JPS6337261B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a fuel injection control device equipped with a flow rate control device particularly suitable for use in a fuel injection control system for an internal combustion engine, particularly in a control system for controlling injection timing, injection rate, injection amount, etc. It is related to.

In internal combustion engines, especially diesel engines, highly accurate fuel injection control is required to always obtain the best performance under all operating conditions. For this purpose, it is desirable that the injection timing, injection rate, injection amount, etc. be electronically controlled, and in this case, a valve device as an electrically actuated actuator is required.

However, conventional electrically operated valve devices are small and insufficient to directly control fuel injection. In addition, if it were made larger, the response would be impaired, and the disadvantage was that the improved accuracy of dynamic response that could be obtained by electrically operating it would be sacrificed. .

Another method is to control a large hydraulic servo valve using a small electric on-off valve, but this method has the disadvantage that it does not provide sufficient functionality equivalent to fine adjustment such as injection rate control. There is.

The present invention relieves a small amount of the hydraulic pressure supplied to open the fuel injection nozzle using a relatively small electric on-off valve, and controls the injection start timing and injection rate with fine detail and high precision. A flow control device that detects when the relief speed from the on-off valve is not sufficient and automatically opens the valve using hydraulic pressure to quickly inject and stop fuel. The aim is to combine the advantages of both the fine adjustment function of electric on-off valves and the excellent high-speed relief function of hydraulic on-off valves.

The configuration of a first embodiment in which the flow rate control device of the present invention is used in a fuel control system for an internal combustion engine will be described below with reference to FIG. Reference numeral 1 denotes a high-pressure pump, and a distribution type pump that is normally used as an injection pump is used as the high-pressure pump 1, but the high-pressure pump does not need a governor and a timer. The plunger 11 of the high-pressure pump 1 is driven by an engine (not shown), and rotates and reciprocates synchronously at 1/2 rotation of the engine. When the first notch groove 12 of the plunger 11 is in communication with the suction port 14 of the cylinder 13, it is the suction stroke, and the plunger 11
pumps fuel oil into cylinder 13 while moving to the left in the diagram.
and into the pressure chamber 131 formed by the tip of the plunger 11. The discharge stroke is when the second notch groove 15 of the plunger and the discharge port 16 of the cylinder 13 are electrically connected, and the plunger 11 moves fuel oil from the pressure chamber 131 to the notch groove while moving to the right in the figure. 15, high pressure line 18 via discharge port 16
send to. The time when the plunger 11 starts to move to the right is sufficiently earlier than the time when the injection nozzle 2 is requested to start injection, and the time when the plunger 11 stops moving to the right is when the injection nozzle 2 is requested to stop injection. A fixed time is given that is sufficiently later than the time.

A low pressure line 17 is connected to the intake port 14 of the cylinder 13.
Fuel is supplied from the feed pump 3 via. Fuel is supplied from the discharge port 16 of the cylinder 13 via a high pressure line 18 to the servo piston device 4 as an actuator. The servo piston device 4 includes a large diameter servo piston 41, a smaller diameter plunger piston 42, a large cylinder 43,
It is composed of a small cylinder 44. The servo piston 41 is slidable within the large cylinder 43, and the plunger piston 42 is slidable within the small cylinder 44. The lower end of the servo piston 41 is always in contact with the upper end of the plunger piston 42. Servo piston 41 and plunger piston 4
The cross-sectional area ratio of 2 is 9:1.

A hydraulic chamber formed at the upper end of the servo piston 41 communicates with the high pressure line 18. For example, when a hydraulic pressure of 200 Kg/cm ² is supplied from the high-pressure pump 1 into this hydraulic chamber 45, 1800 Kg/cm ² is supplied into the pump chamber 46 formed at the lower end of the plunger piston 42.
Can generate ultra-high pressure. This ultra-high pressure is supplied to the injection nozzle 2 via an ultra-high pressure line 21. When the pressure within the pump chamber 46 decreases, fuel is supplied from the low pressure line 17 via the check valve 5. A metering hydraulic chamber 47 is located at the lower end of the servo piston 41.
is provided. Furthermore, when the hydraulic pressure in the hydraulic chamber 45 decreases, the servo piston 41 is pushed up by the pressure in the metering hydraulic chamber 47, but the cylinder 43
A spring 451 is provided within the hydraulic chamber 45 to prevent violent collision with the upper end of the hydraulic chamber 45. Measuring hydraulic chamber 4
The fuel oil in 7 flows in and out through a metering device 6. The metering hydraulic chamber 47 and the metering device 6 are communicated through a metering line 48 .

