JP5223765B2 - Fuel injection valve - Google Patents

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. When the fuel pressure sensor is actually mounted on the fuel injection valve, there is a problem in securing the arrangement path for arranging the lead wire provided in the fuel pressure sensor and outputting the detection signal.

  In particular, when the fuel pressure sensor is disposed in the high-pressure fuel, an extraction hole for extracting the lead wire from the high-pressure passage is required, and a seal member is required in the extraction hole. Therefore, the mounting position of the fuel pressure sensor is restricted so that an installation space for the extraction hole and the seal member (arrangement path of the lead wire) can be secured.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a fuel injection valve equipped with a fuel pressure sensor, and a fuel injection valve that suppresses the restriction of the mounting position of the fuel pressure sensor. It is to provide.

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

  The invention described in claim 1 includes a body that forms a high-pressure passage through which high-pressure fuel flows toward the nozzle hole, a sensor element that is attached to the body and outputs a detection signal corresponding to the pressure of the high-pressure fuel, and A fuel pressure sensor having a transmission unit that wirelessly transmits a detection signal output from the sensor element, and a reception unit that receives the detection signal wirelessly transmitted from the transmission unit.

  According to the present invention, since the detection signal output from the sensor element can be transmitted wirelessly, the problem of securing the lead wire arrangement path, which is a problem when the lead wire for outputting the detection signal is provided in the fuel pressure sensor, can be solved. . Therefore, it can suppress that the mounting position of a fuel pressure sensor receives restrictions, and can improve the mounting position freedom degree of a fuel pressure sensor.

Furthermore, the invention according to claim 1 is characterized in that the sensor element (for example, a piezoelectric element) is arranged in high-pressure fuel. According to this, the pressure of the high-pressure fuel can be directly detected as compared with the case where the strain gauge (sensor element) is attached to the strain generating body that is elastically deformed by receiving the pressure of the high-pressure fuel and the fuel pressure sensor is configured. The fuel pressure can be detected with high accuracy.

In addition, in the invention according to claim 1 , fuel injection from the nozzle hole is blocked by seating a needle housed in the body on a seating surface formed in the body, and the seating surface The annular fuel passage is formed between the inner peripheral surface of the body and the outer peripheral surface of the needle, and extends in the axial direction of the body. In the inside of the body, a sac chamber is formed downstream of the seating surface to collect fuel distributed in an annular manner in the fuel passage and lead it to the nozzle hole, and the sensor element is the sac chamber It is characterized by being arranged in.

  For example, when the sensor element is arranged on the upstream side of the seating surface contrary to the above invention, the following problems occur.

  That is, the time required for the fuel pressure fluctuation generated in the nozzle hole to propagate to the upstream side of the seating surface becomes a propagation delay (time lag), and the detection accuracy of the injection state is lowered. Furthermore, when the needle lift is small, such as immediately after the needle is separated from the seating surface or just before seating, the gap between the seat surface of the needle and the seating surface of the body is small. As a result, fuel will be squeezed. Then, the pressure fluctuation generated in the nozzle hole is attenuated in the gap. In addition, since the state changes depending on the lift amount of the needle and changes to the non-restricted state, the magnitude of the attenuation also changes depending on the lift amount. As described above, the detection accuracy of the injection state is lowered due to the occurrence of attenuation by the diaphragm and the fact that the magnitude of the attenuation changes according to the lift amount.

  In view of these points, in the above invention, since the fuel pressure element is disposed in the sac chamber located downstream of the seating surface in the fuel passage inside the fuel injection valve, the fuel pressure can be detected at a position close to the injection hole. it can. Therefore, the time lag can be reduced. In addition, since the fuel pressure downstream of the seating surface is detected, it is possible to detect the fuel pressure not affected by the restriction. As described above, according to the present invention, the detection accuracy of the injection state can be improved.

  When the sensor element is arranged in the sack chamber as described above, it is extremely difficult to secure the wiring path of the lead wire with the structure in which the lead wire is provided in the fuel pressure sensor as described above. On the other hand, in the above invention, since the lead wire can be made unnecessary by wirelessly transmitting a detection signal, it is possible to realize the placement of the sensor element in the sack chamber.

According to a second aspect of the present invention, there is provided an electric actuator that opens and closes a needle that opens and closes the nozzle hole, and a drive unit that includes a casing that houses the electric actuator in an airtight state. It is characterized by being housed in an airtight state inside the casing together with the electric actuator.

