JP4998235B2 - Variable compression ratio internal combustion engine - Google Patents

Description

  The present invention relates to a variable compression ratio internal combustion engine.

  In recent years, techniques for changing the compression ratio of an internal combustion engine have been proposed for the purpose of improving the fuel efficiency and output performance of the internal combustion engine. As such a technique, for example, a cylinder block and a crankcase are connected so as to be relatively movable, a camshaft is provided at the connecting portion, and the camshaft is rotated to connect the cylinder block and the crankcase in the cylinder axial direction. There is a technique in which the volume of the combustion chamber is changed by relatively moving the internal combustion engine to change the compression ratio of the internal combustion engine (see, for example, Patent Document 1).

  Here, in the variable compression ratio internal combustion engine as disclosed in Patent Document 1, the relationship between the rotation angle of the drive motor and the compression ratio is not linear, and the change in the rotation angle of the drive motor is low in the low compression ratio region. The rate of change in compression ratio (hereinafter referred to as “compression ratio change rate”) is low. Therefore, in the variable compression ratio internal combustion engine disclosed in Patent Document 1, the rotational speed of the drive motor is basically increased in the low compression ratio region, and the rotational speed of the drive motor is decreased in the high compression ratio region. ing.

  Furthermore, in the variable compression ratio internal combustion engine disclosed in Patent Document 1, when the compression ratio of the internal combustion engine is changed to the target compression ratio in order to suppress overshoot due to over-rotation of the drive motor, the actual compression ratio is When the vicinity of the target compression ratio is reached, the rotational speed of the drive motor is reduced.

JP 2007-56837 A

  By the way, like the variable compression ratio internal combustion engine disclosed in Patent Document 1, the drive motor increases the rotation speed of the drive motor in the low compression ratio region and decreases the rotation speed of the drive motor in the high compression ratio region. When the rotation speed is controlled, it becomes slower for the compression ratio to reach the target compression ratio.

  On the other hand, in a region where the compression ratio change rate is high, the convergence of the compression ratio to the target compression ratio decreases when the rotational speed of the drive motor is fast. Conversely, in a region where the compression ratio change rate is low, the convergence of the compression ratio to the target compression ratio is high even if the rotational speed of the drive motor is high. Therefore, when changing the compression ratio toward the target compression ratio in the region where the compression ratio change rate is low, the convergence of the compression ratio to the target compression ratio is kept high even if the rotational speed of the drive motor is high. .

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a variable compression ratio internal combustion engine in which the responsiveness of the compression ratio is increased when the target compression ratio is in a region where the compression ratio change rate is low while maintaining the controllability of the compression ratio high. There is.

In order to solve the above-described problem, the first invention includes a variable compression ratio mechanism capable of changing the compression ratio of the internal combustion engine by rotating the actuator, and the rotation angle of the actuator is set according to the engine operating state. The actuator is controlled to achieve a target rotation angle corresponding to the target compression ratio, and when the rotation angle of the actuator is changed to the target rotation angle, the rotation speed of the actuator is set so that the compression ratio change speed is substantially constant. In the controlled variable compression ratio internal combustion engine, even when the rotation angle of the actuator is changed to the target rotation angle, if the target rotation angle is within the low compression ratio change rate region, the compression ratio change speed is actuator to vary is found rotated, when rotating the actuator so that the compression ratio variation speed varies The actuator is rotated at a higher rotational speed than the rotational speed as the compression ratio changing speed is substantially constant.
According to the first aspect of the invention, the rotational speed of the actuator is basically controlled so that the compression ratio change speed is substantially constant, so that the controllability of the compression ratio is maintained high. On the other hand, when the target rotation angle is within the low compression ratio change rate region, it is not necessary to keep the compression ratio change speed constant, so that the response of the compression ratio can be improved.

In order to solve the above problems, in the second invention, a variable compression ratio mechanism capable of changing the compression ratio of the internal combustion engine by rotating the actuator is provided, and the rotation angle of the actuator is set according to the engine operating state. The actuator is controlled to achieve a target rotation angle corresponding to the target compression ratio, and when the rotation angle of the actuator is changed to the target rotation angle, the rotation speed of the actuator is set so that the compression ratio change speed is substantially constant. In a controlled variable compression ratio internal combustion engine, even when the rotation angle of the actuator is changed to the target rotation angle, the target rotation angle is within the low compression ratio change rate region, and the rotation angle of the actuator is reduced. When it is necessary to change from the ratio change rate region to the low compression ratio change rate region via the high compression ratio change rate region, Contraction ratio change speed actuator to vary is found rotated, when rotating the actuator to change the compression ratio changing speed is faster rotational speed than the rotational speed as the compression ratio change speed is approximately constant With this, the actuator is rotated .

In the third invention, in the first or second invention, when the actuator is rotated at a rotational speed faster than the rotational speed at which the compression ratio change speed is substantially constant, the actuator is rotated at a constant rotational speed. It is done.

