JPH04292538A - Engine having auxiliary combustion chamber - Google Patents

Abstract

PURPOSE:To improve combustion efficiency of an engine with auxiliary combustion chamber under the operation condition in a wide range. CONSTITUTION:An auxiliary combustion chamber 3 communicated with a main combustion chamber 2 is provided, and a main part of this auxiliary combustion chamber 3 consists of a bellows 6. A gear part 8 is provided in a rod 9, which is welded to the closed end of the bellows 6, to be engaged with a screw part 13 formed in one end of a rotary shaft 12, and the other end of the rotary shaft 12 is connected to a servo motor 14. When the servo motor 14 is rotated by controlling an angle of rotation with a factor related to the operation condition as a parameter, the bellows 6 is extended and shrunk by a quantity corresponding to the angle of rotation, and capacity of the auxiliary combustion chamber 3 is changed in response to the operation condition. The optimum capacity can be therefore maintained under the operation condition in a wide range to maintain the maximum combustion efficiency, and combustion efficiency at the time of partial load is improved by lowering compression ratio in a knocking generation zone.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine equipped with a sub-combustion chamber.

0002

[Prior Art] It is known to provide an auxiliary combustion chamber for the purpose of improving combustion efficiency.
There is one described in Publication No.-687. In this type, the cylinder head is provided with an auxiliary combustion chamber that communicates with the main combustion chamber,
The spark plug faces into this auxiliary combustion chamber. In addition, an on-off valve is provided between the auxiliary combustion chamber and the main combustion chamber, and by opening the valve during the compression process, the combustible mixture is injected from the auxiliary combustion chamber to the main combustion chamber, creating a swirling flow. ing.

0003

By the way, FIG. 8 is a graph showing the relationship between the volume change of the sub-combustion chamber, the compression ratio, and the SFC (fuel consumption rate) in a general engine with a sub-combustion chamber under constant operating conditions. It can be seen that when the sub-combustion chamber volume is changed, the compression ratio changes linearly and proportionally, but SFC has a minimum point. That is, this minimum point is the optimum volume of the sub-combustion chamber, and if the sub-combustion chamber volume differs from the optimum volume, the maximum combustion efficiency cannot be obtained. Furthermore, the optimum volume changes depending on the operating conditions. Therefore, if the volume of the auxiliary combustion chamber is fixedly set under a certain standard operating condition, it will differ from the optimum volume as the operating condition changes, and the combustion efficiency will also deviate from the maximum combustion efficiency. It is desirable that it can be maintained within the operating conditions. However, conventional auxiliary combustion chambers are mainly used as a means to improve combustion efficiency under certain standard operating conditions, and the volume remains constant throughout all operating conditions, and the optimum volume and changes in operating conditions are No consideration has been given to the relationship yet.

Further, FIG. 9 shows the relationship between the ignition timing and the rotation speed in the fixed ignition system (a system in which the setting of ignition timing does not depend on the load level or throttle opening) in the above-mentioned general engine at WOT (full load state). FIG. As is clear from this figure, when the ignition timing is advanced to a predetermined value, a knocking occurrence zone occurs, and MTB (advance amount at maximum output) is located within this knocking occurrence zone. For this reason, the ignition timing in a normal fixed ignition system is set to avoid the knocking occurrence zone, and the intermediate region between this set ignition timing and MTB becomes a range that cannot be used to improve combustion efficiency. However, the ignition timing at partial load is set to M
If the engine can be advanced to about TB, it should be possible to improve combustion efficiency, and for this purpose, it is only necessary to reduce the compression ratio in the knocking generation zone. Therefore, it is also desired to realize such a compression ratio variable means. Therefore, an object of the present invention is to simultaneously realize these demands.

[0005]

[Means for Solving the Problems] In order to solve the above problems, an engine having a sub-combustion chamber according to the present invention includes a main combustion chamber and a sub-combustion chamber communicating with the main combustion chamber. The present invention is characterized in that the combustion chamber is provided with a volume variable means for controlling the volume of the auxiliary combustion chamber so as to be variable using a factor corresponding to the operating state of the engine as a parameter.

[0006]

[Operation] Since the volume varying means uses a factor corresponding to the operating state of the engine as a parameter, it is possible to change the volume of the auxiliary combustion chamber in accordance with the operating state of the engine. Therefore, by changing the volume of the sub-combustion chamber to the optimum volume, maximum combustion efficiency can be maintained over a wider range of operating conditions. Also,
As the volume of the auxiliary combustion chamber changes, the compression ratio also changes, so if the volume variable means is set so that the compression ratio decreases in the knocking zone that occurs during WOT, combustion efficiency during partial load improves.

