CN103429857A - Gas exchange valve arrangement and cylinder head - Google Patents

Abstract

A gas exchange valve arrangement for a supercharged internal combustion engine, the arrangement comprising an exhaust valve (1b) having a valve head (2) and a valve stem connected to said valve head (2) (3), the device also includes a valve spring (4), a chamber (5) and a thrust device (6, 19), the valve spring (4) being arranged around the valve stem (3) for generating a closing The force of the valve (1b), the chamber (5) is arranged around the valve stem (3), the thrust device (6, 19) is attached to the valve stem (3) and can move along the The direction of the longitudinal axis of the valve stem (3) moves together with the exhaust valve (1b). Said arrangement comprises means (7, 14) for introducing intake air into said chamber (5), said means (7, 14) for introducing pressurized intake air from an intake duct (10) of said engine introduced into the chamber (5) between the thrust device (6, 19) and the inner end of the chamber (5) to help keep the exhaust valve (1b) closed.

Description

Gas exchange valve assembly and cylinder head

technical field

The invention relates to a gas exchange valve arrangement for a supercharged internal combustion engine as defined in the preamble of claim 1 . The invention also relates to a cylinder head according to the preamble of claim 14 .

Background technique

Very high intake pressures are used in prior art compression ignition internal combustion engines for better fuel efficiency. A practical method for obtaining high intake pressures is to use two-stage turbocharging, where two turbochargers are connected in series. The intake pressure of more than ten bar can be obtained by adopting two-stage turbocharging. Advantageously, high intake pressure is accompanied by Miller timing, wherein the intake valve closes before bottom dead center during the intake stroke. Miller timing reduces cylinder temperatures during combustion and contributes to lower NOx emissions. Since all gas exchange valves are closed while the piston is still moving down, the cylinder pressure at the end of the intake phase can be significantly lower than the pressure in the intake line. The problem with the large pressure differential across the intake valve is that standard valve springs have been designed for smaller pressure differentials and the intake valve tends to open. Exhaust valves suffer from the same problem. Because the high intake pressure also increases the pressure in the exhaust manifold, more force is required to keep the exhaust valve closed at the end of the intake phase and the beginning of the compression phase. An obvious solution to this problem would of course be to use stiffer valve springs. However, this is often not possible without major modifications to the cylinder head. In many cases, it is difficult or even impossible to redesign the cylinder head to accommodate the larger springs required to accommodate the large pressure differential across the gas exchange valve.

One option to reduce the force that the valve spring needs to withstand is to use an air spring to assist the conventional mechanical spring.

Patent document US6745738B1 discloses a valve spring arrangement that uses pressurized gas to bias a gas exchange valve. The device includes a dynamic housing having a chamber into which pressurized gas can be communicated such that the dynamic housing moves the associated valve away from the static housing. The device uses a separate pressure source and control equipment for controlling the flow of pressurized gas into and out of the dynamic chamber.

Patent document US5988124A discloses an electromagnetically actuated cylinder valve with a pneumatic return spring. The valve is opened and closed by an electromagnetic actuator. A control device is required to operate the gas spring. The device also includes a mechanical spring for closing the valve when the gas spring is in a depressurized state.

Patent application GB2326444A discloses another electrically actuated gas exchange valve. The system can also use a mechanical spring for closing the valve when the electropneumatic is not actuated. Furthermore, this system requires control equipment and a separate compressor for regulating the pressure in the gas spring.

In none of the above documents, the air springs are intended to be used to assist the mechanical springs, they are only used for valve timing. A mechanical spring is provided to close the valve when the air spring decompresses. All of the disclosed systems use an external source of pressurized gas and control equipment to regulate the flow of gas into the gas spring. This makes the system complex and prone to failure.

Contents of the invention

It is an object of the present invention to provide an improved gas exchange valve arrangement for a supercharged internal combustion engine. Another object of the present invention is to provide an improved cylinder head. The particular features of the device according to the invention are given in the characterizing part of claim 1 . The particular features of the cylinder head according to the invention are given in the characterizing part of claim 14 .

According to the present invention, a gas exchange valve arrangement for a supercharged internal combustion engine is disclosed, comprising a gas exchange valve having a valve head and a valve stem connected to the valve head, the valve A spring is arranged around the valve stem to generate the force to close the valve. The device also comprises a chamber arranged around the valve stem and a thrust device attached to the valve stem and movable with the gas exchange valve in the direction of the longitudinal axis of the valve stem . The apparatus also includes means for introducing air into said chamber for introducing pressurized air from the intake duct of the engine into the chamber between the thrust means and the inner end of the chamber to facilitate Keep the gas exchange valve closed.

