JP3564876B2 - Engine air-fuel ratio control device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control device for an engine, and more particularly, to a device for predicting an intake valve temperature when fuel is injected and supplied toward an intake valve and obtaining a transient correction amount using the predicted intake valve temperature.
[0002]
[Prior art]
Generally, the deviation of the air-fuel ratio from the target value at the time of acceleration / deceleration of the engine is caused by a so-called quantitative change of the wall-flow fuel, which adheres to the intake manifold and the intake port and flows through the wall surface to the cylinder in a liquid state. Various proposals have been made for performing fuel correction using the excess or deficiency caused by the wall flow fuel as a transient correction amount.
[0003]
In this embodiment, two values, an equilibrium adhesion amount Mfh and a quantity ratio Kmf, are determined in advance based on the engine load, the engine speed Ne, and the cooling water temperature Tw, and are calculated per unit cycle using a certain arithmetic expression. The adhesion amount (per injection) Vmf is determined, and the basic injection amount Tp is corrected with the adhesion speed Vmf. The above-mentioned quantity ratio Kmf is a coefficient indicating how much the fuel of the difference (Mfh-Mf) between Mfh and the adhesion amount (predictive variable) Mf at that time is reflected in the correction of the fuel injection amount. is there.
[0004]
However, even when fuel is injected not toward the intake port but toward the intake valve, the use of the above-mentioned equilibrium adhesion amount Mfh calculated from the cooling water temperature Tw and the distribution ratio Kmf makes it particularly cold. An air-fuel ratio error occurs immediately after starting. Since the wall flow fuel amount at this time depends on the temperature of the intake valve through which the wall flow fuel flows, the temperature difference between the intake valve temperature and the cooling water temperature Tw becomes the estimation error of the wall flow fuel, and the air-fuel ratio error It happens.
[0005]
Therefore, in the apparatus disclosed in JP-A-1-305142, Mfh and Kmf are obtained by predicting the intake valve temperature and using the predicted intake valve temperature in place of the cooling water temperature Tw. The intake valve temperature is almost equal to the cooling water temperature Tw immediately after the start, and after warming up, settles to a temperature (for example, about 80 ° C.) higher than the cooling water temperature Tw by a predetermined value, and its change depends on a time constant determined by the amount of intake air. Since the first-order lag occurs, the equilibrium intake valve temperature Th and the lag time constant SPTF are determined in advance using the load and the rotation speed as parameters.
Tf = Th × SPTF + Tf _-1 × (1-SPTF) (1)
Where Tf _-1 : Previous value of Tf
(That is, a first-order lag equation) is used to determine the predicted intake valve temperature Tf.
[0006]
However, on the actual arithmetic logic, a value Twf that converges from the temperature lower than the cooling water temperature Tw by a predetermined value toward the cooling water temperature Tw with a first-order delay at the time of starting (this is referred to as a wall flow correction temperature) Twf is given at the time of starting. (See JP-A-3-134237).
[0007]
[Problems to be solved by the invention]
By the way, the data for obtaining the above Mfh and Kmf are adapted in a state where the cooling water temperature Tw is originally fixed and the intake valve temperature is settled to a temperature higher than the cooling water temperature Tw by a predetermined value (that is, a temperature equilibrium state). I have. Conversely, it is practically impossible to match Mfh and Kmf in a temperature non-equilibrium state. Therefore, Twf when Mfh and Kmf are determined using the wall flow correction temperature Twf instead of the cooling water temperature Tw must also be a temperature in an equilibrium state.
[0008]
However, in the above-described apparatus in which the data of Mfh and Kmf adapted to the cooling water temperature in the equilibrium state is simply used as the wall flow correction temperature Twf instead of the cooling water temperature Tw, the temperature non-equilibrium state is simulated. It is intended to handle. To give an example, the above-mentioned apparatus has a temperature equilibrium state where Twf is 40 ° C. (the cooling water temperature Tw is 40 ° C.) and a temperature non-equilibrium state where Twf is 40 ° C. (the cooling water temperature Tw is 40 ° C.) This is equivalent to treating the same as the same state. For this reason, an air-fuel ratio error occurs immediately after the engine starts, in which the wall-flow correction temperature Twf is continuously in a temperature non-equilibrium state.
[0009]
For this reason, as shown in FIG. 13, Mfh using Twf is less than the required Mfh, and a change in Mf due to Kmf using Twf is too slow in response to a change in Mf due to the required Kmf, Conversely, Mfh is excessive and the response of Mf is too fast.
[0010]
More specifically, as shown in FIG. 24, (1) shows a change in Twf in a temperature equilibrium state of 20 ° C., (2) shows a change in Twf in a case of starting at 40 ° C., and (3) shows a change in Twf in a case of starting at 80 ° C. It is a thing. However, the cooling water temperature Tw is constant for convenience of explanation. In (1), since Twf is in the temperature equilibrium state of 20 ° C., the data of Mfh and Kmf that are suitable in the temperature equilibrium state can be used as they are. However, in the cases (2) and (3), the data at the time of equilibrium needs to be corrected at the time of temperature non-equilibrium. It should be noted that, even in the same temperature non-equilibrium state shown in (2) and (3), it is needless to say that (3) in which the difference between Twf and Tw at the position of the mark is larger requires larger correction.
[0011]
Therefore, when the data for obtaining Mfh and Kmf is adapted to the cooling water temperature in the temperature equilibrium state, this data is replaced with the detected value Tw of the cooling water temperature and the predicted intake valve temperature (or the wall flow correction temperature). ) To calculate Mfh and Kmf, and calculate the correction magnifications Mfhas and Kmfas at the time of temperature non-equilibrium according to the difference Dtwf (= Tw-Twf) between Tw and Twf, and calculate the Mfhas and Kmfas. Proposed a method of correcting the conventional Mfh and Kmf to improve the control accuracy of the air-fuel ratio immediately after the start, in which the predicted intake valve temperature (or the wall flow correction temperature) becomes a continuous temperature non-equilibrium state. No. 7-120026). This device is hereinafter referred to as a prior application device.
[0012]
However, when the prior application apparatus is actually applied to an engine, when the throttle valve is widely opened and acceleration is performed immediately after a cold start (temperature non-equilibrium state), as shown in FIG. Although the air-fuel ratio became flat in the first half of the acceleration and the target was achieved, it became clear that the air-fuel ratio became lean in the second half of the acceleration in the temperature non-equilibrium state. Then, when experiments were conducted at different temperatures, it was found that the leaner component became more noticeable as the temperature became lower. Analysis shows that the effect of unburned fuel that exists in the temperature non-equilibrium state (wall flow fuel has a response delay but almost always enters the cylinder and contributes to combustion. There is a fuel component that becomes unburned HC and a fuel component that enters the crankcase from the cylinder through the gap of the piston ring and melts into the oil. Such unburned component does not contribute to combustion. It has been found that there is a problem in trying to apply all of the flow correction fuel (which is different from the flowing fuel) to the transient correction amount Kathos. That is, in order to prevent a lean portion in the first half of the acceleration in the temperature non-equilibrium state, the larger the temperature difference Dtwf between Tw and Twf, the larger the correction magnification Mfhas is. Since the ratio of the first half of the acceleration in the temperature non-equilibrium state is set appropriately by the correction magnification, Mfh in the first half of the acceleration in the temperature non-equilibrium state (see the solid line in the third row in FIG. 20) and Kathos (FIG. (See the fourth solid line). Thereafter, as Dtwf decreases, Mfh rapidly decreases. After the amount Mf (see the dash-dot line in the third row) catches up with the decreasing equilibrium amount Mfh, Kathos (from the bottom to the second). Since the value of (see the stage) is a negative value and becomes a large value (fuel reduction correction is performed), the air-fuel ratio becomes lean corresponding to the period in which Kathos is a negative value. In view of this, the present invention applies the prior application device to a device in which the basic injection amount is corrected based on the target fuel-air ratio equivalent amount, and sets the unburned fuel correction amount according to the temperature difference (Tw-Tf). It is intended to flatten the air-fuel ratio even in the latter half of the transition of the temperature non-equilibrium state by calculating and correcting the target fuel-air ratio equivalent amount with the unburned portion correction amount.
