JP2005155324A - Piston profile processing method for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piston profile processing method for an internal combustion engine for keeping low lubricating oil consumption for a long period of time, reducing noise, and preventing cavitation erosion of a cylinder liner. <P>SOLUTION: After an engine in which a top ring is locked against rotation in a top ring groove 11 is operated under a predetermined operating condition, wear angles θ1, θ2 with respect to a sliding face of the cylinder liner on a thrust side and an anti-thrust side are measured. Based on the measurement result, the piston profile a, ... is processed so that wear angle difference ¾θ1-θ2¾ with respect to the sliding face of the cylinder liner on the thrust side and the anti-thrust side of the top ring is kept to the minimum. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for processing a piston profile of an internal combustion engine, and more particularly, to measures for keeping the consumption amount of lubricating oil low over a long period of time.

  In general, the piston profile of an internal combustion engine is closely related to problems such as consumption of lubricating oil, noise and cavitation erosion caused by vibration of the cylinder liner, and seizure of the piston and ring.

  Therefore, conventionally, as a method for determining the optimum piston profile, the amount of thermal deformation during piston operation is obtained from thermal deformation analysis, and it is determined so as to match the proven piston profile. It was very difficult to determine the optimum piston profile because the dimensions and operating conditions of each part of the engine had subtle effects.

  On the other hand, with the recent tightening of exhaust gas regulations, demands for reducing the consumption of lubricating oil that can cause HC, which is a component of PM (particulate matter), tend to become very strong. For this reason, in determining the optimum piston profile, it has been necessary to rely on trial and error of the trial and error as described above.

By the way, among the piston rings, the top ring located on the combustion chamber side of the piston seals the combustion gas, and the lubricating oil temperature rises in the second land portion (between the top ring groove and the second ring groove below it). By suppressing gas pressure and keeping the gas pressure low, the behavior of the top ring is stabilized and the consumption of lubricating oil is kept low. In that case, to keep the consumption of the lubricant low for a long time, the shape of the sliding surface of the top ring against the cylinder liner is properly maintained, that is, the wear angle of the sliding surface of the top ring against the cylinder liner is properly adjusted. It is conventionally known that it is necessary to maintain (see, for example, Patent Document 1 and Patent Document 2).
Japanese Utility Model Publication No. 57-073340 Japanese Patent Application Laid-Open No. 07-286667

  By the way, since a large thrust force acts on the piston near the top dead center where the compression stroke moves to the expansion stroke, the piston rotates to the thrust side around the piston pin by the thrust force (the center of gravity of the piston is above the piston pin). However, the piston moves laterally, and one point of the outer peripheral portion of the piston collides with the sliding surface of the cylinder liner, and a so-called swing motion is generated in which the piston rotates with the collision point as a fulcrum. When such a swing motion occurs, the sliding surface of the top ring with respect to the cylinder liner wears most, so the amount of piston collapse when the swing motion occurs (when the thrust force acts) and the sliding of the top ring with respect to the cylinder liner. There is a deep relationship between the wear angle of the moving surface.

  In that case, the direction in which the piston falls is different depending on the profile of the piston. Specifically, if the maximum diameter of the piston in operation is a so-called bell-shaped piston below the piston pin, the top of the piston is around the piston pin. It falls to the thrust side. On the other hand, in the case of a so-called barrel-shaped piston in which the maximum diameter of the piston is on the upper side of the piston pin, the top of the piston falls to the anti-thrust side around the piston pin. In this way, when a strong thrust force acts on the piston and swings near the top dead center, a strong in-cylinder pressure acts on the top ring and the back of the top ring. The sliding surface of the cylinder liner is slid against the lower surface and the sliding surface of the cylinder. The sliding surface of the top ring with respect to the cylinder liner is roughly the bottom surface of the top ring groove and the sliding surface of the cylinder liner. It will be worn at an angle between. In other words, the sliding surface of the top ring with respect to the cylinder liner has a wear angle difference corresponding to twice the amount of piston collapse between the thrust side and the anti-thrust side. Therefore, when the amount of tilting of the piston is large, even if an appropriate wear angle is obtained on the thrust side (or anti-thrust side), an inappropriate wear angle is obtained on the anti-thrust side (or thrust side). Consumption increases.

