Control device for internal combustion engine

Abstract

Provided is a control device for an internal combustion engine capable of suppressing variations in combustion pressure between cylinders. The control device for a multi-cylinder engine capable of individually controlling the ignition timing and the fuel injection amount is also provided with a generator for generating a reaction torque corresponding to the torque transmitted from the engine, and a resolver for detecting the rotational angle of the generator. The combustion pressure of each cylinder is estimated from the change in the rotational angle of the generator detected by the resolver (step S3), the combustion pressure difference between the estimated combustion pressure and the ideal combustion pressure is calculated for each cylinder (step S4), and when all the combustion pressure differences are not within a predetermined range, the combustion pressure is calculated. The ignition timing or the fuel injection amount of all the cylinders is corrected uniformly; when a certain combustion pressure difference is not within a predetermined range, the ignition timing or the fuel injection amount of the cylinder for which the combustion pressure difference is not within the predetermined range is individually corrected (steps S8, S10).

Description

TECHNICAL FIELD

[0001] The present application relates to a control device of an internal combustion engine having a plurality of cylinders. BACKGROUND

[0002] Patent Document 1 describes a control device that, at the time of cold start of an internal combustion engine, delays the ignition timing compared to the normal ignition timing in order to warm up a catalyst for purifying exhaust gas as soon as possible, and generates a variation in rotational speed by thus delaying the ignition timing to suppress a deviation in combustion pressure among the cylinders. Specifically, first, at the time of cold start, the ignition timing is delayed in order to warm up the catalyst as soon as possible, and it is determined whether the combustion state in each cylinder is good based on the generation angle of ion current. The generation angle of ion current is the crank angle at which the ion current output from the ion current measurement circuit via the spark plug is above a reference level. Next, when there is a cylinder in which the combustion state is determined to be reduced because the generation angle of ion current is above a prescribed value, the ignition timing for that cylinder is advanced. Also, the ignition timing of the other cylinders is advanced in such a way that the difference between the correction amount of the ignition timing of the advanced cylinder and the correction amount of the ignition timing of the other cylinders that are not advanced is a predetermined protection amount.

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2006-057554 SUMMARY PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] The control device of the internal combustion engine described in Patent Document 1 determines whether the combustion state is good for each cylinder, and corrects the ignition timing of the cylinder in which the combustion state is not good, and in conjunction therewith, corrects the ignition timing of the other cylinders in order to suppress a deviation in the ignition timing of all of the cylinders. However, since the determination of whether the combustion state is good is made based on the crank angle at which the ion current is above a reference level, the combustion pressure of each cylinder cannot be detected or estimated. Therefore, even if the combustion state of all of the cylinders is made good, a deviation in the combustion pressure of each cylinder occurs, and the torque output from the internal combustion engine can fluctuate (pulsate).

[0005] The present application has been made in view of the above-described technical problems, and aims to provide a control device of an internal combustion engine that can suppress a deviation in the combustion pressure among the cylinders. MEANS FOR SOLVING PROBLEMS

[0006] To achieve the above objectives, the present invention provides a control device for an internal combustion engine, the internal combustion engine having multiple cylinders for burning a mixture of air and fuel, and capable of individually controlling at least one of the ignition timing and the fuel injection quantity injected into the cylinders. The control device is characterized by further comprising: a generator for generating a reaction torque corresponding to the torque transmitted from the internal combustion engine; a sensor for detecting the rotation angle of the generator; and a controller for controlling at least one of the ignition timing and the fuel injection quantity, the controller controlling the rotation angle of the generator detected by the sensor. The combustion pressure of each cylinder is estimated by changing the rotation angle. For each cylinder, the combustion pressure difference between the estimated combustion pressure and the predetermined ideal combustion pressure is calculated. When all of the calculated combustion pressure differences are not within the predetermined range, the ignition timing or fuel injection quantity in all cylinders is corrected. When one of the combustion pressure differences is not within the predetermined range, the ignition timing or fuel injection quantity in the cylinder whose combustion pressure difference is not within the predetermined range is corrected individually. Invention Effects

[0007] According to the present invention, the combustion pressure of each cylinder is estimated based on the change in the rotation angle of the generator, and the combustion pressure difference between the estimated combustion pressure and the ideal combustion pressure is calculated for each cylinder. The sensor used to detect the generator's rotation angle uses a component with higher accuracy than that used to detect the internal combustion engine's rotation angle, and is less susceptible to resonance and other effects. Therefore, compared to estimating the combustion pressure of each cylinder based on the detection value of a sensor that detects the internal combustion engine's rotation angle, the combustion pressure of each cylinder can be estimated individually with high accuracy.

