JP2005226572A - Internal combustion engine with variable compression ratio - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology capable of reducing a cooling loss, in a internal combustion engine with variable compression ratio for changing the compression ratio by changing the volume of a combustion chamber. <P>SOLUTION: This internal combustion engine with variable compression ratio changes the compression ratio by changing the volume of the combustion chamber; and has a cooling means for cooling the internal combustion engine with variable compression ratio and a cooling capacity reducing means for reducing cooling capacity of the cooling means in response to an increase in the compression ratio; and restrains a heat radiating quantity from the combustion chamber when the S/V ratio becomes large. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a variable compression ratio internal combustion engine in which the compression ratio is changed by changing the volume of a combustion chamber.

  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.

As such a variable compression ratio internal combustion engine, for example, an inner piston and an outer piston constitute a piston, and the compression ratio is changed by supplying pressure oil between the inner piston and the outer piston. In such a case, a technique is known in which the piston crown is cooled by discharging the pressure oil from between the inner piston and the outer piston at a low compression ratio (see, for example, Patent Document 1).
JP-A 63-186926 JP-A 63-195340 JP 63-302150 A JP 2003-206871 A JP 2003-129817 A

  In an internal combustion engine, if the temperature of the internal combustion engine rises too much, problems such as knocking may occur. Therefore, the internal combustion engine is provided with a cooling means for cooling the internal combustion engine, for example, a heat medium circulation passage through which a heat medium such as cooling water circulates through the internal combustion engine in order to suppress excessive temperature rise. ing.

  On the other hand, in a variable compression ratio internal combustion engine, the volume of the combustion chamber is reduced by, for example, moving the cylinder block and the crankcase relative to each other, or changing the stroke amount of the piston by bending the connecting rod. It is increased at the time of the ratio and decreased at the time of the high compression ratio. At this time, the ratio of the surface area of the combustion chamber to the volume of the combustion chamber (hereinafter referred to as the S / V ratio) is larger at the high compression ratio than at the low compression ratio.

  Here, when the S / V ratio is increased, the heat generated in the combustion chamber is more easily radiated than when the S / V ratio is small. Therefore, at the time of a high compression ratio, the cooling loss increases, and as a result, the effect of improving the thermal efficiency due to the high compression ratio may be reduced.

  The present invention has been made in view of the above problems, and provides a technique capable of reducing cooling loss in a variable compression ratio internal combustion engine in which the compression ratio is changed by changing the volume of the combustion chamber. The task is to do.

  In the variable compression ratio internal combustion engine in which the compression ratio is changed by changing the volume of the combustion chamber, the cooling capacity for cooling the variable compression ratio internal combustion engine is higher at the time of the high compression ratio than at the time of the low compression ratio. It is to reduce.

More specifically, the variable compression ratio internal combustion engine according to the first invention is
In a variable compression ratio internal combustion engine in which the compression ratio is changed by changing the volume of the combustion chamber,
Cooling means for cooling the variable compression ratio internal combustion engine;
Cooling capacity reducing means for reducing the cooling capacity of the cooling means in accordance with an increase in compression ratio;
It is characterized by providing.

  In the present invention, as the compression ratio increases, the cooling capacity for cooling the variable compression ratio internal combustion engine (hereinafter simply referred to as the internal combustion engine) is reduced. That is, as the S / V ratio increases and the heat generated in the combustion chamber is easily radiated, the cooling of the internal combustion engine by the cooling means is suppressed, and as a result, the amount of heat released from the combustion chamber is suppressed.

  Therefore, according to the present invention, the cooling loss of the internal combustion engine can be reduced by reducing the cooling capacity for cooling the internal combustion engine in accordance with the increase in the compression ratio.

  In the present invention, the cooling capacity reducing means may reduce the cooling capacity of the cooling means when the compression ratio is equal to or higher than a specified value than when the compression ratio is lower than the specified value.

  The specified value here is a compression ratio at which the S / V ratio becomes excessively large and it can be determined that the cooling loss becomes excessively large when the internal combustion engine is cooled to the same value or higher than when the compression ratio is lower than the specified value. It is. This specified value can be determined in advance by experiments or the like.

  In general, in an internal combustion engine, the high compression ratio operation is performed when the engine load is relatively low. And since the amount of heat generated in the combustion chamber is low when the load is low, it is highly necessary to reduce the cooling loss. In that respect, according to the present invention, when the compression ratio is higher, the cooling capacity for cooling the internal combustion engine is further reduced, so that the cooling loss at the time of the high compression ratio can be reduced. On the other hand, the low compression ratio operation is performed when the engine load is relatively high. And when the load is high, the amount of heat generated in the combustion chamber is large, and the temperature rises more easily than when the load is low. On the other hand, according to the present invention, when the compression ratio is lower, the cooling capacity for cooling the internal combustion engine is not reduced, that is, the cooling capacity is high, so that the excessive temperature rise at the time of low compression ratio, that is, at high load is suppressed. I can do it.

An internal combustion engine according to the second invention is
In a variable compression ratio internal combustion engine in which the compression ratio is changed by changing the volume of the combustion chamber,
Cooling means for cooling the variable compression ratio internal combustion engine;
S / V ratio deriving means for deriving an S / V ratio that is a ratio of the surface area of the combustion chamber to the volume of the combustion chamber;
Cooling capacity reducing means for reducing the cooling capacity of the cooling means in accordance with an increase in the S / V ratio derived by the S / V ratio deriving means;
It is characterized by providing.

