JP3047634B2 - Fuel injection start timing detection device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine provided with a fuel injection device including a fuel injection pump, a fuel injection nozzle, and the like, and more specifically, a timing at which fuel injection from the fuel injection device to the internal combustion engine is started. The present invention relates to a fuel injection start timing detecting device for detecting a fuel injection start time.

[0002]

2. Description of the Related Art Conventionally, a diesel engine, a high-pressure gasoline injection engine, or the like can be given as an internal combustion engine equipped with the above-described fuel injection device. Then, in these internal combustion engines, in order to control the fuel injection amount and the injection timing from the fuel injection device to target values, the timing at which the fuel injection is actually started, the actual injection at that time, It is important to know the amount.

For example, in a fuel injection pump of an electronically controlled diesel engine, the fuel in a high pressure chamber is pressure-fed to a fuel injection nozzle by a plunger lift and injected into each cylinder of the diesel engine. Then, the spill ring, the spill valve, and the like provided in the fuel injection pump are driven and controlled by the actuator such that the fuel injection amount at that time becomes the target injection amount determined according to the engine operating state. Further, by this control, the plunger high pressure chamber is opened to the fuel chamber, and a part of the fuel in the plunger high pressure chamber overflows (spills) to the fuel chamber. Thus, the end of the fuel pumping from the fuel injection pump to the fuel injection nozzle, that is, the end timing of the fuel injection from the fuel injection nozzle to each cylinder is controlled.

[0004] However, in this type of fuel injection pump, there is a possibility that the control characteristics of the fuel injection amount may change due to a change with time of the components or a change in the properties of the fuel used. For example, in a fuel injection pump, when wear occurs in a cam mechanism that reciprocates a plunger, a lift amount of the plunger changes due to the wear. Therefore, a fuel injection amount from a fuel injection nozzle is smaller than an intended injection amount. There was a risk that it would increase. Further, in the fuel injection nozzle connected to the fuel injection pump, when the urging force of the spring for adjusting the valve opening pressure decreases, the valve opening pressure of the fuel injection nozzle decreases, so that the fuel injection amount from the nozzle increases. There was a risk. Alternatively, when the fuel property, particularly the fuel temperature, increases, the compression ratio of the fuel changes, so that the fuel injection amount from the fuel injection nozzle and the injection start timing may change.

[0005] In view of the above disadvantages, several techniques have been proposed. For example, Japanese Patent Application Laid-Open No. 57-32
In the “fuel injection device” disclosed in Japanese Patent No. 021 (first prior art), even if the components of the fuel injection pump are worn or the like, the actual fuel injection amount (actual injection amount) is not affected by the wear. ) Is accurately detected to stabilize high-precision fuel injection amount control over a long period of time. That is, in this conventional technique, the plunger internal pressure is detected by the pressure sensor, and the actual injection amount is calculated based on the peak value of the internal pressure. Then, the position of the spill valve is controlled so that the actual injection amount matches the target injection amount. Alternatively, JP-A-57-6
In a “fuel injection timing control device for a diesel engine” disclosed in Japanese Patent No. 2935 (second related art),
The pressure of the fuel pumped from the fuel injection pump to the fuel injection nozzle, or a change in the pressure, is detected by one pressure sensor. Then, the signal indicating the detected pressure rising timing is fed back to the control of the target injection timing as a signal indicating the actual injection timing (actual injection timing).

However, in each of the above-described prior arts, although the peak value of the plunger internal pressure detected by the pressure sensor and the signal indicating the rise time of the fuel pressure are referred to, the change of the actual injection amount and the actual injection timing is referred to. It could not always be said that it was appropriately reflected. In the first place, in order to accurately obtain the actual injection amount and the actual injection timing, it is necessary to accurately grasp the timing at which fuel injection from the fuel injection nozzle is started (fuel injection start timing).

Therefore, an "injection timing transducer" disclosed in Japanese Patent Application Laid-Open No. 58-70028 (No. 3)
(Prior art) discloses a technique for accurately determining the fuel injection start timing. In this prior art, a transducer made of a piezo element is provided in a non-contact manner with fuel with respect to a housing of an injector for fuel injection. In addition, the transducer detects a change that is at least partially proportional to the time derivative (fuel pressure differential value) of the fuel pressure in the injector and directly corresponds to the fuel injection timing, and outputs the detection result as an electric signal. Is done.

[0008]

However, the third prior art also discloses that the timing at which fuel injection is started is determined by a function of the fuel pressure and the fuel pressure differential value. It was not so accurate. That is, the third
In the prior art, no specific and detailed study was made as to what change in the function of the fuel pressure and the fuel pressure differential value is to be used as the injection start timing, and an error caused by noise or the like was not performed. There was a problem in the judgment. Therefore, it has been an important issue how to specifically specify the fuel injection start timing from the change in the fuel pressure.

The present invention has been made in view of the above-mentioned circumstances, and has been made by paying attention to the point at which the rate of increase in inflection in the process of increasing the fuel pressure first becomes the fuel injection start timing. It is. And, the purpose is, in an internal combustion engine equipped with a fuel injection pump and a fuel injection nozzle,
Without being affected by fuel system aging or manufacturing errors,
It is an object of the present invention to provide a fuel injection start timing detecting device for an internal combustion engine capable of detecting the fuel injection start timing more accurately.

[0010]

In order to achieve the above object, according to the present invention, as shown in FIG. 1, a fuel injection nozzle M2 for injecting fuel into an internal combustion engine M1 by obtaining a fuel pressure higher than a predetermined level is provided. A fuel injection pump M3 for pumping the fuel to the fuel injection nozzle M2, a fuel pressure detecting means M4 for detecting the pressure of the fuel pumped from the fuel injection pump M3 to the fuel injection nozzle M2, and a fuel pressure detecting means A fuel pressure change rate calculating means M5 for calculating a change rate of the fuel pressure based on the detection result of M4, and a fuel pressure change rate during the process of increasing the fuel pressure based on the calculation result of the fuel pressure change rate calculating means M5. And an injection start timing determining means M6 for determining a timing at which the increase rate of the first time changes from positive to negative to determine the start timing of fuel injection from the fuel injection nozzle M2.

[0011]

According to the above arrangement, as shown in FIG. 1, when fuel is fed from the fuel injection pump M3 to the fuel injection nozzle M2, the fuel pressure is detected by the fuel pressure detection means M4. Further, the fuel pressure change rate calculating means M5 calculates the change rate of the fuel pressure based on the detection result of the fuel pressure detecting means M4. Then, in the injection start timing determining means M6, based on the calculation result of the fuel pressure change rate calculating means M5,
During the process of increasing the fuel pressure, a point in time at which the rate of increase first changes from positive to negative is determined, and that point is determined as the fuel injection start time.

Here, the point in time at which the rate of increase in fuel pressure changes from positive to negative means an inflection point during the increase in fuel pressure. Therefore, the fuel injection start timing is specifically specified by the inflection point of the fuel pressure, and the determination of the fuel injection start timing is performed without the influence of noise or the like.

[0013]

【Example】

(First Embodiment) A first embodiment in which the fuel injection start timing detecting device for an internal combustion engine according to the present invention is embodied in an electronically controlled diesel engine of an automobile will be described in detail with reference to FIGS.

FIG. 2 shows a schematic structure of a diesel engine system with a supercharger in this embodiment, and FIG. 3 shows an enlarged view of the distribution type fuel injection pump 1. As shown in FIG. The fuel injection pump 1 includes a drive pulley 2 which is drivingly connected to a crankshaft 40 of a diesel engine 3 as an internal combustion engine via a belt or the like. When the drive pulley 2 is driven to rotate by the crankshaft 40 and the fuel injection pump 1 is driven, fuel injection provided for each cylinder (here, four cylinders are provided) of the diesel engine 3 is provided. Fuel is pumped to the nozzle 4 through the fuel pipe 4a.

In this embodiment, the fuel injection nozzle 4 is an automatic valve including a needle valve and a spring for adjusting the valve opening pressure of the needle valve. The valve is opened. Therefore, a fuel pressure P equal to or higher than a predetermined level is applied to the fuel injection nozzle 4 by the fuel pumped from the fuel injection pump 1 so that the fuel
The fuel is injected from the engine to the diesel engine 3.

