JP2004156544A - Fuel injection device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify the structure of a fuel injection device by using a two-way valve in a boost mechanism, to improve the reliability and stability of operation by directly controlling the pressure of a piston actuating chamber, and to reduce the loss of an actuating fluid for actuating the boost mechanism. <P>SOLUTION: The boost mechanism 5 is placed between an accumulator 4 where a fuel from a fuel pump 1 is discharged and an injection mechanism 6. The piston actuating chamber 55 of the booster mechanism 5 is connected to the accumulator 4 through a supply channel 23 and a diaphragm 31. The boost control valve 32 having a two-way valve applies and discharges a pressure to and from the piston actuating chamber 55 to drive a piston with a large diameter and a plunger with a small diameter, thereby boosting the fuel of a plunger chamber 56. A control device 7 achieves desired injection by opening and closing the boost control valve 32 to control the boost action. Further, since the boost control valve 32 allows prompt pressure discharge from the piston actuating chamber 55, the boost control valve 32 is controlled to minimize a valve opening time so as to suppress fuel discharge and reduce energy loss. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel injection device for an internal combustion engine having a pressure increasing mechanism, and more particularly, to control of a pressure increasing operation by the pressure increasing mechanism.
[0002]
[Prior art]
From the viewpoint of preventing global warming, a diesel engine that emits less CO ₂ has been attracting attention. For diesel engines, it has become an important issue to purify exhaust gas, and as a countermeasure, it has been required to increase the fuel injection pressure. In order to easily realize this, a fuel injection device including a pressure intensifier for increasing the pressure of the fuel supplied from the fuel pump has been proposed, which enables high-pressure injection without increasing the size of the device. (For example, Patent Document 1).
[0003]
[Patent Document 1]
German Patent Application Publication No. 199 10 970
In Patent Literature 1, a piston for increasing the pressure of fuel in a pressure intensifier and a piston working chamber for operating the piston are provided to increase the pressure of the fuel as the piston is driven. The introduction of pressure into the piston working chamber and the control for releasing the pressure in the piston working chamber to the drain passage are performed by a two-position three-way valve. Further, in another embodiment, a configuration for operating a piston by introducing pressure from a pressure source to a piston compartment provided on the opposite side of the piston working chamber is disclosed, and introduction of pressure to the piston compartment is disclosed. , And the opening to the drain passage are controlled by a two-position three-way valve.
[0005]
[Problems to be solved by the invention]
However, the three-way valve used for controlling the pressure intensifier in Patent Literature 1 requires two seat portions, and has a problem that the configuration is complicated and expensive. Patent Literature 1 also discloses an embodiment in which a two-position two-way valve is connected to a piston compartment to switch communication with a drain passage, and pressure is introduced into the piston compartment from a pressure source via a throttle. Since the control valve is a two-way valve and the number of seats may be one, the configuration is simplified. However, in a system in which the piston compartment is controlled by a control valve (two-way valve or three-way valve), the pressure intensifier is hydraulically balanced in the process of returning the piston. For this reason, the return force of the piston relies on the spring force, which is small compared to the hydraulic pressure, and there is a problem in the reliability and stability of the operation. Normally, control is performed so that the process immediately returns to the returning process after the pressure increasing process of the piston. However, depending on the configuration, waste of the working fluid used for driving the pressure intensifier increases, resulting in a large energy loss. There was a problem.
[0006]
In the present invention, the use of a two-way valve for the pressure increasing mechanism of the fuel injection device simplifies the configuration, and improves the reliability and stability of operation by directly controlling the pressure of the piston working chamber. Aim. Another object is to reduce the waste of the working fluid for operating the pressure increasing mechanism.
