JP2762573B2 - Fuel injection control device for diesel engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a fuel injection control device for a diesel engine.

(Prior art) There is a distribution type fuel injection pump in which the fuel injection timing, fuel injection amount, etc. are electronically controlled. (Reference: SAE Paper 860145 issued in February 1986, and Japanese Utility Model Application Laid-Open No. 63-177638) ).

Referring to FIG. 19, reference numeral 4 denotes a drive shaft connected to an output shaft of an engine (not shown), and reference numeral 2 denotes a vane-type feed pump driven by the drive shaft 4. The sucked fuel is supplied to the pump chamber 5 in the housing 1 and the pump chamber 5
It is sent to the plunger chamber 12 of the plunger pump 3 through the suction passage 6 which opens to the side.

A nail 9a of a face cam 9 fixed to the left end of the plunger 7 is slidably connected in the axial direction to one end (right end in the figure) of the drive shaft 4, and the face cam 9 is
And the plunger 7 are located on the same axis as the drive shaft 4 and the plunger 7 is configured to be displaceable in the axial direction.

On the outer periphery of the connecting portion between the drive shaft 4 and the face cam 9,
A roller holder 10 carrying a plurality of rollers 11 is arranged concentrically with the drive shaft 4, and the face cam 9 is formed with a cam surface 9 b which forms a number of unequal speed cams corresponding to the number of cylinders. The surface 9b is pressed against the roller 11 by a spring 16. Reference numeral 15 denotes a fuel cut valve that closes when the engine is stopped.

The plunger 7 has the same number of suction grooves 8 at its tip as the number of cylinders of the engine, and the cam surface 9b reciprocates by a predetermined cam lift over the roller 11 disposed on the roller holder 10 while rotating together with the drive shaft 4. When it moves, the fuel sucked into the plunger chamber 12 from the suction groove 8 is pumped from the distribution port for each cylinder (not shown) leading to the plunger chamber 12 to the injection nozzle through the delivery valve.

Reference numeral 13 denotes a fuel return passage communicating the plunger chamber 12 with the low-pressure pump chamber 5. The fuel return passage 13 is driven at high speed by a signal (drive pulse) from a drive circuit in accordance with the operating conditions of the engine. A type solenoid valve 14 is interposed. The solenoid valve 14 is provided for fuel control. When the solenoid valve 14 is closed during the compression stroke of the plunger 7, fuel injection starts, and when the solenoid valve 14 is opened, the injection ends. That is, the fuel injection start timing is controlled at the valve closing timing of the solenoid valve 14, and the injection amount is controlled according to the valve closing period.

The solenoid valve 14 is controlled by a control unit (not shown) for inputting various operating condition signals, and a microcomputer is used for the control unit. For example, the optimum injection timing and injection amount corresponding to various engine conditions such as engine speed, accelerator opening, cooling water temperature, fuel temperature, etc. are obtained in advance through experiments and the like, and the values are stored in a ROM or the like in the control unit. It is stored in the element. Then, during actual operation, one pulse (reference pulse) per rotation of the injection pump as shown in FIG.
And 36 pulses per revolution (scale pulse) are input to calculate the engine revolutions N, and in consideration of the revolutions N and the accelerator opening, the cooling water temperature and the fuel temperature are also taken into consideration. The injection timing and the basic injection amount are read, a drive pulse is created from the read information, and output to the solenoid valve 14.

(Problems to be Solved by the Invention) By the way, in recent diesel engines, in order to reduce idle noise, improve exhaust performance and improve output at the same time, the engine is operated at idle or in a low load region and in a high load region. Injection systems having different injection rates have been developed.
As one of the methods, as shown in FIG. 3, in response to a fuel pressure difference between a high-pressure chamber 43 communicating with the pump chamber 5 and a low-pressure chamber 46 communicating with the suction side of the feed pump 2, a face is formed. It is conceivable to provide a timer mechanism (mainly composed of a timer piston 42 and a control valve 51) that can advance and retard the phase of the cam 9 to change the speed use range of the face cam 9.

