JPH0633805A - Variable compression ratio device of engine - Google Patents

Abstract

PURPOSE:To give strong swirl to mixture which flows into a combustion chamber while securing a sufficient intake air quantity. CONSTITUTION:One of intake ports formed on a cylinder head 5 is composed of a swirl port 11b which gives swirl S to mixture F which flows into a combustion chamber 6, and a piston 15 for variable compression ratio which can advance/restreat in relation to the combustion chamber 6 is arranged on the exhaust port 12 side of the cylinder head facing to the swirl port 11b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable compression ratio device for varying a compression ratio of an engine, and more particularly to a variable compression ratio device for an engine having a swirl port.

[0002]

2. Description of the Related Art Japanese Utility Model Laid-Open No. 63-82041 is known as a prior art relating to an engine for changing a compression ratio. In the device of this publication, a movable member for variable compression is provided on the intake valve side, and the movable member moves forward and backward with respect to the combustion chamber according to a change in load. In such a variable compression ratio device, the compression ratio is increased by the protrusion of the movable member into the combustion chamber, and the combustion efficiency is improved. At a low compression ratio in which the movable member retracts from the combustion chamber, avoiding knocking improves output and reduces noise.

As an example of the improvement of combustion in a piston engine, an intake port is composed of a swirl port, and a strong vortex (swirl) is given to the air-fuel mixture flowing into the combustion chamber. As one of the swirl ports, for example, a helical port in which the shape of the intake port around the intake valve is spiral is adopted. As described above, if the swirl port is added to the variable compression ratio device that varies the compression ratio, the combustion can be further improved by sufficiently stirring the air-fuel mixture, and the engine output performance can be enhanced.

[0004]

However, in the case of a device in which the movable member forming the intake port advances and retreats with respect to the combustion chamber as in the above-mentioned Japanese Utility Model Application Laid-Open No. 63-82041, the midway of the intake port. A step will occur, making it difficult to make the intake port an ideal swirl port,
It was difficult to give a strong swirl to the mixture.
In addition, providing a movable member for varying the compression ratio on the intake port side has no choice but to keep the opening area of the intake port small in an engine that requires a plurality of intake valves, for example. It is difficult to secure a sufficient intake air amount.

An object of the present invention is to provide a variable compression ratio device for an engine capable of imparting a strong swirl to a mixture flowing into a combustion chamber while ensuring a sufficient intake air amount.

[0006]

To achieve this object, a variable compression ratio device for an engine according to the present invention is provided with an air-fuel mixture which enters one of intake ports formed in a cylinder head into a combustion chamber. And a swirl port for imparting swirl to the combustion chamber, and a variable compression ratio piston capable of advancing and retracting with respect to the combustion chamber is disposed on the exhaust port side of the cylinder head facing the swirl port.

[0007]

In the engine variable compression ratio device thus constructed, the variable compression ratio piston is arranged on the exhaust port side of the cylinder head, so that a sufficient opening area of the intake port to the combustion chamber is secured. It becomes possible.

Further, since the variable compression ratio piston is arranged independently of the intake port, a step does not occur in the intake port even if the compression ratio changes. Therefore, it is possible to form an ideal swirl port, and it is possible to give a strong swirl to the mixture flowing into the combustion chamber.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of a variable compression ratio device for an engine according to the present invention will be described below with reference to the drawings.

First Embodiment FIGS. 1 to 6 show a first embodiment of the present invention.
In FIG. 2, reference numeral 1 denotes a cylinder block of the engine. A piston 3 is slidably fitted in the cylinder bore 2 of the cylinder block 1. A cylinder head 5 is attached to the upper surface of the cylinder block 1 via a gasket 4.

The combustion chamber 6 is formed by the cylinder bore 2 of the cylinder block 1, the top surface of the piston 3, and the wall surface of the cylinder head 5. The combustion chamber 6 is a pent roof type combustion chamber. As is well known, the pentroof type combustion chamber is similar in shape to the roof of a house, and has a roof top 6a.
Is divided into an intake port side and an exhaust port side.

