JP2013079607A - Vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a position change of the center of gravity as much as possible during cornering or braking of a vehicle to improve handling performance and stability of the vehicle.SOLUTION: The vehicle includes: an internal combustion engine of which a compression ratio is variable such that a position of the center of gravity in the vehicle is vertically varied; an obtaining portion for obtaining at least one of lateral acceleration (lateral G) and forward acceleration of the vehicle; and a limitation portion for limiting variation width of a compression ratio ε within a predetermined range of ±β, while the at least one obtained by the obtaining portion exceeds a predetermined value of α, with respect to a compression ratio of ε0 at a time point of t0 where the at least one first exceeds the predetermined value.

Description

  The present invention relates to a vehicle such as an automobile, and more particularly to a vehicle equipped with an internal combustion engine having a variable compression ratio.

  2. Description of the Related Art 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 performance and output performance of the internal combustion engine. As this type of technology, a compression ratio variable mechanism that connects the cylinder block and the crankcase so as to be relatively close to and away from each other in the vertical direction is provided, and the compression ratio is controlled by operating or controlling the variable compression ratio mechanism. A technique for changing is proposed (see, for example, Patent Document 1).

JP 2007-239592 A

  By the way, when such a variable compression ratio internal combustion engine is mounted on a vehicle, the center of gravity position of the vehicle changes up and down in accordance with the change in the compression ratio, and the running characteristics of the vehicle change. Then, for example, the driver's illusion that the vehicle behavior (turning characteristics and braking force) has changed due to the change in the center of gravity during cornering (turning) or braking (braking) of the vehicle. There is a possibility of performing a correction operation different from the driving operation. This is disadvantageous in improving the maneuverability and stability of the vehicle.

  Therefore, the present invention has been made in view of the above circumstances, and its object is to suppress the change in the center of gravity position during cornering or braking of the vehicle as much as possible, and improve the maneuverability and stability of the vehicle. To provide a vehicle.

According to one aspect of the invention,
An internal combustion engine having a variable compression ratio so as to change the position of the center of gravity of the vehicle up and down;
Obtaining means for obtaining at least one of a lateral acceleration and a front acceleration of the vehicle;
Limiting means for limiting the change width of the compression ratio within a predetermined range while at least one acquired by the acquiring means exceeds a predetermined value;
A vehicle characterized by comprising:

  Preferably, the limiting means is configured such that, while at least one acquired by the acquiring means exceeds a predetermined value, the compression ratio change width with respect to the compression ratio at the time when at least one of the limiting means first exceeds the predetermined value. Is limited within a predetermined range.

  Preferably, the limiting means changes the predetermined range according to the at least one value while the at least one exceeds a predetermined value.

  Preferably, the limiting means narrows the predetermined range as the at least one value increases while the at least one exceeds a predetermined value.

  Preferably, the acquisition unit includes at least one of a sensor that detects a lateral acceleration of the vehicle and a sensor that detects a front acceleration.

Preferably, the internal combustion engine is
A crankcase to which the crankshaft is assembled;
A cylinder block in which a cylinder is formed;
A variable compression ratio mechanism for connecting the crankcase and the cylinder block so that they can move close to and away from each other in the vertical direction;
Is provided.

According to another aspect of the invention,
An internal combustion engine having a variable compression ratio so as to change the position of the center of gravity of the vehicle up and down;
Detecting means for detecting an emergency braking state of the vehicle;
Emergency braking control means for controlling the compression ratio so as to lower the position of the center of gravity of the vehicle when an emergency braking state is detected by the detection means;
A vehicle characterized by comprising:

  According to the present invention, it is possible to suppress the change in the position of the center of gravity during cornering or braking of the vehicle as much as possible, and to exhibit an excellent operational effect that the maneuverability and stability of the vehicle can be improved.

