Control device of internal combustion engine system

Abstract

To provide technique for protecting a catalyst in an internal combustion engine system.SOLUTION: A control device of an internal combustion engine system includes an internal combustion engine, a fuel pressure sensor provided in a fuel supply passage of the internal combustion engine, a catalyst provided in an exhaust passage of the internal combustion engine, and an air-fuel ratio sensor provided in the exhaust passage of the internal combustion engine. Catalyst OT preventing control is carried out when a fuel pressure measured by the fuel pressure sensor is less than a threshold and an air-fuel ratio measured by the air-fuel ratio sensor exceeds a threshold.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a control device for an internal combustion engine system. [Background technology]

[0002] When the fuel tank is low on fuel, air gets mixed in with the fuel, causing a drop in fuel pressure in the fuel supply line. This drop in fuel pressure can cause a misfire in the internal combustion engine. In this case, unburned air-fuel mixture is discharged into the exhaust line of the internal combustion engine. Because the unburned air-fuel mixture has a high oxygen concentration, there is a risk that the catalyst will melt due to oxidation heat.

[0003] Patent Document 1 discloses a technique for protecting a catalyst by restricting the running of a vehicle when the remaining fuel level is low. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-214773 A Summary of the Invention [Problem to be solved by the invention]

[0005] In addition to a low fuel level, other possible causes of a drop in fuel pressure include a malfunction of the fuel pump or clogging of the fuel supply line with foreign matter. Technology is needed to protect the catalyst in such cases as well. [Means for solving the problem]

[0006] The control device disclosed in this specification may be used in an internal combustion engine system including an internal combustion engine, a fuel pressure sensor provided in a fuel supply path of the internal combustion engine, a catalyst provided in an exhaust path of the internal combustion engine, and an air-fuel ratio sensor provided in the exhaust path of the internal combustion engine. The control device may be configured to execute catalyst OT prevention control when the fuel pressure measured by the fuel pressure sensor is less than a threshold value and the air-fuel ratio measured by the air-fuel ratio sensor exceeds a threshold value.

[0007] The control device of the internal combustion engine system monitors the fuel pressure in the fuel supply path, and can therefore detect not only a case where the amount of fuel remaining in the fuel tank is low, but also a malfunction of the fuel pump and clogging of the fuel supply path by foreign matter. Furthermore, the control device of the internal combustion engine system monitors the air-fuel ratio measured by the air-fuel ratio sensor, and can therefore detect a case where the internal combustion engine misfires and the air-fuel ratio becomes lean. As a result, the control device of the internal combustion engine system can effectively suppress melting and damage of the catalyst by executing the catalyst OT prevention control when a misfire occurs in the internal combustion engine due to a drop in fuel pressure. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 shows a configuration diagram of an internal combustion engine system. [Diagram 2] 3 shows a flowchart of a process executed by a control device of an internal combustion engine system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] As shown in Fig. 1, an internal combustion engine system 1 is mounted on, for example, a vehicle and is equipped with an internal combustion engine 2. An exhaust purification catalyst 4, which is a three-way catalyst, is provided in an exhaust path of the internal combustion engine 2. The exhaust purification catalyst 4 can purify hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) even if the air-fuel ratio deviates to a certain extent from the theoretical air-fuel ratio (stoichiometric).

[0010] An air-fuel ratio sensor (A / F sensor) 6 is provided in an exhaust path between the internal combustion engine 2 and the exhaust purification catalyst 4. The air-fuel ratio sensor 6 transmits an air-fuel ratio signal corresponding to the air-fuel ratio in the exhaust gas discharged from the internal combustion engine 2 to the ECU 8.

[0011] Fuel stored in a fuel tank 10 is delivered to a fuel supply path 14 by a fuel pump (F / P) 12. The fuel supplied to a delivery pipe 18 is injected into a combustion chamber of the internal combustion engine 2 by an injector 20. Here, the fuel supply path 14 is a path configured between the fuel tank 10 and the injector 20, and the delivery pipe 18 is a part of it. A fuel pressure sensor 16 is provided in this fuel supply path 14. The fuel pressure sensor 16 transmits a fuel pressure signal corresponding to the fuel pressure to the ECU 8.

[0012] The ECU 8 is composed of a microcomputer including a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory), and a program pre-stored in the ROM is expanded in the RAM and executed by the CPU. The ECU 8 is connected to the injector 20, and configured to perform injection control by transmitting a control signal for injection to the injector 20. The ECU 8 is further connected to an electronically controlled throttle 22, and configured to perform throttle opening control by transmitting a control signal for controlling the throttle opening to the electronically controlled throttle 22. In this way, the ECU 8 functions as a control device for the internal combustion engine system 1.

[0013] Hereinafter, the catalyst protection operation executed by the internal combustion engine system 1 will be described with reference to FIG.

