US-20260126000-A1 - CONTROL DEVICE AND INJECTION METHOD OF UREA SOLUTION

US20260126000A1US 20260126000 A1US20260126000 A1US 20260126000A1US-20260126000-A1

Abstract

An exhaust pipe discharges an exhaust gas discharged from a hydrogen engine to an outside of a vehicle. An exhaust gas control apparatus reduces nitrogen oxides contained in the exhaust gas. A nitrogen oxide sensor acquires a measurement value reflecting a concentration of the nitrogen oxide contained in the exhaust gas and outputs an output value that is a value obtained by subtracting, from the measurement value, a value that increases as a moisture content contained in the exhaust gas is greater. An injector injects a urea solution to the exhaust gas control apparatus. A control device is configured to cause, in a case where the output value is equal to or greater than a reference value, an injector to inject an amount of the urea solution that is determined based on the output value and a flow rate of the exhaust gas.

Inventors

Yuto Ikeda
Satoshi Ido
Hibiki Ueura

Assignees

TOYOTA JIDOSHA KABUSHIKI KAISHA

Dates

Publication Date: 20260507
Application Date: 20250818
Priority Date: 20241106

Claims (5)

1 . A control device controlling an injector by acquiring an output value of a nitrogen oxide sensor in an exhaust system including an exhaust pipe discharging exhaust gas discharged to an outside of a vehicle from a hydrogen engine using hydrogen as a fuel, an exhaust gas control apparatus installed in an intermediate portion of the exhaust pipe and reducing a nitrogen oxide contained in the exhaust gas, the nitrogen oxide sensor disposed upstream of the exhaust gas control apparatus in the exhaust pipe, the nitrogen oxide sensor being configured to acquire a measurement value reflecting a concentration of the nitrogen oxide contained in the exhaust gas, and to output the output value that is a value obtained by subtracting, from the measurement value, a value that increases as a moisture content contained in the exhaust gas is greater, and the injector disposed downstream of the nitrogen oxide sensor and upstream of the exhaust gas control apparatus in the exhaust pipe, the injector being configured to inject a urea solution to the exhaust gas control apparatus, wherein the control device is configured to: cause, in a case where the output value is equal to or greater than a reference value, the injector to inject an amount of the urea solution determined based on the output value and a flow rate of the exhaust gas; and cause, in a case where the output value is lower than the reference value, the injector to inject an amount of the urea solution determined based on the reference value and the flow rate.
2 . The control device according to claim 1 , wherein the control device is configured to cause the injector to inject, during a fuel cut, the amount of the urea solution determined based on the output value and the flow rate.
3 . The control device according to claim 1 , wherein the reference value is determined based on a concentration of the nitrogen oxide contained in the exhaust gas when the vehicle is idling.
4 . The control device according to claim 1 , wherein the control device is configured to: estimate, in a case where the nitrogen oxide sensor is in an inactive state, a concentration of a nitrogen oxide contained in the exhaust gas based on an operating state of the hydrogen engine; and cause the injector to inject an amount of the urea solution determined based on the concentration of the nitrogen oxide that is estimated and the flow rate.
5 . An injection method of a urea solution in an exhaust system including an exhaust pipe discharging exhaust gas discharged to an outside of a vehicle from a hydrogen engine using hydrogen as a fuel, an exhaust gas control apparatus installed in an intermediate portion of the exhaust pipe and reduces nitrogen oxides contained in the exhaust gas, a nitrogen oxide sensor disposed upstream of the exhaust gas control apparatus in the exhaust pipe, the nitrogen oxide sensor being configured to acquire a measurement value reflecting a concentration of nitrogen oxides contained in the exhaust gas, and to output an output value that is a value obtained by subtracting, from the measurement value, a value that increases as a moisture content contained in the exhaust gas is greater, an injector disposed downstream of the nitrogen oxide sensor and upstream of the exhaust gas control apparatus in the exhaust pipe, the injector being configured to inject the urea solution to the exhaust gas control apparatus, and a control device controlling the injector by acquiring the output value of the nitrogen oxide sensor, the injection method comprising: determining, by the control device, an amount of the urea solution to be injected by the injector based on the output value and a flow rate of the exhaust gas in a case where the output value is equal to or greater than a reference value, and an amount of the urea solution to be injected by the injector based on the reference value and the flow rate in a case where the output value is lower than the reference value; and injecting, by the injector, the amount of the urea solution that is determined by the control device to the exhaust gas control apparatus.