JP7529374B2 - Single cylinder or multi-cylinder internal combustion engine with synchronized pistons - Google Patents

Description

The present invention relates to a single-cylinder internal combustion engine or a multi-cylinder internal combustion engine in which multiple pistons rise and fall synchronously, and is particularly characterized by a blow-by gas processing technology.

Internal combustion engines are classified into single-cylinder and multi-cylinder engines based on the number of cylinders (cylinder bores). In single-cylinder internal combustion engines, the rising and falling of the piston causes pressure fluctuations in the crank chamber, which alternate between positive and negative pressure states. On the other hand, in four-stroke, two-cylinder internal combustion engines, the two pistons generally rise and fall synchronously, shifting the stroke by 360 degrees, but in this case too, pressure fluctuations occur in the crank chamber, just like in single-cylinder engines.

Now, in a reciprocating internal combustion engine, regardless of the number of cylinders, a portion of the combustion gases blows through to the crankcase. Therefore, the blow-by gas that blows through to the crankcase passes through an oil separator chamber where the oil is collected, and the blow-by gas from which the oil has been removed is returned to the intake system (intake manifold) via the PCV passage.

In this case, the return of blow-by gas is controlled by a PCV valve that opens when negative pressure is applied. In naturally aspirated internal combustion engines that are not equipped with a turbocharger, the blow-by gas is returned to the intake system at any time, but in internal combustion engines that are equipped with a turbocharger, the blow-by gas is returned only when the turbocharger is cut and negative pressure is created, such as when decelerating.

However, as mentioned above, in single-cylinder internal combustion engines and four-stroke two-cylinder internal combustion engines in which pressure fluctuations occur in the crank chamber, the negative pressure in the crank chamber can become smaller than the negative pressure in the intake system. As a result, even if there is negative pressure in the intake manifold of the intake system, the PCV valve may not open and blow-by gas may not flow back to the intake manifold.

Regarding this point, Non-Patent Document 1 discloses that a ventilation passage is provided to send intake air to the crank chamber from a portion of the intake system upstream of the throttle valve, and that this ventilation passage is provided with a one-way valve (check valve) that allows intake air to flow only into the crank chamber and prevents backflow, and an electromagnetic on-off valve (flow control valve), and that when negative pressure is created in the crank chamber, the on-off valve is opened to send intake air to the crank chamber, thereby opening and operating the PCV valve.

Honda R&D Technical Review Vol.16 No.2 pages 165-170

In Non-Patent Document 1, while it is assumed that pressure fluctuations in the crank chamber are unavoidable, it is possible to ensure the operation of the PCV valve even if the crank chamber is in a negative pressure state, thereby ensuring the return of blow-by gas . However, there are problems in that an expensive electromagnetic opening/closing valve and a control circuit are required, which increases costs, and there are also problems in that if the cable breaks or the control circuit breaks, the blow-by gas cannot be removed.

The present invention was made to solve this problem.

The present invention relates to a single-cylinder internal combustion engine or a multi-cylinder internal combustion engine in which a plurality of pistons rise and fall synchronously, the internal combustion engine comprising:
"It is equipped with a PCV passage that returns the blow-by gas that has flowed into the crank chamber to the downstream side of the throttle valve in the intake system, and a ventilation passage that connects the upstream side of the throttle valve in the intake system to the crank chamber and allows only fresh air to flow.
The PCV passage is provided with a PCV valve that opens when negative pressure is applied.
In the ventilation passage, a one-way valve for allowing fresh air to flow only to the crank chamber side, and a control valve having a valve body operated by negative pressure in an input passage branching off from a portion of the intake system downstream of the throttle valve are disposed such that the one-way valve is located upstream and the control valve is located downstream, and the input passage is always closed by the valve body to block the flow of intake air and blow-by gas between the input passage and the ventilation passage ,
The input passage is held in a closed state by the valve body, so that the valve body moves in proportion to the negative pressure in the input passage, thereby increasing the opening amount of the ventilation passage.
The structure is as follows.

In the present invention, the intake system and the crank chamber may be connected by a pipe as a ventilation passage, or the intake system and the valve chamber may be connected by an external ventilation passage, while the valve chamber and the crank chamber are connected by an internal ventilation passage opened in the cylinder head and the cylinder block, and a control valve may be inserted in the external ventilation passage .

In the present invention, when the part of the intake system downstream of the throttle valve, such as the intake manifold, becomes under negative pressure or the negative pressure becomes high toward the vacuum side, the control valve opens or the opening degree increases, allowing fresh air to be introduced into the crank chamber or the amount of air introduced to be increased.

