CN113167200A

CN113167200A - Fuel injection device

Info

Publication number: CN113167200A
Application number: CN201980081150.0A
Authority: CN
Inventors: 桥本雄太; 藤野友基
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2019-01-28
Filing date: 2019-12-23
Publication date: 2021-07-23
Anticipated expiration: 2039-12-23
Also published as: JP7197383B2; JP2020118142A; CN113167200B; DE112019006747T5; WO2020158249A1; DE112019006747B4

Abstract

The movable core (50) has: an upper core part (51) forming a core-side buffer chamber (56) with the fixed core (60); a lower core part (52) forming a shell-side buffer chamber (57) with the shell (20); and a middle core part (53) provided between the upper core part (51) and the lower core part (52). A buffer flow path (54) is provided in the movable core (50), the buffer flow path (54) penetrates the upper core part (51), the middle core part (53), and the lower core part (52), the core side buffer chamber (56) is connected with the shell side buffer chamber (57), and the fuel is passed through in a manner of attenuating the kinetic energy of the movable core (50).

Description

Fuel injection device

Cross reference to related applications

The present application claims the benefit of this priority based on japanese patent application No. 2019-012076, filed on day 28, 1/2019, the entire contents of which are incorporated by reference into the present specification.

Technical Field

The present disclosure relates to a fuel injection device.

Background

Fuel injection devices are generally required to inject the proper fuel. As a factor that hinders the injection of appropriate fuel, there is a rebound of the valve member caused by collision with another member at the time of the valve opening operation and the valve closing operation of the fuel injection device. The rebound of the valve member may cause a deviation in the injection amount associated with deterioration of the exhaust gas state.

There is a possibility that an increase in the injection amount may occur due to abrasion caused by the valve member colliding with the fixed core during the valve opening operation and colliding with the valve seat during the valve closing operation to apply an impact load to the fixed core and the valve seat. The rebound of the valve member can be suppressed by reducing the impact applied to another member that collides when the valve member opens and closes the nozzle hole.

As a conventional technique for suppressing the rebound of the valve member, there is a technique as follows: a damper chamber and an orifice are provided in the fuel injection device to decelerate the valve member (see patent document 1).

Patent document 1: japanese laid-open patent publication No. 2012-197739

Disclosure of Invention

In the technique disclosed in patent document 1, a buffer chamber and an orifice are provided in a body portion of the fuel injection device. If the buffer chamber and the orifice are provided in the body portion, the build of the fuel injection device increases in accordance with the arrangement.

An object of the present disclosure is to provide a fuel injection device that reduces the impact applied to surrounding members by a valve member during a valve opening operation and a valve closing operation without increasing the size of the fuel injection device.

The present disclosure is a fuel injection device including: a housing provided with a nozzle hole for injecting fuel into a combustion chamber of an internal combustion engine; a valve member that is driven to open and close the nozzle hole; a movable core for driving the valve member in a valve opening direction; a spring for pressing the valve member in a valve closing direction; a fixed core for sucking the movable core in the valve opening direction; and an electromagnetic circuit for generating an attractive force to the stationary core. The fuel injection device is provided with a core-side damper chamber provided between the movable core and the fixed core, and a housing-side damper chamber provided between the movable core and the housing. The movable core has: an upper core part forming a core-side buffer chamber with the fixed core; a lower core portion forming a housing-side buffer chamber with the housing; and a middle core portion disposed between the upper core portion and the lower core portion. The movable core is provided with a buffer flow passage that passes through the upper core portion, the middle core portion, and the lower core portion, connects the core-side buffer chamber and the housing-side buffer chamber, and allows fuel to pass therethrough so as to attenuate the kinetic energy of the movable core.

Since the buffer flow passage is provided in the movable core, the kinetic energy of the movable core can be directly attenuated by the action of the fuel passing through the buffer flow passage, and the impact applied to the peripheral members by the valve member can be reduced without increasing the size of the fuel injection device. The movable core is configured to include 3 parts, i.e., an upper core part, a middle core part, and a lower core part, and thus can be configured according to characteristics required for each part. Since the upper core portion faces the fixed core and forms the core-side buffer chamber between the upper core portion and the fixed core, the upper core portion can be easily attracted to the fixed core. Since the lower core portion forms the housing-side cushion chamber with the housing, the lower core portion can have a characteristic suitable for forming the housing-side cushion chamber. Since the middle core portion is disposed between the upper core portion and the lower core portion, the middle core portion can have a characteristic suitable for forming the buffer flow path while being in close contact with the upper core portion and the lower core portion.

In the present disclosure, it is also preferable that a part of the lower core is provided to penetrate the middle core and the upper core and face the fixed core, the middle core is mounted to the lower core by a clearance fit, and the upper core is mounted to the lower core by an interference fit, whereby the middle core is held between the lower core and the upper core.