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 a mode that a cylinder block moves relatively with respect to a crankcase. 1 is a diagram illustrating a schematic configuration of a vehicle according to an embodiment of the present invention. It is a flowchart of the routine concerning the 1st example of compression ratio change width restriction control. It is a time chart which shows the mode of the change of the compression ratio at the time of routine execution. The map for variably setting the limit range regulation value at the time of turning is shown. It is a flowchart of the routine concerning the 2nd example of compression ratio change width restriction control. The map for variably setting the limitation range regulation value at the time of braking is shown. It is a flowchart of the routine concerning the 3rd example of compression ratio change width restriction control. It is a flowchart of the routine concerning the suitable example of compression ratio control.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, an internal combustion engine (engine) 1 is a variable compression ratio internal combustion engine, and a cylinder block 3 in which a cylinder 2 is formed is attached to a crankcase 4 to which a crankshaft 20 (see FIG. 3) is assembled. Thus, the compression ratio is changed by relatively moving the cylinder 2 in the central axis direction. The crankcase 4 and the cylinder block 3 are connected to each other by a compression ratio variable mechanism 21 so as to be able to move close to and away from each other in the vertical direction of the vehicle. The internal combustion engine 1 of the present embodiment is a gasoline engine (spark ignition internal combustion engine), but the present invention is also applicable to a diesel engine (compression ignition internal combustion engine).

  Here, the configuration of the variable compression ratio mechanism 21 will be described. As shown in the drawing, 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 on one side of the cylinder block 3 are all located on the same axis. A pair of central axes of the bearing housing holes 5 on both sides of the cylinder block 3 are parallel to each other.

  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. 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 arranged on both sides of the cylinder block 3, and the plurality of cam storage holes 8 on one side are all located coaxially. A pair of central axes of the cam storage holes 8 on both sides of the cylinder block 3 are parallel to each other. 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 respectively inserted into the bearing storage holes 5 and the cam storage holes 8 in two rows on both sides. Thereby, the cylinder block 3 and the crankcase 4 are connected to each other. The cam shaft 9 is fixed to the shaft portion 9a in a state of being eccentric with respect to the shaft portion 9a and the central axis of the shaft portion 9a, and has the same outer shape as the cam portion 9b having a regular circular cam profile. And a movable bearing portion 9c that is rotatably attached to the shaft portion 9a. The cam portions 9b and the movable bearing portions 9c are alternately arranged. The pair of cam shafts 9 have a mirror image relationship. Further, a mounting portion 9d of a gear 10 to be described later is formed at the end of the cam shaft 9. The center 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 with each other.

  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. The outer shape of the movable bearing portion 9c is a perfect circle having the same diameter as the cam portion 9b. By rotating the movable bearing portion 9c relative to the shaft portion 9a, the outer peripheral surface of the cam portion 9b and the outer peripheral surface of the movable bearing portion 9c can be matched.

  A gear 10 is attached to the attachment portion 9d of each camshaft 9. Worm gears 11a and 11b are meshed 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 in one direction, the pair of cam shafts 9 and 9 rotate in the opposite directions via the worm gears 11 a and 11 b and the gears 10 and 10. The motor 12 is fixed to the cylinder block 3.

  Next, the operation when changing the compression ratio of the internal combustion engine 1 will be described. 2A to 2C are cross-sectional views showing the relationship between the cylinder block 3, the crankcase 4, and the camshaft 9 disposed between them. The center 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 peripheral surfaces 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, 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. 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 is slid relative to the crankcase 4 toward the top dead center side, that is, separated. Can move in the direction. 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. doing.

  Although not shown, when the motor 12 is driven from the state of FIG. 2 (c) to rotate the shaft portion 9a in the direction opposite to the arrow direction, the crank is moved to the state of FIG. 2 (b) or FIG. 2 (a). The cylinder block 3 can be slid relative to the case 4 toward the bottom dead center, that is, moved in the proximity direction.

  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.

  Next, a vehicle equipped with the above-described internal combustion engine 1 will be described with reference to FIG. FIG. 3 is a front view of the vehicle as viewed from the front. As shown in the figure, in the present embodiment, the crankcase 4 of the internal combustion engine 1 is fixed to the vehicle 50 via mounts 22a and 22b. In particular, in the internal combustion engine 1, the center axis of the cylinder 2 extends in the vertical direction of the vehicle 50, and the above-described approaching / separating movement between the crankcase 4 and the cylinder block 3, that is, the compression ratio changing operation determines the height position of the center of gravity of the vehicle 50. It is being fixed to vehicle 50 so that it may change.

