JP2922367B2 - Sealed air system for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed air system for an internal combustion engine having a valve housing for an exhaust valve, wherein the housing is connected to a working cylinder of the engine, and a valve stem of the exhaust valve is a valve housing. And a pneumatic spring mounted on the valve housing and fixed to the pneumatic spring chamber and the valve stem and closed with a pneumatic spring mounted on the valve housing. It is possible to operate the exhaust valve in the direction, the exhaust valve is operated in the opening direction by an operating piston connected via a bearing to the hydraulic cylinder, and the valve stem is sealed in the area above the journal in the valve housing. The present invention relates to a sealed air device penetrating a sealed air chamber provided with an inlet opening for supplying air.

When the exhaust valve is opened by the actuator piston at the end of the combustion stroke of the engine, the discharge of the combustion gas through the exhaust flow passage in the valve housing generates a strong pressure wave in the flow passage and then the pressure inside the exhaust passage. Descends to approach ambient pressure until the valve closes again. The valve stem of the exhaust valve penetrates a guide in the valve housing upward and is supported via a bearing, and forms a slight gap with the guide. When the valve is open, the exhaust gas is urged into the gap between the valve rod and the valve guide by the strong pressure wave and the associated relatively high pressure in the flow path. As a result, combustion residues in the form of slag particles and aggregates accumulate on the journal surface of the sliding valve or valve stem. Since the temperature of the valve stem is lower through the guide, sulfuric acid contained in the exhaust gas may condense on the valve stem and the guide. Therefore, the life of the valve stem is shortened due to corrosion and abrasion of the valve stem and the guide surface.

[0003] It is known to reduce the amount of exhaust gas entering the gap between the guide and the valve stem by pressurizing the sealed air chamber located above the guide. The exhaust gas contains small particles of various sizes, and despite the downward flow of the sealing air, a part of said air flow is energized by the pressure pulses that occur when the exhaust valve opens, causing it to enter the gap. Penetrate. This pressure pulse creates an instantaneous upward airflow within the gap. In addition, particles of a certain size are mechanically transported upward through the gap despite the downward airflow within the gap. It has been empirically shown that by supplying the sealing air to the sealing air chamber, the particles are blown off from the valve shaft and the particles are deposited in the sealing air chamber downwind of the valve shaft. In addition to restricting the ingress of exhaust gas into the gap, the sealed air chamber also plays an important role as a trap for upwardly transported particles. This prevents particles from penetrating and corroding the sealing ring around the valve stem at the bottom of the pneumatic spring.

The disclosure of US Pat. No. 3,120,221 relates to an internal combustion engine having a pneumatic reset device with an exhaust valve operated by a camshaft. In this engine, the valve housing does not have a sealing air chamber, and if a sealing ring is used around the valve shaft, it may be worn by particles penetrating into the gap between the valve shaft and the guide. . The air leaking from the pneumatic spring enters the gap in an uncontrollable state and descends, contributing to cooling of the valve stem. In prior art engines, the sealed air is generally taken from an engine scavenge receiver. However, this leads to the accumulation of soot-containing oil in the sealed air chamber. To prevent this, precompressed working air is supplied to the sealed air chamber of another known engine at an effective pressure of about 0.2 bar above the actual scavenging pressure of the engine. As a result, at all engine loads, the intrusion of exhaust gas into the gap is reduced to a relatively acceptable range.

[0005] A common feature of prior art sealed air systems is that
The engine cylinder has a common external pipe system for conveying the sealing air to the sealing air chamber of each engine cylinder. Apart from the high manufacturing costs, such pipe systems have a very large volume in comparison with the volume of the sealed air chamber, so that the ingress of exhaust gases into the sealed air chamber can occur in the pipe system. It does not necessarily lead to a significant pressure increase. In addition, prior art devices have the problem that the scavenging pressure of the engine drops sharply when the engine load is low, and the sealing air pressure does not become sufficiently high under such load conditions.

