JP2015068199A - Internal combustion engine for automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve fuel efficiency and increase torque while preventing damage to an exhaust system member, when advancing an opening/closing timing for an intake valve for transition to an acceleration region.SOLUTION: In the case of transition to an acceleration mode in which fuel is made richer by stepping on an accelerator pedal, the temperature of an exhaust system member is actually measured or estimated. If the temperature of the member does not rise to a dangerous temperature but there is a rise margin (allowance), an advance amount K of an intake valve 21 is increased to a provisional advance amount K2 which is greater than a safety advance amount K1, and at a certain maintenance time t1 after then, it is set back to the safety advance amount K1. Wasteful fuel consumption is suppressed when the temperature of the exhaust system member does not rise to a dangerous region, thus suppressing worse fuel efficiency and improving acceleration responsiveness with a torque increase.

Description

  The present invention relates to a variable valve type internal combustion engine mounted on an automobile such as a passenger car or a truck.

  In an internal combustion engine for automobiles, a VVT mechanism that can change the opening / closing timing of an intake valve is widely adopted. Negative pressure) etc. are set.

  In general, when there is an acceleration request (output increase request) due to depression of the accelerator pedal, the fuel is enriched and the opening / closing timing of the intake valve is advanced to control the acceleration response. However, depending on the operating conditions such as the engine temperature, the acceleration response may not necessarily be improved by the advance angle control. Therefore, in Patent Document 1, the combustion deterioration is expected by the advance angle control of the intake valve. Propose to prohibit advance angle control.

  On the other hand, the internal combustion engine mounted on the automobile has a large difference in engine temperature depending on the outside air temperature, road conditions, operation time, etc., but if the temperature of the combustion gas becomes too high, piston burn-in or oil combustion occurs, There is a risk of damaging exhaust system members such as an exhaust manifold, a turbocharger, or an exhaust gas purification catalyst. In particular, the exhaust purification catalyst has the property of deteriorating when exposed to an excessively high temperature.

  Therefore, when the accelerator pedal is depressed and acceleration is requested, the combustion temperature is suppressed by enriching the air-fuel ratio under a predetermined condition and cooling the cylinder.

JP 2007-211649 A

  The intake valve opening / closing timing control program is designed with comprehensive consideration of fuel consumption, torque, and amount of fuel blown into the exhaust system as target values, but it is difficult to satisfy all during acceleration. It is. For example, if the amount of fuel blown into the exhaust system is large due to fuel enrichment, even if torque can be secured, not only fuel consumption will deteriorate, but exhaust system members (exhaust turbochargers and catalysts) will also be generated by fuel afterburning. Etc.) may be damaged.

  For example, in the full throttle state, the opening / closing timing of the intake valve is advanced to increase the output responsiveness while preventing fuel blow-through. However, if the angle is excessively advanced, the combustion temperature becomes abnormally high and the exhaust member Therefore, the advance amount (target phase angle) is suppressed within a range that does not lead to abnormal combustion. Therefore, there is a problem that the amount of the enriched fuel that blows through the exhaust system increases and the required torque does not come out.

  The present invention has been made in view of such a current situation, and while preventing damage to exhaust system members due to abnormally high exhaust gas temperature (or abnormally high combustion temperature), suppressing deterioration of fuel consumption and improving torque. It is intended.

  The internal combustion engine of the present invention is configured so that the opening / closing timing of the intake valve in the steady operation state is controlled to approach the target phase angle based on a preset condition, and when the accelerator pedal is depressed, the exhaust system member When the measured value or estimated value of the temperature is lower than the preset reference temperature and the exhaust system member has a margin for temperature rise, the opening / closing timing of the intake valve is advanced more than the target phase angle, and then Control is made to change to the target phase angle.

