JP4136602B2 - Engine compression ratio changing method and variable compression ratio engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a variable compression ratio engine that changes the compression ratio of an engine.
[0002]
[Prior art]
In the variable compression ratio engine, various advantages can be obtained by changing the compression ratio according to the operating conditions. For example, by reducing the compression ratio at a high load at which knocking is likely to occur, the self-ignition of the fuel can be suppressed, whereby the occurrence of knocking can also be suppressed. When the compression ratio is increased at low loads, the temperature of the air-fuel mixture increases and the combustibility of the fuel increases. For this reason, during acceleration traveling, etc., where load fluctuations are likely to occur, the compression ratio is changed from a high compression ratio to a low compression ratio according to load fluctuations (fluctuations from low loads to high loads). Yes. By performing compression ratio control according to such load fluctuations, fuel efficiency and drivability are improved.
[0003]
[Problems to be solved by the invention]
In this way, when a load change occurs from a low load to a high load, if there is a delay in changing from a high compression ratio to a low compression ratio, a situation of a high load / high compression ratio occurs. Under these circumstances, the frequency of knocking increases because self-ignition of the fuel can occur due to a high compression ratio. In order to cope with such a situation, it is desirable to quickly perform a compression ratio transition from a high compression ratio to a low compression ratio.
[0004]
For example, when the engine operating state is expected to shift to a low compression ratio, a change command to the low compression ratio side is issued to shift the compression ratio from a high compression ratio to a low compression ratio. (For example, Patent Document 1).
[Patent Document 1]
JP-A-4-219428 [0005]
However, even if the compression ratio is shifted from the high compression ratio to the low compression ratio in this manner, the time required for shifting to the low compression ratio is not changed, although the transition timing to the low compression ratio is advanced. Therefore, there is room for improvement in speeding up the transition of the compression ratio from the high compression ratio to the low compression ratio.
[0006]
A technique for changing the compression ratio of the engine is also proposed in the following document.
[Patent Document 2]
JP-A 64-35047 [Patent Document 3]
JP-A-1-125528 [Patent Document 4]
Japanese Utility Model Publication No. 63-96254 [0007]
The present invention has been made to solve the above-described problems, and an object of the present invention is to increase the speed of transition when shifting the compression ratio of an engine from a high compression ratio to a low compression ratio.
[0008]
[Means for solving the problems and their functions and effects]
In order to solve at least a part of such problems, in the compression ratio changing method and the variable compression ratio engine of the present invention, when the compression ratio is changed, the driving force for changing the compression ratio is transmitted to the compression ratio changing mechanism. . As a result, the compression ratio changing mechanism is driven to change the compression ratio between the high compression ratio and the low compression ratio.
[0009]
In changing the compression ratio, the compression ratio changing method and variable compression ratio engine of the present invention change the compression ratio from a high compression ratio to a low compression ratio and change the compression ratio from a low compression ratio to a high compression ratio. Therefore, the drive speed of the compression ratio changing mechanism is made different, and the drive speed of the compression ratio changing mechanism from the high compression ratio to the low compression ratio is increased. Therefore, according to the variable compression ratio engine of the present invention, the time required for changing the compression ratio from the high compression ratio to the low compression ratio can be shortened, so that the compression ratio transition from the high compression ratio to the low compression ratio is achieved. Can increase the speed.
[0010]
In the above-described variable compression ratio engine of the present invention, the transmission mechanism can be as follows. That is,
The transmission mechanism is
A first transmission mechanism involved in driving the compression ratio changing mechanism from a high compression ratio to a low compression ratio and driving the compression ratio changing mechanism from a low compression ratio to a high compression ratio;
When the compression ratio changing mechanism is driven from the high compression ratio to the low compression ratio, the driving force for driving the compression ratio changing mechanism from the high compression ratio to the low compression ratio is cooperated with the first transmission mechanism. And a second transmission means for energizing.
For example, the second transmission means may be configured to have a spring mechanism, and may be urged in cooperation with the first transmission mechanism using the spring force exhibited by the second transmission means as a driving force.
[0011]
If it carries out like this, in the compression ratio change aspect from a high compression ratio to a low compression ratio, the driving force of the 1st, 2nd transmission mechanism will act on a compression ratio change mechanism together. Therefore, as described above, it is possible to shorten the time required for changing the compression ratio from the high compression ratio to the low compression ratio and to speed up the transition of the compression ratio from the high compression ratio to the low compression ratio.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Next, the form of this invention is demonstrated based on an Example. FIG. 1 is an explanatory diagram schematically illustrating the configuration of a variable compression ratio engine 20 according to the first embodiment.
