JPH0318645A - Accumulator fuel injection device for diesel engine - Google Patents

Abstract

PURPOSE:To prevent overshoot by changing a correction coefficient in relation to a control signal for controlling a high pressure feed pump on the basis of the engine load rate-of-climb, thereby enabling the actual common rail pressure to follow the command value accurately. CONSTITUTION:The characteristic among the engine speed, the engine load rate-of-climb and a pressure rise correction coefficient for correcting a control signal for controlling a high pressure feed pump 7 are previously stored in a characteristic storage means 100. At the time of accelerating operation, a pressure rise correction coefficient enumerating means 101 enumerates a pressure rise correction coefficient from the characteristic storage means 100 on the basis of the engine speed and the engine load rate-of-climb operated by an engine load rate-of-climb arithmetic means 102, and the high pressure feed pump 7 is controlled by a control signal operated by an arithmetic processing means 103 on the basis of the enumerated high pressure correction coefficient. The common rail pressure can thus follow the command value accurately so as to prevent the generation of overshoot and thereby reduce the fuel cost as well as prevent the generation of noise.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an accumulator fuel injection device for a diesel engine. ``Prior Art'' The configuration and control method of a pressure accumulator fuel injection device for a diesel engine have already been proposed in Japanese Patent Laid-Open Publication No. 62-258160. "Problem to be Solved by the Invention" However, the control methods in the prior art are aimed at optimal control during steady operation of the diesel engine, and do not actively control during transient operation. ．Especially when controlling a high-pressure supply pump during sudden acceleration operation, it is necessary to raise the common rail pressure to a predetermined pressure in a short time. Overshoot can cause energy loss in the high-pressure supply pump.Also, if you try to prevent this overshoot, it takes time to raise the pressure to the specified pressure, which causes problems such as the generation of black smoke. This is because the correction value of the control signal for the high-pressure supply pump determined by the rotational speed NE and the accelerator opening is fixed, and cannot respond extremely precisely to the magnitude of acceleration.The present invention has been made with attention to the above-mentioned points. can be,
Engine load change rate Δ determined by accelerator opening
A pressure accumulator fuel injection system for a diesel engine that uses α/Δt as a control parameter to control the discharge amount of a high-pressure supply pump during acceleration operation to avoid so-called overshoot when increasing common rail pressure to a predetermined pressure. The purpose is to provide ``Means for Solving the Problems'' The specific means for achieving the above purpose is to input various detections such as engine rotation speed, accelerator opening, etc. Control signals calculated according to the program determine the amount of high-pressure fuel discharged from the high-pressure supply pump into the common rail, and the opening of injection nozzles that inject high-pressure fuel at a predetermined pressure accumulated in the common rail into each cylinder. In an accumulator fuel injection device for a diesel engine, the engine load increase rate calculation means calculates the engine load increase rate from the accelerator opening degree, and the engine load increase rate, engine speed, and control for the high pressure supply pump are provided in advance. a characteristic storage means for storing characteristics between the boost correction coefficient and the boost correction coefficient for correcting the signal; and a boost correction coefficient calculation means for calculating the boost correction coefficient from the characteristic storage means based on the values of the engine load increase rate and the engine rotation speed. The high-pressure supply pump is controlled by a control signal calculated by a calculation processing means based on the calculated boost correction coefficient. "Effect" According to the specific means, as shown in FIG. 1, during acceleration operation, the difference between the engine speed, the engine load increase rate, and the boost correction coefficient for correcting the control signal for controlling the high-pressure supply pump is determined in advance. From the characteristic storage means 100 that stores the characteristics, the boost correction coefficient calculation stage 101 calculates the boost correction coefficient based on the engine rotation speed and the engine load increase rate calculated by the engine load increase rate calculation stage 102. The high-pressure supply pump is controlled by a control signal calculated by the calculation processing means 103 based on the pressure increase correction coefficient. ``Example'' A first example of the present invention will be described based on the accompanying drawings 2 to 11. Figure 2 shows a schematic diagram of the accumulator fuel injection system for diesel engines. diesel engine 1
