JP4033173B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine that controls a fuel injection amount, an intake air amount, and the like in order to realize a target torque required for the internal combustion engine.

  A so-called torque demand control is known in which a torque required through a driver's operation of an accelerator pedal is obtained as a target torque, and the fuel injection amount, intake air amount, etc. are controlled so that the output torque of the internal combustion engine becomes the target torque. It has been. In this control, the target torque is calculated based on the accelerator operation amount by the driver, the engine speed, and the like, and the target torque is corrected by adding the friction torque thereto. Most of the friction torque is occupied by a pressure loss (pumping loss) that is an intake resistance component of a throttle valve, an EGR valve, or the like. In addition, the friction torque includes a mechanical loss that is a friction loss that is lost at a sliding portion of the internal combustion engine, and an auxiliary drive loss that is lost to drive an auxiliary device such as an alternator and an air conditioner. .

As such torque demand control, for example, in Patent Document 1, when the air-fuel ratio is lean, a large amount of air is sucked into the combustion chamber, the intake pressure is high, and the pumping loss is reduced. The pumping loss torque is calculated based on the pressure) or a parameter related thereto, for example, the total gas amount in the cylinder.
JP-A-11-62658

  However, when the pumping loss torque is obtained based on only the intake pressure and the total gas amount in the cylinder as in Patent Document 1, the calculation accuracy of the pumping loss torque is improved as compared with the case where the pumping loss torque is not, but the calculation accuracy is It cannot be said that the level has risen to a sufficient level, and there is still room for improvement. For example, the pumping loss torque differs between when the engine is operating on flat ground and when the engine is operating on high ground. However, in the above Patent Document 1, it is impossible to calculate the pumping loss torque in consideration of such a difference.

  The present invention has been made in view of such a situation, and an object thereof is to obtain a pumping loss torque with higher accuracy and to generate an output torque closer to a required target torque in an internal combustion engine. An object of the present invention is to provide a control device for an internal combustion engine.

In the following, means for achieving the above object and its effects are described.
The invention according to claim 1 is used for an internal combustion engine in which a mixture of air and fuel is burned in a combustion chamber to reciprocate a piston in a cylinder to rotationally drive an output shaft. A pumping loss torque calculating means for calculating a loss of the output torque of the output shaft due to the pumping loss caused by the reciprocating motion of the piston as a pumping loss torque, and setting the torque required for the internal combustion engine as a target torque, In the control device for an internal combustion engine, at least the pumping loss torque by the pumping loss torque calculating means is added, and the parameter affecting the output torque is controlled based on the target torque after the addition. The calculating means is configured to change the piston from both sides in the reciprocating direction of the piston. And it is intended to calculate the pumping loss torque based on the differential pressure between the crank chamber pressure and the intake pressure for use.

  According to the above configuration, when controlling the internal combustion engine, the loss of the output torque of the output shaft (pumping loss torque) due to the pumping loss caused by the reciprocating motion of the piston is calculated by the pumping loss torque calculating means. The target torque is corrected by adding at least the pumping loss torque to the target torque required for the internal combustion engine. Based on the target torque after the addition, parameters that affect the output torque are controlled. Accordingly, a pumping loss torque is generated with the operation of the internal combustion engine, but an output torque corresponding to the required target torque is generated from the internal combustion engine.

  By the way, the pumping loss torque is generated when the piston descends and sucks air into the combustion chamber, so that it is basically greatly influenced by the pressure (intake pressure) in the combustion chamber. However, when the pressure of the crank chamber is high when the piston is lowered, the piston is prevented from lowering and the pumping loss torque is reduced as compared with the case where the pressure is low. Therefore, the pumping loss torque is affected not only by the pressure in the combustion chamber (intake pressure) but also by the crank chamber pressure.

  In this regard, in the first aspect of the invention, the crank chamber pressure and the intake pressure that act on the piston from both sides in the reciprocating direction of the piston and affect the pumping loss torque are used, and the differential pressure between them is used. Based on this, the pumping loss torque is calculated. For this reason, it is possible to calculate the pumping loss torque with higher accuracy as compared with the case where it is based solely on the intake pressure or the total gas amount in the cylinder. Accordingly, an output torque closer to the target torque required for the internal combustion engine can be generated.