[0015]
As shown in the figure, the variable compression ratio engine 20 includes a cylinder block 22 and a cylinder head 24, and a piston 28 is incorporated in the cylinder 26. The piston 28 is connected to the crankshaft 29 via a connecting rod 27 configured to be bendable, and the vertical reciprocation of the piston 28 in the cylinder is converted into a rotational motion of the crankshaft 29 via the connecting rod 27. The connecting rod 27 constitutes a compression ratio variable mechanism 30 to be described later, and simultaneously changes the top dead center position and the bottom dead center position of the piston 28 through the change of the bending degree. Thereby, the variable compression ratio engine 20 can change the compression ratio. Details of this will be described later.
[0016]
The variable compression ratio engine 20 includes an intake pipe 50 connected to an intake port (not shown) of the cylinder head 24. The intake pipe 50 guides the fuel injected by the injector 52 into the intake pipe flow path to the combustion chamber through an intake port in a mixed state with air. In this case, the air intake amount is adjusted by the throttle valve 54, and the fuel mixture ratio is adjusted.
[0017]
The variable compression ratio engine 20 includes an ECU 60 that controls the compression ratio change, the drive of the throttle valve 54, and the like. The ECU 60 is configured as a logical operation circuit centered on a microcomputer, and in addition to an actuator 63 for driving a throttle valve, a throttle sensor 55, and an accelerator sensor 61, an engine speed and a crank angle sensor for detecting an engine speed and a crank angle. 56, an actuator (servo motor) 57 for changing the compression ratio, a compression ratio sensor 58 for detecting the compression ratio, an oxygen sensor 62 for detecting the oxygen concentration in the exhaust, an air flow meter 64 for detecting the amount of intake air, and the like. ing.
[0018]
Next, a configuration for changing the compression ratio will be described in detail. FIG. 2 is a schematic perspective view showing the compression ratio variable mechanism 30 including the connecting rod 27, and FIG. 3 is an explanatory diagram for explaining the compression ratio change by the compression ratio variable mechanism 30. As shown in FIG.
[0019]
As shown in the drawing, the compression ratio variable mechanism 30 is configured by connecting a connecting rod 27 to a first connecting rod 31 and a second connecting rod 32 on the piston 28 side. The first connecting rod 31 is pivotally connected by a piston 28 and a piston pin 34 at a small end portion 33 at an upper portion thereof. The second connecting rod 32 is rotatably connected to a crank pin (not shown) of the crankshaft 29 at the lower end 35 thereof. The first and second connecting rods are connected to each other via a connecting rod pin 36 at the lower end side of the first connecting rod and the upper end side of the second connecting rod, and this connecting portion constitutes a link mechanism. ing.
[0020]
The first connecting rod 31 has a protruding portion 31 a on the lower end side, and is connected to the one end side of the control rod 37 by a pin 38 so as to be rotatable. The control rod 37 is provided with a through hole 37a on the other end side, and a control shaft 39 is rotatably fitted and assembled in the through hole 37a. The link mechanism configured at the connection location of the first and second connecting rods also includes the protrusion 31a and the pin 38, and the control rod 37 is connected to the link mechanism.
[0021]
In addition, the compression ratio variable mechanism 30 has a control shaft guide 40 and rotatably supports the shaft guide on the cylinder block 22 (see FIG. 1). This control shaft guide 40 is provided with bearing portions 41 having circular cross sections at both ends and a plurality of locations along the middle, and a connecting portion 42 is formed between adjacent bearing portions 41 with a crescent cross section. The same number of connecting portions 42 as the number of cylinders of the engine are prepared, and the control shaft 39 is fitted and fixed to the control shaft guide 40 so that the control shaft 39 is positioned in the notch region 43 of each connecting portion. That is, the control shaft 39 is fitted and fixed at a position eccentric from the rotation center axis (center axis) X of the control shaft guide 40. Therefore, when the control shaft guide 40 rotates, the control shaft 39 swings with respect to the central axis X and changes its position, whereby the control rod 37 moves the first connecting rod 31 to the second via the pin 38. The connecting rod 32 is bent and displaced. When the connecting rod 27 is bent in this way, the top dead center position and the bottom dead center position length of the piston 28 change simultaneously according to the degree of bending, and the variable compression ratio engine 20 changes the compression ratio. In this case, the compression ratio change, that is, the turning state of the control shaft guide 40 is controlled by the ECU 60 according to the operating state of the engine.
