JP2006170034A - Fuel injection device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a booster piston type fuel injection device using only one electromagnetic valve 7 due to cost-practicability and controlling a lift amount of a booster piston 5 and a lift amount of a nozzle needle of a fuel injection nozzle 1. <P>SOLUTION: When the electromagnetic valve 7 is changed from a first position to a second position, a throttle valve 6 expands an opening area of a fuel discharge passage 45-47 and therefore oil pressure in a piston control chamber 32 is lowered. This causes the booster piston 5 to start lifting and fuel introduced from a common rail 2 into a booster chamber 33 is pressurized. Oil pressure in a nozzle hole part is increased with a rise of oil pressure in the booster chamber 33. When the oil pressure in the nozzle hole part exceeds a sum of oil pressure and spring biasing force in a nozzle back pressure chamber, the nozzle needle of the fuel injection nozzle 1 is separated from a valve seat and fuel injection into the combustion chamber of a corresponding cylinder of an engine is started. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel injection device for an internal combustion engine, and in particular, a fuel pressure (jerk pressure) pumped from a fuel supply pump or a fuel pressure accumulated in a common rail. The present invention relates to a pressure-increasing piston type fuel injection device having a fuel pressure-increasing mechanism capable of increasing pressure more than (common rail pressure).

[Conventional technology]
In recent years, for example, regulations on exhaust gas purification of diesel engines have become stricter, and elucidation of the combustion phenomenon of diesel engines has progressed. Along with this, in order to make the exhaust gas discharged from the engine cleaner, in particular, the fuel injected from the nozzle hole portion of the fuel injection nozzle in order to reduce diesel particulates typified by black smoke (smoke) It is important to atomize to the limit. In order to promote the atomization of the fuel, it is effective to increase the fuel injection pressure. However, increasing the injection pressure in diesel engine fuel injection systems mounted on vehicles such as automobiles is approaching the limit. For example, even in common rail fuel injection systems, the demand for higher fuel injection pressure is extremely severe. Therefore, a value exceeding the pressure limit of a supply pump that supplies high pressure fuel into the common rail has been demanded.

  Thus, a pressure-increasing piston type fuel injection device having a fuel pressure-increasing mechanism for increasing the fuel injection pressure over the fuel pressure accumulated in the common rail (common rail pressure) has been proposed (for example, Patent Document 1). reference). This is because the pressure is increased when fuel is injected from the fuel injection nozzle, so that the injection rate immediately rises immediately after the nozzle needle of the fuel injection nozzle is opened, and the pressure of the increased pressure fuel is increased when the nozzle needle is closed. Since the nozzle needle is closed only by the urging force of the spring, it is not possible to use the valve, so that the decrease in the injection rate is moderate.

[Conventional technical problems]
However, in the pressure-increasing piston type fuel injection device described in Patent Document 1, the injection rate waveform is substantially trapezoidal, and an injection rate waveform (a square injection rate) that can make exhaust gas discharged from the engine cleaner. Waveform, boot type injection rate waveform, delta type injection rate waveform, etc.) could not be set. In particular, at the end of fuel injection, there is a problem that the occurrence of smoke and particulates cannot be suppressed by quickly closing the nozzle needle to improve the injection cut (sharp cut).

  Further, there has been proposed a pressure-intensifying piston type fuel injection device having a pressure-increasing piston for increasing the pressure of fuel in a pressure chamber in a cylinder in which a back pressure chamber, an intermediate chamber, and a pressure chamber are formed (for example, , See Patent Document 2). This is provided between the opening timing and closing timing of the injector-driven solenoid valve that controls the start and stop of fuel injection, and the flow path that connects the intermediate chamber and the fuel tank. By controlling the valve opening timing and valve closing timing of the booster piston solenoid valve to be controlled, the fuel injection rate waveform is switched between an injection rate waveform suppressing initial injection and a substantially rectangular injection rate waveform. Yes. In addition, by reducing the closing time of the booster piston solenoid valve earlier than the closing timing of the injector drive solenoid valve, the period or time during which high-pressure fuel acts on the injector is shortened, and the leaked fuel from the injector is reduced. is doing. However, in the pressure-increasing piston type fuel injection device described in Patent Document 2, two solenoid valves, ie, an injector-driven solenoid valve and a pressure-increasing piston solenoid valve are required. Therefore, the configuration is complicated, the number of parts is large, and the large-sized There is a problem of increasing the cost and cost.

From the above viewpoints, it is desirable that the pressure increasing piston type fuel injection device satisfies the following requirements. First, one solenoid valve is desirable because of cost feasibility. Secondly, it is desirable that the injection rate waveform can be set to at least two or more because of the restriction of exhaust gas purification, and the injection rate at the end of fuel injection is rapidly reduced. Third, it is desirable that the injection rate waveform shape can be switched, for example, between a square type and a boot type depending on the operating conditions of the engine. Fourth, it is desirable that the amount of fuel used does not greatly exceed the injection amount × pressure increase ratio (the amount of leaked fuel is small). Fifth, it is desirable that the entire system does not increase in size.
German Patent Application Publication No. 1012393917 JP 2003-148220 A (page 1-9, FIGS. 6 to 8)

  An object of the present invention is an internal combustion engine capable of controlling the lift amount of a pressure increasing piston and the lift amount of a nozzle needle while using only one actuator such as a solenoid valve because of cost feasibility. It is providing the fuel injection device for vehicles. Another object of the present invention is to provide a fuel injection device for an internal combustion engine that can control the shape of the injection rate waveform. Furthermore, it is providing the fuel-injection apparatus for internal combustion engines which can switch an injection rate waveform.

  According to the first aspect of the present invention, the valve device changes the opening area of the fluid introduction passage or the fluid discharge passage by driving the valve device through an electric operation by the actuator. When the fluid pressure in the piston back pressure chamber becomes larger than the fluid pressure in the piston control chamber, the pressure-increasing piston slidably accommodated in the cylinder lifts to the side that increases the oil pressure in the pressure-increasing chamber. As a result, the oil pressure of the fuel introduced from the fuel pumping means into the pressure-increasing chamber increases, so that the oil pressure of the fuel introduced from the pressure-increasing chamber into the nozzle oil reservoir of the fuel injection nozzle increases. When the oil pressure of the fuel introduced from the pressure increasing chamber into the nozzle oil reservoir of the fuel injection nozzle exceeds the nozzle opening pressure, the nozzle needle of the fuel injection nozzle is opened (the side that opens the nozzle hole, the valve opening) The fuel is injected from the fuel injection nozzle into the cylinder of the internal combustion engine.

  Therefore, by controlling the lift amount of the pressure increasing piston and the lift of the nozzle needle by driving the valve device through an electrical operation using the actuator while using only one actuator for cost feasibility. Therefore, the system configuration is simple, the number of parts is small, and the entire system can be downsized. Moreover, the shape of the injection rate waveform can be controlled while using only one actuator because of cost feasibility. For example, it is possible to obtain an optimal injection rate waveform corresponding to exhaust gas purification regulations. Furthermore, for example, since it is possible to switch to an optimal injection rate waveform corresponding to the operating conditions of the internal combustion engine while using only one actuator due to cost feasibility, the combustion state of the internal combustion engine is improved and emission is reduced. It can be improved and fuel consumption is reduced.

  According to the second aspect of the present invention, the fuel pressure increasing means is provided with the piston urging means for urging the pressure increasing piston to the opposite side to the pressure increasing pressure in the pressure increasing chamber. At the end of fuel injection, the lift position of the booster piston can be returned to the initial position. Further, the fuel injection nozzle is provided with a nozzle back pressure chamber for applying a fluid pressure in the valve closing direction to the nozzle needle, and needle urging means for urging the nozzle needle in the valve closing direction. The pressure can be set based on a force obtained by adding the urging force of the needle urging means to the fluid pressure in the nozzle back pressure chamber. That is, the nozzle valve opening pressure can be arbitrarily changed by changing the fluid pressure in the nozzle back pressure chamber or the urging force of the needle urging means.

  According to the invention described in claim 3, as the actuator, one electromagnetic actuator having a solenoid coil that generates a magnetomotive force when energized may be used. In this case, the valve device changes the opening area of the fluid introduction passage or the fluid discharge passage by driving the valve device according to the drive current value to the solenoid coil of the electromagnetic actuator. As a result, the amount of control fluid introduced into the piston back pressure chamber or the amount of control fluid discharged from the piston control chamber is adjusted, so that the fluid pressure in the piston back pressure chamber and the fluid pressure in the piston control chamber The pressure difference varies continuously or stepwise. As a result, the lift amount of the pressure-intensifying piston can be controlled by driving the valve device via an electric operation using the electromagnetic actuator while using only one electromagnetic actuator because of cost feasibility. And the control of the lift amount of the nozzle needle.

