CN218717206U - Oil injector for diesel engine and diesel engine - Google Patents

Abstract

The utility model relates to a sprayer for diesel engine, wherein, the sprayer includes at least: a housing forming a control oil chamber adapted to receive high pressure fuel and an injection chamber leading to an injection nozzle; a valve rod arranged in the housing, facing the oil control chamber with a first end and facing the oil nozzle with a second end; a valve ball which is adapted to abut against the valve seat in a closed state and to rise from the valve seat in an open state, wherein an oil return passage is provided between the oil control chamber and the valve seat, the oil return passage comprising a throttle portion extending from the oil control chamber toward the valve seat and a diffuser portion extending next to the throttle portion up to the valve seat, the throttle portion having a radial dimension smaller than that of the diffuser portion, wherein the throttle portion comprises a first section adjoining the oil control chamber and a second section connecting the first section and the diffuser portion, the radial dimension of the second section increasing in a direction toward the diffuser portion. It also relates to a corresponding diesel engine. Damage to the valve seat and the valve ball due to cavitation can be avoided.

Description

Oil injector for diesel engine and diesel engine

Technical Field

The utility model belongs to the technical field of the diesel engine and specifically relates to a sprayer for diesel engine is related to.

The utility model discloses still relate to a corresponding diesel engine.

Background

Diesel engines are engines that obtain energy by burning diesel oil, have the advantages of large torque and good economic performance, and are therefore widely used in large industrial equipment and transportation machinery.

Here, in order to achieve a desired atomization effect and control accuracy of the diesel engine to obtain high power and heat conversion efficiency, high-pressure fuel is selectively injected into a combustion chamber of the diesel engine, usually through an injector. In the conventional oil injector, high-pressure fuel oil flows to an oil control chamber and an oil injection chamber through an oil supply pipeline respectively, wherein the oil control chamber is connected with a valve seat of a ball valve through an oil return passage, the valve seat and the ball valve act together to open and close the oil return passage, a high-pressure region and a low-pressure region of the fuel oil are separated by cooperation of the valve seat and the ball valve, and the oil injection chamber extends to an oil injection nozzle. When the valve ball is in sealing contact with the valve seat, the oil return passage is closed, the oil pressure in the oil control cavity and the oil injection cavity is balanced, and the end part of the valve rod of the oil injector is in contact with the oil injection nozzle, so that the closed state of the oil injection nozzle is realized; when the valve ball rises from the valve seat, the opening of the valve seat is opened, the oil return passage is opened, the high-pressure fuel in the oil control cavity flows out of the opening of the valve seat through the oil return passage, so that the pressure of the fuel in the oil control cavity is reduced, the valve rod moves towards the direction of the oil control cavity under the action of the pressure difference between the oil injection cavity and the oil control cavity, the end part of the valve rod is not abutted against the oil injection nozzle, and the oil injection nozzle is in an open state and injects the high-pressure fuel in the oil injection cavity into a combustion chamber of the diesel engine.

Generally, a throttle portion and a diffuser portion are sequentially provided in an oil return passage between an oil control chamber and a valve seat in a flow direction of fuel, a radial dimension of the throttle portion is significantly smaller than a radial dimension of the oil control chamber and also smaller than a radial dimension of the diffuser portion, and a flow speed of fuel can be increased by the throttle portion. When the fuel accelerates in the restriction, the local pressure of the fuel drops below the vapor pressure and forms bubbles that move with the fuel to the vicinity of the valve seat and burst at high pressure, the differential pressure created by the burst can impact the valve seat and ball causing critical high pressure cavitation erosion, also known as "cavitation" or "cavitation". Under the action of long-time cavitation erosion, the valve seat and the valve ball can generate obvious erosion damage and damage, so that the sealing between the valve seat and the valve ball is failed, fuel backflow, pressure precision reduction and injection deviation in the oil control cavity are further caused, and even the diesel engine cannot work in severe cases.

SUMMERY OF THE UTILITY MODEL

Therefore, an object of the present invention is to provide an improved injector for a diesel engine, by which cavitation can be effectively prevented from occurring at an outlet of a diffuser portion, thereby reliably avoiding erosion damage of a valve seat and a valve ball and ensuring a sealing function between the valve seat and the valve ball.

