Engine crankcase oil gas separation control method and system

Abstract

The application relates to an engine crankcase oil-gas separation control method and system, which is used for optimizing the oil-gas separation efficiency of an engine crankcase oil-gas separation unit. The method comprises the following steps: determining an opening control parameter Delta P of a gravity one-way valve according to the pressure difference between the air flow pressure P2 of an outer cavity of the oil-gas separation unit and the air flow pressure P1 of an inner cavity of the oil-gas separation unit; acquiring the liquid surface pressure P of a dynamic oil liquid surface height H in an ascending process when the oil-gas separation unit is running; when P is smaller than Delta P, the gravity one-way valve is controlled to be closed; when P is larger than Delta P, the gravity one-way valve is controlled to be opened; in the opened state of the gravity one-way valve, the oil is discharged to make the dynamic oil liquid surface height H drop, and the state switching of the gravity one-way valve makes the dynamic oil liquid surface height H maintain small-amplitude fluctuation in a set interval. The application has the beneficial effects that the oil-gas separation system selection efficiency and control precision can be improved, and the one-time success rate and overall reliability of system development can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vehicle engine, in particular to an engine crankcase oil-gas separation control method and system. BACKGROUND

[0002] With the development of engines, domestic engine emission requirements have been repeatedly improved, and people pay more and more attention to engine oil-gas separation devices. The separation effect of oil-gas separation devices is becoming more and more demanding. Oil-gas separators play an indelible role in meeting regulatory emission requirements, improving engine performance, and improving fuel economy.

[0003] Because the current mainstream scheme structure and design method of the crankcase ventilation system of the engine are mainly based on previous experience and actual machine verification for design and optimization, the overall is relatively rough. And because of the different selection strategies and design methods in the selection process, the separation efficiency of the oil-gas separation scheme is uneven, the difference is significant, and the long-term stability of the scheme also has great uncertainty, which causes a lot of unnecessary repetition and waste of cost and cycle for product development. SUMMARY

[0004] The embodiment of the present application provides an engine crankcase oil-gas separation control method and system, which improves the oil-gas separation system selection efficiency and control precision by modularizing and fine controlling the oil-gas separation structure, and improves the success rate and overall reliability of system development.

[0005] In a first aspect, the embodiment of the present application provides an engine crankcase oil-gas separation control method, which specifically includes the following steps:

[0006] An engine crankcase oil-gas separation control method is used to optimize the oil-gas separation efficiency of the engine crankcase oil-gas separation unit, and the method includes:

[0007] Determine the opening control parameter ΔP of the gravity one-way valve according to the pressure difference between the oil-gas separation unit outer cavity airflow pressure P2 and the oil-gas separation unit inner cavity airflow pressure P1; wherein ΔP=P2-P1;

[0008] Obtain the oil surface pressure P of the dynamic oil surface height H in the rising process of the oil-gas separation unit during operation;

[0009] When P is less than ΔP, control the gravity one-way valve to be in a closed state; wherein the gravity one-way valve is in a closed state, and the oil continues to accumulate in the oil return cavity, and the dynamic oil surface height H continuously rises;

[0010] When P is greater than ΔP, the gravity one-way valve is controlled to open; wherein, in the open state of the gravity one-way valve, the oil discharge makes the oil dynamic liquid level height H drop, and the state switching of the gravity one-way valve makes the oil dynamic liquid level height H maintain small amplitude fluctuation within the set interval.

[0011] Further, the engine crankcase oil-gas separation control method provided by the embodiment of the present application also has the following additional technical features.

[0012] Preferably, the opening control parameter ΔP of the gravity one-way valve is less than or equal to 0.5 KPa.

[0013] Preferably, the setting height range of the oil return hole arranged in the engine crankcase is within 10 mm below the assembly plane of the cylinder head cover.

[0014] Preferably, the stable blow-by gas amount of the engine crankcase is less than or equal to 80 L / min, and the limit blow-by gas amount is less than or equal to 100 L / min.

[0015] Preferably, the volume range of the oil return cavity V is 0.1-0.15 L.

[0016] In the second aspect, the embodiment of the present application provides a crankcase oil-gas separation control system. The system comprises: an air inlet unit, a rough separation unit, a fine separation unit, an oil return unit and an air outlet structure unit; wherein, the air inlet unit is provided with an air inlet, and the rough separation unit is provided with a baffle.

[0017] Preferably, the baffle comprises at least two vertical baffles arranged at the upper and lower ends of the cavity of the rough separation unit, so that the gas flow in the cavity of the rough separation unit is in a wave shape.

