JP5278286B2 - Variable compression ratio system for internal combustion engines - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To further improve the vibration reduction effect of an internal combustion engine, in a variable compression ratio system which changes the compression ratio of the internal combustion engine by relatively displacing a cylinder block and a crankcase in a cylinder axis direction. <P>SOLUTION: The variable compression ratio system of the internal combustion engine changes the compression ratio by changing the position of the cylinder block with respect to the crankcase in the cylinder axis direction. When the position of the cylinder block with respect to the crankcase is changed, the change of the center-of-mass position of the internal combustion engine is controlled by displacing the balance weight to the reverse direction of the cylinder block in the cylinder axis direction. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a technique for changing a compression ratio by relatively displacing a cylinder block and a crankcase in a cylinder axial direction.

  As a system for changing a mechanical compression ratio of an internal combustion engine, a system for changing a combustion chamber volume by relatively displacing a cylinder block and a crankcase in a cylinder axial direction is known.

  In the internal combustion engine provided with the variable compression ratio system as described above, the cylinder block and the crankcase are not fixed integrally, and thus there is a case where specific vibration is generated. On the other hand, in an internal combustion engine equipped with a variable compression ratio system, a technique for providing a rotary balance weight has been proposed (see, for example, Patent Document 1).

JP 2006-207505 A JP 2006-144614 A JP 2008-144720 A

  An object of the present invention is to increase the vibration reduction effect of an internal combustion engine in a variable compression ratio system that changes the compression ratio of the internal combustion engine by relatively displacing the cylinder block and the crankcase in the cylinder axial direction.

The present invention employs the following means in order to solve the above-described problems. That is, the present invention provides a variable compression ratio system for an internal combustion engine that changes the compression ratio by displacing the cylinder block and the crankcase in the cylinder axial direction.
A variable compression ratio mechanism that changes the position of the cylinder block relative to the crankcase in the cylinder axial direction;
When the variable compression ratio mechanism displaces the position of the cylinder block, a balance weight that is displaced in the direction opposite to the cylinder block in the cylinder axis direction;
I was prepared to.

  When the cylinder block and the crankcase are relatively displaced in the cylinder axis direction, the position of the center of mass of the internal combustion engine also changes. When the center of mass position of the internal combustion engine changes, the resonance frequency of the mechanism (engine mount) that supports the internal combustion engine changes. As a result, depending on the relative position between the cylinder block and the crankcase, the engine mount may not be able to completely attenuate the vibration of the internal combustion engine.

  On the other hand, a method of attaching a rotary balance weight to the internal combustion engine is conceivable. According to this method, the vibration generated by the internal combustion engine can be reduced, but there is a possibility that a change in the resonance frequency of the engine mount cannot be suppressed.

Accordingly, the variable compression ratio system for an internal combustion engine according to the present invention is provided with a balance weight that is displaced in the direction opposite to the cylinder block in the cylinder axial direction when the compression ratio of the internal combustion engine is changed.

  According to this invention, since the amount of change in the center of mass position of the internal combustion engine is reduced, the amount of change in the resonance frequency of the engine mount is also reduced. As a result, the vibration characteristics of the internal combustion engine fall within a range where the engine mount can be attenuated. Therefore, the vibration reduction effect of the internal combustion engine by the engine mount can be enhanced.

  Note that the amount of displacement of the balance weight may be determined so that the center of mass position of the internal combustion engine is maintained at a constant position. In this case, if the relationship between the position of the cylinder block (or displacement) and the position of the balance weight (or displacement) is obtained experimentally in advance under the condition that the center of mass position of the internal combustion engine is kept constant. Good. When the position of the balance weight is determined in this way, the resonance frequency of the engine mount can be maintained at a constant frequency. Therefore, even when the compression ratio changes, the vibration of the internal combustion engine can be attenuated by the engine mount.

  ADVANTAGE OF THE INVENTION According to this invention, the vibration reduction effect of an internal combustion engine can be heightened in the variable compression ratio system which changes the compression ratio of an internal combustion engine by relatively displacing a cylinder block and a crankcase in a cylinder axial direction.