The fuel injection pump 1 has a drive shaft 5
The drive pulley 2 is attached to the tip of the drive shaft 5. In the middle of the drive shaft 5 is provided a fuel feed pump 6 (developed by 90 degrees in this figure) composed of a vane type pump. A disk-shaped pulsar 7 is attached to the base end side of the drive shaft 5. On the outer peripheral surface of the pulsar 7, missing teeth of the same number as the number of cylinders of the diesel engine 3, that is, four (in total, “eight”) missing teeth are formed at equal angular intervals in this embodiment. Also, between each missing tooth,
Fourteen projections (a total of "56") are formed at equal angular intervals. The base end of the drive shaft 5 is connected to the cam plate 8 via a coupling (not shown).

A roller ring 9 is provided between the pulsar 7 and the cam plate 8. A plurality of cam rollers 10 facing the cam face 8a of the cam plate 8 are mounted in the circumferential direction of the roller ring 9. The cam faces 8 a are provided in the same number as the number of cylinders of the diesel engine 3. The cam plate 8 is urged by a spring 11 so as to engage with the cam roller 10.

A base end of a plunger 12 for fuel pressurization is attached to the cam plate 8 so as to be integrally rotatable. Then, the cam plate 8 and the plunger 12 are integrally driven to rotate as the drive shaft 5 rotates.
That is, the rotational force of the drive shaft 5 is transmitted to the cam plate 8 via the coupling, so that the cam plate 8 rotates while engaging with the cam roller 10. As a result, the cam plate 8 is reciprocated in the horizontal direction in the figure by the same number as the number of cylinders while being rotated, and the plunger 12 is reciprocated in the same direction while being rotated. That is, the cam face 8a is the cam roller 1 of the roller ring 9.
Plunger 12 moves forward (lift) in the process of climbing to zero
Is done. On the contrary, the cam face 8a is
Plunger 12 moves back in the process of getting over 0 (down)
Is done.

A cylinder 14 is formed in the pump housing 13, and the plunger 12 is fitted into the cylinder 14. A high-pressure chamber 15 is provided between the tip surface of the plunger 12 and the bottom surface of the cylinder 14. In addition, suction grooves 16 and distribution ports 17 are formed on the outer periphery of the distal end side of the plunger 12 by the same number as the number of cylinders. Further, corresponding to the suction groove 16 and the distribution port 17,
A distribution passage 18 and a suction port 19 are formed in the pump housing 13.

When the drive shaft 5 is rotated and the fuel feed pump 6 is driven, fuel is introduced from a fuel tank (not shown) into the fuel chamber 21 through the fuel supply port 20. In the suction stroke in which the plunger 12 is moved back and the high-pressure chamber 15 is depressurized, fuel is introduced from the fuel chamber 21 into the high-pressure chamber 15 by one of the suction grooves 16 communicating with the suction port 19. on the other hand,
In the compression stroke in which the plunger 12 moves forward and the high-pressure chamber 15 is pressurized, the fuel is pressure-fed from the distribution passage 18 to the fuel injection nozzle 4 of each cylinder through the fuel pipe 4a and injected.

In the pump housing 13, the high pressure chamber 1
A spill passage 22 for causing fuel to overflow (spill) is formed between the fuel chamber 5 and the fuel chamber 21. An electromagnetic spill valve 23 is provided in the middle of the spill passage 22. Then, the electromagnetic spill valve 23 is opened and closed to adjust the spill of the fuel from the high-pressure chamber 15. The electromagnetic spill valve 23 is a normally open type valve. When the coil 24 is not energized (off), the spill passage 22 is opened by the valve body 25, that is, the valve is opened, and the fuel in the high-pressure chamber 15 is released from the fuel chamber 21. Spilled into On the other hand, when the coil 24 is energized (turned on), the spill passage 22 is closed by the valve body 25, that is, the valve is closed, and the spill of fuel from the high-pressure chamber 15 to the fuel chamber 21 is shut off.

Therefore, the electromagnetic spill valve 23 is controlled to be turned on and off by energization, whereby the valve 23 is controlled to close and open, and the spill of fuel from the high-pressure chamber 15 to the fuel chamber 21 is adjusted. When the electromagnetic spill valve 23 is opened during the compression stroke of the plunger 12, the high-pressure chamber 1 is opened.
The fuel in the fuel injection nozzle 4 is depressurized and the fuel injection from the fuel injection nozzle 4 is stopped. That is, even when the plunger 12 moves forward, while the electromagnetic spill valve 23 is opened,
The fuel pressure in the high-pressure chamber 15 does not increase and the fuel injection nozzle 4
Is not injected. Also, during the forward movement of the plunger 12, by controlling the valve opening timing of the electromagnetic spill valve 23, the end timing of the fuel injection from the fuel injection nozzle 4 is adjusted, and the fuel injection amount to the cylinder is controlled. .

Below the pump housing 13, there is provided a timer device (expanded by "90 degrees" in this figure) 26 for controlling the fuel injection timing to the advance side or the retard side. . This timer device 26 changes the rotation position of the roller ring 9 with respect to the rotation direction of the drive shaft 5 to change the timing at which the cam face 8a engages with the cam roller 10, that is, the timing at which the plunger 12 reciprocates. belongs to.

The timer device 26 is driven by control hydraulic pressure, and includes a timer housing 27 and a timer piston 28 fitted in the housing 27. Further, both sides of the timer piston 28 in the timer housing 27 are a low-pressure chamber 29 and a pressurizing chamber 30, respectively. The low-pressure chamber 29 has a timer piston 28
A timer spring 31 is provided to urge the pressure chamber 30 into the pressure chamber 30. Further, the timer piston 28 is connected to the roller ring 9 via a slide pin 32.

The fuel pressurized by the fuel feed pump 6 is introduced into the pressurizing chamber 30. The position of the timer piston 28 is determined by the balance between the fuel pressure and the urging force of the timer spring 31. Further, by determining the position of the timer piston 28, the position of the roller ring 9 is determined, and the reciprocating timing of the plunger 12 via the cam plate 8 is determined.

The fuel pressure in the fuel injection pump 1 is used as the control oil pressure of the timer device 26. To adjust the fuel pressure, the timer device 26 is provided with a timer control valve (TCV) 33. That is, a communication passage 34 is provided between the pressurizing chamber 30 and the low-pressure chamber 29 of the timer housing 27, and a TCV 33 is provided in the middle of the communication passage 34. The TCV 33 is an electromagnetic valve whose opening and closing are controlled by a duty-controlled energization signal. The TCV 33 is controlled to open and close to adjust the fuel pressure in the pressurizing chamber 30. Then, by adjusting the fuel pressure, the reciprocating timing of the plunger 12 is controlled, whereby the fuel injection timing from the fuel injection nozzle 4 is controlled to be advanced or retarded.

On the upper part of the roller ring 9, a rotation speed sensor 35 composed of an electromagnetic pickup coil is mounted so as to face the outer peripheral surface of the pulser 7. This rotation speed sensor 35
Detects the passage of the pulsar when it is crossed by a projection or the like of the pulsar 7 and outputs the signal as a pulse signal. That is, the rotation speed sensor 35 outputs an engine rotation pulse signal for each constant crank angle. At the same time, the rotation speed sensor 35 outputs an engine rotation pulse signal corresponding to a fixed crank angle due to a missing tooth of the pulser 7 as a reference position signal. The rotation speed sensor 35 outputs a series of engine rotation pulse signals as signals for obtaining the engine rotation speed NE.
Since the rotation speed sensor 35 is integrated with the roller ring 9, it can output a reference engine rotation pulse signal at a fixed timing with respect to the reciprocation of the plunger 12 regardless of the control operation of the timer device 26. .

Next, the diesel engine 3 will be described. 2, in the diesel engine 3, a main combustion chamber 44 corresponding to each cylinder is formed by a cylinder bore 41, a piston 42, and a cylinder head 43. In the cylinder head 43, sub combustion chambers 45 communicating with the main combustion chambers 44 are formed. Then, fuel is injected into each sub-combustion chamber 45 from each fuel injection nozzle 4. Further, each sub-combustion chamber 45 is provided with a well-known glow plug 46 as a start-up assist device.

As shown in FIGS. 2 and 4, each fuel injection nozzle 4 of this embodiment is provided with a pressure sensor 47 as fuel pressure detecting means and a lift sensor 48. The pressure sensor 47 detects the pressure of the fuel pressure-fed from the fuel injection pump 1 to each fuel injection nozzle 4, that is, the fuel pressure P, and outputs a signal corresponding to the magnitude of the detected value. The lift sensor 48 detects a needle valve lift amount L that correlates with the opening area of the fuel injection nozzle 4 when the valve is opened, and outputs a signal corresponding to the magnitude of the detected value.