[0022]
The connecting portion 42 has a cross-sectional shape and dimensions so that the control rod 37 does not interfere with the connecting portion 42 when the control shaft 39 swings.
[0023]
The variable compression ratio mechanism 30 includes a servo motor 57 and a worm gear 47 as actuators for causing the control shaft 39 to swing as shown in FIG. The worm gear 47 includes a worm 48 connected to the shaft of the servo motor 57 and a directly connected worm wheel 49 connected to the control shaft guide 40. Therefore, the control shaft guide 40 rotates with the rotation of the servo motor 57, and the rotation direction and the rotation angle are determined by motor control.
[0024]
That is, when the worm 48 is rotated by the servo motor 57, the control shaft guide 40 is rotated by an angle corresponding to the rotation degree, and the control shaft 39 and the control rod 37 are displaced as described above. Due to the displacement of the control rod 37, the bent state of the connecting rod 27 is determined, and the compression ratio of the engine changes. In this embodiment, the control shaft 39 can be displaced around the central axis X of the control shaft guide 40 in a range of 90 ° from the direction of about 3 o'clock to the direction of about 6 o'clock. Is set to be high.
[0025]
The variable compression ratio mechanism 30 has a spring 70 interposed between the worm wheel 49 and a cylinder block (not shown). The spring 70 is configured to bias its own spring force BF to the worm wheel 49 in the same direction as when the worm wheel 49 is driven from the high compression ratio side to the low compression ratio side. In this case, the spring 70 is adjusted by the spring force BF so that the worm wheel 49 can be driven in the above-described direction even by the spring force alone. More specifically, when the worm wheel 49 is rotationally driven to the high compression ratio side, the spring 70 is compressed so that its winding becomes small, and the worm wheel 49 is brought to the low compression ratio side by the spring force BF exerted in this state. It can be rotated. That is, the torque when rotating the worm wheel 49 from the high compression ratio side to the low compression ratio side is the sum of the torque generated by the spring force BF of the spring 70 and the torque generated by the servo motor 57. The torque is higher than that of the existing variable compression engine only by
[0026]
The compression ratio sensor 58 detects the rotation angle (including the direction) of the control shaft guide 40 or the worm wheel 49 and outputs this to the ECU 60. The ECU 60 is configured to calculate an actual compression ratio based on the sensor output.
[0027]
Here, how the compression ratio is changed in the variable compression ratio engine 20 of the present embodiment will be described. FIG. 4 is a flowchart showing compression ratio change control.
[0028]
The compression ratio change control routine shown in FIG. 4 is repeatedly executed every predetermined time. First, an accelerator sensor 61 that reads the engine speed from the speed / crank angle sensor 56 and outputs an accelerator depression state, and a throttle Torque is read according to the sensor output from the sensor 55 or an intake pipe negative pressure sensor (not shown) (step S100). Subsequently, a target compression ratio εt is calculated based on the read rotation speed / torque and a map (not shown) in which both are associated with the compression ratio (step S110). Note that a plurality of maps for calculating the target compression ratio are prepared in accordance with the engine cooling water temperature, the intake air temperature, the emission, or the like, and can be switched as appropriate according to the engine operating condition at that time.
[0029]
Next, the current compression ratio is read from the compression ratio sensor 58 (step S120), and it is determined whether or not the compression ratio needs to be changed based on the coincidence state between the read compression ratio εi and the target compression ratio εt. Determination is made (step S130). If the two compression ratios do not match, it is determined that the compression ratio needs to be changed, and the ECU 60 outputs a change command for setting the compression ratio to the target compression ratio εt to the servo motor 57 (step S140). ). Specifically, a drive signal necessary for setting the current compression ratio εi to the target compression ratio εt is output to the servomotor 57, and the above processes are repeated. By such control, the variable compression ratio engine 20 changes the degree of bending of the connecting rod 27 by the compression ratio variable mechanism 30 using the servo motor 57 as a drive source, and changes the compression ratio of the engine.
