JP2007085300A - Variable compression ratio internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for surely promoting exhaust purification or promoting warm-up of an exhaust emission control dvice by supplying secondary air, in a variable compression ratio internal combustion engine provided with secondary air supply sytsem. <P>SOLUTION: When supplying the secondary air to an exhaust passage by the secondary air supply system (S103), a compression ratio of the variable compression ratio internal combustion engine is lowered to control the compression ratio to be a compression ratio for the secondary air (S104). Therefore, unburnt fuel in exhaust is increased to activate secondary combustion of the unburnt fuel. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention has a function of supplying secondary air to the exhaust passage of the internal combustion engine to promote exhaust purification and warm-up of the exhaust purification apparatus, and a variable having a function of changing the compression ratio of the internal combustion engine. The present invention relates to a compression ratio internal combustion engine.

  In recent years, a technique for changing the compression ratio of an internal combustion engine for the purpose of improving the fuel consumption performance and output performance of the internal combustion engine has been proposed. As this type of technology, the cylinder block and the crankcase are connected so as to be relatively movable, and a camshaft is provided at the connecting portion, and the camshaft is rotated to connect the cylinder block and the crankcase in the axial direction of the cylinder. A technique has been proposed in which the volume of the combustion chamber is changed by relative movement to the internal combustion engine, thereby changing the compression ratio of the internal combustion engine (see, for example, Patent Document 1).

  Further, the connecting rod is divided into two, a connecting member connected to the crankshaft is connected to a swinging member capable of swinging around a predetermined swinging center, and the swinging center is moved by rotating the camshaft. Thus, a technique has also been proposed in which the volume of the combustion chamber and the stroke of the piston are changed, thereby changing the compression ratio of the internal combustion engine (see, for example, Patent Document 2).

On the other hand, there is known an apparatus in which an exhaust purification catalyst is disposed in an exhaust system of an internal combustion engine to purify CO, HC and NOx components in exhaust gas. Furthermore, a technique is known in which secondary air is supplied into the exhaust passage to increase the oxygen concentration by pumping air from an air pump to a secondary air supply passage having an open / close valve connected to the exhaust passage. According to this technique, exhaust gas purification can be promoted by oxidizing HC and CO in the exhaust gas, and warming-up of the exhaust gas purification catalyst can be promoted (see, for example, Patent Document 3).
JP 2003-206871 A JP 2001-317383 A JP-A-2005-009412 JP 2003-328794 A JP 2004-308431 A JP 2002-285898 A JP 2004-278415 A

  The present invention is intended to make the effects of the above-described prior art more prominent. The object of the present invention is to supply secondary air in a variable compression ratio internal combustion engine equipped with a secondary air supply device. An object of the present invention is to provide a technology that can more reliably promote exhaust purification or promote warm-up of an exhaust purification device.

  The present invention for achieving the above object is characterized in that, when the secondary air is supplied to the exhaust passage of the internal combustion engine by the secondary air supply device, the compression ratio is lowered.

More specifically, a variable compression ratio mechanism that changes the compression ratio of the internal combustion engine by changing the volume of the combustion chamber of the internal combustion engine and / or the stroke of the piston;
An exhaust purification device that is provided in an exhaust passage through which exhaust from the internal combustion engine passes, and purifies the exhaust;
A secondary air supply device for supplying secondary air upstream of the exhaust purification device in the exhaust passage;
Compression ratio control means for controlling the compression ratio of the internal combustion engine to a predetermined compression ratio corresponding to the engine state by the variable compression ratio mechanism according to the operating state or warm-up state of the internal combustion engine;
A variable compression ratio internal combustion engine comprising:
In at least a part of a period during which secondary air is supplied from the secondary air supply device to the exhaust passage, the variable compression ratio mechanism causes the compression ratio of the internal combustion engine to be lower than the compression ratio corresponding to the engine state. It is characterized by controlling to a compression ratio corresponding to air.

  Here, when the secondary air is supplied to the exhaust passage of the internal combustion engine by the secondary air supply device, the combustion of unburned fuel existing in the exhaust is promoted by the oxygen in the supplied secondary air. As a result, exhaust gas purification is promoted, and the exhaust gas temperature is raised to promote warm-up of the exhaust gas purification device.

  On the other hand, when the secondary air is supplied to the exhaust passage of the internal combustion engine, if the compression ratio in the internal combustion engine is set to a low compression ratio, the combustion efficiency in the combustion chamber of the internal combustion engine is reduced, and accordingly, Increases the amount of unburned fuel. If it does so, the emitted-heat amount of combustion of the unburned fuel by supplying secondary air can be increased. Further, the back pressure of the exhaust passage due to the exhaust from the internal combustion engine can be reduced, and the supply of secondary air from the secondary air supply device can be facilitated.

