High-pressure common-rail fuel injector

Abstract

A clapping type electromagnetic valve with a lever effect is adopted, an armature of the electromagnetic valve is in a flat plate shape, and the stress of the armature has lever characteristics when viewed from the longitudinal section: the upper part of the left end is in contact with a shell or a magnetic attraction surface to form a rotating fulcrum; the upper part of the right end is contacted with the reset spring to form an elastic fulcrum; the middle lower part is contacted with the valve to form an action output fulcrum; and the upper part of the middle part faces the magnetic attraction surface to form an attraction point. According to the clapper type electromagnetic valve, the structure of the armature is simplified, the weight of the armature is reduced, the magnetic gap is in a wedge-shaped state, the total magnetic gap in a magnetic circuit is smaller, the suction force of the electromagnetic valve is larger, the miniaturization of the electromagnetic valve is facilitated, and the clapper type electromagnetic valve sinks and is arranged in the middle of an oil injector; the mass of moving parts in the whole oil injector is lighter, the moving inertia is smaller, the response speed of the oil injector is higher, the structure is simpler, and the cost is lower.

Description

Technical Field

[0001] The present invention relates to an engine fuel injector, and more particularly to a high-pressure common rail injector. Background Art

[0002] A high-pressure common rail injector for engine fuel injection is a device that controls a hydraulic device through an electromagnetic valve, and the hydraulic device further controls the nozzle needle valve to achieve the opening and closing of fuel injection of the injector.

[0003] The high-pressure common rail injector includes a housing, an electromagnetic valve, a hydraulic device, a nozzle, and a tightening cap; the nozzle includes a nozzle body, a needle valve, and a preloading spring. The nozzle body has a hollow fuel chamber inside, the needle valve is arranged in the fuel chamber, and the lower end of the nozzle body is provided with spray holes communicating with the outside.

[0004] The electromagnetic valve includes an iron core, a coil, an armature, and a return spring. The coil is placed in the iron core, the armature suction surface faces the magnetic suction surface of the iron core, and a certain air gap, i.e., magnetic gap, is maintained. The return spring is arranged in parallel with the iron core at the center of the iron core.

[0005] When the electromagnetic valve is not energized, the armature is pushed away from the magnetic suction surface by the elastic force of the return spring. When the electromagnetic valve is energized, the coil generates an electromagnetic field, forming a magnetic circuit closed loop in the iron core, magnetic gap, and armature. The armature overcomes the elastic force of the return spring and generates an axial displacement. To meet the needs of high-speed engine control, this displacement is generally only about dozens of micrometers, and neither the displacement nor the force generated by the electromagnetic valve can directly drive the nozzle needle valve. Therefore, a hydraulic device that can amplify the movement to hundreds of micrometers needs to be introduced.

[0006] The hydraulic device includes a valve, a valve body, a piston, and a push rod; a control chamber is arranged in the valve body. The control chamber is a cylindrical hole with an inverted opening. The piston is arranged in the control chamber and can slide axially. The control chamber is provided with an inlet throttle hole and an outlet throttle hole. The valve is arranged at the outlet of the outlet throttle hole and blocks the outlet of the outlet throttle hole under normal conditions. The piston is connected to the nozzle needle valve through the push rod and is basically synchronized with the movement of the needle valve.

[0007] When the high-pressure common rail injector works, a certain fuel pressure is maintained in the fuel chamber of the nozzle body, but the injector only sprays fuel outward through the spray holes when the needle valve is lifted, and the injector closes the fuel injection when the needle valve drops.

[0008] Controlling the energization and de-energization of the electromagnetic valve can control the opening and closing of the injector. Due to the high operating speed of the engine, to accurately control the fuel injection performance, very high requirements are put forward for the response speed of the armature of the electromagnetic valve and the hydraulic device for movement amplification.