[0008] Furthermore, when the combustion pressure difference between the ideal combustion pressure and the estimated combustion pressure is not within the specified range, the ignition timing and fuel injection quantity are adjusted uniformly for all cylinders. This prevents the control required to correct for appropriate combustion pressure from becoming cumbersome. When a certain combustion pressure is not within the specified range, the ignition timing and fuel injection quantity are adjusted individually for the cylinders whose combustion pressure difference is outside the specified range. This prevents deviations in combustion pressure between cylinders. As a result, large pulsations in the torque output from the internal combustion engine can be suppressed, and fluctuations in driving force can be suppressed. In other words, deterioration in driving performance can be suppressed. Attached Figure Description

[0009] Figure 1 This is a schematic diagram illustrating an example of a hybrid vehicle equipped with an internal combustion engine according to an embodiment of the present invention. Figure 2 This is a flowchart illustrating an example of control performed by the control device in an embodiment of the present invention. Detailed Implementation

[0010] The present invention will be described based on the embodiments shown in the accompanying drawings. It should be noted that the embodiments described below are merely examples of embellishing the present invention and are not intended to limit the invention.

[0011] Figure 1 This is a schematic diagram illustrating an example of a hybrid vehicle equipped with an internal combustion engine according to an embodiment of the present invention. Figure 1 The hybrid vehicle (hereinafter referred to as "vehicle") Ve shown has an internal combustion engine (hereinafter referred to as "engine") 1, a first electric motor 2 and a second electric motor (not shown) as driving power sources.

[0012] The engine (ENG) 1 can be configured similarly to engines used as the driving force source in existing engine vehicles and hybrid vehicles. That is, it includes an intake manifold for drawing in outside air, multiple cylinders that supply air from the intake manifold, fuel injectors 3 for injecting fuel, spark plugs 4 for igniting the fuel-air mixture, and an exhaust manifold for expelling exhaust gases from the cylinders. Alternatively, it can be a port-injection engine with the fuel injector 3 located in the intake manifold, or a direct-injection engine with the fuel injector 3 located in the cylinder. The aforementioned fuel injectors 3 and spark plugs 4 are configured to correspond to the cylinders, allowing for independent control of the fuel injection quantity and ignition timing. Furthermore, Figure 1 For convenience, only one injector 3 and spark plug 4 are shown in the image.

[0013] The first electric motor (MG) 2 and the second electric motor can be configured in the same way as electric motors used as driving power sources in existing hybrid vehicles and electric vehicles. That is, in addition to functioning as an electric motor that outputs driving torque by supplying electricity, they also function as a generator that converts the power of the output shaft into electricity by being driven to rotate. Specifically, they can be configured as permanent magnet synchronous motors or induction motors. Furthermore, the first electric motor 2 is equivalent to a "generator" in the embodiments of the present invention.

[0014] Figure 1 The vehicle Ve shown has a power distribution mechanism 5 that distributes the output torque of engine 1 to a first electric motor 2 and drive wheels (not shown). This power distribution mechanism 5 consists of a single-pinion type planetary gear. Specifically, it comprises a sun gear S, a ring gear R arranged on a circle concentric with the sun gear S, and a planet carrier C that holds the planetary gear P meshing with the sun gear S and the ring gear R, enabling it to rotate on its own axis and revolve around the sun. The sun gear S is connected to the first electric motor 2, the planet carrier C is connected to the engine 1, and the ring gear R is connected to an output gear 6 for transmitting torque to the drive wheels.

[0015] Additionally, a gear transmission unit (not shown) is provided for transmitting torque from the gear ring R to the drive wheel, and a second electric motor is connected to this gear transmission unit in a manner capable of transmitting torque. That is, it is configured to superimpose the torque transmitted from the engine 1 to the gear transmission unit via the power distribution mechanism 5 with the torque output from the second electric motor. It is configured to supply the second electric motor with electricity charged into an energy storage device (not shown) and electricity generated by the first electric motor 2.

