JP2019078170A - Method for controlling discharge amount of high-pressure pump, and common rail type fuel injection controller - Google Patents

Abstract

To appropriately set a discharge amount of a high-pressure pump according to an operation state of an internal combustion engine.SOLUTION: A discharge amount of a high-pressure pump is calculated from a precontrol amount and a feedback control amount based on PID control. The precontrol amount is obtained by multiplying a sum of a degree of opening in an accelerator, an instruction injection amount determined based on an engine speed, and dynamic leak of a fuel injection valve, by the engine speed and the number of operating cylinders, where the number of operating cylinders is obtained by subtracting the number of fuel injection valves being under an operation stop state from the number of all cylinders, and by adding static leak of the fuel injection valve to the multiplication result. Consequently, the high-pressure pump is prevented from discharging unnecessary fuel, thereby securing an appropriate discharge amount based on an operation state of an internal combustion engine.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for controlling the discharge amount of a high pressure pump in a common rail fuel injection control device, and more particularly to improvement in accuracy, reliability, etc. of discharge amount control.

  A so-called common rail type fuel injection control device pressurizes fuel by a high pressure pump, pumps and stores the pressure to a common rail which is a pressure accumulator, and supplies the stored high pressure fuel to the fuel injection valve, thereby causing internal combustion by the fuel injection valve. It is well known as one that is capable of injecting high pressure fuel into an engine and is excellent in fuel consumption, emission characteristics, and the like (see, for example, Patent Document 1).

  In such a common rail fuel injection control device, the discharge amount of fuel discharged from the high pressure pump to the common rail is generally referred to as a precontrol amount determined from the number of cylinders (number of cylinders) in which fuel injection is performed and the engine speed. It is determined by adding the amount of correction by PID control to the basic fuel amount to be calculated.

By the way, depending on the vehicle, there are some vehicles that perform cylinder reduction operation by intentionally stopping the fuel injection valve from the viewpoint of fuel efficiency improvement etc., and fuel injection by all the fuel injection valves is not always performed.
In addition, the occurrence of an electrical failure may cause the fuel injection valve to not operate and the fuel injection can not be performed.

JP, 2014-84810, A

However, the presence or absence of the actual operation of the fuel injection valve is not considered at all in the calculation of the above-mentioned pre-control amount used when determining the discharge amount of the high pressure pump.
Therefore, as described above, when the intentional cylinder reduction operation or the electrical failure has occurred, the high pressure pump discharges more fuel than necessary, and in some cases, the fuel injection valve At the moment when the valve is shut off (shut off), the rail pressure may rapidly increase and the high pressure safety valve may open.

  In addition, when the discharge amount of the high-pressure pump becomes more than necessary, the rail pressure overshoots or the actual rail pressure continues to be higher than the target rail pressure, thus deteriorating the exhaust gas performance. And the components may be deteriorated.

  The present invention has been made in view of the above circumstances, and provides a high pressure pump discharge amount control method and a common rail fuel injection control device capable of appropriately adjusting the discharge amount of a high pressure pump according to the operating state of an internal combustion engine. It is.

In order to achieve the above object of the present invention, a high pressure pump discharge control method according to the present invention is:
The fuel of the fuel tank is pressurized and fed to the common rail by the high pressure pump, and it becomes possible to inject the high pressure fuel to the engine through the fuel injection valve connected to the common rail, and at least upstream of the high pressure pump A high-pressure pump discharge amount control method in a common rail fuel injection control device, comprising a valve, wherein the rail pressure of the common rail can be controlled by drive control of the metering valve.
The discharge amount of the high-pressure pump is determined based on a pre-control amount calculated based on the instructed injection amount and a feedback control amount obtained based on PID control.
The pre-control amount is obtained by multiplying the sum of the instructed injection amount determined based on the accelerator opening degree and the engine rotational speed and the dynamic leak of the fuel injection valve by the engine rotational speed and the number of cylinders, Calculated by adding the static leak of the fuel injection valve,
The number of cylinders is set to a value obtained by subtracting the number of fuel injection valves in the operation stop state from the total number of cylinders.
Further, to achieve the above object of the present invention, a common rail fuel injection control device according to the present invention is:
The fuel of the fuel tank is pressurized and fed to the common rail by the high pressure pump, and it becomes possible to inject the high pressure fuel to the engine through the fuel injection valve connected to the common rail, and at least upstream of the high pressure pump A common rail type fuel injection control device comprising a valve, wherein the control valve is driven and controlled by an electronic control unit to control the rail pressure of the common rail,
The electronic control unit
The pre-control amount is calculated based on the instructed injection amount, the feedback control amount is calculated based on the PID control, and the pre-control amount is added to the feedback control amount to calculate the discharge amount of the high pressure pump
The pre-control amount is obtained by multiplying the sum of the instructed injection amount determined based on the accelerator opening degree and the engine rotation speed and the dynamic leak of the fuel injection valve by the engine rotation speed and the number of cylinders, Calculated by adding the static leak of the fuel injection valve,
The number of cylinders is set to a value obtained by subtracting the number of fuel injection valves in the operation stop state from the total number of cylinders.

