JP4858300B2 - Split stroke cycle engine - Google Patents

Description

  The present invention relates to a split stroke cycle engine having a cylinder that performs an intake / compression stroke and a cylinder that performs an expansion / exhaust stroke separately.

  2. Description of the Related Art Conventionally, there is known a split stroke cycle engine that includes a compression cylinder that performs an intake / compression stroke and an expansion cylinder that performs an expansion / exhaust stroke separately, and communicates these two cylinders through a communication path (for example, patent Reference 1). In such a split stroke cycle engine, the engine efficiency is achieved by introducing the air compressed in the compression cylinder into the expansion cylinder through the communication path and performing combustion in the expansion cylinder to obtain power. It is intended to improve emissions and reduce emissions.

US Pat. No. 6,543,225B2

  By the way, in the above-described split stroke cycle engine, since the temperature of the air after being compressed in the compression cylinder is high, fuel is injected and supplied to this high-temperature compressed air introduced into the expansion cylinder via the communication path. Then, self-ignition or knocking may occur. As a result, normal combustion control becomes difficult, and the intended improvement in engine efficiency and reduction in emissions may not be achieved. Further, when high-temperature compressed air is introduced into the expansion cylinder, the air density is lowered and the charging efficiency is deteriorated, so that the margin for improving the engine output is lowered.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a split stroke cycle engine that can suppress the occurrence of self-ignition or knocking to improve engine efficiency and reduce emissions.

  A split stroke cycle engine according to an aspect of the present invention includes a compression cylinder that performs a suction / compression stroke and an expansion cylinder that performs an expansion / exhaust stroke separately, and the two cylinders communicate with each other through a communication path. The stroke cycle engine includes a cooling means for cooling the air in the communication path.

  Here, the cooling means may be a heat pipe having one end arranged in the communication passage and the low temperature side of the other end arranged in a water jacket of a cylinder head or an intake passage of the compression cylinder.

  The compression cylinder communicates with the intake passage via a first intake valve and communicates with the communication passage via a non-return discharge valve, and the expansion cylinder communicates with the communication passage via a second intake valve. A valve opening means that communicates with the passage and communicates with the exhaust passage via the exhaust valve and opens the second intake valve during a predetermined period during the opening of the exhaust valve may be provided.

  In addition, it is preferable that the communication path communicates with the expansion cylinder in a direction parallel to a tangent line in a plan view.

  According to one aspect of the present invention, the air in the communication path that connects the compression cylinder that performs the suction / compression stroke and the expansion cylinder that performs the expansion / exhaust stroke is cooled by the cooling means, and this is introduced into the expansion cylinder. Thus, even if fuel is injected and supplied, the occurrence of self-ignition or knocking is suppressed. Furthermore, since the air density is increased and the charging efficiency is improved, the engine output can be increased. Thus, engine efficiency can be improved and emissions can be reduced.

  Here, according to the form in which the cooling means is a heat pipe having one end disposed in the communication passage and the low temperature side of the other end disposed in a water jacket of a cylinder head or an intake passage of the compression cylinder. The layout can be facilitated and the air in the communication path can be efficiently cooled.

  The compression cylinder communicates with the intake passage via a first intake valve, and communicates with the communication passage via a non-return discharge valve, and the expansion cylinder communicates with the communication passage via a second intake valve. According to an aspect provided with the valve opening means that communicates with the passage and communicates with the exhaust passage through the exhaust valve, and that opens the second intake valve during a predetermined period during the opening of the exhaust valve. When the second intake valve is opened, a part of the exhaust gas in the expansion cylinder enters the communication path. The exhaust gas that has entered the communication path is held in the communication path and cooled by the cooling means. Then, the cooled exhaust gas is introduced into the expansion cylinder together with the compressed air as internal EGR gas in the next cycle. Therefore, since a relatively large amount of EGR gas can be easily introduced, it is possible to reduce emissions such as NOx.

  Further, according to the form in which the communication path communicates with the expansion cylinder in a direction parallel to the tangent in a plan view, a strong swirling flow or turbulence can be generated in the expansion cylinder. Good combustion can be performed and engine efficiency can be improved.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a split stroke cycle engine according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic longitudinal sectional view showing an embodiment of a split stroke cycle engine 100, and FIG.

