JPH1182222A - Common-rail fuel injection controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent any drop in the durability of a timing belt from occurring by checking the resonance of this belt attendant upon the drive of a variable delivery high-pressure pump. SOLUTION: A variable delivery high-pressure pump P discharging pressurized fuel to a common rail R is constituted so as to reduce its torque variation at a time when the discharge is maximal, and thereby a relief passage R2 is connected to the common rail R via common-rail pressure reducing solenoid valve B3. An electronic control unit ECU maximizes the discharge amount of this pump P at an engine rotational speed area where a timing belt resonates, checking the torque variation, and any vibration in this timing belt is prevented, while the discharge amount of fuel from the relief passage R2 is regulated by the common-rail pressure reducing solenoid valve B3, whereby common-rail pressure is controlled to the extent of specified high pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a common rail type fuel injection control apparatus for injecting high pressure fuel stored in a common rail (accumulation pipe) into each cylinder of a diesel engine by an injector.

[0002]

2. Description of the Related Art As one of systems for injecting fuel into a diesel engine, a common rail type fuel injection control device is known. In the common rail type fuel injection control device, a common pressure accumulation pipe (common rail) communicating with each cylinder
The high pressure fuel at a required flow rate is supplied under pressure by a variable discharge high pressure pump to maintain the fuel pressure of the pressure accumulation pipe constant. The high-pressure fuel in the pressure accumulation pipe is injected into each cylinder by an injector at a predetermined timing (for example, Japanese Patent Application Laid-Open No. 64-73166).

FIG. 17 shows an example of a variable discharge high-pressure pump of a common rail type fuel injection control device. A plunger 92 driven by a cam (not shown) is inserted in a cylinder 91 in a reciprocating manner. A pressure chamber 93 is formed by the inner wall surface of 91 and the upper end surface of the plunger 92. An electromagnetic valve 94 is mounted above the pressure chamber 93, and the electromagnetic valve 94 has a valve body 96 that opens and closes a space between the low-pressure flow path 95 and the pressure chamber 93 formed therein.

The valve body 96 is in the valve-opening position in the state shown in the drawing, in which the coil 97 is not energized. When the plunger 92 is lowered, the fuel is supplied from the low-pressure supply pump (not shown) to the low-pressure flow path 95 and the gap around the valve body 96. Through the pressure chamber 93. When the coil 97 is energized, the valve body 96 is attracted upward, and its substantially conical tip sits on the seat portion 98 to close the valve. At the same time, the fuel in the pressure chamber 93 is pressurized by the rise of the plunger 92, and is fed to the common rail (not shown) from the flow path 99 provided on the side wall of the pressure chamber 93.

When the plunger 92 is raised, a force in the valve closing direction acts on the valve body 96 due to the fuel pressure in the pressure chamber 93. Therefore, once the valve body 96 is closed, energization of the coil 97 is stopped. Even if it does not open. For this reason, in the variable discharge high-pressure pump having the above-described configuration, the flow rate sent to the pressure accumulation pipe is controlled by so-called pre-stroke control that controls the valve closing timing. That is, after the plunger 92 moves to the rising stroke, the valve is not closed immediately, the valve is kept open until the fuel in the pressure chamber 93 reaches a predetermined amount, and excess fuel is released to the low-pressure flow path 95 side, Thereafter, by closing the valve and starting pressurization, a required amount of pressurized fluid is pressure-fed to the common rail.

However, when the oil feed rate of the pump increases with an increase in the engine speed, there arises a problem that the valve 96 closes (self-closes) regardless of the valve closing signal. This is because when the plunger 92 is raised, the valve body 96 directly receives the dynamic pressure of the fuel in the pressure chamber 93 on the lower end surface.
This is due to a force in the valve closing direction due to the throttle effect of the fuel flowing toward the low pressure flow path 95 from the gap between the valve and the seat portion 98, and the flow rate control may not be performed properly.

As a countermeasure, it is conceivable to increase the operating stroke of the valve body 96 or to increase the return spring force of the valve body 96, but in any case, the valve closing response is reduced. In order to maintain the valve-closing response, it is necessary to increase the amount of power supplied to the coil or increase the size of the coil to increase the attraction force of the solenoid valve, which increases the power cost and manufacturing cost of the solenoid valve. There was a problem.

In the variable discharge high-pressure pump having the above-described structure, the flow passage to the pressure chamber 93 is opened and closed by the solenoid valve 94, and the valve body 96 is seated in response to a valve closing signal to close the flow passage. Since a certain period of time is required until this time, usually, the operation response time is calculated in advance to control the valve closing timing.
However, when the rotation speed of the engine increases and the oil supply rate of the pump increases, the opening / closing operation cannot be performed in time, and there is a possibility that sufficient control cannot be performed.

Accordingly, the present inventors have made it possible to easily and reliably control the flow rate of pressure-feeding to the pressure accumulating pipe even when the engine speed is increased and the oil supply rate of the pump is high. For the purpose of not increasing the pressure, a valve body that opens and closes between the low-pressure flow path and the pressure chamber and a valve body that controls the flow rate of the low-pressure fuel drawn into the pressure chamber from the low-pressure flow path are separately provided. Proposed a variable discharge high pressure pump (Japanese Patent Application 8-
No. 195653).

Referring to FIG. 18, a drive shaft 101 is inserted and held in a pump housing 100, and a low-pressure fuel is supplied to a low-pressure passage 103 by a feed pump 102 which rotates integrally with the drive shaft 101. From 104, the fuel flows into the fuel pool 105.

