JP2000088709A - Method for predicting inclination of crankshaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit simple and accurate measurement of the amount of inclination of a crankshaft by obtaining a force acting on the crankshaft at the time of the rotation of the crankshaft, obtaining the rigidity of the crankshaft at every crank angle, and obtaining the inclination of the crankshaft with respect to a bearing at every crank angle. SOLUTION: Initial conditions are first inputted to a computer to perform processing to compute a force acting on a crankshaft in one stroke of an engine. Next, on the basis of the obtained force acting on the crankshaft and the rigidity of the crankshaft, the inclination of the crankshaft is obtained. In other words, the rigidity of the crankshaft at the time when a crank angle θ is 0 degree is first computed. Next, on the basis of the obtained force acting on the crankshaft at the time when the crank angle θ is 0 degree and the rigidity of the crankshaft, the inclination of the crankshaft at the time when the crank angle θ is 0 degree is obtained. In addition, the inclination of the crankshaft is similarly obtained at every predetermined angle over one stroke of the operation of the crankshaft.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for estimating the inclination of a crankshaft, and more particularly to a method for estimating the inclination of a crankshaft in a piston / crank mechanism such as an engine.

[0002]

2. Description of the Related Art An engine such as a diesel engine generally has a configuration in which a reciprocating motion of a piston is converted into a rotary motion by a crankshaft. Such a piston
Ideally, in a crank mechanism, the crankshaft is arranged without inclination. However, in practice, a tilt occurs in the crankshaft, and if the tilt amount is large, a one-sided contact occurs between the crankshaft and the bearing, which causes damage to the bearing.

[0003] In this case, conventionally, when a trouble such as damage to a bearing occurs, a place where a one-sided contact occurs is estimated from a place where the trouble occurs.
The installation amount of the main bearing is changed based on the experience of skilled technicians.

[0004]

However, there is a problem that such a conventional method is only a trial and error response based on the experience of a technician.

SUMMARY OF THE INVENTION It is an object of the present invention to solve such a problem and to easily and accurately obtain a tilt amount for correcting a tilt of a crankshaft.

[0006]

SUMMARY OF THE INVENTION In order to achieve this object, the present invention predicts the inclination of a crankshaft of a piston / crank mechanism in an engine or the like with respect to its bearing. In addition to determining the acting force, the crankshaft rigidity at each crank angle is determined, and the inclination of the crankshaft with respect to the bearing at each crank angle is determined from the force acting on the crankshaft and the crankshaft rigidity.

In this case, since the inclination of the crankshaft is obtained in consideration of not only the force acting on the crankshaft but also its rigidity, the amount of the inclination is generally high accuracy but requires several hours or more for processing. Compared to a case where analysis is performed using a supercomputer or the like, it can be obtained in a matter of seconds with ease and with good practical accuracy.

Further, according to the present invention, a change in bearing position due to thermal expansion of a device having a piston / crank mechanism is obtained, and a difference between the bearing positions of a pair of adjacent bearings is determined. The inclination angle of the crankshaft due to the effect of thermal expansion in the bearing is obtained by calculating the difference between the inclination angle of one bearing and the inclination angle of the other side in each bearing. The inclination of the crankshaft due to the influence of thermal expansion and the sum of the inclination of the crankshaft obtained from the force acting on the crankshaft and the rigidity of the crankshaft are determined, and this sum is used as the inclination of the crankshaft.

In this case, in addition to the inclination of the crankshaft obtained from the above-described force acting on the crankshaft and the rigidity of the crankshaft, the inclination of the crankshaft due to the influence of thermal expansion is taken into consideration. The inclination amount can be obtained with higher accuracy.

Further, according to the present invention, the maximum inclination and the minimum inclination of the crankshaft in each bearing are determined based on the result of the inclination amount obtained as described above, and the average value thereof is determined. The difference between the average values of the bearings is divided by the distance between the bearings to determine the inclination angle between the bearings, and the position of the bearing is changed so that the inclination angle between the bearings becomes zero.

In this case, the amount of installation of the bearing can be adjusted so that the inclination of the crankshaft is significantly reduced.

