CN106704066A - Micro-dynamic fuel return bypass type electronically controlled fuel injector - Google Patents

Abstract

The object of the present invention is to provide a micro-dynamic oil return bypass electronically controlled fuel injector, which includes a fuel injector head, a fuel injector body, a flow limiting valve assembly, a solenoid valve assembly, a needle valve assembly, and a nozzle. The flow limiting valve assembly is located inside the pressure accumulator chamber to ensure the stability of the fuel injection process of each cylinder under the condition of large fuel injection volume. A solenoid valve assembly and a needle valve assembly are arranged below. They are connected together by tight caps. The solenoid valve adopts the form of a two-position three-way valve to reduce the dynamic oil return volume and realize the micro-dynamic oil return function. A control slider is placed inside the control chamber, and it is in contact with the middle block to slow down the fuel injection rate at the initial stage of injection and accelerate the response of the needle valve seat. There is no static pressure difference inside the injector, and there is no static leakage of the injector.

Description

A micro-dynamic oil return bypass type electronically controlled fuel injector

technical field

The invention relates to an engine fuel injection device.

Background technique

In order to optimize the fuel economy and emission indicators of diesel engines, the current diesel engine system begins to adopt high-speed electromagnetic switch valve control, which has the advantages of fast system response, high control precision, flexible control strategy and reliable working performance. But as emission regulations impose higher and stricter requirements on fuel injection systems, injectors need faster response, lower fuel leakage and more appropriate fuel injection rates.

Diesel engine emission limits mainly lie in two aspects of nitrogen oxides and particulate matter. On the one hand, the formation of nitrogen oxides is mainly due to the reaction of _N2 and _O2 in the cylinder under high temperature and pressure. Therefore, to reduce the emission of nitrogen oxides, it is required to control the instantaneous fuel injection rate during the fuel injection process and reduce the fuel injection rate at the initial stage of injection. On the other hand, at the end of the injection process, the injector must cut off the fuel quickly, that is, the needle valve seat response should be fast, so as to reduce the formation of particulate matter. To sum up, the requirement of diesel engine emissions for injectors is that the fuel injection process can form a "slow first and then fast" fuel injection rate curve.

Contents of the invention

The object of the present invention is to provide a micro-dynamic oil return bypass type electronically controlled fuel injector with a micro-dynamic oil return quantity, a function of no static leakage, and a time-history curve of the injection rate that can be realized "slow first and then urgent".

The purpose of the present invention is achieved like this:

The present invention is a micro-dynamic oil return bypass type electronically controlled fuel injector, which is characterized in that it includes a fuel injector head, a fuel injector body, a flow limiting valve assembly, a solenoid valve assembly, a needle valve assembly, a nozzle, and a downward high-pressure fuel injector. The fuel injector head is installed above the fuel injector body, the main oil inlet hole is set inside the fuel injector head, the pressure storage chamber is set inside the fuel injector body, the main oil inlet hole communicates with the pressure storage chamber, and the flow limiting valve assembly is set In the pressure accumulator chamber, the lower end of the injector body is equipped with solenoid valve assembly, needle valve assembly, and nozzle in sequence. The tight cap is located outside the solenoid valve assembly, needle valve assembly, and nozzle. The upper end of the tight cap is connected to the injector by thread The lower end of the body is connected;

The flow-limiting valve assembly includes a limit spring seat, a flow-limiting piston, a ball valve reset spring seat, and a supporting slider, and the limit spring seat, the flow-limiting piston, and the ball valve return spring seat are arranged from top to bottom, and the limit spring seat and the limit Damping springs are installed between the flow pistons, and the supporting slider is installed in the ball valve reset spring seat. A ball valve is installed between the upper end of the supporting slider and the flow limiting piston, and a ball valve is installed between the lower end of the supporting slider and the ball valve reset spring seat below. Spring, the piston blind hole and flow limiting hole are set in the flow limiting piston, the axial center through hole is set in the support slider, the transition oil chamber is set between the ball valve return spring seat and the injector body below, and the piston blind hole is connected to the pressure storage Cavity and restricting hole, the restricting hole and the axial center through hole are connected or disconnected under the control of the ball valve, and the axial center through hole is connected with the transition oil chamber;