According to a fourth invention, in the third invention, a rotation speed is determined such that the compression ratio change speed is substantially constant for each rotation angle of the actuator, and the constant rotation speed corresponds to a target rotation angle. It is equal to the rotation speed determined as follows.

In a fifth aspect based on the third aspect , the constant rotational speed is a maximum rotational speed of the actuator.

In the sixth invention, in the first to fifth inventions, when the rotational speed of the actuator is controlled so that the compression ratio change speed is substantially constant, the compression ratio is within the low compression ratio region and the high compression ratio region. The rotation speed of the actuator when passing is made faster than the rotation speed of the actuator when the compression ratio passes through the middle compression ratio region.

  According to the present invention, the responsiveness of the compression ratio is increased when the target compression ratio is in a region where the compression ratio change rate is low while maintaining the controllability of the compression ratio high.

  Hereinafter, a variable compression ratio internal combustion engine according to a first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a side sectional view of a spark ignition type internal combustion engine.

  Referring to FIG. 1, 1 is a crankcase, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5 is a combustion chamber, 6 is a spark plug disposed at the center of the top surface of the combustion chamber 5, and 7 is an intake air 8 is an intake port, 9 is an exhaust valve, and 10 is an exhaust port. The intake port 8 is connected to a surge tank 12 via an intake branch pipe 11, and a fuel injection valve 13 for injecting fuel into the corresponding intake port 8 is arranged in each intake branch pipe 11. The fuel injection valve 13 may be arranged in each combustion chamber 5 instead of being attached to each intake branch pipe 11.

  The surge tank 12 is connected to an air cleaner 15 via an intake duct 14, and a throttle valve 17 driven by an actuator 16 and an intake air amount detector 18 using, for example, heat rays are arranged in the intake duct 14. On the other hand, the exhaust port 10 is connected to a catalytic converter 20 containing, for example, a three-way catalyst via an exhaust manifold 19, and an air-fuel ratio sensor 21 is disposed in the exhaust manifold 19.

  On the other hand, in the embodiment shown in FIG. 1, the piston 4 is positioned at the compression top dead center by changing the relative position of the crankcase 1 and the cylinder block 2 in the cylinder axis direction at the connecting portion between the crankcase 1 and the cylinder block 2. Is provided with a variable compression ratio mechanism A capable of changing the volume of the combustion chamber 5 when the engine is operated, and a variable valve timing capable of controlling the closing timing of the intake valve 7 in order to change the actual start timing of the compression action. A mechanism B is provided.

  The electronic control unit 30 is composed of a digital computer, and is connected to each other by a bidirectional bus 31. A ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a CPU (Microprocessor) 34, an input port 35 and an output port 36. It comprises. The output signal of the intake air amount detector 18 and the output signal of the air-fuel ratio sensor 21 are input to the input port 35 via the corresponding AD converters 37, respectively. A load sensor 41 that generates an output voltage proportional to the amount of depression of the accelerator pedal 40 is connected to the accelerator pedal 40, and the output voltage of the load sensor 41 is input to the input port 35 via the corresponding AD converter 37. The Further, a crank angle sensor 42 that generates an output pulse every time the crankshaft rotates, for example, 30 ° is connected to the input port 35. Further, the cylinder block 2 is provided with a relative position sensor 43 for detecting the relative position between the cylinder block 2 and the crankcase 1, and the output voltage of the relative position sensor 43 is passed through a corresponding AD converter 37. Input to the input port 35. On the other hand, the output port 36 is connected to the spark plug 6, the fuel injection valve 13, the throttle valve drive actuator 16, the variable compression ratio mechanism A, and the variable valve timing mechanism B through corresponding drive circuits 38.

  Next, the configuration of the variable compression ratio mechanism A of the present embodiment will be described with reference to FIGS. 2 is an exploded perspective view of the variable compression ratio mechanism A shown in FIG. 1, and FIG. 3 is a side sectional view of the internal combustion engine schematically shown.

  Referring to FIG. 2, a plurality of block-side protrusions 50 are formed below the both side walls of the cylinder block 2 so as to be spaced from each other. A cam insertion hole 51 is formed. These block side cam insertion holes 51 are formed on the same axis so as to be parallel to the arrangement direction of the cylinders.

  On the other hand, a plurality of case-side protrusions 52 are formed on the upper wall surface of the crankcase 1 so as to be fitted between the corresponding block-side protrusions 50 spaced apart from each other. Case-side cam insertion holes 53 each having a circular cross section are also formed in the portion 52. The case side cam insertion holes 53 are also formed on the same axis so as to be parallel to the cylinder arrangement direction, similarly to the block side cam insertion holes 51.