[0007]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a fuel injection device for an internal combustion engine, comprising: fuel supply means for delivering fuel; pressure increase means for increasing the pressure of fuel from the fuel supply means; and fuel from the fuel supply means or the pressure increase means. Injection means for injecting the pressurized fuel and control means for controlling the operation of the pressure increase means are provided. The pressure increasing means includes a large-diameter piston and a small-diameter plunger that slide together, a plunger chamber that is interposed between the fuel supply means and the injection means and expands or contracts in volume with the operation of the small-diameter plunger. A piston working chamber for applying a fluid pressure to the large-diameter piston, fluid supply means for supplying working fluid to the piston working chamber, and a two-way valve structure for pressurizing and releasing the fluid in the piston working chamber The control means controls the pressure increase operation by opening and closing the pressure increase control valve, and the opening time of the pressure increase control valve is shorter than the valve closing time. To control.
[0008]
When the control means opens and closes the pressure increase control valve to release the pressure in the piston working chamber and then pressurize the fuel, the fuel in the plunger chamber is increased due to the operation of the large diameter piston and the small diameter plunger. . Therefore, by operating the above-described injection means in response to this, high-pressure injection can be performed. When the injection means is operated while the pressure increase control valve is kept open or closed, low-pressure fuel is injected from the fuel supply means. Therefore, with a simple configuration using a two-way valve, the pressurization and release of the piston working chamber are directly controlled, and a reliable and stable operation can be realized. Further, while the pressure increasing control valve is open, the working fluid flows out, so that the working fluid is made shorter than the valve closing time, so that the waste of the working fluid can be reduced.
[0009]
In the invention described in claim 2, the pressure increase control valve is provided in a return passage from the piston working chamber or a fluid supply passage communicating the fluid supply means with the piston working chamber. Even if the pressure increase control valve is provided in the return passage to control outflow from the piston working chamber, the pressure increase control valve is provided in the fluid supply passage to control the outflow to the piston working chamber. In any configuration, the above effect can be obtained by operating as in claim 1.
[0010]
According to the third aspect of the present invention, the control means performs control such that the valve opening time of the pressure increase control valve is minimized in accordance with the injection request. Specifically, the injection pressure required according to the operating state of the internal combustion engine, when operating the pressure increase means so that the injection rate is, when the valve opening time of the pressure increase control valve is minimized, For example, after the low-pressure injection, just before the high-pressure injection is performed, by driving the pressure-intensifying means, it is possible to minimize the outflow of the working fluid and suppress the energy loss.
[0011]
According to the fourth aspect of the present invention, the on-off valve of the injection means can be controlled by a two-way valve or a three-way valve. For example, if a two-way valve is used to open and close between the back pressure chamber of the on-off valve and the return passage communicating with the passage from the pressure increasing means, the injection control can be performed with a simple configuration. Also, the port of the three-way valve may be connected to the passage from the pressure increasing means and the return passage, and the communication between these passages and the port to the back pressure chamber of the on-off valve may be switched, so that the fuel injection can be performed with good controllability. It can be performed.
[0012]
In the invention according to claim 5, the fuel supply means is used as the fluid supply means. The fuel from the fuel supply means can be used as the working fluid of the fluid supply means, and the pressure increasing means can be operated with a simpler configuration.
[0013]
In the invention according to claim 6, the fluid supply means is separate from the fuel supply means. Another pressure source provided in the internal combustion engine can be used as the fluid supply means, and the fuel consumption can be reduced.
[0014]
In the invention according to claim 7, an accumulator is provided in at least one of the fluid supply unit and the fuel supply unit. Thereby, the pressure in the fluid passage or the fuel passage can be further stabilized.
[0015]
In the invention described in claim 8, the same number of the injection means as the number of cylinders of the internal combustion engine are provided, and two or more of these injection means are supplied with the fuel whose pressure has been increased from the pressure increasing means. The high-pressure fuel increased in pressure by the pressure increasing means can be supplied to a plurality of injection means, and accurate injection control can be performed without increasing the size of the apparatus.
[0016]
According to the ninth aspect of the present invention, the number of the injection means and the number of the pressure increasing means are set to be equal to the number of cylinders of the internal combustion engine. The pressure increasing means may be provided corresponding to each of the injection means. Since the pressure increasing operation is performed for each cylinder, the stability is excellent and more accurate control is possible.
