JPH11210597A - Common-rail fuel supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a common-rail fuel supply device usable in common for an engine different in the number of cylinders. SOLUTION: Fuel is force-fed to a common rail 3 connected to fuel injection- valves 1 of an internal combustion engine 10, using an inner cam type high pressure fuel feed pump 5. The inner cam shape and cylinder layout of the pump 5 are so constituted as to make the total of discharge from each cylinder constant throughout the operating cycle of the pump 5. A force-feed control valve is provided at a force-feed passage connecting the discharge port of each cylinder of the pump 5 to the common rail, and the force-feed control valve is opened/closed every fuel injection from the fuel injection valves 1 to force-feed fuel to the common rail. Since the total of discharge from each cylinder of the pump 5 is constant throughout the operating cycle of the pump 5, fuel can be force-fed to the common rail even at the time other than force-feed stroke timing of each cylinder, and the same pump 5 can be used in common for an engine different in the number of cylinders.

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 device for storing pressurized fuel in a common rail (accumulation chamber) and injecting fuel into each cylinder from a fuel injection valve connected to the common rail. The present invention relates to a common rail fuel supply device that supplies pressurized fuel to a common rail.

[0002]

2. Description of the Related Art An inner cam ring having a cam formed on an inner peripheral surface thereof, and an inner cam type high pressure fuel supply pump for feeding fuel by a plunger which reciprocates in a cam ring radial direction along a cam profile while being in contact with the inner cam ring are known. Have been. As a fuel supply device for an internal combustion engine using this kind of inner cam type high pressure fuel supply pump, there is one described in, for example, JP-A-8-61179.

[0003] The inner cam type high pressure fuel supply pump of the fuel supply device disclosed in the above publication has a center drive shaft for driving the plunger to rotate along the inner periphery of the inner cam ring, and a pair of symmetrically arranged drive shafts. It has a plunger. The cam profile of the inner cam ring is formed symmetrically with respect to the center drive shaft so that the pair of plungers move simultaneously in the center drive shaft direction. That is, the pair of plungers of the fuel supply pump disclosed in the above publication operate in synchronization with each other, and simultaneously perform the pressure feeding and suction strokes.

[0004]

In the inner cam type high pressure fuel supply pump of the apparatus disclosed in the above publication, since a pair of plungers repeats the pressure feeding and suction strokes at the same time, the number of times equal to the number of cam ridges of the inner cam per rotation of the pump (for example, 4
Times). In addition, since the discharge amount changes in accordance with the cam profile even during the pumping stroke, the discharge amount per unit operation amount of the pump (unit rotation angle of the pump) is large during one operation cycle of the pump (one rotation of the pump). Will change. That is, the pump can discharge a sufficient amount of fuel only while the plunger is in a specific range during the pumping stroke.

On the other hand, since the pressure in the common rail decreases every time fuel injection is performed in each cylinder, it is necessary to supply fuel to the common rail each time fuel injection is performed in each cylinder in order to maintain the common rail pressure constant. . Therefore, when the pump of the above publication is used for a common rail fuel supply device, fuel can be supplied to the common rail only when the pair of plungers of the pump are in a specific range during the pressure feeding stroke. For this reason, when supplying fuel to the common rail using the above-mentioned pump, it is necessary to set the pump rotation speed in accordance with the number of cylinders so that a fuel pressure feed stroke occurs each time fuel is injected into each cylinder.

In this case, if the inner cam shape is set so that, for example, four pumping strokes occur per one rotation of the pump, when the pump is driven from the engine output shaft,
For example, if the pump speed is set to １ ／ of the engine speed, four pumping strokes occur per two engine revolutions. If the pump speed is driven at the same speed as the engine speed, eight pumping strokes will occur. Will occur. In a four-cycle engine, fuel injection is performed the same number of times as the number of cylinders during two revolutions of the engine. Therefore, only four-cylinder or eight-cylinder engines can use the four-cam mountain inner cam as described above. It cannot be used for an engine having another number of cylinders (for example, six cylinders). That is, when fuel is supplied to the common rail using a pump using a pair of plungers as described above, there is a problem that the number of cylinders of the engine that can be used is determined by the number of cam ridges of the inner cam. Also, in the case where a pump having a plurality of plungers is used, the number of cylinders of the engine that can be used is determined by the number of pumping strokes (number of plungers x number of cam lobes) per one operating cycle of the pump in the same manner as described above. A problem arises in that the same pump cannot be used for several engines.

Although the above description has been made by taking an example of an inner-cam type fuel pump, these problems are not limited to the inner-cam type fuel pump. For example, a plunger disposed radially around a pump drive shaft may be provided around the drive shaft. This also occurs in a plunger type fuel pump of the type driven by a cam provided in the above. Further, in the pump of the above publication, the discharge amount per unit operation amount of the pump greatly changes during one operation cycle of the pump, so that the load on the pump drive system, for example, the drive belt or chain, is changed due to the fluctuation of the drive torque of the pump. There is a problem of growing.

