JPH0778376B2 - Fuel injection rate controller for diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial field of application" The present invention uses pilot injection prior to main fuel injection (hereinafter referred to as "main injection") in order to reduce noise and vibration of a diesel engine, for example, during idling. The present invention relates to a fuel injection rate control device having a function of performing.

"Prior Art" Japanese Patent Application Laid-Open No. 60-125753, in which pilot injection is controlled so that the combustion noise of a diesel engine is minimized.
JP-A-61-185638 and JP-A-61-277846
It is disclosed in the publication.

The fuel injection control method for a diesel engine disclosed in Japanese Patent Application Laid-Open No. 60-125753 is one in which the timing of the main injection following the pilot injection is determined based on the combustion state of the pilot injection.

The fuel pre-injection control method for a diesel engine disclosed in Japanese Unexamined Patent Publication No. 61-185638 is such that the fuel injection amount during pre-injection is always controlled to the optimum injection amount that is in the combustion state of the engine. is there.

Further, a fuel injection control method in a diesel engine disclosed in JP-A-61-225753 controls an auxiliary injection amount so that a pressure increase rate after ignition reaches a set value, engine operating conditions, fuel It is designed to satisfactorily burn under a quiet operating condition regardless of the properties.

[Problems to be Solved by the Invention] However, each of the above methods controls the timing of main injection, the injection amount, or the sub-injection amount to perform good and gentle combustion, which results in knocking noise during idling or low speed rotation. To reduce combustion noise as a result. Therefore, not only the difference in operating conditions,
There is a problem in that the effect of reducing combustion noise is different due to variations among machines, such as machine differences of the engine and aging of the valve opening pressure of the injection nozzle.

The present invention has been made to solve the above problems,
An object of the present invention is to provide an injection rate control device for a diesel engine, which can minimize combustion noise of the engine without being affected by variations among the machines such as machine difference and secular change.

[Means for Solving Problems] In order to achieve the above object, the injection rate control device for a diesel engine of the present invention detects an ignition timing for detecting a timing at which fuel injected into a combustion chamber of a diesel engine ignites. Means and
Injection timing control means for controlling the fuel injection timing so that the actual ignition timing detected by the ignition timing detection means becomes the target ignition timing of the engine, combustion noise detection means for detecting the combustion noise of the engine, and into the combustion chamber. Pilot injection means for performing pilot injection prior to the main injection of, and the injection stop engine between the pilot injection amount or the pilot injection and the main injection is forcibly changed to a predetermined direction for a predetermined amount or for a predetermined period, The combustion noise detected by the combustion noise detection means is compared before and after the change, and when the combustion noise increases, the direction is opposite to the predetermined direction, and when the combustion noise decreases, the direction is the predetermined direction. Pilot injection control means for controlling the pilot injection means so that the combustion noise is minimized by changing the amount or the injection stop timing. The features.

Further, in the fuel injection rate control device for a diesel engine having the above structure, the injection amount of the pilot injection and the injection stop period have an initial value which is a function of a cooling water temperature of the engine.

[Operation] According to the configuration described above, the pilot injection amount or the pilot injection is performed while detecting the ignition timing of the fuel injected into the combustion chamber of the diesel engine and controlling the injection timing to reach the target ignition timing of the engine. The injection stop engine between the main injection and the main injection is forcibly changed to a predetermined amount or for a predetermined period in a predetermined direction, and the combustion noise detected by the combustion noise detecting means is compared before and after the change, and the combustion noise increases. If so, the pilot injection amount or the injection stop period is changed in the direction opposite to the predetermined direction and in the predetermined direction when the combustion noise decreases to minimize the actually measured combustion noise.

Since the injection amount and the injection stop period of the pilot injection have an initial value that is a function of the cooling water temperature of the engine, it is possible to properly control the pilot injection during idling both during cold and after warm-up. .