The solenoid valve assembly includes an electromagnet, a coil, an armature, a balance valve stem, a valve seat, and an intermediate block. The coil is wound on the electromagnet. The solenoid valve reset spring seat is arranged above the electromagnet, and the armature is arranged below the electromagnet. The armature and the solenoid valve reset The return spring of the solenoid valve is arranged between the spring seats, the balance valve stem is located in the valve seat, the upper end of the balance valve stem is fixedly connected with the armature, the middle block is arranged under the valve seat, and the balance valve stem is formed between the middle part of the balance valve stem and the valve seat The upper cavity, the lower end of the balanced valve stem, the valve seat and the middle block form the lower cavity of the balanced valve stem. The oil inlet damping hole is set in the valve seat, and the oil return hole, the middle oil passage, and the middle throttle hole are set in the middle block. The oil inlet damping hole is connected to the upper chamber of the balance valve stem, the middle throttle hole is respectively connected to the middle oil passage and the lower chamber of the balance valve stem, and the oil return hole is connected to or disconnected from the middle throttle hole and the fuel tank under the control of the balance valve stem;

The needle valve assembly includes a needle valve limit sleeve, a control slider, and a needle valve body. The control slider is located in the needle valve limit sleeve, the upper part of the needle valve body is located in the needle valve limit sleeve, and the lower part of the needle valve body Part is located in the nozzle, a control cavity is formed between the control slider and the needle valve body, a control slider return spring is set in the control cavity, a raised part is set in the middle of the needle valve body, and the gap between the raised part and the needle valve limit sleeve above it The needle valve return spring is set, the upper end surface of the control slider is provided with an intermediate cavity, and the control slider through hole and the bypass oil passage are arranged in the control slider. In the control chamber, an oil tank is formed between the needle valve body and the nozzle, and a spray hole is set at the end of the nozzle;

The middle oil passage is connected to the middle cavity, and the upper end of the downward high-pressure oil passage is connected to the transition oil chamber, which is connected to the oil tank through the injector body, the valve seat, the middle block, the needle valve limit sleeve, and the nozzle, and the oil inlet damping hole is connected to the downward high-pressure oil passage. .

The present invention may also include:

1. When injecting fuel from the injection hole, the fuel pressure in the transition oil chamber drops, and the flow-limiting piston, ball valve, and support slider move downward as a whole, and the ball valve is not seated on the return spring seat of the ball valve. The flow-limiting hole and the axial center through hole When the quality of fuel flowing out of the injection hole exceeds the threshold, the flow-limiting piston presses the ball valve and makes it seat on the return spring seat of the ball valve, and the flow-limiting hole is disconnected from the axial center through hole; when the injection hole stops injecting fuel, the ball valve Under the action of the return spring, the flow-limiting piston, the ball valve and the support slider return to their initial positions as a whole.

2. When the coil is energized, the balance valve stem moves upward, the upper chamber of the balance valve stem is disconnected from the lower chamber of the balance valve stem, the oil return hole is connected to the fuel tank, and the fuel in the control chamber passes through the middle oil passage and the middle throttling The hole and the oil return hole return oil to the oil tank, the needle valve body is lifted upwards, and the injection hole is opened to inject oil; after the coil is powered off, the balance valve stem moves downward under the action of the return spring of the solenoid valve and is pressed against the upper end surface of the middle block , the upper cavity of the balanced valve stem is connected with the lower cavity of the balanced valve stem, and the oil return hole is disconnected from the fuel tank. The channel and the middle cavity enter the control cavity.

3. When the injection hole stops fuel injection, the fuel pressure on the upper end surface of the control slider is higher than that on the lower end surface, the control slider overcomes the spring preload of the return spring of the control slider and moves downward, the bypass oil circuit is opened, and as the fuel enters In the control cavity, the control slider returns to the initial position under the force of the return spring of the control slider.