  The internal combustion engine 1 is provided with a crank position sensor 16 so that the engine speed can be acquired. Further, the vehicle 50 includes a lateral acceleration sensor 17 that detects a lateral acceleration (lateral G, left-right G, or turning G) of the vehicle 50, a front acceleration (front G or braking G), and a rear acceleration (rear G) of the vehicle 50. A longitudinal acceleration sensor 18 for detecting the engine load and an accelerator position sensor 15 capable of acquiring the engine load required by the driver are provided. Further, the vehicle 50 includes a brake pedal stroke sensor 24 and a hydraulic pressure sensor 25 that respectively detect a brake pedal stroke and a brake hydraulic pressure that change according to a brake operation by the driver, and wheels that change according to a steering operation by the driver. A steering angle sensor 26 for detecting the steering angle of the vehicle and a vehicle speed sensor 27 for detecting the vehicle speed are provided.

  The vehicle 50 is provided with an electronic control unit (ECU) 35 as a control means for mainly controlling the internal combustion engine 1. The ECU 35 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver.

  Sensors related to control of the operation state of the internal combustion engine 1 such as the crank position sensor 16 and the accelerator position sensor 15 are connected to the ECU 35 via electric wiring, and an output signal is input to the ECU 35. In addition, sensors related to control of the traveling state of the vehicle 50 such as the lateral acceleration sensor 17 are also connected. On the other hand, a fuel injection valve (not shown) in the internal combustion engine 1 is connected to the ECU 35 via electric wiring, and a motor 12 is connected to the ECU 35 via electric wiring. Is to be controlled.

  The ECU 35 includes a CPU, a ROM, a RAM, and the like. The ROM stores a program for performing various controls of the internal combustion engine 1 and a map storing data. ECU35 controls the compression ratio of the internal combustion engine 1 according to the driving | running state (especially engine speed and engine load) of the internal combustion engine 1 by operating the motor 12 suitably. Such compression ratio control according to the operating state of the internal combustion engine 1 is referred to as normal control or basic control.

  In the compression ratio control, the cylinder block 3 is moved closer (down) or moved away (up) with respect to the crankcase 4 fixed to the vehicle 50. As a result, the cylinder volume is substantially changed, and the compression ratio is changed. When the cylinder block 3 is moved closer, the compression ratio increases and the positions of the center of gravity of the internal combustion engine and the vehicle are lowered. When the cylinder block 3 is moved away, the compression ratio decreases and the positions of the center of gravity of the internal combustion engine and the vehicle increase.

  By the way, in the vehicle 50 of the present embodiment, the position of the center of gravity of the vehicle changes up and down in accordance with the change in the compression ratio, and the running characteristics of the vehicle change. Then, for example, the driver's illusion that the vehicle behavior (turning characteristics and braking force) has changed due to the change in the center of gravity during cornering (turning) or braking (braking) of the vehicle. There is a possibility of performing a correction operation different from the driving operation. This is disadvantageous in improving the maneuverability and stability of the vehicle.

  Therefore, in this embodiment, the change width of the compression ratio is limited during cornering or braking of the vehicle. As a result, the change in the center of gravity of the vehicle during cornering or braking can be suppressed as much as possible, and the controllability and stability of the vehicle can be improved.

  Specifically, at least one of the lateral acceleration and the front acceleration of the vehicle is acquired, and while the acquired at least one exceeds a predetermined value, the compression ratio at the time when at least one of the vehicle first exceeds the predetermined value The range of change of the compression ratio is limited with respect to the initial compression ratio.

  In this way, during cornering and / or braking where at least one exceeds a predetermined value, the compression ratio of the internal combustion engine is limited to the vicinity of the initial compression ratio, and changes in the center of gravity height position of the vehicle are suppressed. Thereby, it is possible to prevent the driver from having the illusion that the vehicle behavior has changed, and to avoid the correction operation by the driver. And it is possible to improve the controllability and stability of the vehicle.

  Here, the lateral acceleration of the vehicle is detected by the lateral acceleration sensor 17. Lateral acceleration refers to acceleration in either the lateral direction or the left-right direction of the vehicle, and is mainly generated when the vehicle turns. The lateral acceleration may be estimated. These “detection” and “estimation” are referred to as “acquisition”. In the case of estimation, the ECU 35 estimates the lateral acceleration according to a predetermined map (which may be a function, the same applies below) based on the steering angle detected by the steering angle sensor 26 and the vehicle speed detected by the vehicle speed sensor 27, for example.

