Internal combustion engine system

Abstract

The present invention provides an internal combustion engine system that makes it possible to enhance responsiveness and stability of control relating to downstream-side pressure of a high-pressure fuel pump. A control device of the internal combustion engine system calculates a flow rate target value of a high-pressure fuel pump on the basis of a pressure deviation between a pressure target value of fuel and a pressure detection value detected by a pressure sensor, calculates a flow rate limit value on the basis of the pressure deviation and a variation thereof, selects, as a flow rate control value, the smaller value among the flow rate target value and the flow rate limit value, and controls an open / close valve of the high-pressure fuel pump in accordance with the flow rate control value. The control device calculates the adjustment amount by multiplying the difference between the flow rate target value and the flow rate control value by the reciprocal of a proportional gain, uses the restriction amount to restrict the adjustment amount, calculates an adjustment value of the pressure deviation by subtracting the restricted adjustment amount from the pressure deviation, and calculates the flow rate target value by adding an integral term, which is obtained by integrating the adjustment value of the pressure deviation and multiplying the integrated adjustment value by an integral gain, and a proportional term, which is obtained by multiplying the pressure deviation by the proportional gain.

Description

Internal combustion engine system

[0001] The present invention relates to internal combustion engine systems.

[0002] Patent Document 1 discloses an internal combustion engine system that includes a high-pressure fuel pump that supplies high-pressure fuel to the internal combustion engine, a pressure sensor that detects the pressure of the fuel downstream of the high-pressure fuel pump, and a control device that controls the high-pressure fuel pump based on the pressure detected by the pressure sensor.

[0003] The high-pressure fuel pump has a pressurizing chamber for pressurizing the fuel and an electromagnetic valve located upstream of the pressurizing chamber. The discharge flow rate of the high-pressure fuel pump is variable by adjusting the opening and closing timing of the valve.

[0004] The control device calculates a target flow rate of the high-pressure fuel pump based on a pressure deviation between a target fuel pressure and a pressure detected by a pressure sensor. Specifically, the control device calculates an integral term based on the pressure deviation, calculates a proportional term based on the pressure deviation, and calculates the target flow rate by adding the integral term and the proportional term. The control device then controls the opening and closing timing of the on-off valve based on the target flow rate.

[0005] When the pressure deviation changes suddenly due to a sudden change in the pressure target value, the control device prohibits calculation of the integral term and fixes the integral term (anti-windup processing). This prevents the detected pressure value from significantly exceeding the pressure target value, thereby improving the stability of control of the pressure downstream of the high-pressure fuel pump.

[0006] Japanese Patent Application Laid-Open No. 2007-032322

[0007] In the conventional technology described in Patent Document 1, when a pressure target value changes suddenly and the pressure deviation changes suddenly, the integral term is fixed to improve the stability of the control related to the downstream pressure of the high-pressure fuel pump. However, there is room for improvement in terms of improving the responsiveness of the control.

[0008] Furthermore, when the integral term is fixed, pressure oscillations (in other words, repeated increases and decreases in pressure) may occur depending on conditions such as the fuel temperature, etc. Therefore, there is room for improvement in terms of further improving the stability of control.

[0009] An object of the present invention is to provide an internal combustion engine system that can improve the response and stability of control related to the downstream pressure of a high-pressure fuel pump.

[0010] In order to achieve the above object, the present invention provides an internal combustion engine system comprising: a high-pressure fuel pump having a pressurizing chamber that pressurizes fuel and an on-off valve arranged upstream of the pressurizing chamber, and supplying fuel pressurized in the pressurizing chamber to an internal combustion engine; a pressure sensor that detects the pressure of fuel downstream of the high-pressure fuel pump; and a control device that calculates a target flow rate value of the high-pressure fuel pump based on a pressure deviation between a target fuel pressure value and a pressure detection value detected by the pressure sensor, calculates a flow rate limit value based on the pressure deviation and a change amount thereof, selects the smaller of the target flow rate value and the flow rate limit value as a flow rate control value, and controls the on-off valve in accordance with the flow rate control value, wherein the control device calculates an adjustment amount by multiplying a difference between the target flow rate value and the flow rate control value by a reciprocal of a proportional gain, limits the adjustment amount by a limit amount, calculates an adjustment value of the pressure deviation by subtracting the limited adjustment amount from the pressure deviation, and calculates the target flow rate value by adding an integral term obtained by integrating the adjustment value of the pressure deviation and multiplying it by an integral gain to a proportional term obtained by multiplying the pressure deviation by the proportional gain.

