JPH01100348A - High pressure fuel pump control device - Google Patents

Abstract

PURPOSE:To enhance the durability of a high pressure fuel pump control device, which is used to a common rail type fuel injection control device, by furnishing a restricting means to restrict the fuel discharge starting timing when the engine exceeds its rated operating condition into the high speed operating condition. CONSTITUTION:A high pressure fuel pump control device includes a pressure boosting means M3, which pressurizes and discharges the fuel in accordance with the discharge start timing commanded externally, and the discharged fuel is once stored in a pressure accumulator M2 and supplied to a Diesel engine M1. This pressure boosting means M3 is given a command about discharge start timing, which is decided by a control means M4 on the basis of the engine operating condition and the fuel pressure at the pressure accumulator M2. Here a restricting means M5 is furnished to restrict the discharge start timing decided by control means M4 to the specified discharge start timing when the discharge start timing decided by the control means M4 is earlier than the specified discharge start timing decided previously so that the max. amount of pressure feeding of the fuel is practicable until the engine M1 attains the rated operating condition.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is used for a so-called common rail type fuel injection control device equipped with a high pressure accumulation pipe, among fuel injection control devices for diesel engines. The present invention relates to a high pressure fuel pump control device.

[Prior Art] In recent years, injection characteristics such as fuel injection amount, fuel injection timing, fuel injection pressure, and fuel injection rate have been effectively controlled in order to improve the fuel consumption efficiency, exhaust purification rate, and operating performance of diesel engines. As a possible fuel injection control device, one has been developed that includes a high-pressure accumulation pipe for accumulating high-pressure fuel in a fuel supply system, a so-called common rail, and injects fuel from the common rail to a diesel engine via a fuel injection valve. As such a technique, for example, "Electromagnetically Controlled Injection System for Diesel Engine" (Japanese Unexamined Patent Publication No. 165858/1983) has been proposed. That is, as shown in FIG. 11, the fuel pressurized by the high-pressure supply water pump J1 is sent under pressure to the common rail J2, and the fuel accumulated inside the common rail J2 is injected from the injection valve J4 by opening and closing the fuel injection solenoid valve J3. This is injected into each cylinder of diesel engine J5. As shown in Fig. 12, this system operates by maintaining the common rail pressure Pc inside the common rail J2 at a substantially constant pressure, and injecting a predetermined amount of high-pressure fuel when the fuel injection solenoid valve J3 opens. In order to increase the common rail pressure Pc which has decreased due to the injection, a predetermined amount of high pressure fuel is discharged from the high pressure supply pump J1 to the common rail J2.

[Problems to be Solved by the Invention] By the way, in the fuel injection control device equipped with the common rail as described above, the high pressure supply pump is controlled to discharge a predetermined amount of high pressure fuel to the common rail, and the pressure inside the common rail is adjusted to The target common rail pressure was maintained depending on the operating status of the diesel engine. However, when the diesel engine shifts from the rated operating state to the high-speed operating state, it is necessary to reduce the comol pressure to a pressure determined by the mechanical strength limit of the fuel supply system of the fuel injection control device. However, this pressure reduction control is generally performed by an electronic control device that controls the high-pressure supply pump, so for example, a rotation speed sensor that detects the rotation speed of a diesel engine, or a pressure sensor that measures common rail pressure, etc. There is also a problem in that when the pressure is erroneously detected, the pressure reduction control described above is not executed throughout the period, resulting in a decrease in the reliability and durability of the device.

As described above, if the poor operating conditions continue, there is a problem in that the fuel supply system, especially the mechanical parts, accelerates deterioration.

Furthermore, in order to prevent problems caused by high-pressure fuel during high-speed operation as described above, for example, if the discharge amount of the high-pressure supply pump is limited by providing sufficient margin in advance to the strength limit of the fuel supply system, Conversely, when the diesel engine is operated in an operating range from a low speed operating state to a rated operating state, there is a problem in that the target common rail pressure cannot be sufficiently achieved, resulting in a reduction in operating performance.

Furthermore, if the discharge amount of the high-pressure supply bomb is limited by providing a sufficient margin in advance to the strength limit of the fuel supply system, there is also the problem that the versatility of the device is reduced.

