EP4696880A1

EP4696880A1 - Injector valve seat and preparation method therefor, injector, engine, and vehicle

Info

Publication number: EP4696880A1
Application number: EP24858770.1A
Authority: EP
Inventors: Guosong XUE; Feng GE; Litao Zhang; Yang Yang; Jianxiong MA; Chuanan YANG; Zhihui Song; Yan Liu
Original assignee: Zhejiang Intelligent Transportation Technology Innovation Center; Zhejiang Geely Holding Group Co Ltd
Current assignee: Zhejiang Intelligent Transportation Technology Innovation Center; Zhejiang Geely Holding Group Co Ltd
Priority date: 2023-08-31
Filing date: 2024-08-31
Publication date: 2026-02-18
Also published as: WO2025045241A1

Abstract

The present application provides an injector valve seat, applied to a methanol direct injection injector. The injector valve seat includes a valve seat body and a protective coating provided at the outer surface of the valve seat body. The present application also provides a method for preparing the injector valve seat, an injector, an engine, and a vehicle using the injector valve seat. The injector valve seat, the injector, the engine, and the vehicle provided herein are suitable for use with methanol fuel, improving not only the corrosion and wear resistance of the injector valve seat but also the reliability of the injector, the engine, and the vehicle.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Chinese Patent Application No. 202311114940.9, filed on August 31, 2023 , entitled "INJECTOR VALVE SEAT, METHOD FOR PREPARING THE SAME, INJECTOR AND ENGINE", Chinese Patent Application No. 202311442569.9, filed on November 1, 2023 , entitled "METAL PART", and Chinese Patent Application No. 202311568124.5, filed on November 21, 2023 , entitled "INJECTOR VALVE SEAT, METHOD FOR PREPARING THE INJECTOR VALVE SEAT, INJECTOR AND VEHICLE", the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present application relates to the technical field of vehicles, and in particular relates to an injector valve seat and a method for preparing the same, an injector, an engine, and a vehicle using the same.

BACKGROUND

Methanol, as a fuel, is abundant in raw materials, clean and environmentally friendly, and has excellent power performance, making it an ideal clean and renewable energy source. Methanol vehicles are one of the effective approaches to achieving carbon peaking and carbon neutrality.
The fuel supply system for methanol vehicles once adopted the intake manifold multi-point injection technology. However, this technical solution did not achieve satisfactory results, since the methanol injection pressure was relatively low and the atomization effects was poor, leading to unsatisfactory fuel economy and emission indicators. As users place increasing emphasis on economy performance and emissions regulations become increasingly stringent, the technological innovation of methanol supply systems has become more urgent. Direct injection has already been proven in the field of gasoline engines as a mature technology that significantly improves fuel economy and emission performance. Therefore, adopting the direct injection mode in methanol engines also represents a technical route with broad prospects.

SUMMARY

The objective of the present application is to provide an injector valve seat suitable for methanol fuel, a method for preparing the same, an injector, engine, and vehicle using the same. The injector valve seat and the method for preparing the same balance the requirements for low-carbon stainless steel, which require good corrosion resistance to high-temperature methanol and formic acid, and high hardness, thereby alleviating the technical contradiction in the carbon content requirement for the injector valve seat. The injector valve seat and the method for preparing the same also improves the corrosion and wear resistance of the injector valve seat, effectively overcoming the technical problem of abnormal injection in methanol direct-injection injectors in related art and enhancing the reliability of the injector, engine, and vehicle.
To achieve the above objectives, according to a first aspect, the present application provides an injector valve seat, including:

a valve seat body; and
a protective coating provided at an outer surface of the valve seat body,
a material of the protective coating includes Ti and CrN.

In an embodiment, the protective coating includes at least a Ti primer layer and a CrN layer, and the Ti primer layer and the CrN layer are stacked.
In an embodiment, the protective coating includes a primer layer, an intermediate layer, and a surface layer, the primer layer, the intermediate layer, and the surface layer are sequentially stacked on at least a portion of the outer surface of the valve seat body; a material of the primer layer includes Ti, a material of the intermediate layer includes CrN, and a material of the surface layer includes Ti.
In an embodiment, a thickness of the primer layer is 0.3µm to 3.0µm, a thickness of the intermediate layer is 0.6µm to 6.0µm, and a thickness of the surface layer is 0.3µm to 3.0µm.
In an embodiment, the valve seat body is provided with an injection hole and an inner cavity for accommodating a valve ball, the injection hole is provided at and passes through the bottom wall of the inner cavity, the bottom wall of the inner cavity is configured to match a shape of a spherical surface of the valve ball, and the injection hole is configured to cooperate with the valve ball to open or close the injection hole.
According to the first aspect, the present application also provides an injector valve seat, including:

a valve seat body,
the valve seat body is made of low-carbon stainless steel and includes a contact surface, and a protective coating includes a nitrided layer provided at the contact surface and a silicon coating provided at a surface of the nitrided layer.

In an embodiment, a carbon content of the low-carbon stainless steel is less than 0.1%.
In an embodiment, a thickness of the nitrided layer is 2µm to 20µm; and a thickness of the silicon coating is 0.1µm to 0.5µm.
In an embodiment, a chromium nitride coating is provided at a surface of the silicon coating away from the nitrided layer; a content of chromium nitride in the chromium nitride coating is greater than 80%, and a thickness of the chromium nitride coating is 0.6µm to 1µm.
In an embodiment, a sealing functional layer is formed at a surface of the chromium nitride coating away from the silicon coating, a hardness of the sealing functional layer is lower than a hardness of the chromium nitride coating, and a corrosion resistance of the sealing functional layer is higher than a corrosion resistance of the chromium nitride coating.
In an embodiment, the sealing functional layer is a chromium coating; and a thickness of the chromium coating is 0.3µm to 0.7µm.
In an embodiment, a gradual transition layer is provided between the chromium coating and the chromium nitride coating; in the gradual transition layer, a content of chromium nitride gradually decreases and a content of chromium gradually increases along a direction from the chromium nitride coating to the chromium coating.
In an embodiment, the valve seat body is provided with an injection hole, a cross-sectional area of the injection hole decreases from an inlet of the injection hole to an outlet of the injection hole; and the inlet of the injection hole is rounded with a rounded corner.
In an embodiment, the injection hole is conical with a cone angle of 2° to 15°, and a radius of the rounded corner is 0.003mm to 0.15mm.
In an embodiment, a hardness of a surface layer of the injector valve seat is 700HV to 1500HV, and a thickness of the surface layer is 0.02mm to 0.5mm.
According to a second aspect, the present application provides a method for preparing an injector valve seat, including:

making a valve seat body of the injector valve seat from a valve seat substrate, and a material of the valve seat substrate includes C, Si, Mn, P, S, Cr, Mo, and V;
forming a primer layer on at least a portion of an outer surface of the valve seat body;
forming an intermediate layer on an outer surface of the primer layer; and
forming a surface layer on an outer surface of the intermediate layer.

