JPH08158936A - Cylinder block of internal combustion engine - Google Patents

Abstract

PURPOSE: To provide a cylinder block of an internal combustion engine which is designed to enhance silentness by suppressing the amplitude of the flexural resonance of the skirt of the cylinder block. CONSTITUTION: An internal combustion engine 1 is a four-cylinder automobile engine having a cylinder block 2, a cylinder head 3 secured to the top of the cylinder block 2, and an oil pan 4 secured to the bottom of the cylinder block 2. The cylinder block 2 has cylinders 6a to 6d provided between partition walls 5a to 5e, with pistons 7a to 7d freely slidably inserted into the respective cylinders 6a to 6d. In a crankshaft 9, of crank caps 18a to 18e journalled to the lower ends of the partition walls 5a to 5e, the crank caps 18b to 18c located at the m iddle are made higher than the crank caps 18a, 18e located at both axial ends, so as to increase the mass of the crank caps 18b, 18c.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder block of an internal combustion engine, and more particularly to a cylinder block of an internal combustion engine configured to suppress the amplitude of a skirt portion of the cylinder block at the time of bending resonance to improve quietness.

[0002]

2. Description of the Related Art In an internal combustion engine such as a gasoline engine or a diesel engine, a combination of periodic accelerations of moving parts (pistons, connecting rods, cranks, etc.) of respective cylinders driven at different timings and periodic changes in gas pressure are combined. Causes various vibrations. Therefore, researches for suppressing engine vibration are in progress, and the following methods are known.

For example, Japanese Utility Model Publication No. 58-51388 discloses a method of suppressing axial vibration of a crankshaft. In the engine of this publication, the crankshaft is axially supported by the bearing of the cylinder block by the crankcap, and two types of crankcaps having different masses are alternately arranged. Also,
Japanese Utility Model Laid-Open No. 56-150837 discloses a structure in which a reinforcing rib is provided on a skirt portion of a cylinder block so that the reinforcing rib becomes wider as it moves from one end to the other end of the cylinder block. It is disclosed.

Further, Japanese Patent Laid-Open No. 55-57645 discloses a structure in which the skirt portion of the cylinder block is thicker at both end portions of the cylinder block and thinner at the middle portion of the cylinder block.

[0005]

In the structure of the above publication, the crank caps having different masses are alternately arranged. Therefore, by making the natural frequencies of the adjacent crank caps different, the axial direction of the crankshaft is increased. The noise due to the crank cap resonance can be reduced by reducing the amplitude of the resonance of the crank cap excited by the input of. However, since the mode forms of the crank cap resonance and the skirt bending resonance are different and both resonance modes are non-coupling, the cylinder block excited by the lateral force orthogonal to the axial direction of the crankshaft is disclosed by the configuration of this publication. There is a problem that noise due to skirt bending resonance cannot be reduced.

Further, by changing the mass of the adjacent crank caps as in the configuration of the publication, it is possible to accidentally suppress one resonance mode among the first, second and third modes of the crank cap resonance. Even if it does, there arises a problem that other resonance modes cannot be suppressed. In addition, in order to reduce the radiated sound emitted from the cylinder block to the surroundings, it is necessary to reduce the vibration of the resonance mode (skirt bending first / third order vibration, skirt opening / closing vibration, block up / down bending) in which the center part of the skirt of the cylinder block is antinode. is important. However, in the configuration of the publication, the purpose is to improve the rigidity of the skirt portion, and the mass distribution is such that the end portion has a relatively large mass rather than the central portion of the skirt where the kinetic energy is large. However, there is a problem that the vibration of the central portion of the skirt, which is the antinode of the resonance mode, deteriorates and the radiated sound cannot be effectively reduced.

Therefore, in view of the above problems, the present invention suppresses the amplitude of the skirt bending resonance by increasing the mass of the crank cap at the intermediate position, or suppresses the amplitude of the central part of the skirt by thickening the central part of the skirt. With the goal.

[0008]

The invention according to claim 1 is
In a cylinder block of an internal combustion engine in which a crankshaft is pivotally supported by a crankcap, a mass of a crankcap located in the middle of the cylinder block among the crankcaps is compared with a mass of crankcaps located at both ends of the cylinder block. It is characterized by being large.

