JPH0223252A - Fuel injection rate control device for compression ignition engine - Google Patents

Abstract

PURPOSE:To always perform pilot injection suitably for suppressing engine noise and the like by varying fuel injection quantity so as to become into an appointed running condition, while performing pilot injection in accordance with the variation before main injection. CONSTITUTION:When a drive shaft 2 of a fuel injection pump is made to rotate, a plunger 16 is reciprocated via a cam plate 28. Fuel in a pump chamber 12 is sucked into a high pressure chamber 18 from a suction port 14 therefor, and further delivered on push opening a delivery valve 36 through a distribution port 26 and a distribution passage 38. Thereupon, a microcomputer 82 controls plural numbers of electromagnetic valves 44, 48 or a cut valve 64 in opening and closing and controls fuel injection. Namely, the same valys fuel injection quantity so as to become into an appointed running condition, for instance to become into a set running condition on an idle running condition, while performs pilot injection before main injection. The pilot injection is controlled in accordance with the variation of fuel injection quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an injection rate control device that controls pilot injection in a compression ignition engine such as a diesel engine.

[Conventional technology and issues]

Conventionally, in the fuel injection of a diesel engine, a so-called pilot injection P is performed prior to the main injection M0, as shown in FIG. 6(a). is known to reduce engine noise and exhaust gas emissions. However, in a fuel injection valve configured to open based on the pressure inside the nozzle chamber, it is understood from Fig. 6(b) that the performance of the fuel injection valve deteriorates due to changes over time and the opening pressure decreases. As a result, the opening time of the fuel injector becomes longer as shown in Fig. 6(a).
There is a problem in that the pilot injection is no longer performed and the fuel injection amount increases as shown by the - dotted chain line I.

Conventionally, in diesel engines, a configuration is known in which the fuel injection amount during idling operation is controlled to control the idling rotation speed to a target value (for example, Japanese Patent Laid-Open No.
181940). However, the conventional idle speed control device changes only the fuel injection amount, and controls only the end of injection as shown by the two-dot chain line J in Fig. 6(a). Depending on the degree of performance deterioration, pilot injection may not be possible.

If pilot injection is not performed properly in this way,
Problems arise in that engine noise increases and exhaust gas emissions worsen.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel injection rate control device that can always perform pilot injection appropriately regardless of changes in the performance of a fuel injection valve, and can always suppress engine noise and exhaust gas emissions.

[Means to solve the problem]

The fuel injection rate control device according to the present invention changes the fuel injection amount so that a predetermined operating state becomes a predetermined state, and also performs pilot injection prior to main injection. It is characterized in that it is controlled according to the amount of change in the fuel injection amount.

〔Example〕

The present invention will be explained below with reference to illustrated embodiments.

FIG. 2 is a schematic diagram of a diesel engine equipped with an electromagnetic spill distribution type fuel injection pump. An electromagnetic spill distribution type fuel injection pump is equipped with a solenoid valve in a communication passage that communicates a high pressure chamber formed by the cylinder inner wall surface and the plunger tip surface with a low pressure chamber (pump chamber) inside the pump. By controlling this, the communication path is shut off and the fuel injection amount is controlled.

The fuel filtered by the filter is transferred to the drive shaft 2
A vane-type field pump (shown unfolded at 90°) 4 driven by the oil supply port 6 is guided to the pressure regulating valve 8, and after being regulated by the pressure regulating valve 8, the oil inside the pump housing 10 is It is supplied into the pump chamber 12 which is a low pressure chamber.

The fuel supplied into the pump chamber 12 lubricates the operating parts within the pump chamber 12, and also lubricates the operating parts within the pump chamber 12.
A high pressure chamber 1 formed at the tip of the plunger 16 through the
Sent to 8th. A portion of the fuel is also returned to the fuel tank through the 1, i-H flow valve 20, thereby discharging excess fuel and cooling the operating parts.

Suction groups 22 of the same number as the number of cylinders are provided at the tip of the plunger 16, and a distribution port 26 communicating with the axial port 24 is bored in the radial direction of the plunger 16.

