JP2827742B2 - Fuel injection timing control 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 having a fuel injection pump and a fuel injection nozzle, and more particularly, to a fuel injection for controlling fuel injection timing in response to a change in valve opening pressure at the fuel injection nozzle. The present invention relates to a timing control device.

[0002]

2. Description of the Related Art Conventionally, in an electronically controlled diesel engine, for example, as an internal combustion engine having a fuel injection pump and a fuel injection nozzle, fuel in a high-pressure chamber is pressure-fed to the fuel injection nozzle by a lift of a plunger in the fuel injection pump. And injected into each cylinder of the engine. And
The drive of a timer device provided in the fuel injection pump is controlled such that the fuel injection timing at that time becomes a target injection timing determined according to the engine operating state. By this control, the injection timing of the fuel injected from the fuel injection nozzle to each cylinder is controlled.

[0003] By the way, even in an electronically controlled diesel engine in which the fuel injection timing is controlled as described above,
The fuel injection nozzle is generally a mere mechanical automatic valve. Since the fuel injection nozzle is a mechanical automatic valve, there is a possibility that the actual fuel injection timing and the fuel injection amount from the nozzle may change due to the temporal decrease of the valve opening pressure. . That is, this type of fuel injection nozzle includes a needle valve and a spring for adjusting the valve opening pressure of the needle valve, and is opened by obtaining a fuel pressure equal to or higher than a predetermined level. The valve opening pressure of the needle valve is adjusted in advance to a constant value by a spring. Then, when the force of the spring is weakened due to the temporal change of the fuel injection nozzle, the valve opening pressure of the needle valve has become smaller than the set pressure initially set.

In the production of a fuel injection nozzle,
A slight manufacturing error may occur, in which case the valve opening pressure may differ from the initially set pressure.

Therefore, as described above, when the valve opening pressure differs from the initially set pressure due to aging or manufacturing error, the fuel injection timing from the fuel injection nozzle is changed. It will be shifted to the advance side or the retard side. As a result, smoke from the diesel engine, an increase in nitrogen oxides (NOx), or an increase in knock noise may be caused. In addition, the fuel consumption of diesel engines deteriorates and the amount of white smoke increases.
May be increased.

Therefore, as a technology capable of coping with the above-mentioned problems, Japanese Patent Application Laid-Open No.
No. 242, “Method of controlling fuel injection timing of diesel engine” can be cited as an example.
In this conventional technique, in the idle state of the diesel engine, a fuel injection amount required to control the engine speed to a desired idle speed is calculated. Further, a control value (ISC control value) of the valve opening timing of the fuel injection nozzle required to obtain the calculated fuel injection amount is calculated. Then, the fuel injection timing is corrected according to the deviation obtained from the ISC control value. According to this method, the fuel injection timing is appropriately corrected in accordance with the aging of the fuel injection nozzle and the manufacturing error.

[0007]

However, in the above-mentioned prior art, the fuel injection timing is corrected based on the ISC control value required to maintain the idle rotation speed at a desired target rotation speed. Therefore, in order to properly correct the fuel injection timing, it is necessary to use the ISC control value obtained in the idling stable state where there is little change in the idling rotational speed. For this reason, at the time of starting a diesel engine that is not stable in an idle state, for example, it has not been possible to execute appropriate correction of the fuel injection timing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has as its object to deal with a change with time of a fuel injection nozzle and a change in valve opening pressure caused by a manufacturing error, thereby achieving high-precision fuel injection. An object of the present invention is to provide a fuel injection timing control device for an internal combustion engine that can perform timing control from the start of the internal combustion engine.