  Here, since the crank chamber pressure is generally close to the atmospheric pressure, this atmospheric pressure can be used as an equivalent value of the crank chamber pressure. Therefore, according to the invention described in claim 2, in the invention described in claim 1, the pumping loss torque calculation means calculates the pumping loss torque using atmospheric pressure as an equivalent value of the crank chamber pressure. It may be a thing.

  In addition, since the crank chamber pressure can change according to the operating state of the internal combustion engine, the atmospheric pressure is corrected based on the operating state of the internal combustion engine, and the corrected value (estimated value) is used as the crank chamber pressure. it can. Therefore, as in the invention described in claim 3, in the invention described in claim 1 or 2, the crank chamber pressure for estimating the crank chamber pressure by correcting the atmospheric pressure based on the operating state of the internal combustion engine. The pumping loss torque calculating unit may further include an estimating unit that calculates the pumping loss torque using an estimated value obtained by the crank chamber pressure estimating unit as the crank chamber pressure. In this way, it is possible to calculate the pumping loss torque with higher accuracy than in the case where the atmospheric pressure is set to a value equivalent to the crank chamber pressure.

  Further, according to the invention described in claim 4, in the invention described in claim 1, further comprising crank chamber pressure detecting means for detecting the crank chamber pressure, wherein the pumping loss torque calculating means includes the crank chamber pressure. The pumping loss torque may be calculated using a value detected by the detecting means as the crank chamber pressure. In this way, it is possible to calculate the pumping loss torque with higher accuracy than in the case where the atmospheric pressure or the estimated value described above is set to the equivalent value of the crank chamber pressure.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the pumping loss torque calculating means calculates the pumping loss torque when calculating the top surface area of the piston or its equivalent. It is assumed that the differential pressure is corrected based on the value.

  Here, as an equivalent value of the top surface area, for example, an inner diameter (bore diameter) of a cylinder (cylinder) in which a piston reciprocates can be cited. In general, as the top surface area and the bore diameter increase, the area on which the differential pressure acts increases, the force required to lower the piston increases even with the same differential pressure, and the pumping loss torque increases. In this regard, in the invention described in claim 5, when calculating the pumping loss, the differential pressure is corrected based on the top surface area of the piston or its equivalent value. Therefore, by using the differential pressure corrected in this way, it is possible to calculate the pumping loss torque with higher accuracy.

  According to a sixth aspect of the present invention, in the invention according to any one of the first to fifth aspects, the pumping loss torque calculating means calculates the pumping loss torque based on the number of cylinders of the internal combustion engine. It is assumed that the differential pressure is corrected.

  When the internal combustion engine has a plurality of cylinders, a pumping loss occurs in each cylinder. Therefore, the overall pumping loss of the entire engine is obtained by multiplying the pumping loss per cylinder by the number of cylinders. In this regard, in the invention described in claim 6, when calculating the pumping loss torque, the differential pressure is corrected based on the number of cylinders. Therefore, by using the differential pressure corrected in this way, it is possible to calculate the pumping loss torque with higher accuracy.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
As shown in FIGS. 1 and 2, a vehicle is equipped with a gasoline engine (hereinafter simply referred to as an engine) 11 as an internal combustion engine. The engine 11 includes a cylinder block 13 having a plurality of cylinders (cylinders) 12. A crankcase 14 and an oil pan 15 are attached to the lower side of the cylinder block 13, and a cylinder head 16 is attached to the upper side. A piston 17 is accommodated in each cylinder 12 so as to reciprocate. Each piston 17 is connected to a crankshaft 19 that is an output shaft of the engine 11 via a connecting rod 18. Therefore, when each piston 17 reciprocates, the movement is converted into a rotational movement by the connecting rod 18 and then transmitted to the crankshaft 19.

  An intake passage 22 and an exhaust passage 23 are connected to the combustion chamber 21 of each cylinder 12, and air outside the engine 11 is taken into the combustion chamber 21 through the intake passage 22, and in the combustion chamber 21. The generated exhaust gas is discharged to the exhaust passage 23. The cylinder head 16 is provided with an intake valve 24 that opens and closes between the intake passage 22 and the combustion chamber 21 and an exhaust valve 25 that opens and closes between the exhaust passage 23 and the combustion chamber 21, respectively. An intake camshaft 26 is provided above the intake valve 24, and an exhaust camshaft 27 is provided above the exhaust valve 25. These intake and exhaust camshafts 26 and 27 are drivingly connected to the crankshaft 19 by pulleys, belts, and the like, and rotate in conjunction with the crankshaft 19. The intake valve 24 is driven by an intake camshaft 26, and the exhaust valve 25 is driven by an exhaust camshaft 27.

