JP2004183527A - Internal combustion engine controlling compression ratio focusing on variance in driving conditions - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly switch a compression ratio of an internal combustion engine corresponding to driving conditions. <P>SOLUTION: The driving conditions of the internal combustion engine is detected to determine a degree of stationary driving which indicates such a degree that the internal combustion engine is driven in the stationary conditions to set the compression ratio of the internal combustion engine in consideration of the stationary driving degree determined in the above way and the detected driving conditions. The proper compression ratio can be set by predicting the variance in the driving conditions in this way, ignition timing is delayed in order to avoid generation of knocking or large energy is consumed in order to frequently and promptly switch the compression ratio even when the driving conditions vary to avoid degradation in a fuel consumption ratio. When the compression ratio is properly switched, the fuel consumption ratio can be largely improved. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique for changing the compression ratio of an internal combustion engine, and more particularly to a technique for reducing the fuel consumption of the internal combustion engine by appropriately changing the compression ratio.
[0002]
[Prior art]
The internal combustion engine has the excellent characteristics of being able to output relatively large power even though it is small, so it is used as a power source for various transportation machines such as automobiles, ships, and airplanes, or a power source for various stationary machines. Widely used as. The operating principle of these internal combustion engines is to burn a compressed air-fuel mixture in a combustion chamber, convert the combustion pressure generated at this time into mechanical work, and take it out as power.
[0003]
Generally, in an internal combustion engine, it is possible to efficiently extract power as the compression ratio, which is an index indicating the compression ratio of the air-fuel mixture, increases, but if the compression ratio is too high, the friction loss increases and the efficiency decreases. There is a tendency. Therefore, it is known that the compression ratio theoretically has an optimum compression ratio that maximizes the thermal efficiency. However, in an actual internal combustion engine, if the compression ratio is increased, abnormal combustion called knocking may occur depending on the operating conditions.To avoid this, the compression ratio must be set to a value lower than the optimal compression ratio. There are many.
[0004]
In view of these points, attempts have been made to switch the compression ratio according to operating conditions in order to improve the thermal efficiency of the internal combustion engine (for example, Patent Documents 1 and 2). That is, it is possible to improve the thermal efficiency of the internal combustion engine by increasing the compression ratio under operating conditions where knocking does not occur and decreasing the compression ratio under operating conditions where knocking occurs. According to the above-mentioned patent document, knocking is liable to occur under conditions where the amount of intake air of the internal combustion engine is large (that is, when the accelerator opening is large), so that the compression ratio is set to a low value to avoid the occurrence of knocking. Under the condition where the amount is small (that is, the condition where the accelerator opening is small), knocking hardly occurs. Therefore, a technique for improving the thermal efficiency by setting the compression ratio to a high value is disclosed.
[0005]
[Patent Document 1]
JP-A-62-258153
[Patent Document 2]
JP-A-63-159624
[0006]
[Problems to be solved by the invention]
However, when the compression ratio is switched according to the operating conditions such as the accelerator opening, no matter how the compression ratio is set for the operating conditions, the effect of improving the fuel consumption is as expected at the beginning. There is a problem that often cannot be obtained.
[0007]
The present invention has been made to solve the above-described problems in the conventional technology, and provides a technology capable of further reducing the fuel consumption by appropriately changing the compression ratio of the internal combustion engine. With the goal.
[0008]
[Means for Solving the Problems and Their Functions and Effects]
In order to solve at least a part of the problems described above, the internal combustion engine of the present invention has the following configuration. That is,
An internal combustion engine having a compression ratio control mechanism capable of controlling a compression ratio,
Operating condition detecting means for detecting operating conditions of the internal combustion engine,
Steady state operation degree indicating the degree of operation of the internal combustion engine in a steady state, a steady state operation degree determination unit that determines based on the detected operating conditions,
Target compression ratio setting means for setting a control target value of the compression ratio while considering the detected operating conditions and the determined steady operation degree,
The gist is to provide
[0009]
Further, the control method of the internal combustion engine of the present invention corresponding to the above internal combustion engine,
A control method for an internal combustion engine having a compression ratio control mechanism capable of controlling a compression ratio,
A first step of detecting operating conditions of the internal combustion engine;
A second step of determining, based on the detected operating conditions, a steady operation degree indicating a degree in which the internal combustion engine is operated in a steady state;
A third step of setting a control target value of a compression ratio while considering the detected operating condition and the determined steady operation degree;
A fourth step of controlling a compression ratio of the internal combustion engine to the set control target value;
The gist is to provide
[0010]
In the internal combustion engine and the control method for the internal combustion engine according to the present invention, the operating condition of the internal combustion engine is detected, and the steady operation degree indicating the degree of the internal combustion engine being operated in the steady state is determined. That is, a determination is made as to whether the internal combustion engine is operating under certain operating conditions, or whether the operating conditions are large or frequently changed. Next, after setting the control target value of the compression ratio in consideration of the detected operating conditions and the degree of steady operation, the compression ratio of the internal combustion engine is set to this target value using the compression ratio control mechanism.
[0011]
Normally, an internal combustion engine is often operated while operating conditions are changed, so in an internal combustion engine whose compression ratio can be changed, if the compression ratio is set according to the operating conditions, every time the operating conditions are changed. It is necessary to change the compression ratio. In view of these points, in the internal combustion engine and the method for controlling the internal combustion engine of the present invention, the compression ratio is set in consideration of not only the operating conditions but also the degree of steady operation. Therefore, when the operating conditions are frequently changed, by setting the compression ratio in anticipation of the change, it is possible to avoid a situation in which the compression ratio is frequently changed. Changing the compression ratio requires energy, so changing it frequently consumes a large amount of energy and may reduce the fuel consumption reduction effect that would be obtained by changing the compression ratio. . On the other hand, if the compression ratio is set in consideration of the degree of steady operation, such a situation can be avoided, so that the effect of reducing the fuel consumption by changing the compression ratio can be reliably obtained. Become.
