Patent Application
20180128188
This application is based on Japanese Patent Application No. 2015-106221 filed on May 26, 2015, the disclosure of which is incorporated herein by reference.
The present disclosure relates to a high-pressure pump control device applied to an internal combustion engine which supplies an injector with fuel discharged from a high-pressure pump.
In an in-cylinder injection internal combustion engine configured to inject fuel directly into a cylinder, a time from injection to combustion is short in comparison with an intake port injection internal combustion engine configured to inject fuel to an intake port. Hence, a time secured to atomize injected fuel is so short that it is necessary to turn injected fuel to fine particles by increasing an injection pressure to a high pressure. Accordingly, in the in-cylinder injection internal combustion engine, fuel pumped up from a fuel tank using an electric low-pressure pump is supplied to a high-pressure pump driven by power of the internal combustion engine, and high-pressure fuel discharged from the high-pressure pump is pressure-fed to an injector.
Generally, the in-cylinder injection internal combustion engine is provided with a fuel pressure sensor detecting a pressure of fuel (fuel pressure) supplied to the injector. A target fuel pressure is set according to an operating state of the internal combustion engine and a discharge quantity of the high-pressure pump is controlled by feedback in such a manner that an actual fuel pressure detected by the fuel pressure sensor coincides with the target fuel pressure.
In the in-cylinder injection internal combustion engine as above, a discharge quantity of the low-pressure pump is varied according to an operating state of the internal combustion engine as is described in Patent Literature 1. Hence, a discharge quantity of the low-pressure pump is restricted from becoming excessive for fuel consumption (that is, a fuel injection quantity) by varying a discharge quantity of the low-pressure pump in response to fuel consumption that varies with an operating state of the internal combustion engine. Wasteful power consumption by the low-pressure pump is thus restricted.
In the in-cylinder injection internal combustion engine, the target fuel pressure tends to be set to a higher fuel pressure as a rotation speed and a load of the internal combustion engine are increased with an aim of increasing a dynamic range of the injector and improving atomization of injected fuel. Meanwhile, the low-pressure pump tends to reduce a margin of discharge performance with an aim of saving energy and restricting a rise in fuel temperature (that is, reducing an evaporation gas). Hence, a discharge quantity of the high-pressure pump may temporarily exceed a discharge quantity of the low-pressure pump, for example, in a process of fuel pressure rising when transition from a low-load low-fuel pressure state to a high-load high-fuel pressure state is taking place while the internal combustion engine is rotating at a high speed due to an increase in fuel consumption for a high load or an increase in fuel consumption for raising a pressure. When a discharge quantity of the high-pressure pump exceeds a discharge quantity of the low-pressure pump, a pressure of fuel supplied to the high-pressure pump decreases, in which case cavitation erosion (that is, damage caused when air bubbles are formed and burst) occurs inside the high-pressure pump when a fuel temperature is high. Hence, the high-pressure pump is likely to have a shorter life.
An object of the present disclosure is to provide a high-pressure pump control device applied to an internal combustion engine which can extend a life of a high-pressure pump by preventing or restricting cavitation erosion occurring inside the high-pressure pump.
According to an aspect of the present disclosure, the high-pressure pump control device is applied to the internal combustion engine including a high-pressure pump supplied with fuel discharged from a low-pressure pump and an injector supplied with fuel discharged from the high-pressure pump. The high-pressure pump control device includes a prediction unit predicting whether a discharge quantity of the high-pressure pump exceeds a discharge quantity of the low-pressure pump and a restricting unit executing a discharge quantity restriction control to restrict a discharge quantity of the high-pressure pump not to exceed a predetermined value when the prediction unit predicts that a discharge quantity of the high-pressure pump exceeds a discharge quantity of the low-pressure pump.
According to the configuration as above, when it is predicted that a discharge quantity of the high-pressure pump exceeds a discharge quantity of the low-pressure pump, a discharge quantity of the high-pressure pump can be restricted not to exceed a predetermined value by executing the discharge quantity restriction control. Hence, cavitation erosion occurring inside the high-pressure pump can be prevented or restricted by preventing or restricting a discharge quantity of the high-pressure pump from exceeding a discharge quantity of the low-pressure pump. Consequently, a life of the high-pressure pump can be extended.