[0009]

In order to achieve the above object, according to the present invention, as shown in FIG. 1, a fuel is opened by obtaining a fuel pressure higher than a predetermined level and injecting fuel into an internal combustion engine M1. Injection nozzle M2, and fuel injection pump M driven and controlled to pump fuel to fuel injection nozzle M2
3, a valve opening pressure detecting means M4 for detecting the fuel pressure when the fuel injection nozzle M2 is opened as a valve opening pressure, and a fuel injection pump based on a change in the valve opening pressure based on the detection result of the valve opening pressure detecting means M4. A residual fuel amount change amount calculating means M6 for calculating a change amount of the residual fuel amount in the fuel system M5 from M3 to the fuel injection nozzle M2, and a fuel injection pump M3
And a calculation result of the residual fuel amount change amount calculating means M6 for calculating a change amount of the residual fuel amount in the fuel system M5 from the fuel injection nozzle M2 to the fuel injection nozzle M2. Injection timing control amount calculating means M7 for calculating the target injection timing control amount by reflecting the target injection timing on the target injection timing
And the calculation result of the injection timing control amount calculation means M7,
The gist of the invention is to include an injection timing control means M8 for controlling the fuel injection timing by driving and controlling the fuel injection pump M3.

[0010]

According to the above construction, as shown in FIG. 1, when fuel is pumped from the fuel injection pump M3 to the fuel injection nozzle M2, the valve opening pressure detecting means M4 uses the fuel injection nozzle M2.
The fuel pressure at the time of opening the valve 2 is detected as the valve opening pressure. The residual fuel amount change amount calculating means M6 calculates the residual fuel amount in the fuel system M5 from the fuel injection pump M3 to the fuel injection nozzle M2 based on the change in the valve opening pressure based on the detection result of the valve opening pressure detecting means M4. The amount of change is calculated. Here, it is known that the amount of change in the residual fuel amount in the fuel system M5 differs depending on the valve opening pressure and the like in the fuel injection nozzle M2. It is also known that the fuel injection timing from the fuel injection nozzle M2 changes due to the difference in the amount of change in the residual fuel amount. Then, the injection timing control amount calculating means M7 calculates the target injection timing control amount by reflecting the calculated change amount of the residual fuel amount on the target injection timing for the next fuel injection. That is, the target injection timing is corrected based on the amount of change in the residual fuel amount affected by the change in the valve opening pressure. In the injection timing control means M8, the drive of the fuel injection pump M3 is controlled based on the calculated target injection timing control amount, and the fuel is pressure-fed to the fuel injection nozzle M2 through the fuel system M5.

Therefore, in the injection timing of the fuel that is pumped from the fuel injection pump M3 to the fuel injection nozzle M2 in each fuel injection, a change in the residual fuel amount due to a change in the valve opening pressure is considered. The effect of the change in fuel quantity has been eliminated. Therefore, without waiting for the internal combustion engine M1 to enter a special operating state, for example, an idling stable state,
The fuel injection timing is controlled according to the change in the valve opening pressure of the fuel injection nozzle M2.

[0012]

【Example】

(First Embodiment) A first embodiment in which the fuel injection timing control apparatus 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 configuration of a diesel engine system with a supercharger in this embodiment, and FIG. 3 shows the distribution type fuel injection pump 1 in an enlarged manner. 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, the fuel injected from the fuel injection pump 1 applies a fuel pressure P equal to or higher than a predetermined level to the fuel injection nozzle 4, whereby fuel is injected from the nozzle 4 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.

In the pump housing 13 of this embodiment, a delivery valve 3 composed of a constant pressure valve (CPV) is provided at the outlet side of each distribution passage 18.
6 are provided. The delivery valve 36 is for preventing the backflow of the fuel pressure-fed from the distribution passage 18 to the fuel pipe 4a, and is opened by obtaining a fuel pressure P of a certain level or more. .

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.

