JP2010255427A - Fuel injection valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection valve including a sensor element detecting fuel pressure capable of suppressing an increase in the number of components, suppressing an increase in machining cost, and relaxing the mounting position accuracy of the sensor element. <P>SOLUTION: The fuel injection valve inserted and arranged in the cylinder head of an internal combustion engine and injecting high-pressure fuel from a nozzle port includes a body 40 internally forming a high-pressure passage 422 extending in an insertion direction into the cylinder head and circulating high-pressure fuel toward the nozzle port. The high-pressure passage 422 is formed in a position decentered with respect to the shaft center J1 of the body 40, and a sensor chip 81 (sensor element) outputting an electric signal according to the amount of distortion of the outer peripheral surface of a thin-walled portion 41 is attached to the outer peripheral surface of the thin-walled portion where the body 40 around the high-pressure passage 422 becomes thinnest. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel injection valve that is mounted on an internal combustion engine and injects fuel for combustion from an injection hole.

  In order to accurately control the output torque and the emission state of the internal combustion engine, it is important to accurately control the injection state such as the injection start timing and the injection amount of the fuel injected from the fuel injection valve. Therefore, conventionally, there has been proposed a technique for detecting an actual injection state by detecting the pressure of fuel that fluctuates with the injection. For example, the actual injection start time can be detected by detecting the time when the fuel pressure starts to decrease with the start of injection, or the actual injection end time can be determined by detecting the time when the increase in fuel pressure has stopped with the end of injection. Or detected (see Patent Documents 1 to 3).

  When detecting such fluctuations in fuel pressure, the fuel pressure sensor (rail pressure sensor) installed directly on the common rail (accumulation vessel) buffers the fuel pressure fluctuation caused by injection in the common rail. Variation cannot be detected. Therefore, in the inventions described in Patent Documents 1 to 3, by mounting the fuel pressure sensor on the fuel injection valve, it is intended to detect the fuel pressure fluctuation before the fuel pressure fluctuation caused by the injection is buffered in the common rail. .

JP 2008-144749 JP 2009-57926 A JP 2009-57927 A

  However, although Patent Documents 1 to 3 disclose that the fuel pressure sensor is mounted on the fuel injection valve, the details of the mounting structure are not disclosed. Therefore, the present inventors examined a structure in which the fuel pressure sensor is mounted on the body 40x as shown in FIG. A body 40x shown in FIG. 6A extends in a direction in which the fuel injection valve is inserted into the cylinder head (vertical direction in FIG. 6A), and passes through a high-pressure passage 422x through which high-pressure fuel flows toward the nozzle hole. It is formed inside.

  A bottomed cylindrical strain body 89 formed separately from the body 40x is attached to the attachment hole 41x of the body 40x. The bottom portion (thin portion 89a) of the strain body 89 is formed to be thin so as to function as a diaphragm, and a sensor chip 81x having a strain gauge (sensor element) is attached to the outer surface of the thin portion 89a. A branch passage 423x branched from the high pressure passage 422x is formed inside the body 40x so that the high pressure fuel in the high pressure passage 422x is introduced into the internal passage 89b of the strain body 89. As described above, the pressure of the fuel is detected by detecting the amount of strain of the strain generating body 89 by the sensor chip 81x.

  However, in the configuration of FIG. 6A, the strain body 89 separate from the body 40x is required, which increases the number of parts. On the other hand, as shown in FIG. 6B, if the branch passage 423x is drilled so as to form the thin portion 41x in the body 40x, the strain generating body 89 can be eliminated, but the branch passage is separate from the high pressure passage 422x. Since drilling of 423x is required, the processing cost is increased.

