts at the center line of the crankshaft and a bearing cap part and a skirt part are integrated to form a lower case, and a bearing beam in which a bearing cap is connected by a beam or a plate.

Further, in order to improve the support rigidity of the cylinder block bearing portion, the bearing side is also opened back and forth as the crankshaft is bent so as to be opened in the front-rear direction by the combustion excitation force, so that the bearing caps are mutually opened. It is also possible to suppress the deformation of the crankshaft by improving the bending rigidity in the front-back direction by connecting to the.

However, when the flexural rigidity of the crankshaft is not so high, even if the rigidity of the bearing portion can be extremely increased, the deformation when considering the clearance causes the oil film of the crank journal portion only in the crankshaft. It bends in the clearance and slips to open back and forth.Therefore, there is a limit in suppressing bending deformation of the crankshaft only by measures on the bearing side, and it is not sufficient for stress relaxation and vibration noise reduction. is there.

The above case has the following problems. That is, when the weight of the flywheel is very large due to, for example, mounting of a flywheel damper, the resonance frequency of the bending vibration at the rear end of the crankshaft decreases, the amplitude increases, the bending stress of the crankshaft increases, and V6 When the crank pin portion is offset as in an engine, the rigidity of the crank shaft is generally low, and the combustion excitation force must be reduced as compared with other types of engines.

By the way, in Japanese Utility Model Laid-Open No. 1-145945, an arm member for supporting a balance weight adjacent to a crank pin located at least at an end of a crankshaft on a flywheel side is formed in a disk shape, and the arm member of the arm member is formed. There is described an engine noise reduction structure in which a cylinder block is provided with a guide member that rotatably supports an arm member with a part sandwiched from both sides thereof.

[0007]

Generally, it is necessary to form a lubricating oil film having a necessary and sufficient thickness in the sliding portion between the counterweight portion of the crankshaft and the supporting portion of the cylinder block. The supply of lubricating oil required for the above must be taken into consideration, but in the one described in the above publication, a part of the arm member formed in the counterweight part of the crankshaft is supported by the guide member provided in the cylinder block. Therefore, the oil film formed between both members is not formed over the entire circumference of the disc-shaped arm member, and the lubricating oil leaks when it comes off the guide member, so that the lubricating oil is not supplied to the thrust bearing portion. There is a problem that, in the worst case, it will result in bake damage unless a considerably large amount of supply is performed.

Further, in the one disclosed in the above publication, the arm member is thrust-supported only by the tip end portion of the balance weight, and only the tip end portion of the balance weight is fixedly held. There is a problem in that the device itself is originally bent in the same manner and the desired effect cannot be obtained.

The present invention solves the above problems of the prior art, reduces the amount of bending deformation of the crankshaft, relieves the bending stress of the crankshaft, and further, in the conventional engine, the crankpin portion and the crank journal portion of the crankshaft. It is an object of the present invention to provide a crankshaft support structure for an internal combustion engine, which can maintain the same stress level even if the diameter of the internal combustion engine is reduced, is light in weight, and can reduce friction loss.

[0010]

A crankshaft supporting structure for an internal combustion engine according to the present invention has a groove-shaped portion that fits into a bearing portion of a cylinder block and supports a crank journal portion of a crankshaft. A crank bearing having a thrust support portion that supports the side surface of the crank web portion is fitted to the bearing portion of the cylinder block through the groove portion.

[0011]

[Operation] When an explosive load is applied to the crank pin portion and the crank shaft is bent and deformed so as to open back and forth, the side surface of the crank web portion is also supported and constrained by the bearing portion of the cylinder block, so that the amount of bending deformation of the crank shaft Becomes smaller.

A crank bearing having a groove supporting portion which fits into a bearing portion of a cylinder block and having a journal supporting portion for supporting a crank journal portion of a crank shaft and a thrust supporting portion for supporting a side surface of a crank web portion, Since it is fitted into the bearing portion of the cylinder block through the groove portion, a sufficiently high reinforcing effect can be exhibited by thrust-supporting the crank web portion over the entire side wall of the crank journal portion.

Since the thrust bearing is formed continuously from the crank journal bearing portion and over the entire circumference, the oil film can be always held, and the oil film oil amount and the oil supplied to the journal bearing portion can be used, and the original oil pump can be used. It is enough to cover.

[0014]

1 to 5 are all for explaining one embodiment of a crankshaft support structure for an internal combustion engine according to the present invention. FIG. 1 is a sectional view of the crankshaft support structure for an internal combustion engine,
2 is a conceptual diagram showing the relationship between the upper cylinder block, the upper crank bearing and the crank shaft, FIG. 3 is a conceptual diagram showing the relationship between the lower cylinder block, the lower crank bearing and the crank shaft, and FIG. 4 is the outer diameter of the crank journal portion. FIG. 5 is a diagram for explaining the clearance between the crank web portion and the clearance, and FIG. 5 shows the outer width and crank of the upper crank bearing and the lower crank bearing fitted to the bearing portion of the upper cylinder block and the bearing portion of the lower cylinder block, respectively. It is a sectional view for explaining a clearance with an inner diameter of a journal part.