The cylinder head 5 is formed with two intake ports 11a and 11b opening to the combustion chamber 6 and one exhaust port 12. Two intake ports 11a, 11
b is arranged on one side of the top portion 6a of the combustion chamber 6 of the cylinder head 5, and one exhaust port 12 is arranged on the other side of the top portion 6a of the combustion chamber 6 of the cylinder head 5. An intake valve 7 is arranged at the opening of each intake port 11a, 11b to the combustion chamber 6, and the exhaust port 1
An exhaust valve 8 is arranged at the opening of the second combustion chamber 6. A spark plug 9 faces the top 6 a of the combustion chamber 6.

One of the two intake ports 11a and 11b is formed as a swirl port (helical port) for applying the swirl S. A swirl control valve (SCV) 26 is provided in the intake port 11a that is not the swirl port. S
The CV 26 is connected to the actuator 27 and is controlled to be opened / closed according to operating conditions of the engine.

On the side of the cylinder head 5 where the exhaust port 12 is formed, there is provided a variable compression ratio piston 15 which can move forward and backward with respect to the combustion chamber 6. The variable compression ratio piston 15 is arranged adjacent to the swirl port 11b. The exhaust valve 8 is located downstream of the variable compression ratio piston 15 with respect to the flow of the air-fuel mixture F. The variable compression ratio piston 15 is formed in a cylindrical shape, and a piston ring 16 is attached to the tip thereof. The tip end of the variable compression ratio piston 15 to which the piston ring 16 is attached is slidably inserted into the piston hole 17 of the cylinder head 5.

A male screw 18 is formed at the axial center of the variable compression ratio piston 15. The male screw 18 is screwed with a female screw 19 formed on the cylinder head 5 side. When the female screw 19 and the male screw 18 are screwed together,
When the variable compression ratio piston 15 is rotated about its axis, the compressible ratio piston 15 moves in the axial direction.

A screw gear (helical gear) 20 is formed on the upper portion of the variable compression ratio piston 15. A drive shaft 21 is arranged at a position adjacent to the upper portion of the variable compression ratio piston 15. The drive shaft 21 extends in a direction orthogonal to the axial direction of the variable compression ratio piston 15. A screw gear (helical gear) 22 is attached to the drive shaft 21. Screw gear 20 of variable compression ratio piston 15 and screw gear 2 of drive shaft 21
2 is meshed.

A pinion gear 23 is attached to the shaft end of the drive shaft 21. The pinion gear 23 is meshed with the rack 24. A solenoid 25 as an electromagnetic actuator is connected to the rack 24.
When a voltage is applied to the solenoid 25, the rack 24 moves to the solenoid 25 side and the drive shaft 21 rotates. The rotation of the drive shaft 21 is driven by the screw gear 2 of the variable compression ratio piston 15 via the screw gear 22.
When the screw gear 20 rotates, the variable compression ratio piston 15 moves in the axial direction.

The tilt angle of the variable compression ratio piston 15 is
It is set to the same angle as the inclination angle of the exhaust valve 8.
Further, the tip end surface of the variable compression ratio piston 15 has the combustion chamber 6
It is desirable to set it to be almost the same as the roof inclination angle. In this embodiment, a screw gear is used to connect the variable compression ratio piston 15 and the drive shaft 21. However, a worm gear or a bevel gear may be used, or the variable compression ratio piston 15 is directly driven by an actuator. It may be configured.

FIG. 4 shows a drive circuit for driving the solenoid 25 which is an electromagnetic actuator. As shown in FIG. 4, the solenoid 25 has an output interface 30.
It is connected to a CPU (central processing unit) 31 via. A water temperature sensor 33, a throttle opening sensor 34, an intake air temperature sensor 35, an ignition advance sensor 36, and an engine speed sensor 37 are connected to the CPU 31 via an input interface 32. The CPU 31 grasps the engine operating state based on the information from each sensor, and controls ON / OFF of the solenoid 25.

In this embodiment, the solenoid 25 is used as an actuator, but the drive shaft 21 is rotated by a stepping motor, for example.
The compression ratio may be controlled steplessly. Originally, it is desirable that the forward / backward control of the variable compression ratio piston 15 be performed based on the combustion pressure, and a combustion pressure sensor may be used instead of each of the above sensors.