  6 (a) and 6 (b), the thin-walled portions 89a and 41x are oriented in a direction orthogonal to the internal passage 89b or the branch passage 423x, so that they are radially distorted (FIGS. 6 (c) and (d). ) See the arrow in the middle). Then, the detection value of the sensor chip 81x changes only by slightly shifting the mounting position of the sensor chip 81x (sensor element) to the thin portions 89a and 41x (see FIGS. 6E and 6F). Therefore, it is required to manage the mounting position of the sensor chip 81x (sensor element) with high accuracy.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to suppress increase in the number of parts, suppression of increase in processing cost, and sensor in a fuel injection valve provided with a sensor element for detecting fuel pressure. An object of the present invention is to provide a fuel injection valve in which the mounting position accuracy of an element is eased.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

  According to a first aspect of the present invention, in a fuel injection valve that is inserted into a cylinder head of an internal combustion engine and injects high-pressure fuel from an injection hole, the high-pressure fuel extends toward the cylinder head and is injected toward the injection hole. A body that forms a high-pressure passage to be circulated therein, the high-pressure passage is formed at a position deviated from an axial center of the body, and an outer peripheral surface of a thin-walled portion where the body is thinnest among the periphery of the high-pressure passage Further, a sensor element (for example, a strain gauge or a piezoelectric element) that outputs an electric signal corresponding to the amount of strain on the outer peripheral surface is attached.

  According to this, since the thin wall portion is formed in the body by decentering the high-pressure passage from the axial center of the body, the strain body 89 shown in FIG. 6A can be made unnecessary, and FIG. The described branch passage 423x can be dispensed with. Therefore, an increase in the number of parts and an increase in processing cost can be suppressed.

  Further, according to the present invention, since the thin portion is parallel to the high-pressure passage, the thin portion is mainly distorted in the circumferential direction of the body (see arrow Y1 in FIG. 3B), and the axis of the body Almost no distortion occurs in the central direction (see arrow Y2 in FIG. 3B). Therefore, the detected value of the sensor element hardly changes if the mounting position of the sensor element on the thin wall portion is slightly shifted in both the circumferential direction Y1 and the axial center direction Y2. Therefore, the mounting accuracy of the sensor element can be relaxed.

  The invention according to claim 2 includes an amplifier circuit that amplifies the detection signal of the sensor element, and forms a recess in a range including the outer peripheral surface of the thin portion of the outer peripheral surface of the body, The amplifier circuit and the sensor element are attached.

  By the way, although the fuel pressure detection accuracy by the sensor element can be improved as the thickness of the thin portion is reduced, for example, when the high pressure passage is formed by drilling, there is a limit to reducing the thickness of the thin portion. According to the above-described invention in view of this point, since the concave portion is formed in the range including the outer peripheral surface of the thin portion of the outer peripheral surface of the body, the thickness of the thin portion can be reduced and the fuel pressure detection accuracy can be improved. And since it is the structure which aims at the further thinning of a thin part using the recessed part for forming the bottom face which attaches an amplifier circuit, the processing cost increase of a body can be suppressed.

  According to a third aspect of the present invention, an upstream side passage extending in a bent direction from an upstream end portion of the high pressure passage is formed inside the body, and the upstream side passage and the high pressure passage are arranged in the insertion direction. The concave portion is positioned on the side of the high-pressure passage with respect to the connecting portion.

  Here, as in the connection portion of the upstream passage and the high pressure passage, the bent portion of the passage (portion illustrated by the one-dot chain line P in FIG. 2) is more likely to concentrate stress than the other portions. There is concern that the pressure strength of the body will be low. According to the above-mentioned invention in view of this point, since the concave portion is positioned on the downstream side of the connection portion (bent portion), it can be avoided that the thickness of the body in the bent portion is reduced by the concave portion. Therefore, it is possible to suppress a decrease in the pressure strength at the bent portion, and to solve the above-mentioned concern.

  In the invention according to claim 4, the sensor element (for example, a strain gauge or a piezoelectric element) has directivity so as to detect a strain amount or a stress in a specific direction (detection direction), and the specific direction ( The sensor element is arranged so that a detection direction) intersects with a longitudinal direction of the high-pressure passage.

  As described above, the thin portion is mainly distorted in the circumferential direction Y1 of the body and hardly distorted in the axial direction Y2 of the body (that is, the longitudinal direction of the high-pressure passage). Therefore, if the detection direction of the sensor element is parallel to the axial center direction Y2 contrary to the above invention, the detection sensitivity is lowered. According to the above invention in view of this point, the detection direction of the sensor element is set to a direction intersecting with the axial center direction Y2, so that the detection sensitivity can be improved. In particular, it is preferable to make the detection direction orthogonal to the axial direction Y2 because the detection sensitivity can be further improved. Alternatively, when a bridge circuit is formed by combining a plurality of sensor elements, the detection sensitivity can be improved by arranging the plurality of sensor elements so as to intersect with the axial center direction Y2 (see FIG. 5). Is preferred.