The advantage of the present invention is that: the present invention adopts the structure of the pressure accumulator, and under the condition of large fuel injection volume, it can ensure that the continuous progress of the fuel injection process of the fuel injector will not cause large fluctuations in the common rail fuel pressure and cause other injection The fuel injector process is affected. The present invention adopts a flow limiting valve assembly, which effectively reduces the occurrence of abnormal fuel injection conditions and ensures a normal and stable fuel injection process. The fuel injector uses a solenoid valve to control the balance valve stem to adjust the switch of the oil return circuit, which improves the control accuracy and flexibility, effectively improves the emission of the entire diesel engine, and improves the fuel economy. The balance valve stem of the injector adopts the form of two-position three-way, which can realize the two-way sealing of the cone surface and the plane, reduce the dynamic oil return volume, and realize the micro-dynamic oil return function. The bypass oil channel of the control slider in the control chamber can make the control chamber quickly build up pressure and improve the response characteristics of the needle valve. The design of the throttle hole of the control slider and the middle throttle hole ensures that the fuel injector can inject fuel slowly at the initial stage and reduce the formation of nitrogen oxides. And there is no static pressure difference inside the fuel injector, which ensures that the fuel injector can realize the static and non-leakage function.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is a schematic diagram of a restrictor valve assembly;

Fig. 3 is a schematic diagram of a solenoid valve assembly;

Figure 4 is a schematic diagram of the needle valve assembly;

Figure 5 is a schematic diagram of A-A.

detailed description

The present invention is described in more detail below in conjunction with accompanying drawing example:

Referring to Figures 1-5, the main structure of a micro-dynamic oil return bypass electronically controlled fuel injector of the present invention includes a fuel injector head 1, a fuel injector body 11, a restrictor valve assembly 3, a solenoid valve assembly 10, and a tight cap 9. Needle valve assembly 5, nozzle 6. The fuel injector head 1 is connected with the fuel injector body 11 through threads, and is sealed with a sealing ring 12 placed on the fuel injector body 11 . The main oil inlet hole 13 on the injector head 1 communicates with the accumulator chamber 2 in the injector body 11 . Below the injector body 11 is a solenoid valve assembly 10 , a nozzle 6 and a needle valve assembly 5 , which are assembled and connected by a tight cap 9 . The flow limiting valve assembly 3 is placed inside the fuel injector body 11, and its structure mainly includes a retaining ring 14, a limit spring seat 25, a damping spring 15, a flow limiting piston 16, a ball valve 23, a support slider 18, a ball valve return spring 19, Ball valve return spring seat 21. A flow-limiting hole 17 and a piston blind hole 24 are processed on the flow-limiting piston 16, and an axial center through hole 22 is processed on the support slider 18 to ensure that the fuel oil can lead to the lower oil circuit. A solenoid valve assembly 10 is arranged between the bottom of the injector body 11 and the upper part of the nozzle 6. The main structure includes a solenoid valve return spring 26, a solenoid valve return spring seat 37, a coil 27, an electromagnet 36, an armature 35, and a valve seat 28. , middle block 32, balance valve rod 34. The armature 35 and the balance valve rod 34 are combined and placed in the valve seat 28, and the oil inlet damping hole 29 is processed in the valve seat 28. The middle block 32 is processed with an oil return hole 30 , a middle oil passage 31 , a middle throttle hole 33 and the like. Below the solenoid valve assembly 10 is the needle valve assembly 5 , the main structure includes a control slider 44 , a needle valve stop sleeve 42 , a control slider return spring 39 , a needle valve body 40 , and a needle valve return spring 41 . The control slider 44 is placed in the control cavity 43 and is processed with a control slider through hole 45 and a bypass oil passage 38 .

