Fuel injection device

Abstract

Fuel injection device with: a valve body (40) in which a high-pressure fuel passage is provided, the valve body having an injection opening (44) at a tip from which the high-pressure fuel is injected into a combustion chamber of an internal combustion engine; a valve element (60) which is movable in the valve body in its axial direction and opens or closes the injection opening; a pressure control chamber (53) provided in the valve body on a side opposite the injection port with respect to the valve element, which introduces the high-pressure fuel and controls the movement of the valve element by means of the fuel pressure; an inlet channel (52) through which the high-pressure fuel is introduced into the pressure control chamber; an outlet channel (54) through which the fuel is discharged from the pressure control chamber to an outer low-pressure side; and a control element (70) which is present in the valve body in its axial direction and opens or closes the inlet channel, wherein the valve body includes a cylindrical inner wall portion (356a) defining the pressure control chamber in its radial direction, and the cylindrical inner wall portion includes a connecting groove (357a) connecting an inlet chamber (53a) provided in the pressure control chamber on one side of the inlet channel with respect to the control element with a back pressure chamber (53b) provided in the pressure control chamber on one side of the valve element with respect to the control element, wherein the valve body is provided with a restricting portion (358a) opposite an end face of the control element on a side of the back pressure chamber, and the restricting portion is provided with a sub-connecting groove (357g) which, together with the connecting groove (357a), connects the inlet chamber to the back pressure chamber and ensures the flow of fuel from the inlet chamber (53a) to the back pressure chamber (53b).

Description

TECHNICAL FIELD

[0001] The present invention relates to a fuel injection device that injects high-pressure fuel into a combustion chamber of an internal combustion engine.

[0002] The following state of the art is already known.

[0003] Patent specification DE 10 2006 036 843 A1 discloses a fuel injector, wherein the hydraulic control device of the fuel injector has an annular intermediate valve body designed to interact with the first end face of the control body and, when in contact therewith, to close the fuel supply passages. A gap exists between the intermediate valve body and the guide sleeve surrounding it. This gap is permanently connected to the second control chamber, which is circumferentially delimited radially outward by the guide sleeve, radially inward by the piston element, below by the annular end face of the control piston, and above by the intermediate valve body. The piston element protruding from the control piston engages the intermediate valve body with a sliding fit and, with its free end face, delimits the first control chamber, which is delimited on the other side by the control body and on the circumferential side by the intermediate valve body.When the intermediate valve is closed, the otherwise closed second control chamber is connected to the first control chamber only via the throttle connection. At the end of an injection cycle, the intermediate valve body is rapidly lifted from the control body, allowing high-pressure fuel to flow rapidly into the first control chamber and through the gap into the second control chamber.

[0004] Patent document JP 2 586 613 B2 discloses a fuel injection device for preventing the breakage of a plate valve in a pressure regulating chamber, which is provided with the plate valve and has an opening corresponding to an oil passage. For free separation from a seat portion in a pressure regulating chamber, the device is constructed such that the movement of the plate valve is guided along the inner wall of the pressure regulating chamber. In a fuel injection device, a nozzle needle is slidably fitted into a valve body sliding hole formed in a valve housing. A plunger integrally connected to the needle is also installed in a cylinder formed in a lower body, and a pressure control portion is divided at the upper edge portion of the plunger in the cylinder.A plate valve provided with an opening corresponding to the oil passage is installed in the pressure control part, in which case the plate valve is pushed along the inner wall of the pressure control chamber, and a cutout part 38 is closed when it is in contact with a seat part and released when it is separated from the seat part formed on the plate valve.

[0005] Patent document D3 DE 10 2004 023 381 A1 discloses a fuel injection valve for an internal combustion engine, wherein a fuel injection valve expands a piezo actuator to drive a small-diameter piston through a large-diameter piston and a stroke-increasing chamber when the fuel injection valve performs fuel injection. Thus, a valve element is pushed to reduce pressure in a control oil pressure chamber. At that time, high-pressure fuel flows from a spill chamber through a valve chamber into the control oil pressure chamber. The high-pressure fuel quickly flows from the spill chamber through a spring chamber to a drain passage because a plurality of communication passages are provided by flat portions formed on an outer peripheral wall surface of a cylinder body.As a result, fuel injection is stabilized and refilling with fuel from a check valve into the stroke increasing chamber is facilitated. BACKGROUND OF THE INVENTION

[0006] A fuel injection device including a valve body having a high-pressure passage and a pressure control chamber therein, and a valve element for opening / closing an injection port in response to valve element movement in the axial direction of the valve body inside the valve body, is known. The valve element movement is controlled by fuel pressure in the pressure control chamber. For example, as an example of the fuel injection device, Patent Document 1 teaches a method for the fuel injection device having a control element that is slidable or movable in the axial direction of the valve body in the pressure control chamber and opens or closes an intake port. When the control element closes the intake port, high-pressure fuel can be prevented from flowing into the pressure control chamber. The fuel pressure in the pressure control chamber is rapidly increased by the operation of the control element.Thus, the valve element, which is controlled by the fuel pressure in the pressure control chamber, can quickly open the injection port. STATE OF THE ART DOCUMENT

[0007] [Patent document 1] EP 1656498 A1

[0008] In the fuel injection device disclosed in Patent Document 1, the pressure control chamber may be partitioned by the control element disposed therein. To prevent deterioration of pressure recovery in a backpressure chamber located on the valve element side of the pressure control chamber with respect to the control element, a passage must be provided for the fuel flowing from an inlet chamber located on the intake port side of the pressure control chamber with respect to the control element to the backpressure chamber. Therefore, a gap through which the fuel can flow may be provided between an inner wall surface portion defining the pressure control chamber and an outer wall surface portion, which is one of the control elements and is opposite to the inner wall surface portion.

[0009] However, if the gap between the inner wall surface portion defining the pressure control chamber and the wall surface portion of the control element is increased to provide a sufficient channel area of ​​a passage for fuel flow, the control element may tilt with respect to the axial direction of the valve body. Thus, the tilted control element may be difficult to smoothly slide or reciprocate within the pressure control chamber, resulting in wear and tear on the opening operation of the inlet channel of the pressure control chamber. Thus, the control element may restrict fuel flow into the pressure control chamber.

[0010] If the gap between the inner wall surface portion defining the pressure control chamber and the wall surface portion of the control element is narrowed to restrict the tilt or deflection of the control element, pressure recovery in the backpressure chamber may take longer. Conversely, if the gap between the inner wall surface portion defining the pressure control chamber and the control element is widened for faster pressure recovery in the backpressure chamber, the flow of high-pressure fuel into the intake chamber is restricted, so it may be difficult to improve pressure recovery in the backpressure chamber. Thus, it may be difficult to improve the response of the valve element when the valve is closed. SUMMARY OF THE INVENTION

[0011] In view of the above and other problems, it is an object of the present invention to provide a fuel injection device which improves a response of the valve element to the valve closing timing.

[0012] This object is achieved by the features of claim 1. Further advantageous embodiments and further developments are the subject of the subsequent claims.

[0013] According to an example of the present invention, a fuel injection device includes a valve body in which a high-pressure fuel passage is provided, and which has an injection port at a tip end.a tip from which the high-pressure fuel is injected into a combustion chamber of an internal combustion engine; a valve element which is movable in the axial direction of the valve body inside the valve body and opens or closes the injection port; a pressure control chamber which is provided in the valve body on a side opposite to the injection port with respect to the valve element and which introduces the high-pressure fuel and controls the movement of the valve element by the fuel pressure; an inlet channel through which the high-pressure fuel is introduced into the pressure control chamber; an outlet channel through which the fuel is discharged from the pressure control chamber to an outer low-pressure side; and a control element which is movable in the axial direction of the pressure control chamber inside the pressure control chamber and opens or closes the inlet channel.In the fuel injection device, the valve body includes a cylindrical inner wall portion defining the pressure control chamber in its radial direction, and the cylindrical inner wall portion includes a communication groove communicating an inlet chamber provided in the pressure control chamber on a side of the intake passage with respect to the control element with a back pressure chamber provided in the pressure control chamber on a side of the valve element with respect to the control element.

[0014] According to the above aspect of the present invention, the fuel introduced into the inlet chamber located in the pressure control chamber on the inlet passage side relative to the control element flows through the communication groove provided on the cylindrical inner wall portion into the back pressure chamber located in the pressure control chamber on the valve element side relative to the control element. Therefore, a sufficient passage area is ensured for the fuel flow from the inlet chamber to the back pressure chamber, so that the pressure recovery in the back pressure chamber can be prevented from being interrupted by the control element.

[0015] Furthermore, due to the appropriate channel area or channel cross-section, by providing the connecting groove, a gap between the cylindrical inner wall portion and a wall portion of the control element that is opposite to the cylindrical inner wall portion in the radial direction can be reduced. Reducing the gap can limit the displacement of the axis of the control element from being inclined relative to the axial direction of the valve body. This allows the control element to be displaced smoothly within the pressure control chamber, allowing rapid opening of the inlet channel to the pressure control chamber. This can prevent the control element from restricting the fuel introduction into the pressure control chamber.

[0016] Thus, when the control element opens the intake port, fuel is quickly introduced into the intake chamber, and fuel can also flow smoothly into the backpressure chamber. This can shorten the time required for pressure recovery until the valve element starts moving, thus improving the response of the valve element at the valve closure start time in the fuel injector.

[0017] For example, the cylindrical inner wall portion may be provided with a slidable contact wall surface that slidably contacts an outer peripheral wall portion about the displacement axis of the control member. Thus, the sufficient passage area that allows the inlet chamber to communicate with the backpressure chamber is ensured by providing the communication groove. Thus, even if the slidable contact wall surface that slidably contacts or contacts the outer peripheral wall portion about the displacement axis of the control member is provided on the cylindrical inner wall portion, the pressure recovery in the backpressure chamber can be prevented from being disturbed by the control member. In addition, the sliding and reciprocating movement of the control member on the slidable contact wall surface can accurately restrict an inclination of the axis of the control member.Thus, the control element can be shifted and reciprocated in the pressure control chamber with such precision that high-pressure fuel introduction into the intake port can be performed without disruption. Therefore, the time required for pressure recovery in the backpressure chamber is shortened so precisely that the responsiveness of the valve element during valve closure can be effectively improved.

[0018] In addition, the cylindrical inner wall portion may be provided with a connecting wall surface defining a connecting gap between the cylindrical inner wall portion and an outer peripheral wall about a displacement axis of the control member, and the connecting gap connects the inlet chamber to the back pressure chamber.

[0019] Thus, the sufficient passage area can be ensured by providing the communication groove, so that the passage area defined by the communication gap does not need to be enlarged. Therefore, the size of the communication gap can be reduced to reduce the inclination of the axis of the control element. Even if the channel area of ​​the communication gap is small as described above, forming the communication gap results in the enlargement of an overall area of ​​the passage connecting the inlet chamber and the backpressure chamber. Thus, the time required for pressure recovery in the backpressure chamber can be shortened, so that the response of the valve element at the valve closing time can be improved.