  According to the fourth aspect of the present invention, a fluid pressure actuated throttle valve interposed in the middle of the fluid introduction passage or the fluid discharge passage may be used as the valve device. Further, as the actuator, a solenoid coil that generates a magnetomotive force when energized and a solenoid valve having a valve element that operates in accordance with the magnetomotive force of the solenoid coil may be used. In this case, the valve body is operated in accordance with the magnetomotive force of the solenoid coil of the solenoid valve to introduce the control fluid introduced into the pressure control chamber of the throttle valve and the control fluid discharged from the pressure control chamber of the throttle valve. Adjust the amount of emissions. Then, the throttle valve changes the opening area of the fluid introduction passage or the fluid discharge passage according to the fluid pressure in the pressure control chamber. As a result, the amount of control fluid introduced into the piston back pressure chamber and the amount of control fluid discharged from the piston control chamber are adjusted, so that the fluid pressure in the piston back pressure chamber, the fluid pressure in the piston control chamber, The pressure difference varies continuously or stepwise. As a result, the lift of the pressure-increasing piston can be achieved by using a solenoid valve to drive a fluid pressure actuated throttle valve through electrical operation while using only one solenoid valve for cost feasibility. Control of the amount and control of the lift amount of the nozzle needle can be carried out.

  Here, the flow rate or flow rate of the control fluid introduced into the piston back pressure chamber or the control discharged from the piston control chamber is controlled by controlling the valve opening timing or valve closing timing and valve opening period or valve closing period of the solenoid valve. The lift start timing and the lift amount of the pressure increasing piston may be changed by controlling the flow rate or flow rate of the fluid. In this case, the pressure increase start timing, pressure increase rate (pressure increase amount per unit time) or pressure decrease rate (pressure decrease amount per unit time), and pressure increase end timing can be changed. The valve opening timing, the valve opening period, and the lift amount of the nozzle needle of the fuel injection nozzle are adjusted. Thus, by controlling the valve opening timing or valve closing timing and valve opening period or valve closing period of the electromagnetic valve, the injection timing, fuel injection amount and injection rate of the fuel injected from the fuel injection nozzle into the cylinder of the internal combustion engine It becomes possible to control the shape of the waveform.

  According to the invention described in claim 5, the electromagnetic valve has a first position for introducing the control fluid into the pressure control chamber of the throttle valve and a second position for discharging the control fluid from the pressure control chamber of the throttle valve. A position switching valve may be used. Thereby, since the opening area of the fluid discharge passage can be switched to at least two stages, the flow velocity or flow rate of the control fluid discharged from the piston control chamber can be switched to at least two stages. Therefore, since the lift amount of the pressure increasing piston can be increased in at least two stages, the lift amount of the nozzle needle can also be increased in at least two stages. As a result, for example, a boot-type injection rate waveform that reduces the combustion noise and vibration of the internal combustion engine and suppresses the initial injection rate for improving the emission of exhaust gas discharged from the internal combustion engine can be obtained. Note that the stroke amount of the throttle valve can be increased or decreased linearly (continuously or stepwise) with the position control of the two-position switching valve.

  According to the sixth aspect of the present invention, a flow rate control valve that varies the flow rate of the control fluid discharged from the pressure control chamber of the throttle valve may be used as the electromagnetic valve. Thereby, since the opening area of the fluid discharge passage can be switched continuously, the flow velocity or flow rate of the control fluid discharged from the piston control chamber can be switched continuously. Therefore, since the lift amount of the pressure increasing piston can be continuously increased, the lift amount of the nozzle needle can also be continuously increased. As a result, for example, a boot-type injection rate waveform that reduces the combustion noise and vibration of the internal combustion engine and suppresses the initial injection rate for improving the emission of exhaust gas discharged from the internal combustion engine can be obtained. Note that the stroke amount of the throttle valve can be increased or decreased linearly (continuously or stepwise) in accordance with the position control of the flow control valve. According to the seventh aspect of the present invention, the stroke amount (lift amount) of the throttle valve may be set in the range of 30 to 200 μm.

  According to the eighth aspect of the present invention, the throttle valve can change the opening area of the fluid introduction passage for introducing the control fluid into the piston back pressure chamber from the pressure source (high pressure side), for example. The flow rate or flow rate of the control fluid introduced into the chamber can be controlled. Alternatively, the flow rate or flow rate of the control fluid discharged from the piston control chamber can be controlled by varying the opening area of the fluid discharge passage for discharging the control fluid from the piston control chamber to the low pressure side.

  According to the ninth aspect of the present invention, the valve device is driven by an actuator through an electric operation so that the valve device has an area ratio between the opening area of the second fluid introduction passage and the opening area of the fluid discharge passage. To change. When the fluid pressure in the piston back pressure chamber becomes larger than the fluid pressure in the piston control chamber, the pressure-increasing piston slidably accommodated in the cylinder lifts to the side that increases the oil pressure in the pressure-increasing chamber. As a result, the oil pressure of the fuel introduced from the fuel pumping means into the pressure-increasing chamber increases, so that the oil pressure of the fuel introduced from the pressure-increasing chamber into the nozzle oil reservoir of the fuel injection nozzle increases. When the oil pressure of the fuel introduced from the pressure increasing chamber into the nozzle oil reservoir of the fuel injection nozzle exceeds the nozzle opening pressure, the nozzle needle of the fuel injection nozzle is opened (the side that opens the nozzle hole, the valve opening) The fuel is injected from the fuel injection nozzle into the cylinder of the internal combustion engine.

  Therefore, by controlling the lift amount of the pressure increasing piston and the lift of the nozzle needle by driving the valve device through an electrical operation using the actuator while using only one actuator for cost feasibility. Therefore, the system configuration is simple, the number of parts is small, and the entire system can be downsized. Moreover, the shape of the injection rate waveform can be controlled while using only one actuator because of cost feasibility. Furthermore, it is possible to switch to an optimum injection rate waveform corresponding to the operating conditions of the internal combustion engine, for example, while using only one actuator because of cost feasibility.

  According to the tenth aspect of the present invention, the valve device is driven by an actuator through an electric operation so that the valve device has an area ratio between the opening area of the second fluid introduction passage and the opening area of the fluid discharge passage. To change. As a result, the amount of control fluid introduced into the piston back pressure chamber or the piston control chamber or the amount of control fluid discharged from the piston control chamber is adjusted, so that the fluid pressure in the piston back pressure chamber and the piston control chamber are adjusted. The pressure difference from the fluid pressure varies continuously or stepwise. As a result, while using only one actuator for cost feasibility, the actuator is used to drive the valve device via an electric operation, thereby controlling the lift amount of the pressure increasing piston and the nozzle needle. The lift amount can be controlled.

  The best mode for carrying out the present invention is to obtain an optimal injection rate waveform corresponding to the regulations of exhaust gas purification while using only one actuator such as a solenoid valve because of cost feasibility. The purpose of switching to the optimum injection rate waveform corresponding to the operating conditions of the internal combustion engine is to adjust the fluid pressure in the piston back pressure chamber or the fluid pressure in the piston control chamber with an actuator such as a single solenoid valve. This was realized by controlling the lift amount of the booster piston and the lift amount of the nozzle needle.

[Configuration of Example 1]
FIGS. 1 to 8 show Embodiment 1 of the present invention, FIG. 1 is a diagram showing the overall configuration of a pressure-increasing piston type fuel injection device, and FIG. 2 is a diagram showing a schematic configuration of a fuel injection nozzle. FIG. 3 is a view showing a throttle valve.

  A fuel injection device for an internal combustion engine according to the present embodiment is a common rail fuel injection system as a fuel injection system for an internal combustion engine (hereinafter referred to as an engine) such as a multi-cylinder (4-cylinder) diesel engine mounted on a vehicle such as an automobile. It is applied to (accumulation type fuel injection device). In addition, the fuel injection device for the internal combustion engine is configured such that the fuel injection pressure from the fuel injection nozzle 1 is a fuel pressure (jerk pressure) pumped from a fuel supply pump (supply pump: not shown) or in the common rail 2. This is a pressure-increasing piston type fuel injection device provided with a fuel pressure-increasing mechanism that can increase the fuel pressure (common rail pressure) accumulated in the fuel. FIG. 1 shows in detail only the fuel injection nozzles 1 for one cylinder and the fuel system among the fuel injection nozzles 1 of each cylinder of the engine, and the other three fuel injection nozzles 1 are shown in the figure. Is omitted.

  The supply pump is rotationally driven by the engine, pressurizes the fuel pumped from the fuel tank 3 by a feed pump (not shown), and discharges the low-pressure fuel into the common rail 2. Here, the fuel discharge amount discharged from the supply pump is controlled based on a pump drive signal from an engine control unit (hereinafter referred to as ECU) (not shown). The supply pump changes the discharge pressure (jerk pressure) discharged from the supply pump by adjusting the fuel discharge amount discharged into the common rail 2 in accordance with the pump drive signal, and the fuel pressure (common rail pressure) in the common rail 2 is changed. ).