According to the present invention, extra fuel discharge from the high pressure pump to the common rail is reliably avoided by using the number of cylinders in operation unlike the conventional method in the process of calculating the discharge amount of the high pressure pump. Therefore, even if the failure of the fuel injection valve in the operation stop state occurs, the rail pressure controllability equivalent to that in the normal operation can be maintained by preventing the rapid rise of the rail pressure.
In addition, unlike the conventional case, since the high pressure pump discharge amount does not continue to be excessive, the rail pressure overshoots or the actual rail pressure continues to be higher than the target rail pressure. Is surely prevented. Therefore, it is possible to provide a more reliable and stable common rail fuel injection control device that does not cause deterioration of the exhaust gas performance, and further suppresses deterioration of components of the fuel system due to a rapid rise in rail pressure and the like. The effect of being able to

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows the structural example of the common rail type fuel injection control apparatus with which the high pressure pump discharge amount control method in embodiment of this invention is applied. FIG. 3 is a functional block diagram showing basic functions required to execute high-pressure pump discharge amount control in the common rail fuel injection control device in the embodiment of the present invention, represented by functional blocks. FIG. 3A is a functional block diagram showing basic functions required to execute pre-control amount calculation processing in high-pressure pump discharge amount control according to an embodiment of the present invention, which are represented by functional blocks, and FIG. Is a functional block diagram for determining the number of working cylinders by subtracting the number of fuel injection valves in the operation stop state from the total number of fuel injection valves, and FIG. 3 (B) shows the fuel in the operating state of the number of working cylinders It is a functional block diagram in the case of setting it as the number of injection valves. It is a subroutine flow chart which shows the procedure of precontrol amount calculation processing in high pressure pump discharge amount control processing in the embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 4.
The members, arrangements, and the like described below do not limit the present invention, and various modifications can be made within the scope of the present invention.
First, a common rail fuel injection control system according to an embodiment of the present invention will be described with reference to FIG.
The common rail fuel injection control device includes a high pressure pump device 50 for pumping high pressure fuel, a common rail 1 for storing high pressure fuel pumped by the high pressure pump device 50, and high pressure fuel supplied from the common rail 1 as an internal combustion engine. An electronic control unit (in FIG. 1, a plurality of fuel injection valves 2-1 to 2-n injected and supplied to the cylinders of the engine 3 as an engine, and fuel injection control processing and high pressure pump discharge amount control processing described later). It is configured as the main component of “ECU” 4). This configuration itself is the same as the basic configuration of this type of fuel injection control device that is well known from the prior art.

The high-pressure pump device 50 has a known and well-known configuration that includes the supply pump 5, the metering valve 6, and the high-pressure pump 7 as main components.
In this configuration, the fuel of the fuel tank 9 is pumped up by the supply pump 5 and supplied to the high pressure pump 7 through the metering valve 6. As the metering valve 6, an electromagnetic proportional control valve is used, and the amount of energization thereof is controlled by the electronic control unit 4, so that the flow rate of the supplied fuel to the high pressure pump 7, in other words, the discharge of the high pressure pump 7 The amount is to be adjusted.
The fuel pressurized by the high pressure pump 7 is pressure fed to the common rail 1.

A return valve 8 is provided between the output side of the supply pump 5 and the fuel tank 9 so that surplus fuel on the output side of the supply pump 5 can be returned to the fuel tank 9. .
Further, the supply pump 5 may be provided separately from the high pressure pump device 50 on the upstream side of the high pressure pump device 50 or may be provided in the fuel tank 9.

  The fuel injection valves 2-1 to 2-n are provided for each cylinder of the engine 3, receive high-pressure fuel from the common rail 1, and perform fuel injection by injection control by the electronic control unit 4. It has become.

  The common rail 1 in the embodiment of the present invention is provided with a so-called mechanical pressure limiting valve 10 in a return passage (not shown) for returning the surplus fuel to the tank 9. Therefore, when the rail pressure in the common rail 1 exceeds the predetermined pressure (opening pressure) set in the pressure limiting valve 10, the pressure limiting valve 10 is opened, and the fuel in the common rail 1 is returned to the low pressure side return passage. By discharging to the tank 9 via (not shown), the careless rise of the rail pressure is limited.