As the control oil pressure of the timer device 26, the fuel pressure inside the fuel injection pump 1 is used. To adjust the fuel pressure, the timer device 26 is provided with a timer control valve (TCV) 33. That is, a communication path 34 is provided between the pressurizing chamber 30 and the low-pressure chamber 29 of the timer housing 27, and the communication path 34
The TCV 33 is provided in the middle of. 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 valve opening pressure detecting means. The pressure sensor 47 detects the pressure of the fuel fed from the fuel injection pump 1 to each of the fuel injection nozzles 4, that is, the fuel pressure P, and also detects the fuel pressure P when the nozzles 4 are opened. A signal corresponding to the magnitude is output.

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 residual fuel amount change amount calculating means, a target injection timing control amount calculating means, and an injection timing control means.
1 includes the above-described sensors 72 to 77 and the rotation speed sensor 35.
And the pressure sensor 47 are connected to each other. E
The CU 71, based on each signal output from each of the sensors 35, 47, 72 to 77, uses the electromagnetic spill valve 23, the TCV 33,
Glow plug 46, EVRV58 and VSV64,6
5 and the like 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-mentioned intake air temperature sensor 72, accelerator sensor 73, intake air pressure sensor 74, water temperature sensor 75 and pressure sensor 47.
9, 90, 91, 92, multiplexer 94 and A / D
It is connected via a converter 95. Similarly, the input port 85 is connected to the above-described rotation speed sensor 35, crank angle sensor 76, and vehicle speed sensor 77 via a waveform shaping circuit 96. Then, the CPU 81 controls each of the sensors 35, 47, 72 to 7 input through the input port 85.
7 are read as input values. or,
The output port 86 is connected to each of the driving circuits 97, 98, 99, 10
Electromagnetic spill valve 23, TCV via 0, 101, 102
33, glow plug 46, EVRV58 and each VSV6
4, 65, etc. are connected. Then, the CPU 81 suitably controls the electromagnetic spill valve 23, the TCV 33, the glow plug 46, the EVRV 58, and the VSVs 64, 65 based on the input values read from the sensors 35, 47, 72 to 77, respectively.

In this embodiment, the CPU 81 has a timer function. Also, in this embodiment,
The glow plug 46 and the pressure sensor 47 are provided for each cylinder of the diesel engine 3.
Only one of them is shown in the block diagram of FIG.

Next, a processing operation for fuel injection timing control executed by the above-described ECU 71 will be described with reference to FIGS. 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 is sampled based on the signal from the pressure sensor 47. Subsequently, in step 120, the fuel pressure Pi at the time ti at that time is calculated.

Next, in step 130, 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 140, 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 150, 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-described "subroutine" processing, each time one fuel injection is executed, the fuel pressure Pi corresponding to each time ti 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 calculation data.

FIG. 7 shows “ts, ts,” for calculating the injection start time ts and the injection start pressure Ps used for controlling the fuel injection amount, among the processes executed by the ECU 71.
Is a flowchart showing processing of a "Ps calculation routine", which is periodically executed at predetermined time intervals.

When the process proceeds to this routine, first, at step 210, 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 220, 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 210 and repeats the processes of steps 210 and 220.
If the fuel pressure Pi is higher than the previous fuel pressure P (i-1) in step 220, it is determined that the fuel pressure P is in the process of increasing and the process proceeds to step 230.

In step 230, it is determined whether or not the once-differentiated value (dPi / dti) read this time exceeds 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 210 and repeats the processing of steps 210 to 230. Step 23
At 0, 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 in the process of increasing the fuel pressure P to start fuel injection, and step 240 is performed. Move to.

Then, in step 240, 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, at step 250, it is determined whether or not the currently read second derivative (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 dropped significantly, and the routine jumps to step 240, where it jumps to step 240. Step 250 is repeated. On the other hand, in step 250, 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 260.

Then, in step 260, the once-differentiated value (dPi / dti) read this time falls below a predetermined threshold value d2 on the negative side and 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 240 and repeats the processing of steps 240 to 260. Step 26
At 0, 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 270 assuming that the change in the fuel pressure P has definitely decreased.

