JPS6118013B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in engines.

Conventionally, general spark ignition engines have a constant compression ratio regardless of operating conditions, and this compression ratio is set in consideration of output, occurrence of knocking, etc. Therefore, for example, in a gasoline engine with a carburetor, when the throttle valve opening is small and the load is low, the intake air filling efficiency is low, the fuel consumption rate (g/PS-H, hereinafter referred to as fuel efficiency) increases, and this fuel efficiency decreases. If the compression ratio is set high to reduce this, knocking will occur at high loads when the valve opening is large and the intake air filling efficiency is high, resulting in a decrease in output and, in extreme cases, engine burnout or damage. It was hot.

The present invention has been proposed in view of the above, and includes a sub cylinder communicating with a combustion chamber formed by the top surface of the main piston, a wall surface of the main cylinder into which the main piston is fitted, a cylinder head surface closing the cylinder, etc. A secondary piston that is fitted into the cylinder and is slidable between a first position where the volume of the combustion chamber is reduced and a second position where the volume is increased; the secondary piston is moved to the second position; a biasing means for biasing the secondary piston to the second position against the biasing force of the biasing unit so that the secondary piston is in the first position at a specific time in the operating cycle of the engine; A variable compression system characterized by comprising: a sub-piston drive device that periodically drives the sub-piston drive device toward the first position; and a control device that detects the operating state of the engine and controls the operation of the sub-piston drive device. A sub-cylinder that communicates with the combustion chamber formed by the specific engine, the top surface of the main piston, the wall surface of the main cylinder into which the main piston is fitted, and the cylinder head surface that closes the cylinder, and which is fitted inside the sub-cylinder. A secondary piston that is slidable between a first position where the volume of the combustion chamber is reduced and a second position where the volume is increased; an urging force that urges the secondary piston toward the first position; means, a sub-piston holding means for holding the sub-piston in the first position, and a control device for detecting the operating state of the engine and controlling the operation of the sub-piston holding means, wherein the control device is configured to hold the sub-piston in the first position. The variable compression engine is characterized in that the auxiliary piston is moved toward the second position by the pressure within the combustion chamber when the means is deactivated. Since the compression ratio can be changed according to the operating condition of the engine, it is possible to provide an engine with improved fuel efficiency and output.

Hereinafter, a first embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2. A main piston 14 is slidably fitted into a plurality of cylinders 12 formed in the cylinder block 10, and the main piston 14 is connected to a crankshaft via a connecting rod (not shown). A cylinder head 16 is fixed to the upper surface of the cylinder block 10 by bolts or the like via a gasket (not shown), and the hemispherical concave surface of the cylinder head 16, the inner wall surface of the cylinder 12, and the top surface of the main piston 14 cause combustion. room 18
is formed. An ignition plug 22 is screwed onto the cylinder head 16 so that a spark gap 20 faces the combustion chamber 18, and an intake port 24 and an exhaust port 26 are formed which are opened and closed by intake and exhaust valves (not shown). room 18
A bottomed cylindrical member 30 in which a sub-cylinder 28 is formed is attached. The intake and exhaust valves are operated by a conventionally known valve drive mechanism (not shown). The above sub-cylinder 28
A sub-piston 32 is slidably fitted into the sub-piston 32, and one end of a rod 34 is fixed to the sub-piston 32, and the rod 34 passes through a hole 36 provided at the bottom of the cylindrical member 30. A spring seat 38 is attached to the outer end of the sub cylinder 28.
A spring 40 is interposed between the cylindrical member 30 and the cylindrical member 30, and urges the sub-piston 32 upward in the figure. The outer end of the rod 34 is in contact with the outer end of a plunger 44 that is slidably fitted into the hydraulic cylinder 42.

The hydraulic cylinder 42 is formed at one end of a rocker arm 48 that is swingably supported on a hollow shaft 46, and the other end of the rocker arm 48 rotates in conjunction with a crankshaft (not shown). It is configured to come into contact with the cam 50 that is pressed. The rocker arm 48 has a groove 52 provided on the outer peripheral surface of the shaft 46 and the hydraulic cylinder 4.
An oil passage 54 is provided which communicates with the oil passage 2, and a switching valve 56 and a check valve 58 are interposed in the middle of the oil passage 54. The hydraulic cylinder 42 is provided with a plunger 44 which pushes outward and substantially locks the rod 3.
A spring 60 that presses the sub-piston 32 inward (downward in the drawing) of the combustion chamber 18 via the auxiliary piston 4 is installed inside the combustion chamber 18, and is communicated with an atmosphere opening passage 62 that is opened and closed by the switching valve 56. The switching valve 56 has a bottomed cylindrical valve body 64 that is slidably displaced by the oil pressure in the oil passage 54, and when pressure oil is supplied to the oil passage 54, the valve body 64 is moved by the pressure. The oil passage 54 is placed in the position shown in FIG.
and the hydraulic cylinder 42 through the check valve 58, and the atmosphere release passage 62 is shut off. When the pressure oil in the oil passage 54 is discharged or becomes low pressure, the oil passage 54 and the hydraulic pressure are in the position shown in FIG. While cutting off communication with the cylinder 42, the atmosphere opening passage 6
It is configured to open 2. Further, the check valve 58 is connected to the hydraulic cylinder 42 from the oil passage 54.
It is configured to allow the flow of pressure oil to the pipe and immediately stop its reverse flow.