[0012]

FIG. 5 is a front view showing a schematic configuration around a crankshaft of a seven-cylinder marine diesel engine. Here, the crankshaft 1 has seven cranks 2A to 2C.
G. 3A to 3H are journals. The journals 3A to 3G are supported by bearings 4A to 4G. The journal 3H at the rear end of the engine corresponding to the rear side of the boat is formed longer than the other journals and is supported by a pair of bearings 4H and 4I. 5 is a connection part to a propeller shaft. Each of the bearings 4A to 4I
It is installed at a position at a certain height h from an engine installation surface 6 such as a ship bottom by a housing (not shown).

FIG. 6 is a side view of the portion shown in FIG. In this figure, a connecting rod 9 is formed by a crank 2A to 2G and a piston 8 sliding up and down inside a cylinder 7.
Indicates a connected state. is the crank angle, and here the top dead center position is set to 0 degree.

FIG. 1 shows a flow of a method for estimating the inclination of a crankshaft according to the present invention, which will be described below with reference to FIG. A detailed description will be given later. First, when the process is started in step 101, in step 102, initial conditions are input to a computer that performs the process. Next, in step 103, the force acting on the crankshaft is calculated for one step of operating the engine. One step of this operation is, for example, two rotations of the crankshaft, that is, 0 to 720 degrees for a four-cycle engine, and one rotation, that is, 0 to 360 degrees for a two-cycle engine. This force includes gas pressure in the cylinder, inertial force, centrifugal force, and the like.

Then, the inclination of the crankshaft is obtained based on the force acting on the crankshaft thus obtained and the rigidity of the crankshaft. That is, step 1
In step 04, first, the stiffness of the crankshaft when the crank angle θ is 0 degree is calculated. Next, in step 105, the force acting on the crankshaft when the crank angle θ obtained in step 103 is 0 degree, The inclination (1) of the crankshaft when the crank angle θ is 0 degrees is obtained based on the rigidity of the crankshaft. In addition, in steps 106 and 107, the inclination of the crankshaft is similarly obtained at predetermined angles over one step of the operation of the crankshaft. As a result, not only the force acting on the crankshaft,
Since the inclination of the crankshaft is determined in consideration of the rigidity, the amount of inclination can be easily and accurately obtained.

In the present invention, it is possible to end the process at the stage where the inclination of the crankshaft for each predetermined crank angle θ is obtained in this way. Alternatively, it is also possible to obtain the inclination of the crankshaft with higher accuracy in consideration of the influence of thermal expansion as described below.

That is, when the crankshaft is provided in the engine as described above, the temperature of the crankshaft rises above normal temperature during operation, and accordingly, a bearing for supporting the journal of the crankshaft, that is, a shaft supporting portion. Height changes.
In this case, if the temperature conditions and the like differ between a pair of bearings supporting the journal portions on both sides of each crank in FIG. 5, the heights of these bearings change mutually, and the crankshaft is tilted. In step 108 in FIG. 1, the inclination (2) of the crankshaft thus generated is obtained.

In step 109, in addition to the crankshaft tilt (1) obtained from the above-mentioned force acting on the crankshaft and the crankshaft rigidity, the crankshaft tilt (2) due to the influence of thermal expansion is calculated. In consideration of the above, the inclination of the crankshaft is obtained from the sum of the two inclinations (1) + (2). As a result, the inclination amount can be obtained with higher accuracy.

Finally, the calculation result is output in step 110, and the process ends in step 111.

Hereinafter, each of the above processes will be described in detail. FIG. 2 shows the details of the input processing of the initial condition in step 102 and the calculation of the force acting on the crankshaft in step 103 in FIG. If the process is started in step 201, step 20 corresponding to step 102
In 2, an initial condition is input. That is, specifications data such as the length, diameter, and weight of the crankshaft, bearing spacing, reciprocating mass, rotating mass, center of gravity position, cylinder diameter, cylinder stroke, connecting rod length, number of revolutions, ignition sequence, gas explosion Data such as force, engine lubricating oil temperature, engine ambient temperature, and height from the engine installation surface to the center of the crankshaft are given as initial conditions.