[Example] Hereinafter, an injection rate control device according to the present invention will be described in detail with reference to an example shown in the drawings. FIG. 1 is an overall configuration diagram showing an embodiment of the present invention. The ignition timing detection means 2 for detecting the ignition timing of the fuel injected into the combustion chamber 1 of the diesel engine includes an ignition sensor 20 for detecting the combustion light of the combustion chamber 1 and an ignition sensor.
It is composed of a waveform shaping circuit 21 for shaping the signal from 20. Here, as the ignition sensor 20, for example,
A known ignition sensor that converts light into an electric signal using a phototransistor or the like can be used. The combustion noise detection means 10 of the engine includes a microphone 11 known as a combustion noise sensor and a known bandpass filter circuit 12 and a peak hold circuit 13 that pass this output only in a main frequency band of combustion noise (approximately 1 to 3 KHZ). Made of The analog signal is the A / D converter 3 of the microcomputer 3 described later.
Entered in 4. The microcomputer 3 receives a signal from the ignition timing detection means 2 and a signal from a crank angle sensor 6 described later, and controls a known injection timing control means 5 as shown in FIG. 2 to set the ignition timing of the engine. Pilot injection control means for controlling the target ignition timing and for controlling the pilot injection means 4 which will be described later in response to the signal from the combustion noise detection means 10. The CPU 31, ROM 32, RAM 33, A / D
It consists of converter 34, timer 35, I / _O 36, etc. In the pilot injection means 4, the piezo drive circuit 41 charges and discharges the piezo actuator 40 in response to the control signal from the microcomputer 3, and controls the pilot injection amount or the injection stop period from the pilot injection to the main injection. It is a thing. A pulser detector to which a magnetoresistive element is applied can be applied to the crank angle sensor 6 described above.
The crank angle sensor 6 is a sensor for detecting the reference angle of the engine, and generates a reference signal such as a timing for outputting a control signal to the injection timing control means 5 and the pilot injection means 4. Then, the ignition timing detection means 2 based on the signal from the crank angle sensor 6
The actual ignition timing is calculated by the microcomputer 3 based on the phase of the signal from the. In addition, in the present embodiment, signals from the accelerator amount sensor 7, the cooling water temperature sensor 8 and the like are also taken into the microcomputer 3 via the A / D converter 34.

FIG. 2 shows the injection timing control means 5, and a case where the present invention is applied to a Bosch distribution type fuel injection pump will be described. In FIG. 2, the timer piston 51 is a lever
It is connected to the roller ring 53 at 54 and the timer piston
When 51 moves to the left in the figure, the roller ring 53 rotates in the right rotation direction, and the fuel injection timing changes to the advance side. The vane type fuel pump 55 is rotated by a drive shaft (not shown) of the injection pump, and pumps the fuel from the fuel tank 58 to the pump internal pressure chamber A. The overflow check valve 56
This is to prevent the pressure in the pressure chamber A in the pump from being excessively increased. The fuel in the pump pressure chamber A is injected into the engine and is guided to the timer piston high pressure chamber B through the throttle. Accordingly, the position of the timer piston 51 is determined at the position where the pressure of the timer piston high pressure chamber B and the force of the timer piston return spring 52 in the low pressure chamber C are balanced, so that the position of the roller ring 53 is determined and the injection timing is determined. The pressure control valve 57 controls the pressure of the timer piston high-pressure chamber B by changing the ON / OFF time ratio of the drive pulse from the microcomputer 3 to change the opening / closing time ratio and determine the timer piston position, that is, the injection timing. Therefore, the microcomputer 3 inputs each detection signal indicating the operating state, calculates the target ignition timing most suitable for the operating state of the engine, calculates the error between the actual ignition timing and the target ignition timing, and calculates the error value. By changing the valve opening time of the pressure control valve 57 according to the above, the pressure of the timer piston high pressure chamber B is controlled, the timer piston 51 is moved, and the ignition timing is feedback-controlled to set the actual ignition timing to the target ignition. Control the time.

