JPH04128518A - Fuel feeding pump control unit for internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce electric power consumption and elongate a life by suppressing the operation frequency of an electric actuator at the time of high engine revolution speed, when the electric actuator is driven to stop overflow of fuel from a pressurized fuel passage. CONSTITUTION:An accumulator 4 is connected to a fuel tank 7 via a pressurized fuel feed control device 5 and a fuel pump 6, and high pressure fuel stored in the accumulator 4 is injected into respective cylinders 2 via fuel distributing pipes 8 and respective fuel injection valves 3. An actuator 47 of the pressurized fuel feed control device 5 is driven so as to stop overflow of fuel from a pressurized fuel passage. At this case, when engine revolution speed is lower than a set revolution speed, the actuator 47 is driven in every delivery stroke of the fuel pump 6, and when the engine revolution speed is higher than the set revolution speed, the actuator 47 is driven in every integral number time of delivery stroke of the fuel feeding pump.

Description

[Detailed description of the invention] C Industrial application field] The present invention relates to a fuel supply pump control device for an internal combustion engine.

Conventional technology] A fuel overflow passage is branched from a pressurized fuel passage connected to the discharge side of a plunger pump of an engine drive t, and an overflow control valve controlled by an electric actuator is arranged in the fuel overflow passage. The overflow control valve is opened and closed once within a certain crank angle, and the opening and closing times of the overflow control valve are controlled in order to control the amount of fuel sent out from the pressurized fuel passage. A fuel supply pump control device for an internal combustion engine that is controlled at every constant crank angle is known (see Japanese Patent Laid-Open No. 62-258160).

The problem that σFahu is trying to solve] However, if the overflow control valve is opened and closed once within a certain crank angle in this way, as the engine speed increases, the overflow control valve will open and close within a certain period of time. There is a problem that the number of times increases, thus increasing the power consumption of the electric actuator for controlling the overflow control valve and shortening the life of the electric actuator.

In particular, when a piezoelectric element is used as the electric actuator, there is a problem that as the engine speed increases, power consumption further increases and noise increases. In other words, since the piezoelectric element is operated by charging and discharging, the amount of charge consumed increases as the number of charging and discharging increases, and as the engine speed increases, power consumption increases significantly. do. Further, the piezoelectric element is made of a stack of piezoelectric element plates, and a small gap exists between each piezoelectric element plate. Therefore, when the piezoelectric element is charged with electric charge and the piezoelectric element plates are expanded, the piezoelectric element plates collide with each other, thus generating collision noise. On the other hand, when the charge charged in the piezoelectric element is discharged and each piezoelectric element plate contracts, the gap between each piezoelectric element plate temporarily increases, and then each piezoelectric element plate collides with each other. Collision noise is also generated. Therefore, as the engine speed increases and the number of times the piezoelectric element is charged and discharged increases, the noise gradually increases.

[Means to solve the problem]

In order to solve the above problems, according to the present invention, a pressurized fuel passage is connected to the discharge side of a fuel supply pump that is driven by an engine and repeats a discharge stroke every predetermined crank angle, and fuel is supplied from the pressurized fuel passage. The overflow passage is branched and an overflow control valve driven by an electric actuator is arranged in the fuel overflow passage, and when the actuator is driven, the overflow control valve closes and the pressurized fuel is removed from the pressurized fuel passage. In a fuel supply pump control device for an internal combustion engine, the actuator is driven every discharge stroke of the fuel supply pump when the engine rotation speed is lower than a predetermined set rotation speed, and the engine When the rotational speed is higher than the set rotational speed, the actuator is driven every predetermined integral number of discharge strokes of the fuel supply pump.

[For production]

When the engine speed becomes higher than the set speed, the number of times the electric actuator operates is reduced.

〔Example〕

FIG. 4 shows an overall diagram of the internal combustion engine. Referring to FIG. 4, 1 is the engine body, 2 is a cylinder, 3 is a fuel injection valve arranged for each cylinder 2, 4 is a pressure accumulation chamber, and the pressure accumulation chamber 4 is a pressurized fuel supply control device. 5 and a fuel tank 7 via a fuel pump 6. The fuel pump 6 is provided to feed low pressure fuel to the pressurized fuel supply control device 5.

This low-pressure fuel is made into high-pressure fuel by the pressurized fuel supply control device 5, and then this high-pressure fuel is supplied into the pressure storage chamber 4. High-pressure fuel stored in the pressure storage chamber 4 is injected into each cylinder 2 via a fuel distribution pipe 8 and each fuel injection valve 3. A pressure sensor 9 is arranged within the pressure accumulation chamber 4 to detect the fuel pressure within the pressure accumulation chamber 4 .