Further, the invention of claim 2 is characterized in that, in a cylinder block of an internal combustion engine having a bottom rail portion formed at a lower end thereof, an intermediate portion of the bottom rail portion is thicker than both ends thereof. .

[0010]

According to the first aspect of the present invention, the mass of the crank cap located in the middle of the cylinder block is made larger than that of the crank caps located at both ends, so that the crank cap is excited by the lateral force orthogonal to the axial direction of the crankshaft. It is possible to suppress the amplitude at the skirt bending resonance of the cylinder block, and the noise due to the skirt bending resonance is reduced.

Further, according to the second aspect, by making the middle portion of the bottom rail portion thicker than both ends, it is possible to suppress the vibration of the central portion of the skirt which is the antinode of the resonance mode, and the central portion of the skirt. Radiated sound due to the vibration of is effectively reduced.

[0012]

1 to 3 show a first embodiment of a cylinder block of an internal combustion engine according to the present invention. 1 is a vertical cross-sectional view of a cylinder block of an internal combustion engine, FIG. 2 is a perspective view of a crankshaft, and FIG. 3 is a perspective view of the cylinder block as seen obliquely from below. In each figure, an internal combustion engine 1 is a four-cylinder engine for a vehicle, and generally includes a cylinder block 2 and a cylinder head 3 fixed to an upper portion of the cylinder block 2.
It has an oil pan 4 fixed to the lower part of the cylinder block 2.

The cylinder block 2 has cylinders 6a to 6d provided between partition walls 5a to 5e.
Pistons 7a to 7d are slidably inserted in a to 6d. Of the four pistons 7a to 7d, pistons 7a and 7d located at both ends and a piston 7 located in the middle
b and 7c reciprocate with a phase difference of 180 °. The pistons 7a to 7d are connected to the connecting rod 8
It is connected to the crankshaft 9 via a to 8d.

The connecting rods 8a-8d are
Each has the same structure, and the big end at the lower end is connected to the crank pins 10a to 10d of the crankshaft 9 shown in FIG. The crankshaft 9 includes the crank pins 10a to 10d, crank arms 12a to 12d that support the crank pins 10a to 10d from both sides, balance weights 13a to 13d having a larger mass than the crank arms 12a to 12d, and the cylinder block 2. Partition wall 5
crank journals 14a to 14 axially supported by a to 5e
with e. A crank pulley 15 is fitted to one end of the crankshaft 9, and a flywheel 16 is fitted to the other end of the crankshaft 9.

FIG. 3 is a perspective view of the cylinder block 2 as seen obliquely from below, but for convenience, only the partitions 5c to 5e and the parts corresponding to the partitions 5c to 5e are shown. FIG.
And, as shown in FIG. 3, the partition wall 5a of the cylinder block 2
Bearings 17a to 17e that pivotally support the crank journals 14a to 14e of the crankshaft 9 are provided in the lower part of the to 5e, and a crank cap (also referred to as a bearing cap) 1 so as to face the bearings 17a to 17e.
8a to 18e are fixed by bolts 19.

The bearings 17a to 17e of the partition walls 5a to 5e are
Skirt portion 22 provided at the bottom of the cylinder block 2
And is provided so as to cross the inside of the skirt portion 22. The bearing surfaces 17a of the bearings 17a to 17e
_{1 ~17e 1} and are opposed to each other with the bearing surface 18a ₁ ~18e ₁ of the crank cap 18 a to 18 e, journals the crank journal 14a~14e of the crankshaft 9 through the arcuate metal 20,21.

In the present embodiment, among the crank caps 18a to 18e fixed to the lower ends of the partition walls 5a to 5e, the mass of the crank caps 18b to 18d located in the middle portion of the cylinder block 2 is located at both ends of the cylinder block 2. The mass of the crank caps 18a and 18e is increased. 4 shows the crank caps 18a and 18e located at both ends of the cylinder block 2, and FIG. 5 shows the crank caps 18b to 18d located at the intermediate portion of the cylinder block 2. The height dimensions La of the crank caps 18a and 18e are normal dimensions. On the other hand, the height dimension Lb of the crank caps 18b to 18d is higher than the height dimension La of the crank caps 18a and 18e by the dimension α.