On the other hand, the diesel engine 3 is provided with an intake passage 49 and an exhaust passage 50 communicating with each cylinder. Further, a compressor 52 of a turbocharger 51 constituting a supercharger is provided in the intake passage 49,
A turbine 53 of a turbocharger 51 is provided in the exhaust passage 50.
Is provided. Further, a waste gate valve 54 is provided in the exhaust passage 50. As is well known, the turbocharger 51 uses the energy of the exhaust gas to rotate the turbine 53, and rotates the compressor 52 coaxially therewith to increase the pressure of the intake air. When the intake air is pressurized, high-density air is sent into the main combustion chamber 44 and a large amount of fuel injected through the sub-combustion chamber 45 is burned, so that the output of the diesel engine 3 is increased. Further, by opening and closing the waste gate valve 54, the pressure increase level of the intake air by the turbocharger 51 is adjusted.

Between the intake passage 49 and the exhaust passage 50,
Exhaust gas recirculation valve passage (EG
An R path 56 is provided. Then, a part of the exhaust gas in the exhaust passage 50 is recirculated by the EGR passage 56 near the intake port 55 in the intake passage 49.
An EGR valve 57 is provided in the middle of the EGR passage 56, and the EGR valve 57 controls the exhaust gas recirculation amount (E
GR amount) is adjusted. Further, in order to open and close the EGR valve 57, an electric vacuum regulating valve (EVRV) 58 whose opening is adjusted is controlled.
Is provided. Then, EGRV58 is used for EGR
When the valve 57 is driven to open and close, the EGR passage 5
E guided from the exhaust passage 50 to the intake passage 49 through
The GR amount is adjusted.

A throttle valve 59 is provided in the middle of the intake passage 49. The throttle valve 59 is opened and closed in conjunction with the depression of an accelerator pedal 60. In the intake passage 49,
A bypass passage 61 is provided alongside the throttle valve 60, and a bypass throttle valve 62 is provided in the passage 61. In order to open and close the bypass throttle valve 62, a two-stage diaphragm chamber type actuator 63 is provided. Also, two vacuum switching valves (VS) for driving the actuator 63 are provided.
V) 64, 65 are provided. And each VSV6
The bypass throttle valve 62 is controlled to open and close by driving the actuator 63 with the on / off control of the valves 4 and 65. For example, the bypass throttle valve 62 is controlled to be in a half-open state in order to reduce noise and vibration during idling operation, is controlled to be in a fully open state in normal operation, and is controlled to be in a fully closed state in order to smoothly stop the operation. Is done.

The above-described electromagnetic spill valve 23, TCV3
3, glow plug 46, EVRV58 and each VSV6
4 and 65 are electronic control units (hereinafter simply referred to as “ECU”).
71 are electrically connected to each other. The drive timing of each of the members 23, 33, 46, 58, 64, 65 is controlled by the ECU 71.

As sensors for detecting the operating state of the diesel engine 3, in addition to the rotation speed sensor 35 described above, the following various sensors are provided. That is, near the air cleaner 66 provided at the inlet of the intake passage 49, an intake air temperature sensor 72 that detects the intake air temperature THA and outputs a signal corresponding to the magnitude of the detected value is provided. In the vicinity of the throttle valve 59, the valve 5
An accelerator sensor 73 that detects an accelerator opening ACCP corresponding to the engine load from the open / close position 9 and outputs a signal corresponding to the magnitude of the detected value. In the vicinity of the intake port 55, an intake pressure sensor 74 that detects the pressure of the intake air after being supercharged by the turbocharger 51, that is, the supercharging pressure PiM, and outputs a signal corresponding to the magnitude of the detected value. Is provided. Further, a water temperature sensor 7 for detecting the temperature of the cooling water of the diesel engine 3, that is, the cooling water temperature THW, and outputting a signal corresponding to the magnitude of the detected value.
5 are provided. Further, a crank angle sensor 76 for detecting a rotation reference position of the crankshaft 40, for example, a rotation position of the crankshaft 40 with respect to a top dead center of a specific cylinder, and outputting a signal corresponding to the rotation position is provided. Further, a transmission (not shown) is provided with a vehicle speed sensor 77 for detecting a vehicle speed (vehicle speed) SPD. The vehicle speed sensor 77 includes a magnet 77a rotated by an output shaft of the transmission. When the reed switch 77b is periodically turned on by the magnet 77a, a pulse signal corresponding to the vehicle speed SPD is output.

In this embodiment, the ECU 71 comprises a fuel pressure change rate calculating means and an injection start timing judging means.
To 77 are connected respectively, and the rotation speed sensor 3
5, the pressure sensor 47 and the lift sensor 48 are connected respectively. In addition, the ECU 71 controls the sensors 35, 47,
48, 72 to 77, the electromagnetic spill valve 23, the TCV 33, the glow plug 46, the EVR
V58 and the respective VSVs 64 and 65 are suitably controlled.

Next, the configuration of the ECU 71 will be described with reference to the block diagram of FIG. The ECU 71 includes a central processing unit (CPU) 81, a read-only memory (ROM) 82 in which a predetermined control program, a map, and the like are stored in advance,
A random access memory (RAM) 83 for temporarily storing the calculation results of the PU 81, a backup RAM 84 for storing the stored data, and the like are provided. And ECU
Reference numeral 71 denotes a logical operation circuit in which these units 81 to 84 are connected to an input port 85, an output port 86, and the like via a bus 87.

The input port 85 is provided with the above-described intake temperature sensor 72, accelerator sensor 73, intake pressure sensor 74, water temperature sensor 75, pressure sensor 47, and lift sensor 48.
The buffers 88, 89, 90, 91, 92, 93, the multiplexer 94, and the A / D converter 95 are connected. Similarly, the input port 85 includes the above-described rotation speed sensor 35, crank angle sensor 76, and vehicle speed sensor 77.
Are connected via a waveform shaping circuit 96. Then, the CPU 81 reads, as input values, signals from the sensors 35, 47, 48, 72 to 77, etc., which are input via the input port 85. The output ports 86 are connected to the respective driving circuits 97, 98, 99, 100, 101, 102.
The electromagnetic spill valve 23, the TCV 33, the glow plug 46, the EVRV 58, and the VSVs 64 and 65 are connected via the. Then, the CPU 81 controls the sensors 35, 47,
48, 72 to 77, the electromagnetic spill valve 23, the TCV 33, the glow plug 46, the EVR
V58 and the respective VSVs 64 and 65 are suitably controlled.

In this embodiment, the CPU 81 has a timer function. Also, in this embodiment,
Glow plug 46, pressure sensor 47 and lift sensor 4
Numeral 8 is provided for each cylinder of the diesel engine 3, but in the block diagram of FIG. 5, only one of them is shown for convenience.

Next, the processing operation for controlling the fuel injection amount executed by the ECU 71 will be described with reference to FIGS.
0 will be described. FIG. 6 is a flowchart showing a “subroutine” process executed at each time ti measured by the timer function of the CPU 81 among the processes executed by the ECU 71.

When the process proceeds to this routine, first, at step 110, the fuel pressure P and the needle valve lift amount L are sampled based on signals from the pressure sensor 47 and the lift sensor 48.

Subsequently, at step 120, the fuel pressure Pi at the time ti at that time is calculated. In step 130, the needle valve lift amount Li at the time ti at that time is calculated.

Next, at step 140, a one-time differential value (dPi / dti) is calculated as a change rate of the fuel pressure Pi at the time ti at that time. Further, at step 150, the fuel pressure P at the current time ti
The second derivative (d ² Pi / d) corresponding to the change in the rate of change of i
ti ² ) is calculated.

In step 160, the fuel pressure Pi, the needle valve lift amount Li, the first differential value (dPi / dti), and the second differential value (d ² Pi / dt) are determined.
i ² ) is stored in the RAM 83 as calculation data corresponding to the time ti, and the subsequent processing is temporarily terminated.

Therefore, according to the processing of the above-mentioned "subroutine", each time one fuel injection is executed, the fuel pressure Pi, the needle valve lift amount Li, and the one-time differential value (dPi / dti) and the second derivative (d ² Pi / dti)
² ) are sequentially stored in the RAM 83 as operation data.