The metering device 6 includes a constriction section 61, a pressure adjustment section 62, and a differential pressure sensor section 63. The aperture part 61 is
It consists of a diaphragm 611, a pre-diaphragm chamber 612, and a post-diaphragm chamber 613, and the post-diaphragm chamber 613 is connected to the metering line 48.
The pre-throttling chamber 612 is electrically connected to the low pressure line 17 , and the pre-throttling chamber 612 and the post-throttling chamber 613 are electrically connected to each other via the diaphragm 611 . The pressure adjustment section 62 includes a cylinder 621, a spool 622, and a spring 6.
Consists of 23. The spool 622 slides oil-tightly inside the cylinder 621, and has a hydraulic chamber 624 communicating with the post-throttling chamber 613 at its left end, and a hydraulic chamber 625 communicating with the pre-throttling chamber 612 at its right end. is forming. A spring 623 is installed in the hydraulic chamber 624.
is provided to press the spool 622 to the right in the figure.

Two openings 626 and 627 at different axial positions are provided on the outer peripheral surface of the spool 622 on which it slides. Opening 626 to hydraulic chamber 624;
27 are each connected to a hydraulic chamber 625. The cylinder 621 is provided with an annular groove 628 on its inner peripheral surface, and the annular groove 628 is electrically connected to the drain line 71 . Drain line 71 is connected to fuel tank 7
It is electrically conductive. If the pressure in the pre-throttling chamber 612 becomes excessive than the pressure in the post-throttling chamber 613, the spool 62
2 moves to the left in the figure against the pressing force of the spring 623, and when the opening 627 coincides with the annular groove 628, the pressure in the hydraulic chamber 625 is relieved. Therefore, the differential pressure across the throttle 611 is always maintained constant by the action of the pressure regulator 62. The differential pressure across the throttle 611 is determined by the pressing force of the spring 623, and here, for example, 2 kg/cm ²
Assume that it is set to .

By the way, when the servo piston 41 descends,
It is necessary to allow the fuel in the metering hydraulic chamber 47 to flow back into the post-throttling chamber 613, but at that time the oil pressure in the pre-throttling chamber 612 is maintained at the maximum pressure in the low pressure line 17, for example 5 kg/cm ² . The oil pressure in the post-throttling chamber 613 rises above the oil pressure in the pre-throttling chamber 612. This state continues until the spool 622 is moved to the right by the oil pressure in the rear throttling chamber 613 and the opening 626 and the annular groove 628 coincide.

Conversely, when the servo piston 41 rises,
It functions to cause fuel to pass through the throttle 611 and flow into the metering hydraulic chamber 47 with a differential pressure of 2 kg/cm ² .
The servo piston 4 is activated by the pressure in the metering hydraulic chamber 47.
When the force applied to servo piston 1 and the pressure of spring 451 are balanced, servo piston 41 stops. At this time, the amount of fuel passing through 611 again becomes zero,
At this time as well, the differential pressure maintaining function of the spool 622 has to be stopped, and the pressures in the pre-throttling chamber 612 and the post-throttling chamber 613 are both maintained at the maximum pressure in the low pressure line 17. The spool 622 takes a position where neither the openings 626, 627 are electrically connected to the annular groove 628. Note that at this time, the spring 623 is in a free length state. The differential pressure sensor section 63 is connected to the cylinder 631
, a large piston 632 that can slide oil-tightly inside the cylinder 631, small pistons 633 and 634 that protrude from both ends of the large piston 632, and a pressure sensor 63 that outputs an output when pressed by the small piston 633.
5, and a pressure sensor 636 that outputs an output when pressed by the small piston 634. The hydraulic pressure of the rear throttle chamber 613 is introduced to the left side of the large piston 632 except for the small piston 633, and the large piston 632
The hydraulic pressure of the throttle front chamber 612 is introduced to the right side of 32 except for the small piston 63. When the oil pressure in the front throttle chamber 612 is higher than the oil pressure in the rear throttle chamber 613, the piston 632 is pressed to the left in the figure, and at the same time the small piston 633 presses the pressure sensor 635. The output signal from the pressure sensor 635 is input to an external computing unit (not shown) via a lead wire 637. Further, when the oil pressure in the rear throttle chamber 613 is higher than the oil pressure in the front throttle chamber 612, the large piston 632 is pressed to the right in the figure, and at the same time the piston 634 presses the pressure sensor 636. The output signal from the pressure sensor 636 is input to an external computing unit (not shown) via a lead wire 638. Here, the pressure sensor 63
5,636 uses a piezoelectric element.