  As shown in FIG. 2, a pair of camshafts 54 and 55 are provided, and on the camshafts 54 and 55, every other one is rotatably inserted into each case-side cam insertion hole 53. A circular cam 56 is fixed. These case-side circular cams 56 are coaxial with the rotational axes of the camshafts 54 and 55. On the other hand, an eccentric shaft 57 arranged eccentrically with respect to the rotation axis of each camshaft 54, 55 extends between the case side circular cams 56, as shown in FIG. A circular cam 58 is eccentrically mounted for rotation. As shown in FIG. 2, these block-side circular cams 58 are arranged between the case-side circular cams 56, and these block-side circular cams 58 are rotatably inserted into the corresponding block-side cam insertion holes 51. ing.

  As shown in FIG. 2, a pair of worm gears 61, 62 having opposite spiral directions are attached to the rotation shaft 60 of the drive motor 59 in order to rotate the camshafts 54, 55 in opposite directions, respectively. Gears 63 and 64 that mesh with the worm gears 61 and 62 are fixed to end portions of the camshafts 54 and 55, respectively. In this embodiment, by driving the drive motor 59, the volume of the combustion chamber when the piston 4 is located at the compression top dead center can be changed over a wide range.

  Next, a method for changing the compression ratio by the variable compression ratio mechanism A having the above-described configuration will be described in detail with reference to FIGS. FIG. 4 is a diagram modeling the movement of the center of the case-side circular cam 56, the eccentric shaft 57, and the block-side circular cam 58. 3 and 4, a is the center of the case-side circular cam 56, b is the center of the eccentric shaft 57, and c is the center of the block-side circular cam 58. In this embodiment, the diameter of the block-side circular cam 58 is larger than the diameter of the case-side circular cam 56 as shown in FIG. The distance m between the center b of the eccentric shaft 57 is longer than the distance n between the center a of the case side circular cam 56 and the center b of the eccentric shaft 57.

  The drive motor 59 is driven from the state shown in FIGS. 3A and 4A, and the case-side circular cam 56 rotates in opposite directions as indicated by arrows in FIG. Accordingly, when the camshafts 54 and 55 are rotated, the eccentric shaft 57 moves downward around the center a of the case-side circular cam 56. As the eccentric shaft 57 moves, the block-side circular cam 58 is rotated in the direction opposite to the direction indicated by the arrow in FIG. When the case-side circular cam 56 rotates 90 ° from the state shown in FIGS. 3A and 4A, the state shown in FIGS. 3B and 4B is obtained.

  Further, when the drive motor 59 is driven to rotate the camshafts 54 and 55 to rotate the case-side circular cam 56 in opposite directions as indicated by arrows in FIG. It moves further downward about the center a of the side circular cam 56. As the eccentric shaft 57 moves, the block-side circular cam 58 is also rotated in the direction indicated by the arrow in FIG. When the case-side circular cam 56 rotates 90 ° from the state shown in FIGS. 3B and 4B, the state shown in FIGS. 3C and 4C is obtained.

  Here, the block-side circular cam 58 and the case-side circular cam 56 are accommodated in the block-side cam insertion port 51 and the case-side cam insertion port 53, respectively, and cannot move in a direction perpendicular to the cylinder axis. . Accordingly, the block-side circular cam 58 or the case-side circular cam 56 can be relatively moved only in a direction parallel to the cylinder axis. Therefore, the cams 56 and 58 are always positioned on the same straight line l parallel to the cylinder axis. To do. Accordingly, when the case-side circular cams 56 fixed on the camshafts 54 and 55 are rotated in opposite directions as shown by arrows in FIG. 3A from the state shown in FIG. The center c of the block-side circular cam 58 is moved downward so as to approach the center a of the case-side circular cam 56.

  3A to 3C, the relative position between the crankcase 1 and the cylinder block 2 is determined by the distance between the center a of the case-side circular cam 56 and the center c of the block-side circular cam 58. As the distance between the center a of the case-side circular cam 56 and the center c of the block-side circular cam 58 increases, the cylinder block 2 moves away from the crankcase 1. When the cylinder block 2 moves away from the crankcase 1, the volume of the combustion chamber 5 when the piston 4 is located at the compression top dead center increases. Therefore, the volume of the combustion chamber 5 when the piston 4 is located at the compression top dead center (hereinafter referred to as “combustion chamber volume”) can be changed by rotating the camshafts 54 and 55.

  Even if the volume of the combustion chamber 5 when the piston 4 is located at the compression top dead center is changed by rotating the camshafts 54 and 55 in this way, the stroke volume of the piston 4 during the compression stroke (the piston 4 The volume of the combustion chamber 5 that changes when moving from the intake bottom dead center to the compression top dead center does not change. Therefore, the compression ratio represented by (combustion chamber volume + stroke volume) / combustion chamber volume changes according to the change of the combustion chamber volume. That is, according to the variable compression ratio mechanism A of the present embodiment, the compression ratio of the internal combustion engine can be changed by rotating the camshafts 54 and 55 by the drive motor 59.

  The variable compression ratio mechanism A shown in FIGS. 1 to 4 is an example, and any type of variable compression ratio mechanism can be used as long as the compression ratio can be changed by driving an actuator such as a drive motor. Can be used.

