JP4556877B2 - Variable compression ratio internal combustion engine - Google Patents

Description

  The present invention relates to a variable compression ratio internal combustion engine, and more particularly, to a highly responsive variable compression ratio internal combustion engine capable of efficiently burning an air-fuel mixture in a subcombustion chamber as well as a main combustion chamber with a simple configuration.

  In recent years, variable compression ratio internal combustion engines in which the compression ratio is changed by changing the volume of the combustion chamber have been developed for the purpose of improving the fuel efficiency performance and output performance of the internal combustion engine. For example, an annular groove provided in the stem of the cam-driven sub-chamber valve has a configuration in which the intake pipe and the sub-chamber communicate with each other without passing through the combustion chamber, and fresh air is introduced into the sub-chamber by the communication, A technique for scavenging the unburned residue of the air-fuel mixture has been proposed (see Patent Document 1).

  In addition, for the purpose of purifying exhaust gas in accordance with the engine speed, a sub-chamber having a solenoid valve is provided, and a technique for controlling opening and closing of the solenoid valve according to the engine speed and load (see Patent Document 2) or a cam drive type A technology has been proposed in which high pressure gas is confined in the sub chamber by closing the sub chamber valve during the expansion stroke, and turbulence is generated in the combustion chamber when the valve is opened (see Patent Document 3). ).

JP-A-8-28269 Japanese Patent No. 2847314 JP-A-5-187279

  However, in the prior art according to Patent Document 1, fresh air is directly introduced from the intake pipe for scavenging the sub chamber, so that the sub-chamber and the air-fuel mixture are sufficiently transferred through the combustion chamber. Therefore, when the air-fuel mixture flows from the combustion chamber into the sub chamber when the sub chamber valve having a low compression ratio is opened, it is difficult for the flame to propagate from the combustion chamber to the sub chamber. Therefore, it is necessary to efficiently burn the air-fuel mixture in the sub chamber as well as the combustion chamber (main combustion chamber).

  In addition, since it is a cam-driven sub-chamber valve, its opening and closing is inevitably synchronized with the crank angle, and in order to improve the controllability of the opening and closing timing, a major modification of the existing device is required.

  In the prior art disclosed in Patent Document 2, the main chamber and the sub chamber communicate with each other under the piston top dead center state by opening the on-off valve, but the gas in the suction / exhaust port and the main chamber is communicated. Since there was no traffic, there was no gas flow between the sub chamber and the intake / exhaust port, and there was a risk that unburned mixture would easily occur in the sub chamber.

  Moreover, in the prior art which concerns on the said patent document 3, since it is a cam drive type subchamber valve, the limit occurred in the operation | movement response property, and it was difficult to open and close at the timing requested.

  The present invention has been made in view of the above, and it is an object of the present invention to provide a highly responsive variable compression ratio internal combustion engine capable of efficiently combusting an air-fuel mixture in a sub chamber as well as a main combustion chamber with a simple configuration. And

In order to solve the above-described problems and achieve the object, a variable compression ratio internal combustion engine according to claim 1 of the present invention has at least a main combustion chamber, an intake port having an intake valve, and an exhaust valve. An exhaust port, an ignition plug for igniting the air-fuel mixture in the main combustion chamber, a sub chamber provided in communication with the main combustion chamber, and the main combustion chamber and the sub chamber by opening according to a crank angle And a shutoff valve that shuts off the communication between the main combustion chamber and the sub chamber by closing the valve, and the shutoff valve and the sub chamber are in positions where the air-fuel mixture is easily introduced. And the sub chamber communicates with the intake port or the exhaust port via the main combustion chamber by opening the shut-off valve and opening the intake valve or the exhaust valve. The shut-off valve is an electromagnetically driven valve or hydraulically driven Made, and is closed in the course of in-cylinder pressure decreases, the valve closing operation is characterized in that ends before the exhaust valve is opened.

A variable compression ratio internal combustion engine according to claim 2 of the present invention includes at least a main combustion chamber, an intake port having an intake valve, an exhaust port having an exhaust valve, and an air-fuel mixture in the main combustion chamber. By igniting an ignition plug, a sub chamber provided in communication with the main combustion chamber, and opening the valve according to a crank angle, the main combustion chamber and the sub chamber are connected to each other, and the valve is closed. A shutoff valve that shuts off the communication between the main combustion chamber and the sub chamber, the shutoff valve and the sub chamber are arranged at positions where air-fuel mixture is easily introduced, and the sub chamber is the shut off valve. The valve is configured to communicate with the intake port or the exhaust port via the main combustion chamber by opening the valve and opening the intake valve or the exhaust valve. It consists of a drive valve and immediately after the exhaust valve is closed Others closed and will open the simultaneously started, the valve opening operation is characterized in that the ends until the intake valve is closed.

According to a third aspect of the present invention, there is provided a variable compression ratio internal combustion engine comprising at least a main combustion chamber, an intake port having an intake valve, an exhaust port having an exhaust valve, and an air-fuel mixture in the main combustion chamber. By igniting an ignition plug, a sub chamber provided in communication with the main combustion chamber, and opening the valve according to a crank angle, the main combustion chamber and the sub chamber are connected to each other, and the valve is closed. A shutoff valve that shuts off the communication between the main combustion chamber and the sub chamber, the shutoff valve and the sub chamber are arranged at positions where air-fuel mixture is easily introduced, and the sub chamber is the shut off valve. The valve is configured to communicate with the intake port or the exhaust port via the main combustion chamber by opening the valve and opening the intake valve or the exhaust valve. When it consists of a drive valve and a low compression ratio is required , The shut-off valve is opened during the compression stroke, it is characterized in that is closed to the time when the intake valve opening after the exhaust stroke immediately after the end of the.

