JP4415464B2 - Turbocharged internal combustion engine with variable compression ratio device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an internal combustion engine including a turbocharger driven by exhaust gas and a variable compression ratio device.
[0002]
[Prior art]
For example, Japanese Patent Publication No. 7-3201 discloses a supercharged internal combustion engine equipped with a variable compression ratio device. This is a mechanical supercharger, and when the load is high, the turbocharger is operated to improve the output and reduce the compression ratio to prevent knocking. At medium and low loads that do not require supply, the turbocharger is turned off and no supercharging is performed, and the compression ratio is increased to improve fuel efficiency.
[0003]
[Problems to be solved by the invention]
However, when a turbocharger is used as a turbocharger, a response delay occurs in the change of the supercharging pressure during a transition, unlike a mechanical supercharger, and the compression ratio is simply changed according to the load and rotation speed. So it ’s not optimal.
[0004]
An object of the present invention is to use a variable compression ratio control by a variable compression ratio device to offset a response delay of a turbocharger and improve drivability.
[0005]
[Means for Solving the Problems]
According to a first aspect of the present invention, in an internal combustion engine having a turbocharger driven by exhaust gas and having a variable compression ratio device, the required supercharging due to a response delay of the turbocharger at the time of transition. The variable compression ratio device controls the compression ratio so as to compensate for the delay in torque change based on the difference between the pressure and the actual supercharging pressure.
[0006]
That is, in a turbocharger driven by exhaust, even if the throttle opening is suddenly increased or decreased from a steady state, a response delay is accompanied by a change in the supercharging pressure mainly due to the inertia of the rotor. That is, the actual supercharging pressure cannot follow the change in the required supercharging pressure, and the torque change is delayed. In contrast, in the present invention, the compression ratio is controlled by the variable compression ratio device so as to compensate for the response delay of the supercharging pressure, and the delay in torque change is offset or reduced. Here, the response delay of the boost pressure is not necessarily limited to that obtained by detecting the actual boost pressure with a sensor. For example, the elapsed time from the change in the throttle opening, the degree of change in the engine speed, the acceleration / deceleration It is also possible to estimate the supercharging pressure response delay using parameters such as the degree, and to perform compression ratio control to compensate for this.
[0007]
In the invention of claim 2, which further embodies the invention of claim 1, the variable compression ratio device increases the compression ratio during acceleration from a low load range, and then gradually decreases the compression ratio. ing.
[0008]
That is, the torque quickly rises due to the increase in the compression ratio, and the delay in the torque increase due to the delay in response of the supercharging pressure is compensated. Thereafter, since the supercharging pressure rises with a delay, a smooth torque change can be obtained while suppressing knocking by gradually reducing the compression ratio. In particular, in a low load region, even when the compression ratio is low in order to reduce the pumping loss and increase the exhaust temperature, the torque increases rapidly due to the increase in the compression ratio.
[0009]
Furthermore, the invention of claim 3 is provided with an intake pressure sensor for detecting the actual supercharging pressure, and the correction amount of the compression ratio at the time of transition is obtained according to the difference between the required supercharging pressure and the actual supercharging pressure. It is characterized by being able to.
[0010]
In this case, the actual supercharging pressure by the turbocharger is detected as the actual supercharging pressure by the intake pressure sensor. Since the required supercharging pressure is determined based on engine operating conditions such as the throttle opening and the rotational speed, the difference between the two is large at the time of transition, and the compression ratio is greatly corrected accordingly. Thereafter, when the actual supercharging pressure approaches the required supercharging pressure, the correction amount of the compression ratio becomes small.
[0011]
According to a fourth aspect of the present invention, when decelerating from a high load range, the supercharged air discharged from the compressor is supplied to the internal combustion engine without bypassing, and the compression ratio is reduced by the variable compression ratio device. It is characterized by.
[0012]
When the throttle opening is suddenly decreased from the high load range, intake noise is generated because the decrease in the supercharging pressure is delayed due to the response delay of the turbocharger. In general, the turbocharger is configured to circulate the supercharged air from the compressor downstream to the compressor upstream via a recirculation valve to reduce the supercharging pressure and avoid intake noise. In the invention of claim 4, the supercharged air is supplied to the internal combustion engine without being bypassed in this way. Then, while the intake air amount becomes substantially excessive, the compression ratio quickly decreases, so that generation of excessive torque is avoided.