  A throttle valve 28 is rotatably provided in the intake passage 22. An actuator 29 such as a motor is drivingly connected to the throttle valve 28. The amount of air flowing through the intake passage 22 varies according to the angle of the throttle valve 28 (throttle opening). The throttle opening is adjusted by driving the actuator 29 in accordance with the amount of depression of the accelerator pedal 31 operated by the driver.

  A fuel injection valve 32 is attached to the engine 11 corresponding to each cylinder 12. Each fuel injection valve 32 is supplied with high-pressure fuel discharged from a fuel pump (not shown). Each fuel injection valve 32 is controlled to open and close, thereby directly injecting and supplying high-pressure fuel to the corresponding combustion chamber 21. The injected fuel is mixed with the air in the combustion chamber 21 to become an air-fuel mixture.

  Note that the engine 11 in which fuel is directly injected from the fuel injection valve 32 into the combustion chamber 21 as described above and an air-fuel mixture is generated is generally called a cylinder injection engine. Instead of this type, a port injection engine may be an application target of the present invention. In this type of engine, fuel is injected from the fuel injection valve disposed in the middle of the intake passage 22 toward the downstream side of the intake port. This fuel is mixed with the air flowing through the intake passage 22 and becomes an air-fuel mixture.

  A spark plug 33 is attached to the engine 11 corresponding to each cylinder 12. The spark plug 33 is driven based on the ignition signal from the igniter 34. A high voltage output from the ignition coil 35 is applied to the spark plug 33. The air-fuel mixture is ignited by spark discharge of the spark plug 33 and explodes and burns. The piston 17 is reciprocated by the high-temperature and high-pressure combustion gas generated at this time, the crankshaft 19 is rotated, and the driving force (output torque) of the engine 11 is obtained. The combustion gas is discharged into the exhaust passage 23 when the exhaust valve 25 is opened.

  In the engine 11, gas leaks into the crank chamber 36 from the gap between the wall surface of the cylinder 12 and the piston 17 in the compression stroke and the expansion stroke. This gas consists of an air-fuel mixture that leaks in the compression stroke, a combustion gas that leaks in the expansion stroke, and the like, and is called blow-by gas. Blow-by gas can cause engine oil to deteriorate and rust inside the engine 11. Therefore, the blow-by gas indicated by the solid arrow in FIG. 2 is returned (circulated) to the intake system by the blow-by gas recirculation device 37 and recombusted in the combustion chamber 21. The crank chamber 36 is a space in which the crankshaft 19 is accommodated, and is a space surrounded by the cylinder block 13, the crankcase 14, the oil pan 15, and the like.

  The blow-by gas recirculation device 37 includes a blow-by gas passage 39 that connects the crank chamber 36 and a downstream side of the throttle valve 28 in the intake passage 22. In the blow-by gas recirculation device 37, negative pressure (pressure lower than the atmospheric pressure) generated downstream of the throttle valve 28 acts on the crank chamber 36 through the blow-by gas passage 39. In the middle of the blow-by gas passage 39, a PCV valve 41 for adjusting the ring flow rate of the blow-by gas is provided.

  Further, the blow-by gas recirculation device 37 causes air outside the engine 11 (also referred to as fresh air) to enter the crank chamber 36 as shown by the wavy arrow in FIG. 2 in order to reduce the concentration of blow-by gas in the crank chamber 36. An air introduction passage 42 is provided for introduction into the air. One end of the air introduction passage 42 is connected upstream of the throttle valve 28 in the intake passage 22, and the other end is connected to the crank chamber 36 through the head cover 43, the cylinder head 16, the cylinder block 13, etc. on the cylinder head 16. Yes.

  As shown in FIG. 1, the engine 11 is provided with an exhaust gas recirculation (hereinafter referred to as “EGR”) device 44 for circulating a part of the exhaust gas flowing through the exhaust passage 23 to the intake passage 22. The EGR device 44 increases the ratio of inert gas in the air-fuel mixture by exhaust gas (EGR gas) mixed with the intake air with recirculation, lowers the maximum combustion temperature, and suppresses the generation of nitrogen oxides (NOx) Thus, exhaust emission is reduced.