According to the invention there is disclosed a cylinder head for an internal combustion engine comprising an exhaust valve having a valve head and a valve stem connected to the valve head, a valve spring, a chamber and a thrust device , the valve spring is arranged around the valve stem for generating a force to close the exhaust valve, the chamber is arranged around the valve stem, the thrust device is attached to the valve stem and can move along the The direction of the longitudinal axis of the valve stem moves together with the exhaust valve, and the cylinder head includes perforations for introducing pressurized intake air from the intake duct of the engine to the thrust device and the exhaust valve. between the inner ends of the chamber to help keep the exhaust valve closed.

The present invention has many advantages. Because pressurized intake air from the intake duct is used to help keep the valves closed, leakage from the intake and exhaust ducts into the cylinder is prevented even at very high intake pressures. The unit is very compact and is suitable even for existing cylinder heads, requiring only minor modifications. Because the intake air from the intake duct is used to keep the valves closed, no auxiliary system for charge air is required. Stronger steel springs are also not required and standard springs can be used. The device is also self-adjusting. When higher inlet pressures are used, a greater force is required to keep the gas exchange valve closed, and, in the device of the present invention, this greater force is automatically generated. Similarly, when the engine is running at low loads, there is less force preventing the valves from opening, and friction in the camshaft and rocker arm bearings is minimized. Since the unit also has standard springs, there are no problems with starting the engine.

According to an embodiment of the invention, the means for introducing the intake air into the chamber comprises an orifice in the chamber and a perforation in the cylinder head. If the intake air is introduced into the chamber via perforations in the cylinder head, no additional ducting on the cylinder head is required. According to an embodiment of the invention, the perforation is arranged in the cylinder head between the chamber and the intake duct. This is the easiest way to introduce air into the chamber. The perforation can also be provided with a non-return valve. The cylinder head may also be provided with a second perforation for discharging intake air out of the chamber.

According to an embodiment of the invention, the thrust device is a thrust plate arranged in the chamber. This arrangement provides good sealing performance relatively easily, and the thrust plate can also act as a valve rotator. Another alternative is that the thrust device is a cover that becomes part of the chamber.

Other features of embodiments of the invention are given in the dependent claims.

Description of drawings

1 shows a cross-sectional view of a cylinder head of an internal combustion engine with a gas exchange valve arrangement according to an embodiment of the invention.

FIG. 2 shows a cross-sectional view of a cylinder head according to another embodiment of the invention.

FIG. 3 shows a cross-sectional view of a cylinder head according to a third embodiment of the invention.

FIG. 4 shows a cross-sectional view of a cylinder head according to a fourth embodiment of the invention.

Detailed ways

Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings.

Figure 1 shows a simplified cross-sectional view of a cylinder head 9 of a large compression ignition internal combustion engine, which may be, for example, the main or auxiliary engine of a ship or an internal combustion engine that may be used in a power plant. However, the invention is not limited to compression ignition engines, but can be used in spark ignition engines as well. The engine is boosted for high intake pressure. For example, two turbochargers connected in series, each comprising a turbine and a compressor, may be used. Only a single cylinder 12 is shown, however, the engine may comprise a plurality of cylinders 12 each fitted with its own cylinder head 9 . The cylinders 12 may be arranged, for example, in-line or V-shaped. The intake duct 10 and the exhaust duct 11 pass through the cylinder head 9 , the intake duct introduces the pressurized intake air into the cylinder 12 , and the exhaust duct guides the exhaust gas out of the cylinder 12 . Only the part of the intake duct 10 and the exhaust duct 11 located in the cylinder head 9 is shown in FIG. 1 . However, an intake duct 10 and an exhaust duct 11 continue outside the cylinder head 9 and are respectively connected to the compressor and the turbine of the turbocharger. The intake duct 10 is equipped with an intake valve 1a, and the exhaust duct 11 is equipped with an exhaust valve 1b. The intake valve 1 a and the exhaust valve 1 b are collectively referred to as a gas exchange valve 1 . Components related to the intake valve 1a are denoted by reference numerals ending in "a" in the figure, and components related to the exhaust valve 1b are denoted in the figure by reference numerals ending in "b". In the description and claims, identical or similar components may also be indicated by reference numerals without any letter at the end.

The engine comprises two intake valves 1 a and two exhaust valves 1 b, however, only one of each of these two valves can be seen in FIG. 1 . Of course, the number of gas exchange valves 1 can also be different. The gas exchange valve 1 comprises a valve head 2 and a valve stem 3 . When the gas exchange valve 1 is closed, it forms a tight engagement with the valve seat 13 . A valve stem 3 is connected to the valve head 2 and is required to move the gas exchange valve 1 in a reciprocating manner, thereby opening and closing the fluid connection between the cylinder 12 and the intake duct 10 or exhaust duct 11 . The cylinder head 9 is provided with a valve guide 15 for positioning the gas exchange valve 1 . A conventional cam mechanism with a push rod and a rocker arm (not shown in the figure) is used to open the gas exchange valve 1 .