  The front acceleration of the vehicle is detected by the longitudinal acceleration sensor 18. Here, the front acceleration refers to the acceleration in the front direction of the vehicle, and is mainly the acceleration generated during braking of the vehicle. On the other hand, rear acceleration refers to acceleration in the rear direction of the vehicle. Here, the front acceleration is detected by the longitudinal acceleration sensor 18 capable of detecting both the longitudinal acceleration, but the front acceleration may be detected by a sensor capable of detecting only the front acceleration.

  The front acceleration can also be estimated. In this case, for example, based on the brake pedal stroke detected by the brake pedal stroke sensor 24 or its changing speed, the ECU 35 estimates the front acceleration according to a predetermined map. The brake fluid pressure detected by the fluid pressure sensor 25 may be used instead of the brake pedal stroke.

  Hereinafter, some preferred examples of the compression ratio change width restriction control will be described. These controls are executed by the ECU 35.

  FIG. 4 shows a routine according to a first example of compression ratio change width restriction control. This routine is repeatedly executed by the ECU 35 at a predetermined calculation cycle (for example, 16 msec).

  In step S101, it is determined whether or not the lateral acceleration detected by the lateral acceleration sensor 17, that is, the lateral G, exceeds a predetermined turning threshold value α. If the lateral G does not exceed the turning threshold value α, the routine ends. If the lateral G exceeds the turning threshold value α, the process proceeds to step S102.

  In step S102, the range of change of the compression ratio ε is within a predetermined range, that is, the turning limit range ± β (where β is the same as the initial compression ratio ε0 when the lateral G first exceeds the turning threshold value α. > 0).

  FIG. 5 shows how the compression ratio ε changes when this routine is executed. FIG. 5A shows a case where the lateral G does not exceed the turning threshold value α and the compression ratio change width is not limited during the illustrated period. As shown in the figure, the compression ratio ε is changed to a free value according to the engine operating state according to the normal control.

  On the other hand, FIG. 5B shows a case where the lateral G exceeds the turning threshold value α and the compression ratio change width is restricted for a certain period in the illustrated period. The compression ratio change in the illustrated example is based on the compression ratio change as shown in FIG.

  In the illustrated example, at time t0, the lateral G first exceeds the turning threshold value α, and this state continues until time t6 thereafter. This corresponds to a cornering operation of the vehicle that generates a relatively large lateral G at time t0, and this cornering operation continues until time t6. The compression ratio ε at time t0 according to the normal control is the initial compression ratio ε0. Within the time limit period from time t0 to time t6, the range of change in the compression ratio ε is limited within a turning limit range of ± β from the initial compression ratio ε0 as a reference or center.

  As a result, according to the original normal control, the compression ratio ε is maintained and limited to ε0 + β within the periods t1 to t2 and t5 to t6 in which the compression ratio ε exceeds ε0 + β. Further, according to the original normal control, the compression ratio ε is maintained and limited to ε0-β within the period t3 to t4 in which the compression ratio ε is less than ε0-β. In other periods, the compression ratio ε is a value according to normal control.

  Here, referring again to FIG. 4, if the lateral G does not exceed the turning threshold value α in step S101, the restriction in step S102 is not executed, so the compression ratio ε is freely controlled as in normal control. It will be. On the other hand, if the lateral G exceeds the turning threshold value α in step S101, the restriction in step S102 is executed. As a result, the compression ratio ε is controlled to a value according to the normal control unless the value according to the normal control is outside the turning limit range (ε0 ± β), and if the value according to the normal control is outside the turning limit range. It is controlled to the nearest upper limit value (ε0 + β) or lower limit value (ε0−β) of the turning limit range.

  Here, the predetermined range that defines the change range of the restricted compression ratio ε, that is, the turning restriction range, does not appear as vehicle behavior during cornering (ie, vehicle roll) in which the change of the compression ratio is recognized by the driver. It is preferable that the range allows the change in the compression ratio. By doing so, it is possible to effectively suppress a change in turning feeling due to a vehicle behavior that the driver does not intend, that is, a roll change. Since the actual cornering radius change due to the change in the compression ratio is minute, the change in the compression ratio often leads to a driver's discomfort.