An injector 2 is disposed in each fuel chamber, and injection of fuel from the injector 2 to the diesel engine 1 is controlled by turning on and off an injection control solenoid valve 3. The injector 2 is connected to a high-pressure accumulator pipe common to each cylinder, so-called common rail 4, and while the injection control solenoid valve 3 is open, fuel in the common rail 4 is injected into the diesel engine l by the injector 2. Therefore, it is necessary to continuously accumulate a high predetermined pressure corresponding to the fuel injection pressure in the common rail 4, and a high-pressure supply pump 7 is connected to the common rail 4 through a supply pipe 6 with a check valve 5 interposed therebetween. The high-pressure supply pump 7 boosts the fuel sucked from the fuel tank 8 through the fuel supply pump 9 to a required predetermined high pressure by reciprocating the plunger using a cam (not shown) synchronized with the rotation of the diesel engine. common rail 4
It is equipped with a discharge amount control device 10 to constantly maintain the common rail pressure at a predetermined high pressure. The injection control solenoid valve 3 and the discharge amount control device? t 1 0 is electronic 016m unit (hereinafter simply referred to as ECU) 1l
Its operation is controlled by the control signal output from the
The ECUI 1 receives detection signals from an engine speed sensor 12 and an accelerator opening sensor l3, and also receives signals from a pressure sensor 14 that detects actual common rail pressure, and various sensors 15 such as water temperature, intake air temperature, and intake pressure. Input signals are input, and the ECU II determines the operating state of the horse mackerel engine based on these input signals, performs arithmetic processing according to a predetermined button program, and controls the injection control solenoid valve 3 and the discharge amount control device [ 10, and the ECU II is equipped with a memory (RAM, ROM, both not shown) for storing detection data, control programs, etc. 6 Figure 3 shows this embodiment using the ECU II. It is a flowchart showing the control of the device. First, steps (hereinafter simply referred to as S) 200 and S
In step 202, the engine speed NE and engine load α are detected, and in step S204, the engine load increase rate Δα/Δt is calculated. Next, the process advances to 8206 to calculate the basic injection amount QIIAJII. Basic injection iQ I
A l * is the engine speed N as shown in Fig. 4.
Characteristics consisting of E and engine load α? In step S208, water temperature, intake air temperature, intake pressure, etc. are detected by various sensors 15. Next, at 8210, the actual common rail pressure Pc' is detected by the pressure sensor 14 and converted from analog to digital. Next, the process proceeds to 8212, and the commanded injection JIQ, . ．． Calculate.
The commanded injection amount Q y t- corresponds to the final injection amount of fuel injected from the injector 2 to the diesel engine l. Next, in S214, the command common rail pressure P
Calculate e. The command common rail pressure P@ is determined by the engine speed NE and the command injection amount Q r as shown in FIG.
S2 calculated from the characteristic map (B) consisting of im
Proceed to step 16 to determine the basic pumping start time T of the high-pressure supply pump 7.
Calculate Fm^am. The basic shipping start time is T.
As shown in FIG. 6, it is calculated from a characteristic map (C) consisting of the commanded common rail pressure Pc and the commanded injection quantity Qvtw. Subsequently, in S218, the pressure of the high pressure supply pump 7?
The start time T, is expressed as T − ” T ts@v1+
TF■ calculated from Tv** is. T wmw = k (P e P
6'). As shown in FIG. 7, the pressure increase correction coefficient k is calculated using a characteristic map (D) consisting of the engine load increase rate Δα/Δ7 and the engine speed NE. This characteristic matua (D) increases the value of the boost correction coefficient k as the engine speed NB decreases, and also increases the value of the boost correction coefficient k as the engine speed NB decreases.