FIG. 7 is a flowchart showing a ".DELTA.Q calculation routine" for calculating an injection amount deviation value .DELTA.Q used for fuel injection amount control, among the processes executed by the ECU 71. It is executed periodically at intervals.

When the processing shifts to this routine, first, at step 201, the fuel pressure Pi corresponding to the time ti stored in the RAM 83 and its one-time differential value (d
Pi / dti) and time t (i−
The fuel pressure P (i-1) corresponding to 1) is read.

Subsequently, at step 202, the time t
The fuel pressure Pi corresponding to i is the time t (i−
It is determined whether the fuel pressure is higher than the fuel pressure P (i-1) corresponding to 1). If the fuel pressure Pi is not higher than the previous fuel pressure P (i-1), the fuel pressure P
It is determined that the process is not an increase process, and the process jumps to step 201 and repeats the processes of steps 201 and 202.
If it is determined in step 202 that the fuel pressure Pi is higher than the previous fuel pressure P (i-1), the process proceeds to step 203 assuming that the fuel pressure P is in the process of increasing.

In step 203, it is determined whether or not the once-differentiated value (dPi / dti) read this time has exceeded a predetermined threshold value d1 on the plus side for a predetermined reference time T1. Here, the first derivative (dPi / dt)
If i) exceeds the threshold value d1 and the reference time T1 has not elapsed, the process jumps to step 201 and repeats the processing of steps 201 to 203. Step 20
In step 3, if the one-time differential value (dPi / dti) exceeds the threshold value d1 and the reference time T1 has elapsed, it is determined that the fuel pressure P is to be increased and fuel injection P is to be started. Move to.

Then, in step 204, RA
The fuel pressure P corresponding to the time ti stored in M83
i (dPi / dti) and the second derivative (d
² Pi / dti ² ).

Next, in step 205, it is determined whether or not the currently read second differential value (d ² Pi / dti ² ) is smaller than a reference value α. Here, if the second derivative (d ² Pi / dti ² ) is not smaller than the reference value α, it is determined that the rate of change of the fuel pressure Pi has not fallen significantly, and the routine jumps to step 204, where Step 205 is repeated. On the other hand, in step 205, the second derivative (d ² Pi / dt)
If i ² ) is smaller than the reference value α, it is determined that the rate of change of the fuel pressure P has greatly decreased during the process of increasing the fuel pressure P, and the routine proceeds to step 206.

Then, in step 206, the once-differentiated value (dPi / dti) read this time falls below a predetermined threshold value d2 on the negative side and reaches a predetermined reference time T2.
Is determined. Here, when the one-time differential value (dPi / dti) is less than the threshold value d2 and the reference time T2 has not elapsed, the one-time differential value (dPi / dti) is reduced due to the start of fuel injection. Assuming that no change has occurred, the process jumps to step 204 and repeats the processing of steps 204 to 206. Step 20
In 6, when the one-time differential value (dPi / dti) falls below the threshold value d2 and the reference time T2 has elapsed, the one-time differential value (dPi / dti) due to the start of fuel injection.
Then, the process proceeds to step 207 on the assumption that the change in the fuel pressure P has definitely decreased.

In step 207, the RAM 83 is traced back to the time ti when the one-time differential value (dPi / dti) becomes "0" from the time when it is determined that the rate of change of the fuel pressure P has definitely decreased. Search the stored operation data. Here, the time ti when the one-time differential value (dPi / dti) becomes “0” is the time when the rate of increase of the fuel pressure P first changes from positive to negative during the process of increasing the fuel pressure P. Yes, it is.

Next, in step 208, at the time ti when the one-time differential value (dPi / dti) becomes “0” in the retrieved calculation data, the time ti is changed to the fuel from the fuel injection nozzle 4. Judgment is made at the injection start time, and the injection start time ts is set. Further, the fuel pressure Pi at the time ti is set as the injection start pressure Ps.

Subsequently, at step 209, the fuel pressures Pi at the respective times ti after the injection start time ts are sequentially read. Then, in step 210, it is determined whether or not the read fuel pressure Pi is equal to or less than the value of the injection end pressure Ph corresponding to the previously confirmed fuel pressure P at the end of fuel injection. Here, if the fuel pressure Pi is not equal to or less than the injection end pressure Ph, the process jumps to step 209 and repeats the processing of steps 209 and 210.
On the other hand, if the fuel pressure Pi is equal to or less than the injection end pressure Ph, the process proceeds to step 211. Then, in step 211, after the injection start time ts, the fuel pressure Pi
Is set as the injection end time te for the time ti at which becomes equal to the injection end pressure Ph.

Next, in step 212, calculation data corresponding to each time ti from the injection start time ts to the injection end time te is read. Step 2
At 13, from the injection start time ts to the injection end time te, the fuel injection nozzle 4
Lift coefficient KL correlated with the opening area when the valve is opened
i is calculated. The calculation of the lift coefficient KLi is performed by referring to a map in which the relationship between the needle valve lift amount L and the lift coefficient KL is predetermined as shown in FIG.

Further, in step 214, from the injection start time ts to the injection end time te, the fuel injection amount (time injection amount) Qi at each time ti is calculated based on each lift coefficient KLi and each fuel pressure Pi. I do. The injection quantity Qi at this time is obtained according to the following formula.

Qi = KLi * √Pi In step 215, the actual injection amount Qr corresponding to the actual fuel injection amount is calculated by integrating the injection amount Qi at each time from the injection start time ts to the injection end time te. I do.
That is, the integral value of the point-in-time injection amount Qi is obtained from the injection start time ts to the injection end time te.

Further, in step 216, the target injection amount Q0 used for executing the previous fuel injection is read in a separate "fuel injection amount control routine" described later.
Then, in step 217, the previous target injection amount Q
The actual injection amount Qr obtained this time is subtracted from 0, the result of the subtraction is set as the injection amount deviation value ΔQ, and the subsequent processing is temporarily terminated.

Therefore, according to the processing of the above-mentioned “ΔQ calculation routine”, each time one fuel injection is executed, the injection start time ts and the injection start pressure Ps at that time are obtained and based on them. Thus, the actual injection amount Qr is obtained. Further, a difference between the previous target injection amount Q0 and the actual injection amount Qr is obtained as an injection amount deviation value ΔQ which is data for correcting the next fuel injection amount. Then, those values are respectively stored in the RAM 83.

Here, as described above, the injection start time ts, the injection end time te, each fuel pressure P, the one-time differential value (dPi / An example of the behavior of dti) and the actual injection amount Qr will be described with reference to the time chart of FIG.

When the plunger 12 of the fuel injection pump 1 starts to move forward during fuel injection, the fuel pressure P starts to increase at time t1, as shown in FIG. Then, the fuel pressure P is determined by the plunger 12
It gradually increases with the forward movement of. At this time, the one time differential value (dP / dt) of the fuel pressure P changes as shown in FIG. Here, immediately after the time t1, the first derivative (dP
/ Dt) exceeds the threshold value d1 on the positive side and the reference time T
After the elapse of one, the ECU 71 determines that the fuel pressure P is in the process of increasing, which should lead to the start of fuel injection.

Thereafter, at time t2, when the increasing fuel pressure P undergoes a large inflection, its one-time differential value (dP / d
t) falls greatly. Then, immediately after the time t2, when the first derivative (dP / dt) falls below the negative threshold value d2 and the reference time T2 elapses, the ECU 71 sets the fuel pressure P due to the start of fuel injection. It is determined that the change rate has definitely decreased. In the ECU 71,
One-time differential value (dPi / dti) retroactively from the judgment time
Is obtained at time t2 at which becomes “0”, and the time t2 is obtained as the injection start time ts. Further, at time t2
Is obtained as the injection start pressure Ps. That is, as shown in FIG. 7A, the injection start time ts corresponding to the inflection point A where the rate of increase of the fuel pressure P first changes from positive to negative, and the injection start pressure Ps at that time are obtained. .