  By the way, in the internal combustion engine having the variable compression ratio mechanism A configured as described above, the rotation angle of the camshafts 54 and 55 or the drive motor 59 and the compression ratio are not proportional. Below, this reason is demonstrated easily. In this specification, the relationship between the rotation angle of the camshafts 54 and 55 and the compression ratio will be described as an example, but the same applies to the relationship between the rotation angle of the drive motor 59 and the compression ratio.

図５はｍ：ｎを２：１とした場合における回転角度θに対する相対距離Ｌを示す図である。図５からわかるように、カムシャフト５４、５５の回転角度θに対して相対距離Ｌは比例しない。 Referring to the model shown in FIG. 4, the camshaft 54 from the state shown in FIGS. 3A and 4A (that is, the state where the centers a, b, and c are on the straight line l), When the rotation angle of 55 is θ, the relative distance L of the cylinder block 3 with respect to the crankcase 1 is expressed by the following formula (1).

FIG. 5 is a diagram showing the relative distance L with respect to the rotation angle θ when m: n is 2: 1. As can be seen from FIG. 5, the relative distance L is not proportional to the rotation angle θ of the camshafts 54 and 55.

In the model as shown in FIG. 6A, the compression ratio ε is expressed by the following equation (2) using the height h of the combustion chamber 5 determined according to the relative distance L and the stroke s of the piston 4. It is expressed as follows.
ε = ((π · (D / 2) ² · (h + s) / (π · (D / 2) ² · h)
= (H + s) / h (2)

  As shown in FIG. 6B, the rate of change of the compression ratio ε with respect to the change in the height h increases as the compression ratio becomes higher and the height h of the combustion chamber 5 becomes smaller. That is, the compression ratio ε does not change in proportion to the height of the combustion chamber 5.

  Due to the synergistic effect of these two principles, the rotation angle of the camshafts 54 and 55 and the compression ratio are not proportional. Specifically, the relationship between the rotation angle θ of the camshafts 54 and 55 and the compression ratio ε is as shown in FIG. 7A, for example, and the compression ratio ε per unit rotation angle of the camshafts 54 and 55 is The amount of change (hereinafter referred to as “compression ratio change rate”) is as shown in FIG. That is, when the rotation angle θ of the camshafts 54 and 55 is small, that is, when the compression ratio is low, and when the rotation angle θ of the camshafts 54 and 55 is large, that is, when the compression ratio is high, the compression ratio change rate is small. Conversely, when the rotation angle θ of the camshafts 54 and 55 is around 90 °, that is, when the compression ratio is medium, the compression ratio change rate is large. FIG. 7 shows the relationship between the rotation angle, the compression ratio, and the compression ratio change rate when m: n is 2: 1, but it is also fundamental when m: n is set to other ratios. A similar tendency is observed.

  As described above, when the compression ratio change rate varies according to the rotation angle θ of the camshafts 54 and 55, that is, according to the compression ratio, it becomes difficult to appropriately control the internal combustion engine when the compression ratio is changed. For example, when the compression ratio is changed, the intake air amount supplied into the combustion chamber 5 is also changed accordingly. In order to stabilize the engine operating state during the change of the compression ratio and the intake air amount, the compression ratio is changed. It is necessary to change the amount of intake air in accordance with the change of. However, when the compression ratio change rate varies according to the rotation angle of the camshafts 54 and 55, for example, if the rotation speed of the camshafts 54 and 55 is constant, the compression ratio change speed is not constant. For this reason, it becomes difficult to change the amount of intake air supplied into the combustion chamber 5 in accordance with the change in the compression ratio.

  Therefore, in the embodiment of the present invention, even if the compression ratio change rate fluctuates according to the rotation angle θ of the camshafts 54 and 55, the camshaft 54 so that the compression ratio change speed is constant (inversely proportional). , 55 is controlled.

  FIG. 8 shows the relationship between the rotation angle θ of the camshafts 54 and 55, the compression ratio change rate and the rotation angle, and the rotation angle θ of the camshafts 54 and 55 and the compression ratio change speed with respect to time. The solid line in the figure indicates the rotation angle θ of the camshafts 54 and 55, and the broken line indicates the compression ratio change rate.

  As shown by the solid lines in FIGS. 7B and 8, the compression ratio change rate with respect to the change in the rotation angle of the camshafts 54 and 55 is when the rotation angle of the camshafts 54 and 55 is small or large, that is, compression. The ratio ε is small when it is in the low compression ratio region or the high compression ratio region, while it is large when the rotation angle of the camshafts 54 and 55 is medium, that is, when the compression ratio ε is in the medium compression ratio region. In the embodiment of the present invention, the rotational speeds of the camshafts 54 and 55 are controlled to be inversely proportional to the compression ratio change rate. Therefore, when the compression ratio change rate is small, the rotational speeds of the camshafts 54 and 55 are increased. When the compression ratio change rate is high, the rotational speed of the camshafts 54 and 55 is slowed down. In other words, in the embodiment of the present invention, when the rotation angle of the camshafts 54 and 55 is small or large, that is, the compression ratio ε is within the low compression ratio region or the high compression ratio so that the compression ratio changing speed is constant. When the camshafts 54 and 55 are within the region, the rotational speed of the camshafts 54 and 55 is increased. Conversely, when the rotational angle of the camshafts 54 and 55 is medium, that is, when the compression ratio ε is within the medium compression ratio region, The rotational speed of 55 is slowed down.

