JP2512960B2 - High-pressure fuel pump controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a fuel injection control device for a diesel engine,
The present invention relates to a high-pressure fuel pump controller used in a so-called common rail fuel injection controller having a high-pressure accumulator pipe.

[Prior Art] In recent years, in order to improve fuel consumption efficiency, exhaust gas purification rate, operation performance, etc. of a diesel engine, injection characteristics such as fuel injection amount, fuel injection timing, fuel injection pressure and fuel injection rate are effectively controlled. As a possible fuel injection control device, a high pressure accumulator pipe for accumulating high pressure fuel in a fuel supply system, that is, a so-called common rail, has been developed which injects fuel from the common rail to a diesel engine through a fuel injection valve. As such a technique, for example, "an electromagnetically controlled injection system for a diesel engine" (Japanese Patent Laid-Open No. Sho 61-206)
59-165858) and the like have been proposed. That is,
As shown in Fig. 11, the fuel pressurized by the high-pressure supply pump J1 is pressure-fed to the common rail J2, and the fuel accumulated inside the common rail J2 is opened and closed by opening and closing the fuel injection solenoid valve J3.
From the diesel engine J5 to each cylinder. As shown in FIG. 12, the operation of this system is such that the common rail pressure Pc inside the common rail J2 is maintained at a substantially constant pressure, and a predetermined amount of high-pressure fuel is injected with the opening of the fuel injection solenoid valve J3. In order to increase the common rail pressure Pc lowered by the injection, the high pressure supply pump J1
A predetermined amount of high-pressure fuel is discharged from the common rail J2.

[Problems to be Solved by the Invention] By the way, in the fuel injection control device provided 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 to reduce the pressure inside the common rail. The target common rail pressure determined according to the operating condition of the diesel engine was maintained. However, when the diesel engine shifts from the rated operating state to the high-speed operating state, it is necessary to reduce the common rail pressure below the pressure determined by the mechanical strength limit of the fuel supply system of the fuel injection control device. However, since this depressurization control was generally performed by an electronic control device that controls the high-pressure supply pump,
For example, if a rotation speed sensor that detects the rotation speed of a diesel engine or a pressure sensor that measures the common rail pressure is erroneously detected, the decompression control is not performed properly, and the reliability and durability of the device are reduced. There was also the problem of a decrease.

As described above, if the poor operation state is continued, there is also a problem that the deterioration of the fuel supply system, particularly the mechanical portion is accelerated.

Further, in order to prevent obstacles due to high-pressure fuel during high-speed operation as described above, for example, if the discharge amount of the high-pressure supply pump is limited with a sufficient margin for the strength limit of the fuel supply system, On the other hand, when the diesel engine is operated in the operating range from the low speed operating state to the rated operating state, the target common rail pressure cannot be sufficiently achieved, which causes a problem that the operating performance is deteriorated.

Further, if the discharge amount of the high-pressure supply pump is limited by giving a sufficient margin to the strength limit of the bubble bite fuel supply system, there is a problem that the versatility of the device is reduced.

The present invention suitably controls the discharge amount of the high-pressure supply pump and raises the common rail pressure to the strength limit or more when the diesel engine goes beyond the rated operation state to the high-speed operation state. Moreover, it is an object of the present invention to provide a high-pressure fuel pump control device that can be reliably prevented.

Configuration of the Invention [Means for Solving the Problems] The present invention made to solve the above problems, as illustrated in FIG. 1, includes a pressure accumulator M2 for accumulating high-pressure fuel to be supplied to the diesel engine M1. According to the discharge start timing commanded from the outside, the earlier the discharge start timing is, the higher the pressure of a large amount of fuel is increased to a high pressure, and the pressure increasing means M3 is pressure-fed to the pressure accumulating section M2, the operating state of the diesel engine M1 and the pressure accumulating section. M2
In the high-pressure fuel pump control device equipped with the control means M4 for instructing the boosting means M3 to determine the discharge start timing determined based on the fuel pressure, the maximum amount of the diesel engine M1 is reached until the diesel engine M1 reaches the rated operating state. When the discharge start timing determined by the control means M4 is earlier than the predetermined discharge start timing predetermined to enable fuel pressure feeding, the discharge start timing determined by the control means M4 is limited to the predetermined discharge start timing. The gist of the present invention is a high-pressure fuel pump control device characterized by including a limiting means M5.