At the right end of the drive shaft 101, an inner cam 106 is integrally formed, and the left end of the head 107 is inserted into the inner cam 106. Four sliding holes 108 are formed radially in the left end portion of the head 107 (in the figure, two sliding holes 108 are formed).
Only one plunger is shown in each sliding hole 108.
9 are supported reciprocally. These plungers 1
09 and the inner wall of the sliding hole 108 form a pressure chamber 110
Is formed, and the introduced fuel is pressurized by the reciprocating motion of the plunger 109.

In the flow path from the fuel reservoir 105 to the pressure chamber 110, an electromagnetic valve 111 for controlling the flow is provided from the upstream side.
And a check valve 112 are provided. The check valve 112 is opened by the pressure of the inflowing fuel while the solenoid valve 111 is open, and is closed when the solenoid valve 111 is closed. Thus, the required flow rate is previously adjusted by the solenoid valve 111 to the pressure chamber 110.
When the low pressure fuel is supplied to the solenoid valve 111, the flow path to the pressure chamber 110 is closed by the check valve 112 from the start of pressurization of the low-pressure fuel to the end of the pumping. ) Only works. Therefore, the solenoid valve 111
There is no need to increase the physique of the user, and the cost can be reduced.

[0013]

However, the variable discharge amount high pressure pump has a configuration in which the four plungers 109 reciprocate simultaneously to pressurize the fuel in the pressure chamber 110, and the pressure of the pressurized fuel is reduced. The driving torque required for pumping is large. FIG. 9A shows the maximum drive torque (in the case of the maximum discharge amount) when the plunger 109 is used in the variable discharge amount high pressure pump having the above configuration and four cam ridges are formed on the inner peripheral surface of the inner cam 106. (Drive torque). The pumping is performed four times per rotation of the inner cam 109, that is, the drive shaft 101, and the pumping is performed intermittently at a pumping period of about 45 ° and a suction period of about 45 °. At this time, the maximum driving torque is 50 Nm,
In this case, if a timing belt is used to rotationally drive the drive shaft 101 integrated with the inner cam 106, the durability of the timing belt may be insufficient.

As a countermeasure against this, the present inventors have further proposed:
Pressure chambers are provided for each of the four plungers,
A variable discharge high-pressure pump has been proposed in which the plunger alternately feeds two pumps at a time, thereby making it possible to lower the peak value of the driving torque (Japanese Patent Application No. 9-1502).
No. 33). According to this variable discharge amount high pressure pump, the peak value of the driving torque is greatly reduced, and the reduction in the durability of the timing belt due to this is avoided. However, when the resonance frequency of the timing belt and the generation frequency of the driving torque match, it was found that the timing belt resonated and vibrated significantly. There was a fear that it would be.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a common rail fuel injection control device capable of preventing resonance of a timing belt due to driving of a variable discharge high pressure pump and preventing deterioration of durability of the timing belt. is there.

[0016]

According to a first aspect of the present invention, a common rail type fuel injection control device includes a common rail for accumulating high pressure fuel, and an injector for injecting high pressure fuel in the common rail to each cylinder of the engine. A variable discharge high-pressure pump for discharging pressurized fuel to the common rail and setting the common rail pressure to a predetermined high pressure; and connecting the variable discharge high-pressure pump to the engine and driving at a rotational speed according to the engine speed. Timing belt. The variable discharge amount high pressure pump is configured so that the torque fluctuation is reduced when the discharge amount is the maximum. The common rail is connected to a relief flow path for discharging fuel, a common rail pressure reducing solenoid valve for opening the relief flow path and reducing the common rail pressure is provided, and a resonance frequency of the timing belt is provided. Controlling the discharge amount of the variable discharge amount high pressure pump in the engine speed range corresponding to
Further, control means is provided for controlling the common rail pressure to a predetermined pressure by adjusting the amount of fuel discharged to the relief flow passage by the common rail pressure reducing solenoid valve.

The resonance of the timing belt occurs when the driving torque is generated intermittently and the generated frequency matches the resonance frequency of the timing belt. Therefore, in order to prevent this, it is preferable to make the fluctuation of the driving torque small, and the control means minimizes the discharge amount of the variable discharge amount high pressure pump around the engine speed at which the timing belt resonates. As a large amount, fluctuations in drive torque are suppressed. At this time, the common rail pressure cannot be controlled by the discharge amount, but since the discharge amount is maximum, the common rail pressure can be controlled to a predetermined high pressure by adjusting the relief amount from the common rail pressure reducing solenoid valve. Thus, the resonance of the timing belt can be prevented, the durability can be sufficiently increased, and the controllability of the common rail pressure can be ensured.

According to a second aspect of the present invention, the variable discharge amount high pressure pump is reciprocally fitted in a cylinder, a cam for reciprocating the plunger in the cylinder, and an inner wall surface of the cylinder. And a plurality of pressure chambers formed by the end face of the plunger and pressurizing the low-pressure fuel introduced from the low-pressure flow path by the reciprocating motion of the plunger, communication between the plurality of pressure chambers and the low-pressure flow path,
Switching the cutoff, distributing means for distributing the low-pressure fuel to the plurality of pressure chambers, and adjusting the suction amount of the low-pressure fuel from the low-pressure flow path to the plurality of pressure chambers to control the amount of the pressurized fuel discharged to the common rail. A solenoid valve for controlling the amount of common rail pressure, provided between the solenoid valve for common rail pressure pressurization and the plurality of pressure chambers, and allowing low-pressure fuel to flow only from the low-pressure flow path toward the plurality of pressure chambers. It consists of a check valve.