As shown in FIG. 5, the actuator 27 for driving the SCV 26 is controlled based on the information of the cooling water temperature, the engine speed, and the intake pipe negative pressure (throttle opening) input to the CPU 31. ing. In this embodiment, the actuator 27 is composed of a diaphragm type actuator that utilizes negative pressure in the intake pipe.

Next, the operation of the first embodiment will be described. When the engine is running at low speed and light load, the variable compression ratio piston 15 projects into the combustion chamber 6, increasing the compression ratio and improving the combustion efficiency. When the engine is running at high speed and under high load, the variable compression ratio piston 15 retracts with respect to the combustion chamber 6 and is switched to a low compression ratio. As a result, the occurrence of knocking is avoided and a high output can be obtained.

Variable compression ratio piston access control and SC
The relationship between the V and the opening / closing control is shown in Table 1.

[0024]

[Table 1]

As shown in Table 1, when the engine speed is low and the intake pipe negative pressure is low, the variable compression ratio piston 15 projects into the combustion chamber 6 and the SCV 26 is closed. In this state, the intake air is guided into the combustion chamber 6 via only the swirl port 11b. As a result, a strong swirl S is imparted to the air-fuel mixture flowing into the combustion chamber 6 from the swirl port 11b, and good combustion is performed under a lean air-fuel ratio.

Since the variable compression ratio piston 15 is arranged on the side where the exhaust port 12 of the cylinder head 5 is formed, a large area is secured on the side where the intake ports 11a and 11b of the cylinder head 5 are formed. It Therefore, the intake air amount can be sufficiently secured, and the engine output performance can be improved.

Intake port 11b as a swirl port
Is not limited to the helical port of FIG. 1, and as shown in FIG. 6, a partition 11c is provided in the intake port, and the sub intake port 11e formed by the partition 11c is SCV.
It may be configured to open and close by 26. With such a configuration, when the SCV 26 is closed, the air-fuel mixture flows into the combustion chamber 6 through only the main intake port 11d, and the air-fuel mixture that has flowed into the combustion chamber 6 flows along the cylinder wall surface. Can be washed away.

Second Embodiment FIG. 7 shows a second embodiment of the present invention. The second embodiment is different from the first embodiment only in the arrangement of the variable compression ratio piston, and other configurations are the same as those in the first embodiment. Therefore, the same reference numerals are given to the corresponding parts. Therefore, the description of the corresponding parts will be omitted, and only different parts will be described. The same applies to other embodiments described later.

In the case of the variable compression ratio device of the first embodiment, since the swirl port 11b and the variable compression ratio piston 15 are adjacent to each other, the mixture F flowing into the combustion chamber 6 and having the swirl S applied thereto. Directly collides with the variable compression ratio piston 15 protruding into the combustion chamber 6, and the flow of the swirl S is weakened. Therefore, in this embodiment, the swirl port 11b is used.
From the exhaust valve 8 to the most upstream position with respect to the flow of the air-fuel mixture F that has flowed into the combustion chamber 6 from the
Are arranged.

In the second embodiment thus constructed, the exhaust valve 8 is arranged at the most upstream position with respect to the flow of the air-fuel mixture F to which the swirl S has been added, so that the swirl port 11b. It is avoided that the air-fuel mixture F from directly collides with the variable compression ratio piston 15. Here, the swirl S that has passed directly below the exhaust valve 8 reaches the variable compression ratio piston 15 located downstream of the exhaust valve 8, but by the time the swirl S reaches this point, it will be mixed by the effect of the swirl S. The stirring of the gas F is sufficiently promoted. Therefore, in this state, even if the swirl S collides with the variable compression ratio piston 15 and the flow of the swirl S is obstructed to some extent, the fuel cannot be combusted sufficiently, and combustion of It can be improved. As a result, engine output performance and exhaust gas purification performance can be improved.

