JPH0326854A - Accumulation type fuel injection device of diesel engine - Google Patents

Abstract

PURPOSE:To decrease pressure rising energy of a high pressure pump by maintaining common rail pressure at a level of pressure power upon judgement or by gradually decreasing it, when an engine load decreasing rate is judged less than a specified threshold value. CONSTITUTION:An electronic control unit 11 inputs signals from an engine speed sensor 11, an acceleration opening sensor 12, a real common rail pressure sensor 14, and respective kinds of sensors 15. The unit 11 also judges engine operation condition so as to control injection from an injector 2 by a solenoid valve 3, and controls the pressure of a common rail 4 by means of a discharge controller 10. When the load decreasing rate of an engine 1 is judged less than a specified threshold value, the pressure of the common rail 4 is maintained at a level of the pressure at the time of judgement for a specified time, or decreased gradually so as to control the discharge controller 10. In the case of increase in engine load, therefore, operation is made possible with the reduced pressure rising energy of a high pressure pump 7, and generation of vibration can be restrained.

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 j The construction and control method of a pressure accumulation type fuel injection device for a diesel engine has already been proposed in Japanese Patent Application Laid-Open No. 62-258160, etc. ``Problems to be Solved by the Invention'' The above-mentioned prior art The ILJ control method in technology is a control method necessary exclusively for steady operation of a diesel engine. However, the actual operating state of a diesel engine is constantly repeating transient states such as acceleration, deceleration, and then re-acceleration. In the conventional control method, when engine load = 0 is detected by the accelerator opening signal, the command common rail pressure is unilaterally calculated based on the detection signal.
Based on this command value, the actual common rail pressure is controlled and reduced. Due to this state of deafness, when depressing the accelerator to accelerate again, it is necessary to increase the reduced actual common rail pressure to the original pressure using a high pressure supply bomb.
During this period, there are problems such as discharge loss of the high-pressure supply pump and rapid pressure increase, which worsens fuel efficiency and causes vibration. The present invention has been made in order to solve the above-mentioned problems, and reduces the boost energy required to increase the actual common rail pressure during re-acceleration in the operating state of a diesel engine that repeatedly accelerates, decelerates, and then re-accelerates. The purpose of this invention is to provide a pressure accumulation type fuel injection device for a diesel engine that is capable of reducing fuel consumption and preventing the occurrence of vibrations, etc. "Means for solving the problem" The specific means for achieving the above-mentioned purpose is to input various detection signals such as engine rotation speed and accelerator opening into a calculation processing means, and to execute a predetermined program in the calculation processing means. Based on the control signal calculated according to In the pressure accumulation type fuel injection device for a diesel engine, the engine load reduction rate calculation means calculates the engine load reduction rate from the accelerator opening degree, and the calculated engine load reduction rate is compared and determined with a predetermined threshold value. and a common rail pressure control means for maintaining the common rail pressure output at the time of the determination for a predetermined time or gradually reducing it when the engine load reduction rate is determined to be below a predetermined threshold. It is characterized by this. "Operation" According to the specific means, when the engine load reduction rate is comparatively determined to be below a predetermined threshold value during diesel engine operation, the common rail pressure is outputted by the common rail pressure control means at the time of the comparative determination. It is controlled to maintain the common rail pressure for a predetermined period of time or to gradually reduce the pressure. Embodiment J An embodiment of the present invention will be explained based on the accompanying drawings. Fig. 1 shows a schematic configuration of a pressure accumulation type fuel injection device for a diesel engine. The diesel engine 1 includes:
An injector 2 is provided for each fuel chamber, and the injection of m-fuel from the injector 2 into the diesel engine 1 is controlled by turning on and off the injection control TI and magnetic valve 3. The injector 2 is connected to a so-called common rail 4, which is a high-pressure accumulator pipe common to each cylinder, 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. For this reason, 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 bomb 7 is connected to the common rail 4 through a supply pipe 6 with a check valve 5 interposed therein. 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) that synchronizes 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 operations of the injection control solenoid valve 3 and the discharge amount control device 1f10 are controlled by control signals output from an electronic control unit (hereinafter simply referred to as ECU) 11.
1 receives detection signals from the engine speed sensor 12 and the accelerator opening sensor 13 manually, and also includes a pressure sensor 14 that detects the actual common rail pressure, and a water temperature sensor 14 that detects the actual common rail pressure. Intake temperature. Input signals from various sensors 15 such as intake pressure are input, and the ECU II determines the operating state of the engine based on these input signals, performs arithmetic processing according to a predetermined program, and controls the injection control solenoid valve 3 and the discharge An optimal control signal for the quantity control device 10 is output. Also ECUII
The detection data. Memory (RAM, ROM) that stores control programs, etc.? Both are equipped with (not shown). FIG. 2 is a flowchart showing the control of the device of this embodiment by ECU II. First, steps (hereinafter simply referred to as S) 200 and S
202, the engine speed NE and the engine load α (the signal from the accelerator opening sensor 13 is substituted)
Detect. Note that α is positive or has a value of 0. S204