In step 270, 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 surely 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 280, at the time ti when the one-time differential value (dPi / dti) becomes “0” in the retrieved calculation data, the time ti is determined by the fuel injection nozzle 4 from the fuel injection nozzle 4. Is started, that is, when the needle valve is opened, and the time ti is set as the injection start time ts. Further, the fuel pressure Pi at the time ti is set as the injection start pressure Ps.

Therefore, according to the processing of the "ts, Ps calculation routine" described above, every time one fuel injection is executed, the injection start time ts and the injection start pressure Ps at that time are executed.
Is temporarily stored in the RAM 83.

Here, the injection start time ts, the injection start pressure Ps, the fuel pressure P, and the one-time differential value (dPi / dti) obtained at the time of one fuel injection by the processing of the above “ts, Ps calculation routine”. An example of the behavior 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 to move forward during fuel injection, the fuel pressure P starts increasing 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. .

In this embodiment, the following fuel injection control is executed using the injection start pressure Ps at the injection start time ts obtained as described above. That is, FIG. 9 is a flowchart showing the processing of the "fuel injection control routine" performed using the above-described injection start pressure Ps among the processing performed by the ECU 71, and is periodically performed at predetermined intervals. .

When the process proceeds to this routine, first, at step 300, 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.
Further, the target injection amount Q0 used in the previous fuel injection is read.

Subsequently, in step 310, it is determined whether or not the current operation state of the diesel engine 3 is in the injection amount feedback (FB) execution region. The determination of the injection amount FB execution region is performed with reference to a map predetermined as shown in FIG. 10 based on the relationship between the engine speed NE and the previous target injection amount Q0. That is, in this map, the injection amount FB is set to be in the low-rotation / low-load region. If it is determined in step 310 that the injection amount is in the FB execution region, step 3
Then, the process goes to step 20 to execute the processing of step 320 and step 330.

That is, in step 320, "t
s, Ps calculation routine "and reads and stores the injection start pressure Ps. Also, the injection start pressure Ps
Is set as the actual fuel pressure when the fuel injection nozzle 4 is opened, that is, the actual valve opening pressure Pnr.

Next, at step 330, the actual valve opening pressure Pn is calculated based on the calculated actual valve opening pressure Pnr and the like.
A change amount (remaining fuel amount change amount) Qre of the remaining fuel amount to be changed according to the difference of r is predicted and calculated. The calculation of the residual fuel amount change amount Qre is performed according to the following formula.

Qre = Vi * ε * (Pns−Pnr) = Vi * ε * ΔPn Here, “Vi” means a volume volume of the fuel system from the fuel injection pump 1 to the fuel injection nozzle 4, and “ε”. Represents the bulk modulus of the fuel, and “Pns” represents the standard valve opening pressure as the reference pressure in the standard state of the fuel injection nozzle 4. Therefore, in the above formula, the residual fuel amount change amount Qre in the fuel system is predicted and calculated based on the valve opening pressure deviation ΔPn which is the difference between the standard valve opening pressure Pns and the actual valve opening pressure Pnr. Here, it is known that the change amount Qre of the residual fuel amount in the fuel system changes due to the difference in the actual valve opening pressure Pnr in the fuel injection nozzle 4. It is also known that the amount of fuel injection from the fuel injection nozzle 4 and the timing of fuel injection change due to the difference in the amount of change Qre of the residual fuel amount.

On the other hand, if it is determined in step 310 that the injection amount is not in the FB execution region, the process proceeds from step 310 to step 340. In step 340 after shifting from step 310 or step 330, a target injection amount Q1 according to the current operating state is calculated based on the engine speed NE, the accelerator opening ACCP, and the like. In this embodiment, the basic injection amount is obtained based on the engine speed NE, the accelerator opening ACCP, and the like, and the correction injection amount is added to the basic injection amount as necessary, thereby obtaining the target injection amount Q1. Examples of the correction injection amount include a cold correction injection amount obtained based on the cooling water temperature THW.

