JPH0538340U - Internal combustion engine pistons - Google Patents

Abstract

(57) [Summary] [Purpose] In an automatic thermal piston with a notch formed in the skirt to avoid interference due to oil jets, etc., an internal combustion engine that does not crack in the piston skirt from the notch Provide the piston. A piston having an elliptical shape when the engine is cold and having a strut plate that restricts deformation due to thermal expansion so as to have a circular shape during operation, and having a cutout at a lower end of a skirt portion, at least the cutout The strut plate of this part is retracted so as to avoid the vicinity, and the thickness of the skirt part of this retracted part is thickened so that the piston has a circular shape at the time of thermal expansion. Was formed so as to be gradually connected to the outer peripheral profile of the portion having.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an improvement of a piston (automatic piston) of an internal combustion engine having a strut plate that regulates the direction of thermal expansion of the piston.

[0002]

[Prior Art]

 Conventional pistons for internal combustion engines include pistons, which are also called auto-thermatic pistons, that have a strat plate that regulates the direction of thermal expansion, and pistons that do not have such strut plates. .. Known examples disclosing such a type of piston having a strut plate are JP-A-49-19681, JP-A-60-61192, and JP-A-62-143052. As shown in the vertical sectional view of FIG. 5 and the plan sectional view of FIG. 6, these are a piston main body 1 including a head portion 2 having a ring groove 4 and a skirt portion 5 located therebelow. A strut plate 3 is provided inside the skirt shoulder portion 9 of the skirt portion 5 adjacent to the head portion 2.

FIG. 7 shows a perspective view of the piston body 1 provided with the strut plate 3 as described above, and FIG. 8 shows a developed state of the outer periphery thereof. This type of piston body 1 has an elliptical shape when the engine is cold, and is made to be a perfect circle due to the temperature rise during operation. Then, by providing the strut plate 3 and regulating the direction of thermal expansion of the skirt portion 5 of the piston main body 1 which is preliminarily made flexible by the tension force, the elliptical piston main body 1 is directly expanded by thermal expansion. The elliptical shape that is enlarged in a similar shape is not used.

A characteristic of an automatic thermistor piston that has such a strut plate 3 and becomes a perfect circle when the engine is operating is that the piston that has an elliptical shape that is expanded during operation because the strut plate 3 is not provided. In comparison, it is possible to reduce the clearance between the piston and the cylinder liner when cold. Therefore, in an elliptical piston, there is a gap between the piston in the minor axis direction and the cylinder liner that is larger than in the major axis direction, and due to the swinging in the thrust direction and the anti-thrust direction generated during the reciprocating motion of the piston. As for the noise caused by the sound of the piston striking when the piston collides with the cylinder liner, the noise at low load is the same as that at the time of an automatic thermistor piston that can keep the clearance small. Can be made smaller.

[0005]

[Problems to be solved by the invention]

 On the other hand, the engine is equipped with an oil jet at the lower end of the cylinder to cool the piston and lubricate the connecting rod metal. Since this oil jet needs to have a sufficient injection pressure and injection direction for efficient and reliable lubrication and cooling, the installation position and installation direction are actually limited to some extent. At the bottom dead center of the piston, a piston having a notch at the lower end of the piston skirt is often used to avoid interference between the oil jet and the piston skirt.

However, by providing the strut plate 3 as described above, the direction of thermal expansion of the skirt portion 5 of the piston body 1 is regulated, and the piston shape during engine operation is aimed to be a perfect circle. The skirt portion 5 of the thermatic piston needs to be thinner than the piston without the strut plate 3 to intentionally weaken the rigidity and make it easier to bend.

Therefore, as shown in FIG. 8, when a cutout 7 is formed in the skirt portion 5 of the piston in order to avoid an obstacle such as an oil jet, the piston 7 is cut from the cutout 7 portion. There is a problem that cracks C are likely to occur in the skirt portion 5. The present invention, which has been made in view of the above problems, is an automatic thermal piston in which a notch is formed in the skirt to avoid interference due to oil jets, etc. An object is to provide a piston of an internal combustion engine that does not generate.

[0008]

[Means for Solving the Problems]

 The piston of the internal combustion engine according to the present invention for achieving the above object has an elliptical shape when the engine is cold, has a strut plate that restricts deformation due to thermal expansion so as to be circular during operation, and has a skirt portion. In a piston having a notch at the lower end, the strut plate at this portion is retracted so as to avoid at least the vicinity of the notch, and the skirt portion of this retracted portion is made thicker to allow thermal expansion. The configuration is characterized in that the outer peripheral profile of this portion is gradually changed to the outer peripheral profile of the portion having the strut plate so that the piston becomes circular in some cases.

The cutout is formed so that the piston skirt does not interfere with an oil jet or the like provided on the cylinder block side. Preferably, the cutout is formed in a semi-circular shape or the like to prevent stress. It is preferable to make the shape easy to disperse.

[0010]

[Work]

 The piston of the internal combustion engine of the present invention has the above-mentioned structure, and the strut plate provided to regulate the direction of thermal expansion of the scat part of the piston is arranged so as to avoid at least the vicinity of the notch at the lower end of the scat part. Since it is set back to the position, the stress applied to the notch caused by the tension force of the strut plate can be reduced.

In addition, the skirt portion of the portion where the strut plate is retracted is formed to have a large thickness, and the outer peripheral profile and the strut plate of this portion are formed so that the thick portion and the strut plate are smoothly connected. Since it is connected by gradually changing the outer peripheral profile of the part that has, it is possible to increase the rigidity of this part and prevent the occurrence of cracks from the notch of the skirt part in the auto-thermatic piston with strut plate. It can be prevented.