  According to the variable compression ratio internal combustion engine according to the present invention (Claim 1), since the air-fuel mixture is configured to easily enter the sub chamber with a simple structure, it is possible to suppress the occurrence of an unburned state in the sub chamber, Active combustion takes place. Therefore, the air-fuel mixture can be efficiently burned in the sub chamber as well as the main combustion chamber. Further, the shut-off valve can be opened and closed with a high response timing according to the crank angle. Also, by closing the shut-off valve using the in-cylinder pressure, it becomes possible to close the shut-off valve while receiving the in-cylinder pressure at the umbrella portion of the shut-off valve, and the driving force required to close the shut-off valve Can be reduced. For example, when the shut-off valve is an electromagnetically driven valve, the current applied to the electromagnet can be reduced by the amount that the in-cylinder pressure can be used when the shut-off valve is closed, and the power consumption as the actuator can be reduced. Also, by closing the shutoff valve before the exhaust valve is opened, the compression ratio of the internal combustion engine that has been on the low compression ratio side changes to the high compression ratio side. Since it is the time of completion, the compression ratio can be switched without causing knocking, and the combustion gas can be prevented from entering the sub chamber.

Further, according to the variable compression ratio internal combustion engine according to the present invention (Claim 2 ), the air-fuel mixture easily enters the sub chamber with a simple structure, so that the occurrence of an unburned state in the sub chamber is suppressed. It is possible to perform aggressive combustion. Therefore, the air-fuel mixture can be efficiently burned in the sub chamber as well as the main combustion chamber. Further, the shut-off valve can be opened and closed with a high response timing according to the crank angle. Further, it is possible to avoid a situation in which would confine the combustion gases trying to exhaust the secondary chamber, the combustion can be closed shutoff valve from becoming a stable state.

Further, according to the variable compression ratio internal combustion engine according to the present invention (Claim 3 ), the air-fuel mixture easily enters the sub chamber with a simple structure, so that the occurrence of an unburned state in the sub chamber is suppressed. It is possible to perform aggressive combustion. Therefore, the air-fuel mixture can be efficiently burned in the sub chamber as well as the main combustion chamber. Further, the shut-off valve can be opened and closed with a high response timing according to the crank angle. In addition, when a low compression ratio is required, that is, when a high load operation is requested, the sub chamber can sufficiently exhibit its ability as a combustion chamber, and thus a high output internal combustion engine can be provided.

  Hereinafter, embodiments of a variable compression ratio internal combustion engine (hereinafter referred to as a variable compression ratio engine or an engine as appropriate) according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

[Example 1]
1 is a cross-sectional view showing a variable compression ratio engine according to Embodiment 1 of the present invention, and is a cross-sectional view taken along line AA of FIG. 2 to be described later. FIG. 2 is a bottom view showing the cylinder head viewed from the main combustion chamber, and FIG. 3 is a cross-sectional view showing a state in which the shut-off valve is opened.

  As shown in FIGS. 1 to 3, the engine 10 includes an intake port 16 and an exhaust port (not shown), a spark plug 15, an injector for port injection (not shown), an intake valve 17 and an exhaust valve 25 (see FIG. 2) and the like, and a basic structure and basic operation of the engine 10 are the same as those of a known engine (a normal engine not provided with a sub chamber). It is almost the same.

  The difference is that the sub-chamber 30 provided in communication with the main combustion chamber 14 (hereinafter referred to as “in-cylinder” as appropriate) and the main combustion chamber 14 and the sub-chamber 30 are communicated with each other by opening the valve. It is provided with the shut-off valve 32 which interrupts | blocks communication with the main combustion chamber 14 and the subchamber 30 by valve | bulb.

  That is, the engine 10 has a low compression ratio set by opening the shut-off valve 32 of the sub chamber 30 and the volume of the combustion chamber increases by the volume of the sub chamber 30, and closing the shut valve 32. A high compression ratio determined only by the volume of the main combustion chamber 14 is set.

  The main combustion chamber 14 and the sub chamber 30 communicate with each other by opening the shutoff valve 32, and the sub chamber 30 is connected to the intake port 16 via the main combustion chamber 14 by opening the intake valve 17 or the exhaust valve 25. Alternatively, it communicates with an exhaust port (not shown).

  The main combustion chamber 14 is formed by a piston 13 that is reciprocally movable in the cylinder block 11 and a lower surface of the cylinder head 12. Further, the lower surface of the cylinder head 12 that forms a part of the main combustion chamber 14 has a shape that forms a part of a spherical surface.

  The sub chamber 30 and the shutoff valve 32 are disposed between the exhaust valves 25 as shown in FIG. Further, the opening of the sub chamber 30 with respect to the main combustion chamber 14 faces the main combustion chamber 14 and is disposed so as to be substantially the same height as the opening of the intake port 16 and the opening of the exhaust port (not shown). ing.

  Further, the shut-off valve 32 and the sub chamber 30 are arranged at positions where the air-fuel mixture can be easily introduced. Further, in order to facilitate the introduction of the air-fuel mixture into the sub chamber 30, the main combustion chamber 14 has a predetermined volume (or a predetermined height dimension).

  The shut-off valve 32 is configured to be opened and closed according to the crank angle by an electromagnetically driven shut-off valve actuator 34. The shut-off valve actuator 34 includes a case 35, an armature 36 that is disposed in the case 35 and is movably supported by the valve stem guide 43, and presses the armature 36 by electromagnetic force. The upper core 37 and the lower core 40 for moving up and down, the upper spring 38 and the screw 39 for biasing the armature 36 downward, the lower spring 42 for biasing the shut-off valve 32 in the valve closing direction, and the like. Yes.