Further, at step 350, the latest residual fuel amount change amount Q is calculated from the target injection amount Q1 obtained this time.
The result obtained by subtracting re is set as the corrected target injection amount Q for the next fuel injection. In other words, the target injection amount Q determined by the operation state of the diesel engine 3
The fuel amount obtained by subtracting the residual injection amount change amount Qre in the fuel system from 1 is obtained as the corrected target injection amount Q. Here, in the case of the injection amount FB execution region,
The residual injection amount change amount Qre obtained this time is adopted for the above subtraction. In addition, when the injection amount is not in the FB execution region, a learning value of the residual injection amount change amount Qre previously learned is adopted.

Next, at step 360, the result obtained by dividing the latest residual fuel amount change amount Qre by the pump injection rate Ri is set as the target injection timing control amount ΔT. here,
The pump injection rate Ri is a constant peculiar to the fuel injection pump 1, and is a value experimentally obtained in advance. This step 3
Also in the case of 60, if the injection amount FB is in the execution range similarly to the above, the residual injection amount change amount Qre obtained this time is adopted for the above division. In addition, when the injection amount is not in the FB execution region, a learning value of the residual injection amount change amount Qre previously learned is adopted.

In step 370, the target injection timing control amount ΔT set in step 360 is set.
, The fuel injection timing control is executed by controlling the timer device 26. That is, the TCV 33 controls the fuel injection timing from the fuel injection nozzle 4 to advance or retard.
Is controlled based on the target injection timing control amount ΔT.

Subsequently, in step 380, fuel injection is executed based on the corrected target injection amount Q obtained this time. That is, based on the corrected target injection amount Q, the electromagnetic spill valve 2
By controlling 3, the fuel pumping from the fuel injection pump 1 to the fuel injection nozzle 4 is controlled, thereby controlling the fuel injection amount from the fuel injection nozzle 4.

Further, in step 390, the corrected 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. Thus, the fuel injection amount control and the fuel injection timing control are executed. As described above, according to the fuel injection control of this embodiment, when the operation state of the diesel engine 3 is in the injection amount FB execution region, the residual fuel amount change amount Qre in the fuel system is determined by the actual target injection timing. The fuel injection timing control and the fuel injection amount control are executed by feeding back to the control amount ΔT and the target injection amount Q1. That is,
When the current fuel injection is performed, the latest residual fuel amount change amount Qre is determined by the actual valve opening pressure P at the fuel injection nozzle 4.
It is determined based on nr. Then, a result obtained by dividing the change amount Qre of the residual fuel amount at that time by the pump injection rate Ri is set as a target injection timing control amount ΔT, and the fuel injection timing is advanced or retarded based on the target injection timing control amount ΔT. Controlled to the side. That is, the fuel injection timing is corrected based on the residual fuel amount change amount Qre, and the fuel injection timing control is executed. Further, a result obtained by subtracting the residual fuel amount change amount Qre from the target injection amount Q1 obtained according to the operating state is set as the corrected target injection amount Q, and the fuel injection is executed based on the corrected target injection amount Q. You. That is, the target injection amount Q1 is corrected by the residual fuel amount Qre in the fuel system, and the fuel injection amount control is executed.

Therefore, the change in the residual fuel amount due to the change in the valve opening pressure is taken into account in the injection timing and the injection amount of the fuel that is pumped from the fuel injection pump 1 to the fuel injection nozzle 4 in each fuel injection. Therefore, the effect of the change in the residual fuel amount is eliminated. Therefore, unlike the related art in which the fuel injection timing cannot be controlled until the idle stable state is reached, even when the diesel engine 3 is started, the actual valve opening pressure Pnr due to a change with time or a manufacturing error in the fuel injection nozzle 4 is reduced. It is possible to execute highly accurate fuel injection timing control and highly accurate fuel injection amount control without being affected by the change. As a result, an increase in smoke and nitrogen oxides (NOx) from the diesel engine 3 or an occurrence of knocking noise can be suppressed. Further, it is possible to suppress deterioration of fuel efficiency of the diesel engine 3, increase of white smoke, increase of hydrocarbon (HC), and the like.

