Rail pressure control and calibration method for load-sensitive high-pressure common rail diesel engine

Abstract

The invention discloses a rail pressure control and calibration method for a load-sensitive high-pressure common-rail diesel engine. A flow control valve, an engine controller, a one-way valve, a high-pressure oil pump, a high-pressure common-rail pipe, a rail pressure sensor, a high-pressure oil pipe and an oil injector are included. The flow control valve receives a duty ratio signal sent by an engine controller and is used for adjusting the flow entering a fuel oil system. The high-pressure oil pump is used for compressing the low-pressure fuel oil from the flow control valve into high-pressure fuel oil; the one-way valve is used for preventing fuel backflow; according to the rail pressure control and calibration method for the load-sensitive high-pressure common rail diesel engine, dynamic balance between the oil quantity and the consumption quantity entering a high-pressure fuel pipe system is achieved, an integral compensation adjustment component is converted into a part of a high-pressure fuel consumption feedforward component in a memory conversion mode, and the integral compensation adjustment range is reduced; and the oil quantity calculation accuracy of the high-pressure piping system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of diesel engine control, and in particular to a rail pressure control and calibration method for a load-sensitive high-pressure common rail diesel engine. Background Art

[0002] The rail pressure stability of high-pressure common rail diesel engines has an important impact on engine burst pressure, speed stability, emission performance stability, thermal stability and other performances. Therefore, rail pressure control of high-pressure common rail diesel engines has become an important part of the high-pressure common rail diesel engine control system.

[0003] The change in the injection amount of a high-pressure common rail diesel engine is affected by the change in the diesel engine load. When used in engineering machinery, ship main engines, and generator sets with sudden loading and unloading requirements, the load of the diesel engine is variable, which leads to the variability of the injector injection amount. When the injector injection amount is variable, the oil output of the high-pressure fuel pipe system is variable, forming a load-variable effect of the high-pressure fuel common rail pipe system, which has a significant impact on the rail pressure change. A load-sensitive high-pressure common rail diesel engine rail pressure control and calibration method is needed to control it.

[0004] In the prior art, for example, patent CN102192033A discloses an apparatus and method for controlling a high-pressure common rail system of a diesel engine, which obtains a feedforward control variable through PID feedback regulation. The patent also details feedforwards for high-pressure oil pumps, injectors, flow metering valves, and the like, and methods for PID feedback control. PID feedback control is the core of this technology, and inaccurate PID calculations lead to inaccurate control. However, the PID control variable is complex and heavily dependent on the operator's experience and skills, and the published technology does not describe a PID control strategy. Secondly, this technology uses the obtained feedback value lead as the feedforward input value, and implements control regulation through control variables such as the high-pressure oil pump and flow metering valve. The patent also provides a detailed calculation method for the control. However, it is well known that physical components are subject to wear, and components of the same specification from different samples also have errors. The technology does not include any relevant content for error elimination, resulting in inaccurate calculation of the oil volume in the high-pressure piping system. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the existing defects and provide a load-sensitive high-pressure common rail diesel engine rail pressure control and calibration method, so that the amount of oil entering the high-pressure fuel pipe system and the consumption are dynamically balanced in and out, and the integral compensation adjustment component is converted into a part of the high-pressure fuel consumption feedforward component through memory conversion, thereby reducing the integral compensation adjustment range and improving the accuracy of the high-pressure pipe system oil quantity calculation, which can effectively solve the problems in the background technology.

[0006] To achieve the above-mentioned object, the present invention provides the following technical solutions: a method for controlling and calibrating rail pressure of a load-sensing high-pressure common rail diesel engine, comprising a flow control valve, an engine controller, a one-way valve, a high-pressure oil pump, a high-pressure common rail pipe, a rail pressure sensor, a high-pressure oil pipe, and a fuel injector;

[0007] The flow control valve receives a duty cycle signal from the engine controller to regulate the flow into the fuel system;

[0008] The high-pressure fuel pump is used to compress the low-pressure fuel from the flow control valve into high-pressure fuel;

[0009] The one-way valve is used to prevent fuel from flowing back;

[0010] The specific steps are as follows:

[0011] First, the total fuel injection amount F inj , Total leakage between the high-pressure oil pump and the injector D inj Obtain the diesel engine high pressure fuel consumption feedforward component F con ;

[0012] Then, to address the difference between the calculated high-pressure fuel consumption and the amount of fuel entering the high-pressure fuel line, supplementary adjustments are made by integrating the difference between the target value and the actual value. This compensates for the gradual change in high-pressure fuel consumption caused by wear and tear between the high-pressure fuel pump and injector, as well as the calculation error of the high-pressure fuel consumption feedforward value. This results in a two-stage adjustment strategy for rail pressure, combining a feedforward component and an integral compensation adjustment component.