Therefore, in this embodiment, the mass of the crank caps 18b to 18d is increased by increasing the height of the crank caps 18b to 18d located in the middle portion. Therefore, the crank caps 18b to
Since 18d has a larger mass than a normal one, it functions as a mass damper for suppressing the amplitude. The sizes of the crank caps 18b to 18d are set so that the crank caps 18b to 18d have an optimum mass according to the magnitude of vibration of the cylinder block 2 in the left-right direction. In the present embodiment, the difference α between the dimensions La and Lb is, for example, 60 mm.

Further, in this embodiment, since the height of the crank caps 18b to 18d located in the middle portion is simply increased, the weight increase is small and a new mass damper is not installed. There is no increase in points. During operation of the internal combustion engine 1, the crank cap 18a
The inputs to 18e include an axial input acting in the axial direction of the crankshaft 9 (front-rear force) and an axial right-angled input (lateral force, vertical force) orthogonal to the axial direction of the crankshaft 9. However, the vibration mode of the cylinder block 2 in which the engine noise becomes large is excited by the lateral force orthogonal to the axial direction of the crankshaft 9. In particular, the skirt portion 22 provided at the bottom of the cylinder block 2
Since the inside is a space, noise is increased when the skirt portion 22 is vibrated by a lateral force.

6 (A) to 6 (C) show the skirt portion 1
It is a top view which shows the secondary, secondary, and tertiary resonance states, and these states are easily excited by the lateral force. In the figure, the broken line shows the state of the skirt portion 22 when there is no vibration, and the solid line shows the maximum amplitude state of the skirt portion 22 at the time of resonance. Further, in the first resonance state shown in FIG. 6A, both end portions of the skirt portion 22 become nodes of vibration, and the skirt portion 22
The middle part of is the antinode of vibration. In the second resonance state shown in FIG. 6 (B), three portions of the skirt portion 22, that is, both end portions and the center of the skirt portion 22 serve as nodes of vibration, and one end portion of the skirt portion 22 and the center thereof are separated from each other. Also, the antinode of vibration is between the other end and the center. In the third-order resonance state shown in FIG. 6C, four points of the skirt 22 are vibration nodes, and three points between the nodes are antinodes of vibration of the skirt section 22.

As described above, in the middle portion of the skirt portion 22 excluding both end portions of the skirt portion 22, the primary and secondary portions are formed.
In any of the third and third resonance states, vibrations are antinodes. Therefore, in the present embodiment, the mass of the crank caps 18b to 18d corresponding to the intermediate portion of the skirt portion 22 is determined by the crank caps 18a and 18e at both ends. By also increasing the value, the amplitude of bending resonance of the skirt portion 22 due to the lateral force acting on the cylinder lock 2 can be effectively suppressed.

Therefore, as shown in FIGS. 6A to 6C, the primary and secondary skirt portions 22 of the cylinder block 2 are
The amplitudes of all second and third resonance modes are suppressed, noise due to bending resonance of the cylinder block 2 is reduced, and quietness during engine operation can be enhanced. Since the mode form of bending resonance generated in the cylinder block 2 differs depending on the individual configuration of each internal combustion engine 1, a mounting position of a crank cap having a large mass is selected according to each mode form, and the partition walls 5a to 5e are selected. It may be fixed to any of the above. For example, antinodes of the bending resonance of the skirt portion 22 due to the left-right force acting on the cylinder block 2 are the partition walls 5a to 5e.
In the case of corresponding to the second and third partition walls 5b and 5c, the same effect can be obtained by making the second and third crank caps 18b and 18c of the crank caps 18a to 18e larger than others. .

Alternatively, when the antinode of bending resonance of the skirt portion 22 corresponds to the third and fourth partition walls 5c and 5d of the partition walls 5a to 5e, the third and fourth cranks of the crank caps 21a to 21e. The caps 18c and 18d may be larger than the others. FIG. 7 shows the experimental results of measuring the change in vibration level in the case of the present embodiment in which the masses of the third and fourth crank caps 18c and 18d are increased and in the case where all the crank caps 18a to 18e have normal masses. . In the figure, comparing the change of the vibration level with respect to the frequency of this embodiment and the change of the vibration level with respect to the frequency in the case of the normal configuration, this embodiment is effective in reducing the vibration level in the vicinity of 2 KHz. I understand.