  In addition, if the piston profile is inappropriate and the amount of tilting of the piston is large, the speed and distance of sliding on the cylinder liner sliding surface of the top ring during swinging motion will increase, and the combustion gas seal on the bottom surface of the top ring will increase. In addition to the deterioration of performance and the amount of wear on the sliding surface of the top ring and cylinder liner, this not only increases the amount of lubricating oil consumption, but also the impact force when the piston collides with the cylinder liner becomes excessive. This increases vibration and noise, and in some cases, causes cavitation erosion of the cylinder liner.

  The present invention has been made in view of the above points, and an object of the present invention is to keep the consumption of the lubricating oil low over a long period of time and to reduce noise and prevent cavitation erosion of the cylinder liner. An object of the present invention is to provide a method for machining a piston profile of an internal combustion engine.

  In order to achieve the above object, the solution of the invention according to claim 1 is an internal combustion engine in which a piston having a top ring abutment fixed in a pin direction in a top ring groove is incorporated as a piston profile processing method for an internal combustion engine. After the engine is operated under predetermined operating conditions, the wear angle of the top ring on the thrust side and the anti-thrust side with respect to the sliding surface of the cylinder liner is measured, and based on the measurement result, the thrust side of the top ring and The piston profile is machined so as to minimize the wear angle difference with respect to the sliding surface of the cylinder liner on the anti-thrust side.

  Due to this specific matter, after operating an internal combustion engine incorporating a piston with the top ring locked against the top ring groove under predetermined operating conditions, the cylinder liners on the thrust side and the anti-thrust side of the top ring are operated. By measuring the wear angle with respect to the sliding surface, a half of the wear angle difference is grasped as the amount of fall during the swinging motion due to the thrust force near the top dead center where the compression stroke moves to the expansion stroke. . Since the amount of piston collapse generally corresponds to the maximum amount of piston collapse (fall angle) during the entire stroke, how much the shape of the piston profile at each part of the piston should be changed based on the direction and amount of piston collapse. Is easily and accurately determined.

  Thus, based on the measurement result of the wear angle with respect to the sliding surface of the cylinder liner on the thrust side and the anti-thrust side of the top ring, the difference in wear angle with respect to the sliding surface of the cylinder liner on the thrust side and the anti-thrust side of the top ring. If the piston profile is machined so that the piston is as small as possible, the amount of tilting during the operation of the piston can be kept low, and the entire circumference of the top ring on the thrust side and the anti-thrust side is against the sliding surface of the cylinder liner. The wear shape is properly maintained, and the amount of lubricating oil consumed can be kept low over a long period of time.

  In addition, the amount of tilting during operation of the piston is kept low, so that the impact load when colliding with the cylinder liner due to the swinging motion caused by the thrust force during operation of the piston is kept low, reducing vibration and noise of the cylinder liner. In addition, the cavitation erosion of the cylinder liner can be prevented.

  As described above, according to the present invention, after operating an internal combustion engine incorporating a piston whose top ring is prevented from rotating in a top ring groove under predetermined operating conditions, the thrust side and the anti-thrust side of the top ring The piston profile is adjusted to minimize the difference in wear angle with respect to the sliding surface of the cylinder liner on the thrust side and anti-thrust side of the top ring based on the measurement results of the wear angle with respect to the sliding surface of the cylinder liner. By processing, the amount of tilting of the piston during operation is kept low, the wear shape on the sliding surface of the cylinder liner on the thrust side and the anti-thrust side of the top ring is properly maintained, and the amount of lubricant consumption is increased. Can be kept low over time. In addition, the impact load when colliding with the cylinder liner due to the swinging motion of the thrust force during operation of the piston can be kept low, the vibration and noise of the cylinder liner can be reduced, and cavitation erosion of the cylinder liner can be prevented. Can do.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIGS. 1 and 2 are external views of a piston showing the piston structure of the four-cycle internal combustion engine according to the first embodiment of the present invention. As the piston, the maximum diameter of the skirt portion 10 below the piston pin 14 is shown. A bell-shaped piston 1 formed into a so-called bell-shaped piston, which is located on the lower side and gradually increases as it goes to the lower end of the skirt portion 10, is applied.

  A top ring groove 11 positioned at the uppermost position and three piston ring grooves 12 to 14 positioned sequentially below the top ring groove 11 are provided on the upper portion of the bell-shaped piston 1.