  1 and 2, reference numeral 10 denotes a compression cylinder that performs an intake / compression stroke, 20 denotes an expansion cylinder that performs an expansion / exhaust stroke, and 30 denotes a communication path that connects these two cylinders. A compression piston 11 is fitted in the compression cylinder 10 so as to be able to reciprocate. The compression piston 11 is connected to a first crank pin of a crankshaft (not shown) via a connecting rod 12 so as to be rotatable. The compression cylinder 10 communicates with the intake passage 14 via a first intake valve 13 constituted by a reed valve, and communicates with the communication passage 30 via a discharge valve 15 constituted by a check valve. The discharge valve 15 is urged with a predetermined set load by a spring 17 toward a compression chamber 16 formed at an upper portion of the compression piston 11.

  An expansion piston 21 is fitted in the expansion cylinder 20 so as to freely reciprocate. The expansion piston 21 is connected to the first crank pin of the above-described crank shaft connected to the connecting rod 12 via a connecting rod 22. The second crank pins having different phase angles are rotatably connected. This phase angle is set so that the expansion piston 21 operates slightly ahead of the compression piston 11. Further, the expansion cylinder 20 is connected to the communication passage 30 through a second intake valve 23 that is configured by a poppet valve and electromagnetically driven by a solenoid 28, and an exhaust valve 25 that is also configured by a poppet valve. It communicates with the exhaust passage 24 via (two in this embodiment). The exhaust valve 25 is opened and closed by a camshaft cam that is driven in synchronization with the crankshaft. An ignition plug 26 is disposed on the expansion cylinder 20 so as to protrude from the cylinder upper wall to the combustion chamber 29 substantially on the center line. In the present embodiment, the communication passage 30 is communicated with the expansion cylinder 20 in a direction parallel to the tangent in a plan view, and the spark plug 26 is disposed at a peripheral portion of the communication passage 30 substantially on the extension line. The fuel injection valve 27 is arranged in such a manner that the injection direction is directed to the front.

  Further, an intercooler 40 is disposed in the communication path 30. More specifically, the intercooler 40 is constituted by a plurality of heat pipes 42 provided with a large number of cooling fins 41 at the end, and the cooling fins 41 are arranged in parallel in the communication path 30. And in 1st Embodiment, as shown in FIG.1 and FIG.3, in the water jacket 102 in which the low temperature side edge part of the said heat pipe 42 is formed in the cylinder head through which the cooling water of the engine 100 is circulated. Is arranged. Further, in the second embodiment, as shown in FIG. 2, the low temperature side end of the heat pipe 42 is disposed in the intake passage 14 of the compression cylinder 10 through which relatively low temperature air flows. Note that the intercooler 40 is provided by a caster when the cylinder head is manufactured.

  Further, the engine 100 includes a crank angle sensor (not shown) for detecting the rotational speed of the engine 100 (hereinafter referred to as a rotational speed sensor), an accelerator opening sensor for detecting a required load (accelerator opening), Various sensors such as an air flow meter for measuring the intake air amount and a water temperature sensor for detecting the cooling water temperature of the engine 100 are provided. The outputs of these various sensors are sent to an electronic control unit (not shown) constituted by a microcomputer or the like.

  In the present embodiment, an electronic control unit (hereinafter referred to as “ECU”), in addition to the fuel injection amount, the fuel injection timing, and the ignition timing, corresponds to the output values sent from the various sensors described above. Controls the opening and closing time of the. The basic control values used for controlling the fuel injection amount, the fuel injection timing, the ignition timing, the opening / closing timing of the second intake valve 23, and the like are, for example, an engine whose vertical axis represents the intake air amount and the like. In the basic map representing the operating state of the engine 100 with the horizontal axis representing the engine speed, the optimum value obtained experimentally in accordance with the required characteristics of the engine 100 is set as the control value. These basic maps are stored in the ROM of the electronic control unit.

  The operation of the engine 100 according to the embodiment of the present invention will be described with reference to the graphs shown in FIGS. In the following description, “period” is represented by a crank angle (° CA) that is the rotation angle of the crankshaft, and “time” is top dead center (referred to as TDC) or bottom dead center (BDC). It is expressed by the crank angle before and after the top dead center or the bottom dead center.