[0030]
By the way, in this embodiment, the spring force BF of the spring 70 is biased to the worm wheel 49. Therefore, there are the following advantages.
In the above-described compression ratio change control routine, when the current compression ratio εi is changed to a target compression ratio εt lower than this, the driving force of the worm wheel 49 by the servo motor 57 and the driving force of the worm wheel 49 by the spring 70 (spring Force BF) acts on the worm wheel 49 as a force in the same rotational direction. Therefore, since the driving speed of the worm wheel 49 from the current compression ratio εi (compression ratio on the high compression ratio side) to the low compression ratio (target compression ratio εt) can be increased, compression from the high compression ratio to the low compression ratio is possible. The time required for the ratio change itself is shortened. As a result, according to the variable compression ratio engine 20 of the present embodiment, it is possible to increase the speed of the compression ratio transition from the high compression ratio to the low compression ratio.
[0031]
For this reason, the compression ratio can be quickly changed from a high compression ratio to a low compression ratio in an operating situation that causes a load fluctuation from a low load to a high load, such as during acceleration traveling, so that a high load / high compression ratio can be achieved. The occurrence of the situation can be effectively avoided, which is also beneficial in terms of avoiding knocking.
[0032]
Moreover, in order to improve the quickness of the compression ratio transition, no special oil pressure equipment / electrical equipment and its control equipment are required. Therefore, it is possible to prevent an increase in the number of parts and an accompanying cost increase.
[0043]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and embodiments, and can of course be implemented in various modes without departing from the gist of the present invention. is there.
[0044]
For example, in each of the above-described embodiments, the servo motor 57 is used to bend the connecting rod 27. However, the control shaft guide 40 may be configured to rotate by a hydraulic mechanism type helical spline.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram schematically illustrating the configuration of a variable compression ratio engine 20 according to a first embodiment.
FIG. 2 is a schematic perspective view showing a compression ratio variable mechanism 30 including a connecting rod 27. FIG.
FIG. 3 is an explanatory view for explaining a state of changing a compression ratio by the variable compression ratio mechanism 30;
FIG. 4 is a flowchart showing compression ratio change control.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 20 ... Variable compression ratio engine 22 ... Cylinder block 24 ... Cylinder head 26 ... Cylinder 27 ... Connecting rod 28 ... Piston 29 ... Crankshaft 30 ... Compression ratio variable mechanism 31 ... 1st connecting rod 31a ... Projection part 32 ... 2nd connecting rod 33 ... Small End 34 ... Piston pin 35 ... Large end 36 ... Connecting rod pin 37 ... Control rod 37a ... Through hole 38 ... Pin 39 ... Control shaft 40 ... Control shaft guide 41 ... Bearing portion 42 ... Connecting portion 43 ... Notch region 47 ... Worm gear 48 ... Worm 49 ... Worm wheel 50 ... Intake pipe 52 ... Injector 54 ... Throttle valve 55 ... Throttle sensor 56 ... Rotation speed / crank angle sensor 57 ... Servo motor 58 ... Compression ratio sensor 61 ... Accelerator sensor 62 ... Oxygen sensor 3 ... actuator 64 ... air flow meter 70 ... Spring X ... central axis

Claims (2)

An engine that can change the compression ratio of the engine,
A compression ratio changing mechanism driven to change the compression ratio between a high compression ratio and a low compression ratio;
A transmission mechanism for transmitting a driving force for changing the compression ratio to the compression ratio changing mechanism,
The transmission mechanism is
A first transmission mechanism involved in driving the compression ratio changing mechanism from a high compression ratio to a low compression ratio and driving the compression ratio changing mechanism from a low compression ratio to a high compression ratio;
When the compression ratio changing mechanism is driven from the high compression ratio to the low compression ratio, the driving speed of the compression ratio changing mechanism from the high compression ratio to the low compression ratio is the driving speed from the low compression ratio to the high compression ratio. as the faster, the driving force for driving the high compression ratio to the compression ratio changing mechanism to a low compression ratio, that having a second transmission means for urging in cooperation with the first transmission mechanism, Variable compression ratio engine. A variable compression ratio engine according to claim 1 Symbol placement,
The variable compression ratio engine, wherein the second transmission means includes a spring mechanism and biases the spring force exhibited by the spring mechanism as the driving force in cooperation with the first transmission mechanism.

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