[0016] In addition, Figure 1 The vehicle Ve shown is equipped with an electronic control device (hereinafter referred to as "controller") 7 that controls the engine 1, the first electric motor 2, and the second electric motor. Specifically, the controller 7 is configured to control the fuel injection quantity of the injector 3 located on the engine 1, the ignition timing of the spark plug 4, the output torque of the first electric motor 2, and the output torque of the second electric motor.

[0017] The controller 7, like the controllers installed in existing vehicles, is mainly composed of a microcomputer and is configured to take input signals from various sensors installed in the vehicle Ve, and output command signals for controlling the engine 1 and each electric motor based on the input signals and pre-stored calculation formulas, mappings, etc.

[0018] Figure 1 The controller 7 shown receives input signals from an intake air temperature sensor 8 that detects the temperature of the air flowing in the intake manifold, a water temperature sensor 9 that detects the temperature of the coolant used to cool the engine 1, a crankshaft angle sensor 11 that detects the rotational speed of the engine 1, specifically the rotational angle of the engine 1's output shaft, i.e., the crankshaft 10, an air flow meter 12 that detects the amount of air drawn into the engine 1, a first rotary transformer 13 that detects the rotational speed (rotational angle) of the first electric motor 2, and a second rotary transformer (not shown) that detects the rotational speed (rotational angle) of the second electric motor. The first rotary transformer 13 corresponds to the "sensor" in the embodiments of the present invention.

[0019] The aforementioned power distribution mechanism 5 distributes the torque input from the engine 1 to the first electric motor 2 (sun gear S) and the drive wheel (ring gear R) according to its gear ratio. Specifically, it transmits a torque corresponding to the counteracting torque transmitted from the engine 1 to the first electric motor 2 by outputting a counteracting torque from the first electric motor 2. In other words, when the counteracting torque generated by the first electric motor 2 is less than the torque transmitted from the engine 1 to the first electric motor 2, the speed of the engine 1 and the first electric motor 2 increases accordingly to the magnitude of the insufficient torque; conversely, when the counteracting torque generated by the first electric motor 2 is greater than the torque transmitted to the first electric motor 2, the speed of the engine 1 and the first electric motor 2 decreases accordingly to the magnitude of the excess torque. That is, by controlling the torque of the first electric motor 2, the speed of the engine 1 and the first electric motor 2 can be controlled.

[0020] Therefore, the controller 7 described above calculates the target speed and target torque of the engine 1 based on the vehicle speed and the operation of the accelerator device (not shown). Furthermore, it calculates the target speed of the first electric motor 2 based on the target speed of the engine 1, the vehicle speed (i.e., the speed of the gear ring R), and the gear ratio of the power distribution mechanism 5, and calculates the target reaction torque of the first electric motor 2 by multiplying the target torque of the engine 1 by the gear ratio of the power distribution mechanism 5. Here, during the transition period when the engine speed shifts towards the target speed, the target reaction torque of the first electric motor 2 can also be calculated by adding or subtracting the torque obtained based on the rate of change of that speed from the torque transmitted to the first electric motor 2 via the power distribution mechanism 5. Additionally, the second electric motor performs torque control based on the difference between the torque transmitted from the engine 1 via the power distribution mechanism 5 and the driving torque required by the vehicle Ve.

[0021] As described above, engine 1 has multiple cylinders. Because each cylinder burns the air-fuel mixture at staggered timings, the output torque of engine 1 pulsates. On the other hand, as described above, since the first electric motor 2 outputs a counter-torque opposing the torque transmitted from engine 1, and the rotational speed (change in rotation angle or rate of change) of the first electric motor 2 is maintained, the rotational speed of the first electric motor 2 changes when the torque of engine 1 pulsates. That is, based on the output torque of the first electric motor 2 and the rotational angle of the first electric motor 2 detected by the first rotary transformer 13, the pulsating torque of engine 1 can be estimated; in other words, the combustion pressure generated by each cylinder through the combustion of the air-fuel mixture can be estimated.

[0022] Therefore, the control device in the embodiments of the present invention is configured to estimate the combustion pressure generated by each cylinder and correct the ignition timing and fuel injection quantity of each cylinder based on the estimated combustion pressure. Figure 2 A flowchart illustrating one example of its control is shown. Figure 2 In the control example shown, various parameters are first calculated based on the detection values ​​of sensors that detect the operating status of engine 1 (step S1). The parameters in step S1 include, for example, engine intake air temperature, engine coolant temperature, engine speed, and engine intake air volume.