In this preferred aspect, the lower core portion is formed so as to penetrate the middle core portion and the upper core portion, and therefore the movable core can be formed without using a member such as another fastening member. The upper core portion is disposed between the middle core portion and the lower core portion, and is attached to the lower core portion by interference fit, and therefore can be integrated with the lower core portion by a method such as press fitting. Since the middle core portion is mounted by a clearance fit, a close contact degree can be improved between the middle core portion and the lower core portion by a method such as co-grinding. The close contact between the middle core and the upper core can be improved by a method such as co-grinding before mounting the middle core and the upper core to the lower core. As a result, the degree of close contact between the 3 portions constituting the movable core can be increased to reduce the leakage of the fuel from the middle of the buffer flow path, and the performance of the buffer flow path can be ensured.

In the present disclosure, it is also preferable that the lower core has: a flange portion having a close contact surface in close contact with the core portion; and a cylindrical portion extending from a central side of the flange portion to an upper core portion side, the cylindrical portion being provided to penetrate the middle core portion and the upper core portion, the middle core portion being attached to the cylindrical portion by a clearance fit, the upper core portion being attached to the cylindrical portion by an interference fit.

In this preferred embodiment, since the flange portion is provided, the center core portion can be positioned by abutting the center core portion against the flange portion by inserting the center core portion into the cylindrical portion. Since the flange portion is formed with the close contact surface, the close contact state with the core portion can be achieved. The upper core portion is inserted into the cylindrical portion so as to sandwich the center core portion with the flange portion, and is attached to the cylindrical portion by interference fit.

Drawings

Fig. 1 is a sectional view of a fuel injection device in the present embodiment.

Fig. 2 is an enlarged view of the periphery of the movable core shown in fig. 1.

Fig. 3 is an exploded view of the movable core shown in fig. 2.

Fig. 4 is an enlarged view of the periphery of a movable core in a fuel injection device as a modification.

Fig. 5 is an exploded view of the movable core shown in fig. 4.

Fig. 6 is a sectional view showing a section VI-VI of fig. 4.

Fig. 7 is a view of the movable core shown in fig. 4 as viewed from the direction VII.

Fig. 8 is a graph for explaining the effect of the fuel injection device.

Fig. 9 is a diagram enlarging the area a in fig. 8.

Fig. 10 is a diagram enlarging a region B in fig. 8.

Detailed Description

The present embodiment will be described below with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals as much as possible, and redundant description thereof will be omitted for ease of understanding.

The configuration of the fuel injection device 1 according to the present embodiment will be described with reference to fig. 1. The fuel injection device 1 is a device for supplying fuel to a combustion chamber of an internal combustion engine at an appropriate timing. The fuel injection device 1 includes, as main components, a housing 20, a valve member 40, a movable core 50, a fixed core 60, a coil 70, a first spring 81, and a second spring 82.

The housing 20 has a first barrel member 21, a second barrel member 22, and a third barrel member 23. The valve member 40 has a small diameter portion 41 and a large diameter portion 42. The small diameter portion 41 is provided with a seal portion 411, a fuel passage 412, and a hole 413.

The movable core 50 has an upper core portion 51, a lower core portion 52, and a middle core portion 53. The fixed core 60 has an outer fixed core 61 and an inner fixed core 62.

The first tubular member 21 is formed such that the outer diameter of one end is larger than that of the other end. The end portion having a smaller outer diameter is provided with a nozzle hole 30. A part of the small diameter portion 41 is housed in the hollow portion of the first tubular member 21 from one end to the other end of the first tubular member 21. A valve seat 31 that abuts against the valve member 40 is provided so as to surround the injection hole 30.

The second cylindrical member 22 is formed to abut against the first cylindrical member 21 at the end portion on the valve opening direction side of the first cylindrical member 21. The outer diameter and the inner diameter of the second cylindrical member 22 are substantially the same as those of the end portion of the first cylindrical member 21 on the valve opening direction side.

The third cylindrical member 23 is formed to abut against the second cylindrical member 22 at the end portion on the valve opening direction side of the second cylindrical member 22. The outer diameter and the inner diameter of the third cylindrical member 23 are substantially the same as those of the end portion of the first cylindrical member 21 on the valve opening direction side.

As the material of each member, for example, the first tubular member 21 and the third tubular member 23 are magnetic bodies such as ferrite stainless steel, and the second tubular member 22 is a nonmagnetic material such as austenitic stainless steel.

The valve member 40 is driven to open and close the nozzle hole 30. When the valve member 40 moves in the direction toward the injection hole 30, the valve member 40 moves so as to close the injection hole 30, and therefore, the direction from the valve member 40 toward the injection hole 30 is set to the valve closing direction. The direction opposite to the valve closing direction is set as the valve opening direction. An inlet 14 for taking in fuel is provided at an end of the fuel injection device 1 opposite to the nozzle hole 30. The inlet 14 side is a supply side, and the nozzle hole 30 side is a discharge side.

In the valve member 40, the small diameter portion 41 is provided at the end portion on the discharge side. In the valve member 40, the large diameter portion 42 is provided at the end portion on the supply side.