It is an object of the present invention to improve the design of the sealed air system so that the exhaust valve can be operated without problems.

[0007]

For this purpose, the device according to the invention is characterized in that the air flow path defines an inlet opening of the sealed air chamber.
Connected to a pneumatic spring chamber, the air flow path is
A control member, wherein the air flow control member has a small
At least with the opening of the discharge valve, the pneumatic spring chamber
If a pressure equal to or higher than the predetermined value is obtained in
The air was introduced from the chamber to the sealed air chamber
And wherein the Iruko.

The arrangement of the sealing air is simplified by taking the sealing air from a pneumatic spring chamber associated with the exhaust valve .
Because the individual cylinders carry the sealing air
External pipe systems previously used in
Because there is no. And when the exhaust valve is open air
Because the type spring piston moves down with the valve rod,
The air in the pneumatic spring chamber is compressed, and
Pressure when the exhaust valve is closed.
The spring chamber is in a low pressure state. Air flow control member
Is at least the maximum value of the pneumatic spring chamber
Empty from pneumatic spring chamber to sealed air chamber when under pressure
Introduce qi. For this reason, the exhaust valve is moved to the open position
At this time, air is supplied to the sealed air chamber at a relatively high pressure.
As a result, the air pressure in the sealed air chamber increases every time the exhaust valve opens.
To be increased. The sealed air is discharged from the exhaust valve and the combustion chamber.
Pressure in the exhaust passage increases due to the outflow of exhaust gas
Although it is particularly necessary at times, with this method, every time the exhaust valve opens,
The pressure in the sealed air chamber corresponds to the maximum pressure in the pneumatic spring chamber
Can be raised to a higher level. Since the sealing air is not supplied when the exhaust valve is closed, the sealing air pressure is reduced from the exhaust air pressure of the engine without significantly increasing the consumption of the sealing air compared to the consumption of the prior art engine. It can be set substantially higher. Because of the high sealing air pressure and the fact that the sealing air pressure is independent of the engine load, the cleaning effect of the gap between the valve stem and its guide is greatly improved. Furthermore, by completely removing the commonly used common pipe system, it is not necessary to remove the pipe system when the exhaust valve is removed due to overhaul of the engine, so that maintenance of the engine is easier.

The air flow passage has a substantially smaller internal volume than the conventionally known pipe system, and the volume of the sealed air chamber is also smaller, so that the intrusion of the exhaust gas results in an increase in the pressure in the sealed air chamber and the exhaust gas. Has the advantage of preventing further intrusion. It is inevitable that a certain amount of hydraulic oil from the hydraulic cylinder passes through the working piston and the spring piston and reaches the bottom of the pneumatic spring chamber. In a preferred embodiment of the device according to the invention, wherein the air passage communicates with the bottom of the pneumatic spring chamber,
The hydraulic oil may be used for lubrication of the valve shaft. Hydraulic oil is entrained with the sealing air and enters the gap between the valve stem and the guide. In addition to the hydraulic oil reducing the wear of the valve stem, in the prior art engines, when the pneumatic spring stops functioning during overhaul, the oil deposits blown into the engine room as troublesome oil mist are removed from the pneumatic spring chamber. It has the advantage that it can be removed.

[0010] The advantage of the preferably small volume of the sealed pneumatic device described above is that a stop member (air flow control) in the air flow path is provided.
This is further enhanced by positioning the control member) preferably near the sealed air chamber so that invading exhaust gas compresses only air in the sealed air chamber. The sealed pneumatic device according to the present invention may be applied to an existing engine in which a pneumatic spring has a safety valve. In this case, at the same time as removing the existing external sealing air device, close the sealing air outlet on the exhaust air receiver,
Furthermore, the engine can be readjusted with a simple modification consisting of connecting the air outlet of the safety valve on each engine cylinder via an external conduit to the air inlet of the associated sealed air chamber. In view of the fact that the safety valve before the modification of the engine is usually set to open only at abnormally high pneumatic spring pressure, the opening pressure of the valve and the maximum pressure in the pneumatic spring chamber during one engine cycle are: It is necessary to coordinate with each other such that the sealing air is transferred from the pneumatic spring chamber to the sealing air chamber during substantially each engine cycle.

