JP2009144595A - Reciprocal engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reciprocal engine capable of reducing particulate by activating combustion in an initial state by high pressure injection by adopting a pre-mix compression ignition system, decreasing a flame temperature by suppressing rapid elevation of an internal pressure of a combustion chamber at an initial stage of combustion, attaining reduction of NOx and prevention of generation of knocking, and enlarging a range of usage of the pre-mix compression ignition limited only in low load until now. <P>SOLUTION: A cylinder 2 pressure rise relaxing means 11 capable of expanding the volume of the combustion chamber 4 when the internal pressure of the combustion chamber 4 of the cylinder rises over a set pressure is provided on a piston 3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a reciprocating engine.

  In general, a reciprocating engine is an internal combustion engine that is also called a reciprocating engine or a piston engine. First, a reciprocating motion of a piston is performed using thermal energy generated by combustion of fuel in a combustion chamber of a cylinder as a pressure of a working fluid. This is the prime mover that extracts the reciprocating motion as mechanical energy of rotational motion by transmitting the reciprocating motion to the crankshaft via the connecting rod. ing.

  In recent years, especially in the case of a diesel engine, even a reciprocating engine, the fuel and air are premixed by injecting the fuel at a high pressure and earlier than the top dead center in the piston stroke, and the mixture is compressed to a high temperature to self-ignite at once. A so-called premixed compression ignition method for burning is drawing attention.

For example, Patent Document 1 shows a general technical level of a reciprocating engine in which the compression ratio is changed according to the rotational speed.
JP-A-9-228858

  In the premixed compression ignition method, if the initial combustion is activated by high pressure injection, the particulate matter (Particulate Matter) can be reduced, but the flame temperature rises as a result of the sudden increase in the combustion chamber pressure. As NOx increases, knocking may occur and the engine may be adversely affected, so that the range of use is limited only to low loads where knocking does not occur.

  In the case of the reciprocating engine disclosed in Patent Document 1, a bridge is attached to the crankshaft, a connecting rod of a piston is connected to one end of the bridge, and a swing arm end that swings around a predetermined axis at the other end of the bridge , And the position of the shaft as an eccentric shaft is changed to increase the position of the top dead center of the piston in the low-speed rotation range and increase the compression ratio for stable ignition combustion. Although a sufficient compression rate can be secured by lowering the compression ratio, it is difficult to cope with a rapid increase in the pressure in the combustion chamber with such a structure.

  In view of such circumstances, the present invention adopts a premixed compression ignition system and activates initial combustion by high-pressure injection, thereby reducing particulates and increasing the combustion chamber pressure at the early stage of combustion rapidly. An attempt is made to provide a reciprocating engine that can suppress the flame temperature, reduce NOx and prevent knocking, and can extend the use range of premixed compression ignition, which has been limited only at low load until now. Is.

The present invention relates to a reciprocating engine that reciprocates a piston by burning fuel in a combustion chamber of a cylinder.
The present invention is directed to a reciprocating engine characterized in that a piston is provided with in-cylinder pressure increase mitigation means capable of expanding the combustion chamber volume when the combustion chamber pressure of the cylinder rises above a set pressure.

  According to the above means, the following operation can be obtained.

  When premixed compression ignition is used and the initial combustion is activated by high-pressure injection, the particulates are reduced, and when the combustion chamber pressure rises above the set pressure, the cylinder provided in the piston Since the combustion chamber volume is expanded by the internal pressure increase mitigation means, a rapid increase in the combustion chamber pressure at the beginning of combustion is suppressed, the flame temperature decreases, NOx is less likely to increase, knocking does not occur, and the engine is adversely affected. The range of use is not limited only to low loads where knocking does not occur, and the premixed compression ignition system can be used even at high loads.

In the reciprocating engine, the cylinder pressure rise mitigating means is
An inner piston connected to the crankshaft by a piston pin via a connecting rod;
An outer piston which is externally fitted so as to be displaceable in a direction in which the combustion chamber volume is expanded with respect to the inner piston, and is fitted so as to be capable of reciprocating in the combustion chamber of the cylinder;
It is interposed between the inner piston and the outer piston, and contracts when the pressure in the combustion chamber of the cylinder rises above a set pressure and displaces the outer piston in a direction to expand the combustion chamber volume with respect to the inner piston. In this way, if the pressure in the combustion chamber of the cylinder is equal to or lower than a set pressure, the outer piston expands the combustion chamber volume with respect to the inner piston by the urging force of the elastic member. However, when the pressure in the combustion chamber of the cylinder rises above a set pressure, the outer piston displaces in a direction that expands the combustion chamber volume with respect to the inner piston against the biasing force of the elastic member. The increase in the pressure in the combustion chamber is suppressed.