The seal portion 411 is a portion abutting against the valve seat 31. The fuel passage 412 is an internal space formed from the supply side to the discharge side inside the small diameter portion 41. The hole 44 is provided at the discharge-side end of the fuel passage 412. The fuel passing through the fuel passage 412 is configured to pass through the hole 44 toward the injection hole 30.

The movable core 50 will be described with reference to fig. 2 and 3. The upper core 51 is a substantially cylindrical member. The lower core portion 52 has a flange portion 521 and a cylindrical portion 522. The flange portion 521 is a portion formed so as to radially expand the outer peripheral surface of the cylindrical portion 522. The cylindrical portion 522 is provided to extend from the center side of the flange portion 521 toward the upper core portion 51 side. The middle core portion 53 is a substantially cylindrical member.

The middle core portion 53 is formed to be attached to the cylindrical portion 522 by a clearance fit. The middle core portion 53 is arranged to be slidable with the outer peripheral surface of the cylindrical portion 522.

The upper core 51 is formed to be attached to the cylindrical portion 522 by interference fit. The upper core 51 is press-fitted into the cylindrical portion 522. The manner of attaching the upper core 51 to the cylindrical portion 522 is not limited to press fitting, and a method such as so-called thermal press fitting or shrink fitting may be used. The upper core 51 may be attached to the cylindrical portion 522 by welding or the like, instead of interference fit, but in addition to clearance fit.

The flange portion 521 is provided with a close contact surface 523 that is in close contact with the core portion 53. The core portion 53 is provided with a close contact surface 531 which is in close contact with the flange portion 521. The center core 53 is provided with a close contact surface 532 that is in close contact with the upper core 51. The close contact surfaces 531 and 532 are formed as surfaces on respective opposite sides of the disc-shaped core portion 53. The upper core portion 51 is provided with a close contact surface 511 that is in contact with the center core portion 53 in a close contact state.

The upper core portion 51 and the middle core portion 53 are subjected to a process for improving flatness by a method such as co-grinding so that the close contact surface 511 and the close contact surface 532 are brought into close contact when the movable core 50 is assembled. Similarly, the center core portion 53 and the lower core portion 52 are subjected to the processing for improving the flatness by the common grinding or the like so that the close contact surface 531 and the close contact surface 523 are brought into close contact.

After the processing for improving the flatness is performed, the middle core portion 53 is inserted into the cylindrical portion 522 of the lower core portion 52. After the middle core portion 53 is inserted into the cylindrical portion 522, the upper core portion 51 is press-fitted into the cylindrical portion 522.

The movable core 50 is provided with a buffer flow passage 54 so as to pass through the upper core portion 51, the middle core portion 53, and the lower core portion 52. The buffer flow path 54 includes a communication path 541, a communication path 542, and an orifice portion 543.

The communication passages 541 are provided in the upper core portion 51. The communication passage 541 penetrates to connect the supply side and the discharge side of the upper core 51.

The communication passages 542 are provided in the lower core portion 52. The communication passage 542 penetrates so as to connect the supply side and the discharge side of the flange portion 521 of the lower core portion 52.

The orifice portion 543 is provided in the middle core portion 53. The orifice portion 543 penetrates to connect the supply side and the discharge side of the center core portion 53. The orifice portion 543 is narrowed in the middle of the flow path, and is formed to increase the flow resistance of the fuel to generate a damping force.

The communication passage 541, the orifice portion 543, and the communication passage 542 are arranged so as to communicate with each other, forming the buffer passage 54. Although one buffer flow path 54 is illustrated in fig. 2 and 3, the number of buffer flow paths 54 to be provided is not particularly limited, and is determined according to design requirements such as a required damping force.

In the present embodiment, the throttle portion 543 is provided in the center portion 53, but the installation location is not limited to the center portion 53. The orifice portion 543 may be provided in the flange portion 521 of the upper core portion 51 or the lower core portion 52.

The upper core 51 and the center core 53 are made of a soft magnetic material such as ferrite stainless steel. The lower core 52 is made of a metal material such as martensitic stainless steel. The lower core 52 is subjected to quenching treatment to adjust the hardness.

The fixed core 60 is formed in a substantially cylindrical shape. The fixed core 60 has an outer fixed core 61 and an inner fixed core 62. The outer fixing core 61 is welded to the third cylindrical member 23 and fixed to the inside of the housing 20.

The inner fixing core 62 is press-fitted into the outer fixing core 61 from the valve closing direction side. A part of the inner surface of the inner fixing core 62 has an inner diameter larger than the outer diameter of the large diameter portion 42 of the valve member 40, and is configured to allow the valve member 40 to slide. The adjustment pipe 11 is press-fitted from the end of the inner fixed core 62 on the valve opening direction side.

The outer fixed core 61 is made of a soft magnetic material such as ferrite stainless steel. The inner fixed core 62 is made of a metal material such as martensitic stainless steel. The inner fixed core 62 is subjected to quenching treatment to have a predetermined hardness. The portion of the inner fixed core 62 that collides with the cylindrical portion 522 of the lower core portion 52 is subjected to nitriding treatment.

