JP3924972B2 - Fuel injection amount control method for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection amount control method for correcting a fuel injection amount for each cylinder of an internal combustion engine, particularly a diesel engine.
[0002]
[Prior art]
In general, a diesel engine has much more vibration during idling than a gasoline engine, and the engine that is elastically supported by the engine mount mechanism resonates due to the vibration, not only deteriorating the habitability of the vehicle but also surrounding the engine. There was a risk of adversely affecting the equipment placed in the. For example, in a four-cycle engine, this vibration is caused mainly by a 1 / 2-order low-frequency vibration with respect to engine rotation, and due to periodic variations in the pumping amount of fuel pumped to each cylinder in a half cycle of engine rotation. is there.
[0003]
In order to solve such a problem, it is conceivable to manufacture the engine body, the fuel injection pump and the injection nozzle with extremely high accuracy to reduce the variation in the pumping amount of the fuel supplied to each cylinder. This is accompanied by great difficulty in production technology and is expensive. On the other hand, it is conceivable to improve the engine mount mechanism to suppress engine vibration, but it becomes complicated and expensive, and it does not suppress vibration of the engine itself. It can't be.
[0004]
As a solution to this problem, for example, there is a fuel injection amount control method for an internal combustion engine described in Japanese Patent Publication No. 6-50077. This fuel injection amount control method for an internal combustion engine is used in a predetermined operating state (such as an idle stable state where the idling speed continues for a certain period of time), for example, at two locations before and after a predetermined explosion in one explosion cycle. The time required for the engine to rotate 45 ° CA (hereinafter referred to as 45 ° CA every hour) (THN, THL) is detected, and the fuel injection amount between cylinders in a predetermined operating state is determined based on the detection result. The leveling level is learned, and the fuel injection amount of each cylinder is corrected based on the learning result.
[0005]
In this internal combustion engine fuel injection amount control method, as shown in FIG. 5, the rotational fluctuation range (DNEk: k is the cylinder number 1 to 4) from the deviation of time (THN) and time (THL), which are variations in engine speed. ) To obtain the average rotational fluctuation range (WNDNLT) from the average rotational fluctuation range (DNEk). Each rotation fluctuation range (DNEk) is compared with the average rotation fluctuation range (WNDNLT), and when the rotation fluctuation range (DNEk) of the cylinder is smaller than the average rotation fluctuation range (WNDNLT), the fuel injection amount of the cylinder Is determined to be relatively insufficient, and when the rotational fluctuation range (DNEk) of the cylinder is larger than the average rotational fluctuation range (WNDNLT), it is determined that the fuel injection amount of the cylinder is relatively excessive, and the excess The fuel injection amount correction amount (QCMPk) is updated and set to compensate for the amount and the shortage amount. The fuel injection amount correction amount (QCMPk) is updated by adding or subtracting an integral correction amount (DQCMP) calculated according to a deviation (DDNEk) between the rotational fluctuation range (DNEk) and the average rotational fluctuation range (WNDNLT). .
[0006]
The updated fuel injection amount correction amount (QCMPk) is reflected in the next fuel injection amount command value of the cylinder, and the fuel injection amount is increased / decreased until the rotational fluctuation range (DNEk) becomes uniform among the cylinders. The vibration is suppressed. Then, when the engine speed becomes a predetermined value or more away from the predetermined operating state, the fuel injection amount is corrected by correcting so as to gradually decrease from the learned fuel injection amount correction amount (QCMPk), The connection from the predetermined operation state to another operation state is smoothed.
[0007]
[Problems to be solved by the invention]
However, the level of fuel injection amount unevenness between cylinders changes depending on the warm-up state of the engine body and the fuel injection pump, so even if the fuel injection amount correction amount is set in the cold state immediately after starting, the warm-up state is not If it changes, there is a problem that the set fuel injection amount correction value becomes invalid and the engine vibration cannot be sufficiently suppressed.
[0008]
The present invention has been made in view of the above circumstances, and an object thereof is to provide a fuel injection amount control method for an internal combustion engine that can obtain an appropriate correction amount of the fuel injection amount even when the warm-up state changes.
[0009]
[Means for Solving the Problems]
In the present invention, the variation in the engine rotation speed in each cylinder when the operation state of the multi-cylinder internal combustion engine is in a predetermined operation state is detected, and the variation in the engine rotation speed is made uniform among the cylinders. Every time, the correction amount of the fuel injection amount is set according to the variation in the engine speed . When the cooling water temperature of the internal combustion engine is detected and the operating state departs from the predetermined operating state, the correction amount increases as the cooling water temperature increases from the time when the correction amount is set in the predetermined operating state. to reset the correction amount for each cylinder by the coolant temperature correction coefficient set so that subtracting.