The shaft 46 has a hollow portion configured as an oil passage 66 and is provided with an oil passage 68 for communicating the groove 52 and the oil passage 66.
is communicated with an oil passage 70 at the end of the shaft 46, and the oil passage 70 is communicated with a control valve 72. The control valve 72 is composed of a valve body 77 that switches and controls communication between the oil passage 70 and the high-pressure oil passage 74 or the low-pressure oil passage (drainage passage) 76, and a diaphragm device 78 that operates the valve body 77. The diaphragm device 78 has two chambers 82 and 8 inside the casing 80.
The diaphragm 86 is connected to the valve body 77 and the valve body 77 is connected to the oil passage 70 and the low pressure oil passage 76.
and a spring 88 that biases in the direction of communication between the two. Further, the chamber 82 is communicated with a negative pressure generation source such as an intake pipe of the engine body (not shown) via a negative pressure passage 90, and the chamber 84 is opened to the atmosphere through a hole 92.

The negative pressure passage 90 is connected to an atmosphere opening passage 94, and the atmosphere opening passage 94 is connected to the atmosphere opening passage 94.
A solenoid valve 96 for opening and closing is interposed.
The solenoid valve 96 includes a valve body 98, a spring 100 that biases the valve body 98 in the closing direction, and a solenoid 102 that moves the valve body 98 to the open position against the biasing force of the spring 100 when excited.
The solenoid 102 operates according to the engine speed and closes when the engine speed falls below a predetermined value (in this embodiment, 3500 rpm or less), and the solenoid 102 operates according to the engine's intake manifold negative pressure. It is connected to a power source 108 via a switch 106 which is activated accordingly and is closed when the negative pressure falls below a set value (in this embodiment, 200 mmHg or less).

The cam 50 holds the rocker arm 48 at the position shown in FIG. 1, that is, the first position, at specific times in the engine operating cycle, that is, during the compression, explosion, and exhaust strokes, and holds the rocker arm 48 at the first position shown in FIG. 1 during the intake stroke. The secondary piston 32 is configured to be rotated counterclockwise from the illustrated position and moved to an upper position, that is, a second position, by the urging force of a spring 40 serving as an urging means.

Further, in this embodiment, the cam 50, the rocker arm 4
8. The plunger 44 and the hydraulic cylinder 42 constitute a sub-piston drive device, and the control valve 72;
A control device is configured centering on the solenoid valve 96.

In the above configuration, under high speed conditions where the rotation speed is 3500 rpm or more or when the manifold negative pressure is 200 mm
When the engine is operated under a low load condition where the engine pressure is Hg or higher (that is, an operating condition in which knocking is unlikely to occur), the switches 104 and 106 are switched on.
Since both or one of the solenoid valves 10 and 10 are opened and the solenoid 102 is demagnetized, the valve body 98 of the solenoid valve 96 closes the atmosphere opening passage 94 due to the biasing force of the spring 100. Therefore, the negative pressure of the engine is conducted to the chamber 82 of the diaphragm device 78 through the negative pressure passage 90, and the action of the negative pressure causes the diaphragm 86 to move upward in the figure (see FIG. 1) against the biasing force of the spring 88. ) to move the valve body 7 to the position shown in
7 also moves upward, and the control valve 72 communicates the high pressure oil passage 74 with the oil passage 70. From high pressure oil line 74 to oil line 7
The oil pressure led to 0 is led to the switching valve 56 via the oil passages 66 and 68 provided in the shaft 46, the groove 52, and the oil passage 54 provided in the rocker arm 48, and the valve of the switching valve 56 is The main body 64 is moved to the position shown in FIG.
It is fixedly held in the protruding position shown in the figure. Therefore, the sub piston 32 in the sub cylinder 28 is driven by the cam 50 via the rod 34, plunger 44, and rocker arm 48, so during the compression, explosion, and exhaust strokes of the engine, the sub piston 32 is driven by the cam 50.
It is pushed down to the lower position shown in the figure, and is pulled up to the upper position by the biasing force of the spring 40 during the intake stroke. As a result, it is possible to obtain a relatively high compression ratio and improve intake efficiency in high-speed or low-load operating conditions of the engine, thereby improving output and fuel efficiency.