Thereafter, when fuel injection continues from time t2,
Accordingly, the fuel pressure P and the first derivative (dPi / dt)
i) shows a change as shown in FIGS. Then, at time t3, the fuel pressure P becomes the injection end pressure Ph.
Is reached, the time t3 is obtained as the injection end time te by the ECU 71. Therefore, the injection start time ts
To the injection end time te is an injection period during which fuel injection is actually performed. FIG. 7C shows a change in the actual injection amount Qr during the injection period. The actual injection amount Qr is obtained by integrating the instantaneous injection amount Qi obtained from each fuel pressure Pi and the lift coefficient KLi at each time ti from the injection start time ts to the injection end time te. And E
In the CU 71, the actual injection quantity Qr and the previous target injection quantity Q
With 0, the injection amount deviation value ΔQ is obtained.

In this embodiment, the fuel injection amount control is executed as follows using the injection amount deviation value ΔQ obtained as described above as correction data. That is, FIG. 10 is a flowchart showing the processing of the “fuel injection amount control routine” performed using the above-described injection amount deviation value ΔQ among the processing executed by the ECU 71, and is executed periodically at predetermined intervals. Is done.

When the process proceeds to this routine, first, at step 310, the engine speed N obtained from the engine speed sensor 35, the accelerator sensor 73, and the like.
E and the accelerator opening ACCP are read.
Also, the injection amount deviation value ΔQ obtained in the “ΔQ calculation routine” is read.

Subsequently, at step 320, based on the engine speed NE and the accelerator opening ACCP, etc.
The basic injection amount Qb according to the operation state at that time is calculated. In step 330, the current target injection amount Q is calculated based on the basic injection amount Qb and the injection amount deviation value ΔQ. In this embodiment, as a method of calculating the target injection amount Q, a method of adding an injection amount deviation value ΔQ to the basic injection amount Qb is adopted. Here, as the injection amount deviation value ΔQ added to the basic injection amount Qb, only the latest injection amount deviation value ΔQ obtained at the time of the previous fuel injection may be used. Alternatively, a plurality of injection amount deviation values ΔQ obtained in the past
The result of the simple average of the latest injection amount deviation value ΔQ and the latest injection amount deviation value ΔQ may be added to the basic injection amount Qb. Or, in the past, the target injection amount Q
May be added to the basic injection amount Qb. The injection amount deviation value ΔQ determined from the learning value using the actually used individual injection amount deviation value ΔQ as data.

Then, in step 340, fuel injection is executed based on the current target injection amount Q obtained.
That is, by controlling the electromagnetic spill valve 23 based on the target injection amount Q, the fuel injection pump 1
Thus, the amount of fuel injected from the fuel injection nozzle 4 is controlled.

In step 350, the target injection amount Q used for executing the current fuel injection is set as the previous target injection amount Q0, and the subsequent processing is temporarily terminated. As described above, according to the fuel injection amount control of this embodiment, each time fuel injection is performed, the actual injection amount Qr that is actually injected becomes equal to the fuel pressure P at the fuel injection nozzle 4 and the needle. It is obtained based on the valve lift amount L. Then, the difference between the actual injection amount Qr and the target injection amount Q0 at that time is obtained as an injection amount deviation value ΔQ, and the fuel injection is executed based on the new target injection amount Q corrected by the injection amount deviation value ΔQ. You. That is, the fuel injection amount control is performed such that the actual injection amount Qr matches the target injection amount Q. Therefore, in this embodiment, even if the components and the like of the fuel injection pump 1 change over time, there is a manufacturing error in the components and the like, or even if the properties of the fuel used change. Each time fuel injection is performed, the actual injection amount Qr
Is controlled so that the fuel injection amount matches the target injection amount Q. As a result, highly accurate fuel injection amount control can be stabilized for a long period of time without being affected by temporal changes or manufacturing errors of components of the fuel injection pump 1 or changes in fuel properties.

That is, even if the cam plate 8 and the roller ring 9 are worn by the fuel injection pump 1 and the lift amount of the plunger 12 is changed, the fuel to be injected from the fuel injection nozzle 4 is affected by the change. The amount does not increase. Further, in the fuel injection nozzle 4 connected to the fuel injection pump 1, even if the set valve opening pressure of the nozzle 4 decreases, the amount of fuel to be injected from the fuel injection nozzle 4 increases due to the change. There is no. Or, even if the fuel temperature rises with the fuel injection pump 1,
The change does not affect the amount of fuel to be injected from the fuel injection nozzle 4 or the injection start timing. As a result, highly accurate fuel injection amount control suitable for the current operation state can be realized. Therefore, the generation of smoke from the diesel engine 3 can be significantly suppressed, the variation in exhaust gas can be suppressed, and the fuel efficiency can be improved.

Further, in this embodiment, in order to obtain a more accurate actual injection amount Qr, a specific study has been made on how to obtain the fuel injection start timing. That is, in this embodiment,
The waveform of the fuel pressure P obtained by the pressure sensor 47 provided in each fuel injection nozzle 4 is monitored. During the process of increasing the fuel pressure P, the rate of increase, that is, the one-time differential value (d
The point in time when Pi / dti) first changes from positive to negative is determined. Here, the first derivative of the fuel pressure P (dPi /
It has been confirmed that the point where dti) first changes from positive to negative corresponds to a portion where the fuel pressure P drops momentarily due to the start of fuel injection. That is, it has been experimentally confirmed that the change in the pressure of the fuel pumped from the fuel injection pump 1 to the fuel injection nozzle 4 actually shows a waveform pattern as shown in FIG. In addition, a one-time differential value (dPi / dt) which is a change rate of the fuel pressure P at that time.
It has been experimentally confirmed that the change in i) actually shows a waveform pattern as shown in FIG. 9B. Then, in these waveform patterns, the first derivative of the fuel pressure P (dP
It has been confirmed that the point in time at which i / dti) changes from positive to negative means an inflection point A when the fuel pressure P first drops only for a moment while increasing to some extent.

Therefore, the fuel injection start timing is specifically specified as the inflection point A of the fuel pressure P based on the change of the first derivative (dPi / dti) together with the change of the fuel pressure P. The determination of the fuel injection start timing is performed while eliminating the influence of noise or the like.

As a result, in the diesel engine 3 equipped with the fuel injection pump 1 and the fuel injection nozzle 4, etc., the fuel injection start timing at the time of the fuel injection is not affected by the aging of the fuel system and the manufacturing error. Can be determined more accurately. Therefore, the actual injection amount Qr used for controlling the fuel actually injected from the fuel injection nozzle 4 to be the target injection amount Q can be obtained more accurately.

In this embodiment, in order to determine the fuel injection start timing from the waveform of the fuel pressure P and its one-time differential value (dPi / dti), a description will be given of the processing of the "ΔQ calculation routine" in FIG. As described above, the first derivative (dPi /
It is determined that dti) has exceeded the threshold value d1 by the reference time T1. At the same time, the first derivative (dPi /
It is determined that dti) has fallen below the threshold value d2 by the reference time T2. Therefore, even if the waveform of the fuel pressure P slightly changes due to noise, the change is not erroneously determined as the inflection point A of the fuel pressure P corresponding to the start of fuel injection. Therefore, the fuel injection start timing can be more accurately determined from this.

Further, in this embodiment, when obtaining the actual injection amount Qr from the obtained fuel injection start timing, each lift coefficient is calculated based on the actual needle valve lift amount Li at each time ti obtained from the lift sensor 48. KLi is required.
Then, the actual injection amount Qr is obtained based on each of the lift coefficients KLi and each of the fuel pressures Pi. Therefore, the actual injection amount Qr can reliably reflect the actual behavior of the needle valve when fuel is injected from the fuel injection nozzle 4, and the actual injection amount Qr can be determined more precisely.

(Second Embodiment) Next, a second embodiment in which the fuel injection start timing detecting device for an internal combustion engine according to the present invention is embodied in an electronically controlled diesel engine of an automobile will be described with reference to FIGS.
This will be described with reference to FIG. In this embodiment, the structure of a turbocharged diesel engine system and its ECU 71 and the like are the same as those of the first embodiment, and the same members are denoted by the same reference numerals. Omitted. Hereinafter, a processing operation of the fuel injection amount control which is particularly different from the first embodiment will be described.

FIG. 11 is a flowchart showing a “subroutine” process executed at each time ti measured by the timer function of the CPU 81 among the processes executed by the ECU 71.

When the process proceeds to this routine, first, at step 410, the fuel pressure P and the needle valve lift amount L are sampled based on the signals from the pressure sensor 47 and the lift sensor 48.

