Internal combustion engine system

Abstract

Provided is an internal combustion engine system capable of improving the responsiveness and stability of the control of the downstream-side pressure of a high-pressure fuel pump. A control device for an internal combustion engine system calculates a flow rate target value for a high-pressure fuel pump on the basis of a pressure deviation between a pressure target value for fuel and a pressure detection value detected by a pressure sensor, and calculates a flow rate limit value on the basis of the pressure deviation and the amount of change thereof. The smaller one of the flow rate target value and the flow rate limit value is selected as a flow rate control value, and an on-off valve of the high-pressure fuel pump is controlled on the basis of 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 the proportional gain, limits the adjustment amount by the limiting amount, and calculates the adjustment value of the pressure deviation by subtracting the limited adjustment amount from the pressure deviation. A flow rate target value is calculated by adding an integral term obtained by integrating the adjustment value of the pressure deviation and multiplying the integral gain to a proportional term obtained by multiplying the pressure deviation by the proportional gain.

Description

TECHNICAL FIELD

[0001] The present application relates to an internal combustion engine system. BACKGROUND

[0002] Patent Document 1 discloses an internal combustion engine system. The internal combustion engine system is provided with a high-pressure fuel pump that supplies high-pressure fuel to an internal combustion engine; a pressure sensor that detects a fuel pressure on a downstream side of the high-pressure fuel pump; and a control device that controls the high-pressure fuel pump based on a pressure detection value of the pressure sensor.

[0003] The high-pressure fuel pump has a pressure chamber that pressurizes fuel, and an electromagnetic on-off valve that is disposed on an upstream side of the pressure chamber. By the opening and closing timing of the on-off valve, the discharge flow rate of the high-pressure fuel pump can be made variable.

[0004] The control device calculates a flow rate target value of the high-pressure fuel pump based on a pressure deviation between a pressure target value of the fuel and the pressure detection value detected by the pressure sensor. Specifically, an integral term is calculated based on the pressure deviation, and a proportional term is calculated based on the pressure deviation, and the flow rate target value is calculated by adding the integral term and the proportional term. Then, the opening and closing timing of the on-off valve is controlled in accordance with the flow rate target value.

[0005] The control device prohibits the operation of the integral term and fixes the integral term (anti-windup processing) in a case where the pressure target value is abruptly changed and the pressure deviation is abruptly changed. Thereby, overshoot in which the pressure detection value greatly exceeds the pressure target value is avoided. Therefore, the control stability with respect to the pressure on the downstream side of the high-pressure fuel pump can be improved.

[0006] PRIOR ART DOCUMENTS

[0007] PATENT DOCUMENTS

[0008] Patent Document 1: Japanese Patent Application Publication No. 2007-032322 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] In the related art described in Patent Document 1, in a case where the pressure target value is abruptly changed and the pressure deviation is abruptly changed, the control stability with respect to the pressure on the downstream side of the high-pressure fuel pump is improved by fixing the integral term. However, there is room for improvement in terms of improving the control responsiveness.

[0011] Further, in a case where the integral term is fixed, pressure oscillation (in other words, repeated rise and fall of the pressure) can occur depending on the conditions such as the fuel temperature. Therefore, there is room for improvement in terms of further improving the control stability.

[0012] The present application has an object to provide an internal combustion engine system capable of improving the responsiveness and stability of control over the pressure on the downstream side of a high-pressure fuel pump.

[0013] Means for solving the problem

[0014] To achieve the above object, the present application provides an internal combustion engine system including: a high-pressure fuel pump having a pressure chamber that pressurizes fuel and an on-off valve disposed on the upstream side of the pressure chamber, and supplying the fuel pressurized by the pressure chamber to an internal combustion engine; a pressure sensor that detects the fuel pressure on the downstream side of the high-pressure fuel pump; and a control device that calculates a flow rate target value of the high-pressure fuel pump based on a pressure deviation between a pressure target value of the fuel and a pressure detection value detected by the pressure sensor, and calculates a flow rate limit value based on the pressure deviation and a change amount thereof, selects the smaller one of the flow rate target 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 the difference between the flow rate target value and the flow rate control value by the inverse of a proportional gain, limits the adjustment amount by a limit amount, and subtracts the limited adjustment amount from the pressure deviation, thereby calculating an adjustment value of the pressure deviation, and calculates the flow rate target value by adding an integral term obtained by integrating the adjustment value of the pressure deviation and multiplying by an integral gain, to a proportional term obtained by multiplying the pressure deviation by the proportional gain.