[0018] Preferably, the oil return unit comprises a deep V-shaped liquid surface rapid rising area at the lower end and a wide area liquid surface slow rising area above the deep V-shaped liquid surface rapid rising area, and the gravity single-phase valve is arranged at the bottom of the oil return unit.

[0019] Preferably, the setting height of the air inlet is lower than the bottom surface of the cavity of the rough separation unit.

[0020] The beneficial effects of the present application at least include: through the parameter control method, using the setting core control parameters, controlling or setting the opening control parameter ΔP (rough / fine separation unit pressure difference) of the one-way valve, the oil accumulation dynamic height H after the fine separation unit and the oil return cavity volume V for storing the separated oil of the fine separation unit, the oil-gas separation structure is modularized and fine controlled. The present application can be used to improve the selection efficiency and control accuracy of the oil-gas separation system, and improve the one-time success rate and overall reliability of system development.

[0021] The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the application will be apparent from the description of the embodiments and from the claims. BRIEF DESCRIPTION OF DRAWINGS

[0022] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:

[0023] Figure 1 is a schematic diagram of the differential pressure relationship of the engine crankcase oil-gas separation unit according to the first embodiment of the application;

[0024] Figure 2 is a schematic diagram of the deterioration of the oil content in the crankcase cavity;

[0025] Figure 3 is a schematic diagram of a vertical sinking type air inlet structure according to the embodiment of the application;

[0026] Figure 4 is a schematic diagram of a side opening type air inlet structure according to the embodiment of the application;

[0027] Figure 5 is a schematic diagram of an internal baffle type air inlet structure according to the embodiment of the application;

[0028] Figure 6 is a schematic diagram of the oil return unit structure according to the embodiment of the application;

[0029] Figure 7 is a schematic diagram of the cylinder head cover assembly structure integrated with the oil-gas separation unit according to the application;

[0030] Explanation of main component symbols: DETAILED DESCRIPTION

[0031] In order to make the objects, technical solutions and advantages of the application clearer, the application is described and explained below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and do not limit the application. Based on the embodiments provided in the application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the application.

[0032] It is apparent that the drawings in the following description merely show some examples or embodiments of the present application, and the present application can be applied to other similar situations without creative labor by those skilled in the art based on these drawings. In addition, it can be understood that although the efforts made in the development process can be complex and lengthy, some modifications, such as design, manufacture or production, etc. based on the technical content disclosed in the present application, are only routine technical means for those skilled in the art related to the content disclosed in the present application, and should not be understood as insufficient disclosure of the content disclosed in the present application.

[0033] Reference to "an embodiment" in this application means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. It is explicitly contemplated that embodiments described herein can be combined with other embodiments in a non- conflicting manner.

[0034] Unless otherwise defined, technical terms or scientific terms used in the present application shall have the ordinary meaning understood by one of ordinary skill in the art to which the present application pertains. The terms "a", "an", "one", "this", and similar terms as used in the present application are not limited to the singular form but include plural forms unless otherwise defined. The terms "include", "comprise", "have", and any variations thereof as used in the present application are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or device including a list of steps or modules (units) is not limited to the listed steps or units, but can further include other steps or units not listed or can further include other steps or units inherent to such a process, method, product, or device. The terms "connect", "connected", "coupled", and similar terms as used in the present application are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The term "multiple" as used in the present application means two or more. The term "and / or" describes the association relationship between the associated objects, which means that there can be three relationships, for example, "A and / or B" can mean that A exists alone, A and B exist together, and B exists alone. The character " / " generally represents an "or" relationship between the associated objects. The terms "first", "second", "third", and the like as used in the present application are merely to distinguish similar objects, and do not represent a specific order for the objects.

[0035] Since the current mainstream scheme structure and design method of the crankcase ventilation system of the current engine are mainly based on the design and optimization of previous experience and real machine verification, the overall is relatively rough. And due to the different selection strategies and design methods in the selection process, the separation efficiency of the oil-gas separation scheme is uneven and significantly different, and the long-term stability of the scheme also has great uncertainty, which causes a lot of unnecessary repetition and waste of cost and period in product development. Mainly manifested in:

[0036] 1. The current design scheme is mainly based on experience development, and excessively relies on design and development experience, so the development period is long, and the design scheme is significantly different;

[0037] 2. The product design scheme is not stable, mainly manifested in:

[0038] 1) The initial separation effect is poor, and cannot meet the development requirements;

[0039] 2) Poor robustness, the oil-gas separation effect deteriorates significantly with the endurance time, and the separation effect does not meet the requirements in the later stage of product life;

[0040] 3) In extreme conditions, such as continuous rated point working condition, the oil-gas separation efficiency deteriorates, and returns to normal in normal working condition.

