JP2015158154A - Engine piston structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine piston structure capable of suppressing a piston, a piston pin, and a small end portion of a connecting rod from integrally resonating with respect to a large end portion of the connecting rod in a combustion stroke, suppressing noise increase in the other strokes, facilitating adjusting vibration control performance even for a dynamic vibration absorber attached into the piston pin, attaining desired vibration control performance, and facilitating measuring an eigen frequency in a nocontact manner.SOLUTION: A dynamic vibration absorber 20 includes: a fixed portion 20a fixed to a piston pin 2; a movable portion 20b extending in an axial direction of the piston pin 2; and a support portion 20c swingably supporting the movable portion 20b with respect to the fixed portion 20a, the dynamic vibration absorber 20 being assembled so that end portions of the movable portion 20b are located axially outward of axial end portions of the piston pin 2.

Description

  The present invention connects a piston that reciprocates in a cylinder, a connecting rod having a small end connected to the piston and a large end connected to a crankshaft, and the piston and the small end of the connecting rod. The present invention relates to a piston structure of an engine provided with a piston pin having a hollow cross section and a dynamic vibration absorber provided inside the piston pin.

  Generally, in an engine mounted on a vehicle such as an automobile, a piston and a small end portion of a connecting rod are connected by a piston pin. Specifically, the piston pin is inserted through a pin insertion hole formed at the small end portion of the connecting rod, and the small end portion of the connecting rod is positioned at the central portion in the central axis direction of the piston pin. Two bosses are formed at both ends of the piston pin central axis direction on the back surface of the piston (the surface opposite to the top surface, that is, the surface on the anti-combustion chamber side) so as to sandwich the small end portion of the connecting rod. The two boss portions are respectively formed with pin support holes for inserting the both end portions of the piston pin in the central axis direction and supporting the both end portions (see, for example, Patent Document 1).

  In the above engine, it is known that combustion noise is generated by resonance determined by the basic structure of the engine (for example, see Non-Patent Document 1). In Non-Patent Document 1, the engine sound has three peaks of 1.7 kHz, 3.3 kHz, and 6 kHz, and one of those peaks (3.3 kHz) is due to the expansion and contraction resonance of the connecting rod, and the amplitude of the resonance It is said that there is almost no room for reduction.

JP 2004-353500 A

Masaya Otsuka, “Diesel Combustion Noise Reduction Method in Engine Structure”, Automobile Engineering Society Academic Lecture Preprints No. 36-05, Society of Automotive Engineers of Japan, May 2005, p7-10

  The inventors of the present invention have intensively studied the spring mass model of the piston and the connecting rod, and as a result, have found the following.

In the spring mass model of the piston and connecting rod, the small end of the piston, piston pin, and connecting rod as a whole corresponds to the mass point (mass is defined as M (unit kg)), and the small end and large end of the connecting rod The connecting portion connecting the two corresponds to a spring (the spring constant is K (unit N / m)) that supports the mass point with respect to the large end portion. As a result, assuming that the piston, piston pin, and small end of the connecting rod are integrated, the resonance frequency is (1 / 2π) · (K / M) ^1/2 Hz with respect to the large end of the connecting rod. Resonance occurs (for example, 3 kHz to 4 kHz). This resonance corresponds to the expansion / contraction resonance of the connecting rod described in Non-Patent Document 1.

  By the way, a lubricating oil film is formed between the piston pin and the pin insertion hole of the connecting rod. This lubricating oil film corresponds to a spring that connects the piston pin and the small end of the connecting rod. In addition, when a full-float assembly method that allows the piston pin to rotate with respect to both the boss and the small end of the connecting rod is adopted, it is added between the piston pin and the pin insertion hole of the connecting rod. Thus, a lubricating oil film is also formed between the piston pin and the pin support hole of the boss portion of the piston. This lubricating oil film corresponds to a spring that connects the piston pin and the piston.

  If there is a lubricating oil film between the piston pin and the pin insertion hole of the connecting rod (in the full float type, the lubricating oil film and the lubricating oil film between the piston pin and the pin support hole of the boss portion of the piston), the piston The small end portion of the connecting rod is supported via a spring, and the piston, piston pin, and small end portion of the connecting rod are not integrally resonated with respect to the large end portion of the connecting rod. Except for the combustion stroke (expansion stroke), the piston is not pressed with a large force, so that the lubricating oil film exists, and thus the resonance does not occur.

  On the other hand, in the combustion stroke, since the piston is pressed with a large force, the lubricating oil film disappears, and as a result, the piston, piston pin, and the small end of the connecting rod are united to resonate with the large end of the connecting rod. It will be.

  From the above viewpoint, since the piston, piston pin, and connecting rod small end are integrated in the combustion stroke, it is considered to use a dynamic vibration absorber to suppress the resonance (reduce the vibration at the resonance frequency). It is done. However, by simply providing a dynamic vibration absorber, even though the noise due to the resonance can be reduced in the combustion stroke, the vibration, due to the vibration of the dynamic vibration absorber, in other strokes where the piston, piston pin and connecting rod small ends are not integrated. Noise will increase.

  In addition, when the dynamic vibration absorber is assembled in the piston pin and deviates from the target vibration absorption characteristic, there is a problem that the target vibration damping performance cannot be obtained. In particular, in the dynamic vibration absorber assembled in the piston pin, it is structurally difficult to adjust the vibration damping performance.

  In addition, after assembling the dynamic vibration absorber inside the piston pin, in order to investigate whether it is the target vibration absorption characteristic, the natural frequency of the dynamic vibration absorber will be measured. It is conceivable to perform measurement using a contact-type measuring device such as an acceleration pickup. However, as a dynamic vibration absorber, a small and lightweight one is used assuming that it is assembled inside the piston pin, so if measurement is performed using a contact-type measuring device such as an acceleration pickup, the dynamic vibration absorber The mass of the attached measuring device itself may affect the measurement result. Therefore, it is conceivable to measure the natural frequency of the dynamic vibration absorber in a non-contact manner. However, in this case as well, how to measure the dynamic vibration absorber assembled in the piston pin is a big problem.