  In particular, in the embodiment of the present invention, since the variable compression ratio mechanism A is configured as shown in FIGS. 2 to 4, as the rotation angle of the camshafts 54 and 55 increases, the compression ratio change rate becomes the first. Gradually increases and then gradually decreases. For this reason, as the rotation angle of the camshafts 54 and 55 increases, the rotation speed gradually decreases gradually first and then gradually increases.

  Thus, in the embodiment of the present invention, by controlling the rotational speed of the camshafts 54 and 55 as described above, the compression ratio is independent of the rotational angle of the camshafts 54 and 55, that is, regardless of the compression ratio. The rate of change can be made almost constant. As a result, the internal combustion engine can be appropriately controlled even when the compression ratio is changed.

  By the way, if the compression ratio change speed is controlled to be constant, the response of the actual compression ratio to the target compression ratio may be reduced. Such a tendency is from the middle compression ratio region to the lower compression ratio region or the higher compression ratio region than when the compression ratio is changed from the low compression ratio region or the high compression ratio region to the middle compression ratio region. The case of changing is more prominent. The reason will be described below.

  First, if there is a target compression ratio in a region where the compression ratio change rate is high (for example, a region where the compression ratio change rate region is higher than a specific change rate, hereinafter referred to as a “high compression ratio change rate region”), this target If the rotational speed of the camshafts 54 and 55 is fast when going to the compression ratio, the compression ratio will not easily converge to the target compression ratio. This is because, in the high compression ratio change rate region, if there is a slight deviation between the actual rotation angle and the target rotation angle, a large deviation occurs between the actual compression ratio and the target compression ratio. It is. Therefore, when the target compression ratio is in the high compression ratio change rate region, that is, in the medium compression ratio region, the rotation angle of the camshafts 54 and 55 is changed to the target rotation angle corresponding to this target compression ratio. In this case, it is preferable that the rotational speed of the camshafts 54 and 55 is initially increased and gradually decreased as it approaches the target rotational angle.

  Conversely, if the target compression ratio is within a region where the compression ratio change rate is low (for example, a region where the compression ratio change rate is lower than the specific change rate, hereinafter referred to as a “low compression ratio change rate region”), Even when the rotational speed of the camshafts 54 and 55 is high when moving toward the target compression ratio, the compression ratio easily converges to the target compression ratio. In the low compression ratio change rate region, even if there is a slight deviation between the actual rotation angle and the target rotation angle, there is almost no deviation between the actual compression ratio and the target compression ratio. Because. Therefore, when the target compression ratio is in the low compression ratio change rate region, that is, in the low compression ratio region or the high compression ratio region, the rotation angle of the camshafts 54 and 55 corresponds to this target compression ratio. When changing to the target rotation angle, the rotation speed of the camshafts 54 and 55 is preferably kept relatively high until reaching the vicinity of the target rotation angle.

  Here, when the target compression ratio is in the middle compression ratio region, the rotation angle of the camshafts 54 and 55 corresponds to this target compression ratio by controlling the compression ratio change speed to be constant as described above. When changing to the target rotation angle, the rotation speed of the camshafts 54 and 55 can be initially increased and gradually decreased as the position approaches the target rotation angle. On the other hand, when the target compression ratio is in the low compression ratio region or the high compression ratio region, if the compression ratio change speed is controlled to be constant as described above, the rotation angle of the camshafts 54 and 55 is set to this value. When changing to the target rotation angle corresponding to the target compression ratio, the rotation speed of the camshafts 54 and 55 is initially slowed down and gradually increased as it approaches the target rotation angle.

  Therefore, in the embodiment of the present invention, when the target compression ratio is in the low compression ratio change rate region, that is, in the low compression ratio region or the high compression ratio region, the compression ratio change rate is constant. It is supposed to be allowed to fluctuate.

  FIG. 9 shows the relationship between the rotation angle of the cam shafts 54 and 55 and the rotation speed, and the relationship between the rotation angle of the cam shafts 54 and 55 and the compression ratio change speed. In FIG. 9, the transition of the rotational speed and the compression ratio change speed (X in the figure) when the compression ratio is changed from the compression ratio in the low compression ratio region to the compression ratio in the medium compression ratio region, and the compression ratio Shows the transition (Y in the figure) of the rotational speed and the compression ratio change speed when the compression ratio in the medium compression ratio region is changed to the compression ratio in the low compression ratio region. Also, the broken line in FIG. 9A shows a curve (hereinafter referred to as “constant change speed maintenance curve”) representing the rotational speed of the camshafts 54 and 55 for changing the compression ratio change speed at a predetermined constant speed. The broken line in FIG. 9B shows the transition of the compression ratio change speed when the rotation speed of the camshafts 54 and 55 is changed on the constant change speed maintenance curve.