[0009] The solenoid valves in the current technology are all direct-acting structures, that is: the armature has a guide rod structure, the suction surfaces of the armature and the iron core are a pair of parallel surfaces, and the armature slides axially as a whole under the restriction of the guiding part. The total magnetic gap of the magnetic circuit is the sum of the N-pole magnetic gap and the S-pole magnetic gap. The characteristic of the direct-acting solenoid valve is that the minimum magnetic gaps of both the N-pole and the S-pole must be greater than or equal to the armature movement displacement, and the minimum total magnetic gap is twice the magnetic gap of one of the magnetic poles (N-pole or S-pole). This structure has the following deficiencies: the structure is complex; the weight of the armature is not conducive to lightweight due to the existence of the guide rod; the return spring is placed in the center of the iron core, which is not conducive to the miniaturization of the solenoid valve. The solenoid valve must be set at the top of the fuel injector, so a very long push rod needs to be set between the piston of the hydraulic device and the needle valve of the fuel injector, further increasing the weight of the moving parts and reducing the response speed of the fuel injector; the magnetic gap utilization rate of the direct-acting solenoid valve is not high, which is not conducive to the improvement of the magneto-induced suction force. In short, restricted by the structure of the direct-acting solenoid valve in the current technology, there are deficiencies such as large inertia of the moving parts, slow response speed, and low energy conversion efficiency. Summary of the Invention

[0010] The purpose of the present invention is to provide a high-pressure common rail fuel injector, which optimizes the use of a clapper-type solenoid valve with a lever effect to solve the problems of large inertia of the moving parts, slow response speed, and low energy conversion efficiency of the solenoid valve.

[0011] To achieve this purpose, the present invention adopts the following technical solutions.

[0012] The present invention provides a high-pressure common rail fuel injector, which includes a housing, a solenoid valve, a hydraulic device, a nozzle, and a nut; the nozzle includes a nozzle body, a needle valve, and a preloading spring. There is a hollow fuel chamber inside the nozzle body. The needle valve is arranged in the fuel chamber, and spray holes communicating with the outside are arranged at the lower end of the nozzle body.

[0013] The solenoid valve includes an iron core, a coil, an armature, and a return spring. The coil is placed in the iron core, and the magnetic force suction surface of the iron core faces the armature. The return spring is arranged beside the iron core in parallel with the iron core.

[0014] The hydraulic device includes a valve, a valve body, and a piston; a control chamber is arranged inside the valve body. The control chamber is an inverted open cylindrical hole. The piston is arranged in the control chamber and can slide axially. An oil outlet throttle hole is arranged at the top of the control chamber. The valve is arranged at the outlet of the oil outlet throttle hole and blocks the outlet of the oil outlet throttle hole under normal conditions.

[0015] The armature is in the shape of a flat plate. From the longitudinal section, its force has a lever characteristic: the upper left end contacts the housing or the magnetic force suction surface to form a rotation fulcrum; the upper right end contacts the return spring to form an elastic force fulcrum; the lower middle part contacts the valve to form an action output fulcrum; the upper middle part faces the magnetic force suction surface to form a suction point.

[0016] When the solenoid valve is not energized, the armature is pushed away from the magnetic attraction surface by the elastic force of the reset spring. Under the combined action of the reaction force of the rotating fulcrum, the armature pushes the valve to block the oil outlet throttle hole; the magnetic gap between the armature and the magnetic attraction surface is wedge-shaped, gradually increasing from left to right.

[0017] When the solenoid valve is energized, the coil generates an electromagnetic field, forming a closed magnetic circuit in the iron core, magnetic gap, and armature. The armature overcomes the elastic force of the return spring and rotates around the rotating fulcrum toward the magnetic attraction surface until the armature contacts the housing or the magnetic attraction surface. The pressure applied to the valve below the middle of the armature is released, and the valve is pushed open by the fuel pressure in the oil outlet throttle hole below, and the fuel pressure in the control room is released.

[0018] Preferably, the upper end of the needle valve is integrated with the piston of the hydraulic device.

[0019] A preload spring and a spring seat are provided in the nozzle. The preload spring acts on the needle valve stem through the spring seat. Under normal conditions, the combined force of the fuel pressure in the control chamber of the hydraulic device at the top of the needle valve and the preload spring force is greater than the fuel pressure below the needle valve, and the lower end of the needle valve keeps the spray hole blocked. When the solenoid valve is energized, the fuel pressure in the control chamber decreases, and the fuel pressure below the needle valve overcomes the combined force of the fuel pressure in the control chamber and the preload spring force, the needle valve rises, and the spray hole opens to spray outward.