[0015] Effects of the Invention

[0016] According to the present application, it is possible to improve the responsiveness and stability of control over the pressure on the downstream side of a high-pressure fuel pump. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a diagram showing the main part configuration of an internal combustion engine system in one embodiment of the present application.

[0018] Figure 2 is a block diagram showing the functional configuration of a control device and its related devices in one embodiment of the present application.

[0019] Figure 3 is a diagram showing a correction amount map used in the calculation of a flow rate limit value in one embodiment of the present application.

[0020] Figure 4 is a diagram showing the time changes of a pressure target value, a pressure detection value, a flow rate control value, and an actual flow rate in a comparative example.

[0021] Figure 5 is a diagram showing the time changes of a pressure target value, a pressure detection value, a flow rate control value, and an actual flow rate in one embodiment of the present application. DETAILED DESCRIPTION

[0022] An embodiment of the present application will be described with reference to the accompanying drawings.

[0023] Figure 1 is a schematic view showing the main part configuration of the internal combustion engine system in the embodiment.

[0024] The internal combustion engine system of the embodiment is a system mounted on a vehicle (not shown), and has an internal combustion engine 1, a fuel system 2, and a control device 3.

[0025] The internal combustion engine 1 has a plurality of cylinders (not shown), a plurality of intake valves (not shown) that suck air from an intake system (not shown) into the plurality of cylinders, a plurality of fuel injection valves 4 that are disposed on the upstream side or the downstream side of the plurality of intake valves and inject fuel from the fuel system 2, a plurality of spark plugs (not shown) that ignite the fuel that is sucked into the plurality of cylinders along with the air to cause the fuel and the air to burn, 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 perform reciprocating motion due to the expansion of the combustion gas in the plurality of cylinders, and a crankshaft (not shown) that rotates by the reciprocating motion of the plurality of pistons. The intake valves and the exhaust valves are opened and closed in conjunction with the crankshaft.

[0026] The intake system has a throttle valve (not shown) whose opening degree is variable according to the operation amount of an accelerator pedal 5, and the air flow rate supplied to the internal combustion engine 1 is varied by the opening degree of the throttle valve. The operation amount of the accelerator pedal 5 is detected by an accelerator pedal sensor 6 and output to the control device 3.

[0027] The fuel system 2 has a fuel tank 7 that stores fuel, a low-pressure fuel pump 8 that pressurizes the fuel in 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 fuel pressure on the downstream side of the high-pressure fuel pump 9 (the common rail 10 in the embodiment) is detected by a pressure sensor 11 and output to the control device 3.

[0028] The high-pressure fuel pump 9 has a pressurizing chamber 14 that is formed in a cylinder 12 and whose volume changes with the reciprocating motion of a plunger 13, an electromagnetic on-off valve 15 that is disposed on the upstream side of the pressurizing chamber 14, a pressure pulsation reducing portion 16 that is disposed on the upstream side of the on-off valve 15, and a check valve 17 that is disposed on the downstream side of the pressurizing chamber 14.

[0029] The plunger 13 is reciprocated by a cam mechanism (not shown) linked to the crankshaft. The cam mechanism has a cam shaft that rotates in linkage with the crankshaft, and an eccentric cam provided on the cam shaft and reciprocating the plunger 13. The cam shaft rotation angle corresponding to the phase (position of reciprocation) of the plunger 13 is detected by a cam angle sensor (not shown) and output to the control device 3.

[0030] When the on-off valve 15 is in the open state and the plunger 13 moves to one side to increase the volume of the pressurizing chamber 14, fuel is drawn into the pressurizing chamber 14. When the on-off valve 15 is in the closed state and the plunger 13 moves to the opposite side to decrease the volume of the pressurizing chamber 14, the fuel in the pressurizing chamber 14 is pressurized. Thereafter, if the pressure on the upstream side of the one-way valve 17 is higher than the pressure on the downstream side by a prescribed value or more, the fuel pressurized by the pressurizing chamber 14 is discharged. The discharge flow rate of the high-pressure fuel pump 9 is made variable by the opening and closing timing of the on-off valve 15.