The present invention has a simple device configuration that appropriately controls the discharge amount of the high-pressure supply pump and prevents the common rail pressure from rising above the strength limit when the diesel engine exceeds the rated operating state and shifts to a high-speed operating state. It is an object of the present invention to provide a high-pressure fuel pump control device that can reliably prevent the above problems.

1. Bile-Abdominal Type [Means for Solving the Problems] The present invention, which has been made to solve the above problems, as illustrated in FIG. M2, a pressure boosting means M3 that pressurizes a large amount of fuel to a high pressure according to an externally commanded discharge start time, the earlier the discharge start time is, and force-feeds it to the pressure accumulator M2; and the diesel engine M
In the high-pressure fuel pump control device, the diesel engine M1 is in a rated operating state, and a control means M4 for instructing the pressure boosting means M3 to start the discharge timing determined based on the operating state of the diesel engine M1 and the fuel pressure of the accumulated pressure gPJM2. If the discharge start time determined by the control means M4 is earlier than the predetermined discharge start time determined in advance so as to enable the maximum amount of fuel to be pumped until the maximum amount of fuel is reached, the discharge start time determined by the control means M4 The gist of the present invention is a high-pressure fuel pump control device characterized in that it includes a limiting means M5 for limiting the discharge start timing to the predetermined discharge start timing.

The pressure accumulator M2 is for accumulating high pressure fuel to be supplied to the diesel engine M1. For example, this can be realized by a so-called common rail, which is a high-pressure accumulating pipe that communicates with injectors arranged corresponding to each cylinder of a diesel engine.

The pressure boosting means M3 pressurizes a larger amount of fuel to a higher pressure as the discharge start time is earlier, and pressure-feeds the fuel to the pressure accumulator M2 according to a discharge start time commanded from the outside. For example, a variable valve equipped with a plunger that is slidably fitted into a cylinder and a solenoid valve that discharges high-pressure fuel inside a pressure chamber formed by the two into a pressure accumulator M2 in response to a discharge start signal transmitted from the outside. This can be achieved using a high-pressure pump.

Further, for example, the fuel injection pump may be configured by various types of fuel injection pumps whose discharge amount can be controlled in accordance with external control signals.

The control means M4 instructs the pressure increasing means M3 to start discharge, which is determined based on the operating state of the diesel engine M1 and the fuel pressure in the pressure accumulator M2. For example, the target fuel pressure inside the pressure accumulator M2 is calculated from the rotational speed and load of the diesel engine M1, and then the pressure boosting means Find the target fuel discharge amount of M3, and further calculate the target fuel discharge amount and diesel engine M1.
Based on the rotational speed of , the pressure increasing means M3 can be configured to determine the discharge start timing at which the target discharge amount can be pumped to the pressure accumulating portion M2. The calculation of each value can be realized using, for example, a predetermined arithmetic expression or a map that defines the relationship between various quantities.

The limiting means M5 is when the discharge start time determined by the control means M4 is earlier than a predetermined discharge start time that is predetermined to enable the maximum amount of fuel to be pumped until the diesel engine M1 reaches the rated operating state. This is to limit the ejection start time determined by the control means M4 to a predetermined ejection start time. Here, the predetermined discharge start timing means that during the period from the low speed operating state of the diesel engine M1 to the rated operating state, the pressure boosting means M3 can pump the desired fuel up to the maximum amount;
The discharge start time at which the maximum amount of fuel can be pumped under rated operating conditions can be determined as the predetermined discharge start time. For example, if the discharge start time determined by the control means M4 is later than a predetermined discharge start time, the discharge start time is not changed; on the other hand, if the discharge start time is earlier than the predetermined discharge start time, the discharge start time is changed. can be configured to be changed to a predetermined discharge start time.

The control means M/1 and the restriction means M5 can be realized, for example, by independent discrete logic circuits. Further, for example, it may be configured as a logic operation circuit together with a well-known CPU, ROM, RAM, and other peripheral circuit elements, and may realize each of the above means according to a predetermined processing procedure.