[0013]
Note that, as an invention very similar to the invention of the present application, an invention has been proposed in which Mfh is calculated using Tfbya of Expression (8) described later without adding the unburned matter correction coefficient Kub to Tfbya. (Refer to Japanese Patent Application No. 8-96854), when the target fuel-air ratio equivalent amount Tfbya is switched (when the target air-fuel ratio is switched) such as when decelerating from the output air-fuel ratio range, the transient correction amount Kathos is changed. The purpose of the present invention is to prevent the air-fuel ratio from temporarily becoming over-rich or over-lean due to the shortage, and the technical idea is different from the present invention.
[0014]
[Means for Solving the Problems]
In the first invention, as shown in FIG. 25, means 21 for calculating a basic injection amount Tp according to operating conditions, means 22 for calculating a target fuel-air ratio equivalent, and a target fuel-air ratio equivalent Means 23 for correcting the basic injection amount Tp, means 24 for detecting the coolant temperature, means 25 for calculating the predicted intake valve temperature Tf, A map that matches the equilibrium adhesion amount per unit injection amount of fuel to the cooling water temperature in the temperature equilibrium state, By referring to the intake valve predicted temperature Tf instead of the detected value Tw of the cooling water temperature, The amount of fuel attached to the intake pipe in the equilibrium state Means 26 for calculating the equilibrium adhesion amount Mfh; A map that matches the equilibrium adhesion amount per unit injection amount of fuel to the cooling water temperature in the temperature equilibrium state, By referring to the intake valve predicted temperature Tf instead of the detected value Tw of the cooling water temperature, Is the rate at which the amount of fuel attached to the intake pipe at that time approaches the equilibrium attached amount. Means 27 for calculating the amount ratio Kmf, means 28 for calculating the difference (Mfh-Mf) between the calculated equilibrium adhesion amount Mfh and the adhesion amount Mf at that time, and the adhesion of the difference (Mfh-Mf). Based on the amount and the calculated amount ratio Kmf Is the amount of adhesion to the intake pipe per injection of the fuel injection valve Means 29 for calculating the adhesion speed Vmf; At that time Means 30 for updating the adhesion amount Mf by adding the adhesion amount Mf in synchronism with the fuel injection, and a fuel amount by further correcting the basic injection amount corrected by the target fuel-air ratio equivalent amount by the adhesion speed Vmf. In an air-fuel ratio control device for an engine, comprising a means 31 for calculating an injection amount Ti and a means 32 for supplying this amount of fuel to the intake pipe, the detected value Tw of the cooling water temperature and the predicted intake valve temperature Tf are calculated. Means 33 for calculating the difference (Tw-Tf), and means 33 for calculating a temperature non-equilibrium according to the temperature difference (Tw-Tf). For correcting equilibrium coverage or volume fraction A means 34 for calculating the correction amount, and the calculated equilibrium adhesion amount Mfh or the calculated mass ratio with the correction amount at the time of temperature non-equilibrium (for example, Mfhas for equilibrium adhesion amount, Kmfas for mass ratio). Means 35 for correcting Kmf, means 36 for calculating an unburned portion correction amount according to the temperature difference (Tw-Tf), and means 37 for correcting the target fuel-air ratio equivalent amount using the unburned portion correction amount. And provided.
[0015]
In the second invention, as shown in FIG. 26, means 21 for calculating a basic injection amount Tp according to operating conditions, means 22 for calculating a target fuel-air ratio equivalent amount, and a target fuel-air ratio equivalent amount A means 23 for correcting the basic injection amount Tp, a means 24 for detecting a cooling water temperature, A map that matches the equilibrium adhesion amount per unit injection amount of fuel to the cooling water temperature in the temperature equilibrium state, By referring to the intake valve predicted temperature Tf instead of the detected value Tw of the cooling water temperature, The amount of fuel attached to the intake pipe in the equilibrium state Means 26 for calculating the equilibrium adhesion amount Mfh; A map that matches the equilibrium adhesion amount per unit injection amount of fuel to the cooling water temperature in the temperature equilibrium state, By referring to the intake valve predicted temperature Tf instead of the detected value Tw of the cooling water temperature, Is the rate at which the amount of fuel attached to the intake pipe at that time approaches the equilibrium attached amount. Means 27 for calculating the amount ratio Kmf, means 28 for calculating the difference (Mfh-Mf) between the calculated equilibrium adhesion amount Mfh and the adhesion amount Mf at that time, and the adhesion of the difference (Mfh-Mf). Based on the amount and the calculated amount ratio Kmf Is the amount of adhesion to the intake pipe per injection of the fuel injection valve Means 29 for calculating the adhesion speed Vmf, means 25 for calculating the predicted intake valve temperature Tf, means 33 for calculating the difference (Tw-Tf) between the detected value Tw of the cooling water temperature and the predicted intake valve temperature Tf. At the time of temperature non-equilibrium according to this temperature difference (Tw-Tf). For correcting the adhesion speed Vmf Means 41 for calculating the correction amount Vmfas, means 42 for correcting the calculated adhesion speed Vmf with the correction amount Vmfas when the temperature is not balanced, At that time Means 30 for updating the adhesion amount Mf by adding the adhesion amount Mf in synchronization with the fuel injection, and correcting the basic injection amount corrected by the target fuel-air ratio equivalent amount with the corrected adhesion speed Vmf. Means 31 for calculating the fuel injection amount Ti, means 32 for supplying the fuel of this injection amount to the intake pipe, and means 36 for calculating the unburned portion correction amount according to the temperature difference (Tw-Tf). Means 37 for correcting the target fuel-air ratio equivalent amount with the unburned portion correction amount.
[0016]
According to a third aspect, in the first or second aspect, the equilibrium adhesion amount calculating means 26 comprises: A map that matches the equilibrium adhesion amount per unit injection amount of fuel to the cooling water temperature in the temperature equilibrium state, Means for calculating the equilibrium adhesion magnification Mfhtvo by referring to the predicted intake valve temperature Tf instead of the detected value Tw of the cooling water temperature, the adhesion magnification Mfhtvo, the calculated basic injection amount Tp, and the unburned fuel content. Means for obtaining the product of the target fuel-air ratio equivalent amount corrected by the correction amount as the equilibrium adhesion amount Mfh.
[0017]
In the fourth invention, as shown in FIG. 27, means 21 for calculating a basic injection amount Tp according to operating conditions, means 22 for calculating a target fuel-air ratio equivalent amount, and a target fuel-air ratio equivalent amount Means 23 for correcting the basic injection amount Tp, means 24 for detecting the coolant temperature, means 25 for calculating the predicted intake valve temperature Tf, A map that matches the equilibrium adhesion amount per unit injection amount of fuel to the cooling water temperature in the temperature equilibrium state, By reference using the detected value of the cooling water temperature The amount of fuel attached to the intake pipe in the equilibrium state Means 51 for calculating the equilibrium adhesion amount Mfh; A map that matches the equilibrium adhesion amount per unit injection amount of fuel to the cooling water temperature in the temperature equilibrium state, By referring to the detected value Tw of the cooling water temperature, Is the rate at which the amount of fuel attached to the intake pipe at that time approaches the equilibrium attached amount. Means 52 for calculating the amount ratio Kmf, means 28 for calculating the difference (Mfh-Mf) between the calculated equilibrium adhesion amount Mfh and the adhesion amount Mf at that time, and the adhesion of the difference (Mfh-Mf). Based on the amount and the calculated amount ratio Kmf Is the amount of adhesion to the intake pipe per injection of the fuel injection valve Means 29 for calculating the adhesion speed Vmf; At that time Means 30 for updating the adhesion amount Mf by adding the adhesion amount Mf in synchronism with the fuel injection, and a fuel amount by further correcting the basic injection amount corrected by the target fuel-air ratio equivalent amount by the adhesion speed Vmf. In an air-fuel ratio control device for an engine, comprising a means 31 for calculating an injection amount Ti and a means 32 for supplying this amount of fuel to the intake pipe, the detected value Tw of the cooling water temperature and the predicted intake valve temperature Tf are calculated. Means 33 for calculating the difference (Tw-Tf), and means 33 for calculating a temperature non-equilibrium according to the temperature difference (Tw-Tf). For correcting equilibrium coverage or volume fraction Means 34 for calculating the correction amount, and the calculated equilibrium adhesion amount Mfh or the calculated mass ratio with the correction amount at the time of temperature non-equilibrium (for example, Mfhas for equilibrium adhesion amount and Kmfas for mass ratio). Means 35 for correcting Kmf, means 36 for calculating an unburned portion correction amount according to the temperature difference (Tw-Tf), and means 37 for correcting the target fuel-air ratio equivalent amount using the unburned portion correction amount. And provided.