The lower the NE, the lower the engine load. The promotion correction coefficient k is set to decrease rapidly when the E promotion rate Δα/Δshi is large. As shown in No. 10 [2], during acceleration operation, there is a delay between the rise of the command common rail pressure Pc and the rise of the actual common rail pressure Pc'. This is due to the longer time it takes for pump 7 to raise the pressure to the specified pressure. This characteristic map (D) and each of the above characteristic maps (8), (B)
, (C) is F. It is stored in advance in the memory (11.0M>) of the CU 11. In ?<3220, the injection control solenoid valve 3 is activated to inject the commanded injection ffiQ■. calculated in the above S212 from the injector 2 to the diesel engine 1. Further, in S222, a discharge amount control device !10 that controls the discharge amount of the high-pressure supply pump 7 is output based on the pumping start timing Ty of the high-pressure supply pump 7 calculated in S218. The driving Takae supply pump electromagnetic valve pulse is output. Fig. 8 shows the processing by pulse interrupt in the execution cycle (engine 1 K interval) of the flowchart shown in the above-mentioned No. 3 [!I]. The processing of each step shown in the flowchart is normally executed by pulse interrupts, but the detected values of engine load α, water temperature, intake temperature, and actual common rail pressure Pa' are input by time interrupts at fixed time intervals. The reason why the engine load α, etc. is input by time interrupt is that if input by pulse interrupt, the input interval is too wide when the engine speed NE is low.Among these, in particular, the actual common rail Pc' is input at fixed time intervals. Detection using only the time interrupt and detection using the pulse interrupt described above are used together. The timing for performing the pulse interrupt is regulated based on the pulse signal output from the pickup coil of the engine rotation speed sensor 12. The engine speed sensor 12 is provided corresponding to a gear-shaped balsa (not shown) that synchronizes with the rotation of the diesel engine 1, and outputs one pulse every time one tooth of the balsa passes. In the balsa, missing teeth are formed at intervals of one cylinder.Hereinafter, several examples of step processing using pulse interrupts in execution synchronization of the flowchart in FIG. 3 will be described with reference to FIG. 8. The engine rotation speed NE is detected by calculating the pulse interval time of pulses "6" to "6" including the long rectangular pulse "P" due to missing teeth provided for each cylinder interval. At timing "0", injector 2
The energization start timing TT of the injection control solenoid valve 3 (hereinafter simply referred to as T
T) and energization interval TQ (hereinafter referred to as TQ) are set. Specifically, TT is determined from the relationship between rotation speed and fuel injection amount, TQ is determined from the relationship between rotation speed and common rail pressure, and TT is determined from the injection timing,
TQ corresponds to the injection amount and is set by angle calculation or time calculation. At the timing of pulse "2", the actual common rail pressure Pa' of S210 is detected and converted from analog to digital. At the timing of pulse "3", the boost correction coefficient k is calculated using the characteristic map made up of the engine load increase rate Δa/Δt and the engine rotation *NB described above. Furthermore, at the timing of pulse "5", the pumping start timing T of the high pressure supply pump 7 for the next batch is calculated, and during this period, the TT. The TQ calculation is also executed. The solenoid valve pulse at the pumping start timing Tr of the high-pressure supply pump 7 in this brief is turned on at a time in the middle of the promotion process counted from the pulse "0" of the previous cylinder by an amount set by angle calculation or time calculation. It turns off with pulse r4.