  The electronic control unit 4 includes, for example, a microcomputer (not shown) having a known and known configuration, and a storage element (not shown) such as a RAM and a ROM, and a fuel injection valve 2- A circuit (not shown) for energizing and driving 1 to 2-n, and a circuit (not shown) for energizing and driving the metering valve 6 and the like are configured as main components.

  The electronic control unit 4 receives not only a detection signal of the pressure sensor 11 for detecting the pressure of the common rail 1 but also various detection signals such as the engine speed, the accelerator opening, and the fuel temperature. It is input for use in control processing, high pressure pump discharge amount control processing in the embodiment of the present invention described later, and the like.

Next, the high pressure pump discharge amount control process in the embodiment of the present invention will be described with reference to FIGS. 2 to 4.
First, the basic processing procedure of the discharge amount calculation process of the high pressure pump 7 executed in the electronic control unit 4 will be described with reference to the functional block diagram of FIG.
The basic procedure of the high pressure pump discharge amount calculation process is the same as that of the prior art.
That is, the high-pressure pump discharge amount is obtained by adding the feedback control amount obtained based on the PID control to the pre-control amount.
The feedback control performed based on PID control so that the actual rail pressure becomes the target rail pressure is basically the same as that in the prior art.

The pre-control amount is to be a basic target discharge amount of the high pressure / high pressure pump 7 which is determined with respect to the instructed injection amount and the target engine speed. Here, the instructed injection amount and the target engine rotational speed are calculated in the injection control process or the like separately executed in the electronic control unit 4 as in the prior art.
The previous feedback control amount added to the pre-control amount compensates for the high-pressure pump discharge amount which is insufficient only with the above-mentioned pre-control amount in the state of the actual fuel injection operation.

The high-pressure pump discharge amount control process in the embodiment of the present invention differs in the calculation process of the pre-control amount from the conventional one, and will be described below with reference to FIGS. 3 and 4.
When the process by the electronic control unit 4 is started, the command injection amount is calculated (see step S100 in FIG. 4). The instructed injection amount is calculated based on the accelerator opening degree and the engine speed. The calculation method is basically the same as the conventional method.

Next, the control amount is calculated (see step S110 in FIG. 4).
Specifically, this control amount is the amount of dynamic leak occurring in the fuel injection valves 2-1 to 2-n.
The dynamic leak occurs in the configuration in which the fuel injection valves 2-1 to 2-n have a back pressure chamber for control of the seat and the lift relative to the valve seat surface of the needle valve.

That is, in the fuel injection valve, the back pressure chamber is provided to apply pressure to the rear end side of the needle valve, and by introducing the fuel, the needle valve is made to seat on the valve seat surface to close the injection hole. By leaking a part of the fuel in the back pressure chamber by back pressure control means such as an electromagnetic solenoid, the needle valve is lifted from the valve seat surface to open the injection holes.
Dynamic leak is a portion of the fuel that leaks from the back pressure chamber when lifting the needle valve from the valve seat surface as described above.

  The dynamic leak in the case where fuel injection is performed in, for example, three stages of pilot injection, main injection, and post injection is the total of the dynamic leaks generated in the respective injections.

  The dynamic leak differs depending on the specific specification of the vehicle, the engine rotation speed at that time, the target fuel injection amount, and the like. Therefore, in order to obtain the dynamic leak, for example, based on the test result and the simulation result, using the engine speed and the target fuel injection amount as input parameters, a map is used which can read out the corresponding dynamic leak amount. Is preferred.

Next, a unit fuel amount is calculated as the sum of the instructed injection amount and the control amount (see step S120 in FIG. 4).
The unit fuel amount thus calculated corresponds to the sum of the instructed injection amount and the dynamic leak in one injection by one cylinder.

Next, the total number of cylinders is calculated (see step S130 in FIG. 4).
Here, the total number of cylinders is the number of cylinders requiring fuel injection. In other words, it is the number of cylinders in which the fuel injection valve is in operation (the number of operating cylinders).

The total number of cylinders can be calculated in two ways as described below.
One is a method of obtaining by subtracting the number of fuel injection valves in the operation stop state from the total number of cylinders (see FIG. 3A). Here, the operation stop state of the fuel injection valve includes both the case where the operation is intentionally stopped from the viewpoint of fuel efficiency improvement and the like, and the case where the operation is stopped due to an electrical failure. .
Further, as a method of determining the number of operating cylinders, there is also a method of determining the number of fuel injection valves in an operating state, that is, the number of operating injection valves (see FIG. 3B).