The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:
Hereinafter, the present disclosure will be described by some specific embodiments.
A first embodiment of the present disclosure will now be described according to
Firstly, a schematic configuration of a fuel supply system of an in-cylinder injection engine (internal combustion engine) will be described according to
As is shown in
As is shown in
The fuel pressure control valve 23 is energized under control in such a manner that the fuel pressure control valve 23 opens and fuel is drawn into the pump chamber 18 in an intake stroke of the high-pressure pump 14 (when the plunger 19 moves downward), whereas the fuel pressure control valve 23 closes and fuel in the pump chamber 18 is discharged in a discharge stroke of the high-pressure pump 14 (when the plunger 19 moves upward).
A fuel pressure (pressure of fuel) is controlled by controlling a discharge quantity of the high-pressure pump 14 by controlling a valve-closing period of the fuel pressure control valve 23 by controlling energization start timing of the fuel pressure control valve 23. For example, when a fuel pressure is raised, a discharge quantity of the high-pressure pump 14 is increased by extending a valve-closing period of the fuel pressure control valve 23 by advancing the valve-closing start timing of the fuel pressure control valve 23 by advancing energization start timing of the fuel pressure control valve 23. Conversely, when a fuel pressure is lowered, a discharge quantity of the high-pressure pump 14 is reduced by shortening the valve-closing period of the fuel pressure control valve 23 by lagging the valve-closing start timing of the fuel pressure control valve 23 by lagging energization start timing of the fuel pressure control valve 23.
Meanwhile, a check valve 25 preventing a backflow of discharged fuel is provided on a side of a discharge port 24 of the high-pressure pump 14. As is shown in
A fuel pressure sensor 29 detecting a fuel pressure in a high-pressure fuel passage, such as the high-pressure fuel pipe 26 and the delivery pipe 27, is provided to the high-pressure fuel pipe 26 (or the delivery pipe 27). The delivery pipe 27 may be provided with a relief valve (not shown) which opens when a fuel pressure in the high-pressure fuel passage rises above a predetermined upper-limit value to connect an exhaust port of the relief valve to the fuel tank 11 (or the fuel pipe 13 on a low-pressure side) via a relief pipe.
The engine is provided with an air flowmeter 30 detecting an intake air quantity and a crank angle sensor 31 outputting a pulse signal for every predetermined crank angle in synchronization with a rotation of a crank shaft (not shown). A crank angle and an engine speed are detected according to an output signal of the crank angle sensor 31.
Outputs of the various sensors described above are inputted into an electronic control unit (ECU) 32. The ECU 32 is chiefly formed of a micro-computer and controls a fuel injection quantity, ignition timing, and a throttle opening degree (intake air quantity) according to an engine operating state by running various engine control programs pre-stored in an internal ROM (storage medium). In the present embodiment, the ECU 32 corresponds to a high-pressure pump control device for the internal combustion engine.
The ECU 32 functions also as a fuel pressure control unit and executes a fuel pressure control to control a fuel pressure by controlling a discharge quantity of the high-pressure pump 14 by controlling valve-closing start timing of the fuel pressure control valve 23 by controlling energization start timing of the fuel pressure control valve 23. The ECU 32 calculates an F/B control quantity according to a deviation of an actual fuel pressure detected by the fuel pressure sensor 29 from a target fuel pressure, and executes a fuel pressure F/B control to correct a discharge quantity of the high-pressure pump 14 by using the calculated F/B control quantity. Herein, “F/B” stands for feedback. Hence, the F/B control quantity is the feedback control quantity when written in a complete form.
More specifically, as is shown in
The ECU 32 also calculates a target fuel pressure according to an engine operating state (for example, an engine speed or an engine load) by using a map or the like and reads out an actual fuel pressure detected by the fuel pressure sensor 29. Subsequently, a feedback control unit 34 calculates a deviation of the actual fuel pressure from the target fuel pressure as a fuel pressure deviation and calculates an F/B control quantity according to the fuel pressure deviation by a PI control, a PID control, or the like. For example, in the PI control, the feedback control unit 34 calculates a proportional term by using the fuel pressure deviation and a proportional gain as well as an integral term by using the fuel pressure deviation and an integral gain, and calculates the F/B control quantity by using the proportional term and the integral term.