FIG. 3 shows an example of the configuration of the pilot injection means 4. 60 is, for example, a bosch type distribution type fuel injection pump, 61 is a plunger, which is pushed in the left direction in the figure by a face cam (not shown) to increase the pressure of the fuel in the high pressure chamber 62, and a diesel engine (not shown) from the nozzle 63. The fuel is injected into the combustion chamber of the. The piezo actuator 40, which is mounted facing the high pressure chamber 62 and which applies the piezo voltage effect, has a known structure as disclosed in, for example, Japanese Patent Laid-Open No. 59-18249. The piezo drive circuit 41 charges the piezo actuator 40 or discharges the generated charge to expand or contract the piezo element to change the pressure in the high pressure chamber 62, thereby performing pilot injection. This drive circuit 41 uses the signal Vg from the microcomputer 3.
In response to _2, transistor 411 for discharging the electric charge stored in the piezoelectric actuator 40, the transistor 4
A resistor 412 for protecting 11; an inductor 413 for storing energy from the battery in the form of a current; a diode 414 for preventing current from flowing backward from the piezo actuator 40 through the inductor 413 to the battery; a microcomputer. It comprises a transistor 415 for receiving the signal Vg ₁ from 3 and transferring energy in the path of battery → inductor 413 → piezo actuator 40 to generate a high voltage between both terminals of the piezoelectric actuator 40.

Next, the operation of the pilot injection means 4 will be described with reference to the timing chart shown in FIG. In the figure, (a) is a signal from the crank angle sensor 6, which is set so that one pulse is generated when the injection is completed and the fuel is completed. FIG. 6B shows the lifted state of the plunger 61. FIG. 7C shows a control signal of the transistor 415, and in this embodiment, the transistor 415 is brought into the “ON” state in synchronization with the signal of the crank angle sensor 6. When the transistor 415 is in the "ON" state, the current I _L starts to flow in the inductor 413 as shown in FIG. Then, when the control signal Vg ₁ from the microcomputer 3 is cut off after a time tw and the transistor 415 is turned to the “OFF” state, all the energy stored in the inductor 413 in the form of current is transferred to the piezo actuator 40. As in f), the voltage V _P between both terminals of the piezo actuator 40 becomes the high voltage V _CM . After that, when the plunger 61 starts to lift, the pressure in the high pressure chamber 62 rises, and the piezo actuator 40 generates a voltage by itself, so that the voltage V _P rises to V _PM . At this time, the pressure in the high pressure chamber 62 becomes equal to or higher than the nozzle opening pressure, and the injection is started as shown in FIG. At this time, as shown in FIG. 7D, the transistor 411 receives the control signal Vg ₂ from the microcomputer 3 and becomes the “ON” state, and the high voltage V _PM stored in the piezo actuator 40 is discharged and the piezo actuator 40. Shrinks, the pressure in the high-pressure chamber 62 drops, the injection is temporarily stopped, and pilot injection is formed. After that, the plunger 61 is further lifted, the pressure in the high pressure chamber 62 rises again, and the injection is restarted. Then, the injection is stopped by a governor mechanism (not shown), and the main injection is formed.

Here, as indicated by the dotted line in the figure, the transistor 415 turns “ON”.
When the state time tw is lengthened, the value of the charge voltage V _CM increases and the value of the high voltage V _PM also increases. The larger the value of V _PM, the larger the contraction amount of the piezo actuator 40 and the longer the injection stop period T becomes. That is, the "O of transistor 415
The injection stop time T can be controlled by the N "state time tw. Also, by changing the" ON "timing TMG of the transistor 411, the timing at which the injection stop timing starts changes. The injection quantity can also be controlled.

Further, (h) of the figure shows an ignition signal representing a combustion waveform output from the ignition sensor 20. After the pilot injection is started, the pilot injection fuel is ignited after an ignition delay period of _TL , This ignition phenomenon serves as a fire type of the main injection fuel to be injected later, and the main injection fuel to be supplied next is based on the fire type of the pilot injection fuel,
The figure shows a state of burning in a diffused manner.

FIG. 7I shows the signal after the ignition signal is shaped by the waveform shaping circuit 21. Here, the actual ignition timing T _IG of the injected fuel is detected from the phase difference between the rising timing at which the injected fuel ignites and the rising timing of the crank angle sensor signal in FIG. Then, the injection timing control means 5 is controlled so that the actual ignition timing becomes the target ignition timing of the engine.

