JP5713241B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to a technical field of an internal combustion engine that can suppress the occurrence of knocking by cooling exhaust gas remaining in a combustion chamber during an exhaust stroke in the internal combustion engine.

  In an internal combustion engine such as a vehicle engine, fresh air is taken into the combustion chamber from the intake passage via the intake valve, and combustion gas generated by the explosion in the combustion chamber is discharged to the exhaust passage via the exhaust valve. The exhaust gas generated in the combustion chamber is discharged so as to be pushed out to the exhaust passage side by reducing the volume of the combustion chamber by raising the piston in the exhaust stroke. However, even at the exhaust top dead center, a considerable gap remains between the top of the piston and the cylinder head, and the capacity of the combustion chamber does not become completely zero. Therefore, not a little exhaust gas that has not been discharged into the exhaust passage remains in the gap.

  Since the exhaust gas (so-called residual gas) remaining in the combustion chamber is very high in this way, the temperature of new air taken into the combustion chamber in the next cycle is raised, and this is compressed and heated in the compression stroke. Further, it becomes a high temperature, and causes knocking.

  As described above, the residual gas causes knocking, so how to reduce the residual gas is an important problem. On the other hand, in Patent Document 1, a sub-piston that protrudes and retracts from the cylinder head to the combustion chamber side is provided, and the sub-piston is retracted to the cylinder head side in the expansion stroke after the ignition timing, thereby reducing the volume of the combustion chamber. A technique is described that suppresses knocking by increasing and temporarily reducing the compression ratio in the combustion chamber.

Japanese Patent Laid-Open No. 2-271636

  In Patent Document 1, knocking is avoided by variably controlling the compression ratio of the combustion chamber by moving the sub-piston back and forth toward the inside of the combustion chamber. However, in order to sufficiently change the volume of the combustion chamber, it is necessary to use a sub-piston having a somewhat large volume. On the other hand, since the interval between the piston and the cylinder head is narrow near the compression top dead center that is the ignition timing, the volume of the combustion chamber is small in the first place, and it is not possible to further change the volume of the combustion chamber in this limited space. Structurally, it is not easy because of the balance with the sub-piston and the surrounding structure.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an internal combustion engine that can effectively suppress the occurrence of knocking due to the residual gas in the combustion chamber in the exhaust stroke.

  In order to solve the above problems, an internal combustion engine according to the present invention is an internal combustion engine that introduces intake air from an intake passage via an intake valve and discharges combustion gas generated in a combustion chamber to an exhaust passage via an exhaust valve. A cooling member made of a metal material that cools the combustion gas remaining in the combustion chamber by protruding from the inner wall side of the combustion chamber in the exhaust stroke into the combustion chamber, and a protruding amount of the cooling member, and And a control means for controlling the protrusion timing.

  According to the present invention, the amount of heat that the combustion gas (residual gas) has is obtained by causing the cooling member formed of a metal material having good thermal conductivity to protrude inward from the inner wall side of the combustion chamber during the exhaust stroke. Can be absorbed by the cooling member and cooled. By reducing the temperature of the residual gas in this way, the residual gas can be substantially reduced by reducing the mixed gas temperature in the compression stroke of the next cycle, and knocking can be effectively suppressed.

As one aspect of the present invention, the control means may set the protrusion timing of the cooling member in the second half of the exhaust stroke.
Even if the cooling member protrudes in the first half of the exhaust stroke to cool the combustion gas in the combustion chamber, most of the combustion gas is exhausted to the exhaust passage side, and as a result, remains in the combustion chamber at the end of the exhaust stroke. The temperature of the combustion gas can not be lowered sufficiently. Therefore, in this aspect, the temperature of the combustion gas remaining in the combustion chamber at the end of the exhaust stroke can be effectively reduced by projecting the cooling member in the latter half of the exhaust stroke.

  In this case, the control means may be set so that the increasing rate of the protrusion amount of the cooling member is larger than the decreasing rate. In general, in the exhaust stroke, the volume of the combustion chamber gradually decreases. In this aspect, by rapidly increasing the protruding amount of the cooling member at a stage where the capacity of the combustion chamber is relatively large, a large contact area between the cooling member and the combustion gas in the combustion chamber is secured, and the cooling effect is improved. be able to.