  The above invention pays attention to the fact that the drive unit provided in the fuel injection valve has a casing for accommodating the electric actuator in an airtight state, and the receiving means is accommodated in the casing together with the electric actuator. By using the casing of the drive unit, the receiving means can be prevented from being exposed to fuel, and the reliability of the receiving means can be improved.

In the first configuration , the fuel pressure sensor is configured by attaching a strain gauge as the sensor element to a strain generating body that is elastically deformed under the pressure of high-pressure fuel, and is screwed to the body. It is characterized by being.

In this way, in the configuration in which the fuel pressure sensor is screwed to the body, for example, a configuration in which an output terminal is provided in the fuel pressure sensor contrary to the above configuration and a detection signal output from the sensor element is output (wired transmission) from the output terminal is adopted. Since the rotational position of the fuel pressure sensor at the time when the screw fastening is completed is unspecified, the rotational position of the output terminal is also unspecified. Therefore, the electrical connection structure between a circuit board (for example, an amplifier circuit) disposed outside the fuel pressure sensor and the output terminal becomes complicated. In contrast, in this configuration , since the detection signal is wirelessly transmitted, a complicated electrical connection structure can be eliminated, and the advantages of wireless transmission are effectively exhibited.

In the second configuration , a diaphragm portion that elastically deforms under the pressure of high-pressure fuel is provided, and the sensor element is a strain gauge attached to the diaphragm portion, and energy is supplied to an electric circuit constituted by the strain gauge. Energy transmitting means for wirelessly transmitting, and energy receiving means for receiving the energy wirelessly transmitted from the energy transmitting means, provided in the fuel pressure sensor.

Here, specific examples of the sensor element include a piezoelectric element and a strain gauge. Piezoelectric elements do not require external power supply, whereas strain gauges require external power supply. In the above-described configuration in view of this point, when a strain gauge is employed as the sensor element, the energy transmitting unit and the energy receiving unit are provided. Therefore, in addition to transmitting the detection signal from the sensor element (strain gauge) wirelessly, The power supply to the gauge can also be performed wirelessly. Therefore, the problem of securing the lead wire arrangement path, which becomes a problem when the lead wire for supplying power to the fuel pressure sensor is provided, can be solved. Therefore, it can suppress that the mounting position of a fuel pressure sensor receives restrictions, and can improve the mounting position freedom degree of a fuel pressure sensor.

1 is an overall view of a fuel injection valve according to a first embodiment of the present invention. Sectional drawing which shows the mechanism which opens and closes a nozzle hole in the fuel injection valve of FIG. The enlarged view which shows the nozzle hole part of FIG. The figure which shows the electric actuator in FIG. FIG. 5 is a circuit diagram for transmitting and receiving a detection signal, which is configured by the transmission unit in FIG. The circuit diagram for transmitting / receiving a detection signal concerning 2nd Embodiment of this invention. The figure which shows the transmission means concerning 3rd Embodiment of this invention. The figure which shows the transmission means concerning 4th Embodiment of this invention. The figure which shows the fuel pressure sensor concerning 5th Embodiment of this invention. The enlarged view of FIG. The figure which shows the arrangement layout of the receiving means concerning 6th Embodiment of this invention.

  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 view of the fuel injection valve, and FIG. 2 is a cross-sectional view showing a mechanism for opening and closing the injection hole 11 in the fuel injection valve of FIG. The fuel injection valve is inserted and mounted in a cylinder head (not shown) of the engine, and directly injects high-pressure fuel supplied from a common rail into each cylinder of the engine.

  First, the overall structure of the fuel injection valve will be described with reference to FIGS. 1 and 2. The fuel injection valve includes a cylindrical body 10 extending in the direction of insertion into the cylinder head. An injection hole 11 for injecting high-pressure fuel is formed at the tip of the body 10 in the axial direction (vertical direction in FIG. 1). Inside the body 10, high-pressure fuel supplied from the common rail to the high-pressure port 12a is injected into the injection hole. A high-pressure passage 12 that circulates toward 11 is formed. The “axial direction” in the present specification refers to the longitudinal direction of the fuel injection valve, and also refers to the insertion direction of the fuel injection valve that is inserted and mounted in the cylinder head.