  First, in the engine 100 according to the present embodiment, one cycle including four strokes of suction, compression, expansion, and exhaust is completed by one rotation (360 ° CA) of a crankshaft (not shown). That is, as shown in FIG. 5A, when the crank angle corresponding to the TDC of the compression piston 11 in the compression cylinder 10 is 0 ° CA, the compression piston 11 reaches the BDC having a crank angle of 180 ° CA. Then, the suction stroke is executed, and thereafter, the compression stroke is executed while the compression piston 11 reaches TDC at a crank angle of 360 ° CA. At the same time, in the expansion cylinder 20, as shown in FIG. 5B, during the same rotation of the crankshaft, during the movement of the expansion piston 21 from TDC to BDC in which the crank angle reaches 0 ° CA to 180 ° CA. Then, the explosion / expansion stroke is executed, and thereafter, the exhaust stroke is executed while the expansion piston 21 reaches TDC where the crank angle becomes 360 ° CA. In other words, the compression stroke in the compression cylinder 10 and the exhaust stroke in the expansion cylinder 20 are almost at the same time with a phase difference slightly preceded by the exhaust stroke, and the intake stroke in the compression cylinder 10 and the expansion stroke in the expansion cylinder 20. The expansion stroke is performed almost at the same time with a phase difference slightly preceding the expansion stroke.

  Therefore, the compression piston 11 descends in the compression cylinder 10, and the crank angle as shown in FIG. 4A is changed from 0 ° CA to 180 ° CA in the first cycle and from 360 ° CA to 540 ° CA in the next cycle. In the meantime, the first intake valve 13 constituted by a reed valve is opened along with the pressure drop in the cylinder, and the intake stroke in which air is drawn from the intake passage 14 is performed. Then, the compression piston 11 rises in the compression cylinder 10, and the crank angle as shown in FIG. 4A is changed from 180 ° CA in the first cycle to 360 ° CA and from 540 ° CA to 720 ° CA in the next cycle. In the meantime, the first intake valve 13 constituted by a reed valve is closed, the air in the compression chamber 16 is compressed, and the pressure rises. When the compression pressure in the compression cylinder 10 becomes larger than a predetermined set load of the spring 17 urging the discharge valve 15, the discharge valve 15 constituted by a check valve is opened, and the compressed air is continuously connected. It is sent to the passage 30.

  Here, the compressed air sent into the communication path 30 is cooled by the intercooler 40 disposed in the communication path 30. That is, the intercooler 40 is a first embodiment (FIG. 1 and FIG. 1) configured with a heat pipe 42 having one end disposed in the communication path 30 and the other end on the low temperature side disposed in the water jacket 102 of the cylinder head. 3)), heat is recovered from the high-temperature compressed air through the cooling fins 41 provided at one end thereof, and the heat is transferred to the cooling water in the water jacket 102 in which the low-temperature side at the other end is disposed. By being transferred, the compressed air in the communication path 30 is efficiently cooled. On the other hand, a second embodiment in which the intercooler 40 includes a heat pipe 42 having one end disposed in the communication passage 30 and the low temperature side of the other end disposed in the intake passage 14 of the compression cylinder 10 (see FIG. 2). ), Heat is recovered from the high-temperature compressed air through the cooling fin 41 provided at one end thereof, and the heat is transferred to the intake air in the intake passage 14 where the other end is disposed at the low temperature side. As a result, the compressed air in the communication passage 30 is efficiently cooled.

  Then, before the compression piston 11 continues to rise in the compression cylinder 10 and reaches its compression TDC (typically described for 360 ° CA), in other words, in the expansion cylinder 20, the expansion piston 21 almost reaches the exhaust TDC. When this occurs (for example, TDC 0 ° CA: indicated by t1 in FIGS. 4B and 5B), the solenoid 28 is driven by a command signal from the ECU, and the second intake valve 23 is opened. When the second intake valve 23 is opened, the compressed air that has been cooled by being sent to the communication passage 30 is ejected to the expansion cylinder 20 (see “ejection” in FIG. 5B). At this time, in the present embodiment, the communication passage 30 communicates with the expansion cylinder 20 in a direction parallel to the tangent in a plan view. Is born. Immediately after the second intake valve 23 is opened and the introduction of compressed air is started, the fuel injection valve 27 is driven by a command signal from the ECU, and fuel injection is started ("" in FIG. 4B). See “Injection”. The injected fuel is mixed with the swirling flow or turbulent flow by the compressed air, and an air-fuel mixture suitable for combustion is formed.