  Although the number of fuel injection valves in the operating state and the number of fuel injection valves in the operation stop state are usually detected by the failure diagnosis process separately executed in the electronic control unit 4, which is detected Are often different depending on the specification of each vehicle. Therefore, it is preferable to determine which one of the above-described methods for calculating the total number of cylinders is to be used, in accordance with the content of the failure diagnosis process relating to the operation of the fuel injection valve.

Next, the pre-control amount is calculated (see step S140 in FIG. 4).
That is, the pre-control amount [mm3 / s] is the pre-control amount [mm3 / s] = unit fuel amount [mm3 / st] x total number of cylinders x (engine speed [rpm] / 60/2) + injector leak amount It is calculated as [mm3 / s].

Here, the reason why the engine speed is divided by 60 and 2 is to match the unit dimensions with other physical quantities.
Further, the injector leak amount is a so-called static leak and is the amount of fuel leaking from the sliding portion such as a needle valve. Such an injector leak amount may be zero depending on the structure of the fuel injection valves 2-1 to 2-n.
The injector leak amount can be calculated by a predetermined arithmetic expression based on the rail pressure and the fuel temperature, and also in the embodiment of the present invention, the value calculated by the arithmetic expression is used as in the conventional case. .

  As described above, in the high pressure pump discharge amount control process according to the embodiment of the present invention, unlike the conventional method, the number of cylinders corresponding to the fuel injection valve in the operating state is used to calculate the precontrol amount. Unnecessary fuel discharge by the pump 7 is prevented, and unnecessary increase of the rail pressure due to the excess fuel is surely prevented, and the further safety and reliability of the device are ensured.

  The present invention can be applied to a common rail fuel injection control device in which setting of an appropriate discharge amount of a high pressure pump is desired according to the operating state of an internal combustion engine.

1 ... common rail 3 ... engine 4 ... electronic control unit 7 ... high pressure pump

Claims (4)

The fuel of the fuel tank is pressurized and fed to the common rail by the high pressure pump, and it becomes possible to inject the high pressure fuel to the engine through the fuel injection valve connected to the common rail, and at least upstream of the high pressure pump A high-pressure pump discharge amount control method in a common rail fuel injection control device, comprising a valve, wherein the rail pressure of the common rail can be controlled by drive control of the metering valve.
The discharge amount of the high-pressure pump is determined based on a pre-control amount calculated based on the instructed injection amount and a feedback control amount obtained based on PID control.
The pre-control amount is obtained by multiplying the sum of the instructed injection amount determined based on the accelerator opening degree and the engine rotational speed and the dynamic leak of the fuel injection valve by the engine rotational speed and the number of cylinders, Calculated by adding the static leak of the fuel injection valve,
The high-pressure pump discharge amount control method, wherein the number of cylinders is set to a value obtained by subtracting the number of fuel injection valves in the operation stop state from the total number of cylinders.   Instead of setting the value obtained by subtracting the number of fuel injection valves in the operation stop state from the total number of cylinders as the number of cylinders, the number of fuel injection valves in the operation state is the number of cylinders. The high pressure pump discharge amount control method described. The fuel of the fuel tank is pressurized and fed to the common rail by the high pressure pump, and it becomes possible to inject the high pressure fuel to the engine through the fuel injection valve connected to the common rail, and at least upstream of the high pressure pump A common rail type fuel injection control device comprising a valve, wherein the control valve is driven and controlled by an electronic control unit to control the rail pressure of the common rail,
The electronic control unit
The pre-control amount is calculated based on the instructed injection amount, the feedback control amount is calculated based on the PID control, and the pre-control amount is added to the feedback control amount to calculate the discharge amount of the high pressure pump
The pre-control amount is obtained by multiplying the sum of the instructed injection amount determined based on the accelerator opening degree and the engine rotation speed and the dynamic leak of the fuel injection valve by the engine rotation speed and the number of cylinders, Calculated by adding the static leak of the fuel injection valve,
A common rail type fuel injection control device, wherein the number of cylinders is a value obtained by subtracting the number of fuel injection valves in the operation stop state from the total number of cylinders. The electronic control unit
Instead of setting the value obtained by subtracting the number of fuel injection valves in the operation stop state from the total number of cylinders as the number of cylinders, the number of fuel injection valves in the operation state is set as the number of cylinders. The common rail fuel injection control device according to claim 3, wherein

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