[0014] First, in step S1, the ECU 8 judges whether or not the fuel pressure has decreased based on the fuel pressure signal transmitted from the fuel pressure sensor 16. Specifically, the ECU 8 judges whether or not the fuel pressure is less than a threshold value. If the fuel pressure is not less than the threshold value, the catalyst protection operation is terminated. If the fuel pressure is less than the threshold value, the process proceeds to step S2. Here, the threshold value is set based on the fuel pressure at which a misfire is estimated to occur in the internal combustion engine 2. In addition, since the fuel pressure oscillates, the fuel pressure used for the comparison judgment may be a moving average calculated over a predetermined time period. Although not particularly limited, in step S1, it may be judged whether or not the fuel pressure average is less than 20 kPa. By executing step S1, the ECU 8 can monitor a malfunction of the fuel pump 12, a foreign object clogging the fuel supply path 14, and the like, in addition to a case where the remaining amount of fuel in the fuel tank 10 is low.

[0015] Next, in step S2, the ECU 8 determines whether the air-fuel ratio is lean or not based on the air-fuel ratio signal transmitted from the air-fuel ratio sensor 6. Specifically, the ECU 8 determines whether the air-fuel ratio exceeds a threshold value. If the air-fuel ratio does not exceed the threshold value, the catalyst protection operation ends. If the air-fuel ratio exceeds the threshold value, the process proceeds to step S3. Here, the threshold value is set based on an air-fuel ratio at which it is estimated that a misfire has occurred in the internal combustion engine 2. Although not particularly limited, in step S2, it may be determined whether the air-fuel ratio has exceeded 17 or not. The ECU 8 can monitor the occurrence of a misfire in the internal combustion engine 2 by executing step S2.

[0016] Next, in step S3, the ECU 8 executes catalyst OT prevention control. The catalyst OT prevention control is a control that limits the output of the internal combustion engine 2 in order to prevent the temperature of the exhaust purification catalyst 4 from becoming too high. The ECU 8 limits the output of the internal combustion engine 2 by controlling the throttle opening of the electronically controlled throttle 22. The catalyst OT prevention control may be a control that executes at least one of limiting the rotation speed of the internal combustion engine 2, limiting the torque of the internal combustion engine 2, cutting fuel, and a combination thereof. The limiting of the rotation speed of the internal combustion engine 2 is not particularly limited, but may be set to be less than 2000 rpm, for example. The limiting of the torque of the internal combustion engine 2 is not particularly limited, but may be set to be less than 50 Nm, for example.

[0017] As described above, the ECU 8 monitors the fuel pressure in the fuel supply path 14, and therefore can detect not only a case where the remaining amount of fuel in the fuel tank 10 is low, but also a malfunction of the fuel pump 12 and clogging of the fuel supply path 14 by foreign matter. Furthermore, the ECU 8 monitors the air-fuel ratio measured by the air-fuel ratio sensor 6, and therefore can detect a case where a misfire occurs in the internal combustion engine 2 due to a drop in fuel pressure, causing the air-fuel ratio to become lean. As a result, the ECU 8 can effectively suppress melting and damage of the exhaust purification catalyst 4 by executing catalyst OT prevention control when a misfire occurs in the internal combustion engine 2 due to a drop in fuel pressure caused by various causes.

[0018] 2, instead of the comparison judgment based on the fuel pressure, the ECU 8 may judge whether or not the remaining fuel amount in the fuel tank 10 is less than the threshold value based on the sender gauge output transmitted from a level sensor in the fuel tank 10. In this case, the ECU 8 can detect that a misfire has occurred in the internal combustion engine due to a drop in fuel pressure caused by a decrease in the remaining amount of fuel in the fuel tank 10. As a result, when a misfire has occurred in the internal combustion engine 2 due to a drop in fuel pressure caused by a decrease in the remaining amount of fuel, the ECU 8 can effectively suppress the exhaust purification catalyst 4 from melting by executing the catalyst OT prevention control. [Explanation of symbols]

[0019] 1: internal combustion engine system, 2: internal combustion engine, 4: exhaust purification catalyst, 6: air-fuel ratio sensor, 8: ECU, 10: fuel tank, 12: fuel pump, 14: fuel supply path, 16: fuel pressure sensor, 18: delivery pipe, 20: injector, 22: electronically controlled throttle

Claims

[Claim 1] A control device for an internal combustion engine system including an internal combustion engine, a fuel pressure sensor provided in a fuel supply path of the internal combustion engine, a catalyst provided in an exhaust path of the internal combustion engine, and an air-fuel ratio sensor provided in the exhaust path of the internal combustion engine, A control device for an internal combustion engine system configured to execute catalyst overturn prevention control when the fuel pressure measured by the fuel pressure sensor is less than a threshold value and the air-fuel ratio measured by the air-fuel ratio sensor exceeds a threshold value.

Images