[Function] As illustrated in FIG. 1, the high-pressure fuel pump control device of the present invention controls the operating state of the diesel engine M1 and the pressure accumulator M2 that accumulates pressure of high-pressure fuel to be supplied to the diesel engine M1.
When the control means M4 commands the discharge start timing determined based on the fuel pressure of the diesel engine to the pressurizing means M3, which pressurizes a large amount of fuel to a high pressure and feeds it to the pressure accumulating part M2, the earlier the discharge start timing, the faster the discharge start timing. When the discharge start time determined by the control means M4 is earlier than the predetermined discharge start time which is predetermined to enable the maximum amount of fuel to be pumped until the engine M1 reaches the rated operating state, the restriction means M5 ,
It functions to limit the ejection start time determined by the control means M4 to the predetermined ejection start time.

That is, when the diesel engine M1 exceeds the rated operating state and shifts to a high-speed operating state, the discharge start timing for pressurizing and pumping fuel is limited so that it does not come earlier than the predetermined discharge start timing, and the discharge amount of high-pressure fuel is reduced. This reduces the

Therefore, when the diesel engine M1 shifts from the rated operating state to the high-speed operating state, the high-pressure fuel pump control device of the present invention works to reduce the discharge amount of high-pressure fuel and reduce the accumulated fuel pressure.

The technical problems of the present invention are solved by each component of the present invention acting as described above.

[Example] Next, a preferred example of the present invention will be described in detail based on the drawings. FIG. 2 shows a system configuration of a common rail fuel injection control device that is an embodiment of the present invention.

As shown in the figure, a common rail fuel injection control device 1
a four-cylinder diesel engine 2; a fuel injection valve 3a for injecting fuel into each cylinder of the diesel engine 2;
3b, 3c, 3d, the fuel injection valves 3a, 3b,
3c and 3d, a high-pressure accumulation pipe that accumulates pressure of high-pressure fuel, a so-called common rail 4, and a variable discharge amount high-pressure pump 5, which is a high-pressure supply pump that pumps high-pressure fuel to the common rail 4.
and an electronic control unit (hereinafter simply EC) that controls them.
Call it U. )6.

Fuel injection characteristics such as the fuel injection amount and fuel injection timing from the fuel injection valves 3a, 3b, 3c, and 3d to each cylinder of the diesel engine 2 are transmitted from the ECU 6 to the fuel injection solenoid valve 7a,
It is controlled by energizing/de-energizing 7b, 7c, and 7d.

High-pressure fuel is supplied from a variable discharge amount high-pressure pump 5 via a supply pipe 8 and a discharge valve 9 to the common rail 4 where high-pressure fuel is stored.

The variable discharge amount high-pressure pump 5 pressurizes the fuel sucked from the fuel tank 10 via the low-pressure supply pump 11 to a high pressure, and then pressure-feeds it to the common rail 4 to maintain the fuel pressure inside the common rail 4, that is, the common rail pressure. maintain high pressure.

The common rail type fuel jet control device 1 includes, as detectors, a rotation speed sensor 21 that detects the rotation speed of the diesel engine 2, an accelerator sensor 22 that detects the amount of accelerator pedal operation corresponding to the load, and a common rail pressure inside the common rail 4. A pressure sensor 23 for detecting the rotation angle of the camshaft of the variable discharge amount high pressure pump 5 is provided.

The signals of each of the above sensors are input manually to the ECU 6, and the ECU 6
controls the fuel injection valves 3a, 3b, 3c, 3d and the variable discharge amount high pressure pump 5.

The ECUS is configured as a logic operation circuit mainly including a CPU 6a, a ROM 6b, a RAM 6C, and a timer 6d, and is connected to a human output section 6f via a common bus 6e to perform human output with the outside. The detection signals of each of the above sensors are input to the input/output section 6f.
It is manually powered by the CPU 6a. On the other hand, the CPU 6a outputs the fuel injection solenoid valve via the human output section 6f. a,
7b, 7c.

7d and a control signal to the variable discharge amount high pressure pump 5.

Next, the structure of the variable discharge amount high pressure pump 5 will be explained based on FIG. 3. The variable discharge amount high-pressure pump 5 includes a cam chamber 31 provided at the lower end of the pump housing 30, a cylinder 32 provided inside the pump housing 30, and a cylinder 32 that communicates with the cylinder 32 and is connected to the low-pressure supply pump 11 described above. It is comprised of an introduction pipe 33 that receives low-pressure fuel supply, and a solenoid valve 34 that is screwed onto the upper end surface of the cylinder 32 so as to face the cylinder 32 .