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

The pressurizing means M3 pressurizes a larger amount of fuel to a higher pressure as the discharge start timing is earlier, according to the discharge start timing commanded from the outside, and pressure-feeds the fuel to the pressure accumulator M2. For example, a variable valve equipped with a plunger slidably fitted to a cylinder and a solenoid valve for discharging high-pressure fuel in a pressure chamber formed by both of them to a pressure accumulator M2 in response to a discharge start signal transmitted from the outside. It can be realized by a discharge high-pressure pump. Further, for example, various fuel injection pumps that can control the discharge amount according to a control signal from the outside may be used.

The control means M4 is for instructing the boosting means M3 the discharge start timing determined based on the operating state of the diesel engine M1 and the fuel pressure of the pressure accumulator M2. For example, the target fuel pressure inside the pressure accumulating section M2 is calculated from the rotation speed and load of the diesel engine M1, and then the target fuel pressure, the measured fuel pressure inside the pressure accumulating section M2 and the rotation speed of the diesel engine M1 are used to increase the pressure. The target fuel discharge amount of M3 is obtained, and further, based on the target fuel discharge amount and the rotation speed of the diesel engine M1, the booster M3 can be configured to determine the discharge start timing at which the target discharge amount can be pumped to the pressure accumulator M2. . Such calculation of each value can be realized by, for example, a predetermined arithmetic expression that defines the relationship between various amounts or a map.

The control means M5 means that the discharge start timing determined by the control means M4 is earlier than the predetermined discharge start timing predetermined to enable the maximum amount of fuel pressure feed until the diesel engine M1 reaches the rated operating state. Is to limit the discharge start timing determined by the control means M4 to a predetermined discharge start timing.
Here, the predetermined discharge start timing means that during the low-speed operating state of the diesel engine M1 to the rated operating state, the boosting means M3 can pump desired fuel up to the maximum amount, and in the rated operating state the maximum amount of fuel can be delivered. The discharge start timing at which fuel can be pumped can be set as the predetermined discharge start timing. For example, when the discharge start timing determined by the control means M4 is later than the predetermined predetermined discharge start timing, the discharge start timing is not changed, while when the discharge start timing is earlier than the predetermined discharge start timing, the discharge start timing is changed. It can be configured to change and set the predetermined discharge start timing.

The control means M4 and the limiting means M5 can be realized by, for example, independent discrete logic circuits. Further, for example, a configuration may be adopted in which a well-known CPU, ROM, RAM, and other peripheral circuit elements are configured as a logical operation circuit, and the above-described units are realized in accordance with a predetermined processing procedure.

[Operation] As illustrated in FIG. 1, the high-pressure fuel pump control device of the present invention is based on the operating state of the diesel engine M1 and the fuel pressure of the pressure accumulator M2 that accumulates the high-pressure fuel supplied to the diesel engine M1. The determined discharge start time is controlled by the control means M4.
However, when the discharge start time is early, a large amount of fuel is pressurized to a high pressure, and when instructing the pressure increasing means M3 that pressure-feeds to the pressure accumulating section M2, the maximum amount of fuel pressure-feeding is performed until the diesel engine M1 reaches the rated operating state. When the discharge start timing determined by the control means M4 is earlier than the predetermined discharge start timing predetermined to enable the above, the limiting means M5 causes the control means M4 to
The discharge start timing determined by the above-mentioned operation is limited to the predetermined discharge start timing.

That is, when the diesel engine M1 exceeds the rated operating state and shifts to the high-speed operating state, the discharge start timing at which the fuel is pressurized and pumped is restricted so as not to be earlier than the predetermined discharge start timing, and the discharge amount of the high-pressure fuel is reduced. Is reduced.

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 the high-pressure fuel and reduce the accumulated fuel pressure.

As described above, the technical problems of the present invention are solved by the operation of each component of the present invention.

[Embodiment] Next, a preferred embodiment of the present invention will be described in detail with reference to the drawings. FIG. 2 shows the system configuration of a common rail fuel injection control device which is an embodiment of the present invention.