Subsequently, at step 420, the fuel pressure Pi at the time ti at that time is calculated. In step 430, the needle valve lift amount Li at the time ti at that time is calculated, and a lift coefficient KLi correlated with the opening area of the fuel injection nozzle 4 when the fuel injection nozzle 4 is opened is calculated from the obtained needle valve lift amount Li. . This lift coefficient KL
The calculation of i is performed with reference to a map as shown in FIG. 8, as in the first embodiment.

Next, at step 440, a one-time differential value (dPi / dti) is calculated as a change rate of the fuel pressure Pi at the time ti at that time. Further, at step 450, the fuel pressure P at the current time ti
The second derivative (d ² Pi / d) corresponding to the change in the rate of change of i
ti ² ) is calculated.

In step 460, the fuel pressure Pi, the lift coefficient KLi, the first derivative (dPi / dti), and the second derivative (d ² Pi / dt) obtained this time are obtained.
i ² ) is stored in the RAM 83 as calculation data corresponding to the time ti, and the subsequent processing is temporarily terminated.

Therefore, according to the above-described "subroutine" processing, every time one fuel injection is executed, the fuel pressure Pi, the lift coefficient KLi, and the one-time differential value (dPi / dti) corresponding to each time ti are obtained. And the second derivative (d ² Pi / dti)
² ) are sequentially stored in the RAM 83 as operation data.

FIG. 12 is a flowchart of the processing executed by the ECU 71 for calculating the injection start time ts and the injection start pressure Ps used for controlling the fuel injection amount.
s, Ps calculation routine ", which is periodically executed at predetermined time intervals. Incidentally, each step 510, 52 of this "ts, Ps calculation routine"
0,530,540,550,560,570,580
Is exactly the same as the processing in steps 201 to 208 of the “ΔQ calculation routine” in the first embodiment, and a description thereof will not be repeated.

Therefore, this "ts, Ps calculation routine"
According to the above process, each time one fuel injection is executed, the injection start time ts and the injection start pressure Ps at that time are obtained and stored in the RAM 83 once.

In this embodiment, the following fuel injection control is executed based on the injection start time ts and the injection start pressure Ps obtained as described above. That is, FIG. 13 is a flowchart showing the processing of a “fuel injection amount control routine” performed using the above-described injection start time ts and injection start pressure Ps among the processing performed by the ECU 71, and is performed at predetermined intervals. Executed periodically.

When the process proceeds to this routine, first, at step 610, the injection start time ts obtained by the “ts, Ps calculation routine” is read. In step 620, the engine speed NE, the accelerator opening ACCP, and the like obtained from the engine speed sensor 35, the accelerator sensor 73, and the like are read.

Subsequently, in step 630, based on the engine speed NE and the accelerator opening ACCP, etc.
The target injection amount Q according to the operating state at that time is calculated.
In this embodiment, the basic injection amount Qb is obtained based on the engine speed NE, the accelerator opening ACCP, and the like, and the target injection amount Q is obtained by adding a correction injection amount to the basic injection amount Qb as necessary. Can be Examples of the correction injection amount include a cold correction injection amount obtained based on the cooling water temperature THW.

Next, at step 640, calculation data at each time ti from the injection start time ts is sequentially read. That is, each lift coefficient KLi and each fuel pressure Pi required for obtaining the actual injection amount Qr are read.

In step 650, the injection start time t
At each time ti from s, the point-in-time injection amount Qi is calculated based on each lift coefficient KLi and each fuel pressure Pi. This point-in-time injection amount Qi is obtained according to the following calculation formula similar to that in the first embodiment.

Qi = KLi * √Pi Further, in step 660, the instantaneous injection amount Qi obtained from the injection start time ts to each time ti is integrated, and corresponds to the actual fuel injection amount up to that time. The actual injection amount Qr is calculated. That is, the integral value of the point-in-time injection amount Qi from the injection start time ts to each subsequent time ti is determined.

Then, at step 670, the actual injection amount Qr obtained at each time ti from the injection start time ts
Is equal to or equal to the target injection amount Q obtained at the time of the current fuel injection. Here, if the actual injection amount Qr is not equal to the target injection amount Q, it is determined that the actual injection amount Qr has not reached the target injection amount Q up to the time ti, and the process jumps to step 640, and proceeds to step 640 to step 640. Step 670 is repeated. On the other hand, if the actual injection amount Qr is equal to the target injection amount Q, it is determined that the actual injection amount Qr up to the time ti has reached the target injection amount Q in step 680.
Move to.

Then, in step 680, the electromagnetic spill valve 23 is turned "off" in order to end the fuel pumping from the fuel injection pump 1 to the fuel injection nozzle 4, and the subsequent processing is temporarily ended. That is, the current fuel injection end timing is controlled.

Here, the injection start time ts, the injection end time te, the fuel pressure P, and the one-time differential value (dPi / d) in one fuel injection executed by the above-described fuel injection amount control processing. dti), actual injection amount Qr and electromagnetic spill valve 2
The behavior 3 and the like will be described with reference to the time chart of FIG.

When the plunger 12 of the fuel injection pump 1 starts going forward during fuel injection, the fuel pressure P gradually increases from time t1, as shown in FIG. At this time, the first derivative of the fuel pressure P (dP /
dt) indicates a change as shown in FIG. Here, immediately after time t1, when the one-time differential value (dP / dt) exceeds the threshold value d1 on the positive side and elapses by the reference time T1,
In the ECU 71, the fuel pressure P to reach the start of fuel injection
Is determined to be in the process of increasing.

Thereafter, at time t2, when the increasing fuel pressure P undergoes a large inflection, its one-time differential value (dP / d
t) falls greatly. Then, immediately after the time t2, when the one-time derivative value (dP / dt) falls below the negative threshold value d2 for the reference time T2, the ECU 71 sets the fuel pressure P due to the start of the fuel injection. It is determined that the change rate has definitely decreased. In the ECU 71,
One-time differential value (dPi / dti) retroactively from the judgment time
Is obtained at time t2 at which becomes “0”, and the time t2 is obtained as the injection start time ts. Further, at time t2
Is obtained as the injection start pressure Ps.

Thereafter, when fuel injection continues from time t2,
Accordingly, the fuel pressure P and the first derivative (dPi / dt)
i) shows a change as shown in FIGS. The change in the actual injection amount Qr at that time is shown in FIG. EC
In U71, based on each fuel pressure Pi and the lift coefficient KLi obtained at each time ti from the injection start time ts,
The point-in-time injection amount Qi at each time ti is obtained, and the integrated value of the point-in-time injection amount Qi up to the time ti is obtained as the actual injection amount Qr.

Then, at time t3, when the actual injection amount Qr reaches the current target injection amount Q, the ECU 71 sets the time t3 as the fuel injection end timing and turns the electromagnetic spill valve 23 from "on" to "off". Is switched to "."

As described above, according to the fuel injection amount control of this embodiment, each time fuel injection is executed,
The injection start time ts and the injection start pressure Ps at the time when the injection is actually started are obtained based on the fuel pressure P. Then, based on the fuel pressure Pi and the lift coefficient KLi obtained at each time ti from the injection start time ts, the time t
The actual injection amount Qr up to i is obtained. Then, when the actual injection amount Qr reaches the target injection amount Q, the fuel pumping from the fuel injection pump 1 is terminated, and the fuel injection from the fuel injection nozzle 4 is stopped. That is, when each fuel injection is performed, the fuel injection amount is adjusted in real time so that the actual injection amount Qr matches the target injection amount Q.

Therefore, in this embodiment, even if the components of the fuel injection pump 1 change over time, if there is a manufacturing error in the components, or if the fuel property changes, the fuel injection pump 1 changes every time. Each time the fuel injection is performed, the actual injection amount Qr
Is controlled to match the target injection amount Q. As a result, high-precision fuel injection amount control can be stabilized for a long period of time without being affected by temporal changes or manufacturing errors of components of the fuel injection pump 1 or changes in fuel properties. In addition, it is possible to realize highly accurate fuel injection amount control adapted to the current operation state,
The generation of smoke from the diesel engine 3 can be significantly suppressed, the variation in exhaust gas can be suppressed, and the fuel efficiency can be improved.

Further, in this embodiment, since the fuel injection amount of each time is adjusted in real time, it is possible to prevent the variation of the fuel injection amount among the cylinders and the occurrence of irregular injection in each cylinder. Therefore, the fuel injection of each cylinder can be stabilized.