Fig. 1 is a schematic diagram of the overall structure of the fuel injector of the present invention. The fuel injector head 1 is processed with a main fuel inlet hole 13, and the high-pressure fuel delivered by the high-pressure fuel pipe enters the interior of the fuel injector through the main fuel inlet hole 13. The fuel injector head 1 and the fuel injector body 11 are assembled through threads, and there is a sealing ring 12 between them for sealing. The main oil inlet hole 13 communicates with the accumulator chamber 2 . The fuel in the accumulator chamber 2 will pass through the restrictor valve assembly 3 downwards. After the fuel flows out from the restrictor valve assembly 3 , it enters the control cavity 45 and the oil tank 8 through the downlink high-pressure oil circuit 4 . A solenoid valve assembly 10 is installed between the lower part of the injector body 11 and the needle valve assembly 5 . Electromagnetic force is used in the solenoid valve assembly 10 to control the lifting and seating of the armature 35 and the balance valve rod 34 . When the balance valve stem 34 was lifted upwards, the oil return hole 30 was opened, and the fuel in the control chamber 43 flowed through the control slider through hole 45, the middle oil passage 31 and the middle throttle hole 33, and was discharged through the oil return hole 30. The fuel pressure in the control chamber 43 drops, forming a fuel pressure difference with the oil tank 8, so that the needle valve body 40 is lifted, and fuel injection starts. At this time, the limitation of the needle valve body 40 is realized by the needle valve limitation sleeve 42 . Due to the two-stage throttling effect of the through hole 45 of the control slider and the middle throttle hole 33 , the fuel pressure in the middle oil passage 31 will not drop rapidly, thereby slowing down the drop speed of the fuel pressure in the control chamber 43 . When the balance valve stem 34 sits down, the oil return hole 30 is closed, and the fuel will pass through the oil inlet damping hole 29, and flow through the balance valve stem 34, the middle throttle hole 33, the middle oil passage 35, the control slider through hole 45 and the balance valve stem 34. The bypass oil passage 38 enters the control chamber 43, so that the pressure of the control chamber 43 builds up, the needle valve body 40 is seated, and the fuel injection process ends. The middle oil passage 31 plays a role of connecting the oil inlet oil passage and the oil outlet oil passage. At the same time, a needle valve body 40 pressed by a needle valve return spring 41 is placed inside the nozzle 6 , as shown in FIG. 5 , which is an enlarged cross-section A-A of the needle valve body 40 . The arc surface of the needle valve body 40 can well play a guiding role. There is no static pressure difference inside the entire needle valve assembly 5, which ensures the characteristic of no static leakage of the fuel injector. Both the needle valve assembly 5 and the solenoid valve assembly 10 are placed in the tight cap 9, and then fastened by the threaded wire and the injector body 11.