Furthermore, when the engine is operated at low speed and high load (in other words, a state where knocking is likely to occur) where the rotational speed is 3500 rpm or less and the manifold negative pressure is 200 mmHg or less, both switches 104 and 106 are is closed, solenoid 102
is excited, the valve body of the electromagnetic valve 96 is moved downward (to the position shown in FIG. 2) against the biasing force of the spring 100, thereby opening the atmosphere release passage 94. Therefore, the atmosphere is introduced into the chamber 82 through the atmosphere opening passage 94 and the negative pressure passage 90, and the diaphragm 86 is moved downward in the drawing (to the position shown in FIG. 2) by the biasing force of the spring 88. , the valve body 77 also moves downward, and the control valve 72 closes to the high pressure oil passage 74.
The oil passage 70 and the low pressure oil passage (drainage oil passage) 76 are communicated with each other. Therefore, the oil pressure in the oil passages 70, 66, 68, and 54 is reduced or discharged, and the valve body 64 of the switching valve 56 is moved to the position shown in FIG. 2, so that the atmosphere release passage 62 is opened and the oil pressure is The hydraulic pressure in the cylinder 42 is discharged, and relative sliding displacement of the plunger 44 with respect to the hydraulic cylinder 42 becomes possible, and when the biasing force of the spring 40 is larger than the biasing force of the spring 60, the rocker arm 48 is oscillated by the cam 50. Regardless, the sub-piston 32 is fixedly held in the upper position shown in FIG. As a result, during low-speed, high-load operation where knocking is likely to occur, it is possible to increase the substantial volume of the combustion chamber 18 and reduce the compression ratio, thereby preventing the occurrence of knocking and reducing the combustion temperature accordingly. This can also reduce the amount of _NOx generated.

As is clear from the above, according to the first embodiment of the present invention, the compression ratio can be changed depending on the operating state of the engine, so the optimum compression ratio for each operating state can be obtained. It is possible to improve output and fuel efficiency without causing knocking.

In addition, combustion sludge that tends to accumulate on the wall of the sub-cylinder 28 can be scraped off by the sub-piston 32, which slides every cycle of the engine, resulting in less sludge accumulation and high durability and reliability. becomes.

Furthermore, it is only necessary to add the sub cylinder 28, the sub piston 32, and the drive system for the sub piston to a normal engine, and the lubricating oil of the engine can be used as the pressure oil supplied to and discharged from the hydraulic cylinder 42.
This has advantages such as being able to provide a variable compression ratio engine with a relatively simple structure and at low cost.

In the first embodiment, when driving the sub-piston 32 in operating states other than low-speed and high-load states, the sub-piston 32 is configured to slide upward only during the intake stroke. By changing the shape and changing the sliding timing of the auxiliary piston 32 as appropriate, it is also possible to create a configuration that achieves effects such as reducing residual exhaust gas, reducing _NOx by approaching isobaric combustion, and improving fuel efficiency. It is possible.

In addition, in the first embodiment, the spring 60 biases the sub-piston 32 toward the combustion chamber 18.
Although the case is shown in which the biasing force of the spring 40 that biases the secondary piston 32 toward the outside of the combustion chamber 18 (upward in the figure) is greater than the biasing force of the secondary piston 32, even when the biasing force of the spring 60 is larger. The configuration is such that the sum of the force that presses the auxiliary piston 32 upward due to the pressure generated in the combustion chamber 18 during the compression or explosion stroke of the engine and the biasing force of the spring 40 is sufficiently larger than the biasing force of the spring 60. Then, when the hydraulic pressure in the hydraulic cylinder 42 is being discharged, the pressure generated in the combustion chamber 18 pushes the auxiliary piston 32 upward.
The compression ratio can be substantially reduced, and the same effects as in the first embodiment can be achieved.

Next, a second embodiment of the present invention will be described in detail with reference to FIG. Incidentally, the same members or members having substantially the same functions as those shown in the first embodiment are given the same reference numerals, and the explanation thereof will be omitted.

This embodiment differs from the cam 50 in the first embodiment.
A hydraulic cylinder 42 and a plunger 44 are installed in the cylinder head 16, and the hydraulic cylinder 42 and the plunger 44 are connected to a rocker arm 48 that is swung by The configuration is the same as that of the first embodiment, except that the oil passage 70 is directly connected to the switching valve 56. Further, a cylindrical member 200 in which a sub cylinder 28 is formed
A damper cylinder 202 is formed in the
A damper piston 204, which is slidably fitted into the damper cylinder 202, is fixed to the other end of the rod 34, one end of which is fixed to the sub-piston 32. Furthermore, a spring 206 for pressing the sub-piston 32 downward in the figure is disposed inside the sub-cylinder 28, and an oil passage 208 communicating with an engine lubricating hydraulic circuit (not shown) is connected to the check valve 210. The lubricating oil is supplied into the sub-cylinder 28 through the sub-cylinder 28. The lubricating oil supplied into the sub-cylinder 28 is discharged to the outside via oil passages 212 and 214 formed in the sub-piston 32 and the rod 34.