In view of the above problems, the present invention provides a common rail fuel supply apparatus which can be used commonly for engines having different numbers of cylinders, and which can maintain a small load on a drive system with a small fluctuation in pump driving torque. It is intended to provide.

[0009]

According to the first aspect of the present invention, there is provided a common rail fuel supply device for supplying pressurized fuel to a common rail connected to a fuel injection valve of an internal combustion engine, comprising a plurality of cylinders. A plunger pushed by a cam to reciprocate in each cylinder, a pump chamber formed in each cylinder and having a volume that changes in accordance with the reciprocation of the plunger, and each cylinder reduces the volume of the pump chamber. A pumping passage that communicates with the pump chamber when the pumping stroke is performed, and a suction passage that connects the pump chamber and a fuel supply source when each cylinder is in a suction stroke in which the volume of the pump chamber increases. A fuel pump, and a pumping amount control means disposed between the pumping passage and the common rail for communicating and blocking the pumping passage and the common rail. The cam and the cylinder are configured to maintain the total amount of fuel discharged from the pump chamber of each cylinder into the pumping passage per unit operating amount of the pump substantially constant throughout the entire operation cycle of the pump. The control means provides a common rail fuel supply device that controls the amount of fuel supplied to the common rail by communicating the pressure feed passage with the common rail for a predetermined time.

That is, in the first aspect of the present invention, the total amount of fuel discharged from the pump chamber of each cylinder to the pressure feed passage per unit operation amount of the pump (for example, per unit rotation angle of the pump drive shaft) is equal to the total operation amount of the pump. The cam and the cylinder are configured to be constant throughout the cycle, and the discharge amount does not fluctuate during one rotation of the pump. This is, for example, 1
This is made possible by arranging the cam and the cylinder such that the pumping stroke of one cylinder and the pumping stroke of another cylinder overlap.

That is, when looking at one cylinder, the discharge fuel amount per unit operation amount of the pump from the pump chamber to the pumping passage (hereinafter, the discharge amount from the pump chamber to the pumping passage per unit operation amount of the pump is referred to as "unit pumping amount". Is smaller at the beginning and end of the pumping stroke, depending on the cam profile. Therefore, the unit pumping amount of one cylinder varies during the pumping stroke. However, by overlapping the pumping stroke of one cylinder with the pumping stroke of another cylinder, when the unit pumping amount of one cylinder decreases at the start and end of the pumping stroke, fuel from other cylinders Because it can be discharged to the pressure feed passage,
The sum of the unit pumping amounts of all cylinders (hereinafter, the sum of the unit pumping amounts of all cylinders is referred to as “total pumping amount”) can be kept constant throughout the pump operation cycle.

In the present invention, since the total pumping amount of the pump is maintained constant throughout the pump operation cycle as described above, the pumping amount control means causes the pumping passage to communicate with the common rail at any time during the pump operation cycle. Even
The amount of fuel supplied to the common rail per unit time is constant. That is, in the present invention, it is not necessary to synchronize the supply of fuel to the common rail with the pressure feed stroke of each cylinder. This makes it possible to supply fuel to the common rail for each fuel injection even when the number of cam lobes or the number of plungers and the number of cylinders of the cam do not correspond, and the same fuel pump is commonly used for engines with different numbers of cylinders. It is possible to do. Further, in the present invention, since the total pumping amount of the pump does not fluctuate, the pump driving torque is also substantially constant, and it is possible to prevent the load on the pump driving system from increasing due to the fluctuation of the driving torque, and to keep the driving system load small. .

According to the second aspect of the present invention, the pumping amount control means includes an electromagnetic on-off valve disposed between the pumping passage and the common rail, and the electromagnetic on-off valve is provided in the pumping passage. When the valve is closed against fuel pressure, the pressure feed passage and the common rail communicate with each other, and when the solenoid on-off valve is opened, the pressure feed passage and the common rail are shut off,
2. The common rail fuel according to claim 1, wherein the pumping amount control unit controls the exciting current to adjust a valve closing force of the electromagnetic on-off valve to adjust a fuel pressure pumped from the pumping passage to the common rail. 3. A supply device is provided.