A camshaft 35 that rotates at half the rotational speed of the diesel engine 2 is inserted into the cam chamber 31, and the camshaft 35 includes a cam 36. The cam 36 causes the camshaft 35 to perform two upward strokes per revolution.

A plunger 37 is fitted into the cylinder 32 so as to be reciprocally and slidably movable. The plunger 37 has a cylindrical shape without any leads, and the upper end surface of the plunger 37 and the inner peripheral surface of the cylinder 32 form a pump chamber. Further, the cylinder 32 is provided with a feed hole 39 that communicates with the pump chamber 38 and a discharge hole 40 that communicates with the pump chamber 3 at a position above the feed hole 39. Above feed hole 39
communicates with a fuel reservoir 41 formed between the cylinder 32 and the pump housing 30, and the fuel reservoir 41 is provided with an orifice 42 that can limit the flow rate per unit time to a predetermined flow rate. Low pressure fuel is supplied from the low pressure supply pump 11 through the introduction pipe 33 .

A discharge valve 9 is disposed in the cylinder 32, and the discharge valve 9
communicates with the pump chamber 38 mentioned above via the discharge hole 40. The fuel pressurized inside the pump chamber 38 pushes the valve body 43 of the discharge valve 9 open against the combined force of the biasing force of the return spring 44 and the common rail pressure, and connects the previously described supply pipe 8 from the discharge hole body 45. It is fed under pressure to the common rail 4.

The lower end of the plunger 37 described above is connected to a valve seat 46, which is pressed against the tappet 4 by a plunger spring 47. The tappet 4 is equipped with a cam roller 49, and the cam roller 49 is connected to the cam chamber 31 described above.
It is in sliding contact with the internal cam 36. For this reason, the camshaft 35
As the plunger 37 rotates, the plunger 37 reciprocates via the cam roller 49 and the valve seat 46. In addition, the plunger 37
The reciprocating stroke of is determined by the cam profile of cam 36. Therefore, when the plunger 37 reciprocates inside the cylinder 32, the outer peripheral surface of the plunger 37 opens and closes the feed hole 39, and when the outer peripheral surface of the plunger 37 does not close the feed hole 39, the outer peripheral surface of the plunger 37 opens and closes the feed hole 39. low pressure fuel was supplied to the pump room on the 3rd day.

A solenoid valve 34 is screwed onto the cylinder 32 at a position opposite to the upper end surface of the plunger 37 . As shown in FIG. 4, the solenoid valve 34 has a negative end connected to the pump chamber 3.
When the body 51 is energized via the lead wire 52, the magnetic force of the solenoid 53 resists the biasing force of the spring 54, and the body 51 has a low pressure passage 50 that opens at the end of the body 51 and communicates with the low pressure side at the other end. The armature 55 is sucked in the direction shown by the arrow A, and the armature 55 moves integrally with the armature 55 and separates from the seat portion 56 formed at the opening to the pump chamber 3, thereby communicating the low pressure passage 50. It is composed of a mushroom-shaped valve body 57 which is a shutoff valve. The valve body 57 receives the fuel pressure inside the pump chamber as a pushing force in the valve closing direction (indicated by arrow A in the figure). The solenoid valve 3
4 is a pre-stroke in which when the outer peripheral surface of the plunger 37 closes the feed hole 39 and is energized at a predetermined time, the valve body 57 seats on the seat portion 56 and sets the timing to start pressurizing the plunger 37; It is a controlled solenoid valve. Therefore, by controlling the timing of energizing the solenoid valve 34, the amount of discharge to the common rail 4 can be adjusted. As shown in FIG. 3, the low pressure passage 50 communicates with the fuel reservoir 41 described above via a gear rally 58 and a passage 58.

In order to control the electromagnetic valve 34, as shown in FIGS. 5 and 6, a pulse gear 61 having a number of protrusions corresponding to the number of cylinders of the diesel engine 2 (four in this embodiment) is connected to the above-mentioned cam. A cam angle sensor 24 consisting of an electromagnetic pickup is disposed coaxially with the shaft 35 and closely facing the pulse gear 61 . Every time the protrusion of the pulse gear 61 passes near the cam angle sensor 24, a cam angle signal is transmitted to the ECUS. Here, the pulse gear 61
The mounting phase for each cam 36a, 36 with respect to the camshaft 35 is
It is set to approach the cam angle sensor 24 at a rotational phase near each bottom dead center of b.