Fig. 2 is a partial structural diagram of the flow limiting valve assembly of the present invention. The flow limiting valve assembly 3 mainly includes a retaining ring 14, a limit spring seat 25, a damping spring 15, a flow limiting piston 16, a ball valve 23, a support slider 18, a ball valve return spring 19, a ball valve return spring seat 21 and the like. The entire restrictor valve assembly 3 is placed inside the injector body 11 through the accumulator chamber 2 and is limited by the stop ring 14 . The limit spring seat 25 cooperates with the retaining ring 14, on the one hand as a spring seat for the damping spring 15, and on the other hand to limit the maximum displacement of the flow limiting piston 16. By the spring pre-tightening force of the damping spring 15 and the ball valve return spring 19, the ball valve 23 cooperates with the lower end surface of the flow limiting piston 16 and the upper end surface of the supporting slider 18. Ball valve return spring seat 21 is subjected to the spring force of ball valve return spring 19, is pressed on the bottom, and its top variable section is the seating surface of ball valve 23. Fuel enters the piston blind hole 24 in the flow limiting piston 16 from the pressure accumulator chamber 2 , and then enters the axial center through hole 22 of the supporting slider 18 through the flow limiting hole 17 . The fuel flowing out from the axial central through hole 22 passes through the downward high-pressure oil passage 4 to the lower oil passage. When the fuel injector injects fuel normally, the fuel oil is sprayed out from the nozzle hole 7, and the fuel oil pressure in the transition oil chamber 20 drops. Due to the throttling effect of the flow-limiting hole 17 on the fuel, the fuel pressure in the piston blind hole 24 in the flow-limiting piston 16 and the pressure storage chamber 2 is relatively high, forming a pressure difference with the transition oil chamber 20, so that the flow-limiting piston 16, the ball valve 23 and the support slider 18 are displaced downwards to compensate the fuel injected by the injector, but the ball valve 23 cannot be seated on the ball valve return spring seat 21. At the end of fuel injection, as the fuel flows through the flow-limiting hole 17, the pressure difference between the upper and lower sides of the flow-limiting piston 16 gradually decreases. bit. When the injector continuously injects fuel, the quality of the outflowing fuel exceeds the threshold, and the injector is in an abnormal working state, due to the large flow rate and fast flow rate of the fuel injected by the injection hole 7, the transition oil chamber below the flow-limiting piston 16 The oil pressure at 20 drops rapidly, forming a pressure difference between up and down, causing the restrictor piston 16 to press the ball valve 23 to be seated on the ball valve return spring seat 21, preventing the fuel oil from circulating. Due to the lack of fuel supply, the fuel injector stopped working, which prevented the continuation of abnormal fuel injection.

Fig. 3 is a partial structural diagram of the solenoid valve assembly of the present invention. The solenoid valve assembly 10 mainly includes a solenoid valve return spring 26 , a solenoid valve return spring seat 37 , a coil 27 , an electromagnet 36 , an armature 35 , a valve seat 28 , an intermediate block 32 , and a balance valve stem 34 . Solenoid valve return spring seat 37, solenoid valve return spring 26, coil 27 and electromagnet 36 are built inside the fuel injector body 11, wherein solenoid valve return spring seat 37 is fastened to the top of the solenoid valve by threads. Between the electromagnetic valve return spring seat 37 and the armature 35 is the electromagnetic valve return spring 26 . The armature 35 and the balance valve stem 34 are placed inside the valve seat 28 below the injector body 11 . The part that is combined with the valve seat 28 below is the intermediate block 32 . The whole solenoid valve is in the form of a two-position three-way valve. When the injector starts to inject fuel, the coil 27 of the solenoid valve is energized, forms a magnetic circuit with the electromagnet 36 and the armature 35, generates electromagnetic force, attracts the balance valve stem 34 to move upward, and opens the oil return hole 30 in the middle block 32, And block the oil inlet damping hole 29. At this time, the fuel in the control chamber 43 returns to the fuel tank through the middle oil passage 31, the middle throttle hole 33 and the oil return hole 30, and the oil pressure in the control chamber 43 drops, and the pressure on the upper surface of the needle valve body 40 decreases, which is consistent with The fuel pressure in the oil sump 8 forms a pressure difference. The needle valve body 40 is lifted up, and the spray hole 7 is opened to spray oil. When the injector stops injecting oil, since the armature 35 and the balance valve rod 34 are closely integrated, they are jointly pressed against the middle block 32 by the spring preload of the return spring 26 of the solenoid valve, and block it. Oil return hole 30. At the same time, the balance valve rod 34 opens the oil path leading to the control chamber 43 from the oil inlet damping hole 29 , the middle throttle hole 33 and the middle oil passage 31 .