[0018]
In the fifth invention, as shown in FIG. 28, means 21 for calculating a basic injection amount Tp according to operating conditions, means 22 for calculating a target fuel-air ratio equivalent amount, and a target fuel-air ratio equivalent amount A means 23 for correcting the basic injection amount Tp, a means 24 for detecting a cooling water temperature, A map that matches the equilibrium adhesion amount per unit injection amount of fuel to the cooling water temperature in the temperature equilibrium state, By referring to the detected value Tw of the cooling water temperature, The amount of fuel attached to the intake pipe in the equilibrium state Means 51 for calculating the equilibrium adhesion amount Mfh; A map that matches the equilibrium adhesion amount per unit injection amount of fuel to the cooling water temperature in the temperature equilibrium state, By referring to the detected value Tw of the cooling water temperature, Is the rate at which the amount of fuel attached to the intake pipe at that time approaches the equilibrium attached amount. Means 27 for calculating the amount ratio Kmf, means 28 for calculating the difference (Mfh-Mf) between the calculated equilibrium adhesion amount Mfh and the adhesion amount Mf at that time, and the adhesion of the difference (Mfh-Mf). Based on the amount and the calculated amount ratio Kmf Is the amount of adhesion to the intake pipe per injection of the fuel injection valve Means 29 for calculating the adhesion speed Vmf, means 25 for calculating the predicted intake valve temperature Tf, means 33 for calculating the difference (Tw-Tf) between the detected value Tw of the cooling water temperature and the predicted intake valve temperature Tf. At the time of temperature non-equilibrium according to this temperature difference (Tw-Tf). To correct the adhesion speed Means 41 for calculating the correction amount Vmfas, means 42 for correcting the calculated adhesion speed Vmf with the correction amount Vmfas when the temperature is not balanced, At that time Means 30 for updating the adhesion amount Mf by adding the adhesion amount Mf in synchronization with the fuel injection, and correcting the basic injection amount corrected by the target fuel-air ratio equivalent amount with the corrected adhesion speed Vmf. Means 31 for calculating the fuel injection amount Ti, means 32 for supplying the fuel of this injection amount to the intake pipe, and means 36 for calculating the unburned portion correction amount according to the temperature difference (Tw-Tf). Means 37 for correcting the target fuel-air ratio equivalent amount with the unburned portion correction amount.
[0019]
In a sixth aspect based on the fourth or fifth aspect, the equilibrium adhesion amount calculating means 51 comprises: A map that matches the equilibrium adhesion amount per unit injection amount of fuel to the cooling water temperature in the temperature equilibrium state, Means for calculating an equilibrium adhesion ratio Mfhtvo by referring to the detected value of the cooling water temperature, and a target fuel-air ratio corrected by the adhesion ratio Mfhtvo, the calculated basic injection amount Tp, and the unburned portion correction amount. Means for obtaining a product of a considerable amount as the equilibrium adhesion amount Mfh.
[0020]
In a seventh aspect, in any one of the first to sixth aspects, the unburned portion correction amount is corrected according to the detected value of the cooling water temperature.
[0021]
In an eighth aspect, in any one of the first to sixth aspects, the unburned portion correction amount is corrected according to an engine load.
[0022]
In a ninth aspect of the present invention, in any one of the first to sixth aspects, the unburned portion correction amount is corrected according to an engine speed.
[0023]
【The invention's effect】
The data for calculating the equilibrium adhesion amount and the volume ratio are adapted to the cooling water temperature in the temperature equilibrium state, and the data are equilibrated by referring to this data using the predicted intake valve temperature instead of the detected cooling water temperature. When calculating the amount of deposit and the proportion of the amount, it is possible to calculate the equilibrium amount and the proportion of the amount in consideration of the temperature of the part where the fuel actually adheres. The point at which the temperature state of the engine is different (equilibrium and non-equilibrium) between when and when the calculation is actually performed cannot be considered. On the other hand, in the same part as the prior application of the first invention, the equilibrium adhesion amount and the amount ratio obtained using the detected value of the cooling water temperature are corrected by the correction amount at the time of temperature non-equilibrium. The equilibrium adhesion amount or the adhesion amount meets the requirement at the time of temperature non-equilibrium, and the control accuracy of the air-fuel ratio immediately after starting can be improved. That is, according to the correction amount based on the temperature difference between the cooling water temperature and the predicted intake valve temperature, the above two points can be considered at the same time.
[0024]
Further, in the same part of the second invention as in the prior application, the compatible factor is one constant for the deposition speed as compared with the case where both the equilibrium deposition volume and the correction amount at the time of non-equilibrium for the volume ratio are adapted. Therefore, the number of man-hours for adaptation can be reduced as compared with the case where the adaptation work of the correction amount at the time of temperature non-equilibrium is performed for both the equilibrium adhesion amount and the amount ratio.
[0025]
On the other hand, in the prior application, on the other hand, the effect of unburned fuel in the temperature non-equilibrium state is set only by the deposition rate (transient correction amount). In the latter half of the transition of the equilibrium state, the air-fuel ratio becomes lean with the decrease in the deposition rate. On the other hand, in the first and second inventions, the target fuel-air ratio equivalent is increased and corrected by the unburned fuel correction amount corresponding to the temperature difference between the cooling water temperature and the predicted intake valve temperature. In the first half of the acceleration of the state, the steady-state injection amount (determined by the basic injection amount and the target fuel-air ratio equivalent amount) is increased by compensating for the effect of the unburned portion compared with the prior application device (transient correction amount). Is reduced, and in the latter half of the acceleration in the temperature non-equilibrium state, the decrease in the deposition rate is compensated for by the increase in the steady-state injection amount. In other words, the influence of the unburned fuel in the temperature non-equilibrium state is not only applied to the deposition rate (transient correction amount) but also to the steady injection amount. The air-fuel ratio becomes flat. Similarly, when deceleration is performed by returning the accelerator pedal in the temperature non-equilibrium state, the air-fuel ratio is prevented from becoming lean in the latter half of the deceleration.
[0026]
In each of the third and sixth aspects of the present invention, the transient correction amount in consideration of the unburned portion can be set by obtaining the equilibrium adhesion amount in proportion to the target fuel-air ratio equivalent in consideration of the unburned portion. Therefore, the air-fuel ratio from the time of cold start to the time of temperature equilibrium can be made flat.
[0027]
In each of the fourth and fifth inventions, the equilibrium adhesion amount and the amount ratio are obtained using the detected value of the cooling water temperature. At this time, the difference between the detected value of the cooling water temperature and the predicted intake valve temperature is used by using the intake valve predicted temperature. Although the equilibrium adhesion ratio is smaller than the case of obtaining the equilibrium adhesion ratio, the equilibrium adhesion amount can be appropriately set by the correction amount at the time of temperature non-equilibrium (Mfhas and Kmfas in the fourth invention, Vmfas in the fifth invention). . As in the other inventions, the air-fuel ratio from the time of cold start to the time of temperature equilibrium can be further flattened by the unburned portion correction.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
In FIG. 1, intake air passes through an intake pipe 8 from an air cleaner, and fuel is injected from a fuel injection valve 7 toward an intake valve of the engine 1 based on an injection signal from a control unit (abbreviated as C / U in the figure) 2. You. The gas burned in the cylinder is introduced into a catalytic converter 10 through an exhaust pipe 9, where harmful components (CO, HC, NOx) in the combustion gas are purified by a three-way catalyst and discharged.
[0029]
The flow rate Qa of the intake air is detected by a hot wire type air flow meter 6, and the flow rate is controlled by an intake throttle valve 5 linked to an accelerator pedal.
[0030]
The air flow signal from the air flow meter 6 includes an air-fuel ratio sensor 3 for detecting oxygen concentration in exhaust gas, a crank angle sensor 4 for outputting a crank angle reference position signal (Ref signal) and an angle signal, and a cooling water temperature of a water jacket. It is input to the control unit 2 together with signals from the water temperature sensor 11 for detecting Tw and the starter switch 12 for detecting the operation of the starter.