In this embodiment, the fuel injection nozzle 4
The valve opening pressure of the fuel injection nozzle 4 is not adjusted in order to control the fuel injection amount from the fuel injection amount according to the current operation state. It has been adjusted. As a result, it is possible to eliminate the need for providing a special means for adjusting the valve opening pressure in the fuel injection nozzle 4.

In this embodiment, no special means for adjusting the valve opening pressure of the fuel injection nozzle 4 is provided.
The mechanism is not complicated by that much, and there is no need to provide a special control program for the means.

Further, in this embodiment, when determining the actual valve opening pressure Pnr of the fuel injection nozzle 4, the pressure sensor 4
The waveform of the fuel pressure P obtained from 7 is monitored. Further, during the process of increasing the fuel pressure P, the differential value (dPi / d
The point in time when ti) first changes from positive to negative is determined. Here, the first derivative of the fuel pressure P (dPi / dt)
It has been confirmed that the point where i) changes from positive to negative for the first time corresponds to a portion where the fuel pressure P drops momentarily due to the start of fuel injection. The point in time when the first differential value (dPi / dti) of the fuel pressure P changes from positive to negative means that the fuel pressure P has increased to some extent,
First, it has been confirmed that it means the inflection point A at the time of a momentary drop.

Accordingly, the injection start time ts is determined based on the change in the first derivative (dPi / dti) together with the change in the fuel pressure P, and the injection start pressure Ps at that time, that is, the actual valve opening pressure Pnr is determined by the fuel pressure. The inflection point A of P is specifically specified, and the actual valve opening pressure Pnr is eliminated by eliminating the influence of noise and the like.
Is determined.

As a result, the actual valve opening pressure Pnr at the fuel injection nozzle 4 can be obtained more accurately. Therefore, the residual fuel amount change amount Qre obtained based on the actual valve opening pressure Pnr can be more accurately obtained, and the target injection timing control amount ΔT and the corrected target injection amount Q can be obtained more accurately. In this sense, the fuel injection timing control and the fuel injection amount control can be performed with higher accuracy.

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), the "ts, Ps calculation routine" of FIG. 7 is executed. As described above, the first derivative (d
Pi / dti) exceeds threshold value d1, and it is determined that reference time T1 has elapsed. At the same time, the first derivative (d
Pi / dti) falls below the threshold value d2 and the reference time T2
Is determined to have passed. 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, from this, it is possible to more accurately determine the injection start time ts and the injection start pressure Ps, and thus the actual valve opening pressure Pnr.

(Second Embodiment) Next, a second embodiment in which the fuel injection timing control 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 FIG. In this embodiment, the configuration 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 and described. Omitted. Hereinafter, a processing operation of the fuel injection control which is particularly different from the first embodiment will be described.

In this embodiment, among the processing executed by the ECU 71, the following fuel injection control is executed by using the injection start time ts obtained in the first embodiment. That is, FIG. 11 is a flowchart showing the processing of the “fuel injection control routine” performed using the above-described injection start time ts among the processing performed by the ECU 71, and is periodically performed at predetermined intervals. .

When the processing shifts to this routine, first, at step 400, 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.
Further, the target injection amount Q0 used in the previous fuel injection is read.

Subsequently, at step 410, it is determined whether or not the current operation state of the diesel engine 3 is in the injection amount feedback (FB) execution region. The determination of the injection amount FB execution region is performed in the same manner as in the first embodiment.
This is performed by referring to a map that is predetermined based on the relationship between the engine speed NE and the previous target injection amount Q0 as shown in FIG. That is, in this map, the injection amount FB is set to be in the low-rotation / low-load region. If it is determined in step 410 that the injection amount FB is in the execution area, the process proceeds to step 420, and step 420 is performed.
And the processing of step 430 is executed.