1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. It is a figure which shows schematic structure of a variable compression ratio mechanism. It is a figure which shows the mechanism which displaces a balance weight. It is a figure which shows the change of the mass center position accompanying the change of a compression ratio. It is a figure which shows the displacement of the balance weight accompanying the change of a compression ratio. It is a figure which shows an example of the map which prescribed | regulated the relationship between compression ratio (epsilon) and displacement amount (DELTA) i of a balance weight. It is a flowchart which shows the control routine which ECU performs when changing a compression ratio.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention to those unless otherwise specified.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. An internal combustion engine 1 shown in FIG. 1 is a spark ignition type internal combustion engine (gasoline engine) in which a mechanical compression ratio (combustion chamber volume) is changed by relative displacement of a cylinder block 2 and a crankcase 3 in a cylinder axial direction. is there. The internal combustion engine 1 may be a compression ignition type internal combustion engine (diesel engine).

  The internal combustion engine 1 includes a cylinder block 2 and a crankcase 3 that are connected so as to be relatively displaceable in the cylinder axial direction. A cylinder head 4 is fixed to the cylinder block 2. The crankcase 3 is supported by the vehicle body 200 via the engine mount 50.

A cylinder (cylinder) 5 is formed in the cylinder block 2. A piston 6 is loaded in the cylinder 5 so as to be slidable in the cylinder axial direction. A crankshaft 7 is rotatably supported on the crankcase 3. The piston 6 and the crankshaft 7 are connected via a connecting rod 8.

  The cylinder head 4 is provided with an intake port 9 and an exhaust port 10 that communicate with the cylinder 5. The cylinder head 4 is provided with an intake valve 11 for opening and closing the opening end of the intake port 9 and an exhaust valve 12 for opening and closing the opening end of the exhaust port 10. The intake valve 11 is driven to open and close by an intake camshaft 13 that is rotatably supported by the cylinder head 4. The exhaust valve 12 is driven to open and close by an exhaust camshaft 14 that is rotatably supported by the cylinder head 4. In addition, a fuel injection valve 15 that injects fuel into the intake port 9 and a spark plug 16 that generates a spark in the cylinder 5 are attached to the cylinder head 4.

  Next, a variable compression ratio mechanism 100 for displacing the cylinder block 2 in the cylinder axial direction with respect to the crankcase 3 is provided at a connecting portion between the cylinder block 2 and the crankcase 3. As shown in FIG. 2, the variable compression ratio mechanism 100 includes a shaft portion 101 and a cam portion having a regular circular cam profile fixed to the shaft portion 101 in a state of being eccentric with respect to the central axis of the shaft portion 101. 102, a movable bearing portion 103 having the same outer shape as the cam portion 102 and capable of rotating with respect to the shaft portion 101 and mounted in an eccentric state in the same manner as the cam portion 102, and provided concentrically with the shaft portion 101. A mechanism including a worm wheel 104, a worm 105 that meshes with the worm wheel 104, and a motor 106 that rotationally drives the worm 105 can be used. The cam portion 102 is installed in a storage hole provided in the cylinder block 2, and the movable bearing portion 103 is installed in a storage hole provided in the crankcase 3. The motor 106 is fixed to the cylinder block 2 and is displaced integrally with the cylinder block 2.

  According to the variable compression ratio mechanism 100 configured as described above, the power of the motor 106 is transmitted to the shaft portion 101 via the worm 105 and the worm wheel 104, and the cam portion 102 and the movable bearing portion 103 in the eccentric state are transmitted. Is driven. As a result, the cam portion 102 and the movable bearing portion 103 are relatively displaced in the cylinder axial direction, and accordingly, the cylinder block 2 and the crankcase 3 are also relatively displaced in the cylinder axial direction.

  Here, when the cylinder block 2 moves away from the crankcase 3 in the cylinder axial direction, the combustion chamber volume increases, and therefore the mechanical compression ratio (the value obtained by dividing the sum of the stroke volume and the combustion chamber volume by the combustion chamber volume) is low. Become. On the other hand, when the cylinder block 2 approaches the crankcase 3 in the cylinder axial direction, the volume of the combustion chamber is reduced and the mechanical compression ratio is increased.