[0011] According to the present invention, it is possible to improve the response and stability of control relating to the downstream pressure of the high-pressure fuel pump.

[0012] It is a schematic diagram showing the configuration of a main part of an internal combustion engine system according to one embodiment of the present invention. It is a block diagram showing the functional configuration of a control device according to one embodiment of the present invention together with related devices. It is a diagram showing a correction amount map used in calculating a flow rate limit value according to one embodiment of the present invention. It is a diagram showing changes over time in a pressure target value, a pressure detection value, a flow rate control value, and an actual flow rate in a comparative example. It is a diagram showing changes over time in a pressure target value, a pressure detection value, a flow rate control value, and an actual flow rate according to one embodiment of the present invention.

[0013] An embodiment of the present invention will be described with reference to the drawings.

[0014] FIG. 1 is a schematic diagram showing the configuration of the main parts of an internal combustion engine system according to this embodiment.

[0015] The internal combustion engine system of this embodiment is mounted on a vehicle (not shown) and includes an internal combustion engine 1 , a fuel system 2 , and a control device 3 .

[0016] The internal combustion engine 1 includes a plurality of cylinders (not shown), a plurality of intake valves (not shown) that draw air from an intake system (not shown) into the plurality of cylinders, a plurality of fuel injection valves 4 arranged upstream or downstream of the plurality of intake valves and that inject fuel from a fuel system 2, a plurality of spark plugs (not shown) that ignite the fuel drawn into the plurality of cylinders together with the air, thereby burning the fuel and air, a plurality of exhaust valves (not shown) that discharge combustion gas from the plurality of cylinders to an exhaust system (not shown), a plurality of pistons (not shown) that reciprocate due to the expansion of the combustion gas in the plurality of cylinders, and a crankshaft (not shown) that rotates due to the reciprocating motion of the plurality of pistons. The intake valves and exhaust valves open and close in conjunction with the crankshaft.

[0017] The intake system has a throttle valve (not shown) whose opening is variable in accordance with the amount of depression of an accelerator pedal 5, and the flow rate of air supplied to the internal combustion engine 1 is varied depending on the opening of the throttle valve. The amount of depression of the accelerator pedal 5 is detected by an accelerator sensor 6 and output to the control device 3.

[0018] The fuel system 2 includes a fuel tank 7 that stores fuel, a low-pressure fuel pump 8 that pumps out the fuel from the fuel tank 7, a high-pressure fuel pump 9 that pressurizes the fuel from the low-pressure fuel pump 8, and a common rail 10 that distributes the fuel from the high-pressure fuel pump 9 to the plurality of fuel injection valves 4. The pressure of the fuel downstream of the high-pressure fuel pump 9 (the common rail 10 in this embodiment) is detected by a pressure sensor 11 and output to the control device 3.

[0019] The high-pressure fuel pump 9 has a pressurized chamber 14 formed in a cylinder 12 and whose volume changes with the reciprocating motion of a plunger 13, an electromagnetic on-off valve 15 arranged upstream of the pressurized chamber 14, a pressure pulsation reducer 16 arranged upstream of the on-off valve 15, and a check valve 17 arranged downstream of the pressurized chamber 14.

[0020] The plunger 13 is reciprocated by a cam mechanism (not shown) that operates in conjunction with the crankshaft. This cam mechanism has a camshaft that rotates in conjunction with the crankshaft, and an eccentric cam that is attached to the camshaft and causes the plunger 13 to reciprocate. The rotation angle of the camshaft that corresponds to the phase (reciprocating position) of the plunger 13 is detected by a cam angle sensor (not shown) and output to the control device 3.

[0021] When the on-off valve 15 is open and the plunger 13 moves to one side, increasing the volume of the pressurization chamber 14, fuel is drawn into the pressurization chamber 14. When the on-off valve 15 is closed and the plunger 13 moves to the other side, decreasing the volume of the pressurization chamber 14, the fuel in the pressurization chamber 14 is pressurized. Thereafter, when the pressure upstream of the check valve 17 becomes higher than the pressure downstream by a predetermined value or more, the pressurized fuel in the pressurization chamber 14 is discharged. The discharge flow rate of the high-pressure fuel pump 9 can be varied by controlling the opening and closing timing of the on-off valve 15.

[0022] Although not shown, the control device 3 has a processor that executes processing according to a program and a memory that stores the program and data. The control device 3 controls the fuel injection valve 4 to control the fuel injection timing. The control device 3 also controls the on-off valve 15 of the high-pressure fuel pump 9 to control the flow rate of fuel supplied to the internal combustion engine 1.