  Inside the body 10, a needle 13 (valve element) that opens and closes the nozzle hole 11 is accommodated so as to be slidable in the axial direction. Specifically, as shown in FIG. 3, by seating the seat surface 13a of the needle 13 (the part indicated by the halftone dot in FIG. 3) on the conical seating surface 10a formed inside the body 10. The fuel injection from the nozzle hole 11 is shut off. Further, the fuel is injected from the injection hole 11 by separating the seat surface 13a from the seating surface 10a.

  In the portion of the body 10 that accommodates the needle 13, an annular fuel passage 10 e that extends in the axial direction is formed between the inner peripheral surface of the body 10 and the outer peripheral surface of the needle 13. High pressure fuel is supplied from the high pressure passage 12 to the fuel passage 10e. Further, in the inside of the body 10, a sack chamber 10f that collects the fuel distributed annularly in the fuel passage 10e is formed on the downstream side of the seating surface 10a. The sac chamber 10 f communicates with the nozzle hole 11.

  A back pressure chamber 10b for applying high pressure fuel to the needle 13 as a back pressure is formed on the back side of the needle 13 (on the side opposite to the injection hole) in the body 10. Fuel from the high pressure passage 12 is supplied to the back pressure chamber 10b through the orifice 14. Further, the back pressure chamber 10b is provided with a needle spring 15 that applies an elastic force to the needle 13 so as to press the seat surface 13a against the seating surface 10a. Hereinafter, the side of the nozzle hole 11 (lower side in FIG. 1) with respect to the body 10 is referred to as “lower side”, and the opposite side of the nozzle hole 11 (upper side in FIG. 1) is referred to as “upper side”.

  A housing chamber 19 that houses a three-way valve 16 (back pressure control valve) is formed inside the body 10, and the back pressure chamber 10 b can communicate with the low-pressure passage 17 through the housing chamber 19. The three-way valve 16 is pushed above the body 10 by a valve spring 18. When the three-way valve 16 is moved upward by the elastic force of the valve spring 18 and is seated on the low pressure side valve seat portion 19a, and is separated from the high pressure side valve seat portion 19b, the communication between the low pressure passage 17 and the back pressure chamber 10b is established. Is blocked, and the high pressure passage 12 and the back pressure chamber 10 b communicate with each other through the storage chamber 19.

  On the other hand, when the three-way valve 16 moves downward against the elastic force of the valve spring 18 and is separated from the low pressure side valve seat portion 19a, and seated on the high pressure side valve seat portion 19b, the low pressure passage 17 and the back pressure are separated. While the chamber 10b communicates, the communication between the high pressure passage 12 and the back pressure chamber 10b in the storage chamber 19 is blocked.

  The lower end surface of the small-diameter piston 20 is in contact with the surface of the three-way valve 16 on the low-pressure side valve seat portion 19a side. On the other hand, the upper end surface of the small diameter piston 20 faces the lower end surface of the large diameter piston 21.

  Inside the body 10, a displacement expansion chamber 10 c defined by the upper end surface of the small diameter piston 20 and the lower end surface of the large diameter piston 21 is formed. When the displacement of the large diameter piston 21 is transmitted to the small diameter piston 20 by an appropriate fluid (for example, fuel for injection) filled in the displacement expansion chamber 10c, the displacement amount is expanded by the displacement expansion chamber 10c.

  The housing unit 10d of the body 10 houses a drive unit 30 that displaces the large-diameter piston 21 downward. The drive unit 30 is configured by housing a piezo stack 32 (electric actuator) in a metal casing 31. The piezo stack 32 is configured by alternately laminating a plurality of piezo elements and electrode plates. The piezo element is a capacitive load that expands and contracts due to the piezoelectric effect, and can be switched between an expanded state and a contracted state by charging and discharging. Thus, the piezo stack 32 functions as an electric actuator that operates the three-way valve 16.

  A metal fixed pedestal 33 is attached to the upper end surface of the piezo stack 32, and a metal moving pedestal 35 is attached to the lower end surface of the piezo stack 32 via a ceramic member 34. The movable pedestal 35 is accommodated in the casing 31 in a displaceable state together with the piezo stack 32 that expands and contracts. The extension driving force of the piezo stack 32 is transmitted to the large-diameter piston 21 through the ceramic member 34, the moving base 35, and the shim member 21a.

  A leaf spring 36 (elastic member) is disposed between the casing 31 and the movable base 35. Each of the outer peripheral surface of the movable pedestal 35 and the inner peripheral surface of the casing 31 is welded to a leaf spring 36, and the leaf spring 36 is elastically deformed as the movable pedestal 35 is displaced. As a result, the lower opening of the casing 31 is closed in an airtight state by the leaf spring 36. On the other hand, the upper opening of the casing 31 is closed in an airtight state by welding the outer peripheral surface of the fixed base 33 and the inner peripheral surface of the casing 31. Accordingly, the piezo stack 32 is housed in the casing 31 in an airtight state so as not to be exposed to the fuel.

