Control system for exhaust circulation device

Abstract

This control system for an exhaust circulation device comprises: an exhaust circulation valve for opening and closing a passage through which exhaust of an internal combustion engine is circulated to an intake pipe; an exhaust circulation gas introduction pipe extending from the exhaust circulation valve to the intake pipe of the internal combustion engine; and a control device. The control device: estimates the residual exhaust circulation gas concentration, which is the amount of exhaust circulation gas remaining in the exhaust circulation gas introduction pipe after the exhaust circulation valve is closed; and calculates the amount of exhaust circulation gas and air flowing into the intake pipe the next time the exhaust gas circulation valve is opened.

Description

Exhaust gas recirculation control system

[0001] The present disclosure relates to a control system for an exhaust gas recirculation system.

[0002] A control system for controlling an exhaust gas recirculation device that recirculates exhaust gas from an internal combustion engine is known (see, for example, Patent Document 1). The control system for the exhaust gas recirculation device in Patent Document 1 accurately calculates the introduction rate of the exhaust gas recirculation gas by estimating the concentration of the exhaust gas recirculation gas in the intake pipe of the internal combustion engine.

[0003] Japanese Patent Application Publication No. 2019-7460

[0004] The exhaust gas recirculation system has an exhaust gas recirculation valve that adjusts the amount of exhaust gas introduced into the intake pipe. The exhaust gas recirculation valve is preferably located close to the intake pipe. However, depending on the layout of the various components of the internal combustion engine, the exhaust gas recirculation valve may be located away from the intake pipe. In such cases, the introduction rate of exhaust gas recirculation must be calculated taking into account the exhaust gas remaining in the introduction pipe connecting the exhaust gas recirculation valve to the intake pipe.

[0005] An object of the present disclosure is to provide a control system for an exhaust gas recirculation device that can accurately calculate the amount of exhaust gas recirculation gas and the amount of air that enter the intake pipe, taking into account the exhaust gas recirculation gas remaining in the intake pipe.

[0006] The control system for the exhaust recirculation device disclosed herein comprises an exhaust recirculation valve that opens and closes a passage that circulates exhaust gas from an internal combustion engine to an intake air, an exhaust recirculation gas inlet pipe that extends from the exhaust recirculation valve to the intake pipe of the internal combustion engine, and a control device that controls the opening and closing of the exhaust recirculation valve, wherein the control device estimates the residual exhaust recirculation gas concentration, which is the amount of exhaust recirculation gas remaining in the exhaust recirculation gas inlet pipe after the exhaust recirculation valve is closed, and calculates the amount of exhaust recirculation gas and the amount of air that will flow into the intake pipe the next time the exhaust recirculation valve is opened.

[0007] According to this exhaust gas recirculation control system, the control device estimates the exhaust gas recirculation gas concentration remaining in the exhaust gas recirculation gas inlet pipe and calculates the amount of exhaust gas recirculation gas and the amount of air flowing into the intake pipe from the estimated exhaust gas recirculation gas concentration. As a result, it is possible to provide an exhaust gas recirculation control system that can accurately calculate the amount of exhaust gas recirculation gas and the amount of air entering the intake pipe, taking into account the exhaust gas recirculation gas remaining in the inlet pipe.

[0008] Fig. 1 is a system diagram of a control system for an exhaust gas recirculation device according to an embodiment of the present disclosure. Fig. 2 is a diagram for explaining a method for estimating the concentration of residual gas in an exhaust gas recirculation gas introduction pipe according to an embodiment of the present disclosure. Fig. 3 is a flowchart showing a calculation procedure executed by a control device according to an embodiment of the present disclosure.

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings.

[0010] As shown in FIG. 1 , the control system 2 of the exhaust gas recirculation device 1 includes an exhaust gas recirculation valve 4 , an inlet pipe (an example of an exhaust gas recirculation gas inlet pipe) 6 , and a control device 8 .

[0011] The exhaust gas recirculation system 1 is a device for recirculating exhaust gas from an internal combustion engine 10 to an intake pipe 12. The exhaust gas recirculation system 1 is connected to an exhaust pipe 14 and has a passage 16 that recirculates the exhaust gas to the intake pipe 12. The inlet pipe 6 is a pipe that extends from the exhaust gas recirculation valve 4 to the intake pipe 12 of the internal combustion engine 10. The exhaust gas recirculation valve 4 is disposed between the passage 16 and the inlet pipe 6, and adjusts the amount of exhaust gas recirculation by opening and closing the passage 16. In this embodiment, the exhaust gas recirculation valve 4 is a valve driven by a stepper motor. The exhaust gas recirculation valve 4 is electrically connected to a control device 8, and the valve opening degree is controlled by the control device 8.