[0017]
According to a tenth aspect of the present invention, in the configuration of the eighth aspect, the injection means and the pressure increasing means are provided integrally. Accordingly, the injection means and the pressure increasing means are close to each other, so that the dead volume of the high pressure part can be reduced, and the energy loss can be further reduced.
[0018]
According to an eleventh aspect of the present invention, a throttle is provided in a fluid supply passage communicating the fluid supply means with the piston working chamber, and the pressure increase control valve is provided in a return passage from the piston working chamber. In this configuration, the piston working chamber is opened to the return passage by opening the pressure increasing control valve, and the working fluid quickly flows out, so that the operation of the pressure increasing means is excellent in reliability and stability. Further, the above control for shortening the valve opening time of the pressure increase control valve can reduce the waste of the working fluid, so that the effect of applying the present invention is high.
[0019]
According to a thirteenth aspect of the present invention, there is provided a fuel supply means for delivering fuel, a pressure increasing means for increasing the pressure of the fuel from the fuel supply means, and a fuel from the fuel supply means or a fuel which is increased in pressure by the pressure increasing means. And a fuel injection device for an internal combustion engine provided with an injection means for injecting fuel. The pressure increasing means includes a large-diameter piston and a small-diameter plunger that slide together, a plunger chamber that is interposed between the fuel supply means and the injection means and expands or contracts in volume with the operation of the small-diameter plunger. A fluid supply passage that has a piston working chamber for applying a fluid pressure to the large-diameter piston, and fluid supply means for supplying working fluid to the piston working chamber, and that communicates the fluid supply means with the piston working chamber. A throttle is provided, and a pressure increase control valve having a two-way valve structure is provided in a return passage from the piston working chamber. The pressure increasing operation is controlled by pressurizing and releasing the fluid in the piston working chamber.
[0020]
In the above configuration, when the pressure increase control valve is in an open state, the working fluid flows out from the piston working chamber to the return passage, so that the piston and the small-diameter plunger move in a direction to increase the volume of the plunger chamber. Move and stop. Next, when the pressure increase control valve is closed, the pressure of the piston working chamber is increased by the working fluid supplied from the throttle, so that the piston and the small diameter plunger reduce the volume of the plunger chamber. , The fuel is increased in pressure and supplied to the injection means. At this time, if the injection means is operated, high-pressure injection is performed.
[0021]
Therefore, with a simple configuration using the above-described pressure increase control valve composed of a two-way valve and a throttle, the pressure increase operation can be controlled and the high-pressure injection and the low-pressure injection can be arbitrarily switched. Injection according to the operation state of the internal combustion engine can be realized.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the overall configuration of a fuel injection device for a diesel engine to which the present invention is applied. The main components are a fuel pump 1, a fuel tank 2, a pressure accumulator 4, a pressure booster 5, an injection mechanism 6, and a controller. 7. In the figure, a fuel pump 1 draws fuel from a fuel tank 2 through a filter 21 and sends pressurized fuel from a fuel passage 22 to an accumulator 4. A pressure increasing mechanism 5 is provided between the pressure accumulator 4 and the injection mechanism 6.
[0023]
As the fuel pump 1 as a fuel supply means, a known configuration having a mechanism for changing the discharge amount is used, and the control device 7 controls the discharge amount. The control device 7 monitors the pressure of the pressure accumulator 4 with a pressure sensor 71 attached to the pressure accumulator 4 and changes the discharge amount of the fuel pump 1 to accumulate a desired pressure.