[0012]
Further, when changing the compression ratio from a high compression ratio to a low compression ratio in response to a change in operating conditions, strong knocking may occur if a change in the compression ratio is delayed with respect to a change in operating conditions. When strong knocking occurs in this way, it is necessary to retard the ignition timing until the compression ratio change is completed in order to avoid this. However, when the ignition timing is retarded, the thermal efficiency of the internal combustion engine is reduced, so that the fuel consumption is increased by that much, and as a result, the effect of reducing the fuel consumption that would be obtained by changing the compression ratio is reduced. It becomes. Of course, if the compression ratio is changed more quickly so as not to be delayed by the change in the operating condition, the ignition timing is not required to be retarded, so that a decrease in the thermal efficiency of the internal combustion engine can be avoided. However, in order to quickly change the compression ratio, a correspondingly large amount of energy is required, so that the fuel consumption is increased and the effect of changing the compression ratio is diminished. According to the internal combustion engine and the control method of the internal combustion engine of the present invention described above, when setting the compression ratio, by taking into account the steady operation degree in addition to the operating condition, the compression ratio is set in anticipation of the change in the operating condition, As a result, it is possible to avoid an increase in fuel consumption for such a reason, and to reliably obtain an effect of improving fuel consumption by changing the compression ratio.
[0013]
In such an internal combustion engine and the control method for the internal combustion engine, at least a value related to a load on the internal combustion engine may be detected as the operating condition. As the value related to the load, various values can be detected.For example, a value for instructing an output to the internal combustion engine, an opening degree of a throttle valve provided in the internal combustion engine, Various values capable of indirectly detecting the pressure in the intake passage, the amount of intake air, and the like can be used.
[0014]
Among the operating conditions of the internal combustion engine, since the load-related conditions are frequently or significantly changed, if the operating condition is detected at least a value related to the load, the steady-state operation degree can be appropriately adjusted. It is possible to make a determination.
[0015]
Further, in the internal combustion engine and the control method, a value related to the load is detected, a change amount and a change frequency of the load are extracted from the detection result, and the steady operation degree is determined based on these. Is also good.
[0016]
When the operating conditions are changed significantly or frequently, it is not always possible to say that the vehicle is operating in a steady state. It is desirable to consider the following. Therefore, it is preferable to extract the change amount and the change frequency of the load from the detection result of the value related to the load of the internal combustion engine and determine the degree of steady operation based on these, since it is possible to appropriately determine, and it is preferable. .
[0017]
In the control method of the internal combustion engine and the internal combustion engine described above, when the determined steady-state operation degree does not satisfy the predetermined criterion, the control target value of the compression ratio is set to a lower value than when the criterion is satisfied. Is also good.
[0018]
In this way, the compression ratio of the internal combustion engine is set lower as the operating conditions of the internal combustion engine depart from the steady operation state, in other words, as the operating conditions are changed more or more frequently. Normally, knocking is more likely to occur as the compression ratio becomes higher. Therefore, if the compression ratio is set to a lower value, knocking due to fluctuations in operating conditions can be avoided. As a result, it is possible to reliably avoid an increase in fuel consumption by delaying the ignition timing in order to avoid knocking, or consuming a large amount of energy to quickly switch the compression ratio. It becomes.
[0019]
Alternatively, in the above-described internal combustion engine and the control method of the internal combustion engine, when the determined steady-state operation degree does not satisfy a predetermined criterion, the control target value of the compression ratio is limited to a value equal to or less than a predetermined value. Is also good.
[0020]
By limiting the compression ratio to a value equal to or less than the predetermined value in this way, it is possible to avoid occurrence of knocking due to fluctuations in operating conditions and to reliably prevent an increase in fuel consumption. It becomes.
[0021]
Further, in the above-described internal combustion engine and control method, the upper limit of the compression ratio is stored in advance according to the degree of steady operation, and the control target value of the set compression ratio exceeds the upper limit. Then, the control target value may be changed to the upper limit value.
[0022]
As the operating condition of the internal combustion engine departs from the steady operating state, knocking is more likely to occur with a change in the operating condition. Therefore, if the upper limit value of the compression ratio is stored in accordance with the degree of steady operation, and the control target value of the compression ratio is clipped to this upper limit value, occurrence of knocking due to a change in operating conditions is appropriately avoided. In addition, it is possible to reduce fuel consumption.
[0023]
In the internal combustion engine and the control method described above, in the internal combustion engine and the control method that detects at least a value related to a load as the operating condition, the control target value of the compression ratio may be set as follows. Is also good. That is, the allowable value of the compression ratio is stored in advance for each of a plurality of regions determined according to the load change amount and the load change frequency. When the control target value of the compression ratio set based on the operating condition exceeds the allowable value stored for each region, the control target value of the compression ratio may be changed to the allowable value. good.
[0024]
As described above, if the allowable value of the compression ratio is determined for each of a plurality of regions defined according to the load change amount and the load change frequency, an appropriate allowable value is determined according to the steady operation degree. Therefore, it is possible to reduce the fuel consumption while appropriately avoiding the occurrence of knocking due to the fluctuation of the operating conditions.
[0025]
Further, as the allowable value of the compression ratio, a larger value may be stored at least in a region where the load change amount and the load change frequency are smaller.
[0026]
With this configuration, the compression ratio is set to a higher value as the operating condition of the internal combustion engine approaches the steady state, and conversely, the compression ratio is set to a lower value as the operating condition gets away from the steady state. Accordingly, the internal combustion engine can be operated at an appropriate compression ratio, which is preferable.