  According to a fifth aspect of the present invention, the body is inserted and disposed in a body insertion hole formed in the cylinder head, and is configured to be pressed against the body insertion hole by a clamp. A pressing surface that is pressed by contact is formed, and the sensor element is located on the side opposite to the injection hole (upper side in FIG. 1) than the pressing surface.

  According to this, since the sensor element is arranged above the pressing surface on which the force from the clamp acts on the body, the portion of the body where the distortion increases (that is, the portion supported by the cylinder head and the pressing surface) The sensor element will be located at a location deviating from the portion between the two. Therefore, it is possible to suppress the sensor element from being affected by the distortion generated in the body, and the fuel pressure detection accuracy can be improved.

1 is an overall cross-sectional view of a fuel injection valve according to a first embodiment of the present invention. The enlarged view of FIG. 1A is a cross-sectional view of FIG. 1 in the sensor chip portion, FIG. 1B is a view taken along an arrow A in FIG. 1A, and FIGS. . Sectional drawing of the fuel injection valve concerning 2nd Embodiment of this invention. Sectional drawing of the fuel injection valve concerning 3rd Embodiment of this invention. It is a figure which shows the comparative example for demonstrating the effect of this invention, Comprising: (a) (b) is sectional drawing of a body, (c) (d) is an A arrow view of (a) (b), e) (f) is an A arrow view showing a state where the mounting position of the sensor chip is shifted from the positions shown in (c) and (d).

  Embodiments in which a fuel injection valve according to the present invention is applied to a common rail fuel injection system of a diesel engine (internal combustion engine) mounted on a vehicle will be described below with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are denoted by the same reference numerals in the drawings, and the description of the same reference numerals is used.

(First embodiment)
1 is an overall cross-sectional view of the fuel injection valve 10, and FIG. 2 is an enlarged view of FIG. The fuel injection valve 10 is inserted and mounted in a cylinder head E2 of the internal combustion engine, and directly injects fuel supplied from a common rail into the combustion chamber E1 of each cylinder of the engine.

  First, the overall structure of the fuel injection valve 10 will be described with reference to FIG. The fuel injection valve 10 includes a nozzle body 20, a needle 30, a main body 40, an orifice plate 50, an electromagnetic unit 60, and the like.

  A part of the nozzle body 20 and the main body 40 is inserted and disposed in a body insertion hole E3 formed in the cylinder head E2. The body body 40 is formed with an engaging portion 40a (pressing surface) that engages with one end of the clamp K. By tightening the other end of the clamp K to the cylinder head E2 with a bolt, one end of the clamp K is engaged. The part 40a is pressed toward the body insertion hole E3. Thereby, the fuel injection valve 10 is fixed in a state of being pressed into the body insertion hole E3.

  The nozzle body 20 is fixed to the lower side (injection hole side) of the main body body 40 via the orifice plate 50 by the retaining nut 11. The nozzle body 20 is formed with a guide hole 21 (needle accommodating chamber) for slidably accommodating the needle 30 and an injection hole 22 for injecting fuel when the needle 30 is lifted up. In this specification, the side of the nozzle hole 22 with respect to the nozzle body 20 (lower side in FIG. 1) is referred to as “lower side”, and the opposite side of the nozzle hole 22 (upper side in FIG. 1) is referred to as “upper side”.

  The guide hole 21 is drilled from the upper end surface of the nozzle body 20 toward the tip of the nozzle body 20, and a high-pressure passage 23 that guides high-pressure fuel to the injection hole 22 through a gap between the inner peripheral surface of the guide hole 21 and the outer peripheral surface of the needle 30. Is formed. Further, a fuel reservoir chamber 24 in which the inner diameter of the nozzle body 20 is enlarged is formed in the middle of the guide hole 21. The high-pressure passage 23 (guide hole 21) is connected to a high-pressure passage 51 formed in the orifice plate 50 with an upstream end opened to the upper end surface of the nozzle body 20.

