JPH08121127A - Sealing structure for auxiliary chamber valve guide section in gas engine - Google Patents

Abstract

PURPOSE: To enhance sealing performance and lubricating ability as well by adjusting the tense force of an elastic seal for sealing a guide section for the valve stem of an auxiliary chamber valve in response to change in pressure within an auxiliary chamber. CONSTITUTION: An auxiliary chamber 15 made of ceramics is provided for a cylinder head 25, a fuel feed means feeding natural gas to the auxiliary chamber 15 is provided, and a secondary cell valve 18 opening/closing a communication hole 15b is provided for the communication hole 15b connecting a cylinder main chamber 17 with the auxiliary chamber 15. An elastic seal is outwardly inserted on the valve stem 18a of the secondary cell valve 18 which is received by the guide cylinder 8 of the cylinder head 25 in such a way that it can be slid. An actuator composed of a piezo-electric element is provided, which is for pressing the elastic seal to a valve stem 18a toward the inside of the elastic seal from the outer circumferential side. A pressing force control means is provided, which controls the pressing force of the actuator in response to the inner pressure of the auxiliary chamber 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a gas engine for compression ignition of natural gas fuel, and more particularly, a guide for a sub-chamber valve for opening and closing a connecting hole connecting the sub-chamber (sub-combustion chamber) and the main chamber (main-combustion chamber). The present invention relates to a seal structure of a part.

[0002]

2. Description of the Related Art A gas engine of this type is provided with a sub chamber made of ceramics inside a cylinder head, and a valve stem of a sub chamber valve for opening and closing a communication hole connecting the sub chamber of the cylinder head and the main chamber of the cylinder. , Penetrates the sub chamber and is brought into contact with the valve operating mechanism above the cylinder head. During the intake stroke of the engine, the sub-chamber valve is closed while the internal pressure of the sub-chamber is low, gas fuel is supplied to the sub-chamber, and the sub-chamber valve is opened in the latter half of the compression stroke to transfer hot intake air from the main chamber to the sub-chamber. It is supplied and the intake air is rapidly and uniformly mixed with the gas fuel to achieve the primary combustion.

The portion where the valve stem of the sub chamber valve is supported by the guide cylinder of the cylinder head is sealed by an elastic seal so that the combustion gas in the sub chamber does not leak. That is, as shown in FIG. 6, the valve stem 18a of the sub-chamber valve is fitted and inserted into the guide tube 8 which is fitted and supported in a portion above the sub-chamber of the cylinder head.
A tubular sealing means A is attached to the upper end of the guide tube 8.
The sealing means A is composed of an elastic seal 30 made of rubber or the like, and an inverted cup-shaped catching cylinder 34 for locking the elastic seal 30 to the upper end of the guide cylinder 8. The elastic seal 30 has a protruding portion 30a that protrudes above the end wall 34a of the catching cylinder 34.
Is formed with a main lip 30b which is always in contact with the valve stem 18a, and an outer peripheral wall of the protruding portion 30a is provided with an annular groove having a semicircular cross section. The main lip 30b is pressed against the valve stem 18a. The lower half portion of the elastic seal 30 fitted into the catching cylinder 34 has an annular groove 8a formed on the outer peripheral wall of the guide cylinder 8 in order to suppress the axial movement of the elastic seal 30.
The protrusion 30d is fitted and is pressed by the catching cylinder 34.

However, in the conventional gas engine, when the pressure of the combustion gas increases with the primary combustion of the gas fuel in the sub chamber, it can be said that the elastic seal 30 of the sub chamber valve guide portion functions sufficiently. Absent. Therefore, if the elastic force of the elastic seal 30 externally fitted to the valve stem 18a is increased, the friction loss increases, and there is a concern that the oil for lubricating the sub chamber valve guide portion will run short.

[0005]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to adjust the tightening force of an elastic seal that seals a sub-chamber valve guide portion according to a change in internal pressure of the sub-chamber. Another object of the present invention is to provide a seal structure for a sub chamber valve guide portion in a gas engine, which is configured to obtain good sealability and lubricity.

[0006]

In order to achieve the above object, the structure of the present invention is a fuel supply system in which a sub-chamber made of ceramic is arranged inside a cylinder head and a natural gas fuel is supplied to the sub-chamber. In a gas engine equipped with a sub chamber valve that opens and closes the communication hole that connects the main chamber and the sub chamber of the cylinder, an elastic seal is attached to the valve stem of the sub chamber valve that is slidably supported by the guide tube of the cylinder head. And an actuator that presses the elastic seal against the valve stem from the outer peripheral side inside the elastic seal, and a pressing force control means that controls the pressing force of the actuator in accordance with the internal pressure of the sub chamber.