  The turning limit range may be a predetermined constant value, but is preferably changed according to the value or size of the lateral G while the lateral G exceeds the turning threshold value α. Specifically, the value β that defines the turning limit range (referred to as a turning restriction range specified value) is during the time when the lateral G exceeds the turning threshold value α (the restriction period t0 to t0 in FIG. 5B). In accordance with the detected value of the lateral G at t6), it is preferable that the ECU 35 variably sets, for example, according to a map as shown in FIG. The value of the lateral G in the map is larger than the turning threshold value α.

  As shown in FIG. 6, it is preferable that the value of β is decreased and the turning limit range is narrowed as the value of the lateral G increases. This is because it is assumed that the cornering is performed at a higher speed as the value of the lateral G is larger, and the influence of the change in the compression ratio, that is, the change in the center of gravity of the vehicle on the vehicle behavior and the driver's uncomfortable feeling increases.

  Next, FIG. 7 shows a routine according to a second example of the compression ratio change width restriction control. The routine according to the second example is substantially the same as the routine according to the first example.

  In step S201, it is determined whether or not the front acceleration detected by the longitudinal acceleration sensor 18, that is, the front G, exceeds a predetermined braking threshold value γ. If the previous G does not exceed the braking threshold γ, the routine is terminated, and if the previous G exceeds the braking threshold γ, the process proceeds to step S202.

  In step S202, the variation range of the compression ratio ε is within a predetermined range, that is, the braking restriction range ± δ (where δ is δ) with respect to the compression ratio when the front G first exceeds the braking threshold γ, that is, the initial compression ratio ε0. > 0).

  The change of the compression ratio ε when this routine is executed is substantially the same as that shown in FIG. That is, as shown in FIG. 5A, if the front G does not exceed the braking threshold value γ, the compression ratio change width is not limited, and the compression ratio ε is freely set to a value according to the engine operating state. Be controlled.

  On the other hand, as shown in FIG. 5B, if the front G exceeds the braking threshold value γ in response to the braking operation of the vehicle, the compression ratio change width is limited, and the compression ratio ε The change width is limited within a braking time limit range of ± δ from the initial compression ratio ε0 as a reference or center.

  As a result, according to the original normal control, the compression ratio ε is maintained and limited to ε0 + δ within a period in which the compression ratio ε exceeds ε0 + δ. Further, according to the original normal control, the compression ratio ε is maintained and limited to ε0-δ within a period in which the compression ratio ε is less than ε0-δ. In other periods, the compression ratio ε is a value according to normal control.

  Referring again to FIG. 7, if the front G does not exceed the braking threshold value γ in step S201, the restriction in step S202 is not executed, and the compression ratio ε is freely controlled as in normal control. Become. On the other hand, if the front G exceeds the braking threshold γ in step S201, the restriction in step S202 is executed. As a result, the compression ratio ε is controlled to a value according to the normal control unless the value according to the normal control is outside the braking time limit range (ε0 ± δ), and if the value according to the normal control is outside the braking time limit range. It is controlled to the nearest upper limit value (ε0 + δ) or lower limit value (ε0−δ) of the braking restriction range.

  Here, the predetermined range that defines the range of change in the restricted compression ratio ε, that is, the braking restriction range, is expressed as a vehicle behavior during braking (ie, nose dive) in which the change in the compression ratio is perceived by the driver. It is preferable that the range is such that the change in the compression ratio is allowed to such an extent that it does not occur. By so doing, it is possible to effectively suppress changes in vehicle behavior, i.e., deceleration feeling or braking feeling caused by nose diving, which is not intended by the driver. Since the actual deceleration change due to the compression ratio change is minute, the change in the compression ratio often leads to a driver's uncomfortable feeling.

  As described above, the braking time limit range may be a predetermined constant value, but is preferably changed according to the value or magnitude of the previous G while the previous G exceeds the braking threshold γ. . Specifically, a value δ that defines a braking time limit range (referred to as a braking time limit range specified value) is, for example, according to the detected value of the previous G while the previous G exceeds the braking time threshold γ, for example. It is preferable to variably set the ECU 35 according to a map as shown in FIG. The previous G value in the map is larger than the braking threshold value γ.