In an embodiment, a chemical composition mass fractions of the valve seat substrate are as follows: C<0.35%-0.9%, Si<1.0%, Mn<1.0%, P<0.04%, S<0.04%, Cr<15%-18%, Mo<1.8%, and V<0.3%.
In an embodiment, the forming the primer layer on at least the portion of the outer surface of the valve seat body includes:
using Ti as a target material and using argon as a shielding gas to form a primer layer on at least the portion of the outer surface of the valve seat body through an arc plating process; a gas pressure during the arc plating process is 0.3Pa to 0.9Pa, a bias voltage is 250V, a target current is 65A to 75A, a deposition temperature is 240°C to 270°C, and an arc plating duration 5h to 8h.
In an embodiment, the forming the intermediate layer on the outer surface of the primer layer includes:
using pure chromium as a target material and using nitrogen as a reaction gas to form the intermediate layer on the outer surface of the primer layer through the arc plating process; a nitrogen flow rate during the arc plating process is in a range of 250sccm-500sccm, a target current is 80A-100A, and an arc plating duration is 20h-25h.
In an embodiment, the forming the surface layer on the outer surface of the intermediate layer includes:
using Ti as a target material and using argon as a shielding gas to form the surface layer on the outer surface of the intermediate layer through the arc plating process; a gas pressure during the arc plating process is 0.3Pa-0.9Pa, a bias voltage is 250V, a target current is 65A-75A, a deposition temperature is 240°C-270°C, and an arc plating duration is 5h-8h.
In an embodiment, further including:

processing on the valve seat body to form an injection hole; and
processing on an inlet of the injection hole to form a rounded corner.

In an embodiment, the processing on the valve seat body to form the injection hole includes:
processing on the valve seat body by a laser drilling device to form the injection hole, processing conditions of the injection hole include: laser power of 0.8kW~1.5kW, repetition frequency of 7kHz~10kHz, defocus amount of -350µm~450µm, scanning speed of 0.01mm/s-0.02mm/s, and number of scans of 15-25 times.
In an embodiment, the processing on the inlet of the injection hole to form the rounded corner includes:
impacting the inlet of the injection hole by using an abrasive fluid to form the rounded corner at the inlet of the injection hole.
In an embodiment, the abrasive fluid includes silicone rubber, lubricating liquid, silicon carbide particles and an anti-sticking agent;

a mass proportion of the silicone rubber in the abrasive fluid is 30%-40%; and/or
a mass proportion of the lubricating liquid in the abrasive fluid is 20%-30%; and/or
a mass proportion of the silicon carbide particles in the abrasive fluid is 35%-45%.

In an embodiment, the processing on the inlet of the injection hole to form the rounded corner further includes:

after processing on the inlet of the injection hole to form the rounded corner, obtaining an intermediate piece of the injector valve seat;
mounting a shielding fixture on the surface to be welded of the intermediate piece of the injector valve seat; and
performing a nitriding treatment on the intermediate piece of the injector valve seat mounted with the shielding fixture to form a protective coating to obtain the injector valve seat.

In an embodiment, processing conditions of the nitriding treatment include: a nitriding medium is ammonia gas, a nitriding temperature is less than or equal to 460°C, a nitriding duration is greater than or equal to 150 hours, a nitriding thickness is 0.02mm-0.5mm, and a deformation of the injector valve seat before and after the nitriding treatment is less than or equal to 0.01mm.
According to a third aspect, the present application also provides an injector, including: the injector valve seat as described above.
In an embodiment, further including:

a valve body;
a valve needle; and
a valve ball,
the injector valve seat is fixed at one end of the valve body, the valve body is provided with a valve cavity, the injector valve seat is communicated with the valve cavity, the valve needle is movably provided in the valve cavity, the valve ball is fixed to an end of the valve needle, and the valve ball is movably provided in the injector valve seat.

According to a fourth aspect, the present application also provides an engine, including: the injector as described above.
According to a fourth aspect, the present application also provides a vehicle, including: the engine as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional schematic view of an injector valve seat and an injector using the injector valve seat according to an embodiment of a first aspect of the present application.
FIG. 2 is a cross-sectional schematic view of a protective coating of the injector valve seat shown in FIG. 1.
FIG. 3 is a cross-sectional view of a valve seat body of the injector valve seat shown in FIG. 1.
FIG. 4 is a cross-sectional view of the valve seat body shown in FIG. 3 when it is mounted in the coating fixture.
FIG. 5 is a flow chart of a method for preparing an injector valve seat according to a first embodiment of the second aspect of the present application.
FIG. 6 is a schematic diagram of the injector valve seat manufactured by the method shown in FIG. 5 after a durability test.
FIG. 7 is a partial cross-sectional schematic diagram of the injector valve seat according to a second embodiment of the first aspect of the present application.
FIG. 8 is a cross-sectional schematic diagram of the injector using the injector valve seat shown in FIG. 7.
FIG. 9 is a cross-sectional schematic view of a valve core in FIG. 8.
FIG. 10 is a schematic cross -sectional view of the injector valve seat in FIG. 8.
FIG. 11 is a cross -sectional schematic diagram of the injector valve seat according to the third embodiment of the first aspect of the present application.
FIG. 12 is a schematic diagram of cavitation occurring in the injection hole of the injector valve seat in the related art.
FIG. 13 is a schematic structural diagram of a rounded corner in the injector valve seat shown in FIG. 11.
FIG. 14 is a schematic cross-sectional view of the injection hole in the injector valve seat shown in FIG. 11.
FIG. 15 is a schematic diagram showing that no cavitation occurs in the injection hole of the injector valve seat shown in FIG. 11.
FIG. 16 is a flow chart of a method for preparing the injector valve seat according to a second embodiment of the second aspect of the present application.
FIG. 17 is a schematic diagram of a scenario in which a shielding fixture is mounted in the injector valve seat shown in FIG. 11.

DETAILED DESCRIPTION OF THE EMBODIMENTS

To make the above-mentioned purposes, features, and advantages of the present application more clearly understood, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making any creative work are within the scope of protection of the present application.
At present, there are still some difficulties in applying the direct injection mode in methanol engines, such as:

1. Methanol itself has poor lubricity, and its corrosiveness to metals increases significantly with increasing temperature. At the same time, the injector valve seat is in the high-temperature and high-pressure environment of the engine combustion chamber and is often subjected to high-frequency impact forces. Therefore, the valve seat is prone to corrosion, wear and other problems during operation, which may cause the seal of the injector valve seat to fail and affect the reliability of the injector.
2. When the methanol direct injection injector operates in a high-temperature and high-pressure environment, due to the physical and chemical properties of methanol itself, methanol fuel is prone to generate bubbles during the injection process of the injector. During the bubble bursting process, micro-jets and impact force are generated, which will destroy the surface characteristics of the injection hole in the injector, that is, cavitation problems, resulting in abnormal injection status of the injector.
3. In terms of physical properties, injector valve seats require high hardness and wear resistance. Therefore, traditional valve seat materials typically such as stainless steel with a carbon content of 0.2% or higher is used to achieve sufficient hardness. However, in terms of chemical properties, methanol direct injection injectors require strong corrosion resistance because they must resist corrosion from high-temperature methanol as well as and formic acid and other derivatives generated by methanol in the high-temperature environment. Stainless steels with good resistance to high-temperature methanol and formic acid corrosion are generally low-carbon alloy stainless steels with a carbon content of 0.1% or lower. Furthermore, during validation testing of methanol direct injection injectors, multiple cases of injector valve seat wear occurred. After failure mode analysis, it was determined that the cause was that carbon elements on the valve seat surface precipitated in the high-temperature methanol environment, causing accelerated surface wear, resulting in failure of the valve seat's sealing function and methanol leakage from the injector. Therefore, to improve corrosion resistance and mitigate damage caused by carbon precipitation, methanol direct injection injectors should be manufactured from low-carbon stainless steel. However, corrosion-resistant stainless steels with a carbon content of less than 0.1% have a low hardness and cannot meet the wear resistance requirements for valve seats. In other words, the performance requirements of both physical and chemical properties create a technical contradiction with the demand for the carbon content of the valve seat material.