Further, in this embodiment, the waveform of the fuel pressure P obtained by the pressure sensor 47 is monitored in order to obtain a more accurate actual injection amount Qr. Further, during the process of increasing the fuel pressure P, the time point at which the first derivative value (dPi / dti) first changes from positive to negative is obtained. Here, the point where the one-time differential value (dPi / dti) of the fuel pressure P first changes from positive to negative corresponds to a portion where the fuel pressure P decreases momentarily due to the start of fuel injection. Have been. Then, the first derivative of the fuel pressure P (dPi /
The point in time when dti) changes from positive to negative means that the fuel pressure P
Has been confirmed to mean an inflection point A when it first drops only for a moment in the middle of an increase that has increased to some extent.

Therefore, the fuel injection start timing is specifically specified as the inflection point A of the fuel pressure P based on the change of the first derivative (dPi / dti) together with the change of the fuel pressure P. The determination of the fuel injection start timing is performed while eliminating the influence of noise or the like.

As a result, in the diesel engine 3 equipped with the fuel injection pump 1 and the fuel injection nozzle 4, etc., the fuel injection start timing at the time of the fuel injection is not affected by the aging of the fuel system and the manufacturing error. Can be determined more accurately. Therefore, the actual injection amount Qr used for controlling the fuel actually injected from the fuel injection nozzle 4 to be the target injection amount Q can be obtained more accurately.

In this embodiment, in order to determine the fuel injection start timing from the change in the fuel pressure P and its one-time differential value (dPi / dti), the processing in step 530 of the “ts, Ps calculation routine” is performed. As shown, the first derivative (dP
It is determined that i / dti) has exceeded the threshold value d1 by the reference time T1. In addition, as shown in the processing of step 560, it is determined that the one-time differential value (dPi / dti) has fallen below the threshold value d2 and the reference time T2 has elapsed. Therefore, even if the waveform of the fuel pressure P slightly changes due to noise, the change is not erroneously determined as the inflection point A of the fuel pressure P corresponding to the start of fuel injection. Therefore, the fuel injection start timing can be more accurately determined from this.

Further, in this embodiment, when obtaining the actual injection amount Qr from the obtained fuel injection start timing, each lift coefficient is obtained based on the actual needle valve lift amount Li at each time ti obtained from the lift sensor 48. KLi is required.
Then, the actual injection amount Qr is obtained based on each of the lift coefficients KLi and each of the fuel pressures Pi. Therefore, the actual injection amount Qr can reliably reflect the actual behavior of the needle valve when fuel is injected from the fuel injection nozzle 4, and the actual injection amount Qr can be determined more precisely.

(Third Embodiment) FIGS. 15 to 15 show a third embodiment in which the fuel injection start timing detecting device for an internal combustion engine according to the present invention is embodied in an electronically controlled diesel engine of an automobile.
This will be described with reference to FIG. In this embodiment, the structure of a turbocharged diesel engine system and its ECU 71 and the like are the same as those of the first embodiment, and the same members are denoted by the same reference numerals. Omitted. And, in the following, the first and second
A processing operation of the fuel injection timing control which is particularly different from the embodiment will be described.

FIG. 15 is a flowchart showing a "subroutine" process executed at each time ti measured by the timer function of the CPU 81 among the processes executed by the ECU 71.

When the process proceeds to this routine, first, at step 710, the fuel pressure P is sampled based on the signal from the pressure sensor 47. Subsequently, at step 720, the fuel pressure Pi at the time ti at that time is calculated.

Next, at step 730, a one-time differential value (dPi / dti) is calculated as a change rate of the fuel pressure Pi at the time ti at that time. Further, in step 740, the fuel pressure P at the current time ti
The second derivative (d ² Pi / d) corresponding to the change in the rate of change of i
ti ² ) is calculated.

In step 750, the fuel pressure Pi determined this time and the one-time differential value (dPi / dt)
i) and the second derivative (d ² Pi / dti ² ) at time ti
Are stored in the RAM 83 as calculation data corresponding to the above, and the subsequent processing is temporarily terminated.

Therefore, according to the above-mentioned "subroutine", each time one fuel injection is executed, the fuel pressure Pi corresponding to each time ti and the one-time differential value (dPi / dti) are obtained.
And the second derivative (d ² Pi / dti ² ) are sequentially stored in the RAM 83 as calculation data.

FIG. 16 is a flowchart showing a ".DELTA..theta. Calculation routine" for calculating an injection timing deviation value .DELTA..theta. Used for fuel injection timing control, among the processes executed by the ECU 71. It is executed periodically every hour. Each step 801, 802, 803, 804, 805, 80 of this “Δθ calculation routine”
The processing of steps 6,807 and 808 is exactly the same as the processing of each of steps 201 to 208 of the “ΔQ calculation routine” in the first embodiment, and a description thereof will be omitted. And, in the following, step 80 following step 808
9, 810, 811 and 812 will be described.

Step 80 shifts from step 808
In step 9, the target injection timing θo in this routine is read. The target injection timing θo is obtained in a separate processing routine according to the operating state at that time.

Next, at step 810, it is determined whether or not the read target injection timing θo is equal to the injection start time ts obtained in this routine. If the target injection timing θo is equal to the injection start time ts in step 810, the injection timing deviation value Δθ is set to “0” in step 811 and the subsequent processing is temporarily terminated. On the other hand, in step 810,
If the target injection timing θo is not equal to the injection start time ts, in step 812, the difference between the target injection timing θo and the injection start time ts is set as the injection timing deviation value Δθ, and the subsequent processing is temporarily terminated. .

Therefore, according to the processing of the “Δθ calculation routine”, every time one fuel injection is executed, the injection timing deviation value Δθ at that time is obtained and temporarily stored in the RAM 83.

In this embodiment, the following fuel injection timing control is executed based on the injection timing deviation value Δθ obtained as described above. That is, FIG.
1 is a “fuel injection timing control routine” performed using the above-described injection timing deviation value Δθ.
5 is a flowchart showing the processing of FIG.

When the processing shifts to this routine, first, at step 910, the engine speed N obtained from the engine speed sensor 35, the accelerator sensor 73, and the like.
E and the accelerator opening ACCP are read. At the same time, the injection timing deviation value Δθ obtained in the “Δθ calculation routine” is read.

Next, at step 920, a basic injection timing θb is calculated based on the engine speed NE, the accelerator opening ACCP, etc., according to the current operating state. Subsequently, at step 930, the injection timing deviation value Δθ read this time and the basic injection timing θb
, A final target injection timing θ as a command value for injection timing control is calculated. That is, the basic injection timing θb
Is corrected by the injection timing deviation value Δθ to obtain the final target injection timing θ.

At step 940, the timer device 2 is set based on the obtained final target injection timing θ.
6 is controlled. That is, in order to control the fuel injection timing from the fuel injection nozzle 4 to the advance side or the retard side, the TCV 33
Is controlled based on the final target injection timing θ.
Thereafter, the processing of this routine is temporarily terminated.

As described above, according to the fuel injection timing control of this embodiment, each time the fuel injection is executed, the injection start time ts at which the injection is actually started becomes equal to the fuel pressure P. Required based on. Further, a difference between the injection start time ts and the target injection timing θo at that time is obtained as an injection timing deviation value Δθ. Further, the basic injection timing θb at that time is corrected by the injection timing deviation value Δθ to obtain the final target injection timing θ, and the fuel injection timing control is executed based on the final target injection timing θ. That is, the fuel injection timing control is performed such that the actual injection start time ts matches the target injection timing θo.

Therefore, in this embodiment, even if the components and the like of the fuel injection pump 1 change over time, if there is a manufacturing error in the components and the like, or if the fuel properties change, the fuel injection pump 1 will not change every time. Each time the fuel injection is performed, the fuel injection timing is controlled such that the actual injection start time ts coincides with the target injection timing θo. As a result, high-precision fuel injection timing control can be stabilized for a long period of time without being affected by temporal changes or manufacturing errors of components of the fuel injection pump 1 or changes in fuel properties. Further, it is possible to realize highly accurate fuel injection timing control adapted to the current operation state, and to increase nitrogen oxides (NOx) discharged from the diesel engine 3 and knock noise in the diesel engine 3. Can be greatly reduced.
Further, it is possible to suppress an increase in white smoke emitted from the diesel engine 3 and a deterioration in fuel efficiency in the diesel engine 3, and to reduce hydrocarbons (HC) emitted from the diesel engine 3. Can be.