According to a first aspect of the present invention, a fuel injector for a diesel engine is provided, wherein the fuel injector comprises at least:

-a housing forming a control oil chamber configured to receive high pressure fuel and a fuel injection chamber leading to a fuel injector;

-a valve stem provided in the housing, facing the oil control chamber with a first end and the oil injector with a second end;

a valve ball which is adapted to bear against a valve seat in a closed state and to lift off from the valve seat in an open state,

wherein an oil return passage is provided between the oil-control chamber and the valve seat, the oil return passage including a throttle portion extending from the oil-control chamber toward the valve seat and a diffuser portion extending next to the throttle portion up to the valve seat, the throttle portion having a radial dimension smaller than that of the diffuser portion, wherein the throttle portion includes a first section adjoining the oil-control chamber and a second section connecting the first section and the diffuser portion, the radial dimension of the second section increasing in a direction toward the diffuser portion.

Compared with the prior art, in the fuel injector for a diesel engine according to the present invention, the throttle portion is provided with a first section adjacent to the fuel control chamber and a second section located downstream of the first section and connecting the first section and the diffuser portion, and the radial dimension of the second section increases in a direction toward the diffuser portion or a flow direction of the fuel, whereby the fuel gradually decreases in speed and gradually increases in pressure while flowing through the second section of the throttle portion, which causes bubbles generated in the first section of the throttle portion to mix with the fuel in advance and to break under pressure, so that cavitation occurs in the region of the diffuser portion and away from the valve seat and the valve ball, which can effectively avoid a failure of the seal between the valve seat and the valve ball and significantly improve the service life and the workability of the fuel injector.

According to the utility model discloses a second aspect provides a diesel engine, the diesel engine has high pressure common rail unit and at least one according to the utility model discloses a sprayer.

Drawings

The principles, features and advantages of the present invention may be better understood by describing the invention in more detail below with reference to the accompanying drawings. The drawings include:

fig. 1 shows a schematic cross-sectional view of a fuel injector for a diesel engine according to an exemplary embodiment of the present invention;

FIG. 2 shows a partial pictorial view of the fuel injector of FIG. 1 for a diesel engine;

FIG. 3 shows a partial pictorial view of the fuel injector of FIG. 2 for a diesel engine;

fig. 4 shows a graph of fuel pressure for a fuel injector according to an exemplary embodiment of the present invention.

Detailed Description

In order to make the technical problems, technical solutions and advantageous technical effects to be solved by the present invention clearer, the present invention will be described in further detail with reference to the accompanying drawings and a plurality of exemplary embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the scope of the invention.

In the drawings, the size of each component, the thickness of a layer, or a region may be exaggerated for clarity. Accordingly, the shapes and sizes of each of the elements in the drawings are not to be considered true scale.

In this specification, the terms "mounted," "connected," and "connected" are to be construed broadly unless otherwise specifically indicated and limited. For example, it may be a fixed connection, or a removable connection, or an integral connection; either directly or indirectly through intervening components, or both may be interconnected. The meaning of the above terms in the present disclosure can be understood by those of ordinary skill in the art as appropriate.

Fig. 1 shows a schematic cross-sectional view of a fuel injector 100 for a diesel engine according to an exemplary embodiment of the present invention. Illustratively, the diesel engine has a high pressure common rail unit capable of delivering high pressure fuel generated from a high pressure fuel pump to a common fuel supply pipe, and precise control is achieved by adjusting the oil pressure in the common fuel supply pipe to separate the generation of injection pressure and the injection process from each other. Here, the injector 100 is connected to a high pressure common rail unit of a diesel engine for selectively injecting high pressure fuel into a combustion chamber of the diesel engine.

As shown in fig. 1, a fuel injector 100 for a diesel engine has a housing 10, which is exemplarily configured as a split-unit type casting and includes a first housing 11 and a second housing 12, which are fixedly connected to each other, for example, by a screw connection or the like, wherein the housing 10 forms an oil control chamber 13 and an injection chamber 14 configured to receive high-pressure fuel, which are respectively connected to a high-pressure common rail unit of the diesel engine through an oil supply line 15, and the high-pressure fuel from the high-pressure common rail unit flows into the oil control chamber 13 and the injection chamber 14 through the oil supply line 15.