[0020] Preferably, there is a tiny oil inlet throttling gap between the inner wall surface of the control chamber of the hydraulic device and the outer wall surface of the piston, so that the control chamber and the fuel chamber maintain a constant flow with throttling characteristics.

[0021] The shell is provided with an oil inlet, an oil inlet passage, and an oil return port, the hydraulic device is provided with an oil hole, and the nozzle body is provided with an oil passage. External high-pressure fuel enters the fuel chamber through the shell's oil inlet, oil inlet passage, the hydraulic device's oil hole, and the nozzle body's oil passage. The high-pressure fuel in the fuel chamber enters the control chamber of the hydraulic device through the oil inlet throttling gap to accumulate pressure. When the valve is opened, the fuel in the control chamber flows into the solenoid valve through the oil outlet throttling hole, flows through the iron core to cool the coil, and then flows out of the injector through the shell's oil return port.

[0022] A terminal block is provided at the upper end of the shell, with a wire inside the terminal block and a terminal outside. The wire connects the solenoid valve coil and the terminal. The fuel injector controls whether the fuel injector sprays or not by whether the external terminal is energized or not.

[0023] Preferably, the cross-sectional shape of the oil inlet throttling gap is a group of open grooves surrounding the cylindrical surface of the piston and opened along the axial direction of the piston. The cross-sectional shape of the grooves can be a plane, an arc, a triangle or a trapezoid.

[0024] Preferably, the cut groove on the cylindrical surface of the piston is composed of multiple steps with different cross-sectional areas or is formed by a gradual transition. The beneficial effect is that during the upward movement of the piston, the throttling degree brought by the cut groove changes, which helps to accelerate the action response speed of the piston.

[0025] The beneficial effects of the present invention:

[0026] By adopting a clapper-type solenoid valve, the structure of the armature is simplified, the weight of the armature is reduced, the magnetic gap is in a wedge shape, the total magnetic gap in the magnetic circuit is smaller, the suction force of the solenoid valve is larger, which is beneficial to the miniaturization of the solenoid valve. Further, the piston of the hydraulic device and the head of the nozzle needle valve are integrated into one body. The mass of the moving parts in the entire injector is lighter, the moment of inertia is smaller, the response speed of the injector is faster, the structure is simpler, and the cost is lower. Brief Description of the Drawings

[0027] Figure 1 is a schematic structural diagram of the high-pressure common rail injector according to the first embodiment of the present invention.

[0028] Figure 2 is a partial structural schematic diagram of the solenoid valve in the non-energized state according to the first embodiment of the present invention.

[0029] Figure 3 is a partial structural schematic diagram of the solenoid valve in the energized state according to the first embodiment of the present invention.

[0030] Figure 4 is a partial structural schematic diagram of the hydraulic device according to the second embodiment of the present invention.

[0031] Figure 5 is Figure 4 a partial enlarged schematic diagram of the A-A cross-section in

[0032] Figure 6 is a partial structural schematic diagram of the hydraulic device according to the third embodiment of the present invention.

[0033] Figure 7 is a partial structural schematic diagram of the hydraulic device according to the fourth embodiment of the present invention.

[0034] In the figure: 1 - housing 1; 1a - oil inlet; 1b - oil inlet passage; 1c - oil return port; 2 - solenoid valve; 2a - iron core; 2b - return spring; 2c - armature; 2d - coil; 2e - magnetic attraction surface; 2f - pivot point of rotation; 3 - hydraulic device; 3a - valve; 3b - valve body; 3c - oil passage hole; 3d - piston; 3e - oil outlet throttle hole; 3f - control chamber; 3g - oil inlet throttle clearance; 4 - nozzle; 4a - oil passage; 4b - fuel chamber; 4c - nozzle body; 4d - needle valve; 4e - head; 4f - preloading spring; 4g - spring seat; 4h - injection hole; 5 - locknut; 6 - terminal block; 6a - terminal; 6b - wire; β - magnetic gap; t - valve lift; L1 - step one; L2 - step two. Specific embodiments

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Additionally, it should be noted that for the sake of description, only the parts related to the present invention are shown in the drawings, rather than all the structures.