  Therefore, in the present invention, the compression ratio of the internal combustion engine is adjusted by the compression ratio control means during at least a part of the period in which the secondary air is supplied from the secondary air supply device to the exhaust passage. It was decided to control the compression ratio corresponding to the secondary air, which is lower than the compression ratio corresponding to the engine state set according to the operation state or the warm-up state.

  Then, the unburned fuel in the exhaust from the internal combustion engine can be increased during at least a part of the period during which the secondary air is supplied to the exhaust passage by the secondary air supply device, and the secondary air The supply of secondary air from the air supply device can be made easier.

  Here, the compression ratio corresponding to the engine state is a compression ratio set by the compression ratio control means in accordance with the operating state or warm-up state of the internal combustion engine. For example, when the warm-up is insufficient, such as when the internal combustion engine is cold-started, the compression ratio corresponding to the engine state is set to a relatively high compression ratio, and the combustion efficiency is increased to promote warm-up of the internal combustion engine. In addition, after the warm-up is completed, the engine state-corresponding compression ratio is set to the high compression ratio side within a range where knocking does not occur, thereby improving fuel efficiency.

  In the present invention, the compression ratio corresponding to the secondary air is a compression ratio set lower than the compression ratio corresponding to the engine state as described above, and improves the purification efficiency by the afterburning of the exhaust and warms up the exhaust purification device. The compression ratio is experimentally obtained in advance from the viewpoint of promotion.

  By performing this control, exhaust gas purification can be promoted more reliably, and warm-up of the exhaust gas purification device can be promoted.

The present invention further includes an atmospheric pressure acquisition means for detecting or estimating an atmospheric pressure around a vehicle on which the internal combustion engine is mounted,
When the atmospheric pressure detected or estimated by the atmospheric pressure acquisition means is below a predetermined value, the variable compression is performed at least during a period during which secondary air is supplied from the secondary air supply device to the exhaust passage. The compression ratio of the internal combustion engine may be controlled to the compression ratio corresponding to the secondary air by a ratio mechanism.

  Here, when the atmospheric pressure around the vehicle on which the internal combustion engine is mounted decreases, for example, when the vehicle travels on a highland, the amount of secondary air that can be supplied by the secondary air supply device decreases. In addition, the temperature of the exhaust from the internal combustion engine decreases. Therefore, in a state where the atmospheric pressure around the internal combustion engine is reduced, the degree to which the combustion of unburned fuel in the exhaust can be promoted by the supply of secondary air is reduced, and the promotion of exhaust purification is hindered, and the exhaust purification device There is a risk that the warm-up efficiency of the engine will be reduced. That is, in a state where the atmospheric pressure around the vehicle on which the internal combustion engine is mounted is reduced, secondary air is supplied from the secondary air supply device, and the compression ratio of the internal combustion engine is set to the compression ratio corresponding to the secondary air. The need for control is increased.

  On the other hand, when the compression ratio is reduced in the internal combustion engine, the fuel efficiency deteriorates due to the reduction in the combustion efficiency in the cylinder of the internal combustion engine, and the warm-up efficiency of the internal combustion engine itself decreases particularly during cold start. There is a fear. Therefore, it is desirable to execute the control to limit the compression ratio of the internal combustion engine to the compression ratio corresponding to the secondary air.

  In view of the above circumstances, in the present invention, the compression ratio is set in at least a part of the period during which the secondary air is supplied only when the atmospheric pressure around the vehicle on which the internal combustion engine is mounted is equal to or lower than a predetermined value. It was decided to control to a compression ratio corresponding to the secondary air. In that case, if the state is as it is, the promotion of exhaust purification is hindered, and the compression ratio is controlled to the compression ratio corresponding to the secondary air only when there is a possibility that the warm-up efficiency of the exhaust purification device may be reduced. Therefore, it is possible to suppress a decrease in the degree of promotion of exhaust purification and a delay in warming up of the exhaust purification device. At the same time, since the compression ratio in the internal combustion engine in other cases is made the compression ratio corresponding to the engine state by the compression ratio control means, the improvement in fuel consumption and the warm-up of the internal combustion engine itself during cold start are promoted as much as possible. be able to.

The present invention further includes an atmospheric pressure acquisition means for detecting or estimating an atmospheric pressure around a vehicle on which the internal combustion engine is mounted,
As the atmospheric pressure detected or estimated by the atmospheric pressure acquisition means is lower, the compression ratio corresponding to the secondary air may be lowered.

