JP2000282938A - Control method of variable discharge high pressure pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To propose a control method of a variable discharge amount high pressure pump for supplying high pressure fuel to a pressure accumulator with good controllability of a pressure of a pressure accumulator. SOLUTION: A control valve 6a and a check valve 4a are provided from an upstream side in a flow path from a low-pressure pump P1 to a pressure chamber 23a for sucking and feeding low-pressure fuel by expanding and contracting a volume,
When the volume of the pressure chamber 23a is expanded, air is closed by the control valve 6a while the variable discharge high-pressure pump sucks fuel into the pressure chamber 23a until the control valve 6a closes and the check valve 4a closes. Later, the fuel pressure decreases from the feed pressure and expands, and the fuel is released from the pressure chamber 23.
In order to avoid excessive pressure in the pressure chamber 23a and prevent over-pressure feed, the control valve 6a is prohibited from opening if the pressure of the accumulator is higher than the target pressure by an allowable value or more, and the check valve 4a is upstream. So that air mixed with fuel from the low-pressure pump P1 is not introduced into the section.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for controlling a variable discharge high pressure pump.

[0002]

2. Description of the Related Art A common rail injection system is known as one of the systems for injecting fuel into a diesel engine. In the common rail injection system, a common pressure accumulating chamber (common rail) communicating with each cylinder is provided, and a variable discharge high pressure pump is used to supply high pressure fuel at a required flow rate by pressure to supply the fuel pressure of the pressure accumulating chamber to a predetermined pressure. Hold at pressure. The high-pressure fuel in the accumulator is injected into the combustion chamber of each cylinder by an injector at a predetermined timing.

The variable discharge high pressure pump has a pressure chamber which is connected to a common rail and expands and contracts in volume. The fuel sucked into the pressure chamber by opening and closing a control valve provided between the low pressure pump for delivering low pressure fuel and the pressure chamber. Conventionally, when the volume of the pressure chamber is reduced, the control valve is closed at a predetermined timing to set the amount of fuel in the pressure chamber to obtain a desired amount of pressure feed to the common rail. A stroke type is generally used. However, in the case of the pre-stroke type, the high pressure of the pumping fuel is applied to the control valve, so the control valve is required to operate with high accuracy even at a high pressure. However, there is a problem of an increase in cost. In order to solve this problem, a variable discharge amount high pressure pump shown in FIG. 19 has been proposed.

In this variable discharge high pressure pump, a drive shaft 101 is inserted and held in a pump housing 100, and a low pressure pump (feed pump) 102 which rotates integrally with the drive shaft 101 allows a low pressure fuel to flow through the low pressure flow. From the roads 103 and 104, the fuel pool 10
Flow into 5.

[0005] An inner cam 106 is integrally formed at the right end of the drive shaft 101, and the left end of the head 107 is inserted into the inner cam 106. Four cylinders 108 are radially formed in the left end of the head 107 (only two of them are shown in the figure), and a plunger 109 is supported in each cylinder 108 so as to be able to reciprocate. A pressure chamber 110 is formed by the inner end surface of the plunger 109 and the inner wall of the cylinder 108, and the introduced fuel is supplied to the plunger 109.
Pressurized by reciprocating motion.

[0006] A control valve 111 and a suction valve 112 are disposed in the flow path from the fuel reservoir 105 to the pressure chamber 110 from the upstream side. The control valve 111 is an electromagnetic valve that is energized and controlled by an electronic control unit (not shown), and the suction valve 112 is a check valve whose forward direction is from the control valve 111 toward the pressure chamber 110.

The suction valve 112 is opened when the control valve 111 is opened and the volume of the pressure chamber 110 is increased due to the retreat of the plunger 109 and the pressure in the pressure chamber is reduced. When the control valve 111 is closed, the suction valve 112 is closed. I do. Thus, the control valve 1
After supplying a required flow rate from the feed pump 102 into the pressure chamber 110 in advance in accordance with the valve opening period of 11, the suction valve 112 controls the flow path to the pressure chamber 110 from the start of pressurization of the low-pressure fuel to the end of pumping. Since it is closed, only the feed pressure (about 15 atm) acts on the control valve 111 even at the maximum pressure. Therefore, it is not necessary to use a control valve that operates with high accuracy even under high pressure, and sufficient common rail pressure control can be obtained at low cost. The control method of the variable discharge amount high pressure pump is, for example, the control valve 11 according to the fuel injection amount which is the amount of the high pressure fuel flowing out from the common rail.
In some cases, a command value for the first valve-opening period is determined, and the control valve 111 is opened and closed according to the command value to replenish the common rail with high-pressure fuel.

[0008]

However, in the variable discharge high-pressure pump having the above-described structure, overpressure feeding may occur during restarting after gas shortage, before gas shortage, or during a sharp turn. There was a possibility that high controllability of the common rail pressure could not be obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a control method of a variable discharge amount high pressure pump which prevents over-pressure feeding and improves pressure controllability of a pressure accumulation chamber.