[0023] Next, based on the parameters calculated in step S1, the ideal combustion pressure Pcyl(n) is calculated for each cylinder (step S2). The ideal combustion pressure Pcyl(n) in step S2 can be obtained by constructing a multidimensional mapping for calculating the ideal combustion pressure Pcyl(n) using the parameters calculated in step S1 through prior experiments or simulations, and by referring to this mapping.

[0024] Next, the estimated combustion pressure P'cyl(n) is calculated (step S3). Specifically, based on the torque (command torque) output from the first motor 2 and the rate of change of the rotation angle obtained from the detection signal of the first rotary transformer 13 under the timing of combustion of the air-fuel mixture in the first cylinder, the estimated combustion pressure P'cyl(1) of the first cylinder is calculated. Similarly, the estimated combustion pressures P'cyl(2) and P'cyl(3) are calculated for each cylinder.

[0025] Furthermore, the difference between the ideal combustion pressure Pcyl(n) and the estimated combustion pressure P'cyl(n) of each cylinder (combustion pressure difference) ΔP(n) is calculated (step S4). Specifically, the combustion pressure difference ΔP(n) in each cylinder is calculated by subtracting the estimated combustion pressure P'cyl(n) obtained in step S3 from the ideal combustion pressure Pcyl(n) obtained in step S2. That is, in the case of a three-cylinder engine, the combustion pressure differences ΔP(1), ΔP(2), and ΔP(3) are calculated for each of the first, second, and third cylinders.

[0026] After step S4, it is determined whether the combustion pressure of all cylinders has increased or decreased to the same level (step S5). Specifically, it is determined whether all combustion pressure differences ΔP(all) calculated in step S4 are greater than a predetermined upper limit value THH1, or whether all combustion pressure differences ΔP(all) are less than a predetermined lower limit value THL1. The predetermined upper limit value THH1 and the predetermined lower limit value THL1 in step S5 are allowable values ​​for the generated combustion pressure differences and are pre-stored in the controller 7. In addition, the predetermined upper limit value THH1 and the predetermined lower limit value THL1 can also be changed according to the output torque of engine 1, etc.

[0027] When a positive judgment is made in step S5 because all combustion pressure differences ΔP(all) are greater than the specified upper limit THH1 or all combustion pressure differences ΔP(all) are less than the specified lower limit THL1, the expected torque cannot be output from engine 1. Therefore, when a positive judgment is made in step S5, the ignition timing and fuel injection quantity for all cylinders are corrected in a way that makes the actual combustion pressure equal to the ideal combustion pressure Pcyl(n) (step S6), and the routine is temporarily terminated.

[0028] Specifically, when a positive judgment is made in step S5 because all combustion pressure differences ΔP(all) are greater than the specified upper limit value THH1, the ignition timing is delayed or the fuel injection quantity is reduced. Conversely, when a positive judgment is made in step S5 because all combustion pressure differences ΔP(all) are less than the specified lower limit value THL1, the ignition timing is advanced or the fuel injection quantity is increased.

[0029] In addition, in step S6, the advance or delay of ignition timing or the amount of fuel injection can be determined based on the maximum or average value of the combustion pressure difference ΔP(n) obtained in step S4, or it can be determined to be a predetermined amount.

[0030] On the other hand, when a negative judgment is made in step S5 because all combustion pressure differences ΔP(all) or a certain combustion pressure difference ΔP(n) is below the specified upper limit THH1, or all combustion pressure differences ΔP(all) or a certain combustion pressure difference ΔP(n) is above the specified lower limit THL1, the ignition timing and fuel injection quantity are adjusted for each cylinder. That is, the following steps S7 and subsequent steps perform judgment and control for each cylinder.

[0031] Specifically, firstly, for each cylinder, it is determined whether the combustion pressure difference ΔP(n) is greater than the specified upper limit value THH2 (step S7). In addition, the specified upper limit value THH2 in step S7 can be the same as the specified upper limit value THH1 in step S5, or it can be a smaller value.

[0032] When there is a target cylinder that is affirmatively determined in step S7 because the combustion pressure difference ΔP(n) is greater than the specified upper limit value THH2, the ignition timing for the target cylinder is delayed or the fuel injection quantity is reduced (step S8), and the routine is temporarily terminated.