That is, in the second aspect of the present invention, the pressure of the fuel fed from the pressure feed passage to the common rail is controlled by changing the closing force of the solenoid on-off valve. Since the fuel pressure fed to the common rail is the fuel discharge pressure from each cylinder, if the pumped fuel pressure is high, the pump driving torque increases even if the unit pumping amount is the same. In general, a pump drive system such as a drive chain or a belt has a natural frequency. When the pump drive speed matches the natural frequency, resonance occurs and the drive torque fluctuation increases.
Load on chains, belts, etc. increases. In the present invention,
The exciting current of the solenoid on-off valve is controlled in accordance with the operating state of the engine to change the closing force of the solenoid on-off valve. For example, when the engine speed becomes close to the natural frequency of the pump drive system, the valve closing force of the solenoid on-off valve is reduced so that the solenoid on-off valve opens at a low pressure. As a result, the pressure of the fuel fed to the common rail is reduced, and the pump driving torque is reduced. Therefore, it is possible to keep the torque fluctuation during resonance small.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing a schematic configuration of an embodiment when the present invention is applied to an automobile diesel engine. In FIG. 1, reference numeral 1 denotes a fuel injection valve for directly injecting fuel into each cylinder of an internal combustion engine 10 (a four-cylinder diesel engine in this embodiment), and reference numeral 3 denotes a common accumulator (common rail) to which each fuel injection valve 1 is connected. ). The common rail 3 stores pressurized fuel supplied from a high-pressure fuel supply pump 5 (hereinafter, referred to as “high-pressure fuel pump”), which will be described later.
It has a function of distributing to each fuel injection valve 1.

In FIG. 1, reference numeral 7 denotes a fuel tank for storing fuel (light oil in this embodiment) of the engine 10, and reference numeral 9 denotes a low-pressure feed pump for supplying fuel to a high-pressure fuel pump 5 through a low-pressure pipe 8. I have. The fuel discharged from the high-pressure fuel injection pump 5 is supplied to the common rail 3 through the high-pressure pipe 17 and is injected from the common rail 3 into each cylinder of the internal combustion engine via each fuel injection valve 1.

In FIG. 1, reference numeral 19 denotes a recirculation pipe connecting a low-pressure passage of the high-pressure fuel pump 5 to be described later and the fuel tank 7. In FIG. 1, reference numeral 20 denotes an engine control circuit (ECU) for controlling the engine. The ECU 20
It is configured as a microcomputer having a known configuration in which a read-only memory (ROM), a random access memory (RAM), a microprocessor (CPU), and an input / output port are connected by a bidirectional bus. Further, the ECU 20 controls the valve opening time and the valve opening timing of the fuel injection valve 1 to perform fuel injection control for controlling the amount of fuel injected into the cylinder. The ECU 20 controls the opening / closing operation of the pumping control valve of the high-pressure fuel injection pump 5 to adjust the amount of fuel pumped from the pump 5 to the common rail 3 as described later, and adjusts the fuel pressure in the common rail 3 to the engine load and the engine speed. The fuel pressure control is performed in accordance with the engine pressure, and the injection rate of the fuel injection valve is adjusted in accordance with the engine load, the number of revolutions, and the like.

That is, in this embodiment, the ECU 20
It functions as a pumping amount control means together with a pumping control valve described later. For the above control, the input port of the ECU 20
A voltage signal corresponding to the fuel pressure in the common rail 3 is input from a fuel pressure sensor 31 provided on the common rail 3 via an AD converter 34, and an accelerator opening sensor provided on an engine accelerator pedal (not shown). From 35, a signal corresponding to the operation amount (depressed amount) of the accelerator pedal is similarly input via the AD converter 34.

An output port of the ECU 20 is connected to the fuel injection valves 1 via a drive circuit 40 to control the operation of each of the fuel injection valves 1. Is connected to a solenoid actuator for controlling the opening and closing of the pressure feed valve, and controls the discharge amount of the pump 5. Next, the pump 5 of the present embodiment will be described. The pump 5 of the present embodiment is an inner cam type high pressure fuel supply pump having an inner cam ring.

FIGS. 2 and 3 are sectional views showing the structure of an embodiment of the inner cam type high pressure fuel supply pump 5 of the present embodiment. 2 and 3, reference numeral 50 denotes a housing of the pump 5 (not shown in FIGS. 2 and 3 for clarity and is indicated by a dotted line), 51 is an inner cam ring fixed to the housing 50, and 53 is a housing 2 shows a fixed cylindrical pintle.

Reference numeral 55 in FIGS. 2 and 3 denotes a cylinder block mounted around the pintle 53 and driven to rotate around the pintle 53 from outside through a drive shaft 57. In this embodiment, the drive shaft 57 is connected to, for example, the crankshaft of the internal combustion engine 10 and is driven to rotate by the engine 10 at the same speed as the crankshaft. In the cylinder block 55, a plurality of (four cylinders # 1 to # 4 in the examples of FIGS. 2 and 3) are radially formed at equal intervals. A plunger 61 that reciprocates in the cylinder is provided in the cylinder.