  Accordingly, the present invention suppresses the resonance of the piston, piston pin, and the small end of the connecting rod with respect to the large end of the connecting rod in the combustion stroke, and suppresses an increase in noise in the other stroke. In addition, it is possible to easily adjust the damping performance even in the dynamic vibration absorber attached inside the piston pin, so that the desired damping performance can be obtained, and the natural frequency is measured without contact. In some cases, the object is to provide an engine piston structure that can easily do this.

  The piston structure of the engine according to the present invention includes a piston that reciprocates in a cylinder, a connecting rod having a small end connected to the piston and a large end connected to a crankshaft, and a small end of the piston and the connecting rod. A piston structure of an engine comprising a piston pin having a hollow cross section connecting the parts, and a dynamic vibration absorber provided inside the piston pin, wherein the dynamic vibration absorber is fixed to the piston pin; A movable portion extending in the axial direction of the piston pin, and a support portion that supports the movable portion so as to be swingable with respect to the fixed portion, and the end of the movable portion is more axial than the axial end of the piston pin. It is assembled so as to be located outside the direction.

  According to the above configuration, in the combustion stroke, the lubricating oil film between the piston pin and the connecting rod (in the full float type, the lubricating oil film and the lubricating oil film between the piston pin and the piston) is lost, and the piston, the piston pin, and When the small ends of the connecting rods are integrated, the dynamic vibration absorber can prevent them from resonating together. In addition, since the dynamic vibration absorber is provided inside the piston pin, when there is a lubricating oil film between the piston pin and the connecting rod, that is, in the intake stroke, the compression stroke, and the exhaust stroke, the lubricating oil film (spring) The vibration of the vibration absorber is not transmitted to the connecting rod, and noise does not increase due to the vibration. Further, by providing a dynamic vibration absorber inside the piston pin, the space can be used effectively and the piston does not need to be large.

In addition, by assembling the end of the movable part so that it is positioned outside the axial end of the piston pin in the axial direction, it is easy to grind the end of the dynamic vibration absorber provided inside the piston pin. Yes. For this reason, the natural frequency (resonance frequency) of the dynamic vibration absorber can be easily adjusted, and a target vibration absorption performance can be obtained.
In addition, when measuring the natural frequency of a dynamic vibration absorber without contact, the end of the movable part positioned outside the axial direction of the piston pin in the axial direction can be easily measured. The frequency can be measured.

  In one embodiment of the present invention, the dynamic vibration absorber includes a shaft portion extending from the support portion in the axial direction of the piston pin, and the movable portion is fixed to the shaft portion and an outer periphery of the shaft portion and can swing together with the support portion. The dynamic vibration absorber is assembled so that the end portion of the shaft portion or the end portion of the mass adjustment portion is positioned outside the axial direction end portion of the piston pin in the axial direction. .

According to the said structure, the mass adjustment of a movable part is possible by replacement | exchange of a mass adjustment part, and it is excellent in convenience, such as correction of a manufacturing error.
In addition, when the masses of the movable parts of the two dynamic vibration absorbers are made different from each other by the mass adjustment by the mass adjustment part, the peak of the frequency characteristic, that is, the resonance frequency can be shifted from each other due to the difference in mass. In addition to vibration at a frequency, vibration can be reduced in a relatively wide frequency range including the resonance frequency.

  In one embodiment of the present invention, the natural frequency of the dynamic vibration absorber is measured, and when the natural frequency deviates from a predetermined value, the end of the movable part is ground to adjust the natural frequency. It is configured.

  According to the above configuration, the natural frequency can be adjusted more accurately by performing the adjustment based on the difference between the actual natural frequency of the dynamic vibration absorber and the predetermined value.

  In one embodiment of the present invention, two dynamic vibration absorbers are provided, and the natural frequency is individually measured and adjusted individually.

  According to the above configuration, it is possible to appropriately adjust the one of the two dynamic vibration absorptions where the resonance frequency is deviated from the predetermined value.

  According to the present invention, the piston, the piston pin, and the small end of the connecting rod are prevented from resonating with the large end of the connecting rod in the combustion stroke, and noise is prevented from increasing in other strokes. In addition, the dynamic vibration absorber mounted inside the piston pin can be adjusted easily so that the desired vibration absorption performance can be obtained, and the natural frequency is measured without contact. Has the effect of making this easy.

The figure which shows the piston and connecting rod of the engine by which the piston structure of this invention was employ | adopted. 1 is a cross-sectional view taken along line AA in FIG. 2 is an enlarged cross-sectional view of the main part Diagram showing spring mass model of piston and connecting rod Perspective view showing measuring equipment for inertance inspection Explanatory diagram for explaining inertance inspection (A) is explanatory drawing for demonstrating the grinding process of an assembly type damper, (b) is explanatory drawing for demonstrating the grinding process of an integrated damper Sectional drawing which shows the other Example of the piston structure of an engine The principal part expanded sectional view of FIG. Sectional drawing which shows other Example of the piston structure of an engine 10 is an enlarged cross-sectional view of the main part of FIG. Sectional drawing which shows other Example of the piston structure of an engine The principal part expanded sectional view of FIG.