[0010]

According to the first aspect of the present invention, the control valve for controlling the passing fuel amount according to a command value for controlling the passing fuel amount between the low pressure pump and the check valve is controlled. Then, in the control method for replenishing the accumulator with high-pressure fuel in accordance with the amount of the high-pressure fuel flowing out of the pressure chamber, the pressure of the accumulator is detected, and the detected pressure is set to be higher than the target pressure of the accumulator. It is determined whether a control condition including a value higher than an allowable value is satisfied, and when it is determined that the control condition is satisfied, opening of the control valve is prohibited and suction of low-pressure fuel into the pressure chamber is performed. Pause.

[0011] If air is mixed into the fuel delivered by the low pressure pump due to lack of gas or the like and feed pressure air is present in the flow path from the control valve to the check valve, the air is discharged to the check valve. With the opening of the valve and the expansion of the volume of the pressure chamber, the pressure expands by decreasing from the feed pressure, and the fuel corresponding to the expansion is pushed into the pressure chamber. This results in overpressure. According to the present invention, when the control condition is satisfied and there is a high probability that air is mixed in the fuel delivered by the low-pressure pump, the opening of the control valve is prohibited. Air is not delivered from the low pressure pump to the flow path portion. Therefore, it is possible to prevent the fuel from being sent to the pressure accumulating chamber under excessive pressure.

In the invention according to claim 2, the control valve changes its valve opening period in accordance with the command value.
The control condition includes that the detected pressure is higher than the target pressure of the accumulator by a predetermined allowable value or more, including that the valve opening period command value of the control valve is shorter than a predetermined lower limit value, and the valve opening period When the command value is shorter than a predetermined lower limit value, opening of the control valve is prohibited.

The shorter the valve opening period command value, the smaller the required amount of fuel to be pumped in the accumulator. The shorter the valve opening period command value, the greater the effect of overpressure feeding. Only when the effect of inhibiting the opening of the control valve is particularly large, the overpressure feeding prevention effect can be made to work.

According to the third aspect of the present invention, in calculating the valve opening period command value, integral compensation is executed in accordance with the integrated amount of the deviation between the detected pressure of the accumulator and the target pressure. When the opening of the control valve is prohibited, the update of the integral compensation value is prohibited.

When the opening of the control valve is prohibited, it is highly probable that the valve is in an over-pressure feeding state due to the mixed air. Therefore, the valve opening period command value is determined based on the deviation between the detected pressure and the target pressure in such a case. By not updating the integral compensation amount,
An inappropriate valve opening period command value can be prevented.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) An example in which a control method of a variable discharge high pressure pump according to the present invention is applied to a common rail fuel injection system of a diesel engine will be described below. In the system diagram of FIG. 2, the engine E is provided with a plurality of injectors I corresponding to the combustion chambers of each cylinder, and these injectors I are connected to a common rail R which is a common pressure accumulating chamber for each cylinder. Injection of fuel from the injector I into each combustion chamber of the engine E is controlled by ON / OFF of the injection control solenoid valve B1, and the solenoid valve B1
While the valve is open, the fuel in the common rail R is injected into the engine E by the injector I. In the following description, the engine E will be described as having four cylinders.

The common rail R is connected via a supply pipe R1 and a discharge valve B2 to a variable discharge amount high pressure pump P for continuously accumulating the common rail R with fuel having a high predetermined pressure corresponding to the fuel injection pressure. Variable discharge high pressure pump P
Pressurizes 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 predetermined high pressure.

The common rail injection system has an electronic control unit C. Electronic control unit C is CP
U and the like, and outputs a control signal to each of the injector I and the variable discharge high-pressure pump P based on the input of various sensors S1, S2, S3 and the like input thereto. The variable discharge amount high pressure pump P is controlled. The electronic control unit C receives information on the engine state from, for example, an engine speed sensor S2 and a cylinder discrimination sensor (G1 sensor) S3. The common rail R is provided with a pressure sensor S1 for detecting a common rail pressure, from which information of a common rail pressure value is input to the electronic control unit C. The electronic control unit C determines the optimal injection timing and injection amount (injection period) based on the information, outputs a control signal to the injection control solenoid valve B1, and determines the discharge amount of the variable discharge amount high pressure pump P. Control.

Next, the details of the variable discharge amount high pressure pump P will be described with reference to FIG. In the figure, a drive shaft D that is rotationally driven by an engine E (see FIG. 2) in synchronization with a half rotation of the engine is inserted and held in a pump housing 1. A pump timing pulley 51 is fixed to the left end of the drive shaft D, and is driven to rotate by a timing belt 52 suspended around the outer periphery thereof, as shown in FIG. In the figure, a camshaft timing pulley 53 is fixed to the engine camshaft, and a crankshaft timing pulley 54 is fixed to the engine crankshaft. Pulley 51 and camshaft timing pulley 5
3 is rotationally driven. 55 and 56 in the figure are idlers. Among them, the idler 56 gives tension to the timing belt 52 by the spring force of the spring 57,
It has a function to prevent deflection.