In order to resolve the above-mentioned technical contradictions, some existing methanol direct injection injectors are made of low-carbon stainless steel, and coating technology is used to improve the surface strength to take into account both corrosion resistance and wear resistance. In the currently disclosed valve seat coating technology, such as the valve seat diamondlike carbon (DLC) coating, the coating material is usually a metastable amorphous material generated by combining sp3 and sp2 bonds. Due to the low hardness of the low-carbon acid-resistant stainless steel valve seat material, the valve seat surface will produce slight deformation when the injector is working. The deformation will cause the internal stress of the DLC coating to increase, and eventually lead to the fracture and failure of the sp3 and sp2 bonds. Therefore, the valve seat currently made of conventional materials and DLC technology is not suitable for methanol direct injection injector valve seats.
To address the above-mentioned technical issues, it is necessary to provide an injector valve seat suitable for methanol fuel with improved performance, a method for preparing the same, and an injector, engine, and vehicle using the same. As shown in FIG. 1 to FIG. 3, a first embodiment of the first aspect of the present application provides an injector valve seat 10 suitable for a methanol direct injection injector. The injector valve seat 10 includes a valve seat body 11 and a protective coating 12 provided at the outer surface of the valve seat body 11. The protective coating 12 includes a primer layer 121, an intermediate layer 122, and a surface layer 123. The primer layer 121, the intermediate layer 122, and the surface layer 123 are sequentially stacked on at least a portion of the outer surface of the valve seat body 11. The material of the primer layer 121 includes Ti, the material of the intermediate layer 122 includes CrN, and material of the surface layer 123 includes Ti.
The valve seat body 11 is provided with an injection hole 112 and an inner cavity 111 for accommodating a valve ball 20 (as shown in FIG. 1 and described in detail below). The injection hole 112 is provided at and passes through the bottom wall 1111 of the inner cavity 111 to inject the fuel. The bottom wall 1111 is configured to match the shape of the spherical surface of the valve ball 20, and the injection hole 112 is configured to cooperate with the valve ball 20 to open or close the injection hole 112.
The protective coating 12 is only provided at the outer surface of the valve seat body 11, and the cavity wall (not marked in the figure) of the inner cavity 111 is not provided with the protective coating 12, so as to prevent the presence of the protective coating 12 on the cavity wall of the inner cavity 111 from changing the gap between the valve ball 20 and the cavity wall, thereby affecting the movement of the valve ball 20 in the inner cavity 111 and the cooperation between the valve ball 20 and the injection hole 112.
In an embodiment, the primer layer 121 has a strong bonding force with the substrate of the valve seat body 11 and the primer layer 121 itself has strong corrosion resistance; the intermediate layer 122 has the characteristics of low stress, high adhesion, high toughness, and high corrosion resistance, and has corrosion resistance and chemical resistance to aqueous solutions, and has a certain lubricity; the surface layer 123 is provided at the outer surface of the intermediate layer 122, which can further enhance the corrosion resistance and wear resistance of the protective coating 12.
As shown in FIG. 1 to FIG. 6, a first embodiment of the second aspect of the present application further provides a method for preparing an injector valve seat, which can be used to prepare the injector valve seat 10 provided in the first embodiment of the first aspect of the present application. The method includes the following steps:

(1) Preparing the valve seat body 11: the valve seat body 11 of the injector valve seat 10 is made of a preset valve seat substrate, the material of the valve seat substrate includes C, Si, Mn, P, S, Cr, Mo, and V, and the corresponding chemical composition mass fractions are: C<0.35%-0.9%, Si<1.0%, Mn<1.0%, P<0.04%, S<0.04%, Cr<15%-18%, Mo<1.8%, and V<0.3%;
(2) Pre-treating the valve seat body 11: the valve seat body 11 is immersed in a special cleaning solution and ultrasonic cleaning is performed twice, each time for 15 minutes to 30 minutes, and then dry it. After the valve seat body 11 is cleaned and dried, the pre-prepared coating fixture 100 is mounted in the inner cavity 111 of the valve seat body 11, and then they are placed in the coating furnace together;
(3) Evacuating the coating furnace: the furnace chamber of the coating furnace is sealed, the rotary vane vacuum pump is turned on, when the air pressure in the furnace drops below 10 Pa, the molecular pump is started, further the air pressure is pumped to the ultimate vacuum degree, and the ultimate vacuum environment is maintained for a period of time to remove the air in the furnace to the maximum extent;
(4) Forming a primer layer 121: Ti is used as a target material and argon is used as a shielding gas, an arc plating process is performed to form a primer layer 121 having a thickness of 0.3µm to 3.0µm, preferably 1.2µm or 1.5µm, on at least a portion of the outer surface of the valve seat body 11. The arc plating process is performed at a gas pressure of 0.3Pa to 0.9Pa, a bias voltage of 250V, a target current of 65A to 75A, a deposition temperature of 240°C to 270°C, and an arc plating duration of 5h to 8h.
(5) Forming the intermediate layer 122: pure chromium is used as a target material and nitrogen is used as a reaction gas, the intermediate layer 122 having a thickness of 0.6µm to 6.0µm is provided at the outer surface of the primer layer 121 by the arc plating process, the nitrogen flow rate during the arc plating process is in the range of 250sccm to 500sccm, the target current is 80A to 100A, and the arc plating duration is 20h to 25h;
(6) Forming a surface layer 123: Ti is used as a target material and argon is used as a shielding gas, the surface layer 123 having a thickness of 0.3µm to 3.0µm is provided at the outer surface of the intermediate layer 122 by the arc plating process, the gas pressure during the arc plating process is 0.3Pa to 0.9Pa, the bias voltage is 250V, the target current is 65A to 75A, the deposition temperature is 240°C. to 270°C, and the arc plating duration is 5h to 8h;
(7) After preparation, all power supplies, ion sources and gas sources are turned off.