In addition to the above, engine load α. water temperature. Intake temperature. The actual common rail pressure Pc' is input by interrupting it at certain fixed time intervals, and predetermined step processing is executed based on this. FIG. 9 is a timing chart of the gastrointestinal system (6 cylinders) of this embodiment. (A) shows the crank angle of the diesel engine, (
B) and (C) show the simple discrimination signals, respectively. (D) is a pulse signal corresponding to the pulse rQJ shown in FIG. 7 above. (C) shows a pulse signal that regulates TT and TQ, which control the opening of the injection control solenoid valve 3, at the pulse output timing indicated by (D>) for each cylinder. (F>) Actual common rail pressure Pc during fuel injection
This shows the fluctuation of . (G). 、． Is (pull) and (1) one F per cylinder each? l1! Discharge amount control device 10/J? The pressure feeding start timing T, which is determined by counting the force t from the timing of the pre-air -6 pulse rQJ, is shown above. The actual common rail pressure P can be determined by
Increase c' to the specified pressure. The high-pressure supply pumps 7 of this embodiment each have a function of applying two pressures per rotation, and the number of high-pressure supply pumps 7 is half the number of engine cylinders. Further, (G'), (H') and (l') indicate cam lifts of cams for reciprocating the plungers of each of the high-pressure supply pumps 7. The operation of the device of this embodiment during acceleration will be explained with reference to FIG. When the diesel engine 1 is in an accelerating operation state, the engine load α increases as shown in (a). With this increase, the commanded injection amount Q, . ．． (actual injection amount) and command common rail pressure Pc increase as shown in (b) and (c), respectively. With the increase in command common rail pressure Pc,
When starting the basic pumping of the high-pressure supply pump 7, T■. ■ is calculated sequentially. Furthermore, the boost correction coefficient k is determined from the leap between the engine load increase rate Δα/Δt and the engine speed NE,
Directive Common Re? Calculate T2■ by multiplying the deviation between common rail pressure Pc and actual common rail pressure P1. The pumping start timing T of the high-pressure supply pump 7 is calculated by adding the T FBI to the basic pumping start timing TFIIAIII+, and based on this, the discharge amount of high-pressure fuel from the high-pressure supply pump 7 to the common rail 4 is controlled. By doing so, the common rail pressure is increased to the command common rail pressure Pc. The command common rail pressure Pc and the actual common rail pressure Pe' are the same IM.
Although a certain delay occurs as shown in (d), the actual common rail pressure Pc' is fed back by the pressure sensor 14, and the command common rail pressure Pc and the actual common rail pressure P are fed back.
For the deviation of a', the boost correction coefficient k is determined as described above. Therefore, it is possible to control the delay that changes depending on the engine speed, and also to control the delay based on the engine load increase rate Δα/Δt that changes every moment during acceleration operation.
By making the boost correction coefficient k variable, as shown by the dotted line in the same figure (d), the overshoot of the actual common rail pressure Pc' that occurred when the correction coefficient was fixed is suppressed, and the command common rail pressure Pc is accurately tracked. You can FIG. 11 is a graph showing changes in the command common rail pressure Pc and the actual common rail pressure Pc' when an experiment was performed by changing the engine load α stepwise. Same 1ff
i(a) shows the case where the boost correction coefficient k is fixed, and an overshoot of about 18 MPa occurs in the actual common rail pressure Pc'; In this case, no overshoot occurs. FIG. 12 is a flowchart showing the control of the device of the second embodiment. Since this flowchart is a modification of only the flowchart 8216 of the first embodiment (FIG. 3), the modified portion will be explained. After the command common rail pressure Pc is calculated in S214,
In S217, the commanded common rail pressure Pc is corrected, and the corrected commanded common rail pressure P6v*t is
Calculated by P @, ■= k' ・P a. k″
is a pressure increase correction coefficient, which is calculated from a characteristic map (E) consisting of the engine load increase rate Δα/Δt and the engine speed NE, as shown in FIG. The characteristic map (E
) is similar to the characteristic map (D) (Fig. 7) for calculating the boost correction coefficient k explained in the first embodiment, the lower the engine speed NE is, the larger the value of the boost correction coefficient k' is. Also, the lower the engine speed NE, the engine load increase rate Δ
The boost correction coefficient k' is set to decrease rapidly with a large value of α/Δt. Based on the previous offense correction command common rail pressure P av **, the pumping start timing T of the high pressure supply pump 7 is calculated in S218, and as explained in the first embodiment, if the continuation < 8220, it is calculated in S212. In order to inject the commanded injection amount QFll+ from the injector 2 into the diesel engine 1, an injector solenoid valve pulse is output that drives the injection control solenoid valve 3. Furthermore, in S222, a high-pressure supply pump solenoid valve pulse that drives the discharge control device 10 that controls the discharge amount of the high-pressure supply pump 7 is output. In this embodiment, by making the pressure increase correction coefficient k'◆ for the command common rail pressure Pc variable based on the engine load increase rate Δα/Δt that changes during acceleration operation, the actual common rail pressure Pc' can be changed to the command common rail pressure Pe. It can be followed accurately. In each of the above embodiments, the engine load increase rate Δα/
Although Δt was used as the control parameter, it is also possible to use the rate of change ΔPc/Δt of the command common rail pressure Pe as the control parameter. "Effects of the Invention" The present invention provides extremely fine control of the high-pressure supply pump during acceleration by varying the correction coefficient for the control signal that controls the high-pressure supply bomb based on the engine load increase rate instead of fixing it. Since the actual common rail pressure can accurately follow the commanded common rail pressure and no overshoot occurs, there is less wasted energy loss required for boosting the pressure, which is excellent in terms of fuel efficiency and noise prevention. There is.