According to the variable discharge high pressure pump having the above structure, the fuel sucked into the plurality of pressure chambers can be independently pressurized and alternately pumped, so that the peak value of the maximum discharge amount is low and the torque is low. It is possible to easily realize a pumping characteristic in which the fluctuation becomes small.

According to a third aspect of the present invention, the distribution means is a distribution rotor having a flow path communicating with the low-pressure flow path and having at least one distribution groove communicating with the flow path on an outer peripheral surface. A flow path reaching each of the plurality of pressure chambers is arranged on the outer periphery of the distribution rotor, and communication between the distribution groove and the flow path to the plurality of pressure chambers is cut off with rotation of the distribution rotor. To By using such a distribution rotor, fuel can be supplied to each pressure chamber with good controllability.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a common rail fuel injection control device according to the present invention will be described below with reference to the drawings. In the system diagram of FIG. 1, the engine E is provided with a plurality of injectors I corresponding to the combustion chambers of the respective cylinders, and these injectors I are connected to a common high-pressure accumulator pipe, a so-called common rail R, for each cylinder. Injection of fuel from the injector I to each combustion chamber of the engine E is controlled by ON / OFF of an injection amount control solenoid valve B1,
While the solenoid valve B1 is open, the fuel in the common rail R is injected into the engine E by the injector I. Therefore, it is necessary to continuously accumulate a high predetermined pressure of fuel corresponding to the fuel injection pressure in the common rail R. For this purpose, the variable discharge amount high pressure is supplied through the supply pipe R1, which is a high pressure flow path, and the discharge valve B2. The pump P is connected. The common rail R is connected to the fuel tank T by a relief flow path R2, and is configured to relieve fuel in the common rail R by a common rail pressure reducing solenoid valve B3 and return the fuel to the fuel tank T.

This variable discharge high pressure pump P presses the low pressure fuel sucked from the fuel tank T via the feed pump P1 to a high pressure, and controls the fuel in the common rail R to a high pressure. The common rail R is provided with a pressure sensor S1 for detecting a common rail pressure, and an electronic control unit ECU serving as control means for controlling the system includes:
The discharge amount of the variable discharge amount high-pressure pump P and the fuel amount relieved from the common rail R by the common rail pressure reducing solenoid valve B3 so that the signal from the pressure sensor S1 becomes an optimum value set in advance according to the load and the number of revolutions. Control. Further, the electronic control unit ECU receives information on the number of revolutions and the load from the engine rotation angle sensor S2 and the load sensor S3, and the electronic control unit ECU determines the optimum value according to the engine state determined by these signals. The injection timing and injection amount (injection period) are determined, and a control signal is output to the injection amount control solenoid valve B1.

Next, details of the variable discharge amount high pressure pump P will be described with reference to FIG. In the figure, a drive shaft D, which is rotationally driven by an engine E (see FIG. 1) in synchronization with a half rotation of the engine, is inserted and held in a pump housing 1. Vane type feed pump P1 for fuel supply
Are connected. The feed pump P1 rotates integrally with the drive shaft D, sucks fuel from the fuel tank T (see FIG. 1), and pressurizes the fuel pressurized to a low pressure in the low-pressure flow paths 11, 1.
2. It is delivered to the fuel reservoir 52 through the filter 51 and the low-pressure channel 13 in the head 14. Feed pump P
The fuel discharge side and the fuel suction side are connected via a pressure adjusting valve (not shown) so that the discharge pressure can be adjusted. As described above, in the present embodiment, the variable discharge amount high pressure pump P has a configuration in which the feed pump P1 shown in FIG. 1 is built.

The drive shaft D has a bearing D
1, and D2, it is rotatably supported by the pump housing 1, and the inner cam 8 is integrally formed in the right end part. A head 14 is fitted into the opening at the right end of the pump housing 1, and the head 14 is inserted into the inner cam 8 with a central portion at the left end protruding. In the center of the left end of the head 14, a distribution rotor 70 and a check valve 4, which will be described in detail later, are provided. At the right end of the head 14, there is provided a common rail pressure pressurizing solenoid valve 6 for controlling the amount of pressurized fuel discharged to the common rail by adjusting the amount of low pressure fuel sucked into the pressure chamber. The pressurizing solenoid valve 6 is fixed by inserting a bolt (not shown) through a flange 63 provided on the outer periphery of the housing 61. The common rail pressure pressurizing solenoid valve 6, the check valve 4, and the distribution rotor 70 constitute the discharge control device P2 in FIG. In the present embodiment, the drive shaft D and the inner cam 8 are integrated, but they may be separated and connected by a joint.

The driving of the variable discharge high pressure pump P is performed by a timing belt 53 shown in FIG. The variable discharge high pressure pump P is connected to the screw 5 of the drive shaft D.
4 (see FIG. 2), a pump timing pulley 55 is fixed.
The pump timing pulley 55 is suspended around the outer periphery.
The camshaft timing pulley 56 is provided on the engine camshaft, and the crankshaft timing pulley 57 is provided.
Are fixed to the crankshaft of the engine, respectively, and the crankshaft timing pulley 57 transmits the rotational force of the crankshaft of the engine to the pump timing pulley 55 and the camshaft timing pulley 56 via the timing belt 53, These pulleys 55 and 56 are rotationally driven. Figure 58
And 59 are idlers, of which idler 5
Numeral 9 applies a tension to the timing belt 53 by the spring force of the spring 60 so that the timing belt 53 does not bend.