  The shut-off valve 32 is pressed against the valve seat 32a by the urging of the lower spring 42 when the valve is closed. The shut-off valve 32 is opened by the armature 36 being attracted downward against the urging force of the lower spring 42 by the electromagnetic force generated by the lower core 40.

  The electromagnetically driven shut-off valve 32 may have a valve opening stroke of about 2 to 4 mm, which is about half of that of an electromagnetically driven actuator for an engine valve, and the valve opening speed may be one digit or more slower. For this reason, the spring constants of the upper spring 38 and the lower spring 42 can be reduced, and the required electromagnetic force can be reduced. Therefore, a small electromagnetically driven actuator may be used for the shutoff valve 32.

  Reference numeral 20 denotes a retainer, reference numeral 21 denotes a valve lifter, reference numeral 22 denotes a valve spring, and reference numeral 23 denotes a valve stem guide, which is constituted by a known member.

  Further, the actuator related to the exhaust valve 25 is configured in substantially the same manner as that of the intake valve 17 and is not shown.

  Next, opening / closing control of the shutoff valve 32 according to the present embodiment will be described with reference to FIG. This control is executed by an electronic control unit (ECU) (not shown). Here, FIG. 4 is an explanatory diagram showing the opening / closing timing of the shut-off valve, and also shows the opening / closing of the engine valve and the change in the in-cylinder pressure.

  As shown in FIG. 4, the shut-off valve 32 is closed when the in-cylinder pressure can be used, that is, within the process in which the in-cylinder pressure decreases, and the closing operation is performed when the engine valve (exhaust valve 25) is opened. It is controlled so as to end at a point P1 that is before.

  By closing the shut-off valve 32 using the in-cylinder pressure in this manner, it becomes possible to close the shut-off valve 32 while receiving the in-cylinder pressure at the umbrella portion of the shut-off valve 32. Necessary electromagnetic driving force can be reduced. That is, the current applied to the upper core (electromagnet) 37 can be reduced by the amount that the in-cylinder pressure can be used when the valve is closed, and the power consumption as the actuator can be reduced.

  Further, by closing the shutoff valve 32 before the exhaust valve 25 is opened, the compression ratio of the engine 10 that has been on the low compression ratio side changes to the high compression ratio side, Since it is the time when the combustion is finished, the compression ratio can be switched without generating knock, and the combustion gas can be prevented from entering the sub chamber 30.

  As described above, according to the variable compression ratio engine 10 according to this embodiment, since the air-fuel mixture is configured to easily enter the sub chamber 30, the occurrence of an unburned state in the sub chamber 30 can be suppressed. , Aggressive combustion takes place. Therefore, the air-fuel mixture can be efficiently burned in the sub chamber 30 together with the main combustion chamber 14.

  Further, in the variable compression ratio engine according to the above-described prior art, since the configuration in which the moving parts are variable is adopted, an increase in mass and a decrease in rigidity of peripheral parts are problems, and further, the apparatus Problems such as an increase in the overall length have occurred. On the other hand, the variable compression ratio engine 10 according to the first embodiment can be easily manufactured because it is only necessary to add the sub chamber 30 and the shutoff valve 32 in the cylinder head 12 because the scale of modification of the ready-made engine is small. Further, since the electromagnetically driven shut-off valve 32 is used, the responsiveness of switching the compression ratio is remarkably high.

  In the first embodiment, the shut-off valve 32 has been described as an electromagnetically driven valve having good response. However, the present invention is not limited to this, and if a highly responsive opening / closing timing can be realized according to the crank angle, for example, It may be a hydraulic drive type. In this case, responsiveness of 1 to 2 digits or more can be ensured as compared with the prior art in which the second camshaft or the like is operated by a mechanical variable mechanism.

  In the first embodiment, the example in which the present invention is applied to the port injection type engine 10 has been described. However, the present invention is not limited thereto, and may be applied to a direct injection type engine in a cylinder.

  Moreover, in the said Example 1, although the subchamber 30 and the cutoff valve 32 demonstrated as what was arrange | positioned between the exhaust valves 25 as shown in FIG. 2, it is not limited to this, For example, FIG. As shown in FIG. 2, an engine having one intake valve 17 and one exhaust valve 25 may be configured to include two shutoff valves 32 and two sub chambers 30 (not shown). Thereby, a multistage compression ratio is realizable. Here, FIG. 5 is a bottom view showing a cylinder head having another arrangement configuration of the shut-off valve. FIG. 1 is also a BB cross section shown in FIG.

  Further, as shown in FIG. 6, a configuration in which two exhaust valves 25 and one intake valve 17 are provided, and a shutoff valve 32 and a sub chamber 30 (not shown) are arranged on the intake valve 17 side may be adopted. it can. The valve diameter of the intake valve 17 is formed to be large so that intake air is introduced into the sub chamber 30 without reducing the intake efficiency. Further, the upper shape of the main combustion chamber 14 is also kept substantially spherical. Here, FIG. 6 is a bottom view showing a cylinder head having another arrangement configuration of the shutoff valve 32. FIG. 1 is also a CC cross section shown in FIG.

In addition, the temperature environment is enhanced by providing the sub chamber 30 on the intake valve 17 side, so that cooling can be enhanced compared to the case where it is provided on the exhaust valve 25 side, which is advantageous in terms of avoiding knock. Moreover, the ventilation in the subchamber 30 can be made favorable by applying this structure to the structure which concerns on the reference example 1 mentioned later, and introduce | transducing a tumble flow into the subchamber 30. FIG.