  A conical seating surface 20 s is formed at the tip of the high pressure passage 23 on the inner peripheral surface of the nozzle body 20, and a seat surface 30 s seated on the seating surface 20 s is formed at the tip of the needle 30. When the seat surface 30 s is seated on the seating surface 20 s, the needle 30 blocks and blocks the high-pressure passage 23 leading to the injection hole 22.

  A cylindrical cylinder 25 is disposed in the guide hole 21, and a spring that presses the needle 30 in the valve closing direction (downward in FIG. 1) between the lower end surface of the cylinder 25 and the upper end surface of the needle 30. 26 is arranged. A back pressure chamber 27 is formed on the inner peripheral surface of the cylinder 25 to apply a high pressure fuel pressure as a back pressure to the upper end surface of the needle 30. This back pressure biases the needle 30 in the valve closing direction (downward in FIG. 1). Further, the pressure of the high-pressure fuel in the fuel reservoir 24 urges the needle 30 in the valve opening direction (upward in FIG. 1).

  A high-pressure port 44 (high-pressure pipe connection portion) connected to a high-pressure pipe (not shown) and a low-pressure connector 90 (low-pressure pipe connection portion) connected to a low-pressure pipe (not shown) are provided on the upper end surface of the cylindrical body body 40. It is attached. The surplus of high-pressure fuel supplied from the common rail to the high-pressure port 44 through the high-pressure pipe is discharged through the low-pressure connector 90. The supply port 44 a that opens to the high-pressure port 44 is disposed on the axial center J1 of the main body 40.

  In the main body 40, an upstream side passage 421, a high pressure passage 422, a low pressure passage 423 (see FIG. 3), an electromagnetic unit accommodation hole 43, and the like described below are formed.

  The upstream passage 421 is formed by drilling so as to extend downward from the supply port 44a, and the extending direction (drilling direction) of the upstream passage 421 is inclined with respect to the axis center J1 of the main body 40. A filter 421a is inserted into the upstream passage 421 from the supply port 44a.

  The high-pressure passage 422 has a shape extending linearly in the direction of insertion into the body insertion hole E3 of the fuel injection valve 10 (the vertical direction in FIG. 1). Specifically, it is formed by drilling so as to extend upward from the lower end surface 40R of the main body 40, and the extending direction (drilling direction) of the high-pressure passage 422 is parallel to the axis center J1 of the main body 40. . Further, the high pressure passage 422 is formed so that the axial center J2 of the high pressure passage 422 is eccentric from the axial center J1 of the main body 40 (see FIG. 2). The upstream end of the high pressure passage 422 is connected to the downstream end of the upstream passage 421.

  In short, the high-pressure passage 422 that extends parallel to the shaft center J1 at a position that is eccentric from the shaft center J1 of the main body 40 is the center of the shaft at the connecting portion with the upstream passage 421 (bent portion indicated by the dashed line P in FIG. 2). Bend toward J1.

  The low pressure passage 423 is a fuel passage for guiding excess fuel from the back pressure chamber 27 to the low pressure connector 90, and is formed by drilling so as to penetrate the main body 40 in the vertical direction.

  The electromagnetic unit 60 is inserted and disposed in the electromagnetic unit accommodation hole 43. This electromagnetic unit accommodation hole 43 is formed by drilling so as to extend upward from the lower end surface 40R of the main body 40, and the extending direction (drilling direction) of the high-pressure passage 422 is relative to the axial center J1 of the main body 40. Parallel.

  In the present embodiment, the electromagnetic unit 60 and the high-pressure passage 422 are laid out in a direction perpendicular to the direction of the axis center J1 (the left-right direction in FIG. 1).

  The orifice plate 50 is formed with an inflow passage 52 through which high pressure fuel flows from the high pressure passage 51 to the back pressure chamber 27 and an outflow passage 53 through which the high pressure fuel flows out from the back pressure chamber 27 to the low pressure side. The inflow passage 52 is formed with an inflow side orifice, and the outflow passage 53 is formed with an outflow side orifice.

