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DE-102018121695-B4 - Injection control device

DE102018121695B4DE 102018121695 B4DE102018121695 B4DE 102018121695B4DE-102018121695-B4

Abstract

Injection control device applied to an exhaust gas purification system comprising an injector (50) arranged in an exhaust passage (31a) of an internal combustion engine (30) and performing an injection to deliver a reducing agent in a liquid state to a NOx purification catalyst (33) that purifies NOx in an exhaust gas, and a pump (44) which compresses the reducing agent and delivers it via a reducing agent passage (42) to the injector (50), wherein the injection control device comprises: a acquisition unit (S28) which is configured such that it acquires a current value of an excitation current flowing through the pump (44) when the pump (44) is excited as a rotation variation parameter (ΔN); a determination unit (S30) configured to determine, based on the rotation variation parameter (ΔN), whether air is present at the reducing agent passage (42); and a control unit (S42) which is configured to control an air release quantity (Dc) of an air release valve (60) based on a determination of whether air admixture is present in the reducing agent passage (42).

Inventors

  • Eiji Takemoto
  • Tomomi Oshima

Assignees

  • DENSO CORPORATION

Dates

Publication Date
20260513
Application Date
20180905
Priority Date
20180109

Claims (6)

  1. An injection control device applied to an exhaust gas purification system comprising an injector (50) arranged in an exhaust passage (31a) of an internal combustion engine (30) and performing an injection to deliver a reducing agent in a liquid state to a NOx purification catalyst (33) that purifies NOx in an exhaust gas, and a pump (44) that compresses the reducing agent and delivers it via a reducing agent passage (42) to the injector (50), wherein the injection control device comprises: a acquisition unit (S28) configured to acquire a current value of an excitation current flowing through the pump (44) when the pump (44) is excited, as a rotation variation parameter (ΔN); a determination unit (S30) configured to determine, based on the rotation variation parameter (ΔN), whether air is present in the reducing agent passage (42); and a control unit (S42) configured to control an air release quantity (Dc) of an air release valve (60) based on a determination of whether air is present in the reducing agent passage (42).
  2. Injection control device according to Claim 1 , further comprising: a setting unit (S24) configured to set a threshold (Ru, Rd) for determining the air mixture according to an injection quantity (Dm) of the injector (50) per unit of time, wherein the determination unit (S30) determines, based on a comparison result between the rotation variation parameter (ΔN) obtained by the acquisition unit (S28) and the threshold (Ru, Rd) set by the setting unit (S24), whether the air mixture is present at the reducing agent passage (42).
  3. Injection control device according to Claim 2 , wherein the exhaust gas purification system further comprises a tank (40) which stores the reducing agent, an air release port (54) which is connected to the reducing agent port (42) and communicates with the tank (40), and the air release valve (60) which is attached to the air release port (54) and opens and closes the air release port (54), the injection control device further comprising: the control unit (S42) which is configured to variably control the air release quantity (Dc) per unit of time, wherein the control unit (S42) controls the air release quantity (Dc) such that, when the determining unit (S30) determines that air is present at the reducing agent port (42), it is greater than the air release quantity (Dc) when the determining unit (S30) determines that air is not present at the reducing agent port (42).
  4. Injection control device according to Claim 3 , further comprising: an estimating unit (S40) configured to estimate an air admixture quantity (Ax) in the reducing agent passage (42) based on the rotation variation parameter (ΔN) obtained by the acquisition unit (S28) when the determination unit (S30) determines that the air admixture is present at the reducing agent passage (42), wherein the control unit (S42) sets the air release quantity (Dc) based on the air admixture quantity (Ax) estimated by the estimating unit (S40) when the determination unit (S30) determines that the air admixture is present at the reducing agent passage (42).
  5. Injection control device according to one of the Claims 2 until 4 , wherein the adjustment unit (S24) sets the injection quantity (Dm) per unit of time in response to an operating condition of the internal combustion engine (30) to be greater than a predetermined reference injection quantity (Do) when the injection quantity (Dm) per unit of time is less than the reference injection quantity (Do), and the adjustment unit (S24) sets the threshold (Ru, Rd) in response to the injection quantity (Dm) per unit of time set by the adjustment unit (S24).
  6. Injection control device according to one of the Claims 1 until 5 , wherein the exhaust gas purification system further comprises a pressure sensing unit (48) which detects a pressure in the reducing agent passage (42), and the injection control device further comprises: a feedback control unit (S16) configured to perform feedback control of a pump drive (44) to control the pressure of the reducing agent detected by the pressure sensing unit (48) during injection by the injector (50) to a predetermined setpoint pressure (Ptg), wherein the acquisition unit (S28) acquires the rotation variation parameter (ΔN) when the pressure in the reducing agent passage (42) is controlled to the setpoint pressure (Ptg) by the feedback control unit (S16).

