JPH0141835B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an air pump device mainly applied to two-wheeled motor vehicles.

(Prior art) This type of device is an air pump having a labyrinth piston, which has a labyrinth section formed by a plurality of upper and lower annular grooves on the outer periphery of the piston to prevent grease or other lubricating oil from being applied between the piston and the cylinder liner. A device is known, for example, from Japanese Utility Model Publication No. 33-385.

(Problem to be Solved by the Invention) However, in such a device, when the piston is connected to the connecting rod via the piston pin, the piston swings around the piston pin due to the labyrinth passage between the piston and the cylinder liner. It comes with the inconvenience of

(Means for Solving the Problems) The present invention aims to improve the above-mentioned disadvantages, and the present invention has a labyrinth piston in which a labyrinth portion consisting of a plurality of upper and lower annular grooves is provided on the outer periphery of the piston. In an air pump device connected to a cooking stove via a piston pin, the labyrinth portion is formed above the piston pin, and the bottom of the upper annular groove of the labyrinth portion is formed deeper than the bottom of the lower annular groove. It is characterized by

(Example) An example of implementing the present invention will be explained with reference to attached drawings. In the drawings, reference numeral 1 indicates a cylinder, which is provided with a cylinder liner 2 on the outer periphery, and a piston 4 that reciprocates back and forth in conjunction with a motor or other prime mover 3 on the side. is equipped with an intake and exhaust valve 5.

The prime mover 3 is installed horizontally on the side of the cylinder 1, and the gear 7 that engages with the gear 6 on the output shaft is moved rearward from the piston 4 via the piston pin 12 at the crank 8 on the side. The piston 4 is connected to a connecting rod 9 extending from the piston 4, and the piston 4 is caused to reciprocate back and forth by the prime mover 3.

The piston 4 is provided with a labyrinth portion consisting of annular grooves 11 in multiple stages above and below the outer periphery. The upper layer was considered to be the deep bottom, and the lower layer was considered to be the shallow bottom.

To explain its action, the piston 4 tends to oscillate around the piston pin due to the labyrinth passage 10, but the annular groove 11 is formed on the outer periphery of the piston above the piston pin. Since the upper part of the bottom has a deep bottom, the volume of the upper groove is large, and the amount of air held here is large, and the flow velocity of the air flowing inside the groove is lower than other grooves. , the pressure is high.

When the piston tries to tilt due to oscillation, there is a large amount of leakage and low pressure on the side where the gap between the inner surface of the piston and the piston is increasing, and there is no pressure drop on the side where the gap is decreasing, so the gap between the side and the gap is decreasing. = A pressure gradient occurs on the expansion side. Then, air flows from the high-pressure side to the low-pressure side through the groove and the piston surface, and the pressure gradient is maintained for a while until the pressure is balanced. In the upper groove, the pressure is high as described above, so the pressure gradient is also large. This pressure gradient forces the piston toward the low pressure side, i.e., toward the expanding side, creating a force toward the center of the cylinder. Since the upper concave groove is located at a large distance from the piston pin, the generated moment is large and exerts a large restoring action on the piston, suppressing its oscillation.

(Effects of the Invention) According to the present invention, the labyrinth part on the outer periphery of the piston 4 consisting of the annular groove 11 is formed above the piston pin, and the annular groove 11 is formed above the piston pin.
Since the bottom of 1 has a deeper bottom than the upper one, the force that holds the piston concentrically at a position away from the piston is greater, effectively suppressing the swinging of the piston due to the labyrinth passage, and allowing the piston to operate smoothly. Although a labyrinth is formed around the outer periphery of the piston, the lower part of the annular groove has a shallow bottom, which has the effect of not reducing the strength near the piston pin where stress concentration is particularly likely to occur. have

[Brief explanation of drawings]

Fig. 1 is a cutaway side view of one example of the device of the present invention;
The figure is an enlarged sectional view of the main part. 1...Cylinder, 2...Cylinder liner, 3...Driving shaft, 4...Piston, 10...Between, 11...Concave groove.

Claims (1)

[Claims] 1. In an air pump device in which a labyrinth piston is provided with a labyrinth portion consisting of a plurality of upper and lower annular grooves on the outer periphery of the piston and is connected to a connecting rod via a piston pin, the labyrinth portion is formed above the piston pin, and the labyrinth portion An air pump device characterized in that the bottom of the upper annular groove is deeper than the bottom of the lower annular groove.