  The electromagnetic unit 60 includes a stator 63 having an electromagnetic coil 62, an armature 64 that moves to face the stator 63, a ball valve 65 (control valve) that moves integrally with the armature 64 and opens and closes the outflow passage 53. It is prepared for.

  A connector 70 is attached to the upper portion of the main body 40, and the connector 70 includes a resin connector housing 71, a drive connector terminal 72 and a sensor connector terminal 73 held by the connector housing 71. Yes. The electromagnetic coil 62 of the electromagnetic unit 60 and the drive connector terminal 72 are electrically connected by a lead wire 74. Incidentally, the lead wire 74 is inserted into the electromagnetic unit accommodation hole 43 while being held by the holding member 74a.

  When the electromagnetic coil 62 is energized, the armature 64 is attracted to the stator 63 and moved. Further, the spring 66 housed in the central portion of the stator 63 urges the armature 64 in the direction in which the ball valve 65 is closed (downward in FIG. 1).

  Here, the pressure of the high-pressure fuel in the nozzle body 20 and the main body 40 varies with the fuel injection from the nozzle hole 22. A fuel pressure sensor 80 that detects this pressure fluctuation is attached to the outer peripheral surface of the main body 40.

  In the pressure fluctuation waveform detected by the fuel pressure sensor 80, the actual injection start timing can be detected by detecting the timing at which the fuel pressure starts decreasing with the start of injection from the nozzle hole 22. Moreover, the actual injection end time can be detected by detecting the time when the fuel pressure starts to increase with the end of injection. Further, in addition to the injection start timing and the injection end timing, the injection amount can be detected by detecting the maximum value of the fuel pressure decrease amount caused by the injection.

  Next, the structure of the fuel pressure sensor 80 will be described with reference to FIGS. 2 and 3A and 3B. 2 is an enlarged view of FIG. 1, and FIG. 3A is a cross-sectional view of FIG. FIG. 3B is a view taken in the direction of arrow A in FIG. 3A and shows a state in which a shield cover 84 and a connector housing 71 described later are removed from the main body 40.

  The fuel pressure sensor 80 includes a sensor chip 81, a circuit board 82, a sensor terminal 83, and a shield cover 84, which will be described below, and the outer peripheral surface of the main body 40 so as to detect the fuel pressure in the high pressure passage 422. Is attached.

  Here, the shape of the part to which the fuel pressure sensor 80 is attached in the main body 40 will be described in detail. As described above, the high-pressure passage 422 is formed to be eccentric from the axial center J1 of the main body 40. Therefore, as shown in FIG. 3 (a), the thin portion 41 where the main body 40 is the thinnest is formed in the portion of the main body 40 on the eccentric side (the right side of FIG. 3 (a)) with respect to the high pressure passage 422. Will be formed.

  A recess 45 is formed in the outer peripheral surface of the main body 40 including the outer peripheral surface of the thin portion 41 by cutting the outer peripheral surface of the main body 40. The bottom surface 45a of the recess 45 is formed as a flat surface, and the circuit board 82 and the sensor chip 81 are attached to the bottom surface 45a.

  That is, the sensor chip 81 is attached to the outer peripheral surface of the thin portion 41 where the main body 40 is the thinnest around the high pressure passage 422. In other words, the sensor chip 81 is arranged on an extension line of an imaginary line connecting the axis center J1 of the main body 40 and the axis center J2 of the high-pressure passage 422.

  Moreover, the recessed part 45 is arrange | positioned below the connection part (bending part P) of the upstream channel | path 421 and the high voltage | pressure channel | path 422 in the direction of the axial center J1. Specifically, the upper end of the recess 45 is positioned below the bent portion P in the direction of the axis center J1.

  The sensor chip 81 includes a sensor substrate 811 (for example, a silicon substrate) made of a semiconductor bonded and fixed to the bottom surface 45a via an insulating film (for example, a low melting point glass), and a strain gauge 812 (sensor) formed on the sensor substrate 811. Element).

  Due to the pressure of the high-pressure fuel flowing through the high-pressure passage 422, the thin wall portion 41 is elastically deformed so as to expand in the radial direction and the circumferential direction of the main body 40, so that the bottom surface 45a of the recess 45 is distorted. Thus, the strain gauge 812 converts the magnitude of the strain (strain amount) generated on the bottom surface 45a into an electrical signal.