As shown in FIG. 4, the common rail pressure pressurizing solenoid valve 6 has a housing 61 containing a coil 62 and a valve body 68 fitted and fixed in the left end thereof.
A valve body 73 is provided in a cylinder 69 provided in the valve body 68.
Is slidably held. An annular flow path 74a is formed around the left end of the valve body 73, and the flow path 74a
b, it communicates with the fuel pool 52 and the flow path 7
At 4c, it communicates with the flow path 72 leading to the distribution rotor 70.

An armature 64 is press-fitted and fixed to the right end of the valve body 73. The armature 64 faces the stator 65 at a fixed interval. The coil 62 is disposed outside the stator 65, and a spring 67 is disposed in a spring chamber 66 provided inside the stator 65, and urges the armature 64 to the left in the drawing.

A substantially conical seat surface 75 is formed at the open end of the flow passage 74c. In the state shown in the drawing where the coil 62 is not energized, the tip of the valve body 73 is seated on the seat surface 75. The space between the flow paths 74a and 74c is closed. When the coil 62 is energized, the armature 64 is attracted, the distal end of the valve body 73 integrated therewith separates from the seat surface 75, and opens between the flow paths 74a and 74c. As described above, the common rail pressure pressurizing electromagnetic valve 6 is configured to be closed in a non-energized state, so that there is an effect that the fuel is not pumped when the coil 62 is damaged.

A filter 51 is provided upstream of the common rail pressure pressurizing solenoid valve 6 as shown in FIG.
Should a foreign matter bite between the seat surface 75 and the valve body 73, the flow paths 74a and 74c are always opened. That is, since the pumping is always performed, in the present embodiment, for example, the lift amount of the valve body 73 is set to 0.
The opening of the filter 51 is set to 2 mm, and the opening of the filter 51 is set to 0.15 mm, which is smaller than the opening to prevent foreign matter from being caught.

In FIG. 4, a sliding hole 2 serving as a cylinder forming a pressure chamber therein is formed in the center of the left end of the head 14.
Are formed. As shown in FIG. 5, in the present embodiment, four plungers 21a to 21d are respectively reciprocally movable and slidable in the four sliding holes 2 arranged at equal intervals. It is supported by. Spaces formed between the inner wall of each sliding hole 2 and the inner end faces of the plungers 21a to 21d are pressure chambers 23a to 23d, respectively. In addition, shoes 24a to 24d are provided at outer ends of the plungers 21a to 21d, respectively.
Cam rollers 22a to 22d are rotatably held at 24d.

The inner cam 8 is formed by the cam roller 2.
It is arranged to be in sliding contact with the outer periphery of 2a to 22d,
The inner peripheral surface is a cam surface 81 having a plurality of cam ridges. Here, two cam ridges are formed at equal intervals (positions facing the plungers 21b and 21d in the figure). Thus, when the inner cam 8 integrated with the drive shaft D rotates, the plungers 21a to 21d reciprocate in the cylinder 2, and the plungers 21a and 21c and the plungers 21b and 22d alternately rise and the pressure chamber 23a ~ 2
Pressurize the fuel in 3d. Thus, in the present embodiment, four plungers are arranged at equal intervals, and two cam ridges are formed at equal intervals on the inner peripheral surface of the inner cam 8. Thus, by reducing the number of cam lobes with respect to the number of plungers, the maximum torque can be more effectively reduced.

In FIG. 4, the pressure chambers 23a to 23d
A distribution rotor 70 serving as a distribution means is rotatably held in a cylinder 40 formed on the left side of the cylinder, and a plurality of check valves 4 are arranged on the outer periphery of the distribution rotor 70. In this embodiment, four check valves are provided, and the pressure chamber 23
It is provided in the middle of the flow path from a to 23d. A shoe guide 30 is provided on the left side of the head 14 and is fixed to the head 14 by bolts (not shown). The distribution rotor 70 is connected to a drive shaft D by a pin 80 (see FIG. 2), and is adapted to rotate with the drive shaft D. A washer 76 is inserted between the distribution rotor 70 and the shoe guide 30 so that the rotation between the distribution rotor 70 and the washer 76 and between the washer 76 and the shoe guide 30 can be performed.

The distribution rotor 70 has one end communicating with a flow path 78 extending in the vertical direction in the figure and an intermediate portion of the flow path 78.
The other end has a flow path 71 communicating with the flow path 72. As shown in FIG. 6, two distribution grooves 77 are formed at the upper and lower ends of the flow path 78, and the feed port 82a reaching the flow path 41 in the check valve 4 by the rotation of the distribution rotor 70 is formed.
To 82d. The communication between the feed ports 82a to 82d and the distribution groove 77 and the cutoff state will be described later.

When the fuel in the pressure chambers 23a to 23d is pressurized, the pressure chambers 23a to 23d of the head 14 are deformed by the pressure, but as shown in FIG.
0 is disposed sufficiently away from the axis of the plungers 21a to 21d, so that rotation of the distribution rotor 70 and the head 14 is not hindered.

Each check valve 4 has a body 42 having a flow path 41 formed therein, and the body 42 is press-fitted and fixed in the head 14. The flow path 41 is provided in the middle of the pressure chambers 23a-
The conical seat surface 4 is enlarged in the direction of 23d (right side in the figure).
5 and a ball 44 as a valve element is seated on the flow path 41.
Is to be closed. A spring 47 for biasing the ball 44 in the valve closing direction is disposed on the right side of the ball 44, and a shim 43 is disposed on the right side of the ball 44 so as to be sandwiched between the head 14 and the body 42. Pressure chambers 23a to 23d
During the suction step in which the fuel is sucked, the ball 44 of the check valve 4 opens against the spring force of the spring 47,
Fuel is supplied from the flow passage 46 to the pressure chambers 23a to 23d. During the pressure feeding process of the plungers 21a to 21d, the ball 44 is seated on the seat surface 45 by the spring force of the spring 47, and the check valve 4 is closed.