FIG. 1 shows a side sectional view of the pressurized fuel supply control device 5 as a whole. The pressurized fuel supply control device 5 is roughly composed of a fuel supply pump A and a discharge amount control device B that controls the discharge amount of the fuel supply pump A. FIG. 2 shows a sectional view of the fuel supply pump A, and FIG. 3 shows an enlarged side sectional view of the discharge amount control device B. First of all, the first thing to do is to start the contract.
The structure of the fuel supply pump A will be explained with reference to the drawings and FIG. 2, and then the structure of the discharge amount control device B will be explained with reference to FIG.

Referring to FIGS. 1 and 2, 20 is a pair of plungers, 21 is a pressurizing chamber formed by each plunger 20, 22 is a plate attached to the lower end of each plunger 20, 23 is a tappet, and 24 is a pressurized chamber formed by each plunger 20. A compression spring 25 presses the plate 22 toward the tappet 23;
26 is a camshaft driven by the engine, 27 is a cam integrally formed on the camshaft 26, and roller 25 is rotatably supported by the cam 2.
It rolls on the cam surface of 7. Therefore, when the shaft 26 is rotated, each plunger 20 moves up and down accordingly.

Referring to FIG. 1, a fuel supply port 28 is formed at the top of the fuel supply pump A, and this fuel supply port 28 is connected to the discharge port of the fuel pump 6 (FIG. 4).

This fuel supply 128 is connected to the fuel supply passage 29 and the check valve 3.
0 to the pressurizing chamber 21. Therefore, when the plunger 20 is lowered, the fuel supply passage 29 is connected to the pressurizing chamber 21.
Fuel is supplied inside. Reference numeral 31 indicates a fuel return passage for returning leaked fuel from around the plunger 20 to the fuel supply passage 29. On the other hand, as shown in FIGS. 1 and 2, each pressurizing chamber 21 is connected to a common pressurized fuel passage 33 through a corresponding check valve 32. This pressurized fuel passage 33 is connected to a pressurized fuel outlet 35 via a check valve 34, and this pressurized fuel outlet 35 is connected to the pressure storage chamber 4.
(Fig. 4). Therefore, when the plunger 20 rises and the fuel pressure in the pressurizing chamber 21 increases, the high-pressure fuel in the pressurizing chamber 21 is discharged into the pressurizing fuel passage 33 via the check valve 32, and then this fuel is reversed. The fuel is fed into the pressure accumulation chamber 4 (FIG. 4) via the stop valve 34 and the pressurized fuel discharge port 35.

The phases of the pair of cams 27 are shifted by 180 degrees, so that when one plunger 20 is in the upward stroke and discharges pressurized fuel, the other plunger 20 is in the downward stroke and discharges the fuel into the pressurized chamber 2. Inhaled inside. Therefore, high-pressure fuel is always supplied into the pressurized fuel passage 33 from one of the pressurizing chambers 21, and therefore high-pressure fuel is constantly supplied into the pressurized fuel passage 33 by each plunger 20. As shown in FIG. 1, a fuel overflow passage 40 branches off from the pressurized fuel passage 33, and this fuel overflow passage 40 is connected to the discharge amount control device.

Referring to FIG. 3, the discharge amount control device B has a fuel overflow chamber 41 formed in its nozzing and a fuel overflow passage 40.
The overflow control valve 42 controls the fuel flow from the fuel overflow chamber 41 to the fuel overflow chamber 41. The overflow control valve 42 is connected to the fuel overflow chamber 41
The valve boat 44 has a valve portion 43 disposed therein, and the opening and closing of the valve boat 44 is controlled by the valve portion 43. Furthermore, an actuator 45 for driving the overflow control valve 42 is disposed within the housing of the discharge amount control device B. This actuator 45 includes a pressure piston 46 slidably inserted into the housing of the discharge amount control device B, and a pressure piston 46 that is slidably inserted into the housing of the discharge amount control device B.
a piezoelectric element 47 for driving the pressurizing piston 4; a pressurizing chamber 48 defined by the pressurizing piston 46;
6 toward the piezoelectric element 45, and a pressure bottle 50 slidably inserted into the housing of the discharge amount control device B. The upper end surface of the pressurizing bottle 50 is in contact with the valve portion 43 of the overflow control valve 42, and the lower end surface of the pressurizing bottle 50 is exposed in the pressurizing chamber 48.