  Returning to FIG. 1, the crankcase 3 is provided with an oil pan 30 for storing lubricating oil (oil) of the internal combustion engine 1. A balance weight 300 is disposed inside the oil pan 30 so as to be freely displaceable in the cylinder axial direction. Further, an actuator 301 for displacing the balance weight 300 in the cylinder axial direction is attached to the oil pan 30.

  As a mechanism for displacing the balance weight 300 in the cylinder axis direction, as shown in FIG. 3, a rack 302 standing in the cylinder axis direction with respect to the balance weight 300, a pinion gear 303 meshing with the rack 302, A mechanism including a motor (actuator) 301 that rotates the pinion gear 303 can be used.

  Returning to FIG. 1, the internal combustion engine 1 configured as described above includes an electronic device for electrically controlling various devices such as the fuel injection valve 15, the spark plug 16, the variable compression ratio mechanism 100, and the actuator 301. A control unit (ECU) 17 is also provided.

  The ECU 17 is a unit including a CPU, a ROM, a RAM, a backup RAM, and the like, and electric signals from various sensors such as a crank position sensor 18, an accelerator position sensor 19, and a lift sensor 20 are input thereto. The crank position sensor 18 is a sensor that is disposed in the vicinity of the crankshaft 7 and outputs a pulse signal correlated with the rotational position of the crankshaft 7. The accelerator position sensor 19 is a sensor that outputs a signal correlated with the amount of operation of the accelerator pedal (accelerator opening). The lift sensor 20 is disposed in the crankcase 3 in the vicinity of the connecting portion with the cylinder block 2 and is correlated with the lift amount of the cylinder block 2 relative to the crankcase 3 (the displacement amount toward the top dead center side in the cylinder axis direction). It is a sensor that outputs a signal.

  ECU17 discriminate | determines the driving | running state (engine driving | running state) of the internal combustion engine 1 according to the electric signal of above-mentioned various sensors, and controls the above-mentioned various apparatuses according to the discrimination | determination result. For example, the ECU 17 controls the variable compression ratio mechanism 100 based on the engine speed and the engine load determined from the output signals of the crank position sensor 18 and the accelerator position sensor 19.

  At this time, when the engine speed and the engine load are in a predetermined low load / low rotation operation region, the ECU 17 controls the variable compression ratio mechanism 100 so that the compression ratio of the internal combustion engine 1 becomes high. Specifically, the ECU 17 controls the variable compression ratio mechanism 100 so that the cylinder block 2 approaches the crankcase 3 (displaces toward the bottom dead center side in the cylinder axis direction).

  Further, when the engine speed and the engine load deviate from the low load / low rotation operation region described above, the ECU 17 causes the cylinder block 2 to move away from the crankshaft 7 (displaces toward the top dead center side in the cylinder axis direction). In addition, the compression ratio of the internal combustion engine 1 is reduced by controlling the variable compression ratio mechanism 100.

  When changing the compression ratio of the internal combustion engine 1 as described above, the ECU 17 controls the variable compression ratio mechanism 100 so that the output signal value of the lift sensor 20 matches the target value. The target value is a value obtained by converting the target compression ratio into the lift amount of the cylinder block 2 and is experimentally obtained in advance. It should be noted that the compression ratio of the internal combustion engine 1 may be switched in two steps as described above, or may be switched in a stepless manner according to the engine speed and the engine load.

  Thus, when the compression ratio of the internal combustion engine 1 is changed, it is possible to achieve both improvement in combustion efficiency in the low load / low rotation operation region and suppression of knocking in the high load / high rotation operation region.