As shown in FIG. 2, the inner cam ring 51
Is formed with a cam (in FIG. 2, a two-peak cam having two peaks 51A and 51B and two valleys 51C and 51D), and the plunger 61 is connected to the inner cam ring 51 via a roller 63. Are engaged with the cam surface. Thus, when the cylinder block 55 rotates, each plunger is pushed by the cam and reciprocates in the cylinder. When the plunger moves from the center of the cam valley to the center of the cam peak,
The volume of the space (pump chamber) between the end of the plunger and the pintle in the cylinder decreases, and the fuel in the pump chamber is pressurized and discharged to the outside of the cylinder. That is, at this time, the cylinder is in the fuel feeding stroke. When the plunger moves from the center of the cam ridge to the center of the cam valley, the volume of the pump chamber increases, and fuel is sucked into the cylinder. That is, at this time, the cylinder is in a fuel intake stroke. In the present embodiment, the cam ridges 51A and 51B and the cam valley 51
Since C and 51D are formed symmetrically with respect to the center axis of the pintle 53, # 1, # 3 and # 2
The # 1 and # 4 cylinders respectively undergo the pressure feeding stroke and the suction stroke at the same time, and the stroke cycles of the # 1 and # 3 cylinder groups and the # 2 and # 4 cylinder groups are 90 degrees out of phase with each other. In the present specification, a cam portion (a cam valley portion 51) that causes a pressure feed stroke to a cylinder is provided.
D from the bottom to the top of the cam peak 51A and the cam trough 51
From the bottom of C to the top of the cam ridge 51B, the cam surface (the cam ridge 51) which causes the suction stroke of the cylinder to the suction cam surface.
From the top of A to the bottom of the cam valley 51C, and the cam ridge 51
The top from B to the bottom of the cam valley 51D) is referred to as a suction cam surface.

At the center of the pintle 53, a center hole 65 is formed along the axis. The center hole 65 is provided with a tapered portion 65a in the middle, and a portion (small diameter portion) deeper than the tapered portion 65a forms a low-pressure fuel supply passage 65b as described later. The valve hole 67a of the pressure control valve 67 is fitted in the center hole 65 as described later. In the outer peripheral portion of the pintle 53, a high-pressure fuel pressure feeding groove (hereinafter referred to as a "pressure feeding groove") 69 is formed at a portion where the cylinder slides during the above-described pressure feeding process, and a low-pressure fuel supply groove ( Hereinafter, referred to as a “supply groove” 71. As shown in FIG. 3, in the present embodiment, since two sets of cylinders simultaneously undergo a pressure feeding stroke and a suction stroke, two pressure feeding grooves 69 and two supply grooves 71 are respectively provided at symmetrical positions with respect to the center axis of the pintle 53. Is provided. As shown in FIG. 3, the pressure feeding groove 69 and the supply groove 71 are provided at positions separated from each other in the axial direction of the pintle 53.

As shown in FIGS. 2 and 3, the pressure feed groove 69 is formed with a tapered portion 65a on the inner peripheral surface of the center hole 65 through a passage 69a.
A high-pressure fuel pressure-feeding passage (hereinafter, referred to as a “high-pressure passage”) having a circumferential groove provided in a portion on the side of the pressure-feeding control valve valve element 67a.
65c. The high-pressure passage 65c is connected to a high-pressure pipe 17 for feeding fuel to the common rail 3 via a passage 65d and a fuel control valve 73. In the present embodiment, the fuel control valve 73 is opened when the fuel pressure in the high pressure passage 65c becomes higher than the fuel pressure in the common rail 3 to cause a flow of fuel from the high pressure passage 65c to the common rail 3. Is used. On the other hand, the supply groove 7
1 is connected to a low-pressure fuel supply passage (hereinafter, referred to as “low-pressure passage”) 65b of the center hole 65 via a passage 71a. The low-pressure passage 65b is connected to the low-pressure pipe 8 of FIG. 1 via the passages 65e and 65f and the check valve 75. Further, in the present embodiment, a return passage 77 that connects the passage 65f to the return pipe 19 (FIG. 1) is provided. The recirculation passage 77 is provided with a recirculation control valve 79 for restricting the flow of the fuel recirculated from the low pressure passage 65b to the fuel tank 7. In the present embodiment, a differential pressure control valve that opens when the fuel pressure in the low pressure passage 65b becomes higher than the fuel tank 7 pressure by a predetermined value is used as the recirculation control valve 79.

The pressure feed control valve 67 has a solenoid actuator 67b for driving a valve body 67a. By exciting the solenoid 67b, the valve body 67a moves to the left in FIG. 3 and contacts the tapered portion 65a of the center hole 65.
The pressure control valve 67 is closed. In this state, the high pressure passage 65c and the low pressure passage 65b are shut off by the valve body 67a. When the solenoid 67b is demagnetized, the valve body 67
a is pushed by the fuel pressure in the low pressure passage 65b and moves rightward in FIG. 3 to be in the valve open state. In this state, the high pressure passage 65
c communicates with the low-pressure passage 65b. For this reason, when the pumping control valve 67 is closed, the fuel in the pump chamber of the cylinder in the pumping stroke is pressurized by the plunger, and when the pump chamber pressure becomes higher than the common rail 3 pressure, the check valve 73 opens. The high-pressure fuel is pressure-fed to the common rail 3 from the pump chamber through the high-pressure passage 65c and the high-pressure pipe 17.
On the other hand, when the solenoid 67b is demagnetized and the pressure control valve 67 is opened, the high pressure passage 65c and the low pressure passage 65b communicate with each other. Then, the fuel directly flows into the common rail 3, and the fuel supply to the common rail 3 is stopped. Therefore, by controlling the valve opening period of the pressure control valve 67, the amount of fuel pumped from the pump 5 to the common rail 3 can be controlled.