FIG. 8 shows the results of experiments in which changes in noise level were measured when the masses of the third and fourth crank caps 18c and 18d were increased and when the crank caps 18a to 18e all had normal masses. is there. In the figure,
Comparing the change in the noise level with respect to the engine speed of the present embodiment and the change in the noise level with respect to the engine speed in the case of the normal configuration, 100 in the case of the present embodiment.
It can be seen that the noise level is significantly reduced in the range of 0 to 4000 rpm.

FIG. 9 shows a modification of the crank caps 18b to 18d. The shape of the crank caps 18b to 18d may be increased in the vertical direction to increase the mass as described above, or the weights 23 protruding horizontally as shown in FIG. 9 may be provided on both sides of an ordinary crank cap. It may be configured to be integrally provided in the. In that case, the crank caps 18b to 18d have the same vertical dimension as that of a normal crank cap, but require a horizontal lateral spacing.

In this embodiment, since the mass damper is provided below the partition walls 5b to 5d located in the middle portion of the cylinder block 2, the amplitude of the skirt portion 22 at the time of bending resonance is reduced. Cap 18
Needless to say, the shapes of b to 18d may be shapes other than those shown in FIGS. 10 to 13 show a second embodiment of the present invention.

In each figure, the skirt portion 22 of the cylinder block 2 has bottom rail portions 31 and 32 on both sides. Thick-walled portions 31a, 3 that are thicker than both ends are formed at intermediate portions in the front-rear direction (axial direction) of the bottom rail portions 31, 32.
2a is integrally provided. Bottom rail parts 31, 3
While both ends of 2 are formed to have a normal thickness, the thick-walled portions 31a and 32a swell in a gentle curved shape so as to be thicker in the left-right direction and the vertical direction than the both ends. Therefore, in the bottom rail portions 31 and 32, as shown in FIG. 13, the position of the BB cross section, which is the center of the thick portions 31a and 32a, is thickest in the left-right direction and the vertical direction.

The shapes and thickness dimensions of the thick portions 31a and 32a can be appropriately changed in accordance with the vibration characteristics of each cylinder block 2. Therefore, since the masses of the thick portions 31a and 32a provided in the middle portions of the bottom rail portions 31 and 32 are larger than those on both sides, the thick portions 31a and 32a function as mass dampers. Further, the thick portions 31a and 32a are formed so that the mass in the middle portion of the skirt portion 22 becomes the largest because the thick portions 31a and 32a become thicker in the left-right direction and the vertical direction as they move to the center in the axial direction.

Furthermore, since the skirt portion 22 has bottom rail portions 31 and 32 at the lower end, the rigidity is improved and
The thick-walled portion 31 is provided at an intermediate portion between the bottom rail portions 31 and 32.
Since a and 32a are provided, the rigidity of the intermediate portion is further enhanced as compared with the both ends. FIG. 14 (A)-
(E) shows the resonance state of the skirt portion 22. Incidentally, FIG.
(A), (B), (D), and (E) are shown in FIG.
(C) is easily excited by vertical force. In the figure, the broken line shows the state of the skirt portion 22 when there is no vibration, and the solid line shows the maximum amplitude state of the skirt portion 22 at the time of resonance.

FIG. 14A is a plan view showing a primary resonance state when the skirt portion 22 vibrates in the left-right direction, and FIG.
14B is a plan view showing a third resonance state when the skirt portion 22 vibrates in the left-right direction, and FIG. 14C shows the skirt portion 2.
2 is a front view showing a resonance state when vertically vibrating, FIG. 14D is a plan view showing a resonance state when the skirt portion 22 vibrates to open and close left and right, and FIG. 14E is a skirt. It is CC sectional drawing which shows the resonance state when the part 22 vibrates so that it may open and close in the left-right direction.

The radiated sound generated from the cylinder block 2 due to the operation of the internal combustion engine 1 becomes loud in the resonance state as shown in FIGS. 14 (A) to 14 (E). Therefore, the radiated sound when the cylinder block 2 vibrates as shown in FIGS. 14A to 14E becomes engine noise. In addition, in FIG.
What is common to the resonance states of (A) to (E) is that the middle portion in the front-rear direction of the skirt portion 22 is the antinode of vibration. The portion of the cylinder block 2 where the kinetic energy is the largest is the lower end portion of the skirt portion 22 as can be seen from the CC cross sectional view of FIG. That is, the amplitude of the portion where the bottom rail portions 31 and 32 are provided becomes maximum.