[0013] The integral compensation value is stored in memory, and the integral compensation adjustment component is converted into a part of the high-pressure fuel consumption feedforward component, thereby reducing the integral compensation adjustment range. At the same time, the compressibility of the high-pressure piping system and fuel under high-pressure conditions is utilized to form a high-pressure piping system pressure storage component.

[0014] Finally, the high-pressure fuel consumption feedforward component, the integral compensation adjustment component, and the high-pressure pipeline pressure storage component are coupled to achieve a dynamic balance between the amount of oil entering the high-pressure fuel pipeline and the consumption.

[0015] As a preferred technical solution of the present invention, a high-pressure oil pump flow map under the system maximum high-pressure oil pump outlet pressure Prail is established, and the injection time t given by the injector to the engine controller is obtained through component platform testing. hub and the fuel injection quantity F under the conditions of rail pressure Prail hub The engine controller can be controlled by the number of injectors m, injection time t hub , rail pressure Prail and diesel engine speed n eng Get the total injection volume F of the injector inj .

[0016] As a preferred technical solution of the present invention, the diesel engine high pressure fuel consumption feedforward component F con is the total injection amount F of the injector inj Total leakage between the injector and the gap D inj sum.

[0017] As a preferred technical solution of the present invention, the diesel engine high pressure fuel consumption feedforward component F con Need to use rail pressure integral compensation adjustment component F KI be compensated.

[0018] As a preferred technical solution of the present invention, the target rail pressure P is obtained. req The amount of fuel Q in the high-pressure pipe system under the condition req and the fuel quantity Q in the high-pressure pipe system under the actual rail pressure Prail act , further obtain the balanced target rail pressure P req The fuel replenishment requirement ΔQ between the actual rail pressure Prail, ΔQ=Q req -Q act If it is required to replenish the required amount of oil within the time t, the oil replenishment rate is The rail pressure integral compensation adjustment component

[0019] As a preferred technical solution of the present invention, the rail pressure integral compensation adjustment component F KI The integral compensation F of the diesel engine high-pressure fuel consumption feedforward component is calculated as con-KI The dynamic balance of the inlet and outlet flow of the high-pressure common rail pipe is the balance between the diesel engine high-pressure fuel consumption feedforward component obtained by calculating the physical model of the injector, the integral compensation of the diesel engine high-pressure fuel consumption feedforward component obtained by the rail pressure integral compensation adjustment component, the rail pressure integral compensation adjustment component, and the flow of the high-pressure fuel pump at the current rail pressure. The expression is:

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: the rail pressure control and calibration method of the load-sensitive high-pressure common rail diesel engine achieves dynamic balance of the high-pressure common rail pressure by establishing a dynamic balance between the flow rate of the high-pressure oil pump entering the high-pressure common rail system and the fuel consumption flowing out of the high-pressure common rail system, which can meet the rail pressure fluctuation problem caused by large load changes of the high-pressure common rail diesel engine, and uses an integral compensation method to compensate for the mismatch between the calculated value and the actual value of the high-pressure oil pump flow rate and fuel consumption due to metering errors or component wear, and solidifies the integral compensation value through memory solidification to reduce the adjustment range and calculation amount of the integral compensation amount. When calculating the integral compensation amount, the pressure storage performance of the high-pressure common rail system, such as the volume of the common rail system and the compressibility of the fuel, is fully considered, thereby improving the accuracy of the high-pressure system oil quantity calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a composition diagram of the control system of the present invention;

[0022] Figure 2 This is a flow chart of the control system of the present invention.