A cam plate 28 is fixed to the base end of the plunger 16, and the same number of rollers 32 as the number of cylinders fitted into the roller ring 30 are engaged with the cam plate 28. The plunger 16 is inserted into the cylinder 34 , and a high pressure chamber 18 is formed by the tip end surface of the pressure regulating valve 16 and the inner wall surface inside the cylinder 34 . The cylinder 34 is provided with the suction port 14 and the same number of distribution passages 38 as the number of cylinders that communicate with the delivery valve 36 from the inner surface of the cylinder. A solenoid valve 44 that communicates and blocks the communication path 40 is attached to the pump housing 10. This communication path 40 is connected to the high pressure chamber 18 and the pump chamber 1.
2. In the electromagnetic valve 44, when the solenoid 46 is turned off, the valve body 42 is pushed by a spring to communicate the communication passage 40, and when the solenoid 46 is turned on, the valve body 42 protrudes and the communication passage 40 is opened. Configured to block.

The drive shaft 2 projects into the pump chamber 12 and is connected to a cam plate 28 via a coupling. The cam plate 28 is fixed to the plunger 16 and is pressed against the roller 32 by a spring 50. Therefore, when the cam plate 28 is rotationally driven by the drive shaft 2, the roller 32 and the cam plate 28
The state of engagement with the cam ridge changes, and the plunger 16 reciprocates a number of times equal to the number of cylinders during one rotation.

A hydraulic timer 52 (shown unfolded at 90°) is provided at the bottom of the fuel injection pump. This hydraulic timer 52 utilizes changes in fuel supply pressure to control the drive shaft 2.
The phase of the cam plate 28 that drives the plunger 16 is changed to change the fuel injection timing. According to this timer 52, when the spring 54 pushes the timer piston 56 in the direction of the injection amount and the engine speed increases, the oil feeding pressure increases and the piston 56 resists the elastic force of the spring 54. Rod 58 to be pushed
The roller ring 30 is rotated in a direction opposite to the rotational direction of the injection pump, and the fuel injection timing is advanced in proportion to the oil pressure. The fuel injection timing is controlled by the solenoid valve 48 so as to match the target injection timing according to the engine conditions.
It is controlled by controlling the oil pressure acting on 6.

A signal rotor 60 is fixed coaxially to the drive shaft 2, and a pickup 62 is attached to the roller ring 30 so as to face the circumferential surface of the signal rotor 60. The signal rotor 60 is provided with a plurality of convex teeth arranged at predetermined angles (for example, 5.625"), and these convex teeth are notched at equal intervals in the same number as the number of cylinders to form missing teeth. That is, in the case of a 4-cylinder diesel engine, as shown in Fig. 3, convex teeth 60α, 60β, . A plurality of teeth are arranged, and missing teeth 60a to 60d are formed every 90 degrees (corresponding to 180 degrees CA).Therefore, when the signal rotor rotates, the convex teeth move toward and away from the pickup. Therefore, a pulse signal as shown in FIG. 4 is output from the pickup due to electromagnetic induction.

The wide valley portion of this pulse signal acts as a reference position signal, and the other portion acts as a rotation angle signal. In addition, the relative position of the pickup and the signal rotor is such that before the plunger is moved forward in the direction in which the high pressure chamber is compressed, that is, before the plunger lifts, one of the missing teeth approaches the pickup. It is determined so that the position signal is output, that is, the width of the trough of the pulse signal is widened.

A fuel injection cut valve 64 is attached to the pump housing 10 to stop fuel injection by cutting off the suction boat 14.

The delivery vibe 65 is connected to a fuel injection valve 68 that is attached to protrude into the auxiliary combustion chamber of the diesel engine 66. A glow plug 70 is attached to this sub-combustion chamber. A throttle valve 88 is arranged in the intake passage, and a bundle 90 includes this throttle valve 88.

In addition, 74 is an accelerator sensor that detects the accelerator opening degree;
76 is a pressure sensor that detects intake pipe pressure, 78 is a water temperature sensor that detects engine cooling water temperature, 80 is a glow relay, and 92 is a vehicle speed sensor.