That is, in step 420, "t
s, Ps calculation routine ", and reads the stored injection start time ts. In addition, the injection start time ts
Is set as the actual fuel injection timing when the fuel injection nozzle 4 is opened, that is, the actual valve opening timing tnr.

Next, at step 430, the actual valve opening timing tn is calculated based on the calculated actual valve opening timing tnr and the like.
A change amount (remaining fuel amount change amount) Qre of the remaining fuel amount to be changed according to the difference of r is predicted and calculated. The calculation of the residual fuel amount change amount Qre is performed according to the following formula.

Qre = X * (tns−tnr) = X * Δtn Here, “X” represents a correction coefficient, and “tns” represents a standard valve opening timing as a reference timing in the standard state of the fuel injection nozzle 4. Means. Therefore, in the above formula,
Based on the valve opening timing deviation Δtn, which is the difference between the standard valve opening timing tns and the actual valve opening timing tnr, the residual fuel amount variation Qre in the fuel system is predicted and calculated. Here, it is known that the residual fuel amount change amount Qre in the fuel system changes due to the difference in the actual valve opening timing tnr in the fuel injection nozzle 4. It is also known that the amount of fuel injection from the fuel injection nozzle 4 and the timing of fuel injection change due to the difference in the amount of change Qre of the residual fuel amount.

On the other hand, if it is determined in step 410 that it is not in the injection amount FB execution region, the process proceeds from step 410 to step 440. In step 440 after shifting from step 410 or step 430, the target injection according to the current operating state is performed based on the engine speed NE, the accelerator opening ACCP, and the like, as described in step 340 of the first embodiment. Calculate the quantity Q1.

Also, in steps 450 to 490, steps 350 to 3 of the first embodiment are performed.
As described in 90, the fuel injection timing control and the fuel injection amount control are executed based on the residual fuel amount change amount Qre or the like calculated in step 430.

As described above, in the fuel injection control of this embodiment, similarly to the first embodiment, when the operation state of the diesel engine 3 is in the injection amount FB execution region, the fuel injection control in the fuel system is performed. The fuel injection timing control and the fuel injection amount control are executed by feeding back the residual fuel amount change amount Qre to the actual target injection timing control amount ΔT and the target injection amount Q1. However, when the current fuel injection is performed, the latest residual fuel amount change amount Qre is a valve opening timing deviation Δtn that is a difference between the standard standard valve opening timing tns and the actual valve opening timing tnr at the fuel injection nozzle 4. This is greatly different from the first embodiment in that it is obtained based on That is, in this embodiment, the residual fuel amount change amount Qre is predicted and calculated using the valve opening timing deviation Δtn as a substitute for the valve opening pressure deviation ΔPn in the first embodiment. By calculating the amount of change Qre of the residual fuel amount in this way, the same operation and effect as in the first embodiment can be obtained.

The present invention is not limited to the above-described embodiments, but may be implemented as follows by appropriately changing a part of the configuration without departing from the spirit of the invention. (1) In the first embodiment, the residual fuel amount change amount Qre
Qre = Vi * ε * (Pns−Pnr) = Vi * ε * Δ
It was determined according to a calculation formula such as Pn. Then, the result obtained by dividing the amount of change in residual fuel amount Qre by the pump injection rate Ri is set as the target injection timing control amount ΔT.
On the other hand, as shown in FIG.
The timing correction amount ΔT can be obtained by referring to a map in which the relationship between the timing correction amount ΔT and the timing correction amount ΔT is predetermined.

(2) In the above embodiment, the actual valve opening pressure Pnr
Pressure sensors 47 for detecting fuel pressure are provided at the fuel injection nozzles 4 of the respective cylinders. However, the pressure sensors are provided in the middle of the fuel pipes leading to the fuel injection nozzles, Can also be provided.