[0023] The control of the on-off valve 15 of the high-pressure fuel pump 9 in this embodiment will be described with reference to Fig. 2. Fig. 2 is a block diagram showing the functional configuration of the control device in this embodiment together with related devices.

[0024] The control device 3 has, as functional components related to the control of the on-off valve 15 of the high-pressure fuel pump 9, a pressure target value calculation unit 21, a pressure deviation calculation unit 22, a flow rate target value calculation unit 23, a flow rate limit value calculation unit 24, a flow rate control value acquisition unit 25, an on-off valve control unit 26, an adjustment amount calculation unit 27, and an adjustment amount limiting unit 28.

[0025] The pressure target value calculation unit 21 calculates a fuel pressure target value Pt based on the amount of operation of the accelerator pedal 5 detected by the accelerator sensor 6 (i.e., the air flow rate corresponding to the opening of the throttle valve).

[0026] The pressure deviation calculation unit 22 calculates a pressure deviation ΔP between the pressure target value Pt calculated by the pressure target value calculation unit 21 and the pressure detection value Pd detected by the pressure sensor 11 .

[0027] The flow rate target value calculation unit 23 calculates a flow rate target value Qt of the high-pressure fuel pump 9 based on the pressure deviation ΔP calculated by the pressure deviation calculation unit 22 (more specifically, so that the pressure deviation ΔP becomes zero).

[0028] The flow rate limit value calculation unit 24 obtains a flow rate upper limit value Qmax for the high-pressure fuel pump 9 based on the rotation speed of the internal combustion engine 1 detected by a rotation speed sensor (not shown) and the battery voltage detected by a voltage sensor (not shown). The flow rate limit value calculation unit 24 also calculates a change amount of the pressure deviation (more specifically, a change amount per unit time, or a change rate) dΔP from the history of the pressure deviation ΔP calculated by the pressure deviation calculation unit 22, and obtains a correction amount L based on the pressure deviation ΔP and the change amount dΔP. The flow rate limit value Ql is then calculated by subtracting the correction amount L from the flow rate upper limit value Qmax.

[0029] A case will be described where the correction amount L is obtained using the correction amount map shown in Fig. 3. When the pressure deviation ΔP exceeds a predetermined value A (for example, A = 0.368 when converted into the ratio between the pressure deviation ΔP and the target pressure value Pt), the flow rate limit value calculation unit 24 obtains the correction amount L = 0. On the other hand, when the pressure deviation ΔP is equal to or less than the predetermined value A, the flow rate limit value calculation unit 24 obtains the correction amount L = La or the correction amount L = Lb depending on the combination of the pressure deviation ΔP and its change amount dΔP. That is, the smaller the pressure deviation ΔP, the smaller the threshold B for the change amount dΔP of the pressure deviation is. When the change amount dΔP of the pressure deviation exceeds the threshold B, the correction amount L = La (where La > 0) is obtained, and when the change amount dΔP of the pressure deviation is equal to or less than the threshold B, the correction amount L = Lb (where La > Lb > 0) is obtained.

[0030] The flow rate control value acquisition unit 25 selects the smaller of the flow rate target value Qt calculated by the flow rate target value calculation unit 23 and the flow rate limit value Ql calculated by the flow rate limit value calculation unit 24 as the flow rate control value Qc.

[0031] The on-off valve control unit 26 controls the opening and closing timing of the on-off valve 15 based on the flow rate control value Qc acquired by the flow rate control value acquisition unit 25. More specifically, the on-off valve control unit 26 calculates a current distribution start phase and a current distribution end phase based on the flow rate control value Qc, and acquires a current distribution start angle and a current distribution amount angle corresponding to the current distribution start phase and the current distribution end phase. Then, when the rotation angle detected by the cam angle sensor becomes the current distribution start angle, the on-off valve 15 starts to be energized, and the on-off valve 15 is opened. Thereafter, when the rotation angle detected by the cam angle sensor becomes the current distribution end angle, the on-off valve 15 stops being energized, and the on-off valve 15 is closed.

[0032] The adjustment amount calculation unit 27 and the adjustment amount limiting unit 28 are for performing anti-windup processing when the flow rate control value Qc is limited (in other words, when the flow rate control value Qc is smaller than the target flow rate value Qt).