  Thereafter, the second intake valve 23 at a predetermined crank angle at which the expansion piston 21 has passed the exhaust TDC in the expansion cylinder 20 (for example, 60 ° CA after TDC: indicated by t2 in FIGS. 4B and 5B). Is closed. A command signal from the ECU is sent and ignition is performed by the spark plug 26 at substantially the same timing as when the second intake valve 23 is closed (see “ignition” in FIG. 4B). Thus, combustion is started explosively in the expansion cylinder 20, and an expansion stroke is performed in which the expansion piston 21 is lowered by the combustion pressure.

  Further, at a final stage of the expansion stroke, exhaust is performed at a predetermined crank angle before the expansion piston 21 reaches the expansion BDC (for example, 30 ° CA before BDC: indicated by t3 in FIGS. 4B and 5B). The valve 25 is opened. The exhaust valve 25 is closed when it passes through the expansion BDC having a crank angle of 540 ° CA and the expansion piston 21 performs the exhaust stroke to reach the exhaust TDC (720 ° CA).

  In the present embodiment, a command signal from the ECU is output during an initial predetermined period (for example, a period from exhaust BDC to 60 ° CA: X in FIG. 5B) during opening of the exhaust valve 25 described above. As a result, the solenoid 28 is driven to open the second intake valve 23. When the second intake valve 23 is opened, a part of the exhaust gas in the expansion cylinder 20 enters the communication path 30. As is apparent from FIG. 4C showing the change in the in-cylinder pressure of the expansion cylinder 20, there is some residual pressure in the expansion cylinder 20 during the initial predetermined period X. On the other hand, because the compression cylinder 10 is in the initial stage of the compression stroke, a sufficient compression pressure is not generated, and the discharge valve 15 constituted by a check valve is kept closed.

  The exhaust gas that has entered the communication path 30 is held in the communication path 30 and cooled by the intercooler 40. Then, in the next cycle, the cooled exhaust gas is introduced into the expansion cylinder 20 together with the compressed air as internal EGR gas due to an increase in the compression pressure accompanying the rise of the compression piston 11 as described above. Accordingly, since a relatively large amount of EGR gas can be easily introduced, emission of NOx and the like can be reduced.

1 is a schematic longitudinal sectional view showing an embodiment of a split stroke cycle engine according to the present invention. 1 is a schematic plan view showing an embodiment of a split stroke cycle engine according to the present invention. It is an expanded sectional view of the intercooler part in the division stroke cycle engine of FIG. 5 is a graph for explaining the operation of the split stroke cycle engine according to the present invention, in which (A) is a timing for opening and closing the first intake valve and the discharge valve in the compression cylinder, and (B) is a second intake valve and the exhaust in the expansion cylinder. Valve opening / closing timing and fuel injection / ignition timing, (C), also show changes in in-cylinder pressure in the expansion cylinder. It is a graph for demonstrating the action | operation of the split stroke cycle engine by this invention, (A) is the relationship between the intake stroke in a compression cylinder, the compression stroke, and a crank angle, (B) is the expansion stroke and exhaust stroke in an expansion cylinder. The relationship with a crank angle and the opening / closing timing of a 2nd intake valve and an exhaust valve are shown.

Explanation of symbols

10 Compression cylinder 11 Compression piston 13 First intake valve (reed valve)
14 Intake passage 15 Discharge valve (check valve)
Reference Signs List 16 Compression chamber 17 Spring 20 Expansion cylinder 21 Expansion piston 23 Second intake valve 25 Exhaust valve 26 Spark plug 27 Fuel injection valve 28 Solenoid 29 Combustion chamber 30 Communication path 40 Intercooler 41 Cooling fin 42 Heat pipe 100 Engine 102 Water jacket

Claims (3)

In a split stroke cycle engine that includes a compression cylinder that performs suction / compression strokes and an expansion cylinder that performs expansion / exhaust strokes separately, and these two cylinders communicate with each other through a communication path.
A cooling means for cooling the air in the communication path;
The compression cylinder communicates with the intake passage via a first intake valve and communicates with the communication passage via a check discharge valve, and the expansion cylinder communicates with the communication passage via a second intake valve. Communicated with the exhaust passage through an exhaust valve,
Divided stroke cycle engine characterized by Rukoto provided with opening means for opening the second intake valve at a predetermined period during the opening of the exhaust valves.   The cooling means is a heat pipe having one end disposed in the communication passage and the low temperature side of the other end disposed in a water jacket of a cylinder head or an intake passage of the compression cylinder. Split stroke cycle engine as described in.   3. The split stroke cycle engine according to claim 1, wherein the communication path communicates with the expansion cylinder in a direction parallel to a tangent in a plan view.

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