A high-pressure fuel injector

Abstract

The present invention discloses a high-pressure fuel injector, which includes a fuel injector body, a control valve pair (2) and a nozzle needle valve pair (1) installed at the upper end of the fuel injector body. In the fuel injector body, the part from the nozzle seat surface (10) of the needle valve body of the nozzle needle valve pair to below the control valve pair (2) is all set as a pressure accumulation volume chamber (A'); the control rod of the control valve pair (2) and the needle valve of the nozzle needle valve pair (1) are placed in this volume chamber (A'). A connecting sleeve is provided between the control rod and the needle valve. The connecting sleeve is in interference fit with the lower part of the control rod, and the lower end of the connecting sleeve is in clearance fit with the needle valve, forming a floating connection structure. For the common rail fuel injector of the present invention, the injection pressure reaches 2200 bar - 2400 bar, while the injection pressure of the traditional common rail fuel injector can only reach 2000 bar at most. The increase in injection pressure can effectively improve the fuel atomization effect, make the combustion more complete, and reduce pollutant emissions.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel supply systems for internal combustion engines, and particularly relates to a high-pressure injector for a common rail fuel injection system. Background Art

[0002] The main technical index of the injector of the existing common rail fuel injection system is an injection pressure of 2000 bar, and there is static leakage. That is, high-pressure fuel leaks into the low-pressure chamber at the gaps between the nozzle needle valve pair and the control valve pair.

[0003] Due to the continuous leakage of high-pressure fuel at the gaps between the pairs, the nozzle needle valve and the control plunger are prone to wear, and the service life is reduced; the maximum injection pressure can only reach 2000 bar. When the pressure is further increased, the wear intensifies, the life drops rapidly, and it cannot be used normally; when there are impurities in the fuel, the moving pairs wear faster or even get stuck, resulting in the failure of the injector function.

[0004] At the same time, since the gap values between the nozzle needle valve pair and the control valve pair need to be strictly controlled, the machining accuracy requirements for the parts are extremely high. This leads to an increase in the machining difficulty and manufacturing cost of the injector, affecting the market competitiveness.

[0005] In the existing common rail injector, there is a low-pressure chamber Q between the nozzle needle valve pair 1 and the control valve pair 2.

[0006] The high-pressure volume chamber A at the lower end of the nozzle pair 1 flows through the gap 11 of the needle valve pair to the low-pressure volume chamber Q, and there is always fuel leakage. This causes an increase in fuel consumption and carbon emissions.

[0007] The high-pressure volume chamber C at the upper end of the control valve pair 2 flows through the gap 21 of the control valve pair to the low-pressure volume chamber Q, and there is always fuel leakage. This causes an increase in fuel consumption and carbon emissions.

[0008] The high-speed flow of fuel at the gap between the pairs cuts the metal surface, which will also cause the parts to wear faster and reduce the life of the injector.

[0009] Therefore, the injection pressure of the traditional common rail injector reaches a maximum of 2000 bar and cannot work reliably at higher pressures. Summary of the Invention

[0010] Aiming at the problems existing in the prior art, the present invention provides a high-pressure injector with an injection pressure that can reach 2200 - 2400 bar.

[0011] The present invention is realized as follows: A high-pressure injector includes an injector body, a control valve pair (2) and a nozzle needle valve pair (1) installed at the upper end of the injector body.

[0012] In the part of the nozzle seat surface (10) of the nozzle body of the nozzle needle valve pair in the injector body, from the nozzle seat surface (10) to below the control valve pair (2), the whole is set as a pressure accumulation volume chamber (A'); the control rod of the control valve pair (2) and the needle valve of the nozzle needle valve pair (1) are placed in this volume chamber (A').

[0013] A connecting sleeve is provided between the control rod and the needle valve. The connecting sleeve is in interference fit with the lower part of the control rod, and the lower end of the connecting sleeve is in clearance fit with the needle valve, forming a floating connection structure.

[0014] Preferably, the large outer diameter D1' of the nozzle body is φ12.5mm - φ14.3mm; the length L1' of the large outer circle is between 5mm and 10mm; the small outer diameter D3' is φ7.2mm, and the length L3' of the small outer circle is 25mm.

[0015] Preferably, the large outer diameter D1' is φ13mm; the length L1' of the large outer circle is 6mm.

[0016] Preferably, the pressure accumulation volume chamber in the nozzle body is a two-stage stepped hole.

[0017] Preferably, the distance from the middle hole (11) that plays a guiding role by being in clearance fit with the needle valve in the middle of the two-stage stepped hole to the nozzle seat surface (10) is 5mm - 15mm.

[0018] Preferably, the distance from the middle hole (11) to the nozzle seat surface (10) is 8mm.