"Operation" The pilot injection means 4 and the injection timing control means 5 capable of controlling the pilot injection amount and the injection stop period as described above.
And the ignition timing detection means 2 for detecting the ignition timing of the injected fuel based on the signal from the ignition sensor 20, the fuel noise detection means 10, the crank angle sensor 6 and the like for the injection timing control and the optimum pilot injection. An example of an algorithm in the microcomputer 3 to be executed is shown in FIGS.
This will be described with reference to the flowcharts of FIGS. 8 and 9.

FIG. 5 is a flow chart showing the main program of the microcomputer 3. After confirming the start of the diesel engine in step 911, in step 912 the pilot injection amount reference value q _B and the injection stop engine reference value T _B are initialized. Enter the value. For example, as shown in FIGS. 6 (a) and 6 (b), this initial value may give the pilot injection amount and the injection stop period as a function of the cooling water correlated with the warm-up state of the engine. In step 913, the reference values q _B and T _B are used as they are as the actual pilot injection amount q _N and the injection stop period T _N. These q _N and T _N are converted to the time TMG and the time tw in FIG. 4 according to the conversion formula obtained experimentally, and then output to the pilot injection means 4 by using the timer interrupt function of the microcomputer 3. It is a thing. Next, in step 94, the combustion noise is input from the fuel noise detection means 10, and the variable
Put it in S _B. Subsequently, in step 915, injection timing control is performed so that the actual ignition timing is always the target ignition timing of the engine.

Details of the injection timing control portion in step 915 will be described with reference to the flowchart shown in FIG. Step 931
Then, in order to calculate the engine speed N _E , N _E = 60 / (T _N × 2) rpm from the period T _N of the signal from the crank angle sensor 6
Ask for. In step 932, the engine operating state signal is read. That is, the injection amount signal Q _T from the accelerator amount sensor 7 and the water temperature signal from the cooling water temperature sensor 8 are A / D.
A / D conversion is performed by the converter 34, and the converted data is stored in the corresponding RAM 33. In step 933, a known four-point linear interpolation calculation is performed from the two-dimensional map of the basic ignition timing from the engine speed N _E and the injection amount Q _T to obtain the basic ignition timing T _B. Then, the target ignition timing T _M is calculated by correcting the water temperature based on the engine cooling water temperature.

In step 934, the actual ignition timing T _A is calculated from the crank angle signal and the signal from the ignition sensor by the method described above. In step 935, an error T _ERR = T _M −T _A is obtained from the target ignition timing T _M obtained in step 933 and the actual ignition timing T _A obtained in step 934.
To calculate. In step 936, the sign of the error calculated in step 935 is determined. If T _M > T _A , then T _ERR > 0, jump to step 939 and increase the duty ratio to increase the OFF time of the pressure adjustment valve 57 to increase the timer piston 5
The ignition timing is advanced by moving the position of 1 to the advance side and advancing the injection timing. If T _M <T _A , then T _ERR > 0, and the process jumps to step 938 to decrease the duty ratio and decrease the OFF time of the pressure adjusting valve 57, and move the position of the timer piston 51 to the retard side. When T _M = T _A , T _ERR = 0 and the duty ratio is the same as the previous value. That is, when the measured value T _A lags the target value T _M , the adjustment valve 57
The OFF time is lengthened to increase the pressure in the timer piston high pressure chamber B, and the timer piston 51 is moved to the advance side to advance the combustion timing, that is, the injection timing to match the target value. Thereafter, the process is repeated from step 931 to 939 every pressure control valve control cycle.

Next, in step 916, the pilot injection amount is updated, and the pilot injection amount approaches the optimum value from the initial value by a predetermined value. In step 917, the injection stop period is similarly updated, and the injection stop period approaches the optimum value from the initial value by a predetermined value. Thereafter, step 916 and step 917 are repeated, and the pilot injection amount and the injection stop period settle at the optimum values.