  In addition, as shown in FIG. 7, a configuration in which two intake valves 17 and one exhaust valve 25 are provided, and a shutoff valve 32 and a sub chamber 30 (not shown) are arranged on the exhaust valve 25 side may be adopted. it can. Further, the upper shape of the main combustion chamber 14 is also kept substantially spherical. Here, FIG. 7 is a bottom view showing the cylinder head 12 having another arrangement configuration of the shutoff valve 32. FIG. 1 is also a DD cross section shown in FIG.

Moreover, the ventilation in the subchamber 30 can be made favorable by applying this structure to the structure which concerns on the reference example 1 mentioned later, and introduce | transducing a tumble flow into the subchamber 30. FIG.

  In the first embodiment, as shown in FIG. 3, the shut-off valve 32 opens to the main combustion chamber 14 side. However, the present invention is not limited to this. For example, as shown in FIG. It can also be configured to open to the 30 side. Here, FIG. 8 is a cross-sectional view showing the variable compression ratio engine 10 including another shutoff valve 32.

[Example 2]
FIG. 9 is an explanatory diagram showing the opening / closing timing of the shut-off valve 32 according to Embodiment 2 of the present invention, and also includes the opening / closing timing of the engine valves 17, 25, the change in the cylinder pressure, and the opening / closing timing of the shut-off valve according to the prior art. It is shown. In the following description, members that are the same as or correspond to those already described are denoted by the same reference numerals, and redundant description is omitted or simplified.

  The second embodiment is controlled by using the engine 10 according to the first embodiment. As shown in FIG. 9, the shutoff valve 32 is opened immediately after the exhaust valve 25 is closed or simultaneously with the valve closing. The valve opening operation is started (see point P2), and the valve opening operation is controlled to end before the intake valve 17 is closed (see point P3).

  By controlling as described above, the following points are different from the open / close control of the shut-off valve according to the prior art. That is, it is possible to avoid a situation where the combustion gas to be exhausted is trapped in the sub chamber 30, and after the combustion becomes stable without immediately closing the shutoff valve 32 in the next cycle. Can be closed.

Example 3
FIG. 10 is an explanatory diagram showing the opening / closing timing of the shutoff valve 32 according to the third embodiment of the present invention, and also shows the opening / closing timing of the engine valves 17 and 25. In the third embodiment, control is performed using the engine 10 according to the first embodiment. When a low compression ratio is required, the shut-off valve 32 is opened during the compression stroke as shown in FIG. The intake valve 17 is controlled to be closed when the intake valve 17 is opened immediately after the exhaust stroke is completed.

  That is, since the pressure in the main combustion chamber 14 is higher than that in the sub chamber 30, if the shutoff valve 32 is opened during the compression stroke, the air-fuel mixture is easily introduced into the sub chamber 30 immediately after that. Further, at this time, a new turbulence component is generated in the main combustion chamber 14, which contributes to improvement in combustion. Further, by keeping the shutoff valve 32 open during the exhaust stroke, the burned gas remaining in the sub chamber 30 can be exhausted most efficiently.

  Further, by closing the shutoff valve 32 while the intake valve 17 is open, the high intake flow velocity during the intake stroke is experienced while the shutoff valve 32 is kept open, so that the interior of the sub chamber 30 is maintained. It is possible to ventilate fresh air more efficiently. Further, by closing the shutoff valve 32 during the intake stroke, it is possible to prepare for the opening of the valve during the next compression stroke.

  By controlling as described above, when the low compression ratio is demanded, that is, when the high load operation is demanded, the sub chamber 30 can also fully exhibit its capability as a combustion chamber, so a high output engine 10 can be provided.

[Reference Example 1]
FIG. 11 is a cross-sectional view showing the variable compression ratio engine 10 according to Reference Example 1 , and shows a state where the shutoff valve 32 is opened. That is, in the first reference example , as shown in FIG. 11, the intake port 16 and the top of the piston 13 for restricting the direction of the tumble flow 60 by the intake air to be clockwise and making it easy to introduce into the sub chamber 30. Tumble flow restricting means such as an inclined portion 13a provided on the surface is provided, and the sub chamber 30 and the shut-off valve 32 are arranged at positions where the tumble flow 60 can be easily introduced.

  By configuring as described above, gas flow by the tumble flow 60 in the sub chamber 30 can be improved, and generation of an unburned portion in the sub chamber 30 can be avoided. Thereby, the combustion deterioration at the time of a compression ratio change can be suppressed, and the deterioration of drivability can be suppressed.

[Reference Example 2]
FIG. 12 is a cross-sectional view showing the variable compression ratio engine 10 according to Reference Example 2, and is a cross-sectional view taken along line EE of FIG. FIG. 12 shows a state where the shutoff valve 32 is opened. FIG. 13 is a bottom view showing the cylinder head viewed from inside the main combustion chamber 14.

That is, as shown in FIGS. 12 and 13, the present reference example 2 regulates the direction of the tumble flow 60 by the intake air so that it is counterclockwise and facilitates introduction into the sub chamber 30 (tumble flow restriction). Means) 16 and the sub chamber 30 and the shutoff valve 32 are arranged at positions where the tumble flow 60 can be easily introduced.

  By configuring as described above, gas flow by the tumble flow 60 in the sub chamber 30 can be improved, and generation of an unburned portion in the sub chamber 30 can be avoided. Thereby, the combustion deterioration at the time of a compression ratio change can be suppressed, and the deterioration of drivability can be suppressed.