  By doing so, the compression ratio can be lowered according to the degree of hindrance to the acceleration of exhaust purification or the degree of delay of warm-up of the exhaust purification device due to the lower atmospheric pressure, and the combustion of unburned fuel in the exhaust Can be promoted more reliably. By doing so, it is possible to efficiently promote exhaust purification and warm-up of the exhaust purification device regardless of the atmospheric pressure state.

  In the present invention, the amount of secondary air supplied from the secondary air supply means may be increased as the atmospheric pressure detected or estimated by the atmospheric pressure acquisition means is lower.

  That is, when the atmospheric pressure decreases, the amount of air that can be supplied from the secondary air supply device to the exhaust passage itself may decrease. Correspondingly, if the atmospheric pressure detected or estimated by the atmospheric pressure acquisition means is lower, the amount of air supplied to the exhaust passage by the secondary air supply means is increased. It is possible to suppress a reduction in the amount of secondary air that can be supplied from the secondary air supply device to the exhaust passage due to the decrease. As a result, the exhaust air purification and the warm-up of the exhaust gas purification device can be more reliably promoted by supplying the secondary air.

Here, the lower the atmospheric pressure detected or estimated by the atmospheric pressure acquisition means, the more the amount of secondary air supplied from the secondary air supply means is to increase the atmospheric pressure and the amount of secondary air. It is not restricted to the aspect which changes 1 to 1 correspondingly. For example, when the atmospheric pressure is equal to or less than a predetermined value, the compression ratio of the internal combustion engine is controlled to the compression ratio corresponding to the secondary air during at least a part of the period during which the secondary air is supplied. The secondary air amount is increased in two stages, in which the secondary air amount is increased when the atmospheric pressure is less than or equal to the predetermined value compared to when the atmospheric pressure is higher than the predetermined value. Aspects are included.

  The means for solving the above-described problems of the present invention can be used in combination as much as possible.

  In the present invention, in a variable compression ratio internal combustion engine equipped with a secondary air supply device, exhaust gas purification can be promoted more reliably or more reliably by supplying secondary air. Can help to warm up.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings.

  The internal combustion engine 1 described below is a variable compression ratio internal combustion engine, and a compression ratio is obtained by moving a cylinder block 3 having a cylinder 2 in the direction of the central axis of the cylinder 2 with respect to a crankcase 4 to which a piston is connected. Is to change.

First, the configuration of the variable compression ratio mechanism according to the present embodiment will be described with reference to FIG. As shown in FIG. 1, a plurality of raised portions are formed at the lower portions on both sides of the cylinder block 3, and bearing housing holes 5 are formed in the raised portions. The bearing housing hole 5 has a circular shape, and is formed so as to be perpendicular to the axial direction of the cylinder 2 and parallel to the arrangement direction of the plurality of cylinders 2. The bearing housing holes 5 are all located on the same axis. The pair of axes of the bearing housing holes 5 on both sides of the cylinder block 3 are parallel.

  The crankcase 4 is formed with a standing wall portion so as to be positioned between the plurality of raised portions in which the bearing housing holes 5 described above are formed. A semicircular recess is formed on the surface of each standing wall portion facing the outside of the crankcase 4. Moreover, the cap 7 attached with the volt | bolt 6 is prepared for each standing wall part, and the cap 7 also has a semicircle recessed part. Further, when the cap 7 is attached to each standing wall portion, a circular cam housing hole 8 is formed. The shape of the cam storage hole 8 is the same as that of the bearing storage hole 5 described above.

  Similar to the bearing housing hole 5, the plurality of cam housing holes 8 are perpendicular to the axial direction of the cylinder 2 when the cylinder block 3 is attached to the crankcase 4 and parallel to the arrangement direction of the plurality of cylinders 2. Each is formed to be. The plurality of cam storage holes 8 are also formed on both sides of the cylinder block 3, and the plurality of cam storage holes 8 on one side are all located on the same axis. The pair of axes of the cam storage holes 8 on both sides of the cylinder block 3 are parallel. Further, the distance between the bearing housing holes 5 on both sides and the distance between the cam housing holes 8 on both sides are the same.