As shown in the figure, the common rail fuel injection control device 1 includes a 4-cylinder diesel engine 2 and fuel injection valves 3a, 3b, 3 for injecting fuel into each cylinder of the diesel engine 2.
c, 3d, high-pressure accumulating pipe for accumulating high-pressure fuel to be supplied to the fuel injection valves 3a, 3b, 3c, 3d, so-called common rail 4, variable-discharge high-pressure pump that is a high-pressure supply pump for pumping high-pressure fuel to the common rail 4. 5 and an electronic control unit (hereinafter, simply referred to as an ECU) 6 that controls them.

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

The high pressure fuel is supplied from the variable discharge amount high pressure pump 5 to the common rail 4 in which the high pressure fuel is accumulated via a supply pipe 8 and a discharge valve 9.

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

The common rail fuel injection control device 1 serves as a detector,
A rotation speed sensor 21 for detecting the rotation speed of the diesel engine 2, an accelerator sensor 22 for detecting an accelerator pedal operation amount corresponding to a load, a pressure sensor 23 for detecting a common rail pressure inside the common rail 4, and a cam of the variable discharge amount high pressure pump 5. A cam angle sensor 24 for detecting the rotation angle of the shaft is provided.

Signals from the above sensors are input to the ECU 6, which controls the fuel injection valves 3a, 3b, 3c, 3d and the variable discharge high pressure pump 5.

The ECU 6 is configured as a logical operation circuit centering on the CPU 6a, ROM 6b, RAM 6c, and timer 6d, and the input / output unit 6f via the common bus 6e.
It is connected to and performs input and output with the outside. The detection signal of each sensor is input to the CPU 6a from the input / output unit 6f. On the other hand, the CPU 6a outputs a control signal to the fuel injection solenoid valves 7a, 7b, 7c, 7d and the variable discharge high pressure pump 5 via the input / output unit 6f.

Next, the structure of the variable discharge high pressure pump 5 will be described with reference to FIG. The variable discharge 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
It comprises an introduction pipe 33 communicating with 32 and receiving low-pressure fuel supply from the low-pressure supply pump 11 described above, and an electromagnetic valve 34 screwed to face the upper end surface of the cylinder 32.

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

A plunger 37 is reciprocally and slidably fitted in the cylinder 32. The plunger 37 has a columnar shape without any leads, and a pump chamber 38 is formed by the upper end surface of the plunger 37 and the inner peripheral surface of the cylinder 32. The cylinder 32 has a feed hole 39 communicating with the pump chamber 38 and a discharge hole 40 communicating with the pump chamber 38 at a position above the feed hole 39. The feed hole 39 communicates with a fuel reservoir 41 formed between the cylinder 32 and the pump housing 30, and the fuel reservoir 41 can limit the flow rate per unit time to a predetermined flow rate. Introductory pipe 33 with orifice 42
Low-pressure fuel is supplied from the low-pressure supply pump 11 via.

The cylinder 32 is provided with a discharge valve 9, and the discharge valve 9
Communicates with the above-described pump chamber 38 via the discharge hole 40. The fuel pressurized inside the pump chamber 38 is the valve body of the discharge valve 9.
43 is pushed open against the combined force of the biasing force of the return spring 44 and the common rail pressure, and is sent from the discharge hole body 45 to the common rail 4 via the supply pipe 8 described.

The lower end of the plunger 37 described above is connected to the valve seat 46,
The valve seat 46 is pressed against the tappet 48 by a plunger spring 47. The tappet 48 comprises a cam roller 49, which is in sliding contact with the cam 36 inside the described cam chamber 31. Therefore, as the cam shaft 35 rotates, the plunger 37 reciprocates via the cam roller 49 and the valve seat 46. The reciprocating stroke of the plunger 37 is
Determined by the Cal Profile of. 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 block the feed hole 39, it passes through the feed hole 39. Low-pressure fuel is supplied to the pump chamber 38.