  A piston pin 15 extending in the crankshaft direction (not shown) is provided on the lower side of the bell-shaped piston 1 (not shown). The piston pin 15 is connected to the crankshaft via a connecting rod (not shown). As shown in FIGS. 2 and 3, the top ring groove 11 of the bell-shaped piston 1 is fitted with a ring-shaped top ring 3 having an end portion 31. Further, each of the piston ring grooves 12 to 14 is fitted with a ring-shaped endless piston ring 4 (only the uppermost one is shown in the figure) having a joint portion (not shown). Reference numeral 16 denotes a second land portion of the bell-shaped piston 1 positioned between the top ring groove 11 and the uppermost piston ring groove 12 below the top ring groove 11.

  A large thrust force F acts on each piston 1 in the vicinity of the top dead center where the compression stroke moves to the expansion stroke. Therefore, the bell-shaped piston 1 is rotated around the piston pin 15 by the thrust force F toward the thrust side (piston). 1 is located above the piston pin 15), the piston 1 moves sideways, and one point on the outer periphery of the piston 1 collides with the sliding surface 51 of the cylinder liner 5. Thus, a so-called swinging motion in which the piston 1 rotates in the arrow N direction (thrust direction) is generated. In this case, as shown in FIG. 1, the bell-shaped piston 1 has a collision point below the piston pin 15, so that the top of the bell-shaped piston 1 rotates to the thrust side with the collision point as a fulcrum, that is, the center of the piston The axis p is inclined in the direction of arrow N by an inclination angle θ {unit: ′ (1/60 °)}.

  When a strong thrust force F acts on the bell-shaped piston 1 and swings near the top dead center, a strong in-cylinder pressure is also acting on the upper surface and the rear surface of the top ring 3, so that FIG. As shown in FIG. 5, the top ring 3 slides on the sliding surface 51 of the cylinder liner 5 in a state where the top ring 3 is strongly pressed against the lower surface of the top ring groove 11 and the sliding surface 51 of the cylinder liner 5. The sliding surface (outer peripheral surface) with respect to the cylinder liner 5 is worn at angles θ1 and θ2 formed by the orthogonal line y that is substantially orthogonal to the lower surface of the top ring groove 11 and the sliding surface 51 of the cylinder liner 5. That is, the sliding surface (outer peripheral surface) of the top ring 3 with respect to the cylinder liner 5 is defined by an orthogonal line y orthogonal to the lower surface of the top ring groove 11 on the thrust side and the anti-thrust side, and the sliding surface 51 of the cylinder liner 5. A difference occurs in the wear angle between θ1 and θ2 and the thrust side and the anti-thrust side (considering the sign), and the difference (considering the sign) corresponds to twice the tilting amount (falling angle θ) of the piston 1.

In this case, if the amount of tilting of the piston 1 is large, even if an appropriate wear angle θ1 is obtained on the thrust side, an inappropriate wear angle θ2 is obtained on the anti-thrust side, and the amount of consumption of the lubricating oil increases. . In addition, the amount of tilting of the piston 1 (falling angle θ) is
θ = | θ1-θ2 | / 2
Is required.

  Here, an example of the processing method of the piston profile of the bell-shaped piston 1 will be described with reference to FIGS.

  First, the abutment 31 of the top ring 3 is fixed in the direction of the piston pin 15 orthogonal to the rotation direction of the bell-shaped piston 1 that rotates in the thrust direction with the collision point as a fulcrum by the thrust force acting on the bell-shaped piston 1. In the case of the bell-shaped piston 1, as shown by a two-dot chain line in FIG. 6, the abutment portion 31 of the top ring 3 is thrust when a swing motion occurs in which the piston 1 rotates in the arrow N direction (thrust side). If it is fixed to the side, the consumption rate of the lubricating oil will be very large, but if it is fixed within the range of about 180 ° on the opposite side of the thrust side, the lubricating oil will have a substantially constant low consumption rate. That's it. Specifically, as shown in FIGS. 2 and 3, the abutment portion 31 of the top ring 3 of the bell-shaped piston 1 is thrust side (in the direction of arrow N) with the collision point as a fulcrum by the thrust force F acting on the piston 1. In the direction of the piston pin 15 that is orthogonal to the rotation direction of the piston 1 that rotates at the top, the top ring 3 is locked and fixed by a knock pin 35 that is inserted into the top ring groove 11. In this case, on the upper part of the joint portion 31 of the top ring 3, substantially quarter arc-shaped cutout portions 31 a and 31 a that abut against the knock pin 35 and regulate the periphery of the top ring 3 are provided corresponding to each other. ing.