  In the combustion stroke, the piston, piston pin, and the small end of the connecting rod can be prevented from resonating integrally with the large end of the connecting rod, and noise can be suppressed from increasing in other strokes, The dynamic vibration absorber installed inside the piston pin can also be easily adjusted to obtain the desired vibration absorption performance. When measuring the natural frequency without contact, this can be done easily. The purpose of making it possible to do this is to provide a piston that reciprocates in a cylinder, a connecting rod having a small end connected to the piston and a large end connected to a crankshaft, and the piston and connecting rod. Piston structure of an engine comprising a piston pin having a hollow cross section for connecting a small end portion and a dynamic vibration absorber provided inside the piston pin The dynamic vibration absorber includes a fixed portion that is fixed to the piston pin, a movable portion that extends in the axial direction of the piston pin, and a support portion that supports the movable portion so as to be swingable with respect to the fixed portion. The movable part is assembled so that the end of the movable part is positioned outside the axial end of the piston pin in the axial direction.

An embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a view showing a piston structure of a diesel engine, FIG. 1 is a view showing a piston and a connecting rod of the engine, FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, and FIG. .

  1 and 2, the piston 1 repeats a cylinder cycle (intake stroke, compression stroke, combustion stroke (expansion stroke), and exhaust stroke), thereby causing a cylinder axis direction (FIG. 1, FIG. 1) in a cylinder (cylinder). 2 up and down).

  The piston 1 is connected via a piston pin 2 to a small end portion 10 a (so-called small end) that is one end portion of a connecting rod 10. A large end 10b (so-called large end), which is the other end of the connecting rod 10, is connected to a crankshaft (not shown). The small end portion 10a and the large end portion 10b of the connecting rod 10 are connected by a connecting portion 10c. The reciprocating motion of the piston 1 is transmitted to the crankshaft through the connecting rod 10 to rotate the crankshaft. The central axial direction of the piston pin 2 (the horizontal direction in FIG. 2) coincides with the axial direction of the crankshaft.

  The small end portion 10a of the connecting rod 10 is formed with a pin insertion hole 10d through which the piston pin 2 is inserted, and the large end portion 10b of the connecting rod 10 is formed with a shaft insertion hole 10e through which the crankshaft is inserted. Yes. Although not shown in FIG. 1, the large end portion 10b of the connecting rod 10 is divided into two at the center of the shaft insertion hole 10e in the longitudinal direction of the connecting portion 10c.

  The piston pin 2 is inserted into the pin insertion hole 10 d in the small end portion 10 a of the connecting rod 10, and the small end portion 10 a of the connecting rod 10 is located in the central portion of the piston pin 2 in the central axis direction. Further, the small end portion 10 a of the connecting rod 10 is located at the center of the piston 1 in the central axis direction of the piston pin 2.

  The piston pin 2 is rotatably inserted into the pin insertion hole 10 d of the connecting rod 10. A bush 11 is fixed to the inner peripheral surface of the pin insertion hole 10d of the connecting rod 10, and strictly speaking, the piston pin 2 is rotatably inserted into the bush 11.

  A lubricating oil film is formed between the piston pin 2 and the pin insertion hole 10d (specifically, the bush 11) of the connecting rod 10 by supplying lubricating oil circulated in the engine. With the bush 11, the piston pin 2 rotates smoothly with respect to the pin insertion hole 10 d of the connecting rod 10.

As shown in FIG. 2, a cavity 1 a is formed on the top surface (piston head) of the piston 1, and a top ring groove 1 b, a second ring groove 1 c, and an oil ring groove 1 d are formed on the land portion of the piston 1. At the same time, a cooling channel 1 e is formed in the piston 1.
As shown in FIG. 1, a top ring 12, a second ring 13, and an oil ring 14 are mounted in the ring grooves 1b, 1c, and 1d, respectively.

  Two boss portions 1f sandwich the small end portion 10a of the connecting rod 10 from both sides at both ends in the central axis direction of the piston pin 2 on the back surface of the piston 1 (the surface opposite to the top surface, that is, the anti-combustion chamber side). As described above, the bulge is formed on the crankshaft side. These two boss portions 1 f are respectively formed with pin support holes 1 g extending in the central axis direction of the piston pin 2. Both end portions in the central axis direction of the piston pin 2 are inserted into and supported by the pin support holes 1g of the two boss portions 1f.

In this embodiment, a full float type is adopted as an assembly method of the piston pin 2.
That is, the piston pin 2 can be rotated with respect to the pin insertion hole 10 d of the connecting rod 10, and can also be rotated with respect to the pin support hole 1 g of the boss portion 1 f of the piston 1.

  A lubricating oil film is also formed between the piston pin 2 and the pin support hole 1g of the boss portion 1f of the piston 1 in the same manner as between the piston pin 2 and the pin insertion hole 10d of the connecting rod 10. The pin 2 rotates smoothly with respect to the pin support hole 1g of the boss 1f of the piston 1.

  A circlip 15 is inserted and fixed to each end of the pin 1 in the pin support hole 1g of the two boss portions 1f on the outer peripheral surface side of the piston 1, and the two circlips 15 are both fixed in the direction of the central axis of the piston pin 2. Positioned so as to be in contact with the outer end surfaces, respectively, the movement of the piston pin 2 in the central axis direction is restricted.

  The piston pin 2 is hollow in cross section, and a through-hole 2 a extending in the central axis direction of the piston pin 2 is formed at the radial center of the piston pin 2. A press-fit portion 2b into which a fixed portion 20a of a dynamic vibration absorber 20 to be described later is press-fitted into a central portion in the central axis direction of the piston pin 2 on the inner peripheral surface of the through hole 2a (that is, a central portion in the longitudinal direction of the piston pin 2). Is provided. The inner diameter of the through hole 2a in the press-fit portion 2b is set smaller than the inner diameter of the through hole 2a in the other part.

  Specifically, the through-hole 2a is located in the central portion of the piston pin 2 in the central axis direction, is connected to the press-fit portion 2b formed in a small diameter cylindrical shape, and both sides of the press-fit portion 2b, and the central axis of the piston pin 2 It has the accommodating part 2c formed in the cylindrical shape of a large diameter located in the both ends of a direction.