  As another aspect of the present invention, the control means may control the change rate of the protrusion amount of the cooling member to be equal to the change rate of the opening degree of the exhaust valve in the exhaust stroke. In this aspect, by making the cooling member protrude from the initial stage of the exhaust stroke, it is possible to ensure a long contact time between the cooling member and the combustion gas in the combustion chamber. Therefore, heat can be sufficiently absorbed from the combustion gas by the cooling member, and a good cooling effect can be obtained.

  In another aspect of the present invention, the cooling member may be provided so as to protrude from the inner wall of the cylinder head toward the center of the combustion chamber. According to this aspect, since the amount of heat can be transmitted from the combustion gas remaining in the combustion chamber to the cylinder head side by the cooling member protruding from the cylinder head, a good cooling effect can be obtained.

  In another aspect of the present invention, the cooling member may be incorporated in at least one of the intake valve and the exhaust valve so as to protrude in the same direction as the drive direction of the valve. According to this aspect, a cooling member is not provided in a member with little extra space, such as a cylinder head. In particular, by incorporating a cooling member into an intake / exhaust valve, which is an essential member for an internal combustion engine, the cooling member can be provided with an efficient layout.

  In this case, the cooling member is built in each of the intake valve and the exhaust valve, and the control means has a protrusion amount of the cooling member built in the intake valve built in the exhaust valve. It is good to control so that it may become large compared with the protrusion amount of a cooling member. According to this aspect, by causing the cooling member of the intake valve to protrude larger than the exhaust valve side, the flow path of the combustion gas discharged to the exhaust passage via the exhaust valve is hindered by the protrusion of the cooling member on the intake valve side. This can be suppressed. Therefore, the combustion gas can be smoothly discharged into the exhaust passage, and the effect of improving the scavenging efficiency in addition to the above cooling effect can be obtained, and the residual gas can be reduced more favorably.

  The cooling member may be driven by a cam mechanism that is driven by a camshaft that is shared with a driving cam for the intake valve or the exhaust valve in which the cooling member is incorporated. According to this aspect, the present invention can be realized with a simple and efficient configuration by driving the cam mechanism by the camshaft common to the intake and exhaust valves. Further, by driving the cooling member with a cam mechanism, the protrusion timing and the protrusion amount can be controlled easily and accurately.

The present invention further includes a rotation speed detection means for detecting the rotation speed of the internal combustion engine, and the control means determines the protrusion amount of the cooling member as the rotation speed detected by the rotation speed detection means decreases. It is characterized by a large setting. Generally, there is a tendency that knocking due to residual gas tends to occur as the rotational speed of the internal combustion engine decreases. Therefore, in this aspect, by increasing the protruding amount of the cooling member as the rotational speed of the internal combustion engine decreases, the temperature cooling of the residual gas is promoted, and knocking can be effectively prevented according to the operating state of the internal combustion engine.

  According to the present invention, the amount of heat that the combustion gas (residual gas) has is obtained by causing the cooling member formed of a metal material having good thermal conductivity to protrude inward from the inner wall side of the combustion chamber during the exhaust stroke. Can be absorbed by the cooling member and cooled. By reducing the temperature of the residual gas in this way, the residual gas can be substantially reduced by reducing the mixed gas temperature in the compression stroke of the next cycle, and knocking can be effectively suppressed.

It is the schematic which shows typically the internal structure of the engine which concerns on 1st Example. It is a top view which shows the valve layout of the engine which concerns on 1st Example from the cylinder head side. It is a top view which shows the other example of the valve layout of the engine which concerns on 1st Example from the cylinder head side. It is a schematic diagram which shows operation | movement of the cooling member in 1st Example for every step. It is sectional drawing which shows the internal structure of the cooling member in 1st Example. It is the schematic which shows typically the internal structure of the engine which concerns on 2nd Example. It is sectional drawing which expands and shows the structure of the valve periphery of FIG. 6 with a drive mechanism. It is a timing chart which shows an example of the protrusion timing and protrusion amount of an intake valve, an exhaust valve, and a cooling member. It is a timing chart which shows the other example of the protrusion timing and protrusion amount of an intake valve, an exhaust valve, and a cooling member. It is an example of the map which prescribes | regulates the relationship between the protrusion amount of a cooling member, and the rotation speed of an engine.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