  According to the reciprocating engine of the present invention, the premixed compression ignition system is employed and the initial combustion is activated by high-pressure injection, whereby the particulates can be reduced and the rapid increase in the combustion chamber pressure at the initial stage of combustion is suppressed. Thus, the flame temperature can be lowered, NOx can be reduced and knocking can be prevented, and the range of use of premixed compression ignition, which has been limited only at the time of low load, can be expanded.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  1 and 2 show an example of an embodiment of the present invention. In the figure, 1 is a diesel engine as a reciprocating engine, 2 is a cylinder of the diesel engine 1, and 3 is slidably inserted into the cylinder 2. 4 is a combustion chamber formed on the top surface side of the piston 3 in the cylinder 2, 5 is a cylinder head provided in the upper part of the cylinder 2, 6 is provided in the cylinder head 5 and a fuel injection pump (FIG. A fuel injection valve that injects fuel pumped from the fuel into the combustion chamber 4, 7 is an intake port formed in the cylinder head 5, 8 is an intake valve that opens and closes the intake port 7, and 9 is formed in the cylinder head 5. The exhaust port 10 is an exhaust valve that opens and closes the exhaust port 9, and when the internal pressure of the combustion chamber 4 of the cylinder 2 rises above the set pressure, the cylinder pressure can be expanded. Relaxation means 11 is obtained by adapted to provided in the piston 3.

  In the case of the illustrated example, the piston 3 can be displaced in the direction of expanding the volume of the combustion chamber 4 with respect to the inner piston 3a connected to the crankshaft 12 by a piston pin 14 via a connecting rod 13. The outer piston 3b is fitted into the combustion chamber 4 of the cylinder 2 so as to be reciprocally movable, and the combustion of the cylinder 2 is performed between the inner piston 3a and the outer piston 3b. By interposing an elastic member 15 that contracts when the internal pressure of the chamber 4 rises above a set pressure and displaces the outer piston 3b in the direction of expanding the volume of the combustion chamber 4 relative to the inner piston 3a, the in-cylinder pressure The rise mitigating means 11 is configured.

  In the example of FIG. 1, the elastic member 15 is a compression coil spring, but a plate spring or a member having a desired elastic coefficient such as heat-resistant rubber or synthetic resin may be employed.

  Next, the operation of the illustrated example will be described.

  When the internal pressure of the combustion chamber 4 of the cylinder 2 is equal to or lower than the set pressure during operation of the diesel engine 1, the outer piston 3 b constituting the in-cylinder pressure increase mitigating means 11 burns against the inner piston 3 a by the urging force of the elastic member 15. Although the displacement of the chamber 4 is not displaced in the direction of expansion (see the solid line in FIG. 1), when the internal pressure of the combustion chamber 4 of the cylinder 2 rises above a set pressure, the outer piston 3b is biased by the elastic member 15. Against this, the inner piston 3a is displaced in the direction of expanding the volume of the combustion chamber 4 (see the phantom line in FIG. 1), and the increase in the internal pressure of the combustion chamber 4 is suppressed.

  That is, if the in-cylinder pressure increase mitigating means 11 is not provided, the internal pressure of the combustion chamber 4 with respect to a certain crank angle jumps up as shown by the solid line in FIG. 3, it is possible to suppress an increase in the internal pressure of the combustion chamber 4 with respect to a certain crank angle, as indicated by the phantom line in FIG.

  As a result, when the premixed compression ignition method is adopted and the initial combustion is activated by high pressure injection, the particulates are reduced, and when the internal pressure of the combustion chamber 4 rises above the set pressure, the piston 3 is expanded by the in-cylinder pressure increase mitigating means 11 provided in No. 3, the rapid increase in the internal pressure of the combustion chamber 4 at the initial stage of combustion is suppressed, the flame temperature is lowered, NOx is hardly increased, and knocking is performed. Is not limited, and the range of use is not limited only to low loads when knocking does not occur, and the premixed compression ignition system can be used even at high loads.

  In this way, by adopting the premixed compression ignition method and activating the initial combustion by high pressure injection, the particulates can be reduced and the rapid increase of the internal pressure of the combustion chamber 4 at the initial stage of combustion is suppressed to lower the flame temperature. Thus, NOx can be reduced and knocking can be prevented, and the range of use of premixed compression ignition, which has been limited to only when the load is low, can be expanded.

  Note that the reciprocating engine of the present invention is not limited to the illustrated examples described above, and it is needless to say that various changes can be made without departing from the gist of the present invention.

It is a schematic sectional drawing which shows an example of the form which implements this invention. It is a diagram which shows the relationship between the crank angle and combustion chamber pressure in an example of embodiment which implements this invention.

Explanation of symbols

1 Diesel engine (reciprocating engine)
2 Cylinder 3 Piston 3a Inner piston 3b Outer piston 4 Combustion chamber 5 Cylinder head 11 In-cylinder pressure rise mitigating means 12 Crankshaft 13 Connecting rod 14 Piston pin 15 Elastic member

Claims (2)

In a reciprocating engine that reciprocates a piston by burning fuel in a combustion chamber of a cylinder,
A reciprocating engine characterized in that a piston is provided with in-cylinder pressure increase mitigating means capable of expanding a combustion chamber volume when a combustion chamber pressure of a cylinder rises above a set pressure. The cylinder pressure rise mitigating means,
An inner piston connected to the crankshaft by a piston pin via a connecting rod;
An outer piston which is externally fitted so as to be displaceable in a direction in which the combustion chamber volume is expanded with respect to the inner piston, and is fitted so as to be capable of reciprocating in the combustion chamber of the cylinder;
It is interposed between the inner piston and the outer piston, and contracts when the pressure in the combustion chamber of the cylinder rises above a set pressure and displaces the outer piston in a direction to expand the combustion chamber volume with respect to the inner piston. The reciprocating engine according to claim 1, wherein the reciprocating engine comprises:

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