Note that a disc spring 51 is disposed within the fuel overflow chamber 41 to constantly bias the pressurized bottle 50 upward. Overflow control valve 4
A spring chamber 52 is formed above 2, and a compression spring 53 is inserted into this spring chamber 52. The overflow control valve 42 is constantly pressed downward by this compression spring 53. The fuel overflow chamber 41 communicates with the spring chamber 52 through a fuel outflow hole 54, and this spring chamber 52 communicates with the fuel tank 7 through a fuel outflow hole 55, a check valve 56, and a fuel outflow port 57.
(Fig. 4). This check valve 56 is usually composed of a check ball 58 that closes the fuel outlet hole 55 and a compression spring 59 that presses the check ball 58 toward the fuel outlet hole 55.

Further, the fuel overflow chamber 41 includes a fuel outflow hole 60, a check valve 61, and a fuel outflow passage 62 formed around the piezoelectric element 47.
and is connected to the fuel tank 7 (FIG. 4) via a fuel outlet 63. This check valve 61 is normally connected to the fuel outlet hole 60.
It is composed of a check ball 64 that closes the fuel outlet hole 60, and a compression spring 65 that presses the check ball 64 toward the fuel outlet hole 60. Further, the fuel overflow chamber 41 is connected to the throttle passage 66.
and is connected to the inside of the pressurizing chamber 48 via a check valve 67.

This check valve 67 normally includes a check ball 68 that closes the throttle passage 66 and a check ball 68 that closes the throttle passage 66.
It is composed of a compression spring 69 that presses toward. The cross-sectional area of the throttle passage 66 is smaller than the cross-sectional area of the fuel outflow hole 60.

Further, the opening pressures of the pair of check valves 56 and 61 are set to be approximately constant, and the opening pressure of the check valve 67 is set to be approximately constant.
・It is set lower than the valve opening pressure of 61. That is, the spring forces of the compression springs 59 and 65 of the check valves 56 and 61 are approximately equal, and the spring force of the compression spring 69 of the check valve 67 is equal to that of the compression spring 59.
The piezoelectric element 47, which is set to be smaller than the spring force of =65, is connected to the electronic control unit 10 (FIG. 4) via a lead wire 70, and therefore the piezoelectric element 47 is connected to the output of the electronic control unit 10. Controlled by signals. The piezoelectric element 47 has a laminated structure in which a large number of piezoelectric element plates are laminated, and when the piezoelectric element 47 is charged with an electric charge, the piezoelectric element 47 expands in the axial direction, and the electric charge charged on the piezoelectric element 47 is expanded. When discharged, the piezoelectric element 47 contracts in the axial direction.

The fuel overflow chamber 41 and the pressurizing chamber 48 are filled with fuel. Therefore, when the piezoelectric element 47 is charged with an electric charge and the piezoelectric element 47 expands in the axial direction, the fuel pressure in the pressurizing chamber 4B increases. . When the fuel pressure in the pressurizing chamber 48 increases, the pressurizing bottle 50 is raised, and the overflow control valve 42 is also raised accordingly. As a result, the valve portion 43 of the overflow control valve 42 closes the valve port 44, and as a result, the overflow of fuel from the fuel overflow passage 40 into the fuel overflow chamber 41 is stopped and stopped. Therefore, at this time, all the pressurized fuel discharged from the pressurizing chamber 21 of the plunger 20 into the pressurized fuel passage 33 (FIG. 2) is sent into the pressure accumulating chamber 4 (FIG. 4).

On the other hand, when the electric charge stored in the piezoelectric element 47 is discharged and the piezoelectric element 47 contracts, the volume of the pressurizing chamber 48 increases as the pressurizing piston 46 descends. As a result, the fuel pressure in the pressurizing chamber 48 decreases, so the overflow control valve 42 and the pressurizing bottle 50 are lowered by the spring force of the compression spring 53, and thus the valve body 43 of the overflow control valve 42 is lowered. The valve boat 44 is opened. At this time, all the pressurized fuel discharged from the pressurization chamber 21 of the plunger 20 into the pressurized fuel passage 33 (FIG. 2) flows into the fuel overflow chamber 41 via the fuel overflow passage 40 and the valve boat 44. sent. Therefore, at this time, pressurized fuel is not supplied into the pressure storage chamber 4 (FIG. 4).

The fuel overflowing from the fuel overflow passage 40 into the fuel overflow chamber 41 flows through each fuel outflow hole 54, 55, 60 and the check valve 5661.
The fuel is returned to the fuel tank 7 (FIG. 4) via the fuel tank 7 (FIG. 4).