(First embodiment)
FIG. 1 is a schematic view schematically showing the internal structure of the engine 1 according to the first embodiment, and FIG. 2 is a plan view showing the valve layout of the engine 1 according to the first embodiment from the cylinder head 3 side. is there. 1 shows the internal structure of the engine in a cross-sectional view, which schematically shows the cross-sectional structure in a line indicated by a broken line A in FIG.

  As shown in FIG. 1, the combustion chamber 2 of the engine 1 is constituted by a cylinder head 3, a piston 4 and a cylinder 5, and the reciprocating motion of the piston 4 is transmitted to a crankshaft (not shown) via a connecting rod 6. It is configured. A spark plug 7 for igniting the air-fuel mixture in the combustion chamber 2 is provided at the center of the cylinder head 3. The engine 1 is a direct-injection gasoline engine. The combustion chamber 2 is provided with an in-cylinder injector 8 for injecting and supplying fuel directly to the combustion chamber 2.

  Fresh air is introduced into the combustion chamber 2 from the intake passage 9 via the intake valve 10 to form an air-fuel mixture with the fuel supplied from the in-cylinder injector 8 in the combustion chamber 2, and after combustion, exhaust gas ( Combustion gas) is discharged to the exhaust passage 12 through the exhaust valve 11. The intake passage 9 is provided with an air filter (not shown) for purifying intake air and a throttle valve 13 for adjusting the intake air amount. The exhaust passage 12 is provided with a three-way catalyst (not shown) for removing harmful components (CO, NOx, etc.) contained in the exhaust gas.

  The cooling member 14 is a rod-shaped member made of a metal material that protrudes from the inner wall of the cylinder head 3 toward the inside of the combustion chamber 2. As shown in FIG. 2, the cooling member 14 has a cylindrical shape so as to surround a spark plug 7 provided at the center of the cylinder head 3.

  FIG. 3 is a plan view showing another example of the valve layout of the engine 1 according to the first embodiment from the cylinder head 3 side. In this example, the cooling member 14 is provided in the remaining space by adopting a three-valve layout having two intake valves 10 and one exhaust valve 11. In this case, although the exhaust valve 11 is reduced by one as compared with the example of FIG. 2, a large space for providing the cooling member 14 in the cylinder head 3 can be secured, so the cooling member 14 having a large volume and a large heat capacity is provided. Therefore, a higher cooling effect can be expected.

  Referring back to FIG. 1, the opening degree and the opening / closing timing of the intake valve 10 and the exhaust valve 11 are controlled by variable valve timing mechanisms (intake VVT 15 and exhaust VVT 16) provided correspondingly. The control of the intake VVT 15 and the exhaust VVT 16 is performed by the ECU 18 described below.

  Further, in the vicinity of the connecting rod 6 that is rotationally driven in accordance with the reciprocating cycle of the piston 4, a rotational speed sensor 19 that can measure the engine rotational speed by detecting the rotational angle of the connecting rod 6 ("revolution detection" of the present invention). An example of “means” is provided, and the detected value is also transmitted to the ECU 18 for use in control.

  The ECU 18 is a control unit that controls the entire control of the engine 1, and based on detection values acquired from various sensors (for example, the rotation speed sensor 19) provided in the engine 1, the fuel injection timing and fuel injection of the in-cylinder injector 8. The amount of ignition, the ignition timing of the spark plug 7, the operation timing and operation amount of various VVTs (intake VVT 15, exhaust VVT 16), and the driving mechanism (not shown) for driving the cooling member 14 to drive the cooling member 14. Comprehensive control of protrusion amount and protrusion timing.

  Next, the operation of the cooling member 14 will be specifically described with reference to FIG. FIG. 4 is a schematic diagram showing the operation of the cooling member 14 in the first embodiment for each stage. The cooling member 14 is vertically arranged (typically) by a crank driving mechanism 20 including a rotating portion 21 that is rotated by a power source such as an electric motor or a hydraulic mechanism (not shown) and an arm 22 connected to the rotating portion 21. Specifically, it is configured to be able to enter and exit along the center line direction of the cooling member 14 having a cylindrical shape.