[0020] Furthermore, the cross section of a bottom portion of the connecting groove may be arcuate when viewed in the radial direction. In this case, high pressure is applied by the high-pressure fuel to the connecting groove through which high-pressure fuel flows. Since the bottom portion of the connecting groove is arcuate, excessive forces do not occur near the bottom portion of the connecting groove on the cylindrical inner wall portion. Thus, by providing the connecting groove, wear of the cylindrical inner wall portion can be prevented. Thus, the response of the valve element at the valve closing time in the fuel injection device can be improved, thereby achieving longevity of the fuel injection device.

[0021] Furthermore, a plurality of communication grooves may be arranged on the cylindrical inner wall portion and spaced apart from each other in the circumferential direction of the cylindrical inner wall portion. In this case, the channel area of ​​the passage through which the fuel flows from the intake chamber to the backpressure chamber can be easily enlarged. This allows a large amount of fuel to flow into the backpressure chamber, so that pressure recovery in the backpressure chamber is achieved quickly. Therefore, the responsiveness of the fuel injector at a valve closing timing can be improved as desired.

[0022] Furthermore, the connecting grooves may be evenly spaced from each other in the circumferential direction. In this case, the fuel flow around the control element becomes uniform. This limits the inclination of the control element. Arranging the plurality of connecting grooves results in an increase in the flow rate of fuel flowing into the backpressure chamber. Furthermore, the uniform fuel flow is achieved by arranging the connecting grooves at equal intervals, whereby the pressure recovery in the backpressure chamber is quickly achieved without change. Thus, a movement start timing of the valve element can be advanced, and time fluctuation can be reduced. Therefore, the responsiveness of the valve element to the valve closing timing in the fuel injection device can be improved and stabilized.

[0023] Furthermore, the valve body is provided with a restricting portion that opposes a surface of the control element on one side of the backpressure chamber and restricts displacement of the control element by contacting its end surface during displacement in the direction of disengagement from the inlet channel. Furthermore, the restricting portion is provided with a sub-connecting groove that, together with the connecting groove, connects the inlet chamber to the backpressure chamber.

[0024] Thus, the provision of the restricting portion, which restricts the displacement of the control element by contacting the control element end surface located on the backpressure chamber side, results in the restriction of the control element displacement in the direction of detachment from the intake passage. Therefore, the displacement amount of the control element is restricted by the restricting portion. As a result, at the time the valve element closes, the control element quickly closes the intake passage and stops the introduction of high-pressure fuel into the pressure control chamber.

[0025] Furthermore, the sub-connecting groove, which connects the inlet chamber to the backpressure chamber together with the connecting groove, is provided in the restricting portion. Therefore, the fuel flow from the inlet chamber to the backpressure chamber can be ensured in such a way that pressure recovery in the backpressure chamber is prevented from being interrupted by contact between the end surface and the restricting portion. Thus, the responsiveness of the valve element at both the valve closing and valve opening timings in the fuel injection device can be improved.

[0026] Further, the restricting portion may be configured in a step shape extending radially inward with respect to the cylindrical inner wall portion, so that the restricting portion can accurately restrict the displacement of the control member while keeping the structure simple.

[0027] A channel area of ​​the sub-connecting groove may be configured to become larger downstream in the flow direction, ie, in the flow direction from the inlet chamber to the back pressure chamber.

[0028] In this case, the pressure of the fuel flowing through the sub-connecting groove decreases upon reaching the downstream side. This draws the fuel flowing through the connecting groove and the sub-connecting groove downstream, allowing the fuel to flow more smoothly from the inlet chamber into the backpressure chamber. This can shorten the pressure recovery time until the valve element moves, further improving the responsiveness of the valve element at valve closure time.

[0029] For example, the cylindrical inner wall portion may be provided with the connecting grooves equally spaced from each other in the circumferential direction of the cylindrical inner wall portion, the restricting portion may be provided with the sub-connecting grooves respectively connected to the plurality of connecting grooves and spaced from each other in the circumferential direction, and the connecting grooves and the sub-connecting grooves may be equally spaced from each other in the circumferential direction.

[0030] In this case, the channel area of ​​the passage through which the fuel flows from the inlet chamber to the backpressure chamber can be easily increased. Furthermore, by equally spacing the plurality of connecting grooves and the plurality of sub-connecting grooves from each other in the circumferential direction of the cylindrical inner wall portion, the fuel can flow smoothly around the control element. This limits the tilt or deflection of the control element. As described above, by increasing the channel area while stabilizing the position of the release plate or the floating plate, the pressure recovery in the backpressure chamber can be achieved quickly and easily. Thus, the movement timing of the valve element can be advanced further, and the time fluctuation can be small. Therefore, the response or responsiveness of the valve element at the valve closing time can be steadily enhanced.

[0031] In addition, the bottom portion of the connecting groove may have a circular arc-shaped cross section in the radial direction, and the sub-connecting groove may be configured in a circular arc shape that is coaxial with the bottom portion and has the same radius as the bottom portion.

[0032] Thus, at the time of forming the connecting grooves and sub-connecting grooves on the valve body by cutting, the cutting process for forming the connecting grooves and sub-connecting grooves can be performed simultaneously with the same tool. Therefore, due to the configuration for simultaneously forming the connecting groove and sub-connecting groove, it is possible to provide the valve body with both the connecting groove and the sub-connecting groove at a low cylinder manufacturing cost. This can improve the responsiveness of the valve element in both the valve closing timing and the valve opening timing in the fuel injection device at a lower manufacturing cost.

[0033] Furthermore, the center of the circular arc shape of the sub-connecting groove may be located on an inner peripheral side of the restricting portion in its radial direction. In this case, the channel area of ​​the sub-connecting groove from the inlet chamber to the backpressure chamber becomes larger in the flow direction as it approaches downstream in the flow direction. Thus, the fuel can flow smoothly from the inlet chamber into the backpressure chamber, so that the responsiveness of the valve element at the valve closing time can be further improved.

[0034] Furthermore, the cylindrical inner wall portion may be knurled as the connecting grooves. Even in this case, the fuel can flow from the inlet chamber to the backpressure chamber. For example, knurling defined in JISB-0951 is preferred in this case, such as parallel knurling, in which multiple grooves extend along the axial direction, or diamond knurling, in which each groove intersects with another, forming the diamond pattern.

[0035] In addition, due to the configuration of the connecting groove extending in the axial direction of the valve body, the resistance to high-pressure fuel flow through the connecting groove can be reduced. This allows the fuel to flow more smoothly from the intake chamber to the backpressure chamber. Therefore, the time required for pressure recovery in the backpressure chamber can be shortened, further improving the responsiveness of the valve body at valve closure time.

[0036] Furthermore, the configuration of the connecting groove is not limited to the shape extending along the axial direction, so that the connecting groove may also extend, for example, spirally around the central axis of the cylindrical inner wall portion.

[0037] Furthermore, the valve body may be provided with a supply passage through which the high-pressure fuel flows into the injection port located at the tip end thereof, and a cylindrical member held in the supply passage, configuring the cylindrical inner wall portion on the inner peripheral side, and separating the pressure control chamber from the supply passage.

[0038] Furthermore, the valve body may include a nozzle element forming the tip end at which the injection port is provided, the nozzle element constituting the pressure control chamber defined by the cylindrical inner wall portion and the supply passage disposed on an outer peripheral side of the pressure control chamber and feeding the high-pressure fuel into the injection port.

[0039] As described above, the component defining the pressure control chamber can be changed depending on the configuration of the fuel injection device. However, regardless of the component defining the pressure control chamber, if the communication groove is formed on the cylindrical inner wall portion defining the pressure control chamber, pressure recovery in the backpressure chamber can be achieved quickly, allowing fuel to flow into the backpressure chamber. Thus, regardless of the configuration of the fuel injection device, the formation of the communication groove results in an improvement in the responsiveness of the valve element at the valve closing time. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram of a fuel supply system including a fuel injection device according to a first comparative example; Fig. 2 shows a longitudinal sectional view of the fuel injection device according to the first comparative example; Fig. 3 is a partially enlarged view showing a portion of the fuel injection device according to the first comparative example; Fig. 4 is an enlarged partial view showing the portion of the fuel injection device according to the first comparative example; Fig. Figure 5 shows a cross-sectional view along a line VV in Fig. 4, which shows an embodiment of the connecting groove of the first comparative example; Fig. Fig. 6 is a partially enlarged view showing a part of the fuel injection device according to a second comparative example, which is a modification example of Fig. 4 is; Fig. Figure 7 shows a cross-sectional view along a line VII-VII in Fig. 6, which is a modification example of Fig. 5 represents; Fig. Fig. 8 is a partially enlarged view showing a portion of the fuel injection device according to a first embodiment of the present invention and a cross-sectional view taken along a line VII-VII in Fig. 9, in which a floating plate is held in a cylinder; Fig. 9 shows a cross-sectional view along a line IX-IX in Fig. 8, which illustrates a structure of a connecting groove and a sub-connecting groove of the first embodiment according to the present invention; Fig. 10 is a cross-sectional view showing a portion of a fuel injection device according to a third comparative example, which is a modification example of Fig. 7 is; Fig. Fig. 11 is a cross-sectional view showing a portion of a fuel injection device according to a fourth comparative example, which is another modification example of Fig. 7 is; Fig. 12 shows a cross-sectional view along a line XII-XII in Fig. 6 and illustrates a portion of a fuel injection device for describing a communication groove according to a fifth comparative example; Fig. Fig. 13 is a cross-sectional view showing a portion of a fuel injection device according to a sixth comparative example, which is a modification example of Fig. 12 is; and Fig. Fig. 14 is a cross-sectional view showing a portion of a fuel injection device according to the sixth comparative example, which is another modification example of Fig. 3 is. PREFERRED EMBODIMENTS FOR CARRYING OUT THE INVENTION

[0040] Various embodiments of the present invention will be described with reference to the accompanying drawings. In the following embodiments, similar or corresponding components are denoted by the same reference numerals, and redundant descriptions are omitted. (First comparative example)

[0041] A fuel supply system 10 in which a fuel injection device 100 according to a first comparative example is used is shown in Fig. 1. The fuel supply system 10 is a so-called direct injection fuel supply system in which fuel is directly injected into a combustion chamber 22 of a diesel engine 20 as an internal combustion engine.

[0042] The fuel supply system 10 consists of a feed pump 12, a high-pressure fuel pump 13, a common rail 14, an engine control device 17 (engine ECU), the fuel injection device 100, and the like.