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims priority to Japanese Patent Application No. 2024-194526 filed on Nov. 6, 2024. The disclosure of the above-identified application, including the specification, drawings, and claims, is incorporated by reference herein in its entirety. BACKGROUND 1. Technical Field The present disclosure relates to a control device and an injection method of a urea solution. 2. Description of Related Art Japanese Unexamined Patent Application Publication No. 2010-71192 (JP 2010-71192 A) discloses an exhaust system. The exhaust system includes an exhaust gas control apparatus, an injector, and a nitrogen oxide (NOx) sensor. The exhaust gas control apparatus includes a catalyst that adsorbs ammonia. The exhaust gas control apparatus uses ammonia to reduce NOx in an exhaust gas discharged from an engine. The injector adds urea to the exhaust gas control apparatus as a reducing agent. The nitrogen oxide sensor measures a concentration of NOx in an exhaust gas flowing upstream of the exhaust gas control apparatus. The exhaust system determines the amount of the urea solution to be injected toward the exhaust gas control apparatus by the injector based on a measurement value of the nitrogen oxide sensor. Thereafter, the exhaust system causes the injector to inject an amount of the urea solution that is determined. The nitrogen oxide sensor also reacts to moisture in the exhaust gas in addition to NOx in the exhaust gas. Therefore, the measurement value of the nitrogen oxide sensor may be greater than a value reflecting the concentration of NOx contained in the exhaust gas. The exhaust system corrects the measurement value of the nitrogen oxide sensor in accordance with a moisture content in the exhaust gas and then determines the amount of the urea solution to be injected by the injector. SUMMARY As a mode in which the exhaust system corrects the measurement value, a mode in which an arbitrary value is subtracted from an actual measurement value obtained by the nitrogen oxide sensor and the measurement value is treated as zero in a case where the measurement value is zero or less can be considered. In this case, the exhaust system increases a value to be subtracted from the measurement value as the moisture content in the exhaust gas increases. In a case where the engine uses hydrogen gas as a fuel, the moisture content in the exhaust gas increases. Therefore, in a case where the engine uses a hydrogen gas as a fuel, the value to be subtracted from the measurement value in the exhaust system also increases. The degree to which the nitrogen oxide sensor reacts to the moisture in the exhaust gas changes not only depending on the moisture content in the exhaust gas but also depending on a flow velocity of the exhaust gas or the temperature of the nitrogen oxide sensor. The flow velocity of the exhaust gas or the temperature of the nitrogen oxide sensor may be a condition in which the nitrogen oxide sensor is less likely to react with the moisture, while the moisture content in the exhaust gas is large, and a value to be subtracted from the measurement value is large. In this case, even though NOx is contained in the exhaust gas, the measurement value that is corrected may be zero. In this case, the exhaust system does not cause the injector to inject the urea solution, and thus NOx passes through the exhaust gas control apparatus. A control device for solving the above problem controls an injector by acquiring an output value of a nitrogen oxide sensor in an exhaust system. The exhaust system includes an exhaust pipe discharging exhaust gas discharged to an outside of a vehicle from a hydrogen engine using hydrogen as a fuel. The exhaust system includes an exhaust gas control apparatus installed in an intermediate portion of the exhaust pipe and reducing a nitrogen oxide contained in the exhaust gas. The exhaust system includes the nitrogen oxide sensor disposed upstream of the exhaust gas control apparatus in the exhaust pipe, the nitrogen oxide sensor being configured to acquire a measurement value reflecting a concentration of the nitrogen oxide contained in the exhaust gas, and to output the output value that is a value obtained by subtracting, from the measurement value, a value that increases as a moisture content contained in the exhaust gas is greater. The exhaust system includes the injector disposed downstream of the nitrogen oxide sensor and upstream of the exhaust gas control apparatus in the exhaust pipe, the injector being configured to inject the urea solution to the exhaust gas control apparatus. The control device is configured to cause, in a case where the output value is equal to or greater than a reference value, the injector to inject an amount of the urea solution determined based on the output value and a flow rate of the exhaust gas. The control device is configured to cause, in a case where the output value is lower than the reference value, the i