  Next, the operation of the fuel injection valve configured as described above will be described.

  When the driving power is not supplied to the piezo stack 32 and the piezo element is in the contracted state, the large-diameter piston 21 is positioned above the body 10 by the piezo spring 22. Then, the three-way valve 16 is positioned upward together with the small-diameter piston 20 by the valve spring 18. Therefore, the low pressure side valve seat portion 19a is closed and the high pressure side valve seat portion 19b is opened. For this reason, the needle 13 is pushed downward by the fuel pressure in the back pressure chamber 10b and the elastic force of the needle spring 15 to be seated on the seating surface 10a (valve closed state), and fuel injection from the nozzle hole 11 is performed. Stopped.

  On the other hand, when driving power is supplied to the piezo stack 32 and the piezo element is extended, the large-diameter piston 21 moves below the body 10 against the force of the piezo spring 22. Then, the small diameter piston 20 displaces the three-way valve 16 downward, the low pressure side valve seat portion 19a is opened, and the high pressure side valve seat portion 19b is closed. As a result, the pressure of the fuel in the back pressure chamber 10b decreases, and the high pressure fuel in the fuel passage 10e pushes the needle 13 upward, so that the fuel in the back pressure chamber 10b and the needle spring 15 move the needle 13 downward. When it becomes larger than the pressing force by a predetermined amount or more, the needle 13 is pushed upward and is in a state of being separated from the seating surface 10a (valve open state), and high-pressure fuel is injected from the injection hole 11.

  Here, the pressure of the high-pressure fuel inside the body 10 varies with the fuel injection from the nozzle hole 11. A fuel pressure sensor 40 for detecting the pressure fluctuation is attached to the body 10 (see FIG. 3). In the pressure fluctuation waveform detected by the fuel pressure sensor 40, 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 11. 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.

  As shown in FIG. 3, the fuel pressure sensor 40 is attached to the lower end surface 13b of the needle 13 and disposed in the sac chamber 10f, and detects the pressure of the high-pressure fuel in the sac chamber 10f. More specifically, the fuel pressure sensor 40 includes a piezoelectric element 41 (sensor element) that outputs a detection signal corresponding to the pressure of the high-pressure fuel, and a transmission circuit 42 (transmission) that wirelessly transmits the detection signal output from the piezoelectric element 41. Means).

  As shown in FIG. 5, the transmission circuit 42 includes electronic components such as a primary coil 43 and is attached to the lower end surface 13 b of the needle 13 while being molded with a resin material. The transmission circuit 42 is electrically connected to the piezoelectric element 41. When the piezoelectric element 41 receives the pressure of fuel and generates a current I1, the current I1 flows through the primary coil 43 to generate an electromagnetic wave. That is, an electromagnetic wave having a magnitude corresponding to the fuel pressure is wirelessly transmitted as a detection signal.

  The piezoelectric element 41 is attached to the lower end surface of the resin material molding the transmission circuit 42. Specifically, in a state where the piezoelectric element 41 is disposed on the lower end surface of the resin material, it is sealed (baked) with a glass member (not shown) and fixed. Therefore, the piezoelectric element 41 is disposed so as to be exposed to the sack chamber 10f.

  As shown in FIG. 4, the receiving circuit 50 (receiving means) that receives the detection signal transmitted from the transmitting circuit 42 is disposed in the casing 31 of the drive unit 30 in an airtight state together with the piezo stack 32. . The receiving circuit 50 is configured by molding electronic components such as a secondary coil 51 and an amplifier 52 with a resin material.

  In the present embodiment, the resin material for molding the secondary coil 51 is formed in an annular shape that extends along the outer periphery of the piezo stack 32. That is, the receiving circuit 50 is arranged in the gap between the outer peripheral surface of the piezo stack 32 and the inner peripheral surface of the casing 31. The receiving circuit 50 is disposed at the lowermost part of the gap (position adjacent to the movable pedestal 35), and a portion of the gap above the receiving circuit 50 is filled with a resin material.