[0023] In the figure: 1 flow control valve, 2 engine controller, 3 check valve, 4 high-pressure fuel pump, 5 high-pressure common rail pipe, 6 rail pressure sensor, 7 high-pressure fuel pipe, 8 injector. DETAILED DESCRIPTION

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0025] See also Figure 1-2 The present invention provides a technical solution: a method for controlling and calibrating rail pressure of a load-sensing high-pressure common rail diesel engine, comprising a flow control valve 1, an engine controller 2, a one-way valve 3, a high-pressure fuel pump 4, a high-pressure common rail pipe 5, a rail pressure sensor 6, a high-pressure fuel pipe 7, and a fuel injector 8. The output end of the engine controller 2 is signal-connected to the input end of the flow control valve 1. A one-way valve 3 is provided on the pipeline between the flow control valve 1 and the high-pressure fuel pump 4. The output end of the high-pressure fuel pump 4 is connected to the high-pressure common rail pipe 5 via the high-pressure fuel pipe 7. The high-pressure common rail pipe 5 is also provided with a one-way valve 3. The high-pressure common rail pipe 5 is connected to multiple fuel injectors 8. The rail pressure sensor 6 is provided on the high-pressure common rail pipe to detect fuel pressure.

[0026] The flow control valve 1 receives a duty cycle signal from the engine controller 2 to regulate the flow into the fuel system;

[0027] The high-pressure fuel pump 4 is used to compress the low-pressure fuel from the flow control valve 1 into high-pressure fuel;

[0028] One-way valve 3 is used to prevent fuel from flowing back;

[0029] The piping system can be divided into control signal transmission lines, fuel operation lines, and fuel leakage lines.

[0030] Because the leakage between the 4 plungers of the high-pressure oil pump is D P It leads to the outlet of flow control valve 1, which is the inlet of high pressure oil pump 4. Therefore, the flow rate F of flow control valve 1 is I Equivalent to the high-pressure oil pump oil volume F P ;

[0031] Furthermore, the high-pressure oil pump oil volume F of the high-pressure oil pump 4 under the control condition of the flow control valve 1 can be obtained by the device platform test method. P and flow control valve 1 flow F I , establish a high pressure oil pump speed n P and flow control valve 1 flow F I The coordinate axis is a three-dimensional map in which the duty ratio signal Duty received by the flow control valve 1 from the engine controller 2 is the control amount.

[0032] Furthermore, the flow control valve 1 is affected by the duty cycle and the power supply voltage U. Since the power supply voltage U is reasonable within a certain range, it is necessary to correct the power supply voltage. The preferred standard duty cycle Duty is the control amount under the 24VDC voltage. The duty cycle of the actual operation flow control valve 1 is U act is the actual power supply voltage. In particular, due to the influence of factors such as duty cycle control inductive reactance, the influence of duty cycle has a nonlinear relationship with voltage change. However, in this scheme, the calculation error can be eliminated by the integral compensation method.

[0033] Furthermore, the outlet pressure Prail of the high pressure oil pump 4 affects the oil volume F of the high pressure oil pump 4. P In order to reduce the complexity of the component platform test, only the high-pressure oil pump flow map under the standard high-pressure oil pump 4 outlet pressure Prail condition is established. It is preferred to establish the high-pressure oil pump flow map under the system maximum high-pressure oil pump 4 outlet pressure Prail requirement. The high-pressure oil pump 4 oil volume F under the other high-pressure oil pump 4 outlet pressure Prail p Corrected using the following method:

[0034] F P-prailis the flow rate of the high-pressure oil pump 4 under the current outlet pressure of the high-pressure oil pump 4, Pmax is the maximum outlet pressure of the high-pressure oil pump 4, that is, the outlet pressure of the high-pressure oil pump 4 corresponding to the standard flow map of the high-pressure oil pump 4, Prail is the current outlet pressure of the high-pressure oil pump 4, K is the correction coefficient, and its recommended value is less than 5%, which can be obtained based on the platform test of the high-pressure oil pump 4.

[0035] Furthermore, the injection time t given by the injector 8 under the engine controller 2 can be obtained through component platform testing. hub and the fuel injection quantity F under the conditions of rail pressure Prail hub In this way, the engine controller 2 can control the number m of the injectors 8 and the injection time t hub , rail pressure Prail and diesel engine speed n eng Get the total injection amount F of injector 8 inj :

[0036]

[0037] Furthermore, the leakage amount D of the injector 8 hub Obtained through the platform test of the injector, the total leakage of injector 8 D inj =m×D hub .