[0019] Preferably, the interference amount between the connecting sleeve and the lower part of the control rod is 0.01 - 0.03mm.

[0020] Preferably, the clearance between the connecting sleeve and the needle valve is 0.006 - 0.012mm.

[0021] Advantages and technical effects of the present invention: The present invention has the following advantages by adopting the above technical solutions:

[0022] 1) For the common rail injector of the present invention, the injection pressure reaches 2200 bar - 2400 bar, while the injection pressure of the traditional common rail injector can only reach 2000 bar at most. The increase in injection pressure can effectively improve the fuel atomization effect, make the combustion more complete, and reduce pollutant emissions.

[0023] 2) The common rail injector of the present invention adopts a structure of a middle hole for pressure accumulation without static leakage. Different from the static leakage existing in the moving pair clearance of the traditional common rail injector, it has no static leakage, that is, there is no oil return when not injecting fuel, which can directly reduce the fuel consumption rate and reduce carbon emissions.

[0024] 3) Since there is no high-pressure fuel leakage at the clearance between the mating parts, the wear of the moving parts is also significantly reduced. Especially when the fuel contains contaminants such as impurities or moisture, since the high-speed flow of fuel at the clearance between the mating parts that cuts the surface of the parts is avoided, the contaminant sensitivity of the injector is also significantly reduced, and the fuel robustness is enhanced.

[0025] 4) The lower end of the control plunger of the injector control valve mating parts of the present invention directly acts on the nozzle seat surface, and its rising and falling directly control the start and end of fuel injection; between the control valve mating parts and the nozzle seat surface is a pressure accumulation volume chamber filled with high-pressure fuel.

[0026] 5) The injector of the present invention cancels the nozzle needle valve mating parts of the traditional common rail injector, as well as the low-pressure chamber between the control valve mating parts and the needle valve mating parts, and enlarges the volume of the middle-hole pressure accumulation chamber, which can reduce the pressure fluctuation during fuel injection, improve the average effective injection pressure, and at the same time improve the accuracy of multiple fuel injections. The fuel supply part of the traditional common rail injector is a slender oil passage, and pressure fluctuations occur in the oil passage during fuel injection, resulting in a decrease in the average effective injection pressure; and during multiple fuel injections, there are differences in the fuel injection volume due to different injection intervals.

[0027] 6) For the injector of the present invention, the two parts of the mating part of the control plunger and the nozzle seat surface are functionally separated into two parts, namely the control rod and the needle valve; these two parts are floatingly connected by a connecting sleeve. The processing difficulty is reduced, which is beneficial to the reduction of manufacturing costs and the improvement of market competitiveness.

[0028] 7) It is mainly reflected in that the injector housing adopts a large-middle-hole structure, eliminating structures such as slender oil passages and cross holes, significantly improving the manufacturing difficulty and cost. The nozzle body adopts a shorter total length, and at the same time, the inclined oil passage and the "peach-shaped" oil storage groove are also cancelled. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the schematic diagram of the principle of the present invention;

[0030] Figure 2 is the schematic diagram of the structure of the nozzle body;

[0031] Figure 3 is the schematic diagram of the principle of the prior art;

[0032] Figure 4 is the schematic diagram of the structure of the prior art nozzle body. DETAILED DESCRIPTION OF THE INVENTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention clearer, the following further describes the present invention in detail with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0034] Please refer to Figure 1 andFigure 2 , a high-pressure injector, comprising an injector body, a control valve pair 2 and a nozzle needle valve pair 1 mounted on the upper end of the injector body,

[0035] In the injector body, the part from the nozzle seat surface 10 of the needle valve body of the nozzle needle valve pair to below the control valve pair 2 is all set as a pressure accumulation volume chamber A'; the control rod 22 of the control valve pair 2 and the needle valve 12 of the nozzle needle valve pair 1 are placed in this volume chamber A'. The larger the pressure accumulation volume chamber A' is, the more beneficial it is to reduce the pressure loss and fluctuation during fuel injection, and improve the average effective injection pressure and the fuel quantity accuracy of multiple injections. The needle valve 12 and the needle valve body 13 only have a guiding function and do not have the sealing function of traditional nozzle pairs. That is, the cross-section of the needle valve 12 is not a complete circle, but is cut into a three-flat shape to allow fuel to pass through.

[0036] A connecting sleeve is provided between the control rod 22 and the needle valve. The connecting sleeve is in interference fit with the lower part of the control rod, and the lower end of the connecting sleeve is in clearance fit with the needle valve, forming a floating connection structure.

[0037] In order to further optimize the present invention, the following technical content optimizations are also made.