[0041] Therefore, the present application provides an engine crankcase oil-gas separation control method to solve the above problems.

[0042] It can be understood that the oil-gas separation technology of the engine crankcase is mainly based on fluid mechanics, and according to Bernoulli equation of fluid mechanics:

[0043]

[0044] Where p, rho, v are the pressure, density and velocity of the fluid; h is the vertical height; g is the weight acceleration; C is a constant.

[0045] For gas, the gravity can be ignored, and the Bernoulli equation can be simplified as:

[0046]

[0047] According to the above equation, it can be concluded that the smaller the flow rate in the gas, the higher the pressure; the larger the flow rate, the smaller the pressure. Please refer to Figure 1 The embodiment provided by the present application is a schematic diagram of the pressure difference relationship of the oil-gas separation unit of the crankcase section. The engine crankcase oil-gas separation control method specifically comprises:

[0048] The flow includes the following steps:

[0049] Step S10: Determine the opening control parameter ΔP of the gravity check valve based on the pressure difference between the airflow pressure P2 in the outer cavity of the oil-gas separation unit and the airflow pressure P1 in the inner cavity of the oil-gas separation unit.

[0050] like Figure 1 As shown, according to Bernoulli's equation, the outer cavity (lower layer) of the gas separation unit has low structural resistance, relatively low flow velocity, and high relative pressure (P2). Inside the oil-gas separation unit, the fluid must pass through the coarse and fine separation structures, which have high structural resistance and fast flow velocity. Upon reaching this point, the relative pressure (P1) is low. The two gas streams form a pressure difference (ΔP) at the gravity check valve at the bottom of the return oil hole. Where ΔP = P2 - P1;

[0051] Step S20: Obtain the oil surface pressure P during the rising process of the dynamic oil level H when the oil-gas separation unit is running.

[0052] Understandably, the surface pressure P of a liquid can be calculated using the formula for liquid pressure difference:

[0053] P=ρgH

[0054] Where P is the pressure exerted by the liquid, and ρ is the density of the liquid, taken as 0.91 × 10⁻⁶. 3 kg / m 3 g is the acceleration due to gravity, and H is the dynamic height of the liquid.

[0055] Step S30: When P is less than ΔP, control the gravity check valve to be in the closed state.

[0056] Step S31: When P is greater than ΔP, control the gravity check valve to open.

[0057] It should be noted that when the gravity check valve is closed, the engine oil continuously accumulates in the oil return chamber, and the dynamic oil level H continuously rises. When the dynamic oil level H reaches a certain height, the resulting liquid pressure P > ΔP. At this time, the gravity check valve of the oil return hole opens, and the dynamic oil level H falls back down until the gravity valve closes, at which point the dynamic oil level rises again. This process repeats, and by switching the state of the gravity check valve, the dynamic oil level H is maintained within a set range with slight fluctuations.

[0058] In summary, the engine crankcase oil-gas separation control method provided by this invention obtains the opening control parameter ΔP of the gravity check valve, the dynamic oil level H, and the corresponding surface pressure P. By comparing the difference between the two parameters, the opening and closing of the gravity check valve is controlled. This ensures that the dynamic oil level H remains within a relatively stable range. This achieves the goal of modular and refined control of the oil-gas separation structure. This invention can be used to improve the selection efficiency and control accuracy of oil-gas separation systems, and enhance the first-time success rate and overall reliability of system development.

[0059] Understandably, the larger the pressure difference ΔP, the higher the corresponding requirement H, and the more stringent the requirements for the structural height of the oil-gas separation unit. Specifically, in engine design, control parameters can be adjusted according to operating conditions to achieve precise development.

[0060] Preferably, in this embodiment of the invention, due to the limitations of engine crankcase structural flow resistance, intake manifold pressure, and structural compactness, the opening control parameter ΔP of the gravity check valve is required to be ≤0.5Kpa.

[0061] Furthermore, under the premise that the opening control parameter ΔP of the gravity check valve is ≤0.5Kpa, the dynamic height H (e.g.) Figure 1 (Illustrative image) A height of ≥56mm is required. However, in practical applications, it is difficult to achieve a structural height of ≥56mm from the cylinder head cover mounting surface to the oil baffle of the fine filter unit (to prevent filtered oil from being swept away by high-speed airflow). To achieve effective oil return efficiency, the oil return hole often protrudes from the cylinder head cover mounting surface. To address the layout compatibility issues and potential damage to the oil return hole during transport and assembly, as well as the risk of the gravity check valve detaching, this case study sets the dynamic height of the oil return hole to 45-55mm based on the actual layout space. Specifically, the oil return hole installed inside the engine crankcase is positioned within 10mm below the cylinder head cover mounting plane.