  “Preset conditions” for setting the opening / closing timing of the intake valve to the target phase angle are, as described above, the accelerator pedal depression amount (or depression acceleration), engine speed, intake amount, throttle opening, intake system The pressure is set based on the pressure, the outside air temperature, and the like. Examples of the estimated value of the reference temperature of the exhaust system member include the temperature of cooling water and the temperature of oil. As secondary use of the temperature of the cooling water, it is also possible to determine from the presence / absence of water flow of the cooling water to the radiator and the presence / absence of driving of the radiator fan. Furthermore, it is also possible to use a plurality of elements (factors) such as the temperature of the cooling water and the outside air temperature in combination.

  As described above, the target phase angle of the opening / closing timing of the intake valve in the steady operation state is performed based on values of the accelerator opening (or throttle opening), the engine speed, the intake pressure, etc. These values are derived by actually operating the internal combustion engine and measuring the exhaust gas temperature and each member temperature. In other words, it is not a theoretical calculation value, but if the throttle opening, rotation speed, etc. are values of this level, data based on actual operation results will indicate that the combustion gas (exhaust gas) will rise to a dangerous temperature. It is a numerical value drawn deductively from.

  Since the operation for extracting the conditions in the steady operation state is performed after the warm-up operation is finished at a predetermined temperature (for example, about 20 ° C.), the outside air temperature is, for example, in winter. If the engine temperature is low or the engine is warming up so long that it has not started, even if the individual factors such as speed and throttle opening satisfy the set conditions, the engine temperature will actually reach the danger range. In many cases, the temperature of the engine such as an exhaust system member does not rise to the danger zone without rising.

  The present invention has been made on the basis of such knowledge, and when the measured value or estimated value of the temperature of the exhaust system member does not reach the reference value, the opening / closing timing of the intake valve is advanced more than the steady state. By doing so, fuel can be burned as much as possible to increase the torque, and deterioration of fuel consumption can be suppressed. In particular, in the case of traveling where acceleration and deceleration are frequently performed, it can be said that the advantages of the present invention are strongly exerted.

  The time for advancement larger than the advance amount in the steady operation state may be set in accordance with the degree of deviation between the actual temperature of the exhaust system member and the set temperature.

It is a schematic diagram of an internal combustion engine. It is a figure which shows the relationship of each element (factor). It is a flowchart which shows an example of control.

(1). Outline of Internal Combustion Engine Next, an embodiment of the present invention will be described with reference to the drawings. First, an outline of an internal combustion engine will be described with reference to FIG.

  The internal combustion engine has a cylinder block 1, a cylinder head 2 fixed to the cylinder block 1, and a cylinder head cover 3 fixed to the cylinder head 2, and an oil pan 4 is fixed to the opening edge of the crankcase in the cylinder block 1. doing. A cylinder bore 6 in which a piston 5 is slidably fitted is formed in the cylinder block 1, and a crankshaft 8 that is rotationally driven by the piston 5 via a connecting rod 7 is rotatably held.

  A chain case 9 is fixed to one side of the cylinder block 1 and the cylinder head 2, and the camshaft is driven in a space formed between one side of the cylinder block 1 and the cylinder head 2 and the chain case 9. Timing chain is arranged. One end of the crankshaft 8 protrudes outside the chain case 9, and an auxiliary machine driving pulley 10 is fixed to the protruding part, thereby driving the alternator 11 and the water pump 12.

  A rotation speed detecting rotor 13 having a large number of protrusions on the outer periphery is fixed to a portion between one end portion of the crankshaft 8 and the chain case 9 and the accessory drive pulley 10. A rotation sensor 14 for detecting a protrusion on the outer periphery of the rotation speed detection rotor 13 is fixed.

  The internal combustion engine includes an oil pump (trochoid pump) 15 that feeds lubricating oil to each part. In the oil pump 15 of this embodiment, the rotor is fixed to the crankshaft 8 by using the chain case 9 also as a pump housing. A pump cover is fixed to the inner surface of the chain case 9, and a pump chamber and an oil passage in which a rotor (an inner rotor and an outer rotor) rotates are formed between the chain case 9 and the pump cover. The oil pump 13 is connected to a suction passage 16 connected to the oil pan 4 and an oil feed passage 17 for sending oil to each lubrication part. The oil that detects the oil temperature in the oil feed passage 17 is connected to the chain case 9. A temperature sensor 18 is provided.