  By the way, when the cylinder block 2 is relatively displaced with respect to the crankcase 3, the center of mass position of the internal combustion engine 1 is also displaced. For example, as shown in FIG. 4, when shifting from a state where the compression ratio is high (state shown in (a) in FIG. 4) to a state where the compression ratio is low (state shown in (b) in FIG. 4), Since the cylinder block 2 is displaced to the top dead center side in the cylinder axial direction (upward in FIG. 4), the center of mass position A of the internal combustion engine 1 is also displaced to the top dead center side in the cylinder axial direction. Conversely, when the compression ratio is low (the state shown in FIG. 4B) and the compression ratio is high (the state shown in FIG. 4A), the cylinder block 2 is connected to the cylinder shaft. The center of gravity A of the internal combustion engine 1 is also displaced toward the bottom dead center side in the cylinder axial direction because it is displaced toward the bottom dead center side in the direction (downward in FIG. 4).

  As shown in FIG. 4, when the mass center position A is displaced with the change in the compression ratio, the resonance frequency of the engine mount 50 also changes with the change in the compression ratio. As a result, depending on the compression ratio (lift amount of the cylinder block 2), the engine mount 50 may not be able to completely attenuate the vibration of the internal combustion engine 1.

  In contrast, in this embodiment, when the compression ratio is changed, the balance weight 300 is displaced in the direction opposite to the cylinder block 2 in the cylinder axis direction. Specifically, as shown in FIG. 5, the ECU 17 changes from a state where the compression ratio is high (state shown in FIG. 5A) to a state where the compression ratio is low (state shown in FIG. 5B). When shifting to, the cylinder block 2 is displaced to the top dead center side in the cylinder axial direction (upward in FIG. 5), and the balance weight 300 is moved to the bottom dead center side in the cylinder axial direction (downward in FIG. 5). Displace. Conversely, when shifting from a state where the compression ratio is low (the state shown in (b) in FIG. 5) to a state where the compression ratio is high (the state shown in (a) in FIG. 5), the ECU 17 Is displaced to the bottom dead center side (downward in FIG. 5) in the cylinder axis direction, and the balance weight 300 is displaced to the top dead center side (upward in FIG. 5) in the cylinder axis direction.

  At this time, the displacement amount Δi of the balance weight 300 relative to the displacement amount Δh of the cylinder block 2 is determined so that the mass center position A does not change. It is desirable that the relationship between the displacement amount Δh of the cylinder block 2 and the displacement amount Δi of the balance weight 300 is experimentally obtained in advance and the relationship is mapped. Since the displacement amount Δh of the cylinder block 2 correlates with the compression ratio of the internal combustion engine 1, the relationship between the displacement amount Δi of the balance weight 300 and the compression ratio may be mapped.

  Here, an example of a map defining the relationship between the displacement amount Δi of the balance weight 300 and the compression ratio ε is shown in FIG. Since the relationship between the displacement amount Δi and the compression ratio ε varies depending on the specifications of the internal combustion engine 1 and the damping characteristics of the engine mount 50, the map shown in FIG. 6 is merely an example.

  The displacement amount Δi in FIG. 6 indicates the displacement amount from the lowest part (the displacement end on the bottom dead center side in the cylinder axis direction). According to the map shown in FIG. 6, the amount of displacement Δi of the balance weight 300 increases when the compression ratio ε is high compared to when it is low. In other words, when the compression ratio ε is high, the balance weight 300 is positioned upward (at the top dead center side in the cylinder axis direction) as compared with the low compression ratio ε. As a result, as shown in FIG. 5 described above, the mass center position A of the internal combustion engine 1 can be maintained at a constant position.

  When the mass center position A of the internal combustion engine 1 is maintained at a constant position, the resonance frequency of the engine mount 50 is also maintained at a constant frequency, so that the engine mount 50 can attenuate the vibration of the internal combustion engine 1. Therefore, the vibration of the internal combustion engine 1 is attenuated regardless of the compression ratio of the internal combustion engine 1.

  Hereinafter, the control procedure of the actuator 301 in the present embodiment will be described with reference to FIG. FIG. 7 is a flowchart showing a control routine executed when the ECU 17 changes the compression ratio. This control routine is a routine stored in advance in the ROM of the ECU 17 and is periodically executed by the ECU 17.

  In the control routine of FIG. 7, the ECU 17 first reads various data in S101. More specifically, data serving as parameters for calculating a compression ratio target value (target compression ratio) εt (for example, engine speed, engine load, throttle opening, vehicle speed, transmission gear ratio, torque converter lockup) Status, output signal value of the lift sensor 20, etc.).