  As shown in FIG. 8, it is preferable to decrease the value of δ and narrow the braking time limit range as the value of the front G increases. This is because it is assumed that braking is performed more strongly as the value of the front G is larger, and the influence of the change in the compression ratio, that is, the change in the center of gravity of the vehicle, on the vehicle behavior and the driver's discomfort increases.

  Next, FIG. 9 shows a routine according to a third example of the compression ratio change width restriction control. This third example corresponds to a combination of the first example and the second example.

  In step S301, it is determined whether or not the front G detected by the longitudinal acceleration sensor 18 exceeds the braking threshold value γ. If the previous G does not exceed the braking threshold γ, the process proceeds to step S302, and if the previous G exceeds the braking threshold γ, the process proceeds to step S304.

  In step S302, it is determined whether or not the lateral G detected by the lateral acceleration sensor 17 exceeds the turning threshold value α. If the lateral G does not exceed the turning threshold value α, the routine is terminated, and the compression ratio ε is freely changed or controlled according to normal control.

  On the other hand, if the lateral G exceeds the turning threshold value α, the process proceeds to step S303, where the change width of the compression ratio ε is limited to the turning limit range ± β.

  In step S304, as in step S302, it is determined whether or not the lateral G detected by the lateral acceleration sensor 17 exceeds the turning threshold value α. If the lateral G does not exceed the turning threshold value α, the process proceeds to step S305, where the change width of the compression ratio ε is limited to the braking time limit range ± δ.

  On the other hand, if the lateral G exceeds the turning threshold value α, the process proceeds to step S306, and the change width of the compression ratio ε is limited to the narrower one of the turning restriction range ± β and the braking restriction range ± δ. Is done.

  This third example is particularly effective when the braking operation and cornering operation of the vehicle are performed simultaneously in coordination. Even during such operations, the driver's uncomfortable feeling can be effectively suppressed, and the maneuverability and stability of the vehicle can be improved. In particular, in step S306, the change width of the compression ratio ε is limited to the narrower one of the turning limit range ± β and the braking limit range ± δ, so that both the braking operation and the cornering operation are being performed simultaneously. It is possible to reliably suppress the driver's uncomfortable feeling and feeling change.

  The initial compression ratio ε0 serving as a reference for the restriction range in the third example is a compression ratio at the time when at least one of the front G and the lateral G first exceeds the threshold values γ and α. After this first time point, the state where only the previous G exceeds the threshold value γ, the state where only the lateral G exceeds the threshold value α, and the state where both exceed the threshold values γ and α alternately Although it may occur continuously, inconvenience in control can be eliminated by setting the initial compression ratio ε0 as described above.

  Next, a preferred example of compression ratio control will be described. In this example, when the emergency braking state of the vehicle is detected, the compression ratio is controlled to lower the position of the center of gravity of the vehicle.

  In general, the accelerator pedal is released during braking while the vehicle is running, and the engine load detected by the accelerator position sensor 15 is zero. The engine speed is higher than the predetermined fuel cut return speed. Therefore, the fuel cut condition is satisfied, and the internal combustion engine 1 is controlled to the fuel cut state (fuel injection stop state).

  During the fuel cut, the compression ratio of the internal combustion engine is controlled to the lowest compression ratio in preparation for the firing after the fuel cut is restored according to the normal control. However, this increases the position of the center of gravity of the vehicle, which is somewhat disadvantageous for improving the braking force during braking.

  Therefore, in this example, even during a fuel cut, the compression ratio is controlled so as to lower the position of the center of gravity of the vehicle during emergency braking of the vehicle. Specifically, the compression ratio of the internal combustion engine is unconditionally controlled to the maximum compression ratio during emergency braking of the vehicle.

  In this way, the position of the center of gravity of the vehicle based on the compression ratio becomes low, particularly low, and the nose dive during braking is reduced, the rear wheel load is increased, and the braking force of the vehicle can be increased.