Further, 84 is a signal rotor that is fixed to the crankshaft and has a protrusion at the top dead center position of the fixed cylinder; 86 is a top dead center sensor that outputs a top dead center signal as the protrusion passes; 94
is the shift position switch.

In addition to the accelerator sensor 74, the microcombinator 82 includes a pickup 62, a pressure sensor 76, and a water temperature sensor 7.
8, a vehicle speed sensor 92, a shift position switch 94, and a top dead center sensor 86 are connected. The output port of the microcomputer 82 is connected to the glow plug 70 via the glow relay 80 and to the solenoid 46 of the solenoid valve 44, the solenoid of the solenoid valve 48, and the solenoid of the fuel injection cut valve 64. The microcomputer 82 is a CPU as is well known.

It consists of RAM, ROM, ^D converter, input port, output port, etc. Microcomputer 82 R
The OM stores a control routine program to be described later, and also stores accelerator opening α, engine speed Ne, water temperature,
and final injection amount θf corrected by engine load
in and the command value of the pilot injection amount (pilot amount θp
1 pilot interval θm) is stored in advance.

The fuel injection pump having the above configuration performs fuel injection as follows. That is, the cam plate 28 is rotationally driven by the drive shaft 20 rotations, and in response, the plunger 16 rotates around the axis and reciprocates along the axial direction.

The fuel in the pump chamber 12 is sucked into the high pressure chamber 18 through the suction port 14 as the plunger 16 retreats, and the fuel sucked into the high pressure chamber 18 is compressed and distributed as the plunger 16 moves forward. It passes through the port 26 and distribution passage 38 and is discharged by pushing open the delivery valve 36. The fuel injection rate is controlled by opening and closing the electromagnetic valve 44 and releasing the fuel in the high pressure chamber 18 to the pump chamber via the communication path 40. Also, during deceleration driving, etc.
The fuel supply to the engine is cut off by closing the fuel injection cut valve 64.

Generally, when controlling the amount of fuel injection into a diesel engine, for example, the engine rotation speed is detected by a rotation speed detection sensor attached to the engine or injection pump, and the accelerator opening degree is detected by an accelerator position sensor attached to the accelerator. The basic fuel injection amount is calculated from a two-dimensional map or a calculation formula based on the rotational speed and the accelerator opening. This injection amount pattern is a governor pattern unique to diesel injection pumps, and the characteristic of this pattern is that when idling (accelerator opening 0%), the injection amount increases as the rotation speed increases, as shown in Figure 5. This is a pattern in which there is a rapid decrease in The idle speed of a diesel engine is determined near the intersection of this pattern and the engine's load curve (a curve connecting the required injection amount at each speed with a constant load). That is, when the rotational speed increases on the governor pattern, the rotational speed decreases due to a decrease in the injection amount, and conversely, when the rotational speed decreases, the rotational speed increases due to an increase in the injection amount. When the period of such feedback control is fast, the rotational speed becomes stable at the intersection of the load curve and the banner pattern. In Figure 5, the stable points of rotation speed are N1 for governor pattern 1 and N1 for pattern 2.
In pattern 3, it is N2, and in pattern 3, it is N2. If the fuel injection amount changes according to pattern 2 in the initial stage, pattern 1 will result in a small injection amount when the valve opening pressure is high, and pattern 3 will result in a large injection amount when the valve opening pressure is small. Further, when the characteristics of the fuel injection valve deteriorate and the valve opening pressure becomes small, the fuel injection amount becomes as shown in pattern 3. In this embodiment, by moving such a governor pattern in parallel according to the error between the target rotation speed determined according to the engine operating state and the actual rotation speed, the intersection of the load curve and the governor pattern is adjusted to the target rotation speed. The engine speed is controlled to be higher than the idle rotation speed, and the pilot injection end timing and main injection start timing are also controlled based on the parallel movement correction amount for correcting this error.

FIG. 1 shows a flowchart of a routine for controlling idle speed and pilot injection.

This control routine is started by turning on a key switch for starting the engine, and thereafter interrupt processing is performed at predetermined time intervals.

First, in steps 100 to 110, idle rotation speed control is corrected.