[0033] The adjustment amount calculation unit 27 calculates the adjustment amount by multiplying the difference between the flow rate target value Qt calculated by the flow rate target value calculation unit 23 and the flow rate control value Qc acquired by the flow rate control value acquisition unit 25 by the reciprocal of a predetermined proportional gain. The adjustment amount limiting unit 28 limits the adjustment amount by selecting the smaller of the adjustment amount calculated by the adjustment amount calculation unit 27 and a predetermined limiting amount.

[0034] The flow rate target value calculation unit 23 calculates an adjustment value ΔP' of the pressure deviation by subtracting the adjustment amount limited by the adjustment amount limiting unit 28 from the pressure deviation ΔP calculated by the pressure deviation calculation unit 22 (however, if the flow rate control value Qc is not limited, ΔP' = ΔP).The flow rate target value calculation unit 23 then calculates the flow rate target value Qt by adding together an integral term obtained by integrating the adjustment value ΔP' of the pressure deviation and multiplying it by a predetermined integral gain, and a proportional term obtained by multiplying the pressure deviation ΔP by a predetermined proportional gain.

[0035] Next, the effects of this embodiment will be described using a comparative example (specifically, a case in which the flow rate control value Qc is limited to the flow rate upper limit value Qmax and anti-windup processing is not performed). Fig. 4 is a diagram showing changes over time in the pressure target value, the detected pressure value, the flow rate target value, and the actual flow rate in the comparative example. Fig. 5 is a diagram showing changes over time in the pressure target value, the detected pressure value, the flow rate target value, and the actual flow rate in this embodiment.

[0036] Assume that the pressure target value Pt suddenly increases stepwise at time t0, causing the flow rate target value Qt to increase. The control device of the comparative example selects the smaller of the flow rate target value Qt and the flow rate upper limit value Qmax as the flow rate control value Qc, and controls the on-off valve of the high-pressure fuel pump in accordance with this flow rate control value Qc. Therefore, as shown in FIG. 3 , the actual flow rate Qd of the high-pressure fuel pump increases and exceeds the flow rate upper limit value Qmax. This also increases the pressure detection value Pd, causing an overshoot in which the pressure detection value Pd significantly exceeds the pressure target value Pt. Furthermore, although not shown, pressure oscillations may occur depending on conditions such as the fuel temperature.

[0037] On the other hand, the control device 3 of this embodiment calculates the flow rate limit value Ql based on the pressure deviation ΔP and its change amount dΔP, selects the smaller of the flow rate target value Qt and the flow rate limit value Ql as the flow rate control value Qc, and controls the on-off valve 15 of the high-pressure fuel pump 9 in accordance with this flow rate control value Qc. As shown in FIG. 4 , between time t0 and time t1, the pressure deviation ΔP exceeds the predetermined value A, so the correction amount L=0, and the flow rate limit value Ql=the flow rate upper limit value Qmax. At time t1, the pressure deviation ΔP is equal to or less than the predetermined value A and the change amount dΔP of the pressure deviation exceeds the threshold value B, so the correction amount L=La, and the flow rate limit value Ql=Qla (=Qmax−La). In other words, at time t1, the flow rate control value Qc is limited to the flow rate limit value Qla, which is smaller than the flow rate upper limit value Qmax. Therefore, an increase in the actual flow rate Qd of the high-pressure fuel pump 9 is suppressed, and the actual flow rate Qd does not exceed the flow rate upper limit value Qmax. This suppresses an increase in the pressure detection value Pd and prevents overshooting, thereby improving the stability of control over the pressure downstream of the high-pressure fuel pump 9.

[0038] At time t2, the pressure deviation ΔP is equal to or less than the predetermined value A and the amount of change dΔP in the pressure deviation is equal to or less than the threshold value B, so the correction amount L=Lb (where Lb<La) and the flow rate limit value Ql=Qlb (=Qmax-Lb). That is, at time t2, the flow rate control value Qc is limited to the flow rate limit value Qlb, which is smaller than the flow rate upper limit value Qmax and larger than the flow rate limit value Qla. Therefore, an excessive decrease in the actual flow rate Qd of the high-pressure fuel pump 9 is suppressed. This also suppresses an excessive decrease in the pressure detection value Pd. Therefore, the responsiveness of the control related to the downstream pressure of the high-pressure fuel pump 9 can be improved.

[0039] Furthermore, in calculating the flow rate target value Qt, the control device 3 of this embodiment adjusts the pressure deviation using an adjustment amount obtained by multiplying the difference between the flow rate target value Qt and the flow rate control value Qc by the reciprocal of the proportional gain, and calculates the integral term using the adjustment value of the pressure deviation (in other words, performs anti-windup processing). This makes it possible to further prevent overshooting of the pressure downstream of the high-pressure fuel pump 9. Furthermore, the control device 3 of this embodiment limits the above-mentioned adjustment amount by a limit amount. This makes it possible to avoid pressure oscillations and further improve the stability of control.