  As described above, in the internal combustion engine, the heat generated in the combustion chamber is easily radiated as the S / V ratio increases. Therefore, in the present invention, the cooling of the internal combustion engine by the cooling means is suppressed according to the increase in the S / V ratio. As a result, the cooling loss of the internal combustion engine can be reduced.

  In the present invention, the cooling capacity reducing means may reduce the cooling capacity of the cooling means when the S / V ratio is equal to or higher than a specified value than when the S / V ratio is smaller than the specified value.

  The specified value here is an S / V ratio at which it is possible to determine that the cooling loss is excessively increased when the internal combustion engine is cooled in the same manner as or more than when the S / V ratio is lower than the specified value. This specified value can be determined in advance by experiments or the like.

  In the first or second aspect of the invention, when the cooling means has a heat medium circulation passage through which the heat medium circulates through the internal combustion engine, the cooling capacity reduction means has the heat flowing through the heat medium circulation passage. The cooling capacity of the cooling means may be reduced by reducing the flow rate of the medium.

  When the flow rate of the heat medium flowing through the heat medium circulation passage decreases, the cooling effect of the internal combustion engine by the heat medium decreases. Therefore, the cooling capacity of the cooling means can be reduced.

  Here, when the internal combustion engine is further provided with a pumping means for pumping the heat medium into the heat medium circulation passage, the cooling capacity reducing means reduces the pumping amount of the heat medium per unit time by the pumping means. Accordingly, the flow rate of the heat medium flowing through the heat medium circulation passage may be reduced.

  Further, the internal combustion engine is connected to the heat medium circulation passage and is formed so as to bypass the internal combustion engine, and the bypass that is provided in the bypass passage and changes the flow rate of the heat medium that flows through the bypass passage. When the flow rate change valve is further provided, the cooling capacity reducing means increases the flow rate of the heat medium flowing through the heat medium circulation passage by increasing the flow rate of the heat medium flowing through the bypass passage by the bypass flow rate change valve. It may be decreased.

  In the configuration as described above, the bypass passage and the heat medium circulation passage communicate with each other. Therefore, by increasing the amount of the heat medium flowing to the bypass passage side, the flow rate of the heat medium flowing to the heat medium circulation passage side can be reduced.

  In this case, the heat medium circulation passage may be formed so that the heat medium circulates through the cylinder head of the internal combustion engine, and the bypass passage may be formed so as to bypass the cylinder head of the internal combustion engine.

  In such a configuration, when the flow rate of the heat medium flowing through the bypass passage is increased by the bypass flow rate change valve, the flow rate of the heat medium passing through the cylinder head of the internal combustion engine is decreased. As a result, cooling on the cylinder head side of the internal combustion engine is suppressed. Therefore, the amount of heat radiation from the cylinder head side of the combustion chamber can be suppressed.

  In the first or second aspect of the invention, when the cooling means has a heat medium circulation passage through which the heat medium circulates through the internal combustion engine, the cooling capacity reduction means has the heat flowing through the heat medium circulation passage. The cooling capacity of the cooling means may be reduced by increasing the temperature of the medium.

  When the temperature of the heat medium flowing through the heat medium circulation passage increases, the cooling effect of the internal combustion engine by the heat medium decreases as described above. Therefore, the cooling capacity of the cooling means can be reduced.

  Here, the internal combustion engine flows through a radiator, a communication passage that communicates the radiator and the heat medium circulation passage, a communication switching valve that is provided in the communication passage and opens or closes the communication passage, and the heat medium circulation passage. A temperature detection means for detecting the temperature of the heat medium; and when the temperature of the heat medium detected by the temperature detection means exceeds a set temperature, the communication switching valve is opened to open the communication path. In the case of further comprising valve opening / closing switching means for circulating a heat medium through the internal combustion engine and the radiator, and set temperature changing means for changing the set temperature, the cooling capacity reducing means is set temperature changing means. The temperature of the heat medium flowing through the heat medium passage may be increased by increasing the set temperature by the above.

By increasing the set temperature, the heat medium circulates through the radiator after the heat medium reaches a higher temperature. In other words, the heat medium does not pass through the radiator until the heat medium reaches a higher temperature, and cooling of the heat medium in the radiator is not started. As a result, the temperature of the heat medium flowing through the medium circulation passage can be increased.

  The contents described in the means for solving the above problems can be combined as much as possible without departing from the problems and technical ideas of the present invention.

  According to the present invention, it is possible to reduce cooling loss in a variable compression ratio internal combustion engine in which the compression ratio is changed by changing the volume of the combustion chamber.

  Hereinafter, specific embodiments of a variable compression ratio internal combustion engine according to the present invention will be described with reference to the drawings.

<Schematic configuration of variable compression ratio internal combustion engine>
First, a first embodiment of a variable compression ratio internal combustion engine according to the present invention will be described. FIG. 1 is a diagram showing a schematic configuration of a variable compression ratio internal combustion engine according to the present embodiment.