[0031] 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 injection timing of fuel by controlling the fuel injection valve 4. Further, the control device 3 controls the fuel flow rate supplied to the internal combustion engine 1 by controlling the on-off valve 15 of the high-pressure fuel pump 9.

[0032] Regarding the control of the on-off valve 15 of the high-pressure fuel pump 9 in the present embodiment, the following will be described using Figure 2 Figure 2 is a block diagram collectively showing the functional configuration of the control device in the present embodiment and its related devices.

[0033] As the functional configuration related to the control of the on-off valve 15 of the high-pressure fuel pump 9, the control device 3 has a pressure target value calculation section 21, a pressure deviation calculation section 22, a flow rate target value calculation section 23, a flow rate limit value calculation section 24, a flow rate control value acquisition section 25, an on-off valve control section 26, an adjustment amount calculation section 27, and an adjustment amount limit section 28.

[0034] The pressure target value calculation section 21 calculates the pressure target value Pt of fuel based on the operation amount of the accelerator pedal 5 detected by the accelerator pedal sensor 6 (i.e., the air flow rate corresponding to the throttle opening degree).

[0035] The pressure deviation calculation section 22 calculates the pressure deviation ΔP between the pressure target value Pt calculated by the pressure target value calculation section 21 and the pressure detection value Pd detected by the pressure sensor 11.

[0036] The flow rate target value calculation section 23 calculates the flow rate target value Qt of the high-pressure fuel pump 9 based on the pressure deviation ΔP calculated by the pressure deviation calculation section 22 (specifically, in such a manner that the pressure deviation ΔP becomes zero). ​

[0037] The flow limit calculation unit 24 obtains the upper limit value Qmax of the high-pressure fuel pump 9 based on the rotational speed of the internal combustion engine 1 detected by the speed sensor (not shown) and the battery voltage detected by the voltage sensor (not shown). Furthermore, based on the historical records of the pressure deviation ΔP calculated by the pressure deviation calculation unit 22, it calculates the change in pressure deviation (specifically, the change per unit time, i.e., the rate of change) dΔP, and obtains a correction amount L based on the pressure deviation ΔP and its change amount dΔP. Then, the flow limit value Q1 is calculated by subtracting the correction amount L from the upper limit value Qmax.

[0038] For use Figure 3 The correction amount L is obtained using the correction amount mapping diagram shown. When the pressure deviation ΔP exceeds a predetermined value A (for example, if it is the ratio of pressure deviation ΔP to the pressure target value Pt, then A = 0.368), the flow limit calculation unit 24 obtains a correction amount L = 0. On the other hand, when the pressure deviation ΔP is below the predetermined value A, the correction amount L = La or L = Lb is obtained based on the combination of the pressure deviation ΔP and its change dΔP. That is, the smaller the pressure deviation ΔP, the smaller the threshold B for the pressure deviation change dΔP becomes; if the pressure deviation change dΔP exceeds the threshold B, the correction amount L = La (where La > 0); if the pressure deviation change dΔP is below the threshold B, the correction amount L = Lb (where La > Lb > 0).

[0039] The flow control value acquisition unit 25 selects the smaller of the flow target value Qt calculated by the flow target value calculation unit 23 and the flow limit value Ql calculated by the flow limit value calculation unit 24 as the flow control value Qc.

[0040] The on / off valve control unit 26 controls the opening and closing timing of the on / off valve 15 based on the flow control value Qc acquired by the flow control value acquisition unit 25. Specifically, it calculates the energizing start phase and energizing end phase based on the flow control value Qc, and acquires the energizing start angle and current angle corresponding to the energizing start phase and energizing end phase. Then, when the rotation angle detected by the cam angle sensor reaches the energizing start angle, energizing the on / off valve 15 begins, thereby opening the on / off valve 15. Subsequently, when the rotation angle detected by the cam angle sensor reaches the energizing end angle, energizing the on / off valve 15 ends, thereby closing the on / off valve 15.

[0041] The adjustment amount calculation unit 27 and the adjustment amount limiting unit 28 are used to perform anti-saturation processing when the flow control value Qc is limited (in other words, the flow control value Qc is less than the flow target value Qt).