Next, the basic operation of the variable discharge amount high pressure pump 5 having the above configuration will be explained based on FIG. 3.

As shown in the figure, when the plunger 37, which reciprocates as the camshaft 35 rotates, opens the feed hole 39 when descending, fuel is sucked into the pump chamber through the feed hole 39, and - On the other hand, if the feed hole 39 is closed during the ascent, a pressing force is exerted on the fuel sucked into the pump chamber. However, at this time, if the electromagnetic valve 34 is not energized, the valve body 57 of the electromagnetic valve 34 is open, so the fuel inside the pump chamber is transferred to the low pressure passage 50,
through the gear rally 58 and the passage 59);
Not pressurized.

In this manner, when the electromagnetic valve 34 is energized while fuel is overflowing inside the pump chamber, the valve body 57 seats on the seat portion 56 and the low pressure passage 50 is closed.

Therefore, as the plunger 37 rises, the fuel inside the pump chamber begins to be pressurized, and when the fuel pressure inside the pump chamber exceeds the biasing force of the return spring 44 of the discharge valve 9, the fuel inside the pump chamber begins to be pressurized. The fuel pressure-fed through the discharge valve 9
is pushed open and discharged to the common rail 4 through the discharge port body 45.

Note that when the feed hole 39 opens when the plunger 37 descends, fuel is sucked into the pump chamber 3 through the feed hole 39, but as the rotational speed of the diesel engine 2 increases, the fuel is sucked into the pump chamber 3. The amount of time it can be inhaled during the day is shortened. Here, since the flow rate of fuel sucked in by the orifice 42 is restricted, when the rotational speed exceeds a predetermined rotational speed, the amount of fuel that can be sucked into the pump chamber decreases.

Next, the operation of the common rail fuel injection control device 1 using the variable discharge amount high pressure pump 5 will be explained based on the flowchart shown in FIG.

This variable discharge amount high pressure pump control process is executed in conjunction with the activation of the ECU 6. First, in step 100, a process of reading the load α, rotational speed Ne, and common rail pressure PC is performed. In the following step 110, a process is performed to calculate the target common rail pressure PCO from the load α and the rotational speed Ne read in the above step 100 using an arithmetic expression or a map. Next, the process proceeds to step 120 to calculate the fuel discharge amount Q from the target common rail pressure βCO5 calculated in step 110, the common rail pressure PC5 read in step 100, and the rotational speed Ne using an arithmetic expression or a map. It will be done. In the following step 130, the above step 1
A process is performed to calculate the control time T1 from the discharge amount Q calculated in step 20 and the rotational speed Ne read in step 100, based on an arithmetic expression or a map. Next, the process proceeds to step 140, in which it is determined whether the control time T1 calculated in step 130 is less than the minimum control time 10. If the judgment is affirmative, the process proceeds to step 150, and if the judgment is negative, the process proceeds to step 160. move on. In step 150, which is executed when it is determined that the control time T1 is less than the minimum control time 10, the control time T1 is changed to the minimum control time T.
Processing to set the value to o is performed. In the following step 160, it is determined whether or not a cam angle signal has been detected. If the determination is affirmative, the process proceeds to step 170. On the other hand, if the determination is negative, the process waits while repeating the same steps until the cam angle signal is detected. In step 170, the timer T is reset and started. In the following step 180, it is determined whether or not the clock value of the timer T that started counting in the step 170 is equal to or longer than the control time T1 calculated in the step 130 or set in the step 150, and an affirmative determination is made. and step 19
0, and on the other hand, if a negative determination is made, the process waits while repeating the same steps until the limited i immediate time T1 has elapsed.

In step 190, a process of outputting a control signal to close the solenoid valve 34 is performed. Through the process of step 190, pressurization and pressure feeding of fuel is started. In the following step 200, it is determined whether a cam angle signal has been detected,
If the determination is affirmative, the process proceeds to step 210, whereas if the determination is negative, the process waits while repeating the same steps until a cam angle signal is detected. In step 210, a process of outputting a control signal to open the solenoid valve 34 is performed.