  The variable compression ratio internal combustion engine 1 (hereinafter simply referred to as the internal combustion engine 1) is a water-cooled gasoline engine. The internal combustion engine 1 includes a cylinder block 2 having cylinders 5, a cylinder head 4 provided above the cylinder block 2, a lower case 3 to which a piston 6 is connected via a connecting rod and a crankshaft. Then, the compression ratio is changed by changing the volume of the combustion chamber 7 by moving the cylinder block 2 in the axial direction of the cylinder 5 with respect to the lower case 3 by the variable compression ratio mechanism 8.

  The compression ratio variable mechanism 8 includes a cam storage hole 9 provided in the lower part on both the left and right sides of the cylinder block 2 and a bearing storage hole 10 provided in the upper part on the left and right sides of the lower case 3 in FIG. . Cam shafts 11 are inserted into the cam housing holes 9 and the bearing housing holes 10 on both the left and right sides. The camshafts 11 on both the left and right sides are respectively driven and rotated by the motor 24, whereby the cylinder block 2 moves in the axial direction of the cylinder 5 with respect to the lower case 3. At this time, the cylinder head 4 also moves integrally with the cylinder block 2. The details of the variable compression ratio mechanism 8 are disclosed in Japanese Patent Application Laid-Open No. 2003-206771.

  The cylinder head 4 is provided with an intake port 12 and an exhaust port 13 formed so as to open to the combustion chamber 7 in the cylinder 5. The intake port 12 is connected to the intake passage 14, and the exhaust port 13 is connected to the exhaust passage 15. The openings of the intake port 12 and the exhaust port 13 to the combustion chamber 7 are opened and closed by an intake valve 16 and an exhaust valve 17, respectively.

  A fuel injection valve 20 is installed in the intake port 12, and an ignition plug 21 that ignites an air-fuel mixture formed in the combustion chamber 7 is installed in the combustion chamber 7. The cylinder head 4 and the cylinder block 2 are formed with a water jacket 18 through which cooling water flows.

  The internal combustion engine 1 includes a cam position sensor 31 that outputs an electrical signal corresponding to the rotation angle of the cam shaft 11 of the variable compression ratio mechanism 8 and an accelerator opening sensor 33 that outputs an electrical signal corresponding to the accelerator opening. A crank position sensor 34 that outputs an electric signal corresponding to the rotation angle of a crankshaft provided in the lower case 3 and to which the piston 6 is connected, and a water temperature that outputs an electric signal corresponding to the temperature of the cooling water flowing in the water jacket 18 Various sensors such as the sensor 35 are provided.

  Further, the internal combustion engine 1 is provided with an electronic control unit (ECU) 30 for controlling the internal combustion engine 1. The ECU 30 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver. Various sensors such as a cam position sensor 31, an accelerator opening sensor 33, a crank position sensor 34, and a water temperature sensor 35 are connected to the ECU 30 through electric wiring, and these output signals are input to the ECU 30. It has become. The ECU 30 derives the engine load of the internal combustion engine 1 from the detected value of the accelerator opening sensor 33 and derives the engine speed of the internal combustion engine 1 from the detected value of the crank position sensor 34.

  The ECU 30 is electrically connected to a fuel injection valve 20, a spark plug 21, a motor 24, and the like, and these can be controlled. The ECU 30 controls the rotation of the camshaft 11 by the motor 24 to change the volume of the combustion chamber 7, thereby changing the compression ratio of the internal combustion engine 1. At this time, the ECU 30 derives the compression ratio from the output value of the cam position sensor 31.

  In the present embodiment, the ECU 30 changes the compression ratio according to the engine load of the internal combustion engine 1. That is, when the engine load is relatively low, the compression ratio is high, and when the engine load is relatively high, the compression ratio is low.

<Schematic configuration of cooling water circulation system>
Next, a schematic configuration of the cooling water circulation system of the variable compression ratio internal combustion engine according to the present embodiment will be described with reference to FIG. FIG. 2 is a diagram illustrating a schematic configuration of a cooling water circulation system of the variable compression ratio internal combustion engine according to the present embodiment.

  One end of the first cooling water channel 41 is connected to one end of the water jacket 18 of the internal combustion engine 1. The other end of the first cooling water channel 41 is connected to one end of the engine related device 43. Examples of the engine-related device 43 include a cooling water tank in which cooling water is stored and a heater core of a vehicle interior heater. One end of the second cooling water passage 42 is connected to the other end of the water jacket 18 of the internal combustion engine 1. The other end of the second cooling water passage 42 is connected to the other end of the engine-related device 43.

  A water pump 44 that pumps cooling water from the engine-related device 43 side to the internal combustion engine 1 side is provided in the middle of the first cooling water channel 41. The water pump 44 is electrically connected to the ECU 30, and the ECU 30 can change the pumping amount of the cooling water per unit time.

  Thus, in the cooling water circulation system according to the present embodiment, the first cooling water circulation passage 45 through which the cooling water circulates through the water jacket 18, the first cooling water passage 41, the second cooling water passage 42, and the engine-related device 43 is provided. It is formed. The cooling water circulates through the first cooling water circulation passage 45 to cool the internal combustion engine 1.

<Relationship between compression ratio and S / V ratio>
Here, the relationship between the compression ratio and the S / V ratio of the combustion chamber 7 in the internal combustion engine 1 will be described based on the graph shown in FIG. In this graph, the vertical axis represents the S / V ratio of the combustion chamber 7, and the horizontal axis represents the compression ratio.