In an embodiment, the coating fixture 100 includes a top cover 101 and a mounting post 102. The top cover 101 is fixed to the mounting post 102. The shape and size of the mounting post 102 is matched with the inner cavity 111 of the valve seat body 11. The mounting post 102 is used to mount the coating fixture 100 into the valve seat body 11. The top cover 101 is used to block the protective coating 12 from being applied to the inner cavity 111 during the preparation of the injector valve seat 10. The coating fixture 100 cooperates with the inner cavity 111 of the valve seat body 11 and is used to prevent the protective coating 12 from being applied to the walls of the inner cavity 111.
In an embodiment, the effect of evacuating the coating furnace is to increase the density of the coating and reduce the porosity of the coating.
In an embodiment, when forming the primer layer 121 and the surface layer 123, shielding gas (argon) is introduced with a gas pressure ranging from 0.3Pa to 0.9Pa, which prevents the primer layer 121 and the surface layer 123 from being oxidized and nitrided.
When the thickness of the primer layer 121 is 0.3µm-1.5µm, the thickness of the intermediate layer 122 is 0.6µm-2.0µm, and the thickness of the surface layer 123 is 0.3µm-1.5µm, the injector valve seat 10 is subjected to an injector monomer durability test of 600 million times and an engine bench durability test of 800 hours. The injector valve seat 10 shows no signs of corrosion, and the flow rate and air tightness of the injector meet the design requirements, proving that the injector valve seat 10 meets the use requirements.
As shown in FIG. 1 and FIG. 3, a first embodiment of the third aspect of the present application further provides an injector 1 including a valve body 30, a valve needle 40, a valve ball 20, a return spring 60, an electromagnetic actuator 50, and the injector valve seat 10 described above. The injector valve seat 10 is fixed to one end of the valve body 30. The valve body 30 is provided with a valve cavity 31 filled with fuel. The injector valve seat 10 is communicated with the valve cavity 31. The valve needle 40 is movably provided within the valve cavity 31. The valve ball 20 is fixed to the distal end of the valve needle 40 and movably provided in the injector valve seat 10. The return spring 60 is fixed in the valve cavity 31 and connected to the top end of the valve needle 40. The return spring 60 is in a compressed state. The electromagnetic actuator 50 is fixed to the valve body 30 and connected to the valve needle 40. The electromagnetic actuator 50 can drive the valve needle 40 to move up and down along the valve cavity 31.
The initial position of the valve ball 20: the valve ball 20 is abutted against the bottom wall 1111 of the inner cavity 111 of the injector valve seat 10 and cooperates with the injection hole 112 to prevent the fuel from passing through the injection hole 112. When the injector 1 needs to inject the fuel, the injector 1 drives the valve needle 40 to move upward along the valve cavity 31 through the electromagnetic actuator 50. The valve ball 20 follows the valve needle 40 to move upward and away from the bottom wall 1111. The fuel is sprayed into the combustion chamber (not shown in the figure) through the injection hole 112. When the injector does not need to inject the fuel, the electromagnetic actuator 50 stops working, the return spring 60 stretches and drives the valve needle 40 to move downward along the valve cavity 31. The valve ball 20 follows the valve needle 40 to move downward until it is abutted against the bottom wall 1111 and cooperates with the injection hole 112 to prevent the fuel from passing through the injection hole 112.
In addition, the first embodiment of the fourth aspect of the present application further provides an engine (not shown in the figure) including the injector 1.
The beneficial effects of the above-mentioned injector valve seat and method for preparing the same, injector and engine provided by the above-mentioned embodiments of the first to fourth aspects of the present application are: being suitable for methanol fuel, not only improving the corrosion resistance and wear resistance of the injector valve seat, but also improving the reliability of the injector and engine.
As shown in FIG. 7, a second embodiment of the first aspect of the present application provides an injector valve seat 10A suitable for high-temperature methanol corrosive environments. The injector valve seat 10A includes a valve seat body 1A and a protective coating provided on the outer surface of the valve seat body 1A. The valve seat body 1A is made of low-carbon stainless steel, preferably with a carbon content of 0.1% or less. The type of stainless steel exhibits excellent corrosion resistance to high-temperature methanol and formic acid. The valve seat body 1A has a contact surface S. The protective coating includes a nitrided layer 2A provided at the contact surface S and a silicon coating 3A provided at the surface of the nitrided layer 2A. The contact surface S is the contact and sealing surface of the valve seat body 1A for contact with the valve core. The nitrided layer 2A improves the cavitation resistance of the contact surface S of the valve seat body 1A, particularly the cavitation resistance of the micropore inner surface. It also increases the hardness of the contact surface S of the low-carbon stainless steel metal substrate, thereby ensuring that the low-carbon stainless steel exhibits excellent hardness while maintaining high-temperature methanol and formic acid corrosion resistance. A silicon coating 3A is provided at the surface of the nitrided layer 2A. The acid corrosion resistance of the silicon coating 3A is leveraged, the risk of trace amounts of carbon precipitating as carbon compounds on the contact surface S of the low-carbon stainless steel is further reduced, thereby further strengthening the corrosion resistance of the contact surface S of the valve seat body 1A. The silicon coating 3A can be formed using a siliconizing process, serving as a high-temperature methanol corrosion-resistant layer to prevent corrosion of the valve seat body 1A by high-temperature methanol. Specifically, the silicon coating 3A can be formed using an ion sputtering process.
The contact surface S refers to the surface that contacts methanol or a high-temperature methanol environment and bears impact loads or friction loads. The surface may be the sealing contact surface between the valve seat, the valve core and valve ball.
In an embodiment, the thickness of the nitrided layer 2A is between 2µm and 20µm, and can be specifically 2µm, 4µm, 6µm, 7µm, 9µm, 12µm, 14µm, 15µm, 17µm, 19µm and 20µm, etc. Within the thickness range, the anti-cavitation performance of the inner surface of the micropore can be fully improved, while the surface hardness of the valve seat body 1A is improved, and at the same time the nitriding cost is limited to a reasonable range.
In an embodiment, the thickness of the silicon coating 3A is between 0.1µm and 0.5µm, and can be specifically 0.1µm, 0.2µm, 0.3µm, 0.4µm, 0.5µm, etc. When the thickness of the silicon coating 3A is within the range, the precipitation of carbon in the form of carbon compounds can be sufficiently reduced, thereby achieving sufficient corrosion resistance while also taking into account reasonable costs.
In an embodiment, a chromium nitride coating 4A is provided at the surface of the silicon coating 3A away from the nitrided layer 2A. The chromium nitride coating 4A can simultaneously improve the wear resistance and corrosion resistance of the contact surface S of the valve seat body 1A for bearing the impact loads. The chromium nitride coating 4A can be formed using a chromium nitriding process and has a higher hardness and better impact resistance than the silicon coating 3A.
In an embodiment, the content of chromium nitride in the chromium nitride coating 4A is greater than 80%, and the thickness of the chromium nitride coating 4A is between 0.6µm and 1µm, specifically 0.6µm, 0.7µm, 0.8µm, 0.9µm, and 1µm. When the thickness of the chromium nitride coating 4A is within this range, the wear resistance and corrosion resistance of the contact surface S can be maintained while maintaining reasonable cost.
In an embodiment, a sealing functional layer 5A is provided at the surface of the chromium nitride coating 4A away from the silicon coating 3A. The hardness of the sealing functional layer 5 A is lower than that of the chromium nitride coating 4A. This can accelerate the running-in speed between the contact surface S and the mating surface, such as increasing the running-in speed between the valve seat, the valve core and valve ball, and quickly forming a sealing surface in the initial stage of injector operation. In addition, the corrosion resistance of the sealing functional layer 5 A is higher than that of the chromium nitride coating 4A, thereby further improving the corrosion resistance.
In an embodiment, the functional sealing layer 5A is a chromium coating. The chromium coating has lower hardness than the chromium nitride coating 4A and higher corrosion resistance than the chromium nitride coating 4A, making it an ideal material for the functional sealing layer 5A. The thickness of the chromium coating can be between 0.3µm and 0.7µm, specifically 0.3µm, 0.4µm, 0.5µm, 0.6µm, and 0.7µm. This thickness range balances hardness, corrosion resistance, and reasonable cost.
In an embodiment, a gradual transition layer is provided between the chromium coating and the chromium nitride coating 4A. In the gradual transition layer, the content of chromium nitride gradually decreases and the content of chromium gradually increases along the direction from the chromium nitride coating 4A to the chromium coating, so as to gradually evolve toward the composition of the chromium coating and avoid a poor combination due to a large difference in composition between the two.
As shown in FIG. 8 to FIG. 10, a second embodiment of the third aspect of the present application further provides an injector including the aforementioned injector valve seat 10A, a valve core 20A, and a valve body 30A. A conical surface on the injector valve seat 10A contacts the ball head of the valve core 20A to form a contact sealing surface. The ball head of the valve core 20A and the conical sealing surface of the injector valve seat 10A form a kinematic pair subject to impact loads. In an embodiment, the injector valve seat 10Ais a valve seat for a methanol direct injection injector, and the contact surface S is the contact sealing surface between the valve seat body 1A and the valve core 20A. The injector valve seat 10A is provided at the oil outlet end of the valve body 30A, and the valve core 20A is provided within the space of the valve body 30A, with the valve ball at the end sealingly engaging the contact sealing surface of the valve seat body 1A. By performing surface treatment on the contact surface S of the valve seat body 1A, the hardness of the contact sealing surface between the valve seat body 1A and the valve core 20A can be increased, while the use of low-carbon stainless steel can prevent carbon precipitation of the valve seat body 1A.
The third embodiment of the first aspect of the present application also provides an injector valve seat 10B, including a valve seat body and a protective coating provided at the outer surface of the valve seat body. The valve seat body may be the valve seat body 11 described in the first embodiment of the first aspect of the present application or the valve seat body 1A described in the second embodiment of the first aspect of the present application, and no further description is required here. As shown in FIG. 11, the valve seat body of the injector valve seat 10B is provided with an injection hole 11B. The cross-sectional area of the injection hole 11B decreases from the inlet of the injection hole 111B to the outlet of the injection hole 112B. The injection hole 11B has rounded corners at the inlet of the injection hole 111B and / or the outlet of the injection hole 112B.
In the embodiment, it should be noted that methanol can be produced from a wide range of raw materials, such as coal, natural gas, and biomass, making it possible for industrial application. In addition, methanol is a high-oxygen fuel with a fast combustion rate, a wide ignition range, and no soot is produced after combustion. Therefore, it is a carbon-neutral fuel with broad development prospects. In the field of automotive and marine internal combustion engines, methanol fuel is becoming increasingly important. Currently, methanol vehicles use an intake manifold multi-point injection technology solution. This solution has low methanol injection pressure and poor atomization, resulting in poor fuel economy and emissions. As users' requirements for economy become higher and higher and emission regulations become more and more stringent, technological innovation in the methanol supply system is becoming more urgent. Direct injection technology has been verified in the field of gasoline engines and has obvious effects on economy and emission improvement. Therefore, direct injection methanol engines are also a technical route with great development prospects.
However, methanol direct injection injectors have experienced abnormal fuel injection. Actual bench testing has verified that gasoline direct injection injectors do not exhibit surface cavitation in the injection holes. To address the technical issues surrounding methanol direct injection injectors, further research has revealed that methanol direct injection injectors, mounted within the cylinder, operate at pressures of 350-1000bar and temperatures of 300-500°C. During injection, fuel enters the smaller injection holes from the larger injector cavity, causing a further surge in pressure at the inlet of the injection hole. In the case of methanol fuel, this can easily generate bubbles at the inlet of the injection hole and be accompanied by bubble bursting. The bubble bursting can impact the inlet of the injection hole, damaging its surface characteristics and, in severe cases, causing injector failure.
As shown in FIG. 12, a case where the inlet of the injection hole of an existing methanol direct injection injector is damaged due to impact force.