  FIG. 4A shows a normal state where the cooling member 14 is housed in the cylinder head 3 and does not protrude into the combustion chamber 2. In the state of FIG. 4A, the arm 22 of the crank driving mechanism 20 is located away from the combustion chamber 2, and the cooling member 14 is pulled up and stored in the cylinder head 3. At this time, the contact area between the cooling member 14 and the combustion gas in the combustion chamber 2 is small, and there is little or almost no cooling effect. In order to prevent unintentional cooling by the cooling member 14 when stored in the cylinder head 3, the tip of the cooling member 14 (surface exposed to the combustion chamber 2 when stored in the cylinder head 3) is insulated. Material may be applied.

  Subsequently, as shown in FIG. 4B, when the rotating portion 21 is driven to rotate counterclockwise, the arm 22 moves to a position close to the combustion chamber 2, and accordingly, the cooling member 14 moves to the combustion chamber 2. It is exposed so that it is pushed out toward the center of the. Then, the contact area between the cooling member 14 and the combustion gas in the combustion chamber 2 increases, and the cooling member 14 absorbs the amount of heat that the combustion gas has, thereby exhibiting a cooling effect. Thereby, the temperature of the residual gas in the combustion chamber 2 is lowered, and the mixed gas temperature in the compression stroke of the next cycle can be lowered, so that the residual gas can be substantially reduced.

  Further, since the volume of the combustion chamber 2 is reduced by projecting the cooling member 14 having a predetermined volume toward the inside of the combustion chamber 2, in addition to the cooling effect of the residual gas described above, the effect of promoting the discharge of the residual gas is also achieved. Can be obtained. Thus, in the present invention, the occurrence of knocking can be effectively suppressed by promoting the cooling of the residual gas and the exhaust to the exhaust passage 12.

  Then, as shown in FIG. 4C, when the rotating portion 21 is driven to rotate clockwise, the arm 22 returns to a position away from the combustion chamber 2, and the cooling member 14 is brought into the cylinder head 3 again. After being stored, the state returns to the state of FIG. Such an operation of the cooling member 14 is realized by the crank drive mechanism 20 being controlled by the ECU 18, and the cycle shown in FIGS. 4A to 4C is repeated at an arbitrary cycle.

  FIG. 5 is a sectional view showing the internal structure of the cooling member 14 in the first embodiment. Inside the cooling member 14, a cavity portion 14a for enclosing sodium, which is a substance having good thermal conductivity, is provided. The sodium sealed in the hollow portion 14a is vaporized by the amount of heat absorbed from the combustion gas when the cooling member 14 protrudes into the combustion chamber 2, and when the cooling member 14 is stored in the cylinder head 3 and cooled. The liquid is liquefied again by being cooled by dissipating heat to the peripheral members. By repeating such a vaporization and liquefaction cycle, the cooling member 14 can absorb heat from the remaining gas and improve the cooling performance.

(Second embodiment)
FIG. 6 is a schematic view schematically showing the internal structure of the engine 1 according to the second embodiment. In the second embodiment, portions common to the first embodiment described above will be denoted by the same reference numerals, and redundant description will be omitted as appropriate.

  The cooling member 14 in the second embodiment is built in each of the intake valve 10 and the exhaust valve 11 and is formed so as to protrude in the same direction as the drive direction of these valves. Providing the cooling member 14 in this way is advantageous in that it is not necessary to provide the cooling member 14 on a member with little extra space such as the cylinder head 3 as in the first embodiment (see FIG. 2). . In particular, by incorporating the cooling member 14 in the intake valve 10 and the exhaust valve 11 which are essential members for the engine 1, the cooling member 14 can be provided with an efficient layout.