  The strain gauge 812 according to the present embodiment employs a well-known strain gauge having directivity so as to detect a strain amount with respect to a specific direction (detection direction). More specifically, the detection direction is set so that the detection direction of the strain gauge 812 intersects the longitudinal direction of the high-pressure passage 422 (the direction indicated by the arrow Y2 in FIG. 3B). Is aligned with the circumferential direction of the main body 40 (the direction indicated by the arrow Y1 in FIG. 3B).

  Various electronic components (not shown) are mounted on the circuit board 82, and a plurality of sensor terminals 83 are connected thereto. These sensor terminals 83 are electrically connected to the sensor connector terminal 73 described above. The circuit board 82 and the sensor chip 81 are electrically connected by bonding wires W.

  The circuit board 82 includes an amplifier circuit that amplifies the detection signal output from the strain gauge 812, a filtering circuit that removes noise superimposed on the detection signal, a circuit that applies a voltage to the strain gauge 812, and the like.

  When the resistance value of the strain gauge 812 changes according to the magnitude of the strain generated in the thin portion 41, the output voltage of the strain gauge 812 applied with a voltage from the voltage application circuit changes, and the output voltage is the pressure of the high-pressure fuel. The detected value is output to the amplifier circuit of the circuit board 82. The amplifier circuit amplifies the pressure detection value output from the strain gauge 812, and the amplified signal is output from the sensor connector terminal 73 through the sensor terminal 83.

  The plurality of sensor connector terminals 73 include a terminal for outputting a detection signal of the fuel pressure sensor 80, a terminal for supplying power, a grounding terminal, and the like. The connector 70 is connected to a connector of an external harness that is connected to an external device such as an engine ECU (not shown). Thereby, the pressure detection signal output from the circuit board 82 is input into the engine ECU via the external harness.

  The circuit board 82 and the sensor chip 81 are covered with a metal shield cover 84. Accordingly, the shield cover 84 blocks external noise and protects various circuits and the sensor chip 81 included in the circuit board 82.

  The drive connector terminal 72, the sensor connector terminal 73, and the shield cover 84 are molded with a resin material together with the main body 40, and a part of the resin material functions as the connector housing 71.

  Next, the operation of the fuel injection valve 10 will be described.

  When the energization of the electromagnetic coil 62 is stopped, the ball valve 65 closes the outflow passage 53, and therefore the force that urges the needle 30 in the valve closing direction (the force due to the fuel pressure in the back pressure chamber 27). + The urging force of the spring 26) becomes larger than the force that pushes the needle 30 in the valve opening direction (the lift force due to the fuel pressure of the fuel reservoir 24). As a result, the seat surface 30 s of the needle 30 is seated on the seating surface 20 s and the gap between the high-pressure passage 23 and the injection hole 22 is blocked, so that no fuel is injected.

  When the electromagnetic coil 62 is energized, the armature 64 is attracted to the magnetized stator 63, and the armature 64 moves toward the stator 63 against the biasing force of the spring 66, so that the ball valve 65 is moved back. In response to the fuel pressure in the pressure chamber 27, the outflow passage 53 is opened. Therefore, the high pressure fuel in the back pressure chamber 27 is opened to the low pressure side through the outflow passage 53, and the fuel pressure in the back pressure chamber 27 decreases. As a result, the needle 30 is lifted when the force that pushes the needle 30 in the valve opening direction (lift force due to the fuel pressure in the fuel reservoir chamber 24) exceeds the force that biases the needle 30 in the valve closing direction. Then, the high-pressure fuel supplied from the common rail to the fuel injection valve 10 is injected from the injection hole 22 through the upstream passage 421 of the main body 40, the high-pressure passage 422, the high-pressure passage 51 of the orifice plate 50, and the high-pressure passage 23 of the nozzle body 20. Is done.

  As described above, according to the present embodiment, the following effects can be obtained.