  The EGR device 44 includes an EGR passage 45 that connects the exhaust passage 23 and the downstream side of the throttle valve 28 in the intake passage 22, and an EGR valve 46 that is provided in the middle of the EGR passage 45. In the EGR device 44, the negative pressure downstream of the throttle valve 28 in the intake passage 22 acts on the exhaust passage 23 via the EGR passage 45. Therefore, a part of the exhaust gas discharged from the exhaust passage 23 is circulated to the intake passage 22 through the EGR passage 45 as EGR gas. The flow rate of the recirculated EGR gas changes in accordance with the degree of opening of the EGR valve 46 (EGR opening degree).

  Various auxiliary machines (not shown) are attached to the engine 11. Examples of these auxiliary machines include an alternator, a power steering pump, an air conditioner compressor, an engine oil pump, and an engine water pump. The output shaft of each accessory is drivingly connected to the crankshaft 19 by pulleys, belts, and the like, and rotates by receiving power from the crankshaft 19.

  The vehicle is provided with various sensors for detecting the state of each part including the operating state of the engine 11. For example, a crank angle sensor 51 that generates a pulse signal every time the crankshaft 19 rotates by a certain angle is provided in the vicinity of the crankshaft 19. The signal of the crank angle sensor 51 is used to calculate the crank angle that is the rotation angle of the crankshaft 19, the engine rotation speed that is the rotation speed of the crankshaft 19 per unit time, and the like.

  An intake pressure sensor 52 that detects an intake pressure epim (absolute pressure) that is the pressure of intake air is provided downstream of the throttle valve 28 in the intake passage 22. An atmospheric pressure sensor 53 that detects an atmospheric pressure epa that changes depending on altitude (for example, coast and mountainous areas), weather, and the like is provided in the passenger compartment. An accelerator sensor 54 that detects the amount of depression of the accelerator pedal 31 by the driver is provided at or near the accelerator pedal 31.

  In order to control each part of the engine 11 based on the detection values of the various sensors 51 to 54 and the like described above, an electronic control unit 56 configured mainly with a microcomputer is provided. In the electronic control unit 56, a central processing unit (CPU) performs arithmetic processing according to a control program and initial data stored in a read-only memory (ROM), and executes various controls based on the calculation results. The calculation result by the CPU is temporarily stored in a random access memory (RAM).

  One of the controls performed by the electronic control unit 56 is “output torque control” for controlling a parameter that affects the output torque so that the output torque of the engine 11 becomes the torque required by the driver (target torque Tt). (Also called torque demand control). Here, the target torque Tt is basically calculated based on the accelerator operation amount by the driver, the engine speed, and the like. However, since there is friction (friction loss) associated with the operation of the engine 11, when this target torque is set as a command value, the actually generated output torque is lower than the target torque Tt. Therefore, the target torque Tt is corrected by increasing the amount consumed by the friction (friction torque Tf) for the output torque, and the value after the correction is used as the final target torque (final target torque T). Controlling parameters that affect

  Here, the friction is roughly divided into “pumping loss” which is a pressure loss (intake pressure loss) due to the intake resistance of the throttle valve 28, the EGR valve 46, and the like, and a loss due to friction in the sliding portion of the engine 11, etc. It consists of "mechanical loss" and "auxiliary drive loss" lost to drive various auxiliary machines. Among the above, the mechanical loss and the accessory driving loss are uniquely determined by the viscosity of the oil and the like. The viscosity of the oil changes gradually with time and does not change constantly. From this, the mechanical loss and the auxiliary drive loss can be estimated relatively easily by the oil temperature, water temperature, etc., which are parameters related to the viscosity of the oil. On the other hand, since the throttle valve 28 and the EGR valve 46 can basically operate at all times, it can be said that the pumping loss is constantly changing. Therefore, it is difficult to calculate (estimate) the pumping loss as compared to the mechanical loss and the auxiliary machine driving loss. Therefore, in order to realize the target torque Tt, it is important to accurately obtain the friction torque Tf.

  Next, a process for calculating the friction torque Tf and a process for controlling the output torque of the engine 11 based on the friction torque Tf will be described with reference to the flowcharts of FIGS.