Third Embodiment FIG. 8 shows a third embodiment of the present invention. As shown in FIG. 8, two intake valves 7 are exposed to one side of the top portion 6a of the combustion chamber 6, and two exhaust valves 8 are exposed to the other side of the top portion 6a of the combustion chamber 6. . A variable compression ratio piston 15 is arranged on the side of the cylinder head 5 where the exhaust port is formed. In this embodiment, the variable compression ratio piston 15 is arranged between the two exhaust valves 8.

In the third embodiment thus constructed, the swirl S is added to the mixture gas flowing into the combustion chamber 6 from the swirl port 11b. The air-fuel mixture provided with the swirl S will collide with the variable compression ratio piston 15 projecting into the combustion chamber 6 after passing just below one exhaust valve 8, but like in the second embodiment. The influence of the swirl S collision at the position is small, and the combustion is improved.

Fourth Embodiment FIG. 9 shows a fourth embodiment of the present invention. In this embodiment, the positions of the intake port 11a as a straight port and the intake port 11b as a swirl port are the first.
It is the opposite of the example. When the SCV 26 is closed, the air-fuel mixture that has flowed into the combustion chamber 6 from the swirl port 11b and has the swirl S is applied to the straight port 11a.
After passing just below the intake valve 7 on the side, it passes just below the exhaust valve 8. The swirl S that has passed immediately below the exhaust valve 8 faces the variable compression ratio piston 15 that projects into the combustion chamber 6.

In the fourth embodiment constructed as described above, the distance until the air-fuel mixture F flowing into the combustion chamber 6 from the swirl port 11b collides with the variable compression ratio piston 15 is long. The influence of the collision of the swirl S on the combustion becomes smaller than in the cases of the first embodiment and the second embodiment, and the combustion can be further improved.

[0035]

According to the present invention, the following effects can be obtained.

One of the intake ports formed in the cylinder head is composed of a swirl port for imparting swirl to the air-fuel mixture flowing into the combustion chamber, and on the exhaust port side of the cylinder head facing the swirl port, Since a variable compression ratio piston that can move forward and backward with respect to the combustion chamber is placed, there is no step in the middle of the intake port even if the compression ratio changes as in the past, and an ideal swirl port can be formed. Is possible. Therefore, a strong swirl can be imparted to the mixture flowing into the combustion chamber, and engine output performance can be improved.

Further, since the variable compression ratio piston is arranged on the exhaust port side of the cylinder head, it is possible to secure a large opening area of the intake port to the combustion chamber, and to secure a sufficient intake air amount. The engine output performance can be further enhanced.

[Brief description of drawings]

FIG. 1 is a perspective plan view of a combustion chamber in a variable compression ratio device for an engine according to a first embodiment of the present invention.

FIG. 2 is a sectional view of FIG.

3 is a perspective view of the device of FIG. 1. FIG.

4 is a drive circuit diagram for driving the variable compression ratio piston in FIG. 3. FIG.

5 is a swirl control valve (S
FIG. 6 is a drive circuit diagram for driving a CV) to open and close.

6 is a cross-sectional view showing a modified example of the swirl port of FIG.

FIG. 7 is a perspective plan view of a combustion chamber in a variable compression ratio device for an engine according to a second embodiment of the present invention.

FIG. 8 is a perspective plan view of a combustion chamber in a variable compression ratio device for an engine according to a third embodiment of the present invention.

FIG. 9 is a perspective plan view of a combustion chamber in a variable compression ratio device for an engine according to a fourth embodiment of the present invention.

[Explanation of symbols]

 5 Cylinder Head 6 Combustion Chamber 7 Intake Valve 8 Exhaust Valve 11b Swirl Port 12 Exhaust Port 15 Variable Compression Ratio Piston 26 SCV (Swirl Control Valve) S Swirl F Mixture

Claims (1)

[Claims] 1. An exhaust port side of a cylinder head, wherein one of intake ports formed in the cylinder head comprises a swirl port for imparting swirl to a mixture flowing into a combustion chamber, the exhaust port side of the cylinder head facing the swirl port. A variable compression ratio device for an engine, characterized in that a variable compression ratio piston capable of advancing and retracting with respect to the combustion chamber is disposed in the.