[0007]

According to the present invention, the elastic seal locked to the upper end of the guide tube of the cylinder head is externally fitted to the valve stem, and the elastic seal is applied to the valve stem by a piezoelectric element as an actuator depending on the stroke of the engine. To adjust. That is, if a preset voltage is applied to the piezoelectric element for each cycle of the engine by the output of the electronic control device based on the signals of various sensors that detect the stroke of the engine, the elastic sealing force corresponding to the voltage is generated. Acts on the valve stem. Since the elastic seal tension changes with each engine cycle, friction loss due to sliding of the valve stem associated with opening and closing of the auxiliary chamber valve is reduced, and the flow of lubricating oil into the auxiliary chamber valve guide is improved. , Oil shortage is avoided.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a gas engine has a metal cylinder body 19 fitted with a cylinder liner 20 preferably made of ceramics, while a metal cylinder head 25 has a lower cylindrical portion 25a made of ceramics. A reverse cup type headliner 16 is fitted, a cylinder head 25 is connected to the upper end of a cylinder body 19, and a piston 22 is fitted to the cylinder liner 20 and the headliner 16. Preferably, the piston 22 has a crowned piston liner 22a made of ceramics. Thus, the main chamber 17 surrounded by the ceramics and having a high heat insulating property is defined between the head liner 16 and the piston liner 22a. Although not shown, in the cylinder head 25, an intake valve is provided in an intake passage communicating with the main chamber 17, and an exhaust valve is provided in an exhaust passage, as in a normal diesel engine.

A sub-chamber 15 is provided inside the cylinder head 25 in order to obtain compression ignition of gas fuel. Sub-chamber 15
Is composed of a ceramic cup 14 and is preferably formed integrally with a headliner 16. Sub-chamber 15
The main chamber 17 and the main chamber 17 are communicated with each other by a communication hole 15b.
The sub chamber valve 18 opens and closes 5b. The valve stem 18a of the sub chamber valve 18 penetrates the sub chamber 15 and is supported by the guide cylinder 8 supported by the cylinder head 25 so as to be able to move up and down. The sub chamber valve 18 is brought into contact with the valve seat at the lower end of the communication hole 15b by the spring 3 interposed between the upper end wall of the cylinder head 25 and the tapette 2 connected to the upper end of the valve stem 18a. When the tapette 2 is pushed down by a cam (not shown) that rotates in association with the reciprocating movement of the piston 22, the sub chamber valve 18 is connected to the communication hole 15
Open b. The fuel supply valve 4 arranged on the wall of the sub chamber 15 is
In association with the reciprocating movement of the piston 22, the gas fuel in the fuel tank is jetted into the sub chamber 15 via the fuel supply pipe 7.

As shown in FIG. 2, the valve stem 18a of the sub-chamber valve 18 is fitted and inserted in the guide cylinder 8 which is fitted and supported in a portion above the sub-chamber 15 of the cylinder head 25. The tubular sealing means A attached to the upper end of the guide tube 8 is composed of an elastic seal 30 made of rubber or the like, and an inverted cup-shaped catch tube 34 that locks the elastic seal 30 to the upper end of the guide tube 8. Composed. The elastic seal 30 is formed with a main lip 30b that is in constant contact with the valve stem 18a on a protruding portion 30a that protrudes above the end wall 34a of the catch tube 34. Is formed with a plurality of sub-lips 30c that do not abut. An annular groove 40 having a semicircular cross section is provided on the outer peripheral portion of the protrusion 30a, and the main lip 30b is pressed against the valve stem 18a by the contracting force of the metal elastic ring 31 engaged with the annular groove 40.

In the middle portion of the elastic seal 30, a large number of fan-shaped grooves 35 having an upward opening are arranged at equal intervals in the circumferential direction. An actuator B formed by stacking a plurality of piezoelectric elements 36 is housed in each groove 35, and the groove 35 is closed by the end wall 34 a of the catching cylinder 34. The elastic seal 30 has a lower half portion fitted on the guide cylinder 8. An annular groove 8a formed in the outer peripheral wall of the guide cylinder 8 in order to suppress the axial movement of the elastic seal 30.
The ridge 30d of the elastic seal 30 is engaged with and is pressed by the catching cylinder 34.

As shown in FIGS. 3 and 4, a plate-shaped piezoelectric element 3
6 are radially overlapped, and the piezoelectric elements 36 on the outside and the inside
Lead wires 37 and 38 are connected to the electronic control unit 4
4 is connected to the output terminal. The electronic control unit 44 includes an engine speed sensor 41, a fuel injection timing sensor 42,
Based on each signal from the top dead center sensor 43 that detects the top dead center of the piston 22, the voltage and timing applied to the piezoelectric element 36 of the actuator B are controlled.

As shown in FIG. 5, the intake valve, the exhaust valve, the auxiliary chamber valve 18, and the fuel supply valve 4 of the gas engine open and close in association with the reciprocating movement of the piston 22. When the sub chamber valve 18 is closed at the beginning of the intake stroke, the fuel supply valve 4 is opened and the gas fuel is supplied from the fuel supply valve 4 to the sub chamber 15. On the other hand, the intake air sucked into the main chamber 17 is compressed to a high temperature in the compression stroke, the fuel supply valve 4 is closed at the end of the compression stroke, and the auxiliary chamber valve 18 is opened. After that, it is jetted into the sub chamber 15 and mixed with the gas fuel to ignite the gas fuel. The mixture of gas fuel and intake air ignited in the sub chamber 15 flows into the main chamber 17 of the cylinder through the communication hole 15b in the expansion stroke, and while burning, exerts an explosive load on the piston 22 and causes the piston 22 to move forward.