In the embodiment, the injector valve seat 10B is provided at the distal end of the injector. A spray hole 11B is provided in the injector valve seat 10B, through which the injector can spray a high-pressure fuel spray. It should be noted that while the embodiment is based on a technical defect in which bubbles are easily generated during methanol fuel injection, damaging the surface characteristics of the spray hole 11B of the injector and, in severe cases, causing the injector failure, the injector valve seat 10B of the embodiment can be applied to methanol direct injection injectors, other injectors using methanol as fuel, or injectors using other fuels, and the embodiment is not intended to limit this.
The injection hole 11B decreases from the inlet of the injection hole 111B to the outlet of the injection hole 112B. That is, the diameter of the injection hole 11B gradually decreases from the inlet of the injection hole 111B to the outlet of the injection hole 112B. This gradually reduces the space for fuel to enter, dispersing the pressure at the inlet of the injection hole 111B and preventing the sudden influx of fuel into a small space, which would cause a sudden increase in pressure at the inlet of the injection hole 111B.
In an embodiment, the injection hole 11B is conical, and the cone angle of the injection hole 11B is 2°-15°.
In the embodiment, the smoother the inner wall of the injection hole 11B, the more stable the gas pressure of the fuel in the injection hole 11B. When the injection hole 11B is conical, the fuel flows smoothly from the inlet of the injection hole 111B to the outlet of the injection hole 112 B in the injection hole 11B, which can achieve uniform pressure dispersion, thereby reducing local cracking or damage. If the cone angle of the injection hole 11B is too small, the greater the pressure change at the inlet of the injection hole 111B, the greater the impact that the inlet of the injection hole 111B needs to withstand, and the more likely it is to be damaged. However, if the cone angle of the injection hole 11B is too large, since the overall structure and volume of the injector valve seat 10B are fixed, this may affect other structures of the injector valve seat 10B, such as the quantity of injection holes 11B and the wall thickness of the injection holes 11B. A reduction in the quantity of injection holes 11B may affect injector performance, and excessively thin wall thickness of the injection hole 11B may also lead to insufficient strength at the injection hole 11 and cause damage. Therefore, the cone angle of the injection hole 11B is determined to be 2° to 15°, for example, 2°, 5°, 8°, 10°, 12°, 15°, etc.
The injection hole 11B is rounded with a rounded corner at the inlet of the injection hole 111B. During the injection process, stress is easily concentrated at corners, which can cause cracks. Rounded corners help reduce stress concentration, thereby preventing damage caused by stress concentration. They also further disperse pressure at the inlet of the injection hole 111B, mitigating sudden pressure changes when fuel enters the injection hole 11B from the injector chamber. This improves the durability of the injector valve seat 10B and extends its service life.
In an embodiment, the radius of the rounded corner is 0.003mm-0.15mm.
In the embodiment, the larger the radius of the rounded corner, the larger the curvature of the rounded corner, and the smaller the wall thickness at the inlet of the injection hole 111B. Excessively thin wall thickness may result in insufficient strength of the injection hole 11B. If the radius of the rounded corner is too small, the pressure dispersion effect is not obvious. Therefore, the radius of the rounded corner is determined to be 0.003mm-0.15mm, for example, 0.003mm, 0.01mm, 0.05mm, 0.1mm, 0.15mm, etc.
In an embodiment, the rounded corners are as shown in FIG. 13.
In an embodiment, the hardness of the surface layer of the injector valve seat 10B is 700HV-1500HV, and the thickness of the surface layer is 0.02mm-0.5mm.
In the embodiment, the surface layer of the injector valve seat 10B refers to a region with a thickness of 0.02mm to 0.5mm near the surface of the injector valve seat 10. This may be a region on the valve body of the injector valve seat 10 where a protective coating is provided, or a region on the valve body of the injector valve seat 10 where no protective coating is provided. The specific thickness of the surface layer can be determined based on actual needs and is not limited in the embodiment.
The higher the hardness of the surface layer of the injector valve seat 10B, the less likely it is to be damaged when impacted. However, if the hardness is too high, the surface layer of the injector valve seat 10B will be more brittle and more likely to be damaged when impacted. Therefore, the hardness of the surface layer of the injector valve seat 10B is determined to be between 700HV and 1500HV, for example, 700HV, 900HV, 1200HV, 1500HV, etc. The hardness of the surface layer of the injector valve seat 10 can be controlled by selecting the material of the injector valve seat 10, performing surface treatment, and processing a high-hardness surface layer. The specific hardness can be determined based on actual conditions and is not limited in the embodiment.
In an embodiment, as shown in FIG. 14, the injector valve seat 10B further includes a large injection hole 12B. The injection hole 11B is communicated with the injector chamber and the large injection hole 12B, and the large injection hole 12B is communicated with the injection hole 11B and the combustion chamber. The large injection hole 12B can be designed based on actual needs and is not limited in the embodiment.
In the embodiment, the injector valve seat is provided with an injection hole, the cross-sectional area of the injection hole decreases from the inlet of the injection hole to the outlet of the injection hole; and the inlet of the injection hole is rounded with a rounded corner. Before the injector injects fuel, the injection hole on the injector valve seat is not communicated with the injector chamber within the injector. During fuel injection, the injection hole is communicated with the injector chamber, and the fuel enters the smaller injection hole from the larger injection chamber, causing a sudden increase in pressure at the inlet of the injection hole. In the case of methanol fuel, methanol fuel is prone to generating bubbles at the inlet of the injection hole, which are accompanied by bubble bursting. The bubble bursting causes impact force at the inlet of the injection hole, damaging the surface characteristics at the inlet of the injection hole. By making the cross-sectional area of the injection hole gradually decrease from the inlet of the injection hole to the outlet of the injection hole, the present application can achieve a pressure dispersion effect, gradually increasing the pressure as the fuel passes through the injection hole, avoiding sudden changes in pressure at the inlet of the injection hole. Furthermore, by making the inlet of the injection hole rounded, the present application can further disperse the pressure at the inlet of the injection hole, mitigating the sudden change in pressure when the fuel enters the injection hole from the injector chamber. This allows the fuel to enter the injection hole and be ejected through it more smoothly. Thus, even when methanol fuel is used, the generation and bursting of bubbles at the inlet of the injection hole can be reduced, thereby reducing damage at the inlet of the injection hole and reducing abnormal fuel injection caused by damage at the inlet of the injection hole. Therefore, the technical issue of abnormal fuel injection from methanol direct injection injectors in the related art is solved, and the durability of the injector can be effectively improved, extending the service life of the injector. Furthermore, after 600 million cycles of durability testing of the injector unit and 800 hours of bench durability test on the engine, the injection hole is shown in FIG. 15. As can be seen from FIG. 15, no cavitation failure occurs in the injection hole. The performance of the injector valve seat provided by the present application meets the design requirements and meets the use requirements.
Furthermore, a second embodiment of the second aspect of the present application further provides a method for preparing an injector valve seat, which can be used to prepare the injector valve seat 10B provided in the third embodiment of the first aspect of the present application. As shown in FIG. 16, the method includes the following steps :
Step S10, providing a valve seat body; the valve seat body can adopt the valve seat body 11 in the first embodiment of the first aspect of the present application or the valve seat body 1A in the first embodiment of the first aspect of the present application, which need not be repeated here.
Step S20, forming a spray hole on the valve seat body.
In the embodiment, it should be noted that the valve seat body can be a block having a certain shape and structure of the injector valve seat and requiring injection hole processing. For example, a valve seat body without an injection hole or with an injection hole that does not meet the requirements can be processed by cutting, injection molding, 3D printing, or the like, based on the required shape and structure of the injector valve seat. The requirement of injection hole is that the cross-sectional area decreases from the inlet of the injection hole to the outlet of the injection hole. If an existing production line can produce a valve seat body with an injection hole that does not meet the requirements, or if a valve seat body with an injection hole that does not meet the requirements is available for purchase, the injection hole that does not meet the requirements can be reprocessed so that the cross-sectional area of the injection hole decreases from the inlet of the injection hole to the outlet of the injection hole. The processing method of the valve seat body can be determined according to actual needs and is not limited in the embodiment.
In an embodiment, the steps S10 to S20 include: providing a pre-prepared valve seat body, and using a drilling device to form the injection hole on the valve seat body, the cross-sectional area of the injection hole decreases from the inlet of the injection hole to the outlet of the injection hole.
In an embodiment, before processing on the valve seat body to form the injection hole, the method may further include: cleaning the valve seat body. For example, the valve seat body may be immersed in a cleaning solution and ultrasonically cleaned one or more times, each ultrasonic cleaning lasting 15 to 30 minutes. The injection hole may then be processed after drying.
In an embodiment, the step of processing on the valve seat body to form the injection hole includes:
processing on the valve seat body by laser drilling device to form the injection hole, the processing conditions of the injection hole include: laser power of 0.8kW-1.5kW, repetition frequency of 7kHz-10kHz, defocus amount of -350µm-450µm, scanning speed of 0.01mm/s-0.02mm/s, and number of scans of 15-25 times.
In an embodiment, a laser drilling device may be used to machine a spray hole on the valve seat body with a cross-sectional area decreasing from the inlet of the spray hole to the outlet of the spray hole by adjusting the direction of the workpiece or the direction of the laser. The processing conditions of the laser drilling device for processing the injection hole include: laser power of 0.8kW~1.5kW, such as 0.8kW, 1.0kW, 1.2kW, 1.5kW, etc., repetition frequency of 7kHz~10kHz, such as 7kHz, 8kHz, 9kHz, 10kHz, etc., defocus amount of -350µm~450µm, such as -350µm, -200µm, 50µm, 250µm, 450µm, etc., scanning speed of 0.01mm/s-0.02mm/s, such as 0.01mm/s, 0.015mm/s, 0.02mm/s, etc., and the number of scans is 15-25 times, such as 15 times, 20 times, 25 times, etc.
Step S30, processing on the inlet of the injection hole to form the rounded corner, thereby obtaining the injector valve seat 10B.
In an embodiment, step S30 includes: after the injection hole is machined, the inlet of the injection hole may be further machined to form a rounded corner, thereby obtaining the injector valve seat 10B. The rounded corner processing method includes grinding, impacting, etc.
In an embodiment, the step of processing on the inlet of the injection hole to form the rounded corner includes:
impacting the inlet of the injection hole by using an abrasive fluid to form a rounded corner at the inlet of the injection hole.
In an embodiment, an abrasive fluid can be used to impact the inlet of the injection hole. The impact of the abrasive fluid on the inlet of the injection hole can be used to form a rounded corner with a certain arc, thereby forming the injector valve seat 10B. The abrasive fluid can be prepared or purchased according to actual needs and is not limited in the embodiment.
In an embodiment, the abrasive fluid includes silicone rubber, lubricating liquid, silicon carbide particles and an anti-sticking agent.
In an embodiment, a mass proportion of the silicone rubber in the abrasive fluid is 30%-40%.
And/or, a mass proportion of the lubricating liquid in the abrasive fluid is 20%-30%.
And/or, a mass proportion of the silicon carbide particles in the abrasive fluid is 35%-45%.
In the embodiment, the silicone rubber has a certain hardness and size distribution, and the silicon carbide particles have greater hardness and strong cutting force. The combination of the two can achieve rounded corner processing while improving the smoothness of the rounded corners, and the efficiency of polishing the rounded corners is high. At the same time, the lubricant and anti-sticking agent can reduce surface friction and avoid scratching and damage to the injector valve seat surface. The mass proportion of silicone rubber in the abrasive fluid is 30%-40%, for example, 30%, 35%, 40%, etc. The mass proportion of the lubricating liquid in the abrasive fluid is 20%-30%, for example, 20%, 25%, 30%, etc. The mass proportion of the silicon carbide particles in the abrasive fluid is 35%-45%, for example, 35%, 40%, 45%, etc.
In an embodiment, the step of processing on the inlet of the injection hole to form the rounded corner includes:

Step S31, after processing on the inlet of the injection hole to form the rounded corner, obtaining an intermediate piece of the injector valve seat;
Step S32, mounting a shielding fixture on the surface to be welded of the intermediate piece of the injector valve seat; and
Step S33, performing a nitriding treatment on the intermediate piece of the injector valve seat mounted with the shielding fixture to form a protective coating to obtain the injector valve seat.

In the embodiment, it should be noted that a protective layer can be provided at all or part of the surface of the valve seat body by surface nitriding, thereby increasing the hardness of the surface layer of the injector valve seat 10B. However, after processing, the injector valve seat 10B needs to be welded to the injector body. During the welding process, nitrogen will be precipitated in the nitrided area due to heat, and the area after nitrogen precipitation will form a porous structure. When the surface with the porous structure is welded to the injector body, the weld tightness is low, which may lead to insufficient durability and a short service life of the injector in subsequent use. Therefore, in the embodiment, before nitriding, a shielding fixture is mounted on the surface to be welded of the intermediate piece of the injector valve seat (that is, the valve seat body that has been processed with a rounded corner structure at the inlet of the injection hole but has not yet been surface nitrided) to prevent the surface to be welded from being affected by the nitriding treatment. When only the surface layer is nitrided, the nitriding duration and other process parameters can be controlled to prevent the nitriding of other areas from affecting the surface to be welded.
In an embodiment, steps S31-S33 include: after forming the injection hole, further processing the inlet of the injection hole to form a rounded corner, thereby obtaining the intermediate piece of the injector valve seat. Then, a shielding fixture is mounted on the surface to be welded of the intermediate piece of the injector valve seat. The intermediate piece of the injector valve seat with the shielding fixture mounted is placed in a nitriding medium. Under certain conditions, the remaining areas of the injector valve seat, excluding the surface to be welded, are nitrided. After the nitriding treatment is completed, the shielding fixture is removed to obtain the injector valve seat 10B.
In an embodiment, the processing conditions of the nitriding treatment include: the nitriding medium is ammonia gas, the nitriding temperature is less than or equal to 460°C., the nitriding duration is greater than or equal to 150 hours, and the nitriding thickness is 0.02mm-0.5mm.
In the embodiment, ammonia gas can be used as the nitriding medium, and the nitriding temperature is controlled below 460°C. The nitriding treatment includes three processes: thermal decomposition of ammonia gas to generate active atoms, adsorption of active atoms on the surface of the injector valve seat, and diffusion of the active atoms on the surface of the injector valve seat into the interior of the injector valve seat. The nitriding duration is greater than or equal to 150 hours, and the nitriding thickness is 0.02mm-0.5mm. The nitriding thickness at different locations will vary to a certain extent, but it is sufficient to be within the range of 0.02mm-0.5mm. After nitriding, the hardness of the injector valve seat can reach the range of 700HV-1500HV, and the deformation of the injector valve seat before and after nitriding is controlled to be less than or equal to 0.01mm.
In an embodiment, as shown in FIG. 17, the outer surface of the upper end of the intermediate piece of the injector valve seat serves as the surface to be welded. Therefore, a shielding fixture 20B can be installed on this surface to be welded. The shielding fixture 20B can create an interference fit with the upper end of the intermediate piece of the injector valve seat to ensure secure installation of the shielding fixture. For example, the outer diameter of the upper end of the intermediate piece of the injector valve seat is Ǿ4.822mm (0.01mm/0.02mm), and the inner diameter of the shielding fixture is Ǿ4.822mm (-0.02mm/-0.01mm), achieving an interference fit. The shielding fixture can be made of TP2 (deoxidized copper) material for ease of sealing and removal.
The method for preparing the injector valve seat provided in the present application addresses the technical issue of abnormal fuel injection in methanol direct injection injectors in the related art. Compared to the related art, the beneficial effects of the method for preparing the injector valve seat provided in the embodiment of the application are similar to those of the injector valve seat 10B in the aforementioned embodiment and are not further elaborated here.
The third aspect of the present application provides an injector, which may be a methanol direct injection injector, including the injector valve seat provided by any one of the first to third embodiments of the first aspect of the present application as described above.
The fourth aspect of the present application provides an engine including the injector as described above.
The fifth aspect of present application provides a vehicle including the engine as described above.
Compared with the related art, the injector, engine and vehicle provided in the embodiments of the present application can solve the technical issue of abnormal fuel injection of methanol direct injection injectors in the related art. Its specific beneficial effects are the same as the beneficial effects of the injector valve seat described in the above embodiments, and will not be repeated here.
The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