Through the process of step 210, pressurization and pressure feeding of fuel is stopped. After executing step 210, the present variable discharge amount high pressure pump control process is ended. From then on,
This variable discharge amount high pressure pump control process is executed by repeating steps 100 to 210 at predetermined time intervals.

Next, an example of the above control will be explained according to the timing chart of FIG. 8. As shown by the solid line in the figure, a control signal to close the solenoid valve is output at time t2 after control time T1 has elapsed from time t1 when the cam angle signal is detected, and a time after delay time TL has elapsed from time t2. Pressurization and pressure feeding of fuel is started from t3. Here, the operating time TFF from the time when the cam angle signal is detected to the time when fuel pressurization and pumping start is the sum of the control time T1 and the delay time TL.

Since the plunger lift amount S is a constant value, the earlier the pressurization and pressure feeding start time, the larger the pressure feeding stroke amount and the larger the discharge amount Q. For example, as shown above, the operating time T
When the FF is used and the diesel engine 2 is in a low speed rotation state, the pumping stroke amount becomes the value S1. Note that the operating time TFF is set short, that is, the control time T1
By shortening , the maximum pumping stroke amount SL is obtained.

In this way, when the control time T1 is shortened, the pumping stroke amount increases, and on the other hand, when the control time T1 is extended, the pumping stroke amount decreases. Therefore, by adjusting the control time T1, the discharge amount Q can be controlled to a desired value. Here, when the diesel engine 2 is in the rated rotation state,
In order to bring the pumping stroke amount to the maximum value SN, the plunger lift amount S and the pumping stroke amount SN in the rated rotation state may be made equal. That is, pressure feeding of fuel is started at time t4, which is after the operating time TPO has elapsed since the cam angle signal detection time t1. The control time at this time is the time To obtained by subtracting the delay time TL from the operating time TPO.
become. That is, as shown by the broken line in the figure, at time t5
In this case, it is necessary to output a solenoid valve control signal. The control time TO in this case is set to the minimum control time. Then, in the range from the low speed rotation state to the rated rotation state, if the control time T1 is set to a predetermined time longer than the minimum control time TO, the pumping stroke amount can be adjusted from O to the entire stroke of the maximum plunger lift amount S. Since it can be adjusted to any desired amount, the fuel discharge amount Q can also be controlled from 0 to the maximum discharge amount Qmax. However, when the rated rotation state is exceeded and the state shifts to a high speed rotation state, the control time T1 is limited not to become less than the minimum control time TO, so that at t4 when pressure feeding starts, the plunger has already reached the stroke. It has increased by the amount SM. Therefore, in this case, since the maximum value of the pumping stroke amount is limited, the fuel discharge amount Q is also limited to an amount less than the maximum discharge amount Qmax, and as the rotational speed increases, the fuel can be discharged. The amount is controlled to decrease.

In this embodiment, the diesel engine 2 corresponds to the diesel engine M1, the common rail 4 corresponds to the pressure accumulation part M2, and the variable discharge amount high pressure pump 5 corresponds to the pressure boosting means M3. Also, among the processes executed by the ECU 6 and the ECU 6, steps (100, 110, 120, 130, 160, 1
70, 180° 190) function as control means M4, and steps (140, 150) function as #J limit means M5, respectively.

As explained above, according to this embodiment, due to erroneous detection of the rotational speed sensor 21 that detects the rotational speed of the diesel engine 20 and the pressure sensor 23 that measures the fuel pressure inside the common rail 4, the diesel engine 2 Even when the operating state shifts from the rated rotational speed operating state to the high rotational speed operating state, the discharge amount Q of high-pressure fuel from the variable discharge amount high-pressure pump 5 is reduced, and the fuel pressure accumulated inside the common rail 4, that is, the common rail To reduce the pressure PC,
It is possible to operate the common rail fuel injection control device 1 while maintaining the fuel pressure within a range that does not exceed the mechanical strength limits of the variable discharge amount high pressure pump 5, the supply pipe 8, the common rail 4, and the injector 3. Therefore, the reliability and durability of the common rail fuel injection control device 1 are improved even when false detection occurs due to a failure of the rotational speed sensor 21 or the pressure sensor 23. That is, as shown in FIG. 9, when the engine rotation speed Ne is less than the rated rotation speed, the discharge amount Q can be set to a desired value within the range up to the maximum displacement amount Qmax, whereas when it exceeds the rated rotation speed, The discharge amount decreases quickly. Therefore, the engine rotation speed Ne
Even if the rotational speed exceeds the rated rotational speed, the discharge amount Q is reduced and the fuel pressure inside the common rail 4 decreases, so that it does not shift to the strength limit region and cause a failure.