[0042] The adjustment amount calculation section 27 calculates an adjustment amount by multiplying the difference between the flow target value Qt calculated by the flow target value calculation section 23 and the flow control value Qc acquired by the flow control value acquisition section 25 by the inverse of a prescribed proportional gain. The adjustment amount limiting section 28 limits the adjustment amount by selecting the smaller one of the adjustment amount calculated by the adjustment amount calculation section 27 and a prescribed limit amount.

[0043] The flow target value calculation section 23 calculates an adjusted value ΔP' of the pressure deviation (where ΔP' = ΔP if the flow control value Qc is not limited) by subtracting the adjustment amount limited by the adjustment amount limiting section 28 from the pressure deviation ΔP calculated by the pressure deviation calculation section 22. Then, the flow target value Qt is calculated by adding an integral term obtained by integrating the adjusted value ΔP' of the pressure deviation and multiplying it by a prescribed integral gain, to a proportional term obtained by multiplying the pressure deviation ΔP by a prescribed proportional gain.

[0044] Next, the effects of the present embodiment will be described using a comparative example (specifically, a case in which the flow control value Qc is limited by the flow upper limit value Qmax and no anti-windup processing is performed). Figure 4 is a graph showing the temporal changes in the pressure target value, the pressure detection value, the flow target value, and the actual flow in the comparative example. Figure 5 is a graph showing the temporal changes in the pressure target value, the pressure detection value, the flow target value, and the actual flow in the present embodiment.

[0045] Suppose that at time to, the flow target value Qt increases due to a stepwise surge in the pressure target value Pt. The control device of the comparative example selects the smaller one of the flow target value Qt and the flow upper limit value Qmax as the flow control value Qc, and controls the on-off valve of the high-pressure fuel pump in accordance with this flow control value Qc. Therefore, as shown in Figure 3 , the actual flow Qd of the high-pressure fuel pump increases and exceeds the flow upper limit value Qmax. As a result of this, the pressure detection value Pd also increases, and an overshoot phenomenon in which the pressure detection value Pd greatly exceeds the pressure target value Pt occurs. Furthermore, although not shown, pressure oscillation can occur depending on the conditions such as the fuel temperature.

[0046] On the other hand, the control device 3 of the present embodiment calculates the flow limit value Ql on the basis of the pressure deviation ΔP and the amount of change dΔP thereof, selects the smaller one of the flow target value Qt and the flow limit value Ql as the flow control value Qc, and controls the on-off valve 15 of the high-pressure fuel pump 9 in accordance with this flow control value Qc. As shown in Figure 4As shown, between time t0 and time t1, since the pressure deviation ΔP exceeds the prescribed value A, the correction amount L = 0, and the flow rate limit value Ql = the flow rate upper limit value Qmax. At time t1, since the pressure deviation ΔP is below the prescribed value A and the pressure deviation change amount dΔP exceeds the threshold value B, the correction amount L = La, and the flow rate limit value Ql = Qla (= Qmax - La). That is, at time t1, the flow rate control value Qc is limited by the flow rate limit value Qla, which is smaller than the flow rate upper limit value Qmax. Therefore, the 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. Thus, the increase in the pressure detection value Pd is also suppressed, and overshoot can be avoided. Therefore, the control stability with respect to the pressure on the downstream side of the high-pressure fuel pump 9 can be improved.

[0047] At time t2, since the pressure deviation ΔP is below the prescribed value A and the pressure deviation change amount dΔP is below the threshold value B, 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 by 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, the excessive decrease in the actual flow rate Qd of the high-pressure fuel pump 9 is suppressed. Thus, the excessive decrease in the pressure detection value Pd is also suppressed. Therefore, the control responsiveness with respect to the pressure on the downstream side of the high-pressure fuel pump 9 can be improved.

[0048] Further, in calculating the flow rate target value Qt, the control device 3 of the present 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 inverse of the proportional gain, and calculates the integral term using the adjusted value of the pressure deviation (in other words, performs anti-windup processing). Thus, with respect to the pressure on the downstream side of the high-pressure fuel pump 9, overshoot can be further avoided. Also, the control device 3 of the present embodiment limits the above adjustment amount using the limit amount. Thus, pressure oscillation can be avoided, and the stability of the control can be further improved.