Here, the check valve 4 may be provided in the middle of the flow path from the common rail pressure pressurizing solenoid valve 6 to each of the pressure chambers 23a to 23d, as in the present embodiment. Check valve 4 is connected to distribution rotor 70 and pressure chambers 23a to 23a.
It is desirable to provide between d. At this time, there is an advantage that the dead volume of the high pressure part can be reduced. Further, since the high pressure does not act on the distribution rotor 70, the distribution rotor 70
Leakage from the sliding portion between the head and the head 14 can be reduced.

In the fuel reservoir 52 formed inside the head 14, about 1 mm is supplied by the feed pump P1.
Low pressure fuel pressurized to 5 atm is filled. The low-pressure fuel passes from the fuel reservoir 52 through the solenoid valve 6, the flow path 72 in the head 14, the flow path 71 in the distribution rotor 70, and the check valve 4 to the pressure chambers 23a to 23d from the flow path 15. Inflow. The fuel pressurized in the pressure chambers 23a to 23d (FIG. 2) is supplied to the delivery valve 3 (corresponding to the discharge valve B2 in FIG.
1 to the common rail R (see FIG. 1).
The supply pressure varies depending on the operation state of the engine E, and is 200 to 1200 atm. The delivery valve 3 has a function as a check valve, has a valve body 31 and a return spring 32 for urging the valve body 31 in a valve closing direction, and opens when the pressurized fuel exceeds a predetermined pressure. .

Although only one delivery valve 3 is shown in FIG. 2, another delivery valve is installed at a position not shown. That is, as shown in FIG. 7, in the present embodiment, four plungers 21a
21d, the head 14 and the plunger 2
Of the four pressure chambers 23a to 23d surrounded by 1a to 21d, two opposing pressure chambers 23a and 23c and pressure chambers 23b and 23d pressurize alternately. Therefore, the pressure chambers 23a and 23c are connected to the delivery valve 3a by the discharge holes 16a and 16c, and the pressure chambers 23b and 23d are connected to the discharge holes 16a.
b and 16d communicate with the delivery valve 3b. The fuel pressurized in each of the pressure chambers 23a to 23d is supplied from these delivery valves 3a and 3b to the common rail R through the common pipe R1 in FIG. The number of the delivery valves 3 is four, and the pressure chambers 23a to 23a
It may be configured to communicate with each of the 3d.

Next, the operation of the variable discharge high pressure pump P having the above-mentioned structure will be described with reference to FIG. In FIG.
The lift (a, c) of the cam 8 corresponds to a point 81a on the cam surface 81 facing the plungers 21a, 21c in FIG.
The lift amount at 81c is shown. That is, as the inner cam 8 rotates, the lift amount at the points 81a and 81c changes. The lift (b, d) of the cam 8 is
The lift amounts at points 81b and 81d on the cam surface 81 that face the plungers 21b and 21d are shown.

At the point shown in FIG.
(A, c) enters the suction process, and feed ports 82a,
The distribution groove 82c communicates with the distribution groove 77 (the state shown in FIG. 6). The energization of the coil 62 of the common rail pressure pressurizing solenoid valve 6 is performed prior to this, and the valve body 73 of the solenoid valve 6 is open at the time of FIG. Therefore, from the fuel reservoir 52, the fuel passes through the flow passages 74c, 72, 79, 78, the distribution groove 77, the feed ports 82a, 82c, the flow passage 41 in the check valve 4, and the flow passage 15, and the fuel flows into the pressure chamber 23a, 2
3c. At this time, the plungers 21a and 21c are pressed against the cam surface 81 by the inflowing fuel, and the fuel is sucked until the valve body 73 of the common rail pressure pressurizing electromagnetic valve 6 closes.

When the power supply from the electronic control unit ECU to the coil 62 of the common rail pressure pressurizing solenoid valve 6 is cut off, the valve body 73 of the solenoid valve 6 closes (point (b) in FIG. 8) and the fuel pool 52 And the flow path 74c, that is, the pressure chamber 23
a and 23c are cut off. Further, the check valve 4 is also closed by the urging force of the spring 47. After that, the lift (a, c) of the inner cam 8 continues to descend, but when the suction is completed, the lift of the plungers 21a, 21c stops, and the cam rollers 22a, 22c and the inner cam 8 separate. Thereafter, the communication between the feed ports 82a and 82c and the distribution groove 77 is interrupted by the rotation of the distribution rotor 70 (point (c) in FIG. 8). As described above, while the valve body 73 is open, the fuel is sucked, and this amount is the amount of pumping (the amount of discharge). Therefore, by adjusting the valve opening angle of the valve body 73, the discharge amount of the variable discharge amount high-pressure pump P can be controlled.

When the coil 62 of the solenoid valve 6 for pressurizing the common rail pressure is supplied again from the electronic control unit ECU, the valve body 73 of the solenoid valve 6 is opened (FIG. 8D).
At this time, all the feed ports 82a to 82d and the distribution groove 77 are shut off, and all the pressure chambers 23 are closed.
No fuel is sucked in a to 23d. In the present embodiment, all of the feed ports 82a to 82d
The period in which the gap between the valve and the distribution groove 77 is cut off is set to about 30 °, and the valve 73 of the solenoid valve 6 is controlled to open during this time. Next, at a point (e) in FIG. 8, the feed ports 82b and 82d communicate with the distribution groove 77, and the inner cam 8 (b, d) enters the suction stroke. Hereinafter, in the same manner as in the case of the plungers 21a and 21c, the pressure chamber 23
Fuel is sucked into b and 23d.