  Next, an engine (internal combustion engine) (not shown) incorporating the bell-shaped piston 1 in which the top ring 3 is prevented from rotating by the knock pin 35 in the direction of the piston pin 15 is operated under predetermined operating conditions.

  Thereafter, the bell-shaped piston 1 is removed from the engine, and the wear angle of the sliding surface of the top ring 3 with respect to the bottom surface of the top ring 3 on the thrust side and the anti-thrust side of the top ring 3 is measured. As the difference, wear angles θ1 and θ2 with respect to the sliding surface 51 of the cylinder liner 5 are obtained.

  Thereafter, the cylinder liner 5 on the thrust side and the anti-thrust side of the top ring 3 based on the measurement results of the wear angles θ1 and θ2 with respect to the sliding surface 51 of the cylinder liner 5 on the thrust side and the anti-thrust side of the top ring 3. The piston profile is processed so that the difference in wear angle with respect to the sliding surface 51 is minimized.

  A specific processing procedure of the piston profile will be described with reference to FIG. In this case, it is not necessary to correct the piston profile if the tilting amount (falling angle) of the bell-shaped piston 1 is not more than a certain reference value θ0, and if it is not less than the reference value θ0, it is necessary to correct the piston profile. However, the reference value θ0 here means that the predetermined operating condition is not necessarily the maximum load condition of the engine, variation in the deformation at the time of construction, and further, the amount of thermal deformation resulting from deterioration of the cooling performance due to long-term use This is a value that should be determined in consideration of an increase in the value, and is determined empirically.

  First, since the piston profile is generally displayed as a diameter, thermal deformation due to temperature distribution acting during operation under predetermined operating conditions and mechanical deformation due to in-cylinder pressure are obtained using a stress (deformation) analysis program or the like. The amount of deformation at each point is doubled, and in addition to the piston profile for processing (not shown), the piston profile a during operation (shown by a broken line in FIG. 7) is obtained.

  Next, a maximum diameter line b (a line parallel to the piston center axis p) in contact with the piston profile a of the piston 1 is drawn, and a wear angle difference | θ1-θ2 | (the piston center axis by the thrust force F) on the piston center axis p side. A tangent line c inclined at an angle corresponding to an angle twice the tilt amount θ of p) is drawn. An imaginary line e (indicated by a two-dot chain line in FIG. 7) passing through the intersection d of the tangent line c and the maximum diameter line b and inclined with respect to the maximum diameter line b toward the piston central axis p by the reference value θ0 is the maximum diameter. Draw between line b and tangent c.

  Then, a piston profile f (shown by a thick solid line in FIG. 7) of the piston main body h in contact with the virtual line e and the maximum diameter line b is obtained. The piston profiles f and f of the ring land portion r and the top portion t are obtained by adding the amount of change in the diameter of the portion to the piston profiles a and a at the ring land portion r and the top portion t, respectively.

  Therefore, the modified piston profile for machining is subtracted from the modified operating piston profile f, the amount of operation change (thermal deformation due to temperature distribution and mechanical deformation due to in-cylinder pressure) first added. Is required.

  In this case, since the amount of mechanical deformation due to the in-cylinder pressure is generally small, only the thermal deformation due to the temperature distribution may be considered in obtaining the piston profile a during operation.

  Thus, in the above embodiment, after the engine incorporating the piston 1 in which the top ring 3 is prevented from rotating in the top ring groove 11 and operated under predetermined operating conditions, the thrust side of the top ring 3 and By measuring the wear angles θ1 and θ2 with respect to the sliding surface 51 of the cylinder liner 5 on the thrust side, the top angle where an angle θ which is a half of the wear angle difference | θ1−θ2 | shifts from the compression stroke to the expansion stroke. It is grasped as the amount of fall during the swinging motion due to the thrust force near the point. Since the amount of piston 1 tilting substantially corresponds to the maximum piston tilting amount (falling angle) during the entire stroke, each part of the piston 1 (piston body h) is determined from the tilting direction (thrust side) of the piston 1 and the tilting amount θ. , How much the piston profiles a,... In the ring land part r and the top part t) should be changed can be easily and accurately determined.