To explain this, the timer piston 42 responds to the pressure difference between the fuel pressure acting to displace the piston 42 downward in the figure and the sum of the fuel pressure acting on the low-pressure chamber 46 and the resilient force of the timer spring 47. And stop at a position where both forces are balanced.

In this case, the fuel pressure in the high-pressure chamber 43 is adjusted by the control valve 51. That is, the solenoid 52 of the control valve 51 is energized by a control signal from the control unit, and opens the valve body according to the valve opening duty ratio of the control signal. For example, while the control valve 51 is open (at this time, the valve opening duty ratio is 100%), the high-pressure chamber 43 and the low-pressure chamber
Part of the fuel oil 3 flows into the low-pressure chamber 46 and the fuel oil pressure in the high-pressure chamber 43 decreases, whereby the timer piston 42 is displaced upward (to the retard side) in the figure. This displacement causes the connection lever 41
The roller holder 10 rotates in the circumferential direction via the
The contact position between the plunger 7 and the cam surface 9b of the face cam 9 moves, and this movement retards the phase of the reciprocating motion of the plunger 7 with respect to the rotation of the drive shaft 4 (ie, the phase of the face cam 9). On the other hand, when the control valve 51 is closed from this state (the valve opening duty ratio is 0% at this time), the fuel oil from the high-pressure chamber 43 stops flowing out, the fuel oil pressure in the high-pressure chamber 43 increases, and the timer piston 42 is displaced downward (advance angle side) in the figure. Due to this displacement, the phase of the face cam 9 is advanced, which is opposite to the case where the control valve 51 is opened.

In this way, by controlling the magnitude of the fuel oil pressure in the high-pressure chamber 43 according to the valve opening duty ratio given to the control valve 51, the phase of the face cam 9 can be freely adjusted.

FIG. 21 shows the characteristics of the unequal-speed cam. The injection rate increases in a region where the cam speed is high, and conversely, the injection ratio decreases in a region where the cam speed decreases. In order to use a portion having a large cam angle, the face cam 9 should be shifted to the retard side, and conversely, to use a portion having a small cam angle, the face cam 9 should be shifted to the advance side.

Therefore, the injection rate is arbitrarily set according to the phase of the face cam (actually, the position of the timer piston corresponding to the phase). For example, as shown in FIG. 21, at idle and low load, the timer piston position is shifted to the advanced side (3rd
Perform control such that the low injection rate portion is used by greatly displacing it downward (in the figure), and the high injection rate portion is used by displacing the timer piston position to the retard side (upward in FIG. 3) when the load is high. Can be.

In this case, especially during rapid acceleration from idle to full throttle, the face cam is once controlled to the retard side, and then the cam is advanced with the subsequent rotation increase. Since the operation response delay of the timer mechanism is larger than that of the valve 14, the use area of the low injection rate portion becomes longer due to the relative response delay of the timer mechanism at the time of this rapid acceleration from the idle state. If the basic injection amount is set such that the same injection amount is supplied, the injection period becomes longer, and smoke and fuel consumption deteriorate.

The present invention has been made in view of such a conventional problem. While setting the target injection rate, the actual injection rate is detected, and how much response delay is caused according to the deviation between the two injection rates. It is an object of the present invention to provide a device that determines the basic fuel injection amount and corrects the amount according to the degree of the response delay.

(Means for Solving the Problems) As shown in FIG. 1, the present invention provides a feed pump and a plunger pump that rotate in synchronization with engine rotation, and a low-pressure pump chamber formed on the discharge side of the feed pump. A solenoid valve 21 that is opened and closed by a drive pulse is interposed in a fuel return passage that communicates with the plunger chamber of the plunger pump, and a high-pressure chamber into which fuel is introduced from the pump chamber and suction of the feed pump. A fuel injection pump provided with a timer mechanism 22 capable of advancing or retarding the phase of the face cam in response to a fuel pressure difference from the low-pressure chamber into which the fuel on the side is introduced. A fuel injection pump is provided which controls the injection timing and both injections and controls the injection rate during the injection period until the solenoid valve 21 is closed and opened by the timer mechanism 22. A sensor for detecting the condition (for example, engine speed sensor 24 and engine load sensor 25), and means 26, 27 for setting the basic injection timing I _TM and the basic injection amount A _VM respectively in response to the detected value, also detected value Means 28 for setting a target injection rate during the injection period in accordance with the following, means 29 for generating a drive signal corresponding to the target injection rate and outputting this to the timer mechanism 22; a sensor 30 for detecting the injection rate, the means 31 for calculating the decreasing correction amount .DELTA.A _V of the basic injection amount in accordance with the deviation between the detected value and the target injection rate,
Means 32 for reducing the basic injection amount A _VM by this correction amount ΔA _V to determine the injection amount A _V to be output, and the driving based on the determined injection amount A _V and the basic injection timing _ITM. Means 33 for generating a pulse and outputting the pulse to the electromagnetic valve 21 interposed in the fuel return passage.