In view of the fact that the consumption of the sealing air during each engine cycle is merely small compared to the volume of the pneumatic spring, the required sealing air at each opening of the exhaust valve is precisely supplied. Until the opening pressure of the safety valve is reduced. If it is not desired that the maximum pressure of the pneumatic spring is slightly reduced, the supply air pressure to the pneumatic spring may be increased instead of, or in addition to, reducing the opening pressure of the valve. Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

[0012]

1 shows an exhaust valve housing 1 mounted on top of a cover, not shown, of an engine cylinder. The valve housing 1 has an exhaust passage 2 for conveying exhaust gas from a combustion chamber of the engine. Exhaust valve 3
Is provided with a valve body 4 that abuts on a valve seat 5 at the illustrated closed position of the valve and that shuts out of the exhaust passage 2. A valve stem 6 extending upward from the valve body 4 extends upward through an upper portion of the valve housing 1. The valve stem 6 is supported via a bearing in a guide bush 7 inserted into a lumen passing through the upper part of the valve housing.

A pneumatic spring 8 and a hydraulic cylinder 9 are mounted on the top of the valve housing 1 coaxially with the bush 7. The actuator piston 10 supported on the top of the valve stem 6 via a bearing applies a downward opening force to the valve 3 when hydraulic oil is applied to the operating chamber 11 of the hydraulic cylinder. Since the pneumatic spring piston 12 is fixed to the valve stem in a known manner, the piston 12 is
, And moves downward to compress the air in the pneumatic spring chamber 13 located below the piston 12. When the exhaust valve closes, the pressure in the working chamber 11 is released, and subsequently
The pressure in the pneumatic spring chamber 13 exerts a closing force acting upward on the piston 12 and also on the valve stem 6, so that the exhaust valve is reversed to the closed position by the pneumatic spring 8. An air inlet with a check valve 14 supplies the required air to the pneumatic spring chamber 13 at a pressure corresponding to the desired closing force. Lateral lumen 15
Extends from the bottom of the pneumatic spring chamber 13 and communicates with a pressure-adjustable safety valve 16. In that position, the valve stem 6 passing through the pneumatic spring 8 is connected to the annular sealing ring 1 surrounding the valve stem 6.
7 seals downward.

As described above, a gap is provided between the valve stem 6 and the bush 7 in a range of, for example, 2 to 10 mm. Immediately above the upper flange of the bush 7, a sealed air chamber 18 is provided to prevent exhaust gas from entering upward through a gap. The sealed air chamber 18 is defined laterally by a side wall of a recess provided at the upper end of the valve housing, and is axially defined by an upper side of the upper flange of the bush 7 and a lower side of the housing of the pneumatic spring 8. It is defined. The inlet opening 19 in the side wall of the sealing air chamber 18 is provided in the lateral bore 2 of the valve housing 1.
0 and communicates with the pipe socket 21 at one end of the conduit 22. The other end of the conduit 22 is mounted on the air outlet 23 of the safety valve 16 (see FIG. 2).

In a large, low-speed, two-stroke internal combustion engine, the diameter of the valve shaft is very large. Therefore, it is necessary to provide a large gap so as to cope with fluctuations in the diameter of the shaft caused by a difference in conditions of cold and warm. The area of the gap may be equal to the area of the entrance opening 19. Therefore, in such a two-stroke engine, the sealing ring 17 and the sealing air chamber 18 are important for obtaining a sufficient pneumatic spring function.