A core-side buffer chamber 56 is provided between the outer fixed core 61 and the upper core 51. A housing-side buffer chamber 57 is provided between the first tubular member 21 and the flange portion 521 of the lower core 52.

The coil 70 is mounted on a bobbin 71, forming an electromagnetic circuit. The holder 15 is provided in such a manner as to cover the coil 70. A cover 16 is provided between the third cylindrical member 23 and the holder 15. The holder 15 and the cover 16 are made of a magnetic material such as ferritic stainless steel, and form a part of an electromagnetic circuit.

The fuel introduction pipe 12 is provided from the introduction port 14 toward the injection side. A filter 13 for trapping foreign matter in the fuel is provided at the end of the fuel introduction pipe 12 on the injection side. The filter 13 abuts on the adjustment pipe 11.

One end of the first spring 81 abuts against the large diameter portion 42 of the valve member 40, and the other end abuts against one end of the adjustment pipe 11. The first spring 81 applies a force to the valve member 40 to press the valve member in the valve closing direction. One end of the second spring 82 abuts against the injection-side end surface of the lower core 52, and the other end abuts against the inner stepped surface of the first tubular member 21. The second spring 82 applies a force to the movable core 50 to press the movable core in the valve opening direction.

Next, the operation of the fuel injection device 1 will be described. The fuel injected by the fuel injection device 1 flows in from the inlet 14 of the fuel introduction pipe 12, passes through the filter 13 and the adjustment pipe 11, and flows between the hollow portion of the fixed core 60, the fuel passage 43 of the valve member 40, the first cylindrical member 21, and the valve member 40. During operation of the fuel injection device 1, the core-side damper chamber 56 and the case-side damper chamber 57 are filled with fuel.

The valve member 40 is opened when it is separated from the valve seat 31, and the valve member 40 is closed when it is in contact with the valve seat 31. The valve member 40 is driven in the valve opening direction, and the operation until the valve member shifts from the closed state to the open state and ends the movement in the valve opening direction is set as the valve opening operation. The valve member 40 is driven in the valve closing direction, and an operation until the valve member shifts from the valve open state to the valve closed state and ends the movement in the valve closing direction is referred to as a valve closing operation.

The valve member 40 can move to a position abutting against the end surface of the inner fixed core 62 on the valve opening direction side. The state in which the valve member 40 is moved into contact with the end surface of the inner fixed core 62 on the valve opening direction side is referred to as a full lift.

When the valve member 40 is in the valve-closed state, the first spring 81 presses the valve member 40 in the valve-closing direction, and the seal portion 411 of the valve member 40 abuts against the valve seat 31, so that the injection hole 30 is closed.

When power is supplied to the coil 70, a magnetic force is generated in the coil 70. When a magnetic force is generated in the coil 70, a magnetic circuit is formed in the outer fixed core 61, the upper core 51, the first barrel member 21, and the third barrel member 23. Thereby, a magnetic attraction force is generated between the outer fixed core 61 and the upper core 51, and the upper core 51 moves in the valve opening direction.

By the movement of the upper core portion 51, the lower core portion 52 and the middle core portion 53 also move in the valve opening direction. Since the cylindrical portion 522 of the lower core portion 52 abuts against the large diameter portion 42 of the valve member 40, the valve member 40 moves in the valve opening direction in accordance with the movement of the lower core portion 52.

In the valve-closed state, the flange portion 521 of the lower core portion 52 abuts against the first tubular member 21 of the housing 20, and therefore, the fuel is pushed out from the housing-side buffer chamber 57. On the other hand, since the upper core 51 is separated from the outer fixed core 61, the core-side buffer chamber 56 is filled with fuel.

When the valve member 40 moves in the valve opening direction, the fuel in the core-side buffer chamber 56 flows through the buffer flow path 54 to the housing-side buffer chamber 57. The resistance received by the fuel passing through the buffer flow path 54 is applied to the movable core 50 as a damping force. The movable core 50 receives a force in a direction opposite to the moving direction, and thus decelerates. The kinetic energy of the movable core 50 is attenuated by the movable core 50 being decelerated.

In the valve opening operation, the valve member 40 moves while sliding with the inner fixed core 62 while compressing the first spring 81. The valve member 40 is opened by moving in the valve opening direction, and the fuel in the fuel injection device 1 is injected from the injection hole 30. Since the kinetic energy of the movable core 50 is attenuated by the buffer flow path 54, the kinetic energy of the valve member 40 is also attenuated.

The valve member 40 moves in the valve opening direction until it collides with the inner fixed core 62, reaches the full lift, and stops moving. Since the kinetic energy of the valve member 40 is attenuated, the impact force when the valve member 40 collides with the inner stationary core 62 is attenuated. The valve member 40 is fully lifted, and the valve opening operation is completed.