  As shown in FIG. 14, the present invention can also be applied to an engine provided with two intake valves 17 and two exhaust valves 25 and provided with a shutoff valve 32 between the intake valves 17. In this case, the engine 10 shown in FIG. 12 corresponds to the DD sectional view of FIG. Here, FIG. 14 is a bottom view showing a cylinder head having another arrangement configuration of the shut-off valve 32.

[Reference Example 3]
15 is a plan view of the cylinder head of the variable compression ratio engine 10 according to Reference Example 3 seen through, FIG. 16 is a perspective view showing the main part of the shut-off valve 32, and FIG. 17 is the cylinder head and swirl flow. It is the top view which looked at transparently.

That is, as shown in FIG. 15, this reference example 3 is provided with one intake valve 17 and one exhaust valve 25, and a shut-off valve 32 is provided between them, and the sub chamber 30 and the shut-off valve 32 are It is arranged at a position where the swirl flow 65 due to intake air can be easily introduced. The shutoff valve 32 includes a fin (guide means) 32 b for guiding the swirl flow 65 into the sub chamber 30. The fin 32b has a curved shape along the direction in which the swirl flow 65 is generated.

  With the above configuration, gas flow due to the swirl flow 65 in the sub chamber 30 can be improved, and generation of an unburned portion in the sub chamber 30 can be avoided. Thereby, the combustion deterioration at the time of a compression ratio change can be suppressed, and the deterioration of drivability can be suppressed.

[Reference Example 4]
18 is a flowchart showing the control operation according to Reference Example 4 , and FIG. 19 is a time chart showing the opening / closing operation of the shutoff valve 32 and the like. The reference example 4 uses the engine 10 according to the first embodiment to perform pressure accumulation control for accumulating the air compressed in the compression stroke in the sub-chamber 30 at the time of deceleration, and the accumulated compressed air is compressed at the time of acceleration. It is intended to be supplied inside.

  That is, as shown in FIG. 18, first, it is determined whether or not the engine 10 is decelerating and the sub chamber 30 is not accumulating pressure (step S10). If the vehicle is decelerating and has not accumulated pressure (Yes at Step S10), as shown in FIG. 19 (at the time of deceleration), the shutoff valve 32 is opened before starting the compression stroke (Step S20), and the compression top dead center (TDC) The shutoff valve 32 is closed at a time close to that (step S30). This need not be done every cycle. It is also desirable to increase volumetric efficiency by opening the throttle.

  Subsequently, it is determined whether or not there is an acceleration request (step S40). If there is no acceleration request (No at Step S40), the process returns to the determination step of Step S10, and if there is an acceleration request (Yes at Step S40), it is determined whether or not the supply control of the accumulated air is appropriate. Step S50). The reason for making such a determination in step S50 is as follows.

  That is, it is desirable that the supply of the pressure-accumulated air into the cylinder is completed after the intake valve 17 is closed and when the cylinder pressure at the beginning of the compression stroke is low. However, the closing of the shut-off valve 32 is delayed due to a long minimum valve opening period of the shut-off valve 32 or a high engine speed, and the progress of the compression stroke (in-cylinder pressure) rather than the merit of supplying compressed air into the cylinder. In some cases, the demerit caused by the backflow of compressed air to the sub chamber 30 due to the increase in

  In order to avoid such a demerit, whether or not the implementation of the supply control of the accumulated air is appropriate is determined based on the operating conditions. This determination can be made, for example, by comparing a map created in advance by experiments with the current operating conditions (engine speed, minimum valve opening period).

  Therefore, if execution of the supply control of the accumulated air is not appropriate (No at Step S50), the present control is terminated. If appropriate (Yes at Step S50), as shown in FIG. Immediately after closing, the shutoff valve 32 is opened, and compressed air (accumulated air) is supplied into the cylinder (step S60).

  Then, after the supply of compressed air into the cylinder is completed, the shutoff valve 32 is immediately closed to finish the control. As a result, an effect such as supercharging is temporarily obtained, and the amount of air increases, so that a response delay of the throttle can be covered, and the response and acceleration performance during acceleration can be improved.

[Reference Example 5]
20 is a flowchart showing the control operation according to Reference Example 5 , and FIG. 21 is a time chart showing the opening / closing operation of the shutoff valve 32 and the like. The reference example 5 uses the engine 10 according to the first embodiment, and at the time of deceleration, the shutoff valve 32 is opened after the intake valve 17 is closed, and is closed near the compression top dead center. The pressure accumulation control is performed.

That is, the present reference example 5 is configured to execute step S15 as shown in FIG. 20 instead of step S20 in the flowchart of the reference example 4 shown in FIG. The other steps are the same as in the case of the reference example 4 described above, and thus the same step numbers are assigned and redundant description is omitted.

  In step S15, as shown in FIG. 21 (during deceleration), the shutoff valve 32 is opened after the intake valve 17 is closed. Thereby, the air accumulated in the sub chamber 30 in the previous cycle can be supplied into the cylinder. Thereafter, the shutoff valve 32 is closed in step S30. By continuing this for several cycles, the pressure to be accumulated can be increased.

By controlling as described above, high-pressure air, that is, a larger amount of air can be accumulated in the sub chamber 30, so that the response and acceleration at the time of acceleration are further improved compared to the case of the reference example 4. can do.

[Reference Example 6]
FIG. 22 is a flowchart illustrating a control operation according to Reference Example 6 . In the control operation according to Reference Example 4 or Reference Example 5 , when the air accumulated in the sub chamber 30 is supplied into the cylinder, the air sucked into the cylinder through the intake valve 17 in the intake stroke. In addition, the accumulated air supplied from the sub chamber 30 is added. Therefore, in this reference example 6 , the amount of the accumulated air (compressed air) is detected, and the fuel injection amount is increased according to the amount.