[Brief explanation of the drawing]

The accompanying drawings illustrate embodiments of the present invention, with FIG. 1 being a schematic block diagram, FIG. 2 being a schematic structural diagram of an accumulator fuel injection device for a diesel engine, and FIG. 3 showing control of the device of this embodiment. Flow chart, Fig. 4 is a diagram showing the characteristic map (A), Fig. 5 is a diagram showing the characteristic map (B), Fig. 6 is a diagram Ii showing the characteristic map (C), Fig. 7 is a diagram showing the characteristic map (D), FIG. 8 is an explanatory diagram explaining processing by pulse interrupt, FIG. 9 is a timing chart of the device of this embodiment, and FIG. 10 is a timing chart showing operation during acceleration. , FIG. 11 is a graph showing the experimental results,
12(a) shows the case of the conventional device, FIG. 1(b) shows the case of the device of this embodiment, FIG. 12 is a flowchart showing the control of the device of the second embodiment, and FIG. 13 shows the case of the second embodiment. It is a diagram showing a characteristic map (E) used in an example. 1. ．． ．． Diesel engine, 2. ．． ．． Injector, 3. ．． ．． Solenoid valve for injection control, 4. ．． ．． Common rail, 7. ．． ．． High pressure supply pump, 10. ．． ．． Discharge amount control device, 1 1. ．． ．． Electronic control unit (ECU)
), 12. ．． ．． Engine speed sensor, 13. ．． ．．
Accelerator opening sensor, 14. ．． ．． pressure sensor,
100. ．． ．． Characteristic storage means, 1 0 1. ．． ．． Boost correction coefficient calculation means, 1 0 2. ．． ．． engine n
Load rise rate calculation means, 1.03. ．． ．． performance processing means, (
A). ．． ．． Characteristic map, (E). ．． ．． Characteristic map. 2 Fig. 1 Fig. 4 Fig. 5 Fig. 6 Fig. 7 (D) Δα/Δt Engine load increase rate (%/sec) Fig. 8 Fig. 10 (a) 11 Fig. (b)

Claims (1)

[Claims] Various detection signals such as engine rotation speed and accelerator opening are input to the calculation processing means, and the control signals calculated by the calculation processing means according to a predetermined program are used to discharge high-pressure fuel from the high-pressure supply pump into the common rail. In a pressure accumulation type fuel injection system for a diesel engine that controls the amount of high-pressure fuel accumulated in the common rail and the opening of an injection nozzle that injects high-pressure fuel at a predetermined pressure into each cylinder, the engine load increases depending on the accelerator opening. engine load increase rate calculation means for calculating the engine load increase rate; characteristic storage means for storing in advance the characteristics between the engine load increase rate and the engine rotation speed and the boost correction coefficient for correcting the control signal for the high pressure supply pump; step-up correction coefficient calculating means for calculating the step-up correction coefficient from the characteristic storage means based on the values of the engine speed and the engine speed; A pressure accumulation type fuel injection device for a diesel engine characterized by controlling a supply pump.