The lateral lumen 15, safety valve 16, conduit 22,
The lateral lumen 20 forms an air flow path connecting the pneumatic spring chamber 13 with the sealed air chamber 18. The opening pressure of the safety valve 16 is adjusted so that air is blown from the pneumatic spring chamber 13 to the sealed air chamber 18 when the exhaust valve 3 is in the open state. The safety valve 16 may be adjusted, for example, to open and supply sealed air when the pressure in the pneumatic spring chamber reaches 15 bar. The pressure in the sealed air chamber 18 is
Thus, since the pressure of the exhaust gas in the exhaust passage 2 becomes considerably higher, the sealed air flows through the gap between the valve stem 6 and the bush 7, and impurities generated from the exhaust gas do not enter the valve stem. Absent.

In the embodiment of the exhaust valve shown in FIG. 4, the safety valve 16 is mounted in a bore 24 at the bottom of the pneumatic spring 8. The inlet opening of the safety valve 16 communicates with the bottom of the pneumatic spring chamber 13 through a lumen (not shown), and the outlet of the safety valve 16 communicates with the downwardly extending passage 25 and the valve housing 1 in the housing of the pneumatic spring. , This passage 25
Communicates with a lateral passage 26 located in the valve housing 1 and extending to the sealed air chamber 18. The check valve 27 is located at the outlet of the passage 26 in the sealed air chamber. The check valve is
The air from the sealed air chamber 18 is prevented from flowing back into the passage 26. A long-axis bolt 28 screwed into the thread of the passage 26 may be inserted into the passage 26 in a direction extending radially outward. In this case, the end face of the bolt is located in the passage 26 just outside the outlet of the passage 25. The safety valve 16
It is connected to an oil drain of an exhaust valve located outside the pneumatic spring chamber 13 through a lumen 36 and a spring check valve 37 in the lumen. The check valve 37 is adjusted to open at a pressure higher than the normal operating pressure of the pneumatic spring. Thereby, the check valve is connected to the air passages 16, 25, 2
6 functions as a safety valve that opens when blocked by impurities.

In another embodiment, not shown, the passages 25 and 26 of the valve housing 1 may be formed as upwardly open channels on the upper surface of the valve housing. In this case, the flow path is a lumen 25 in a pneumatic spring housing.
To the sealed air chamber 18. This embodiment is characterized in that it is very simple to manufacture. FIG.
Shows a third embodiment of a sealed pneumatic device in which the pneumatic spring safety valve does not form part of the device. A hydraulic oil collecting groove 29 is provided at the bottom of the pneumatic spring chamber 13 in the circumferential direction so that the hydraulic oil flows into the passage 30 little by little. The passage 30 extends downward from the groove 29 to the valve housing 1 and communicates with the lumen 31. The lumen 31 connects to the sealed air chamber 18 via a relatively small passage 32. A female screw is provided in the innermost length portion of the lumen 31, and a bolt 33 that shields the lumen 31 outward is screwed into the female thread. Bolt 3
3 so that one end of the passage 34 faces the passage 30 and the other end communicates with the lumen 31 extending to the inlet opening 19 of the sealed air chamber. I have. The innermost portion of the passage 34 is formed so as to have a larger diameter to form a female screw that is screwed with a spring check valve 35 as a stop member . When the pressure in the pneumatic spring chamber 13 reaches its peak value, the check valve 35 as a stop member opens to supply sealing air. The air flow path connecting the pneumatic spring chamber 13 and the sealed air chamber 18 includes passages 30, 3
2 and 34.

It is of course possible to limit the consumption of sealing air by inserting a throttle stop at one suitable position in the air flow path. Since the pressure in the pneumatic spring chamber 13 is substantially higher than the pressure of the exhaust gas in the exhaust passage 2, the sealed pneumatic device provided with such a throttle valve member functions well. The throttle valve member may be used in combination with the check valve 16 or may be provided separately if it is desired to keep the pneumatic spring chamber connected to the sealed air chamber.