  As shown in FIG. 3, in the internal combustion engine 1, the S / V ratio increases as the compression ratio increases. And if S / V ratio becomes large, the heat | fever which generate | occur | produced in the combustion chamber 7 will become easy to thermally radiate. Therefore, when the compression ratio is high, there is a possibility that the cooling loss is increased as compared with when the compression ratio is low.

<Control of pumping amount of cooling water by water pump>
Therefore, in the present embodiment, as shown in FIG. 4, in order to reduce the cooling capacity for cooling the internal combustion engine 1 as the compression ratio increases, the pumping amount of cooling water per unit time by the water pump 44 (hereinafter referred to as the cooling capacity) , Simply referred to as pumping amount). FIG. 4 is a graph showing the relationship between the pumping amount and the compression ratio, where the vertical axis represents the pumping amount and the horizontal axis represents the compression ratio.

  When the pumping amount is decreased, the flow rate of the cooling water flowing through the first cooling water circulation passage 45 is decreased. As a result, the cooling effect of the internal combustion engine 1 by the cooling water is reduced. That is, the cooling capacity for cooling the internal combustion engine 1 can be reduced. As a result, the amount of heat released from the combustion chamber 7 can be suppressed.

  Therefore, according to the present embodiment, the cooling capacity for cooling the internal combustion engine 1 in accordance with the increase in the compression ratio is reduced, whereby the cooling loss of the internal combustion engine 1 can be reduced.

  In the present embodiment, the flow rate of the cooling water flowing through the first cooling water circulation passage 45 is larger at the time of the low compression ratio than at the time of the high compression ratio. That is, when the load is high, the cooling capacity for cooling the internal combustion engine 1 is relatively high, so that the excessive temperature rise of the internal combustion engine 1 can be suppressed.

  In this embodiment, the relationship between the pumping amount and the compression ratio as shown in FIG. 4 is stored in advance in the ECU 30 as a map, and the compression ratio derived from the output value of the cam position sensor 31 is substituted into this map. By doing so, it is preferable to derive the pumping amount and thereby control the pumping amount.

<Modification>
Here, a modification of the present embodiment will be described.
In this modification, the relationship between the S / V ratio and the compression ratio as shown in FIG. 3 and the relationship between the pumping amount and the S / V ratio as shown in FIG. 5 are stored in advance in the ECU 30 as a map. Yes. FIG. 5 is a graph showing the relationship between the pumping amount and the S / V ratio, where the vertical axis represents the pumping amount and the horizontal axis represents the S / V ratio.

  In such a case, the ECU 30 substitutes the compression ratio derived from the output value of the cam position sensor 31 into a map showing the relationship between the S / V ratio and the compression ratio as shown in FIG. To derive. Then, by substituting the derived S / V ratio into a map showing the relationship between the pumping amount and the S / V ratio as shown in FIG. 5, the pumping amount is derived, thereby controlling the pumping amount.

  As described above, as the S / V ratio increases, the heat generated in the combustion chamber 7 is easily radiated. Therefore, in this modified example, as shown in FIG. 5, the control amount as described above reduces the pumping amount in accordance with the increase in the S / V ratio, thereby reducing the cooling capacity for cooling the internal combustion engine 1. . As a result, the cooling loss of the internal combustion engine 1 can be reduced.

  Next, a second embodiment of the variable compression ratio internal combustion engine according to the present invention will be described. Since the schematic configuration of the variable compression ratio internal combustion engine and the schematic configuration of the cooling water circulation system according to the present embodiment are the same as those of the first embodiment described above, description thereof will be omitted.

<Control of pumping amount of cooling water by water pump>
In this embodiment, the pumping amount is controlled by a control routine of the pumping amount as shown in FIG. FIG. 6 is a flowchart showing a control routine for controlling the pumping amount of the cooling water per unit time by the water pump 44 according to the present embodiment. This routine is executed by the ECU 30.
Is stored in advance, and is repeated every specified time during the operation of the internal combustion engine 1.

  In this routine, first, the ECU 30 determines in S101 whether or not the compression ratio is equal to or greater than a specified value P. Here, the specified value P can be determined that when the internal combustion engine 1 is cooled to the same value or higher than when the S / V ratio is excessively increased and the compression ratio is lower than the specified value, the cooling loss is excessively increased. Compression ratio. The specified value P is determined in advance by experiments or the like and stored in the ECU 30.

  If a negative determination is made in S101, the ECU 30 once terminates execution of this routine. On the other hand, if a positive determination is made in S101, the ECU 30 proceeds to S102.

  In S102, the ECU 30 reduces the pumping amount as compared with the case where the compression ratio is lower than the specified value P, and then temporarily ends the execution of this routine.

  Also by such control, the cooling capacity for cooling the internal combustion engine 1 can be reduced according to the increase in the compression ratio, and thus the cooling loss of the internal combustion engine 1 can be reduced.

  Also in this embodiment, when the compression ratio is low, the flow rate of the cooling water flowing through the first cooling water circulation passage 45 is larger than when the compression ratio is high. That is, when the load is high, the cooling capacity for cooling the internal combustion engine 1 is relatively high, so that the excessive temperature rise of the internal combustion engine 1 can be suppressed.