In this embodiment, the ECU 20 separately calculates the fuel injection amount from each fuel injection valve, opens the fuel injection valve when the fuel injection timing of each cylinder comes, and transfers the high-pressure fuel in the common rail 3 into the cylinder. Inject. Further, every time the fuel injection is performed from each fuel injection valve, the ECU 20 calculates the fuel injection amount in the common rail 3 detected by the common rail pressure sensor 31 and the fuel injection amount in the fuel injection executed immediately before.
The amount of fuel required to maintain the fuel pressure in the common rail 3 at a predetermined set pressure is calculated. The closing period of the pumping control valve 67 is set so that the amount of fuel to be pumped to the common rail 3 matches the required fuel amount calculated as described above, and the amount of fuel that escapes from the cylinder in the pumping stroke to the low-pressure passage 65b is determined. Adjust. Since the amount of fuel to be pumped in the pumping stroke of each cylinder is determined by the closing period of the pumping control valve 67 during the pumping stroke, the required amount of fuel determined according to the fuel injection amount and the common rail 3 pressure each time each fuel injection is performed is thereby determined. The fuel is pumped from the pump 5 to the cylinder.
For this reason, it is possible to control the pressure in the common rail 3 with good responsiveness to the set pressure that changes according to the operating conditions.

Next, the inner cam profile of this embodiment and the total pumping amount of the pump 5 will be described with reference to FIG. FIG. 4A is a cam lift diagram illustrating the inner cam profile of the present embodiment, and FIG. 4B is a diagram illustrating a change in the unit pumping amount of each cylinder during one operation cycle (one rotation) of the pump. FIG. 4C is a diagram showing a change in the total pumping amount of the pump during the pump 1 operation cycle.

FIG. 4A shows the cam lift of the inner cam, that is, the change in the stroke of one plunger, and the abscissa shows the pump rotation converted to the crank angle. In this embodiment, one operation cycle (one rotation) of the pump is 360 ° in terms of the crank angle. As shown in FIG. 4A, the inner cam ring 51 has a double cam shape having two cam ridges 51A and 51B and two cam valleys 51C and 51D out of phase by a crank rotation angle of 180 °. . In each of the cam shapes, the range of the pressure-feeding cam surface (from the bottom of the cam valley to the top of the cam) is a crank rotation angle of 90 degrees
4 ° (90 ° + 2α in FIG. 4A), and the range of the suction cam surface (from the top of the cam to the bottom of the cam valley) is narrower than the crank rotation angle of 90 ° (90 ° −2α) (α is Any angle). In this embodiment, since four plungers # 1 to # 4 are provided at 90 ° intervals, # 1 and # 4 are provided.
The set No. 3 and the sets No. 2 and No. 3 simultaneously perform the pressure feeding and suction strokes, respectively. Further, as described above, in the present embodiment, since the pressing cam surface of the inner cam ring 51 is wider than 90 °, the start and end of the pressing stroke of the set of plungers # 1 and # 3 are # 2 and # 2. At the end of the pumping stroke of the plunger # 4, it overlaps with the start.

FIG. 4B shows a change in the unit pumping amount of each cylinder in this embodiment. In the present embodiment, a linear portion (FIG. 4 (B)) is formed on each compression cam surface of the inner cam ring 51.
Section H) is provided, and correspondingly, a portion where the unit pumping amount becomes constant in the pumping stroke of each cylinder (FIG. 4B).
A section indicated by F in FIG. In the pumping stroke, the unit pumping amount of each cylinder increases substantially linearly from the start of the pumping stroke, reaches the constant unit pumping amount (section F), and decreases substantially linearly at the end of the pumping stroke. The shape of the inner cam is set as described above. In FIG. 4B, a solid line indicates a change in the unit pumping amount of the cylinders # 1 and # 3, and a dotted line indicates a change in the unit pumping amount of the cylinders # 2 and # 4. As shown in FIG. 4 (B), the phases of the cylinders # 2 and # 4 are 90 ° out of phase with the cylinders # 1 and # 3 by the crank rotation angle.

FIG. 4C shows the change in the total pumping amount of the pump 5 of this embodiment, that is, the total amount of the unit pumping amounts of all the cylinders. In the present embodiment, the unit pumping amount increasing period of the # 1 and # 3 cylinders at the beginning of the pumping stroke and the unit pumping amount decreasing period of the # 2 and # 4 cylinders at the end of the pumping stroke overlap each other. Therefore, the increase in the unit pumping amount at the beginning of the pumping stroke and the decrease in the unit pumping amount at the end of the pumping stroke of the other cylinders cancel each other, and the total pumping amount of the pump 5 is maintained constant throughout the pump operation cycle. (FIG. 4 (C)).