[0031]
The control unit 2 calculates the basic injection pulse width Tp from the intake air amount detected by the air flow meter 6 and the engine speed Ne, and adds a transient correction amount Kathos to this Tp during acceleration / deceleration to perform fuel correction. Is going. Since the transient correction amount Kathos is specifically a correction amount for the fuel wall flow, it works not only at the time of acceleration / deceleration but also at the time of starting when the fuel wall flow changes greatly. In this case, the amount of wall-flow fuel greatly depends on the temperature of the portion where the wall-flow fuel flows. Therefore, when injecting all of the fuel from the injection valve toward the back of the umbrella of the intake valve, (part of the fuel is In the case of injection, the intake valve temperature is predicted, and the transient correction amount Kathos is calculated using the predicted intake valve temperature Tf.
[0032]
The intake valve temperature is almost equal to the cooling water temperature Tw immediately after starting, and after warming up, settles to a temperature (for example, about 80 ° C.) higher than the cooling water temperature Tw by a predetermined value. It will be late. For this reason, a method for predicting the intake valve temperature has been proposed as disclosed in Japanese Patent Application Laid-Open No. 1-305142. However, on an actual calculation logic, the temperature starts from a temperature lower than Tw by a predetermined value and changes toward Tw. The temperature Twf for wall flow correction which is a value to be performed is introduced.
[0033]
This is outlined (for details, see Japanese Patent Application Laid-Open No. 3-134237). The flowchart in FIG. 2 is for calculating the wall flow correction temperature Twf, and is executed once every 1 second, for example, in synchronization with a timer.
[0034]
In step 1, it is determined whether or not firing is being performed (combustion). If not, the process proceeds to step 2.
[0035]
In step 2, the initial value Inwft of the wall flow correction temperature is obtained from the current cooling water temperature Tw with reference to the table having the contents shown in FIG. In the figure, the one-dot chain line is the line of Inwft = Tw, and here, the fuel is injected toward the intake valve. Therefore, depending on the ratio of the injected fuel toward the intake valve, it is smaller than Tw as shown by the solid line. Set to a low value.
[0036]
In Steps 3 and 4, it is determined whether the engine is rotating and the start switch is ON, and if it is determined that the engine is rotating and the start switch is ON, it is immediately before starting, or If it is determined in step 3 that the engine is not running because it is not running, the process proceeds to step 5 and the wall flow correction temperature Twf is calculated using the wall flow correction temperature initial value Inwft.
Twf = Inwft × ENSTSP # + Twf _{-1 sec} × (1-ENSTSP #) (2)
However, Twf _{-1 sec} Twf before 1 sec
ENSTSP #: Temperature change rate before start or engine stall (constant value)
Is obtained with a first-order delay according to the following equation, and the flow of FIG. 2 is terminated.
[0037]
On the other hand, if it is determined in step 1 that it is during the firing, in steps 6 and 7, the temperature change rate Fltsp during the firing is obtained from the intake air amount Qa with reference to the table containing FIG. Using Tw, the wall flow correction temperature Twf at the time of firing is calculated as follows:
Twf = Tw × Fltsp + Twf _{-1 sec} × (1-Fltsp) (3)
Is obtained with a first-order delay according to the following equation, and the flow of FIG. 2 is terminated.
[0038]
In FIG. 4, the reason why the value of Fltsp increases as Qa increases is that the heat generated by combustion per unit time increases as Qa increases, and the speed of heat transfer to the fuel attachment portion increases.
[0039]
The flowchart in FIG. 5 is for initializing the wall flow correction temperature. In step 11, an initial value Inwft of the wall flow correction temperature is calculated from the current cooling water temperature Tw, and in step 12, Twf = Inwft is set. I have.
[0040]
When the wall flow correction temperature Twf obtained in this manner is warmed up, the temperature becomes equal to the cooling water temperature Tw as shown in the right half of FIG. 6, but the Twf immediately after the start is the left half of FIG. As shown in (1), the cooling water temperature Tw converges to the cooling water temperature Tw with a first-order delay starting from the initial value Inwft. Note that the left half of FIG. 6 is each waveform immediately after the start, and the right half is each waveform during warm-up (when the vehicle is accelerated at the same water temperature as immediately after the start of the left half of FIG. 6). Starter / sw is an abbreviation for starter switch.
[0041]
Next, the flowchart of FIG. 7 is for calculating the transient correction amount Kathos, and this routine is executed at a period of 10 ms. Steps 22, 23, 24, 26, and 27 in FIG. 7 will be described later and will not be described.
[0042]
In step 21,
Mfh = Tp × Mfhtvo (4)
Where Tp: basic injection pulse width
Mfhtvo: Adhesion magnification
The equilibrium adhesion amount Mfh is calculated by the following equation.
[0043]
Here, the adhesion magnification Mfhtvo is obtained in the same manner as in the related art. Mfhtvo is an equilibrium adhesion amount per unit basic injection pulse width, which is adapted using load (Tp), rotation speed N, and cooling water temperature Tw as parameters, so that wall flow correction is performed instead of the cooling water temperature Tw. It is determined using the service temperature Twf.
[0044]
Specifically, each upper and lower reference temperature Twf of Twf _i And Twf _{i + 1} (I is an integer from 1 to 4 (or 5)) and the reference adhesion magnification data Mfhtwf _i And Mfhtwf _{i + 1} And Twf, Twf _i , Twf _{i + 1} Is calculated by interpolation calculation. For example, Mfhtwf ₁ , Mfhtwf ₂ And the reference temperature Twf ₁ , Twf ₂ Using the current wall flow correction temperature Twf
Mfhtvo = Mfhtwf ₁ + (Mftwff ₂ -Mfhtwf ₁ ) × (Twf ₁ −Twf) / (Twf) ₁ -Twf ₂ …… (5)
(Linear interpolation calculation formula) is used to calculate Mfhtvo.
[0045]
The above reference adhesion magnification data Mfhtwf _i Is
Mfhtwf _i = Mfhq _i × Mfhn _i … (6)
However, Mfhq _i : Standard adhesion magnification load term
Mfhn _i ： Rotation term of standard adhesion magnification
It is calculated by the following equation.
[0046]
Where Mfhq _i Is adapted using the α-N flow rate Qh0 and the cooling water temperature Tw as parameters, the wall flow correction temperature Twf is used instead of the cooling water temperature Tw, and the map is obtained with interpolation calculation and referring to the map. Note that Qh0 is the throttle valve opening TVO and the rotation speed. Ne This is the air flow rate of the throttle valve portion obtained from the above, which is already known. Mfhn _i Is obtained from the rotational speed N with reference to a predetermined table with interpolation calculation. Mfhq _i Map and Mfhn _i Table stores data matched at the time of the stoichiometric air-fuel ratio together with a map of Kmfat and a table of Kmfn to be described later.
[0047]
In step 25, a coefficient (that is, a proportion ratio) Kmf representing a ratio of how much the currently attached amount (predicted variable) Mf approaches per injection with respect to Mfh obtained in this manner is basically used in step 25. It is calculated from the product of the quantity ratio Kmfat and the quantity rate rotation correction rate Kmfn.
[0048]
Here, since the map of Kmfat is adapted using the α-N flow rate Qh0 and the cooling water temperature Tw as parameters, the wall flow correction temperature Twf is used instead of the cooling water temperature Tw, and the map is referred to with interpolation calculation. I do. Kmfn refers to a predetermined table from N with interpolation calculation.
[0049]
In step 28, the quantity ratio Kmf obtained in this way is multiplied by the difference between Mfh and the current adhesion quantity Mf,
Vmf = (Mfh−Mf) × Kmf (7)
The adhesion speed (adhesion amount per injection) Vmf is determined by the following equation.
[0050]
Here, Mf is a predictive variable of the attached amount at that time, and therefore, the attached amount of (Mfh-Mf) indicates an excess or deficiency from the equilibrium attached amount, and this value (Mfh-Mf) is used as It is further corrected.
[0051]
After the adhesion speed Vmf is obtained in this manner, in steps 29 and 30, Vmf is further corrected by a correction factor Ghf for preventing overlean during deceleration when using light fuel, and a transient correction amount Kathos is obtained. Ends the flow.
[0052]
The flowchart of FIG. 8 shows a process of calculating the final fuel injection pulse width Ti in consideration of the transient correction amount Kathos thus obtained, which is also executed at a period of 10 ms.
[0053]
In step 41, a basic injection pulse width Tp (= K · Qa / Ne, where K is a constant) for obtaining a predetermined air-fuel ratio (for example, a stoichiometric air-fuel ratio) is obtained from the intake air amount Qa and the rotation speed Ne at that time. At 42, the target fuel-air ratio equivalent amount Tfbya is calculated. The calculation of Tfbya will be described with reference to the flowchart of FIG.