<Modification>
Here, a modification of the present embodiment will be described.
In this modification, a map showing the relationship between the S / V ratio and the compression ratio as shown in FIG. In this modification, the pumping amount is controlled by a pumping amount control routine as shown in FIG. FIG. 7 is a flowchart showing a control routine for controlling the pumping amount of the cooling water per unit time by the water pump 44 as in FIG. 6 described above. This routine is stored in the ECU 30 in advance, and is repeated every specified time during the operation of the internal combustion engine 1. In this routine, S102 is the same as the control routine shown in FIG.

  In this routine, first, in S201, the ECU 30 calculates the S / V ratio by substituting the compression ratio into a map showing the relationship between the S / V ratio and the compression ratio as shown in FIG.

  Next, the ECU 30 proceeds to S202, and determines whether or not the S / V ratio is equal to or greater than a specified value R. Here, the specified value R is an S / V ratio at which it is possible to determine that when the internal combustion engine 1 is cooled to the same or more than when the S / V ratio is lower than the specified value, the cooling loss becomes excessively large. The specified value R is determined in advance by experiments or the like and stored in the ECU 30.

  If a negative determination is made in S202, the ECU 30 once terminates execution of this routine. On the other hand, if a positive determination is made in S202, the ECU 30 proceeds to S102.

  Also by such control, the cooling capacity for cooling the internal combustion engine 1 can be reduced according to the increase of the S / V ratio, and thus the cooling loss of the internal combustion engine 1 can be reduced.

  In this embodiment, the pumping amount may be reduced according to an increase in the compression ratio or the S / V ratio by dividing into not only two stages but also three stages or more as in the control described above.

Next, a third embodiment of the variable compression ratio internal combustion engine according to the present invention will be described. Since the schematic configuration of the variable compression ratio internal combustion engine according to the present embodiment is the same as that of the first embodiment, the description thereof is omitted.

<Schematic configuration of cooling water circulation system>
A schematic configuration of the cooling water circulation system of the variable compression ratio internal combustion engine according to the present embodiment will be described with reference to FIG. FIG. 8 is a diagram showing a schematic configuration of a cooling water circulation system of the variable compression ratio internal combustion engine according to the present embodiment. In addition, about the structure similar to Example 1 mentioned above, the same reference number is attached | subjected and the description is abbreviate | omitted.

  In this embodiment, a bypass passage 46 formed so as to bypass the internal combustion engine 1 is provided. One end of the bypass passage 46 is connected to the first cooling water passage 41 between the water pump 44 and the internal combustion engine 1, and the other end is connected to the second cooling water passage 42.

  The bypass passage 46 is provided with a bypass flow rate change valve 47 that changes the flow rate of the cooling water flowing through the bypass passage 46 by changing the opening degree thereof. The bypass flow rate changing valve 47 is electrically connected to the ECU 30, and the opening degree of the bypass flow rate changing valve 47 can be controlled by the ECU 30.

<Opening control of bypass flow rate change valve>
Next, the opening degree control of the bypass flow rate changing valve 47 according to the present embodiment will be described. In this embodiment, as shown in FIG. 9, the opening degree of the bypass flow rate change valve 47 is increased in accordance with the increase in the compression ratio. FIG. 9 is a graph showing the relationship between the opening degree of the bypass flow rate changing valve 47 and the compression ratio, where the vertical axis represents the opening degree of the bypass flow rate changing valve 47 and the horizontal axis represents the compression ratio.

  When the opening degree of the bypass flow rate changing valve 47 increases, the cooling water flowing through the bypass passage 46 increases and the flow rate of the cooling water flowing through the water jacket 18 decreases. As a result, the cooling effect of the internal combustion engine 1 by the cooling water is reduced. That is, the cooling capacity for cooling the internal combustion engine 1 can be reduced. As a result, the amount of heat released from the combustion chamber 7 can be suppressed.

  Therefore, according to the present embodiment, the cooling capacity for cooling the internal combustion engine 1 in accordance with the increase in the compression ratio is reduced, whereby the cooling loss of the internal combustion engine 1 can be reduced.

  Also in this embodiment, when the compression ratio is low, the flow rate of the cooling water flowing through the water jacket 18 is larger than when the compression ratio is high. That is, when the load is high, the cooling capacity for cooling the internal combustion engine 1 is relatively high, so that the excessive temperature rise of the internal combustion engine 1 can be suppressed.

  In this embodiment, the relationship between the opening degree of the bypass flow rate changing valve 47 and the compression ratio as shown in FIG. 9 is stored in advance in the ECU 30 as a map, and the compression derived from the output value of the cam position sensor 31 is used. It is preferable to calculate the opening degree of the bypass flow rate changing valve 47 by substituting the ratio into this map and thereby control the opening degree of the bypass flow rate changing valve 47.

  When the compression ratio is lower than the specified value P (see Example 2), the bypass flow rate change valve 47 is closed, and when the compression ratio becomes equal to or higher than the specified value P, the bypass flow rate change valve 47 is opened. You may do that.

  Also by such control, the cooling capacity for cooling the internal combustion engine 1 can be reduced according to the increase in the compression ratio, and thus the cooling loss of the internal combustion engine 1 can be reduced.

  Also in such control, since the cooling capacity for cooling the internal combustion engine 1 is relatively high at the time of a low compression ratio, that is, at a high load, it is possible to suppress overheating of the internal combustion engine 1.