Therefore, even if the crank chamber tends to become negative pressure as the piston rises, the introduction of fresh air can prevent the negative pressure from occurring or suppress the degree of the negative pressure. This allows the intake manifold to be kept relatively depressurized compared to the crank chamber, and the PCV valve can be opened and operated. As a result, the return of blow-by gas can be ensured even in single-cylinder internal combustion engines or piston-synchronized multi-cylinder internal combustion engines.

And because the control valve is operated by the negative pressure of the intake system, it has a simple structure and does not require a circuit, which means costs can be significantly reduced compared to solenoid valves, and reliability can be improved by eliminating situations such as inoperability due to cable breakage or circuit damage. Another advantage is that no power is used, so there is no increased burden on the battery.

FIG. 1 is an overall schematic diagram of an embodiment. 2A is a cross-sectional view taken along the line B-B of FIG. 1A; and FIG. 2C is a cross-sectional view taken along the line B-B of FIG. 1A. FIG.

Next, an embodiment of the present invention applied to a four-stroke, two-cylinder internal combustion engine for an automobile will be described with reference to the drawings. In the following, the terms front-rear and left-right are used to specify directions, with the front-rear direction being the direction of the crank axis and the left-right direction being the direction perpendicular to the crank axis and the cylinder bore axis. With respect to front and rear, the side where the timing chain is located is referred to as the front, and the side where the transmission case is located is referred to as the rear.

(1) Overview The basic structure of an internal combustion engine is the same as that of a conventional engine, and the engine body comprises a cylinder block 1, a cylinder head 2 fixed to its upper surface, a head cover 3 fixed to the upper surface of the cylinder head 2, and an oil pan 4 fixed to the lower surface of the cylinder block 1. The front faces of the cylinder block 1 and head cover 3 are covered by a front cover (not shown), and a timing chain is disposed in the space surrounded by the front cover, the cylinder block 1, and the head cover 3.

The crankshaft 5 is rotatably held in the cylinder block 1 via a crank cap, and the piston 7 slidably inserted into the cylinder bore 6 and the crank pin 8 of the crankshaft 5 are connected by a connecting rod 9 so that they can move freely relative to each other.

The cylinder head 2 is formed with an intake port 10 whose beginning opens on the intake side surface 2a and whose end opens on the cylinder bore 6, and an exhaust port 11 whose beginning opens on the cylinder bore 6 and whose end opens on the exhaust side surface 2b. The intake port 10 is opened and closed by an intake valve 12, and the exhaust port 11 is opened and closed by an exhaust valve 13.

An intake manifold 14 is fixed to the intake side 2a of the cylinder head 2, and an exhaust manifold or exhaust turbocharger (neither shown) is fixed to the exhaust side 2b of the cylinder head 2. The intake manifold 14 has a surge tank 15 and two branch passages 16 branching off from it. A throttle valve 17 is fixed to the surge tank 15, and the branch passages 16 are connected to the intake port 10.

The internal combustion engine is equipped with an air cleaner 18 as a component of the intake system, and a duct-like intake passage 19 is connected to the clean chamber 18a of the air cleaner 18, which is in turn connected to a throttle valve 17. More precisely, the throttle valve 17 is equipped with a cylindrical throttle body, a butterfly-type valve body, and a motor (actuator) that drives the valve body, and the opening of the valve body is controlled by an ECU (engine control unit).

A PCV separator chamber 20 into which blow-by gas flows is provided on one side of the cylinder block 1, and the PCV separator chamber 20 is connected to the surge tank 15 by a PCV passage 21. The PCV separator chamber 20 is provided with a PCV valve 22 that opens when negative pressure is applied, but the PCV valve 22 can be provided at any location in the PCV passage 21. The PCV separator chamber 20 may also be provided in the head cover 3.

(2) Ventilation Structure The clean chamber 18a of the air cleaner 18 and the head cover 3 are connected by an external ventilation passage 24, while an internal ventilation passage 25 is formed in the cylinder head 2 and the cylinder block 1, and intake air flows into a crank chamber 27 via a valve chamber 26. A control valve 28 that opens due to the negative pressure of the surge tank 15 and a one-way valve 29 that prevents backflow to the air cleaner 18 are interposed in the external ventilation passage 24. The one-way valve 29 is disposed upstream of the control valve 28. The beginning of the external ventilation passage 24 may be connected to the intake passage 19.

The structure of the control valve 28 is shown in Figure 2. The control valve 28 is equipped with a valve cylinder 31 in which a rod-shaped (plunger-shaped) valve body 30 is fitted so as to slide freely but not rotate, and an inlet port 32 and an outlet port 33 which communicate with the valve cylinder 31 and open in opposite directions. An input port 34 opens at one end of the valve cylinder 31, and one end of an input passage 35 consisting of a hose or tube is connected to this input port 34, and the other end of the input passage 35 is connected to the surge tank 15.