  That is, as shown in FIG. 22, it is determined whether or not the pressure accumulation is completed and there is an acceleration request (step S12). If this is affirmative (step S12 affirmative), further control for supplying the pressure-accumulated air is performed. Is determined as appropriate (step S50). This determination is performed in step S50 as described above.

  If it is appropriate to carry out the supply control of the accumulated air (Yes at Step S50), the amount of air supplied from the sub chamber 30 into the cylinder is calculated (Step S52). For example, an in-cylinder pressure sensor (not shown) is provided in the engine 10, the pressure P1 in the sub chamber 30 is detected by the in-cylinder pressure sensor, and the mass ΔG of air supplied into the cylinder is expressed by the following equations (1) to (4). ).

  Other data necessary for the measurement are the atmospheric pressure P0, the atmospheric temperature T0, the intake air temperature T2, and the in-cylinder pressure P2. Of these, the atmospheric pressure P0, the atmospheric temperature T0, and the intake air temperature T2 can usually be measured by sensors provided in the engine 10.

ΔG = M {n1− (n1 + n2) V1 / (V1 + V2)} (1)
n1 = (P1V1) / (RT1) (2)
n2 = (P2V2) / (RT2) (3)
T1 = T0 (P1 / P0) ⁽ κ- ^{1) /} κ (4)

  Here, the subscript 0 of the above symbol indicates the state of the atmosphere, and the subscripts 1 and 2 indicate the state of the sub chamber and the cylinder at the timing of starting the supply of compressed air, respectively. M is the molecular weight of air, R is the gas constant of air, n1 and n2 are the number of moles of air, V1 is the volume of the subchamber 30, V2 is the volume in the cylinder, P1 is the pressure of the subchamber 30, and P2 is the cylinder , P0 is the atmospheric pressure, T0 is the atmospheric temperature, and κ is the specific heat ratio of the air.

  Next, the fuel injection amount is increased according to the air mass ΔG obtained as described above (step S54). As a result, it is possible to suppress the deterioration of the emission due to the deviation of the air-fuel ratio, and it is possible to improve the acceleration performance by increasing the air utilization rate in the cylinder.

Since the control after step S54 is the same as in the case of the reference example 4 or the reference example 5 , the same step numbers 60 and 70 are assigned, and the duplicate description is omitted.

In order to increase the accuracy, various known corrections may be performed on the data. Although limited to application to the reference example 4 , the air mass ΔG may be estimated from the closing timing of the shutoff valve 32 when the intake pressure sensor and the pressure accumulation control are performed.

[Reference Example 7]
FIG. 23 is a flowchart illustrating a control operation according to Reference Example 7 . When the control operation according to the reference example 5 is executed, the pressure of the accumulated air in the sub chamber 30 can be increased, but the deterioration of the vibration of the engine 10 due to the increase in compressive force, and the interruption due to the excessive increase in the pressure in the sub chamber 30 There is a risk of step-out of the valve 32, valve stamping, and the like.

Therefore, the present reference example 7 performs the control shown in FIG. 23 in order to avoid these problems. That is, after the pressure accumulation control is started (step S110), the in-cylinder compression end pressure PTDC is detected by, for example, the in-cylinder pressure sensor (compression end pressure detecting means) (step S120), and the detected compression end pressure PTDC is compressed. When it is determined that the end pressure exceeds the upper limit value PCRI and is excessive (Yes at Step S130), the pressure accumulation control is ended (stopped) (Step S140).

  If the compression end pressure PTDC does not exceed the upper limit value PCRI of the compression end pressure (No at Step S130), the detection of the compression end pressure PTDC is continued until it exceeds the upper limit value PCRI (Step S120).

  By controlling as described above, it is possible to suppress damage to the engine 10 and deterioration of vibration due to excessive pressure.

  As a means for detecting the compression end pressure PTDC, in addition to the direct measurement by the in-cylinder pressure sensor, a crank rotation fluctuation is detected by a sensor for measuring the pressure in the crankcase and estimated based on this, or You may estimate by the elapsed cycle number from the pressure accumulation control start (step S110).

[Reference Example 8]
FIG. 24 is a time chart showing the opening / closing operation of the shutoff valve 32 and the like according to Reference Example 8 . In the control operation (acceleration) according to the reference example 4 or the reference example 5 , the amount of compressed air supplied into the cylinder varies depending on the cylinder pressure at the time of supply. That is, the amount of compressed air supplied into the cylinder is large when the in-cylinder pressure is low at the beginning of the compression stroke, and is small when the in-cylinder pressure is high at a later stage of the compression stroke.

Therefore, in this reference example 8 , in order to appropriately supply the amount of compressed air without excess or deficiency, the opening / closing timing of the shutoff valve 32 is set to the amount of compressed air to be supplied into the cylinder as shown in FIG. Is set (indicated by a broken line when the supply amount is large, and by a solid line when the supply amount is small). The opening / closing timing (compression air supply timing) of the shut-off valve 32 can be set, for example, according to the calculation method of the air mass ΔG shown in Reference Example 6 above.

  By controlling the opening / closing timing (compression air supply timing) of the shut-off valve 32 in this way, the amount of air supplied into the cylinder is adjusted even for a valve that does not have a flow rate adjustment function such as a poppet valve. be able to.