Incidentally, the opening pressure of each check valve 56, 61 is set to a pressure higher than atmospheric pressure, and therefore the fuel pressure in the fuel overflow chamber 41 is maintained at a constant pressure higher than atmospheric pressure. As described above, when the electric charge charged in the piezoelectric element 47 is discharged, the fuel pressure in the pressurizing chamber 48 decreases, and the pressure in the pressurizing chamber 48 becomes lower than the opening pressure of the check valve 67. For example, when the check valve 67 is opened, the fuel in the fuel overflow chamber 41 is supplied into the pressurizing chamber 48 . Note that if the spring force of the compression spring 69 is weakened to the minimum so that the opening pressure of the reverse valve 67 becomes almost zero, the pressure in the pressurizing chamber 48 will be reduced to the level of the fuel overflow chamber 41.
almost equal to the pressure inside. In any case, pressurized chamber 48
will be filled with pressurized fuel. Pressurized chamber 48
If the fuel inside leaks and a space is created in the pressurizing chamber 48, the fuel pressure in the pressurizing chamber 48 will not rise when voltage is applied to the piezoelectric element 47, and therefore the overflow control valve 42 will be raised. This results in the problem of not being able to do so. Therefore, pressurization chamber 4B
It is necessary to keep the inside filled with fuel at all times, and for this purpose, the fuel overflow chamber 41 is maintained at a pressure higher than atmospheric pressure, and a check valve 67 is provided to allow flow only from the fuel overflow chamber 41 to the pressurizing chamber 4B. ing.

FIG. 5 shows an enlarged side cross-sectional view of the fuel injection valve 3 shown in FIG. a needle 82 that performs the same operation, a needle pressurizing chamber 84 formed around a conical pressure receiving surface 83 of the needle 82, a piston 85 that is slidably inserted into the housing 8G, and a piston 85 that is inserted between the housing 80 and the piston 85. a piezoelectric element 86 that urges the piston 85 toward the piezoelectric element 86; a pressure control chamber 88 formed between the needle 82 and the piston 85; A compression spring 89 is provided. The pressure control chamber 88 is a throttle passage 9 formed around the second dollar 82.
0 to a needle pressurizing chamber 84, and the needle pressurizing chamber 84 is connected to a fuel passage 91 and a fuel distribution pipe 8 (FIG. 4).
It is connected to the inside of the pressure accumulation chamber 4 via. Therefore, high-pressure fuel in the pressure accumulator chamber 4 is introduced into the needle pressurizing chamber 84 , and a portion of this high-pressure fuel is sent into the pressure control chamber 88 through the throttle passage 90 . In this way, the fuel pressure in the needle pressurizing chamber 84 and the pressure control chamber 88 is approximately the same high pressure as in the pressure accumulating chamber 4.

When the electric charge charged in the piezoelectric element 86 is discharged and the piezoelectric element 86 contracts, the piston 8
5 increases, the fuel pressure in the pressure control chamber 88 drops rapidly. As a result, the needle 82 rises and fuel injection from the nozzle port 81 is started.

While fuel injection is being performed, the fuel pressure in the pressure control chamber 88 gradually increases as the fuel in the needle pressurizing chamber 84 is sent into the pressure control chamber 88 through the throttle passage 90.

Next, when the piezoelectric element 86 is charged with an electric charge and expands, the piston 85 descends, causing the fuel pressure in the pressure control chamber 88 to rise rapidly. As a result, the needle 82 descends and closes the nozzle port 81,
Thus, fuel injection is stopped and stopped. While fuel injection is stopped, the fuel in the pressure control chamber 88 flows through the throttle passage 90.
Since the fuel flows out into the needle pressurizing chamber 84 through the pressure control chamber 88, the fuel pressure in the pressure control chamber 88 gradually decreases and returns to the original high pressure.

Referring to FIG. 4, the electronic control unit 10 consists of a digital computer with RDM (!I-only memory) IO interconnected by a bidirectional bus 100.
L RAλ (<random access memory) 102, CP
IJ (microprocessor) 103, human powered boat 104
and an output port 105. The pressure sensor 9 generates an output voltage proportional to the fuel pressure within the pressure accumulator 4 , and this output voltage is input to the input port 104 via the AD converter 106 . For example, a crank angle sensor 107 that generates an output pulse every time the crankshaft rotates by 30 degrees is connected to the input boat 104, and the engine speed is calculated from the 8 pulses of the crank angle sensor 107.