In FIG. 1, a vane-type feed pump P1 for supplying low-pressure fuel is connected to the drive shaft D. Feed pump P1 has drive shaft D
And the fuel is sucked from the fuel tank T (see FIG. 2), and the fuel is passed through the low pressure passages 11 and 12 and the low pressure passage 13 in the head 14 at a predetermined feed pressure (about 15 atm). The fuel is supplied to a fuel pool 5 formed inside the fuel cell 14. The fuel discharge side and the fuel suction side of the feed pump P1 are connected via a pressure adjusting valve (not shown) so that the discharge pressure can be adjusted. As described above, the variable discharge amount high pressure pump P is configured to incorporate the feed pump P1 shown in FIG.

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.

At the lower end of the head 14, there is provided a control valve 6a for controlling the amount of low-pressure fuel flowing into the pressure chamber, that is, for controlling the amount of fuel passing between the feed pump P1 and a later-described suction valve 4a. A suction valve 4a, which is a check valve, is provided in the center of the right end of the head 14. The delivery valve 3 is provided above the suction valve 4a. In addition to the control valve 6a and the suction valve 4a, a control valve 6b and a suction valve 4b are provided at positions not shown.

The head 14 has a flow path 72 from the control valve 6a to the suction valve 4a, flow paths 30a and 40a from the suction valve 4a to a pressure chamber 23a, which will be described later, and a delivery valve 3 from the flow path 40a. An ejection hole 16a is formed. The flow path 72 from the control valve 6b to the suction valve 4b, the flow paths 30b and 40b from the suction valve 4b to the pressure chamber 23b, and the delivery valve 3 from the flow path 40b to positions not shown.
Is formed.

The control valve 6a is an electromagnetic valve, as shown in FIG.
It has a housing 61 containing a coil 62 and a valve body 68 fitted and fixed in the upper end thereof. A valve body 73 is slidably held in a cylinder 69 provided in the valve body 68. The control valve 6a is fixed by inserting a bolt (not shown) through a flange 63 provided on the outer periphery of the housing 61. An annular flow path 74a is formed around the upper end of the valve body 73. The flow path 74a communicates with the fuel reservoir 5a through a flow path 74b, and the flow path 74c
, Communicates with the flow path 72 leading to the suction valve 4a.

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

A substantially conical seat surface 75 is formed at the open end of the flow path 74c. In the state shown in the drawing where the coil 62 is not energized, the distal end of the valve body 73 sits on the seat surface 75 and The space between the flow paths 74a and 74c is closed. The coil 6 is controlled by a control signal from the electronic control unit C.
2, the armature 64 is sucked, the tip of the valve body 73 integrated therewith separates from the seat surface 75, and the
Open between a and 74c. Thus, the control valve 6a is
The configuration in which the valve is closed in a non-energized state has an effect of preventing the fuel from being fed when the coil is damaged. The control valve 6b (not shown) has the same configuration.

At the center of the left end of the head 14, first and second cylinders 2a and 2b for forming pressure chambers inside are formed. The cylinder 2a and the cylinder 2b are arranged at an interval in the axial direction of the drive shaft D, and the cylinders 2a and 2b are formed such that their axes are orthogonal to each other. The cylinders 2a and 2b are each formed in a direction orthogonal to the axis of the drive shaft D. FIG. 5A is a cross-sectional view taken along the line AA of FIG. 1 (and FIG. 4).
The first pair of plungers 21a and 21c are arranged in the first cylinder 2a so as to face each other.
Are reciprocally movable and slidably supported. Inner wall surface of cylinder 2a and plungers 21a, 21
The space formed with the end face of c forms a first pressure chamber 23a. FIG. 5B is a cross-sectional view of FIG.
B section, and the second cylinder 2b
The pair of plungers 21b and 21d are arranged to face each other, and are supported reciprocally and slidably with respect to the cylinder 2b. Inner wall surface of cylinder 2b and plunger 2
The space formed by the end faces 1b and 21d forms a second pressure chamber 23b.

The pair of plungers 21a and 21c are formed such that one plunger 21a is shorter than the other plunger 21c.
It is located at a position slightly shifted from the center of the cylinder 2a. The same applies to the pair of plungers 21b and 21d.
Is shorter than the other plunger 21d, and the pressure chamber 23b is formed at a position slightly shifted from the center of the sliding hole 2b. By doing so, the flow paths 40a, 40b, the flow paths 30a, 30b
There is an advantage that it is easy to form

Also, shoes 24a to 24d are provided at the outer ends of the plungers 21a to 21d, respectively.
4a to 24d, the cam rollers 22a, 22b, 22c, 2
2d is rotatably held. Shoe 24a-24
The end face of d is slidable by the shoe guide 15 and the plate 7. The shoe guide 15 and the plate 7 are fixed to the head 14 by bolts (not shown).
A washer 7 is provided between the plate 7 and the drive shaft D.
6 and the drive shaft D and the washer 7
Rotational sliding occurs between the washer 76 and the plate 7 between the plates 6.