[0024]
The pressure-intensifying mechanism 5 serving as a pressure-intensifying means includes a large-diameter piston 51 that can slide in a large-diameter bore 53 while maintaining oil-tightness, and a small-diameter plunger that can slide in a bore 54 while maintaining oil-tightness. The large-diameter piston 51 and the small-diameter plunger 52 are provided integrally with their axes aligned to function as a pressure-increasing piston. A space surrounded by the end surface of the large-diameter piston 51 (the end surface opposite to the plunger 52) and the large-diameter bore 53 forms a piston working chamber 55, and the piston working chamber 55 is defined by the supply passage 23 which is a fluid supply passage. It is connected to the accumulator 4. A throttle 31 is provided in the supply passage 23, and fuel as a working fluid is supplied to the piston working chamber 55 through the throttle 31.
[0025]
The piston working chamber 55 is connected to the fuel tank 2 by a return passage 12, and the return passage 12 is provided with a pressure increase control valve 32. The pressure increase control valve 32 is a two-position two-way valve, and controls the pressurization and release of the piston working chamber 55 by being switched and driven to the open position or the closed position by the control device 7.
[0026]
A plunger chamber 56 is formed on the discharge side of the pressure increasing mechanism 5 in a space surrounded by the end surface of the small-diameter plunger 52 (the end surface opposite to the piston 51) and the small-diameter bore 54. The plunger chamber 56 is connected to the fuel storage chamber 61 of the injection mechanism 6 by the fuel supply path 15. Further, the low-pressure supply path 13 branched from the supply path 23 is connected to the fuel supply path 15 via the check valve 14, so that the fuel from the accumulator 4 flows from the low-pressure supply path 13 to the plunger chamber 56. While being supplied, it is also delivered to the fuel storage chamber 61 of the injection mechanism 6. The plunger chamber 56 expands and contracts in volume with the operation of the large-diameter piston 51 and the small-diameter plunger 52, and increases the pressure of the fuel supplied from the low-pressure supply passage 13.
[0027]
The injection mechanism 6 as an injection means has a nozzle needle 62 which is an opening / closing valve for opening and closing the injection hole 66, and a nozzle control chamber 65 for applying a pressure to the nozzle needle 62 in a valve closing direction. The nozzle needle 62 is slidable inside the nozzle body 63 while keeping oil tight, and a nozzle control chamber 65 is formed by the upper end surface of the nozzle needle 62 and the bore 64. The nozzle control chamber 65 communicates with the fuel supply path 15 via the throttle 16, and communicates with the return passage 18 leading to the fuel tank 2 via the throttle 17. The return passage 18 is provided with an injection control valve 11 composed of a two-position two-way valve.
[0028]
The operation of the fuel injection device having the above configuration will be described with reference to FIG. In FIG. 1, a desired pressure (for example, a pressure of 30 MPa) is accumulated in the accumulator 4 by the control device 7 increasing or decreasing the discharge amount of the fuel pump 1 based on the detection result of the pressure sensor 71. This fuel is supplied to the pressure increasing mechanism 5 and the injection mechanism 6. The control device 7 controls the fuel injection from the injection mechanism 6 according to the operating state of the engine, and controls the injection pressure by controlling the operation of the pressure increasing mechanism 5 in synchronization with the fuel injection. The pressure increasing mechanism 5 opens and closes the pressure increasing control valve 32 to control the lift of the pressure increasing piston, so that the fuel from the pressure accumulator 4 can be increased in pressure and supplied to the injection mechanism 6 at a desired timing. .
[0029]
When the pressure increasing control valve 32 is opened in a state where the fuel from the fuel pump 1 is accumulated in the pressure accumulator 4 (at the time point a in FIG. 2), the throttle 31 is passed through the piston working chamber 55 of the pressure increasing mechanism 5. Fuel flows in from the accumulator 4 and flows out to the return passage 12 through the pressure increase control valve 32. Here, if the throttle area of the seat portion of the pressure increase control valve 32 is set to be larger than the throttle 31, the outflow becomes larger, and the pressure in the piston working chamber 55 is reduced to substantially the atmospheric pressure. The fuel in the pressure accumulator 4 can also flow into the plunger chamber 56 by opening the check valve 14 through the low-pressure supply passage 13 at the same time, so that the plunger 52 having a smaller diameter faces upward than the force received by the piston 51 having a large diameter downward. The force that is received is greater. For this reason, the large-diameter piston 51 and the small-diameter plunger 52 move upward in the drawing (in a direction in which the volume of the plunger chamber 56 is increased) as a substantially integral pressure-increasing piston, and then stop (see FIG. 2B). Time).