[0054]
In steps 51, 52, and 53, a fuel-air ratio correction coefficient Dml, a water temperature increase correction coefficient Ktw, and a post-start increase correction coefficient Kas are obtained in the same manner as in the related art.
Tfbya = Dml + Ktw + Kas (8)
The target fuel-air ratio equivalent amount Tfbya is calculated by the following equation. The unburned portion correction coefficient Kub in step 54 will be described later.
[0055]
Here, the target fuel-air ratio equivalent amount Tfbya is a value centered at 1.0. For example, at the time of idling immediately after cold start (fuel-air ratio correction coefficient Dml = 1.0), the water temperature increase correction coefficient Ktw and Since the post-start increase correction coefficient Kas has a positive value other than 0, the target fuel-air ratio equivalent amount Tfbya becomes larger than 1.0, the air-fuel ratio becomes richer, and the engine stability is improved. At the time of high load after the warm-up (Ktw = 0, Kas = 0), Dml is switched to a value larger than 1.0 (for example, 1.2), and also at this time, the air-fuel ratio on the rich side (output air-fuel ratio) ). Further, when the vehicle enters the lean operation region, the fuel-air ratio correction coefficient Dml becomes, for example, 0.66 (about 22 in air-fuel ratio), and the fuel consumption is suppressed by the operation at this lean air-fuel ratio.
[0056]
After calculating the target fuel-air ratio equivalent amount Tfbya in this manner, the process returns to FIG.
Ti = (Tp + Kathos) × Tfbya × α × 2 + Ts (9)
Where α is the air-fuel ratio feedback correction coefficient
Ts: Invalid injection pulse width
The fuel injection pulse width Ti given to the fuel injection valve is calculated by the following formula, and this Ti is stored in an output register at step 44, so that the fuel injection pulse width Ti is prepared for injection at a predetermined injection timing according to the output of the crank angle sensor.
[0057]
The air-fuel ratio feedback correction coefficient α in equation (9) is set so that the control air-fuel ratio falls within a so-called window centered on the stoichiometric air-fuel ratio. ₂ The value calculated based on the sensor output, the invalid injection pulse width Ts, is a value for compensating the operation delay from when the injection valve receives the injection signal to when the injection valve actually opens. Since the equation (9) is an equation for sequential injection (injection is performed once for every two revolutions of the engine in the case of four cylinders in accordance with the ignition order of each cylinder), the numeral 2 is included.
[0058]
The flowchart of FIG. 10 is a flowchart synchronized with the injection timing (specifically, the Ref signal synchronization). When the predetermined injection timing is reached, the injection is performed in step 61, and then in step 62, the above expression (7) is obtained. The adhesion amount Mf used in the next processing using the adhesion speed Vmf
Mf = Mf _-1Ref + Vmf (10)
Is updated by the following formula.
[0059]
(10) Mf in the equation _-1Ref Is the adhesion amount at the end of the previous injection (before the rotation of the engine 2), and a value obtained by adding Vmf added at the time of the current injection to the adhesion amount Mf at the end of the current injection (Mf on the left side). The value of the adhesion amount Mf is used in the next calculation of Vmf. Mf on the right side of equation (10) _-1Ref Is the value immediately before the calculation of the adhesion speed Vmf, whereas Mf on the left side of the equation (10) is the value immediately after the calculation of Vmf. Therefore, in terms of contents, the value of Mf in equation (7) is changed to Mf in the right side of equation (10). _-1Ref To calculate Mf on the left side of equation (10). The reason why the adhesion amount appears on the left side and the right side in the expression (10) is that the adhesion amount is cyclically updated for each injection.
[0060]
Note that the initial value Mfs of Mf is determined according to the cooling water temperature Tw at the time of starting (the lower the Tw, the greater the value of Mfs).
[0061]
Now, data for calculating the above-mentioned Mfhtvo and Kmf (specifically, the above-mentioned reference adhesion magnification load term Mfhq _i And the map data of the basic amount ratio Kmfat) are suitable for the cooling water temperature in the temperature equilibrium state. Conversely, Mfhq in a temperature non-equilibrium state _i Or Kmfat is virtually impossible. Therefore, Twf when calculating Mfhtvo and Kmf using the wall flow correction temperature Twf instead of the cooling water temperature must also be a temperature in an equilibrium state. Therefore, simply referring to the data adapted to the cooling water temperature in the temperature equilibrium state using the wall flow correction temperature Twf instead of the cooling water temperature is equivalent to the case where the data for obtaining Mfhtvo or Kmf is adapted. It cannot be considered that the temperature state of the engine is different between when Mfhtvo and Kmf are actually calculated.
[0062]
To cope with this, in the prior application (see Japanese Patent Application No. 7-120026), if the data for obtaining Mfh and Kmf is suitable for the cooling water temperature in the temperature equilibrium state, this data is cooled. Mfh and Kmf are calculated by referring to the wall flow correction temperature Twf instead of the water temperature, and a correction magnification at the time of temperature non-equilibrium according to the temperature difference between Tw and Twf (Tw-Twf) is calculated. The calculated Mfh and Kmf are corrected by the correction factor at the time of temperature non-equilibrium. More specifically, steps 22, 23, 24, 26, and 27 are additionally provided in the flowchart of FIG.
[0063]
First, in step 22 of FIG. 7, the temperature difference Dtwf between Tw and Twf is calculated. In steps 23 and 24, the table containing the contents of FIG. A correction magnification Mfhas at the time of equilibrium is obtained, and Mfh is corrected by multiplying this correction magnification Mfhas by Mfh (already obtained in step 21). The value after the correction is set to Mfh in step 24 again.
[0064]
Similarly, in steps 26 and 27, a correction magnification Kmfas at the time of temperature non-equilibrium with respect to Kmf is obtained from the temperature difference Dtwf with reference to the table of FIG. 12, and this correction magnification Kmfas is obtained in Kmf (step 25). ) Is multiplied by Kmf, and the corrected value is set to Kmf again.
[0065]
Here, Mfhas is a value that increases as the temperature difference Dtwf increases as shown in FIG. 11, and Kmfas is a value that approaches 1 as the temperature difference Dtwf decreases as shown in FIG.
[0066]
In the prior application, it has been described that Kmfas decreases as Dtwf increases. However, Kmfas is not exactly a value determined only by the evaporation time constant of the wall flow, but also has a correlation with the adhesion rate to the intake port wall. It cannot be simply said that Kmfas increases as Dtwf increases (or Kmfas decreases as Dtwf increases) (see FIG. 12).
[0067]
Such characteristics of Mfhas and Kmfas are derived from FIG.
[0068]
As shown in FIG. 13, the difference between Mfh and required Mfh when using Twf, and the difference between Kmf and required Kmf when using Twf are both largest immediately after the start, and the temperature difference between Tw and Twf. Should decrease with decreasing size. This corresponds to the fact that the temperature difference between Tw and Twf is the largest immediately after the start, and gradually decreases with the time after the start. The larger the temperature difference between Tw and Twf is, the more imbalanced the intake valve temperature becomes. It is estimated that the degree of the state is large.
[0069]
Here, the operation of the prior application device when the request for Mfh in the non-equilibrium state is larger than the request in the equilibrium state will be described with reference to FIG. In the fourth row, a thin solid line is a waveform diagram according to the conventional example, and a thick solid line is a waveform diagram according to the prior application.
[0070]
In the case of Mfh using Twf as in the conventional example, the requirement is at the time of temperature equilibrium. Therefore, Mfh is less than the requirement at the time of temperature non-equilibrium, and Mf given by Kmf using Twf is Since the change of Mf is too slow (response is too bad) than the demand, Vmf is shorter than the demand at the time of temperature non-equilibrium, and the air-fuel ratio immediately after the start (A / F in FIG. 21 is shifted to the lean side.
[0071]
On the other hand, in the prior application, Mfh and Kmf obtained by using Twf instead of Tw are corrected by the correction magnifications Mfhas and Kmfas when the temperature is not balanced, that is, Mfh is larger than the demand when the temperature is balanced by Mfhas. Since Kmf is corrected to the side where the response of Mf becomes larger than the requirement at the time of temperature equilibrium due to Kmfas, both Mfh and Mf meet the requirement at the time of temperature non-equilibrium, and Vmf becomes the temperature non-equilibrium. It is possible to prevent the air-fuel ratio from becoming lean immediately after the start, approaching the equilibrium requirement.