  A stepped surface 2d facing the central axis direction of the piston pin 2 is formed by a step between the press-fitting portion 2b and the accommodating portion 2c. By making the press-fitting portion 2b have a small diameter, the rigidity of the piston pin 2 can be improved.

  Inside the piston pin 2 (in the through hole 2a), the piston 1, the piston pin 2, and the small end portion 10a of the connecting rod 10 are integrated in the combustion stroke, and resonate with the large end portion 10b of the connecting rod 10. Two dynamic vibration absorbers 20 (so-called dynamic dampers, hereinafter simply referred to as dampers) to be suppressed are disposed. As shown in FIG. 3, these two dampers 20 are located on both sides of a plane that passes through the center of the piston pin 2 in the center axis direction and is perpendicular to the center axis of the piston pin 2. Yes.

  Here, the spring mass model of the piston 1 and the connecting rod 10 is as shown in FIG. That is, the piston 1, the piston pin 2, and the small end portion 10a of the connecting rod 10 as a whole correspond to a mass point (mass is defined as M (unit kg)), and the connecting portion 10c of the connecting rod 10 determines the mass point of the connecting rod 10 This corresponds to a spring (the spring constant is K (unit N / m)) supported with respect to the large end portion 10b.

  The lubricating oil film between the piston pin 2 and the pin insertion hole 10d of the connecting rod 10 corresponds to a spring that connects the piston pin 2 and the small end portion 10a of the connecting rod 10, and the piston pin 2 and the boss portion 1f of the piston 1 The lubricating oil film between the pin support hole 1g corresponds to a spring connecting the piston pin 2 and the piston 1 (boss portion 1f).

In the combustion stroke, since the piston 1 is pressed with a large force, a lubricating oil film between the piston pin 2 and the pin insertion hole 10d of the connecting rod 10 (a spring connecting the piston pin 2 and the small end portion 10a of the connecting rod 10). , And the lubricating oil film (spring connecting the piston pin 2 and the piston 1) between the piston pin 2 and the pin support hole 1g of the boss 1f of the piston 1 is lost. As a result, the piston 1 and the piston pin 2 And the small end part 10a of the connecting rod 10 is united. As a result, the piston 1, the piston pin 2, and the small end portion 10a of the connecting rod 10 are integrated with the large end portion 10b of the connecting rod 10 at a resonance frequency of (1 / 2π) · (K / M) ^1/2 Hz. It will resonate.
In order to suppress this resonance (reducing vibration at the resonance frequency), the two dampers 20 are provided inside the piston pin 2 (in the through hole 2a).

  As shown in FIGS. 2 and 3, each damper 20 includes a fixed portion 20 a that is fixed to a press-fit portion 2 b provided on the inner peripheral surface of the through-hole 2 a of the piston pin 2, and the piston 20 within the piston pin 2. A movable portion 20b extending in the central axis direction of the pin 2 and a support portion 20c that supports the movable portion 20b so as to vibrate in the radial direction of the piston pin 2 with respect to the fixed portion 20a.

  In this embodiment, the two dampers 20 are integrally formed from the viewpoint of reducing the number of parts. Further, one damper 20 on the left side in the figure is formed integrally with a fixed part 20a, a movable part 20b, and a support part 20c (integrated damper), and the other damper 20 on the right side in the figure is assembled with a plurality of members. It is an assembly type damper that is formed in this way (an assembly type damper).

  The integrated damper 20 and the assembled damper 20 are integrally connected to each other by a fixed portion 20a. The integrated fixing part 20a is press-fitted and fixed in the press-fitting part 2b. Thereby, the movable part 20b of the integrated damper 20 is accommodated inside the one accommodating part 2c, and the movable part 20b of the assembled damper 20 is accommodated inside the other accommodating part 2c. And each damper 20 is assembled | attached so that the edge part 20b1 of the movable part 20b may be located in the axial direction exterior rather than the axial direction edge part of the piston pin 2. As shown in FIG.

The movable portion 20b is formed in a substantially cylindrical shape, and the outer diameter thereof is smaller than the inner diameter of the housing portion 2c so that it does not contact the inner peripheral surface of the housing portion 2c even when the movable portion 20b vibrates. The dimensions are designed. Thus, the movable portion 20b is disposed inside the accommodating portion 2c so that the outer peripheral surface of the movable portion 20b is opposed to the inner peripheral surface of the accommodating portion 2c with a slight gap therebetween.
Moreover, each of the dampers 20 and 20 described above is provided with a restricting means for mechanically restricting the axial movement thereof.

  That is, the integrated damper 20 on the left side in FIG. 3 has a larger outer diameter D5 on the support portion 20c side of the movable portion 20b than the inner diameter D4 of the minimum diameter portion of the step surface 2d of the piston pin 2 (D5> D4), thereby constituting the regulating means 30.

In FIG. 3, the assembly type damper 20 on the right side of the figure is integrally formed with a support portion 20 c with a shaft portion 20 d extending from the support portion 20 c in the piston pin axial direction, and a cap portion serving as a mass adjusting member on the outer periphery of the shaft portion 20 d. 40 is fixed, and the movable portion 20b is formed by the shaft portion 20d and the cap portion 40 described above. The assembled damper 20 is assembled so that both the end of the shaft portion 20d and the end of the cap portion 40 are located outside the axial end of the piston pin 2 in the axial direction. The end portion of the shaft portion 20d is located outside the axial direction end portion of the cap portion 40 in the axial direction.
Further, the shaft portion 20d is directed from the support portion 20c toward the outer end side, the first shaft portion 21 having an outer diameter D3, the second shaft portion 22 having an outer diameter D1, and a third shaft having an outer diameter D2. The shaft portion 23 and the fourth shaft portion 24 having an outer diameter of DO are integrally formed in this order, and the outer diameter dimensions of the shaft portions 21 to 24 are set so that the relational expression of DO <D1 <D2 <D3 is satisfied. doing.