[0012] The control device 8 is a device that controls the exhaust gas recirculation valve 4. The control device 8 is actually an ECU (Electronic Control Unit) and is configured by a microcomputer including an arithmetic unit, memory, input / output buffers, etc. In addition to controlling the exhaust gas recirculation valve 4, the control device 8 controls the internal combustion engine 10 so that the internal combustion engine 10 operates in a desired state based on signals from various sensors (e.g., the air flow sensor 18) and various devices (e.g., the throttle valve 20) mounted on the internal combustion engine 10, as well as maps and programs stored in the memory. Note that the various controls are not limited to being processed by software, and can also be processed by dedicated hardware (electronic circuits).

[0013] As shown in Figure 2, exhaust recirculation gas remains in the inlet pipe 6 depending on the opening and closing timing of the exhaust recirculation valve 4. More specifically, as shown in Figure 2(a), when the exhaust recirculation valve 4 is closed, exhaust recirculation gas accumulates in the passage 16. As shown in Figure 2(b), when the exhaust recirculation valve 4 opens, exhaust recirculation gas enters the inlet pipe 6, and as shown in Figure 2(b) to Figure 2(d), the exhaust recirculation gas flows into the intake pipe 12 while filling the inlet pipe 6.

[0014] As shown in Figure 2(e) to Figure 2(g), when the exhaust gas recirculation valve 4 closes, the exhaust gas recirculation gas (residual exhaust gas recirculation) filling the intake pipe 6 is gradually drawn into the intake pipe 12. At this time, the remaining exhaust gas recirculation gas is drawn into the intake pipe 12 in accordance with the intake pulsation of the intake pipe 12. The intake pulsation has the characteristic of differing depending on the rotation speed of the internal combustion engine 10. As shown in Figure 2(h), if the exhaust gas recirculation valve 4 remains closed, all of the remaining exhaust gas recirculation gas in the intake pipe 6 is drawn into the intake pipe 12.

[0015] However, the exhaust gas recirculation valve 4 may open before the remaining exhaust gas recirculation gas in the inlet pipe 6 is depleted. In such cases, the amount of remaining exhaust gas recirculation gas is added to the amount of exhaust gas passing through the exhaust gas recirculation valve 4. As a result, the amount of exhaust gas recirculation gas becomes larger than when there is no remaining exhaust gas recirculation gas.

[0016] For this reason, the control device 8 estimates the amount of remaining exhaust recirculation gas and calculates the amount of exhaust recirculation gas as follows: The calculation procedure of the control device 8 will be explained using the flowchart of FIG.

[0017] In step S1, the control device 8 opens the exhaust gas recirculation valve 4. In step S2, the control device 8 calculates the gas passing rate QEGR, which is the mass flow rate per unit time of the exhaust gas recirculation gas passing through the exhaust gas recirculation valve 4. The gas passing rate QEGR may be calculated by the control device 8, for example, from the opening degree of the exhaust gas recirculation valve 4 and the flow velocity of the exhaust gas recirculation calculated by an intake manifold pressure sensor and an atmospheric pressure sensor (not shown).

[0018] In steps S3 and S4, the control device 8 performs a primary filtering process and a time delay process on the gas passing rate QEGR.

[0019] The primary filtering simulates the increase in the concentration of exhaust recirculation gas due to the intake air in the intake pipe 6, and can be calculated, for example, using the following formula (1): b0(n) = 100 × K1 + b0(n-1) × (1-K1) ... formula (1) where b0(n) is the current concentration of exhaust recirculation gas relative to the intake air immediately after the exhaust recirculation valve 4. b0(n-1) is the previous calculated concentration of exhaust recirculation gas relative to the intake air immediately after the exhaust recirculation valve 4. K1 is the filter gain of the primary filtering determined based on the gas passing rate QEGR and the concentration bx of exhaust recirculation gas immediately after the exhaust recirculation valve, which will be described later. For example, when the exhaust recirculation valve opens with a high concentration bx, the concentration of exhaust recirculation gas at the end of the intake pipe can be increased to 100% more quickly than when the concentration bx is low, and thus K1 is a large value. Similarly, when the gas passing rate QEGR is large, K1 is also a large value.

[0020] The time delay process simulates the time delay that the exhaust recirculation gas takes to travel through the inlet pipe 6 to the end of the inlet pipe 12. For example, this can be calculated using the following equation (2) by using b0(n-D) before the time delay calculation for b0(n): b1(n) = b0(n-D) ...Equation (2) where b1 is the concentration of the exhaust recirculation gas at the end of the inlet pipe 6 on the intake pipe 12 side. D is the time delay determined by the gas passing rate QEGR and the concentration bx of the exhaust recirculation gas immediately after the exhaust recirculation valve. For example, when the exhaust recirculation valve opens when the concentration bx is high, the concentration of the exhaust recirculation gas at the end of the inlet pipe can reach 100% more quickly than when the concentration bx is low, so D is a small value. Similarly, when the gas passing rate is large, D is also a small value.