  Due to the output of an electromagnetic wave (detection signal) from the primary coil 43 of the transmission circuit 42, a secondary current I2 is generated in the secondary coil 51 of the reception circuit 50. The secondary current I2 is amplified by the amplifier 52 and output from the sensor connector terminal 61 (see FIG. 1) via the lead wire 37 (see FIG. 4) connected to the output terminal 53. Thereby, the detection signal of the piezoelectric element 41 is transmitted and received wirelessly.

  The sensor connector terminal 61 is held by a resin connector housing 60 (see FIG. 1) attached to the upper portion of the body 10. The connector housing 60 holds a drive connector terminal 62 together with a sensor connector terminal 61. That is, both the connector terminals 61 and 62 are integrated by one connector housing 60. The electric power supplied from the outside to the drive connector terminal 62 is supplied to the electrodes of the piezo stack 32 via the lead wires 38.

  Both lead wires 37 and 38 are taken out from the inside of the casing 31 through an extraction hole 33 a formed in the fixed base 33. Both lead wires 37 and 38 taken out from the fixed base 33 are inserted and arranged in a lead wire insertion hole 10g (see FIG. 1) formed in the body 10 while being held by the holding member 39. .

  Here, when the fuel pressure sensor 40 is arranged so as to detect the fuel pressure upstream of the seating surface 10a contrary to the present embodiment, the fuel pressure fluctuation generated in the nozzle hole 11 is propagated to the upstream side of the seating surface 10a. As the time lag increases, the attenuation of fuel pressure fluctuations that occur in the propagation path increases, and the detection accuracy of the injection state (change in injection rate) decreases.

  On the other hand, according to the embodiment described in detail above, the fuel pressure sensor 40 is disposed so as to detect the fuel pressure in the sack chamber 10f located downstream of the seating surface 10a, so that the fuel pressure is close to the nozzle hole 11. Can be detected. Therefore, the time lag until the fuel pressure fluctuation generated in the nozzle hole 11 is propagated to the fuel pressure sensor 40 can be reduced, and the attenuation of the fuel pressure fluctuation can also be reduced. Therefore, according to the present embodiment in which the fuel pressure sensor 40 is arranged in the sac chamber 10f, the detection accuracy of the injection state can be improved.

  When the fuel pressure sensor 40 is arranged in the sac chamber 10f in this way, it is difficult to take out the lead wire out of the sack chamber 10f if a detection signal is transmitted from the fuel pressure sensor 40 via a lead wire. It is not practical to arrange the fuel pressure sensor 40 in the sack chamber 10f. On the other hand, in the present embodiment, the detection signal from the piezoelectric element 41 is wirelessly transmitted to the receiving circuit 50 disposed outside the sac chamber 10f, so that the fuel pressure sensor 40 can be disposed in the sac chamber 10f. Become.

  Furthermore, according to this embodiment, since the piezoelectric element 41 is employed as the sensor element, the sensor element can be disposed in the high-pressure fuel. Therefore, the pressure of the high-pressure fuel can be directly detected as compared with the case where the fuel pressure sensor is configured by attaching a strain gauge (sensor element) to the strain body that elastically deforms under the pressure of the high-pressure fuel. Can be detected with high accuracy.

  Furthermore, according to this embodiment, since the receiving circuit 50 is accommodated in the casing 31 of the drive unit 30 together with the piezo stack 32, the receiving circuit 50 is prevented from being exposed to fuel using the casing 31 of the driving unit 30. Thus, the reliability of the receiving circuit 50 can be improved.

  Further, by arranging the receiving circuit 50 in the casing 31, the sensor lead wire 37 and the drive lead wire 38 are taken out from the casing 31 through the same extraction hole 33 a. Therefore, since the wiring paths of both the lead wires 37 and 38 up to the connector terminals 61 and 62 can be made the same, the wiring structure can be simplified. For example, both the lead wires 37 and 38 can be disposed in the same lead wire insertion hole 10 g and can be held by the same holding member 39.

(Second Embodiment)
In the transmission circuit 42 and the reception circuit 50 according to the first embodiment, the detection signal is wirelessly transmitted by electromagnetic waves, whereas in the present embodiment shown in FIG. 6, the detection signal is wirelessly transmitted by electromagnetic induction. .

  Specifically, as shown in FIG. 6, the transmission circuit 420 is electrically connected to the piezoelectric element 41, and when the piezoelectric element 41 receives the pressure of fuel and generates a current I 1, the current I 1 flows through the primary coil 430. Thus, an induced current I2 is generated in the secondary coil 510 of the receiving circuit 500. That is, an electromagnetic wave having a magnitude corresponding to the fuel pressure is wirelessly transmitted as a detection signal.