The other end of the valve cylinder 31 is closed by a lid 36, and the valve body 30 is biased toward the lid 36 by a spring (compression coil spring) 37. When the surge tank 15 becomes negative pressure, the valve body 30 is pulled toward the input passage 35 against the spring 37. Therefore, the valve body 30 has a communication hole 38 that opens in a direction perpendicular to its axis.

When the valve disc 30 is fully advanced by the spring 37 (abutting against the lid 36), the communication hole 38 is entirely out of contact with the inlet port 32 and the outlet port 33, and therefore fresh air is not supplied to the valve train chamber 26 and the crank chamber 27. On the other hand, when the valve disc 30 is pulled back against the spring 37 by negative pressure, the communication area between the communication hole 38 and the inlet port 32 and the outlet port 33 increases in proportion to the degree of retreat, and when the valve disc 30 is fully advanced, the communication hole 38 is fully communicated with the inlet port 32 and the outlet port 33. In any case, the input passage 35 is always closed by the valve disc 30, and intake air or blow-by gas does not flow between the input passage 35 and the ventilation passage 24.

Now, the two pistons 7 rise and fall in sync, even though their strokes are 360 degrees apart, so the internal pressure in the crank chamber 27 tends to alternate between positive and negative pressure at 180-degree intervals. On the other hand, in the intake manifold 14, an increase in negative pressure due to the intake stroke and a decrease in negative pressure due to the compression stroke occur at 360-degree intervals. Therefore, the cycles of pressure fluctuation are different between the intake manifold 14 and the crank chamber 27.

However, in this embodiment, when the intake manifold 14 is in a negative pressure state (or the negative pressure increases toward the vacuum side), the amount of ventilation to the crank chamber 27 increases, and if the crank chamber 27 is tending toward negative pressure, the negative pressure is eliminated or reduced, so that the intake manifold 14 can be kept in a relatively depressurized state. Therefore, the PCV valve 22 can be opened and operated to return the blow-by gas to the intake manifold 14.

The control valve 28 has a simple structure in which the valve body 30 is biased by a spring 37, so costs can be significantly reduced compared to a solenoid valve, and operation is reliable and the reliability is excellent. The control valve 28 can be attached to the head cover 3 or the surge tank 15, so it is also flexible in terms of the mounting position.

Although the embodiment of the present invention has been described above, the present invention can be embodied in various other ways. For example, the control valve is not limited to a rod-shaped valve body type, and a needle valve type can also be adopted. It is also possible to directly connect the air cleaner or the intake passage to the crank chamber through a ventilation passage without providing an internal ventilation passage. Furthermore, when an internal ventilation passage is provided, the chain arrangement space surrounded by the front cover can also be used as the internal ventilation passage.

The present invention can be embodied in a single-cylinder internal combustion engine or a multi-cylinder internal combustion engine in which multiple pistons rise and fall synchronously. Therefore, it can be used industrially.

REFERENCE SIGNS LIST 1 cylinder block 2 cylinder head 3 head cover 7 piston 10 intake port 11 exhaust port 14 intake manifold 15 surge tank 16 branch passage 17 throttle valve 18 air cleaner 19 intake passage 20 oil separator chamber 21 PCV passage 22 PCV valve 24 external ventilation passage 25 internal ventilation passage 28 control valve 29 one-way valve 30 valve body 31 valve cylinder
35 Input passage
37 Spring

Claims (1)

A single-cylinder internal combustion engine or a multi-cylinder internal combustion engine in which multiple pistons rise and fall synchronously,
The system is provided with a PCV passage that returns the blow-by gas that has flowed into the crank chamber to the downstream side of the throttle valve in the intake system, and a ventilation passage that communicates with the crank chamber and a portion of the intake system upstream of the throttle valve and allows only fresh air to flow through.
The PCV passage is provided with a PCV valve that opens when negative pressure is applied.
In the ventilation passage, a one-way valve for allowing fresh air to flow only to the crank chamber side, and a control valve having a valve body operated by negative pressure in an input passage branching off from a portion of the intake system downstream of the throttle valve are disposed such that the one-way valve is located upstream and the control valve is located downstream, and the input passage is always closed by the valve body to block the flow of intake air and blow-by gas between the input passage and the ventilation passage ,
The input passage is held in a closed state by the valve body, so that the valve body moves in proportion to the negative pressure in the input passage to increase the opening amount of the ventilation passage.
Single cylinder or multi-cylinder internal combustion engines with synchronized pistons.

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