Description

Technical field The present disclosure relates to an injection control device which determines whether air enters a reducing agent passage in an exhaust gas purification system comprising an injector, the reducing agent passage and a pump. background Recently, a urea system for selective catalytic reduction (urea SCR system) was developed and produced as an exhaust gas purification system for a machine applied to a vehicle, such as a diesel engine, which cleans nitrogen oxides (NOx) in an exhaust gas with a high cleaning rate. The urea SCR system comprises a pump which conveys urea water stored in a tank as a reducing agent to a reducing agent passage, and an injector which injects the urea water conveyed through the reducing agent passage into an exhaust pipe of the engine. In the urea SCR system, the exhaust gas is cleaned by a NOx reduction reaction in the exhaust pipe using a NOx removal catalyst, which is equivalent to an SCR catalyst. During the NOx reduction reaction, the urea solution injected into the exhaust pipe by the injector is hydrolyzed by heat from the exhaust gas to produce ammonia (NH3), which is then adsorbed by the SCR catalyst. The NOx in the exhaust gas is further reduced by a reduction reaction carried out by the ammonia within the SCR catalyst, thus being cleaned. In the urea SCR system, air can enter the reducing agent passage. In other words, air mixing or admixture can occur in the reducing agent passage. For example, the urea SCR system uses a suction and recirculation process to draw the urea solution into the reducing agent passage and return it to the tank to prevent it from freezing when the engine is off. Therefore, when the engine starts, the reducing agent passage in the urea SCR system fills with the urea solution. In this case, air can enter the reducing agent passage. If air enters the reducing agent passage, the injection quantity of the urea solution injected by the injector at the outlet line becomes unstable. The JP 5 338 696 B2 This technology discloses a method for detecting whether air is entering a fuel passage based on the fuel pressure within that passage. By applying this technology to a urea-based SCR system, the presence of air in the reducing agent passage can be determined from the pressure of the urea solution within that passage. DE 199 47 197 A1 The following is disclosed: Device for metering a reducing agent used in catalytic exhaust aftertreatment, in particular a urea or a urea-water solution, comprising a tank for storing the reducing agent, a pump for conveying the reducing agent from the tank to an injection valve through which the reducing agent can be introduced into a mixing chamber, wherein the tank, the pump and the injection valve are connected to each other via a line system comprising a first line between the tank and the pump and a second line between the pump and the injection valve, with a controllable venting circuit branching off from the second line and connected to the tank via feedback. US 2013 / 0 111 882 A1 The following is disclosed: a method for an SCR system in which reducing agent in liquid form is supplied to a feed device and reducing agent is supplied from a container to at least one point of use via the feed device, comprising the steps of: continuously sensing the feed pressure supplied by the feed device and controlling the operation of the feed device based on changes in the feed pressure, with the aim of reducing the effects of unwanted air ingress at the feed device. Furthermore, a computer program product comprising program code for a computer for carrying out a method according to the invention is disclosed. An SCR system and a motor vehicle equipped with the SCR system are also disclosed. JP 2012- 219 655 A The following is disclosed: An exhaust gas purification device for an internal combustion engine supplies a reducing agent by means of a pump from a reducing agent tank to a reducing agent feed device through a reducing agent feed channel during operation of the internal combustion engine and draws the reducing agent back from the reducing agent feed channel when the internal combustion engine is stopped. If the detected flow pressure is lower than a threshold value, an air leakage condition is detected. determines in which air mixes into the reducing agent supply channel during the supply of the reducing agent from the pump, and the reducing agent increase control is executed in this case to increase the supply quantity of the reducing agent from the reducing agent supply device. DE 10 2016 212 263 B3 The document discloses the following: The document relates to a method for determining the quantity of fluid injected during an injection process carried out by means of an injection system of a motor vehicle, in which the fluid is conveyed through a piping system to an injection element, comprising the following steps: - determining the time of occurrence of the maximum of the pressure gradient caused by the i