A step surface 25 is formed at the end of the fourth shaft portion 24 on the support portion 20 c side, and the inner side is large between the radially outer end of the step surface 25 and the third shaft portion 23. A tapered portion 26 having a small diameter on the outside is formed.
The cap portion 40 is formed in a two-stage cylindrical shape in which a press-fit portion 41 located on the front end side in the press-fit direction and a neck portion 42 loosely fitted on the outer periphery of the fourth shaft portion 24 are integrally formed. A stopper 44 is formed between the cylindrical portion 43 having the same inner and outer diameters as the inner and outer diameters of the portion 41 and the neck portion 42. When the cap portion 40 is press-fitted, the stopper 44 comes into contact with the stepped surface 25 so as to press-fit. Is configured to complete.

A clearance is formed between the inner diameter portion of the cylindrical portion 43 of the cap portion 40 and the outer diameter portion of the third shaft portion 23 in the shaft portion 20d.
Thus, the outer diameter D6 of the cap portion 40 (outer diameter of the movable portion 20b) is made larger than the inner diameter D4 of the minimum diameter portion of the stepped surface 2d of the piston pin 2 (D6> D4), thereby restricting. The means 31 is configured.

  Incidentally, the support portion 20c is also formed in a substantially cylindrical shape, and is interposed between the movable portion 20b and the fixed portion 20a. The outer diameter of the support portion 20c is smaller than the outer diameter of the movable portion 20b and the inner diameter of the press-fit portion 2b, and can be inserted into the press-fit portion 2b.

  Thus, the support portion 20c is disposed inside the press-fit portion 2b so that the outer peripheral surface of the support portion 20c faces the inner peripheral surface of the press-fit portion 2b with a sufficient gap. Thereby, the support part 20c supports the movable part 20b so that it can vibrate in the radial direction of the piston pin 2 with respect to the fixed part 20a.

  The fixed portion 20a is also formed in a columnar shape. The outer diameter of the fixed portion 20a is smaller than the outer diameter of the movable portion 20b, but is slightly larger than the inner diameter of the press-fit portion 2b. Thereby, the fixing part 20a can be press-fitted into the press-fitting part 2b. The fixed portion 20a, the movable portion 20b, and the support portion 20c are connected in series in a state where the central axes are matched.

  The central axis of the integrated damper 20 and the central axis of the assembled damper 20 are arranged so as to coincide with the central axis of the piston pin 2. The masses of the movable parts 20b of the two dampers 20 and 20 are substantially the same, and the center of gravity of the movable part 20b of the two dampers 20 and 20 is located on the central axis of the piston pin 2, and the piston The pins 2 are positioned symmetrically with respect to a plane passing through the center in the central axis direction of the pin 2 (a plane passing through the center and perpendicular to the central axis of the piston pin 2).

  The support portion 20c of each damper 20, 20 corresponds to a spring that supports the movable portion 20b (the mass of the movable portion 20b is m (unit kg)), and its spring constant is k (unit N / m). In order to suppress the resonance, basically, the value of k / m may be configured to be substantially the same as K / M. The length and diameter of the movable portion 20b and the length and diameter of the support portion 20c are set so that such a value of k / m can be obtained. Strictly speaking, it is necessary to consider the mass of the support portion 20c, but the mass of the support portion 20c can be ignored because the mass of the support portion 20c is considerably smaller than the mass of the movable portion 20b. In addition, when vibration may increase at a frequency other than the resonance frequency, the value of k / m does not have to be substantially the same as K / M.

  It is preferable that the masses of the movable portions 20b of the two dampers 20 are substantially the same so that the spring constants of the two dampers 20 (support portions 20c) are different from each other. This is because vibration can be reduced not only at the resonance frequency but also in a relatively wide frequency range including the resonance frequency. In order to make the spring constants of the two dampers 20 different from each other, the lengths or diameters of the support portions 20c in the two dampers 20 may be made different from each other. Alternatively, both the length and the diameter of the support portion 20c in the two dampers 20 may be different from each other. Alternatively, the materials of the support portions 20c in the two dampers 20 may be different from each other. Note that the spring constants of the two dampers 20 may be substantially the same.

  When the spring constants of the two dampers 20 are different from each other, for example, the spring constant of one damper 20 is set so that the value of k / m is substantially the same as K / M, and the spring constant of the other damper 20 is set. Is made larger or smaller than the spring constant of one damper 20.

  As described above, in the combustion stroke, the lubricating oil film (the spring connecting the piston pin 2 and the small end portion 10a of the connecting rod 10) between the piston pin 2 and the pin insertion hole 10d of the connecting rod 10, and the piston pin 2 And the lubricating oil film (spring connecting the piston pin 2 and the piston 1) between the pin supporting hole 1g of the boss portion 1f of the piston 1 is lost, and as a result, the piston 1, the piston pin 2 and the connecting rod 10 are small. The end portion 10d is united to resonate with the large end portion 10b. However, in this embodiment, the resonance is suppressed by the damper 20 provided on the piston pin 2, and noise due to the resonance can be reduced.

  On the other hand, in the intake stroke, the compression stroke, and the exhaust stroke, respectively, between the piston pin 2 and the pin insertion hole 10d of the connecting rod 10, and between the piston pin 2 and the pin support hole 1g of the boss portion 1f of the piston 1, respectively. Lubricating oil film exists. As a result, resonance that occurs in the combustion stroke does not occur. If the damper is provided at the small end of the connecting rod, the above-described resonance can be suppressed in the combustion stroke, but the damper vibrates also in the intake stroke, the compression stroke, and the exhaust stroke where no resonance occurs. For this reason, in the intake stroke, the compression stroke, and the exhaust stroke, noise is increased due to the vibration of the damper. However, in this embodiment, since the damper 20 is provided on the piston pin 2, in the intake stroke, the compression stroke, and the exhaust stroke, a lubricating oil film (piston pin) between the piston pin 2 and the pin insertion hole 10d of the connecting rod 10 is used. 2) and the small end 10a of the connecting rod 10), the vibration of the damper 20 is not transmitted to the connecting rod 10, and noise does not increase by the vibration. Further, by providing the damper 20 inside the piston pin 2, space can be used effectively, and the piston 1 does not need to be large.