  In the case shown by X in FIG. 9, that is, when the current compression ratio is in the low compression ratio region and the target compression ratio is in the medium compression ratio region, the rotation angle of the camshafts 54, 55 is in the low compression ratio region. The rotation angle α corresponding to the predetermined compression ratio is changed to the target rotation angle β corresponding to the target compression ratio in the intermediate compression ratio region. That is, the rotation angle of the camshafts 54 and 55 is within the region (high compression ratio change rate region) where the compression ratio change rate is high from the rotation angle α in the region (low compression ratio change rate region) where the compression ratio change rate is low. The rotation angle β is changed.

  In this case, as shown in FIG. 9A, the camshafts 54 and 55 are rotated at the rotation speed on the constant change speed maintenance curve when the rotation angle α is changed to the rotation angle β. Accordingly, as shown in FIG. 9B, the compression ratio change speed is kept constant until the camshafts 54 and 55 are changed from the rotation angle α to the rotation angle β.

  On the other hand, in the case indicated by Y in FIG. 9, that is, when the current compression ratio is in the medium compression ratio region and the target compression ratio is in the low compression ratio region, the rotation angle of the camshafts 54 and 55 is medium compression. The rotation angle β corresponding to the predetermined compression ratio in the ratio region is changed to the target rotation angle α corresponding to the target compression ratio in the low compression ratio region. That is, the rotation angle of the camshafts 54 and 55 is changed from the rotation angle β in the high compression ratio change rate region to the rotation angle α in the low compression ratio change rate region.

  In this case, as shown in FIG. 9A, the camshafts 54 and 55 are not rotated at the rotation speed on the constant change speed maintenance curve when changing from the rotation angle β to the rotation angle α. It can be rotated at a rotational speed faster than the rotational speed on the change speed maintenance curve. As a result, as shown in FIG. 9B, when the camshafts 54 and 55 are changed from the rotation angle β to the rotation angle α, the compression ratio change speed is not kept constant, and the compression ratio change speed is kept constant. It is assumed that it is faster than the case where it is maintained.

In particular, in the illustrated embodiment, when the camshafts 54 and 55 are changed from the rotation angle α to the rotation angle β, the camshafts 54 and 55 are constantly rotated at the rotation speed V ₁ corresponding to the target rotation angle α in the constant change speed maintenance curve. .

  Thus, in the embodiment of the present invention, when the target compression ratio is in the medium compression ratio region, that is, when the target rotation angle is in the high compression ratio change rate region, the compression ratio change speed is constant. Thus, the rotation of the camshafts 54 and 55 is controlled, thereby improving the controllability of the compression ratio, and accordingly, the internal combustion engine can be appropriately controlled. On the other hand, when the target compression ratio is in the low compression ratio region or the high compression ratio region, that is, when the target rotation angle is in the low compression ratio change rate region, the rotational speed of the camshafts 54 and 55 is increased. This improves the response of the compression ratio. That is, according to the embodiment of the present invention, it is possible to appropriately achieve both responsiveness and controllability of the compression ratio.

  FIG. 10 is a view similar to FIG. 9 showing the relationship between the rotation angle and the rotation speed of the camshafts 54 and 55 and the relationship between the rotation angle of the camshafts 54 and 55 and the compression ratio change speed. In FIG. 10, when the compression ratio is changed from the low compression ratio region to the high compression ratio region, the transition of the rotational speed and the compression ratio change speed (X in the figure) and the compression ratio is within the high compression ratio region. 7 shows the transition of the rotation angle and the compression ratio change speed (Y in the figure) in the case where the rotation ratio is changed into the low compression ratio region. Further, the broken line in FIG. 10 (A) shows a constant rate of change maintenance curve similarly to the broken line in FIG. 9 (A), while the broken line in FIG. 10 (B) is in FIG. 9 (B). Similarly to the broken line, the change of the compression ratio change speed when the rotation speed of the camshafts 54 and 55 is maintained on the constant change speed maintenance curve is shown.

  In the case indicated by X in FIG. 10, that is, when the current compression ratio is in the low compression ratio region and the target compression ratio is in the high compression ratio region, the rotation angle of the camshafts 54 and 55 is the current low compression ratio. The rotation angle α corresponding to the predetermined compression ratio in the ratio region is changed to the target rotation angle γ corresponding to the target compression ratio in the high compression ratio region. That is, the rotation angle of the camshafts 54 and 55 is changed from the rotation angle α in the high compression ratio change rate region to the rotation angle γ in the high compression ratio change rate region with the low compression ratio change rate region interposed therebetween.