Each gas exchange valve 1 is equipped with a spring 4 which generates a force in a direction away from the cylinder 12 . This force tends to close valve 1 and keep it closed. In the embodiment of Fig. 1, a second spring 8 is also provided for each gas exchange valve for increasing this closing force.

A chamber 5 is arranged around the stem 3 of each gas exchange valve 1 . In the embodiment of FIG. 1 , the chamber 5 is partly inside and partly above the cylinder head 9 . The springs 4 , 8 are arranged inside the chamber 5 . Inside the chamber 5 there is also a thrust plate 6 attached to the valve stem 3 . The chamber 5 is equipped with an orifice 7 for introducing pressurized intake air from an intake duct 10 into the chamber 5 . The orifice 7 is located at the inner end of the chamber 5 , that is to say at that end of the chamber 5 which is closer to the cylinder 12 . Thus, intake air can be introduced into the chamber 5 between the inner end of the chamber 5 and the thrust plate 6 .

The thrust plate 6 can move along the longitudinal direction of the valve stem 3 together with the entire gas exchange valve 1 . The thrust plate 6 is in intimate contact with the wall of the chamber 5, so that no significant airflow over the thrust plate 6 is possible. The thrust plate 6 is at the outer end of the chamber 5 when the gas exchange valve 1 is closed. Since the pressure in the intake duct 10 is high due to intake boost, the intake air introduced into the chamber 5 pushes the thrust plate 6 upwards and helps to keep the gas exchange valve 1 closed. The thrust plate 6 also acts as a valve rotator and turns the gas exchange valve 1 slightly every time the valve 1 is closed.

In the embodiment of FIG. 1 , a perforation 14 a is provided in the cylinder head 9 between the intake duct 10 and the chamber 5 a associated with the intake valve 1 a. Intake air is introduced into the chamber 5a through the perforations 14a. When the intake valve 1a is closed, the pressure acting on the top surface of the valve head 2a of the intake valve 1a is the same as the pressure acting on the thrust plate 6a. The force generated by the pressure acting on the valve head 2 a pushes the intake valve 1 a towards the cylinder 12 . Since the area of the valve head 2a is close to that of the thrust plate 6a, the opposing forces largely cancel each other out and the force generated by the springs 4a, 8a is sufficient to keep the intake valve 1a closed.

Intake air is introduced via perforations in the cylinder head 9 into the chamber 5b associated with the exhaust valve 1b. This perforation is not shown in FIG. 1 . The exhaust from the exhaust duct 11 cannot be used due to high temperature and soot. The device suitable for the exhaust valve 1b operates on the same principle as the intake valve 1a. The pressure in the exhaust duct 11 is lower than in the intake duct 10, but of the same magnitude. Therefore, the forces acting on the top surface of the valve head 2b of the exhaust valve 1b and the thrust plate 6b largely cancel each other out, and the force generated by the springs 4b, 8b is sufficient to keep the exhaust valve 1b closed.

The device is self-regulating, and on the intake side, the same pressure acts on two surfaces of almost equal size but opposite directions. Therefore, the forces generated by this pressure largely cancel each other out. On the exhaust side, the different pressures create opposing forces, but, even then, they are related to each other. As the pressure in the intake duct 10 increases, so does the pressure in the exhaust duct 11 , the forces generated by these pressures at least partially canceling each other out.

Figure 2 shows another embodiment of the invention. Only the intake valves 1a, 1a' are shown in the figure. The main difference between the embodiments of Fig. 1 and Fig. 2 is that in the embodiment of Fig. 2 the springs 4a, 4a' are arranged outside the chambers 5a, 5a'. Separate perforations 14a, 14a' are arranged between the intake duct 10 and the chambers 5a, 5a' for introducing the intake air into the chambers 5a, 5a'. The advantage of this embodiment is that the spring force is not directed towards the thrust plates 6a, 6a' and the valve rotates better. Another advantage is that the springs 4a, 4a' can be arranged in an oil sump.

In the embodiment of Figure 3, intake air is introduced into the chamber associated with the second intake valve 1a' from the chamber 5a associated with the first intake valve 1a via the perforation 14a' between the chambers 5a, 5a' 5a groan. In this embodiment, the valve springs 4a, 4a' are located in the chambers 5a, 5a'. However, the springs 4a, 4a' are not supported on the thrust plates 6a, 6a' acting as valve rotators. Instead, the springs 4a, 4a' are supported on the collars 16a, 16a'. Consequently, less force is applied towards the valve rotors 6a, 6a', ensuring better functioning.