[0030]
At this time, the pressure of the plunger chamber 56 becomes substantially the same as that of the pressure accumulator 4, for example, 30 MPa due to the inflow of fuel from the low-pressure supply passage 13. In this state, if the injection control valve 11 is closed, the pressure of the fuel supply passage 15, the fuel storage chamber 61, and the piston working chamber 55 becomes the same as that of the accumulator 4. Here, the force that the nozzle needle 62 receives upward from the fuel storage chamber 61 is smaller than the downward force that is received from the nozzle control chamber 65 because the pressure receiving area is smaller by the inside of the seat. As a result, the nozzle needle 62 is pressed downward, the injection hole 66 is closed, and the injection mechanism 6 enters a non-injection state.
[0031]
At this time, when the injection signal is output from the control device 7 to the injection mechanism 6 and the injection control valve 11 is opened, the fuel in the nozzle control chamber 65 is released from the return passage 18 through the throttle 17 to the fuel tank 2. On the other hand, the fuel from the fuel supply passage 15 flows into the nozzle control chamber 65 through the throttle 16, but by setting the throttle 17 to be larger than the throttle 16, the pressure in the nozzle control chamber 65 can be set to substantially the atmospheric pressure. it can. In this state, the upward force is increased despite the difference in the pressure receiving area, so that the nozzle needle 62 is displaced upward. As a result, the injection hole 66 is opened, and the fuel supplied to the fuel storage chamber 61 at the same pressure (for example, a pressure of 30 MPa) as the pressure accumulator 4 is injected from the injection hole 66.
[0032]
Next, when the injection control valve 11 is again closed, the flow of fuel from the return passage 18 to the fuel tank 2 stops, so that the pressure in the nozzle control chamber 65 increases, and the nozzle needle 62 descends to inject the fuel. The hole 66 is closed and the injection is stopped. That is, when the pressure increase control valve 32 is in the open state, the non-injection state is maintained, and the injection control valve 11 is operated to perform the injection at the pressure of the accumulator 4 of, for example, 30 MPa. Is possible.
[0033]
Next, when the pressure increase control valve 32 is closed in the non-injection state (at the time point c in FIG. 2), the flow of fuel from the piston working chamber 55 of the pressure increase mechanism 5 to the return passage 12 stops, and the throttle 31 Only the inflow through. For this reason, the pressure in the piston working chamber 55 becomes substantially the same as that of the accumulator 4 (for example, 30 MPa), and the force that the large-diameter piston 51 receives downward due to the pressure in the piston working chamber 55 is reduced by the plunger chamber 56 into the small-diameter plunger. Since the force exerted on the piston 52 is larger than the upward force, the large-diameter piston 51 and the small-diameter plunger 52 are displaced downward (in the direction of reducing the volume of the plunger chamber 56) as a unitary body.
[0034]
At this time, if the pressure receiving area ratio is set to, for example, 5: 1, the pressure of the plunger chamber 56 is increased to, for example, 150 MPa. The fuel whose pressure has been increased is prevented from flowing backward by a check valve 14 provided in the low-pressure supply passage 13, and is supplied to the fuel storage chamber 61 of the injection mechanism 6 through the fuel supply passage 15.
[0035]
Here, when the injection signal is given from the control device 7 to the injection mechanism 6 to open the injection control valve 11 (at the time point d in FIG. 2), as described above, the pressure in the nozzle control chamber 65 becomes substantially atmospheric pressure. As a result, the nozzle needle 62 opens, and fuel is injected at a high pressure of, for example, 150 MPa. Next, when the injection control valve 11 is closed (time point e in FIG. 2), the injection is stopped. That is, by operating the injection mechanism 6 corresponding to the pressure increasing operation by the pressure increasing mechanism 5, fuel injection at a high pressure becomes possible.