[0040] In the above embodiment, the adjustment amount limiting unit 28 of the control device 3 has been described with reference to a case where the limiting amount is fixed, but the present invention is not limited to this and the limiting amount may be variable. That is, the adjustment amount limiting unit 28 of the control device 3 may vary the limiting amount in accordance with the pressure deviation ΔP (for example, so that the limiting amount decreases as the pressure deviation ΔP increases). This can enhance the effect of suppressing pressure fluctuations.

[0041] In the above embodiment, the flow rate target value calculation unit 23 of the control device 3 uses fixed integral gains and proportional gains, but this is not limiting and the integral gains and proportional gains may be variable. That is, the flow rate target value calculation unit 23 of the control device 3 may vary the integral gain and proportional gain according to the pressure deviation ΔP (for example, so that the integral gain and proportional gain decrease as the pressure deviation ΔP increases). This can enhance the effect of suppressing pressure oscillations.

[0042] In the above embodiment, the flow rate target value calculation unit 23 of the control device 3 calculates the flow rate target value Qt by adding the integral term and the proportional term described above, but this is not limiting. The flow rate target value calculation unit 23 of the control device 3 may calculate the flow rate target value Qt by adding the integral term, the proportional term, and a differential term obtained by multiplying the amount of change in pressure deviation dΔP by a differential gain.

[0043] In the above embodiment, the flow rate limit value calculation unit 24 of the control device 3 calculates the flow rate limit value Ql by subtracting the correction amount from the flow rate upper limit value Qmax, but this is not limited to this. The flow rate limit value calculation unit 24 of the control device 3 may calculate the flow rate limit value Ql by subtracting the correction amount from the target flow rate value Qt, for example. In the above embodiment, the flow rate limit value calculation unit 24 of the control device 3 obtains the correction amount using the correction amount map shown in FIG. 3, but this is not limited to this. The flow rate limit value calculation unit 24 of the control device 3 may calculate the correction amount so that it increases as the pressure deviation ΔP decreases and so that it increases as the amount of change in the pressure deviation dΔP increases.

[0044] In the above embodiment, the internal combustion engine system has been described as including one control device 3, but this is not limiting and the internal combustion engine system may include a plurality of control devices. That is, the pressure target value calculation unit 21, the pressure deviation calculation unit 22, the flow rate target value calculation unit 23, the flow rate limit value calculation unit 24, the flow rate control value acquisition unit 25, the on-off valve control unit 26, the adjustment amount calculation unit 27, and the adjustment amount limit unit 28 may be configured by a plurality of control devices.

[0045] 1 Internal combustion engine 3 Control device 9 High-pressure fuel pump 11 Pressure sensor 14 Pressurizing chamber 15 Opening / closing valve

Claims

1. An internal combustion engine system comprising: a high-pressure fuel pump having a pressurizing chamber for pressurizing fuel and an on-off valve arranged upstream of the pressurizing chamber, and supplying fuel pressurized in the pressurizing chamber to an internal combustion engine; a pressure sensor for detecting the pressure of fuel downstream of the high-pressure fuel pump; and a control device for calculating a flow rate target value of the high-pressure fuel pump based on a pressure deviation between a target fuel pressure value and a pressure detection value detected by the pressure sensor, calculating a flow rate limiting value based on the pressure deviation and an amount of change therein, selecting the smaller of the flow rate target value and the flow rate limiting value as a flow rate control value, and controlling the on-off valve in accordance with the flow rate control value, wherein the control device calculates an adjustment amount by multiplying the difference between the flow rate target value and the flow rate control value by the reciprocal of a proportional gain, limiting the adjustment amount by a limiting amount, and calculating an adjustment value of the pressure deviation by subtracting the limited adjustment amount from the pressure deviation, an internal combustion engine system, characterized in that the flow rate target value is calculated by adding together an integral term obtained by integrating an adjustment value of the pressure deviation and multiplying the result by an integral gain and a proportional term obtained by multiplying the pressure deviation by the proportional gain.

2. An internal combustion engine system according to claim 1, wherein said control device varies said limit amount in response to said pressure deviation.

3. An internal combustion engine system according to claim 1, wherein the control device varies the proportional gain and the integral gain in response to the pressure deviation.

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