  In this case, as shown in FIG. 10A, the camshafts 54 and 55 are not rotated at the rotation speed on the constant change speed maintenance curve when changing from the rotation angle α to the rotation angle γ. It can be rotated at a rotational speed faster than the rotational speed on the change speed maintenance curve. As a result, as shown in FIG. 10B, when the camshafts 54 and 55 are changed from the rotation angle α to the rotation angle γ, the compression ratio change speed is not maintained constant. The compression ratio change speed is faster than the constant compression ratio change speed indicated by the broken line.

  When Y is shown in FIG. 10, that is, when the current compression ratio is in the high compression ratio region and the target compression ratio is in the low compression ratio region, the rotation angle of the camshafts 54 and 55 is the current high compression ratio. The rotation angle γ corresponding to the predetermined compression ratio in the ratio region is changed to the target rotation angle α corresponding to the target compression ratio in the low compression ratio region. That is, the rotation angle of the camshafts 54 and 55 is changed from the rotation angle γ in the high compression ratio change rate region to the rotation angle α in the high compression ratio change rate region with the low compression ratio change rate region interposed therebetween.

  In this case, when the camshafts 54 and 55 are changed from the rotation angle γ to the rotation angle α as shown in FIG. 10A, the constant change speed is maintained as in the case indicated by X in FIG. It can be rotated at a rotational speed faster than the rotational speed on the curve. As a result, as shown in FIG. 10B, even when the camshafts 54 and 55 are changed from the rotation angle γ to the rotation angle α, the compression ratio change speed is indicated by a broken line in FIG. The compression ratio change speed is faster than the constant compression ratio change speed.

  Thus, when the target compression ratio is in the low compression ratio region or the high compression ratio region, that is, when the target rotation angle is in the low compression ratio change rate region, the current rotation angle and the target rotation angle are Even if there is a high compression ratio change rate region between them, the rotational speed of the camshafts 54 and 55 is increased, thereby improving the response of the compression ratio.

  FIG. 11 is a flowchart of a control routine of rotation angle control in the embodiment of the present invention. The illustrated control routine is performed by interruption at regular time intervals.

  Referring to FIG. 11, first, in step S11, the target compression ratio εt is calculated by the ECU 30 based on the engine operating state and the like. In particular, in the present embodiment, the target compression ratio εt is calculated based on the engine load, the engine speed, the closing timing of the intake valve 7, the opening degree of the throttle valve 17, and the like. Next, in step S12, the target rotation angle θt is calculated from the map as shown in FIG. 7A based on the target compression ratio εt calculated in step S11.

  Next, in step S13, it is determined whether or not the current rotation angle θ of the camshafts 54 and 55 is a value near the target rotation angle θt. Immediately after the engine operating state has changed significantly and the target compression ratio has changed, and the target rotational angle has suddenly changed accordingly, the current rotational angle θ has a value that is significantly different from the target rotational angle θt. In such a case, the process proceeds to step S14.

  In step S14, it is determined whether or not the target rotation angle θt is within the low compression ratio change rate region. If it is determined that the target rotation angle θt is in the low compression ratio change rate region, that is, if it is determined that the target compression ratio is in the low compression ratio region or the high compression ratio region, the process proceeds to step S15. move on. In step S15, a rotation speed Vθt corresponding to the target rotation angle θt in the constant change speed maintenance curve is calculated based on the map as shown in FIG. Next, in step S16, the drive motor 59 is driven so that the camshafts 54 and 55 rotate at the rotational speed Vθt calculated in step S15.

  On the other hand, when it is determined in step S14 that the target rotation angle θt is in a region where the compression ratio change rate is high (hereinafter referred to as “high compression ratio change rate region”), that is, the target compression ratio is in the medium compression ratio region. If it is determined that there is, the process proceeds to step S17. In step S17, a rotational speed Vθ corresponding to the current rotational angle θ in the constant change speed maintenance curve is calculated based on the map as shown in FIG. Next, in step S18, the drive motor 59 is driven so that the camshafts 54 and 55 rotate at the rotational speed Vθ calculated in step S17.

  Thereafter, when the rotation angle θ of the camshafts 54 and 55 approaches the target rotation angle θt, in the next control routine, in step S13, the current rotation angle θ of the camshafts 54 and 55 is a value in the vicinity of the target rotation angle θt. It progresses to step S19. In step S19, the drive motor is driven so that the camshafts 54 and 55 rotate at a rotation speed Vθl lower than the rotation speed Vθt corresponding to the target rotation angle θt at least in the constant change speed maintenance curve. As a result, when the rotation angle θ of the camshafts 54 and 55 reaches the vicinity of the target rotation angle θt, the rotation speed of the camshafts 54 and 55 is reduced, so that the rotation angle θ of the camshafts 54 and 55 converges to the target rotation angle θt. It becomes easy to do.