[0027]
In the above-described internal combustion engine and control method, at least a value related to a load of the internal combustion engine and a rotation speed of the internal combustion engine are detected as the operating conditions, and a control target value of a compression ratio is determined as follows. May be set. That is, a reference compression ratio corresponding to the operating condition is stored for each operating condition including at least the rotation speed. At this time, as the reference compression ratio, a reference compression ratio is stored such that at least a region where the rotation speed is lower includes a region where the stored compression ratio decreases as the rotation speed decreases. Keep it. Then, after reading out the stored reference compression ratio in accordance with the detected operating condition, a value corrected based on the steady operation degree may be set as the control target value.
[0028]
Normally, in the internal combustion engine, there is a case where knocking is likely to occur in a region where the operating speed is low. Therefore, if the reference compression ratio is stored so as to include an area where the stored value becomes smaller as the rotation speed becomes lower, it is possible to avoid occurrence of knocking in such an area. Further, in such a region, the operating state assumed during the control of the internal combustion engine and the actual operating state are likely to differ from each other, so that knocking also tends to occur at this point. Therefore, in the region where the rotation speed of the internal combustion engine is equal to or lower than the predetermined rotation speed, if the reference compression ratio is stored in the above-mentioned state, that is, in a state where the lower the rotation speed, the smaller the value, the smaller the value, the smaller the value. Knocking is less likely to occur even when operating conditions are changed. For this reason, it is possible to prevent an increase in fuel consumption due to a retarded ignition timing or the like, which is preferable.
[0029]
The present invention can be effectively applied to a vehicle using an internal combustion engine as a power source. That is, such a vehicle of the present invention
A vehicle equipped with an internal combustion engine having a compression ratio control mechanism capable of controlling a compression ratio as a power source,
An accelerator pedal for setting an output required for the internal combustion engine,
Steady-state operation degree indicating a degree that the internal combustion engine is operated in a steady state, a steady-state operation degree determination unit that determines based on the operation amount of the accelerator pedal,
Target compression ratio setting means for setting a control target value of the compression ratio while considering the detected operating conditions and the determined steady operation degree,
The gist is to provide
[0030]
In the vehicle of the present invention, the degree of steady operation is determined based on the operation amount of the accelerator pedal, and the compression ratio of the internal combustion engine is set in consideration of the determination result. This makes it possible to reliably obtain the effect of improving the fuel consumption by changing the compression ratio.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
In order to more clearly explain the operation and effect of the present invention, embodiments of the present invention will be described in the following order.
A. Device configuration:
B. Overview of engine control:
C. Compression ratio change control:
C-1. Steady-state operation degree judgment processing:
C-2. Compression ratio setting processing:
D. Modification:
[0032]
A. Device configuration:
FIG. 1 is an explanatory diagram conceptually showing the configuration of an engine 10 of the present embodiment having a variable compression ratio mechanism. Hereinafter, the engine 10 will be described as a so-called spark-ignition engine. However, it is needless to say that the engine 10 can be applied to a compression ignition engine such as a diesel engine. As shown in the figure, the engine 10 mainly includes a cylinder head 20, a cylinder block ASSY 30, a main moving ASSY 40, an intake passage 50, an exhaust passage 58, an engine control unit (hereinafter, ECU) 60, and the like. It is configured.
[0033]
The cylinder block ASSY 30 includes an upper block 31 to which the cylinder head 20 is attached, and a lower block 32 in which the main moving ASSY 40 is stored. Further, an actuator 33 is provided between the upper block 31 and the lower block 32. By driving the actuator 33, the upper block 31 can be moved vertically with respect to the lower block 32. ing. A cylindrical cylinder 34 is formed inside the upper block 31.
[0034]
The main moving ASSY 40 includes a piston 41 provided inside the cylinder 34, a crankshaft 43 rotating inside the lower block 32, a connecting rod 42 connecting the piston 41 to the crankshaft 43, and the like. The piston 41, the connecting rod 42, and the crankshaft 43 constitute a so-called crank mechanism. As the crankshaft 43 rotates, the piston 41 slides up and down in the cylinder 34 as the crankshaft 43 rotates. , The crankshaft 43 rotates in the lower block 32. When the cylinder head 20 is attached to the cylinder block ASSY 30, a combustion chamber is formed on the lower surface side (the side in contact with the upper block 31) of the cylinder head 20 and the portion surrounded by the cylinder 34 and the piston 41. Therefore, if the upper block 31 is moved upward by using the actuator 33, the cylinder head 20 is also moved upward, and the volume in the combustion chamber is increased, so that the compression ratio can be reduced. Conversely, if the cylinder head 20 is moved downward together with the upper block 31, the volume in the combustion chamber is reduced, and the compression ratio can be increased.
[0035]
The cylinder head 20 is formed with an intake port 23 for taking in air into the combustion chamber and an exhaust port 24 for discharging exhaust gas from the combustion chamber, and at a portion where the intake port 23 opens to the combustion chamber. An intake valve 21 is provided, and an exhaust valve 22 is provided at a portion where the exhaust port 24 opens to the combustion chamber. The intake valve 21 and the exhaust valve 22 are each driven by a cam mechanism in accordance with the vertical movement of the piston 41. By opening and closing the intake valve 21 and the exhaust valve 22 at appropriate timing in synchronization with the movement of the piston, air can be sucked into the combustion chamber or exhaust gas can be discharged from the combustion chamber. The cylinder head 20 is also provided with a spark plug 27 for igniting a mixture formed in the combustion chamber by blowing a spark.
[0036]
An intake passage 50 for guiding outside air to the cylinder head 20 is connected to the intake port 23 of the cylinder head 20, and an air cleaner 51 is provided at an upstream end of the intake passage 50. The air drawn into the combustion chamber flows into the combustion chamber via the intake passage 50 and the intake port 23 after foreign substances such as dust are removed by the air cleaner 51. A throttle valve 52, a fuel injection valve 55, and the like are provided in the intake passage 50. If the opening degree of the throttle valve 52 is controlled by the electric actuator 53, the amount of air flowing into the combustion chamber can be controlled. Fuel is injected from the fuel injection valve 55 toward the intake port 23. A part of the injected fuel spray is vaporized in the intake port 23, and the remainder flows into the combustion chamber in the form of a fuel spray or a fuel liquid film, and is then mixed with air while being vaporized in the combustion chamber. Forming Qi. In addition, an intake pressure sensor 56 is provided in the intake passage 50, so that the pressure in the intake passage can be detected.