[0021] In step S5, the control device 8 obtains the amount Q1 of exhaust recirculation gas flowing into the intake pipe through the above calculation. Specifically, the control device 8 calculates the amount Q1 of exhaust recirculation gas by multiplying the above b1 by the gas passing rate QEGR and the exhaust recirculation gas concentration b1. The control device 8 also calculates the amount Q2 of air flowing into the intake pipe until the exhaust recirculation gas concentration b1 at the end of the intake pipe reaches 100% by multiplying the value (1 - b1) obtained by subtracting the exhaust recirculation gas concentration b1 from 1 by the gas passing rate QEGR.

[0022] Instead of the primary filtering process and the time delay process, the control device 8 may, for example, virtually divide the inlet pipe 6 into a plurality of rooms and perform a calculation to estimate the concentration of the exhaust recirculation gas in each room. For example, as shown in Figure 2, if the inlet pipe 6 is virtually divided into five rooms C1 to C5 of the same volume, the concentration of the exhaust recirculation gas in each room can be calculated as follows. K = VEGR / VPIP C1(n) = K x 1 + (1 - K) x C1 C2(n) = K x C1(n-1) + (1 - K) x C2(n-1) C3(n) = K x C2(n-1) + (1 - K) x C3(n-1) C4(n) = K x C3(n-1) + (1 - K) x C4(n-1) C5(n) = K x C4(n-1) + (1 - K) x C5(n-1) Q1 = C5(n) x VEGR x DNS Q2 = (1 - C5(n)) x VEGR x DNS ...Equation (3) Here, VPIP is the volume of each chamber. VEGR is the volume per unit time of exhaust recirculation gas passing through the exhaust recirculation valve 4. DNS is the density of the exhaust recirculation gas. C1(n) is the concentration of exhaust recirculation gas in chamber C1 in the nth calculation cycle. The same applies to C2(n) to C5(n). QAIR is the amount of intake air flowing into the intake pipe 12 per unit time. C5(n) is the concentration of exhaust recirculation gas at the end (end) of the intake pipe 6 on the intake pipe 12 side, and corresponds to b1 in equation (1). The exhaust recirculation gas amount Q1 and the air amount Q2 can also be calculated by such calculations.

[0023] In step S6, the control device 8 closes the exhaust gas recirculation valve 4. In step S7, the control device 8 acquires the rotation speed (engine rotation speed) of the internal combustion engine 10. In step S8, the control device 8 acquires the replacement rate K2.

[0024] The replacement rate K2 is a value indicating the rate at which the exhaust recirculation gas remaining in the intake pipe 6 is replaced by intake air flowing into the intake pipe 6 from the intake pipe 12. As described above, the exhaust recirculation gas remaining in the intake pipe 6 is replaced with intake air by the intake pulsation of the intake pipe 12. For this reason, in this embodiment, the control device 8 stores in advance the value of the replacement rate K2 for each engine rotation speed. The replacement rate K2 is a value obtained in advance by experiment or the like. The control device 8 obtains the replacement rate K2 corresponding to the rotation speed obtained in step S7.

[0025] In step S9, the control device 8 estimates the exhaust gas recirculation gas concentration bx remaining in the inlet pipe 6 after the exhaust gas recirculation valve 4 is closed, based on the replacement rate K2.

[0026] In this embodiment, the control device 8 uses the replacement rate K2 to calculate the exhaust gas recirculation gas amount Q1 remaining in the inlet pipe 6 immediately after the exhaust gas recirculation valve 4. Specifically, as shown in the following formula (4), the control device 8 uses a primary filter process using the replacement rate K2 as a gain to calculate the remaining exhaust gas recirculation gas concentration bx in the inlet pipe 6 immediately after the exhaust gas recirculation valve 4 until the concentration bx becomes 0%, assuming that the concentration bx when the exhaust gas recirculation valve 4 is closed is 100%. bx(n)=bx(n-1)×(1-K2)...formula (4)

[0027] After executing the process of step S9, the control device 8 proceeds to step S1. When the exhaust gas recirculation valve 4 opens again in step S1, by replacing b0, which is the concentration of exhaust gas recirculation gas relative to the intake air immediately after the exhaust gas recirculation valve 4, with bx in the equation for the primary filter process in step S3, the concentration b1 of exhaust gas recirculation gas at the end of the intake pipe 6 on the intake pipe 12 side becomes the concentration including residual exhaust gas recirculation gas. This allows the control device 8 to calculate the exhaust gas recirculation gas amount Q1 including the residual exhaust gas recirculation gas amount Q1r.