is an engine load reduction rate calculation means, and the engine load reduction rate Δα/Δt is the amount of change in α per predetermined time Δt.
Calculate. Next, proceed to S206 and set the basic injection amount Q.
Calculate IA■. The basic injection amount Q mA■ is calculated from the characteristic map (A) consisting of the engine rotation @NE and the engine load α as shown in FIG. Intake pressure and the like are detected by various sensors 15. Subsequently, in S210, the actual common rail pressure Pc' is detected by the pressure sensor 14 and converted from analog to digital. Next, the process advances to 8212, and the water temperature and suction detected in 8208 are determined based on the basic injection amount Q IIA■ calculated in S206. The commanded injection amount Q v + w is calculated based on temperature, intake pressure, etc. The commanded injection amount Q■ corresponds to the final injection amount of fuel injected from the injector 2 to the diesel engine l. Subsequently, S214 constitutes a comparison and determination means, and compares and determines the engine negative R reduction rate Δα/ΔL calculated in S204 with a predetermined threshold value k. If the engine load reduction rate Δα/ΔL is larger than a predetermined threshold value k (k is 0 or a negative predetermined value), NO
Proceed to 8216. In S216, the commanded gomon rail pressure F'e is calculated. The command common rail pressure Pc is determined by the engine speed NE and the command injection f as shown in FIG.
The common rail pressure Pc calculated in the previous routine and stored in the memory (RAM) of the ECUII is updated by the command common rail pressure Pc calculated from the characteristic map (B) consisting of Q■D. Next, the process proceeds to 8218, and the pumping start timing 'r, of the high-pressure supply bomb 7 is calculated. The pressure feeding start timing 'I'2 is calculated from the characteristic map C consisting of the commanded injection amount QFII+ and the common rail pressure Pc, as shown in FIG. At the start of main pressure feeding #I
T ■． ．． It is calculated by adding corrections (proportional, differential and integral corrections, etc.) due to pressure increase. Each characteristic map (A). (
B) and (C) are stored in advance in the memory (FIOM) of the ECU1. Next, in <3220, the injection control solenoid valve. Outputs the injector solenoid valve pulse that drives 3.
Furthermore, in S222, the high-pressure supply bomb solenoid valve pulse that drives the discharge amount control device 10 that controls the discharge amount of the high-pressure supply bomb 7 is determined based on the pumping start time T of the high-W supply bomb 7 calculated in Sll8. Y l'. Press S to proceed to S230. S230 below
, 8232 and S234 constitute common rail pressure control means. 8230, the preset extension time T
Set the ECU II internal timer. Extra time T. , is 823 after being set 1 and before the time elapses.
It shall not be set each time it advances to 0. Continued<:S23
2, the extension time T. , and if it has not passed, in 8234, the command common rail pressure P
As a, the command common rail pressure Pc calculated in the previous routine and stored in the memory (RAM) of ECLJII
Call A and set it. This command common rail pressure PeA is not updated in the routine until Δα/Δt>k is determined in step S2]4 or the elapse of the extension time Twxy is determined in step S232.
1. Since it is stored in the memory (RAM) of 1,
The command common rail pressure Pc is output as a constant value as pc=PcA. Next, the process proceeds to S2L8, where the pumping start timing T of the high-pressure supply pump 7 is calculated in order to realize this command: 1 Mon rail pressure Pc=PeA. S220,
In S222, the injector solenoid valve pulse and the high pressure supply pump solenoid valve pulse are output, respectively, in the same manner as above. Further, if it is determined in S232 that the extension time 1'1o has elapsed, proceed to S216/\, and proceed to 8200 to S2.
12, a new command common rail pressure Pc is calculated based on each detected value and calculated value, and the command common rail pressure Pc is newly calculated in S220 and S220.
The process proceeds to 222, where the injector solenoid valve pulse and high pressure supply pump solenoid valve pulse corresponding to the calculated command common rail pressure Pc are output. The comparative determination threshold value k for the engine load reduction rate is a predetermined threshold value k that detects a rapid reduction in engine load when the driver suddenly releases the accelerator pedal, such as when changing gears or applying engine braking. It may be a negative value, or it may be set to 0 to simply detect a state of decrease in engine load. FIG. 6 shows processing by pulse interruption in the execution cycle (one engine cylinder interval) of flowchart 1 shown in FIG. 2. The processing of each step shown in the flowchart is normally executed by a pulse interrupt, but if the engine load α. The detected values of water temperature, intake air temperature, and actual common rail pressure Pc' are inputted by time interrupt at fixed time intervals. The reason why the engine load α, etc. is input by time interrupt in this way is that if input by pulse interrupt, the input interval will be too wide if the engine speed NE is low. Among these, the real common rail Pc' is especially
Detection using only time interrupts at fixed intervals and detection using pulse interrupts described above are used together. The timing for performing the pulse interrupts is determined by the pulse signal output from the big up coil of the engine rotation speed sensor 12. It is regulated based on The engine rotation 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 vanores every time one tooth of the balsa passes. The balsa is formed with missing teeth at intervals of one cylinder.Hereinafter, several examples of step processing using pulse interrupts in execution synchronization of the flowchart in FIG. 2 will be explained with reference to FIG. 6. 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 every 1 kfi interval. At the timing of pulse rO, injector 2
The energization start timing TT of the injection control solenoid valve 3 (hereinafter simply referred to as T
(referred to as T) and the continuous t interval TQ (hereinafter simply referred to as 1゛Q)
Specifically, T1' is set based on engine speed NE and commanded injection amount Q. TQ is determined from the relationship between the engine speed NE and the command common rail pressure Pc, TT corresponds to the injection timing, and TQ corresponds to the injection amount, which are set by angle calculation or time calculation.