[0037]
An exhaust passage 58 is connected to the exhaust port 24 of the cylinder head 20, and the exhaust gas discharged from the combustion chamber is guided to the outside by the exhaust passage 58 and discharged.
[0038]
The ECU 60 is a microcomputer in which a ROM, a RAM, an input / output circuit, and the like are connected to each other by a bus centering on a central processing unit (hereinafter, CPU). As will be described in detail later, the ECU 60 includes a crank angle sensor 61 provided on the crankshaft 43, an accelerator opening sensor 62 built in the accelerator pedal, and, if necessary, an intake pressure sensor 56 and the like. By taking in the information and driving the ignition plug 27, the fuel injection valve 55, the electric actuator 53, and the like, the operation of the entire engine 10 is controlled.
[0039]
B. Overview of engine control:
Next, the operation of the engine 10 having the above-described configuration will be described. FIG. 2 is a flowchart showing a flow in which the ECU 60 controls the operation of the engine 10. Hereinafter, description will be made according to the flowchart.
[0040]
When starting the engine control routine, the ECU 60 first detects the engine speed Ne and the accelerator opening θac (step S100). The engine rotation speed Ne is calculated from the output of the crank angle sensor 61, and the accelerator opening θac can be detected by using the accelerator opening sensor 62.
[0041]
In step S100, the pressure in the intake passage detected by the intake pressure sensor 56, the throttle opening, and the like can be used instead of the accelerator opening θac. The throttle opening can be detected by a throttle opening sensor (not shown) built in the electric actuator 53. Of course, since the ECU 60 controls the throttle opening, the opening used for control inside the ECU 60 can be used.
[0042]
When the engine rotation speed Ne and the accelerator opening θac are detected in this manner, a process for determining the steady operation degree of the engine 10 is started (step S102). As will be described later in detail, the “steady state of operation” refers to an operating state such as whether the engine 10 is operating in a steady state, whether the operating conditions are frequently changed, and whether the change is large or small. Is an index representing The details of the process for determining the steady operation degree will be described later.
[0043]
After determining the degree of steady operation of the engine 10, a process for setting a compression ratio is started (step S104). As described with reference to FIG. 1, the engine 10 of the present embodiment can change the compression ratio of the engine using the actuator 33. In step S104, an appropriate compression ratio according to the operating conditions of the engine is obtained while taking into account the previously determined degree of steady operation, and then the actuator 33 is driven to reduce the compression ratio of the engine 10 to an appropriate compression ratio. Perform processing to set the ratio. The details of the compression ratio setting process will be described later.
[0044]
The ECU 60 starts the fuel injection control following the compression ratio setting process (step S106). In this control, the amount of air sucked into the combustion chamber is detected, and control is performed to inject a quantity of fuel having a predetermined air-fuel ratio from the fuel injection valve 55 at an appropriate timing. In this embodiment, the amount of air taken into the combustion chamber is calculated based on the pressure in the intake passage detected by the intake pressure sensor 56. Of course, an airflow sensor may be provided in the intake passage 50 to measure the amount of air sucked by the engine 10, and more simply, the engine rotation speed and the accelerator opening (the opening of the throttle valve 52) are taken as parameters. The air amount can be measured in advance and stored as a map, and the air amount can be obtained with reference to this map.
[0045]
Fuel is injected so as to have a predetermined air-fuel ratio with respect to the air amount thus obtained. The air-fuel ratio is an index indicating the mixing ratio of fuel and air, and is defined as a value obtained by dividing the weight of air supplied into the combustion chamber by the weight of fuel. The target air-fuel ratio is stored for each compression ratio in a ROM built in the ECU 60 in the form of a map using the engine speed and the accelerator opening (or throttle valve opening) as parameters.
[0046]
FIG. 3 is an explanatory diagram exemplifying a map storing a target air-fuel ratio for each compression ratio of the engine. The compression ratio of the engine is 13 (ε = 13), and the compression ratio is 10.5 (ε = 10.5). ) And three maps having a compression ratio of 9 (ε = 9) are conceptually represented. For example, when the compression ratio of the engine 10 is set to 13 in the compression ratio setting process (step S104 in FIG. 2), the interpolation calculation is performed by referring to the map displayed in the foreground in FIG. It is possible to calculate a target air-fuel ratio with respect to the engine speed and the accelerator opening. Of course, when a map corresponding to the set compression ratio is not stored, the target air-fuel ratio for the set compression ratio can be calculated by performing an interpolation operation between different compression ratios.
[0047]
Next, a fuel injection amount such that the air-fuel ratio becomes the target air-fuel ratio with respect to the previously detected air amount, and a fuel injection start timing corresponding to the fuel injection amount are calculated. If the air amount and the target air-fuel ratio are determined from the above-described definition of the air-fuel ratio, the fuel amount to be injected is naturally determined. Further, when the fuel injection amount is determined, the fuel injection start timing is also determined naturally. That is, in the engine 10 of the present embodiment, the fuel injection end timing is fixed, so that the fuel injection amount and the fuel injection start timing have a one-to-one relationship, and once the fuel injection amount is determined, the fuel injection start timing naturally increases. It is decided. In the fuel injection control (step S106 in FIG. 2), after the fuel injection start timing is determined as described above, control for driving the fuel injection valve 55 at an appropriate timing based on the output of the crank angle sensor 61 is performed. I do.
[0048]
After ending the fuel injection control, the ECU 60 starts the ignition control (step S108). In the ignition control, a process of igniting the air-fuel mixture formed in the combustion chamber is performed by blowing a spark from the ignition plug 27 at an appropriate timing. The ignition timing is set based on a map stored in the ROM of the ECU 60.