In the valve closing operation, the energization of the coil 70 is stopped, and the generation of the magnetic attraction force by the coil 70 is stopped. The valve member 40 is moved in the valve closing direction by the force in the valve closing direction generated by the first spring 81. The valve member 40 moves the lower core portion 52 in the valve closing direction by pressing the lower core portion 52 in the valve closing direction while sliding on the inner fixed core 62. The movable core 50 moves in the valve closing direction by the movement of the lower core portion 52.

When the movable core 50 moves in the valve closing direction, the fuel in the casing-side buffer chamber 57 flows through the buffer flow path 54 to the core-side buffer chamber 56. The resistance received by the fuel passing through the buffer flow path 54 is applied to the movable core 50 as a damping force. The movable core 50 receives a force in a direction opposite to the moving direction, and thus decelerates. The kinetic energy of the movable core 50 is attenuated by the movable core 50 being decelerated.

The valve member 40 is decelerated by deceleration of the movable core 50. The kinetic energy of the valve member 40 is also attenuated. When the seal portion 411 is seated on the valve seat 31, the valve member 40 that moves while decelerating ends its movement in the valve closing direction. The impact force when the valve member 40 collides with the valve seat 31 is attenuated by the attenuation of the kinetic energy of the valve member 40. By seating on the valve seat 31, the injection hole 30 is closed, and the valve is closed.

In the present embodiment, the kinetic energy of the movable core can be attenuated by the buffer flow path 54 having the communication path 541 and the orifice portion 543 provided in the movable core in both the valve opening operation and the valve closing operation. The kinetic energy of the valve member 40 is attenuated by the attenuation of the kinetic energy of the movable core.

Since the kinetic energy of the valve member 40 is attenuated, the impact when the valve member 40 collides with the inner fixed core 62 during the valve opening operation can be reduced. Similarly, the impact when the valve member 40 collides with the valve seat 31 during the valve closing operation can be reduced.

The fuel injection device 1 in the present embodiment includes: a housing 20 provided with injection holes 30 for injecting fuel into a combustion chamber of an internal combustion engine; a valve member 40 driven to open and close the nozzle hole 30; a movable core 50 for driving the valve member 40 in the valve opening direction; a first spring 81 for pressing the valve member 40 in the valve closing direction; a fixed core 60 for sucking the movable core 50 in the valve opening direction; and a coil 70 constituting an electromagnetic circuit for generating an attractive force to the fixed core 60. The fuel injection device 1 is provided with a core-side damper chamber 56 provided between the movable core 50 and the fixed core 60, and a housing-side damper chamber 57 provided between the movable core 50 and the housing 20. The movable core 50 has: an upper core portion 51 forming a core-side buffer chamber with the fixed core 60; a lower core 52 forming a housing-side buffer chamber 57 with the housing 20; and a middle core portion 53 provided between the upper core portion 51 and the lower core portion 52. The movable core 50 is provided with a buffer flow passage 54, and the buffer flow passage 54 penetrates the upper core portion 51, the middle core portion 53, and the lower core portion 52, connects the core-side buffer chamber 56 and the housing-side buffer chamber 57, and allows fuel to pass therethrough so as to attenuate the kinetic energy of the movable core 50.

Since the buffer flow passage 54 is provided in the movable core 50, the kinetic energy of the movable core 50 can be directly attenuated by the action of the fuel passing through the buffer flow passage 54, and the impact of the valve member 40 on the peripheral members can be reduced without increasing the size of the fuel injection device 1. The movable core 50 is configured to include 3 parts, i.e., the upper core portion 51, the middle core portion 53, and the lower core portion 52, and thus can be configured according to characteristics required for the respective parts. Since the upper core portion 51 faces the fixed core 60 and the core-side buffer chamber 56 is formed between the upper core portion and the fixed core 60, the upper core portion 51 can have a characteristic of being easily attracted to the fixed core 60. Since the lower core portion 52 forms the shell-side damper chamber 57 with the shell 20, the lower core portion 52 can have characteristics suitable for forming the shell-side damper chamber 57. Since the middle core portion 53 is disposed between the upper core portion 51 and the lower core portion 52, the middle core portion 53 can have a characteristic suitable for forming the buffer flow path 54 while being in close contact with the upper core portion 51 and the lower core portion 52.

In the present embodiment, a part of the lower core 52 is provided so as to penetrate the middle core 53 and the upper core 51 and face the fixed core 60, the middle core 53 is mounted to the lower core 52 by a clearance fit, and the upper core 51 is mounted to the lower core 52 by an interference fit, whereby the middle core 53 is held between the lower core 52 and the upper core 51.

Since the lower core 52 is formed so as to penetrate the middle core 53 and the upper core 51, the movable core 50 can be formed without using a member such as another fastening member. The upper core 51 is disposed between the lower core 52 and the middle core 53, and is attached to the lower core 52 by interference fit, and therefore can be integrated with the lower core 52 by a method such as press fitting. Since the middle core portion 53 is mounted by a clearance fit, a close contact degree can be improved between the lower core portion 52 and the same by a method such as co-grinding. The close contact between the middle core portion 53 and the upper core portion 51 can be improved by a method such as co-grinding before being mounted on the lower core portion 52. As a result, the degree of close contact between the 3 portions constituting the movable core 50 can be increased, and the leakage of fuel from the middle of the buffer flow path 54 can be reduced, thereby ensuring the performance of the buffer flow path 54.