1, FIG. 2, FIG. 3 and FIG. 5, a journal support portion having a groove portion 11 which fits into the bearing portion 3 of the upper cylinder block 1 and which supports the crank journal portion 8 of the crankshaft 5. Metal crank bearings 6 and 7 divided into upper and lower parts having a thrust support portion 13 for supporting the side surface of the crank web portion 10 of the crankshaft 5 are divided into upper and lower cylinder blocks 1 through the groove portions 11. 2 are fitted to the bearing portions 3 and 4.

Reference numeral 14 is a side surface of the crank web portion 10, and 15 is a side surface.
Is a piston, 16 is a connecting rod, and 17 is a large end of the connecting rod.

In the crank web portion 10 connecting the crank journal portion 8 and the crank pin portion 9 of the crank shaft 5, a surface of the crank web portion 10 which is perpendicular to the line of the crank shaft 5 and which is adjacent to the crank journal portion 8. Are machined into flat surfaces facing each other with a predetermined gap T, and both side walls of the crank journal portions 8 of the upper and lower cylinder blocks 1 and 2 are machined, and the upper and lower cylinder blocks are divided into two upper and lower portions having a U-shaped cross section. The crank bearings 6 and 7 were mounted, the width thereof was set to a predetermined value t, the clearance was set to T-t, the diameter of the crank journal portion 8 was set to D, and the inner diameters of the journal bearings 6 and 7 were set to d, respectively. At this time, the clearance is d-D, and the clearance is set so that T-t≈d-D.

When the crankshaft 5 is bent by an explosive load or the like, the crankshaft 5 is reinforced to reduce the amount of bending, but the crankshaft 5 naturally has high rigidity,
Since the amount of bending is not so large and it is reinforced, it cannot be a reinforcing member unless it has a supporting rigidity sufficiently higher than that of the crankshaft 5. However, it has a groove-shaped portion 11 that fits into the bearing portion 3 of the upper cylinder block 1 and supports the side surface of the crank web portion 10 of the crank shaft 5 and the journal support portion 12 that supports the crank journal portion 8 of the crank shaft 5. A crank bearing 6 made of metal, which is divided into upper and lower parts, and which has a thrust support portion 13.
Since 7 is fitted to the bearing portions 3 and 4 of the upper and lower cylinder blocks 1 and 2 via the groove portion 11, a sufficiently high reinforcing effect can be exhibited.

[0019]

The crankshaft support structure for an internal combustion engine according to the present invention reduces the amount of bending deformation of the crankshaft, alleviates the bending stress of the crankshaft, and, in the conventional engine, the diameter of the pin or journal of the crankshaft. It is possible to maintain the same stress level even when the value is reduced, and it is possible to achieve an excellent effect that the weight can be reduced and the friction loss can be reduced.

[Brief description of drawings]

1 to 5 are all for explaining an embodiment of a crankshaft support structure for an internal combustion engine according to the present invention.

FIG. 1 is a cross-sectional view of a crankshaft support structure for an internal combustion engine.

FIG. 2 is a conceptual diagram showing a relationship between an upper cylinder block, an upper crank bearing and a crankshaft.

FIG. 3 is a conceptual diagram showing a relationship between a lower cylinder block, a lower crank bearing and a crank shaft.

FIG. 4 is a diagram for explaining a clearance between an outer diameter of a crank journal portion and a width between crank web portions.

FIG. 5 is a cross-sectional view for explaining the clearance between the outer widths of the upper crank bearing and the lower crank bearing and the inner diameter of the crank journal, which are fitted into the bearings of the upper cylinder block and the lower cylinder block, respectively. is there.

[Explanation of symbols]

 1 Upper cylinder block 2 Lower cylinder block 3 Bearing part of upper cylinder block 4 Bearing part of lower cylinder block 5 Crankshaft 6 Upper crank bearing 7 Lower crank bearing 8 Crank journal part 9 Crank pin part 10 Crank web part 11 Groove part ( Upper and lower crank bearings) 12 Journal support 13 Thrust support 14 Web side 15 Piston 16 Connecting rod 17 Connecting rod large end

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[Procedure amendment]

[Submission date] February 8, 1995

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Claims (1)

[Claims] 1. A crank bearing having a groove supporting portion that fits into a bearing portion of a cylinder block, the journal supporting portion supporting a crank journal portion of a crankshaft, and a thrust supporting portion supporting a side surface of a crank web portion. But,
A crankshaft support structure for an internal combustion engine, wherein the crankshaft support structure is fitted into a bearing portion of a cylinder block through the groove portion.