[0010]
According to the inventors' experimental studies, it has been found that the fuel injection amount non-uniform amount level is high if the cooling water temperature is low and the warm-up is insufficient, and low if the cooling water temperature is high and the warm-up is sufficient. Yes. Thus, when the operation state departs from the predetermined operation state, the correction amount of the fuel injection amount is changed to the warm-up state change by resetting the correction amount according to the amount of increase in the coolant temperature as described above. The fuel injection amount is adjusted to an appropriate value corresponding to the uneven level change of the fuel injection amount.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a fuel injection amount control method for an internal combustion engine according to the present invention will be described with reference to FIGS. FIG. 2 shows an overall configuration of an electronically controlled diesel engine of an automobile. The engine is an engine main body 1, a fuel injection pump 2 that pumps fuel to an injection nozzle 106 provided in the engine main body 1, and an electronic that controls the whole. It comprises a control device (hereinafter referred to as ECU) 3 and the like.
[0012]
In the engine main body 1, a piston 102 is slidably held in a cylinder 101, air supplied from an intake pipe 107 to a combustion chamber (sub chamber) 105, and an injection nozzle 106 provided to protrude into the combustion chamber 105. The reciprocating motion of the piston 102 is converted into the rotational motion of the crankshaft 104 via the connecting rod 103. Adjustment of the driving force generated by the engine body 1 is performed on the floor surface of the driver's seat by interlocking the opening of the throttle valve 108 provided in the intake pipe 107 leading to the combustion chamber 105 with the throttle valve 108 via a wire. This is done by adjusting the amount of depression of the accelerator pedal 8 by the driver.
[0013]
The fuel injection pump 2 has a pump drive shaft 201 that rotates in synchronization with the rotation of the crankshaft 104 of the engine body 1, and a feed pump (developed by 90 °) 202 is coupled to the drive shaft 201. The fuel discharged from the feed pump 202 is supplied to the fuel chamber 204. The supply fuel pressure is adjusted by a fuel pressure adjustment valve 203. A face cam 208 is also coupled to the drive shaft 201 and is pressed against a roller ring 209 disposed coaxially with the drive shaft 201. As the face cam 208 moves, the plunger 206 integral with the face cam 208 reciprocates in the cylinder bore 205 with rotational movement, and pressurizes and sends out the fuel in the cylinder bore 205. This pumped fuel is supplied to the injection nozzle 106 of the engine main body 1 via a delivery valve 207 that prevents backflow and trailing of the fuel.
[0014]
The roller ring 209 is rotatable around the drive shaft 201, and the operation timing of the plunger 206, that is, the fuel pumping timing (and hence the fuel injection timing) is determined in accordance with the rotation position. The rotation position of the roller ring 209 can be changed by increasing / decreasing the driving hydraulic pressure of the timer piston 210 by the timing control valve 211, by changing the displacement of the timer piston 210 (expanded by 90 °) shown in conjunction with the roller ring 209. . The fuel pumping end time (and hence the fuel injection end time) can be changed by a spill valve 212 that opens the cylinder bore 205 to a low pressure.
[0015]
The ECU 3 is composed of, for example, a microcomputer. Detection signals from various sensors 4, 5, 6, 7, etc. installed in each part of the engine body 1 and the fuel injection pump 2 are input to the ECU 3. The engine speed sensor 4 is an electromagnetic pickup sensor, and detects the passage of the tooth row of the gear 213 fixed to the outer peripheral portion of the drive shaft 201 of the fuel injection pump 2 to detect the crankshaft 104 that rotates synchronously with the drive shaft 201. The rotation state is known. The intake pressure sensor 5 detects the pressure of intake air taken into the combustion chamber 105 via the intake pipe 107 of the engine body 1. The water temperature sensor 6 is attached to the cylinder block 100 of the engine body 1 and detects the cooling water temperature in the water jacket. The accelerator sensor 7 detects an opening degree of the throttle valve 108 (hereinafter referred to as an accelerator opening degree) Accp.
[0016]
The ECU 3 controls the control injection timing and the control injection amount based on the engine speed NE obtained from the output of the engine speed sensor 4, the coolant temperature obtained from the output of the water temperature sensor 6, the accelerator opening Accp obtained from the output of the accelerator sensor 7, and the like. The timing control valve 211, the spill valve 212, and the like are controlled so that a control injection amount of fuel is injected at the control injection timing.