Details of the pilot injection amount updating portion in step 916 will be described with reference to the flowchart of FIG. Step
At 921, the actual pilot injection amount q _N is first increased from the reference pilot injection amount q _B by a very small amount Δq having a predetermined value. Next, in step 922, the combustion noise at this time is input and put in the variable S _N. Combustion noise S _B that is the reference in step 923 and combustion noise S _N that is detected when the amount is increased by Δq
Is comparing with. Here, if S _B is larger, △
This means that combustion noise has been improved by increasing q, and the routine proceeds to step 924, where the increased pilot injection amount q
_N is set as a new reference q _B, and the combustion noise S _N at this time is set as a reference combustion noise S _B. If S _B is smaller in step 923, it means that the combustion noise has deteriorated due to the increase of Δq, and the process proceeds to step 925, this time the reference value q _B
To Δq. In step 926, the combustion noise at this time is input to S _N , and in step 927, the combustion noise S _N when reduced by _Δq and the reference combustion noise S _B are compared. Here, when S _B is larger, it means that the combustion noise has been improved by reducing Δq, and step 92
Proceed to 4 and set the pilot injection amount q _N when the amount is reduced by Δq as a new reference q _B, and set the combustion noise S _N at this time as the reference combustion noise.
S _B. Also, since it means that the combustion noise was exacerbated by even or △ q weight loss by increasing it is the smaller of △ q of S _B at step 927, the reference q _B
Will not be updated. In this way, the pilot injection amount approaches the optimum value (that is, the value that minimizes the fuel noise) by the minute amount Δq. It should be noted that although the combustion noise is input only once for determination here, an average value of a plurality of times may be used in consideration of variations in the combustion noise.

FIG. 9 is a flow chart for explaining step 917 in FIG. 5, that is, the injection stop period updating portion in detail, but the algorithm is the same as that in FIG. 8, and the pilot injection amount q is the injection stop period T. The description thereof is omitted because it has only been replaced with. As described above, according to the algorithms of FIGS. 5 to 9, a set of the pilot injection amount and the injection stop period that minimizes the combustion noise, that is,
Both sets of optimum values can be controlled.

In this way, since the fuel noise is controlled to be small, according to the present embodiment, the optimum injection rate control is performed even after the diesel engine is warmed up without depending on the machine difference of the diesel engine. There is an advantage that combustion noise by the engine can be reduced. At the same time, reducing combustion noise means slowing combustion, which is also advantageous in purifying exhaust gas.

[Other Embodiments] In the above embodiment, the microphone 11 is used as the combustion noise sensor, but the output of the vibration sensor attached to the engine body near the combustion chamber, which has a strong correlation with the combustion noise, may be used instead. Can be obtained. Further, as the ignition timing detecting means, the actual injection timing may be used as a substitute by observing the signal from the nozzle lift sensor. Further, the pilot injection means 4 may be a pilot injection means using an electromagnetic valve as shown in FIG. In FIG. 10, reference numeral 70 designates pilot injection means by a solenoid valve, and its housing 71
Includes a seat portion 71a that determines the pressure receiving area on which the internal pressure from the high pressure chamber 62 acts, and a flow path 71b that returns the fuel in the high pressure chamber 62 to the fuel reservoir 65 in the pump housing. The plunger 72 is axially movable in a cylindrical inner peripheral portion 71c of the housing 71, and is integrated with a moving core 72a made of a magnetic material. The solenoid valve coil 73 is energized and controlled by the microcomputer 3. The return spring 74 presses the plunger 72 against the seat portion 71a with a force that is added to the electromagnetic force due to the current flowing through the coil 73. The spring retainer 75 is an O-ring 75a for sealing.
And it has a screw part 75c, and the spring set load can be adjusted. The valve end 76 is screwed and fixed to the housing 71.

The fuel can be pumped by moving the plunger 61 in the direction of arrow b, and the fuel is injected from the injection nozzle 63 into each cylinder of the engine. Here, the operation of pilot injection is shown by the timing chart of FIG. The figure (a) is a crank angle sensor signal, the figure (b) is a plunger lift, the figure (c) is the voltage applied to the coil of a solenoid valve, and the figure (d) is an injection rate. Here, the pilot injection amount can be changed by changing the timing T _{1 at} which the voltage applied to the solenoid valve coil 73 is "OFF". That is, the pilot injection amount can be increased by delaying T ₁ as T ₁ ′. It goes without saying that T ₁ should be turned “off” a little earlier in consideration of the response delay of the solenoid valve. Further, the injection stop period can be lengthened by increasing T ₂ changed by the time T ₂ during which the applied voltage is “OFF” to T ₂ ′. As for the control method, the same operation and advantages can be obtained even in the pilot injection device using the solenoid valve by performing the same control as in the above embodiment.