  In the control shown in the flowchart, the rotation speed of the camshafts 54 and 55 is decreased when the rotation angle θ of the camshafts 54 and 55 reaches the vicinity of the target rotation angle θt. There is no need to do.

  Further, in the above embodiment, when the target compression ratio is in the low compression ratio region and the high compression ratio region, it corresponds to the target rotation angle in the constant change speed maintenance curve as shown in FIGS. 9 and 10. The camshafts 54 and 55 are rotated at the rotational speed. However, it is not always necessary to rotate the camshafts 54 and 55 at this rotational speed. For example, when the target compression ratio is in the low compression ratio region or the high compression ratio region, the camshafts 54 and 55 are determined in advance regardless of the target rotation angle. The camshafts 54 and 55 may be rotated at a constant high rotational speed (for example, the maximum rotational speed of the drive motor 59).

  Moreover, in the said embodiment, although the rotation angle of the cam shafts 54 and 55 is controlled, you may make it control the rotation angle of the drive motor 59, ie, an actuator.

1 is an overall view of a spark ignition internal combustion engine. It is a disassembled perspective view of a variable compression ratio mechanism. 1 is a schematic side sectional view of an internal combustion engine. It is the figure which modeled the motion of the center of a block side circular cam, an eccentric shaft, and a case side circular cam. It is a figure which shows the relative distance with respect to a rotation angle. It is a figure for demonstrating the relationship between the height of a combustion chamber, and a compression ratio. It is a figure which shows the relationship between a rotation angle, a compression ratio, and a compression ratio change rate. It is a figure which shows the relationship between a rotation angle, a rotation speed, and a compression ratio change speed. It is a figure which shows transition of a rotational speed and a compression ratio change speed. It is a figure which shows transition of a rotational speed and a compression ratio change speed. It is a flowchart which shows the control routine of rotation angle control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Crankcase 2 Cylinder block 3 Cylinder head 4 Piston 5 Combustion chamber 7 Intake valve 54, 55 Camshaft 56 Case side circular cam 57 Eccentric shaft 58 Block side circular cam 59 Drive motor 63, 64 Gear A Variable compression ratio mechanism B Variable valve Timing mechanism

Claims (6)

A variable compression ratio mechanism capable of changing the compression ratio of the internal combustion engine by rotating the actuator is provided so that the rotation angle of the actuator becomes a target rotation angle corresponding to a target compression ratio set according to the engine operating state. In the variable compression ratio internal combustion engine, in which the rotation speed of the actuator is controlled so that the compression ratio change speed is substantially constant when the rotation angle of the actuator is changed to the target rotation angle.
Even when changing the rotational angle of the actuator to the target rotation angle, target rotational angle in the case where a low compression ratio change rate region actuator so that the compression ratio variation speed varies is found rotated,
A variable compression ratio internal combustion engine in which when the actuator is rotated so that the compression ratio change speed fluctuates, the actuator is rotated at a rotational speed faster than a rotational speed at which the compression ratio change speed is substantially constant . A variable compression ratio mechanism capable of changing the compression ratio of the internal combustion engine by rotating the actuator is provided so that the rotation angle of the actuator becomes a target rotation angle corresponding to a target compression ratio set according to the engine operating state. In the variable compression ratio internal combustion engine, in which the rotation speed of the actuator is controlled so that the compression ratio change speed is substantially constant when the rotation angle of the actuator is changed to the target rotation angle.
Even when the actuator rotation angle is changed to the target rotation angle, the target rotation angle is in the low compression ratio change rate region, and the actuator rotation angle is changed from the low compression ratio change rate region to the high compression ratio change rate. If it is necessary to change to a low compression ratio change rate region via the region, the actuator so that the compression ratio variation speed varies is found rotated,
A variable compression ratio internal combustion engine in which when the actuator is rotated so that the compression ratio change speed fluctuates, the actuator is rotated at a rotational speed faster than a rotational speed at which the compression ratio change speed is substantially constant . 3. The variable compression ratio internal combustion engine according to claim 1, wherein when the actuator is rotated at a rotational speed faster than a rotational speed at which the compression ratio change speed becomes substantially constant, the actuator is rotated at a constant rotational speed. . The rotation speed is determined such that the compression ratio change speed is substantially constant for each rotation angle of the actuator, and the constant rotation speed is equal to a rotation speed determined in accordance with a target rotation angle. 3. The variable compression ratio internal combustion engine according to 3. The variable compression ratio internal combustion engine according to claim 3 , wherein the constant rotational speed is a maximum rotational speed of the actuator. When the rotational speed of the actuator is controlled so that the compression ratio change speed is substantially constant, the rotational speed of the actuator when the compression ratio passes through the low compression ratio region and the high compression ratio region is the medium compression ratio. The variable compression ratio internal combustion engine according to any one of claims 1 to 5 , wherein the internal combustion engine is set to be faster than a rotational speed of the actuator when passing through the region.

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