[0028] Instead of the primary filtering process and the time delay process, the control device 8 may, for example, virtually divide the inlet pipe 6 into a plurality of rooms and perform a calculation to estimate the concentration bx of the remaining exhaust recirculation gas in each room. For example, as shown in Figure 2, if the inlet pipe 6 is virtually divided into five rooms C1 to C5 of the same volume, the concentration bx of the exhaust recirculation gas in each room can be calculated as follows. C5(n) = K2 x 0 + (1 - K2) x C5(n-1) C4(n) = K2 x C5(n-1) + (1 - K2) x C4(n-1) C3(n) = K2 x C4(n-1) + (1 - K2) x C3(n-1) C2(n) = K2 x C3(n-1) + (1 - K2) x C2(n-1) C1(n) = K2 x C2(n-1) + (1 - K2) x C1(n-1) Q1 = 0 Q2 = 0 ... equation (5) Here, K2 is the replacement rate. By using these calculations, the control device 8 can calculate the concentration of the remaining exhaust gas recirculation gas in each room. After the exhaust gas recirculation valve 4 opens, the control device 8 can calculate the exhaust gas recirculation gas amount Q1 including the remaining exhaust gas recirculation gas amount Q1r and the air amount Q2 by calculating the above equation (3) from the concentration of the remaining exhaust gas recirculation gas in each room calculated by the above equation (5).

[0029] As described above, the present disclosure provides a control system 2 for an exhaust gas recirculation device 1 that can accurately calculate the amount of exhaust recirculation gas Q1 and the amount of air Q2 that enter the intake manifold, taking into account the amount of exhaust recirculation gas remaining in the inlet pipe 6. The control device 8 calculates the intake manifold EGR rate, which is the ratio of exhaust recirculation gas to air in the intake manifold 12, based on the amount of exhaust recirculation gas Q1 and the amount of air Q2 that flow from the inlet pipe 6 into the intake manifold 12, and ultimately calculates the in-cylinder EGR rate, which is the ratio of exhaust recirculation gas to air in the cylinder. Therefore, the control system 2 for the exhaust gas recirculation device 1 of the present disclosure can accurately calculate the in-cylinder EGR rate.

[0030] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments, and various modifications are possible within the scope of the gist of the invention. In particular, the multiple modifications described in this specification can be arbitrarily combined as necessary.

[0031] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0032] This application is based on a Japanese patent application (Patent Application No. 2023-203287) filed on November 30, 2023, the contents of which are incorporated herein by reference.

[0033] REFERENCE SIGNS LIST 1 exhaust gas recirculation device 2 control system 4 exhaust gas recirculation valve 6 inlet pipe 8 control device 10 internal combustion engine 12 intake pipe 16 passage K2 replacement rate QEGR exhaust gas recirculation gas amount QEGRr remaining exhaust gas recirculation gas amount VEGR gas passing amount

Claims

1. An exhaust circulation valve that opens and closes a passage that circulates the exhaust gas of an internal combustion engine back into the intake, An exhaust circulation gas introduction pipe extending from the exhaust circulation valve to the intake manifold of the internal combustion engine, A control device for controlling the opening and closing of the exhaust circulation valve, Equipped with, The control device is The exhaust circulating gas concentration remaining in the exhaust circulating gas inlet pipe is estimated as the exhaust circulating gas in the exhaust circulating gas inlet pipe changes when it is drawn into the intake pipe after the exhaust circulating valve is closed. Using the estimated exhaust circulating gas concentration, the amount of exhaust circulating gas and the amount of air that will flow into the intake manifold when the exhaust circulating valve is opened next are calculated. Control system for exhaust gas circulation system.

2. In calculating the amount of exhaust circulating gas, the control device, A replacement rate is used, which is the ratio at which the exhaust circulating gas concentration remaining in the exhaust circulating gas inlet pipe is replaced by the intake gas flowing from the intake pipe towards the exhaust circulating valve into the exhaust circulating gas inlet pipe. A control system for an exhaust gas circulation device according to claim 1.

3. The replacement rate is a value that changes according to the rotational speed of the internal combustion engine. The control device has pre-stored the value of the replacement rate for each rotational speed. The control device acquires the rotational speed, acquires the replacement rate corresponding to the rotational speed, and calculates the amount of exhaust circulating gas. A control system for an exhaust gas circulation device according to claim 2.

4. The control device is The amount of exhaust circulating gas passing through the exhaust circulation valve is calculated, The exhaust circulating gas concentration remaining in the exhaust circulating gas inlet pipe is subjected to primary filter treatment, Perform a time delay process, Based on the concentration obtained after the primary filtering process and the time-delay processing, and the amount of gas passed through, the amount of exhaust circulating gas and the amount of air flowing into the intake manifold at the terminal end of the exhaust circulating gas introduction pipe extending to the intake manifold of the internal combustion engine are calculated. A control system for an exhaust gas circulation device according to any one of claims 1 to 3.