(Operation) In the case of rapid acceleration from the idle state to the full accelerator, the face cam is controlled to the retard side for a moment, and then the cam is advanced with the subsequent rotation increase. If there is a relative operation response delay of the timer mechanism 22 with respect to the above, the retard control becomes insufficient and the injection amount becomes insufficient. Therefore, even if a relative response delay occurs, a measure to ensure that the same injection amount is supplied is to lengthen the valve closing period of the solenoid valve. The occurrence is remarkable.

On the other hand, according to the present invention, the fuel is reduced by the correction amount ΔA _V, so that the injection is terminated early, thereby preventing the generation of smoke.

(Embodiment) The specific structure of the fuel injection pump shown in FIG. 2 is almost the same as the conventional one, but this injection pump further comprises a timer piston 42 and a control valve 51, and a face cam. A timer mechanism capable of advancing or retarding the phase of No. 9 is provided. Specifically, the roller holder 10 is arranged concentrically with the drive shaft 4 so as to be rotatable within a limited fixed angle range, and the roller holder 10 and the timer piston 22 are connected by a connection lever 41. .

FIG. 3 is a sectional view taken along line XX of FIG.
The high-pressure chamber 43 formed on one end side (upper side in the figure) of the pump chamber 5 is connected to the pump chamber 5 through an oil passage 44 formed in the timer piston 42 and a connection hole 45 between the connection lever 41 and the piston 42. The high-pressure chamber 43 is supplied with a fuel pressure corresponding to the engine speed. On the other hand, a low-pressure chamber 46 formed at the other end of the timer piston 42 communicates with the suction side of the feed pump 2 via an oil passage (not shown). The timer spring 47 biasing toward the 43 side is contracted.

A fuel passage 48 communicating the high-pressure chamber 43 and the low-pressure chamber 46 is provided in the pump housing 1, and a valve 51 capable of controlling a duty ratio is provided in the fuel passage 48. In the pressure control valve 51, when the solenoid 52 is energized, the spool 53
Moves to the right in the figure against the elastic force of the return spring 54 and opens. On the other hand, when the energization of the solenoid 52 is stopped, the spool 53 moves to the left by the elastic force of the return spring 54 and closes.

Here, the pressure difference between the fuel pressure of the high-pressure chamber 43 and the sum of the fuel pressure of the low-pressure chamber 46 and the resilience of the timer spring 47 is:
It is adjusted according to the duty ratio given to the solenoid valve 51 (valve opening time ratio per fixed time), and the vertical displacement of the timer piston 42 changes (as the valve opening duty ratio increases, the downward displacement of the timer piston 42 (advance angle) Side displacement)
Further, as the valve opening duty ratio decreases, the upward displacement (retard side displacement) of the timer piston 42 increases. When the timer piston 42 is displaced in this way,
The roller holder 10 rotates in the circumferential direction via the connecting lever 41, and the contact position between the roller 11 and the cam surface 9b of the face cam 9 moves. With this movement, the phase of the reciprocation of the plunger 7 with respect to the rotation of the drive shaft 4 (the phase of the face cam 9).
Is advanced or retarded. Here, the phase of the face cam 9 is freely controlled by the duty ratio signal to the control valve 51.

The configurations of the injection pump and the timer mechanism up to this point are known.