Further, in this embodiment, the waveform of the fuel pressure P obtained by the pressure sensor 47 is monitored in order to obtain a more accurate injection start time ts. Also, the fuel pressure P
During the process of increasing the first time, the time point at which the first derivative value (dPi / dti) first changes from positive to negative is determined. Here, the point where the one-time differential value (dPi / dti) of the fuel pressure P first changes from positive to negative corresponds to a portion where the fuel pressure P decreases momentarily due to the start of fuel injection. Have been. Then, the first derivative of the fuel pressure P (dP
It has been confirmed that the point in time at which i / dti) changes from positive to negative means an inflection point A when the fuel pressure P first drops only for a moment while increasing to some extent.

Therefore, the fuel injection start timing is specifically specified as the inflection point A of the fuel pressure P based on the change in the first derivative (dPi / dti) together with the change in the fuel pressure P. The determination of the fuel injection start timing is performed while eliminating the influence of noise or the like.

As a result, in the diesel engine 3 having the fuel injection pump 1 and the fuel injection nozzle 4, etc., the fuel injection start timing at the time of the fuel injection is not affected by the aging of the fuel system and the manufacturing error. Can be determined more accurately. Therefore, the injection start time ts used for controlling the timing at which fuel is actually injected from the fuel injection nozzle 4 to the target injection timing θo can be more accurately obtained.

In this embodiment, in order to determine the fuel injection start timing from the change in the fuel pressure P and its one-time differential value (dPi / dti), as shown in step 803 of the “Δθ calculation routine” , One-time differential value (dPi / dti)
Is greater than the threshold value d1 and the reference time T1 has elapsed. In addition, as shown in step 806, it is determined that the one-time differential value (dPi / dti) has fallen below the threshold value d2 and the reference time T2 has elapsed. Therefore, even if the waveform of the fuel pressure P slightly changes due to noise, the change is not erroneously determined as the inflection point A of the fuel pressure P corresponding to the start of fuel injection. Therefore, the fuel injection start timing can be more accurately determined from this.

The present invention is not limited to the above embodiments, but may be implemented as follows, with a part of the configuration being appropriately changed without departing from the spirit of the invention. (1) In each of the above embodiments, the pressure sensor 47 is provided for each fuel injection nozzle 4 of each cylinder. However, the pressure sensor may be provided in the middle of a fuel pipe leading to each fuel injection nozzle.

(2) In each of the above embodiments, the pressure sensor 47
Is provided in each fuel injection nozzle 4 of each cylinder to detect the fuel pressure P applied to each fuel injection nozzle 4 respectively. However, one pressure sensor is provided in the fuel injection pump and the fuel pressure P in the plunger high pressure chamber is provided. May be configured to be detected. In this case, only one pressure sensor needs to be used, and the number of components can be reduced.

(3) In each of the above embodiments, the lift sensor 4
Although 8 is provided for each fuel injection nozzle 4 together with the pressure sensor 47 to detect the needle valve lift amount L of the nozzle 4, the lift sensor 48 can be omitted.

However, when the lift sensor 48 is omitted, the elapsed time from the injection start time ts is monitored instead of the needle valve lift amount Li actually obtained at each time ti.
Then, the lift coefficient with respect to the elapsed time is referred to from the map, the injection amount Qi at each time point is obtained based on the lift coefficient and the fuel pressure, and the actual injection amount Qr may be obtained. Alternatively, with the lift coefficient being a constant, the injection amount Q at each time is determined based on the lift coefficient and each fuel pressure.
i may be determined, and the actual injection amount Qr may be further determined.

(4) In the first and second embodiments, the injection amount Qi at each point in time is obtained based on the lift coefficient KLi and the fuel pressure Pi at each time ti according to the equation of Qi = KLi * √Pi. However, the method of calculating the injection quantity Qi at each time is not limited to the above formula.

(5) In each of the above embodiments, the fuel injection start timing detecting device is embodied in an electronically controlled diesel engine of an automobile. However, the fuel injection start timing detecting device may be embodied in a high-pressure gasoline injection engine. .

[0131]

As described above in detail, according to the present invention, the pressure of fuel fed from the fuel injection pump to the fuel injection nozzle is detected, and the rate of change of the fuel pressure is calculated based on the detection result. ing. Further, based on the calculation result, a point in time at which the rate of increase first changes from positive to negative during the process of increasing the fuel pressure is determined, and it is determined that it is time to start fuel injection from the fuel injection nozzle. Accordingly, the fuel injection start timing is specifically specified as an inflection point of the fuel pressure, and the determination of the fuel injection start timing is performed without the influence of noise or the like. As a result, in the internal combustion engine equipped with the fuel injection pump and the fuel injection nozzle, an excellent effect that the fuel injection start timing can be more accurately obtained without being affected by the aging of the fuel system, manufacturing errors, and the like. Demonstrate.

[Brief description of the drawings]

FIG. 1 is a conceptual configuration diagram illustrating a basic conceptual configuration of the present invention.

FIG. 2 is a schematic configuration diagram showing a supercharged diesel engine system according to a first embodiment of the present invention.

FIG. 3 is a sectional view showing a distribution type fuel injection pump according to the first embodiment.

FIG. 4 is a diagram showing a pressure sensor and a lift sensor provided in a fuel injection nozzle in the first embodiment.

FIG. 5 is a block diagram showing a configuration of an ECU in the first embodiment.

FIG. 6 is a flowchart showing processing of a “subroutine” executed by an ECU in the first embodiment.

FIG. 7 is a flowchart illustrating a process of a “ΔQ calculation routine” executed by the ECU in the first embodiment.

FIG. 8 is a map in which the relationship between the lift amount of the needle valve and the lift coefficient is determined in advance in the first embodiment.

FIG. 9 is a time chart illustrating behaviors of an injection start time, an injection end time, a fuel pressure, a one-time differential value, and an actual injection amount, which are obtained at the time of one fuel injection in the first embodiment.

FIG. 10 is a flowchart illustrating a process of a “fuel injection amount control routine” executed by an ECU in the first embodiment.

FIG. 11 shows a second embodiment of the present invention.
5 is a flowchart illustrating a “subroutine” process executed by the ECU.

FIG. 12 is a flowchart illustrating processing of a “ts, Ps calculation routine” executed by the ECU in the second embodiment.

FIG. 13 is a flowchart illustrating a process of a “fuel injection amount control routine” executed by an ECU in the second embodiment.

FIG. 14 shows an injection start time, an injection end time, a fuel pressure, a first derivative,
5 is a time chart for explaining the actual injection amount and the behavior of the electromagnetic spill valve.

FIG. 15 shows a third embodiment of the present invention.
5 is a flowchart illustrating a “subroutine” process executed by the ECU.

FIG. 16 is a flowchart illustrating a process of a “Δθ calculation routine” executed by the ECU in the third embodiment.

FIG. 17 is a flowchart showing a process of a “fuel injection timing control routine” executed by the ECU in the third embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fuel injection pump, 3 ... Diesel engine as an internal combustion engine, 4 ... Fuel injection nozzle, 47 ... Pressure sensor as fuel pressure detecting means, 71 ... ECU constituting fuel pressure change rate calculating means and injection start timing determining means .

Continuing from the front page (72) Inventor Takeshi Sato 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Akihiro Yamanaka 1 Toyota Town Toyota City, Aichi Prefecture Toyota Motor Corporation (56) Reference Document JP-A-58-70028 (JP, A) JP-A-58-72626 (JP, A) Jpn. Pat. Appln. KOKAI Publication No. 57-73339 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 45/00 F02D 41/02 F02D 41/20 F02D 41/40 F02M 65/00

Claims (1)

(57) [Claims] 1. A fuel injection nozzle for injecting fuel into an internal combustion engine by obtaining a fuel pressure equal to or higher than a predetermined level, a fuel injection pump for pumping fuel to the fuel injection nozzle, and from the fuel injection pump to the fuel injection nozzle Fuel pressure detecting means for detecting the pressure of the fuel to be pumped; fuel pressure change rate calculating means for calculating a fuel pressure change rate based on the detection result of the fuel pressure detecting means; and fuel pressure change rate calculating means. Injection start timing for determining the time at which the rate of increase of the fuel pressure first changes from positive to negative during the process of increasing the fuel pressure based on the calculation result and determining that it is time to start fuel injection from the fuel injection nozzle A fuel injection start timing detecting device for an internal combustion engine, comprising: a determination unit.