  The cylinder head 2 is formed with a recess that opens toward the cylinder bore 6, and the tip of the spark plug 20 is exposed at the center of the recess. In the cylinder head 2, an intake port 22 that is opened and closed by the intake valve 21 and an exhaust valve 24 that is opened and closed by the exhaust valve 23 are disposed on both sides of the crankshaft 8. The intake valve 21 is pushed by a cam 21b through a hydraulic valve timing variable device 21a, and the opening / closing timing of the intake valve 21 can be adjusted by adjusting the valve timing variable device 21a.

  The intake port 22 opens on one side of the cylinder head 2, and the intake manifold 25 communicates with the intake port 22. The exhaust port 24 opens on the other side of the cylinder head 2, and the exhaust manifold 26 communicates with the exhaust port 24.

  An intake passage 28 starting from an air cleaner 27 is connected to the intake manifold 26, and a throttle valve 29 and a surge tank 30 located downstream thereof are inserted in the intake passage 28. In many cases, the surge tank 30 is integrated with the intake manifold 26 or the throttle valve 29 is integrated with the surge tank 30. A fuel injection noble 31 is provided at each branch portion of the intake manifold 26 or at a collection portion of the intake ports 22.

  An exhaust turbocharger 32 is connected to the exhaust manifold 26. The exhaust turbocharger 32 has a turbine chamber and a compressor chamber. In this embodiment, the rotation axis is in a posture orthogonal to the paper surface, and the compressor chamber is located on the near side toward the paper surface. Yes. The intake port 33 of the compressor chamber opens toward the front, and the intake port 34 opens in the tangential direction of the compressor blades. An intake passage 28 is connected to the intake inlet 33 and the intake outlet 34 of the compressor chamber.

  Further, the exhaust inlet of the turbine chamber in the exhaust turbo supercharger 32 opens in the tangential direction of the turbine blades, and this is connected to the collective part of the exhaust manifold 26. The exhaust outlet of the turbine chamber is opened in the back direction orthogonal to the paper surface, and a vertically long catalyst case 35 is connected to the exhaust outlet via an L-shaped joint. The upper and lower portions of the catalyst case 35 have a trapezoidal shape, an exhaust pipe 36 is connected to the lower end, and a silencer 37 is provided near the end of the exhaust pipe 36.

  A thermostat valve 38 that switches the flow of the cooling water in accordance with the water temperature is provided in a portion of the cylinder head 2 facing the paper, and a water temperature sensor 39 that detects the temperature of the cooling water is provided in the thermostat valve 38. ing. Note that the water flow to the radiator is automatically controlled by the operation of the thermostat valve 38.

  The internal combustion engine includes an ECU (engine control unit) 40 as an example of a control device. The ECU 40 includes a water temperature sensor 39, a spark plug 20, a throttle valve 29, a fuel injection noble 31, a rotation sensor 14, and an oil temperature sensor 18. Are electrically connected. Further, although the depression amount and depression speed of the accelerator pedal 41 can be detected by a potentiometer (angle sensor) 42, the potentiometer 42 is also connected to the ECU 40. An outside air temperature sensor 43 provided in an engine room or the like is also connected to the ECU 40.

  Further, an intake pressure sensor 44 provided in the surge tank 30 or the like is also connected to the ECU 40. The variable valve timing device 21a is also connected to the ECU 40 (more precisely, the drive device of the variable valve timing device 21a is connected to the ECU 40).

(2). Control Mode In FIG. 2, the temperature T (I) of the exhaust system member, the advance amount K (II) of the intake valve 21, the torque R (III), the throttle opening Q (IV), and the accelerator pedal depression amount The relationship with A (V) is shown. Although shown in the figure, in (I), (II), and (III), the embodiment of the present application is indicated by a solid line, and the conventional example is indicated by a dotted line.