The air inlet 14 of the pneumatic spring may carry air at a supply pressure of about 5.5 to 7 bar. If a continuous sealed air supply is required, the stop member in the air flow path may be adjusted to open at a pressure in the range of 4.0 to 5.5 bar. Supply pressure. At 5.5 bar, the consumption of sealing air per cylinder of an engine with a piston diameter of 60 cm is, for example, 1 kg
/ Hour and at a supply pressure of about 7 bar, the consumption of the sealing air is 3 kg / hour.

[Brief description of the drawings]

1 is an axial cross-sectional view of a hydraulically actuated air-reset exhaust valve with a sealed pneumatic device according to the invention, taken along line II in FIG.

FIG. 2 is a view of the exhaust valve as viewed from above.

FIG. 3 is an axial sectional view of the exhaust valve taken along a line III-III in FIG. 2;

FIG. 4 shows an axial section through the upper part of a second embodiment of an exhaust valve with a sealed air device according to the invention.

FIG. 5 is a sectional view corresponding to FIG. 4 of a third embodiment of the sealed air device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Valve housing 3 Exhaust valve 6 Valve rod 7 Guide bush 8 Pneumatic spring 9 Hydraulic cylinder 10 Working piston 12 Pneumatic spring piston 13 Pneumatic spring chamber 15, 30 Air flow path 18 Sealed air chamber

────────────────────────────────────────────────── (5) References JP-A-58-200015 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F01L 3/08 F01L 9/02 F16F 9 / 00

Claims (5)

(57) [Claims] 1. A sealed air system for an internal combustion engine having a valve housing (1) for an exhaust valve (3), wherein the housing is connected to a working cylinder of the engine and a valve stem (6) of the exhaust valve. Is supported in the valve housing via bearings and extends upward into the pneumatic spring (8), said pneumatic spring (8) being mounted on the valve housing and having a pneumatic spring chamber (13) and a valve stem. A pneumatic spring piston (12) fixed to the exhaust valve (3) in the closing direction
The exhaust valve is operated in the opening direction by an operating piston (10) connected via a bearing to a hydraulic cylinder (9), and the valve stem (6) is provided in a region above the journal in the valve housing. )
Air passages (15,16,22,20; 16,25,25 ) in a sealed air device passing through a sealed air chamber (18) provided with an inlet opening (19) for supplying sealed air . 2
6; 30, 32, 34) are the inlets of the sealed air chamber (18).
A mouth opening (19) is connected to the pneumatic spring chamber (13).
The air flow path is provided with an air flow control member (16, 35, 3).
7), wherein the air flow control member includes at least the discharge valve (3).
Is opened in the pneumatic spring chamber (13).
If a pressure equal to or greater than a predetermined value is obtained, the pneumatic spring chamber
Air is introduced from (13) into the sealed air chamber (18).
Sealing air system of an internal combustion engine, it characterized that it is so. 2. The sealed pneumatic device according to claim 1, wherein the air flow path (15; 30) opens at the bottom of the pneumatic spring chamber (13). 3. The sealed air chamber (18) is a recess provided at an upper end of a valve housing, and the air flow path has a passage formed on an upper side of the valve housing, and the passage has one end. 3. A seal as claimed in claim 1 or 2, characterized in that it communicates with the sealing air chamber (18) at the other end and faces the lumen in the housing of the pneumatic spring extending at the other end into the pneumatic spring chamber (13). Air shutoff device. 4. An air flow control member in the air flow path.
A sealed pneumatic device according to any of the preceding claims, characterized in that a stop member (35) is arranged adjacent to the sealed air chamber. 5. The pneumatic spring forms an air flow control member.
A safety valve (16), said air flow path comprising a conduit (22) connecting an air outlet (23) of the safety valve (16) with an air inlet (21) of a sealed air chamber (18); Furthermore, the sealing air is released from the pneumatic spring chamber to the sealed air chamber (substantially between each engine cycle) and the maximum pressure in the pneumatic spring chamber (13) during one engine cycle. The sealed pneumatic device according to any one of the preceding claims, wherein the device is adjusted to be conveyed to (18).