  FIG. 10 shows a routine according to this example. In step S401, it is determined whether or not the vehicle is in emergency braking, that is, whether or not an emergency braking state of the vehicle has been detected. For example, when the front G detected by the longitudinal acceleration sensor 18 exceeds a predetermined emergency braking threshold value γ ′, or when an antilock brake system (ABS) mounted on the vehicle is operating, etc. In addition, it is determined that the vehicle is in emergency braking. The emergency braking threshold value γ 'is larger than the braking threshold value γ.

  When the emergency braking is not being performed, that is, when the emergency braking state is not detected, the routine is ended, and thereby the compression ratio ε is changed or controlled according to the normal control.

  On the other hand, when emergency braking is being performed, that is, when an emergency braking state is detected, emergency braking control is performed in step S402 with the compression ratio ε as the maximum compression ratio. As a result, the position of the center of gravity of the vehicle can be minimized, and the braking force of the vehicle can be increased.

  It is not always necessary to control the compression ratio ε so as to minimize the position of the center of gravity of the vehicle, that is, the maximum compression ratio. For example, the compression ratio may be increased by a predetermined value from the value immediately before the emergency braking state is detected. As a result, the center of gravity of the vehicle is lowered by a predetermined amount from the position immediately before it.

  The preferred embodiment of the present invention has been described in detail above, but various other embodiments of the present invention are conceivable. For example, the mounting method of the internal combustion engine 1 with respect to the vehicle 50 may be reversed, the cylinder block 3 may be fixed to the vehicle 50, and the crankcase 4 may be moved close to and away from the cylinder block 3. In this case, when the crankcase 4 is moved closer, the compression ratio increases and the position of the center of gravity of the vehicle increases. When the crankcase 4 is moved away, the compression ratio decreases and the position of the center of gravity of the vehicle decreases.

  The internal combustion engine may be an internal combustion engine that changes the compression ratio by a method different from the above. For example, the connecting rod is divided into two, a swinging member that can swing around a predetermined swinging center is connected to the connecting rod part connected to the crankshaft, and the swinging center is moved by rotating the camshaft. Thus, the present invention is also applicable to an internal combustion engine provided with a variable compression ratio mechanism that changes the volume of the combustion chamber and the stroke of the piston.

  The embodiment of the present invention is not limited to the above-described embodiment, and includes all modifications, applications, and equivalents included in the concept of the present invention defined by the claims. Therefore, the present invention should not be construed as being limited, and can be applied to any other technique belonging to the scope of the idea of the present invention. The above examples can be combined as much as possible.

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 15 Accel position sensor 16 Crank position sensor 17 Lateral acceleration sensor 18 Longitudinal acceleration sensor 21 Compression ratio variable mechanism 22a, 22b Mount 24 Brake pedal Stroke sensor 25 Hydraulic pressure sensor 26 Rudder angle sensor 27 Vehicle speed sensor 35 Electronic control unit (ECU)
50 vehicles

Claims (6)

An internal combustion engine having a variable compression ratio so as to change the position of the center of gravity of the vehicle up and down;
Obtaining means for obtaining at least one of a lateral acceleration and a front acceleration of the vehicle;
Limiting means for limiting the change width of the compression ratio within a predetermined range while at least one acquired by the acquiring means exceeds a predetermined value;
A vehicle characterized by comprising: The limiting means has a predetermined range of the change ratio of the compression ratio with respect to the compression ratio at the time when at least one of the limiting means first exceeds the predetermined value while at least one acquired by the acquiring means exceeds the predetermined value. The vehicle according to claim 1, wherein the vehicle is limited to within. The vehicle according to claim 1, wherein the limiting unit changes the predetermined range according to the at least one value while the at least one exceeds a predetermined value. The said restriction | limiting means narrows the said predetermined range, so that the said at least one value is large while the said at least one exceeds the predetermined value. vehicle. The vehicle according to any one of claims 1 to 4, wherein the acquisition unit includes at least one of a sensor that detects a lateral acceleration of the vehicle and a sensor that detects a front acceleration. The internal combustion engine
A crankcase to which the crankshaft is assembled;
A cylinder block in which a cylinder is formed;
A variable compression ratio mechanism for connecting the crankcase and the cylinder block so that they can move close to and away from each other in the vertical direction;
The vehicle according to any one of claims 1 to 5, further comprising:

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