Furthermore, the input boat 104 includes an ignition switch 10.
8 on/off signals are input. On the other hand, output port 1
05 is connected to the piezoelectric element 47 of the actuator 45 via the drive circuit 109.

FIG. 6 shows a circuit diagram of a drive circuit 109 for driving the piezoelectric element 47. Referring to FIG. 6, drive circuit 1
09 is a constant voltage source 110, a capacitor 111 charged by the constant voltage source 110, and a charging control thyristor 1.
12 , a charging coil 113 , a discharge control thyristor 114 , and a discharge coil 115 .

As shown in FIG. 7, when the thyristor 112 is turned on, the charge stored in the capacitor 111 is charged to the piezoelectric element 47 via the charging coil 113.

As a result, the piezoelectric element 47 expands and the overflow control valve 42 closes. Next, when the thyristor 114 is turned on, the electric charge charged in the piezoelectric element 47 is discharged via the discharge coil 115. As a result, the piezoelectric element 47 contracts, so that the overflow control valve 4
2 opens.

As described above, when the overflow control valve 42 is opened, all the pressurized fuel discharged from the pressurization chamber 21 of the plunger 20 into the pressurized fuel passage 33 is caused to overflow via the overflow control valve 42. t be beaten. Therefore, pressurized fuel is not supplied to the pressure storage chamber 4 at this time. On the other hand, when the overflow control valve 42 is closed, all the pressurized fuel discharged from the pressure chamber 21 of the plunger 20 is supplied into the pressure accumulation chamber 4, and as a result, the fuel pressure in the pressure accumulation chamber 4 is It will be raised.

Incidentally, the amount of fuel injected from each fuel injection valve 3 is determined by the fuel pressure in the pressure accumulation chamber 4 and the fuel injection time, and the fuel pressure in the pressure accumulation chamber 4 is normally maintained at a predetermined target fuel pressure. On the other hand, looking at each cylinder, the required amount of fuel is injected into each cylinder for every 720° crank angle. Therefore, in a 4-cylinder internal combustion engine as shown in FIG.
It will decrease with every crank angle. Therefore, in order to maintain the fuel pressure in the pressure accumulation chamber 4 at the target fuel pressure, it is preferable to replenish the pressure accumulation chamber 4 with pressurized fuel every 180° crank angle. When the flow control valve 42 is closed, the pressurized fuel discharged from the pressurizing chamber 21 of the plunger 20 is replenished into the pressure storage chamber 4, and then the overflow control valve is closed until the overflow control valve 42 is closed again. 42 is maintained in an open state. In this case, 1
If the proportion of the crank angle in which the overflow control valve 42 is closed within the 80° crank angle increases, the amount of pressurized fuel replenished into the pressure storage chamber 4 increases. Here, as shown in FIG. 7, the crank angle θ is 180°. The proportion of the crank angle θ during which the overflow control valve 42 is closed, that is, the constant time θ
The ratio of the time θ during which the piezoelectric element 47 is extended between The amount of pressurized fuel will increase.

In the embodiment shown in FIG. 1, the fuel supply pump A is rotated at the same speed as the engine, so that each plunger 20
The pressurized fuel discharge rate from the pressurizing chamber 21 is shown in FIG. 8(A),
As shown in (B) and (C,), the fluctuation is repeated every 180° crank angle (CA).

In this case, if the timing to close the overflow control valve 42 is set to the start timing of the discharge stroke of the fuel supply pump A, as shown in FIG.
As shown in A), the overflow control valve 42 is closed every 180° crank angle. However, if the overflow control valve 42 is closed every 180° crank angle, that is, the overflow control valve 42 is closed and opened once within 180° crank angle, as the engine speed N increases, Since the time corresponding to the 180° crank angle gradually becomes shorter, the frequency of opening and closing operations of the overflow control valve 42 within a unit time gradually increases. Therefore, engine speed N
The piezoelectric element 47 per unit time increases as
The number of operations will increase. As the number of times the piezoelectric element 47 is operated per unit time increases in this manner, the power consumption of the piezoelectric element 47 increases, and the operating noise of the piezoelectric element 47 also increases.

Therefore, in one embodiment of the present invention, the engine rotation speed N is a predetermined set rotation speed N +, for example, 4000r, p,
m, the overflow control valve 42 is closed every other discharge stroke as shown in FIG. 8(B), that is, the overflow control valve 42 is closed once every 360° crank angle. The valves are closed and opened one at a time. Therefore, the engine rotation speed N is the set rotation speed N.