[0049] In addition, in the above-described embodiment, the adjustment amount limiting portion 28 of the control device 3 uses a fixed limit amount, but is not limited thereto, and a variable limit amount can also be used. That is, the adjustment amount limiting portion 28 of the control device 3 can change the limit amount according to the pressure deviation ΔP (for example, so that it decreases as the pressure deviation ΔP increases). Thus, the effect of suppressing pressure oscillation can be improved.

[0050] Moreover, in the above-described embodiment, the case where the flow target value calculation section 23 of the control device 3 uses fixed integral gain and proportional gain has been described as an example, but the present application is not limited to this. Variable integral gain and proportional gain can also be used. That is, the flow target value calculation section 23 of the control device 3 can change the integral gain and the proportional gain according to the pressure deviation ΔP (for example, so that they decrease as the pressure deviation ΔP increases). Thus, the effect of suppressing pressure oscillation can be improved.

[0051] In addition, in the above-described embodiment, the case where the flow target value calculation section 23 of the control device 3 calculates the flow target value Qt by adding the above-described integral term and the above-described proportional term has been described as an example, but the present application is not limited to this. The flow target value calculation section 23 of the control device 3 can also calculate the flow target value Qt by adding the above-described integral term, the above-described proportional term, and a differential term obtained by multiplying the pressure deviation change amount dΔP by a differential gain.

[0052] Moreover, in the above-described embodiment, the case where the flow limit value calculation section 24 of the control device 3 calculates the flow limit value Ql by subtracting the correction amount from the flow upper limit value Qmax has been described as an example, but the present application is not limited to this. The flow limit value calculation section 24 of the control device 3 can also calculate the flow limit value Ql by subtracting the correction amount from the flow target value Qt, for example. In addition, in the above-described embodiment, the case where the flow limit value calculation section 24 of the control device 3 acquires the correction amount using the correction amount map shown in FIG. 6 has been described as an example, but the present application is not limited to this. The flow limit value calculation section 24 of the control device 3 can also calculate the correction amount in such a manner that it increases as the pressure deviation ΔP decreases and increases as the pressure deviation change amount dΔP increases. Figure 3

[0053] Moreover, in the above-described embodiment, the case where the internal combustion engine system is provided with one control device 3 has been described as an example, but the present application is not limited to this. A plurality of control devices can also be provided. That is, the pressure target value calculation section 21, the pressure deviation calculation section 22, the flow target value calculation section 23, the flow limit value calculation section 24, the flow control value acquisition section 25, the on-off valve control section 26, the adjustment amount calculation section 27, and the adjustment amount restriction section 28 can be constituted by a plurality of control devices.

[0054] Explanation of Reference Characters

[0055] 1 internal combustion engine

[0056] 3 control device

[0057] 9 high-pressure fuel pump

[0058] 11 pressure sensor

[0059] 14 pressurizing chamber​

[0060] 15 open / close valve.

Claims

1. An internal combustion engine system, characterized in that, have: A high-pressure fuel pump has a pressurization chamber for pressurizing fuel and an on / off valve disposed upstream of the pressurization chamber, and supplies the pressurized fuel from the pressurization chamber to an internal combustion engine; A pressure sensor that detects the fuel pressure downstream of the high-pressure fuel pump; as well as The control device calculates the target flow rate of the high-pressure fuel pump based on the pressure deviation between the target fuel pressure value and the pressure detection value detected by the pressure sensor, and calculates a flow limit value based on the pressure deviation and its change. It selects the smaller of the target flow rate value and the flow limit value as the flow control value, and controls the opening and closing of the valve according to the flow control value. The control device performs the following operations: The adjustment amount is calculated by multiplying the difference between the target flow value and the flow control value by the reciprocal of the proportional gain. The adjustment amount is limited by a limiting value. The adjustment value for the pressure deviation is calculated by subtracting the limited adjustment amount from the pressure deviation. The target flow rate is calculated by adding the integral term obtained by integrating the adjustment value of the pressure deviation and multiplying it by the integral gain, and the proportional term obtained by multiplying the pressure deviation by the proportional gain.

2. The internal combustion engine system according to claim 1, characterized in that, The control device changes the limiting amount based on the pressure deviation.

3. The internal combustion engine system according to claim 1, characterized in that, The control device adjusts the proportional gain and the integral gain based on the pressure deviation.

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