Cam shafts 9 are inserted through the two rows of bearing housing holes 5 and cam housing holes 8 arranged alternately. As shown in FIG. 1, the cam shaft 9 includes a shaft portion 9a and a cam portion 9b having a right circular cam profile fixed to the shaft portion 9a while being eccentric with respect to the central axis of the shaft portion 9a. The movable bearing portions 9c having the same outer shape as the cam portions 9b and rotatably attached to the shaft portions 9a are alternately arranged. The pair of cam shafts 9 have a mirror image relationship. Further, a mounting portion 9d of a gear 10 described later is formed at the end portion of the cam shaft 9. The center axis of the shaft portion 9a and the center of the attachment portion 9d are eccentric, and the center of the cam portion 9b and the center of the attachment portion 9d coincide.

  The movable bearing portion 9c is also eccentric with respect to the shaft portion 9a, and the amount of eccentricity is the same as that of the cam portion 9b. In each camshaft 9, the eccentric directions of the plurality of cam portions 9b are the same. Since the outer shape of the movable bearing portion 9c is a perfect circle having the same diameter as the cam portion 9b, the outer surface of the plurality of cam portions 9b and the outer surfaces of the plurality of movable bearing portions 9c are rotated by rotating the movable bearing portion 9c. Can be matched with the side.

  A gear 10 is attached to one end of each camshaft 9. Worm gears 11a and 11b are engaged with the pair of gears 10 fixed to the ends of the pair of cam shafts 9, respectively. The worm gears 11 a and 11 b are attached to one output shaft of the single motor 12. The worm gears 11a and 11b have spiral grooves that rotate in opposite directions. For this reason, when the motor 12 is rotated, the pair of cam shafts 9 rotate in opposite directions via the gear 10. The motor 12 is fixed to the cylinder block 3 and moves integrally with the cylinder block 3.

  Next, a method for controlling the compression ratio in the internal combustion engine 1 having the above-described configuration will be described in detail. 2 (a) to 2 (c) are cross-sectional views showing the relationship between the cylinder block 3, the crankcase 4, and the cam shaft 9 constructed between them. 2A to 2C, the central axis of the shaft portion 9a is indicated by a, the center of the cam portion 9b is indicated by b, and the center of the movable bearing portion 9c is indicated by c. FIG. 2A shows a state in which the outer peripheries of all the cam portions 9b and the movable bearing portion 9c coincide with each other when viewed from the extension line of the shaft portion 9a. At this time, here, the pair of shaft portions 9 a are located outside the bearing housing hole 5 and the cam housing hole 8.

  When the motor 12 is driven from the state of FIG. 2A to rotate the shaft portion 9a in the direction of the arrow, the state of FIG. 2B is obtained. At this time, since the cam portion 9b and the movable bearing portion 9c are displaced in the eccentric direction with respect to the shaft portion 9a, the cylinder block 3 can be slid to the top dead center side with respect to the crankcase 4. The sliding amount is maximized when the cam shaft 9 is rotated until the state shown in FIG. 2C is reached, and is twice the eccentric amount of the cam portion 9b and the movable bearing portion 9c. The cam portion 9b and the movable bearing portion 9c rotate inside the cam storage hole 8 and the bearing storage hole 5, respectively, and allow the position of the shaft portion 9a to move inside the cam storage hole 8 and the bearing storage hole 5, respectively. is doing.

  By using the mechanism as described above, the cylinder block 3 can be moved relative to the crankcase 4 in the axial direction of the cylinder 2, and the compression ratio can be variably controlled. The above-described mechanism constitutes a variable compression ratio mechanism in the present embodiment.

  Next, details of the intake and exhaust system of the internal combustion engine in the present embodiment will be described with reference to FIG. In FIG. 3, an intake branch pipe 18 and an intake pipe 19 are attached to the intake system of the internal combustion engine 1, and an exhaust branch pipe 28 and an exhaust pipe 29 are attached to the exhaust system of the internal combustion engine 1. The intake pipe 19 is provided with a throttle 20 and an air flow meter 21 for measuring the air amount (primary air amount). On the other hand, an exhaust purification catalyst 30 made of a three-way catalyst is disposed downstream of the exhaust pipe 29. Further, the internal combustion engine 1 is provided with a crank position sensor 31 for detecting the rotational speed Ne and a cooling water temperature sensor 32 for detecting the cooling water temperature, and the output thereof is input to the ECU 35 together with the output of the air flow meter 21. . Further, the vehicle is provided with a pressure sensor 33 that detects the atmospheric pressure around the vehicle on which the internal combustion engine 1 is mounted, and its output is also input to the ECU 35.

The secondary air supply device 40 includes a secondary air supply passage 42 opened to the outside through a secondary air filter 41, and an electric motor is provided on the secondary air supply passage 42 from the secondary air filter 41 side. A drive type air pump (AP) 43, an air switching valve (ASV) 44, and a reed valve (RV) 45 as a check valve are arranged. A pipe 46 extending from the intake branch pipe 18 is connected to the ASV 44, and a vacuum switching valve (VSV) 47 is disposed on the pipe 46.