The lift (a, c) of the inner cam 8 starts from the point (c) in FIG. 8. Even when the lift of the inner cam 8 starts, the plungers 21 a and 21 c start the lift immediately. Point 8 on the cam surface 81 of the inner cam 8
When the lift amounts of the plungers 21a and 21c become the lift amounts of the plungers 21a and 21c (point (f) in FIG. 8), the cam roller 22
a, 22c abut against the inner cam 8 and the cam rollers 22
a and 22c lift the plungers 21a and 21c via the shoes 24a and 24c. In this pressure feeding step, since the check valves 4 are closed, high pressure does not act on the distribution rotor 70. Thereafter, as the plungers 21a, 21c rise, the pressure chambers 23a,
The volume in the pressure chamber 23c decreases, and the pressure in the pressure chambers 23a and 23c gradually increases. When the pressure of the fuel in the pressure chambers 23a and 23c exceeds a predetermined pressure, high-pressure fuel is supplied from the supply pipe R1 to the common rail R through the discharge hole 16 and the delivery valve 3 (FIG. 2). When the lift of the plungers 21a and 21c becomes maximum (point (g) in FIG. 8), the pressure feeding ends. The lift (b, d) of the inner cam 8 is performed in the same manner.

As shown in FIG. 8, in the above structure, the plungers 21a and 21c
The pressure feed by b and 21d is performed by shifting the rotation angle of the inner cam 8 by 90 °. FIG. 9B shows the driving torque at the time of the maximum discharge amount.
The sum of the driving torque by 21c and the driving torque by plungers 21b and 21d, that is, the sum of the solid line and the broken line in FIG. 9B. As described above, in the above configuration, the fluctuation of the driving torque is very small at the time of the maximum discharge amount, and the peak value of the driving torque is significantly reduced as compared with the conventional configuration of FIG. Recognize.

FIG. 10 shows the drive torque when the discharge amount is about 70% of the maximum discharge amount. In this case, the sum of the solid line and the broken line shown in FIG. 10 is the drive torque. As shown in FIG. 10, when the discharge amount is not the maximum discharge amount (full amount pumping), the driving torque is generated intermittently. Engine speed N = 20
At 00 rpm, the rotational speed of the variable discharge high pressure pump P is 1
000 rpm, and the driving torque is generated at about 66.7 Hz. When the frequency of the driving torque generated substantially coincides with the resonance frequency of the timing belt 53 (see FIG. 3), the amplitude of the vibration of the timing belt 53 increases,
If the operation is performed for a long time near the resonance point, the durability of the timing belt 53 may be reduced.

Therefore, according to the present invention, when the frequency of the driving torque generated is near the resonance frequency of the timing belt 53, the maximum discharge amount with small fluctuation of the driving torque is set, and the control of the common rail pressure is performed by reducing the common rail pressure. Solenoid valve B
This is solved by adjusting the amount of fuel discharged from 3 to the relief channel R2. Hereinafter, a control method by the electronic control unit ECU will be described with reference to FIGS.
16 will be described.

A signal rotor 17 shown in FIG. 11 is mounted on the engine E coaxially with the drive shaft D. An engine rotation angle sensor S2 shown in FIG. Are arranged. The outer peripheral surface of the signal rotor 17 has 56 projections 18 except for four missing tooth portions that divide the outer peripheral surface into four equal parts.
Are formed, and the engine rotation angle sensor S2 generates a detection signal every time these projections 18 cross, and outputs the detection signal to the electronic control unit ECU (FIG. 13). At this time, a detection signal as shown in FIG. 12A is output from the rotation angle sensor S2, and is subjected to waveform shaping by the waveform shaping circuit 37 of the electronic control unit ECU, thereby obtaining a signal as shown in FIG. Then, a reference signal A and a rotation angle signal B synchronized with the fuel injection cycle are obtained.

On the other hand, the electronic control unit ECU (FIG. 1)
3) a cooling water temperature sensor 33, an intake air temperature sensor 34, an intake pressure sensor 35, a load sensor S3, and an A / D converter 36 for converting an analog signal output from the pressure sensor S1 into a digital signal. This A / D converter 36
Alternatively, based on the detection signal of each sensor input via the waveform shaping circuit 37, the injection amount control solenoid valves B1,
The control of the common rail pressure increasing solenoid valve 6 and the common rail pressure decreasing solenoid valve B3 is executed. Electronic control unit ECU
A ROM 26 in which a control program and various data necessary for executing the control processing by the CPU 38 are stored in advance; a RAM 27 for temporarily reading and writing data necessary for executing the control processing by the CPU 38;
And drive circuits 48, 49 and 50 for outputting drive signals to the injection amount control solenoid valve B1, the common rail pressure increasing solenoid valve 6, and the common rail pressure decreasing solenoid valve B3, respectively.