[0043] The boost pump 12 is an electrically driven pump housed in a fuel tank 11. The boost pump 12 applies a boost pressure to the fuel stored in the fuel tank 11 that is higher than the vaporization pressure of the fuel. The boost pump 12 is connected to the high-pressure fuel pump 13 via a fuel line 12a and supplies the fuel, which is subjected to a predetermined boost pressure, to the high-pressure fuel pump 13 in a liquid state. The fuel line 12a has a pressure control valve (not shown) fitted therein, and the pressure of the fuel supplied to the high-pressure fuel pump 13 is maintained at a fixed value.

[0044] The high-pressure fuel pump 13 is mounted on the diesel engine 20 and driven by power from an output shaft of the diesel engine 20. The high-pressure fuel pump 13 is connected to the common rail 14 via a fuel line 13a and further pressurizes the fuel supplied by the boost pump 12 to supply high-pressure fuel to the common rail 14. Furthermore, the high-pressure fuel pump 13 includes an electromagnetic valve (not shown) electrically connected to the engine control device 17. The electromagnetic valve is opened or closed by the engine control device 17, thereby optimally controlling the pressure of the fuel supplied from the high-pressure fuel pump 13 to the common rail 14 to a preset pressure.

[0045] The common rail 14 is a tubular member made of metal such as chromium-molybdenum steel and includes a plurality of branch portions 14a. The number of branch portions 14a corresponds to the number of cylinders per bank of the diesel engine. Each of the branch portions 14a is connected to the fuel injector 100 via a fuel line forming a supply passage 14d. The fuel injector 100 and the high-pressure fuel pump 13 are connected to each other by a fuel line forming a return passage 14f. According to the above-mentioned structure, the common rail 14 temporarily stores the fuel supplied by the high-pressure fuel pump 13 in a high-pressure state and distributes the fuel to the plurality of fuel injectors 100 at the pressure maintained in the high-pressure state through the supply passages 14d.Furthermore, the common rail 14 includes a common rail sensor 14b provided at one end portion of the two axial end portions, and a pressure regulator 14c provided at the other end thereof. The common rail sensor is electrically connected to the engine control device 17, detects the pressure and temperature of the fuel, and outputs these values ​​to the engine control device 17. The pressure regulator 14c maintains the fuel pressure in the common rail 14 at a constant value, decompresses excess fuel, and discharges it to a low-pressure side. The excess fuel passing through the pressure regulator 14c is returned to the fuel tank 11 through a passage in a fuel line 14e connecting the common rail 14 to the fuel tank 11.

[0046] The fuel injection device 100 is the device for pressurizing the fuel and injecting the high-pressure fuel supplied through the branch portion 14a of the common rail 14 from an injection port 44. More specifically, the fuel injection device 100 includes a valve portion 50 that controls the injection of the high-pressure fuel injected from the injection port 44 based on a control signal from the engine control device 17. The high-pressure fuel is supplied from the high-pressure pump 13 through the supply passage 14d.Furthermore, in the fuel injection device 100, the excess fuel, which is a part of the high-pressure fuel supplied from the supply passage 14d and not injected from the injection port 44, is discharged into the return passage 14f through which the fuel injection device 100 communicates with the high-pressure fuel pump 13, and then returned to the high-pressure fuel pump 13. The fuel injection device 100 is inserted and fitted into an injection port formed in a head member 21 located in a portion of the combustion chamber 22 of the diesel engine 20. In the present example, a plurality of fuel injection devices 100 are arranged for respective combustion chambers 22 of the diesel engine 20, and each of them injects the fuel directly into the combustion chamber 22, specifically, at an injection pressure in a range between 160 and 220 MPa.

[0047] The engine control device 17 is composed of a microcomputer or the like. The engine control device 17 is electrically connected not only to the above-described common rail sensor 14b, but also to various sensors such as a rotational speed sensor for detecting a rotational speed of the diesel engine 20, a throttle sensor for detecting a throttle opening, an air flow sensor for detecting an intake air volume, a boost pressure sensor for detecting a boost pressure, a water temperature sensor for detecting a cooling water temperature, and an oil temperature sensor for detecting an oil temperature of a lubricating oil.The engine control device 17 outputs an electrical signal to the electromagnetic valve of the high-pressure fuel pump 13 and each fuel injector 100 for controlling the opening / closing of the electromagnetic valve of the high-pressure fuel pump 13 and the valve portion 50 of each fuel injector 100 based on the signal from the respective sensors.

[0048] Next, based on Fig. 2 or Fig. 3, the structure of the fuel injection device 100 is described in detail.

[0049] The fuel injection device 100 includes a control valve actuation part 30, a control body 40, a nozzle needle 60, a spring 76 and a floating plate or movable plate 70.

[0050] The control valve drive part 30 is housed in the control body 40. The control valve drive part 30 includes a terminal 32, a solenoid 31, a fixed element 36, a movable element 35, a spring 34, and a valve seat element 33. The terminal 32, which is made of an electrically conductive material and has two end portions, has one end portion extending outside the control body 40 and the other end portion connected to the solenoid 31. The solenoid 31 is spirally wound and is supplied with a pulse current from the engine control device 17 through the terminal 32. When the pulse current is supplied to the solenoid 31, the solenoid 31 generates a magnetic field circulating along the axial direction.The fixed member 36 is a cylindrical member made of a magnetic material and is magnetized in the magnetic field generated by the solenoid 31. The movable member 35 is made of a magnetic material, has a cylindrical shape with two steps, and is arranged at a tip in the axial direction of the fixed member 36. The movable member 35 is attracted to a base end side in the axial direction by the magnetized fixed member 36. The spring 34, which is a coil spring formed by winding a metal wire in a circular shape, urges the movable member 35 in a direction to space the movable member 35 from the fixed member 36. The valve seat member 33 forms a pressure control valve 80 together with a control valve seat portion 47a of the control body 40. The control valve seat portion 47a will be described later.The valve seat element 33 is arranged on the opposite side of the fixed element 36 in the axial direction of the movable element 35 and is seated on the control valve seat portion 47a. When the magnetic field of the solenoid 31 is not generated, the valve seat element 33 is seated on the control valve seat portion 47a by the restoring force of the spring 34. When the magnetic field of the solenoid 31 is generated, the valve seat element 33 is spaced from the control valve seat position 47a.

[0051] The control body 40, which includes a nozzle body 41, a cylinder 56, an orifice plane 46, a holder 48, and a retaining nut 49, has an elongated shape and contains a high-pressure fuel passage therein. The nozzle body 41, the orifice plane 46, and the holder 48 are arranged in this order from a tip in a direction in which they are introduced into the combustion chamber. In addition, the injection port 44, through which the high-pressure fuel is supplied to the combustion chamber 22 (see Fig. 1) of the diesel engine 20 is arranged at a tip of the control body 40.

[0052] The control body 40 has an inlet channel 52, an outlet channel 54, a pressure control chamber 53 and an opening wall surface 90 facing the pressure control chamber 53. One end of the inlet channel 52 is connected to one side of the supply channel 14d (see Fig. 1), which is connected to the high-pressure fuel pump 13 and the common rail 14, and the other end of the inlet channel 52 is connected to the pressure control chamber 53. The inlet channel 52 has an opening of an inlet port 52a, which is a passage end opposite to one side of the supply channel 14d, on the opening wall side 90. Thus, the high-pressure fuel can be introduced into the pressure control chamber 53 through the inlet channel 52. Furthermore, one end of the outlet channel 54 is connected to one side of the return channel 14f (see Fig. 1) connected to the high-pressure fuel pump 13, and the other end of the outlet passage 54 communicates with the pressure control chamber 53. The outlet passage 54 has an opening of an outlet port 54a, which is a passage end opposite to a side of the return passage 14f, on the orifice wall surface 90. Thus, the fuel in the pressure control chamber 53 can flow to the low-pressure side through the outlet passage 54. The pressure control chamber 53 is defined by the orifice plate 46 and the cylinder 56. The pressure control chamber 53 is provided in the control body 40 on a side opposite to the injection port 44 with respect to the nozzle needle 60. The pressure control chamber 53 is configured such that the high-pressure fuel is introduced from the inlet passage 52 and discharged through the outlet passage 54.

[0053] The nozzle body 41 is made of metal, such as chromium-molybdenum steel, and has a cylindrically shaped bottom portion. The nozzle body 41 has a nozzle body housing portion 43, a valve seat portion 45, and an injection opening 44. The nozzle body housing portion 43 is formed along the axial direction of the nozzle body 41 and is a cylindrical opening in which a nozzle needle 60 is received. High-pressure fuel is contained in the nozzle needle housing portion 43, which is supplied from the high-pressure fuel pump 13 and the common rail 14 (see Fig. 1). A supply passage 43a, through which the high-pressure fuel is supplied to the injection port 44, is defined by the nozzle needle housing portion 43 and the cylinder 56. The valve seat portion 45 is formed on the bottom wall of the nozzle needle housing portion 43 and contacts the tip of the nozzle needle 60. The injection port 44 is located at the tip of the nozzle body 41, which is opposite to the orifice plate 46 with respect to the valve seat element section 45. A plurality of injection ports 44 are formed, radiating outward from the interior of the nozzle body 41. When the high-pressure fuel passes through the injection port 44, the high-pressure fuel is atomized and atomized, allowing the fuel to mix well with the air.

[0054] The cylinder 56, which is made of a metallic material, defines the pressure control chamber 53 in the radial direction of the chamber 53. In addition, the cylinder 56 is coaxially received in the nozzle needle housing portion 43 and defines the supply passage 43a and the pressure control chamber 53.

[0055] The cylinder 56 has an inner wall surface portion 56a having a cylindrical shape. The inner wall surface portion 56a is provided with a control wall surface portion 57, a cylinder displacement surface portion 59, a plate stopper portion 58a, and a needle stopper portion 58b. The control wall surface portion 57 is disposed on one side of the valve body 46 in the axial direction of the cylinder 56 and circumferentially includes the orifice wall surface 90. The cylinder displacement surface portion 59 is disposed at a position opposite the orifice plate 46 in the axial direction of the cylinder 56, so that the nozzle needle 60 slidably rests on the cylinder displacement surface portion 59 along the axial direction. An inner diameter of the cylinder displacement surface portion 59 is reduced with respect to an inner diameter of the control wall surface portion 57.

[0056] The plate stopper portion 58a has a stepped shape extending toward a radially inner side of the inner wall surface portion 56a and is configured or defined by the difference between the inner diameter of the cylinder displacement surface portion 59 and the control wall surface portion 57. The plate stopper portion 58a is located opposite the floating plate 70 in the axial direction of the cylinder 56. The plate stopper portion 58a is configured to contact the floating plate 70 by its displacement from the intake port 52 such that the displacement of the floating plate 70 toward the nozzle needle 60 can be controlled. The needle stopper portion 58b is arranged on an opposite side, which is opposite the control wall surface portion 57 with respect to the cylinder displacement surface portion 59 in the axial direction of the cylinder 56.The needle stopper portion 58b is located on a side opposite to the plate stopper portion 58a in the axial direction of the cylinder 56, so that the displacement of the nozzle needle 60 toward the floating plate 70 can be controlled.