[0049]
FIG. 4 conceptually shows a state in which the ignition timing is stored for each compression ratio in the form of a map using the engine rotation speed and the accelerator opening (or the throttle valve opening) as parameters. Similar to the case of calculating the target air-fuel ratio in the fuel injection control described above, in the ignition control, the ignition timing is calculated by performing an interpolation calculation from the map shown in FIG. In the ignition control, after calculating the ignition timing according to the operating condition of the engine in this way, the ignition plug 27 is driven at an appropriate timing based on the output of the crank angle sensor 61 to ignite the air-fuel mixture in the combustion chamber. Perform control. As a result, the air-fuel mixture burns, the pressure in the combustion chamber rapidly increases, and the piston 41 is pushed down. This force is transmitted to the crankshaft 43 via the connecting rod 42, is converted into rotational force by the crank mechanism, and is output as motive power.
[0050]
Next, the ECU 60 checks whether or not the stop of the engine has been set (step S110). If the stop of the engine has not been set, the ECU 60 returns to step S100 and repeats a series of subsequent processes. When it is set to stop the engine, the engine control routine is ended as it is. Thus, the engine 10 is operated according to the control routine of FIG. 2 under the control of the ECU 60, and generates power according to the setting of the operator.
[0051]
C. Compression ratio change control:
As described above, in the engine 10 of the present embodiment, the compression ratio can be changed, and by setting an appropriate compression ratio in consideration of the steady operation degree of the engine, the fuel consumption efficiency is greatly improved. It is possible. In the following, first, the process of determining the degree of steady operation (step S102 in FIG. 2) will be described, and then the process of setting the compression ratio in consideration of the degree of steady operation (step S104 in FIG. 2) will be described.
[0052]
C-1. Steady-state operation degree judgment processing:
FIG. 5 is a flowchart illustrating a flow of a process for determining the degree of steady operation of the engine 10. This processing is executed by the ECU 60 in the above-described engine control routine. Note that the steady-state operation degree determination process described below uses the accelerator opening detected in the engine control routine to determine the steady-state operation degree, as described later. When the throttle opening or the pressure in the intake passage is detected instead of the opening, it is also possible to make a determination using these. Hereinafter, description will be made according to the flowchart.
[0053]
When the steady operation degree determination process is started, first, a process of incrementing the variable I by 1 is performed (step S200). The steady operation degree determination process is performed once each time the engine control routine makes one turn (see FIG. 2), and the time required for the engine control routine to make one turn is substantially constant. It can be considered as a variable that represents the number of times the engine control routine has been turned, and also roughly represents the elapsed time.
[0054]
Next, the amount of change in the accelerator opening, that is, how much the accelerator opening detected in the current routine has changed from the accelerator opening detected in the previous routine is calculated (step S202). If the accelerator pedal is further depressed, the change amount of the accelerator opening becomes a positive value, and if the accelerator pedal is returned, the change amount becomes a negative value.
[0055]
Then, it is determined whether or not the amount of change in the accelerator opening has been reversed (step S204). If the sign of the change amount has not changed, it can be determined that the change amount has not been inverted. Conversely, if the sign has changed, it can be determined that the change amount has been inverted. If the change amount is inverted (step S204: yes), the number of inversions N is incremented by one (step S206). If the change amount has not been inverted (step S204: no), the process of incrementing the number of inversions N (step S206) is skipped.
[0056]
Next, the absolute value of the change amount is accumulated and stored as an accelerator operation amount (step S208). As a result of accumulating the absolute value of the change amount while counting the number of inversions in this way, for example, if the accelerator pedal is frequently operated while changing in small increments, the number of inversions N takes a large value and the accelerator operation amount becomes It takes a small value for the number of inversions. When the accelerator pedal is slowly and largely operated, the number of reversals N is small, and the accelerator operation amount is a large value. When the accelerator pedal is operated large and frequently, both the number of reversals N and the accelerator operation amount take large values.
[0057]
When the amount of change in the accelerator opening is small (for example, when the absolute value of the amount of change is equal to or less than a predetermined value), the number of inversions N may not be incremented, or the absolute value of the amount of change may not be accumulated. . This makes it possible to more appropriately determine the degree of steady operation by adjusting the threshold to an appropriate value.
[0058]
When the accumulated value of the change amount is stored as the accelerator operation amount in this way, it is determined whether or not the variable I indicating the number of times the engine control routine has reached the predetermined number of times (step S210). (Step S210: no), the steady operation degree determination processing is ended, and the process returns to the engine control routine shown in FIG. Thus, each time the engine control routine is executed once, the steady operation degree determination processing is executed, and the number of reversals N and the accelerator operation amount are updated. When the variable I reaches a predetermined number of times (step S210: yes), the degree of steady-state stability is determined based on the number of reversals N and the accelerator operation amount by a method described later (step S212). The operation amount and the variable I are reset (step S214), and the steady operation degree determination processing ends. That is, in step S210, the degree of steady operation is determined based on the number of times the accelerator pedal has been operated and the amount of operation of the accelerator pedal while the engine control routine has been performed the predetermined number of times. This situation will be additionally described with reference to FIG.
[0059]
FIG. 6 is an explanatory diagram conceptually showing a state in which the accelerator pedal is operated over time. FIG. 6 shows how the accelerator opening changes with the elapsed time on the horizontal axis. Small white circles provided at regular intervals on the curve indicating the change in the accelerator opening indicate that the accelerator opening is detected in the engine control routine. Here, it is assumed that the time required for the engine control routine to make one round is approximately dt time, and therefore the accelerator opening is measured every time dt. Further, dθ shown in the figure is a change amount of the accelerator opening measured every time dt.