The pressure in high pressure line 18 is controlled by flow controller 8 . The flow rate control device 8 includes a solenoid valve 81 as an electric on-off valve and a spool valve 82 as a hydraulic on-off valve. The spool valve 82 is composed of a cylinder 821, a spool 822, and a spring 823. Spool 8
22 slides inside a cylinder 821 in the vertical direction in the figure, and has hydraulic chambers 82 at each of its upper and lower ends.
4,825 are provided. The lower hydraulic chamber 825 is directly connected to the high pressure line 18, and the spool 822
It also communicates with the upper hydraulic chamber 824 via a throttle 826 provided at the central axis of the hydraulic chamber 824 . Upper hydraulic chamber 82
A spring 823 is placed within the spool 4, and this spring force presses the spool 822 downward.
When the hydraulic pressure in the lower hydraulic chamber 825 is sufficiently larger than the hydraulic pressure in the upper hydraulic chamber 824, the spool 822 rises against the spring 823, and the lower end surface 822b of the spool 822 is connected to the inner peripheral surface of the cylinder 821. When it overlaps a part of the annular groove 827, the hydraulic pressure in the lower hydraulic chamber 825 is relieved to the drain line 71 via the annular groove 827. Upper hydraulic chamber 824
is connected to the drain line 71 by the solenoid valve 81.
The conduction to is opened and closed. The solenoid valve 81 is composed of a solenoid 811, a valve body 812, and a spring 813. When the solenoid 811 is energized, the valve body 812 rises against the spring 813 to open the valve. Solenoid valve 8
1 opens, the hydraulic pressure in the upper hydraulic chamber 824 is relieved to the drain line 71. solenoid 8
11 is energized via a lead wire 814 by an external controller (not shown). Low pressure line 1
7 is supplied with fuel from the fuel tank 7 by the feed pump 3, but this low pressure line 17 is equipped with a relief valve 9, and the maximum pressure is set to 5 kg/cm ² , for example.
The settings are managed so that In other words, if the oil pressure in the low pressure line 17 is 5Kg/
When the pressure exceeds cm ² , the relief valve 9 opens, and a portion of the fuel in the low pressure line 17 is relieved to the drain line 71 to maintain the hydraulic pressure in the low pressure line 17 at the set maximum pressure of 5 kg/cm ² .

The operation will be explained below with reference to FIG. 2.