  Furthermore, since the damper 20 includes the assembly type damper 20 in which the movable part 20b is formed by assembling the cap part 40 as a mass adjusting member to the fixed part 20a, the mass of the movable part 20b is obtained by replacing the cap part 40. It can be adjusted and has excellent convenience such as correction of manufacturing errors.

  Here, the masses of the movable portions 20b of the two dampers 20 may be made different from each other by mass adjustment by the cap portion 40. In this case, the peak of the frequency characteristic, that is, the resonance frequency can be shifted from each other due to the difference in mass, thereby reducing the vibration not only at the resonance frequency but also in a relatively wide frequency range including the resonance frequency. be able to.

  By the way, in the assembly process of the damper 20, the inertance inspection is performed after the fixing portion 20a is press-fitted into the press-fitting portion 2b. In this inertance inspection, the natural frequency (resonance frequency) of each damper 20 is measured using the measurement equipment 50 shown in FIG.

  In FIG. 5, the piston pin 2 to which the damper 20 is assembled is placed on the measurement table 51, and the first and second clamping cylinders 52 and 53 attached to the measurement table 51 respectively. Positioning is performed in the piston pin axial direction (X direction) and in the direction orthogonal to the piston pin axial direction (Y direction). Here, a vibration exciter (impulse hammer) 54 is disposed immediately above the piston pin 2. In the above positioning, the lower end of the vibration exciter 54 is located at the top of the central portion in the X direction of the piston pin 2. The piston pin 2 is positioned so as to be positioned.

  Further, in FIG. 5, vibrometers 55 and 55 are disposed above the vibrator 54. As the vibrometers 55 and 55, for example, a non-contact vibrometer such as a laser Doppler vibrometer is used. As shown in FIGS. 5 and 6, the vibrometers 55 and 55 are disposed on both sides in the X direction of the vibrator 54. Is located.

  In the inertance inspection using the measuring equipment 50 shown in FIG. 5, as shown in FIG. 6, the piston pin 2 is vibrated with the vibrator 54, and at the same time, the end 20 b 1 of the movable portion 20 b of each damper 20 vibrates. A total of 55 and 55 irradiate laser light L0 having a predetermined frequency. At this time, the vibrometers 55 and 55 measure the frequencies of the reflected lights L1 and L2 shifted due to the Doppler effect generated by the vibration of the damper 20, and based on the frequencies of the reflected lights L1 and L2, Self inertia (acceleration of vibration of the damper 20 when a load of 1 N is applied to the damper 20) is calculated. The resonance frequency of each damper 20 is obtained individually based on the frequency characteristic of this self-inertance.

  Here, if the resonance frequency of the damper 20 deviates from a predetermined value from the result of the inertance inspection described above, that is, if it deviates from the target vibration absorption characteristic, the mass of the damper 20 is adjusted, and this mass The resonance frequency is adjusted by adjustment.

  When the mass adjustment of the damper 20 is actually performed, for example, a mass adjustment processing device 60 as shown in FIG. 7 is used. The mass adjustment processing device 60 measures the amount of grinding (dimensions) by the chuck portion 61 that holds the piston pin 2, the grinding wheel 62 that is disposed so as to face the chuck portion 61, and the grinding wheel 62. It is comprised with the dimension measuring apparatus 63. FIG.

  In the mass adjustment using the mass adjustment processing device 60 shown in FIG. 7, the end portion of the movable portion 20 b of each damper 20 is driven by rotating the chuck portion 61 and the grinding wheel 62 holding the piston pin 2 in opposite directions. 20b1 is ground. Here, when the assembled damper 20 deviates from the target vibration absorption characteristic, as shown in FIG. 7A, the tip of the shaft portion 20d constituting the end portion 20b1 is ground, and the integrated damper is obtained. When 20 has deviated from the target vibration absorption characteristic, as shown in FIG. 7B, the tip of the movable portion 20b constituting the end portion 20b1 is ground.

  Incidentally, it is generally known that the resonance frequency shifts in the direction of increasing as the mass of the object decreases. For this reason, considering that the mass adjustment is performed by grinding the end portion 20b1 as described above, the resonance frequency of the damper 20 is set lower than a predetermined value at the initial stage of assembly (the size of the end portion 20b1 is aimed at). It is preferable to set it longer than the above-mentioned dimension.

  As described above, the piston structure of the engine of the first embodiment shown in FIGS. 1 to 7 includes the piston 1 reciprocating in the cylinder, the small end portion 10a connected to the piston 1, and the large end portion 10b. A connecting rod 10 connected to the crankshaft, a piston pin 2 having a hollow cross section connecting the piston 1 and the small end portion 10a of the connecting rod 10, and a damper 20 provided inside the piston pin 2 are provided. The piston structure of the engine further includes a fixed portion 20a to which the damper 20 is fixed to the piston pin 2, a movable portion 20b extending in the axial direction of the piston pin 2, and a movable portion 20b with respect to the fixed portion 20a. And a support portion 20c that is movably supported, and is assembled so that the end portion 20b1 of the movable portion 20b is positioned outside the axial direction end portion of the piston pin 2 in the axial direction. Those that are being (FIGS. 1 to 3, refer to FIG. 5 to FIG. 7).