[0013]
【The invention's effect】
According to the present invention, it is possible to cancel or reduce the torque change delay during the transition caused by the response delay of the turbocharger by the change of the compression ratio, and to improve the drivability of the turbocharged internal combustion engine.
[0014]
In particular, according to the second aspect of the present invention, since the torque rapidly increases during acceleration, it is possible to eliminate the feeling of stagnation at the time of acceleration due to the torque delay characteristic of the turbocharged internal combustion engine. In addition, by gradually reducing the compression ratio as the boost pressure increases, a smooth torque change can be obtained while suppressing knocking.
[0015]
According to the invention of claim 3, since the compression ratio correction amount at the time of transition is given according to the difference between the required supercharging pressure and the actual supercharging pressure, the delay of the actual torque change at the time of the transition can be ensured. The compression ratio can be controlled so as to cancel out, and the uncomfortable feeling of torque change peculiar to the turbocharged internal combustion engine can be more effectively eliminated.
[0016]
Further, according to the fourth aspect of the present invention, it is possible to reduce intake noise during deceleration without bypassing the supercharged air downstream of the compressor, and the recirculation valve and the recirculation passage can be omitted. .
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
[0018]
First, the configuration of the variable compression ratio device of the internal combustion engine 1 will be described with reference to FIG.
[0019]
This variable compression ratio device uses a multi-link type piston-crank mechanism, and the crankshaft 31 includes a plurality of journal portions 32, a crankpin portion 33, and a counterweight portion 31a. A journal portion 32 is rotatably supported by a main bearing of a cylinder block (not shown) serving as a main body. The crankpin portion 33 is eccentric from the journal portion 32 by a predetermined amount, and a lower link 34 is rotatably connected thereto.
[0020]
The lower link 34 has a substantially T-shape, and the crank pin portion 33 is fitted in a substantially central connecting hole configured to be split from a main body 34a and a cap 34b.
[0021]
The upper link 35 has a lower end side rotatably connected to one end of the lower link 34 by a connecting pin 36 and an upper end side rotatably connected to a piston 38 by a piston pin 37. The piston 38 receives combustion pressure and reciprocates in the cylinder 39 of the cylinder block.
[0022]
Above the cylinder 39, there are an intake valve 43 that opens and closes the intake port 44 in synchronization with the rotation of the crankshaft 31, and an exhaust valve 45 that opens and closes the exhaust port 46 in synchronization with the rotation of the crankshaft 31. Has been placed.
[0023]
The upper end side of the control link 40 is rotatably connected to the other end of the lower link 34 by a connecting pin 41, and the lower end side is rotatably connected to an appropriate position of an engine body, for example, a cylinder block, via a control shaft 42. . Specifically, the control shaft 42 is supported by the engine body so as to rotate about the small diameter portion 42b, and the lower end portion of the control link 40 is rotatable on the large diameter portion 42a that is eccentric to the small diameter portion 42b. Is fitted.
[0024]
The rotation position of the control shaft 42 is controlled by a compression ratio control actuator described later. The compression ratio control actuator can hold the control shaft 42 at an arbitrary rotational position against a reaction force applied from the control link 40.
[0025]
In the configuration as described above, when the control shaft 42 is rotated by the compression ratio control actuator, the axial center position of the large-diameter portion 42a that is eccentric with respect to the small-diameter portion 42b, in particular, the relative position with respect to the engine body. Change. Thereby, the rocking | fluctuation support position of the lower end of the control link 40 changes. When the swing support position of the control link 40 changes, the stroke of the piston 38 changes, and the position of the piston 38 at the piston top dead center (TDC) becomes relatively high or low. As a result, the engine compression ratio changes.