In the present embodiment, the lower core 52 includes: a flange 521 having a close contact surface 511 that is in close contact with the core 53; and a cylindrical portion 522 extending from the center side of the flange portion 521 toward the upper core portion 51 side. The cylindrical portion 522 is provided so as to pass through the center core portion 53 and the upper core portion 51, the center core portion 53 is attached to the cylindrical portion 522 by a clearance fit, and the upper core portion 51 is attached to the cylindrical portion 522 by an interference fit.

Since the flange portion 521 is provided, the center portion 53 is inserted into the cylindrical portion 522, and the center portion 53 can be positioned in contact with the flange portion 521. Since the flange 521 has the close contact surface 523, the core 53 can be brought into close contact with the same. Since the upper core 51 is inserted into the cylindrical portion 522 so as to sandwich the center core 53 with the flange portion 521 and is attached to the cylindrical portion 522 by interference fit, the upper core can be reliably attached to the center core 53 while ensuring a close contact state.

In the present embodiment, the upper core portion 51 is formed of a soft magnetic material, the lower core portion 52 is formed of a high hardness material, and the cylindrical portion 522 protrudes toward the fixed core 60 side from the upper core portion 51.

By forming the upper core portion 51 of a soft magnetic material, it can be easily attracted to the fixed core 60, and the movable performance of the movable core 50 improves. The cylindrical portion 522 formed of a high-hardness material is configured to penetrate the upper core portion 51 and protrude toward the fixed core 60 side, and thus, when the movable core 50 is attracted to the fixed core 60, the cylindrical portion 522 is brought into contact with the fixed core 60, and the upper core portion 51 formed of a soft magnetic material can be protected.

In the present embodiment, the middle core portion 53 is also preferably formed of a high hardness material.

By using a high-hardness material, the close contact state of the middle core portion 53 with the upper core portion 51 and the lower core portion 52 can be further improved. The close contact state improves to improve the airtightness of the buffer flow path 54, and the buffer effect can be obtained more reliably.

Since the damping force generated by the buffer passage 54 does not differ between the valve opening operation and the valve closing operation in the fuel injection device 1 described with reference to fig. 1 to 3, the damping force acting on the movable core 50 during the valve opening operation and the damping force acting on the movable core 50 during the valve closing operation do not differ. The mode in which the damping force acting on the movable core during the valve opening operation is different from the damping force acting on the movable core during the valve closing operation will be described with reference to fig. 4 to 7.

Fig. 4 to 7 are diagrams for explaining the fuel injection device 1A in which the damping force acting on the movable core during the valve opening operation is different from the damping force acting on the movable core during the valve closing operation. The fuel injection device 1A as a modification of the fuel injection device 1 is mainly explained because the buffer flow path 55 is added to the fuel injection device 1.

The movable core 50A of the fuel injection device 1A has an upper core portion 51A, a lower core portion 52A, and a middle core portion 53A. The movable core 50A includes a buffer flow path 55 in addition to the buffer flow path 54 similar to the movable core 50. The buffer flow path 55 includes a communication path 551, an orifice 552, a check flow path 553, a groove portion 554, and a check valve body 555.

As shown in fig. 6, 2 communication passages 551 are provided in the upper core portion 51A. The communication passage 551 is provided to pass through the upper core 51A in the opening/closing direction. The communication passage 551 is provided to connect the core-side buffer chamber 56 and the center portion 53A.

The orifice portion 552 is provided in 2 in the core portion 53A. The orifice portion 552 is provided to penetrate the center portion 53A in the opening and closing valve direction. The orifice portion 552 is disposed so as to correspond to the position where the communication passage 551 is provided, so that fuel can flow between the communication passage 551 and the orifice portion.

The check valve flow paths 553 are provided in 1 in the lower core portion 52A. The check valve flow path 553 is provided to penetrate the lower core 52A in the opening/closing valve direction. The check valve flow passage 553 is provided to connect the case-side buffer chamber 57 and the core portion 53A. The check valve flow passage 553 has a conical shape with a larger diameter on the side of the core portion 53A to accommodate the check valve body 555.

The groove portion 554 is provided receding from a face of the middle core portion 53A opposed to the lower core portion 52A. The groove portion 553 is provided to connect the 2 orifice portions 552 with the check valve flow passage 553.

Check valve spool 555 is formed as a ball. The check valve body 555 is disposed between the center core portion 53A and the lower core portion 52A. The check valve body 555 is disposed between the check valve flow path 553 and the groove portion 554. The check valve spool 555 is configured to be movable in the opening and closing valve direction.

The operation of the fuel injection device 1A will be described. When the valve member 40 performs a valve opening operation, the movable core 50A moves in a valve opening direction. As the movable core 50A moves, the fuel in the core-side damper chamber 56 flows toward the case-side damper chamber 57.