According to this configuration, the lubricating oil film between the piston pin 2 and the connecting rod 10 (in the full float type, the lubricating oil film and the lubricating oil film between the piston pin 2 and the piston 1) disappears in the combustion stroke. When the piston 1, the piston pin 2, and the small end portion 10 a of the connecting rod 10 are integrated, the damper 20 can prevent them from resonating together. Further, since the damper 20 is provided inside the piston pin 2, when a lubricating oil film exists between the piston pin 2 and the connecting rod 10, that is, in the intake stroke, the compression stroke, and the exhaust stroke, this lubricating oil film (spring). Therefore, the vibration of the damper 20 is not transmitted to the connecting rod 10, and the noise does not increase due to the vibration. Further, by providing the damper 20 inside the piston pin 2, space can be used effectively, and the piston 1 does not need to be large.
Moreover, the end portion of the damper 20 provided inside the piston pin 2 is ground by assembling the end portion 20b1 of the movable portion 20b so as to be positioned outside the axial end portion of the piston pin 2 in the axial direction. Can be done easily. For this reason, the natural frequency (resonance frequency) of the damper 20 can be easily adjusted, and the desired vibration absorption performance can be obtained.
Further, when the natural frequency of the damper 20 is measured in a non-contact manner, it is easy to measure the end 20b1 of the movable portion 20b positioned outside the axial end of the piston pin 2 in the axial direction. The natural frequency can be measured.

  In one embodiment of the present invention, the damper 20 includes a shaft portion 20d extending from the support portion 20c in the axial direction of the piston pin 2, and the movable portion 20b is fixed to and supported by the shaft portion 20d and the outer periphery of the shaft portion 20d. The damper 20 is assembled so that the end portion of the shaft portion 20d or the end portion of the cap portion 40 is located outside the axial end portion of the piston pin 2 in the axial direction. (See FIGS. 2 and 3).

According to this configuration, it is possible to adjust the mass of the movable portion 20b by exchanging the cap portion 40, and it is excellent in convenience such as correction of manufacturing errors.
Further, when the masses of the movable parts 20b of the two dampers 20 are made different from each other by adjusting the mass by the cap part 40, the peak of the frequency characteristic, that is, the resonance frequency can be shifted from each other due to the difference in mass. In addition to vibration at a frequency, vibration can be reduced in a relatively wide frequency range including the resonance frequency.

  In one embodiment of the present invention, the natural frequency (resonance frequency) of the damper 20 is measured, and when the natural frequency deviates from a predetermined value, the end 20b1 of the movable portion 20b is ground and processed. It is configured to adjust the frequency (see FIGS. 6 and 7).

  According to this configuration, the natural frequency can be adjusted more accurately by performing the adjustment based on the difference between the actual natural frequency of the damper 20 and the predetermined value.

  Further, in the embodiment of the present invention, two dampers 20 are provided, and the natural frequency is individually measured and adjusted individually (FIGS. 2 to 4 and 6). FIG. 7).

  According to this configuration, it is possible to appropriately adjust which of the two dampers 20 has a resonant frequency that deviates from a predetermined value.

8 is a cross-sectional view showing another embodiment of the piston structure of the engine, and FIG. 9 is an enlarged cross-sectional view of the main part of FIG.
In the second embodiment shown in FIGS. 8 and 9, as in the first embodiment, each damper 20 is assembled so as to be located outside the axial end of the piston pin 2 in the axial direction. Among these, in the assembly type damper 20, the axial direction end of the cap part 40 is located outside the axial direction rather than the end of the shaft part 20d. For this reason, when performing mass adjustment using the mass adjustment processing apparatus 60 shown in FIG. 7, the end portion of the cap portion 40 constituting the end portion 20b1 is ground.

  In the second embodiment shown in FIGS. 8 and 9, the other configurations, operations, and effects are almost the same as those in the previous embodiment. Therefore, in FIGS. The same reference numerals are assigned and detailed description thereof is omitted.

FIG. 10 is a cross-sectional view showing still another embodiment of the piston structure of the engine, and FIG. 11 is an enlarged cross-sectional view of the main part of FIG.
In the first and second embodiments shown in FIGS. 1 to 9, the right side in the drawing with the fixing portion 20 a separated is the assembled damper 20, and the left side in the drawing with the fixing portion 20 a separated is the integrated damper 20. In the third embodiment shown in FIGS. 10 and 11, both the left and right sides of the drawing with the fixing portion 20a separated are assembled dampers 20 and 20 equivalent to the configuration on the right side of the drawing in FIG.

  In the third embodiment shown in FIGS. 10 and 11, as in the first and second embodiments, the end 20b1 of the movable portion 20b is positioned outside the axial end of the piston pin 2 in the axial direction. The dampers 20 are assembled to each other, and the end portion of the shaft portion 20d is positioned outside the axial end portion of the piston pin 2 in the axial direction to constitute the end portion 20b1.

  In the third embodiment shown in FIGS. 10 and 11, two dampers 20 are provided, and a shaft portion 20d extending from the support portion 20c in the piston pin axial direction is provided on the support portions 20c of the left and right dampers 20 shown in the drawing. The cap portion 40 is fixed to the outer periphery of the shaft portion 20d, the movable portion 20b is formed by the shaft portion 20d and the cap portion 40, and the regulating means 32 is a piston pin for fixing the fixing portion 20a. 2 comprises a step surface 2d having a small diameter part and a large diameter part (the outer diameter part of the cap part 40) of the movable part 20b.

The cap portion 40 is formed in a cylindrical shape having press-fit portions 44 and 45 at the front end side and the rear end side in the press-fit direction, and the shaft portion 20d between the press-fit portions 44 and 45 is the cap portion 40. A gap 46 is formed between the portion formed in this small diameter and the inner peripheral surface of the cap portion 40 between the press-fit portions 44 and 45.
Further, the outer end of the cap portion 40 in the axial direction is fixed and secured by a locking ring 33 such as a C-shaped clip attached to a corresponding portion of the shaft portion 20d.