  When the accelerator pedal 41 is depressed and the throttle valve 29 is fully opened or close to it, such as when going uphill or overtaking, the rotational speed increases rapidly. In this case, when the depression amount (or depression acceleration) of the accelerator pedal 41 exceeds a preset reference value and the engine speed exceeds a preset reference value, the air-fuel ratio is rich to a power air-fuel ratio lower than the output air-fuel ratio. And the intake valve 21 is advanced based on the control map in the steady operation state.

  In this case, the control map in the steady operation state also considers the temperature of the exhaust system member, and the advance amount K of the intake valve 21 is also suppressed so that the combustion temperature does not become abnormally high and damage the exhaust system member. In the prior art, when the rotational speed or the like reaches a set value, the advance amount is simply advanced by the safe advance amount K1 (therefore, in this embodiment, the safe advance amount K1). The phase angle advanced by an amount corresponding to the target phase angle described in the claims).

  In contrast, in the present embodiment, the actual temperature T1 of the exhaust system member is measured or estimated, and when T1 is lower than the reference temperature Tm, the advance amount K of the intake valve 21 is a safe advance angle in a steady operation state. The provisional advance amount K2 that is larger than the amount K1 is set, and when a certain maintenance time t1 elapses, control is performed so as to return to the safe advance amount K1 over a certain transition time t2.

  Thereby, high torque can be obtained without damaging the exhaust system members, and acceleration response can be improved, and fuel blow-off to the exhaust system can be suppressed and deterioration of fuel consumption can be suppressed. Furthermore, the capability and responsiveness of the exhaust turbocharger 32 can be improved by increasing the temperature of the combustion gas.

  Even if the member temperature T is lower than the reference temperature Tm when the accelerator pedal 41 starts to be depressed, it is expected that the temperature T of the exhaust system member will rapidly increase due to an increase in the combustion temperature due to operation with a large provisional advance amount K2. When a certain maintenance time t1 has elapsed, the advance amount K is shifted to the safe advance amount K1.

  The maintenance time t1 is set based on the degree of deviation between the actual member temperature T1 and the reference temperature Tm, the outside air temperature, and the like. That is, when the degree of deviation between the actual member temperature T1 and the reference temperature Tm is large, there is a large margin for the increase in the member temperature T, so that the maintenance time t1 can be increased.

  Further, even when the outside air temperature is low and the temperature rise of the engine is slow, such as the operation in the winter season or the operation in a cold region, since the increase in the member temperature T has a large margin, the maintenance time t1 can be increased. it can. It is also possible to incorporate the operation elapsed time after the start as a setting factor into the program and correct the maintenance time t1 to be longer when the start elapsed time is short.

  In FIG. 2 (III), the advance amount K is returned to the safe advance amount K1 over a certain transition time t2 after the maintenance time t1 has elapsed. It is also possible to return to the angular amount K1. It is also possible to gradually decrease toward the safe advance amount K1 over the time (t1 + t2) after the advance to the provisional advance amount K2.

  As illustrated in FIG. 2 (V), there are a case where the accelerator pedal 41 has a positive depression acceleration when starting from zero and a case where the accelerator pedal 41 is further depressed from a certain degree of depression. Although not shown in the figure, it is often experienced to step in from zero to 100%. It should be noted that there is a slight time lag after the acceleration of the accelerator pedal 41 becomes positive, but it is reflected in the throttle opening Q. However, in the figure, for the sake of convenience, the movement of the accelerator pedal 41 instantaneously reduces the throttle opening Q. It is displayed so that it may be reflected.

(3). Flowchart FIG. 3 shows an example of a flowchart of control. In this embodiment, the program starts simultaneously with the start, and first, it is determined whether or not the accelerator pedal 41 is depressed (ΔA is positive) (S1). When the accelerator pedal 41 is depressed, the difference between the actual rotational speed detected by the rotation sensor 14 and a preset reference rotational speed is calculated by the comparison circuit (S2), and the rotational speed is the reference rotational speed. If so, it is determined whether or not the throttle opening Q is larger than a preset reference opening Q0 (S3). In this case, the reference opening Q0 may be 100%, for example, about 90%.