An electromagnetic valve 34 is screwed to the cylinder 32 at a position facing the upper end surface of the plunger 37. The solenoid valve 34
As shown in FIG. 4, when electricity is supplied through a body 51 and a lead wire 52, one end of which opens into the pump chamber 38 and the other end of which forms a low pressure passage 50 communicating with the low pressure side. The armature 55 is attracted in the direction indicated by the arrow A in the figure against the biasing force of the spring 54 by the magnetic force of the solenoid 53, and is integrally formed with the armature 55 and formed in the opening to the pump chamber 38. By attaching and detaching to the seat portion 56, the low pressure passage 50
It is composed of a mushroom-shaped valve body 57 that is an open valve that connects and disconnects. The valve body 57 receives the fuel pressure inside the pump chamber 38 as a pressing force in the valve closing direction (shown by an arrow A in the figure). When the solenoid valve 34 is energized at a predetermined time after the outer peripheral surface of the plunger 37 closes the feed hole 39, the valve body 57 is seated on the seat portion 56 to set the pressurization start time of the plunger 37. This is a pre-stroke control type solenoid valve. Therefore, by controlling the timing of energizing the solenoid valve 34, the discharge amount 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 the gallery 58 and the passage 59.

In order to control the solenoid valve 34, as shown in FIGS. 5 and 6, a pulse gear having a number of protrusions (four in this embodiment) corresponding to the number of cylinders of the diesel engine 2 is provided.
61 is fixed coaxially with the above-mentioned camshaft 35, and the pulse gear
A cam angle sensor 24 composed of an electromagnetic pickup is disposed in close proximity to 61. Every time the projection of the pulse gear 61 passes near the cam angle sensor 24, the cam angle signal is transmitted to the ECU 6. Here, the mounting phase of the pulse gear 61 with respect to the cam shaft 35 is set so as to approach the cam angle sensor 24 at the rotational phase near the bottom dead center of each of the cams 36a and 36b.

Next, the basic operation of the variable discharge high pressure pump 5 having the above-mentioned configuration will be described with reference to FIG.

As shown in the figure, when the plunger 37 that reciprocates with the rotation of the cam shaft 35 opens the feed hole 39 when descending, fuel is sucked into the pump chamber 38 through the feed hole 39, while If the feed hole 39 is closed during the ascent, the fuel sucked into the pump chamber 38 will be pressed. However, at this time, if the solenoid valve 34 is not energized, the valve body 57 of the solenoid valve 34 is open, so the pump chamber
The fuel inside 38 is the low pressure passage 50, the gallery 58 and the passage.
Overflow through 59, not pressurized.

As described above, when the solenoid valve 34 is energized while the fuel in the pump chamber 38 overflows, the valve body 57 is seated on the seat portion 56 and the low-pressure passage 50 is closed. For this reason, the fuel in the pump chamber 38 starts to be pressurized by the rise of the plunger 37,
When the fuel pressure inside 38 exceeds the urging force of the return spring 44 of the discharge valve 9, the fuel pressure-fed through the discharge hole 40 pushes the discharge valve 9 open and the discharge port body 45 to the common rail 4.
Is discharged through.

When the feed hole 39 opens when the plunger 37 descends, the fuel is sucked into the pump chamber 38 through the feed hole 39. However, as the rotation speed of the diesel engine 2 increases, the fuel is fed into the pump chamber 38. The time that can be inhaled is shortened. Here, since the flow rate of the fuel sucked by the orifice 42 is limited, when the rotation speed exceeds a predetermined rotation speed, the amount of fuel that can be sucked into the pump chamber 38 decreases.