  The secondary air supply device 40 executes the secondary air supply control in a predetermined condition, for example, in a state in which the exhaust purification catalyst 30 is not sufficiently heated and its function is not sufficiently exhibited. Specifically, by controlling the VSV 47 to connect the pipe 46 and the intake branch pipe 18, the negative pressure in the intake branch pipe 18 is guided to the ASV 44 to open the ASV 44 and drive the AP 43. . As a result, part of the air that has passed through the secondary air filter 41 is guided into the exhaust branch pipe 28 via the secondary air supply passage 42 and the secondary air supply pipe 14. As a result, the oxygen concentration in the exhaust gas increases, secondary combustion of the HC and CO in the exhaust gas in the exhaust pipe 29 is promoted to purify the exhaust gas, and the exhaust gas temperature rises to increase the exhaust purification catalyst 30. The temperature increase of the three-way catalyst is promoted.

  Here, by reducing the combustion efficiency in the cylinders of the internal combustion engine 1 and increasing the concentration of unburned HC and CO in the exhaust, the secondary combustion in the exhaust branch pipe 28 and the exhaust pipe 29 can be more activated. I know it. If so, exhaust purification can be further promoted, and the exhaust purification catalyst 30 can be warmed up earlier by further raising the temperature of the exhaust gas introduced into the exhaust purification catalyst 30.

  Therefore, in this embodiment, the compression ratio of the internal combustion engine 1 is reduced during the period in which the secondary air is supplied from the secondary air supply device 40 to the exhaust branch pipe 28 and the exhaust pipe 29. By doing so, it is possible to increase the amount of unburned HC and CO discharged from the internal combustion engine 1 during the period in which the secondary air is being supplied, and to promote the temperature rise of the exhaust gas due to the secondary combustion. can do.

  Further, by reducing the compression ratio of 1 of the internal combustion engine, the back pressure in the exhaust branch pipe 28 and the exhaust pipe 29 due to the exhaust from the internal combustion engine 1 is reduced, so that the exhaust branch pipe 28 from the secondary air supply passage 14 is reduced. In addition, there is an effect that the supply of the secondary air to the exhaust pipe 29 becomes easier.

  FIG. 4 is a graph showing the relationship between the exhaust gas temperature and the exhaust gas purification rate of the exhaust gas purification catalyst 30. A curve indicated by a broken line indicates a case where the compression ratio is high, and a curve indicated by a solid line indicates a case where the compression ratio is low. Here, it can be seen that, in the exhaust purification catalyst 30, the exhaust purification rate increases as the exhaust temperature increases in the range where the exhaust temperature is relatively low, regardless of the compression ratio.

  Then, considering the case where the compression ratio changes from a high state to a low state in FIG. 4, first, the supply of secondary air is easier due to the above-described reduction in back pressure in the exhaust branch pipe 28 and the exhaust pipe 29. The effect of becoming is illustrated by the change from point A to point B in the figure. The effect of being able to further raise the temperature of the exhaust gas introduced into the exhaust purification catalyst 30 is illustrated by the change from point B to point C in the figure. Thus, if the compression ratio of the internal combustion engine 1 is lowered, the exhaust gas purification rate can be greatly improved by the synergistic effect of the two effects as shown in FIG.

  FIG. 5 shows a start-up exhaust temperature raising routine in this embodiment. This routine is a routine executed by the ECU 35 every predetermined period.

  When this routine is executed, it is first determined in S101 whether the internal combustion engine 1 has been started. Specifically, the determination may be made by taking the output of the crank position sensor 31 into the ECU 35 and detecting that the crankshaft of the internal combustion engine 1 is rotating.

  Here, when it is determined that the internal combustion engine 1 has not been started, this routine is temporarily terminated. On the other hand, if it is determined that the internal combustion engine 1 has been started, the process proceeds to S102.

  In S102, it is determined whether secondary air supply conditions for supplying secondary air to the exhaust passage are satisfied. Specifically, the catalyst temperature is detected, and the determination is made based on whether or not the detected value belongs to the secondary air supply range obtained experimentally in advance. This temperature may be estimated by an integrated value from the start of the intake air amount obtained from the output of the air flow meter 21.

  Here, in addition to the above, the secondary air supply condition may be determined by detecting the cooling water temperature or the elapsed time after the start, and whether or not the detected value belongs to a range obtained experimentally in advance. . Moreover, you may determine by the combination of those detection values. The cooling water temperature is detected by taking the output of the cooling water temperature sensor 32 into the ECU 35.