[0026]
Further, the internal combustion engine 1 includes a turbocharger 51 as a supercharger. The turbocharger 51 has a configuration in which a turbine 52 located in an exhaust passage 54 and a compressor 53 located in an intake passage 55 are coaxially arranged. In order to control the supercharging pressure in accordance with operating conditions, An exhaust bypass valve 56 for bypassing a part of the exhaust from the upstream side of the turbine 52 is provided.
[0027]
FIG. 1 is an explanatory diagram showing the control system of the internal combustion engine 1. An air flow meter 2 for detecting the intake air amount is arranged upstream of the compressor 53 in the intake passage 55. An intake pressure sensor 4 that detects the actual supercharging pressure is disposed downstream of the engine 3. Further, the crank angle sensor 5 that detects the crank angle of the engine, the oxygen sensor 6 that responds to the exhaust composition, the water temperature sensor 7 that detects the cooling water temperature, the knocking sensor 8 that detects knocking, and the opening of the throttle valve 9 And a throttle opening sensor 10 for detecting the detection signal, and detection signals from these sensors are input to an engine control module (ECM) 11.
[0028]
As main actuators, an electromagnetic supercharging pressure control valve 12 for controlling the negative pressure supply to the diaphragm portion 56A of the exhaust bypass valve 56, and a compression ratio for controlling the compression ratio by moving the control shaft 42 described above. A control actuator 13 and an AAC valve 15 for controlling the amount of auxiliary air introduced through the intake bypass passage 14 are provided, and these are controlled by an output signal of the engine control module 11 as will be described later. The compression ratio control actuator 13 is composed of, for example, a step motor. The AAC valve 15 is mainly used for feedback control of idle speed and offset of auxiliary machine driving torque. In addition, the engine control module 11 controls the injection amount and injection timing of the fuel injection valve 16 and the ignition timing by the spark plug 17. In FIG. 1, 18 indicates an air cleaner, 19 indicates a catalytic converter, and 20 indicates an exhaust silencer.
[0029]
In the above configuration, as will be described later, the target value tP of the supercharging pressure is set according to the engine operating conditions, and the actual supercharging pressure rP is detected by the intake pressure sensor 4, and this actual supercharging pressure rP. The supercharging pressure control valve 12 is controlled by the supercharging pressure control signal (duty signal) from the engine control module 11 so that becomes the target supercharging pressure tP. This supercharging pressure is controlled to a higher supercharging pressure in the high speed and high load range.
[0030]
On the other hand, the compression ratio is controlled via the compression ratio control actuator 13 so as to be optimized according to the engine operating conditions. Basically, the compression ratio control is controlled so that the higher the supercharging pressure, the lower the compression ratio, and the lower the supercharging pressure, the higher the compression ratio. That is, the compression ratio is lowered to avoid knocking during high supercharging operation, and the compression ratio is kept high to improve thermal efficiency (improve fuel efficiency) during low supercharging operation.
[0031]
FIG. 3 is a flowchart showing a control flow of the supercharging pressure and compression ratio executed in the engine control module 11, and this will be described below.
[0032]
The routine shown in this flowchart is repeatedly executed at predetermined time intervals in the engine control module 11. First, in step 1, from the output of each sensor, the engine speed Ne, the throttle opening TVO, the actual excess Each of the supply pressures rP is read. In step 2, the target boost pressure tP is calculated based on the engine speed Ne and the throttle opening TVO at that time. Specifically, a corresponding value is looked up from a predetermined boost pressure control map in which the target boost pressure tP is stored in correspondence with the engine speed Ne and the throttle opening TVO. As described above, the stored value of the supercharging pressure control map has a larger value under high rotation and high load conditions (high supercharging pressure), and a smaller value under low rotation and low load conditions (low supercharging pressure). .
[0033]
It should be noted that a boost pressure control signal is generated and the boost pressure control valve 12 is controlled by another routine (not shown) so that the target boost pressure tP calculated in Step 2 is obtained.
[0034]
Next, in step 3, the reference compression ratio bE is obtained based on the engine speed Ne and the throttle opening TVO. Specifically, a corresponding value is looked up from a predetermined compression ratio control map in which the reference compression ratio bE is stored in correspondence with the engine speed Ne and the throttle opening TVO. As described above, the value stored in the compression ratio control map has a smaller value (low compression ratio) as the condition becomes higher, and a larger value (high compression ratio) as the condition becomes lower. Yes.