[0072]
As described above with reference to FIG. 12, even when Kmfas is smaller than 1, it goes without saying that the response of Mf is increased by Mfh increased by Mfhas. In fact, immediately after the start, a large amount of fuel is taken in the intake port wall flow, and the change in Mf is fast.
[0073]
Now, when the prior application apparatus is actually applied to an engine, when Tp is corrected by multiplying the target fuel-air ratio equivalent amount Tfbya by the basic injection pulse width Tp, immediately after acceleration in the temperature non-equilibrium state Although the air-fuel ratio becomes flat, it was clarified that the air-fuel ratio became lean in the latter half of the acceleration in the temperature non-equilibrium state as shown in FIG.
[0074]
In order to cope with this, in the first embodiment, a new unburned portion correction coefficient Kub is introduced, the target fuel-air ratio equivalent amount Tfbya is corrected by the unburned portion correction coefficient Kub, and the corrected Tfbya is also calculated. The equilibrium adhesion amount Mfh is calculated as a parameter.
[0075]
More specifically, step 54 is added and step 55 is changed in the Tfbya calculation routine shown in FIG. 9, and step 21 is changed in the Kathos calculation routine shown in FIG. Further, step 43 is changed in the Ti calculation routine shown in FIG. 8 in accordance with this change.
[0076]
First, in step 54 of FIG. 9, an unburned portion correction coefficient Kub is calculated. The calculation of Kub will be described with reference to the flowchart of FIG.
[0077]
In step 71, a basic value Kub0 of the unburned portion correction coefficient is obtained from the temperature difference Dtwf (= Tw-Twf) with reference to the table containing FIG. 16 with interpolation calculation. For example, the intake valve temperature is a value obtained by adding approximately 80 ° C. to the cooling water temperature Tw, which is the equilibrium temperature. Therefore, the initial value of Twf is set at −80 ° C. Therefore, as shown in FIG. 16, the temperature difference Dtwf immediately after the start is 80 ° C., and the value of Kub0 at this time is set to the maximum value (a value smaller than 1.0), and at the time of temperature equilibrium (that is, when Dtwf = 0). Kub0 is set to 0.
[0078]
In steps 72, 73, and 74, the coolant temperature correction rate Kubas, the load correction rate Kubtp, and the rotation are determined based on the cooling water temperature Tw, the basic injection pulse width Tp, and the rotation speed Ne with reference to the tables illustrated in FIGS. 17, 18, and 19, respectively. The correction factor Kubn is determined, and in step 75
Kub = Kub0 × Kubas × Kubtp × Kubn (11)
The unburned portion correction coefficient Kub is calculated by the following equation. These table references are also provided with interpolation calculations.
[0079]
Here, since the basic value Kub0 of the unburned portion correction coefficient is adapted under predetermined conditions of the cooling water temperature, the load, and the rotation speed, when the cooling water temperature, the load, and the rotation speed are different from these conditions, the value of Kub0 is reduced. The value is incorrect. For example, if the temperature of the cooling water becomes higher than the cooling water temperature at the time of adaptation, the unburned portion is reduced. Therefore, as shown in FIG. 17, the value of Kubas is reduced as the cooling water temperature Tw becomes higher. Similarly, Kubtp is given as shown in FIG. 18 in accordance with the decrease in the unburned portion as the load becomes smaller, and Kubn as shown in FIG. 19 in accordance with the decrease in the unburned portion as the rotation speed increases. I have.
[0080]
When the calculation of the unburned portion correction coefficient Kub is completed in this way, the process returns to FIG. 9, and in step 55, instead of the above equation (8),
Tfbya = Dml + Ktw + Kas + Kub (12)
The target fuel-air ratio equivalent amount Tfbya is calculated by the following equation.
[0081]
Tfbya and Tp are values that determine the steady-state injection amount. By adding the unburned fuel correction coefficient Kub according to the equation (12), in the temperature non-equilibrium state at the time of cold start, Dtwf takes a positive value other than 0. The steady-state injection amount is increased.
[0082]
In step 21 of FIG. 7, instead of the above equation (4),
Mfh = Tp × Mfhtvo × Tfbya (13)
Where Tp: basic injection pulse width
Tfbya: target fuel-air ratio equivalent amount
Mfhtvo: Adhesion magnification
The equilibrium adhesion amount Mfh is calculated by the following equation, and accordingly, in step 43 of FIG. 8, instead of the above equation (9),
Ti = (Tp × Tfbya + Kathos) × α × 2 + Ts (14)
Where α is the air-fuel ratio feedback correction coefficient
Ts: Invalid injection pulse width
The fuel injection pulse width Ti given to the fuel injection valve is calculated by the following equation.
[0083]
Since the data for determining the adhesion magnification Mfhtvo is matching data for the target fuel-air ratio equivalent amount Tfbya = 1.0, the equilibrium adhesion amount obtained using this matching data is appropriate for Tfbya = 1.0. However, if the target fuel-air ratio equivalent amount Tfbya is a value other than 1.0, an error occurs in the calculation of the equilibrium adhesion amount Mfh by the difference, and the equilibrium adhesion amount Mfh is substantially proportional to Tfbya. Therefore, as shown in the equation (13), by multiplying the value (Avtp × Mfhtvo) for Tfbya = 1.0 by Tfbya, the equilibrium adhesion amount Mfh is given without any excess or deficiency corresponding to Tfbya at that time. is there.
[0084]
Further, unlike the equation (9), the equation (14) does not multiply the transient correction amount Kathos by the target fuel-air ratio equivalent amount Tfbya. This is because the target fuel-air ratio equivalent amount Tfbya has already been used in the calculation of the equilibrium adhesion amount Mfh by the equation (13).
[0085]
Here, the operation of the present invention will be described with reference to FIG.
[0086]
In the prior application, the effect of the unburned portion in the temperature non-equilibrium state is set only by Kathos. Therefore, even if the air-fuel ratio becomes flat in the first half of the acceleration in the temperature non-equilibrium state, the second half of the acceleration in the temperature non-equilibrium state As mentioned above, the leaning of the air-fuel ratio appears.
[0087]
On the other hand, in the present invention, since Tfbya is increased and corrected by the basic value Kub0 of the unburned portion correction coefficient according to the temperature difference Dtwf (= Tw-Twf), the steady-state injection amount (determined by Tp × Tfbya) first. Mfh becomes smaller than that of the prior application device by increasing the amount in the case of the application device (see the broken line at the bottom of FIG. 21), and the increase by Kathos is suppressed from the first half of the temperature non-equilibrium state acceleration in the prior application device. I have. However, since Mfh increases by an amount proportional to Tfbya, Mfh increases to some extent. As described above, when the weight increase due to Kathos in the first half of the acceleration in the temperature non-equilibrium state becomes small, the weight loss by Kathos in the second half of the acceleration in the temperature non-equilibrium state also becomes small. As described above, by performing the unburned portion correction in accordance with the temperature non-equilibrium state, the decrease in Kathos can be compensated for by the increase in Tp × Tfbya, and during the period from the cold start to the temperature equilibrium state. The air-fuel ratio (see the second solid line) becomes flat.
[0088]
In other words, in the present invention, by adding the basic value Kub0 of the unburned portion correction coefficient Kub to the target fuel-air ratio equivalent amount Tfbya, the unburned portion correction for the steady-state injection amount is performed, and the Tfbya to which the Kub0 is added is added. The uncombusted portion correction for the transient correction amount is also performed (the unburned portion correction is performed separately for the steady-state injection amount and the transient correction amount) by calculating Mfh according to the following equation. As a result, in the present invention, the steady-state injection amount and the transient correction amount can be set in accordance with the effect of the unburned portion in the non-equilibrium state in which the temperature greatly changes. Until that time, the air-fuel ratio can be kept flat.
[0089]
The deceleration in the temperature non-equilibrium state is slightly different from the acceleration in the temperature non-equilibrium state. In the prior application, when compared with acceleration during temperature non-equilibrium state, the air-fuel ratio is likely to become rich in the latter half of deceleration in temperature non-equilibrium state. The air-fuel ratio becomes lean. When acceleration and deceleration in the temperature non-equilibrium state are considered in the prior application, as shown in FIG. 22, since Mfh at the time of deceleration comes to the increasing side from the temperature equilibrium state, Kathos> 0 in the latter half of the deceleration. This is because only the weight reduction correction occurs during deceleration. The leaning of the air-fuel ratio in the latter half of the deceleration in the temperature non-equilibrium state can also be prevented by the unburned component correction of the present invention. However, even in the prior application where no Kub is introduced, by appropriately setting Kmf during deceleration in the temperature non-equilibrium state, it is possible to prevent the air-fuel ratio from becoming lean in the latter half of the deceleration in the temperature non-equilibrium state. Therefore, the difference in operation from the prior application appears particularly during acceleration in a temperature non-equilibrium state.