[0036] In the description of the present invention, unless otherwise clearly defined and limited, the terms "connected", "connected to", and "fixed" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] In the present invention, unless otherwise clearly defined and limited, the first feature being "above" or "below" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through other features between them. Moreover, the first feature being "above", "over", and "on" the second feature includes the first feature being directly above and obliquely above the second feature, or simply indicating that the first feature has a higher horizontal height than the second feature. The first feature being "below", "under", and "beneath" the second feature includes the first feature being directly below and obliquely below the second feature, or simply indicating that the first feature has a lower horizontal height than the second feature.

[0038] In the description of this embodiment, the orientation or positional relationships such as "upper", "lower", "left", "right", etc. are based on the orientation or positional relationships shown in the drawings. They are only for the convenience of description and simplifying the operation, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for distinction in description and have no special meaning. Embodiment 1

[0039] As Figures 1 to 3 shown, the present invention provides a high-pressure common rail injector, which includes a housing 1, a solenoid valve 2, a hydraulic device 3, a nozzle 4 and a tightening cap 5. The tightening cap 5 tightly presses the hydraulic device 3 and the nozzle 4 onto the housing 1; the nozzle 4 includes a nozzle body 4c, a needle valve 4d and a pre-tightening spring 4f. There is a hollow fuel chamber 4b inside the nozzle body 4c. The needle valve 4d is arranged in the fuel chamber 4b. The lower end of the nozzle body 4c is provided with a spray hole 4h communicating with the outside.

[0040] The solenoid valve 2 includes an iron core 2a, a coil 2d, an armature 2c and a return spring 2b. The coil 2d is placed in the iron core 2a. The magnetic force attracting surface 2e of the iron core 2a faces the armature 2c. The return spring 2b is arranged beside the iron core 2a in parallel with the iron core 2a.

[0041] The hydraulic device 3 includes a valve 3a, a valve body 3b and a piston 3d; a control chamber 3f is arranged inside the valve body 3b. The control chamber 3f is an inverted open cylindrical hole. The piston 3d is arranged inside the control chamber 3f and can slide axially. An oil outlet throttle hole 3e is provided at the top of the control chamber 3f. The valve 3a is arranged at the outlet of the oil outlet throttle hole 3e and blocks the outlet of the oil outlet throttle hole 3e under normal conditions.

[0042] The armature 2c is in the shape of a flat plate. From the longitudinal cross-section, its force-bearing has a lever characteristic: the upper left end contacts the housing 1 or the magnetic force attracting surface 2e to form a rotation fulcrum 2f; the upper right end contacts the return spring 2b to form an elastic force fulcrum; the lower middle part contacts the valve 3a to form an action output fulcrum; the upper middle part faces the magnetic force attracting surface 2e to form an attracting point.

[0043] When the solenoid valve 2 is not energized, the armature 2c is pushed away from the magnetic force attracting surface 2e under the elastic force of the return spring 2b. Under the combined action of the reaction force of the rotation fulcrum 2f, the armature 2c pushes the valve 3a to block the oil outlet throttle hole 3e; the magnetic gap β between the armature 2c and the magnetic force attracting surface 2e is in the shape of a wedge and gradually increases from left to right.

[0044] When the solenoid valve 2 is energized, the coil 2d generates an electromagnetic field, forming a closed magnetic circuit in the iron core 2a, magnetic gap β, and armature 2c. The armature 2c overcomes the elastic force of the return spring 2b and rotates around the rotation fulcrum 2f towards the magnetic attraction surface 2e until the armature 2c abuts against the housing 1 or the magnetic attraction surface 2e; the pressure applied to the valve 3a below the middle of the armature 2c is released, and the valve 3a is pushed open by the fuel pressure in the lower oil outlet throttle hole 3e, and the fuel pressure in the control chamber 3f is released. As Figure 2 shown, the magnetic gap β disappears and is replaced by a valve lift t as shown in Figure 3 .