[0038] Furthermore, the diesel engine high pressure fuel consumption feedforward component F con is the total injection amount F of injector 8 inj and the total leakage of injector 8 D inj In particular, if the fuel system contains other components that consume high-pressure fuel, they should also be included in the diesel engine high-pressure fuel consumption feedforward component F con middle.

[0039] Furthermore, the diesel engine high pressure fuel consumption feedforward component F con and high pressure oil pump oil volume F P A balance is established between the two, so that when the amount of fuel leaving the high-pressure pipe system is balanced with the amount of fuel entering the high-pressure pipe system, the rail pressure is always in a balanced state.

[0040] Furthermore, it is necessary to understand that the flow control valve 1, the high pressure oil pump 4 and the injector 8 are mechanical parts, which are subject to wear and tear. When worn, their performance will change and be inconsistent with the actual value. At the same time, the fuel injection amount F of the injector 8 hub , High-pressure oil pump 4 flow F P It is obtained by map calculation method. Map cannot be comprehensive. There will be errors in its difference parameters. There will also be errors in the actual performance between different samples of the same model. conand high pressure oil pump oil volume F P It is difficult to establish an accurate balance between the two, so it is necessary to use the rail pressure integral compensation adjustment component F KI be compensated.

[0041] Furthermore, the fuel quantity Q in the high-pressure pipe system at each rail pressure Prail is calculated. act The amount of fuel in the high-pressure pipe system is the product of the total volume V of the high-pressure pipe system and the fuel density ρ at the actual rail pressure. act The product of: Q act =V×ρ act , the preferred act It can be obtained by establishing a corresponding map with the rail pressure Prail. The total volume V of the high-pressure pipe system is a structural parameter.

[0042] Preferably, the fuel density can be obtained by querying published values, or by the following formula:

[0043] ρ p is the fuel density under current pressure conditions, ρ p-1 is the fuel density under the previous pressure unit condition, one pressure unit is MPa, k p-1 is the elastic model of fuel under pressure p-1, k p =k0+γ×P, k0 is the elastic modulus under standard conditions of 0MPa, which is 1070 for light diesel, and γ is the elastic modulus increment coefficient, which is 7.15 for light diesel. The density of light fuel under standard conditions (pressure of 0MPa) is 848kg / m 3 .

[0044] In particular, it should be noted that a pressure unit is 1 MPa, so the measured high-pressure fuel pressure needs to be rounded to the nearest MPa. Under normal circumstances, a rail pressure fluctuation of 1 MPa is an ideal state, so rounding the rail pressure to the nearest MPa unit is beneficial to reducing the calculation amount of the engine controller 2.

[0045] Furthermore, the target rail pressure P can be obtained req The amount of fuel Q in the high-pressure pipe system under the condition req and the fuel quantity Q in the high-pressure pipe system under the actual rail pressure Prail act , thereby obtaining the balanced target rail pressure P req The fuel replenishment requirement ΔQ between the actual rail pressure Prail, ΔQ=Q req -Q act If it is required to replenish the required amount of oil within the time t, the oil replenishment rate is In particular, the oil replenishment time t can also be equivalent to the integral time parameter.

[0046] Furthermore, the rail pressure integral compensation adjustment component A basic integration time t can be established. The greater the rail pressure deviation, the smaller the integration time t should be.

[0047] Furthermore, the integral compensation adjustment component F of the previous stable operation long-term operation KI The integral compensation F of the diesel engine high-pressure fuel consumption feedforward component is calculated as con-KI , used to compensate for the feedforward component F of high-pressure fuel consumption of diesel engines caused by factors such as metering errors and component wear. con Inaccurate measurement.