<Modification 1>
Here, the modification 1 of a present Example is demonstrated.
In the first modification, the relationship between the S / V ratio and the compression ratio as shown in FIG. 3 and the relationship between the opening degree of the bypass flow rate change valve 47 and the S / V ratio as shown in FIG. 10 are mapped. Is stored in advance in the ECU 30. FIG. 10 is a graph showing the relationship between the opening degree of the bypass flow rate changing valve 47 and the S / V ratio, where the vertical axis represents the opening degree of the bypass flow rate changing valve 47 and the horizontal axis represents the S / V ratio. ing.

  In such a case, as in the modification of the first embodiment, the compression ratio derived from the output value of the cam position sensor 31 is substituted into a map showing the relationship between the S / V ratio and the compression ratio as shown in FIG. To derive the S / V ratio. Then, the degree of opening of the bypass flow rate change valve 47 is derived by substituting the derived S / V ratio into a map showing the relationship between the degree of opening of the bypass flow rate change valve 47 and the S / V ratio as shown in FIG. Thus, the opening degree of the bypass flow rate changing valve 47 is controlled.

  By such control, as shown in FIG. 10, the opening degree of the bypass flow rate change valve 47 is increased in accordance with the increase in the S / V ratio, thereby reducing the cooling capacity for cooling the internal combustion engine 1. As a result, the cooling loss of the internal combustion engine 1 can be reduced.

  Further, when the S / V ratio is smaller than the specified value R (see Example 2), the bypass flow rate changing valve 47 is closed, and when the compression ratio becomes equal to or higher than the specified value R, the bypass flow rate changing valve 47 is set. The valve may be opened.

  Even by such control, the cooling capacity for cooling the internal combustion engine can be reduced according to the increase in the S / V ratio, and the cooling loss of the internal combustion engine 1 can be reduced.

<Modification 2>
Next, a second modification of the present embodiment will be described.
FIG. 11 is a diagram illustrating a schematic configuration of a cooling water circulation system of the variable compression ratio internal combustion engine according to the second modification. In addition, the same reference number is attached | subjected to the structure similar to the cooling water circulation system shown in FIG. 8 mentioned above, and only a different part from FIG. 8 is demonstrated here.

  In the second modification, the water jacket 18 is divided into a cylinder head side water jacket 18a and a cylinder block side water jacket 18b.

  The first cooling water channel 41 is branched between the water pump 44 and the internal combustion engine 1, and one is connected to one end of the cylinder head side water jacket 18a and the other is connected to the cylinder block side water jacket 18b. Connected to one end. The second cooling water channel 42 also has one end branched, and one is connected to the other end of the cylinder head side water jacket 18a and the other is connected to the end of the cylinder block side water jacket 18b.

  One end of the bypass passage 46 is connected to a portion branched to the cylinder head side water jacket 18 a side of the first cooling water passage 41, and the other end of the bypass passage 46 is connected to the cylinder head side water jacket 18 a of the second cooling water passage 41. It is connected to the part branched to the side. That is, in this modification, the bypass passage 46 is formed so as to bypass the cylinder head 4. In the bypass passage 46, a bypass flow rate changing valve 47 is installed as in the cooling water circulation system shown in FIG.

And also in the modification 2 of a present Example comprised in this way, bypass flow volume change valve 4
7 is controlled in the same manner as described above. As a result, the cooling capacity for cooling the cylinder head 4 can be reduced as the compression ratio or S / V ratio increases. Therefore, the amount of heat released from the cylinder head 4 side of the combustion chamber 7 can be suppressed, and the cooling loss of the internal combustion engine 1 can be reduced.

  Next, a fourth embodiment of the variable compression ratio internal combustion engine according to the present invention will be described. Since the schematic configuration of the variable compression ratio internal combustion engine according to the present embodiment is the same as that of the first embodiment, the description thereof is omitted.

<Schematic configuration of cooling water circulation system>
Here, a schematic configuration of the coolant circulation system of the variable compression ratio internal combustion engine according to the present embodiment will be described with reference to FIG. FIG. 12 is a diagram showing a schematic configuration of a cooling water circulation system of the variable compression ratio internal combustion engine according to the present embodiment. In addition, about the structure similar to Example 1 mentioned above, the same reference number is attached | subjected and the description is abbreviate | omitted.

  In this embodiment, the internal combustion engine 1 is provided with a radiator 48. The first cooling water passage 41 between the engine-related device 43 and the water pump 44 and one end of the radiator 48 are communicated with each other by a first communication passage 49. Further, the second cooling water passage 42 and the other end of the radiator 48 are communicated with each other by the second communication passage 50.

  A connection switching valve 51 that opens or shuts off between the second cooling water passage 42 and the second communication passage 50 is provided at a connection portion between the second cooling water passage 42 and the second communication passage 50. This communication switching valve 51 is electrically connected to the ECU 30.

  Then, when the temperature of the cooling water detected by the water temperature sensor 35 becomes equal to or higher than the set temperature Tc, the ECU 30 opens the communication switching valve 51 and establishes a gap between the second cooling water passage 42 and the second communication passage 50. Open. On the other hand, when the temperature of the cooling water detected by the water temperature sensor 35 becomes lower than the set temperature Tc, the ECU 30 closes the communication switching valve 51 and establishes a gap between the second cooling water passage 42 and the second communication passage 50. Shut off. Here, the set temperature Tc can be changed by the ECU 30.