[Reference Example 9]
FIG. 25 is a time chart showing the opening / closing operation of the shutoff valve 32 and the like according to Reference Example 9 . When the pressure in the sub chamber 30 is sufficiently high at the time of acceleration in the reference example 8 , it is possible to supply compressed air from the sub chamber 30 into the cylinder in the latter half of the compression stroke, but the cycle proceeds. Accordingly, the pressure in the sub chamber 30 decreases, and it may be difficult to supply compressed air from the sub chamber 30 into the cylinder.

Therefore, in this reference example 9 , as shown in FIG. 25, the opening timing of the shut-off valve 32 (the supply timing of compressed air into the cylinder) is advanced to the initial stage of the compression stroke as the cycle progresses. It is.

  By controlling in this way, the accumulated air can be supplied into the cylinder over several cycles, the supercharging effect can be maintained, and the acceleration characteristics can be improved.

[Reference Example 10]
In the control operation according to the reference example 4 or the reference example 5 , the compression work and the expansion work are substantially equal in the cycle in which the pressure accumulation control is not performed, but the compression work exceeds the expansion work in the cycle in which the pressure accumulation control is performed. There is a possibility that a shock may occur with the on / off of the pressure accumulation control because the engine brake is effective. When the control operation according to the reference example 5 is executed, the compression work and the expansion work become equal as the pressure accumulation progresses, and the engine brake may not be effective.

Accordingly, the present reference example 10, in accordance with the progress status of the on-off status or accumulator in the accumulator control, so that the throttle opening degree and valve timing, increase or decrease control other braking elements, such as a foot brake (not shown) It is a thing.

  By controlling in this way, changes in pumping work, that is, shocks and discomfort due to changes in braking force can be eliminated or reduced, and drivability can be improved.

[Reference Example 11]
FIG. 26 is a flowchart showing the control operation according to Reference Example 11 , and FIG. 27 is a time chart showing the opening / closing operation of the shut-off valve 32 in each cylinder. The present reference example 11 uses the engine 10 according to the first embodiment to perform pressure accumulation control (see the above reference example 4 ) for accumulating air compressed in the compression stroke in the sub chamber 30 during deceleration. The compressed air thus supplied is supplied to the cylinder in the expansion stroke when the engine 10 is started.

  Further, the engine 10 includes a known means (not shown) for discriminating cylinders that are in the expansion stroke at the start (here, the engine 10 includes four cylinders of cylinder numbers # 1 to # 4). ing.

As shown in FIG. 26, the pressure accumulation control at the time of deceleration is the same as steps S10 to 30 shown in FIG. 18 of the reference example 4 described above. After step S30, it is determined whether there is an engine stall request (step S32).

  If there is an engine stall request (Yes at Step S32), the engine 10 is stopped (Step S34). If there is no engine stall request (No at Step S32), the process returns to Step S10.

  After the engine 10 is stopped (step S34), it is determined whether or not the restart of the engine 10 is requested (step S36). If restart is not requested (No at Step S36), the process waits until requested, and if restart is requested (Yes at Step S36), the cylinder in the expansion stroke is determined and the cylinder is shut off. The compressed air accumulated in the sub chamber 30 by opening the valve 32 is supplied to the cylinder (step S38).

  For example, as shown in FIG. 27, it is determined that cylinder # 1 is in the expansion stroke and the shut-off valve 32 is opened, and the cylinders after # 2 are opened in the initial stage of the expansion stroke. Thus, the compressed air accumulated in the sub chamber 30 is supplied to each cylinder. Further, the shutoff valve 32 after the compressed air is supplied (after opening) is held open. Further, fuel corresponding to the supplied compressed air may be supplied and burned.

Instead of the spark ignition internal combustion engine as in the present reference example 11, when applied to a compression ignition internal combustion engine, the shutoff valve 32 after the supply of compressed air (after opening) is closed It is good.

  By controlling as described above, the startability of the engine 10 can be improved without separately providing an air injection valve, an air compressor, a pipe from the compressor to the air injection valve, etc. for a mechanism having a variable compression ratio. Can be improved.

[Reference Example 12]
FIG. 28 is a time chart showing the opening / closing operation of the shutoff valve 32 in each cylinder according to Reference Example 12 . In this control example 12 , in the control operation according to the reference example 11 , when a cylinder in the expansion stroke is determined and the cylinder is in the later stage of the expansion stroke, compressed air is supplied to the cylinder. Instead, it is supplied at the beginning of the expansion stroke of the next cycle.

  For example, as shown in FIG. 28, when it is determined that the cylinder # 1 is in the later stage of the expansion stroke at the completion of the cylinder discrimination, the shutoff valve 32 is not opened and compressed air is supplied to the cylinder # 1. The valve is opened at the beginning of the expansion stroke of the next cycle, and compressed air is supplied to the cylinder # 1.

  By controlling as described above, the conversion of compressed air into power can be performed efficiently, and the engine startability can be improved to the maximum with the supply of limited compressed air.

  As described above, the variable compression ratio internal combustion engine according to the present invention is useful for a highly responsive variable compression ratio internal combustion engine that can efficiently burn the air-fuel mixture in the subcombustion chamber as well as the main combustion chamber with a simple configuration. In particular, the present invention is suitable for a variable compression ratio internal combustion engine that aims to reliably propagate the flame to the air-fuel mixture in the auxiliary chamber even in an operation state with a low compression ratio.