  (1) Since the thin portion 41 is formed in the main body 40 by decentering the high-pressure passage 422 from the axial center J1 of the main body 40, the strain body 89 shown in FIG. The branch passage 423x illustrated in FIG. 6B can be eliminated. Therefore, an increase in the number of parts and an increase in processing cost can be suppressed.

  (2) Since the thin portion 41 is formed in the main body 40 by decentering the high pressure passage 422 from the axial center J1 of the main body 40, the outer peripheral surface (bottom surface 45a) of the thin portion 41 is parallel to the high pressure passage 422. It becomes. Therefore, the bottom surface 45a to which the sensor chip 81 is attached is distorted mainly in the circumferential direction Y1 (see FIG. 3B) of the main body 40, and hardly distorts in the axial center direction Y2 of the body. Therefore, as shown in FIGS. 3C and 3D, the mounting position of the strain gauge 812 on the thin portion 41 (bottom surface 45a) is slightly shifted in both the circumferential direction Y1 and the axial center direction Y2. Only the detected value of the strain gauge 812 hardly changes. Therefore, the mounting position accuracy of the strain gauge 812 can be relaxed.

  (3) As described above, the thin portion 41 is mainly distorted in the circumferential direction Y1 of the main body 40 and hardly distorted in the axial direction Y2 (that is, the longitudinal direction of the high-pressure passage). In view of this point, in the present embodiment, since the strain gauge 812 is arranged so that the detection direction of the strain gauge 812 coincides with the circumferential direction Y1 of the main body 40, the detection sensitivity can be improved, which is preferable.

  (4) Although the fuel pressure detection accuracy by the strain gauge 812 can be improved as the thickness of the thin portion 41 is reduced, the thin portion is formed when the high pressure passage 422 is formed by drilling from the lower end surface 40R of the main body 40. There is a processing limit to reducing the wall thickness. In view of this point, in the present embodiment, since the recess 45 is formed in the range including the outer peripheral surface of the thin portion 41 in the outer peripheral surface of the main body 40, the thickness of the thin portion 41 can be reduced and the fuel pressure detection accuracy is improved. it can.

  And since it is the structure which aims at the further thinning of the thin part 41 using the recessed part 45 for forming the bottom face 45a which attaches the circuit board 82, the process cost increase of the main body body 40 can be suppressed.

  (5) Here, since the stress is more likely to be concentrated at the connection portion (bent portion P) between the upstream side passage 421 and the high pressure passage 422 than at other portions, there is a concern that the pressure resistance strength of the main body 40 is lowered. Is done. In view of this point, in the present embodiment, the concave portion 45 is positioned on the downstream side of the bent portion P, so that the thickness of the main body 40 at the bent portion P can be prevented from being reduced by the concave portion 45. Therefore, it is possible to suppress a decrease in pressure strength at the bent portion P, and to solve the above-mentioned concern.

  (6) Since the sensor chip 81 is positioned above the engaging portion 40a pressed by one end of the clamp K, it engages with a portion of the main body body 40 where the distortion becomes large (that is, a portion supported by the cylinder head E2). The strain gauge 812 is located at a location deviating from the portion between the portion 40a and the portion 40a. Therefore, it is possible to suppress the strain gauge 812 from being affected by the strain generated in the main body 40, and the detection accuracy of the fuel pressure can be improved.

(Second Embodiment)
In the first embodiment, the recess 45 is formed on the outer peripheral surface of the main body 40 to form a flat surface (bottom surface 45a), and the sensor chip 81 is attached to the bottom surface 45a. On the other hand, in this embodiment shown in FIG. 4, the sensor chip 81 is directly attached on the cylindrical outer peripheral surface 41a of the cylindrical body body 40. The circuit board 82 is also mounted directly on the outer circumferential surface 41a of the cylinder. According to this, the processing cost for forming the recess 45 in the main body 40 can be reduced.

(Third embodiment)
In the first embodiment, the number of strain gauges 812 provided in the sensor chip 81 is one, but in the present embodiment shown in FIG. 5, a plurality of strain gauges 812 a, 812 b, 812 c, and 812 d are provided in the sensor chip 81. Is provided. In the example shown in FIG. 5, a bridge circuit is configured by a plurality of strain gauges 812a to 812d.