  In this embodiment, an example in which the cooling member 14 is incorporated in both the intake valve 10 and the exhaust valve 11 will be described. However, the cooling member 14 may be incorporated in only one of the valves. In this case, by incorporating the cooling member 14 only on the intake valve 10 side, the flow path of the combustion gas discharged to the exhaust passage 12 on the exhaust valve 11 side is not obstructed by the cooling member 14. It is more preferable that the gas is discharged smoothly to 12 and the scavenging efficiency is increased to reduce the residual gas.

  Here, FIG. 6A shows a state in which the cooling member 14 protrudes toward the inside of the combustion chamber 2, and FIG. 6B shows a normal state in which the cooling member 14 does not protrude into the combustion chamber 2. Is shown. In the state where the cooling member 14 protrudes as shown in FIG. 6A, the contact area between the cooling member 14 and the residual gas in the combustion chamber 2 is increased, so that the heat amount of the residual gas is absorbed by the cooling member 14. As a result, a good cooling effect can be obtained. On the other hand, when the cooling member 14 is housed in the valve as shown in FIG. 6B, the contact area between the cooling member 14 and the residual gas in the combustion chamber 2 decreases, and the cooling effect is small or almost absent. In order to prevent an unintended cooling effect from being exhibited when the cooling member 14 is accommodated in the valve, a heat insulating material is provided at the tip of the cooling member 14 (the surface exposed to the combustion chamber 2 when accommodated in the valve). May be constructed.

  FIG. 7 is an enlarged cross-sectional view showing the structure around the valve of FIG. 6 together with the drive mechanism. The drive mechanism 30 includes a valve drive camshaft 31, a valve drive cam 32 and a cooling member drive cam 33 connected to the camshaft. The valve drive cam 32 and the cooling member drive cam 33 have cam shapes suitable for the transition of the projection timing and projection amount of the intake valve 10, the exhaust valve 11 and the cooling member 14, which will be described later. ing.

  The valve driving cam 32 and the cooling member driving cam 33 change in diameter as the camshaft 31 rotates. FIG. 7A shows a state where the valves 10 and 11 and the cooling member 14 are housed, and FIG. 7B shows a state where the valves 10 and 11 and the cooling member 14 are projected. The valves 10 and 11 are urged toward the valve drive cam 32 by a spring 34, and the diameter of the valve drive cam 32 changes as the camshaft 31 rotates, so that the protruding amount of the valves 10 and 11 is increased. Variablely controlled. The cooling member 14 is biased toward the cooling member driving cam 33 by a spring 35, and the diameter of the cooling member driving cam 33 changes as the cam shaft 31 rotates, so that the protruding amount of the cooling member 14 is increased. Variablely controlled.

  The valve driving cam 32 and the cooling member driving cam 33 are connected to the same camshaft 31 and housed so that the cooling member driving cam 33 is sandwiched between the valve driving cams 32. Even when the cooling member 14 is built in each valve so as to provide the drive mechanism 30 as described above, it can be realized with a relatively simple configuration. In particular, since the cooling member 14 can be cam-driven, it is advantageous in that the drive control can be accurately performed by the cam shape design.

  In the present embodiment, the cooling member 14 built in the intake valve 10 side and the exhaust valve 11 side is preferably configured so as to be independently controlled. Therefore, it is preferable to adopt the DOHC format.

  In addition, as shown in FIG. 7, the cooling member 14 in the present embodiment also improves the cooling performance by forming a hollow portion 14a inside and encapsulating sodium, as in the first embodiment. .

(Cooling member control method)
Next, with reference to FIG. 8 to FIG. 10, the control method for the protrusion timing and the protrusion amount of the cooling member shown in the first and second embodiments will be described.

  FIG. 8 is a timing chart showing an example of the protrusion timing and the protrusion amount of the intake valve 10, the exhaust valve 11, and the cooling member 14 in the first and second embodiments. The drive timing and drive amount of the intake valve 10, exhaust valve 11 and cooling member 14 are electronically controlled by the ECU 18, respectively. The engine 1 is a four-cycle gasoline engine, and the horizontal axis in FIG. 8 indicates each stroke (expansion stroke, exhaust stroke, intake stroke, compression stroke). FIG. 8 representatively shows one cycle, and the same cycle is actually repeated.