  As shown in FIGS. 1 and 2, the fuel injection nozzle 1 is connected to the downstream end of each fuel introduction path branched from the common rail 2, and directly injects and supplies high-pressure fuel into the combustion chamber of each cylinder of the engine. Thus, an electromagnetic fuel injection valve (injector) is configured together with a fuel pressure increasing mechanism mounted corresponding to each fuel injection nozzle 1. The fuel injection nozzle 1 includes a nozzle housing 11 attached to a cylinder block or cylinder head of an engine (corresponding to each cylinder), and a valve disposed inside the nozzle housing 11 so as to be slidable in the vertical direction in the figure. It has a nozzle needle 12 as a body and a spring 13 that urges the nozzle needle 12 in the valve closing direction.

  On the tip end side of the nozzle housing 11, a hemispherical top portion forming a nozzle injection hole portion (sack volume) 14 is provided. A plurality of nozzle holes 15 that communicate the inside of the nozzle nozzle hole part 14 with the outside (the combustion chamber of each cylinder of the engine) are provided at the top of the circle. A needle sliding hole 17 through which the large diameter portion 16 of the nozzle needle 12 slides is formed inside the nozzle housing 11. A first fuel flow path 22 is formed inside the nozzle housing 11 and communicates with the pressure increasing chamber 33 of the fuel pressure increasing mechanism via the fuel introduction path 21. In addition, a second fuel flow path 25 communicating with the branch pipe 19 of the common rail 2 through the fuel introduction passages 23 and 24 is formed inside the nozzle housing 11.

  The first fuel passage 22 communicates with a nozzle oil reservoir 26 formed below the large-diameter portion 16 of the nozzle needle 12 inside the tip side (nozzle body) of the nozzle housing 11. The second fuel flow path 25 is a nozzle back pressure provided on the back side (the upper end surface side in the drawing) of the large-diameter portion 16 of the nozzle needle 12 inside the rear end side (nozzle holder) of the nozzle housing 11. It communicates with the chamber 27. In addition, when the nozzle needle 12 reaches the maximum lift amount (full lift amount) inside the nozzle housing 11, a restricting portion that restricts movement toward the side where the plurality of nozzle holes 15 are opened (valve opening direction) is provided. It may be provided.

  The spring 13 is housed in the nozzle back pressure chamber 27 and is provided between the large diameter portion 16 of the nozzle needle 12 and the inner wall of the nozzle housing 11. It functions as a needle urging means for applying an urging force on the side of closing 15 (valve closing direction: downward in the figure). In addition, the oil pressure of the fuel introduced into the nozzle oil reservoir 26 is a needle that applies a force in the valve opening direction (upward in the drawing) to the pressure receiving surface (lower end surface in the drawing) of the large diameter portion 16 of the nozzle needle 12. It functions as a driving (pressing) means. Further, the oil pressure of the fuel introduced into the nozzle back pressure chamber 27 is a needle that applies a force in a direction to push down the pressure receiving surface (upper end surface in the drawing) of the large diameter portion 16 of the nozzle needle 12 in the valve closing direction (downward in the drawing). It functions as a driving (pressing) means. Here, the nozzle opening pressure can be set based on the force obtained by adding the urging force of the spring 13 to the oil pressure in the nozzle back pressure chamber 27. That is, the nozzle valve opening pressure can be arbitrarily changed by changing the oil pressure in the nozzle back pressure chamber 27 or the urging force of the spring 13.

  The common rail 2 accumulates fuel discharged from the supply pump and distributes fuel of a predetermined oil pressure to the nozzle oil reservoirs 26 of the plurality of fuel injection nozzles 1 mounted for each cylinder of the engine. It is. The fuel pressure accumulated in the common rail 2 (common rail pressure) is measured by a common rail pressure sensor (not shown) as fuel pressure detecting means. And between the common rail 2 and the nozzle oil sump part 26 of the some fuel injection nozzle 1, the injection pressure of the fuel injected into the combustion chamber of each cylinder of an engine from the some injection hole 15 of each fuel injection nozzle 1 Is provided with a fuel pressure increasing mechanism for increasing the pressure above the common rail pressure. The fuel pressure increasing mechanism is mounted for each cylinder of the engine, that is, for each fuel injection nozzle 1. The common rail 2 is provided with a branch pipe 19 corresponding to each fuel injection nozzle 1.

  The fuel pressure increasing mechanism of the present embodiment corresponds to the fuel pressure increasing means of the present invention, and includes a cylinder 4 having a piston back pressure chamber 31, a piston control chamber 32 and a pressure increasing chamber 33, and a slide inside the cylinder 4. A pressure-increasing piston 5 that is movably accommodated, a hydraulically operated throttle valve 6 that controls the lift amount of the pressure-increasing piston 5, a solenoid valve 7 that controls the stroke amount of the throttle valve 6, and these and fuel A fuel supply / discharge path for selectively communicating the injection nozzle 1, the common rail 2, and the fuel tank 3 is provided.

  Here, the fuel supply / discharge path is a first fuel introduction path for introducing fuel from the common rail 2 into the piston back pressure chamber 31 of the cylinder 4, and the inside of the piston control chamber 32 of the cylinder 4 via the electromagnetic valve 7 from the common rail 2. A second fuel introduction path for introducing fuel into the nozzle oil reservoir 26 of the fuel injection nozzle 1 from the common rail 2 via the pressure increasing chamber 33 of the cylinder 4 (fuel introduction path). 20, 21), a fourth fuel introduction path for introducing fuel from the common rail 2 to the pressure control chamber 37 of the throttle valve 6 via the electromagnetic valve 7, and the nozzle back pressure chamber 27 of the fuel injection nozzle 1 from the common rail 2 Has a fifth fuel introduction path (fuel introduction passages 23, 24) for introducing fuel into the fuel. The fuel supply / discharge path includes a first fuel discharge path for discharging fuel from the piston control chamber 32 of the cylinder 4 to the fuel tank 3 on the low pressure side via the throttle valve 6, and a pressure control chamber for the throttle valve 6. A second fuel discharge path for discharging fuel from inside 37 to the fuel tank 3 is provided.

  The pressure-increasing piston 5 has a large-diameter piston 34 that can slide while maintaining oil-tightness in a large-diameter bore formed in the cylinder 4, and an oil-tightness in a large-diameter bore formed in the cylinder 4. A small-diameter plunger 35 that can be kept and slid is provided, and the central axes of the large-diameter piston 34 and the small-diameter plunger 35 are substantially coincided with each other so as to be integrally operable. One large-diameter space surrounded by the illustrated upper end surface of the large-diameter piston 34 and the large-diameter bore of the cylinder 4 forms a piston back pressure chamber 31. The piston back pressure chamber 31 is always in communication with the branch pipe 19 of the common rail 2 via a fuel introduction passage (first fluid introduction passage) 41 that forms a first fuel introduction passage.

  The other large-diameter space surrounded by the lower end face (annular end face) of the large-diameter piston 34 and the large-diameter bore of the cylinder 4 forms a piston control chamber 32. The piston control chamber 32 communicates with the branch pipe 19 of the common rail 2 via a fuel introduction passage 23 that forms a second fuel introduction passage, fuel introduction passages (second fluid introduction passages) 42 and 43, and a fuel passage 44. Yes. The piston control chamber 32 communicates with the fuel tank 3 via a fuel passage 44 and fuel discharge passages (fluid discharge passages) 45 to 47 that form a first fuel discharge passage. A check valve 38 for preventing back flow of fuel is interposed in the middle of the fuel introduction passage 43, and a fixed throttle for reducing the cross-sectional area of the passage in the middle of the fuel discharge passage 46. (Orifice) 39 is interposed. Thereby, the fuel as the control fluid in the piston control chamber 32 is introduced (supplied) or shut off and discharged according to the control position of the spool valve 64 of the electromagnetic valve 7.

  A small-diameter space surrounded by the lower end surface (annular end surface) of the small-diameter plunger 35 and the small-diameter bore of the cylinder 4 forms a pressure increasing chamber 33. The pressure increasing chamber 33 communicates with the branch pipe 19 of the common rail 2 through the fuel introduction passage 20 that forms the third fuel introduction path. The pressure increasing chamber 33 communicates with the nozzle oil reservoir 26 of the fuel injection nozzle 1 through the fuel introduction passage 21 that forms the third fuel introduction path. The fuel introduction passage 20 is provided with a check valve 40 for preventing back flow of fuel. A return spring 36 is accommodated in the piston control chamber 32. The return spring 36 is provided between the large-diameter piston 34 of the pressure-increasing piston 5 and the inner wall of the cylinder 4, and applies a biasing force on the side (upward in the drawing) that returns the lift position of the pressure-increasing piston 5 to the initial position. Functions as a piston biasing means.