  First, the friction torque calculation routine of FIG. 3 will be described. In this routine, the electronic control unit 56 first obtains the pumping loss torque Tp in steps 110 and 120. In step 110, a differential pressure ΔP between the intake pressure epim and the pressure in the crank chamber 36 (hereinafter referred to as crank chamber pressure epcr) is calculated. The detected value of the intake pressure sensor 52 can be used as the intake pressure epim.

  Here, the intake pressure epim is used to calculate the pumping loss torque Tp for the following reason. In general, when the throttle opening is small, the pumping loss is large, and the pumping loss tends to decrease as the throttle opening increases (the throttle valve 28 opens). From this, as a method for obtaining the pumping loss torque Tp, a map that prescribes the relationship between the throttle opening and the pumping loss torque Tp is created in advance, and the throttle opening at that time is determined by referring to this map. It is also conceivable to obtain the corresponding pumping loss torque Tp. However, in this method, for example, when the amount of deposit deposited on the throttle valve 28 increases and the resistance of the intake air is generated, the relationship between the throttle opening and the pumping loss torque Tp is the initial relationship defined in the map. Will deviate from. Such a divergence may also occur due to a change with time other than the above-described deposit, an individual difference of the throttle valve 28, or the like.

  Further, since the same relationship as above is also observed between the EGR opening and the pumping loss torque Tp, the relationship between the EGR opening and the pumping loss torque Tp is defined as another method for obtaining the pumping loss torque Tp. It is also conceivable to create a map in advance and obtain the pumping loss torque Tp corresponding to the EGR opening at that time with reference to this map. However, even in this method, the same problem as in the case of the throttle valve 28 can occur due to individual differences of the EGR valve 46, changes with time, and the like.

  Furthermore, it is possible to calculate the pumping loss torque Tp from each of the throttle opening and the EGR opening by referring to each map as described above. However, in actuality, both parameters of the throttle opening and the EGR opening may change simultaneously, and the pumping loss torque Tp corresponding to them may be combined. In this case, the pumping loss torque Tp has a value different from that obtained by simply adding or subtracting the pumping loss torque Tp corresponding to each opening.

  On the other hand, the intake pressure epim is affected by the throttle opening and the EGR opening. In addition, the intake pressure epim is also affected by the combined influence when the above two opening degrees change simultaneously, the individual differences of the throttle valve 28, the EGR valve 46, and the like, and changes with time. The intake pressure epim is a parameter that comprehensively indicates the state after receiving all these effects. Therefore, by using the intake pressure epim for the calculation of the pumping loss torque Tp, it is possible to eliminate the above-described problem that occurs when the map values for the throttle opening and the EGR opening are used. For this reason, in the present embodiment, the intake pressure epim is used instead of the map value for the calculation of the pumping loss torque Tp.

  The crank chamber pressure epcr is used to calculate the pumping loss torque Tp for the following reason. That is, when the pressure of the crank chamber 36 is high when the piston 17 descends, the piston 17 is prevented from descending and the pumping loss torque is reduced compared to when the pressure is low. Accordingly, the pumping loss torque Tp is affected not only by the pressure in the combustion chamber 21 (intake pressure epim) but also by the crank chamber pressure epcr.

  Here, in the blow-by gas recirculation device 37, in order to recirculate the blow-by gas to the intake system, the negative pressure downstream of the throttle valve 28 is merely applied to the crank chamber 36, and the crank chamber pressure epcr is the atmospheric pressure epa. The value is close to. For this reason, in the present embodiment, the atmospheric pressure epa detected by the atmospheric pressure sensor 53 is used as an equivalent value of the crank chamber pressure epcr.

In the next step 120, the pumping loss torque Tp is calculated according to the following equation (i).
Tp = ΔP * C * K (i)
C in the above formula (i) is a coefficient for converting pressure (differential pressure ΔP) into torque. K is a correction coefficient for reflecting the influence of parameters other than the differential pressure ΔP on the pumping loss torque Tp in calculating the pumping loss torque Tp. The correction coefficient K here includes, for example, a basic correction term k1 corresponding to the influence of blow-by gas on the pumping loss torque Tp.

  Subsequently, in step 130, the friction torque Tf is calculated by adding the mechanical loss torque Tm and the accessory driving loss torque Ta to the pumping loss torque Tp. Here, as the mechanical loss torque Tm and the auxiliary machine drive loss torque Ta, those estimated by the oil temperature, the water temperature, etc., which are parameters related to the oil viscosity as described above, are used in another routine. Then, after the processing of step 130, the friction torque calculation routine is terminated.