  If it is determined that the secondary air supply condition is satisfied, the process proceeds to S103. On the other hand, if it is determined that the secondary air supply condition is not satisfied, the process proceeds to S105.

  In S103, supply of secondary air is started, or the supply state of secondary air is continued. Specifically, the VSV 47 is controlled to connect the pipe 46 and the intake branch pipe 18, thereby leading the negative pressure in the intake branch pipe 18 to the ASV 44 to control the opening of the ASV 44 and to drive the AP 43.

  In S105, the supply of secondary air is stopped or the supply stop state of secondary air is continued. Specifically, the VSV 47 is controlled to shut off the pipe 46 and the intake branch pipe 18, thereby closing the ASV 44 and stopping the AP 43.

  In S104, the compression ratio of the internal combustion engine 1 is changed to a compression ratio corresponding to secondary air. Here, in normal compression ratio control, in a predetermined period after the internal combustion engine 1 is started, control is performed so that the compression ratio at the start of the combustion engine 1 is relatively high so as to promote warm-up of the internal combustion engine 1 itself. Is done. The starting compression ratio is a value of a compression ratio experimentally obtained as a compression ratio that can promote warm-up of the internal combustion engine 1 as much as possible within a range in which knocking does not occur in the internal combustion engine 1. This starting compression ratio corresponds to the compression ratio corresponding to the engine state in this embodiment.

  The secondary air-compatible compression ratio is a compression ratio on the lower compression ratio side than the starting compression ratio, and the exhaust gas is exhausted as much as possible within a range in which the fuel efficiency at the start of the internal combustion engine 1 is not extremely deteriorated. This is a value experimentally determined as a compression ratio that can promote secondary combustion of unburned HC and CO, promote exhaust purification, and increase the exhaust temperature.

  In S106, the compression ratio of the internal combustion engine 1 is set to the starting compression ratio. When the process of S104 or S106 ends, this routine is temporarily ended. Here, the ECU 35 that executes the process of S106 corresponds to a compression ratio control means in the present embodiment.

  As described above, in the present embodiment, the compression ratio of the internal combustion engine 1 is set to the compression ratio corresponding to the secondary air during the period in which the secondary air is supplied from the secondary air supply device 40. While increasing unburned HC and CO in the exhaust, the exhaust back pressure was reduced. As a result, secondary combustion of unburned HC and CO in the exhaust by the secondary air becomes more active, and exhaust purification is promoted and warm-up of the exhaust purification catalyst 30 is more reliably promoted.

In the present embodiment, the compression ratio of the internal combustion engine 1 is set to the compression ratio corresponding to the secondary air over substantially the entire period during which the secondary air is supplied from the secondary air supply device 40. However, the compression ratio of the internal combustion engine 1 may be set to the compression ratio corresponding to the secondary air during a part of the period during which the secondary air is supplied from the secondary air supply device 40. Even in this case, the secondary combustion of the unburned HC and CO in the exhaust by the secondary air is activated, and the effect of promoting exhaust purification and warming up of the exhaust purification catalyst 30 can be obtained. it can.

  Next, a second embodiment of the present invention will be described. In the present embodiment, control for changing the compression ratio in accordance with the supply of secondary air will be described only when the atmospheric pressure around the vehicle on which the internal combustion engine 1 is mounted is lower than a predetermined pressure. The internal combustion engine 1 and the intake / exhaust system in the present embodiment are the same as those described in the first embodiment, and the description thereof is omitted.

  FIG. 6 shows a flowchart of the start-up exhaust temperature raising routine 2 in the present embodiment. The difference between this routine and the start-up exhaust temperature raising routine described in the first embodiment is that the process of S201 is added. The other processes are the same as those in the start-up exhaust temperature raising routine, and will not be described.

  In S201, it is determined whether the atmospheric pressure around the vehicle is equal to or less than a predetermined value. Here, when the atmospheric pressure around the vehicle is lower than the predetermined value, the amount of air itself supplied as secondary air from the secondary air supply device 40 decreases, and the exhaust temperature (energy) is further reduced. Is the atmospheric pressure as a threshold value that is considered to reduce the effect of the secondary air supply. This predetermined value is obtained experimentally in advance.