[0048] Furthermore, the dynamic balance of the inlet and outlet flow of the high-pressure common rail pipe is the balance between the diesel engine high-pressure fuel consumption feedforward component obtained by calculating the physical model of the injector, the integral compensation of the diesel engine high-pressure fuel consumption feedforward component obtained by the rail pressure integral compensation adjustment component, the rail pressure integral compensation adjustment component, and the flow of the high-pressure fuel pump at the current rail pressure. The expression is:

[0049] Parts of the invention not described in detail are prior art. Although embodiments of the present invention have been shown and described, it is understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the invention. The scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for controlling and calibrating rail pressure of a load-sensing high-pressure common rail diesel engine, characterized by: It includes a flow control valve (1), an engine controller (2), a one-way valve (3), a high-pressure oil pump (4), a high-pressure common rail pipe (5), a rail pressure sensor (6), a high-pressure oil pipe (7) and a fuel injector (8); The flow control valve (1) receives a duty cycle signal from an engine controller (2) to adjust the flow rate entering the fuel system; The high-pressure fuel pump (4) is used to compress the low-pressure fuel from the flow control valve (1) into high-pressure fuel; The one-way valve (3) is used to prevent the fuel from flowing back; The specific steps are as follows: First, the total fuel injection amount F inj , Total leakage between the high-pressure oil pump and the injector D inj Obtain the diesel engine high pressure fuel consumption feedforward component F con ; Then, to address the difference between the calculated high-pressure fuel consumption and the amount of fuel entering the high-pressure fuel line, supplementary adjustments are made by integrating the difference between the target value and the actual value. This compensates for the gradual change in high-pressure fuel consumption caused by wear and tear between the high-pressure fuel pump and injector, as well as the calculation error of the high-pressure fuel consumption feedforward value. This results in a two-stage adjustment strategy for rail pressure, combining a feedforward component and an integral compensation adjustment component. The integral compensation value is stored in memory, and the integral compensation adjustment component is converted into a part of the high-pressure fuel consumption feedforward component, thereby reducing the integral compensation adjustment range. At the same time, the compressibility of the high-pressure piping system and fuel under high-pressure conditions is utilized to form a high-pressure piping system pressure storage component. Finally, the high-pressure fuel consumption feedforward component, the integral compensation adjustment component, and the high-pressure pipeline pressure storage component are coupled to achieve a dynamic balance between the amount of oil entering the high-pressure fuel pipeline and the consumption.

2. A load-sensing high-pressure common rail diesel engine rail pressure control and calibration method according to claim 1, characterized in that: Establish the high-pressure oil pump flow map under the system's maximum high-pressure oil pump outlet pressure Prail requirement, and obtain the injector injection time t given by the engine controller through component platform testing. hub and the fuel injection quantity F under the conditions of rail pressure Prail hub The engine controller can be controlled by the number of injectors m, injection time t hub , rail pressure Prail and diesel engine speed n eng Get the total injection volume F of the injector inj .

3. The method for controlling and calibrating rail pressure of a load-sensing high-pressure common rail diesel engine according to claim 2, characterized in that: The diesel engine high pressure fuel consumption feedforward component F con is the total injection amount F of the injector inj Total leakage between the injector and the gap D inj sum.

4. The method for controlling and calibrating rail pressure of a load-sensing high-pressure common rail diesel engine according to claim 2, characterized in that: The diesel engine high pressure fuel consumption feedforward component F con Need to use rail pressure integral compensation adjustment component F KI be compensated.

5. The method for controlling and calibrating rail pressure of a load-sensing high-pressure common rail diesel engine according to claim 4, characterized in that: Get the target rail pressure P req The amount of fuel Q in the high-pressure pipe system under the condition req and the fuel quantity Q in the high-pressure pipe system under the actual rail pressure Prail act , further obtain the balanced target rail pressure P req The fuel replenishment requirement ΔQ between the actual rail pressure Prail, ΔQ=Q req -Q act If it is required to replenish the required amount of oil within the time t, the oil replenishment rate is The rail pressure integral compensation adjustment component 6. The method for controlling and calibrating rail pressure of a load-sensing high-pressure common rail diesel engine according to claim 5, characterized in that: The rail pressure integral compensation adjustment component F of the previous stable operation long-term operation KI The integral compensation F of the diesel engine high-pressure fuel consumption feedforward component is calculated as con-KI The dynamic balance of the inlet and outlet flow of the high-pressure common rail pipe is the balance between the diesel engine high-pressure fuel consumption feedforward component obtained by calculating the physical model of the injector, the integral compensation of the diesel engine high-pressure fuel consumption feedforward component obtained by the rail pressure integral compensation adjustment component, the rail pressure integral compensation adjustment component, and the flow of the high-pressure fuel pump at the current rail pressure. The expression is:

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