Next, corresponding to step 103 of FIG.
Perform the calculation of the force acting on the crankshaft. First, in step 203, the calculation is started from the case where the crank angle θ is 0 degrees. Then, first, in step 204, calculation is performed for the crank at the tip of the crankshaft.

At this time, for the sake of simplicity, as shown in FIG. 7, the portion of the crankshaft 1 supported by the pair of bearings 4A, 4B is approximated as a straight round bar, and during operation of the engine, The force acting on the center of the crankshaft is calculated. At this time, a force F1 obtained by adding the load due to the gas pressure, the inertial force of the reciprocating part, and the centrifugal force of the rotating part such as the crankpin is provided at the center between the bearings 4A and 4B.
Works. Based on the structure of the crankshaft, on both sides of the portion where this force F1 acts, a force F which is the sum of the centrifugal force of the crank arm and the centrifugal force of the counterweight is applied.
2. F3 works.

The crankshaft 1 applies these forces F1, F2,
As shown in the figure, the crankshaft 1 is bent at the bearings 4A and 4B by receiving the F3. α is the inclination angle.

In step 204 in FIG. 2, the horizontal component and the vertical component of the force acting on the center of the crankshaft 1 are obtained. Then, in step 205,
The same calculation is performed for the angular crank going from the front end to the rear end of the crankshaft. If it is confirmed in step 205 that the calculation up to the rear end of the crankshaft has been performed, then in steps 206 and 207, the crank angle θ is advanced by a fixed angle, that is, 5 degrees here, and the same calculation is repeated. . If it is confirmed in Step 206 that the calculation for one operation step, that is, two or one rotation of the crankshaft is completed, Step 2
It moves to 08 and ends processing. The calculation result is stored in the memory.

Next, details of the calculation of the stiffness of the crankshaft and the calculation of its inclination (1) shown in steps 104 to 107 of FIG. 1 will be described with reference to FIG. In FIG. 3, if the process is started in step 301, in step 302, the calculation is started from the case where the crank angle θ is 0 degrees, as in the case of the previous step 203.
Then, first, regarding the crank at the tip of the crankshaft, in step 303, the rigidity of the crankshaft is calculated.

Assuming that the crank angle is 0 degree at the top dead center position as described above, the stiffness of the crankshaft at each crank angle θ is expressed by the following equation that makes the inclination of the crankshaft in the main bearing equal. Can be.

[0027]

(Equation 1)

The rigidity of the crankshaft becomes maximum at 90 ° and 270 ° crank angles and becomes minimum at 0 ° and 180 ° with respect to vertical force. The opposite is true for horizontal forces. Note that the stiffness at the crank angles of 0 and 90 degrees in the above equation is a value obtained from a calculation equation of the material dynamics. In the above equation, the first term represents the amount of change in rigidity at the crank angle θ, and φ represents the crank angle phase related to the firing order of each cylinder.
The first term “±” takes “+” for a vertical force and “−” for a horizontal force. The second term represents the average of both stiffness amplitudes.

Thus, in step 303 of FIG. 3, the rigidity of the crankshaft at the crank angle at that time is calculated. Next, at step 304, the force acting on the center of the crankshaft, calculated in the flow of FIG. In step 305, boundary conditions at both ends of the crankshaft necessary for calculating the inclination of the crankshaft are given.

The inclination of the crankshaft is calculated by using a transmission matrix method, which is one of the structural analysis methods, to calculate the inclination of the crankshaft support portion approximated to a straight round bar having arbitrary support conditions. Done by That is, the constant element of the transfer matrix is given in step 306, and the product of the transfer matrix is calculated in step 307. Then, in step 308, the same calculation is performed up to the bearing at the rear end of the crankshaft.

Next, based on the calculation results, in steps 309, 310, and 311 from the front end to the rear end of the crankshaft, the shaft state quantity in each bearing, that is, the displacement and inclination (1) are calculated.

Then, the above calculation is performed for the horizontal direction and the vertical direction as in step 312, and the crank angle θ is advanced by a fixed angle, that is, 5 degrees here as in steps 313 and 314. Is repeated. Then, in step 313, when it is confirmed that the calculation for one operation step has been completed, the process proceeds to step 315, and the process ends. The calculation result is stored in the memory.