Exemplarily, as shown in fig. 1, the housing 10 is divided in the longitudinal extension direction into a first housing 11 and a second housing 12, which are fixedly connected to each other, wherein the first housing 11 forms a control oil chamber 13, a valve seat 17 and an oil return passage 18, the second housing 12 forms an oil jet 16, and the second housing 12 forms an oil jet chamber 14 together with the first housing 11. Other configurations are of course conceivable, which are considered to be expedient by the person skilled in the art, for example a housing 10 formed by a combination of more parts.

As shown in fig. 1, the fuel injector 100 has a valve stem 20 disposed in a housing 10, wherein a first end 21 of the valve stem 20 faces a control oil chamber 13, and a second end 22 of the valve stem 20 faces a fuel injection nozzle 16 formed by the housing 10, through which high-pressure fuel in the injection oil chamber 14 can be injected into a combustion chamber of a diesel engine. Here, when the second end 22 of the valve stem 20 abuts against the fuel injection nozzle 16, the fuel injection nozzle 16 is in a closed state and the fuel injector 100 cannot inject fuel, and when the second end 22 of the valve stem 20 is lifted from the fuel injection nozzle 16, the fuel injection nozzle 16 is in an open state and the fuel injector 100 can inject high-pressure fuel into the combustion chamber.

As shown in fig. 1, a housing 10 of the injector 100 forms a valve seat 17, and an oil return passage 18 through which high-pressure fuel in the oil control chamber 13 can flow out from an opening of the valve seat 17 and return to a tank is provided between the valve seat and the oil control chamber 13. In this case, the injector 100 has a valve ball 30 which, together with a valve seat 17, functions as a ball valve in that the valve ball 30 rests in a sealing manner against the valve seat 17 in the closed state of the ball valve, so that the return channel 18 is closed and the high-pressure fuel in the control chamber 13 is prevented from flowing out via the return channel 18, while the valve ball 30 is lifted from the valve seat 17 in the open state of the ball valve, so that the return channel 18 is open and the high-pressure fuel in the control chamber 13 can flow out via the return channel 18. Here, when the ball valve 30 is in the closed state of the ball valve, the fuel pressure in the control chamber 13 is equal to the fuel pressure in the injection chamber 14, in which case the valve rod 20 cannot move and remains with the second end 22 against the injection nozzle 16, whereby the injection nozzle 16 is also in the closed state; whereas when the valve ball 30 is in the open state of the ball valve, the high-pressure fuel in the fuel control chamber 13 flows out from the opening of the valve seat 17 via the oil return passage 18, so that the fuel pressure in the fuel control chamber 13 is smaller than the fuel pressure in the fuel injection chamber 14, the valve rod 20 is moved toward the fuel control chamber 13 by the pressure difference between the fuel control chamber 13 and the fuel injection chamber 14, so that the second end portion 22 is lifted from the fuel injection nozzle 16, whereby the fuel injection nozzle 16 is in the open state and the high-pressure fuel in the fuel injection chamber 14 can be injected through the fuel injection nozzle 16.

Illustratively, as shown in FIG. 1, fuel injector 100 includes an electromagnetic actuator 40 configured to apply pressure to valve ball 30 toward valve seat 17, thereby controlling the state of valve ball 30. Here, when the pressure applied by the electromagnetic actuator 40 is greater than the fuel pressure in the control oil chamber 13, the valve ball 30 abuts on the valve seat 17 and the ball valve formed by the valve ball 30 and the valve seat 17 is in the closed state, and when the pressure applied by the electromagnetic actuator 40 is less than the fuel pressure in the control oil chamber 13, the high-pressure fuel in the control oil chamber 13 lifts the valve ball 30 from the valve seat 17, whereby the ball valve formed by the valve ball 30 and the valve seat 17 is in the open state.

Illustratively, as shown in FIG. 1, the fuel injector 100 also has a spring member 50 disposed in the fuel injection cavity 14 that applies pressure to the valve stem 20 toward the fuel injector nozzle 16 for effecting a return of the valve stem 20 when transitioning between open and closed states of the fuel injector 100.

Fig. 2 shows a partial view of the fuel injector 100 for a diesel engine of fig. 1.