  If it is determined in S201 that the atmospheric pressure around the vehicle is higher than the predetermined value, it can be determined that the effect of the secondary air supply is sufficient and the compression ratio of the internal combustion engine 1 does not necessarily need to be reduced. Proceed to On the other hand, if it is determined in S201 that the atmospheric pressure around the vehicle is equal to or lower than the predetermined value, it can be determined that it is difficult to sufficiently exert the effect of the secondary air supply as it is, and the process proceeds to S104. Then, the compression ratio is changed to the compression ratio corresponding to the secondary air.

  As described above, in this embodiment, it is determined that the effect of the secondary air supply cannot be obtained sufficiently if the atmospheric pressure of the vehicle is lower than the predetermined value and the compression ratio is set to the compression ratio at the start as it is. Only when this is done, the compression ratio of the internal combustion engine 1 is set to the compression ratio corresponding to the secondary air.

  Therefore, it is possible to suppress the compression ratio from being reduced unnecessarily, to promote exhaust purification and warm-up of the exhaust purification catalyst 30, and to suppress deterioration in fuel consumption due to a decrease in the compression ratio.

  Next, a third embodiment of the present invention will be described. In the present embodiment, the control for deriving the best compression ratio one by one for the atmospheric pressure around the vehicle of the internal combustion engine 1 to obtain the compression ratio corresponding to the secondary air will be described. Note that the internal combustion engine 1 and the intake / exhaust system in this embodiment are the same as those described in the first embodiment, and a description thereof will be omitted.

FIG. 7 shows a flowchart of the startup exhaust temperature raising routine 3 in the present embodiment. The difference between this routine and the start-up exhaust temperature raising routine described in the first embodiment is that the processes of S301 and S302 are added. That is, the atmospheric pressure around the vehicle is read in the process of S301. Specifically, the output of the pressure sensor 33 may be read into the ECU 35, or the atmospheric pressure may be estimated from the relationship between the output of an accelerator position sensor (not shown) and the output of the air flow meter 21. The pressure sensor 33 corresponds to the atmospheric pressure acquisition means in this embodiment. When the process of S301 ends, the process proceeds to S302.

  In S302, the secondary air compression ratio value corresponding to the atmospheric pressure value read in S301 is derived by reading from the secondary air compression ratio map. Here, the compression ratio map corresponding to the secondary air stores the relationship between the atmospheric pressure value and the compression ratio at which the HC and OC in the exhaust gas can be secondarily burned most efficiently in the atmospheric pressure state. It is a map and is experimentally obtained in advance.

  Specifically, the relationship is determined such that the lower the atmospheric pressure value, the lower the value of the compression ratio corresponding to the secondary air. This is because the amount of secondary air that can be supplied by the secondary air supply device 40 decreases as the atmospheric pressure around the vehicle on which the internal combustion engine 1 is mounted decreases, and the temperature of the exhaust from the internal combustion engine 1 also decreases. It corresponds to the decline. That is, the value of the compression ratio corresponding to the secondary air is made lower, the amount of unburned HC and CO is increased, the back pressure of the exhaust gas is lowered, and the secondary air from the secondary air supply device 40 is made easier. To be able to supply.

  Note that the relationship between the atmospheric pressure and the compression ratio corresponding to the secondary air in the compression ratio map corresponding to the secondary air may be determined to be a one-to-one relationship, or the compression corresponding to the secondary air may be performed according to the value of the atmospheric pressure. The ratio value may be determined so as to be divided into two or more stages, that is, a many-to-one relationship.

  If it is determined in S102 that the secondary air supply condition is satisfied, the secondary air supply is started in S103, and in S104, the compression ratio for the secondary air derived in S302 is set to the internal combustion engine. The compression ratio of 1 is changed.

  Then, the compression ratio of the internal combustion engine 1 can be changed to a compression ratio at which the effect of the secondary air supply can be maximized according to the atmospheric pressure, and the exhaust purification and the exhaust purification catalyst can be performed in any environment. The warm-up of 30 can be promoted more efficiently.

  In the start-up exhaust gas temperature raising routine 3 in the present embodiment, the optimum value for the compression ratio corresponding to the secondary air corresponding to the atmospheric pressure value read in S301 is derived. You may make it supply secondary air of the quantity according to the value of atmospheric pressure. Specifically, the amount of secondary air supplied is increased as the atmospheric pressure is lower. The amount of the secondary air may be derived by calculating the relationship between the atmospheric pressure and the required amount of the secondary air in advance by calculation or experiment, mapping it, and reading out the map.

  By doing so, it is possible to sufficiently secure the amount of oxygen that reacts with HC and CO in the exhaust gas regardless of the atmospheric pressure value, and to more reliably promote exhaust purification and warming of the exhaust purification catalyst. .