1 is a cross-sectional view showing a variable compression ratio engine according to Embodiment 1 of the present invention. It is a bottom view which shows the cylinder head seen from the main combustion chamber. It is sectional drawing which shows a mode that the cutoff valve opened. It is explanatory drawing which shows the opening / closing timing of a cutoff valve. It is a bottom view which shows the cylinder head which has the other arrangement structure of the cutoff valve. It is a bottom view which shows the cylinder head which has the other arrangement structure of the cutoff valve. It is a bottom view which shows the cylinder head which has the other arrangement structure of the cutoff valve. It is sectional drawing which shows the variable compression ratio engine provided with the other cutoff valve. It is explanatory drawing which shows the opening / closing timing of the cutoff valve which concerns on Example 2 of this invention. It is explanatory drawing which shows the opening / closing timing of the cutoff valve which concerns on Example 3 of this invention. 1 is a cross-sectional view showing a variable compression ratio engine according to Reference Example 1. FIG. 10 is a cross-sectional view showing a variable compression ratio engine according to Reference Example 2. FIG. It is a bottom view which shows the cylinder head seen from the main combustion chamber. It is a bottom view which shows the cylinder head which has the other arrangement structure of the cutoff valve. 10 is a plan view of a cylinder head of a variable compression ratio engine according to Reference Example 3 seen through. FIG. It is a perspective view which shows the principal part of a cutoff valve. It is the top view which looked at the cylinder head and the swirl flow in perspective. It is a flowchart illustrating a control operation according to Reference Example 4. It is a time chart which shows opening / closing operation | movement of a cutoff valve etc. 10 is a flowchart showing a control operation according to Reference Example 5 . It is a time chart which shows opening / closing operation | movement of a cutoff valve etc. 14 is a flowchart illustrating a control operation according to Reference Example 6 . 10 is a flowchart showing a control operation according to Reference Example 7 ; 10 is a time chart showing an opening / closing operation of a shutoff valve or the like according to Reference Example 8 ; 10 is a time chart showing an opening / closing operation of a shutoff valve or the like according to Reference Example 9 ; 14 is a flowchart showing a control operation according to Reference Example 11 . It is a time chart which shows the opening / closing operation | movement of the cutoff valve in each cylinder. 14 is a time chart showing an opening / closing operation of a shut-off valve in each cylinder according to Reference Example 12 ;

10 Variable compression ratio engine (variable compression ratio internal combustion engine)
11 Cylinder block 12 Cylinder head 13 Piston 13a Inclined part (tumble flow restricting means)
DESCRIPTION OF SYMBOLS 14 Main combustion chamber 15 Spark plug 16 Intake port 17 Intake valve 17a Valve seat 19 Cam 20 Retainer 21 Valve lifter 22 Valve spring 23 Valve stem guide 25 Exhaust valve 30 Subchamber 32 Shutoff valve 32a Valve seat 32b Fin (guide means)
34 Shutoff valve actuator 35 Case 36 Armature 37 Upper core 38 Upper spring 39 Screw 40 Lower core 41 Lower retainer 42 Lower spring 43 Valve stem guide 60 Tumble flow 65 Swirl flow

Claims (3)

At least the main combustion chamber,
An intake port having an intake valve;
An exhaust port having an exhaust valve;
A spark plug for igniting the air-fuel mixture in the main combustion chamber;
A sub chamber provided in communication with the main combustion chamber;
A shut-off valve that connects the main combustion chamber and the sub chamber by opening the valve according to a crank angle, and shuts off the communication between the main combustion chamber and the sub chamber by closing the valve;
With
The shut-off valve and the sub chamber are arranged at a position where the air-fuel mixture can be easily introduced, and the sub chamber is opened by opening the shut-off valve and opening the intake valve or the exhaust valve. Configured to communicate with the intake port or the exhaust port through a chamber,
The shut-off valve is composed of an electromagnetically driven valve or a hydraulically driven valve, and is closed during a process in which the in-cylinder pressure is lowered, and the closing operation is completed before the exhaust valve is opened. A variable compression ratio internal combustion engine. At least the main combustion chamber,
An intake port having an intake valve;
An exhaust port having an exhaust valve;
A spark plug for igniting the air-fuel mixture in the main combustion chamber;
A sub chamber provided in communication with the main combustion chamber;
A shut-off valve that connects the main combustion chamber and the sub chamber by opening the valve according to a crank angle, and shuts off the communication between the main combustion chamber and the sub chamber by closing the valve;
With
The shut-off valve and the sub chamber are arranged at a position where the air-fuel mixture can be easily introduced, and the sub chamber is opened by opening the shut-off valve and opening the intake valve or the exhaust valve. Configured to communicate with the intake port or the exhaust port through a chamber,
The shut-off valve is composed of an electromagnetically driven valve or a hydraulically driven valve, and is opened immediately after the exhaust valve is closed or at the same time as the exhaust valve is closed, and the valve opening operation is completed before the intake valve is closed. A variable compression ratio internal combustion engine. At least the main combustion chamber,
An intake port having an intake valve;
An exhaust port having an exhaust valve;
A spark plug for igniting the air-fuel mixture in the main combustion chamber;
A sub chamber provided in communication with the main combustion chamber;
A shut-off valve that connects the main combustion chamber and the sub chamber by opening the valve according to a crank angle, and shuts off the communication between the main combustion chamber and the sub chamber by closing the valve;
With
The shut-off valve and the sub chamber are arranged at a position where the air-fuel mixture can be easily introduced, and the sub chamber is opened by opening the shut-off valve and opening the intake valve or the exhaust valve. Configured to communicate with the intake port or the exhaust port through a chamber,
The shut-off valve comprises an electromagnetically driven valve or a hydraulically driven valve,
The variable compression ratio internal combustion engine is characterized in that when a low compression ratio is required, the shut-off valve is opened during the compression stroke, and is closed when the intake valve is opened immediately after the exhaust stroke is completed. organ.

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