[0060]
In the example shown in FIG. 6, during the beginning, the accelerator opening increases each time it is detected, and the change dθ continues to take a positive value, but when the time ta is reached, it takes a positive value until then. The change dθ changes to a negative value. Therefore, at this time, the number of inversions N is incremented by one, and N = 1. Next, when the time tb is reached, the change amount dθ of the accelerator opening again changes to a positive value, and the number of inversions N is incremented to N = 2. Hereinafter, similarly, at times tc and td, the number of inversions N is incremented to N = 3 and N = 4, respectively. By performing such an operation, it is possible to detect the number of times that the change amount dθ of the accelerator opening is inverted while the engine control routine is performed a predetermined number of times. Further, by accumulating the absolute value of the change amount dθ, the operation amount of the accelerator can be obtained.
[0061]
As described above, when the number of reversals N and the accelerator operation amount are detected during the execution of the engine control routine a predetermined number of times, the determination of the degree of steady operation is performed by referring to a map as shown in FIG. Do. The ROM of the ECU 60 stores a map in which the steady operation degree is set according to the combination of the number of reversals and the accelerator operation amount. As shown in FIG. 7, in this embodiment, three stages of “steady operation”, “quasi-steady operation”, and “unsteady operation” are set as the degree of steady operation. “Steady operation” corresponds to a case where both the number of reversals and the accelerator operation amount are small. In addition, when the accelerator operation amount is large but the number of reversals is small (for example, when the accelerator pedal is largely moved only once), or when the number of reversals is large but the accelerator operation amount is small (for example, the accelerator pedal is slightly depressed). Although it is adjusted, the system is operated under constant conditions as a whole) is also set to “steady operation”. If both the number of reversals and the accelerator operation amount take a large value, it is set to “unsteady operation”. The number of reversals or the accelerator operation amount is smaller than the unsteady operation, and an intermediate state between the steady operation and the unsteady operation is set to “quasi-steady operation”.
[0062]
In step S212 in the steady operation degree determination process shown in FIG. 5, the steady operation degree is inverted by referring to the map shown in FIG. 7 based on the detected number of inversions N and the accelerator operation amount. It is.
[0063]
In the above description, the number of turns of the engine control routine is counted, the number of inversions N and the amount of accelerator operation during the execution of the predetermined number of times of the routine are detected, and the steady operation degree is determined based on these values. Was determined. Of course, instead of counting the number of times the routine has been turned on, a timer may be set to detect the number of reversals N and the accelerator operation amount during the elapse of the predetermined time to determine the degree of steady operation. .
[0064]
Also, in the above description, the steady operation degree is assumed to have three stages of “steady operation”, “quasi-steady operation”, and “unsteady operation”, but more stages may be set. Is also possible. Further, the steady operation degree may be represented by a numerical value, and the numerical value may be determined based on the number of reversals and the accelerator operation amount.
[0065]
Alternatively, in the above description, the absolute value of dθ (the amount of change in the accelerator opening) during the predetermined number of times of the engine control routine is accumulated, and this accumulated value is used as the accelerator operation amount. On the other hand, the absolute value of the change amount dθ may be accumulated between the time when the change amount dθ is inverted and the time when the change amount dθ is inverted again, and the accelerator operation amount may be obtained every time the change amount dθ is inverted. In this way, the number of inversions and the accelerator operation amount for each inversion during the predetermined number of rotations of the engine control routine may be obtained, and the average accelerator operation amount may be calculated to determine the degree of steady operation. Alternatively, the respective accelerator operation amounts are averaged while appropriately assigning weights according to, for example, the sign of the change amount dθ and the engine operating conditions, and the steady operation degree is determined based on the obtained accelerator operation amount and the number of reversals. The determination may be made.
[0066]
C-2. Compression ratio setting processing:
After the degree of steady operation is determined as described above, the compression ratio is set in consideration of the determination result. FIG. 8 is a flowchart illustrating a flow of processing in which the engine 10 of the present embodiment sets the compression ratio. This process is executed by the ECU 60 every time the engine control routine is turned. Hereinafter, description will be made with reference to FIG.
[0067]
When the compression ratio setting process is started, first, the compression ratio is determined based on the engine speed and the accelerator opening (step S300). The engine rotation speed and the accelerator opening have already been detected in step S100 in the engine control routine. Further, as is apparent from the fact that the degree of steady operation is not taken into account when determining the compression ratio, the compression ratio determined at this time is set so as to be optimal when the engine 10 is operating in a steady state. Compression ratio. These compression ratios are stored in the ROM of the ECU 60 in the form of a map.
[0068]
FIG. 9 is an explanatory diagram conceptually showing a map stored in the ROM of the ECU 60, that is, a map in which the compression ratio is set such that the fuel consumption efficiency is maximized during the steady operation of the engine 10. . As shown, in the present embodiment, the compression ratio is set to decrease as the accelerator opening increases, that is, as the engine load increases. Further, in a region where the engine rotation speed is relatively low, there is a region where the compression ratio is set to be lower as the rotation speed is lower.
[0069]
In general, as the engine load increases, knocking is more likely to occur, and when knocking occurs, it is necessary to retard the ignition timing to avoid knocking, and as a result, fuel consumption efficiency deteriorates. Therefore, if the compression ratio is set lower as the engine load increases, occurrence of knocking can be avoided, and in turn, deterioration of fuel consumption efficiency can be avoided. Further, since knocking is likely to occur under operating conditions where the engine speed is low, it is preferable to provide a region in which the compression ratio becomes lower as the rotation speed decreases, in a region where the engine speed is relatively low. In addition, it is possible to avoid occurrence of knocking and to avoid deterioration of fuel consumption efficiency. In step S300 in the compression ratio setting process shown in FIG. 8, the compression ratio at the time of steady operation is determined by referring to the map shown in FIG.