  Here, the hydraulic pressure in the pressure increasing chamber 33 pressurized by the pressure increasing piston 5 is a ratio between the pressure receiving area of the upper end surface of the large diameter piston 34 and the pressure receiving area of the lower end surface of the small diameter plunger 35 (pressure increasing ratio). ). For example, when the pressure receiving area ratio of the both end surfaces of the pressure increasing piston 5 is 2 to 3, when the oil pressure of 100 MPa is supplied from the common rail 2 into the pressure increasing chamber 33, the fuel injection nozzle 1 is supplied from the pressure increasing chamber 33. The high pressure fuel of 200 to 300 MPa is introduced into the nozzle oil reservoir 26.

  The throttle valve 6 corresponds to the valve device of the present invention, and includes a housing 52 having a pressure control chamber 37 and a valve hole 51, a valve body (valve) 53 that changes the opening area of the valve hole 51, and the valve 53. And a spring 54 that urges the valve hole 51 toward the side (lower side in the drawing) that reduces the opening area of the valve hole 51. The valve hole 51 is formed between the fluid discharge passages 45 and 46 that form the first fuel discharge path. An upper space surrounded by the illustrated upper end surface of the valve 53 and the wall surface of the housing 52 forms a pressure control chamber 37. The pressure control chamber 37 communicates with the branch pipe 19 of the common rail 2 through the fuel introduction passage 23, the fuel introduction passage 42, and the fuel passage 48 that form the fourth fuel introduction passage. The pressure control chamber 37 communicates with the fuel tank 3 via a fuel passage 48, a fuel discharge passage 49, and a fuel discharge passage 47 that form a second fuel discharge passage. Thereby, the fuel as the control fluid in the pressure control chamber 37 is introduced or discharged according to the control position of the spool valve 64 of the electromagnetic valve 7. The spring 54 is housed in the pressure control chamber 37 and is provided between the valve 53 and the inner wall of the housing 52. The needle 54 applies a biasing force in the valve closing direction (downward in the drawing) to the valve 53. It functions as an urging means.

  With the above configuration, the throttle valve 6 opens the valve hole 51 provided in the middle of the fuel discharge passages 45 to 47 when the valve 53 strokes in the axial direction corresponding to the fluid pressure in the pressure control chamber 37. By changing the area, the flow rate or flow rate of the fuel discharged from the piston control chamber 32 of the cylinder 4 can be controlled, so that the oil pressure in the piston control chamber 32 of the cylinder 4 can be controlled. As a result, the lift position of the pressure-increasing piston 5 can be controlled, so that the rate of increase in the oil pressure of the fuel that is increased in the pressure-increasing chamber 33 can be controlled.

In the throttle valve 6 of this embodiment, when the valve 53 is seated on an annular valve seat 55 provided inside the housing 52, the opening area of the valve hole 51 is 0 mm as shown in FIG. ² until the valve 53 reaches the pre-lift amount (for example, about 0.05 mm) from the valve seat 55 until the valve 53 is fitted to the inner diameter surface of the small-diameter hole 51a. When the clearance with the outer diameter surface of the portion (seat portion) 53a is small and the lift amount of the valve 53 becomes larger than the pre-lift amount, the inner diameter surface of the large diameter hole 51b of the valve hole 51 and the fitting portion ( The sheet portion 53a is configured to have a large clearance from the outer diameter surface. Thereby, the valve opening area characteristic with respect to the stroke amount (lift amount) of the throttle valve 6 of the present embodiment has a small opening area of the valve hole 51 from the beginning of the lift until the pre-lift amount is reached as shown in FIG. When the value takes a substantially constant value with respect to the increase in the lift amount and then becomes larger than the pre-lift amount, the opening area of the valve hole 51 takes a large value. The stroke amount (lift amount) of the throttle valve 6 may be set in the range of 30 to 200 μm.

  The electromagnetic valve 7 is an actuator that drives the valve 53 of the throttle valve 6 through electrical operation, and is magnetized when the solenoid coil 61 is energized, and a solenoid coil 61 that generates a magnetomotive force when energized. A stator core (not shown) and a moving core 63, a spool valve (valve element) 64 operating integrally with the moving core 63 in the axial direction, and a side (first position) where the spool valve 64 is seated on the valve seat. And a valve case 66 that houses the spool valve 64. The stator core is provided with a suction portion (not shown) for sucking the moving core 63. Further, the solenoid coil 61 functions as a valve body driving means for driving the spool valve 64 to the side (second position side) away from the valve seat. The spring 65 functions as a valve body urging means that urges the spool valve 64 to the side (first position side) where the spool valve 64 is seated on the valve seat.

  When the energization of the solenoid coil 61 is stopped (OFF), the solenoid valve 7 is positioned at the first position (initial position) where the spool valve 64 is seated on the valve seat of the valve case 66 by the urging force of the spring 65. Be controlled. In this first position, the first port of the switching chamber 67 provided in the valve case 66 is communicated with the fuel introduction passage 42, and the second port of the switching chamber 67 is communicated with the fuel introduction passage 43 and the fuel passage 48. In addition, when the solenoid coil 61 is energized (ON), the solenoid valve 7 attracts the moving core 63 to the suction portion of the stator core, so that the spool valve 64 resists the urging force of the spring 65. The position is controlled to the second position (full lift position) where the case 66 is separated from the valve seat. In this second position, the second port of the switching chamber 67 communicates with the fuel passage 48 and the third port of the switching chamber 67 communicates with the fuel discharge passage 49.

  As a result, the solenoid valve 7 has a first position where the first port and the second port of the switching chamber 67 communicate with each other by turning OFF and ON the solenoid coil 61, and the second port and the third port of the switching chamber 67. A two-position three-way switching valve for switching between the second position and the second position communicating with each other is configured. Further, the electromagnetic valve 7 increases or decreases the oil pressure in the pressure control chamber 37 of the throttle valve 6 in accordance with the position control of the spool valve 64, thereby reducing the stroke amount of the valve 53 of the throttle valve 6. The flow rate can be increased or decreased linearly in accordance with the flow rate or flow rate of the fuel discharged from the inside, or in accordance with the flow rate or flow rate of the fuel introduced into the pressure control chamber 37 and the biasing force of the spring 54.

  On the other hand, the ECU is provided with a known microcomputer configured to include functions such as a CPU that performs control processing and arithmetic processing, and various storage devices (memory such as ROM and RAM) that store various programs and data. . Further, the detection signal (voltage signal) from the common rail pressure sensor and the sensor signals from various other sensors are A / D converted by the A / D converter and then input to the microcomputer. Yes. Then, the ECU calculates an optimal fuel injection amount and fuel injection timing according to the operating state or operating conditions of the engine. Specifically, the engine rotation speed detected by a rotation speed detection means (not shown) such as a crank angle sensor and the accelerator opening detected by an engine load detection means (not shown) such as an accelerator opening sensor To calculate the basic injection amount.

  Next, the command injection amount is calculated by adding the injection amount correction amount considering the engine coolant temperature, the fuel temperature and the like to the basic injection amount. Next, the command injection timing is calculated from the engine speed and the accelerator opening. Alternatively, the command injection timing is calculated from the engine speed and the command injection amount. Next, the energization time (command injection period) to the solenoid coil 61 of the solenoid valve 7 of the fuel pressure increasing mechanism is calculated from the command injection amount and the common rail pressure. Instead of the common rail pressure, the oil pressure in the pressure increasing chamber 33 may be measured to calculate the energization time (command injection period) to the solenoid coil 61 of the solenoid valve 7.

[Operation of Example 1]
Next, the operation of the pressure-increasing piston type fuel injection device of this embodiment will be briefly described with reference to FIGS. Here, FIG. 5 and FIG. 6 are diagrams schematically showing injection pressure characteristics obtained by the pressure-increasing piston type fuel injection device of this embodiment.

  Here, the ECU of the present embodiment controls the position of the spool valve 64 of the electromagnetic valve 7 (first position: OFF or second position: ON), and changes the stroke amount of the throttle valve 6 to change the cylinder amount. The oil pressure in the four piston control chambers 32 can be controlled. As a result, the ECU can variably control the lift amount of the pressure-increasing piston 5, so that it can control the actual valve opening timing and the actual valve opening period of the fuel injection nozzle 1, and the fuel injection rate waveform. Can be switched as follows.

A) When energization of the solenoid coil 61 of the solenoid valve 7 is stopped (OFF) When energization of the solenoid coil 61 of the solenoid valve 7 is stopped (OFF), the spool valve 64 of the solenoid valve 7 is spring-loaded. Since the urging force of 65 is pressed to the first position where the valve case 66 is seated on the valve seat, the fuel introduction passage 23 → the fuel introduction passage 42 → the first port → the switching chamber 67 → the second port from the branch pipe 19 of the common rail 2 The fuel is introduced into the piston control chamber 32 of the cylinder 4 via the fuel introduction passage 43 → the fuel passage 44.