[0036]
If the pressure increase control valve 32 is opened at a predetermined timing after the desired injection (at a time point f in FIG. 2), the fuel flows out from the piston working chamber 55, and the pressure is reduced. Become. Then, the large-diameter piston 51 and the small-diameter plunger 52 are again displaced upward in the drawing (return stroke), and accordingly, the plunger chamber 56 is refilled with fuel from the low-pressure supply passage 13 and the next increase. Be prepared for the pressure stroke.
[0037]
After the injection, the timing at which the pressure increase control valve 32 is opened is preferably such that the valve opening time of the pressure increase control valve 32 is shorter than the valve closing time, preferably immediately before performing high-pressure fuel injection. It is desirable that the valve opening time of the control valve 32 be as short as possible. In the conventional configuration, since the return stroke of the pressure-intensifying piston takes time, the control for starting the return stroke of the pressure-intensifying piston immediately after the injection is usually performed (dotted line in FIG. 2). For example, the outflow of fuel from the piston working chamber 55 is controlled by a two-way valve (pressure increase control valve 32), and can be quickly reduced to the atmospheric pressure, so that the start of the return stroke can be delayed. Specifically, the sum of the return time of the pressure boosting piston and the time at the top dead center (time A in FIG. 2) is shorter than the sum of the time of the pressure boosting stroke and the time at the bottom dead center. Good to do.
[0038]
In the above configuration of the present invention, while the pressure increase control valve 32 is open, fuel flows out of the accumulator 4 via the piston working chamber 55. By performing the above control, the outflow time is shortened. . For example, in the conventional configuration, control for opening the pressure increase control valve 32 immediately after injection is performed, and during that time (time indicated by B in FIG. 2), fuel continues to flow out. Since the valve opening time of the control valve 32 (the time indicated by A in FIG. 2) is significantly reduced, energy loss can be greatly reduced.
[0039]
According to the above configuration, by controlling the opening and closing of the pressure increase control valve 32 by the control device 7, low-pressure fuel or high-pressure fuel can be supplied to the fuel supply path 15. Injection control can be easily performed. For example, when the engine is at a low speed and a low load, the injection mechanism 6 is operated and the injection is performed at a low pressure without operating the pressure increasing mechanism 5. At medium speed and medium load, immediately after the minute injection at low pressure, the pressure increasing mechanism 5 is operated to perform injection at high pressure. This is a so-called pilot injection, and FIG. 2 shows a timing chart for two injections during the pilot injection. When the load is high, the pressure increasing mechanism 5 is operated to perform high-pressure injection. Alternatively, when the injection is started in a low pressure state and the pressure increase mechanism 5 is subsequently operated to perform the high pressure injection, so-called boot injection is performed.
[0040]
As described above, in the present invention, since the control of the injection by the injection mechanism 6 and the control of the pressure increase by the pressure increasing mechanism 5 can be arbitrarily selected so as to maintain a desirable relationship, the pressure and amount of the injection each time are controlled. , Frequency, interval, timing, etc. can be set freely. Therefore, stable injection can be obtained with extremely high degree of freedom, and injection can be performed in an optimal form according to the operating state of the engine. In addition, simpler or more complicated patterns other than the examples described above can be easily ejected. Moreover, since these controls are performed only by two two-way valves, ie, the pressure increase control valve 32 of the pressure increase mechanism 5 and the injection control valve 11 of the injection mechanism 6, the configuration can be simplified and the cost can be reduced.
[0041]
Further, in the conventional configuration, in order to control the pressure of the compartment 57 below the piston 51, the return process of the piston, which is performed in a substantially pressure-balanced state, according to the present invention, the pressure of the piston working chamber 55 is controlled by a two-way valve. Since the pressure can be easily released by the pressure increasing control valve 32, the piston working chamber 55 can be quickly and reliably performed in a substantially atmospheric pressure state. By utilizing this, in the present invention, the start of the return process of the large-diameter piston 51 is delayed, and control such that the valve opening time is shorter than the valve closing time can be easily performed. This can shorten the fuel outflow time from the accumulator 4 that occurs via the piston working chamber 55 due to the opening of the pressure increase control valve 32, and thus has the effect of reducing energy loss.