The inner cam 8 includes a plurality of cylinders 2a,
The plungers 21a to 21d are reciprocated in the cylinders 2a and 2b by the rotation thereof. The inner peripheral surface of the inner cam 8 is a cam surface 81 having a plurality of cam ridges, and the cam surface 81 is arranged such that the outer peripheries of the cam rollers 22a to 22d are in sliding contact with each other. Here, the inner peripheral surface of the inner cam 8 is formed in an elliptical shape, and two cam ridges are formed at equal intervals (a position facing the plungers 21a and 21c in FIG. 5A).

When the inner cam 8 integrated with the drive shaft D rotates, the plungers 21a,
21c moves through the cylinder 2a and the plungers 21b and 21d.
Reciprocates in the cylinder 2b, and the plungers 21a, 21
c and the plungers 21b, 22d rise alternately to pressurize the fuel in the pressure chambers 23a, 23b.

The suction valve 4a is a check valve,
2 and a valve body 44 for opening and closing the flow path 43. The flow path 43 expands in the direction of the pressure chamber 23a (left side in the figure) on the way to form a conical seat surface 45, and the valve body 44 is provided with a spring stopper 41.
The seat 46 is urged rightward by a spring 46 held therein. As described above, the check valve 4a is closed in the illustrated normal state, the control valve 6a is opened, low-pressure fuel flows from the fuel reservoir 5a, and the pressure in the flow passage 30a (therefore, the pressure in the pressure chamber 23a). ) Is reduced so that the valve opens. When the valve is opened, the low-pressure fuel is provided in the flow path 72, the annular flow path 48 provided on the outer periphery of the housing 42, the flow path 49 in the housing 42, the flow path 43, the flow path 50 in the spring stopper 41, and the head 14. Through the flow passages 30a and 40a
flows into a.

The structure of the suction valve 4b (not shown in FIG. 4) is the same as that of the suction valve 4a.
When the valve b is opened and low-pressure fuel flows in from the fuel reservoir 5b and the pressure in the flow path 30b (therefore, the pressure in the pressure chamber 23b) decreases, the valve opens and the low-pressure fuel is provided on the flow path 72 and the outer periphery of the housing 42. Annular channel 48, housing 4
2 Internal flow path 49, flow path 43, spring stopper 41
Channel 50, channels 30b and 40b provided in the head 14
Through the pressure chamber 23b. The suction valves 4a and 4b are fixed in the head 14 by screws 47.

The delivery valve 3 has a check valve function and has balls 31a and 31b as valve bodies. Of these, the ball 31a is connected to the discharge hole 16 communicating with the pressure chamber 23a.
a, the ball 31b is connected to the pressure chamber 23b (FIG. 5).
(See (B)) to open and close a flow path following the discharge hole 16b communicating with the discharge hole 16b.

That is, as shown in FIG. 6, two plungers are respectively arranged in two sliding holes 2a and 2b independent of each other, and a cylinder 2a and a pair of plungers 21a,
21c and a pressure chamber 23a surrounded by the first pumping system, a cylinder 2b and a pair of plungers 2
A second pumping system including 1b, 21d, and a pressure chamber 23b surrounded by them is provided, and the first and second pumping means alternately perform pumping. The pressure chamber 23a communicates with the ball 31a of the delivery valve 3 through the flow path 40a and the discharge hole 16a, and the pressure chamber 23b communicates with the ball 31b of the delivery valve 3 through the flow path 40b and the discharge hole 16b. . When the pressure of the fuel pressurized in each of the pressure chambers 23a and 23b becomes higher than the pressure of the common rail R, the ball 31a or the ball 31b opens and is supplied to the common rail R through the supply pipe R1. Here, since the pressurization of the fuel in the pressure chambers 23a and 23b is performed alternately, the discharge of the fuel via the balls 31a and 31b is also performed alternately. In addition, common rail R
The supply pressure to the engine E depends on the operating state of the engine E,
200-1200 atmospheres.

The system for supplying low-pressure fuel to the pressure chambers 23a and 23b includes a fuel reservoir 5a, a control valve 6a, and a suction valve 4a.
流 路 flow path 30a〜pressure chamber 23a and fuel pool 5
b ~ control valve 6b ~ suction valve 4b ~ flow path 30b ~ pressure chamber 23
Two of the systems b are formed.

Next, the operation of the variable discharge high-pressure pump P having the above-described structure will be described with reference to FIG. In the figure, cam # 1
Indicates a lift amount at points 81a and 81c on the cam surface 81 which face the plungers 21a and 21c in FIG. The cam # 2 indicates a lift amount at points 81b and 81d on the cam surface 81 facing the plungers 21b and 21d. TCV # 1 is the lift amount of the valve body 73 of the control valve 6a, and TCV # 2 is the lift amount of the valve body 73 of the control valve 6b.