When the piston of a diesel engine (not shown) reaches a predetermined crank angle phase θ ₁ well before compression top dead center, the plunger 11 of the high-pressure pump 1
moves to the right, and fuel begins to be supplied to the high pressure line 18 accordingly. This fuel is not supplied to the servo piston device 4 until the crank angle phase θ ₃ at the scheduled time is reached, and is relieved to the drain line 71 by the flow rate control device 8. At this time, the solenoid 811 is energized, and the solenoid valve 8
1 is open, the fuel in the high pressure line 18 mainly flows out to the drain line 71 through the throttle 826 and the solenoid valve 81. If this outflow amount is extremely large, the spool 822 will be pushed up due to the flow resistance caused by the restrictor 826, and the annular groove 827 will be pushed up.
However, since the pressure rise in the high-pressure line 18 is slow, this almost never happens, and even if it were to happen, the movement of the spool 822 is slow and the fuel flowing out from the annular groove 827 is extremely slow. It is minute. When the crank angle phase of the piston of the diesel engine further advances and reaches the scheduled crank angle phase θ ₃ , which is just before the compression top dead center, the energization to the solenoid 811 is stopped and the solenoid valve 81 is closed. As a result, the fuel that continues to be supplied from the high-pressure pump 1 to the high-pressure line 18 has nowhere to escape, causing the oil pressure in the high-pressure line 18 to rapidly rise. Even if fuel were to flow out from the annular groove 827, the annular groove 827 would be blocked by the spool 822 at the same time as the solenoid valve 81 was closed. This is the same as when there is no fuel outflow from the annular groove. This increased oil pressure is utilized by the servo piston device 4. That is, while the solenoid valve 81 is open, both the servo piston 41 and the plunger piston 42 are at the upper limit of their movable range, but as the oil pressure in the high pressure line 18 increases, they begin to descend, and this plunger piston 42, the injection nozzle 2 injects and supplies fuel into a combustion chamber of a diesel engine (not shown). As the servo piston 41 descends, the fuel in the metering hydraulic chamber 47 becomes higher than the maximum pressure of 5 kg/cm ² set in the low pressure line 17, and as a result, the spool 622 of the metering device 6 is moved to the right and the annular groove 62 is moved.
The large piston 632 of the differential pressure sensor section 63 is pressed to the right, and the pressure sensor 636 issues a signal at the crank angle phase θ ₃ '. This signal is the injection start time, and if there is a deviation from the scheduled injection start time, the next energization stop time θ ₃ to the solenoid 81 is corrected. Here, θ ₃ ' is a crank angle phase that is slightly slower than θ ₃ . When the crank angle phase of the piston of the diesel engine advances and reaches a predetermined crank angle phase θ ₄ , which is around compression top dead center, the solenoid 811 is energized and the solenoid valve 81 opens. At this moment, high pressure line 18
The spool 822 rises all at once due to the high pressure of
7 to the drain line 71 to create a pressure effect. Therefore, the servo piston 41 and the plunger piston 42 stop descending and simultaneously start rising, so the injection nozzle 2 immediately stops fuel injection. When the plunger piston 42 is raised, the hydraulic pressure in the low pressure line 17 is applied to the check valve 5.
It acts on the lower end surface of the plunger piston 42 via. When the servo piston 41 is raised, the oil pressure of the low pressure line 17 acts on the lower end surface of the servo piston 41 via the metering device 6. In the metering device 6, at the same time as the servo piston 42 starts to rise, the oil pressure in the front throttle chamber 612 becomes higher than the oil pressure in the rear throttle chamber 613, the large piston 632 is pushed to the left, and the pressure sensor 635 is detected at phase θ ₄ . emit a signal. This becomes the signal to start weighing. When the servo piston 41 reaches the upper limit position of its movement range, the flow of oil through the throttle 611 stops, the differential pressure across the throttle 611 becomes zero, and the large piston 632 is no longer pressed to the left. At this time, the pressure sensor 635 emits a signal at phase θ ₅ . This is the signal to end the measurement. During the metering period, the area of the throttle 611 is fixed and the differential pressure across the throttle 611 is kept constant, so the amount of fuel flowing into the metering hydraulic chamber 47 varies during the metering period, that is, θ ₅ - _{θ 4} . proportional to the length of time. When the amount of fuel thus obtained deviates from the scheduled value, the timing θ ₄ for starting the next energization to the solenoid 811 is corrected. During the measurement period, the high pressure pump 1 stops supplying fuel to the high pressure line 18 and the plunger 11 moves to the left at a predetermined time θ ₂ when the crank angle phase of the piston of the diesel engine is slightly after top dead center. The engine then moves to the fuel intake stroke, and thereafter the operations described above are repeated as one cycle.

In the first embodiment, during the period when fuel is injected from the injection nozzle 2, the solenoid 811
It is not supposed to be energized. That is, the solenoid valve 81 remains closed, but in the second embodiment, a voltage of an appropriate magnitude or a voltage of an appropriate frequency is applied to the solenoid valve 811 to provide appropriate hydraulic relief even during the injection period. The injection rate can also be controlled by doing this.

Further, in the first embodiment, a solenoid valve 81 is used as an electrically operated valve, but in the third embodiment, not only a solenoid but also a magnetostrictive effect or an electrostrictive effect is used. It's good to be warm.

Further, in the first embodiment, the aperture 826 is provided integrally with the spool 822, but the aperture 826 may be provided separately from the spool 822 and provided in parallel.

Further, in the first embodiment, the electric on-off valve 81 and the hydraulic on-off valve 82 were integrally formed as the flow rate control valve device 8, but of course they were formed as separate bodies and combined to form the flow rate control valve. It may also be the device 8.

As explained in detail above, in the present invention, the relatively small electric on-off valve 81 directly relieves the hydraulic pressure prepared for fuel injection.
It has good responsiveness and a fine adjustment function, allowing you to control injection start timing and injection rate with high precision.

Furthermore, the flow rate of oil relieved from this electric on-off valve 81 is converted into hydraulic pressure by a throttle 826,
A relatively large hydraulic on-off valve 8 operated by this hydraulic pressure
2, it is possible to automatically perform relief exceeding the ability of the electric on-off valve 81. In addition, this hydraulic on-off valve 82 functions particularly at the end of fuel injection, and has the excellent effect of quickly stopping the injection from the injection nozzle 2 and improving fuel efficiency and exhaust emissions.