At this time, the pressure control chamber 37 of the throttle valve 6 passes from the branch pipe 19 of the common rail 2 through the fuel introduction passage 23 → the fuel introduction passage 42 → the first port → the switching chamber 67 → the second port → the fuel passage 48. Since the fuel is introduced, the valve 53 of the throttle valve 6 is seated on the valve seat 55, and the opening area of the valve hole 51 provided in the middle of the fuel discharge passages 45 to 47 is set to 0 mm ² . That is, the fuel discharge passages 45 to 47 are closed, and no fuel flows out from the piston control chamber 32 of the cylinder 4 to the fuel tank 3.

  On the other hand, since the fuel is introduced into the piston back pressure chamber 31 of the cylinder 4 from the branch pipe 19 of the common rail 2 via the fuel introduction passage 41, the fuel is introduced to both end surfaces of the large diameter piston 34 of the pressure increasing piston 5. The applied oil pressure becomes substantially the same, and the pressure-increasing piston 5 is positioned on the upper side in the figure in the large-diameter bore of the cylinder 4 by the urging force of the return spring 36 provided in the piston control chamber 32. Thereby, the lift amount of the pressure increasing piston 5 becomes 0 (initial position).

  Therefore, the inner volume of the pressure increasing chamber (volume variable space) 33 surrounded by the lower end surface of the small diameter plunger 35 of the pressure increasing piston 5 and the small diameter bore of the cylinder 4 becomes the widest state. The fuel cannot be increased. As a result, the fuel is introduced from the branch pipe 19 of the common rail 2 into the nozzle oil reservoir 26 of the fuel injection nozzle 1 via the fuel introduction passage 20 → the pressure increasing chamber 33 → the fuel introduction passage 21 → the first fuel passage 22. The oil pressure of the fuel is maintained at the common rail pressure. When the nozzle needle 12 is not open, as shown in FIGS. 7 and 8, the pressure in the nozzle injection hole 14 (nozzle injection hole pressure) is the common rail pressure (= fuel discharge pressure of the supply pump). Is a pressure equivalent to the cylinder pressure of the engine (for example, about 2 MPa).

  On the other hand, fuel is introduced into the nozzle back pressure chamber 27 of the fuel injection nozzle 1 from the branch pipe 19 of the common rail 2 via the fuel introduction passage 23 → the fuel introduction passage 24 → the second fuel passage 25. Therefore, the oil pressure in the nozzle back pressure chamber 27 of the fuel injection nozzle 1 also becomes the same common rail pressure as the oil pressure in the nozzle oil reservoir 26, and the nozzle needle 12 of the fuel injection nozzle 1 is driven by the biasing force of the spring 13. Since it is pressed against the valve seat of the nozzle housing 11, the communication state between the nozzle oil reservoir 26 and the nozzle injection hole 14 is blocked, and the plurality of injection holes 15 cannot be opened. Fuel injection into the combustion chamber of the cylinder is not performed.

B) When the shape of the injection rate waveform is a square type When the piston position of the cylinder of the engine is near the top dead center and the command injection timing of the cylinder of the engine is reached, as shown in FIG. The energization (ON) of the solenoid coil 61 is started. Then, since the stator core and the moving core 63 are magnetized, the moving core 63 is attracted to the attracting portion of the stator core against the urging force of the spring 65. As a result, the spool valve 64 of the electromagnetic valve 7 is controlled to the second position (full lift position) where the spool valve 64 separates from the valve seat of the valve case 66 against the urging force of the spring 65, and therefore the branch pipe 19 of the common rail 2. The fuel introduction passages 42 and 43 for introducing fuel into the piston control chamber 32 of the cylinder 4 are blocked.

  At this time, the valve 53 of the throttle valve 6 is separated from the valve seat 55 and starts an upward stroke in the figure, so that the fuel in the pressure control chamber 37 of the throttle valve 6 depends on the stroke amount of the throttle valve 6. The fuel passage 48 is returned to the fuel tank 3 via the second port → the switching chamber 67 → the third port → the fuel discharge passage 49 → the fuel discharge passage 47. For this reason, the opening areas of the fuel discharge passages 45 to 47 are gradually expanded as the oil pressure in the pressure control chamber 37 decreases as shown in FIG.

  As a result, the fuel is returned from the piston control chamber 32 of the cylinder 4 to the fuel tank 3 via the fuel passage 44 → the fuel discharge passage 45 → the valve hole 51 → the fuel discharge passage 46 → the fuel discharge passage 47. At this time, the opening area of the fuel discharge passages 45 to 47 is restricted by the clearance between the inner periphery of the valve hole 51 of the throttle valve 6 and the outer periphery of the valve 53 and the orifice diameter of the fixed throttle 39 provided in the fuel discharge passage 46. Therefore, the flow rate of the fuel flowing out from the piston control chamber 32 of the cylinder 4 is limited, and the fuel is gradually discharged from the piston control chamber 32 of the cylinder 4.

  On the other hand, since the fuel is introduced into the piston back pressure chamber 31 of the cylinder 4 from the branch pipe 19 of the common rail 2 via the fuel introduction passage 41, the fuel is introduced to both end surfaces of the large diameter piston 34 of the pressure increasing piston 5. A pressure difference occurs in the applied oil pressure. That is, the amount of fuel introduced into the piston back pressure chamber 31 and the amount of fuel discharged from the piston control chamber 32 are adjusted according to the stroke amount of the throttle valve 6, so that the piston back pressure chamber The pressure difference between the oil pressure in 31 and the oil pressure in the piston control chamber 32 changes continuously or stepwise.

  When the force obtained by adding the urging force of the return spring 36 to the oil pressure in the piston control chamber 32 becomes smaller than the oil pressure in the piston back pressure chamber 31, the pressure increasing piston 5 starts to lift downward in the figure. . As a result, as shown in FIG. 5, the internal volume of the pressure increasing chamber 33 starts to narrow after a predetermined waiting time has elapsed since the start of energization (ON) to the solenoid coil 61 of the solenoid valve 7. The pressure increase of the fuel in the pressure increasing chamber 33 is started. For this reason, the increase in the oil pressure in the nozzle oil reservoir 26 of the fuel injection nozzle 1 is started.

  When the lift amount of the pressure increasing piston 5 becomes larger than a predetermined value, the oil pressure in the nozzle oil reservoir 26 of the fuel injection nozzle 1 is changed to the oil pressure in the nozzle back pressure chamber 27 of the fuel injection nozzle 1. When the force becomes larger than the force applied, the nozzle needle 12 of the fuel injection nozzle 1 starts to lift due to the oil pressure in the nozzle oil reservoir 26, and the nozzle needle 12 moves away (separates) from the valve seat.

  That is, when energization (ON) to the solenoid coil 61 of the solenoid valve 7 is started and the spool valve 64 of the solenoid valve 7 is switched from the first position to the second position, the valve 53 of the throttle valve 6 is connected to the fuel discharge passage. In order to increase the opening area of 45 to 47, the hydraulic pressure in the piston control chamber 32 begins to decrease. As a result, the force obtained by adding the urging force of the return spring 36 to the oil pressure in the piston control chamber 32 becomes smaller than the oil pressure in the piston back pressure chamber 31, so that the boosting piston 5 increases the fuel injection pressure. The lift to the pressure side (downward in the figure) is started, the internal volume of the pressure increasing chamber 33 is reduced, and the fuel introduced from the common rail 2 into the pressure increasing chamber 33 is increased from the common rail pressure (= jerk pressure). Is done.

  As the oil pressure in the pressure increasing chamber 33 increases, the oil pressure of the fuel introduced from the pressure increasing chamber 33 into the nozzle oil reservoir 26 increases, so that the internal pressure of the fuel injection nozzle 1 (nozzle oil) The oil pressure in the reservoir 26 starts to rise. Thereafter, the sum of the oil pressure in the push-down direction (valve closing direction) due to the fuel pressure in the nozzle back pressure chamber 27 and the urging force in the push-down direction (valve closing direction) due to the spring 13 is greater in the nozzle oil reservoir 26. When the oil pressure in the push-up direction (valve opening direction) due to the fuel pressure exceeds, the nozzle needle 12 moves away from the valve seat (starts lifting) and starts moving in the valve opening direction.

  Therefore, the fuel injection nozzle 1 opens the valve after a predetermined valve opening delay time has elapsed since the start of energization (ON) of the solenoid coil 61 of the solenoid valve 7 (actual valve opening timing). ). As a result, the nozzle oil reservoir portion 26 and the nozzle injection hole portion 14 communicate with each other, and a plurality of injection holes 15 provided on the front end side of the nozzle housing 11 are opened. Fuel injection into the combustion chamber is started. At this time, high-pressure fuel increased in pressure corresponding to the lift position of the pressure-increasing piston 5 is injected into the combustion chamber of the cylinder of the engine.