Next, the operation of the common rail fuel injection control apparatus 1 using the variable discharge high pressure pump 5 will be described based on the flowchart shown in FIG. The variable discharge high-pressure pump control process is executed when the ECU 6 is started.
First, in step 100, a process of reading the load α, the rotation speed Ne and the common rail pressure PC is performed. In the following step 110, the target common rail pressure PC0 is calculated from the load α and the rotation speed Ne read in the above step 100,
Alternatively, a calculation process using a map is performed.
Next, in step 120, the fuel discharge amount Q is calculated from the target common rail pressure PC0 calculated in step 110, the common rail pressure PC read in step 100, and the rotation speed Ne using an arithmetic expression or a map. Processing is performed. In the following step 130, the control time T1 is calculated from the discharge amount Q calculated in step 120 and the rotation speed Ne read in step 100 based on an arithmetic expression or a map. Next, the process proceeds to step 140, and it is determined whether the control time T1 calculated in step 130 is less than the minimum control time T0. If the determination is affirmative, the process proceeds to step 150. If the determination is negative, the process proceeds to step 160. move on. In step 150 that is executed when it is determined that the control time T1 is less than the minimum control time T0, a process of setting the control time T1 to the minimum control time T0 is performed. In the following step 160, it is determined whether or not the cam angle signal is detected,
If the affirmative judgment is made, the routine proceeds to step 170, while if the negative judgment is made, the routine stands by 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 time value of the timer T that started the time counting in the above step 170 is calculated in the above step 130 or is the control time T1 or more set in the above step 150, and an affirmative judgment is made. Then, the process proceeds to step 190. On the other hand, if a negative determination is made, the process waits while repeating the same steps until the control time T1 has elapsed. Step 19
At 0, a process of outputting a control signal for closing the solenoid valve 34 is performed. By the process of step 190, pressurization and pressure feeding of fuel are started. In the following step 200, it is determined whether or not the cam angle signal is detected. If the affirmative judgment is made, the routine proceeds to step 210. On the other hand, if the negative judgment is made, the same step is repeated and waits until the cam angle signal is detected. In step 210, a process of outputting a control signal for opening the solenoid valve 34 is performed. By the process of this step 210, pressurization and pressure feeding of fuel are stopped. Above steps
After executing 210, the variable discharge amount high pressure pump control process is ended once. After that, the variable discharge high-pressure pump control process is repeatedly executed at every predetermined time by repeating the steps 100 to 210.

Next, an example of the above control will be described with reference to the timing chart of FIG. As shown by the solid line in the figure,
At time t2 after the lapse of control time T1 from the time t1 when the cam angle signal is detected, a control signal for closing the solenoid valve is output, and from the time t2, the pressurization / pressure feeding of fuel is started from time t3 after the lapse of the delay time TL. Be started. Here, the operation time TFF from the cam angle signal detection time to the fuel pressurization / pressure feeding start time 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 / pressure feeding start time, the larger the pressure feeding stroke amount and the larger the discharge amount Q. For example, with the operating time TFF as described above,
When the diesel engine 2 is in the low speed rotation state, the pressure feeding stroke amount is the value S1. It should be noted that when the operating time TFF is set to be short, that is, the control time T1 is shortened, the maximum pressure feeding stroke amount SL is obtained. Thus, when the control time T1 is shortened, the pumping stroke amount increases, while the control time
When T1 is extended, the pumping stroke amount decreases. Therefore,
The discharge amount Q can be controlled to a desired value by adjusting the control time T1. Here, when the diesel engine 2 is in the rated rotation state, the plunger lift amount S and the pumping stroke amount SN in the rated rotation state may be made equal in order to make the pressure feeding stroke amount the maximum value SN. That is, the pressure feed of the fuel is started at time t4 after the operation time TF0 has elapsed from the cam angle signal detection time t1. The control time at this time is the time T0 obtained by subtracting the delay time TL from the operation time TF0. That is, as indicated by the broken line in the figure, the time
At t5, it is necessary to output the solenoid valve control signal. The control time T0 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 that is equal to or longer than the minimum control time T0, the pumping stroke amount is from 0 to the entire stroke of the plunger lift amount S that is the maximum value. Since the amount can be adjusted to an arbitrary amount, the fuel discharge amount Q can also be controlled from 0 to the maximum discharge amount Qmax. However, since the control time T1 is limited so as not to become the minimum control time T0 or less when the rated rotation state is exceeded and the high-speed rotation state is entered, at the pressure feeding start time t4, the plunger has already reached the stroke amount SM. Is just rising. Therefore, in this case, since the maximum value of the pumping stroke amount is limited, the fuel discharge amount Q is also the maximum discharge amount Qm.
The amount is limited to less than ax, and the dischargeable amount is controlled to decrease as the rotation speed increases.

In this embodiment, the diesel engine 2 corresponds to the diesel engine M1, the common rail 4 corresponds to the accumulator M2, and the variable discharge high pressure pump 5 corresponds to the booster M3. Also,
Of the processing executed by ECU6 and ECU6, the step (100,
110,120,130,160,170,180,190) as the control means M4,
The steps (140, 150) each function as the limiting means M5.