When the inner cam 8 rotates, the cam #
1. Cam # 2 repeats ascending and descending. Cylinder 2a,
Since the formation directions of the pressure chambers 2b are orthogonal to each other, the cams # 1 and # 2 have 180 ° CA phases different from each other. (23a) performs a pressure feeding operation.

The suction and pressure feeding operations in the pressure chambers 23a and 23b will be described. The energization of the coil 62 of the control valve 6a is performed prior to this so that the valve element 73 of the control valve 6a opens at the time when the cam # 1 starts to descend.
Then, when the control valve 6a is turned on, the fuel flows from the fuel reservoir 5a to the pressure chamber 2 through the flow paths 74c and 72 of the control valve 6a, the flow path 43 in the suction valve 4a, and the flow paths 30a and 40a.
3a. At this time, the plungers 21a and 21c are lowered while being pressed against the cam surface 81 by the inflowing fuel, and the fuel is sucked in with the expansion of the volume of the pressure chamber 23a.

When the power supply from the electronic control unit C to the coil 62 of the control valve 6a is cut off and the valve body 73 of the control valve 6a is closed and the suction valve 4a is closed, the suction of fuel into the pressure chamber 23a is stopped. I do. After that, although the cam # 1 continues to descend, when the suction ends, the lift of the plungers 21a and 21c stops, and the cam rollers 22a and 22c and the inner cam 8 separate.

Thereafter, the cam # 1 turns up and enters the pressure feeding step. Even if cam # 1 starts to rise, plunger 21
a, 21c do not immediately start rising, and when the lift amount of the cam # 1 becomes the lift amount of the plungers 21a, 21c,
The cam rollers 22a and 22c contact the inner cam 8,
The cam rollers 22a, 22c raise the plungers 21a, 21c via the shoes 24a, 24c. At this time,
The suction valve 4a is closed. Then, plunger 21
As the pressures a and 21c rise, the volume of the pressure chamber 23a decreases, pressurizing the fuel in the pressure chamber 23a, and the pressure in the pressure chamber 23a 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 16a and the delivery valve 3 (FIG. 2). When the lift amount of the cam # 1 reaches the maximum and the lifts of the plungers 21a and 21c reach the maximum point, the pressure feeding ends.

During this time, the control valve 6b is energized with a delay of approximately 180 ° CA from the control valve 6a, and the cam # 2 starts to descend.
As in the case of the above-mentioned pressure chamber 23b, the fuel is sucked and pumped in the pressure chamber 23b. As described above, by making the timing of the pressure feeding different between the pressure chamber 23a and the pressure chamber 23b, the maximum driving torque is reduced.

8, 9, 10, 11, 12, 13, 14, and 15 show control flows of the variable discharge high-pressure pump P executed in the electronic control unit C.
A control method for preventing overpressure from being sent to the common rail R will be described.

In FIG. 8, NE is input every time the NE signal is input.
Execute the signal hard interrupt routine. Step S1
At 01, the pulse interval between the previous input of the NE signal to be pulse input and the NE signal is measured. This pulse interval is the engine speed N
It is used for calculating e. In step S102, the NE pulse counter CNIRQ is updated (one-step increment). In step S103, it is checked whether or not CNIRQ = 0. If the result is affirmative, the cylinder counter PCYLND (= 0, 1, 2, 3) is updated (incremented by one step) in step S104, and the process proceeds to step S105. If so, the process proceeds to step S105. In step S105, a soft interrupt process according to CNIRQ is called, and the NE signal hard interrupt routine is terminated. Note that the cylinder counter PCYLND = 0 is set by the input of the G1 signal from the G1 sensor S3.

The soft interrupt processing called in step S105 will be described. Figure 9 shows the CNI
Soft interrupt processing called when RQ = 1,
In step S201, the engine speed Ne and the accelerator opening Ac are read, and in step S202, the command injection amount QF of the injector I is calculated. In step S203, a command injection timing AF is calculated from the command injection amount QF and the engine speed Ne. Finally, in step S204, the target common rail pressure P is calculated from the command injection amount QF and the engine speed Ne.
Calculate F.

FIG. 10 shows a soft interrupt process called when CNIRQ = 3. In step S301, the common rail pressure PC is fetched. In step S302, the injector I is determined based on the common rail pressure PC and the command injection amount QF.
The power supply period TQF is calculated. In step S303, in order to control the amount of fuel passing between the feed pump P1 and the suction valve 4a and between the feed pump P1 and the suction valve 4b, the pump energization, which is a valve opening period command value as a command value to the control valves 6a and 6b, is performed. The period TF is calculated.