Furthermore, for example, as in the above-described embodiment, the metering hydraulic chamber 4 provided on one side of the servo piston 41
When trying to control the fuel injection amount by detecting the amount of oil flowing into the servo piston 7, the oil pressure in the operating hydraulic chamber 45 of the servo piston 41 quickly decreases as the fuel injection ends, and the servo piston 41 moves at a constant speed. It is necessary to encourage the servo piston 41 to rise, but once the spool 82 of the hydraulic on-off valve 82 rises, it cannot come down for several milliseconds due to its inertia. can be set at a more accurate constant speed, so the accuracy of measuring the flow rate to the metering hydraulic chamber 47 by the metering device 6 can be improved.

Note that it is more effective if the pressure receiving area of the bottom surface 822b is larger when the spool 822 is raised than when it is at the lowest end, as in the first embodiment of the present invention shown in FIG. It is.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of the first embodiment, and FIG. 2 is an operational diagram of the first embodiment. 1... High pressure pump, 2... Injection nozzle, 3...
Feed pump, 4... Servo piston device serving as an actuator, 41... Servo piston, 4
2...Plunger piston, 43...Large cylinder, 44...Small cylinder, 45...Operating hydraulic chamber, 47...Measuring hydraulic chamber, 48...Measuring line, 6...Measuring device, 611,826... ...aperture,
62...Pressure adjustment section, 18...High pressure line, 18
1... Inlet flow path, 632... Differential pressure piston, 63
5,636...Pressure sensor, 71...Drain line, 711...Outlet channel, 712...Bypass channel, 713...Electric shut-off valve drain line,
8...Flow control device, 81...Electric on-off valve (solenoid valve), 82...Hydraulic on-off valve (spool valve).

Claims (1)

[Claims] 1. A pressure chamber 131 that intermittently generates high pressure by the reciprocating motion of the plunger 11 of the high-pressure pump 1 is brought into communication with the actuator 4 or the injection nozzle 2, and the actuator 4 or the injection nozzle 2 is periodically This flow control device is used in a hydraulic system that supplies high-pressure oil, and is composed of a hydraulic on-off valve 82 and an electric on-off valve 81, and the hydraulic on-off valve 82 is A spool valve having three ports, the first port of which communicates with the pressure chamber 131 and the actuator 4 or the injection nozzle 2, and the second port communicates with the low pressure line 17 or the drain line 71. The third port is electrically connected to the electric on-off valve 81, and the valve body 822 of the spool valve receives pressure on one end face of a first hydraulic chamber 825 that is electrically connected to the first port. A second hydraulic chamber 824 is provided on the other end surface of the valve body 822 and communicates with the third port and also with the first hydraulic chamber 825 via a throttle 826 provided inside the valve body 822. The electric on-off valve 81 receives the pressure of the hydraulic on-off valve 8.
2, which opens and closes the third port of No. 2,
When the electric on-off valve 81 is open, the third port is connected to the low pressure line 17 or the drain line 71.
The first hydraulic chamber 825 and the second hydraulic chamber 8 are electrically connected to each other.
When the pressure difference with 24 becomes larger than a predetermined value,
The valve body 822 moves to adjust the high pressure oil supplied from the pressure chamber 131 to the injection nozzle 2 or the actuator 4' by a flow control device that connects the first port and the second port. A fuel injection control device that controls at least one of the injection time, injection rate, and injection amount of high-pressure oil injected from the injection nozzle 2. 2 The actuator 4 includes a large cylinder 43 and a servo piston 4 that slides inside the large cylinder 43.
1. Small cylinder 4 connected to the large cylinder 43
4. A plunger piston 42 that comes into contact with the servo piston 41 and slides inside the small cylinder 44
The pressure in the pressure chamber 131 is applied to the end face of the servo piston 41 on the opposite side of the plunger piston 42, thereby causing the servo piston 41 to
Generates high pressure to be supplied to the injection nozzle 2 on the end face of the plunger piston 42 on the opposite side of the servo piston 41 and on the end face of the servo piston 41 on the side that contacts the plunger piston 42 and the large cylinder 4
3 to form a metering hydraulic chamber 47, and comprising means for measuring the timing of fluid flowing in and out of the metering hydraulic chamber 47. fuel injection control device.