In step 100, engine speed Ne, accelerator opening α, engine coolant temperature THW, engine load signal, and vehicle speed SPD are taken in as engine operating parameters. In step 101, it is determined whether the current driving state is a stable idle state by determining whether the accelerator opening is fully closed and the vehicle speed is below a predetermined value. If the idle state is currently stable, the process proceeds to step 102, and if the idle state is not stable, step 106 is executed. In step 102, it is determined whether or not a predetermined time has elapsed since the idle stable state was reached. If the predetermined time has elapsed, the difference N15c between the target value of the idle rotation speed and the actual rotation speed is determined in steps 103 to 105.

In step 103, the target rotation speed Nf in idle rotation speed control is determined from the engine coolant temperature THW and the engine load.
In step 104, the difference ΔN between the target rotational speed Nf and the actual engine rotational speed Ne acquired in step 100 is calculated. In step 105, step 1
The current correction amount ΔN15c for idle rotation speed control is calculated from the rotation speed difference ΔN obtained in step 04. Note that this correction amount Δ
N increases as the rotational speed difference ΔN increases. Step 1
In 06, the correction amount ΔN15c and the pilot amount correction amount Δθ are set so as not to update the correction amount in idle rotation speed control.
p1 Reset the pilot interval correction amount Δθm to zero. In step 107, the current correction amount ΔN15c is added to the previous correction amount integrated value ΣΔN15c for the idle speed control, thereby obtaining the correction amount integrated value N15c for the idle speed control.

In step 108, it is determined whether or not the correction amount integrated value N15c of the idle rotation speed control is within a predetermined range, that is, whether it is normal. If it is within the predetermined range, the process directly proceeds to step 110, and If not, step 10
9, the correction amount integrated value N15c is reset to A.

In step 110, the engine operating parameters taken in step 100, that is, the engine rotation speed Ne,
A command value θfin for the final injection amount is calculated from the accelerator opening α, the engine water temperature THW, and the correction amount for the idle rotation speed control obtained in the previous steps.

Next, in steps 111 to 124, pilot injection is controlled.

In steps 111 and 112, the current pilot amount correction amount Δθp and pilot interval correction amount Δθm are calculated based on the idle rotation speed control correction amount ΔN15c calculated in step 105. These correction amounts Δθp,
As shown in FIG. 7, Δθm increases linearly with an increase in the idle speed control correction amount ΔN15c, and the rate of increase of the pilot interval correction amount Δθm is larger than that of the pilot amount correction amount Δθp. In step 113,
By adding the current correction amount Δθp to the previous pilot amount correction amount integrated value ΣΔθp, the pilot amount correction amount integrated value dθp is obtained. Similarly, in step 114, the current correction amount Δθm is added to the previous pilot spacing correction amount integrated value ΣΔθm to obtain the pilot spacing correction amount integrated value dθm. In step 115, it is determined whether the correction amount integrated value dθp is within a predetermined range, that is, whether it is normal or not. If normal, the process proceeds to step 117, and if not, in step 116, the correction amount integrated value d0p is set to a predetermined value. Set value B. In step 117, it is determined whether or not the correction amount integrated value dθm is within a predetermined range, that is, whether it is normal or not. If normal, the process proceeds to step 121; if not, in step 118, the correction amount integrated value dθm is set to a predetermined value. Set value C.

In step 121, basic command values θp and θm for the pilot amount and pilot interval are determined based on the engine rotational speed Ne, the idle rotational speed control correction amount N15c, the accelerator opening α, and the engine water temperature THW. In step 122, the basic command value θp of the pilot amount obtained in step 121 is added to the integrated value dθp obtained in step 113.
is added to calculate the final command pilot amount θp. Similarly, in step 123, the basic command value θ of the pilot interval is
The final command pilot interval θm is calculated by adding the integrated value dθm obtained in step 114 to m. Step 124
Then, the final injection amount θfin, the final command pilot amount θp1, and the final command pilot interval θm obtained in steps 110, 122, and 123 are set in the output stage of the microcomputer. These command values are outputted to the solenoid valve 44 at predetermined timing, and thereby the pilot interval is performed.

Note that the correction amounts ΔN15c and Δθm obtained in the routine shown in FIG. Of course it's a good thing.