At the timing of pulse "2", the actual common rail pressure 1)c' of S210 is detected and converted from analog to digital. At the timing of pulse "3", the basic pumping start timing T
Calculate. Furthermore, at the timing of pulse "5",
The pumping start timing T of the next high-pressure supply pump 7 is determined, and during this time, calculations of TT and TQ for the next cylinder are also executed. The solenoid valve pulse of the pumping start timing Tr of the high-pressure supply pump 7 in this brief is based on the pumping start timing T of the high-pressure supply pump 7, which is set by angle calculation or time calculation based on the pulse "0" of the previous pump. It turns on at pulse 4 and turns off at pulse 4. In addition to the above, engine load α,
When the water temperature, intake temperature, and actual common rail pressure Pc' are constant, l? The data is input by interrupting the data at 11 intervals, and predetermined step processing is executed based on the data. The operation of the device of this embodiment will be explained with reference to FIG. The engine speed NE of the diesel engine 1 is decelerated and gradually decreases as shown in (a), and then increases due to re-acceleration. In addition, as shown in (b), the engine load α decreases to 0 (%), continues at 0 (%) for a certain period of time, and then is accelerated again and increases. According to the command injection amount Q, . Also (c)
It changes as shown in . In addition, the command common rail pressure P
c is the engine speed NE and the commanded injection amount Q, 1.c as shown in (d). Since the engine speed NE and commanded injection amount Q v r are calculated from the characteristic map (B) consisting of
It decreases as m decreases. Here, Fuuki engine load α
If it is determined that the engine load reduction rate Δα/Δt when The value of Pe is set to Pc=PcA, and is output for a preset extension time T K 11 t. Extra time T68! After the elapsed time, the engine speed NE and commanded injection amount Q, . sharply decreased based on
The 4-actual common rail pressure Pc', which increases with the increase in the engine load α, follows the change pattern of the command common rail pressure Pc with a certain delay, and exhibits a change pattern as shown in (e). Note that in (d) and (e) above, the change patterns shown by dotted lines indicate the change patterns of the conventional device. If the acceleration is re-accelerated before the extension time TalLt has elapsed, the engine speed NE,
Engine load α and commanded injection ffiQ, . ．． According to the increase in , the command common rail pressure Pa is increased from the value of Pc=PcA. Along with this, the actual common rail positive force Pc° is also increased. FIG. 8 shows another embodiment, in which the engine load reduction rate Δα/
When it is determined that Δt is less than or equal to the predetermined threshold value k, the command common rail pressure Pc is not maintained at the constant value Pc=Pa* for the preset extension time 'rixt as in the above embodiment, but is maintained at Pc. =PcA′T”.・Pc−.