[0035]
Next, the routine proceeds to step 4 where the actual boost pressure rP is subtracted from the target boost pressure tP to calculate the boost pressure difference dP. This supercharging pressure difference dP occurs mainly due to the inertia of the turbocharger 51 at the time of transition, and when accelerating, that is, when the supercharging pressure increases, the supercharging pressure difference dP appears as a positive value, When the vehicle is decelerating, that is, when the supercharging pressure is reduced, a negative value appears. In the steady state, the supercharging pressure difference dP is almost zero.
[0036]
In step 5, it is determined whether or not the absolute value of the supercharging pressure difference dP obtained as described above is larger than a predetermined value dPth. If the value is equal to or less than the predetermined value dPth, it is assumed that the state is close to a steady state, and the process proceeds to step 12 where the target compression ratio tE is set to the reference compression ratio dE and the AAC valve 15 is closed in step 13. State.
[0037]
When the magnitude (absolute value) of the supercharging pressure difference dP is larger than the predetermined value dPth, it is in a transient state, so that the process proceeds from step 5 to step 6. In this step 6, whether the supercharging pressure difference dP is positive or negative is determined. As described above, this positive / negative is used to determine whether the vehicle is accelerating or decelerating. If the supercharging pressure difference dP is positive, it is an acceleration and the routine proceeds to step 7. If the supercharging pressure difference dP is negative, the vehicle is decelerating and the routine proceeds to step 10.
[0038]
In step 7, a compression ratio correction value hE is calculated based on the supercharging pressure difference dP. The larger the supercharging pressure difference dP, the larger the compression ratio correction value hE is given.
[0039]
In the next step 8, the compression ratio correction value hE is added to the reference compression ratio bE corresponding to the operating condition to calculate the target compression ratio tE. Further, in step 9, the AAC valve 15 is controlled to be closed.
[0040]
On the other hand, if it is a deceleration, in step 10, the target compression ratio tE is set to the minimum compression ratio Emin. This minimum compression ratio Emin is the lowest compression ratio that can be realized by the variable compression ratio apparatus. Then, the process proceeds to step 11 and the AAC valve 15 is controlled to be opened.
[0041]
Finally, a compression ratio control signal is generated by another routine (not shown) so that the target compression ratio tE obtained in any one of step 8, step 10 and step 12 is obtained, and the compression ratio control actuator 13 is controlled. Is done.
[0042]
FIG. 4 is a time chart showing the actual behavior of each part under the control as described above, which will be described below.
[0043]
This figure shows a state in which the internal combustion engine 1 that has been operating in the steady state is accelerated at the timing t1 and then decelerated from the steady state at high speed and high load at the timing t3.
[0044]
As shown in the figure, if the throttle opening increases stepwise at timing t1, the target boost pressure tP also increases stepwise accordingly, but the actual boost pressure rP is a constant delay as shown by the broken line. It follows the target supercharging pressure tP with a delay due to the inertia of the turbocharger 51. Therefore, a large boost pressure difference dP is generated at the start of acceleration.
[0045]
On the other hand, the reference compression ratio bE decreases stepwise as the throttle opening increases. Since the supercharging pressure difference dP at this time is larger than the predetermined value (+ dPth), the supercharging pressure difference dP The compression ratio correction value hE is added according to the above, and the target compression ratio tE is once larger than before the acceleration is started. Due to this compression ratio correction, the torque generated by the internal combustion engine 1 is increased and good acceleration can be obtained.
[0046]
The compression ratio once increased gradually decreases as the supercharging pressure difference dP decreases, and after the actual supercharging pressure rP converges in the vicinity of the target supercharging pressure tP (after t2), it returns to the reference compression ratio bE. It is. Thereby, excessive torque generation and knocking can be avoided.
[0047]
Next, if the throttle opening decreases stepwise at timing t3, the target boost pressure tP also decreases stepwise accordingly, but the actual boost pressure rP also has a certain delay as shown by the broken line. And follow the target boost pressure tP. Accordingly, at the start of deceleration, a large supercharging pressure difference dP is generated as a negative value.