  The relationship between the atmospheric pressure and the amount of secondary air may be determined to be a one-to-one relationship, and the amount of secondary air is divided into two or more stages according to the value of atmospheric pressure. In other words, it may be determined to have a many-to-one relationship.

  In the above-described embodiment, the configuration in which the cylinder block is moved relative to the crankcase by rotating the cam shaft has been described as an example. However, the configuration to which the present invention is applied is not limited to the above. For example, the connecting rod is divided into two parts, a swing member that can swing around a predetermined swing center is connected to the connecting rod that is connected to the crankshaft, and the swing center moves by rotating the camshaft. Thus, the present invention may be applied to a configuration in which the volume of the combustion chamber and the stroke of the piston are changed.

Further, in the above-described embodiment, an example in which a three-way catalyst is used as the exhaust purification catalyst 30 has been described. However, other types of catalysts, such as an NOx storage reduction catalyst, may be used.
A filter that collects particulate matter in the exhaust gas may be included.

1 is an exploded perspective view showing a schematic configuration of an internal combustion engine according to an embodiment of the present invention. It is sectional drawing which shows progress which the cylinder block in the internal combustion engine which concerns on the Example of this invention moves relatively with respect to a crankcase. It is a figure for demonstrating the detail of the intake / exhaust system of the internal combustion engine which concerns on the Example of this invention. It is a figure for demonstrating that the purification rate of exhaust_gas | exhaustion raises, when the compression ratio falls in the internal combustion engine of this invention. It is a flowchart which shows the start time exhaust temperature raising routine which concerns on Example 1 of this invention. It is a flowchart which shows the start time exhaust temperature raising routine 2 which concerns on Example 2 of this invention. It is a flowchart which shows the start time exhaust temperature raising routine 3 which concerns on Example 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Cylinder block 4 ... Crankcase 9 ... Cam shaft 10 ... Gear 11a, 11b ... Worm gear 12 ... Motor 14 ... Secondary air supply pipe 18 ... intake branch pipe 19 ... intake pipe 20 ... throttle 21 ... air flow meter 28 ... exhaust branch pipe 29 ... exhaust pipe 30 ... exhaust purification catalyst 31 ... Crank position sensor 32 ... Cooling water temperature sensor 33 ... Pressure sensor 35 ... ECU
40 ... Secondary air supply device 41 ... Secondary air filter 42 ... Secondary air supply passage 43 ... Air pump (AP)
44 ... Air switching valve (ASV)
45 ... Reed valve (RV)
46 ... Pipe 47 ... Vacuum switching valve (VSV)

Claims (4)

A variable compression ratio mechanism for changing the compression ratio of the internal combustion engine by changing the volume of the combustion chamber of the internal combustion engine and / or the stroke of the piston;
An exhaust purification device that is provided in an exhaust passage through which exhaust from the internal combustion engine passes, and purifies the exhaust;
A secondary air supply device for supplying secondary air upstream of the exhaust purification device in the exhaust passage;
Compression ratio control means for controlling the compression ratio of the internal combustion engine to a predetermined compression ratio corresponding to the engine state by the variable compression ratio mechanism according to the operating state or warm-up state of the internal combustion engine;
A variable compression ratio internal combustion engine comprising:
In at least a part of a period during which secondary air is supplied from the secondary air supply device to the exhaust passage, the variable compression ratio mechanism causes the compression ratio of the internal combustion engine to be lower than the compression ratio corresponding to the engine state. A variable compression ratio internal combustion engine controlled to an air-compatible compression ratio. Atmospheric pressure acquisition means for detecting or estimating the atmospheric pressure around the vehicle on which the internal combustion engine is mounted;
When the atmospheric pressure detected or estimated by the atmospheric pressure acquisition means is below a predetermined value, the variable compression is performed at least during a period during which secondary air is supplied from the secondary air supply device to the exhaust passage. The variable compression ratio internal combustion engine according to claim 1, wherein the compression ratio of the internal combustion engine is controlled to the compression ratio corresponding to the secondary air by a ratio mechanism. Atmospheric pressure acquisition means for detecting or estimating the atmospheric pressure around the vehicle on which the internal combustion engine is mounted;
2. The variable compression ratio internal combustion engine according to claim 1, wherein the compression ratio corresponding to the secondary air is lowered as the atmospheric pressure detected or estimated by the atmospheric pressure obtaining unit is lower.   The variable compression according to claim 2 or 3, wherein the amount of secondary air supplied from the secondary air supply means is increased as the atmospheric pressure detected or estimated by the atmospheric pressure acquisition means is lower. Specific internal combustion engine.

Images