The piezoelectric element 36 of the actuator B is applied with a voltage V1 at the beginning of the intake stroke as shown by the line 61 in FIG. 5 and with a high voltage V2 at the middle of the compression stroke as shown by the line 62 in FIG. , At the end of the expansion stroke, the voltage is returned to 0. The piezoelectric element 36 of the actuator B contracts as a whole in proportion to the applied voltage, so that the auxiliary lip 30c is connected to the valve stem 18 and
Press on a (Fig. 4).

The tightening force of the sub-lip 30c increases from the end of the compression stroke where the pressure inside the sub-chamber 15 increases to the end of the expansion stroke, and the combustion gas in the sub-chamber 15 passes through the sliding portion of the valve stem 18a to the outside. To prevent leakage. On the other hand, sub-chamber 1
In the exhaust stroke where the internal pressure of 5 is low, the actuator B
The pressing force of the valve stem 18a is released and the auxiliary lip 30c is released.
Away (FIG. 2), only the main lip 30b is the valve stem 18
Contact a. At this time, the lubricating oil is used in the guide cylinder 8 and the valve stem 1.
Since it is replenished to the gap with 8a, there is no shortage of lubricating oil.

[0016]

As described above, the present invention is provided with a sub chamber made of ceramic inside the cylinder head and provided with a fuel supply device for supplying natural gas fuel to the sub chamber. In a gas engine equipped with a sub-chamber valve that opens and closes a communication hole that connects the chambers, an elastic seal is externally inserted into the valve stem of the sub-chamber valve slidably supported by the guide tube of the cylinder head, and It is equipped with an actuator that presses the elastic seal against the valve stem from the outer peripheral side, and is equipped with a pressing force control means that controls the pressing force of the actuator in accordance with the internal pressure of the sub chamber. A voltage corresponding to the internal pressure is applied to the piezoelectric element, and the elastic sealing force corresponding to the voltage acts on the valve stem. Since the elastic seal tension changes with each engine cycle, friction loss due to sliding of the valve stem associated with opening and closing of the auxiliary chamber valve is reduced, and the flow of lubricating oil into the auxiliary chamber valve guide is improved. , Oil shortage is avoided.

[Brief description of drawings]

FIG. 1 is a front sectional view of a gas engine provided with a seal structure for a sub-chamber valve guide portion according to the present invention.

FIG. 2 is a front sectional view showing a seal structure of the sub chamber valve guide portion.

FIG. 3 is a plan sectional view showing a seal structure of the sub chamber valve guide portion.

FIG. 4 is a front sectional view showing a pressing force control means of the seal structure of the sub chamber valve guide portion.

FIG. 5 is a diagram showing the stroke of the gas engine according to the present invention.

FIG. 6 is a front sectional view showing a conventional seal structure for a sub chamber valve guide portion.

[Explanation of symbols]

A: Sealing means B: Actuator 4: Fuel supply valve 7: Fuel supply pipe 8: Guide cylinder 15: Sub chamber 15b:
Communication hole 16: Headliner 17: Main chamber 18: Sub chamber valve 18a: Valve tem 19: Cylinder body 20: Cylinder liner 22: Piston 25: Cylinder head
30: Elastic seal 30b: Main lip 30c: Sub-lip 30d: Projection 31: Elastic ring 34: Captive tube 34
a: end wall 35: groove 36: piezoelectric element 41: rotation speed sensor 4
2: Fuel injection timing sensor 43: Top dead center sensor 44: Electronic control device 45: Power supply

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location F02F 11/00 P F02M 21/02 H01L 41/09

Claims (3)

[Claims] 1. A sub-chamber made of ceramic is provided inside a cylinder head, and a fuel supply device for supplying natural gas fuel to the sub-chamber is provided. The sub-chamber is provided in a communication hole connecting the main chamber and the sub-chamber of the cylinder. In a gas engine equipped with a sub chamber valve that opens and closes,
An elastic seal is externally inserted on the valve stem of the auxiliary chamber valve that is slidably supported by the guide tube of the cylinder head, and the inside of the elastic seal is equipped with an actuator that presses the elastic seal from the outer peripheral side to the valve stem. A seal structure for a sub-chamber valve guide portion in a gas engine, comprising a pressing force control means for controlling in accordance with an internal pressure of the chamber. 2. The actuator comprises a piezoelectric element,
The seal structure of the sub chamber valve guide part in the gas engine according to claim 1. 3. A voltage applied to the piezoelectric element is controlled based on a signal from a sensor that senses an operating state of an engine, during a period in which primary combustion in a sub chamber and secondary combustion in a main chamber are performed. The seal structure for the auxiliary chamber valve guide portion in the gas engine according to claim 2, further comprising a control device for controlling the auxiliary chamber valve guide portion.