FIG. 11 shows the procedure for calculating the pump energizing period TF in step S303.
Calculates the basic energization period TFJP from the command injection amount QF and the target common rail pressure PF. Subsequent step S402
Steps S406 to S406 are steps for calculating a correction term to be added to or subtracted from the command injection amount QF.
And the target common rail pressure PF, the proportional compensation amount TFJ
Calculate P. In step S403, a power supply
It is confirmed whether the N flag TFON is 1 or not. If the energization ON flag TFON is 1, the integral compensation amount TFJI is calculated and updated based on the deviation between the common rail pressure PC and the target common rail pressure PF in step S404. Power ON flag TF
When ON = 0, the calculation of the integral compensation amount TFJI (step S403) is skipped. As described later, energization ON
The flag TFON is set to 0 when there is a danger of overpressure feeding, and the above-mentioned correction terms are set in the pump energizing period TFON.
Work to shorten the However, if the integral compensation amount TFJI is updated, the integral compensation amount TFJI will contain a component corresponding to the deviation between the abnormal common rail pressure PC and the target common rail pressure PF at this time, which is not preferable. By skipping the update of the integral compensation amount TFJI based on the deviation at the time of abnormality, a proper compensation amount can be obtained.

In the following step S405, control valves 6a, 6
A solenoid valve closing delay compensation amount TFD for compensating a response delay of the valve closing operation in response to the valve closing signal b (disconnection of current to the coil 62).
Is calculated. The calculation of the solenoid valve closing delay compensation amount TFD is performed by converting the valve closing delay time TFDB (μs) stored in advance of the control valves 6a and 6b into a crank angle according to the engine speed Ne according to equation (1). Do. TFD = TFDB × 6 × Ne × 10 ^-6 (1)

In step S406, the pump energizing period TF is calculated by equation (2). TF = TFJB + TFJP + TFJI-TFD + TFOF (2) In the formula, the TFOF is added to the fuel pressure chamber 23a,
The suction to 23b is performed after the control valves 6a and 6b have been energized and after the plungers 21a to 23d have started to descend. This is because the energized period up to that time does not contribute to the intake of fuel. The actual fuel intake period TF
It is added to J (= TFJB + TFJP + TFJI-TFD) to calculate the pump energizing period TF.

FIG. 12 shows a software interrupt called when CNIRQ = 4. In step S501, the injector ON timing AF is set.
After the injector ON period (TQF) of the N timing AF, the injector OFF timing tQF is set, and this software interrupt is ended.

FIG. 13 shows a soft interrupt called when CNIRQ = 5, which is a feature of the present invention. In steps S601 and S602, it is confirmed whether or not the control condition is satisfied. In step S601, the pump energizing period TF
Is smaller than a predetermined lower limit. Here, the lower limit value is set in advance, for example, 5 ° CA. In step S602, it is determined whether or not the common rail pressure PC is larger than the target common rail pressure PF + allowable value. Here, the allowable value is set in advance, for example, 5 MPa. If one of steps S601 and S602 is denied, the energization flag TFON is set to 1 in step S603, and energization ON processing is performed in step S604. When both steps S601 and S602 are affirmed, the process proceeds to step S605 described later.

FIG. 14 shows the energization of step S604.
In step S701, a cylinder counter PCYLND is read, and in step S702, PCY
Check whether LND = 0 or 2. If the result is affirmative, the process proceeds to step S703, and the control valve 6b is turned on.
If the result in step S704 is negative, the process proceeds to step S704, where the control valve 6a is energized, and the energization ON process ends.

FIG. 15 shows a software interrupt called when CNIRQ = 6. In step S801, the cylinder counter PCYLND is read, and in step S802, the PC counter PCYLND is read.
Check whether YLND = 0 or 2. If the result is affirmative, the process proceeds to step S803, and the control valve 6b is energized OF after the pump energization period TF from the energization ON timing.
If the F time is set and the result is negative, step S80
Proceeding to 4, the current supply OFF timing is set for the control valve 6a, and this routine ends.

In the soft interrupt processing at CNIRQ = 5, when the pump energizing period TF is smaller than the predetermined lower limit and the common rail pressure PC exceeds the target common rail pressure PF + allowable value (steps S601 and S601).
602), the energization flag TFON in step S605
Is set to 0, and this routine is terminated without executing the energization process. That is, if both steps S601 and S602 are affirmed, the fuel is not replenished to the common rail with the fuel injection from the injector.

Now, the control method according to the present invention will be described in which the control valve is not opened when the control conditions determined in steps S601 and S602 are satisfied. A difference from a control valve in which a control valve is opened for a certain period in accordance with a required fuel replenishment amount (prior art) will be described with reference to FIG. 16 showing conventional control. At this stage, the control valve is energized and opens. When the control valve is opened, low-pressure fuel flows into the flow path portion (fuel reservoir) from the control valve to the suction valve, and the pressure in the fuel reservoir increases from the atmospheric pressure to the feed pressure. Since the suction valve remains closed, the pressure in the pressure chamber is the same as in the common rail, and the plunger is pressed against the cam surface. Here, if the low-pressure pump sucks air together with the fuel from the fuel tank having a small remaining amount of fuel when the gas is exhausted or the like, the air enters the fuel in the fuel reservoir.