  Thereafter, when a command injection period corresponding to the command injection amount (a time for energizing the solenoid coil 61 of the solenoid valve 7) has elapsed from the command injection timing, as shown in FIG. 5, the solenoid coil 61 of the solenoid valve 7 is used. Stops energization to (OFF). Then, since the stator core and the moving core 63 are demagnetized, the position of the spool valve 64 of the electromagnetic valve 7 is controlled to the first position (initial position) where the solenoid valve 7 is seated on the valve seat of the valve case 66 by the urging force of the spring 65. For this reason, the fuel introduction passages 42 and 43 for introducing fuel from the branch pipe 19 of the common rail 2 into the piston control chamber 32 of the cylinder 4 are opened.

  That is, when energization of the solenoid coil 61 of the solenoid valve 7 is stopped (OFF) and the spool valve 64 of the solenoid valve 7 is switched from the second position to the first position, as described above, the valve of the throttle valve 6 While 53 reduces the opening area of the fuel discharge passages 45 to 47, the common rail pressure is introduced into the piston control chamber 32, and the oil pressure in the piston control chamber 32 begins to rise. When the force obtained by adding the urging force of the return spring 36 to the oil pressure in the piston control chamber 32 becomes larger than the oil pressure in the piston back pressure chamber 31, the pressure is increased while receiving the assist of the urging force of the return spring 36. The lift amount of the piston 5 is reduced, the internal volume of the pressure increasing chamber 33 is expanded, and the oil pressure in the pressure increasing chamber 33 starts to decrease.

  Thereafter, the sum of the oil pressure in the push-down direction (valve closing direction) due to the fuel pressure in the nozzle back pressure chamber 27 and the urging force in the push-down direction (valve closing direction) due to the spring 13 is greater in the nozzle oil reservoir 26. When the oil pressure in the push-up direction (valve opening direction) due to the fuel pressure falls, the nozzle needle 12 starts to move in the valve closing direction, and the nozzle needle 12 is seated on the valve seat.

  Therefore, the fuel injection nozzle 1 is closed after the predetermined valve closing delay time has elapsed since the energization of the solenoid coil 61 of the solenoid valve 7 is stopped (OFF) (actual valve closing timing). ). As a result, the communication state between the nozzle oil reservoir 26 and the nozzle injection hole 14 is cut off, so that the plurality of injection holes 15 are closed, and the fuel from the plurality of injection holes 15 into the combustion chamber of the cylinder of the engine Injection ends.

  As described above, when the position control of the solenoid valve 7 is performed only once, that is, when the energization ON / OFF of the solenoid valve 7 is performed only once during one injection stroke, as shown in FIG. In addition, a substantially rectangular (square type) injection rate waveform is obtained. Here, FIG. 7 is a diagram showing a simulation (experiment) result when a square-type injection rate waveform is obtained. In this simulation, the common rail pressure (jerk pressure) is set to 100 MPa and the pressure increase ratio is set to 2.5, and the energization ON and OFF of the solenoid valve 7 is controlled to obtain a square type injection rate waveform.

C) When the shape of the injection rate waveform is a boot type When the piston position of the cylinder of the engine is near top dead center and the command injection timing of the cylinder of the engine is reached, as shown in FIG. The energization (ON) of the solenoid coil 61 is started. Then, since the stator core and the moving core 63 are magnetized, the moving core 63 is attracted to the attracting portion of the stator core against the urging force of the spring 65. As a result, the spool valve 64 of the electromagnetic valve 7 is controlled to the second position (full lift position) where the spool valve 64 separates from the valve seat of the valve case 66 against the urging force of the spring 65, and therefore the branch pipe 19 of the common rail 2. The fuel introduction passages 42 and 43 for introducing fuel into the piston control chamber 32 of the cylinder 4 are blocked.

  As a result, when the electromagnetic valve 7 is switched from the first position to the second position, the oil pressure in the piston control chamber 32 decreases as described above, so that the pressure increasing piston 5 starts to lift, and the pressure increasing chamber. As the oil pressure in 33 rises, the oil pressure in the nozzle oil reservoir 26 rises, and the nozzle needle 12 moves away from the valve seat. Therefore, the fuel injection nozzle 1 opens the valve after a predetermined valve opening delay time has elapsed since the start of energization (ON) of the solenoid coil 61 of the solenoid valve 7 (actual valve opening timing). ). As a result, the nozzle oil reservoir portion 26 and the nozzle injection hole portion 14 communicate with each other, and a plurality of injection holes 15 provided on the front end side of the nozzle housing 11 are opened. Fuel injection into the combustion chamber is started. At this time, high-pressure fuel increased in pressure corresponding to the lift position of the pressure-increasing piston 5 is injected into the combustion chamber of the cylinder of the engine.

  Thereafter, when the first predetermined time has elapsed from the command injection timing, the energization of the solenoid coil 61 of the solenoid valve 7 is stopped (OFF) as shown in FIG. Thereafter, when the second predetermined time has elapsed (for example, when the actual opening timing at which the nozzle needle 12 is actually opened) is reached, as shown in FIG. Resume energization (ON). Thereafter, when a command injection period corresponding to the command injection amount (energization time for the solenoid coil 61 of the solenoid valve 7) elapses from the command injection timing, the solenoid coil 61 of the solenoid valve 7 as shown in FIG. Stops energization to (OFF).

  Therefore, the injection rate waveform when the position control of the electromagnetic valve 7 is performed twice or more, that is, the injection rate waveform when the energization ON / OFF of the electromagnetic valve 7 is performed twice or more in one injection stroke is shown in FIG. As shown in Fig. 2, it becomes a boot type. Here, FIG. 8 is a diagram showing a simulation (experiment) result when a boot-type injection rate waveform is obtained. In this simulation, the common rail pressure (jerk pressure) was set to 100 MPa and the pressure increase ratio was set to 2.5, and the energization ON / OFF of the solenoid valve 7 was repeated twice or more to obtain a boot-type injection rate waveform. ing.

  Here, in this embodiment, since the fuel injection from the fuel injection nozzle 1 into the combustion chamber of the cylinder of the engine is controlled by the oil pressure in the pressure increasing chamber 33, as shown in FIG. 6 and FIG. In order to obtain a boot-type injection rate waveform, it is necessary to obtain a low fuel injection pressure in the initial stage of fuel injection. That is, it is necessary to obtain a boot-type injection rate waveform in which the initial injection rate is suppressed by injecting low-pressure fuel at the beginning of the fuel injection period and injecting high-pressure fuel after a predetermined time has elapsed. For this reason, in this embodiment, the oil pressure in the piston control chamber 32 is controlled so that the oil pressure in the pressure increasing chamber 33 becomes a pressure slightly higher than the nozzle opening pressure, and then the piston control chamber 32. The throttle valve 6 is greatly stroked so that the internal oil pressure becomes substantially equal to the internal pressure (tank pressure) of the fuel tank 3, and the opening area of the fuel discharge passages 45 to 47 is controlled to be greatly expanded.

  Further, the valve opening area characteristics of the throttle valve 6 (throttle of the variable throttle valve) can be obtained so that a boot-type injection rate waveform can be obtained by performing the position control of the solenoid valve 7 (switching between energization ON and OFF) only once. Set the characteristics. That is, the stroke period that takes a substantially constant value may be lengthened. However, more preferably, as shown in the simulation results of FIGS. 7 and 8, when the position control of the solenoid valve 7 is performed only once, a square injection rate waveform is obtained (FIG. 5). (See FIG. 6) It is desirable to obtain a boot-type injection rate waveform when the position control of the electromagnetic valve 7 is performed twice or more.

  As a switching condition between the square type injection rate waveform and the boot type injection rate waveform, the engine speed and the command injection amount can be selected. Further, the flow rate of the fuel introduced from the common rail 2 into the piston control chamber 32 for the purpose of increasing the valve closing speed of the nozzle needle 12 of the fuel injection nozzle 1 and improving the injection cut (sharp cut) in the later stage of fuel injection. The flow rate of the fuel discharged from the piston back pressure chamber 31 may be increased. For example, a fuel discharge passage communicating with the fuel tank 3 on the low pressure side is connected to the fuel introduction passage 41 in, for example, a T-shape or a Y-shape, and a hydraulically-operated variable throttle valve or a hydraulically-operated A valve device such as a two-position switching valve is installed, or a valve device such as a hydraulically operated variable throttle valve is installed in the fuel introduction passages 42 and 43, and the electromagnetic valve 7 is electrically operated. By driving the valve device, it can be realized without adding an actuator such as a solenoid valve.