[0057] The orifice plate 46, which is made of metal such as chromium-molybdenum steel, has a cylindrical shape and is held between the nozzle body 41 and the holder 48. The orifice plate 46 includes the control valve seat portion 47a, the orifice wall surface 90, the outlet channel 54, and the inlet channel 52. The control valve seat portion 47a is arranged on an end surface of the orifice plate 46, which is one side of the holder 48 in the axial direction of the orifice plate 46, and, together with the valve seat member 33 of the control valve driving part 30, configures or defines the pressure control valve 80. The orifice wall surface 90 is a straight surface arranged on or at one side of the nozzle body 41 and configured at a central position in the radial direction of the other end surface of the orifice plate 46. The opening wall surface 90 is surrounded by the cylinder 56 and has a circular shape.The exhaust passage 54 extends toward the control valve seat portion 47a from a radially central portion of the orifice wall surface 90. The exhaust passage 54 is inclined with respect to the axial direction of the orifice plate 46. The inlet passage 52 extends toward the one end surface having the control valve seat portion 47a from the radially outer side of the exhaust passage 54 into the orifice wall surface 90. The inlet passage 52 is inclined with respect to the axial direction of the orifice plate 46.

[0058] The holder 48 is a member made of a metallic material such as chromium-molybdenum steel in the shape of a cylinder, has elongated holes 48a, 48b along the axial direction, and has a base portion 48c. The elongated hole 48a is a fuel passage that connects the supply passage 14d (see Fig. 1) connects to the intake passage 52. The elongated hole 48b has the control valve driving part 30 on one side of the orifice plate 46 therein. Furthermore, in the elongated hole 48b, the base portion 48c is configured at a portion opposite to the orifice plate 46 to block the opening of the elongated hole 48b. The base portion 48c has one end of the terminal 32 of the control valve driving part 30 extending thereinto and a plug portion (not shown) detachably fitted therein. The plug portion is connected to the engine control device 17. When the base portion 48c is connected to the plug portion (not shown), a pulse current can be transmitted to the control valve driving part 30 from the engine control device 17.

[0059] The retaining nut 49 is made of a metallic material and has a two-stage cylindrical shape. The retaining nut 49 receives a portion of the nozzle body 41 and the orifice plate 46 and is threaded on the orifice plate 46 side of the holder 48. Furthermore, the retaining nut 49 has a stepped portion 49a on its inner peripheral wall portion. When the retaining nut 49 is fitted onto the holder 48, the stepped portion 49a pushes the nozzle body 41 and the orifice plate 46 toward the holder 48. In this way, the retaining nut 49 holds the nozzle body 41 and the orifice plate 46 together with the holder 48.

[0060] The nozzle needle 60, which is made of a metallic material such as high-speed tool steel, is configured in a substantially cylindrical shape and can be moved axially within the control body 40. The nozzle needle 60 includes a seat portion 65, a pressure-receiving surface 61, a spring housing portion 62, a needle displacement portion 63, a needle anchoring portion 68, a return spring 66, and a collar member 67. The seat portion 65 is formed at one end portion, which is one of the two axial end portions of the nozzle needle 60, opposite the pressure control chamber 53, and fitted onto the valve seat portion 45 of the control body 40. The seat portion 65 and the valve seat portion 45 define a valve portion 50 that opens or closes the injection port 44 through which the high-pressure fuel supplied into the nozzle needle housing portion 43 is discharged.

[0061] The pressure receiving surface 61 is formed as an end portion, which is one of the two end portions in the axial direction of the nozzle needle 60, and is arranged on a side of the pressure control chamber 53 opposite the seat portion 65. The pressure receiving surface 61 separates the pressure control chamber 53 together with the orifice wall surface 90 and the control wall surface portion 57, and receives the pressure of the fuel in the pressure control chamber 53. Thus, the displacement of the nozzle needle 60 is controlled by the fuel pressure in the pressure control chamber 53. The spring housing portion 52 is a cylindrical opening or hole arranged coaxially with the nozzle needle 60 and in a radially central portion of the pressure receiving surface 61. The spring housing portion 62 accommodates a portion of a spring 76.

[0062] The needle shifting portion 63, which is a portion of the round, barrel-shaped outer peripheral wall of the nozzle needle 60, is located closer to the pressure-receiving surface 61 than the control wall surface portion 57. The needle shifting portion 63 is slidably supported by the cylinder shifting surface portion 59 defined by the inner peripheral wall of the cylinder 56. The collar member 67 is an annular member fitted onto the outer peripheral wall portion of the nozzle needle 60 and held by the nozzle needle 60. The needle anchoring portion 68 is mounted on the seat portion 65 side relative to the nozzle needle shifting portion 63 in the axial direction and is a stepped portion configured by enlarging an outer diameter of the nozzle needle 60.The needle anchoring portion 68 defines a surface that opposes the needle stopper portion 58b of the cylinder 56 in the axial displacement direction of the nozzle needle 60. The needle anchoring portion 68 is locked to the needle stopper portion 58b such that the displacement of the nozzle needle 60 toward the floating plate 70 is limited.

[0063] The nozzle needle 60 is biased on one side of the valve portion 50 by a return spring 66. The return spring 66 is a coil spring formed by circularly winding a metal wire. The return spring 66 has one end in the axial direction fitted on a side surface of the pressure control chamber 53 of the collar member 57, and the other end fitted on an end surface of the valve portion side of the cylinder 56, respectively. According to the configuration described above, the nozzle needle 60 is linearly reciprocated in the axial direction of the cylinder 56 with respect to the cylinder 56 in response to the pressure applied to the pressure receiving surface 61, that is, the pressure of the fuel in the pressure control chamber 53, to seat the seat portion 65 on the valve seat portion 45 or to space the seat portion 65 from the valve seat portion 45, thereby closing or opening the valve portion 50.

[0064] The floating plate 70, which is made of a metallic material and shaped as a round disk body, presses the opening wall surface 90 such that it blocks the inlet channel 52. The floating plate 70 has a pressure surface 73, a pressure receiving surface 77, a plate anchoring portion 78, an outer peripheral wall surface portion 74, and a communication hole 71. The floating plate 70 is slidably arranged for reciprocating movement in the axial direction of the cylinder 56 of the control body in the pressure control chamber 53. The floating plate 70 has a displacement axis direction that is along the axial direction of the nozzle needle 60. In both end surfaces in the displacement axis direction of the floating plate 70, the end surface opposite to the opening wall surface 90 in the displacement axis direction forms the pressure surface portion 73. The pressure surface portion 73, which is round oris annular, borders the opening wall surface 90 due to the reciprocating movement of the floating plate 70. The end surface of the floating plate 70, which is opposite to the pressure surface 73 in the displacement axis direction, forms the pressure receiving surface 77, which is opposite to the pressure receiving surface 61 in the displacement axis direction. The pressure receiving surface 77 is pressed toward the opening wall surface 90 by the pressurized fuel in the pressure control chamber 53.

[0065] In addition, the outer peripheral edge of the pressure-receiving surface 77 has the plate anchoring portion 78, which is opposite to the plate stopper portion 58a of the cylinder 56 in the displacement axis direction. The plate anchoring portion 78 is locked to the plate stopper portion 58a such that the displacement of the floating plate 70 toward the nozzle needle 60 is restricted.

[0066] The outer peripheral wall surface portion 74 of the floating plate 70, which connects the pressure surface 73 to the pressure-receiving surface 77, is opposite the control wall surface portion 57 in the radial direction of the cylinder 56. Furthermore, an inlet chamber 53a is a space positioned on one side of the inlet port 52 relative to the floating plate 70 in the pressure control chamber 53. Furthermore, a backpressure chamber 53b is a space positioned on one side of the nozzle needle 60 relative to the floating plate 70 in the pressure control chamber 53.

[0067] The communication hole 71 extends from the radial center portion of the pressure-receiving surface 77 to the discharge port 54a in the floating plate 70. The extension direction of the communication hole 71 is along the displacement axis direction of the floating plate. One end of the communication hole 71 is opened at the radial center portion of the pressure surface 73, which is opposite to the discharge port 54a. The pressure control chamber 53 communicates with the discharge port 54a through the communication hole 71 in a state where the pressure surface 73 of the floating plate 70 is adjacent to the port wall 90 side.

[0068] The communication hole 71 has a tapered portion 71a and a recessed portion 72. A minimum passage area of ​​the communication hole 71 is defined by the size of the tapered portion 71a such that the tapered portion 71a controls the volume flow of the fuel flowing through the communication hole 71. The passage area of ​​the tapered portion 71a is smaller than the opening area of ​​the outlet port 54a. The tapered portion 71a is arranged closer to the end surface, which is one of the two end surfaces of the floating plate 70 in the axial direction thereof and forms the pressure surface 73, than to the other end surface, which forms the pressure receiving surface 77. The recessed portion 72, which is coaxial with the floating plate 70 and is a cylindrical hole, is recessed from the pressure receiving surface 77 to a side opposite the pressure receiving surface 61.except that the channel area of ​​the communication hole 71 is partially enlarged by the recessed portion 72. The opening of the communication hole 71 in the pressure-receiving surface 77 is enlarged by the recessed portion 72. However, the pressure-receiving surface 77 is biased in the displacement axis direction by the spring 76.

[0069] The spring 76 is a coil spring made by circularly winding a metal wire. The spring 76 has one end in the axial direction that is placed on the pressure-receiving surface 77 of the floating plate 70. The other end of the spring 76 is accommodated in the spring housing portion 62 of the nozzle needle 60. The spring 76 is arranged coaxially between the floating plate 70 and the nozzle needle 60 and is provided in a compressed state in the axial direction.

[0070] According to the above configuration, the spring 76 biases the floating plate 70 toward the orifice wall surface 90 side with respect to the nozzle needle 60. Even when a pressure difference between the inlet chamber 53a and the backpressure chamber 53b is small, the floating plate 70 is biased toward the orifice wall surface 90 by the biasing force of the spring 56, whereby the pressure surface portion 73 abuts or rests against the orifice wall surface 90.

[0071] Next, the illustrated portion of the fuel injector 100 is compared with Fig. 3 and Fig. 5 described in detail.