[0017]
FIG. 1 is a control flow showing a part of the fuel injection amount control in the ECU 3, and is executed at a predetermined cycle. In this control flow, every time the control flow is executed, a signal indicating the state of each part of the vehicle from the sensors 4 to 7 is read and used. Of the parameters used for the control, the same symbols are attached to the same parameters as those of the above-described conventional technology, and the differences will be mainly described. The description will be made assuming that the number of cylinders is four.
[0018]
In step S10, it is determined whether or not a correction amount learning condition is satisfied based on various sensor signals. When it is determined that the driving state known from the various sensor signals is the predetermined driving state, the learning condition is satisfied and the process proceeds to step S11.
[0019]
In step S11, the rotation fluctuation range (DNEk) is calculated by subtracting the minimum rotation time (TNL) from the maximum rotation time (TNH) for each cylinder.
[0020]
In step S12, the rotation fluctuation range (DNEk) corresponding to the number of cylinders (here, 4, the same applies hereinafter) is added and divided by the number of cylinders to obtain the average rotation fluctuation range (WNDNLT).
[0021]
In step S13, the rotation fluctuation deviation (DDNEk) is obtained by subtracting the average rotation fluctuation width (WNDNLT) from the rotation fluctuation width (DNEk) of each cylinder.
[0022]
In step S14, an integral correction amount (DQCMP) is obtained from the rotational fluctuation deviation (DDNEk) by a function form stored in advance in the memory. The integral correction amount (DQCMP) is given according to the magnitude of the rotational fluctuation deviation (DDNEk).
[0023]
In step S15, the fuel injection amount correction amount (QCMPk) is updated by adding / subtracting the integral correction amount (DQCMP) to / from the fuel injection amount correction amount (QCMPk) for each cylinder, and the cylinder having a large rotation fluctuation range (DNEk) is updated. The fuel injection amount correction amount (QCMPk) is increased, and the fuel injection amount correction amount (QCMPk) is set to decrease in a cylinder with a small rotation fluctuation range (DNEk).
[0024]
In step S16, the rotation correction coefficient (MK5) and the water temperature correction coefficient (MKTHW) are set to 1.0.
[0025]
In step S17, the cooling water temperature (THW) is stored as the learning water temperature (THWFCN).
[0026]
In step S18, a final injection amount command value (QANGF) is obtained by adding a correction value to the basic injection amount command value (QANGB) obtained from the governor pattern. The correction value to be added is calculated by multiplying the fuel injection amount correction amount (QCMPk) of each cylinder by the rotation correction coefficient (MK5) and the water temperature correction coefficient (MKTHW). Since the learning condition is satisfied in step S10 and step S16 is executed, the rotation correction coefficient (MK5) and the water temperature correction coefficient (MKTHW) are 1.0.
[0027]
Next, a case where the learning condition is not satisfied in step S10, that is, a case where the operating state departs from the idle stable state due to an increase in the engine speed or the like will be described. In this case, the process proceeds from step S10 to step S21. In step S21, a rotation correction coefficient (MK5) is calculated based on the engine speed (NE) by a function form stored in advance in a memory. The rotation correction coefficient (MK5) decreases as the engine speed (NE) increases.
[0028]
In step S22, the current coolant temperature (THW) is stored as the current coolant temperature (THWFCG). In the following step S23, it is determined whether or not the difference between the current water temperature (THWFCG) and the learning water temperature (THWFCN) is equal to or greater than a predetermined value (KTHWFC) set in advance. Set (MKTHW) to 1.0, and proceed to Step S18.
[0029]
In step S18, as described above, the final injection amount command value (QANGF) is calculated by adding the correction value to the basic injection amount command value (QANGB). However, the correction value is small as the rotation correction coefficient (MK5) is reduced. Become a thing. That is, the higher the engine speed (NE), the closer the final injection amount command value (QANGF) becomes to the injection amount command value (QANGB), and the connection to other operating states is smoothed.