[Effect of Example 1]
As described above, in the pressure-increasing piston type fuel injection device of the present embodiment, the hydraulically operated type accompanies the position control of the electromagnetic valve 7 while using only one electromagnetic valve 7 because of cost feasibility. By controlling the stroke amount of the throttle valve 6, the opening area of the fuel discharge passages 45 to 47 for discharging the fuel as the control fluid from the piston control chamber 32 of the cylinder 4 to the fuel tank 3 is adjusted. The flow rate of the fuel discharged from the piston control chamber 32 to the fuel tank 3 can be controlled. As a result, the oil pressure in the piston control chamber 32 can be variably controlled, so that the pressure difference between the oil pressure in the piston back pressure chamber 31 and the oil pressure in the piston control chamber 32 is adjusted, and the return spring 36 The lift amount of the pressure increasing piston 5 of the fuel pressure increasing mechanism can be variably controlled against the urging force. The oil pressure of the fuel introduced into the nozzle oil reservoir 26 of the fuel injection nozzle 1 can be finely adjusted in accordance with the lift amount of the pressure increasing piston 5.

  Therefore, the control of the fuel injection amount injected and supplied from the plurality of nozzle holes 15 of the fuel injection nozzle 1 into the combustion chamber of the cylinder of the engine is performed using the piston of the fuel pressure increasing mechanism including the pressure increasing piston 5 having different diameters. This can be performed by controlling the internal pressure of the control chamber 32. That is, adjustment of the fuel injection amount injected from the fuel injection nozzle 1 can be performed by controlling the lift amount of the pressure-increasing piston 5 and controlling the pressure-increasing fuel pressure. The increased fuel pressure can be controlled by controlling the flow rate of the fuel discharged from the piston control chamber 32 to the fuel tank 3. As a result, control of the lift amount of the pressure increasing piston 5 of the fuel pressure increasing mechanism and control of the lift amount of the nozzle needle 12 of the fuel injection nozzle 1 can be performed, so the system configuration is simple and the number of parts is small. In addition, the entire system can be reduced in size.

  Further, during one injection amount control period of the cylinder (injector) of the engine, the electromagnetic valve 7 is turned ON / OFF only once, or is turned ON / OFF twice or more, so that the electromagnetic valve 7 By controlling the position of the spool valve 64, the shape of the injection rate waveform is controlled in accordance with the operating state or operating condition of the engine while using only one electromagnetic valve 7 for cost feasibility. be able to. For example, it is possible to obtain an optimal injection rate waveform (a boot-type injection rate waveform or a delta-type injection rate waveform) corresponding to exhaust gas purification regulations.

  Further, a control pattern (for example, the control position of the spool valve 64 is changed from the first position to the second position) in which the solenoid valve 7 is turned ON / OFF only once during the injection amount control period of the cylinder (injector) of the engine. → When switching to the first position in order to obtain a square-shaped injection rate waveform (see FIG. 5) and the control pattern of repeating the solenoid valve 7 ON and OFF twice or more (for example, the control position of the spool valve 64 is the first position → Switching between the second position, the first position, the second position, and the first position to obtain a boot-type injection rate waveform (see FIG. 6) is selected corresponding to the operating state or operating condition of the engine. Therefore, since only one solenoid valve 7 is used for cost feasibility, it can be switched to an optimal injection rate waveform corresponding to the operating state or operating condition of the engine, so that the combustion state of the engine is good. Ri, you can improve emissions, a low fuel consumption. Here, for example, when a boot-type or delta-type injection rate waveform is obtained, the initial injection rate can be suppressed at the start of fuel injection, so that the amount of nitrogen oxide emissions in the exhaust gas can be reduced. It becomes possible. In addition, for example, when a square-type, boot-type, or delta-type injection rate waveform is obtained, it is possible to improve the injection cut (sharp cut) at the end of fuel injection, thereby suppressing the occurrence of smoke and particulates. Is possible.

  Here, when the nozzle needle 12 of the fuel injection nozzle 1 is moved from the fully closed state to the valve opening direction (initial fuel injection), for example, the rate of increase in the oil pressure of the fuel in the nozzle oil reservoir 26 of the fuel injection nozzle 1 If the position control of the solenoid valve 7 is controlled so that the oil pressure of the fuel in the nozzle oil reservoir 26 of the fuel injection nozzle 1 is slightly increased from the nozzle opening pressure, for example, fuel injection starts. The initial injection rate at the time can be suppressed, and the discharge amount of nitrogen oxides (NOx) can be reduced. Further, when the nozzle needle 12 of the fuel injection nozzle 1 is moved from the fully opened state to the valve closing direction (late fuel injection period), for example, the oil pressure of the fuel in the nozzle oil reservoir 26 of the fuel injection nozzle 1 rapidly decreases. As described above, when the position control of the electromagnetic valve 7 is performed, the nozzle needle 12 of the fuel injection nozzle 1 can be quickly closed to improve the injection cut (sharp cut), and the generation of smoke and particulates can be suppressed. . Therefore, it is possible to reduce the emission of exhaust gas discharged from the engine.

  Further, for example, when fuel injection is not performed, the amount of fuel used can be reduced because the amount of leaked fuel can be reduced by preventing the high pressure fuel from leaking from the fuel injection nozzle 1 to the low pressure side. X The pressure increase ratio does not greatly exceed. Further, even if a fuel pressure increasing mechanism is mounted on the upper end of the fuel injection nozzle 1 shown in the drawing to form a single injector, only one electromagnetic valve 7 needs to be used. There is no increase in size.

  9 and 10 show a second embodiment of the present invention, FIG. 9 is a view showing a pressure-increasing piston type fuel injection device, and FIG. 10 is a view showing a valve opening area characteristic of a throttle valve. .

  In this embodiment, an electromagnetic flow control valve 9 capable of continuously and variably controlling the stroke amount of the throttle valve 6 is mounted. The electromagnetic flow control valve 9 is an electromagnetic actuator that drives the valve 53 of the throttle valve 6 through electrical operation. The solenoid coil 71 generates a magnetomotive force when energized, and the solenoid coil. A stator core 72 and a moving core 73 that are magnetized when energized 71, a valve (valve element) 74 that operates integrally with the moving core 73 in the axial direction, and a spring 75 that urges the valve 74 in the valve closing direction; And a valve case 76 for accommodating the valve 74. The stator core 72 is provided with a suction portion that sucks the moving core 73. Further, the solenoid coil 71 functions as a valve body driving means for driving the valve 74 to the side of increasing the opening area of the valve hole 77 provided at the upstream end of the fuel discharge passage 49 (the valve opening direction). Further, the spring 75 functions as a valve body urging means that urges the valve 74 toward the side (valve closing direction) that reduces the opening area of the valve hole 77.

  The electromagnetic flow control valve 9 controls the lift amount of the valve 74 according to the drive current value to the solenoid coil 71, thereby reducing the opening area of the valve hole 77 provided in the middle of the fuel discharge passages 50, 49, 47. This is variably controlled. By controlling the oil pressure in the pressure control chamber 37 of the throttle valve 6 in accordance with the variable control of the opening area of the valve hole 77, the stroke amount of the valve 53 of the throttle valve 6 is controlled by pressure control. The flow rate can be increased or decreased linearly in accordance with the flow rate or flow rate of the fuel discharged from the chamber 37 or in response to the flow rate or flow rate of the fuel introduced into the pressure control chamber 37 and the biasing force of the spring 54.

  Here, the valve opening area characteristic with respect to the stroke amount (lift amount) of the throttle valve 6 of the present embodiment is as shown in FIG. 10 from the initial stage of the lift until the pre-lift amount (for example, 0.1 mm) is reached. A substantially constant inclination with respect to an increase in the amount (the first inclination that makes the opening area of the valve hole 51 relatively small) and then becomes larger than the pre-lift amount, a substantially constant inclination with respect to the increase in the lift amount (The second inclination of the steeper angle than the first inclination, which makes the opening area of the valve hole 51 relatively large). A check valve 38 is interposed in the middle of the fuel introduction passage 43 of the present embodiment, and a fixed throttle (orifice) 79 for restricting the cross-sectional area of the passage is interposed in the middle of the fuel passage 48. Has been.

[Modification]
In this embodiment, the lift amount of the nozzle needle 12 of the fuel injection nozzle 1 mounted corresponding to each cylinder of an internal combustion engine (engine) such as a diesel engine is controlled, and corresponding to each fuel injection nozzle 1. The example using the electromagnetic valve 7 and the electromagnetic flow control valve 9 made up of a two-position three-way valve has been described as an actuator for controlling the lift amount of the pressure increasing piston 5 of the fuel pressure increasing mechanism. A piezoelectric actuator that performs an expansion / contraction operation corresponding to the above may be used.

  In this embodiment, the fuel injection device for an internal combustion engine according to the present invention is incorporated in a common rail fuel injection system and applied to a pressure increasing piston type fuel injection device including a pressure increasing piston 5. A pressure-increasing piston type fuel injection device of a type that does not have a pressure accumulator or pressure-accumulating piping such as 2 and that supplies low-pressure fuel directly from the fuel supply pump to the fuel injection nozzle 1 and the fuel pressure-increasing mechanism via the fuel supply piping It may be applied. In addition, as a fuel supply pump (fuel pumping means) for discharging low-pressure fuel, a row fuel injection pump or a distribution fuel injection pump may be used.