An injector valve seat, characterized by comprising:
a valve seat body; and

a protective coating provided at an outer surface of the valve seat body,

wherein a material of the protective coating comprises Ti and CrN.
The injector valve seat according to claim 1, wherein the protective coating comprises at least a Ti primer layer and a CrN layer, and the Ti primer layer and the CrN layer are stacked.
The injector valve seat according to claim 1, wherein the protective coating comprises a primer layer, an intermediate layer, and a surface layer, the primer layer, the intermediate layer, and the surface layer are sequentially stacked on at least a portion of the outer surface of the valve seat body; a material of the primer layer comprises Ti, a material of the intermediate layer comprises CrN, and a material of the surface layer comprises Ti.
The injector valve seat according to claim 2, wherein a thickness of the primer layer is 0.3µm to 3.0µm, a thickness of the intermediate layer is 0.6µm to 6.0µm, and a thickness of the surface layer is 0.3µm to 3.0µm.
The injector valve seat according to any one of claims 1 to 4, wherein the valve seat body is provided with an injection hole and an inner cavity for accommodating a valve ball, the injection hole is provided at and passes through the bottom wall of the inner cavity, the bottom wall of the inner cavity is configured to match a shape of a spherical surface of the valve ball, and the injection hole is configured to cooperate with the valve ball to open or close the injection hole.
An injector valve seat, characterized by comprising:
a valve seat body,