  First, in the expansion stroke, after the air-fuel mixture burns in the combustion chamber 2 (that is, in the latter half of the expansion stroke), the exhaust valve 11 starts to open in order to discharge the exhaust gas generated by the combustion to the exhaust passage 12 side (t = t1). Then, the opening degree of the exhaust valve 11 is gradually increased and reaches the maximum value in the exhaust stroke. Thereafter, the opening degree of the exhaust valve 11 is increased toward the end of the exhaust stroke (more precisely, since a valve overlap is provided between the exhaust valve 11 and the intake valve 10 as described later, until the intake stroke reaches t = t3. ) Gradually decrease. In the intake stroke (precisely, immediately before shifting to the intake stroke because a valve overlap is provided between the exhaust valve 11), the intake valve 10 starts to be opened in order to introduce fresh air into the combustion chamber 2 ( t = t2). The opening of the intake valve 10 reaches a maximum value in the intake stroke, and then gradually decreases toward t = t4 in the compression stroke.

  In the example of FIG. 8, in particular, by considering the influence of inertia of intake and exhaust, by providing a valve overlap period (periods t2 to t3 in FIG. 8) in which both the intake valve 10 and the exhaust valve 11 are open, The intake and exhaust efficiency is improved. The overlap period is provided so as to cross the boundary between the exhaust stroke and the intake stroke, and the boundary is set so as to correspond to the exhaust top dead center of the piston 4.

  In FIG. 8, the transition of the protrusion amount of the cooling member 14 is indicated by a one-dot chain line. The ECU 18 sets the protrusion timing of the cooling member 14 in the latter half of the exhaust stroke. Even if the cooling member 14 is protruded in the first half of the exhaust stroke and the combustion gas in the combustion chamber 2 is cooled, most of the combustion gas is exhausted to the exhaust passage 12 side, resulting in combustion at the end of the exhaust stroke. The temperature of the combustion gas remaining in the chamber 2 cannot be effectively reduced. Therefore, in this aspect, the temperature of the combustion gas remaining in the combustion chamber 2 at the end of the exhaust stroke can be lowered by projecting the cooling member 14 in the latter half of the exhaust stroke.

  Particularly in this example, the ECU 18 is set so that the increase rate of the protrusion amount of the cooling member 14 is larger than the decrease rate. In general, in the exhaust stroke, the volume of the combustion chamber 2 gradually decreases. In this embodiment, when the capacity of the combustion chamber 2 is relatively large, the amount of protrusion of the cooling member 14 is rapidly increased to contact the cooling member 14 in a low temperature state with the combustion gas in the combustion chamber 2. By securing a large area, cooling can be promoted and the temperature of the residual gas can be effectively reduced.

  FIG. 9 is a timing chart showing another example of the projection timing and projection amount of the intake valve 10, the exhaust valve 11 and the cooling member 14 in the first and second embodiments. In this example, the ECU 18 performs control so that the change rate of the protrusion amount of the cooling member 14 becomes equal to the change rate of the opening degree of the exhaust valve 11 in the exhaust stroke. Thus, by setting the projection timing of the cooling member 14 simultaneously with the timing at which the exhaust valve 11 starts to open, a long contact time between the cooling member 14 and the combustion gas in the combustion chamber 2 can be secured. Therefore, the cooling member 14 can sufficiently absorb heat from the combustion gas, and a good cooling effect can be obtained.

  When the cooling member 14 is built in both the intake valve 10 and the exhaust valve 11 in the second embodiment, the amount of protrusion of the cooling member 14 built in the intake valve 10 is built in the exhaust valve 11. It is good to control so that it may become large compared with the protrusion amount of the cooling member 14. FIG. In this way, by causing the cooling member 14 of the intake valve 10 to protrude larger than the exhaust valve 11 side, the flow path of the combustion gas discharged to the exhaust passage through the exhaust valve 11 becomes the protrusion of the cooling member 14 on the intake valve 10 side. Can be prevented from being hindered. As a result, the combustion gas can be smoothly discharged into the exhaust passage 12, and the residual gas can be reduced by increasing the scavenging efficiency.