[0072] A communication groove 57a and a sliding contact wall surface 57b are provided in the inner wall surface portion 56a of the cylinder 56. The communication groove 57a extends from an axial end of the cylinder 56, which is the opening wall surface 90 side in the axial direction of the cylinder 56, to the plate stopper portion 58a along the axial direction of the cylinder 56, such that the communication groove 57a connects the inlet chamber 53a to the backpressure chamber 53b. A plurality of communication grooves 57a are provided in the inner wall surface portion 56a and are spaced from each other in the circumferential direction by a predetermined distance. More specifically, according to the first comparative example, three communication grooves 57a are provided in the inner wall surface portion 56a and are equally spaced from each other in the circumferential direction.The connecting groove 57a has an arcuate cross section in the circumferential direction of the cylinder 56, and a central angle of the arcuate connecting groove 57a is approximately 90°.

[0073] The communication groove 57a is defined by a bottom portion 57d provided along the circumferential direction of the cylinder 56 and a side portion 57e provided along the radial direction of the cylinder 56. In the cross-sectional view in the radial direction of the cylinder 56, a corner portion 57f connecting the bottom portion 57d and the side portion 57e is formed in a circular arc shape. As described above, by forming the corner portion 57f in an arc shape, the force applied to the inner wall surface portion 56a by the pressurized fuel flowing through the communication groove 57a is concentrated on the corner portion 57f.

[0074] The movable contact wall surface 57b is arranged between the connecting grooves 57a, which are adjacent to the movable contact wall surface 57b in the circumferential direction of the cylinder 56. The movable contact wall surface 57b slidably contacts or touches the outer peripheral wall surface portion 74 about the displacement axis of the floating plate 70. The connecting grooves 75a are equally spaced from each other in the circumferential direction such that three movable contact wall surfaces 57b are equally spaced from each other in the circumferential direction of the cylinder 56. Therefore, the contact portions between the movable contact wall surface 57b and the outer peripheral wall surface portion 74 are spaced from each other by approximately 120°, so that the floating plate 70 is held by the movable contact wall surface 57b inward in the radial direction of the floating plate 70.

[0075] In addition, even between the sliding contact wall surface 57b and the outer peripheral wall surface portion 74, a small fuel flow, such as a very small fuel leakage, may occur. However, when specifying a total passage area through which the fuel flows from the inlet chamber 53a to the backpressure chamber 53b, the total passage area for obtaining the required flow is defined without considering the volume of fuel flowing between the sliding contact wall surface 57b and the outer peripheral wall surface portion 74 and into the backpressure chamber 53b.Thus, the passage area of ​​the communication groove 57a, the radial groove 77a extending in the radial direction, and the communication hole 71 are defined such that the required fuel flow amount flowing from the intake chamber 53a to the backpressure chamber 53b is determined by forming three communication grooves 57a and the three radial grooves 77a to communicate with the communication hole 71. Furthermore, the total passage areas of the three communication grooves 57a and the communication hole 71 are set larger than the opening area of ​​the intake port 52a.

[0076] Furthermore, the plate anchoring portion 78 of the floating plate 70 is provided with a plurality of radial grooves 77a. The plurality of radial grooves 77a are spaced apart from each other in the circumferential direction. The radial grooves 77a extend in the radial direction of the floating plate 70. The radial groove 77a forms a passage through which the fuel can flow between the plate anchoring portion 78 and the plate stopper portion 58a.

[0077] Next, an operation of the fuel injection device 100, which controls the opening / closing of the valve portion 50 and injects fuel according to a control signal output from the engine control device 17, is described based on the Fig. 2 to 5.

[0078] In a state where the pressure control valve 80 blocks the outlet port 54a and the return passage 14f (see Fig. 1), the pressure surface 73 of the floating plate 70 abuts the orifice wall surface 90 by means of the biasing force of the spring 76 toward the closed position of the intake port 52. When the exhaust port 54a communicates with the return port 14f through the operation of the pressure control valve 80, the fuel in the pressure control chamber 53 begins to flow out through the exhaust port 54. This creates a decompression at a location adjacent to the exhaust port 54a such that the floating plate 70 is pulled toward the orifice wall surface 90, the pressure surface 73 presses the orifice wall surface 90, and the intake port 52a is blocked.

[0079] The fuel in the backpressure chamber 53b of the pressure control chamber 53 flows through the communication hole 71 from the outlet port 54a. If the flow progresses from the outlet port 54a, the fuel pressure in the pressure control chamber 53 is reduced. When the fuel pressure in the pressure control chamber 53 becomes lower than a predetermined pressure value, the nozzle needle 60 is moved toward the pressure control chamber 53, so that the seat portion 65 is spaced apart from the valve seat portion 45, thereby opening the valve portion 50. In the following description, the pressure at a time when the nozzle needle starts to move is referred to as the predetermined pressure for convenience. Thereafter, the movement of the nozzle needle 60 toward the pressure control chamber 53 is restricted by the abutment of the needle anchor portion 68 against the needle stopper portion 58b.

[0080] If the communication or connection between the outlet opening 54a and the return channel 14f (see Fig. 1) is interrupted by closing the pressure control valve 80, the floating plate 70 is pressed toward the nozzle needle 60 by the high-pressure fuel introduced through the intake passage 52. When the force generated by the high-pressure fuel in the intake passage 52 and acting toward the nozzle needle 60 becomes higher than the biasing force of the spring 76 acting toward the orifice wall surface 90, the floating plate 70 begins to slide. Spacing the floating plate 70 away from the orifice wall surface 90 results in communication between the intake passage 52 and the pressure control chamber 53. As a result, high-pressure fuel is introduced into the inlet chamber 53a. The displacement of the floating plate 70 toward the nozzle needle 60 is limited by the abutment of the plate anchoring portion 78 against the plate stopper portion 58a.

[0081] Thereafter, the fuel introduced from the intake port 52 into the intake chamber 53a flows through the three communication grooves 57a and the three radial grooves 77a provided on the inner wall surface portion 56a of the cylinder 56, and the communication hole 71, into the backpressure chamber 53b. Due to the pressure recovery in the backpressure chamber 53b, the nozzle needle 60 is pushed downward toward the valve portion 50. Thus, the nozzle needle 60 causes the seat portion 65 to seat against the valve seat portion 45, blocking the injection port or hole 44.

[0082] Even after the valve portion 50 is closed, the fuel flow advances from the inlet chamber 53a to the backpressure chamber 53b. Thus, the pressure difference between the inlet chamber 53a and the backpressure chamber 53b in the pressure control chamber 53 is gradually reduced. Thus, the biasing force of the spring 56 becomes greater than the force of the floating plate 70 acting toward the nozzle needle 60, so that the floating plate 70 spaced the plate anchoring portion 78 from the plate stopper portion 58a and displaced toward the orifice wall surface 90. Thereafter, the floating plate 70 returns to the state where the pressure surface 73 abuts the orifice wall surface 90 due to the biasing force of the spring 76.

[0083] In the first comparative example, the sufficient or appropriate passage area for enabling fuel flow from the intake passage 53a to the backpressure chamber 53b is provided by the connecting grooves 57a. Thus, the pressure recovery in the backpressure chamber 53a is essentially unrestricted by the floating plate 70.

[0084] However, the gap between the inner wall surface portion 56a of the cylinder 56 and the outer peripheral wall surface portion 74 of the floating plate 70 can be reduced due to the creation of the sufficient passage area by the connecting grooves 57a. By reducing the gap, the inclination of the displacement axis of the floating plate 70 relative to the axial direction of the cylinder 56 can be restricted. Thus, the floating plate 70 is smoothly slidable and can be displaced within the pressure control chamber 53. Thus, the floating plate 70 can quickly open the intake passage 52 into the pressure control chamber 53. Therefore, the introduction of fuel into the pressure control chamber 53 is not restricted by the floating plate 70.

[0085] Thus, when the floating plate 70 opens the intake port 52, the fuel is quickly introduced into the intake chamber 53a and can flow smoothly into the backpressure chamber 53b. This can shorten the time required for pressure recovery during the start of the displacement of the nozzle needle 60. Therefore, the responsiveness of the nozzle needle 60 in the fuel injection device 100 at the valve closing time can be improved.

[0086] Furthermore, according to the comparative example, the sufficient channel area of ​​the passage for communicating the intake port 53a with the backpressure chamber 53b is provided through the communication groove 57a. Thus, even if the slidable contact wall surface 57b slidably contacting the outer peripheral wall surface portion 74 of the floating plate 70 is disposed on the inner wall surface portion 56a of the cylinder 56, the pressure recovery in the backpressure chamber 53a can be prevented from being interrupted by the floating plate 70. The floating plate 70 is slid and reciprocated on the slidable contact wall surface 57b such that an inclination of the axis of the floating plate 70 can be restricted. Thus, the floating plate 70 can be slid and reciprocated in the pressure control chamber 53 so accurately that the high-pressure fuel introduction into the intake port 53a is not interrupted.Therefore, the time required for pressure recovery in the back pressure chamber 53a is shortened so precisely that the responsiveness of the nozzle needle 60 to the valve closing time can be further improved.

[0087] According to the first comparative example, the high pressure of the high-pressure fuel acts on the communication groove 57a, through which the high-pressure fuel flows. In the radial direction of the cross section of the communication groove 57a, the corner portion 57f between the bottom portion 57d and the side portion 57e of the communication groove 57a is formed in a circular arc shape, so that excessive stress can be prevented from acting on the corner 57f. Furthermore, the communication groove 57a is arc-shaped and extends in the circumferential direction to provide the above-described sufficient passage area, and the communication groove 57a can be formed with a shallow depth in the radial direction. Thus, it is easy to provide a sufficient wall thickness of the cylinder 56 in the radial direction, so that aging or deterioration of the cylinder 56 can be restricted.Thus, the wear of the cylinder 56 caused by the provision of the connecting groove 57a can be limited. Therefore, the responsiveness of the nozzle needle 60 at the valve closing time in the fuel injection device 100 can be improved, while achieving a long life of the fuel injection device 100.

[0088] According to the first comparative example, the three communication grooves 57a are arranged separately from each other in the circumferential direction so that the channel area of ​​the passage through which the fuel flows from the inlet chamber 53a into the backpressure chamber 53b can be easily increased. This allows such a large volume of fuel to flow toward the backpressure chamber 53b that pressure recovery in the backpressure chamber 53b can be quickly achieved. Furthermore, the three communication grooves 57a are arranged at equal intervals in the circumferential direction of the cylinder 56 and spaced from each other, so that the fuel flows from the three sections into the backpressure chamber 53b. Thus, the fuel flow around the floating plate 70 can be uniform.

[0089] The provision of the three connecting grooves 57a results in an increase in the flow rate of fuel flowing into the backpressure chamber 53b. Uniform fuel flow is achieved by arranging the connecting grooves 57a at equal intervals, so that the deflection or inclination of the floating plate 70 relative to its axial direction can be restricted. This allows pressure recovery in the backpressure chamber 53b to be achieved quickly and easily. Thus, the movement start timing of the nozzle needle 60 is advanced, and the fluctuation or fluctuation in the movement start timing can be small. Therefore, the responsiveness of the nozzle needle 60 to the valve closing timing in the fuel injection device 100 can be improved.