FIG. 4 is a block diagram of a control system. The control unit is constituted by a microcomputer including an input / output circuit (I / O) 71, a ROM 72, a RAM 73, and a CPU 74, and means 26 to 29, 31 shown in FIG. It has up to 33 functions.

The input / output circuit 41 includes sensors for detecting basic values (engine speed and engine load) of engine operating conditions (sensors 61 and 62 for generating reference pulses and scale pulses, and detecting an accelerator opening as an engine load). The sensor 63 receives signals from other sensors (such as a fuel temperature sensor 64, a coolant temperature sensor 65, and an idle switch 66) for detecting other operating conditions.

Further, 67 is a sensor (DVC sensor) for detecting the actual closing timing and period of the solenoid valve 14, and 68 is a sensor for detecting the position of the timer piston. The signals from these sensors 67 and 68 are also sent to the input / output circuit 71. Is entered. Here, the phase of the face cam is advanced or retarded in accordance with the timer piston position, and this change causes a difference in the cam speed range, that is, the injection rate used during the closing period of the solenoid valve 14. The timer piston position sensor 68 functions as the injection rate sensor 30 in FIG.

The CPU 74 takes in information from the input / output circuit 71 in accordance with the program stored in the ROM 72, performs various arithmetic processes, and controls data (injection timing and injection amount) for controlling the solenoid valve 14 and the control valve 51. Data (timer piston position) is set in the input / output circuit 71. In addition, RA
M73 is used to temporarily save data related to the arithmetic processing of the CPU 74. The input / output circuit 71 outputs a drive pulse to the solenoid valve 14 based on the data output from the CPU 74, and outputs a duty ratio signal (drive signal) to the control valve 51.

 FIG. 5 is a flowchart showing the operation of the CPU 74.

S1 = engine speed N, accelerator opening Acc, cooling water temperature T
_W , fuel temperature _TF , and timer piston position V are read. Note that N is calculated using the reference pulse and the scale pulse.

In S2, according to the values read in S1, the basic injection amount A _{VM of} the fuel, the basic injection timing (basic injection start timing) _ITM, and the target timer piston position _VTM as the target injection rate with reference to the map values. Ask. These map values are shown in FIGS.
Shown in the figure. In the figure,% represents the accelerator opening with respect to the fully opened position. That is, S2 is the setting means 26 in FIG.
It is the part that fulfills the function of ~ 28.

In FIG. 8, the value of the target timer piston position _VTM is, for example, the crank angle from the compression top dead center position TDC to the lift start timing, and has a characteristic that the phase of the face cam is advanced as the engine speed increases. . This takes into account the fact that the ignition delay period in terms of the crank angle increases as the rotational speed increases.

In S3, a deviation ( _VTM- V) between the target timer piston position _VTM and the actual timer piston position V is calculated, and in S4, based on the deviation ( _VTM- V), the reduction correction amount ΔA _V of the basic injection amount is calculated.
Is determined with reference to the map value. This is a part that fulfills the function of the weight loss correction calculating means 31 in FIG.

S5 is a part that fulfills the function of the injection amount determining means 32 in FIG. 1. Here, a value obtained by subtracting the correction amount ΔA _V from the basic injection amount A _{VM is} defined as a determined injection amount A _V (= A _VM −ΔA _V ). Ask. Regarding the injection timing and the timer piston position, the map value is directly used as the determined injection timing _IT (= I _TM ) and the determined timer piston position V _T (= V _TM ) in S5.

If the map value of the correction amount ΔA _V is shown in FIG. 9, a value that increases as the deviation (V _TM -V) increases is given. This is because it is determined that the greater the deviation, the greater the response delay when the face cam is retarded. Furthermore, in this example, the load is enough to increase the reduction correction amount .DELTA.A _V greater. This is because if the load is large, the injection amount is large, and smoke is easily generated accordingly.

The map values shown in FIG. 6 to FIG.
It is stored in M72.

In S6 A _V, and stores each determined value of I _T and V _T at a predetermined address in the RAM73 to end the routine.

Incidentally, the injection end timing I _E from the I _T and A _V is determined, these I _T and I _E is made the drive pulse I / 071 to be transferred.
The V _T is the driving signal is produced is converted to a duty ratio of the control valve 51. That is, I / 071 is the output means 29, 33 in FIG.
Perform the function of

 Here, the operation of the embodiment will be described with reference to FIG.