−(T.: execution cycle time, Pcooww: constant)
During the extension time Ttxt, the command common rail pressure P
This is done so that a gradually decreases. In this case as well, if the acceleration is re-accelerated before the extension time 'Ftllt has elapsed,
The pressure is increased as shown by the two-dot chain line in the same figure. Please note that the extension time is T.

7 is the engine load reduction rate Δα/Δ as shown in FIG.
It may be determined based on the magnitude of the value of t. In addition, the extension time 'T'ixy is determined by ECUII based on the vehicle speed,
The increase/decrease in engine speed and the acceleration/deceleration patterns may be learned and determined for each case of driving on a highway or in a city, for example. When the load reduction rate is compared and judged to be below a predetermined threshold, the common rail pressure control means maintains the common rail pressure at the common rail pressure output at the time of the comparison judgment for a predetermined period of time or gradually decreases the pressure. Therefore, if the engine load α increases due to re-acceleration before the predetermined time elapses, when the common rail positive force increases,
From the low pressure that dropped as the engine load decreased: Za
Since there is no need to increase the pressure, the energy needed to increase the pressure of the high-pressure pump is reduced, and vibrations are suppressed.

Furthermore, the energy required to maintain or gradually reduce the common rail pressure at a constant pressure for a predetermined period of time uses energy during deceleration operation when the engine load reduction rate of the diesel engine is below a predetermined threshold, thereby reducing fuel consumption. It has excellent effects such as not causing any deterioration.

[Brief explanation of drawings]

Fig. 1 is a schematic elliptical diagram of a pressure accumulation type fuel injection device for a diesel engine, Fig. 2 is a flowchart 1 showing the control of an embodiment of the device, Fig. 3 is a diagram showing a characteristic map (A), Fig. 4 is a diagram showing the characteristic map (B), Fig. 5 is a diagram showing the characteristic map <C>, Fig. 6 is an explanatory diagram explaining processing by pulse interrupt, and Fig. 7 is a diagram showing the actual implementation. Timing chart 1. showing the operation of the example device, Fig. 8 is a timing chart showing changes in the command common rail pressure Pc in the case of another embodiment, and No. 9 I2l is a graph when calculating the extension time from the engine load reduction rate. . l. ．． ．． Diesel engine, 2. ．． Injector, 3. ．． Solenoid valve for injection control, 4. ．． ．． Common Rail, 7,. high pressure supply pump, io. ．． ．． lIJ
Singing control device, L1. ．． ．． Electronic control unit (
EC(J), 12. ．． ．． Engine speed sensor, 1
3. ．． ．． Accelerator opening sensor, 1 4. ．． ．． Pressure sensor, step S204. ．． ．． Engine load reduction rate calculation means, step S214. ．． ．． Comparative determination means, steps S230, 232. 2 3 4. ．． ．． Common rail pressure control means, T txt. −． Extra time. 1 Figure 1 Figure 3 Figure 4 Figure 7 Figure 5 Figure 6 Figure 8 Figure 9 Figure Δα/Δt

Claims (1)

[Claims] Various detection signals such as engine rotation speed and accelerator opening are input to a calculation processing means, and the high pressure fuel is discharged from the high pressure supply pump into the common rail based on control signals calculated by the calculation processing means according to a predetermined program. In a pressure accumulation type fuel injection system for a diesel engine that controls the discharge amount of fuel and the opening of an injection nozzle that injects high-pressure fuel at a predetermined pressure accumulated in the common rail into each cylinder, the engine an engine load reduction rate calculation means for calculating a load reduction rate; a comparison determination means for comparing and determining the calculated engine load reduction rate with a predetermined threshold;
A diesel engine characterized by being provided with common rail pressure control means that maintains or gradually reduces the common rail pressure output at the time of determination for a predetermined period of time when the engine load reduction rate is determined to be below a predetermined threshold. Engine accumulator fuel injection system.