As described above, according to the present embodiment, the diesel engine 2 is erroneously detected due to the erroneous detection of the rotation speed sensor 21 that detects the rotation speed of the diesel engine 2 and the pressure sensor 23 that measures the fuel pressure inside the common rail 4. Even when the operating speed changes from the rated rotational speed operating state to the high rotational speed operating state, the discharge amount Q of the high pressure fuel from the variable discharge high pressure pump 5 is increased.
To reduce the pressure of the fuel accumulated inside the common rail 4, that is, the common rail pressure PC, to reduce the fuel pressure to the mechanical strength limit of the variable discharge high pressure pump 5, the supply pipe 8, the common rail 4 and the injector 3. Since it becomes possible to operate the common rail fuel injection control device 1 while maintaining the pressure within the range not exceeding
The reliability and durability of the common rail fuel injection control device 1 are improved even when an erroneous detection occurs due to a failure of the rotation speed sensor 21 or the pressure sensor 23. That is, as shown in FIG. 9, when the engine speed Ne is less than the rated speed,
The discharge amount Q can be set to a desired value within the range up to the maximum discharge amount Qmax, while on the other hand, the discharge amount rapidly decreases when the rated rotation speed is exceeded. Therefore, even if the engine rotation speed Ne exceeds the rated rotation speed, the discharge amount Q is reduced, and the fuel pressure inside the common rail 4 drops, so there is no possibility of shifting to the strength limit region and causing an obstacle. .

Further, since the flow rate of the intake fuel is restricted by the orifice 42, the amount of fuel that can be sucked in one cycle of the variable discharge high pressure pump 5 decreases when it exceeds the rated rotation speed, so that the ECU 6 operates normally due to electromagnetic interference or the like. When I stopped doing
Alternatively, the fuel discharge amount Q decreases and the common rail pressure PC inside the common rail 4 does not rise even if the engine rotation speed Ne exceeds the rated rotation speed when an electrical failure occurs such as when the solenoid valve 34 malfunctions. That is, as shown in FIG. 10, when the engine speed Ne is less than the rated speed,
The discharge amount Q can be set to a desired value within the range up to the maximum discharge amount Qmax, while on the other hand, when the rated rotation speed is exceeded, the discharge amount decreases as shown by the curve in the figure. Therefore, even when the engine speed Ne exceeds the rated speed during abnormal operation of the ECU 6 and the solenoid valve 34, the discharge amount Q is reduced, so that even if a failure occurs in the electric system, the mechanism provided with the orifice 42 allows Since the fuel pressure inside the common rail 4 drops, the fuel does not move to the strength limit region and excessive pressure is applied to the high pressure fuel supply system to cause deterioration or damage.

As described above, the control time T1 is held at the minimum control time T0 or longer by the variable discharge amount high pressure pump control process executed by the ECU 6, and when the ECU 6 is abnormal, the intake fuel amount is mechanically limited by the orifice 42. As described above, since it has a double fail-safe function of electrical and mechanical, the strength reliability and durability of the fuel supply system of the common rail fuel injection control device 1 can be maintained at an extremely high level. This has a particularly remarkable effect when applied to a vehicle-mounted diesel engine that requires high reliability, for example.

Furthermore, when the diesel engine 2 is operated in the operating range from the low rotation speed operation state to the rated rotation speed operation state, within a range that does not exceed the maximum dischargeable amount Qmax,
Common rail pressure PC of fuel accumulated in common rail 4
Is the target common rail pressure PC0 that is determined according to the operating conditions.
Therefore, it is possible to constantly discharge the diesel engine 2 in an amount that can be held, and it is possible to maintain a good operating condition of the diesel engine 2.

Further, the control time T1 calculated from the load α of the diesel engine 2, the rotation speed Ne, and the common rail pressure PC inside the common rail 4 is restricted so as not to be shorter than the minimum control time T0 determined according to the rated rotation 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 only by disposing the orifice 42 in the variable discharge high-pressure pump 5, so that various configurations can be achieved with a simple device configuration. It is possible to reliably prevent the deterioration of the operating conditions of the common rail fuel injection control device 1 caused by the erroneous detection of the sensor and the malfunction of the ECU 6 and the solenoid valve 34 and the action of the excessively strong load on the mechanical portion.

Further, since the minimum control time T1 can be applied to various common rail type diesel engines simply by changing the setting of the variable discharge high pressure pump 5, the versatility of the device is expanded.