[0042]
In the embodiment described above, the working fluid supplied to the piston working chamber 55 for operating the pressure increasing mechanism 5 is used as fuel, and the fuel is supplied from the fuel pump 1 to the pressure increasing mechanism 5. The source can also be used to supply working fluids other than fuel. As another pressure source, for example, an oil pump may be used, and engine oil may be used as a working fluid. This is shown in FIG. 3 as a second embodiment of the present invention. In the drawing, engine oil is supplied from an oil tank 2a to an oil pump 1a via a filter 21a, and is pressurized and discharged to an accumulator 4a. The supply passage 23 downstream of the accumulator 4 a is connected to the piston working chamber 55 of the pressure increasing mechanism 5 via the throttle 31. On the other hand, the fuel supplied from the fuel tank 2b through the filter 21b is pressurized by the fuel pump 1b and discharged to the accumulator 4b. The low pressure supply path 13 downstream of the accumulator 4 b is connected to the plunger chamber 56 of the pressure increasing mechanism 5 and the fuel supply path 15 to the injection mechanism 6.
[0043]
Pressure sensors 71a and 71b are connected to the accumulators 4a and 4b, respectively, and the control device 7 controls the oil pump 1a and the fuel pump 1b based on the detection results. As described above, two pressure sources having the same configuration may be used, and no fuel is used for operating the pressure increasing mechanism 5, so that the fuel consumption can be reduced. Further, as shown by the dotted line in the figure, if the pressure increasing mechanism 5 and the injection mechanism 6 are provided integrally, the dead volume of the high-pressure portion is reduced because the two are close to each other, and the energy loss can be further reduced.
[0044]
In the above-described embodiment, the configuration in which one pressure increasing mechanism 5 is provided and the configuration in which the number of cylinders is provided are shown. However, for example, one pressure increasing mechanism 5 may be provided in two cylinders. It is possible. Further, the configurations of the injection mechanism 6 and other parts are not limited to those described in the above embodiment, and can be appropriately changed. For example, in the above embodiment, the injection control valve 11 of the injection mechanism 6 is a two-way valve, but a three-way valve may be used instead. FIG. 4 shows an example of an injection mechanism 6 ′ using a three-way valve. A three-way solenoid valve 67 serving as an injection control valve has one port communicating with the fuel supply path 15 and the other port communicating with the return path 18. The pressure in the nozzle control chamber 65 is increased or decreased by communicating any one of these ports with a port communicating with the nozzle control chamber 65. The three-way solenoid valve 67 and the nozzle control chamber 65 are connected via a throttle 68 and a check valve 69 so that the moving speed of the nozzle needle 62 can be controlled, and only when fuel flows into the nozzle control chamber 65. By opening the check valve 69, the nozzle needle 62 can be quickly closed.
[0045]
Further, in the above description of the operation, a constant value of, for example, 30 MPa was used as the pressure of the accumulator 4, but it is desirable to control the pressure by changing it to an optimum value, as in a common common rail injection system.
[Brief description of the drawings]
FIG. 1 is a hydraulic circuit diagram illustrating a configuration of a fuel injection device for a diesel engine according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a time chart of an example (pilot injection) of fuel injection control using the fuel injection device of the first embodiment.
FIG. 3 is a hydraulic circuit diagram illustrating a configuration of a fuel injection device for a diesel engine according to a second embodiment.
FIG. 4 is a diagram showing a configuration example of an injection mechanism using a three-way valve.