[0038] As Figure 3 and Figure 4 shown, the size of the traditional needle valve body is relatively large, the structure is relatively complex, the processing difficulty is large, and the cost is high. Specifically, the traditional needle valve body has three-stage outer circles. The large outer circle diameter D1 is φ14.3mm, and the large outer circle length L1 is 15mm; the middle outer circle diameter D2 is φ9.2mm, and the middle outer circle length L2 is 5mm; the small outer circle diameter D3 is φ7.2mm, and the small outer circle length L3 is 20mm.

[0039] As Figure 2 shown, the needle valve body of the present invention has a smaller outer dimension, a simple structure, a lower processing difficulty, and a lower cost. Specifically, the needle valve body of the present invention has two-stage outer circles. The large outer circle diameter D1' can be selected between φ12.5mm and φ14.3mm, and preferably D1' is φ13mm; the large outer circle length L1' can be selected between 5mm and 10mm, and preferably L1' is 6mm. The small outer circle diameter D3' is φ7.2mm, and the small outer circle length L3' is 25mm, which is basically the same as the traditional needle valve body.

[0040] As Figure 3 and Figure 4 shown, for the upper middle hole structure corresponding to the large outer circle of the traditional needle valve body 1, the upper part is the middle hole 1a for pair fitting, and the lower part is a "peach-shaped" oil storage groove 1b; there is an inclined oil passage 1c arranged horizontally and eccentrically. This part of the structure is complex, the processing difficulty is large, and the cost is high. As Figure 2 shown, the middle hole structure of the needle valve body of the present invention is a two-stage stepped hole, and the structure is particularly simple.

[0041] As Figure 1 and Figure 2 shown, for the needle valve body 1 of the present invention, the distance from the lower edge of the middle hole 11, which has a clearance fit with the needle valve and serves as a guiding function, to the seat surface 10 can be selected from 5 mm to 15 mm, preferably 8 mm. The distance from the lower edge of the guiding middle hole of the traditional needle valve body to the seat surface is 28 mm. The needle valve body of the present invention significantly shortens this distance, enhancing the guiding function of the needle valve and improving the accuracy of the needle valve seating.

[0042] As Figure 1 and Figure 2 shown, the control rod 22 and the needle valve 12 are two independent parts. The control rod 22 is the moving rod of the control valve pair 2. The needle valve 12 is the moving rod of the nozzle pair. The control rod 22 and the needle valve 12 are floatingly connected by a connecting sleeve 3. The connecting sleeve 3 and the control rod 22 have an interference fit, and the interference amount is 0.01 - 0.03 mm; the connecting sleeve 3 and the needle valve 12 have a clearance fit, and the fit clearance is between 0.006 - 0.012 mm. Such a floating connection can absorb the position tolerances such as coaxiality, perpendicularity, and parallelism caused by machining and assembly of parts such as the injector housing and the needle valve body, improving the positioning accuracy.

[0043] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high-pressure injector, comprising an injector body, a control valve pair (2) and a nozzle needle valve pair (1) installed at the upper end of the injector body, In the injector body, the part from the nozzle seat surface (10) of the needle valve body of the nozzle needle valve pair to below the control valve pair (2) is all set as a pressure accumulation volume chamber (A'); the control rod of the control valve pair (2) and the needle valve of the nozzle needle valve pair (1) are placed in this volume chamber (A'), A connecting sleeve is provided between the control rod and the needle valve. The connecting sleeve is in interference fit with the lower part of the control rod, and the lower end of the connecting sleeve is in clearance fit with the needle valve, forming a floating connection structure; The large outer diameter D1' of the needle valve body is φ12.5mm - φ14.3mm; the large outer circle length L1' is between 5mm and 10mm; the small outer diameter D3' is φ7.2mm, and the small outer circle length L3' is 25mm; The interference amount between the connecting sleeve and the lower part of the control rod is 0.01 - 0.03mm; The clearance between the connecting sleeve and the needle valve is 0.006 - 0.012mm.

2. The high-pressure fuel injector according to claim 1, characterized in that: The large outer diameter D1' is φ13mm; the large outer circle length L1' is 6mm.

3. The high-pressure fuel injector according to claim 1, characterized in that: The pressure accumulation volume chamber in the needle valve body is a two-stage stepped hole.

4. The high-pressure fuel injector according to claim 3, characterized in that: The distance from the middle hole (11) which is in clearance fit with the needle valve in the middle of the two-stage stepped hole and plays a guiding role to the nozzle seat surface (10) is 5mm - 15mm.

5. The high-pressure fuel injector according to claim 4, characterized in that: The distance from the middle hole (11) to the nozzle seat surface (10) is 8mm.

Images