  In S102, the ECU 17 calculates a target compression ratio εt based on the parameters read in S101.

  In S103, the ECU 17 accesses the map of FIG. 6 using the target compression ratio εt calculated in S103 as an argument, and calculates the displacement amount Δi of the balance weight 300.

  In S104, the ECU 17 controls the variable compression ratio mechanism 100 according to the target compression ratio εt calculated in S102. Specifically, the ECU 17 obtains an actual compression ratio (actual compression ratio) ε from the output signal value of the lift sensor 20, and performs variable compression so that the deviation between the actual compression ratio ε and the target compression ratio εt is within an allowable range. The ratio mechanism 100 is controlled.

  In S105, the ECU 17 controls the actuator 301 in accordance with the displacement amount Δi calculated in S103.

  As described above, when the compression ratio ε is changed and the balance weight 300 is displaced according to the control routine of FIG. 7, the center-of-mass position A of the internal combustion engine 1 is maintained at a constant position regardless of the compression ratio. As a result, the resonance frequency of the engine mount 50 is also maintained at a constant frequency regardless of the compression ratio of the internal combustion engine 1.

  Therefore, according to the present embodiment, the vibration reduction effect of the internal combustion engine 1 is further enhanced in the system that changes the compression ratio of the internal combustion engine 1 by the relative displacement of the cylinder block 2 and the crankcase 3 in the cylinder axial direction. Can do.

  In this embodiment, an example in which the dedicated actuator 301 is provided to displace the balance weight 300 has been described. However, the motor 106 of the variable compression ratio mechanism 100 also serves as an actuator for displacing the balance weight 300. May be. In that case, for example, a pinion gear may be attached to the output shaft of the motor 106. However, if the relationship between the displacement amount of the cylinder block 2 and the displacement amount of the balance weight 300 at that time does not satisfy the relationship that the center of mass position of the internal combustion engine 1 is not displaced, the distance between the output shaft of the motor 106 and the pinion gear. A speed reduction mechanism or a speed increase mechanism may be provided.

  In the present embodiment, the example in which the balance weight 300 is disposed in the oil pan 30 has been described. However, the balance weight 300 may be disposed in a place other than the oil pan 30. For example, it may be arranged in the cylinder head 4 or in the cylinder block 2.

  According to such a configuration, there is an advantage that an actuator for displacing the balance weight 300 is not necessary, and logic for controlling the amount of displacement of the balance weight 300 is also unnecessary. However, according to the configuration in which the dedicated actuator for displacing the balance weight 300 is provided, the mass center position can be easily set when the mass center position deviates from the assumed position due to tolerances of components constituting the internal combustion engine 1. There is an advantage that it can be adjusted.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder block 3 Crankcase 4 Cylinder head 5 Cylinder 6 Piston 7 Crankshaft 8 Connecting rod 9 Intake port 10 Exhaust port 11 Intake valve 12 Exhaust valve 13 Intake camshaft 14 Exhaust camshaft 15 Fuel injection valve 16 Spark plug 18 Crank position sensor 19 Accelerator position sensor 20 Lift sensor 30 Oil pan 50 Engine mount 100 Variable compression ratio mechanism 101 Shaft portion 102 Cam portion 103 Movable bearing portion 104 Worm wheel 105 Worm 106 Motor 200 Car body 300 Balance weight 301 Actuator 302 Rack 303 Pinion gear

Claims (2)

A variable compression ratio mechanism that changes the compression ratio of the internal combustion engine by changing the position of the cylinder block relative to the crankcase in the cylinder axial direction;
When the variable compression ratio mechanism displaces the position of the cylinder block, a balance weight that is displaced in the direction opposite to the cylinder block in the cylinder axis direction;
A variable compression ratio system for an internal combustion engine, comprising:   2. The variable compression ratio system for an internal combustion engine according to claim 1, wherein the displacement amount of the balance weight is determined so that the center of mass position of the internal combustion engine is maintained at a constant position.

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