A stop 131 is provided in the oil control chamber 13, by means of which the movement of the valve rod 20 in the direction of the oil return channel 18 can be limited, wherein the stop 131 can be configured lower than a projection of the oil supply line 15 leading to the oil control chamber 13, on which projection the first end 21 of the valve rod 20 can be stopped. The stopper 131 can effectively prevent the valve rod 20 from being unset.

When the valve ball 30 is lifted from the valve seat 17, the opening of the valve seat 17 is in an open state, and the high-pressure fuel in the oil control chamber 13 can flow out from the opening of the valve seat 17 via the return passage 18, as shown in fig. 2. Here, the oil return passage 18 has a throttle portion 181 and a diffuser portion 182 which are arranged in this order in the flow direction of the fuel, wherein the throttle portion 181 extends from the fuel control chamber 13 toward the valve seat 17, and the diffuser portion 182 extends to the valve seat 17 next to the throttle portion 181. Here, the radial dimension of the throttle portion 181 is significantly smaller than the radial dimension of the oil-controlling chamber 13, so that the cross-sectional area of the throttle portion 181 is significantly smaller than the cross-sectional area of the oil-controlling chamber 13. In this case, the flow speed of the high-pressure fuel at the time of entering the throttle portion from the fuel control chamber 13 is significantly increased, which can be clearly understood by the following flow conservation formula:

V ₁ *S ₁ ＝V ₂ *S ₂

here, V represents a flow velocity of the fuel, and S represents a cross-sectional area through which the fuel flows. As the cross-sectional area through which the fuel flows decreases, the flow velocity of the fuel increases accordingly.

Furthermore, the bernoulli equation below gives a solution:

here, P represents the pressure of the fuel, ρ represents the density of the fuel, and V represents the flow velocity of the fuel. As the flow rate of the fuel increases, the pressure of the fuel decreases accordingly. Therefore, when high-pressure fuel enters the throttle portion 181 from the fuel control chamber 13, the flow speed of the fuel is significantly increased and the pressure of the fuel is significantly reduced, so that the partial pressure of the fuel is lower than the vapor pressure of the fuel, thereby generating bubbles in the fuel, which continue to flow with the fuel to the outlet of the diffuser portion 182.

Here, the radial dimension of the throttle portion 181 is smaller than the radial dimension of the diffuser portion 182. When the fuel flows from the throttle portion 181 to the diffuser portion 182, the flow speed of the fuel is correspondingly reduced and the fuel pressure is increased. In the course of flowing toward the outlet of the diffuser portion 182, the bubbles in the fuel gradually condense under pressure until they break at a location close to the valve seat 17 and the valve ball 30, and the breaking of the bubbles generates a large pressure peak, thereby causing an uneven distribution of pressure and causing an impact on the valve seat 17 and the valve ball 30. This causes critical high pressure cavitation erosion, also referred to as "cavitation" or "cavitation," of the valve seat 17 and valve ball 30. Under the action of cavitation over a long period of time, the valve seat 17 and the valve ball 30 undergo significant erosion damage, thereby causing a failure of the seal between the valve seat 17 and the valve ball 30, which further causes a backflow of fuel toward the control chamber 13, a reduction in pressure accuracy of the injector 100, and an injection deviation, and in severe cases even renders the diesel engine inoperable.

Fig. 3 shows a partial view of the fuel injector 100 for a diesel engine of fig. 2.

According to the present invention, as shown in fig. 3, the throttle portion 181 of the oil return passage 18 includes a first section 1811 adjacent to the oil control chamber 13 and a second section 1812 connecting the first section 1811 and the diffuser portion 182, and the radial dimension of the second section increases, in particular continuously increases, in the direction toward the diffuser portion 182 or the flow direction of the fuel, so that the cross-sectional area of the second section 1812 increases continuously in the flow direction of the fuel. However, it is also conceivable for the radial dimension of the second portion 1812 to increase discontinuously in the direction toward the diffuser portion 182, for example in the form of a step. As is clear from the law of conservation of flow and the bernoulli equation, the flow velocity of the fuel decreases and the pressure of the fuel increases as the fuel flows through the second section 1812. In this case, the bubbles generated in the first section 1811 of the throttle portion 181 are acted on by a higher pressure in the second section 1812 in advance than the conventional throttle portion having a constant cross-sectional area, whereby the bubbles condense relatively early and are broken when the outlet of the diffuser portion 182 has not been reached, for example, at the middle region of the diffuser portion 182. This can effectively prevent the valve seat 17 and the valve ball 30 from being damaged by cavitation, to ensure the sealing action between the valve seat 17 and the valve ball 30. Furthermore, by the cooperation of the first section 1811 and the second section 1812, an optimal balance of the increase in the flow rate of the fuel and the reduction in the cavitation damage of the valve seat 17 and the valve ball 30 can be achieved, thereby improving the operating performance of the fuel injector 100 as much as possible.