[0070]
When the compression ratio at the time of steady operation is determined in this way, a process for correcting the compression ratio in consideration of the degree of steady operation is performed (step S302). The correction amount of the compression ratio is stored in the ROM in the ECU 60 in advance. FIG. 10 is an explanatory diagram exemplifying the correction amount of the compression ratio stored in the ROM. For example, it is assumed that the current steady operation degree is determined to be “steady operation”. In this case, since the compression ratio determined in step S300 may be employed as it is, “0” is stored as the correction amount. If the degree of steady operation is determined to be "quasi-steady operation", the compression ratio determined in step S300 is corrected to a compression ratio lower by "1.5". If the steady operation degree is determined to be “unsteady operation”, the compression ratio is corrected to a compression ratio lower by “2.5”. In step S302 in the compression ratio setting process shown in FIG. 8, the process of correcting the compression ratio in accordance with the degree of steady operation is performed.
[0071]
Next, it is confirmed that the compression ratio does not exceed the upper limit (step S304). That is, in consideration of a case where an abnormally high compression ratio is calculated for some reason, an upper limit value according to the degree of steady operation is predetermined for the compression ratio. FIG. 10 is an explanatory diagram conceptually exemplifying a state in which the upper limit of the compression ratio is stored in the ROM of the ECU 60 according to the degree of steady operation. In step S304, it is confirmed that the corrected compression ratio does not exceed the upper limit of the compression ratio determined according to the degree of steady operation as described above, and if the corrected compression ratio exceeds the upper limit (step S304: No), the compression ratio is changed to the upper limit (step S306). As a result, the compression ratio of the engine 10 is clipped to the compression ratio according to the degree of steady operation, and never exceeds the upper limit.
[0072]
The ECU 60 changes the compression ratio of the engine 10 by driving the actuator 33 according to the compression ratio thus corrected (step S308). The actuator 33 is a linear actuator that operates using electric power as a power source, and forms a servo control system that performs position servo with the ECU 60. Of course, instead of the actuator 33, an actuator operated by another power source such as a hydraulic pressure may be used. After controlling the actuator 33 to change the compression ratio of the engine 10 to the corrected compression ratio, the ECU 60 ends the compression ratio setting process shown in FIG. 8 and returns to the engine control routine of FIG.
[0073]
As described above, in the engine 10 of the present embodiment, the compression ratio is set in consideration of the steady operation degree. For this reason, for the reason described below, it is possible to sufficiently bring out the effect of changing the compression ratio and to greatly improve the fuel consumption efficiency.
[0074]
When the engine is operating in a substantially constant operating state, an appropriate compression ratio is set according to the operating conditions (typically, the engine speed and the engine load), so that the fuel consumption efficiency of the engine is improved. Can be greatly improved. However, the engine is often operated while the change of the operating condition (particularly the engine load) is largely or frequently changed, so that it is necessary to change the compression ratio according to the change of the operating condition. However, changing the compression ratio requires a large amount of energy to drive the actuator 33 to move the upper block 31 and the cylinder head 20. Therefore, if the compression ratio is changed frequently or greatly, The change will reduce the fuel efficiency improvement that would otherwise be obtained. In view of these points, if the compression ratio is set in consideration of the degree of steady operation as described above, it is possible to set an appropriate compression ratio in anticipation of a change in operating conditions, and consequently fuel consumption. The efficiency can be greatly improved.
[0075]
Further, when the compression ratio is changed from the high compression ratio to the low compression ratio, if the change in the compression ratio is delayed with respect to the change in the operating conditions, strong knocking may occur. If the ignition timing is retarded to avoid the occurrence of knocking, the fuel consumption efficiency will be reduced. Of course, if the upper block 31 and the cylinder head 20 are quickly moved by using the large-sized actuator 33 so that the change of the compression ratio is not delayed with respect to the fluctuation of the operating condition, the occurrence of knocking can be avoided. However, in this case, a large amount of energy is required to drive the actuator 33, and eventually, the fuel consumption efficiency is reduced. On the other hand, by considering the degree of steady operation as described above, if an appropriate compression ratio is set in anticipation of a change in operating conditions, such a situation can be avoided, and the fuel consumption efficiency can be reduced. It is possible to greatly improve.
[0076]
D. Modification:
In the embodiment described above, the optimum compression ratio during the steady operation is stored (see FIG. 9), and the compression ratio is corrected according to the steady operation degree. However, the method of setting an appropriate compression ratio while considering the determination result of the degree of steady operation is not limited to such a method, and various methods can be applied. For example, as shown in FIG. 11, an appropriate compression ratio may be stored in advance for each steady operation degree, and the compression ratio may be set with reference to a corresponding map according to the result of determination of the steady operation degree. good.
[0077]
Further, in the above description, the compression ratio of the engine 10 has been described as being continuously changeable. However, it is needless to say that the compression ratio may be switched in several stages. This makes it possible to simplify the control contents.
[0078]
In the embodiment described above, the compression ratio is changed by moving the upper block 31 and the cylinder head 20 using the actuator 33. However, the method of changing the compression ratio is not limited to such a method, and can be applied to various methods. Regardless of which switching method is used, similarly to the above-described embodiment, if the switching of the compression ratio is delayed due to the change in the operating conditions, the ignition timing is retarded to avoid knocking. Need arises. Further, since a large amount of energy is required for switching the compression ratio, frequent or rapid switching requires a large amount of energy. Therefore, it goes without saying that the present invention can be suitably applied to such a case.
[0079]
Further, the engine 10 of the present embodiment described above can be suitably mounted as a power source of a vehicle. Since the running condition of the vehicle changes, the operating conditions of the internal combustion engine are often or frequently changed accordingly. Therefore, if the above-described engine 10 is used as a power source, it is possible to greatly improve the fuel consumption efficiency.
[0080]
Although various embodiments have been described above, the present invention is not limited to all the above embodiments, and can be implemented in various modes without departing from the gist thereof.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram conceptually showing a configuration of an engine according to an embodiment.
FIG. 2 is a flowchart showing a flow of an engine operation control routine.