In the following stage, the cam lift is lowered,
Since the plunger descends while being pressed against the cam surface, the volume of the pressure chamber expands and the pressure in the pressure chamber decreases, but the suction valve is closed at a higher pressure than the feed pressure.

In the subsequent stage, the pressure in the pressure chamber becomes equal to or lower than the feed pressure, the control valve is already closed, the suction valve is opened, and low-pressure fuel is sucked into the pressure chamber through the suction valve. The pressure in the fuel reservoir is reduced from the feed pressure to the atmospheric pressure similarly to the pressure chamber by communicating with the pressure chamber,
The mixed air in the fuel reservoir expands. The air expands significantly more than the fuel due to the pressure drop and pushes the fuel in the fuel reservoir into the pressure chamber. Thus, in the fuel pool,
When the fuel at the feed pressure containing the air flows in, the fuel removed by the expansion of the mixed air due to the change from the feed pressure to the atmospheric pressure is pushed out into the pressure chamber as excess fuel regardless of the power supply period of the control valve. Is not metered to an amount corresponding to the energization period of the control valve.

After the pressure in the pressure chamber has decreased to the atmospheric pressure and the lowering of the cam lift has stopped, at the stage where the cam lift rises again, first, the cam peak starts pressing the plunger. Thereby, the fuel in the pressure chamber is compressed, and the pressure in the pressure chamber increases.

In the subsequent stage, the pressure in the pressure chamber further rises and exceeds the pressure specified by the opening pressure of the delivery valve, the delivery valve opens, and fuel is fed from the pressure chamber into the common rail. As described above, since the amount of fuel sucked into the pressure chamber has an excessive metering error, the fuel is overpressurized. Thus, the common rail pressure tends to rise excessively, and the energization period TF tends to be shorter.However, as long as the fuel mixed with air is sucked from the low-pressure pump, an excess amount of fuel corresponding to the air amount is generated in the pressure chamber. Will flow into
There is a great possibility that the vehicle cannot escape from the overpressure feeding state forever.

On the other hand, according to the control method of the present invention,
By executing the above S601 and S602, there is a risk of overpressure feeding due to mixed air, and the command energizing period T
When F is short and the effect of overpressure feeding is large, energization of the control valve is prohibited (step S605), so that the state of overpressure feeding can be avoided. Thus, it is possible to prevent poor drivability and deterioration in exhaust gas performance without causing deterioration in pressure controllability.

The variable discharge high-pressure pump P shown in FIG.
As described above, the fuel is alternately pumped and supplied to the common rail R from the plurality of pressure chambers 23a and 23b, so that the maximum driving torque is reduced, and the load on the timing belt 52 is reduced, thereby preventing the durability from lowering. However, it is necessary to provide one suction valve 4a, 4b for each of the pressure chambers 23a, 23b. Therefore, due to the layout relationship between the suction valves 4a, 4b and the control valves 6a, 6b, the control valves 6a,
Flow path portions (fuel reservoirs) 73, 74c, 72, 71a, 48, 49 or 7 from 6b to the intake valves 4a, 4b.
3, 74c, 72, 71b, 48, and 49 become longer, and when the feed pump P1 sucks air together with fuel, a large amount of mixed air that causes overpressure feeding flows into this flow path portion. In other words, the variable discharge high pressure pump P shown in FIG.
By applying the control method of the present invention, a particularly large overpressure feeding prevention effect can be obtained.

The lower limit value and the allowable value in steps S601 and S602 are not necessarily limited to these values, but may be set in advance by experiments or the like in accordance with the specifications of the variable discharge high pressure pump and the like.

(Second Embodiment) FIG. 17 shows a control method of a variable discharge high pressure pump according to a second embodiment of the present invention.
In the present embodiment, the CNIRQ = 5 soft interrupt processing executed by the electronic control unit C in the first embodiment is replaced with the CNIRQ = 5 soft interrupt processing shown in FIG.

In the figure, portions denoted by the same reference numerals carry out the same procedure, and therefore the description will be focused on the differences from the first embodiment.

In the present embodiment, in the first embodiment,
Step S601 to determine pump energizing period TF
Is omitted, and only S602 is executed.
The control condition for prohibiting the opening of the solenoid valves 6a and 6b is simply that the common rail pressure PC is larger than the target common rail pressure PF + the permissible value. It has become.

According to such a control method, it is possible to prevent overpressure feeding due to air mixing.

The present invention is not limited to the above-described variable-discharge-amount high-pressure pump, in which a control valve and a suction valve are provided for a plurality of pressure chambers, respectively. The low-pressure fuel delivered from the pump and passing through the common control valve 6 flows into the suction valve 4a through the flow path 71a and flows into the suction valve 4b through the flow path 71b, or a single fuel as shown in FIG. For the pressure chamber of
The present invention can be applied to any variable discharge high-pressure pump configured to supply low-pressure fuel to the pressure chamber via the control valve and the suction valve, such as a single control valve and a single suction valve.