"Effects of the Invention" The fuel injection rate control device for a diesel engine of the present invention has the above-described configuration, and detects the timing at which the fuel injected into the combustion chamber of the diesel engine is ignited to reach the target ignition timing of the engine. While controlling the injection timing, the pilot injection amount or the injection stop period between the pilot injection and the main injection is forcibly changed to a predetermined amount or a predetermined period in a predetermined direction,
The combustion noise detected by the combustion noise detection means is compared before and after the change, and when the fuel noise increases, the pilot injection is performed in the opposite direction to the predetermined direction, and when the combustion noise decreases, the pilot injection is performed in the predetermined direction. By changing the amount or the injection stop period, the measured combustion noise is reduced and minimized, so that a constant combustion noise reduction effect can be obtained without being affected by individual variations and aging. Can be demonstrated.

Further, the injection amount and the injection stop period of the pilot injection have an initial value that is a function of the cooling water temperature of the engine,
Since it is possible to properly control the pilot injection at the time of idling both during cold operation and after warm-up, there is an effect that the quietness of the engine can be enhanced especially during low speed operation.

[Brief description of drawings]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the present invention,
2 is a sectional view showing the injection timing control means, FIG. 3 is a configuration diagram showing an example of pilot injection means, FIG. 4 is a timing chart showing the operation of the pilot injection means, and FIG.
FIG. 6 is a flow chart showing a main program in the computer, FIGS. 6 (a) and 6 (b) are characteristic diagrams showing characteristics of water temperature and pilot injection amount, and water temperature and injection stop period, and FIG. 7 is an injection timing control portion. Flow chart showing details,
FIG. 8 is a flowchart showing details of updating the pilot injection amount, FIG. 9 is a flowchart showing details of updating the injection stop period, FIG. 10 is a sectional view showing another embodiment of the pilot injection means, and FIG. 11 is a pilot. It is a timing chart which shows operation of injection. 1 ... Combustion chamber, 2 ... Ignition timing detection means, 3 ... Microcomputer, 4 ... Pilot injection means, 5 ... Injection timing control means, 8 ... Cooling water temperature sensor, 10 ... Combustion noise detection means.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naritoshi Kameoka 1-1, Showa-cho, Kariya city, Aichi Prefecture, Nihon Denso Co., Ltd. (72) Inventor Fumiaki Kobayashi 1, Toyota-cho, Toyota city, Aichi prefecture Toyota Automobile Co., Ltd. (56) Reference JP 60-125753 (JP, A) JP 61-185638 (JP, A) JP 61-277846 (JP, A)

Claims (2)

[Claims] Claim: What is claimed is: 1. Ignition timing detection means for detecting the timing at which fuel injected into the combustion chamber of a diesel engine is ignited, and fuel so that the actual ignition timing detected by the ignition timing detection means is the target ignition timing of the engine. Injection timing control means for controlling injection timing, combustion noise detection means for detecting combustion noise of the engine, pilot injection means for performing pilot injection prior to main fuel injection into the combustion chamber, the pilot injection amount or the Compulsively changing the injection stop period between the pilot injection and the main fuel injection to a predetermined amount or a predetermined period in a predetermined direction, and comparing the combustion noise detected by the combustion noise detection means before and after the change,
When combustion noise increases, in the direction opposite to the predetermined direction,
Pilot combustion control means for controlling the pilot injection means so as to minimize the combustion noise by changing the pilot injection amount or the injection stop time in the predetermined direction when the combustion noise decreases. A fuel injection rate control device for a diesel engine characterized by the above. 2. The fuel injection rate control device for a diesel engine according to claim 1, wherein the injection amount and the injection stop period of the pilot injection have an initial value which is a function of the cooling water temperature of the engine. .