In addition, since the intake fuel is limited in flow rate by the orifice 42, the amount of fuel that can be sucked in one cycle of the variable discharge amount high-pressure pump 5 decreases when the rated rotation speed is exceeded, so that the ECU 6 cannot operate normally due to electromagnetic interference etc. Even if the engine rotation speed Ne exceeds the rated rotation speed when an electrical fault occurs such as when the solenoid valve 34 malfunctions, the fuel discharge amount Q decreases and the common rail pressure PC inside the common rail 4 decreases. It doesn't rise. That is, as shown in FIG. 10, when the engine rotation speed Ne is less than the rated rotation speed, the discharge amount Q can be set to a desired value within the range up to the maximum displacement amount Qmax, whereas when it exceeds the rated rotation speed, , the discharge amount decreases as shown by the curve in the figure. Therefore,
Even if the engine rotation speed Ne exceeds the rated rotation speed during abnormal operation of the ECU 6 or the solenoid valve 34, the discharge amount Q is reduced. Since the internal fuel pressure decreases, it will not move to the strength limit region and apply excessive pressure to the high-pressure fuel supply system, causing deterioration or damage.

As described above, the variable discharge amount high-pressure pump control process executed by the ECU 6 maintains the immediate control time T1 at least the minimum control time TO, and furthermore, when the ECU 6 is abnormal, the orifice 42 mechanically limits the intake fuel amount. Dual electrical and mechanical fail-safe &! Therefore, the strength, reliability and durability of the fuel supply system of the common rail fuel injection control '+H device 1 can be maintained at an extremely high level. This is particularly effective when applied to a vehicle-mounted diesel engine that requires high reliability, for example.

Furthermore, when the diesel engine 2 is operated in an operating range from a low rotational speed operating state to a rated rotational speed operating state, the fuel pressure accumulated in the common rail 4 is maintained within a range that does not exceed the maximum dischargeable amount QmaX. The common rail pressure PC can be discharged in an amount that can always be maintained at the target common rail pressure PCO determined depending on the operating state, and the operating state of the diesel engine 2 can be maintained in a good condition.

In addition, the control time T1 calculated from the load α of the diesel engine 2, the rotational speed Ne, and the common rail pressure PC of the common rail 4 is limited so that it does not become shorter than the minimum control time TO determined according to the rated rotational speed operating state. At the same time, the pressure of the fuel accumulated in the common rail 4 can be maintained below the mechanical strength limit of the fuel supply system by simply arranging the orifice 42 in the variable discharge amount high pressure pump 5, so with a simple device configuration, Erroneous detection of various sensors and
It is possible to reliably prevent a deterioration in the operating conditions of the common rail fuel injection control device 1 and an excessively strong load on the mechanism due to malfunctions of the CU 6 and the electromagnetic valve 34.

Furthermore, by simply changing the setting of the minimum control time T1 according to the specifications of the variable discharge amount high pressure pump 5, the present invention can be applied to various types of common rail type diesel engines, thereby increasing the versatility of the device.

Further, the valve body 57 of the solenoid valve 34 is configured to receive the fuel pressure inside the pump chamber as a pressing force in the valve closing direction. Therefore, since the valve body 57 is finished so that it is seated with high precision on the seat portion 5, when the valve body 57 is seated on the seat portion 56, the valve body 57 is The fuel pressure inside the pump chamber pressurizes the valve in the direction of valve closing, maintaining extremely excellent sealing performance.

Roughly speaking, since the plunger 37 has a cylindrical shape with no leads, the high-pressure fuel inside the pump chamber formed by the inner peripheral surface of the cylinder 32 and the upper end surface of the plunger 37 leaks to the low-pressure side. Since it does not, plunger 37
Leakage of high-pressure fuel to the low-pressure side during the pressurization and pumping stroke can be reduced.

Moreover, since only the feed hole 39 and the discharge hole 40 are bored in the cylinder 32 as passages communicating with the pump chamber 38, leakage of high pressure fuel inside the pump chamber to the low pressure side can be reduced.