In the embodiment of Figure 4, there are no thrust plates 6a, 6a' inside the chambers 5a, 5a'. Instead, the outer ends of the chambers 5 a , 5 b , ie those ends of the chambers 5 a , 5 b remote from the cylinder 12 , are formed as covers 19 a , 19 b serving as thrust devices 6 , 19 . Covers 19a, 19b are attached to the valve stems 3a, 3b of the gas exchange valves 1a, 1b and seal off the inner walls of the chambers 5a, 5b. The cover 19 thus forms part of the chamber 5a, 5b. The inner ends of the chambers 5 a, 5 b are formed in the cylinder head 9 . The perforations 14 a , 14 b for introducing the intake air into the chambers 5 a , 5 b are provided with check valves 17 a , 17 b which prevent the intake air from flowing back into the intake duct 10 . Second perforations 18a, 18b are arranged in the cylinder head 9 between the chambers 5a, 5b and the exhaust duct 11 for discharging intake air out of the chambers 5a, 5b when the gas exchange valves 1a, 1b are open. The embodiment of Figure 4 works on the same principle as the previous embodiments.

Many modifications of the invention are possible within the scope of the appended claims. For example, it is possible to arrange the chamber completely above the cylinder head. It is not necessary to introduce the intake air into the chamber via perforations in the cylinder head, but a separate duct can be arranged for this. In that case, the device may also comprise means for controlling the pressure in the chamber and/or a storage tank for storing the intake air before it is introduced into the chamber. It is also possible to introduce the intake air from the chamber connected to the intake valve into the chamber connected to the exhaust valve via an external pipe or hose.

Claims (15)

1. A gas exchange valve arrangement for a supercharged internal combustion engine comprising an exhaust valve (1b) having a valve head (2) and a valve connected to the valve head (2) rod (3), said device also includes a valve spring (4), a chamber (5) and a thrust device (6, 19), said valve spring (4) being arranged around said valve stem (3) for generating closing the exhaust valve (1b), the chamber (5) is arranged around the valve stem (3) to which the thrust device (6, 19) is attached and can Moving together with the exhaust valve (1b) along the longitudinal axis of the valve stem (3), the gas exchange valve device is characterized in that it also includes device (7, 14) in said device (7, 14) for introducing pressurized intake air from said engine's intake duct (10) into said thrust device (6, 19) and said cavity in the chamber (5) between the inner ends of the chamber (5) to help keep the exhaust valve (1b) closed. 2. An arrangement according to claim 1, characterized in that said means for introducing the intake air into said chamber (5) comprises an orifice (7) in said chamber (5) and a cylinder head Perforation (14) in (9). 3. The device according to claim 2, characterized in that the perforation (14) is arranged in the cylinder head (9) between the chamber (5) and the intake duct (10) between. 4. Device according to claim 2 or 3, characterized in that the perforation (14) is provided with a non-return valve (17). 5. The device according to any one of claims 2 to 4, characterized in that the cylinder head (9) is provided with a second perforation (18) for discharging the intake air out of the chamber (5) . 6. The device according to claim 5, characterized in that the second perforation (18) is arranged between the chamber (5) and the exhaust duct (11). 7. The arrangement according to any one of the preceding claims, characterized in that said thrust device (6, 19) is a thrust plate (6) arranged inside said chamber (5). 8. Device according to claim 7, characterized in that the thrust plate (6) acts as a valve rotator. 9. An arrangement according to any one of claims 1 to 6, characterized in that the thrust device (6, 19) is a cover (19) forming part of the chamber (5). 10. The arrangement according to any one of the preceding claims, characterized in that the chamber (5) is at least partially arranged within the cylinder head (9). 11. The device according to any one of the preceding claims, characterized in that the valve spring (4) is arranged in the chamber (5). 12. The device according to any one of the preceding claims, characterized in that the intake air is introduced from a chamber (5a) associated with the intake valve (1a) to a chamber associated with the exhaust valve (1b) chamber (5b). 13. An arrangement according to claim 12, characterized in that the intake air is introduced into the chamber (5b) associated with the exhaust valve (1b) via a perforation in the cylinder head (9). 14. A cylinder head (9) for an internal combustion engine comprising an exhaust valve (1b), a valve spring (4), a chamber (5) and a thrust device (6, 19), the exhaust The valve (1b) has a valve head (2) and a valve stem (3) connected to the valve head (2), said valve spring (4) being arranged around said valve stem (3) for generating a valve closing said valve stem (3). The force of the gas valve (1b), the chamber (5) is arranged around the valve stem (3), the thrust device (6, 19) is attached to the valve stem (3) and can move along the valve The direction of the longitudinal axis of the rod (3) moves together with said exhaust valve (1b), said cylinder head is characterized in that said cylinder head comprises perforations (14) for diverting pressurized intake air The intake duct (10) from the engine leads into the chamber (5) between the propulsion device (6, 6') and the inner end of the chamber (5) to help retain all The exhaust valve (1b) is closed. 15. The cylinder head according to claim 14, characterized in that the cylinder head (9) comprises a second perforation (18) for discharging the intake air out of the chamber (5).

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