The role of the car piston ring, is it important?

Piston ring sealing, heat conduction, oil control, support and other functions.

Piston Rings Are Mainly Divided Into Gas Ring And Oil Ring Two Kinds.

The Role Of The Gas Ring Is To Ensure The Sealing Between The Cylinder And The Piston, To Prevent Leakage, And To The Top Of The Piston To Absorb Most Of The Heat To The Cylinder Wall, Taken Away By Cooling Water;

The Oil Ring Plays The Role Of Cloth Oil And Scraping Oil, Scraping The Excess Oil On The Cylinder Wall When Going Down, And Spreading a Layer Of Uniform Oil Film On The Cylinder Wall When Going Up.

This can not only prevent the oil into the cylinder combustion, but also reduce the friction resistance of the piston and cylinder wall. In addition, the oil ring can also play an auxiliary role in sealing gas.

Piston ring is one of the important parts of the engine, the quality of the piston ring will affect the performance of the engine piston ring gas ring and oil ring, the role of the gas ring is to seal the cylinder with the piston, but also play the role of heat conduction. The role of the oil ring is to make the oil evenly distributed on the cylinder wall to ensure good lubrication, while scraping off the excess oil on the cylinder wall, to prevent oil escaping into the combustion chamber to burn.

Pump Oil Action Of Piston Ring

Due to the presence of side clearance and back clearance, the piston ring produces pumping oil while the engine is operating. The reason is that when the piston goes down, the piston ring is above the ring groove, and the oil scraped down from the cylinder wall is charged into the ring groove below; When the piston goes up, the piston ring rests on the bottom of the ring groove and squeezes the oil over the ring groove. This repeated movement will pump the cylinder wall into the combustion chamber. Due to the pump oil effect of the piston ring, the oil into the combustion chamber will form carbon accumulation and increase oil consumption, and may also form carbon accumulation in the ring groove (especially the first gas ring groove), so that the ring stuck, lost the sealing effect, and even break the piston ring.

Gas Ring

Sealing Mechanism Of Gas Ring

The piston ring has a cut, and is not circular in the free state, its size is larger than the inner diameter of the cylinder, therefore, it with the piston into the cylinder, it will produce elastic and close to the cylinder wall.

Under the action of gas pressure, the piston ring is pressed on the lower end of the ring groove, so the gas flows around the back of the ring, and expands, and its pressure drops. At the same time, the force of gas pressure on the back of the ring makes the ring stick more tightly to the cylinder wall. The pressure of the gas has been reduced, from the cut of the first gas ring leakage to the upper plane of the second gas ring, and the gas ring is pressed on the lower surface of the second ring groove, so the gas flows around the back of the ring, and then expands, and the pressure is further reduced.

As this continues, the pressure and velocity of the gas escaping from the last ring are greatly reduced, and the amount of gas escaping is very small. Therefore, a "labyrinth" sealing device consisting of a few gas rings with staggered cuts is sufficient to seal the high-pressure gas in the cylinder effectively.

The section shape of the gas ring and the gas pressure at the clearance of each ring

A Cut In The Gas Ring

The main way of gas leakage into the crankcase in the cylinder is the incision of the piston ring. Therefore, the shape of the incision and the size of the clearance after loading the cylinder have a certain impact on the amount of gas leakage into the crankcase. If the clearance of the incision is too large, the leakage is serious and the engine power is reduced. If the gap is too small, the piston ring may be stuck or broken after being heated and expanded. The incision clearance is generally 0.25~0.8mm. The temperature of the first gas ring is the highest, so the incision gap value is the largest.

The cut shape of the gas ring

Right-angle notch has good technology; Step notch has good sealing performance, but poor technology; Bevel incision, bevel Angle is generally 30° or 45°, its sealing effect and technology are between the first two, but its acute Angle part in the package into the piston is easy to damage; Figure (d) shows a cut in the piston ring of a two-stroke engine with an anti-rotating pin groove. The pin is pressed into the piston ring groove to prevent the piston ring from rotating around the center line of the piston during operation.

Gas Ring Section Shape

Section Shape Of Gas Ring

■ The advantages of rectangular ring are simple structure, convenient manufacturing, good heat dissipation, low reject rate; The main disadvantages are pump oil, easy to cause oil consumption is too large and may form combustion chamber carbon accumulation. In addition, rectangular ring scraping oil, running-in and sealing is poor, modern cars do not use.

■ Conical ring has the advantages of linear contact with cylinder wall, good sealing and running-in performance, obvious scraping effect, easy to form oil film to improve lubrication; The disadvantage is poor heat transfer performance. Conical rings are mainly used in other rings except the first one.

■ Twist ring is a kind of piston ring widely used in contemporary automobile engine, mainly because the twist ring has the advantages of conical ring, but also can reduce pump oil, reduce wear, improve heat dissipation performance. Special attention should be paid to the installation of the twist ring: the inner circle cutting groove upward, the outer circle cutting groove downward, can not be installed backwards.

■The main advantage of the trapezoidal ring is that it can extrude the coke deposited in the ring groove, so as to avoid the piston ring being bonded and broken, and its superior sealing performance and long service life; The disadvantage is that the fine grinding process of the upper and lower ends is more complicated. Trapezoidal ring is widely used in diesel engines with large heat load.

■ The advantage of the barrel surface ring is that the upper and lower stroke of the piston can form a wedge oil film to improve lubrication, good adaptability to the piston swing in the cylinder, small contact area, conducive to sealing; The disadvantage is that the convex arc surface is difficult to process, which is mostly used to strengthen the first ring of diesel engines.

Oil Ring

Oil Ring Is Divided Into Two Kinds: Ordinary Oil Ring And Combined Oil Ring.

Ordinary oil rings are made of alloyed cast iron. The middle of the outer circular surface is cut with a groove, at the bottom of the groove processing a lot of through oil holes or slits. The outer edge of the upper lip of the oil ring is usually chamfered to form an oil wedge when the oil ring moves upward. The oil can push the oil ring away from the cylinder wall so that it can easily enter the groove of the oil ring. The outer edge of the lower end face of the lower lip is not inverted, so that the ability to scrape oil downward is stronger. Nose ring and double nose ring scraping ability is stronger, but processing is more difficult.

Oil Ring And Scraping Action

Section Shape Of Oil Ring

For the combined oil ring composed of three scraping steel sheet and two elastic lining rings, the axial lining ring is clamped between the second and third scraping oil sheet, and the radial lining ring makes the three scraping oil sheet pressed on the cylinder wall. The advantage of this oil ring is that the sheet ring is thin, and the specific pressure (pressure per unit area) on the cylinder wall is large, so the scraping effect is strong; The three oil scrapers are independent, so the adaptability of the cylinder is good; Light weight; Large oil return path. Therefore, combined oil rings are widely used in high speed engines. Its disadvantage is high manufacturing cost (the outer surface of the ring must be plated, otherwise the sliding is not good).