[0090] Furthermore, according to the first comparative example, the configuration of the connecting groove 57a extending in the axial direction of the cylinder 56 can reduce the flow resistance through the connecting groove 56a. Thus, the fuel flow from the intake chamber 53a to the backpressure chamber 53b can be made smoother. Therefore, the time required for pressure recovery in the backpressure chamber 53b can be shortened, so that the response of the nozzle needle 60 at the valve closing time can be further improved.

[0091] Furthermore, according to the first comparative example, the plate stopper portion 58a, which has a stepped portion, is disposed in the cylinder 56 of the control body 40 such that the displacement of the floating plate 70 in the direction of separation from the intake passage 52 is appropriately restricted with a simple structure. Therefore, at the time of closing the nozzle needle 60, the floating plate 70 quickly closes the intake passage 52 and stops the introduction of high-pressure fuel into the backpressure chamber 53. However, the fuel flow from the intake chamber 53a to the backpressure chamber 53b may be restricted between the plate anchoring portion 78 and the plate stopper portion 58a. According to the first comparative example, the radial groove 77a is disposed in the plate anchoring portion 78 such that the fuel can flow even when the plate anchoring portion 78 and the plate stopper portion 58a are in contact.Thus, the function of the connecting groove 57a, which can shorten the pressure recovery time in the backpressure chamber 53b, can be effectively utilized without breaking the contact between the plate anchoring portion 78 and the plate stopper portion 58a. Therefore, the responsiveness of the nozzle needle 60 at both the valve closing and valve opening timings in the fuel injection device 100 can be improved.

[0092] According to the first comparative example, the diesel engine 20 is an example of the internal combustion engine described in the claims, the control body 40 is an example of the valve body described in the claims, the nozzle body 41 is an example of the nozzle element described in the claims, the cylinder 56 is an example of a cylindrical element described in the claims, the inner wall surface portion 56a is an example of a cylindrical inner wall portion described in the claims, the nozzle needle 60 is an example of a valve element described in the claims, and the floating plate 70 is an example of a control element described in the claims. (Second comparative example)

[0093] A second comparative example, which can be found in the Fig. 6 and Fig. 7 shows a modified example of the above-described first comparative example. In a fuel injection device 200 of the second comparative example, a cylinder 256 corresponding to the cylinder 56 (see Fig. 3) of the first comparative example. In addition, in the fuel injection device 200, a configuration corresponding to the spring 76 (see Fig. 3) is omitted in the first comparative example. Next, the detailed structure of the fuel injection device 200 according to the second comparative example will be described.

[0094] A connecting groove 257a and a sliding contact wall surface 257b are arranged in the inner wall surface portion 256a of the cylinder 256. The connecting groove 257a and the sliding contact wall surface 257b correspond to the connecting groove 57a and the sliding contact wall surface 57b arranged in the cylinder 56 of the first comparative example (see Fig. 4).

[0095] The communication groove 257a, which connects the intake chamber 53a to the backpressure chamber 53b, extends from one end of the cylinder 256 on the opening wall surface 90 side to a plate stopper portion 258a along the axial direction of the cylinder 256. In the second comparative example, the four communication grooves 257a are provided at equal intervals from each other in the circumferential direction of the cylinder 256. The communication groove 257a has a semicircular cross-section in the radial direction. As described above, forming a bottom portion 257d of the communication groove 257a with a circular arc shape of cross-section perpendicular to the axial direction results in a lower force concentration on the high-pressure fuel flowing through the communication groove 257a.

[0096] The slidable contact wall surface 257b, which slidably contacts the outer peripheral wall surface portion 74 of the floating plate 70, is disposed between the connecting grooves 257a that are adjacent to each other in the circumferential direction of the cylinder 256. The slidable contact wall surface 257b contacts the outer peripheral wall surface portion 74 such that the floating plate 70 is held radially inward relative to the floating plate 70 by the slidable contact wall surface 257b. Furthermore, according to the first comparative example, even between the slidable contact wall surface 257b and the outer peripheral wall surface portion 74, little fuel, such as a very small fuel leak, can flow.

[0097] Next, the operation for opening and closing the valve portion 50 in the above-described fuel injection device 200 will be explained with respect to the Fig. 2, Fig. 6 and Fig. 7 described.

[0098] Before the outlet opening 54a is connected to the return channel 14b by the operation of the pressure control valve 80, the plate anchoring portion 78 of the floating plate 70 is placed on the plate stopper portion 258a. When the operation of the pressure control valve 80 connects the outlet opening 54a to the return channel 14f (see Fig. 1), the fuel flows from the backpressure chamber 53 through the outlet passage 54. This creates such a decompression near the outlet port 54a that the floating plate 70 is pulled toward the orifice wall surface 90, causing the pressure surface 73 to press against the orifice wall surface 90, thus blocking the inlet port 52a. Therefore, according to the first comparative example, when the pressure in the pressure control chamber 53 becomes lower than the predetermined pressure value, the nozzle needle 60 opens the valve portion 50.

[0099] The floating plate 70, which abuts against the orifice wall surface 90, presses the orifice wall surface 90, thereby blocking the inlet port 52a. Due to the outflow of fuel flowing through the communication hole 71, rapid pressure decompression occurs in the pressure control chamber 53, where the fuel flow from the inlet port 52a is interrupted. Due to the decompression of the pressure in the pressure control chamber 53, the nozzle needle 60 is pushed upward toward the pressure control chamber 53 such that the seat portion 65 is spaced apart from the valve portion 45, thereby maintaining the valve portion 50 in the open state.

[0100] If the connection between the outlet opening 54a and the return channel 14f (see Fig. 1) is interrupted by closing the pressure control valve 80, the floating plate 70 is pressed toward the nozzle needle 60 by the high-pressure fuel introduced through the intake passage 52, so that the floating plate 70 begins to move. The separation or detachment of the floating plate 70 from the orifice wall surface 90 results in the opening of the intake passage 52 into the pressure control chamber 53. As a result, high-pressure fuel is introduced into the intake chamber 53a.

[0101] Thereafter, the fuel introduced from the intake port 52 into the intake chamber 53a flows toward the backpressure chamber 53b through the four communication grooves 257a arranged on the inner wall surface portion 256a of the cylinder 256 and the four communication holes 71. Due to the pressure recovery in the backpressure chamber 53b, the nozzle needle 60 is pushed downward toward the valve portion 50. The nozzle needle 60 causes the seat portion 65 to be seated on the valve seat portion 45 such that the injection port 44 is blocked. According to the second comparative example, unlike the first comparative example, the floating plate 70 remains spaced apart or detached from the port wall surface 90 until the outlet port 54a is connected to the return channel 14f by the pressure control valve 80 (see Fig. 1) is associated with.

[0102] According to the second comparative example, the sufficient passage area to allow fuel flow from the intake passage 53a to the backpressure chamber 53b is ensured by the connecting groove 257a. Thus, the pressure recovery in the backpressure chamber 53a can be prevented from being interrupted by the floating plate 70.

[0103] Furthermore, the sliding contact wall surface 257a slidably contacts the outer peripheral wall surface portion 74 of the floating plate 70 such that the sliding axis of the floating plate 70 is less likely to be inclined with respect to the axial direction of the cylinder 256. Therefore, the floating plate 70 can slide smoothly within the pressure control chamber 53, making it possible to quickly open the intake port 52 into the pressure control chamber 53. Thus, the flow of fuel supplied into the pressure control chamber 53 can be prevented from being restricted by the floating plate 70.

[0104] Thus, the fuel can be quickly introduced into the intake chamber 53a and flow smoothly into the backpressure chamber 53b. This can shorten the time required for pressure recovery during the initial displacement of the nozzle needle 60. Furthermore, according to the fuel injection device 200, the responsiveness of the nozzle needle 60 to the valve closing timing can be improved.

[0105] In addition, according to the second comparative example, the bottom portion 257d of the communication groove 257, to which the pressure of the pressurized fuel is applied, is configured in a circular arc shape such that the stress substantially does not act or is not compressed near the bottom portion 257d. Thus, the wear caused to the cylinder 256 can be prevented by providing the communication groove 257. Furthermore, by dispersing the stresses, the depth of the communication groove 257a in the radial direction of the cylinder 256 can be increased. Therefore, the width of the communication groove 257 can be tapered in the circumferential direction while ensuring the sufficient passage area. Thus, the width of the slidable contact wall surface 257b, which is arranged between the adjacent communication grooves 257, can be increased in the circumferential direction.Therefore, the surface area of ​​the outer peripheral wall surface portion 74 contacting the sliding contact wall surface 257b becomes larger, making it less likely that the floating plate 70 will tilt or deflect relative to the axial direction. Therefore, the responsiveness of the nozzle needle 60 at the valve closing time according to the fuel injection device 200 can be improved while ensuring the durability of the fuel injection device 200.

[0106] According to the second comparative example, the cylinder 256 is an example of a cylindrical member described in the claims, and the inner wall surface portion 256a is an example of a cylindrical inner wall portion described in the claims. (First embodiment)

[0107] A first embodiment of the present invention, which is shown in the Fig. 8 and Fig. 9 shows another modified example of the above-described first comparative example. A control body 340 of a fuel injection device 300 according to the first embodiment has a cylinder 356 corresponding to the cylinder 56 (see Fig. 3) of the first comparative example. Furthermore, the fuel injection device 300 of the first embodiment includes a floating plate 370 corresponding to the floating plate of the first comparative example. Hereinafter, the structure of the fuel injection device 300 according to the first embodiment will be described with respect to the Fig. 8 and Fig. 9 described in detail.

[0108] An inner wall surface portion 356a of the cylinder 356 is provided with a connecting groove 357a, a sliding contact wall surface 357b, a plate stopper portion 358a, and a sub-connecting groove 357g. Corresponding to the connecting groove 257a (see Fig. 6) In the second comparative example, the connecting groove 357a extends along the axial direction of the cylinder 356, thereby connecting the inlet chamber 53a to the backpressure chamber 53b. A pair of connecting grooves 357a are provided on the inner wall surface portion 356a. The connecting grooves 357a are spaced apart from each other by 180° in the circumferential direction of the cylinder 356. In the radial direction of the cross section perpendicular to the axial direction of the cylinder 356, a bottom portion 357d of the connecting grooves 357a has a circular arc shape. The slidable contact wall surface 357b is disposed between the adjacent connecting grooves 357a and slidably contacts an outer peripheral wall surface portion 74 of the floating plate 370.

[0109] The plate stopper portion 358a has a stepped shape extending radially inward relative to the inner wall surface portion 356a and is opposite to the pressure-receiving surface 377, which is an end surface of the floating plate 370 on the back pressure chamber 53b side. The plate stopper portion 358a contacts the pressure-receiving surface 377 of the floating plate 370 due to the displacement of the floating plate 370, which is spaced from the inlet channel 52, such that the plate stopper portion 358a restricts the displacement of the floating plate 370. The two sub-connection grooves 357g are provided on the plate stopper portion 358a.