[Explanation of symbols]
1 fuel pump (fuel supply means, fluid supply means)
11 Injection control valve 18 Return passage 2 Fuel tank 23 Supply passage (fluid supply passage)
31 throttle 32 pressure increase control valve 5 pressure increase mechanism (pressure increase means)
51 Large-diameter piston 52 Small-diameter plunger 55 Piston working chamber 56 Plunger chamber 6 Injection mechanism (injection means)
7 control device (control means)

Claims (13)

A fuel supply means for delivering fuel, a pressure increasing means for increasing the pressure of the fuel from the fuel supply means, an injection means for injecting the fuel from the fuel supply means or the fuel intensified by the pressure increasing means, A fuel injection device for an internal combustion engine including control means for controlling operation of a pressure increasing means, wherein the pressure increasing means includes a large-diameter piston and a small-diameter plunger which slide together, the fuel supply means and the fuel supply means. A plunger chamber that is interposed between the injection means and expands and contracts in volume with the operation of the small-diameter plunger, a piston operating chamber that applies fluid pressure to the large-diameter piston, and supplies a working fluid to the piston operating chamber. A fluid supply means, and a pressure increase control valve having a two-way valve structure for pressurizing and releasing the fluid in the piston working chamber. The control means opens and closes the pressure increase control valve to increase the pressure. Control the operation and A fuel injection system for an internal combustion engine and controls as opening time of the pressure increase control valves is shorter than the closing time. 2. The fuel injection device for an internal combustion engine according to claim 1, wherein the pressure increase control valve is provided in a return passage from the piston working chamber or a fluid supply passage communicating the fluid supply means with the piston working chamber. 3. The fuel injection device for an internal combustion engine according to claim 1, wherein the control unit controls the valve opening time of the pressure increase control valve to be minimized in accordance with an injection request. 4. The fuel injection device for an internal combustion engine according to claim 1, wherein the on-off valve of the injection means is controlled by a two-way valve or a three-way valve. 5. The fuel injection device for an internal combustion engine according to claim 1, wherein said fuel supply means is used as said fluid supply means. 5. The fuel injection device for an internal combustion engine according to claim 1, wherein the fluid supply unit is provided separately from the fuel supply unit. 7. The fuel injection device for an internal combustion engine according to claim 1, wherein an accumulator is provided in at least one of the fluid supply unit and the fuel supply unit. The fuel for an internal combustion engine according to any one of claims 1 to 7, wherein the number of the injection means is equal to the number of cylinders of the internal combustion engine, and the fuel whose pressure is increased from the pressure increasing means is supplied to two or more of the injection means. Injection device. 9. The fuel injection device for an internal combustion engine according to claim 1, wherein said injection means and said pressure increasing means are provided in the same number as the number of cylinders of the internal combustion engine. The fuel injection device for an internal combustion engine according to claim 9, wherein the injection means and the pressure increasing means are provided integrally. The internal combustion engine according to any one of claims 1 to 10, wherein a throttle is provided in a fluid supply passage communicating the fluid supply means with the piston working chamber, and the pressure increase control valve is provided in a return passage from the piston working chamber. Engine fuel injector. The fuel injection device for an internal combustion engine according to claim 11, wherein the control means performs control to open the pressure increase control valve immediately before the pressure increase operation by the pressure increase control valve. Fuel supply means for delivering fuel, pressure increasing means for increasing the pressure of the fuel from the fuel supply means, and injection means for injecting the fuel from the fuel supply means or the fuel increased by the pressure increasing means. Wherein the pressure increasing means comprises a large-diameter piston and a small-diameter plunger which slide together, and the small-diameter plunger interposed between the fuel supply means and the injection means. A plunger chamber that expands and contracts in volume with the operation of the piston, a piston working chamber that applies fluid pressure to the large-diameter piston, and a fluid supply unit that supplies working fluid to the piston working chamber. A throttle is provided in the fluid supply passage communicating with the piston working chamber, and a two-way valve pressure increasing control valve is provided in the return passage from the piston working chamber to apply the fluid in the piston working chamber. , For an internal combustion engine fuel injection system and controls the pressure increasing operation by release of the pressure.

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