Next, the control routine of this embodiment is shown in FIG.
This will be described using 4 to 16. FIG. 14 shows NE pulse signal interruption processing executed each time a NE pulse signal is output from the engine rotation angle sensor S2. When the processing is started, first, in step 201, the previous interruption processing is executed. The time from the execution to the current execution, that is, the pulse interval Tp of the rotation angle signal is calculated. Next, in step 202, step 201
Is compared with the value obtained by multiplying the pulse interval Tp (n-1) obtained in the previous processing by a constant K to obtain the rotation angle signal inputted this time. Is a reference signal. This is because when the reference signal is input, the pulse interval Tp between them is 2.
For example, the value of the constant K is set to 2.28, and if the pulse interval Tp (n) is K times or more of the previous pulse interval Tp (n-1), the value of the current K becomes 2.times. It can be detected that the rotation angle signal is a reference signal. If it is determined in step 202 that the rotation angle signal is not the reference signal, the process proceeds to step 203.

In step 203, the value of the NE pulse number C is increased by one, and the routine goes to the next step 204.
The process of step 204 is a process for detecting the timing of turning on the drive signal of the common rail pressure increasing solenoid valve 6 or the drive signal of the common rail pressure decreasing solenoid valve B3. If C = 1 is not satisfied, It is determined that it is not the timing, and the processing of this routine is terminated as it is.
On the other hand, if it is determined in step 204 that C = 1, the process proceeds to step 205, where the engine speed N becomes 1
It is determined whether or not 800 rpm <N <2200 rpm, that is, whether or not the timing belt 53 (see FIG. 3) is near the engine speed at which resonance occurs. When it is determined in step 205 that 1800 rpm <N <2200 rpm, that is, when the timing belt 53
When it is determined that is near the revolving engine speed, the routine proceeds to step 206.

In step 206, if the drive signal of the common rail pressure pressurizing solenoid valve 6 is OFF, it is turned ON. In step 207, a drive signal processing routine for the common rail pressure reducing solenoid valve B3, which will be described later, is executed, and the processing of this routine ends. On the other hand, at step 205
When it is determined that 00 rpm <N <2200 rpm is not satisfied, the routine proceeds to step 208, where a drive signal processing routine for the common rail pressure pressurizing electromagnetic valve 6 described later is executed, and the processing of this routine is ended. If it is determined in step 202 that the rotation angle signal is the reference signal, the value of the NE pulse number C is cleared in step 209 (the value of C is set to 0). Based on the detection signal from the rotation angle sensor S2, the engine speed N
Is calculated, and the processing of this routine ends.

FIG. 15 shows a solenoid valve 6 for pressurizing the common rail.
When this process is started, step 301 is first executed to turn on the drive signal of the common rail pressure pressurizing solenoid valve 6 (see FIG. 8D). Next, at step 302, the cooling water temperature sensor 3
3. Various detection signals indicating the operating state of the engine E output from the intake air temperature sensor 34, the intake pressure sensor 35, and the load sensor S3 are read, and the routine proceeds to step 303.

In step 303, the target common rail pressure is calculated based on the engine speed N and various detection signals which are read in step 302 and indicate the operating state of the engine E. That is, the basic target fuel injection timing is calculated using the engine speed N and the depression amount of the accelerator pedal detected by the load sensor S3 as parameters, and then the obtained values are used as the cooling water temperature THV and the intake air temperature Ta. The target common rail pressure is determined by correcting the target common rail pressure with the intake pressure Pa and the like.

In the next step 304, the pressure sensor S1
Then, the output detection signal is read to calculate the actual common rail pressure. In step 305, the target common rail pressure calculated in step 303 is compared with the actual common rail pressure calculated in step 304, and an error in the common rail pressure is calculated. In step 306, the ON time of the common rail pressure pressurizing solenoid valve 6 is calculated based on the common rail pressure error, the time at which the drive signal is turned off is set, and the processing of this routine is terminated. Here, the ON time is set longer as the actual common rail pressure is lower than the target common rail pressure.

FIG. 16 shows a solenoid valve B for reducing common rail pressure.
3 is a drive signal processing routine. When this processing is started, first, step 401 is executed, and the drive signal of the common rail pressure reducing solenoid valve B3 is turned ON. Next, at step 402, the cooling water temperature sensor 33 and the intake air temperature sensor 3
4. Read various detection signals indicating the operating state of the engine E, which are output from the intake pressure sensor 35 and the load sensor S3, and proceed to step 403.

In step 403, a target common rail pressure is calculated based on the engine speed N and various detection signals indicating the operating state of the engine E read in step 402. That is, the basic target fuel injection timing is calculated using the engine speed N and the depression amount of the accelerator pedal detected by the load sensor S3 as parameters, and then the obtained values are used as the cooling water temperature THV and the intake air temperature Ta. The target common rail pressure is determined by correcting the target common rail pressure with the intake pressure Pa and the like.

In the next step 404, the pressure sensor S1
Then, the output detection signal is read to calculate the actual common rail pressure. In step 405, the target common rail pressure calculated in step 403 is compared with the actual common rail pressure calculated in step 404, and an error in the common rail pressure is calculated. In step 406, the ON time of the common rail pressure reducing solenoid valve B3 is calculated based on the common rail pressure error, the time at which the drive signal is turned off is set, and the processing of this routine ends. Here, the ON time is set longer as the actual common rail pressure is higher than the target common rail pressure.

As described above, near the engine speed at which the timing belt 53 resonates, the solenoid valve 6 for pressurizing the common rail is always turned on, and the pressure of the common rail R is reduced by the solenoid valve B3 for reducing the common rail pressure.
The control is performed by discharging the fuel in the inside to the relief channel R2. At this time, the variable discharge amount high pressure pump P has the maximum discharge amount, and the drive torque is the sum of the solid line and the broken line shown in FIG. 9B. At this maximum discharge amount, as shown in the figure, since the fluctuation of the driving torque is very small, the vibration by the timing belt is reduced, and the timing belt 53
The problem of durability is solved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a fuel injection control device according to a first embodiment of the present invention.