Next, details of the calculation of the inclination in consideration of the thermal expansion of the engine, which are shown in steps 108 to 110 of FIG.
This will be described with reference to FIG. That is, if the process is started in Step 401, in Steps 402 and 403, the change in the height of the shaft supporting portion, that is, the bearing, due to the thermal expansion of the engine is obtained for all the bearings by the thermal expansion calculation formula. Then, in step 404, the difference between the heights of the adjacent bearings is obtained, and in step 405, the value is divided by the distance between the bearings to calculate the inclination angle. In step 406, similar calculations are performed for all bearings.
Further, in step 407, the difference (2) based on the change in the height of the bearing due to the thermal effect of the engine is obtained by calculating the difference between the tilt angles on both sides of the bearing. Step 4
At 08, similar calculations are performed for all bearings.

Then, in step 409, the data of the inclination (1) previously stored is called, and in step 410, the sum (1) + (2) of the two inclinations is calculated, thereby obtaining the crankshaft to be obtained. The inclination is obtained. If the calculation result is output in step 411, step 41
The process ends at 2.

As described above, the inclination of the crankshaft obtained from the force acting on the crankshaft and the rigidity of the crankshaft (1)
By adding the inclination of the crankshaft (2) due to the effect of thermal expansion, the amount of inclination of the crankshaft can be obtained with extremely high accuracy.

FIG. 8 shows the actual crankshaft inclination (1) +
The calculation result of (2) is shown. In the figure, the horizontal axis represents the crank angle θ, and the vertical axis represents the inclination angle A. The sign of the inclination angle A is
This means that the direction of the inclination is reversed as shown in FIG. Ax is the vertical tilt angle, and Ay is the horizontal tilt angle. In FIG. 8, the inclination angle Ay in the horizontal direction is biased in the negative direction from 0 degrees to 360 degrees, and it can be seen that the inclination in the negative direction occurs. The irregularities in the diagram represent the magnitude of the slope.

In the above description, an engine has been described as an example of a device having a piston / crank mechanism, but the present invention can be applied to other devices as well.
Further, as described above, in the engine, since the device temperature rises at room temperature during operation, it is extremely significant to consider the crankshaft inclination (2) due to the thermal expansion. However, in other devices, it may not be necessary to consider such a rise in device temperature,
In that case, only the inclination (1) obtained from the force acting on the crankshaft and the rigidity of the crankshaft may be sufficient.

Next, the inclination (1) +
From (2), a method of installing a bearing for an engine crankshaft, that is, a method of calculating an installation amount will be described. First, the maximum inclination and the minimum inclination of the crankshaft in each bearing are determined based on the above calculation results, and then the average value thereof is determined. Next, for the pair of bearings on both sides of each crank, the difference between the average values of the crankshaft inclinations obtained as described above is calculated. Then, the tilt angle is calculated by dividing the difference by the distance between the bearings on both sides. As a result, the inclination angle of the crankshaft is obtained for each crank.

Therefore, while considering the inclination angles of the adjacent cranks, the amount of displacement of the bearing required to give the opposite inclination to make the inclination angle zero is determined. Thereby, the final installation amount is obtained. Actually, since the amount of installation, that is, the amount of displacement of the bearing for correcting the inclination is very small, it is possible to adjust the thickness by changing the thickness of the bearing metal without displacing the housing of the bearing. it can. The following table compares the amount of countermeasures to eliminate the amount of installation of the engine bearings, that is, the amount of countermeasures to eliminate the inclination, by trial and error based on the experience of conventional technicians and the calculation results of the present invention. It is. It can be seen that almost the same tendency is observed in both cases.

[0040]

[Table 1]

When the inclination angle is set to 0 in this manner, for example, the diagram of the inclination angle Ay in the horizontal direction in FIG.
In the state where the unevenness is maintained, the value changes so as to approach 0.0E + 0.