The fuel thus flowing presses the check valve body 555 in the valve closing direction. The check valve body 555 is pressed in the valve closing direction and abuts against the check valve flow path 553, thereby restricting the flow of the fuel through the buffer flow path 55. The fuel flows through the movable core 50A only through the buffer flow path 54.

The movable core 50A receives a damping force in the valve closing direction from the buffer passage 54, and thereby decelerates. The kinetic energy of the valve member 40 is attenuated by the deceleration of the movable core 50A. The valve member 40 collides with the valve seat 31 while the kinetic energy is attenuated.

When the valve member 40 performs the valve closing operation, the movable core 50A moves in the valve closing direction. As the movable core 50A moves, the fuel in the casing-side damper chamber 57 flows to the core-side damper chamber 56.

The fuel thus flowing presses the check valve body 555 in the valve opening direction. When the check valve body 555 moves in the valve opening direction, it separates from the check valve flow passage 553, and abuts against the groove portion 554, so that the buffer flow passage 55 is in a state where fuel can pass therethrough. The fuel flows through the buffer flow path 55 in addition to the buffer flow path 54, inside the movable core 50A.

The movable core 50A is decelerated by receiving a damping force in the valve opening direction from the buffer flow path 54 and the buffer flow path 55. The kinetic energy of the valve member 40 is attenuated by the deceleration of the movable core 50A. The valve member 40 collides with the end surface of the inner stationary core 62 while the kinetic energy is attenuated.

The reaction of the resistance received from the movable core 50A when the fuel passes through the

buffer flow passages

54, 55 becomes a force that acts to decelerate the valve member 40. The damping force generated by the

buffer flow paths

54 and 55 varies according to the fuel passing amount inside the movable core 50A.

During the valve opening operation, fuel can flow only through the buffer passage 54, and the fuel does not flow through the buffer passage 55. During the valve closing operation, fuel can flow through both the buffer flow passage 54 and the buffer flow passage 55.

In the case of the valve opening operation, the flow path cross-sectional area is reduced by the size of the buffer flow path 55 compared to the case of the valve closing operation, and therefore the resistance received by the fuel from the movable core 50A becomes larger compared to the case of the valve closing operation. Therefore, the damping force applied to the movable core 50A is larger in the valve opening operation than in the valve closing operation.

The fuel injection device 1A is compared with a conventional fuel injection device. Fig. 8 (a) shows on/off of the drive signal. Fig. 8 (B) shows the state of energization to the coil 70. Fig. 8 (C) shows the injection rate of fuel. In fig. 8 (C), the fuel injection rate of the fuel injection device 1A is indicated by a solid line, and the fuel injection rate of the conventional fuel injection device is indicated by a broken line.

Since the injection amount per unit time is determined by the lift amount of the valve member 40, the injection rate waveform has the same tendency as the waveform of the lift amount of the valve member 40.

Fig. 9 is an enlarged view of the region a in fig. 8 (C), and shows the fuel injection rate when the valve member 40 performs the valve opening operation, with the rising timing of the fuel injection rate being matched. In the fuel injection device 1A, the increase in the fuel injection rate is slower than the increase in the fuel injection rate of the conventional fuel injection device. Since the change in the fuel injection rate is caused by the lift amount of the valve member 40 rising slowly, it is found that the valve member 40 is decelerated by the buffer passage 54.

Fig. 10 is an enlarged view of the region B in fig. 8 (C), and shows the fuel injection rate when the valve member 40 performs the valve closing operation, with the timing of the decrease in the fuel injection rate being made equal. In the fuel injection device 1A, the reduction in the fuel injection rate is slower than that of the conventional fuel injection device. Since the change in the fuel injection rate is caused by the gradual decrease in the lift amount of the valve member 40, it is found that the valve member 40 is decelerated by the buffer passage 54 and the buffer passage 55.

As shown in fig. 9 and 10, when the difference between the fuel injection rate of the fuel injection device 1A and the fuel injection rate of the conventional fuel injection device is compared, the difference in the valve opening operation is larger. This difference is caused by the fact that the buffer effect produced by the buffer flow path 54 during the valve opening operation is greater than the buffer effect produced by the buffer flow path 54 and the buffer flow path 55 during the valve closing operation.

In the fuel injection device 1A, the

buffer flow paths

54 and 55 can make the damping force different between the case where the movable core 50A is driven in the valve opening direction and the case where the movable core 50A is driven in the valve closing direction.

By making the damping force different between the valve opening direction and the valve closing direction, the

buffer passages

54, 55 in the movable core 50A can be configured to match desired valve opening characteristics and valve closing characteristics, and desired valve opening characteristics and valve closing characteristics can be obtained. In the present embodiment, the damping force in the valve opening direction is higher than the damping force in the valve closing direction, but the damping force in the valve closing direction may be higher than the damping force in the valve opening direction.