  The induced current I 2 generated in the secondary coil 510 of the receiving circuit 500 is amplified by the amplifier 52 and output from the sensor connector terminal 61 via the lead wire 37 connected to the output terminal 53. Thereby, the detection signal of the piezoelectric element 41 is transmitted and received wirelessly.

  The structure of the fuel injection valve according to this embodiment is the same as that of the first embodiment. As described above, the same effects as those of the first embodiment are also exhibited by this embodiment.

(Third embodiment)
In the first embodiment, the fuel pressure sensor 40 is disposed in the sac chamber 10f, whereas in the present embodiment shown in FIG. 7, the body 10 has a portion under the sack chamber 10f (sack portion 10h). A fuel pressure sensor 400 is disposed on the end face 10i.

  Specifically, as shown in FIG. 7, the fuel pressure sensor 400 includes a strain gauge 410 (sensor element), a transmission circuit 42, and an energy reception circuit 44 (energy reception means). The transmission circuit 42 and the reception circuit 50 have the same configuration as that in the first embodiment.

  The strain gauge 410 is fixed by being sealed (baked) with a glass member (not shown) in a state of being disposed on the lower end surface 10i of the sack portion 10h. Therefore, the strain gauge 410 detects the magnitude of the strain (elastic deformation amount) of the sac portion 10h generated according to the fuel pressure in the sac chamber 10f, whereby the fuel pressure in the sac chamber 10f is detected.

  Thus, in order to detect the fuel pressure with the strain gauge 410, it is necessary to apply a voltage to the bridge circuit constituted by the strain gauge 410. Therefore, in the present embodiment, an energy transmission circuit (energy transmission means) that wirelessly transmits energy to the bridge circuit is arranged in the casing 31 of the drive unit 30, and the fuel pressure sensor 400 includes the energy reception circuit 44. The configuration of the energy transmission circuit and the energy reception circuit 44 is the same as that of the transmission circuit 42 and the reception circuit 50, and power is supplied wirelessly by electromagnetic waves.

  An energy transmission circuit (not shown) is disposed in the casing 31 in a state of being molded with a resin material together with the reception circuit 50. As described above, the same effects as those of the first embodiment are also exhibited by this embodiment.

(Fourth embodiment)
In the first embodiment, the fuel pressure sensor 40 is disposed in the sack chamber 10f. In the present embodiment, the fuel pressure sensor 40 detects the fuel pressure in the upstream portion of the body 10 inside the seating surface 10a. Is arranged.

  For example, as shown in FIG. 8, it may be disposed in the annular fuel passage 10e, or may be disposed in the high-pressure passage 12 extending in the axial direction. In the case of being arranged in the high-pressure passage 12, although the time lag and the attenuation of the fuel pressure fluctuation are attenuated as compared with the case of being arranged in the sack chamber 10f, the distance between the transmission circuit 42 and the reception circuit 50 becomes short. The reliability can be improved when transmitting and receiving.

  In the example shown in FIG. 8, the sensor element is disposed in the high-pressure fuel, and the piezoelectric element 41 is employed as the sensor element. However, the strain gauge 410 is employed as the sensor element, and the body 10, the needle 13, etc. The amount of distortion may be detected.

(Fifth embodiment)
When the strain gauge 410 is employed as the sensor element, the third embodiment is configured to detect the strain amount of the sac portion 10h by attaching the strain gauge 410 to the sack portion 10h of the body 10. On the other hand, in the present embodiment shown in FIG. 9, a stem 45 (straining body), which is a member different from the body 10, is screwed to the body 10, and a strain gauge 410 is attached to the stem 45. It is configured to detect the quantity.

  Hereinafter, the structure of the fuel pressure sensor 401 according to the present embodiment will be described in detail with reference to FIGS. 9 and 10.

  The stem 45 includes a cylindrical cylindrical portion 45b in which an inflow port 45a for introducing high-pressure fuel therein is formed at one end, and a disc-shaped diaphragm portion 45c that closes the other end of the cylindrical portion 45b. ing. The pressure of the high-pressure fuel flowing into the cylindrical portion 45b from the inflow port 45a is received by the inner surface of the cylindrical portion 45b and the diaphragm portion 45c, whereby the entire stem 45 is elastically deformed.