[0030]
If the difference between the current water temperature (THWFCG) and the learning water temperature (THWFCN) is equal to or greater than a predetermined value (KTHWFC) in step S23, the process proceeds to step S24. In step S24, a current water temperature correction coefficient (KTHWFCG) corresponding to the current water temperature (THWFCG) and a learning water temperature correction coefficient (KTHWFCN) corresponding to the learning water temperature (THWFCN) are obtained by a function form stored in the memory in advance. Ask. Then, a ratio (= KTHWFCN / KTHWFCG) of both coefficients (KTHWFCG, KTHWFCN) is calculated to obtain a water temperature correction coefficient (MKTHW). The function form follows the water temperature correction coefficient-cooling water temperature characteristic diagram shown in FIG. 3, and the water temperature correction coefficient decreases linearly until the cooling water temperature reaches a predetermined temperature, and is constant when the water temperature exceeds a predetermined value. Take. Therefore, when the current water temperature rises from the time of learning, the water temperature correction coefficient (MKTHW) becomes smaller than 1.
[0031]
In the following step S18, the final injection amount command value (QANGF) is determined by adding the correction value QCMPk × MK5 × MKTHW to the basic injection amount command value (QANGB). The final injection amount command value (QANGF) reflects the change in the coolant temperature (THW) since the correction amount learning, in addition to the change in the engine speed (NE).
[0032]
As described above, when the operation state departs from the predetermined state, the value added to the basic injection amount command value (QANGB) is reset according to the change in the coolant temperature (THW). Here, as is known from FIG. 3, the water temperature correction coefficient is given a smaller value as the cooling water temperature (THW) is higher. Therefore, for example, if the cooling water temperature has risen when the operation state has departed from the predetermined state after the correction amount learning (steps 101 to 107) is performed in the cold state, the water temperature correction coefficient (MKTHW) becomes small. The correction value to be added to or subtracted from the basic injection amount command value (QANGB) becomes smaller.
[0033]
FIG. 4 shows the non-uniform amount (ΔQ) characteristic of the fuel injection amount between the cylinders with respect to the cooling water temperature (THW). The non-uniform amount (ΔQ) decreases as the cooling water temperature (THW) increases and the warm-up is sufficient. Tend to be. In the present invention, after learning and setting the fuel injection amount correction amount (QCMPk) in the cold state immediately after starting the engine with a large non-uniform amount (ΔQ), the coolant temperature is changed by the change in the warm-up state when leaving the predetermined operation state. If (THW) is high, as described above, the correction value to be added to the basic injection amount command value (QANGB) is small so as to obtain the final injection amount command value (QANGF). As described above, the fuel injection amount correction amount (QCMPk × MKTHW) corresponding to the non-uniform amount (ΔQ) at the current cooling water temperature (THWFCG) is adjusted, so that an appropriate fuel can be obtained even when leaving a predetermined state. By correcting the injection amount, the fuel injection amount becomes uniform among the cylinders, and the vibration level can be minimized.
[0034]
In addition, since the fuel injection amount variation among cylinders can be reduced, it is possible to loosen the quality standard of the fuel injection pump pressure supply amount variation between cylinders and the variation in the valve opening pressure of the injection nozzle, thereby reducing costs. Can be planned.
[0035]
It should be noted that the water temperature correction coefficient may be given so as to change in a curved shape as shown in the characteristic diagram for the uneven cooling water temperature in FIG. .
[0036]
Further, the function form such as the water temperature correction coefficient may be given by a mathematical expression or a map.
[Brief description of the drawings]
FIG. 1 is a flowchart of a fuel injection amount control method for an internal combustion engine according to the present invention.
FIG. 2 is an overall configuration diagram of a diesel engine to which a fuel injection amount control method for an internal combustion engine according to the present invention is applied.
FIG. 3 is a first graph illustrating a fuel injection amount control method for an internal combustion engine according to the present invention.
FIG. 4 is a second graph illustrating the fuel injection amount control method for the internal combustion engine of the present invention.
FIG. 5 is a time chart showing a typical example of a conventional fuel injection amount control method for an internal combustion engine.
[Explanation of symbols]
1 Engine body 106 Injection nozzle 2 Fuel injection pump 3 Electronic control unit

Claims (1)

Operating state of the internal combustion engine of a multi-cylinder detects a variation in engine speed in each cylinder when in the predetermined operating condition, the engine for each cylinder so makes it uniform variations in the engine rotational speed among the cylinders In a fuel injection amount control method for an internal combustion engine that sets a correction amount of a fuel injection amount according to a variation in rotational speed, when the cooling water temperature of the internal combustion engine is detected and the operating state departs from the predetermined operating state, and wherein resetting the correction amount for each cylinder by the coolant temperature correction coefficient the larger the amount of increase is set to so that subtracting the correction amount of the cooling water temperature from the time of setting the correction amount in a predetermined operating condition A fuel injection amount control method for an internal combustion engine.

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