  Instead of determining the throttle opening Q, it is determined whether or not the magnitude of the intake pressure (intake negative pressure) P is smaller than a preset reference pressure P1, and if it is higher than the reference pressure P1 on the vacuum side, It is also possible to determine the acceleration mode. It is also possible to set both the throttle opening Q and the intake pressure P as determination conditions for the acceleration mode.

  In this example, the cooling water temperature is substituted as an estimated temperature that substitutes for the actual exhaust system member temperature. When the throttle opening Q exceeds the reference opening Q0, the cooling water temperature is set in advance. It is determined whether the reference temperature is exceeded (S4). When the cooling water temperature exceeds the reference temperature, it is considered that there is no increase in the member temperature, and the advance amount of the intake valve 21 is shifted to the safe advance amount K1.

  When the cooling water temperature does not exceed the reference temperature, there is an allowance for increasing the member temperature. Therefore, the advance amount K of the intake valve 21 is changed to the provisional advance amount K2 (S5) and the actual amount is increased. From the difference between the cooling water temperature and the reference temperature, a maintenance time t1 for maintaining the provisional advance amount K2 is calculated (S6). Next, it is determined whether or not the maintenance time t1 has passed in a short interval (S7). When the maintenance time t1 has passed, the advance amount K is decreased from the provisional advance amount K2 (S8), which is very short. It is determined whether or not the advance amount K has reached the safe advance amount K1 in the interval (S9), and then the advance amount K is maintained at the safe advance amount K1.

  When the amount of depression of the accelerator pedal 41 is constant (when ΔA = 0) while the advance amount K is maintained at the safe advance amount K1, the advance amount K is maintained as it is. On the other hand, if the opening degree of the accelerator pedal 41 decreases during operation with the safe advance amount K1 (when ΔA becomes negative), the program is reset, and the throttle opening degree Q and the opening / closing timing of the intake valve 21 are in the normal mode. Return to (Fuel saving mode). Even when the accelerator pedal 41 is returned during the course of the program and ΔA becomes negative, the program is reset and returns to the start.

  In this example, only the temperature of the cooling water is used as an alternative means of estimating the temperature of the exhaust system member, but it is also possible to use the outside air temperature, the operation time after starting, the oil temperature, or a combination of these. Is possible.

  Further, it is stored whether or not the acceleration mode operation has been performed since the start, and when the acceleration mode operation is performed, the maintenance time t1 of the temporary advance amount K2 is shortened even if the member temperature is low. It is also possible to correct it. The setting of the maintenance time t1 of the provisional advance amount K2 may be set in a stepless manner based on the value of factors such as the cooling water temperature, or by setting several time zones, the cooling water temperature, etc. It is also possible to set the time zone based on the range when the value of the factor is within a certain range.

  The present invention is actually applicable to an internal combustion engine for automobiles. Therefore, it can be used industrially.

DESCRIPTION OF SYMBOLS 1 Cylinder block 2 Cylinder head 5 Piston 8 Crankshaft 14 Rotation sensor 18 Oil temperature sensor 21 Intake valve 21a Valve timing variable device 21b Cam 25 Intake manifold 26 Exhaust manifold 31 Fuel injection noble 32 Exhaust turbocharger 35 Catalyst case 39 Cooling water Temperature sensor 40 ECU as an example of control means
41 Accelerator pedal 42 Potentiometer as an example of accelerator opening sensor

Claims (1)

The intake valve opening / closing timing in the steady operation state is controlled to approach the target phase angle based on a preset condition,
When the accelerator pedal is depressed, if the measured value or estimated value of the exhaust system member temperature is lower than a preset reference temperature and the exhaust system member has a margin for temperature rise, the opening / closing timing of the intake valve is set to It is controlled to advance more than the target phase angle and then change to the target phase angle.
Automotive internal combustion engine.

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