[0007]

Embodiment A first embodiment is shown in FIGS. 1 to 4. FIG. 1 shows a cross-sectional structure near the combustion chamber of an engine, and FIG. 2 is a diagram showing the cylinder head 1 from the combustion chamber side. A substantially hemispherical main combustion chamber 2 and a sub-combustion chamber 3 are formed in the cylinder head 1, and the main combustion chamber 2 and the sub-combustion chamber 3 are communicated with each other through an arbitrary number of torch holes 4. The cylinder head 1 is installed in one of the torch holes 4.
The electrode part of the ignition plug 5 attached to is facing. The sub-combustion chamber 3 is mostly formed by a bellows 6. The bellows 6 is a bottomed cylindrical member whose one end is open toward the main combustion chamber 2 and is extendable and retractable in length, and is housed in a cylindrical portion 7 provided in the cylinder head 1 so as to protrude to the outside. . The bellows 6 and each open end of the cylindrical portion 7 are reliably sealed.

One end of a rod 9 having toothed portions 8 on the side surface is welded to the closed end side of the bellows 6. The rod 9 is biased in a direction to compress the bellows 6 by a compression spring 11 disposed between the other end and the bottom 10 of the cylindrical portion 7 . The toothed portion 8 meshes with a threaded portion 13 of a rotating shaft 12, and the rotating shaft 12 is arranged parallel to the rod 9 and rotatably supported by the cylinder head 1, and the other end is connected to a servo motor 14.

When the servo motor 14 rotates by a predetermined angle, the threaded portion 13 rotates, and the toothed portion 8 can be moved in the direction in which the bellows 6 expands and contracts. These bellows 6, rod 9
, the rotating shaft 12, the servo motor 14, and the like constitute the volume varying means of the present invention. The rotation angle of the servo motor 14 is arbitrarily selected from various factors (e.g., throttle opening, engine speed, intake negative pressure, vehicle speed, etc.) that indicate the operating state of the engine that changes depending on the driving state.
Or it is determined using two or more as parameters. A specific example of this determination method is a method of performing microcomputer control based on a function or map created in advance using selected parameters.

Next, the operation of this embodiment will be explained. first,
In order to obtain the optimum volume of the sub-combustion chamber 3, this parameter and the optimum volume of the sub-combustion chamber 3 are determined by microcomputer control based on parameters arbitrarily selected from among factors that vary depending on the operating state of the engine. Furthermore, the rotation angle of the servo motor 14 necessary to obtain this optimum volume is determined. As a result, when the servo motor 14 is controlled to rotate by a predetermined angle depending on the operating state of the engine, the threaded portion 13 rotates in either the forward or reverse direction by an amount corresponding to the rotation angle of the servo motor 14. The rod 9 that engages with the toothed portion 8 is moved in either length direction, and as a result, the bellows 6 is expanded or contracted by a length corresponding to the rotation angle of the servo motor 14, and the volume of the sub-combustion chamber 3 becomes the optimal volume. Change. Therefore, maximum combustion efficiency can be maintained over a wider range of operating conditions. Moreover, the servo motor 14
By using this, the volume of the sub-combustion chamber 3 can be changed continuously.

Furthermore, as the volume of the sub-combustion chamber 3 changes, the compression ratio also changes at the same time. Therefore, by changing the compression ratio, it is possible to improve combustion efficiency over a wide range of operating conditions. In other words, when a fixed ignition system is adopted, the ignition timing is set to be advanced to about the MBT shown in Fig. 9, and the engine is operated at the normal compression ratio during partial load.
When the operating state of the engine enters the knocking generation zone under high load conditions, knocking can be prevented by increasing the sub-combustion chamber volume and decreasing the compression ratio. As a result, combustion efficiency at partial load can be improved over a wider range of engine operating conditions. This compression ratio control can be performed simultaneously as a result of the control for obtaining the optimum volume described above, or can be performed separately and independently. Further, the compression ratio can be controlled so as to change continuously, or it can be controlled stepwise so that it changes only in the knocking occurrence zone.

FIGS. 3 and 4 are diagrams for explaining a method of controlling the servo motor 14 when the compression ratio is continuously controlled. FIG. 3 shows parameters of the compression ratio ε, such as engine speed Ne and throttle opening θT.
This is a ternary characteristic curve when H is used. The compression ratio ε is determined by this three-dimensional characteristic curve. Furthermore, if the volume of the sub-combustion chamber 3 for obtaining the determined compression ratio ε is determined based on a predetermined function, etc., the servo motor 14 is controlled to rotate in the manner described above. 3 volume is changed and the compression ratio is changed to the desired value.

[0013] The compression ratio ε in this case is equal to the engine speed N
The opening rate of the throttle (not shown) is set to decrease more quickly when e is low than when e is high. This is because, generally speaking, the higher the volumetric efficiency per engine cycle, the more likely knocking will occur. By using this characteristic curve and the servo motor 14, the compression ratio ε can be maintained over the entire range of engine operating conditions.
continuous control becomes possible. In addition, the control of the compression ratio in this case does not necessarily simultaneously realize the maintenance of the optimal volume in the sub-combustion chamber 3 as described above, but generally it is possible to control the compression ratio by changing the compression ratio and the combustion efficiency. Therefore, if the compression ratio is continuously changed for the purpose of improving combustion efficiency, it is considered possible to bring the volume of the sub-combustion chamber closer to the optimum volume under a wider range of operating conditions.