  In the cooling water circulation system according to this embodiment, when the communication switching valve 51 is opened by the ECU 30 and the second cooling water passage 42 and the second communication passage 50 are opened, the water jacket 18, the radiator 48, the first A second cooling water circulation passage 52 in which the cooling water circulates through a part of the first cooling water passage 41, a part of the second cooling water passage 42, the first communication passage 49, and the second communication passage 50 is formed. When the cooling water circulates through the second cooling water circulation passage 52, the temperature of the cooling water is lowered by the radiator 48.

<Communication switching valve open / close control>
In this embodiment, the communication switching valve 51 is controlled by a control routine as shown in FIG. FIG. 13 is a flowchart showing an open / close control routine of the communication switching valve 51 according to this embodiment. This routine is stored in the ECU 30 in advance, and is repeated every specified time during the operation of the internal combustion engine 1. In this routine, S101 is the same as the control routine shown in FIG. 6 of the above-described second embodiment, so that the description thereof is omitted, and only S302 different from the second embodiment is described.

  In this routine, if an affirmative determination is made in S101, the ECU 30 proceeds to S302. In S302, the ECU 30 raises the set temperature Tc more than when the compression ratio is lower than the specified value P, and then ends this routine once.

  In such control, when the compression ratio is equal to or greater than the specified value P, the second cooling water passage 42 and the second communication passage 50 are opened after the cooling water reaches a higher temperature. That is, after the temperature of the cooling water reaches a higher temperature, the cooling water circulates through the second cooling water circulation passage 52 through the radiator 48. In other words, the cooling water does not pass through the radiator 48 until the cooling water reaches a higher temperature, and the cooling of the heat medium in the radiator 48 is not started. As a result, the temperature of the cooling water flowing through the first cooling water circulation passage 45 can be raised.

  When the temperature of the cooling water flowing through the first cooling water circulation passage 45 rises, the cooling effect of the internal combustion engine 1 by the cooling water decreases. That is, the cooling capacity for cooling the internal combustion engine 1 can be reduced. As a result, the amount of heat released from the combustion chamber 7 can be suppressed.

  Therefore, according to the present embodiment, the cooling capacity for cooling the internal combustion engine 1 in accordance with the increase in the compression ratio is reduced, whereby the cooling loss of the internal combustion engine 1 can be reduced.

  Further, in this embodiment, at the time of the low compression ratio, the temperature of the cooling water flowing through the first cooling water circulation passage 45 is lower than that at the time of the high compression ratio. That is, when the load is high, the cooling capacity for cooling the internal combustion engine 1 is relatively high, so that the excessive temperature rise of the internal combustion engine 1 can be suppressed.

<Modification>
Here, a modification of the present embodiment will be described.
In this modified example, a map showing the relationship between the S / V ratio and the compression ratio as shown in FIG. In this modification, the communication switching valve 51 is controlled by a control routine as shown in FIG. FIG. 14 is a flowchart showing an open / close control routine of the communication switching valve 51 according to the present embodiment, as in FIG. 13 described above. This routine is stored in the ECU 30 in advance, and is repeated every specified time during the operation of the internal combustion engine 1.

  In this routine, S201 and S202 are the same as the control routine shown in FIG. 7 of the modified example of the second embodiment, and S302 is the same as the control routine shown in FIG. That is, in this routine, when the S / V ratio is equal to or higher than the specified value R (see the second embodiment), the set temperature Tc is increased more than when the S / V ratio is smaller than the specified value R. .

  According to such control, the cooling capacity for cooling the internal combustion engine 1 in accordance with the increase in the S / V ratio is reduced, whereby the cooling loss of the internal combustion engine 1 can be reduced.

  In addition, you may combine the said Example 1, 2, 3, 4 each.

1 is a diagram illustrating a schematic configuration of a variable compression ratio internal combustion engine according to Embodiment 1. FIG. 1 is a diagram illustrating a schematic configuration of a cooling water circulation system of a variable compression ratio internal combustion engine according to Embodiment 1. FIG. The graph which shows the relationship between a compression ratio and S / V ratio of a combustion chamber. The graph which shows the relationship between the pumping amount of the cooling water per unit time by a water pump, and a compression ratio. The graph which shows the relationship between the pumping amount of the cooling water per unit time by a water pump, and S / V ratio. FIG. 10 is a flowchart showing a control routine for controlling the pumping amount of cooling water per unit time by the water pump according to the second embodiment. The flowchart figure which shows the control routine which controls the pumping quantity of the cooling water per unit time by the water pump which concerns on the modification of Example 2. FIG. FIG. 6 is a diagram illustrating a schematic configuration of a cooling water circulation system of a variable compression ratio internal combustion engine according to a third embodiment. The graph which shows the relationship between the opening degree of a bypass flow rate change valve, and a compression ratio. The graph which shows the relationship between the opening degree of a bypass flow volume change valve, and S / V ratio. FIG. 6 is a diagram illustrating a schematic configuration of a cooling water circulation system of a variable compression ratio internal combustion engine according to a second modification of the third embodiment. FIG. 6 is a diagram illustrating a schematic configuration of a cooling water circulation system of a variable compression ratio internal combustion engine according to a fourth embodiment. FIG. 9 is a flowchart showing an open / close control routine for a communication switching valve according to a fourth embodiment. FIG. 10 is a flowchart showing an open / close control routine for a communication switching valve according to a modification of the fourth embodiment.