Illustratively, as shown in fig. 3, the first section 1811 of the throttle portion 181 is cylindrical, and the second section 1812 is conical, whereby the first section 1811 and the second section 1812 have a uniform pressure distribution in the circumferential direction, and the radial dimension of the second section 1812 linearly increases along the flow direction of the fuel, thereby causing a uniform increase in the flow velocity of the fuel in the second section 1812. Such a throttle 181 can be constructed cost-effectively and technically simply. However, it is also contemplated that the second segment 1812 may be configured in other ways deemed appropriate by one skilled in the art, such as where the generatrices of the second segment 1812 are hyperbolic.

Illustratively, the transition between the first section 1811 and the second section 1812 of the throttle 181 is rounded. It is thereby possible to suppress the generation of bubbles in the fuel and to avoid cavitation at the transition by the smooth transition structure between the first section 1811 and the second section 1812. It is also contemplated that the transition between the second section 1812 and the diffuser portion 182 may be rounded and the transition between the diffuser portion 182 and the valve seat 17 may be rounded. This also enables the generation and collapse of bubbles to be suppressed by means of the smooth transition structure, thereby effectively improving the service life of the fuel injector 100.

Illustratively, as shown in fig. 3, the diffuser portion 182 is cylindrically configured. However, it is also conceivable for the diffuser section 182 to be conically configured, which promotes the early collapse of the air bubbles in the fuel and largely prevents cavitation from occurring at the valve seat 17. Here, the taper angle of the second section 1812 is larger than that of the diffuser portion 182, thereby avoiding an excessive decrease in the flow velocity of the fuel.

Illustratively, the ratio of the axial dimensions of the first and second sections 1811 and 1812 of the throttle portion 181 is dependent on the taper angle of the second section 1812 and the axial dimension of the diffuser portion 182. Here, the larger the taper angle of the second section 1812, the faster the cross-sectional area of the second section 1812 increases in the direction of flow of the fuel, so that the bubbles are subjected to a greater pressure in the second section 1812, whereby the bubbles can collapse earlier. In this case, the ratio of the axial dimensions of the first section 1811 and the second section 1812 can be increased accordingly. Further, the larger the axial dimension of the diffuser portion 182, the lower the probability of occurrence of cavitation at the outlet of the diffuser portion 182, and therefore the ratio of the axial dimensions of the first section 1811 and the second section 1812 can also be increased accordingly. Here, the ratio of the axial dimensions of the first section 1811 and the second section 1812 may be obtained from experimental data and/or empirical data. Illustratively, the ratio of the axial dimensions of the first section 1811 and the second section 1812 is in the range of 0.5 to 1.5.

Fig. 4 shows a graph of fuel pressure for a fuel injector 100 according to an exemplary embodiment of the present invention.

As shown in fig. 4, the horizontal axis X represents the distance from the fuel control chamber 13 in the flow direction of the fuel, the vertical axis Y represents the pressure of the fuel, E represents the location where cavitation occurs, curve I represents the pressure curve of the conventional fuel injector having a cylindrical throttle portion, and curve II represents the pressure curve of the fuel injector 100 according to the present invention.