Fig. 4 is a partial structural diagram of the needle valve assembly of the present invention. The needle valve assembly mainly includes a control slider 44 , a control slider return spring 39 , a needle valve stop sleeve 42 , a needle valve body 40 and a needle valve return spring 41 . The control slider 44 is placed inside the control chamber 43 , and is pushed up by the control slider return spring 39 and abuts against the lower end surface of the middle block 32 . The control slider 44 is processed with a control slider through hole 45 and a bypass oil passage 38 . When the fuel injection starts, due to the two-stage throttling effect of the middle throttle hole 33 on the middle block 32 and the through hole 45 of the control slider, the fuel pressure in the control chamber 43 drops more slowly than that of a normal fuel injector to reduce nitrogen. The effect of oxide emissions. When the fuel injection is finished, since the fuel pressure on the upper end surface of the control slider 44 is higher than that on the lower end surface, the control slider 44 will overcome the spring preload of the control slider return spring 39 and move downward, opening the bypass oil passage 38, so that the control The rapid build-up of fuel pressure in chamber 43 improves the needle valve seating response. As the fuel enters the control chamber 43, the oil pressure on the upper and lower surfaces of the control slider 44 tends to be consistent. Under the action of the control slider return spring 39, the control slider 44 resets.

It can be seen from the above working process that in the fuel injection process of a micro-dynamic oil return bypass type electronically controlled fuel injector of the present invention, the form of a two-position three-way valve is adopted, which greatly reduces the dynamic oil return volume and realizes micro-dynamic return. oil function. The structure of the control slider through hole 45 and the bypass oil passage 38 built in the control slider 44 in the control cavity 43 ensures the low fuel injection rate at the beginning of the injection and the characteristics of rapid oil cut-off at the end of the injection. The entire fuel injection process is controlled by a solenoid valve, and the electromagnetic force is used to drive the movement of the balance valve rod 34, which realizes the requirements of fast response to the fuel injection process, high control precision, and variable fuel injection law. The fuel injector body 11 has a built-in restrictor valve assembly 3, which prevents the continuation of the abnormal fuel injection state and ensures the stability of the working process. When the present invention is applied to the common rail system, under the state of large fuel injection, the use of the pressure accumulator 2 can effectively reduce the pressure fluctuation of the common rail, thereby reducing the occurrence of uniformity and stability decline in the fuel injection process of each cylinder .

Claims (5)

1. a kind of On Fluctuations oil return bypass type electric-controlled fuel injector, it is characterized in that：Including injector head, oil injector body, current limliting valve group Part, electromagnetic valve component, needle valve assembly, nozzle, descending high-pressure oil passage, injector head are arranged on oil injector body top, injector head Inside sets main fuel feed hole, and oil injector body inside sets pressure accumulation chamber, and main fuel feed hole is communicated with pressure accumulation chamber, and current limliting valve module is arranged on In pressure accumulation chamber, electromagnetic valve component, needle valve assembly, nozzle are installed in oil injector body lower end successively, and tight cap is located at electromagnetic valve component, needle-valve Component, nozzle exterior, the mode that the upper end of tight cap is connected through a screw thread are connected with oil injector body bottom；

The current limliting valve module includes limit spring seat, current limliting piston, ball valve return spring holder, support slipper, limit spring, Current limliting piston, ball valve return spring holder arranged from top to bottom, and damping spring is installed between limit spring seat and current limliting piston, is supported Sliding block is arranged in ball valve return spring holder, ball valve is set between the upper end of support slipper and current limliting piston, under support slipper Mounting ball valve back-moving spring between end and ball valve return spring holder below, sets piston blind hole and current limliting in current limliting piston Hole, sets axial central through hole in support slipper, bridging oil is set between ball valve return spring holder and oil injector body below Chamber, piston blind hole connection pressure accumulation chamber and metering hole, metering hole is connected or disconnected with axial central through hole under the control of ball valve, axle Connected with transition oil pocket to central through hole；

The electromagnetic valve component include electromagnet, coil, armature, balance valve rod, valve seat, intermediate mass, wound around coil on electromagnet, Electromagnet top sets magnetic valve return spring holder, and electromagnet lower section sets armature, between armature and magnetic valve return spring holder Magnetic valve back-moving spring is set, and balance valve rod is located in valve seat, and balance valve rod upper end is connected with armature, and intermediate mass is arranged on valve Seat lower section, balances and formed between the middle part of valve rod and valve seat balance valve rod epicoele, balances bottom, valve seat and the centre of valve rod Balance valve rod cavity of resorption is formed between block, oil-feed damping hole is set in valve seat, spill port, middle oil duct, centre are set in intermediate mass Throttle orifice, oil-feed damping hole connection balance valve rod epicoele, middle throttle orifice is respectively communicated with middle oil duct peace weighing apparatus valve rod cavity of resorption, returns Oilhole is connected or disconnected under the control of balance valve rod with middle throttle orifice and fuel tank；