As described above, it is necessary to feed the fuel to the common rail 3 every time fuel is injected from each cylinder.
For this reason, for example, in the case where the total pumping amount of the pump fluctuates greatly according to the pumping stroke of each cylinder during one operation cycle of the pump, as in the conventional case, the common rail can only be synchronized with the pumping stroke of each cylinder. And the number of fuel injections per one revolution of the engine must match the number of cylinders in the cylinder. However, in this embodiment, as shown in FIG. 4 (C), since the total pumping amount of the pump 5 is kept constant throughout the operation cycle of the pump, it is possible to pump the fuel to the common rail at any time. it can. For example, in this embodiment, a two-mount cam 4 plunger pump is used. However, the fuel pumping to the common rail does not need to be synchronized with the pumping stroke of each plunger, and is performed twice per rotation of the pump (for a four-cylinder engine). Not only that, but also three (6-cylinder engine) or four (8-cylinder engine) fuel pumping is possible.

As described above, since the total pumping amount of the pump is maintained constant throughout the pump operation cycle, the work (drive torque) of the pump 5 as a whole is also maintained constant throughout the pump operation cycle. Become. Therefore, according to the present embodiment, the fluctuation of the pump driving torque is reduced, and the load on the pump driving system is kept small.

Although the above embodiment has been described by taking as an example a case where a two-mount cam 4 plunger pump is used, the present invention can be applied to a pump having another configuration. For example, FIGS. 5 to 7 are diagrams similar to FIGS. 2 to 4 illustrating an example in which the present invention is applied to a single-mount cam 4 plunger pump. 5 to 7, the same reference numerals as those in FIGS. 2 to 3 indicate the same elements.

As can be seen from FIG. 5, the high pressure pump 5 of the present embodiment differs from the embodiment of FIG. 2 in the cam shape of the inner cam ring 51. That is, the inner cam ring of FIG.
5 and 6, the inner cam ring of the pump of FIG. 5 and FIG. 6 has only one cam valley 51A and one cam valley 51C. The difference is that it is a single cam. The pump of the present embodiment has four cylinders (# 1 to # 4) arranged at 90-degree intervals, similarly to the pumps of FIGS. 2 and 3, but because of the inner cam shape, one cylinder is a pump. Only one pressure feeding and one suction stroke are performed per rotation.

FIG. 7A is a view similar to FIG. 4A showing the cam lift of the present embodiment. In the present embodiment, the cam valley 5
The range of the pressure feeding cam surface from the bottom of 1C to the top of the cam ridge 51A and the suction cam surface from the top of the cam ridge 51A to the bottom of the cam valley 51C are each set to 180 degrees. 2 and FIG. 3 in that one pressure feeding groove 69 and one supply groove 71 are arranged at the outer periphery of the pintle 53 corresponding to the cam shape, respectively. I have. In other respects, the pump 5 of the present embodiment has substantially the same structure as those of FIGS. 2 and 3.

FIG. 7B is a diagram showing a change in the unit pumping amount of each cylinder of the pump 5 of this embodiment. In the present embodiment, the pumping amount linearly increases from the beginning of the pumping stroke, reaches the maximum value at a phase of 90 ° in terms of the crank rotation angle after the start of the pumping stroke, and thereafter linearly decreases. I have. Further, since the pumping strokes of the cylinders are out of phase by 90 °, for example, the first half of the # 1 cylinder pumping stroke is #
The latter half of the four-cylinder pumping stroke and the latter half of the # 1 cylinder pumping stroke overlap the former half of the # 2 cylinder pumping stroke, respectively.

FIG. 7C is a diagram showing a change in the total pumping amount of the pump 5 of this embodiment. Also in the present embodiment, the change in the pumping amount in the first half and the latter half of the pumping stroke of each cylinder cancels the change in the pumping amount in the latter half and the first half of the adjacent cylinder, respectively, so that the total pumping amount of the pump 5 is maintained throughout the pump operation cycle. It is kept constant. Also in this embodiment, since the total pumping amount of the pump is maintained constant throughout the pump operation cycle, there is no need to synchronize the pumping stroke with the fuel pumping to the common rail. For this reason,
As in the previous embodiment, the same pump can be used for engines having different numbers of cylinders.

Further, as described above, in this embodiment, since one cam ridge portion 51A and one cam valley portion 51C are formed respectively, the pumping process of each cylinder is performed on the same cam pressing surface (cam valley portion). (From the center of 51C to the center of cam ridge 51A). As described above, by setting the number of the cam ridges and the valleys to be small and causing the cylinder to perform the pumping stroke on the same cam pumping surface, the phase angle of the cam pumping surface can be set to be large. For this reason, if the maximum lift amount of the cam is the same, the inclination angle of the cam pumping surface (the pumping rate in the pumping stroke) becomes small, and the fluctuation of the driving torque of the pump is reduced.