  The stem 45 is made of metal, and since the metal material is subjected to ultra-high pressure, it has high strength and high hardness, and deformation due to thermal expansion is small, and the strain gauge 410 is less affected (that is, a low thermal expansion coefficient). Specifically, a material mainly composed of Fe, Ni, Co or Fe, Ni and Ti, Nb, Al or Ti, Nb added as a precipitation strengthening material is selected and pressed. It can be formed by cutting or cold forging. Moreover, you may select the material to which C, Si, Mn, P, S, etc. were added.

  A mounting hole 10 j into which the cylindrical portion 45 b of the stem 45 is inserted is formed in a portion of the body 10 above the drive unit 30. The fuel pressure sensor 401 is attached to the body 10 by screwing the male screw portion 45d formed on the outer peripheral surface of the cylindrical portion 45b of the stem 45 to the female screw portion formed on the inner peripheral surface of the mounting hole 10j. It is done. The body 10 is formed with a branch passage 12 b that branches from the high-pressure passage 12 and guides the high-pressure fuel to the inlet 45 a of the stem 45.

  The strain gauge 410 is attached to the diaphragm portion 45c. Therefore, when the stem 45 is elastically deformed so as to expand due to the pressure of the high-pressure fuel flowing into the cylindrical portion 45b, the strain gauge 410 detects the magnitude of the strain (elastic deformation amount) generated in the diaphragm portion 45c. . In addition, a transmission circuit 42 similar to that in FIG. 5 and an energy reception circuit 44 similar to that in FIG. 7 are attached to the stem 45.

  A mold IC 70 described below is attached to the upper portion of the body 10. The mold IC 70 is configured by resin-molding a receiving circuit 50, an energy transmitting circuit 54, and an electronic component 71 and an electrode 73, which will be described below, as in FIG. The plurality of electrodes 73 are electrically connected to each of the plurality of sensor connector terminals 61.

  The electronic component 71 constitutes an amplifier circuit that amplifies the detection signal output from the strain gauge 410, a filtering circuit that removes noise superimposed on the detection signal, a circuit that applies a voltage to the strain gauge 410, and the like.

  The electric power output from the voltage application circuit is supplied to the strain gauge 410 through the energy transmission circuit 54 and the energy reception circuit 44. The strain gauge 410 to which a voltage is applied constitutes a bridge circuit in which the resistance value changes according to the magnitude of the strain generated in the diaphragm portion 45c. As a result, the output voltage of the bridge circuit changes according to the distortion of the diaphragm portion 45c, and the output voltage is output as a pressure detection value of the high-pressure fuel to the amplification circuit of the electronic component 71 through the transmission circuit 42 and the reception circuit 50. .

  The amplifier circuit amplifies the pressure detection value output from the strain gauge 410 (bridge circuit), and the amplified signal is output from the sensor connector terminal 61 through the electrode 73.

  The plurality of sensor connector terminals 61 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 housing 60 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 electronic component 71 is input into the engine ECU via the external harness.

  The fuel pressure sensor 401, the molded IC 70, and the like are held by the body 10 by being molded together with the connector terminals 61 and 62 by the resin material 70m. A part of the resin material 70 m constitutes a connector housing 60.

  By the way, contrary to the present embodiment, if the detection signal output from the strain gauge 410 is wired to the mold IC 70 by electrically connecting the mold IC 70 and the strain gauge 410 by wire bonding, the following problems occur. That is, when the stem 45 is screwed to the body 10, the rotational position of the stem 45 becomes unspecified, and consequently the rotational direction position of the strain gauge 410 becomes unspecified. Therefore, the workability of electrically connecting the strain gauge 410 and the mold IC 70 by wire bonding deteriorates.

  On the other hand, according to the present embodiment, since the detection signal from the strain gauge 410 is wirelessly transmitted to the receiving circuit 50 provided in the mold IC, the fuel pressure sensor 401 (the stem 45 in the present embodiment) is screwed to the body 10. The configuration to be realized can be easily realized without causing the above problem.

  Furthermore, according to this embodiment, since the stem 45 is formed separately from the body 10, the following effects are exhibited.

  That is, when the internal stress of the body 10 caused by thermal expansion and contraction is propagated to the stem 45, the propagation loss can be increased. That is, by configuring the stem 45 separately from the body 10, the influence on the stem 45 due to distortion of the body 10 is reduced. Therefore, according to the present embodiment in which the strain gauge 410 is attached to the stem 45 configured separately from the body 10, as compared with the case where the strain gauge 410 is directly attached to the body 10 as shown in FIG. It is possible to suppress the strain gauge 410 from being affected by the strain generated in the strain. Therefore, the accuracy of fuel pressure detection by the fuel pressure sensor 401 can be improved.