[0033] Conversely, when a negative judgment is made in step S7 because all combustion pressure differences ΔP(all) are below the specified upper limit value THH2, or when there is a cylinder for which a negative judgment is made in step S7 because the combustion pressure difference ΔP(n) is below the specified upper limit value THH2, it is determined for each cylinder whether the combustion pressure difference ΔP(n) is less than the specified lower limit value THL2 (step S9). Furthermore, the specified lower limit value THL2 in step S9 can be the same as the specified lower limit value THL1 in step S5, or it can be a larger value.

[0034] When there is a target cylinder that is affirmatively determined in step S9 because the combustion pressure difference ΔP(n) is less than the specified lower limit THL2, the ignition timing for the target cylinder is advanced or the fuel injection quantity is increased (step S10), and the routine is temporarily terminated.

[0035] Conversely, when a negative judgment is made in step S9 because all combustion pressure differences ΔP(all) are above the specified lower limit THL2, the combustion pressure in all cylinders is approximately equal to or within the allowable range of the ideal combustion pressure Pcyl(n). Alternatively, for cylinders where a negative judgment is made in step S9 because the combustion pressure difference ΔP(n) is above the specified lower limit THL2, their combustion pressure is approximately equal to or within the allowable range of the ideal combustion pressure Pcyl(n). Therefore, when a negative judgment is made in step 9, the routine is temporarily terminated.

[0036] As described above, the combustion pressure generated in each cylinder is estimated based on the reaction torque of the first electric motor 2 and the detection value of the first rotary transformer 13. The detection value of the first rotary transformer 13 is more accurate than the detection value of the crankshaft angle sensor 11 and is less susceptible to the effects of resonance, etc. Therefore, compared with estimating the combustion pressure of each cylinder based on the detection value of the crankshaft angle sensor 11, in other words, based on the change in engine speed, the combustion pressure of each cylinder can be estimated individually with high accuracy.

[0037] Furthermore, when the difference between the ideal combustion pressure Pcyl(n) and the estimated combustion pressure P'cyl(n), i.e. the combustion pressure difference ΔP(n), is greater than the specified upper limit THH1 or less than the specified lower limit THL1, in other words, when the difference is not within the specified range, the ignition timing and fuel injection quantity are adjusted for all cylinders. This can suppress the complexity of control required to make corrections to achieve the appropriate combustion pressure.

[0038] Furthermore, when a combustion pressure difference ΔP(n) is outside the specified range, the ignition timing and fuel injection quantity are individually adjusted for cylinders where the combustion pressure difference ΔP(n) is outside the specified range, thereby suppressing deviations in combustion pressure between cylinders. As a result, it is possible to suppress the deterioration of vibration and the increase of abnormal noise caused by the engine 1 driving. In addition, it is possible to suppress large pulsations in the torque output from the engine 1 and to suppress fluctuations in driving force. In other words, it is possible to suppress the deterioration of driving performance.

[0039] in addition, Figure 1 The vehicle Ve shown is a so-called series-parallel hybrid vehicle that converts a portion of the power from engine 1 into electricity via first electric motor 2 and transmits the remaining power to the drive wheels for propulsion. However, it can also be a so-called series hybrid vehicle that converts the power from engine 1 into electricity via first electric motor 2 and transmits power to the drive wheels only from second electric motor for propulsion. Explanation of reference numerals in the attached figures

[0040] 1: Engine 2: Electric motor 3: Injector 4: Spark plugs 7: Controller 11: Crankshaft angle sensor 13: Rotary Transformer Ve: vehicle.

Claims

1. A control device for an internal combustion engine, the internal combustion engine having a plurality of cylinders for burning a mixture of air and fuel, and capable of individually controlling at least one of the ignition timing of the cylinders and the amount of fuel injected into the cylinders. The control device for the internal combustion engine is characterized in that... It also has: The generator produces a reaction torque corresponding to the torque transmitted from the internal combustion engine; Sensors detect the rotation angle of the generator; and The controller controls at least one of the ignition timing and the fuel injection quantity. The controller estimates the combustion pressure of each cylinder based on the change in the rotation angle of the generator detected by the sensor. For each cylinder, it calculates the combustion pressure difference between the estimated combustion pressure and the predetermined ideal combustion pressure. When all of the calculated combustion pressure differences are not within the predetermined range, the ignition timing or fuel injection quantity in all cylinders is corrected. When one of the combustion pressure differences is not within the predetermined range, the ignition timing or fuel injection quantity in the cylinder whose combustion pressure difference is not within the predetermined range is corrected individually.

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