Next, another embodiment of the present invention will be described. In the present embodiment, the configuration of the pump 5 is
7 is substantially the same as the embodiment of FIG. 2, FIG. 3 or FIG. 5, except that the shape of the tip of the valve body 67a is different from the embodiment of FIG. 2, FIG. 3, FIG. 5, and FIG. . Therefore, only the difference between the configurations of the present embodiment will be described.

FIG. 8 shows a valve body 67 of the pump 5 of this embodiment.
It is an enlarged view explaining the shape of a. As shown in the figure, also in this embodiment, the pintle 53 of the pump 5 has a central hole 65.
Is provided with a tapered portion 65a between the low-pressure passage 65b and the circumferential high-pressure passage 65c. Also in this embodiment, the valve body 67a has the tapered portion 6 when the valve is closed.
A tapered portion 67c is provided to contact the low pressure passage 65b and the high pressure passage 65c so as to be in contact with 5a. However, in the present embodiment, the tapered portion of the valve body 67a is set to be longer than the tapered portion 65a of the center hole 65, and the peripheral portion of the tapered portion 67c is formed into a ring shape in the high-pressure passage 65c when the valve body is closed. It is exposed. For this reason, when the pressure feed control valve is closed, the fuel pressure (discharge pressure of each cylinder) in the high pressure passage 65c acts on the ring-shaped exposed portion of the valve body taper portion 67c to move the valve body 67a rightward in FIG. Will be pressed. This pressing force is the product of the axial projection area of the ring-shaped exposed portion (the area of the ring having a width indicated by S in FIG. 8) and the fuel pressure in the high-pressure chamber 65c. Although the fuel pressure in the low-pressure chamber 65b also acts, since the pressure in the low-pressure chamber 65b is extremely lower than the pressure in the high-pressure chamber 65C, only the pressure in the high-pressure chamber is considered here.)

On the other hand, when the pressure control valve is closed, the valve body 67a
It is pressed leftward in FIG. 8 by the solenoid 67b.
Therefore, even when the pressure control valve 67a is closed, if the pressing force due to the pressure in the high-pressure chamber 65c becomes larger than the urging force by the excitation of the solenoid 67b, the pressure control valve 67 opens,
The low pressure chamber 65b communicates with the high pressure chamber 67c.
In the present embodiment, the solenoid 67b whose biasing force changes continuously according to the supplied excitation current is used.
The CU 20 controls the exciting current of the solenoid 67b according to the operating state of the engine. This makes it possible to control the valve opening pressure of the pressure control valve 67a, that is, the fuel pressure supplied to the common rail 3, according to the engine operating state.

During the operation of the pump 5, the drive torque of the drive shaft 57 changes according to the pressure feed and suction stroke of each cylinder. Further, the higher the discharge pressure of each cylinder (the pressure of the high-pressure chamber 65c), the greater the fluctuation of the driving torque. On the other hand, the drive shaft 57
There is a natural frequency in a drive system such as a chain or a belt for driving the motor, and in a region where the engine speed is close to the natural frequency, the fluctuation of the drive torque is amplified by resonance. For this reason, if the drive torque fluctuation of the pump is large, the increase in the drive torque fluctuation due to resonance also becomes large, and a large load may be applied to the pump drive system. Therefore, in the present embodiment, E
In the engine speed range where resonance may occur in the pump drive system, the CU 20 operates the solenoid 67b of the pumping control valve 67.
Reduce the exciting current. As a result, the valve closing force of the pressure control valve 67 decreases, and the valve is opened with the pressure in the high-pressure chamber 65c relatively low, and the discharge pressure of each cylinder is maintained at a low value. For this reason, the fluctuation of the pump driving torque in the resonance rotation speed region is reduced, and the load on the pump driving system is reduced.

In this embodiment, when the pressure of the high-pressure chamber 65c becomes larger than the urging force of the solenoid 67b, the pressure-feed control valve 67 opens to connect the high-pressure chamber 65c to the low-pressure chamber 65b. On the other hand, when the high-pressure chamber 65c and the low-pressure chamber 65b communicate with each other, the pressure in the high-pressure chamber 65c decreases, so that the force pressing the valve body 67a in the valve opening direction decreases, and the pressure feed control valve 67 closes due to the urging force of the solenoid 67b. Give a valve. By the operation of the valve body, the pressure of the high-pressure chamber 65c (that is, the discharge pressure of the pump 5) is always maintained at a constant value corresponding to the urging force (excitation current) of the solenoid 67b. For this reason, the pressure control valve 67 of the present embodiment can be used as a discharge pressure control valve that can change the set pressure by adjusting the exciting current of the solenoid 67b.