[0090]
Further, since the basic value Kub0 of the unburned portion correction coefficient conforms to predetermined conditions of the cooling water temperature, load, and rotation speed, when the cooling water temperature, load, and rotation speed are different from these conditions, the value of Kub0 becomes Although it becomes inappropriate, in the present invention, the basic value Kub0 is corrected to be smaller as the cooling water temperature Tw increases as the unburned fuel content decreases as the cooling water temperature becomes higher than the temperature at the time of adaptation. Even when the cooling water temperature is different from the cooling water temperature, the unburned portion correction coefficient Kub can be given with high accuracy. Similarly, the lower the load, the lower the unburned portion, the smaller the load, the smaller the basic value Kub0, and the higher the rotation speed, the higher the rotation speed, as the unburned portion decreases. Since the basic value Kub0 is corrected so as to be smaller, the unburned fuel correction coefficient Kub does not become inappropriate even when the load or the rotation speed is different from the load or the rotation speed at the time of the adaptation.
[0091]
The flowchart of FIG. 23 is a second embodiment, and corresponds to FIG. 7 of the first embodiment. The same steps as those in FIG. 7 are denoted by the same step numbers.
[0092]
This embodiment is different from the first embodiment in that the present invention is applied to the prior application apparatus in which only the correction magnification Kmfas at the time of temperature non-equilibrium with respect to Kmf is introduced (that is, there is no step 23 or 24 in FIG. 7). Things. As described in the first embodiment, in the temperature non-equilibrium state, the equilibrium adhesion amount Mfh is increased by the unburned fuel correction coefficient Kub via the target fuel-air ratio equivalent amount Tfbya. Even if the steady-state injection amount (determined by Tp × Tfbya) through the target fuel-air ratio equivalent amount Tfbya by the amount of Kub is made larger than that of the prior application, the same operation and effect as in the first embodiment can be obtained.
[0093]
Although not shown in the flowchart, in the third embodiment, the temperature non-equilibrium is obtained by adding an unburned portion correction coefficient Kub to the target fuel-air ratio equivalent amount Tfbya for the prior application device (introducing Mfhas and Kmfas). The unburned fuel amount is corrected for the steady-state injection amount in the state. That is, unlike the first embodiment, the equilibrium adhesion amount Mfh is not calculated using the target fuel-air ratio equivalent amount Tfbya to which the unburned portion correction coefficient Kub is added as a parameter, but each correction amount of Mfhas and Kmfas is applied in advance. By changing the value of the device, the same effect as in the other embodiments can be obtained.
[0094]
The prior application device based on the present invention is:
{Circle around (1)} a correction factor Mfhas for the temperature non-equilibrium with respect to Mfh and a correction factor Kmfas for the temperature non-equilibrium with respect to Kmf are introduced together (see FIG. 7);
(2) Introducing only the correction magnification Kmfas at the time of temperature non-equilibrium with respect to Kmf (see FIG. 23)
As explained in
(3) Introducing a correction magnification Vmfas at the time of temperature non-equilibrium with respect to Vmf (fourth embodiment of the prior application)
May be used as the prior application device based on the present invention.
[0095]
In the embodiment, Mfhas and Kmfas have been described as being assigned with the temperature difference Dtwf as a parameter.
{Circle over (4)} Mfhas, Kmfas, Vmfas are allotted as one of Tw, Twf, and the starting water temperature as parameters in addition to the temperature difference Dtwf,
(5) Mfhas, Kmfas, and Vmfas are assigned as parameters of the engine load in addition to the temperature difference Dtwf.
It is needless to say that the present invention can be used as a prior application device based on the present invention.
[0096]
In the embodiment, the wall flow correction temperature Twf as the intake valve predicted temperature has been described. However, it is needless to say that the intake valve predicted temperature Tf itself of the above equation (1) can be used.
[0097]
By the way, in the embodiment, Mfhtvo is obtained by using Twf instead of the cooling water temperature Tw, but Mfhtvo may be obtained by using Tw. At this time, Mfhtvo (Mfh) is smaller than the case where Mfhtvo is obtained using Twf by the amount of Tw−Twf. Therefore, by setting the value of Mfhas or Kmfas to a value different from that of the other embodiments, another embodiment is performed. As in the case of the embodiment, the air-fuel ratio from the time of cold start to the time of temperature equilibrium can be made flat.
[Brief description of the drawings]
FIG. 1 is a control system diagram of a first embodiment.
FIG. 2 is a flowchart for explaining calculation of a wall flow correction temperature Twf.
FIG. 3 is a characteristic diagram of an initial value Inwft of a wall flow correction temperature.
FIG. 4 is a characteristic diagram of a temperature change ratio Fltsp during firing.
FIG. 5 is a flowchart illustrating initialization of a wall flow correction temperature.
FIG. 6 is a waveform diagram for explaining a change in a wall flow correction temperature Twf immediately after startup and during warm-up.
FIG. 7 is a flowchart illustrating a calculation of a transient correction amount Kathos.
FIG. 8 is a flowchart for explaining calculation of a fuel injection pulse width Ti.
FIG. 9 is a flowchart for explaining calculation of a target fuel-air ratio equivalent amount Tfbya.
FIG. 10 is a flowchart synchronized with the injection timing.
FIG. 11 is a characteristic diagram of a temperature non-equilibrium correction magnification Mfhas with respect to Mfh.
FIG. 12 is a characteristic diagram of a correction factor Kmfas at a temperature non-equilibrium with respect to Kmf.
FIG. 13 is a waveform diagram for explaining the operation of the prior application device.
FIG. 14 is a waveform chart for explaining the operation of the prior application device.
FIG. 15 is a flowchart for explaining the calculation of an unburned portion correction coefficient Kub.
FIG. 16 is a characteristic diagram of a basic value Kub0 of the unburned portion correction coefficient.
FIG. 17 is a characteristic diagram of a water temperature correction term Kubas.
FIG. 18 is a characteristic diagram of a load correction term Kubtp.
FIG. 19 is a characteristic diagram of a rotation correction term Kubn.
FIG. 20 is a waveform diagram for explaining the operation of the prior application device.
FIG. 21 is a waveform chart for explaining the operation of the first embodiment.
FIG. 22 is a waveform chart for explaining the operation of the first embodiment.
FIG. 23 is a flowchart illustrating a calculation of a transient correction amount Kathos according to the second embodiment.
FIG. 24 is a waveform chart for explaining the operation of the conventional example.
FIG. 25 is a diagram corresponding to claims of the first invention.
FIG. 26 is a diagram corresponding to a claim of the second invention.
FIG. 27 is a diagram corresponding to the claims of the fourth invention.
FIG. 28 is a diagram corresponding to a claim of the fifth invention.
[Explanation of symbols]
1 Engine body
2 Control unit
4 Crank angle sensor
6 Air flow meter
7 Fuel injection valve

Claims (9)

Means for calculating a basic injection amount according to operating conditions;
Means for calculating a target fuel-air ratio equivalent amount;
Means for correcting the basic injection amount with the target fuel-air ratio equivalent amount;
Means for detecting cooling water temperature;
Means for calculating the predicted intake valve temperature;
A map in which the equilibrium adhesion amount per unit injection amount of fuel is adapted to the cooling water temperature in the temperature equilibrium state, by using the intake valve predicted temperature in place of the detected value of the cooling water temperature to refer to the map in the equilibrium state Means for calculating an equilibrium adhesion amount, which is an adhesion amount of fuel to the intake pipe ;
A map in which the equilibrium adhesion amount per unit injection amount of fuel is adjusted to the cooling water temperature in the temperature equilibrium state, by referring to the intake valve predicted temperature instead of the detected value of the cooling water temperature , at that time, Means for calculating a fractional ratio, which is a ratio of how much the amount of fuel attached to the intake pipe approaches the equilibrium attached amount ,
Means for calculating the difference between the calculated equilibrium adhesion amount and the adhesion amount at that time,
Means for calculating an adhesion speed, which is an adhesion amount adhering to the intake pipe per one injection of the fuel injection valve , based on the adhesion amount of the difference and the calculated amount ratio;
Means for updating the adhesion amount by adding the adhesion speed and the adhesion amount at that time in synchronization with the fuel injection;
Means for calculating the fuel injection amount by further correcting the basic injection amount corrected by the target fuel-air ratio equivalent amount with the adhesion speed;
Means for supplying this amount of fuel to the intake pipe.