At the portion where the strut plate is retracted, the thickness of the skirt portion is increased. Since the thick skirt portion has a larger thermal expansion amount than the thin skirt portion, the strut plate is retracted. In order to correct the thermal strain due to this, the piston expands more in the minor axis direction of the elliptical piston when cold, so when the engine is operating (when the piston is hot), this piston It becomes almost circular and there is no problem with thermal deformation.

[0013]

【Example】

 Next, an embodiment of the present invention will be described with reference to the drawings. 1 and 2 show the developed state of the outer peripheral surface of the piston of the internal combustion engine of different embodiments of the present invention. First, in the expanded state of the outer peripheral surface of the piston shown in FIG. 1, the piston body 1 has a strut plate 3 for restricting thermal expansion, and the skirt portion 5 thereof is arranged on the cylinder block side not shown. A notch 7 is formed to avoid an obstacle such as an oil jet. The shape of the notch 7 is semicircular so that the stress can be easily dispersed.

The portion around the notch 7 where the stress is likely to concentrate due to the tension of the strut plate 3 is formed by retracting the strut plate 3 and is applied to this portion by the tension of the strut plate 3. It reduces stress. Further, a thick portion 6 as shown in FIG. 3 is formed on the skirt portion 5 around the cutout 7 where the strut plate 3 is retracted to improve the rigidity of this portion to improve the strut plate 3 It prevents the generation of cracks due to the tension force of.

Next, in the deployed state of the outer peripheral surface of the piston shown in FIG. 2 as the second embodiment, the strut plate 3 is not provided on the side where the notch 7 is formed, and as shown in FIG. The thick portion 6 is formed on the skirt portion 5 of the portion excluding the portion, and this portion is formed in a shape having a high rigidity. Also in this embodiment, the operation and effect are similar to those of the first embodiment.

As described above, according to the embodiments of the present invention described above, the strut plate 3 provided for restricting the thermal expansion of the skirt portion 5 of the piston is provided so as to avoid the vicinity of the notch 7 at the lower end of the skirt portion 5. Since the strut plate 3 is not provided on the side where the strut plate 3 is retracted or the notch 7 is formed, the stress applied to the notch 7 caused by the tension force of the strut plate 3 can be reduced. Then, a thick portion 6 having a larger thickness is formed on the skirt portion 5 of the portion where the strut plate 3 is retracted or the portion where the strut plate 3 is removed, and the thick portion 6 and the strut plate 3 or Since the outer peripheral profile of this portion and the outer peripheral profile of the portion having the strut plate are gradually changed and connected so that the skirt portion 5 is smoothly connected, the rigidity of the skirt portion 5 near the notch 7 should be strengthened. You can

[0017]

[Effect of the device]

 The piston of the internal combustion engine of the present invention has an elliptical shape when the engine is cold, has a strut plate that restricts deformation due to thermal expansion so that it becomes circular during operation, and has a notch at the lower end of the skirt. In the piston that has this, the strut plate of this part is retracted so as to avoid at least the vicinity of the notch, and the thickness of the skirt part of this retracted part is made thick so that the piston becomes circular when thermally expanded. As described above, since the outer peripheral profile of this portion is formed so as to be gradually connected to the outer peripheral profile of the portion having the strut plate, the following effects can be obtained.

Since the strut plate provided to regulate the direction of thermal expansion of the skirt portion of the piston is retracted so as to avoid at least the vicinity of the notch at the lower end of the skirt portion, the cutting force generated by the tension force of the strut plate is eliminated. The stress applied to the notch can be reduced. In addition, the skirt part of the part where the strut plate is retracted is made thicker so that the thicker part and the strut plate are smoothly connected to each other. Since it is connected to the outer peripheral profile by gradually changing the rigidity of this part, it is possible to prevent the occurrence of cracks from the notch in the skirt in the auto-thermatic piston with strut plates. You can

[Brief description of drawings]

FIG. 1 is a diagram showing a developed state of an outer circumference of a piston according to a first embodiment of the present invention.

FIG. 2 is a view showing a developed state of an outer circumference of a piston according to a second embodiment of the present invention.

3 (a) is an enlarged vertical sectional view taken along the line AA of FIG. 1, (b).
FIG. 2 is an enlarged plan sectional view taken along line BB of FIG. 1.

4 (a) is an enlarged vertical sectional view taken along line AA of FIG. 2, (b).
FIG. 3 is an enlarged plan sectional view taken along line BB of FIG.

FIG. 5 is a vertical cross-sectional view of a conventional auto-thermatic piston.

6 is a cross-sectional view taken along the line DD of FIG.

FIG. 7 is a perspective view of the piston of FIG.

8 is a diagram showing a developed state of the outer circumference of the piston of FIG.

[Explanation of symbols]

1 Piston body 3 Strut plate 5 Skirt part 6 Thick part 7 Notch

Claims (1)

[Scope of utility model registration request] 1. A piston having an elliptical shape when the engine is cold, a strut plate that restricts deformation due to thermal expansion so as to be circular during operation, and a notch at a lower end of a skirt portion, at least the cut portion. The strut plate of this part is retracted so as to avoid the vicinity of the notch, and the skirt part of this retracted part is made thicker, and the outer peripheral profile of this part is made so that the piston becomes circular during thermal expansion. A piston for an internal combustion engine, characterized in that it is formed so as to gradually change and connect to the outer peripheral profile of the portion having a strut plate.