Subsequently, a control quantity calculation unit 35 calculates a control quantity of the high-pressure pump 14 (that is, energization start timing of the fuel pressure control valve 23) in accordance with Equation (1) below by using the F/F control quantity and the F/B control quantity.
high-pressure pump control quantity=F/F control quantity+F/B control quantity Equation (1)
When a discharge quantity of the high-pressure pump 14 exceeds a discharge quantity of the low-pressure pump 12, a pressure of fuel supplied to the high-pressure pump 14 decreases. In such a case, cavitation erosion (that is, damage caused when air bubbles are formed and burst) occurs inside the high-pressure pump 14 when a fuel temperature is high. Hence, the high-pressure pump 14 is likely to have a shorter life.
In order to prevent such an inconvenience, the ECU 32 executes a control as follows by executing a routine of
The following will describe a processing content of an F/B control quantity calculation routine of
The F/B control quantity calculation routine shown in
fuel pressure deviation=target fuel pressure−actual fuel pressure Equation (2)
Subsequently, advancement is made to 102, in which a proportional term [° CA] is found by multiplying the fuel pressure deviation by a proportional gain as is expressed by Equation (3) as follows.
proportional term=fuel pressure deviation×proportional gain Equation (3)
Subsequently, advancement is made to 103, in which engine fuel consumption quantity per rotation [mm3/str] is calculated according to an engine load (for example, an intake air quantity or an intake air pressure), and a difference between a low-pressure pump discharge quantity (for example, a maximum value) and the engine fuel consumption quantity is calculated as a pressure rising fuel quantity [mm3/str] in accordance with Equation (4) as follows.
pressure rising fuel quantity=low-pressure pump discharge quantity−engine fuel consumption quantity Equation (4)
Subsequently, advancement is made to 104, in which a high-pressure pump discharge quantity gradient corresponding to an engine speed [rpm] and the target fuel pressure (or the actual fuel pressure) [MPa] is calculated with reference to a map of a high-pressure pump discharge quantity gradient [mm3/° CA]. The map of the high-pressure pump discharge quantity gradient is preliminarily created according to test data, design data, and so on and pre-stored in the ROM of the ECU 32.
Subsequently, advancement is made to 105, in which a proportional term guard value [° CA] is found by dividing the pressure rising fuel quantity by the high-pressure pump discharge quantity gradient as is expressed by Equation (5) as follows.
proportional term guard value=pressure rising fuel quantity/high-pressure pump discharge quantity gradient Equation (5)
The proportional term guard value is set to a value corresponding to a proportional term, with which the F/B control quantity making a discharge quantity of the high-pressure pump 14 and a discharge quantity (for example, a maximum value) of the low-pressure pump 12 equal is calculated.
Subsequently, advancement is made to 106, in which a prediction is made as to whether a discharge quantity of the high-pressure pump 14 exceeds a discharge quantity of the low-pressure pump 12 depending on whether the proportional term calculated in 102 is equal to or greater than the proportional term guard value.
When it is determined in 106 that the proportional term is smaller than the proportional term guard value, it is predicted that a discharge quantity of the high-pressure pump 14 does not exceed a discharge quantity of the low-pressure pump 12. Hence, the proportional term calculated in 102 is adopted intact.
Meanwhile, when it is determined in 106 that the proportional term is equal to or greater than the proportional term guard value, it is predicted that a discharge quantity of the high-pressure pump 14 exceeds a discharge quantity of the low-pressure pump 12 unless a discharge quantity of the high-pressure pump 14 is restricted. Hence, advancement is made to 107, in which the proportional term is restricted with the proportional term guard value as is expressed by Equation (6) as follows.
proportional term=proportional term guard value Equation (6)
Subsequently, advancement is made to 108, in which an integral term [° CA] at a present time is calculated in accordance with Equation (7) below using the fuel pressure deviation, an integral gain, and a last integral term (i−1).
integral term=integral term (i−1)+fuel pressure deviation×integral gain Equation (7)
Subsequently, advancement is made to 109, in which an F/B control quantity [° CA] is calculated in accordance with Equation (8) below using the proportional term and the integral term, and the routine is ended.