The processing of steps 110 and 120 by the electronic control unit 56 in the friction torque calculation routine corresponds to pumping loss torque calculation means.
Next, the output torque control routine of FIG. 4 will be described. First, at step 210, the electronic control unit 56 reads the friction torque Tf calculated by the friction torque calculation routine. Further, the target torque Tt that is the torque requested by the driver through the depression operation of the accelerator pedal 31 is read. The target torque Tt is calculated based on, for example, the depression amount of the accelerator pedal 31 and the engine speed in a separate routine.

  Subsequently, in step 220, the target torque Tt is corrected by adding the friction torque Tf to the target torque Tt in step 210. The corrected target torque Tt is set as the final target torque T.

  In step 230, parameters that affect the output torque of the engine 11 are controlled in order to achieve the final target torque T in step 220. Although this parameter depends on the type of the engine 11, in the case of the gasoline engine 11 as in the present embodiment, the intake air amount, the fuel injection amount, the ignition timing, and the like are applicable. Then, for example, the throttle opening, fuel injection amount, ignition timing, etc. necessary for realizing the final target torque T are obtained by a predetermined map, arithmetic expression, etc., and based on these, the actuator 29, fuel injection valve 32, igniter 34 are obtained. Control etc. An output torque is generated with the operation of the engine 11 according to these controls, but at this time, friction is also generated. Therefore, an output torque smaller than the final target torque T is generated by the loss due to the friction. In this way, an output torque close to the target torque Tt that is the torque requested by the driver is generated. Then, after the processing of step 230, the output torque control routine is terminated.

According to the first embodiment described in detail above, the following effects can be obtained.
(1) The intake pressure epim including the influence of the throttle opening and the EGR opening is used as a parameter for calculating the pumping loss torque Tp (step 110). For this reason, even if the flow rate of the intake air changes due to individual differences of the throttle valve 28, the EGR valve 46, etc., changes with time, etc., it is possible to calculate the pumping loss torque Tp with high accuracy taking them into account.

  (2) Using the crank chamber pressure epcr and the intake pressure epim, which are parameters acting on both sides (upper and lower sides in FIG. 1) in the reciprocating direction of the piston 17 and affecting the pumping loss torque Tp, the differential pressure between them The pumping loss torque Tp is calculated based on ΔP. For this reason, the pumping loss torque Tp can be calculated with higher accuracy than in the case based solely on the intake pressure or the total gas amount in the cylinder (Patent Document 1). As a result, the accuracy of the corrected target torque increases, and even when the atmospheric pressure changes due to the vehicle traveling between flat and high altitudes, the engine 11 is provided with an output torque closer to the target torque Tt. Can be generated.

  (3) A correction coefficient K is set to reflect the influence of parameters other than the differential pressure ΔP on the pumping loss torque Tp in the calculation of the pumping loss torque Tp, and this correction coefficient K is multiplied by the differential pressure ΔP. . This multiplication makes it possible to calculate the pumping loss torque Tp with higher accuracy.

(Second Embodiment)
Next, a second embodiment embodying the present invention will be described. In the second embodiment, the contents of the processing in the above-described friction torque calculation routine (FIG. 3) are slightly different from those in the first embodiment. Specifically, the correction coefficient K in step 120 is calculated according to the following equation (ii).

K = k1 + k2 (ii)
In the above formula (ii), k1 is the basic correction term described above. k2 is an auxiliary correction term for calculating the pumping loss torque per cylinder, and is determined by a function of the top surface area (top surface area S) where the pressure in the combustion chamber 21 acts on the piston 17. Here, in general, as the top surface area S increases, the area on which the differential pressure ΔP acts increases, the force required to lower the piston 17 increases even at the same differential pressure ΔP, and the pumping loss torque Tp increases. . Therefore, the auxiliary correction term k2 is set to take a larger value as the top surface area S increases. Processing other than the above is the same as in the first embodiment.

Therefore, according to 2nd Embodiment, in addition to the effect of (1)-(3) mentioned above, the following effect is acquired.
(4) A correction term (auxiliary correction term k2) corresponding to the top surface area S of the piston 17 that affects the pumping loss torque Tp is added to the correction coefficient K. Therefore, the pumping loss torque Tp can be calculated with higher accuracy than when the auxiliary correction term k2 is not taken into account (first embodiment).