  FIG. 10 is an example of a map that defines the relationship between the protruding amount of the cooling member 14 and the rotational speed of the engine 1 in the engine 1 according to the present invention. The horizontal axis in FIG. 10 indicates the engine rotational speed detected by the rotational speed sensor 19, and the vertical axis indicates the protrusion amount of the cooling member 14.

  The amount of protrusion of the cooling member 14 is controlled by the ECU 18 so as to increase as the rotational speed of the engine 1 decreases. Generally, there is a tendency that knocking due to residual gas tends to occur as the rotational speed of the engine 1 decreases. For this reason, in this aspect, the amount of protrusion is increased as the rotational speed of the engine 1 is decreased, whereby the discharge amount of residual gas can be promoted and knocking can be more effectively prevented.

  As described above, according to the present invention, the cooling member 14 formed of a metal material having good thermal conductivity is projected toward the inside of the combustion chamber 2 during the exhaust stroke, so that the combustion is performed during the exhaust stroke. The combustion gas (residual gas) remaining in the chamber 2 can be cooled. Thus, by reducing the temperature of the residual gas, the mixed gas temperature in the compression stroke of the next cycle can be reduced. Further, since the volume of the combustion chamber 2 is reduced by projecting the cooling member 14, the discharge of the residual gas can be promoted together with the cooling of the residual gas, and the occurrence of knocking can be effectively suppressed.

  INDUSTRIAL APPLICABILITY The present invention is applicable to an internal combustion engine that can suppress the occurrence of knocking by cooling the exhaust gas remaining in the combustion chamber during the exhaust stroke in the internal combustion engine.

DESCRIPTION OF SYMBOLS 1 Engine 2 Combustion chamber 3 Cylinder head 4 Piston 5 Cylinder 6 Connecting rod 7 Spark plug 8 In-cylinder injector 9 Intake passage 10 Intake valve 11 Exhaust valve 12 Exhaust passage 13 Throttle valve 14 Cooling member 15 Intake VVT
16 VVT for exhaust
18 ECU
DESCRIPTION OF SYMBOLS 19 Rotational speed sensor 20 Crank drive mechanism 21 Rotating part 22 Arm 30 Drive mechanism 31 Camshaft 32 Valve drive cam 33 Cooling member drive cam 34, 35 Spring

Claims (8)

An internal combustion engine that introduces intake air from an intake passage via an intake valve and discharges combustion gas generated in the combustion chamber to an exhaust passage via an exhaust valve,
A cooling member made of a metal material that cools the combustion gas remaining in the combustion chamber by projecting into the combustion chamber from the inner wall side of the combustion chamber in the exhaust stroke;
Control means for controlling the protrusion amount and the protrusion timing of the cooling member ;
A rotational speed detection means for detecting the rotational speed of the internal combustion engine,
The internal combustion engine according to claim 1, wherein the control means sets the protruding amount of the cooling member to be larger as the rotational speed detected by the rotational speed detection means decreases .   The internal combustion engine according to claim 1, wherein the control means sets the protrusion timing of the cooling member in the latter half of the exhaust stroke.   The internal combustion engine according to claim 2, wherein the control unit is set so that an increasing rate of the protrusion amount of the cooling member is larger than a decreasing rate.   2. The internal combustion engine according to claim 1, wherein the control means controls the change rate of the protrusion amount of the cooling member to be equal to the change rate of the opening degree of the exhaust valve in the exhaust stroke.   5. The internal combustion engine according to claim 1, wherein the cooling member is provided so as to protrude from an inner wall of a cylinder head toward a central portion of the combustion chamber.   6. The cooling member according to claim 1, wherein the cooling member is incorporated in at least one of the intake valve and the exhaust valve so as to protrude in the same direction as the drive direction of the valve. An internal combustion engine according to claim 1. The cooling member is built in each of the intake valve and the exhaust valve,
The said control means controls so that the protrusion amount of the cooling member incorporated in the said intake valve may become large compared with the protrusion amount of the cooling member incorporated in the said exhaust valve. Internal combustion engine. 8. The cooling member is driven by a cam mechanism that is driven by a camshaft that is shared with a driving cam for the intake valve or the exhaust valve in which the cooling member is incorporated. Internal combustion engine.

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