As shown in FIG. 6(a), when the opening pressure of the fuel injection valve is normal, if main injection M0 and pilot injection P0 are performed as shown by the solid line, then the fuel injection at this time is as shown in FIG. As shown in FIG. 6(C), as the lift amount of the plunger 16 increases, the opening/closing operation is performed at the hatched portion, and the solenoid valve 44 is controlled to open and close as shown by the solid line in FIG. 6(d). Here, when the valve opening pressure decreases, the fuel injection amount changes, and the idle speed changes, the idle speed is corrected to a predetermined value (steps 100 to 110), and at the same time, the idle speed is corrected to a predetermined value. The injection command value is also controlled (steps 111 to 124). In this pilot injection command value control, the pilot interval θ
The fact that m and the pilot amount θp always have a relationship as shown in FIG. 7 is utilized. That is, the correction amount ΔN15c of the idle rotation speed control is detected, and the pilot interval θm and the pilot amount θp are determined according to this correction amount,
A stable pilot injection is obtained. As a result, the opening and closing of the solenoid valve 44 changes as shown by the broken line in FIG. 6(d),
As a result, fuel injection is performed at the timing indicated by the broken line in FIG. 6(C). That is, as shown by the broken line in FIG. 6(a), main injection M+pilot injection P+ is ensured.

As described above, according to this embodiment, in the pilot injection control system, pilot injection is always ensured even if the opening pressure of the fuel injection valve changes due to changes over time or the like. Therefore, the effect is obtained that engine noise and exhaust gas emissions are constantly reduced regardless of changes in the performance of the fuel injection valve.

In the above embodiment, the change in the fuel injection amount during idling is detected based on the difference between the actual rotation speed during idling and the target value, and thereby the change over time in the opening characteristic of the fuel injection valve is detected. However, this change over time may be detected by detecting a change in the rotational speed under other operating conditions.

Further, the change over time in the opening characteristic of the fuel injection valve can also be obtained by detecting the opening period of the needle valve of the fuel injection valve. In the case of a distribution type fuel injection pump with a spill ring, the fuel injection valve is controlled by changing the position of the spill ring for idle speed control, and in the case of an inline fuel injection pump, by changing the position of the metering rack. It is possible to detect changes over time in the valve opening characteristics of the valve.

Furthermore, although the above embodiment was configured to control the pilot injection using one solenoid valve 44, the present invention includes a pilot injection control actuator and a metering actuator for main injection. The same can be applied to a separately provided configuration.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to always appropriately perform pilot injection regardless of changes in the performance of the fuel injection valve, and to always suppress engine noise and exhaust gas emissions.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing a routine for idle speed control and pilot injection control in an embodiment of the present invention; FIG. 2 is a sectional view showing a diesel engine and a fuel injection pump to which an embodiment of the present invention is applied; Figure 3 is a plan view showing the details of the signal rotor, Figure 4 is a diagram showing the waveform of the pulse signal output from the pickup, Figure 5 is a map of the pilot control amount relative to the correction amount of idle rotation speed control, Figures 6 (a>, (b), (c), (d), and 6 are graphs showing the injection rate, nozzle chamber pressure, plunger lift amount, and command signal for the solenoid valve, respectively, for pilot injection, Fig. 7 is a graph showing the relationship between the idle rotation speed and the pilot correction amount. 68... Fuel injection valve, 44... Solenoid valve, 82...
...Microcombi Niichiyo. Figure 3 Figure 4 Figure S Figure Figure

Claims (3)

[Claims] 1. The fuel injection amount is changed so that a predetermined operating state becomes a predetermined state, and a pilot injection is performed prior to the main injection, and the pilot injection is controlled according to the amount of change in the fuel injection amount. A fuel injection rate control device for a compression ignition engine. 2. 2. The fuel injection rate control device for a compression ignition engine according to claim 1, wherein the predetermined operating state is an idling operating state. 3. 2. The fuel injection rate control device for a compression ignition engine according to claim 1, wherein the amount of change in the fuel injection amount in the predetermined operating state is detected according to a deviation between an actual rotational speed and a target value.