F/B control quantity=proportional term+integral term Equation (8)
According to the processing as above, when it is predicted that a discharge quantity of the high-pressure pump 14 exceeds a discharge quantity of the low-pressure pump 12, the discharge quantity restriction control is executed by restricting the F/B control quantity by restricting the proportional term of the F/B control quantity with the proportional term guard value.
In the first embodiment shown in
In the first embodiment, the discharge quantity restriction control is executed by restricting the F/B control quantity. In a system where a fuel pressure F/B control is executed, when a fuel pressure deviation increases with an increase in target fuel pressure, the F/B control quantity and hence a discharge quantity of the high-pressure pump 14 increase, too. Accordingly, by restricting the F/B control quantity, the discharge quantity restriction control can be executed by restricting a discharge quantity of the high-pressure pump 14 easily in a reliable manner.
A second embodiment of the present disclosure will now be described using
In the second embodiment, the ECU 32 executes an F/B control quantity calculation routine of
In the F/B control quantity calculation routine of
Subsequently, advancement is made to 202, in which engine fuel consumption quantity per hour [L/hr] is calculated according to an engine speed [rpm] and an engine load (for example, an intake air quantity or an intake air pressure), and a fuel pressure deviation guard value corresponding to the engine speed and the engine fuel consumption quantity is calculated with reference to a map of the fuel pressure deviation guard value [MPa]. The map of the fuel pressure deviation guard value is preliminary created according to test data, design data, and so on and pre-stored in a ROM of the ECU 32. The fuel pressure deviation guard value is set to a value corresponding to a fuel pressure deviation, with which an F/B control quantity making a discharge quantity of the high-pressure pump 14 and a discharge quantity (for example, a maximum value) of the low-pressure pump 12 equal is calculated.
Subsequently, advancement is made to 203, in which a prediction is made as to whether a discharge quantity of the high-pressure pump 14 exceeds a discharge quantity of the low-pressure pump 12 depending on whether the fuel pressure deviation calculated in 201 is equal to or greater than the fuel pressure deviation guard value.
When it is determined in 203 that the fuel pressure deviation is smaller than the fuel pressure deviation guard value, it is predicted that a discharge quantity of the high-pressure pump 14 does not exceed a discharge quantity of the low-pressure pump 12. Hence, the fuel pressure deviation calculated in 201 is adopted intact.
Meanwhile, when it is determined in 203 that the fuel pressure deviation is equal to or greater than the fuel pressure deviation guard value, it is predicted that a discharge quantity of the high-pressure pump 14 exceeds a discharge quantity of the low-pressure pump 12 unless a discharge quantity of the high-pressure pump 14 is restricted. Hence, advancement is made to 204, in which a fuel pressure deviation is restricted with the fuel pressure deviation guard value as is expressed by Equation (9) as follows.
fuel pressure deviation=fuel pressure deviation guard value Equation (9)
Subsequently, advancement is made to 205, in which a proportional term [° CA] is found by multiplying the fuel pressure deviation by a proportional gain as is expressed by Equation (3) above. Subsequently, advancement is made to 206, in which an integral term [° CA] at a present time is calculated in accordance with Equation (7) above using the fuel pressure deviation, an integral gain, and a last integral term (i−1).
Subsequently, advancement is made to 207, in which an F/B control quantity [° CA] is calculated in accordance with Equation (8) above using the proportional term and the integral term, and the routine is ended.
According to the processing described above, when it is predicted that a discharge quantity of the high-pressure pump 14 exceeds a discharge quantity of the low-pressure pump 12, the discharge quantity restriction control is executed by restricting an F/B control quantity by restricting a fuel pressure deviation used to calculate the F/B control quantity with the fuel pressure deviation guard value.