As shown in FIG. 8, the phase of the face cam is advanced as the rotation speed increases. That is, the face cam is retarded toward the lower rotation speed side. For example, at a low rotation speed close to the idle state, the face cam is retarded to the position indicated by the one-dot chain line in FIG. In this state, a drive pulse indicated by a dashed line is generated, and when the solenoid valve 14 is closed for a predetermined period by the drive pulse, an injection amount determined by the valve closing period and the cam speed at that time is supplied to the engine. .
On the other hand, during idling, the face cam is advanced to the position shown by the solid line as compared to during low rotation in order to reduce the injection rate to reduce noise. For this reason, at the time of sudden acceleration from the idle state to the full accelerator, the single cam is controlled to the retard side to the position shown by the dashed line, and then the cam is advanced as the rotation increases thereafter. .

In this case, if the operation response of the timer piston 42 is relatively poorer than that of the solenoid valve 14, the cam should be retarded to the position shown by the dashed line, but only to the position shown by the broken line. Therefore, if the drive pulse indicated by the dashed line is given even in such a state, the actually supplied injection amount becomes insufficient by the decrease in the cam speed. Therefore, to ensure that the same injection amount is supplied even when the response delay occurs in the timer piston, the countermeasure is to lengthen the valve closing period like the drive pulse shown by the broken line (however, And the drive pulse has the same injection start timing). This lengthened valve closing period is the injection period when _AVM is supplied.

However, if the injection period is lengthened to cover the reduction of the injection rate, the generation of smoke becomes remarkable.

In contrast, according to this example, is the fuel decrease correction amount .DELTA.A _V Deke. Speaking of the drive pulse, a drive pulse indicated by a two-dot chain line is given, thereby preventing generation of smoke.
In other words, in order to supply the same injection amount even if the timer piston 42 has a relative response delay, it is necessary to inject only the basic injection amount _AVM.In this case, smoke reduction is given priority. is there.

Also, the greater the deviation from the target timer piston position _VTM , the more the amount is reduced. In the example of FIG. 10, the illustrated deviation V
ΔA _V is determined according to _TM− V. It should be noted that the method of obtaining the value of _VTM is different from the case of FIG.

As a result, smoke is reduced in accordance with the relative response delay of the timer piston.

Furthermore, even if the load is reduced, if the amount of fuel is reduced, generation of smoke is prevented particularly in a high load region.

FIG. 11 shows another embodiment. In this example, the injection amount is reduced only when the load is full.
It is determined from the accelerator opening Acc whether or not it is at full load.

FIGS. 12 and 13 show another embodiment in which an air-fuel ratio sensor 81 as an excess air ratio sensor is added and based on the air-fuel ratio λ _T in the exhaust gas detected by this sensor 81. Thus, the present invention is applied to a system in which the smoke limit (that is, the maximum injection amount) is feedback-controlled. The output characteristics of this sensor 81 are shown in FIG.

In FIG. 13, the parts different from FIG.
The air-fuel ratio λ _MAP that gives the smoke limit in step 2 is determined with reference to the map values in FIG.

In S14, the smoke limit air-fuel ratio correction amount Δλ is obtained by referring to the map value in FIG. 16 according to the deviation ( _VTM− V) between the target timer piston position _VTM and the actual timer piston position V. This Δλ is an allowable value up to the smoke limit, and if it exceeds this, the smoke limit will be exceeded.

By comparing the air-fuel ratio difference lambda _MAP 1-? _T and Δλ At S15, to determine whether it exceeds the smoke limit, depending on only Δλ when exceeding smoke limit, referring to a map value of FIG. 17 seek weight loss correction amount ΔA _V Te.

Fig. 18 shows the characteristics of the torque and smoke value with respect to the injection amount.In the injection amount region near the smoke limit, even if the injection amount is increased, the torque cannot be expected to increase so much, whereas the smoke value increases sharply. I do. Therefore, by reducing the injection amount near the smoke limit, priority is given to prevention of generation of smoke.