Further, in the above-described embodiment, the one in which the valve opening period of the control valve is controlled to control the amount of fuel passing between the feed pump and the suction valve is employed. But,
Instead of such a control valve, the present invention is applied to a control valve that employs a linear solenoid valve or the like that controls the opening area of the control valve as a control valve, and controls the passing fuel amount by varying the opening area. May be.

[Brief description of the drawings]

FIG. 1 is an overall sectional view of a variable discharge high pressure pump to which a control method of a variable discharge high pressure pump according to the present invention is applied.

FIG. 2 is an overall configuration diagram of a common rail fuel injection system including the variable discharge amount high pressure pump.

FIG. 3 is a view showing a drive system of the variable discharge amount high pressure pump.

FIG. 4 is a partially enlarged sectional view of FIG. 1;

5A is a cross-sectional view taken along line AA of FIG. 4, and FIG.
FIG. 7 is a sectional view taken along line BB of FIG.

FIG. 6 is a schematic configuration diagram of a main part of the variable discharge amount high pressure pump.

FIG. 7 is a time chart for explaining the operation of the variable discharge amount high pressure pump.

FIG. 8 is a first flowchart showing a control method of the variable discharge high pressure pump according to the present invention.

FIG. 9 is a second flowchart showing a control method of the variable discharge high pressure pump according to the present invention.

FIG. 10 is a third flowchart showing a control method of the variable discharge high pressure pump according to the present invention.

FIG. 11 is a fourth flowchart showing a control method of the variable discharge high pressure pump according to the present invention.

FIG. 12 is a fifth flowchart illustrating a method of controlling the variable discharge high pressure pump according to the present invention.

FIG. 13 is a sixth flowchart illustrating a control method of the variable discharge high pressure pump according to the present invention.

FIG. 14 is a seventh flowchart illustrating a method of controlling the variable discharge high pressure pump according to the present invention.

FIG. 15 is an eighth flowchart showing the control method of the variable discharge high pressure pump according to the present invention.

FIG. 16 is a time chart for explaining a conventional control method for comparison with the control method of the variable discharge amount high pressure pump in the first embodiment.

FIG. 17 is a flowchart showing another variable discharge amount high pressure pump control method according to the present invention.

FIG. 18 is a schematic configuration diagram of a main part of another variable discharge high pressure pump to which the control method of the variable discharge high pressure pump of the present invention can be applied.

FIG. 19 is an overall sectional view of a variable discharge amount high pressure pump for explaining a control method of a conventional variable discharge amount high pressure pump.

[Explanation of symbols]

 P variable discharge high pressure pump P1 feed pump (low pressure pump) C electronic control unit R common rail (accumulation chamber) 23a, 23b pressure chamber 3 delivery valve 4 suction valve (check valve) 6, 6a, 6b control valve

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G066 AA07 AB02 AC09 BA10 BA14 BA37 CA04T CA15S CA34 CC63 CC69 CD14 CE12 DA06 DB02 DC05 DC09 DC18 3G301 HA02 HA04 JA21 JA23 KA04 KB06 LB17 MA28 NA04 NB11 ND11

Claims (3)

[Claims] A pressure chamber connected to a pressure accumulating chamber for holding a high-pressure fuel, the pressure chamber expanding and contracting in volume; A check valve having a forward direction, and a control valve for controlling the amount of fuel passing between the low-pressure pump and the check valve, and the low-pressure fuel is supplied by the low-pressure pump via the control valve when the volume of the pressure chamber is expanded. A variable discharge high pressure pump for pumping fluid in the pressure chamber to the pressure accumulating chamber when the volume of the pressure chamber is reduced, wherein a command value for controlling the amount of fuel passed in the previous period is provided. Controlling the control valve according to, the control method of replenishing the accumulator with high-pressure fluid according to the amount of high-pressure fuel flowing out of the pressure chamber, detecting the pressure of the accumulator, the detected pressure is the Predetermined from the target pressure of the accumulator It is determined whether or not a control condition including a value higher than the allowable value is satisfied, and when it is determined that the control condition is satisfied, opening of the control valve is prohibited and low-pressure fuel is supplied to the pressure chamber. A method for controlling a variable discharge high pressure pump, characterized by suspending suction. 2. The control method for a variable discharge amount high pressure pump according to claim 1, wherein the control valve changes a valve opening period according to the command value, and the control condition includes: A method for controlling a variable discharge high pressure pump including that a valve opening period command value is shorter than a predetermined lower limit value. 3. The variable discharge amount high pressure pump control method according to claim 2, wherein in the calculation of the valve opening period command value, integral compensation is performed in accordance with an integrated amount of a deviation between the detected pressure of the accumulator and the target pressure. A control method of a variable discharge high pressure pump, wherein the variable discharge amount high pressure pump is prohibited to update the integral compensation value when the control valve is prohibited from being opened.