The needle valve assembly includes needle-valve stop collar, control slide block, needle-valve body, and control slide block is located in needle-valve stop collar, needle-valve The upper part of body is located in needle-valve stop collar, and the lower part of needle-valve body is located in nozzle, is formed between control slide block and needle-valve body Control chamber, in control chamber set control slide block back-moving spring, needle-valve body middle part set bossing, bossing with its above Needle-valve back-moving spring is set between needle-valve stop collar, and the upper surface of control slide block sets intermediate cavity, control is set in control slide block Slider throughbores, bleed off circuit, control slide block through hole are respectively communicated with intermediate cavity and control chamber, bleed off circuit connection control chamber, needle-valve Oil holding slot is formed between body and nozzle, nozzle-end sets spray orifice；

Middle oil duct connects intermediate cavity, the upper end connection transition oil pocket of descending high-pressure oil passage, through oil injector body, valve seat, intermediate mass, Needle-valve stop collar, nozzle connection oil holding slot, oil-feed damping hole connect descending high-pressure oil passage.

2. a kind of On Fluctuations oil return bypass type electric-controlled fuel injector according to claim 1, it is characterized in that：During spray orifice oil spout, The fuel pressure of transition oil pocket declines, and current limliting piston, ball valve, support slipper are overall to bottom offset, and ball valve is not landed in ball valve On return spring holder, metering hole is communicated with axial central through hole；When the fuel oil quality of spray orifice outflow exceedes threshold value, current limliting piston Compress ball valve and it is seated at ball valve return spring holder, metering hole disconnects with axial central through hole；When spray orifice stops oil spout, In the presence of ball valve back-moving spring, current limliting piston, ball valve and support slipper integrally return to initial position.

3. a kind of On Fluctuations oil return bypass type electric-controlled fuel injector according to claim 1 and 2, it is characterized in that：Coil electricity When, balance valve rod is moved upwards, and balance valve rod epicoele is off-state with balance valve rod cavity of resorption, and spill port is connected state with fuel tank State, the fuel oil in control chamber passes through middle oil duct, middle throttle orifice and spill port oil return to fuel tank, and needle-valve body is lifted up, spray Open oil spout in hole；After coil blackout, balance valve rod is moved downward in the effect of magnetic valve back-moving spring, is crushed on intermediate mass upper end On face, balance valve rod epicoele is connected with balance valve rod cavity of resorption, and spill port disconnects with fuel tank, while the fuel oil in descending high-pressure oil passage Enter control chamber through oil-feed damping hole, balance valve rod epicoele, balance valve rod cavity of resorption, middle oil duct, intermediate cavity.

4. a kind of On Fluctuations oil return bypass type electric-controlled fuel injector according to claim 1 and 2, it is characterized in that：Spray orifice stops During oil spout, control slide block upper surface fuel pressure is higher than its lower surface, and control slide block overcomes the spring of control slide block back-moving spring Pretightning force to bottom offset, open, as fuel oil enters control chamber, work of the control slide block in control slide block back-moving spring by bleed off circuit Under firmly, initial position is returned to.

5. a kind of On Fluctuations oil return bypass type electric-controlled fuel injector according to claim 3, it is characterized in that：Spray orifice stops oil spout When, control slide block upper surface fuel pressure is higher than its lower surface, and control slide block overcomes the spring pre-tightening of control slide block back-moving spring Power to bottom offset, open, as fuel oil enters control chamber, active force of the control slide block in control slide block back-moving spring by bleed off circuit Under, return to initial position.