Explanation of symbols

1. Variable compression ratio internal combustion engine (internal combustion engine)
2 ... Cylinder block 3 ... Lower case 4 ... Cylinder head 5 ... Cylinder 6 ... Piston 7 ... Combustion chamber 8 ... Compression ratio variable mechanism 9 ... Cam housing hole 10 Bearing bearing hole 11 Cam shaft 18 Water jacket 18a Cylinder head side water jacket 18b Cylinder block side water jacket 20 Fuel injection valve 24 Motor 30 ECU
31..Cam position sensor 33.Accelerator opening sensor 34.Crank position sensor 35.Water temperature sensor 41.First cooling water channel 42.Second cooling water channel 43.Engine related device 44.Water pump 45.・ ・ First cooling water circulation passage 46 ・ ・ Bypass passage 47 ・ ・ Bypass flow rate changing valve 48 ・ ・ Radiator 49 ・ ・ First communication passage 50 ・ ・ Second communication passage 51 ・ ・ Communication switching valve 52 ・ ・ Second cooling water circulation aisle

Claims (10)

In a variable compression ratio internal combustion engine in which the compression ratio is changed by changing the volume of the combustion chamber,
Cooling means for cooling the variable compression ratio internal combustion engine;
Cooling capacity reducing means for reducing the cooling capacity of the cooling means in accordance with an increase in compression ratio;
A variable compression ratio internal combustion engine comprising:   2. The variable compression ratio according to claim 1, wherein the cooling capacity reducing means reduces the cooling capacity of the cooling means when the compression ratio is equal to or higher than a specified value than when the compression ratio is lower than the specified value. Internal combustion engine. In a variable compression ratio internal combustion engine in which the compression ratio is changed by changing the volume of the combustion chamber,
Cooling means for cooling the variable compression ratio internal combustion engine;
S / V ratio deriving means for deriving an S / V ratio that is a ratio of the surface area of the combustion chamber to the volume of the combustion chamber;
Cooling capacity reducing means for reducing the cooling capacity of the cooling means in accordance with an increase in the S / V ratio derived by the S / V ratio deriving means;
A variable compression ratio internal combustion engine comprising:   The cooling capacity reducing means reduces the cooling capacity of the cooling means when the S / V ratio is equal to or higher than a specified value than when the S / V ratio is smaller than the specified value. Variable compression ratio internal combustion engine. The cooling means has a heat medium circulation passage through which a heat medium circulates through the variable compression ratio internal combustion engine,
The variable compression ratio internal combustion engine according to any one of claims 1 to 4, wherein the cooling capacity reducing means reduces the cooling capacity of the cooling means by reducing the flow rate of the heat medium flowing through the heat medium circulation passage. organ. A pressure feeding means for pressure feeding the heat medium to the heat medium circulation passage;
The said cooling capacity reduction means reduces the flow volume of the heat medium which flows through the said heat-medium circulation path by reducing the pumping amount of the heat-medium per unit time by the said pressure-feeding means. Variable compression ratio internal combustion engine. A bypass passage connected to the heat medium circulation passage and formed to bypass the variable compression ratio internal combustion engine;
A bypass flow rate change valve that is provided in the bypass passage and changes the flow rate of the heat medium flowing through the bypass passage;
The cooling capacity reducing means decreases the flow rate of the heat medium flowing through the heat medium circulation passage by increasing the flow rate of the heat medium flowing through the bypass passage by the bypass flow rate change valve. 5. The variable compression ratio internal combustion engine according to 5. The heat medium circulation passage is formed so that the heat medium circulates through a cylinder head of the variable compression ratio internal combustion engine;
A bypass passage connected to the heat medium circulation passage and formed to bypass the cylinder head of the variable compression ratio internal combustion engine;
A bypass flow rate change valve that is provided in the bypass passage and changes the flow rate of the heat medium flowing through the bypass passage;
6. The cooling capacity reducing means decreases the flow rate of the heat medium flowing through the heat medium passage by increasing the flow rate of the heat medium flowing through the bypass passage by the bypass flow rate change valve. The variable compression ratio internal combustion engine described. The cooling means has a heat medium circulation passage through which a heat medium circulates through the variable compression ratio internal combustion engine,
The variable compression ratio internal combustion engine according to any one of claims 1 to 4, wherein the cooling capacity reducing means reduces the cooling capacity of the cooling means by increasing the temperature of the heat medium flowing through the heat medium circulation passage. organ. With radiator,
A communication path communicating the radiator and the heat medium circulation path;
A communication switching valve that is provided in the communication path and opens or closes the communication path;
Temperature detecting means for detecting the temperature of the heat medium flowing through the heat medium circulation passage;
When the temperature of the heat medium detected by the temperature detection means becomes equal to or higher than a set temperature, the communication switching valve is opened and the communication passage is opened, whereby heat is passed through the variable compression ratio internal combustion engine and the radiator. Valve opening / closing switching means for circulating the medium;
A set temperature changing means for changing the set temperature,
10. The variable compression ratio internal combustion engine according to claim 9, wherein the cooling capacity reducing means increases the temperature of the heat medium flowing through the heat medium passage by increasing the set temperature by the set temperature changing means. .

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