When the overflow control valve 42 is closed at every discharge stroke, the number of times the piezoelectric element 47 is actuated per unit time is reduced. As a result, the power consumption of the piezoelectric element 47 can be reduced, and the operational noise generated by the piezoelectric element 47 can be reduced. Note that if the number of actuations of the piezoelectric element 47 is suppressed when the engine rotation speed N is higher than the set rotation speed N1, the fuel pressure in the pressure accumulation chamber 4 will fluctuate slightly, but the fuel injection amount will remain the same as the fuel pressure in the pressure accumulation chamber 4. Since it is calculated based on ), it does not affect the fuel injection amount at all. Also, the engine rotation speed N is the set rotation speed N
1, as shown in FIG. 8(C), the overflow control valve 42 is closed every third or every 8 strokes, that is, the overflow control valve 42 is closed every 720° crank angle. It is also possible to close and open the valve once at a time. Furthermore, two set rotational speeds Nl 'N2 (Nl < N2
) is set in advance, and the engine rotation speed N is the set rotation speed N1.
When the engine rotation speed N exceeds the set rotation speed N2, the overflow control valve 42 is closed every other discharge stroke as shown in FIG. 8(B). The overflow control valve 42 is activated every third discharge stroke as shown in C).
It is also possible to close the valve.

On the other hand, when the fuel pressure in the pressure accumulator 4 has dropped to near atmospheric pressure, such as when starting the engine, a large amount of pressurized fuel is injected to raise the fuel pressure in the pressure accumulator 4 to the target fuel pressure. It must be supplied into the pressure accumulation chamber 4. In order to supply a large amount of pressurized fuel into the pressure storage chamber 4, it is necessary to make the closing time of the overflow control valve 42 longer than the opening time. If the valve is closed and opened once at a time, the overflow control valve 42 remains closed for a long time when the engine speed N is low, such as when starting the engine. However, when the overflow control valve 42 closes, that is, when the fuel pressure in the pressurizing chamber 48 increases, the fuel in the pressurizing chamber 48 flows into the pressurizing piston 46 or the pressurizing bottle 50.
The fuel pressure in the pressurizing chamber 48 gradually decreases. Therefore, as mentioned above, the overflow control valve 42
If the time period during which the overflow control valve 42 is closed increases, the fuel pressure within the pressurizing chamber 48 will drop significantly, causing a problem that the overflow control valve 42 cannot be kept closed. Therefore, in one embodiment of the present invention, when the engine speed N is lower than a predetermined set speed N3%, for example, 500r, p, m, the overflow control valve 42 is activated regardless of the engine speed.
The valves are opened and closed once each within a certain period of time, for example, 60m5ec. This 53m5ec
corresponds to 180' crank angle when the engine speed N is Ns, that is, 500 r, p, m. Of course, the above-mentioned fixed time period can also be made shorter. In any case, when the engine speed N is lower than the set speed N3, the overflow control valve 42 is opened and closed once within a 180° crank angle. The time that the valve is closed becomes shorter. the result,
Since the fuel pressure in the pressurizing chamber 48 does not drop significantly, the overflow control valve 42 can be reliably maintained in the closed state.
In this way, the fuel pressure in the pressure accumulating chamber 4 can be quickly raised to the target fuel pressure.

Next, referring to FIGS. 9 to 12, the piezoelectric element 47
The control method will be explained below. In addition, from Figures 9 to 12
The figure shows that the overflow control valve 42 is closed every 5Qmsec when the engine speed N is 50Or, p,m or less, and the overflow control valve 42 is closed every 5Qmsec when the engine speed N is 4DOOr,p,m or more.
As shown in Figure <B), the overflow control valve 42 is closed every other discharge stroke.

FIG. 9 shows a routine for calculating the duty ratio DT, and this routine is executed by an interrupt every 1Qmsec.

Referring to FIG. 9, first, in step 200, it is determined whether the ignition switch 108 has been turned from off to on. When the ignition switch 108 is turned from off to on, the process proceeds to step 201 where the duty-ratio integral term DTI is set to 0.5.
After that, the process proceeds from step 200 to step 202. In step 202, the target fuel pressure P in the pressure accumulator 4 is determined based on the output signal of the pressure sensor 9, which is stored in the ROM 101. Pressure difference △P between and the current fuel pressure P in the pressure accumulator 4
is calculated. Next, in step 203, α is added to the digital ratio term DTl. This α is a function of the pressure difference ΔP as shown in FIG.
The relationship between and ΔP is stored in advance in the RDλ) 101. Next, in step 204, the duty ratio proportional term DT2 is calculated by multiplying the pressure difference ΔP by the proportionality constant K. Next, in step 2D5, the duty ratio DT is calculated by adding the duty ratio integral term DTI and the duty ratio proportional term DT2. Next, in step 206, it is determined whether or not the duty ratio DT has become negative. If DT<0, the process proceeds to step 207, where the duty ratio DT is set to zero. On the other hand, if it is determined in step 206 that DT>Q, the process proceeds to step 208, where it is determined whether or not the deniity ratio DT is greater than 0.95.If DT2Q,95, the process proceeds to step 209, where the duty ratio is - Upper heel DT force '0.95
It is said that