(Effect of the Invention) According to the present invention, a sensor for detecting the actual injection rate is provided, and the injection amount is reduced and corrected in accordance with the detected value of the sensor. Smoke and deterioration of fuel efficiency due to a delay in the operation response of the vehicle.

[Brief description of the drawings]

FIG. 1 is a view corresponding to the claims of the present invention, FIG. 2 is a cross-sectional view of a fuel injection piston of one embodiment, and FIG. 3 is XX of FIG.
FIG. 4 is a block diagram of a control system of this embodiment,
FIG. 5 is a flowchart for explaining the control operation of this embodiment, FIGS. 6 to 9 are characteristic diagrams showing the contents of each map value used in the control operation of FIG. 5, and FIG. FIG. 4 is a waveform chart for explaining the operation of the embodiment. FIG. 11 is a flowchart for explaining a control operation of another embodiment, FIG. 12 is a block diagram of a control system of another embodiment, FIG.
FIG. 13 is a flowchart for explaining the control operation of this embodiment,
FIG. 14 is an output characteristic diagram of the air-fuel ratio sensor, and FIGS.
FIG. 18 is a characteristic diagram showing the contents of each map value used in the control operation of FIG. 13, and FIG. 18 is a characteristic diagram of the torque and the smoke value with respect to the injection amount. FIG. 19 is a sectional view of a conventional injection pump, FIG. 20 is a waveform diagram showing a reference pulse and a scale pulse of the conventional example,
FIG. 21 is a velocity diagram of a conventional non-constant speed cam. 1 ... Pump housing, 3 ... Plunger pump, 5
…… Pump room, 7 …… Plunger, 9 …… Face cam, 12 …… Plunger room, 13 …… Fuel return passage, 14 ……
Solenoid valve, 21 ... Solenoid valve, 22 ... Timer mechanism, 24 ... Engine speed sensor, 25 ... Engine load sensor, 26 ...
Basic injection timing setting means 27 Basic injection amount setting means 28
…… Target injection rate setting means, 29 …… Drive signal output means, 30
…… Injection rate sensor, 31… Reduction amount correction amount calculation means, 32 ……
Injection amount determining means 33 Drive pulse output means 42 Timer piston 43 High pressure chamber 46 Low pressure chamber 47 Timer spring 48 Fuel passage 51 Control valve 61 …
… Reference pulse generation sensor, 62 …… Scale pulse generation sensor, 63 …… Accelerator opening degree sensor, 68 …… Timer piston position sensor, 71 …… Input / output circuit, 72… RO
M, 73 ... RAM, 74 ... CPU, 81 ... Air-fuel ratio sensor.

Claims (1)

(57) [Claims] 1. A feed pump and a plunger pump which rotate in synchronization with engine rotation are provided, and are driven to a fuel return passage which communicates a low pressure pump chamber formed on the discharge side of the feed pump with the plunger chamber of the plunger pump. While interposing an electromagnetic valve that is opened and closed by a pulse, it responds to a fuel pressure difference between a high-pressure chamber in which fuel from the pump chamber is introduced and a low-pressure chamber in which fuel on the suction side of the feed pump is introduced. A fuel injection pump provided with a timer mechanism capable of advancing and retarding the phase of the face cam, wherein the fuel injection timing and injection amount are controlled by opening and closing the solenoid valve, and the timer mechanism controls the solenoid valve. It has a fuel injection pump that controls the injection rate during the injection period from closing to opening, and a sensor that detects the operating conditions of the engine, and a basic injection timing according to the detected value. And a means for setting a basic injection amount, a means for setting a target injection rate during the injection period according to the detected value, and a drive signal corresponding to the target injection rate is generated and output to the timer mechanism. Means for detecting an actual injection rate during the injection period, means for calculating a reduction correction amount of the basic injection amount according to a deviation between the detected value and the target injection rate, and a correction amount Means for reducing the basic injection amount to determine an injection amount to be output, and an electromagnetic wave interposed in the fuel return passage by forming the drive pulse from the determined injection amount and the basic injection timing. A fuel injection control device for a diesel engine, comprising: means for outputting to a valve.