In the second embodiment, as is shown in
A third embodiment of the present disclosure will now be described using
In the third embodiment, the ECU 32 executes an F/B control quantity calculation routine of
In the F/B control quantity calculation routine of
Subsequently, advancement is made to 302, in which a target fuel pressure guard value [MPa] is found by adding the target fuel pressure guard correction value to an actual fuel pressure as is expressed by Equation (10) as follows.
target fuel pressure guard value=actual fuel pressure+target fuel pressure guard correction value Equation (10)
The target fuel pressure guard value is set to a value corresponding to a target fuel pressure, with which an F/B control quantity making a discharge quantity of the high-pressure pump 14 and a discharge quantity (for example, a maximum value) of the low-pressure pump 12 equal is calculated.
Subsequently, advancement is made to 303, in which a prediction is made as to whether a discharge quantity of the high-pressure pump 14 exceeds a discharge quantity of the low-pressure pump 12 depending on whether the target fuel pressure is equal to or greater than the target fuel pressure guard value.
When it is determined in 303 that the target fuel pressure is smaller than the target fuel pressure guard value, it is predicted that a discharge quantity of the high-pressure pump 14 does not exceed a discharge quantity of the low-pressure pump 12 and a present target fuel pressure is adopted intact.
Meanwhile, when it is determined in 303 that the target fuel pressure is equal to or greater than the target fuel pressure guard value, it is predicted that a discharge quantity of the high-pressure pump 14 exceeds a discharge quantity of the low-pressure pump 12 unless a discharge quantity of the high-pressure pump 14 is restricted. Accordingly, advancement is made to 304, in which the target fuel pressure is restricted with the target fuel pressure guard value as is expressed by Equation (11) as follows.
target fuel pressure=target fuel pressure guard value Equation (11)
Subsequently, advancement is made to 305, in which a deviation of an actual fuel pressure from the target fuel pressure is calculated as a fuel pressure deviation [MPa] in accordance with Equation (2) above.
Subsequently, advancement is made to 306, in which a proportional term [° CA] is found by multiplying the fuel pressure deviation by a proportional gain as is expressed by Equation (3) above. Subsequently, advancement is made to 307, in which an integral term [° CA] at a present time is calculated in accordance with Equation (7) above using the fuel pressure deviation, an integral gain, and a last integral term (i−1).
Subsequently, advancement is made to 308, in which an F/B control quantity [° CA] is calculated in accordance with Equation (8) above using the proportional term and the integral term, and the routine is ended.
According to the processing described above, when it is predicted that a discharge quantity of the high-pressure pump 14 exceeds a discharge quantity of the low-pressure pump 12, the discharge quantity restriction control is executed by restricting an F/B control quantity by restricting a target fuel pressure with the target fuel pressure guard value.
In the third embodiment, as is shown in
At least any two of the first to third embodiments above may be combined to perform the discharge quantity restriction control by restricting the F/B control quantity by restricting at least any two of the proportional term, the fuel pressure deviation, and the target fuel pressure with the corresponding guard values.
In the first to third embodiments above, the F/B control quantity is restricted indirectly by restricting, respectively, the proportional term, the fuel pressure deviation, and the target fuel pressure with the corresponding guard values. However, the discharge quantity restriction control may be executed by restricting the F/B control quantity with a guard value. Alternatively, the discharge quantity restriction control may be executed by restricting an F/F control quantity or a control quantity of the high-pressure pump 14 (that is, energization start timing of the fuel pressure control valve 23) with a corresponding guard value.
In the first to third embodiments above, a discharge quantity of the high-pressure pump 14 is restricted not to exceed a discharge quantity of the low-pressure pump 12 during the discharge quantity restriction control. However, the present disclosure is not limited to the restriction in the manner as above. For example, a discharge quantity of the high-pressure pump 14 may be restricted not to exceed a predetermined value slightly greater than a discharge quantity of the low-pressure pump 12 or a discharge quantity of the high-pressure pump 14 may be restricted not to exceed a predetermined value slightly smaller than a discharge quantity of the low-pressure pump 12.
In the first to third embodiments above, functions executed by the ECU 32, either in part or as a whole, may be realized by hardware as a single or two or more ICs or the like.
While the present disclosure has been described with reference to embodiments thereof, it is to be understood that the disclosure is not limited to the embodiments and constructions. The present disclosure is intended to cover various modification and equivalent arrangements. In addition, while the various combinations and configurations, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-106221 | May 2015 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/002252 | 5/7/2016 | WO | 00 |