  In the present embodiment, the fuel injection nozzle 1 provided with a plurality of injection holes 15 in the circular top part forming the nozzle injection hole part (sack volume) 14 is adopted as the fuel injection nozzle. However, the nozzle needle 12 is used as the fuel injection nozzle. A fuel injection nozzle in which a plurality of injection holes are opened on the seat surface (valve seat) on which the seat is seated may be employed. In this case, a sack volume may or may not be provided. In addition, a command piston that is integrally linked to the nozzle needle 12 may be slidably installed in the nozzle housing 11 so that the command piston receives the oil pressure in the nozzle back pressure chamber 27. In addition, as a fuel injection nozzle, a variable injection hole nozzle that changes the opening area of the injection hole according to the lift amount of the nozzle needle, a twin needle type fuel injection nozzle, or the movement amount of the nozzle needle in two stages (prelift amount and full lift amount) A two-spring type fuel injection nozzle that switches between the two types may be adopted.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram showing an overall configuration of a booster piston type fuel injection device (Example 1). (A), (b) is sectional drawing which showed schematic structure of the fuel-injection nozzle (Example 1). (Example 1) which is sectional drawing which showed the hydraulically operated throttle valve. 6 is a graph showing an opening area of a fluid discharge passage with respect to a lift amount of a throttle valve (Example 1). 6 is a timing chart showing changes in the nozzle lift amount and the nozzle nozzle hole pressure (Example 1). 6 is a timing chart showing changes in the nozzle lift amount and the nozzle nozzle hole pressure (Example 1). 6 is a timing chart showing the simulation result of FIG. 5 (Example 1). (Example 1) which is the timing chart which showed the simulation result of FIG. (Example 2) which is the block diagram which showed the pressure increase piston type fuel-injection apparatus. (Example 2) which was the graph which showed the opening area of the fluid discharge passage with respect to the lift amount of a throttle valve.

Explanation of symbols

1 Fuel Injection Nozzle 2 Common Rail 3 Fuel Tank 4 Cylinder 5 Booster Piston 6 Hydraulically Operated Throttle Valve (Valve Device)
7 Solenoid valve (actuator, electromagnetic actuator, 2-position 3-way valve)
9 Electromagnetic flow control valve (actuator, electromagnetic actuator)
12 Nozzle needle (valve element) of fuel injection nozzle
13 Spring (needle biasing means)
26 Nozzle oil reservoir of fuel injection nozzle 27 Nozzle back pressure chamber of fuel injection nozzle 31 Piston back pressure chamber of cylinder 32 Piston control chamber of cylinder 33 Pressure increasing chamber of cylinder 34 Large diameter piston of pressure increasing piston 35 Pressure increasing piston Small-diameter plunger 36 Return spring (piston biasing means)
37 Pressure control chamber of throttle valve 41 Fuel introduction passage (fluid introduction passage, first fluid introduction passage)
42 Fuel introduction passage (second fluid introduction passage)
43 Fuel introduction passage (second fluid introduction passage)
46 Fluid discharge passage 47 Fluid discharge passage 61 Solenoid coil of solenoid valve (valve drive means)
64 Spool valve of solenoid valve (valve)
65 Solenoid valve spring (valve element biasing means)
71 Solenoid coil of electromagnetic flow control valve (valve element drive means)
74 Valve of electromagnetic flow control valve
75 Spring of electromagnetic flow control valve (valve biasing means)

Claims (10)

(A) fuel pumping means for discharging fuel;
(B) fuel pressure increasing means for increasing the pressure of the fuel introduced from the fuel pressure supplying means into the pressure increasing chamber;
(C) A fuel injection nozzle that lifts the nozzle needle to the valve opening side and injects fuel into the cylinder of the internal combustion engine when the oil pressure of the fuel introduced from the pressure increasing chamber into the nozzle oil reservoir exceeds the nozzle opening pressure In a fuel injection device for an internal combustion engine comprising:
The fuel pressure increasing means includes a cylinder having a piston back pressure chamber and a piston control chamber,
A pressure-intensifying piston that is slidably accommodated in the cylinder and lifts to a side that increases the oil pressure in the pressure-increasing chamber when the fluid pressure in the piston back-pressure chamber becomes larger than the fluid pressure in the piston control chamber; ,
A fluid introduction passage for introducing a control fluid into the piston back pressure chamber;
A fluid discharge passage for discharging a control fluid from the piston control chamber;
A valve device for changing an opening area of the fluid introduction passage or the fluid discharge passage;
A fuel injection device for an internal combustion engine, comprising: an actuator for driving the valve device through electrical operation. The fuel injection device for an internal combustion engine according to claim 1,
The fuel pressure-increasing means has piston urging means for urging the pressure-increasing piston in a direction opposite to a side in which the oil pressure in the pressure-increasing chamber is increased.
The fuel injection nozzle has a nozzle back pressure chamber for applying fluid pressure in the valve closing direction to the nozzle needle, and needle urging means for urging the nozzle needle in the valve closing direction,
The fuel injection device for an internal combustion engine, wherein the nozzle opening pressure is set based on a force obtained by adding an urging force of the needle urging means to a fluid pressure in the nozzle back pressure chamber. The fuel injection device for an internal combustion engine according to claim 1 or 2,
The actuator is one electromagnetic actuator having a solenoid coil that generates a magnetomotive force when energized,
The electromagnetic actuator drives the valve device in accordance with a drive current value to the solenoid coil, and introduces a control fluid introduced into the piston back pressure chamber or a control fluid discharged from the piston control chamber. A fuel injection device for an internal combustion engine, characterized by adjusting a discharge amount of the engine. The fuel injection device for an internal combustion engine according to claim 1 or 2,
The valve device includes a pressure control chamber into which a control fluid is introduced or a control fluid is discharged from the inside, and the fluid introduction passage or the fluid discharge corresponds to the fluid pressure in the pressure control chamber. A fluid pressure actuated throttle valve that varies the opening area of the passage,
The actuator is a single solenoid valve having a solenoid coil that generates a magnetomotive force when energized, and a valve body that operates in accordance with the magnetomotive force of the solenoid coil,
The solenoid valve operates the valve body according to the magnetomotive force of the solenoid coil, and introduces the amount of control fluid introduced into the pressure control chamber and the amount of control fluid discharged from the pressure control chamber. A fuel injection device for an internal combustion engine characterized by adjusting. The fuel injection device for an internal combustion engine according to claim 4,
The electromagnetic valve is a two-position switching valve having a first position for introducing a control fluid into the pressure control chamber and a second position for discharging the control fluid from the pressure control chamber. Fuel injection device. The fuel injection device for an internal combustion engine according to claim 4,
The fuel injection device for an internal combustion engine, wherein the electromagnetic valve is a flow rate control valve that varies a flow rate of a control fluid discharged from the pressure control chamber. The fuel injection device for an internal combustion engine according to any one of claims 4 to 6,
The fuel injection device for an internal combustion engine, wherein a stroke amount of the throttle valve is set in a range of 30 to 200 μm. The fuel injection device for an internal combustion engine according to any one of claims 4 to 7,
The throttle valve controls a flow rate or a flow rate of a control fluid introduced into the piston back pressure chamber, or controls a flow rate or a flow rate of a control fluid discharged from the piston control chamber. Fuel injection device. (A) fuel pumping means for discharging fuel;
(B) fuel pressure increasing means for increasing the pressure of the fuel introduced from the fuel pressure supplying means into the pressure increasing chamber;
(C) A fuel injection nozzle that lifts the nozzle needle to the valve opening side and injects fuel into the cylinder of the internal combustion engine when the oil pressure of the fuel introduced from the pressure increasing chamber into the nozzle oil reservoir exceeds the nozzle opening pressure In a fuel injection device for an internal combustion engine comprising:
The fuel pressure increasing means includes a cylinder having a piston back pressure chamber and a piston control chamber,
A pressure-intensifying piston that is slidably accommodated in the cylinder and lifts to a side that increases the oil pressure in the pressure-increasing chamber when the fluid pressure in the piston back-pressure chamber becomes larger than the fluid pressure in the piston control chamber; ,
A first fluid introduction passage for introducing a control fluid into the piston back pressure chamber;
A second fluid introduction passage for introducing a control fluid into the piston control chamber;
A fluid discharge passage for discharging a control fluid from the piston control chamber;
A valve device for changing an area ratio between an opening area of the second fluid introduction passage and an opening area of the fluid discharge passage;
A fuel injection device for an internal combustion engine, comprising: an actuator for driving the valve device through electrical operation. The fuel injection device for an internal combustion engine according to claim 9,
The actuator adjusts the introduction amount of the control fluid introduced into the piston back pressure chamber or the piston control chamber, or the discharge amount of the control fluid discharged from the piston control chamber. apparatus.

Images