[0048]
Since intake noise becomes a problem during such rapid deceleration, a general turbocharger-equipped internal combustion engine performs recirculation of supercharged air as described above. That is, when the throttle valve is suddenly closed, the air downstream of the compressor of the turbocharger is circulated to the upstream side of the compressor, and the supercharging pressure is quickly reduced.
[0049]
On the other hand, in this embodiment, the temporary pressure between the compressor 53 and the throttle valve 9 is opened by opening the AAC valve 15 while the supercharging pressure difference dP is smaller than a predetermined value (−dPth). The generation of intake noise accompanying the rise is avoided, and the supercharging pressure is quickly reduced. This makes it possible to omit passages and valves necessary for recirculation.
[0050]
If the AAC valve 15 is simply opened at the time of deceleration, an excessive torque is generated due to an increase in the amount of intake air, and the driver feels uncomfortable. However, in this embodiment, the AAC valve 15 is at the time of deceleration. Since the target compression ratio tE is fixed at the minimum compression ratio Emin and the torque is suppressed simultaneously with the opening control, no such uncomfortable feeling is given.
[0051]
After deceleration, when the actual boost pressure rP converges to the vicinity of the target boost pressure tP at t4, the AAC valve 15 returns to the closed state and the compression ratio is returned to the reference compression ratio bE.
[0052]
As mentioned above, although one Example of this invention was described, this invention is not limited to this, A various change is possible. For example, in the above embodiment, the supercharging pressure is feedback-controlled to a value corresponding to the operating conditions, but the present invention can be similarly applied to a turbocharged internal combustion engine having such a configuration that does not perform such supercharging pressure control. . Further, in the above embodiment, the actual compression ratio is detected by the intake pressure sensor 4, but it is also possible to estimate the change in the actual compression ratio from the operating conditions and the like.
[0053]
Further, in a general internal combustion engine with a turbocharger, an exhaust turbine 52 of the turbocharger 51 as in the above embodiment is used in order to minimize the delay in boosting pressure due to the inertia of the turbocharger. The exhaust gas catalytic converter 19 is disposed downstream of the exhaust gas. However, according to the present invention, the delay in boost pressure increase can be compensated for by correcting the compression ratio. It is also possible to arrange a catalytic converter 19 for use. In such an arrangement, there is an advantage that the time from the start of the internal combustion engine to the catalyst activity can be shortened.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing the configuration of an entire control system for an internal combustion engine according to the present invention.
FIG. 2 is a configuration explanatory view showing a configuration of a variable compression ratio device.
FIG. 3 is a flowchart showing a control flow in this embodiment.
FIG. 4 is a time chart showing the state of each part during acceleration and deceleration.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 4 ... Intake pressure sensor 11 ... Engine control module 13 ... Compression ratio control actuator 15 ... AAC valve 51 ... Turbocharger 56 ... Exhaust bypass valve

Claims (4)

Provided with a turbocharger driven by exhaust, in the internal combustion engine comprising a variable compression ratio device, during a transient, the difference between the actual supercharging pressure and the required boost pressure due to the response delay of the turbocharger A turbocharged internal combustion engine with a variable compression ratio device, characterized in that the compression ratio is controlled by the variable compression ratio device so as to compensate for a delay in torque change based thereon. 2. The turbocharged internal combustion engine with a variable compression ratio device according to claim 1, wherein when accelerating from a low load range, the compression ratio is increased by the variable compression ratio device, and thereafter the compression ratio is gradually decreased. An intake pressure sensor for detecting an actual supercharging pressure is provided, and a correction amount of a compression ratio at the time of transition is obtained according to a difference between a required supercharging pressure and the actual supercharging pressure. Or a turbocharged internal combustion engine with a variable compression ratio device according to 2; 2. The variable according to claim 1, wherein the supercharged air discharged from the compressor is supplied to the internal combustion engine without being bypassed during deceleration from the high load range, and the compression ratio is lowered by the variable compression ratio device. Turbocharged internal combustion engine with compression ratio device.

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