In this embodiment, the hole diameter of the orifice 42 is constant, but the hole diameter may be changed depending on the engine rotational speed Ne, for example.

Further, although the orifice 42 is used in this embodiment, it is also possible to use a hydraulic circuit element such as a choke, various types of ridges, etc., which can maintain a constant flow rate per unit time, in the same manner as in the previously described embodiments. You can get the following effect.

Although the embodiments of the present invention have been described above, the present invention is not equally limited to these embodiments, and it goes without saying that it can be implemented in various forms without departing from the gist of the present invention. .

1 sai second base! As detailed above, in the high-pressure pump control device of the present invention, when the diesel engine exceeds the rated operating state and shifts to a high-speed operating state, the discharge start time for pressurizing and pumping fuel is set to be longer than the predetermined discharge start time. It is configured to limit the discharge rate of high-pressure fuel so that it does not increase quickly, and to reduce the discharge amount of high-pressure fuel.

For this reason, due to erroneous detection by various detectors that measure the operating status of the diesel engine and the pressure of the accumulated fuel,
Even when the diesel engine shifts from a rated operating state to a high-speed operating state, the discharge amount of high-pressure fuel is reduced to reduce the pressure of the accumulated fuel. For this reason, it is possible to operate the device within a range that does not exceed the mechanical strength limit, resulting in the excellent effect of further improving the reliability and durability of the device even when the detector is abnormal.

In addition, when the diesel engine is operating in the operating range from low-speed operation to rated operation, the accumulated fuel pressure is determined according to the operating condition within a range that does not exceed the maximum amount that can be discharged. It is now possible to discharge only the amount of fuel that can maintain the target pressure at all times, allowing the diesel engine to operate smoothly under optimal conditions.

Roughly speaking, the pressure of the accumulated fuel can be maintained below the strength limit simply by restricting the discharge start time from being earlier than the predetermined discharge start time, so with a simple device configuration, the operating conditions of the device caused by false detection can be reduced. It is possible to reliably prevent deterioration of the structure and deterioration of the mechanical parts of the device.

Furthermore, the present invention can be applied to various diesel engines by simply changing the setting of the predetermined discharge start time, increasing the versatility of the device.

[Brief explanation of the drawing]

Fig. 1 is a basic configuration diagram conceptually illustrating the contents of the present invention, Fig. 2 is a system configuration diagram of an embodiment of the invention, and Fig. 3 is a sectional view showing the structure of the variable discharge amount high pressure pump. ,
FIG. 4 is a cross-sectional view showing the structure of a solenoid valve installed in the variable discharge amount high-pressure pump, FIG. 5 is a configuration diagram of its main parts, and FIG. 6 is an end view taken along the line C-C in FIG. 5. FIG. 7 is a flowchart showing the control, FIG. 8 is a timing chart showing the control, and FIGS.
Similarly, Figure 0 is a graph showing the relationship between the discharge amount of the high-pressure supply pump and the engine rotation speed, Figure 11 is a schematic device configuration diagram showing the configuration of the prior art, and Figure 12 is a timing chart showing the control of the prior art. . Ml... Diesel engine M2... Pressure accumulator M3... Pressure boosting means M4... Control means M5... Limiting means 1... Common rail fuel injection control device 2...
・Diesel engine 4...Common rail 5...Variable discharge amount high pressure pump 6...Electronic control flEj unit (ECU) 6a...
・CPU

Claims (1)

[Scope of Claims] 1. A pressure accumulator for accumulating high-pressure fuel to be supplied to a diesel engine; and a pressure accumulator for pressurizing a large amount of fuel to a high pressure according to an externally commanded discharge start time, the earlier the discharge start time is. In the high-pressure fuel pump control device, the high-pressure fuel pump control device is equipped with: a pressure boosting means for pumping pressure to the fuel pump; and a control means for instructing the pressure boosting means to a discharge start timing determined based on the operating state of the diesel engine and the fuel pressure in the pressure accumulator. If the discharge start time determined by the control means is earlier than the predetermined discharge start time that is predetermined to enable the maximum amount of fuel to be pumped until the diesel engine reaches the rated operating state, the control means determines A high-pressure fuel pump control device comprising: limiting means for limiting the discharge start time of the discharge start time to the predetermined discharge start time.