  Thereby, the cylinder liner 5 on the thrust side and the anti-thrust side of the top ring 3 based on the measurement results of the wear angles θ1 and θ2 with respect to the sliding surface 51 of the cylinder liner 5 on the thrust side and the anti-thrust side of the top ring 3. If the piston profiles a,... Are processed so as to make the wear angle difference | θ1-θ2 | of the sliding surface 51 as small as possible, the amount of collapse of the piston 1 during operation can be suppressed low. The wear shape with respect to the sliding surface 51 of the cylinder liner 5 on the thrust side and the anti-thrust side is appropriately maintained, and the consumption amount of the lubricating oil can be kept low over a long period of time.

  In addition, since the amount of collapse during the operation of the piston 1 is kept low, the impact load when the piston 1 collides with the cylinder liner 5 due to the swinging motion caused by the thrust force during the operation of the piston 1 can be kept low. -Noise can be reduced and cavitation erosion of the cylinder liner 5 can be prevented.

  Next, a second embodiment of the present invention will be described with reference to FIG.

  In this second embodiment, the processing procedure of the piston profile when the amount of thermal deformation of the bell-shaped piston 1 during operation is unknown will be described.

  That is, when the amount of thermal deformation of the bell-shaped piston 1 during operation is unknown, as shown in FIG. 8, the processing piston profile g (shown by a broken line in FIG. 8) is used, and the amount of thermal deformation is known. Similarly to the case, the maximum diameter line j (line parallel to the piston center axis p) contacting the piston profile g of the piston 1 is drawn, and the wear angle difference | θ1-θ2 | (the piston center by the thrust force F) is drawn to the piston profile g. A tangent line k inclined at an angle corresponding to an angle twice the tilt amount θ of the axis p is drawn. Then, an imaginary line m (indicated by a two-dot chain line in FIG. 8) is drawn in contact with the piston profile g that is inclined toward the piston central axis p by the reference value θ0 with respect to the maximum diameter line j.

  Next, a corrected piston profile n is obtained by adding the amount of change in the diameter of the tangent line k and the imaginary line m to the piston profile g.

  In this case, also in the second embodiment, it is possible to obtain the same function and effect as in the first embodiment.

  In each of the above embodiments, the case where the piston profile of the bell-shaped piston 1 is processed has been described. However, the present invention is not limited to this. For example, a so-called barrel-shaped piston whose maximum diameter is above the piston pin. Of course, it can also be applied to. In that case, the barrel-shaped piston falls to the anti-thrust side around the piston pin due to the swing motion by the thrust force.

It is an outline figure showing typically a bell-shaped piston concerning Example 1 of the present invention. It is the external view of the piston which similarly shows the joint part vicinity of a top ring. It is sectional drawing of the piston similarly cut | disconnected in the joint part vicinity of a top ring. It is a sectional view explaining the wear angle to the sliding surface of the cylinder liner on the thrust side of the top ring. It is sectional drawing explaining the wear angle with respect to the sliding surface of the cylinder liner in the anti-thrust side of a top ring similarly. It is a characteristic view which similarly shows the characteristic of the consumption rate of lubricating oil with respect to the fixed position of the joint part of the top ring of a bell-shaped piston. It is explanatory drawing which similarly shows the process sequence of the piston profile of a piston. It is explanatory drawing which shows the process sequence of the piston profile of the bell-shaped piston concerning Example 2 of this invention.

Explanation of symbols

1 Bell-shaped piston (piston)
11 Top ring groove 3 Top ring 5 Cylinder liner 51 Sliding surface a Piston profile θ0 Piston tilt amount reference value θ1 Wear angle on the thrust side of the top ring θ2 Wear angle on the anti-thrust side of the top ring | θ1-θ2 ｜
Wear angle difference

Claims (1)

In a piston profile processing method for an internal combustion engine,
After operating an internal combustion engine that incorporates a piston that prevents the top ring from rotating in the top ring groove under predetermined operating conditions,
Measure the wear angle against the sliding surface of the cylinder liner on the thrust side and anti-thrust side of the top ring,
A piston profile machining method for an internal combustion engine, characterized in that a piston profile is machined so as to minimize a wear angle difference with respect to a sliding surface of a cylinder liner on the thrust side and the anti-thrust side of a top ring based on the measurement result .

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