In the fuel injection device 1A, the buffer flow path 55 is provided with a damping force changing portion that makes the amount of fuel passing in the valve opening direction of the movable core 50A different from the amount of fuel passing in the valve closing direction. By providing the damping force changing portion in the buffer flow path 55, the behavior of the movable core 50A can be set to a desired behavior while passing the fuel.

The buffer flow path of the fuel injection device 1A includes: the buffer flow path 54, which is a constant buffer flow path, is provided with only an orifice; and a buffer flow path 55 as a variable buffer flow path provided with an orifice and a damping force changing unit. Since the fuel throughput is reduced by the orifice, the damping force can be obtained by a simple method of narrowing the flow passage. By providing the buffer flow path 54 as the constant buffer flow path and the buffer flow path 55 as the variable buffer flow path in parallel, the fuel flow on the buffer flow path 54 side can be always ensured, and the damping force can be easily adjusted.

In the fuel injection device 1A, the check valve flow path 553 and the check valve body 555 are provided to function as a damping force changing portion. The damping force can be adjusted reliably in accordance with the directivity by bringing the check valve body 555 into close contact with the check valve flow path 553 to make the fuel flowing through the buffer flow path 55 substantially zero, and by separating the check valve body 555 from the check valve flow path 553 to secure the fuel flowing through the buffer flow path 55.

In the fuel injection device 1A, the check valve flow path 553 and the check valve body 555 are provided in the buffer flow path 55 so as to coexist with the buffer flow path 54, but the damping force adjustment of the movable core is not limited to this embodiment. For example, even if the check valve body 555 approaches the check valve flow passage 553, the fuel flow may not be completely shut off, but the fuel flow may be reduced as compared to the case where the check valve body 555 leaves the check valve flow passage 553. By this, it is possible to provide only the buffer flow path 55 without providing the buffer flow path 54 in parallel.

The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. The embodiment of the present invention is not limited to the above-described embodiment, but may be modified in various ways. The elements, their arrangement, conditions, shapes, and the like included in the above-described specific examples are not limited to those exemplified, and can be appropriately modified. Each element included in each specific example described above can be appropriately combined without technical contradiction.

Claims

1. A fuel injection device is characterized by comprising:

a housing (20) provided with injection holes (30) for injecting fuel into a combustion chamber of an internal combustion engine;

a valve member (40) that is driven to open and close the nozzle hole;

a movable core (50, 50A) for driving the valve member in a valve opening direction;

a spring (81) for pressing the valve member in a valve closing direction;

a fixed core (60) that sucks the movable core in the valve opening direction; and

an electromagnetic circuit (70) for generating an attractive force to the stationary core,

a core-side buffer chamber (56) provided between the movable core and the fixed core, and a housing-side buffer chamber (57) provided between the movable core and the housing,

the movable core has: an upper core portion (51, 51A) forming the core-side buffer chamber with the fixed core; a lower core portion (52, 52A) forming the housing-side buffer chamber between the lower core portion and the housing; and a middle core part (53, 53A) provided between the upper core part and the lower core part,

the movable core is provided with a buffer flow passage (54, 55), and the buffer flow passage (54, 55) penetrates through the upper core portion, the middle core portion, and the lower core portion, connects the core-side buffer chamber and the housing-side buffer chamber, and allows fuel to pass therethrough so as to attenuate the kinetic energy of the movable core.

2. The fuel injection apparatus according to claim 1,

a part of the lower core is disposed to penetrate the middle core and the upper core and face the fixed core,

the middle core is mounted to the lower core by a clearance fit, and the upper core is mounted to the lower core by an interference fit, whereby the middle core is held between the lower core and the upper core.

3. The fuel injection apparatus according to claim 2,

the lower core has: a flange portion having a close contact surface in close contact with the core portion; and a cylindrical portion extending from a center side of the flange portion to the upper core portion side,

the cylindrical portion is provided so as to penetrate the middle core portion and the upper core portion, the middle core portion is attached to the cylindrical portion by a clearance fit, and the upper core portion is attached to the cylindrical portion by an interference fit.

4. The fuel injection apparatus according to claim 3,

the upper core is formed of a soft magnetic material, the lower core is formed of a high hardness material,

the cylindrical portion protrudes toward the fixed core side than the upper core portion.

5. The fuel injection apparatus according to any one of claims 2 to 4,

the middle core is formed of a high-hardness material.

6. The fuel injection apparatus according to any one of claims 1 to 5,

the buffer flow path makes a damping force different between a case where the movable core is driven in the valve opening direction and a case where the movable core is driven in the valve closing direction.

7. The fuel injection apparatus according to claim 6,

the buffer flow path is provided with a damping force changing portion that differs the amount of fuel passing through the movable core in the valve opening direction from the amount of fuel passing through the movable core in the valve closing direction.

8. The fuel injection apparatus according to claim 7,

the buffer flow path includes: a constant buffer flow path (54) provided with only an orifice; and a variable buffer flow path (55) provided with an orifice and the damping force changing unit.

9. The fuel injection apparatus according to claim 8,

the damping force changing unit includes check valves (553, 555).