  Even if comprised in this way, while the movable part 20b can be enlarged in diameter, the step surface 2d in the small diameter part of the piston pin 2 and the large diameter part of the movable part 20b (the outer diameter part of the cap part 40). By both (that is, the restricting means 32), the dampers 20 and 20 can be prevented from being detached. Further, the cap part 40 facilitates mass adjustment.

  In addition, according to this configuration, the two dampers 20 can be configured to be substantially the same or the same, and the degree of freedom in the frequency difference can be increased by adjusting the mass of the cap portion 40.

  Also in the third embodiment shown in FIGS. 10 and 11, the other configurations, operations, and effects are almost the same as those in the previous embodiment. Therefore, in FIGS. The same reference numerals are assigned and detailed description thereof is omitted.

FIG. 12 is a cross-sectional view showing another embodiment of the piston structure of the engine, and FIG. 13 is an enlarged cross-sectional view of the main part of FIG.
In the fourth embodiment shown in FIGS. 12 and 13, the left and right sides of the illustration with the fixing portion 20 a separated from each other are integrated dampers 20 and 20 equivalent to the configuration on the left side of FIG. 3.

  In the fourth embodiment shown in FIGS. 12 and 13, as in the first to third embodiments, the end 20b1 of the movable portion 20b is positioned outside the axial end of the piston pin 2 in the axial direction. The dampers 20 are assembled to each other.

Further, in the fourth embodiment shown in FIGS. 12 and 13, an insertion portion 2e is formed in the central portion of the piston pin 2 in the central axis direction instead of the press-fitting portion 2b of the first embodiment. Further, the outer diameter of the movable portion 20b is made smaller than the outer diameter of the fixed portion 20a.
In addition, the two dampers 20 formed in the same manner as in the first embodiment are annularly connected to the fixed portion 20a formed integrally with each other (the central portion of the single fixed portion 20a in the direction of the central axis of the piston pin 2). The groove 20e is formed, and the C-shaped clip 34 is fitted into the groove 20e. On the other hand, on the inner peripheral surface of the insertion portion 2e of the piston pin 2, an annular groove portion 2f is formed at a location corresponding to the groove portion 20e. When the damper 20 fitted with the C-shaped clip 34 is inserted from one opening of the through hole 2a, the C-shaped clip 34 is contracted in a state where it is in contact with a portion where the groove 2f on the inner peripheral surface is not formed. Although the diameter is increased, the diameter is increased at a position facing the groove 2f and fitted into the groove 2f, whereby the fixing portion 20a is fixed in a state of being prevented from being detached from the insertion portion 2e of the piston pin 2.

  In short, in the second embodiment shown in FIGS. 12 and 13, the restricting means is configured by the C-shaped clip 34 provided in the fixing portion 20a. According to this configuration, the damper 20 can be configured with a simple configuration. Can be achieved. In addition, since the C-shaped clip 34 can be inserted and fixed without press-fitting the fixing portion 20a of the damper 20, the workability of assembling the damper 20 can be improved.

  Also in the second embodiment shown in FIGS. 12 and 13, other configurations, operations, and effects are almost the same as those in the previous embodiment. Therefore, in FIGS. The same reference numerals are assigned and detailed description thereof is omitted.

In the correspondence between the configuration of the present invention and the above-described embodiment,
The dynamic vibration absorber of the present invention corresponds to the damper 20 of the embodiment,
The mass adjustment unit corresponds to the cap unit 40,
The present invention is not limited to the configuration of the above-described embodiment.
For example, in each of the above-described embodiments, the full float type is adopted as the assembly method of the piston pin 2. However, the present invention is not limited to this, and the piston pin 2 rotates with respect to the pin insertion hole 10d of the connecting rod 10. A semi-float type that is movable and fixed to the pin support hole 1g of the boss 1f of the piston 1 may be used.
Further, in the illustrated embodiment, the piston 1 for a diesel engine is illustrated, but the present invention can also be applied to a piston for a gasoline engine.

  As described above, the present invention includes a piston that reciprocates in a cylinder, a connecting rod having a small end connected to the piston and a large end connected to a crankshaft, and a small size of the piston and the connecting rod. The present invention is useful for a piston structure of an engine including a piston pin having a hollow cross section for connecting an end portion and a dynamic vibration absorber provided inside the piston pin.

DESCRIPTION OF SYMBOLS 1 ... Piston 2 ... Piston pin 10 ... Connecting rod 10a ... Small end part 10b ... Large end part 20 ... Damper (dynamic vibration damper)
20a ... fixed part 20b ... movable part 20b1 ... end 20c ... support part 20d ... shaft part 40 ... cap part

Claims (4)

A piston that reciprocates in the cylinder;
A connecting rod having a small end connected to the piston and a large end connected to the crankshaft;
A hollow piston pin that connects the piston and the small end of the connecting rod;
A piston structure of an engine provided with a dynamic vibration absorber provided inside the piston pin,
A fixed portion where the dynamic vibration absorber is fixed to the piston pin;
A movable part extending in the axial direction of the piston pin;
A support portion that supports the movable portion so as to be swingable with respect to the fixed portion, and
The piston structure of an engine assembled so that the end of the movable portion is positioned outside the axial end of the piston pin in the axial direction. The dynamic vibration absorber includes a shaft portion extending from the support portion in the axial direction of the piston pin,
The movable part is composed of a shaft part and a mass adjusting part fixed on the outer periphery of the shaft part and swingable together with the support part,
2. The piston structure for an engine according to claim 1, wherein the dynamic vibration absorber is assembled so that an end portion of the shaft portion or an end portion of the mass adjusting portion is positioned outside the axial direction end portion of the piston pin in the axial direction. The natural frequency of the dynamic vibration absorber is measured, and when the natural frequency deviates from a predetermined value, the end of the movable part is ground to adjust the natural frequency. Engine piston structure. The piston structure of an engine according to claim 1 or 2, wherein two dynamic vibration absorbers are provided, and the natural frequency is individually measured and individually adjusted.

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