[0062] It should be further explained that under the ΔP≤0.5KPa strategy setting, setting the dynamic height of the return oil hole below 56mm will cause a serious problem: due to insufficient return oil height margin, the gravity check valve may fail to open or open late. Without corresponding balancing measures, the consequences will be quite severe. Figure 2 As shown, under certain specific continuous operating conditions, the oil-gas separation efficiency will deteriorate significantly in an instant: the high-speed airflow after fine separation carries away the excessively accumulated engine oil, causing the oil content in the crankcase ventilation system to rise sharply.

[0063] To avoid the above situation, in this embodiment of the invention, the control strategy can be adjusted to balance the delayed opening and non-opening of the gravity check valve by adjusting the oil return chamber storage volume V and structural type. The specific strategy is as follows: the stable blow-by volume of the engine crankcase is ≤80L / min, and the extreme blow-by volume is ≤100L / min.

[0064] Embodiments of the present application also provide a crankcase oil-gas separation control system, which is used to implement the above embodiments and preferred embodiments, and will not be described again. As used below, the terms "module", "unit", "sub-unit", etc. can be a combination of software and / or hardware that implements a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, hardware, or a combination of software and hardware can also be implemented and conceived. The system includes: an air inlet unit, a coarse separation unit, a fine separation unit, an oil return unit, and an air outlet structure unit.

[0065] The air inlet unit is provided with an air inlet, and the height of the air inlet is lower than the bottom surface of the cavity of the coarse separation unit. Specifically, the interface form of the air inlet unit is as shown in Figure 3 、 Figure 4 、 Figure 5 By arranging between the two camshafts of the front end, the air inlet is sunken, which can avoid splashing oil to achieve the least liquid oil entering the coarse separation cavity. The air inlet unit is a rectangular structure, and its structure form is as shown in Figure 3 、 Figure 4 When it is impossible to completely avoid splashing oil due to the arrangement structure, a baffle can be arranged above the air inlet to play a blocking role, and the arrangement of the baffle structure is as shown in Figure 5 .

[0066] In addition, the coarse separation unit is provided with a baffle, and the baffle is a two-baffle labyrinth structure (such as the upper and lower baffles arranged in the coarse separation cavity in Figure 1 ). By arranging the baffle structure, the air inlet is disturbed, the gas flow rate in the coarse separation unit is reduced, and the coarse separation efficiency is optimized.

[0067] By way of example but not limitation, in actual selection, the coarse separation efficiency is optimized by adjusting the baffle position.

[0068] Further, in the embodiments of the present application, the fine separation unit is designed as a separable independent module, which supports quick selection; the standard impact hole diameter and number are as follows: impact hole diameter: 2mm and 2.5mm; hole number: 7-14 (preferably even hole scheme); according to the CFD analysis design and selection of the coarse / fine separation unit scheme, under the premise of ensuring the separation efficiency ≥99.5%, by adjusting the fine filter unit front and rear pressure difference ΔP level, the standard is that the maximum pressure difference is maintained at 0.5±0.3KPa.

[0069] The oil return hole of the oil return unit is limited to not exceeding the assembly surface of the cylinder head cover assembly. In the extreme case, under the premise of meeting the function, the maximum protrusion from the cylinder head cover assembly surface is 10mm; the height (i.e. dynamic oil height) H of the oil return hole from the fine separation oil baffle is as follows: the height H is selected in the range of 50±5mm; the specific requirements are as follows:

[0070] The oil return cavity (oil return unit) is divided into two levels (as shown in Figure 6 Specifically, a deep V-shaped liquid surface rapid rising area H1 at the lower end, and a wide-area liquid surface slow rising area H2 above the deep V-shaped liquid surface rapid rising area. The gravity one-way valve is arranged at the bottom of the oil return unit.

[0071] H1 is a rapid liquid surface rising area, which is used for quickly establishing liquid pressure and shortening the opening time of the gravity one-way valve, and H1≥25mm;

[0072] H2 is a liquid surface slow rising area, and the main purpose is to slow down the liquid surface rising rate under a steady state condition with a large ΔP, so as to avoid the liquid surface exceeding the height of the oil baffle of the fine separation unit. The acceptance standard is that the oil storage cavity volume V≥0.1-0.15L.