As mentioned above, the routine shown in FIG. 9 is executed every 10 m5ec, and the fuel pressure P in the pressure accumulating chamber 4 is the target fuel pressure P. When it is lower than , that is, when ΔP>Q, α becomes positive,
[) Since T2 becomes positive, the duty ratio DT is increased, and when the fuel pressure P in the pressure accumulation chamber 4 is higher than the target fuel pressure P0, that is, when ΔP<0, α becomes a negative pressure, D
Since T2 becomes negative, the decoupage ratio DT is no longer reduced. Therefore, the fuel pressure P in the pressure accumulation chamber 4 is the target fuel pressure P. As long as the duty is larger or smaller than
The ratio DT is updated every 1Qmsec.

FIG. 11 shows a routine for controlling the flag. This routine is executed by an interrupt every 100 m5ec, for example.

Referring to FIG. 11, first, in step 300, the engine speed N is set to N1%, for example, 400[]r.
, p, is higher than m. N2N1
At step 301, the flag F1 is set, and in the next step, the flag F2 is reset in step 302, and then in step 303, the flag F3 is reset. On the other hand, when N<Nl, the process proceeds to step 304 and the engine rotation speed N is set to the set rotation speed N3, for example, 500r, p.
, it is determined whether or not it is lower than m. N > N 3
When this happens, the process proceeds to step 305 where flag F2 is set, then in step 306 flag F1 is reset, and then in step 307 flag F3 is reset. On the other hand, N≦N.

When this happens, the process proceeds to step 308 where flag F3 is set, then in step 309 flag F1 is set, and then in step 310 flag F2 is reset. Therefore, N;! When N, flag F1 is set, and when N 1 > N > N3, flag F2 is set.
is saved, and flag F3 is set when it is N or IN.

Figure 12 shows clan F1. F2. A routine for controlling the piezoelectric element 47 based on F3 is shown.

Referring to FIG. 12, interrupt signals for every 360° crank angle, interrupt signals for every 180° crank angle, and 60°
Interrupt signals are generated every +n5ec, and flags Fl, F2 . It can be seen that it is determined by F3. That is, when the flag F2 is set, that is, when N>N>N3, the process proceeds from step 404 to step 405 every 180° crank angle. In step 405, the time T required for the engine crank and foot to rotate 180 degrees is calculated from the engine speed N, and the process proceeds to step 402.

In step 402, the current Denny-Tee ratio DT calculated by the routine shown in FIG.
By multiplying the time T calculated in step 5, the duty ratio TDT in time is calculated. Next, in step 403, control data for the thyristors 112 and 114 is outputted to the output port 105 so that the time during which the piezoelectric element 47 is expanded becomes the duty ratio TDT. As described above, the fuel pressure P in the pressure accumulation chamber 4 is the target fuel pressure P. If it becomes higher than , the duty ratio TDT is reduced, so the amount of pressurized fuel supplied into the pressure storage chamber 4 is reduced, and thus the fuel pressure P in the pressure storage chamber 4 is reduced.

On the other hand, the fuel pressure P in the pressure accumulation chamber 4 is the target fuel pressure P.

If it becomes lower than , the duty ratio TDT is increased and the fuel pressure P in the pressure accumulator 4 increases.

In this way, the fuel pressure P in the pressure accumulator 4 reaches the target twist (pressure P.

will be maintained. At this time, the duty ratio TDT is calculated for each 180° crank angle as shown in FIG. The valve is forced to close.

On the other hand, when flag F1 is set, immediately N≧N
, sometimes 400 steps every 36° crank angle
The process then proceeds to step 401. In step 4Dl, the time T required for the engine crankset to rotate 360 degrees is calculated from the engine speed N, and the process proceeds to step 402.

Therefore, in this case, the angle is 36o as shown in Fig. 8(B).
Duty ratio TDT is calculated for each crank angle,
The overflow control valve 42 is closed for a time determined by the duty ratio TDT every 36° crank angle.