As shown in fig. 4, when the fuel enters from the fuel control chamber 13 into the throttle portion 181 of the oil return passage 18, the pressure drops approximately stepwise. In the conventional fuel injector, when the fuel enters the diffuser portion 182 from the throttle portion 181, the fuel pressure gradually rises up to a stable value at which bubbles in the fuel are broken, thereby causing cavitation at E. In contrast, in the fuel injector 100 according to the present invention, the pressure of the fuel has started to rise when it enters the second section 1812 of the throttle portion 181, and the pressure of the fuel has reached approximately a stable value when the fuel reaches the diffuser portion 182, thereby advancing the portion where the bubble is broken, i.e., the portion E where cavitation occurs, on the abscissa X. This also proves that the configuration of the throttle portion 181 of the fuel injector 100 according to the present invention can effectively prevent the cavitation from causing damage to the valve seat 17 and the valve ball 30.

The explanations of the embodiments are described below only in the framework of the examples. Of course, the individual features of the embodiments can be freely combined with one another as far as technically meaningful, without departing from the framework of the invention.

Other advantages and alternative embodiments of the present invention will be apparent to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative structures, and illustrative examples shown and described. On the contrary, various modifications and substitutions may be made by those skilled in the art without departing from the basic spirit and scope of the invention.

Claims (10)

1. A fuel injector (100) for a diesel engine, characterized in that the fuel injector (100) comprises at least:

-a housing (10) forming an oil control chamber (13) adapted to receive high pressure fuel and an injection chamber (14) leading to an injection nozzle (16);

-a valve stem (20) provided in the housing (10) facing with a first end (21) the oil control chamber (13) and with a second end (22) the oil injector (16);

-a valve ball (30) adapted to abut against a valve seat (17) in a closed state and to lift from the valve seat (17) in an open state,

wherein an oil return passage (18) is provided between the oil-control chamber (13) and the valve seat (17), the oil return passage comprising a throttle portion (181) extending from the oil-control chamber (13) towards the valve seat (17) and a diffuser portion (182) extending next to the throttle portion (181) up to the valve seat (17), the throttle portion (181) having a radial dimension smaller than that of the diffuser portion (182), wherein the throttle portion (181) comprises a first section (1811) adjoining the oil-control chamber (13) and a second section (1812) connecting the first section (1811) and the diffuser portion (182), the radial dimension of the second section increasing in a direction towards the diffuser portion (182).

2. Fuel injector (100) according to claim 1,

the radial dimension of the second section (1812) increases continuously in a direction toward the diffuser portion (182).

3. Fuel injector (100) according to claim 1 or 2,

the first section (1811) is cylindrical; and/or

The second section (1812) is conical.

4. Fuel injector (100) according to claim 1 or 2,

rounded at a transition between the first section (1811) and the second section (1812); and/or

Rounded at a transition between the second section (1812) and the diffuser portion (182); and/or

Rounded at the transition between the diffuser portion (182) and the valve seat (17); and/or

The second section (1812) and the diffuser portion (182) are conical, wherein the second section (1812) has a cone angle that is greater than the cone angle of the diffuser portion (182).

5. Fuel injector (100) according to claim 1 or 2,

the ratio of the axial dimensions of the first section (1811) and the second section (1812) is dependent on the taper angle of the second section (1812) and the axial dimension of the diffuser portion (182).

6. Fuel injector (100) according to claim 1 or 2,

the oil control cavity (13) and the oil injection cavity (14) are connected to a high-pressure common rail unit of the diesel engine through an oil supply pipeline (15).

7. Fuel injector (100) according to claim 1 or 2,

the housing (10) is a split-block cast part and comprises a first housing (11) and a second housing (12), the first housing (11) and the second housing (12) being fixedly connected to one another, wherein the first housing (11) forms the oil control chamber (13), the valve seat (17) and the oil return passage (18), and the second housing (12) forms the oil jet (16) and, together with the first housing (11), forms the oil injection chamber (14).

8. Fuel injector (100) according to claim 1 or 2,

the fuel injector (100) comprises an electromagnetic actuator (40) configured and adapted to apply a pressure to the valve ball (30) towards the valve seat (17).

9. Fuel injector (100) according to claim 1 or 2,

a stopper (131) is provided in the oil control chamber (13) for restricting movement of the valve rod (20) in the direction of the oil return passage (18); and/or

A spring element (50) is arranged in the oil injection chamber (14) for resetting the valve rod (20).

10. A diesel engine having a high pressure common rail unit and at least one fuel injector (100) according to any one of claims 1 to 9.

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