  Also in this case, the plurality of strain gauges 812a to 812d are arranged so that the detection direction (the direction indicated by the arrow Y3 in FIG. 5) intersects the longitudinal direction of the high-pressure passage 422 (axial center direction Y2). Has been placed. As described above, the same effects as those of the first embodiment are also exhibited by this embodiment.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be modified as follows. Moreover, you may make it combine the characteristic structure of each embodiment arbitrarily, respectively.

  In each of the above embodiments, the strain gauges 812, 812a to 812d are employed as the sensor elements. However, the sensor element of the present invention is not limited to the strain gauges. For example, the thin part 41 (the bottom surface 45a) is used. You may employ | adopt the piezoelectric element which generate | occur | produces an electric charge according to the stress which arises. Specifically, the piezoelectric element is polarized in a specific direction (detection direction), and generates positive or negative charges on both end surfaces based on a change in compressive stress in the detection direction. Even in this case, it is desirable to arrange the piezoelectric element so that the detection direction of the piezoelectric element intersects the longitudinal direction of the high-pressure passage 422 (axial center direction Y2).

  In the first embodiment, both the upstream passage 421 and the high-pressure passage 422 are formed in the main body 40, but the upstream passage 421 is eliminated and the supply port 44a is formed on the shaft center J2 of the high-pressure passage 422. And the high pressure passage 422 may be connected to the supply port 44a.

  In the first embodiment, the electromagnetic unit 60 including the stator 63 and the armature 64 is used as the electric actuator that opens and closes the needle 30. However, a stacked body (piezo stack) in which a large number of piezoelectric elements are stacked. ) May be adopted.

  In each of the above embodiments, the present invention is applied to an injector of a diesel engine. However, the present invention may be applied to a gasoline engine, particularly, a direct injection gasoline engine that directly injects fuel into the combustion chamber E1.

  DESCRIPTION OF SYMBOLS 10 ... Fuel injection valve, 22 ... Injection hole, 40 ... Main body (body), 40a ... Engagement part (pressing surface), 41 ... Thin part, 45 ... Recessed part, 45a ... Bottom face of a recessed part, 421 ... Upstream passage, 422 ... High pressure passage, 812, 812a to 812d ... Strain gauge (sensor element), E2 ... Cylinder head, E3 ... Body insertion hole, J1 ... Body axis center, J2 ... Axis center of high pressure passage, K ... Clamp, P ... Bent part (connecting part of upstream passage and high-pressure passage).

Claims (5)

In a fuel injection valve that is inserted into a cylinder head of an internal combustion engine and injects high-pressure fuel from a nozzle hole,
A body that extends in the direction of insertion into the cylinder head and that forms a high-pressure passage through which high-pressure fuel flows toward the nozzle hole,
Forming the high-pressure passage at a position eccentric from the axial center of the body;
A fuel injection valve, wherein a sensor element that outputs an electrical signal corresponding to a strain amount of the outer peripheral surface is attached to an outer peripheral surface of a thin portion where the body is thinned among the periphery of the high-pressure passage. An amplification circuit for amplifying the detection signal of the sensor element;
Forming a recess in a range including the outer peripheral surface of the thin portion of the outer peripheral surface of the body;
The fuel injection valve according to claim 1, wherein the amplification circuit and the sensor element are attached to a bottom surface of the recess. Inside the body, an upstream side passage extending in a bent direction from the upstream end of the high pressure passage is formed,
3. The fuel injection valve according to claim 2, wherein in the insertion direction, the recess is positioned on the high pressure passage side with respect to a connection portion between the upstream passage and the high pressure passage. The sensor element has directivity to detect strain or stress in a specific direction,
The fuel injection valve according to any one of claims 1 to 3, wherein the sensor element is arranged so that the specific direction intersects with a longitudinal direction of the high-pressure passage. The body is arranged to be inserted into a body insertion hole formed in the cylinder head, and is configured to be pressed against the body insertion hole by a clamp,
The body is formed with a pressing surface against which the clamp abuts and is pressed,
The fuel injection valve according to any one of claims 1 to 4, wherein the sensor element is located on a side opposite to the injection hole from the pressing surface.

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