[0110] The two sub-connecting grooves 357g are connected to the corresponding two connecting grooves 357a. Therefore, each connecting groove 357a is provided with the corresponding sub-connecting groove 357g to connect the inlet chamber 53a with the backpressure chamber 53b. The sub-connecting grooves 357g are provided in the circumferential direction of the cylinder 356 and are spaced 180° apart from each other. In the radial direction of the cross-section perpendicular to the axial direction of the cylinder 356, the sub-connecting groove 357g has a circular arc shape. The sub-connecting groove 357g and the bottom portion 357d of the connecting groove 357a are coaxial with each other and have the same radius. A center or the center of the circular arc shape of the sub-connecting groove 357g is arranged inside the disk stopper portion 358a in the radial direction of the cylinder 356.Thus, a channel area of ​​the sub-connecting groove 357g becomes larger in the flow direction from the inlet chamber 53a to the back pressure chamber 53b as it reaches the downstream side.

[0111] As described above, by providing the plate stopper portion 358a with the sub-connection groove 357g, even when the floating plate 370 and the plate stopper portion 358 communicate with each other, the fuel can flow between the inlet chamber 53a and the backpressure chamber 53b. Thus, in the pressure receiving surface 377 of the floating plate 370, a configuration corresponding to the radial groove 77a (see Fig. 3) can be waived.

[0112] According to the first embodiment, the sub-connecting groove 357g is provided in the plate stopper portion 358a and integrated with the connecting groove 357a to connect the inlet chamber 53a to the backpressure chamber 53b, ensuring the flow of fuel from the inlet chamber 53a into the backpressure chamber 53b. Therefore, the pressure recovery in the backpressure chamber 53b is prevented from being interrupted by the contact between the pressure-receiving surface 377 and the plate stopper portion 358. Thus, the responsiveness of the nozzle needle 60 at both the valve closing and valve opening timings according to the fuel injection device 300 can be improved.

[0113] Furthermore, according to the first embodiment, the passage area of ​​the sub-connecting groove 357g becomes larger as it reaches the downstream side, so that the pressure of the fuel flowing through the sub-connecting groove 357g decreases as the fuel reaches the downstream side. This draws the fuel flowing through the connecting groove 357a and the sub-connecting groove 357g toward the downstream side, allowing the fuel to flow more smoothly from the inlet chamber 53a into the backpressure chamber 53b. Thus, the pressure recovery time can be shortened, so that the responsiveness of the nozzle needle 60 at the valve closing time can be further improved.

[0114] According to the first embodiment, a plurality of connecting grooves 357a and a plurality of sub-connecting grooves 357g, which may be more than two, can be provided, thereby ensuring an increase in the channel area through which the fuel flows from the inlet chamber 53a to the backpressure chamber 53b. Furthermore, by equally spacing the plurality of connecting grooves 357a and a plurality of sub-connecting grooves 357g from each other in the circumferential direction of the cylinder 356, the fuel can flow evenly around the floating plate 370. Thus, the inclination of the floating plate can be limited. As described above, the channel area is increased and the posture of the floating plate 370 is stabilized, so that pressure recovery in the backpressure chamber 53b can be achieved quickly and smoothly. Thus, the movement start time of the nozzle needle 60 is advanced, and the timing fluctuation can be small.Therefore, the responsiveness of the nozzle needle 60 to the valve closing timing can be improved.

[0115] According to the first embodiment, the radial groove for connection can be omitted in the floating plate 370, so that the manufacturing cost of the floating plate 370 can be reduced. Furthermore, in the cross section of the cylinder 356, the sub-connection groove 357g and the connection groove 357a are each defined by their arcs, which are coaxial and have the same radius. Thus, the cutting processes for forming the connection groove 357a and the sub-connection groove 357g in the cylinder 356 can be performed simultaneously with the same tool. Therefore, the simultaneous formation of the connection groove 357a and the sub-connection groove 357g results in a cost reduction in the manufacturing of the cylinder 356. This can improve the responsiveness of the nozzle element according to the fuel injection device 300 at both the valve closing and valve opening timings at a lower cost.

[0116] According to the first embodiment, the control body 340 is an example of a valve body described in the claims, the cylinder 356 is an example of a cylindrical member described in the claims, the inner wall surface portion 356a is a cylindrical inner wall portion described in the claims, and the floating plate 370 is an example of a control member described in the claims. (Third comparative example)

[0117] One in Fig. The third comparative example shown in Figure 10 shows a modification example of the second comparative example. A fuel injection device 400 according to the third comparative example includes a cylinder 456 corresponding to the cylinder 256 in the second comparative example. Hereinafter, the structure of the fuel injection device 400 according to the third comparative example will be described with respect to Fig. 10 and Fig. 6 described in detail.

[0118] An inner wall surface 456a of the cylinder 456 has a connecting wall portion 457c and four connecting grooves 457a, substantially corresponding to the connecting groove 257a of the second comparative example. The connecting wall portion 457c is disposed between the connecting grooves 457a, which are adjacent to each other in the circumferential direction of the cylinder 456, and defines a connecting gap 475, which connects the inlet chamber 53a to the backpressure chamber 53b, between the floating plate 70 and the outer peripheral wall surface portion 74.

[0119] According to the third comparative example, a sufficient channel area of ​​the passage connecting the intake chamber 53a and the backpressure chamber 53b is ensured by the connecting groove 457a. Thus, the responsiveness of the nozzle needle 60 at the valve closing time can be improved.

[0120] Furthermore, the sufficient passage area is ensured by the connecting groove 457a, so that the passage area defined by the connecting gap 375 does not necessarily need to be enlarged. Thus, the depth of the connecting gap 475 can be so small that the inclination of the axis of the floating plate 70 can be restricted. On the other hand, even if the passage area of ​​the connecting gap 375 is small, forming the connecting gap 375 results in an increase in the overall passage area of ​​the passage connecting the intake port 53a and the backpressure chamber 53b. This increases the amount of fuel flowing from the intake chamber 53a into the backpressure chamber 53b. Thus, the pressure recovery time is shortened, so that the responsiveness of the nozzle needle 60 at the valve closing time can be further improved.

[0121] According to the third comparative example, the cylinder 456 shows an example of a cylindrical member described in the claims, and the inner wall surface portion 456a shows an example of a cylindrical inner wall portion described in the claims. (Fourth comparative example)

[0122] One in Fig. The fourth comparative example shown in Figure 11 shows a further modification example of the second comparative example. In a fuel injection device 500 according to the fourth comparative example, a cylinder 556 corresponding to the cylinder 256 of the second comparative example is arranged. Hereinafter, the structure of the fuel injection device 500 according to the fourth comparative example will be described with respect to the Fig. 6 and Fig. 11 described in detail.

[0123] In an inner wall surface portion 556a of a cylinder 556, a connecting groove 557a and a sliding contact wall surface 557b, which correspond to the connecting groove 257a and the sliding contact wall surface 257b of the second comparative example, are arranged. According to the fourth comparative example, four connecting grooves 557a connecting the inlet chamber 53a and the backpressure chamber 53b are equally spaced from each other in the circumferential direction of the cylinder 556. Each connecting groove 557a is spirally wound around the central axis of the cylinder 556. A sliding contact wall surface 557b is provided between the spiral connecting grooves 557a and the sliding contacts of the outer peripheral wall surface portion 74 of the floating plate 70.

[0124] According to the fourth comparative example, even if the communication groove 557a is spirally wound, it is possible for the intake chamber 53a to communicate with the backpressure chamber 53b via the communication groove 557a, so that pressure recovery in the backpressure chamber 53b can be achieved quickly. Thus, even if the communication groove 57a is spirally formed on an inner wall surface portion 556a of the cylinder 556, the responsiveness of the nozzle needle 60 at the valve closing time can be improved.

[0125] According to the fourth comparative example, the cylinder 556 is an example of a cylindrical member described in the claims, and the inner wall surface portion 556a is an example of a cylindrical inner wall portion described in the claims. (Fifth and sixth comparative examples)

[0126] A fifth comparative example and a sixth comparative example, shown in the Fig. 12 and Fig. 13 show further modified examples of the second comparative example. Fuel injection devices 600, 700 according to the fifth comparative example and the sixth comparative example include cylinders 656, 756 corresponding to cylinder 256, respectively (see Fig. 6) The second comparative example. Knurling is performed on each of the inner wall surface portions 656a, 756a of the cylinders 656, 756 relative to the connecting grooves 657a, 757a to connect the inlet chamber 350a with the backpressure chamber 53a. For example, reference is made to JISB-0951, which defines this type of knurling.

[0127] More precisely, as in Fig. 12, the knurling as the connecting groove 657a of the fifth comparative example is formed by equally spacing microgrooves extending along the axial direction of the cylinder 656 from each other in the circumferential direction of the cylinder 656. The knurling in Fig. 12 corresponds to a parallel knurling defined in accordance with JISB-0951 above. The fuel introduced into the inlet chamber 53a flows through the knurls and passes the floating plate 70 in the translational or axial direction, whereby the fuel reaches the backpressure chamber 53b.

[0128] Furthermore, the knurling, as in Fig. 13, in the sixth comparative example, the connecting groove 757a is formed by equally spacing microgrooves spirally extending around the central axis of the cylinder 756 from each other in the circumferential direction of the cylinder 756. By changing a rotation direction of each spiral groove, the plurality of microgrooves intersect with each other, thereby forming a diamond pattern. The knurling corresponds to a diamond knurling defined in JISB-0951 described above. The fuel introduced into the inlet chamber 53a flows through the knurling and passes the floating plate 70 in the displacement axial direction, thereby flowing into the backpressure chamber 53b.

[0129] As described above, according to the fifth and sixth comparative examples, the knurling can be formed as the connecting grooves 657a, 757a. Even the knurling described above allows fuel to flow from the intake port 53a into the backpressure chamber 53b in such a way that pressure recovery in the backpressure chamber 53b can be achieved quickly. Therefore, the responsiveness of the nozzle needle 60 at the valve closing time can be improved. (Seventh comparative example)

[0130] One in Fig. The seventh comparative example shown in Fig. 14 shows another modification example of the first comparative example. In a fuel injection device 800 according to the seventh comparative example, a structure corresponding to the cylinder 56 (see Fig. 3), which defines the radial direction of the pressure control chamber 53 in the first comparative example, is omitted. In addition, the structure corresponding to the nozzle body 41 (see Fig. 3) the first comparative example, a first nozzle body 841a and a second nozzle body 841b are provided. Hereinafter, based on Fig. 14, the structure of the fuel injection device 800 according to the seventh comparative example will be described.