[0045] Preferably, the upper end head 4e of the needle valve 4d is integrated with the piston 3d of the hydraulic device 3.

[0046] A pre-tightening spring 4f and a spring seat 4g are arranged in the fuel injector 4. The pre-tightening spring 4f acts on the rod part of the needle valve 4d through the spring seat 4g. Under normal conditions, the resultant force of the fuel pressure in the control chamber 3f of the hydraulic device 3 (i.e., at the top of the needle valve 4d) and the force of the pre-tightening spring 4f is greater than the fuel pressure below the needle valve 4d, and the lower end of the needle valve 4d keeps blocking the injection hole 4h. When the solenoid valve 2 is energized, the fuel pressure in the control chamber 3f decreases, and the fuel pressure below the needle valve 4d overcomes the resultant force of the fuel pressure in the control chamber 3f and the force of the pre-tightening spring 4f, and the needle valve 4d rises, and the injection hole 4h opens for external injection.

[0047] Preferably, there is a small oil inlet throttle gap 3g between the inner wall surface of the control chamber 3f of the hydraulic device 3 and the outer wall surface of the piston 3d, so that the control chamber 3f and the fuel chamber 4b are kept in constant communication with throttling characteristics.

[0048] The housing 1 is provided with an oil inlet 1a, an oil inlet passage 1b, and an oil return port 1c. The hydraulic device 3 is provided with an oil passing hole 3c, and the nozzle body 4c is provided with an oil passing passage 4a. External high-pressure fuel enters the fuel chamber 4b through the oil inlet 1a of the housing, the oil inlet passage 1b, the oil passing hole 3c of the hydraulic device 3, and the oil passing passage 4a of the nozzle body 4c. The high-pressure fuel in the fuel chamber 4b enters the control chamber 3f of the hydraulic device 3 through the oil inlet throttle gap 3g for pressure accumulation. When the valve 3a opens, the fuel in the control chamber 3f flows into the solenoid valve 2 through the oil outlet throttle hole 3e, flows through the iron core 2a to cool the coil 2d, and then flows out of the fuel injector through the oil return port 1c of the housing 1.

[0049] The upper end of the housing 1 is provided with a terminal block 6. The terminal block 6 is internally provided with a wire 6b and externally provided with a terminal 6a. The wire 6b connects the coil 2d of the solenoid valve 2 and the terminal 6a. Whether the fuel injector is energized through the external terminal 6a controls whether the fuel injector injects fuel. Embodiment 2

[0050] As Figures 4 to 5As shown in the figure, the present invention provides another embodiment, which is different from the first embodiment in that the cross-sectional shape of the oil inlet throttling gap 3g is a set of open grooves formed around the cylindrical surface of the piston 3d and along the axial direction of the piston 3d. The cross-sectional shape of the groove can be a plane, an arc, a triangle or a trapezoid. The schematic diagram of this embodiment gives an inspiration of the groove with a plane shape. Embodiment Three

[0051] As Figure 6 shown in the figure, the present invention provides another embodiment, which is different from the second embodiment in that the grooves on the cylindrical surface of the piston 3d are composed of multiple steps with different cross-sectional areas. The schematic diagram of this embodiment gives an inspiration of two stepped cross-sections with different areas. The depth of the groove within the range of step one L1 is less than that of step two L2. The beneficial effect is that during the upward movement of the piston 3d, the throttling degree brought by the groove gradually decreases from large to small, which helps to accelerate the opening response speed of the piston 3d. Embodiment Four

[0052] As Figure 7 shown in the figure, the present invention provides another embodiment, which is different from the third embodiment in that the grooves on the cylindrical surface of the piston 3d are formed by a gradual change of multiple cross-sectional areas. The schematic diagram of this embodiment gives an inspiration of a gradual change between two different cross-sections. The beneficial effect is that during the upward movement of the piston 3d, the throttling degree brought by the groove gradually increases from small to large, which helps to accelerate the closing response speed of the piston 3d.