FIG. 2 is an overall sectional view of the variable discharge high-pressure pump according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a connection structure between a variable discharge high pressure pump and an engine.

FIG. 4 is a partially enlarged sectional view of FIG. 2;

FIG. 5 is a sectional view taken along line AA of FIG. 2;

FIG. 6 is a sectional view taken along line BB of FIG. 4;

FIG. 7 is a schematic configuration diagram of a main part of the variable discharge high-pressure pump according to the first embodiment.

FIG. 8 is a diagram for explaining the operation of the variable discharge high pressure pump according to the first embodiment.

9A is a diagram showing the pumping characteristic (maximum discharge amount) of the conventional variable discharge amount high pressure pump, and FIG. 9B is a diagram showing the pumping characteristic (maximum discharge amount) of the variable discharge amount high pressure pump of the present invention. It is.

FIG. 10 is a view showing a pumping characteristic (a discharge amount of 70%) of the variable discharge amount high pressure pump of the present invention.

FIG. 11 is a diagram showing a positional relationship between an engine and a rotation angle sensor.

FIG. 12A is a diagram showing an output signal of a rotation angle sensor;
(B) is a diagram showing a signal obtained by shaping the waveform of (A).

FIG. 13 is a diagram showing a configuration of an electronic control unit.

FIG. 14 is a diagram showing a control routine of the electronic control unit.

FIG. 15 is a diagram showing a drive signal processing routine of a common rail pressure pressurizing solenoid valve.

FIG. 16 is a diagram showing a drive signal processing routine of a common rail pressure reducing solenoid valve.

FIG. 17 is an overall sectional view of a conventional variable discharge high pressure pump.

FIG. 18 is an overall sectional view of a conventional variable discharge high pressure pump.

[Explanation of symbols]

 E Engine D Drive shaft I Injector P Variable discharge high pressure pump R Common rail R1 Supply pipe R2 Relief flow path B3 Common rail pressure reducing solenoid valve T Fuel tank ECU Electronic control unit (control means) 1 Pump housing 11, 12, 13 Low pressure flow Path 14 Head 15 Flow path 16 Discharge hole 17 Signal rotor 2 Sliding hole (cylinder) 21a to 21d Plunger 22a to 22d Cam roller 23a to 23d Pressure chamber 3 Delivery valve 4 Check valve 41 Flow path 44 Ball 45 Seat surface 47 Spring 52 Fuel pool 53 Timing belt 6 Common rail pressure pressurizing solenoid valve 62 Coil 70 Distribution rotor (distribution means) 71, 72 Flow path 73 Valve element 74a-74c Flow path 75 Seat surface 76 Washer 77 Distribution groove 78 Flow path 8 Inner Cam 81 cam surface 82a~82d feed port

──────────────────────────────────────────────────続 き Continuing on the front page (51) Int.Cl. ⁶ Identification code FI F02M 63/02 F02M 63/02 A (72) Inventor Yasuhiro Horiuchi 1-1-1, Showa-cho, Kariya-shi, Aichi Pref.

Claims (3)

[Claims] 1. A common rail for accumulating high-pressure fuel, an injector for injecting high-pressure fuel in the common rail to each cylinder of an engine, and discharging pressurized fuel to the common rail to make the common rail pressure a predetermined high pressure. Common-rail type fuel injection control device having a variable discharge high pressure pump, and a timing belt connecting the engine to the variable discharge high pressure pump and driving the variable discharge high pressure pump at a rotational speed corresponding to the rotational speed of the engine. In the above, the variable discharge amount high pressure pump is configured so that the torque fluctuation is reduced when the discharge amount is the maximum, and a relief flow path for discharging fuel in the common rail, and the common flow path is opened by opening the relief flow path. Solenoid valve for reducing common rail pressure for reducing pressure, and engine rotation corresponding to the resonance frequency of the timing belt In several ranges, the discharge rate of the variable discharge high pressure pump is maximized, and the common rail pressure is reduced to a predetermined pressure by adjusting the amount of fuel discharged to the relief passage by the common rail pressure reducing solenoid valve. A common rail type fuel injection control device, comprising: 2. A plunger in which the variable discharge high-pressure pump is reciprocally fitted in a cylinder, a cam for reciprocating the plunger in the cylinder, an inner wall surface of the cylinder and an end face of the plunger. And formed with
A plurality of pressure chambers for pressurizing the low-pressure fuel introduced from the low-pressure flow path by the reciprocating motion of the plunger, communication between the plurality of pressure chambers and the low-pressure flow path, switching between the low-pressure fuel and the low-pressure fuel, the low-pressure fuel Distributing means for distributing to the pressure chambers, and a common rail pressure pressurizing solenoid valve for controlling the amount of pressurized fuel discharged to the common rail by adjusting the suction amount of the low pressure fuel from the low pressure passage into the plurality of pressure chambers. And a check valve provided between the solenoid valve for pressurizing the common rail and the plurality of pressure chambers, and for allowing low-pressure fuel to flow only from the low-pressure passage toward the plurality of pressure chambers. A common rail fuel injection control device as described in the above. 3. The distribution rotor, wherein the distribution means has a flow path communicating with the low-pressure flow path, and at least one distribution groove communicating with the flow path is provided on an outer peripheral surface. A flow path reaching each of the plurality of pressure chambers is arranged, and the distribution groove and the flow path to the plurality of pressure chambers are communicated and shut off with rotation of the distribution rotor. Item 3. The common rail fuel injection control device according to Item 2.