In the present embodiment, since the thick portions 31a and 32a are provided corresponding to the portions where the kinetic energy is the largest, the thick portions 31a and 32a effectively function as a mass damper, and at the time of the above resonance. The amplitude (vibration energy) of can be suppressed. Therefore, by suppressing the amplitude of each resonance mode of the skirt portion 22 of the cylinder block 2, it is possible to reduce the radiated sound due to the resonance of the cylinder block 2 and increase the quietness during engine operation.

In the resonance state, the amplitude of the lower end of the skirt portion 22 is maximum, and the strain energy is also maximum in the middle portion of the lower end of the skirt portion 22. Therefore, the thick part 3
Since the rigidity of the lower end of the skirt portion 22 is improved by 1a and 32a, it is possible to sufficiently withstand the strain energy of the middle portion of the lower end of the skirt portion 22. Therefore, the vibration of the oil pan 4 fixed to the lower end of the skirt portion 22 can also be suppressed by the thick portions 31a and 32a, whereby engine noise can be further reduced.

In the above embodiment, the cylinder block 2 of four cylinders is taken as an example, but the present invention is not limited to this, and it is needless to say that it can be applied to other than four cylinders (three cylinders, six cylinders, etc.). is there. Needless to say, the present invention can be applied to internal combustion engines other than automobiles.

[0035]

As described above, according to the invention of claim 1,
Since the mass of the crank cap located in the middle of the cylinder block is large, the amplitude of the skirt bending resonance of the cylinder block that is excited by the lateral force orthogonal to the axial direction of the crankshaft is suppressed, and the noise due to the skirt bending resonance is reduced. It is possible to improve the quietness of the internal combustion engine.

According to the second aspect of the present invention, since the middle portion of the bottom rail portion is made thick, the amplitude of the central portion of the skirt, which is the antinode of the resonance mode, is suppressed, and the radiated sound due to the vibration of the central portion of the skirt is suppressed. Can be effectively reduced, and the quietness of the internal combustion engine can be further enhanced. Furthermore, since the rigidity of the bottom end of the skirt can be increased by the middle part of the thick bottom rail part, the rigidity effect can be obtained and the emission noise from the oil pan attached to the bottom end of the skirt can be achieved by suppressing the amplitude of the center part of the skirt. Can also be reduced.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an internal combustion engine to which a first embodiment of a cylinder block according to the present invention is applied.

FIG. 2 is a perspective view of a piston, a connecting rod, and a crankshaft.

FIG. 3 is a perspective view of a skirt portion of a cylinder block as seen from below.

FIG. 4 is a side view showing a normal crank cap.

FIG. 5 is a side view showing a crank cap having a larger mass than usual.

FIG. 6 is a plan view for explaining a resonance state of a skirt portion of a cylinder block.

FIG. 7 is a graph showing changes in vibration level with respect to frequency.

FIG. 8 is a graph showing changes in noise level with respect to engine speed.

FIG. 9 is a side view showing a modified example of the crank cap having a larger mass than usual.

FIG. 10 is a front view of a cylinder block according to a second embodiment of the present invention.

FIG. 11 is a plan view of a cylinder block according to a second embodiment.

12 is a vertical cross-sectional view showing a cross section taken along the line AA in FIG.

13 is a vertical cross-sectional view showing a BB cross section in FIG.

FIG. 14 is a diagram showing a resonance state of a skirt portion by a lateral force.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder block 3 Cylinder head 4 Oil pan 5a-5e Partition wall 6a-6d Cylinder 7a-7d Piston 8a-8d Connecting rod 9 Crankshaft 10a-10d Crank pin 12a-12d Crank arm 13a-13d Balance weight 14a-14e Crank journal 17a to 17e Bearing 18a to 18e Crank cap 22 Skirt part 31 and 32 Bottom rail part 31a and 32a Thick part

Claims (2)

[Claims] 1. A cylinder block of an internal combustion engine in which a crankshaft is pivotally supported by a crankcap, wherein the mass of the crankcap located in the middle of the cylinder block among the crankcaps of the crankcaps located at both ends of the cylinder block. A cylinder block for an internal combustion engine, which is characterized in that it is larger than the mass. 2. A cylinder block for an internal combustion engine having a bottom rail portion formed at a lower end thereof, wherein an intermediate portion of the bottom rail portion is thicker than both ends thereof.