While the embodiment of the present invention has been described with reference to the inner-cam type high-pressure fuel supply pump of the type shown in FIGS. 2, 3, 5 and 6, the present invention is not limited to this. Of course, it is also applicable to feed pumps and other types of cam plunger pumps. For example, the present invention is also applicable to a plunger pump as shown in FIG.

In FIG. 9, reference numeral 91 denotes a pump drive shaft, 93 denotes a cam provided around the drive shaft 91, 95 denotes a cylinder arranged radially around the drive shaft 91, and 97 denotes a cylinder driven by the cam 93. A plunger that reciprocates in 95 and a pump chamber 99 whose volume changes due to the reciprocation of the plunger 97. Further, reference numeral 101 in FIG. 9 denotes a suction passage communicating the pump chamber 99 and the low-pressure feed pump 9 via the suction check valve 103 when the plunger 97 is in the suction stroke. The pump chamber 99 via the pressure check valve 107
2 shows a pressure-feeding passage that communicates with the pressure-feeding passage 107.
A pressure control valve (electromagnetic opening / closing valve) 110 is provided between the pressure feed passage 107 and the common rail 3 to return fuel in the pressure feed passage 105 to a fuel tank (not shown) or the suction passage 101 through a return passage 109 when the valve is opened. Have been. In the pump of the type shown in FIG. 9 as well, the same effects as those of the above-described embodiments can be obtained by setting the profile of the cam 93 and the arrangement of the cylinder 95 as described in FIGS. It is.

[0046]

According to the fuel supply device for a common rail described in each claim, the same fuel supply pump can be commonly used for engines having different numbers of cylinders, and fluctuations in pump driving torque can be reduced. A common effect is achieved. Further, according to the fuel supply device for a common rail according to the second aspect, in addition to the above-described common effects, an effect is provided in which the pressure for feeding the fuel to the common rail can be controlled in accordance with the operating state of the engine.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of an embodiment when the present invention is applied to an internal combustion engine for a vehicle.

FIG. 2 is a cross-sectional view showing a configuration of an example of an inner-cam high-pressure fuel supply pump used in the fuel supply device of FIG.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a diagram illustrating a change in the total pumping amount of the pump in FIGS. 2 and 3;

FIG. 5 is a cross-sectional view showing the configuration of another example of the inner-cam high-pressure fuel supply pump used in the fuel supply device of FIG.

FIG. 6 is a sectional view taken along the line VI-VI of FIG. 5;

FIG. 7 is a view similar to FIG. 4, illustrating a change in the total pumping amount of the pumps of FIGS. 5 and 6;

FIG. 8 is a diagram showing a configuration of another example of the inner-cam type high-pressure fuel supply pump used in the fuel supply device of FIG. 1;

9 is a diagram showing a schematic configuration of another example of the high-pressure fuel supply pump used in the fuel supply device of FIG. 1, which is different from FIGS.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fuel injection valve 3 ... Common rail (accumulation chamber) 5 ... Inner cam type high pressure fuel supply pump 20 ... ECU 51 ... Inner cam ring 53 ... Pintle 59 ... Cylinder 67 ... Pressure feed control valve

Claims (2)

[Claims] 1. A common rail fuel supply device for supplying pressurized fuel to a common rail connected to a fuel injection valve of an internal combustion engine, wherein the fuel supply device is reciprocated in each cylinder by being pushed by a plurality of cylinders and a cam. A plunger, a pump chamber formed in each cylinder and having a volume that changes according to the reciprocating motion of the plunger;
A pumping passage communicating with the pump chamber when each cylinder is in a pumping stroke in which the volume of the pump chamber is reduced; and a pumping passage communicating with the pump chamber when each cylinder is in a suction stroke in which the volume of the pump chamber is increasing. A fuel pump provided with a suction passage connecting a source, and a pumping amount control means disposed between the pumping passage and the common rail, communicating with the pumping passage and the common rail, and shutting off the pumping amount. The cam and the cylinder of the fuel pump are configured to maintain the total amount of fuel discharged from the pump chamber of each cylinder to the pumping passage per unit operation amount of the pump substantially constant throughout the entire operation cycle of the pump, The pumping amount control means controls the fuel supply amount to the common rail by connecting the pumping passage and the common rail for a predetermined time. Fuel supply system of Nreru. 2. The pumping amount control means includes an electromagnetic on-off valve disposed between the pumping passage and the common rail, and when the electromagnetic on-off valve closes against fuel pressure in the pumping passage. The pressure passage and the common rail communicate with each other,
When the electromagnetic on-off valve is opened, the pumping passage and the common rail are shut off, and the pumping amount control means controls the exciting current to adjust the valve closing force of the electromagnetic on-off valve so that the pumping passage is separated from the pumping passage. The fuel supply device for a common rail according to claim 1, wherein the pressure of the fuel fed to the common rail is adjusted.