[0073] Parameterized control:

[0074] Fine separation before and after pressure difference ΔP, oil return hole height H and oil return cavity volume V matching control:

[0075] The design maximum pressure difference ΔP≤0.5±0.3KPa, the oil return hole height H≥55mm, basically meeting the ΔP opening height, and the oil return cavity oil storage volume V≥0.1L;

[0076] The design maximum pressure difference ΔP≤0.5±0.3KPa, the oil return hole height H=45-55, which is more than 80% of the ΔP opening height, the oil return cavity oil storage volume V=0.1-0.15L, through the delay compensation strategy, when the pressure difference falls, the power one-way valve is opened, and rapid oil return is realized.

[0077] Please refer to Figure 7 The cylinder head cover assembly is designed based on the application, and is a plastic body structure. The air inlet is a vertical sinking vertical structure, which is arranged at the front of the first camshaft. The coarse separation unit is divided into two baffles, front lower and rear upper. The distance between the two baffles is 22mm. According to the separation efficiency and pressure difference, the impact hole specification of the fine filter unit is 2.5mm, and the number is 10. The steady state pressure difference before and after the fine filter is 0.5KPa, the pressure difference fluctuation range is 0-0.8KPa, the oil return height is 56.3mm, and the oil storage cavity volume is 0.102L. Under the comprehensive endurance working condition, the maximum blow-by quantity is stably less than 0.6g / h before and after the test, and the blow-by quantity is basically stable and does not deteriorate.

[0078] The technical features of the above-described embodiments can be combined in any manner. In order to make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, but as long as the combinations of the technical features do not exist, they should be considered as the scope of the description.

[0079] The above-described embodiments are merely illustrative of several embodiments of the present application, which are described in more detail and in a specific and detailed manner, but should not be construed as limiting the scope of the patent. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, and these are all within the scope of the present application. Therefore, the scope of protection of the patent of the present application should be subject to the appended claims.

Claims

1. A method for controlling oil-gas separation in an engine crankcase, used to optimize the oil-gas separation efficiency of an engine crankcase oil-gas separation unit, characterized in that, The method includes: The opening control parameter ΔP of the gravity check valve is determined based on the pressure difference between the airflow pressure P2 in the outer cavity of the oil-gas separator and the airflow pressure P1 in the inner cavity of the oil-gas separator; where ΔP = P2 - P1. During the operation of the oil-gas separator unit, the dynamic oil level height H and the surface pressure P during the rising process are obtained; When P is less than ΔP, the gravity check valve is controlled to be in the closed state; wherein, when the gravity check valve is in the closed state, the oil continuously accumulates in the oil return chamber, and the dynamic liquid level height H continuously increases; When P is greater than ΔP, the gravity check valve is opened; wherein, when the gravity check valve is open, the oil is discharged, causing the dynamic oil level H to drop, and the state switching of the gravity check valve keeps the dynamic oil level H within a set range with slight fluctuations.

2. The engine crankcase oil-gas separation control method according to claim 1, characterized in that, The opening control parameter ΔP of the gravity check valve is ≤0.5KPa.

3. The engine crankcase oil-gas separation control method according to claim 1, characterized in that, The oil return hole in the engine crankcase is located within a height range of 10mm below the cylinder head cover mounting surface.

4. The engine crankcase oil-gas separation control method according to claim 1, characterized in that, The stable blow-by volume of the engine crankcase is ≤80L / min, and the extreme blow-by volume is ≤100L / min.

5. A crankcase oil-gas separation control system for implementing the method as described in any one of claims 1 to 4, the system comprising: The unit includes an air inlet unit, a coarse separation unit, a fine separation unit, an oil return unit, and an air outlet structure unit; wherein the air inlet unit is provided with an air inlet, and the coarse separation unit is provided with a baffle.

6. The crankcase oil-gas separation control system according to claim 5, characterized in that, The baffle includes at least two partitions that are vertically arranged at the upper and lower ends of the coarse separation unit cavity, so that the gas flow in the coarse separation unit cavity is wave-shaped.

7. The crankcase oil-gas separation control system according to claim 5, characterized in that, The oil return unit includes a deep V-shaped rapid liquid level rise zone at the lower end and a wide-area slow liquid level rise zone above the deep V-shaped rapid liquid level rise zone. The gravity single-phase valve is located at the bottom of the oil return unit.

8. The crankcase oil-gas separation control system according to claim 5, characterized in that, The air inlet is positioned at a height lower than the bottom surface of the cavity of the coarse separation unit.

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