wherein the valve seat body is made of low-carbon stainless steel and comprises a contact surface, and a protective coating comprises a nitrided layer provided at the contact surface and a silicon coating provided at a surface of the nitrided layer.
The injector valve seat according to claim 6, wherein a carbon content of the low-carbon stainless steel is less than 0.1%.
The injector valve seat according to claim 6 or 7, wherein a thickness of the nitrided layer is 2µm to 20µm; and a thickness of the silicon coating is 0.1 µm to 0.5µm.
The injector valve seat according to any one of claims 6 to 8, wherein a chromium nitride coating is provided at a surface of the silicon coating away from the nitrided layer; a content of chromium nitride in the chromium nitride coating is greater than 80%, and a thickness of the chromium nitride coating is 0.6µm to 1µm.
The injector valve seat according to claim 9, wherein a sealing functional layer is formed at a surface of the chromium nitride coating away from the silicon coating, a hardness of the sealing functional layer is lower than a hardness of the chromium nitride coating, and a corrosion resistance of the sealing functional layer is higher than a corrosion resistance of the chromium nitride coating.
The injector valve seat according to claim 10, wherein the sealing functional layer is a chromium coating; and a thickness of the chromium coating is 0.3µm to 0.7µm.
The injector valve seat according to claim 11, wherein a gradual transition layer is provided between the chromium coating and the chromium nitride coating; in the gradual transition layer, a content of chromium nitride gradually decreases and a content of chromium gradually increases along a direction from the chromium nitride coating to the chromium coating.
The injector valve seat according to any one of claims 5 to 12, wherein the valve seat body is provided with an injection hole, a cross-sectional area of the injection hole decreases from an inlet of the injection hole to an outlet of the injection hole; and the inlet of injection hole is rounded with a rounded corner.
The injector valve seat according to claim 13, wherein the injection hole is conical with a cone angle of 2° to 15°, and a radius of the rounded corner is 0.003mm to 0.15mm.
The injector valve seat according to claim 13, wherein a hardness of a surface layer of the injector valve seat is 700HV to 1500HV, and a thickness of the surface layer is 0.02mm to 0.5mm.
A method for preparing an injector valve seat, characterized by comprising:
making a valve seat body of the injector valve seat from a valve seat substrate, and a material of the valve seat substrate comprises C, Si, Mn, P, S, Cr, Mo, and V;

forming a primer layer on at least a portion of an outer surface of the valve seat body;

forming an intermediate layer on an outer surface of the primer layer; and

forming a surface layer on an outer surface of the intermediate layer.
The method according to claim 16, wherein a chemical composition mass fractions of the valve seat substrate are as follows: C<0.35%-0.9%, Si<1.0%, Mn<1.0%, P<0.04%, S<0.04%, Cr<15%-18%, Mo<1.8%, and V<0.3%.
The method according to claim 16 or 17, wherein the forming the primer layer on at least the portion of the outer surface of the valve seat body comprises:
using Ti as a target material and using argon as a shielding gas to form a primer layer on at least the portion of the outer surface of the valve seat body through an arc plating process; a gas pressure during the arc plating process is 0.3Pa to 0.9Pa, a bias voltage is 250V, a target current is 65A to 75A, a deposition temperature is 240°C to 270°C, and an arc plating duration 5h to 8h.
The method according to any one of claims 16 to 18, wherein the forming the intermediate layer on the outer surface of the primer layer comprises:
using pure chromium as a target material and using nitrogen as a reaction gas to form the intermediate layer on the outer surface of the primer layer through the arc plating process; a nitrogen flow rate during the arc plating process is in a range of 250sccm-500sccm, a target current is 80A-100A, and an arc plating duration is 20h-25h.
The method according to any one of claims 16 to 19, wherein the forming the surface layer on the outer surface of the intermediate layer comprises:
using Ti as a target material and using argon as a shielding gas to form the surface layer on the outer surface of the intermediate layer through the arc plating process; a gas pressure during the arc plating process is 0.3Pa-0.9Pa, a bias voltage is 250V, a target current is 65A-75A, a deposition temperature is 240°C-270°C, and an arc plating duration is 5h-8h.
The method according to any one of claims 16 to 20, further comprising:
processing on the valve seat body to form an injection hole; and

processing on an inlet of the injection hole to form a rounded corner.
The method according to claim 21, wherein the processing on the valve seat body to form the injection hole comprises:
processing on the valve seat body by a laser drilling device to form the injection hole, wherein processing conditions of the injection hole comprise: laser power of 0.8kW~1.5kW, repetition frequency of 7kHz~10kHz, defocus amount of -350µm~450µm, scanning speed of 0.01mm/s-0.02mm/s, and number of scans of 15-25 times.
The method according to claim 21 or 22, wherein the processing on the inlet of the injection hole to form the rounded corner comprises:
impacting the inlet of the injection hole by using an abrasive fluid to form the rounded corner at the inlet of the injection hole.
The method according to claim 23, wherein the abrasive fluid comprises silicone rubber, lubricating liquid, silicon carbide particles and an anti-sticking agent;
a mass proportion of the silicone rubber in the abrasive fluid is 30%-40%; and/or

a mass proportion of the lubricating liquid in the abrasive fluid is 20%-30%; and/or

a mass proportion of the silicon carbide particles in the abrasive fluid is 35%-45%.
The method according to any one of claims 21 to 24, wherein the processing on the inlet of the injection hole to form the rounded corner further comprises:
after processing on the inlet of the injection hole to form the rounded corner, obtaining an intermediate piece of the injector valve seat;

mounting a shielding fixture on the surface to be welded of the intermediate piece of the injector valve seat; and

performing a nitriding treatment on the intermediate piece of the injector valve seat mounted with the shielding fixture to form a protective coating to obtain the injector valve seat.
The method according to claim 25, wherein processing conditions of the nitriding treatment comprise: a nitriding medium is ammonia gas, a nitriding temperature is less than or equal to 460°C, a nitriding duration is greater than or equal to 150 hours, a nitriding thickness is 0.02mm-0.5mm, and a deformation of the injector valve seat before and after the nitriding treatment is less than or equal to 0.01mm.
An injector, characterized by comprising:
the injector valve seat according to any one of claims 1 to 15.
The injector according to claim 27, further comprising:
a valve body;

a valve needle; and

a valve ball,

wherein the injector valve seat is fixed at one end of the valve body, the valve body is provided with a valve cavity, the injector valve seat is communicated with the valve cavity, the valve needle is movably provided in the valve cavity, the valve ball is fixed to an end of the valve needle, and the valve ball is movably provided in the injector valve seat.
An engine, characterized by comprising:
the injector according to claim 27 or 28.
A vehicle, characterized by comprising:
the engine according to claim 29.