According to the above configuration, when the engine is operated in a high-speed state where the rotational speed is 3500 rpm or more or in a low-load state where the manifold negative pressure is 200 mmHg or more (i.e., an operating state where knocking is unlikely to occur), Since hydraulic pressure is supplied to the hydraulic cylinder 42, which is the sub-piston holding means, and the plunger 44 is fixedly held at the protruding position shown in the figure, the sub-piston 32 is also fixed at the downward position shown, regardless of the stroke of the engine. Therefore, a relatively high compression ratio can be obtained.

In addition, when the engine is operated in a low speed, high load condition where the rotational speed is 3500 rpm or less and the manifold negative pressure is 200 mmHg or less (i.e., an operating condition where knocking is likely to occur), the inside of the hydraulic cylinder 42 is The hydraulic pressure is reduced or discharged, allowing relative sliding displacement of the plunger 44 with respect to the hydraulic cylinder 42, thereby pushing the secondary piston 32 upward due to the pressure generated in the combustion chamber 18 during the compression or explosion stroke of the engine. The acting force pushes up the secondary piston 32 against the downward biasing force of the springs 206 and 60, and the secondary piston 32 moves to the second position, substantially increasing the combustion chamber volume. This results in a relatively low compression ratio. In this case, in the exhaust and intake strokes of the engine, the piston 3
Needless to say, the biasing force of the springs 206 and 60 brings the position 2 to the lower position shown in the figure, that is, the first position.

Further, according to the above configuration, the sub piston 32
During sliding, the damper function is obtained by the action of the damper cylinder 202 and the damper piston 204, so that the sub piston 32 can operate smoothly.

Further, engine lubricating oil is supplied into the sub-cylinder 28 through an oil passage 208, and oil passages 212, 21
Since the lubricating oil is discharged through the cylinder 4 and circulates within the sub-cylinder 28, the sub-piston 32 can be cooled by both lubricating oils, and overheating of the sub-piston 32 can be prevented. It is. In addition,
It goes without saying that this cooling structure for the sub-piston 32 can also be applied to the first embodiment.

As is clear from the above, the second embodiment can also achieve substantially the same effects as the first embodiment.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the structure of the first embodiment of the present invention, Fig. 2 is a sectional view of essential parts for explaining the operation of the first embodiment, and Fig. 3 is the structure of the second embodiment of the invention. FIG. 12...Main cylinder, 14...Main piston, 1
6...Cylinder head, 18...Combustion chamber, 28...
... Sub-cylinder, 32... Sub-piston, 34... Rod, 40, 60, 206... Spring, 42
...Hydraulic cylinder, 44...Plunger, 72...
...control valve.

Claims (1)

[Scope of Claims] 1. A sub-cylinder that communicates with the combustion chamber formed by the top surface of the main piston, the wall surface of the main cylinder into which the main piston is fitted, and the cylinder head surface that closes the cylinder, and which is fitted into the sub-cylinder. an auxiliary piston that is slidable between a first position where the volume of the combustion chamber is reduced and a second position where the volume is increased; the auxiliary piston is urged toward the second position; a biasing means for moving the sub-piston from the second position to the first position against the biasing force of the biasing unit so that the sub-piston is in the first position at a specific time in the engine operating cycle; 1. A variable compression ratio engine comprising: a sub-piston drive device that periodically drives the sub-piston drive toward a position; and a control device that detects the operating state of the engine and controls the operation of the sub-piston drive device. 2. A sub-cylinder that communicates with the combustion chamber formed by the top surface of the main piston, the wall surface of the main cylinder into which the main piston is fitted, and the cylinder head surface that closes the cylinder, and which is fitted into the sub-cylinder and which also communicates with the combustion chamber. a secondary piston that is slidable between a first position where the volume of the secondary piston is small and a second position where the volume is large; a biasing means that biases the secondary piston toward the first position; Place the secondary piston in the first position above.
auxiliary piston holding means for holding the auxiliary piston holding means in the position of , and a control device for detecting the operating state of the engine and controlling the operation of the auxiliary piston holding means, when the control device deactivates the auxiliary piston holding means; A variable compression ratio engine, characterized in that the auxiliary piston is moved toward the second position by pressure within the combustion chamber.