FIG. 3 is an explanatory diagram conceptually showing a map in which a control target value of an air-fuel ratio is set according to a compression ratio.
FIG. 4 is an explanatory diagram conceptually showing a map in which a control target value of an ignition timing is set according to a compression ratio.
FIG. 5 is a flowchart showing a flow of a steady operation degree determination process of the present embodiment executed in an engine control routine.
FIG. 6 is an explanatory diagram conceptually showing a state in which the number of times the change amount of the accelerator opening is inverted and the accelerator operation amount are detected in order to determine the degree of steady operation.
FIG. 7 is an explanatory diagram exemplifying a state in which a steady operation degree is determined according to the number of reversals and an accelerator operation amount;
FIG. 8 is a flowchart illustrating a flow of a compression ratio setting process of the present embodiment executed in an engine control routine.
FIG. 9 is an explanatory diagram conceptually illustrating a map in which a compression ratio in a steady operation state is set according to an operating condition of an engine.
FIG. 10 is an explanatory diagram exemplifying a state where a correction amount of a compression ratio and an upper limit value of the compression ratio are set according to a degree of steady operation.
FIG. 11 is an explanatory diagram conceptually showing a state in which an appropriate compression ratio is stored in the form of a map in accordance with the degree of steady operation.
[Explanation of symbols]
10 ... Engine
20 ... Cylinder head
21 ... intake valve
22 ... Exhaust valve
23 ... intake port
24… Exhaust port
27 ... Spark plug
30 ... Cylinder block ASSY
31… Upper block
32 ... Lower block
33 ... actuator
34 ... cylinder
40: Main moving ASSY
41 ... Piston
42 ... Connecting rod
43 ... Crankshaft
50 ... intake passage
51 ... Air cleaner
52 ... Throttle valve
53 ... Electric actuator
55 ... Fuel injection valve
56 ... intake pressure sensor
58… Exhaust passage
60 ... ECU
61 ... Crank angle sensor
62 ... accelerator opening sensor

Claims (11)

An internal combustion engine having a compression ratio control mechanism capable of controlling a compression ratio,
Operating condition detecting means for detecting operating conditions of the internal combustion engine,
Steady state operation degree indicating the degree of operation of the internal combustion engine in a steady state, a steady state operation degree determination unit that determines based on the detected operating conditions,
An internal combustion engine comprising target compression ratio setting means for setting a control target value of a compression ratio in consideration of the detected operating conditions and the determined degree of steady operation. The internal combustion engine according to claim 1,
The internal combustion engine, wherein the operating condition detecting means is means for detecting at least a value related to a load of the internal combustion engine as the operating condition. The internal combustion engine according to claim 2,
The steady-state operation degree determining means extracts a change amount and a change frequency of the load from a detection result of a value related to the load, and determines the steady-state operation degree in consideration of the change amount and the change frequency. Is an internal combustion engine. The internal combustion engine according to any one of claims 1 to 3, wherein
The internal combustion engine, wherein the target compression ratio setting unit is a unit that sets the control target value of the compression ratio to a lower value when the steady operation degree does not satisfy a predetermined standard than when the standard is satisfied. The internal combustion engine according to any one of claims 1 to 3, wherein
The internal combustion engine, wherein the target compression ratio setting means limits the control target value of the compression ratio to a value equal to or less than a predetermined value when the degree of steady operation does not satisfy a predetermined reference. The internal combustion engine according to any one of claims 1 to 3, wherein
Upper limit compression ratio storage means for storing an upper limit of the compression ratio according to the degree of steady operation,
When the set control target value of the compression ratio exceeds an upper limit stored according to the steady operation degree, a target compression ratio changing unit that changes the control target value of the compression ratio to the upper limit. An internal combustion engine comprising: The internal combustion engine according to claim 3,
For each of a plurality of areas determined according to the load change amount and the load change frequency, an allowable compression ratio storage unit that stores an allowable value of the compression ratio,
Target compression ratio changing means for changing the control target value of the compression ratio to the allowable value when the set control target value of the compression ratio exceeds the allowable value stored for each area. Internal combustion engine. The internal combustion engine according to claim 7, wherein
The internal combustion engine, wherein the permissible compression ratio storage means stores the permissible value having a larger value at least in a region where the load change amount and the load change frequency are smaller. The internal combustion engine according to claim 1,
The operating condition detecting means is means for detecting, as the operating condition, at least a value related to a load of the internal combustion engine and a rotation speed of the internal combustion engine,
The target compression ratio setting means,
Reference compression ratio storage means for storing a reference compression ratio corresponding to the operation condition for each operation condition including at least the rotation speed;
The reference compression ratio stored in accordance with the operating conditions, the reference compression ratio correction means to set the control target value by correcting based on the steady operation degree, and
The internal combustion engine, wherein the reference compression ratio storage means has, at least in a region at or below a predetermined rotation speed, a region where the stored reference compression ratio decreases as the rotation speed decreases. A vehicle equipped with an internal combustion engine having a compression ratio control mechanism capable of controlling a compression ratio as a power source,
An accelerator pedal for setting an output required for the internal combustion engine,
Steady-state operation degree indicating a degree that the internal combustion engine is operated in a steady state, a steady-state operation degree determination unit that determines based on the operation amount of the accelerator pedal,
A vehicle comprising target compression ratio setting means for setting a control target value of a compression ratio in consideration of the detected operating conditions and the determined degree of steady operation. A control method for an internal combustion engine having a compression ratio control mechanism capable of controlling a compression ratio,
A first step of detecting operating conditions of the internal combustion engine;
A second step of determining, based on the detected operating conditions, a steady operation degree indicating a degree in which the internal combustion engine is operated in a steady state;
A third step of setting a control target value of a compression ratio while considering the detected operating condition and the determined steady operation degree;
And a fourth step of controlling the compression ratio of the internal combustion engine to the set control target value.

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