[0131] The first nozzle body 841a and the second nozzle body 841b are arranged in this order from a tip of a control body 840. The injection opening 44 (see Fig. 2) is formed at a tip of the first nozzle body 841a. The pressure control chamber 53 is arranged in the second nozzle body 841b.

[0132] The first nozzle body 841a and the second nozzle body 841b include a nozzle needle housing portion 843 and a supply passage 843a. The nozzle needle housing portion 843 and the supply passage 843a correspond to the nozzle needle housing portion 43 and the supply passage 43a of the first comparative example.

[0133] The nozzle needle housing portion 843 is arranged in the radial center portion of the first nozzle body 841a and the second nozzle body 841b and is configured to be formed in the nozzle bodies 841a, 841b. On an inner wall surface portion 856a on the side of the second nozzle body 841b, a control wall surface portion 857, a cylinder displacement surface portion 859, a plate stopper portion 858a, and a needle stopper portion 858b are provided as the nozzle needle housing portion 843. The control wall surface portion 857, the cylinder displacement surface portion 859, the plate stopper portion 858a, and the needle stopper portion 858b are substantially similar to the corresponding components 57, 59, 58a, 58b (see Fig. 3) formed in the inner wall surface portion 56a of the cylinder 56 of the first comparative example. The pressure control chamber 53 of the seventh comparative example is defined by the control wall surface portion 854 of the second nozzle body 841b, the pressure-receiving surface 61 of the nozzle needle 60, and the orifice wall surface 90.

[0134] A supply passage 843a is arranged on an outer peripheral side of the pressure control chamber 53 and is configured to extend within the first nozzle body 841a and the second nozzle body 841b. The supply passage 843a extends along the axial direction of the control body 840 and is connected to the nozzle needle housing portion 843 at a tip side in the axial direction. Thus, the supply passage 843a supplies the pressurized fuel through the nozzle needle housing portion 843.

[0135] In the control body 840 of the seventh comparative example, the pressure control chamber 53 and the supply passage 843a are arranged. The pressure control chamber 53 restricts the movement of the nozzle needle 60, and the supply passage 843a is a portion through which the pressurized fuel flows into the injection port 44 (see Fig. 2). According to the first comparative example, the pressure control chamber 53 is supplied from the supply passage 43a (see Fig. 3). In the seventh comparative example, however, the supply passage 843a is arranged on the outer peripheral side of the pressure control chamber 53 such that the pressure control chamber 53 is defined by the second nozzle body 841b in a state where the pressure control chamber 53 is separated from the supply passage 843a.

[0136] As described above, the component defining the pressure control chamber 53 can be changed or replaced depending on the configuration of the fuel injection device. However, regardless of the component defining the pressure control chamber 53, if a communication groove 857a is formed on the inner wall surface portion 856a defining the pressure control chamber 53, and this allows the fuel flow from the inlet chamber 53a into the backpressure chamber 53b, the pressure recovery in the backpressure chamber 53b can be achieved quickly. Therefore, regardless of the configuration of the fuel injection device, the formation of the communication groove 857a results in improving the responsiveness of the nozzle needle 60 at the valve closing time.

[0137] According to the seventh comparative example, a control body 840 shows an example of a valve body described in the claims, the first nozzle body 841a and the second nozzle body 841b show examples of a nozzle element described in the claims, and the inner wall surface portion 856a shows an example of a cylindrical inner wall portion described in the claims.

[0138] Although the present invention has been described together with the preferred embodiments and examples with reference to the accompanying figures, it should be noted that various changes and modifications can be deduced therefrom by those skilled in the art.

[0139] The configuration mentioned above includes two or four connecting grooves equally spaced from each other in the circumferential direction of the cylinder on the inner wall surface portion. However, the number, position, and configuration of the connecting grooves are not limited to this. For example, only one connecting groove may be provided on the inner wall surface portion of the cylinder of the fuel injection device.

[0140] In the above, either the sliding contact wall surface or the connecting wall portion is provided between the connecting grooves arranged on the inner wall surface portion of the cylinder. However, both the sliding contact wall surface and the connecting wall portion may be provided. This provision results in limiting the inclination or deflection of the floating plate and ensuring sufficient fuel flow from the inlet chamber 53a into the backpressure chamber 53b.

[0141] In the first embodiment described above, the channel area of ​​the sub-connection groove 357g is configured to increase in size toward the downstream. However, the configuration of the sub-connection groove 357g is not limited to the configuration of the first embodiment. For example, the sub-connection groove may extend along the radial direction and be configured as a homogeneous channel area. Furthermore, the number and position of the sub-connection groove are not limited to the configuration described above.

[0142] Above, in the axial direction of the fuel injection device, the pressure control chamber 53 is arranged in a portion closer to the tip side, in which the injection port 44 is formed, than to the base side where the pedestal portion 48c is provided. However, in a conventional fuel injection device, a configuration corresponding to the pressure control chamber for controlling the movement of the nozzle needle is arranged at a position closer to the base side than to the tip side. The present invention can be applied to this conventional fuel injection device. More specifically, in the above first to sixth comparative examples and the first embodiment, the pressure control chamber 53 is defined by the plurality of components constituting the control body, and particularly by the cylinder.In the seventh comparative example, the pressure control chamber 53 is basically defined by the second nozzle body 841b. However, the pressure control chamber 53 may also be defined by components constituting the control body other than the cylinder or the nozzle body, such as components corresponding to the holder 48 in the above-described examples and embodiments.

[0143] In the above, the structure for moving the movable member by the electromagnetic force of the solenoid 31 is used as the drive section for opening and closing the pressure control valve 80, which controls the fuel pressure in the pressure control chamber 53. However, a drive section other than the solenoid 31, such as a piezoelectric element, may also be used. In this case, too, the drive section for opening and closing the pressure control valve 80 can be controlled based on the control signal from the engine controller 17.

[0144] In the above, the present invention is applied to a fuel injection device for a diesel engine 20 that injects fuel directly into a combustion chamber 22. However, the present invention is not limited to the diesel engine 20, but can also be applied to an internal combustion engine such as an Otto engine and the like. Furthermore, the fuel injected by the fuel injection device is not limited to light oil or diesel, but can also be, for example, gasoline, LPG, and the like. Furthermore, the present invention can also be applied to a fuel injection device that injects fuel not into a combustion chamber of an internal combustion engine but into an external combustion engine.

Claims

A fuel injection device comprising: a valve body (40) in which a high-pressure fuel passage is provided, the valve body having an injection opening (44) at a tip from which the high-pressure fuel is injected into a combustion chamber of an internal combustion engine; a valve element (60) which is provided in the valve body so as to be movable in its axial direction and which opens or closes the injection opening; a pressure control chamber (53) which is provided in the valve body on a side opposite the injection opening with respect to the valve element and which introduces the high-pressure fuel and controls the movement of the valve element by means of the fuel pressure; an inlet channel (52) through which the high-pressure fuel is introduced into the pressure control chamber; an outlet channel (54) through which the fuel is discharged from the pressure control chamber to an outer low-pressure side; and a control element (70),which is present in the valve body in its axial direction and opens or closes the inlet channel, wherein the valve body includes a cylindrical inner wall portion (356a) defining the pressure control chamber in its radial direction, and the cylindrical inner wall portion includes a connecting groove (357a) connecting an inlet chamber (53a) provided in the pressure control chamber on one side of the inlet channel with respect to the control element with a back pressure chamber (53b) provided in the pressure control chamber on one side of the valve element with respect to the control element, wherein the valve body is provided with a restricting portion (358a) opposite an end face of the control element on one side of the back pressure chamber, and the restricting portion is provided with a sub-connecting groove (357g) which, together with the connecting groove (357a), connects the inlet chamber with the back pressure chamber,and which ensures the fuel flow from the inlet chamber (53a) to the backpressure chamber (53b)., A fuel injection device according to claim 1, wherein the cylindrical inner wall portion is provided with a displaceable contact wall surface (357b) on an outer peripheral wall portion about a displacement axis of the control element. A fuel injection device according to claim 1 or 2, wherein the cylindrical inner wall portion is provided with a connecting wall surface defining a connecting gap between the cylindrical inner wall portion and an outer peripheral wall about a displacement axis of the control element, and the connecting gap connects the inlet chamber to the back pressure chamber. A fuel injection device according to any one of claims 1 to 3, wherein a bottom portion (357d) of the connecting groove (357a) has an arcuate cross section in the radial direction. Fuel injection device according to one of claims 1 to 4, wherein a plurality of connecting grooves (357a) are arranged in the circumferential direction of the cylindrical inner wall portion and spaced from each other. A fuel injection device according to claim 5, wherein the connecting grooves (357a) are evenly spaced from each other in the circumferential direction. A fuel injection device according to claim 1, wherein the restricting portion (358a) is configured in a stepped shape extending toward the radially inner side of the cylindrical inner wall portion. The fuel injection device according to claim 1 or 7, wherein the sub-connection groove (357g) is configured to enlarge a passage area downstream in the flow direction from the inlet chamber to the backpressure chamber. A fuel injection device according to any one of claims 1 or 7 or 8, wherein the cylindrical inner wall portion includes a plurality of communication grooves (357a) spaced from each other in the circumferential direction, the restricting portion (358a) includes a plurality of sub-communication grooves (357g) communicating with the communication grooves (357a) respectively and spaced from each other in the circumferential direction, and the communication grooves (357a) and the sub-communication grooves (357g) are equally spaced from each other in the circumferential direction. A fuel injection device according to any one of claims 1 or 7 to 9, wherein a bottom portion (357d) of the connecting groove(s) (357a) is / are configured in a circular arc shape in cross section, and the sub-connecting groove(s) (357g) is / are configured in a circular arc shape which is coaxial with the bottom portion and has the same radius as the bottom portion. A fuel injection device according to claim 10, wherein the center of the circular arc shape of the sub-connecting groove(s) (357g) is located at the radial center of the restricting portion (358a). Fuel injection device according to one of claims 1 to 11, wherein the connecting groove(s) (357a) extends(s) along the axial direction. A fuel injection device according to any one of claims 1 to 12, wherein the connecting groove(s) (357a) is / are spirally wound along the central axis of the cylindrical inner wall portion. A fuel injection device according to any one of claims 1 to 13, wherein the valve body is provided with a supply passage (43a) through which the high-pressure fuel is supplied into the injection port located at the tip end, and the valve body includes a cylindrical member held in the supply passage, defining the cylindrical inner wall portion on an inner peripheral side, and separating the pressure control chamber from the supply passage. A fuel injection device according to any one of claims 1 to 13, wherein the valve body has a nozzle element (841a, 841b) forming the tip end in which the injection port is provided, and the nozzle element defines the pressure control chamber through the cylindrical inner wall portion, and a supply passage (843a) positioned on an outer peripheral side of the pressure control chamber for supplying the high-pressure fuel into the injection port.

Images