[0053] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, various obvious changes, re-adjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A high-pressure common rail fuel injector, comprising a housing (1), a solenoid valve (2), a hydraulic device (3), a nozzle (4) and a tight cap (5), wherein the tight cap (5) tightly presses the hydraulic device (3) and the nozzle (4) onto the housing (1); the nozzle (4) comprises a nozzle body (4c), a needle valve (4d) and a preload spring (4f), the nozzle body (4c) has a hollow fuel cavity (4b) inside, the needle valve (4d) is arranged in the fuel cavity (4b), and the lower end of the nozzle body (4c) is provided with a spray hole (4h) communicating with the outside, wherein: The solenoid valve (2) comprises an iron core (2a), a coil (2d), an armature (2c) and a return spring (2b); the coil (2d) is disposed in the iron core (2a), the magnetic attraction surface (2e) of the iron core (2a) faces the armature (2c), and the return spring (2b) is disposed side by side with the iron core (2a) on the outside of the iron core (2a); The hydraulic device (3) comprises a valve (3a), a valve body (3b) and a piston (3d); a control chamber (3f) is arranged in the valve body (3b); the control chamber (3f) is a cylindrical hole with an inverted opening; the piston (3d) is arranged in the control chamber (3f) and can slide axially; an oil outlet throttling hole (3e) is arranged at the top of the control chamber (3f); the valve (3a) is arranged at the outlet of the oil outlet throttling hole (3e) and blocks the outlet of the oil outlet throttling hole (3e) in a normal state; The armature (2c) is in the shape of a flat plate, and has the characteristics of a lever when viewed from a longitudinal cross section: the upper left end contacts the housing (1) or the magnetic attraction surface (2e) to form a rotation fulcrum (2f); the upper right end contacts the return spring (2b) to form an elastic fulcrum; the lower middle portion contacts the valve (3a) to form an action output fulcrum; the upper middle portion faces the magnetic attraction surface (2e) to form an attraction point; When the solenoid valve (2) is not energized, the armature (2c) is pushed away from the magnetic attraction surface (2e) by the elastic force of the return spring (2b), and under the combined action of the reaction force of the rotating fulcrum (2f), the armature (2c) pushes the valve (3a) to block the oil outlet throttle hole (3e); the magnetic gap (β) between the armature (2c) and the magnetic attraction surface (2e) is in a wedge shape and gradually increases from left to right; When the solenoid valve (2) is energized, the coil (2d) generates an electromagnetic field, forming a magnetic circuit closed loop in the iron core (2a), the magnetic gap (β), and the armature (2c), and the armature (2c) overcomes the elastic force of the return spring (2b) and rotates around the rotation fulcrum (2f) toward the magnetic attraction surface (2e) until the armature (2c) contacts the housing (1) or the magnetic attraction surface (2e); the pressure applied to the valve (3a) at the lower middle of the armature (2c) is released, the valve (3a) is pushed open by the fuel pressure in the oil outlet throttle hole (3e) at the lower part, and the fuel pressure in the control chamber (3f) is released.

2. A high pressure common rail injector according to claim 1, characterized in that: The upper end head (4e) of the needle valve (4d) is integrated with the piston (3d) of the hydraulic device (3).

3. A high pressure common rail injector according to claim 1, characterized in that: A tiny oil inlet throttling gap (3g) exists between the inner wall surface of the control chamber (3f) of the hydraulic device (3) and the outer wall surface of the piston (3d), so that the control chamber (3f) and the fuel chamber (4b) are always connected with throttling characteristics.

4. A high pressure common rail injector according to claim 3, characterized in that: The cross-sectional shape of the oil inlet throttling gap (3g) is a group of open grooves surrounding the cylindrical surface of the piston (3d) and opened along the axial direction of the piston (3d). The cross-sectional shape of the grooves can be a plane, an arc, a triangle or a trapezoid.

5. A high pressure common rail injector according to claim 4, characterized in that: The groove on the cylindrical surface of the piston (3d) is composed of a plurality of steps with different cross-sectional areas or is formed by gradual transition.

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