  Further, since the stem 45 is formed separately from the body 10 and the material of the stem 45 is made of a material having a smaller thermal expansion coefficient than that of the body 10, the stem 45 itself is thermally expanded and contracted to cause distortion. This can be suppressed. Further, compared to the case where the entire body 10 is made of a material having a small thermal expansion coefficient, only the stem 45 may be made of a material having a small thermal expansion coefficient, so that the material cost can be reduced.

  In addition, since the stem 45 is formed separately from the body 10, it is possible to inspect whether the output value of the strain gauge 410 is abnormal before the stem 45 with the strain gauge 410 attached is attached to the body 10. Therefore, the workability of the inspection can be improved.

(Sixth embodiment)
Regarding the arrangement of the receiving circuit 50, the receiving circuit 50 is arranged on the outer periphery of the piezo stack 32 in the first embodiment. On the other hand, in the present embodiment shown in FIG. 11, the receiving circuit 500 is arranged below the piezo stack 32.

  Specifically, as shown in FIG. 11, the ceramic member 340 has a shape (T-shape) extending in the axial direction, and the receiving circuit 500 is provided between the lower end surface of the piezo stack 32 and the upper end surface of the movable base 35. Deploy.

  According to the present embodiment, the outer diameter of the casing 31 can be made smaller than in the first embodiment, and the drive unit 30 can be reduced in the radial direction.

  However, according to the present embodiment, the ceramic member 340 needs to have a shape extending in the axial direction. Therefore, when the displacement of the piezo stack 32 is transmitted to the large-diameter piston 21, the axial strain generated in the ceramic member 340 is not generated. growing. Therefore, there is a concern that the transmission loss increases when the displacement of the piezo stack 32 is transmitted to the large-diameter piston 21 via the ceramic member 340 or the like. On the other hand, in the said 1st Embodiment, since the ceramic member 34 can be formed in flat plate shape, there exists a merit that the said concern can be suppressed.

(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 the first embodiment, the piezo stack 32 is employed as the electric actuator that opens and closes the needle 13, but an electromagnetic actuator constituted by a stator and an armature may be employed.

  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 a combustion chamber.

  DESCRIPTION OF SYMBOLS 10 ... Body, 10e ... Fuel passage, 10f ... Suck chamber, 11 ... Injection hole, 12 ... High pressure passage, 13 ... Needle, 31 ... Casing, 32 ... Piezo stack (electric actuator), 40, 400, 401 ... Fuel pressure sensor, 41 ... piezoelectric element (sensor element), 41 ... piezoelectric element (sensor element), 42,420 ... transmission circuit (transmission means), 44 ... energy reception circuit (energy reception means), 45c ... diaphragm part, 50,500 ... reception Circuit (reception means), 54... Energy transmission circuit (energy transmission means), 410... Strain gauge (sensor element).

Claims (2)

In a fuel injection valve mounted on an internal combustion engine and injecting fuel from a nozzle hole,
A body that internally forms a high-pressure passage through which high-pressure fuel flows toward the nozzle hole;
A fuel pressure sensor having a sensor element attached to the body and outputting a detection signal corresponding to the pressure of the high-pressure fuel; and a transmission means for wirelessly transmitting the detection signal output from the sensor element;
Receiving means for receiving a detection signal wirelessly transmitted from the transmitting means;
Equipped with a,
The sensor element is disposed in high pressure fuel,
The needle housed in the body is seated on a seating surface formed in the body to block fuel injection from the nozzle hole, and is separated from the seating surface to cause fuel from the nozzle hole. Configured to inject,
An annular fuel passage extending in the axial direction of the body is formed between the inner peripheral surface of the body and the outer peripheral surface of the needle,
A sac chamber is formed on the downstream side of the seating surface inside the body to collect fuel distributed annularly in the fuel passage and lead it to the nozzle hole,
The fuel injection valve according to claim 1, wherein the sensor element is disposed in the sac chamber . An electric actuator that opens and closes a needle that opens and closes the nozzle hole, and a drive unit that includes a casing that houses the electric actuator in an airtight state,
2. The fuel injection valve according to claim 1, wherein the receiving unit is housed inside the casing together with the electric actuator in an airtight state.

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