On the other hand, when flag F3 is set, that is, NKN
When it is 3, the process proceeds from step 406 to step 407 every 5[1 m5ec. In step 407, time T is 5Q
msec, and the process advances to step 402. Therefore, at this time, the decourage ratio TDT is calculated every 53 m5 ec, and the overflow control valve 42 is closed every 60 m5 ec for a time determined by the duty ratio TDT.

During the slight start operation, unless the piezoelectric element 47 is charged and discharged several times, a sufficient amount of electric charge will not be charged to the piezoelectric element 47, and therefore the piezoelectric element 47 will not fully expand. However, when the engine speed N is low, that is, N<50Or, p
, 5Qms regardless of the engine speed N when m
Since the piezoelectric element 47 is charged and discharged every ec, the number of repetitions of charging and discharging the piezoelectric element 47 is increased. As a result, the piezoelectric element 47 can be charged with sufficient electric charge immediately after the slight start movement.

Further, since the number of repetitions of charging and discharging the piezoelectric element 47 increases during the slight start operation, even if air is mixed in the fuel in the pressurizing chamber 48, this air can be immediately removed.

Also, in order to rapidly increase the fuel pressure in the pressure accumulator 4, it is sufficient to charge the piezoelectric element 47 and leave it there, and to keep the overflow control valve 42 closed. become. However, if the piezoelectric element 47 is charged and left unattended, the electric charge is gradually discharged and the piezoelectric element 47 gradually contracts, causing the pressurized chamber 48
The fuel pressure inside the engine gradually decreases. Further, since the fuel itself inside the pressurizing chamber 48 leaks, the fuel pressure inside the pressurizing chamber 48 further decreases. In order to prevent the fuel pressure in the pressurizing chamber 48 from decreasing as described above, it is necessary to periodically discharge the electric charge of the piezoelectric element 47, and for this purpose, in steps 208 and 209 of FIG. The maximum value of is set to 0.95.

Effects between mouths: Since the number of times the electric actuator operates is suppressed when the engine speed is high, the power consumption of the electric actuator can be reduced and the life of the electric actuator can be extended.

[Brief explanation of drawings]

Fig. 1 is a side sectional view of the pressurized fuel supply control device, Fig. 2 is a sectional view of the fuel supply pump taken along the line ■-■ in Fig. 1, and Fig. 3 is the discharge a amount control shown in Fig. 1. Enlarged side sectional view of the device;
Fig. 4 is an overall view of the internal combustion engine, Fig. 5 is a side sectional view of the fuel injection valve, Fig. 6 is a drive circuit diagram of the piezoelectric element, and Fig. 7 shows the operation of the piezoelectric element and the overflow control valve. A time chart, Fig. 8 is a time chart showing the operation of the overflow control valve, Fig. 9 is a flow cheat for calculating the duty ratio, Fig. 10 is a diagram showing the relationship between α and ΔP, 1st
Figure 1 is a flowchart for controlling the flags;
The figure is a flowchart for driving and controlling a piezoelectric element. 20... Plunger, 33... Pressurized fuel passage, 42... Overflow control valve, 47... Piezo piezoelectric element 1, to... Fuel supply pump, 21... Pressurized chamber, 40 ... Fuel overflow passage, 45 ... Actuator, 48 ... Pressurization chamber, B ... Discharge amount control device@. Punishment 20... Plunger 21... Pressurizing chamber 40... Fuel overflow passage 42... Overflow control valve diagram 45... Actuator 47... Piezoelectric element 48... Pressurizing chamber A ...Fuel supply pump Fig. 33... Pressurized fuel passage also Fig. 0B Fig. 10 Fig. 11

Claims (1)

[Claims] A pressurized fuel passage is connected to the discharge side of a fuel supply pump that is driven by the engine and repeats the discharge stroke at every predetermined crank angle, and a fuel overflow passage is branched from the pressurized fuel passage and driven by an electric actuator. an overflow control valve is disposed in the fuel overflow passage, and the overflow control valve closes when the actuator is driven to stop overflow of fuel from the pressurized fuel passage. In the fuel supply pump control device for an internal combustion engine, when the engine speed is lower than a predetermined set speed, the actuator is driven every discharge stroke of the fuel supply pump, and the engine speed is lower than the set speed. A fuel supply pump control device for an internal combustion engine, wherein the actuator is driven every predetermined integer discharge stroke of the fuel supply pump when the temperature is high.