Means for calculating the difference between the detected value of the cooling water temperature and the intake valve predicted temperature,
Means for calculating a correction amount for correcting the equilibrium adhesion amount or the amount ratio at the time of temperature non-equilibrium according to the temperature difference;
Means for correcting the calculated equilibrium adhesion amount or the calculated amount ratio with the correction amount at the time of temperature non-equilibrium,
Means for calculating an unburned portion correction amount according to the temperature difference,
Means for correcting the target fuel-air ratio equivalent amount with the unburned portion correction amount. Means for calculating a basic injection amount according to operating conditions;
Means for calculating a target fuel-air ratio equivalent amount;
Means for correcting the basic injection amount with the target fuel-air ratio equivalent amount;
Means for detecting cooling water temperature;
The fuel in the equilibrium state is obtained by referring to a map in which the equilibrium adhesion amount per unit injection amount of the fuel is adapted to the cooling water temperature in the temperature equilibrium state, using the intake valve predicted temperature in place of the detected value of the cooling water temperature. Means for calculating an equilibrium adhesion amount, which is an adhesion amount of the air to the intake pipe ;
A map in which the equilibrium adhesion amount per unit injection amount of fuel is adjusted to the cooling water temperature in the temperature equilibrium state, by referring to the intake valve predicted temperature instead of the detected value of the cooling water temperature , at that time, Means for calculating a fractional ratio, which is a ratio of how much the amount of fuel attached to the intake pipe approaches the equilibrium attached amount ,
Means for calculating the difference between the calculated equilibrium adhesion amount and the adhesion amount at that time,
Means for calculating an adhesion speed, which is an adhesion amount adhering to the intake pipe per one injection of the fuel injection valve , based on the adhesion amount of the difference and the calculated amount ratio;
Means for calculating the predicted intake valve temperature;
Means for calculating a difference between the detected value of the cooling water temperature and the intake valve predicted temperature;
Means for calculating a correction amount for correcting the adhesion speed at the time of temperature non-equilibrium according to the temperature difference;
Means for correcting the calculated adhesion speed with the correction amount at the time of temperature non-equilibrium,
Means for updating the adhesion amount by adding the corrected adhesion speed and the adhesion amount at that time in synchronization with the fuel injection,
Means for calculating a fuel injection amount by further correcting the basic injection amount corrected by the target fuel-air ratio equivalent amount with the corrected adhesion speed;
Means for supplying this amount of fuel to the intake pipe;
Means for calculating an unburned portion correction amount according to the temperature difference,
Means for correcting the target fuel-air ratio equivalent amount using the unburned fuel correction amount. The equilibrium adhesion amount calculation means,
A map in which the equilibrium adhesion amount per unit injection amount of fuel is adapted to the cooling water temperature in the temperature equilibrium state, the equilibrium adhesion ratio is determined by referring to the intake valve predicted temperature in place of the detected value of the cooling water temperature. Means for calculating;
3. A means for obtaining, as an equilibrium adhesion amount, a product of the adhesion magnification, the calculated basic injection amount, and the target fuel-air ratio equivalent amount corrected by the unburned portion correction amount. An air-fuel ratio control device for an engine according to claim 1. Means for calculating a basic injection amount according to operating conditions;
Means for calculating a target fuel-air ratio equivalent amount;
Means for correcting the basic injection amount with the target fuel-air ratio equivalent amount;
Means for detecting the cooling water temperature, means for calculating the predicted intake valve temperature,
By referring to the map that matches the equilibrium adhesion amount per unit injection amount of fuel to the cooling water temperature in the temperature equilibrium state using the detected value of the cooling water temperature, the fuel adhesion amount to the intake pipe in the equilibrium state can be calculated. Means for calculating a certain equilibrium adhesion amount;
By using a detected value of the cooling water temperature to refer to a map that matches the equilibrium adhesion amount per unit injection amount of fuel with the cooling water temperature in the temperature equilibrium state, the fuel adhesion to the intake pipe at that time Means for calculating a quantity ratio, which is a ratio from which the amount approaches the equilibrium adhesion amount ,
Means for calculating the difference between the calculated equilibrium adhesion amount and the adhesion amount at that time,
Means for calculating an adhesion speed, which is an adhesion amount adhering to the intake pipe per one injection of the fuel injection valve , based on the adhesion amount of the difference and the calculated amount ratio;
Means for updating the adhesion amount by adding the adhesion speed and the adhesion amount at that time in synchronization with the fuel injection;
Means for calculating the fuel injection amount by further correcting the basic injection amount corrected by the target fuel-air ratio equivalent amount with the adhesion speed;
An air-fuel ratio control device for an engine including means for supplying this amount of fuel to the intake pipe, means for calculating a difference between the detected value of the cooling water temperature and the intake valve predicted temperature,
Means for calculating a correction amount for correcting the equilibrium adhesion amount or the amount ratio at the time of temperature non-equilibrium according to the temperature difference;
Means for correcting the calculated equilibrium adhesion amount or the calculated amount ratio with the correction amount at the time of temperature non-equilibrium,
Means for calculating an unburned portion correction amount according to the temperature difference,
Means for correcting the target fuel-air ratio equivalent amount with the unburned portion correction amount. Means for calculating a basic injection amount according to operating conditions;
Means for calculating a target fuel-air ratio equivalent amount;
Means for correcting the basic injection amount with the target fuel-air ratio equivalent amount;
Means for detecting cooling water temperature;
By referring to the map that matches the equilibrium adhesion amount per unit injection amount of fuel to the cooling water temperature in the temperature equilibrium state using the detected value of the cooling water temperature, the fuel adhesion amount to the intake pipe in the equilibrium state can be calculated. Means for calculating a certain equilibrium adhesion amount;
By using a detected value of the cooling water temperature to refer to a map that matches the equilibrium adhesion amount per unit injection amount of fuel with the cooling water temperature in the temperature equilibrium state, the fuel adhesion to the intake pipe at that time Means for calculating a quantity ratio, which is a ratio from which the amount approaches the equilibrium adhesion amount ,
Means for calculating the difference between the calculated equilibrium adhesion amount and the adhesion amount at that time,
Means for calculating an adhesion speed, which is an adhesion amount adhering to the intake pipe per one injection of the fuel injection valve , based on the adhesion amount of the difference and the calculated amount ratio;
Means for calculating the predicted intake valve temperature;
Means for calculating a difference between the detected value of the cooling water temperature and the intake valve predicted temperature;
Means for calculating a correction amount for correcting the adhesion speed at the time of temperature non-equilibrium according to the temperature difference;
Means for correcting the calculated adhesion speed with the correction amount at the time of temperature non-equilibrium,
Means for updating the adhesion amount by adding the corrected adhesion speed and the adhesion amount at that time in synchronization with the fuel injection,
Means for calculating a fuel injection amount by further correcting the basic injection amount corrected by the target fuel-air ratio equivalent amount with the corrected adhesion speed;
Means for supplying this amount of fuel to the intake pipe;
Means for calculating an unburned portion correction amount according to the temperature difference,
Means for correcting the target fuel-air ratio equivalent amount with the unburned portion correction amount. The equilibrium adhesion amount calculating means calculates the equilibrium adhesion ratio by referring to a map in which the equilibrium adhesion amount per unit injection amount of fuel is adjusted to the cooling water temperature in the temperature equilibrium state using the detected value of the cooling water temperature. Means for calculating;
6. A means for obtaining, as an equilibrium adhesion amount, a product of the adhesion magnification, the calculated basic injection amount, and a target fuel-air ratio equivalent amount corrected by the unburned amount correction amount. An air-fuel ratio control device for an engine according to claim 1. The air-fuel ratio control device for an engine according to any one of claims 1 to 6, wherein the unburned amount correction amount is corrected according to the detected value of the cooling water temperature. The air-fuel ratio control device for an engine according to any one of claims 1 to 6, wherein the unburned portion correction amount is corrected according to an engine load. 7. The air-fuel ratio control device for an engine according to claim 1, wherein the unburned amount correction amount is corrected in accordance with an engine speed.

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