  (5) When calculating the pumping loss torque Tp for a plurality of types of engines, even if the engines have different top surface areas S, correction is performed by using the auxiliary correction term k2 corresponding to the top surface area S. The coefficient K can be easily determined, and the number of man-hours for adaptation can be greatly reduced.

(Third embodiment)
Next, a third embodiment embodying the present invention will be described. In the third embodiment, the contents of the processing in the above-described friction torque calculation routine (FIG. 3) are slightly different from those in the second embodiment. Specifically, the correction coefficient K in step 120 is calculated according to the following equation (iii).

K = k1 + (k2 * n) (iii)
In the above formula (iii), n is the number of cylinders (the number of cylinders) of the engine 11. In the case of the engine 11 having multiple cylinders, the number of cylinders n is multiplied in this way because a pumping loss occurs in each cylinder. Therefore, the total pumping loss of the entire engine 11 is equal to the pumping loss per cylinder. This is because the number n is multiplied. Processing other than the above is the same as in the first embodiment.

Therefore, according to the third embodiment, in addition to the effects (1) to (5) described above, the following effects can be obtained.
(6) The auxiliary correction term k2 is multiplied by the number of cylinders n affecting the pumping loss torque Tp. Therefore, the pumping loss torque Tp can be calculated with higher accuracy than in the second embodiment.

  (7) When calculating the pumping loss torque Tp for a plurality of types of engines 11, the auxiliary correction term k2 is multiplied by the number of cylinders n even if those engines have different top surface areas S and different numbers of cylinders n. Thus, the correction coefficient K can be easily determined, and the number of man-hours for adaptation can be greatly reduced.

(Fourth embodiment)
Next, a fourth embodiment embodying the present invention will be described. In the fourth embodiment, an estimated value is used as the crank chamber pressure epcr in step 110 of the above-described friction torque calculation routine (FIG. 3).

  The following points are taken into account when estimating the crank chamber pressure epcr. In general, when the operating state such as the engine speed and the engine load changes, the negative pressure downstream of the throttle valve 28 in the intake passage 22 changes accordingly. Since this negative pressure acts on the crank chamber 36 through the blow-by gas passage 39, the degree of influence of the crank chamber pressure epcr from the negative pressure also changes.

  Therefore, in the fourth embodiment, the degree of influence (influence coefficient L) of these on the crank chamber pressure epcr is obtained based on the engine rotation speed and the engine load. In calculating the influence coefficient L, for example, a map in which the relationship between the engine rotational speed and the engine load and the influence coefficient L is determined in advance is used. In this map, as the influence coefficient L, about what percentage the crank chamber pressure epcr changes with respect to the atmospheric pressure epa is set for various combinations of the engine speed and the engine load.

Based on the influence coefficient L obtained from the map as described above and the atmospheric pressure epa detected by the atmospheric pressure sensor 53, the crank chamber pressure epcr is estimated based on the following equation (iv).
epcr = epa * L (iv)
The estimation processing of the crank chamber pressure epcr by the electronic control unit 56 corresponds to crank chamber pressure estimation means.

  Then, the crank chamber pressure epcr calculated (estimated) according to the above equation (iv) is used for calculating the differential pressure ΔP in step 110. Processing other than the above is the same as in the first to third embodiments.

Therefore, according to the fourth embodiment, in addition to the effects (1) to (7) described above, the following effects can be obtained.
(8) The crank chamber pressure epcr is estimated by multiplying the atmospheric pressure epa by the influence coefficient L, and the estimated value is used to calculate the differential pressure ΔP. Therefore, it is possible to calculate the pumping loss torque Tp with higher accuracy than when simply using the atmospheric pressure epa as the crank chamber pressure epcr.

Note that the present invention can be embodied in another embodiment described below.
The auxiliary correction term k2 in the second embodiment may be determined by an equivalent value of the top surface area S, for example, the inner diameter (bore diameter) of the cylinder 12, the diameter of the piston 17, and further a function thereof.