Furthermore, since the frequency of occurrence of knocking also varies depending on the engine temperature, the compression ratio ε can be controlled simultaneously depending on the engine temperature, as shown in FIG. That is, since knocking occurs more frequently at high temperatures, the compression ratio ε may be controlled to be lowered at this stage. The temperature of the engine at this time can be detected, for example, by the seat temperature of the spark plug.

A second embodiment is shown in FIGS. 5 to 7. In the first embodiment, since the volume of the auxiliary combustion chamber is changed by driving the motor, it takes some time for the change to occur. Therefore, in case a change in a shorter time is required, this is an example in which a hydraulic volume variable means is adopted to quickly change the volume of the auxiliary combustion chamber. Hereinafter, parts common to the previous embodiment will be explained using common reference numerals.

FIG. 5 is a view corresponding to FIG. 1, and a piston 15 is welded to the closed end side of the bellows 6. The piston 15 is slidable within the hydraulic cylinder 16, and is pushed up by the compression spring 11 so that it can reciprocate within the hydraulic cylinder 16. The inside of the hydraulic cylinder 16 is connected to a solenoid valve 18 via an oil passage 17, and is further selectively connected to a high-pressure side passage 19 and a low-pressure side passage 20 by the solenoid valve 18. These bellows 6, piston 15, hydraulic cylinder 16, compression spring 11, solenoid valve 18, etc. constitute the volume varying means of the present invention.

FIG. 6 is a diagram showing the volume variable means in a high compression ratio state, in which the solenoid valve 18 is switched to the high pressure side passage 19 side, and the piston 15 is pushed down by introducing high pressure oil into the hydraulic cylinder 16. This reduces the volume of the secondary combustion chamber and increases the compression ratio. Further, FIG. 7 is a diagram showing the volume variable means in a low compression ratio state, and shows the solenoid valve 18.
When switching to the low pressure passage 20 side, the oil in the hydraulic cylinder 16 can flow out to the low pressure passage 20 side, and the bellows 6 is pushed up by the elasticity of the compression spring 11, so the volume of the auxiliary combustion chamber increases and the compression The ratio decreases. therefore,
When the solenoid valve 18 switches depending on the driving condition,
The sub-combustion chamber volume and compression ratio can be switched in two stages in a short time, which is advantageous for high-speed control.

Furthermore, according to the present invention, by incorporating temperature factors such as water temperature, oil temperature, and plug seat temperature into the parameters, the temperature can be adjusted appropriately according to each operating state such as when cold, during warm-up, and when warm-up is completed. In addition to providing the sub-combustion chamber volume and compression ratio, when the engine becomes overheated, the compression ratio is lowered, thereby protecting the engine and improving its durability.

[0019]

According to the present invention, the volume of the auxiliary combustion chamber can be controlled by providing a volume variable means that can change the volume of the auxiliary combustion chamber using a factor corresponding to the operating state of the engine as a parameter. Therefore, the sub-combustion chamber can maintain its optimum volume over a wider range of operating conditions depending on the operating conditions of the engine, thereby maintaining maximum combustion efficiency. In addition, by utilizing changes in the compression ratio associated with the control of the sub-combustion chamber volume, it is possible to prevent knocking by reducing the compression ratio when the engine operating state reaches the knocking generation zone. The ignition timing can be advanced to the level of MTB, and in this case, the combustion efficiency at partial load can be improved over a wide range of operating conditions. Therefore, the present invention has an effect that cannot be obtained with a mere engine with a sub-combustion chamber or an engine with a variable compression ratio mechanism, that is, it is possible to change the volume of the sub-combustion chamber according to the operating condition of the engine, and at the same time change the compression ratio. Remarkable effects can be obtained.

[Brief explanation of drawings]

[Fig. 1] Side sectional view of main parts of an engine according to a first embodiment

[Fig. 2] Bottom view of the cylinder head facing the combustion chamber according to the first embodiment

[Figure 3] Graph showing the characteristic curve of servo motor control

[Figure 4] Graph for explaining compression ratio control

[Figure 5] Second
A diagram corresponding to FIG. 1 according to the embodiment

[Fig. 6] Diagram for explaining the operation of the second embodiment

[Figure 7]
Diagram for explaining the action of the second embodiment

[Figure 8] Correlation graph between operating conditions and auxiliary combustion chamber volume in a typical engine

[Figure 9] Correlation graph between ignition timing and rotation speed in a typical engine

[Explanation of symbols]

1 Cylinder head 2 Main combustion chamber 3. Secondary combustion chamber 8 Tooth profile part 6 Bellows 9 Rod 11 Compression spring 12 Rotation axis 13 Thread part 14 Servo motor 15 Piston 18 Solenoid valve

Claims (1)

[Claims] Claim 1: In an engine comprising a main combustion chamber and a sub-combustion chamber communicating with the main combustion chamber, the volume of the sub-combustion chamber can be changed using a factor corresponding to the operating state of the engine as a parameter. An engine having an auxiliary combustion chamber, characterized in that it is provided with controlled volume variable means.