The valve body 57 of the solenoid valve 34 is configured to receive the fuel pressure inside the pump chamber 38 as a pressing force in the valve closing direction. Therefore, the valve body 57 is finished so that it can be seated on the seat portion 56 with high precision. 38 The internal fuel pressure exerts a pressing force in the valve closing direction, maintaining extremely excellent sealing performance.

Further, since the plunger 37 has a columnar shape with no leads provided, the inner surface of the cylinder 32 and the plunger 37
Since the high-pressure fuel inside the pump chamber 38 formed by the upper end surface of 37 does not leak to the low-pressure side, pressurization of the plunger 37
It is possible to reduce the leakage of the high pressure fuel to the low pressure side in the pressure feeding process.

Further, since only the feed hole 39 and the discharge hole 40 are formed in the cylinder 32 as a passage communicating with the pump chamber 38, it is possible to reduce the leakage of the high pressure fuel inside the pump chamber 38 to the low pressure side.

Although the hole diameter of the orifice 42 is constant in the present embodiment, for example, the hole diameter may be changed according to the engine rotation speed Ne.

Further, in the present embodiment, the orifice 42 is used. However, even if a hydraulic circuit element capable of holding a constant flow rate per unit time, such as a choke or various throttles, is used, the same as in the above-described embodiment. The effect is obtained.

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

As described above in detail, according to the present invention, the electromagnetic valve closing timing, which is the discharge start timing of the fuel pressurized by the plunger, is the time from the predetermined rotation angle of the cam driven by the engine. Is set as a parameter, and the solenoid valve cannot be closed earlier than the discharge start timing corresponding to the earliest plunger phase used during rated operation.
Should the engine speed exceed the rated speed, the solenoid valve closing timing will be fixed and only the pressure stroke of the plunger will be accelerated.As a result, the fuel to be pumped to the plunger will not be sent to the pressure accumulator, but to the low pressure side. Will be returned to. As described above, it is possible to realize a system excellent in safety that does not exceed the strength limit of the pressure accumulator even though it has a simple structure in which the time determined from the predetermined angle of the cam is limited.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram conceptually illustrating the content of the present invention, FIG. 2 is a system configuration diagram of an embodiment of the present invention, and FIG. 3 is a sectional view showing the structure of the variable discharge high pressure pump. FIG. 4 is a sectional view showing the structure of an electromagnetic valve similarly arranged in the variable discharge high-pressure pump, FIG. 5 is a main part configuration diagram of the same, and FIG. 6 is a C-C end view of FIG. FIG. 7 is a flow chart showing the same control, FIG. 8 is a timing chart showing the same control, and FIGS. 9 and 10 show the relationship between the high-pressure supply pump discharge amount and the engine speed. FIG. 11 is a schematic device configuration diagram showing the configuration of the conventional technique, and FIG. 12 is a timing chart showing the control of the conventional technique. M1 …… Diesel engine M2 …… Accumulator M3 …… 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 unit (ECU) 6a ... CPU

Claims (1)

(57) [Claims] 1. A pressure accumulating portion for accumulating high-pressure fuel to be supplied to a diesel engine, a fuel pressurizing plunger reciprocally driven by a cam rotated in association with the rotation of the diesel engine, and a pressurizing stroke of the plunger. In the above, a solenoid valve for delivering pressurized fuel to the pressure accumulator by closing a passage for releasing pressurized fuel to the low pressure side, and a discharge start timing determined based on the operating state of the diesel engine and the fuel pressure of the accumulator Is defined as a time from the predetermined rotation angle of the cam as a parameter, and the control means for starting the delivery of the pressurized fuel to the pressure accumulating section by controlling the closing of the electromagnetic valve at this discharge start timing. In the high-pressure fuel pump control device configured to deliver a larger amount of fuel to the pressure accumulating portion as the discharge start time is earlier, the diesel engine is operated within the rated operating state. Than a maximum amount of fuel pumped in response to the plunger of the phase that allows a predetermined discharge start timing predetermined for in a state that is rolling,
A high-pressure fuel pump control device comprising: a limiting means for limiting the discharge start timing determined by the control means to the predetermined discharge start timing when the discharge start timing determined by the control means is early.