  The crank chamber pressure epcr may be estimated by a method different from that of the fourth embodiment. For example, since the volume of the crank chamber 36 is constant, if the amount of blow-by gas generated increases, the crank chamber pressure epcr increases correspondingly. Further, the negative pressure for sucking blow-by gas changes according to the engine load, and the crank chamber pressure epcr changes. In general, the negative pressure decreases as the engine load increases. Therefore, it can be said that the amount of blow-by gas generated and the engine load are parameters that affect the crank chamber pressure epcr. Focusing on this point, the crank chamber pressure epcr may be estimated by a predetermined arithmetic expression based on the volume of the crank chamber 36, the amount of blow-by gas generated, the engine load, and the like.

  As shown by a two-dot chain line in FIG. 1, a pressure sensor 61 that directly detects the pressure in the crank chamber 36 is provided as a crank chamber pressure detecting means, and the detected value of the pressure sensor 61 in the first to third embodiments. The crank chamber pressure epcr may be used. By doing so, the calculation accuracy of the pumping loss torque Tp can be further increased as compared with the case where the atmospheric pressure epa (first embodiment) or the estimated value (fourth embodiment or the like) is used as the crank chamber pressure epcr.

  In the calculation of the friction torque Tf in FIG. 3 (step 130), the pumping loss torque Tp is required as a minimum. Other terms (including mechanical loss torque Tm and auxiliary machine drive loss torque Ta) can be changed as appropriate. For example, another term of loss torque may be newly added.

  The present invention can be applied to other types of engines such as diesel engines in addition to the gasoline engine described above. Further, the present invention can also be applied to a type of engine that does not include the blow-by gas recirculation device 37.

1 is a schematic diagram showing the configuration of an engine control device according to a first embodiment of the present invention. The schematic diagram which shows the structure of a blowby gas recirculation apparatus. The flowchart which shows the procedure which calculates friction torque. The flowchart which shows the procedure which controls the output torque of an engine.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Cylinder (cylinder), 17 ... Piston, 19 ... Crankshaft (output shaft), 21 ... Combustion chamber, 36 ... Crank chamber, 56 ... Electronic control unit (pumping loss torque calculation means, Crank chamber pressure estimating means), 61 ... pressure sensor (crank chamber pressure detecting means), epi ... atmospheric pressure, epim ... intake pressure, epcr ... crank chamber pressure, n ... number of cylinders, ΔP ... differential pressure, S ... top surface area , Tp: pumping loss torque, Tt: target torque.

Claims (6)

An air-fuel mixture is used in an internal combustion engine that reciprocates a piston in a cylinder to rotate an output shaft by burning the air-fuel mixture in a combustion chamber.
A pumping loss torque calculating means for calculating a loss of output torque of the output shaft due to a pumping loss caused by the reciprocating motion of the piston as a pumping loss torque;
A torque required for the internal combustion engine is set as a target torque, and at least a pumping loss torque by the pumping loss torque calculating means is added to the target torque, and a parameter that affects the output torque is based on the target torque after the addition. In a control device for an internal combustion engine that is controlled,
The pumping loss torque calculating means calculates the pumping loss torque based on a differential pressure between a crank chamber pressure acting on the piston from both sides in the reciprocating direction of the piston and an intake pressure. Control device. 2. The control device for an internal combustion engine according to claim 1, wherein the pumping loss torque calculating unit calculates the pumping loss torque by using an atmospheric pressure as an equivalent value of the crank chamber pressure. A crank chamber pressure estimating means for estimating the crank chamber pressure by correcting an atmospheric pressure based on an operating state of the internal combustion engine;
3. The control device for an internal combustion engine according to claim 1, wherein the pumping loss torque calculating unit calculates the pumping loss torque by using an estimated value by the crank chamber pressure estimating unit as the crank chamber pressure. 4. A crank chamber pressure detecting means for detecting the crank chamber pressure;
2. The control device for an internal combustion engine according to claim 1, wherein the pumping loss torque calculating unit calculates the pumping loss torque using a value detected by the crank chamber pressure detecting unit as the crank chamber pressure. The internal combustion engine according to any one of claims 1 to 4, wherein the pumping loss torque calculation means corrects the differential pressure based on a top surface area of the piston or an equivalent value when calculating the pumping loss torque. Control device. The control device for an internal combustion engine according to any one of claims 1 to 5, wherein the pumping loss torque calculating means corrects the differential pressure based on the number of cylinders of the internal combustion engine when calculating the pumping loss torque.

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