(3) In the above embodiment, the present invention is embodied in the diesel engine 3. However, the present invention is not limited to the diesel engine 3 as long as it is an internal combustion engine having a fuel injection pump and a fuel injection nozzle.

(4) In the above embodiment, the "subroutine"
At each time ti every time one fuel injection is executed
First derivative value corresponding to (dPi / dti) and have been adapted to calculating the second order differential value ^{(d 2 Pi / dti 2)} , so as to reduce noise by performing the averaging process is well known in this It may be. In this case, there is an effect that the frequency of erroneous determination can be reduced.

[0090]

As described above in detail, according to the present invention, the amount of change in the amount of residual fuel in the fuel system, which is calculated based on the change in the valve opening pressure when the fuel injection nozzle is opened, is calculated in the next time. The target injection timing control amount is calculated by reflecting the target injection timing control amount for the fuel injection. Then, the drive of the fuel injection pump is controlled based on the target injection timing control amount. Therefore, the effect of the residual fuel amount, which changes due to the difference in the valve opening pressure, is excluded from the injection timing of the fuel that is pumped from the fuel injection pump to the fuel injection nozzle. As a result, there is an excellent effect that high-precision fuel injection timing control can be performed from the start of the internal combustion engine in response to a change in valve opening pressure caused by a temporal change or a manufacturing error of the fuel injection nozzle. .

[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 in the first embodiment.

FIG. 4 is a diagram showing a pressure 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 processing of a “ts, Ps calculation routine” executed by the ECU in the first embodiment.

FIG. 8 is a time chart illustrating behaviors of an injection start time, an injection start pressure, a fuel pressure, and a one-time differential value obtained in one fuel injection in the first embodiment.

FIG. 9 is a flowchart showing a process of a “fuel injection control routine” executed by the ECU in the first embodiment.

FIG. 10 is a map in which an injection amount FB execution region is determined in advance from a relationship between an engine rotation speed and a previous target injection amount in the first embodiment.

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

FIG. 12 shows another embodiment of the present invention.
This is a map referred to in a modification of the method of calculating the target injection timing control amount in the first embodiment, and in which the relationship between the target injection timing control amount and the valve opening pressure deviation is determined in advance.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fuel injection pump, 3 ... Diesel engine as internal combustion engine, 4 ... Fuel injection nozzle, 47 ... Pressure sensor as valve opening pressure detection means, 71 ... Residual fuel amount change amount calculation means, target injection timing control amount calculation means And an ECU constituting injection timing control means.

Continuation of the front page (72) Inventor Shinji Kamoshita 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (56) References JP-A-57-102526 (JP, A) JP-A-4-203441 (JP, A) Fully open sho 64-47944 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 41/00-45/00 395 F02M 65/00 304-306

Claims (1)

(57) [Claims] A fuel injection nozzle that opens when a fuel pressure equal to or higher than a predetermined level is obtained and injects fuel into an internal combustion engine; a fuel injection pump that is driven and controlled to pump fuel to the fuel injection nozzle; Valve opening pressure detecting means for detecting a fuel pressure when the fuel injection nozzle is opened as a valve opening pressure; anda detection result of the valve opening pressure detecting means, wherein the fuel is supplied from the fuel injection pump based on a change in valve opening pressure. A residual fuel amount change amount calculating means for calculating a change amount of the residual fuel amount in the fuel system up to the injection nozzle; and a calculation result of the residual fuel amount change amount calculating means reflected in a target injection timing for the next fuel injection. An injection timing control amount calculating means for calculating a target injection timing control amount by controlling the fuel injection pump based on a calculation result of the injection timing control amount calculating means to set a fuel injection timing. Fuel injection timing control apparatus for an internal combustion engine, characterized in that a Gosuru injection timing control means.