The amount of inclination of the crankshaft affects the rigidity of the crankshaft. Therefore, according to the present invention, the inclination amount of the crankshaft, that is, the one-sided contact between the crankshaft and the bearing can be predicted in advance, and if the one-sided amount is known, conversely, the stiffness of the crankshaft is appropriately changed based on it. be able to.

[0043]

As described above, according to the present invention, the force acting on the crankshaft during rotation of the crankshaft is determined, and the rigidity of the crankshaft at each crank angle is determined. Since the inclination of the crankshaft with respect to the bearing at each crank angle is obtained from the rigidity of the crankshaft, the amount of the inclination can be easily and accurately obtained.

According to the present invention, a change in the bearing position due to the thermal expansion of the device having the piston / crank mechanism is obtained, and the difference between the bearing positions of a pair of adjacent bearings is obtained.
The inclination angle between a pair of these adjacent bearings is obtained,
By calculating the difference between the tilt angle of one side of each bearing and the tilt angle of the other side, the tilt of the crankshaft due to the thermal expansion of the bearing is determined, and the crankshaft due to the thermal expansion is determined. The sum of the inclination of the shaft and the inclination of the crankshaft obtained from the force acting on the crankshaft and the rigidity of the crankshaft is obtained, and the sum is used as the inclination of the crankshaft. be able to.

Further, according to the present invention, the maximum inclination and the minimum inclination of the crankshaft in each bearing are determined based on the result of the inclination amount obtained as described above, and the average value thereof is determined. The difference between the average values of the bearings is divided by the distance between the bearings to determine the inclination angle between the bearings, and the position of the bearing is changed so that the inclination angle between the bearings becomes zero. The installation amount of the bearing can be adjusted so that the inclination is significantly reduced.

[Brief description of the drawings]

FIG. 1 is a flowchart of a crankshaft inclination prediction method according to an embodiment of the present invention.

FIG. 2 is a diagram showing details of a main part of FIG. 1;

FIG. 3 is a diagram showing details of another main part of FIG. 1;

FIG. 4 is a diagram showing details of still another main part of FIG. 1;

FIG. 5 is a front view showing a schematic configuration around a crankshaft of a marine diesel engine to which the crankshaft inclination prediction method of the present invention can be applied.

FIG. 6 is a side view of the portion shown in FIG. 5;

FIG. 7 is a diagram for explaining a force acting on a crankshaft.

FIG. 8 is a diagram showing a calculation result of an actual inclination of a crankshaft of a bearing that has a partial contact during operation of an engine.

FIG. 9 is a diagram for explaining a direction of inclination of a crankshaft.

[Explanation of symbols]

 1 Crankshaft 4A-4I Bearing θ Crank angle A Tilt angle

Claims (3)

[Claims] When estimating the inclination of a crankshaft of a piston / crank mechanism in an engine or the like with respect to a bearing, a force acting on the crankshaft when the crankshaft is rotated is determined. A crankshaft inclination prediction method, wherein rigidity is obtained, and a crankshaft inclination with respect to a bearing at each crank angle is obtained from a force acting on the crankshaft and the crankshaft rigidity. 2. A change in a bearing position accompanying thermal expansion of a device having a piston / crank mechanism is determined, and a tilt angle between the pair of adjacent bearings is determined from a difference between the bearing positions of the pair of adjacent bearings. By determining the difference between the inclination angle of one side of the bearing and the inclination angle of the other side, the inclination of the crankshaft due to the thermal expansion of the bearing is determined. The crankshaft tilt obtained by calculating the sum of the tilt of the crankshaft due to the influence and the tilt of the crankshaft obtained from the force acting on the crankshaft and the rigidity of the crankshaft, and calculating the sum as the tilt of the crankshaft. 1. The method for predicting a tilt of a crankshaft according to 1. 3. A maximum inclination and a minimum inclination of a crankshaft in each bearing are determined and an average value thereof is determined based on a result obtained by the crankshaft inclination prediction method according to claim 1 or 2. Obtaining the inclination angle between the bearings by dividing the difference between the average values of the pair of adjacent bearings by the distance between the bearings, and changing the position of the bearing so that the inclination angle between the bearings becomes zero. Characteristic mounting method of crankshaft bearing.