Exhaust treatment system

Abstract

To provide an exhaust gas treatment device that can control the flow velocity of exhaust gas in the GPF and improve the collection efficiency of particulate matter in the GPF. [Solution] The system comprises a secondary air supply device having an injection nozzle that injects air in a direction along the flow of exhaust gas upstream of the GPF, a differential pressure sensor that measures the pressure difference between the upstream and downstream of the GPF, and an ECU that controls the injection of air from the injection nozzle. The ECU estimates the amount of particulate matter deposited in the GPF based on the output value of the differential pressure sensor (step S1), estimates or measures the flow velocity of the exhaust gas upstream of the GPF in the exhaust passage, and estimates the pressure loss of the exhaust gas in the GPF based on the estimated amount of particulate matter deposited and the estimated or measured flow velocity of the exhaust gas (step S5). If the estimated pressure loss value is less than a predetermined threshold (Yes in step S5), the ECU 1 performs air injection from the injection nozzle 6 (step S7).

Description

Technical Field

[0001] The present invention relates to an exhaust gas treatment device.

Background Art

[0002] Patent Document 1 discloses an exhaust gas purification device provided with a gasoline particulate filter (GPF) for collecting particulate matter (PM) in exhaust gas in an exhaust passage of a gasoline engine. In this exhaust gas purification device, the particulate matter collected in the GPF naturally burns and disappears as the exhaust gas temperature rises, and the regeneration of the GPF is performed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, it is known that the collection rate of particulate matter in the GPF is affected by the pressure loss of the exhaust gas in the GPF, and the pressure loss of the exhaust gas changes depending on the flow rate of the exhaust gas. Therefore, in order to improve the collection rate of particulate matter in the GPF, it is desirable to control the flow rate of the exhaust gas to be within an appropriate range.

[0005] However, in the technology described in Patent Document 1, the relationship between the collection rate of particulate matter in the GPF and the flow rate of the exhaust gas is not considered, and there is a problem that the collection rate of particulate matter in the GPF cannot be improved.

[0006] Therefore, an object of the present invention is to provide an exhaust gas treatment device that can control the flow rate of the exhaust gas in the GPF and improve the collection rate of particulate matter in the GPF.

Means for Solving the Problems

[0007] To solve the above problems, the present invention provides an exhaust treatment device to be mounted on a vehicle comprising: an internal combustion engine that uses gasoline as fuel; an exhaust passage through which exhaust gas discharged from the internal combustion engine passes; a three-way catalytic converter provided in the exhaust passage for purifying the exhaust gas; and a GPF provided in the exhaust passage for collecting particulate matter in the exhaust gas, the device comprising: a secondary air supply device having an injection nozzle that injects air in a direction along the flow of exhaust gas upstream of the GPF in the exhaust passage; a differential pressure sensor that measures the pressure difference between the upstream and downstream of the GPF in the exhaust passage; and a control unit that controls the injection of air from the injection nozzle, wherein the control unit estimates the amount of particulate matter deposited in the GPF based on the output value of the differential pressure sensor, estimates or measures the flow velocity of the exhaust gas upstream of the GPF in the exhaust passage, estimates the pressure loss of the exhaust gas in the GPF based on the estimated amount of particulate matter deposited and the estimated or measured flow velocity of the exhaust gas, and executes air injection from the injection nozzle when the estimated pressure loss value is less than a predetermined threshold. [Effects of the Invention]

[0008] Thus, according to the present invention, it is possible to control the flow velocity of exhaust gas in the GPF and improve the collection efficiency of particulate matter in the GPF. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a diagram showing the configuration of a vehicle equipped with an exhaust treatment device according to one embodiment of the present invention. [Figure 2] Figure 2 is a flowchart illustrating the control operation of air injection in an exhaust treatment device according to one embodiment of the present invention. [Figure 3] Figure 3 is a flowchart illustrating the details of the air injection pressure setting of an exhaust treatment device according to one embodiment of the present invention. [Figure 4] Figure 4 is a timing chart illustrating the changes in vehicle state during air injection control of an exhaust treatment device according to one embodiment of the present invention. [Modes for carrying out the invention]

[0010] An exhaust treatment device according to one embodiment of the present invention is an exhaust treatment device mounted on a vehicle comprising: an internal combustion engine that uses gasoline as fuel; an exhaust passage through which exhaust gas discharged from the internal combustion engine passes; a three-way catalytic converter provided in the exhaust passage for purifying the exhaust gas; and a GPF provided in the exhaust passage for collecting particulate matter in the exhaust gas, the device comprising: a secondary air supply device having an injection nozzle that injects air in a direction along the flow of exhaust gas upstream of the GPF in the exhaust passage; a differential pressure sensor that measures the pressure difference between the upstream and downstream of the GPF in the exhaust passage; and a control unit that controls the injection of air from the injection nozzle, wherein the control unit estimates the amount of particulate matter deposited in the GPF based on the output value of the differential pressure sensor, estimates or measures the flow velocity of the exhaust gas upstream of the GPF in the exhaust passage, estimates the pressure loss of the exhaust gas in the GPF based on the estimated amount of particulate matter deposited and the estimated or measured flow velocity of the exhaust gas, and executes air injection from the injection nozzle when the estimated pressure loss value is less than a predetermined threshold. As a result, the exhaust gas treatment device according to one embodiment of the present invention can control the flow velocity of exhaust gas in the GPF and improve the collection rate of particulate matter in the GPF. [Examples]

[0011] Hereinafter, a vehicle control device according to one embodiment of the present invention will be described with reference to the drawings. Figures 1 to 5 are diagrams illustrating a vehicle control device according to one embodiment of the present invention.

[0012] In Figure 1, a vehicle 10 equipped with an exhaust treatment device according to one embodiment of the present invention comprises an internal combustion engine 2 that uses gasoline as fuel, and an ECU (Electronic Control Unit) 1 which serves as a control unit for controlling the vehicle 10.

[0013] The internal combustion engine 2 has multiple cylinders. In this embodiment, the internal combustion engine 2 is configured to perform a series of four strokes for each cylinder, consisting of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke.

[0014] Furthermore, the internal combustion engine 2 is equipped with an exhaust pipe 9. The exhaust pipe 9 forms an exhaust passage 9A through which the exhaust gas discharged from the internal combustion engine 2 passes. The exhaust passage 9A is equipped with a three-way catalytic converter 3 for purifying the exhaust gas and a GPF (Gasoline Particulate Filter) 4 for collecting particulate matter (PM) in the exhaust gas.

[0015] The three-way catalyst 3 consists of a three-way catalyst with precious metals such as palladium and rhodium attached to the surface of a support such as ceramic, and is designed to simultaneously purify three types of harmful substances in exhaust gas—hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx)—through oxidation and reduction reactions. The three-way catalyst 3 is housed in the three-way catalyst case 3A, and the internal space of the three-way catalyst case 3A constitutes part of the exhaust passage 9A.

[0016] The GPF4 is located downstream of the three-way catalytic converter 3 in the exhaust flow direction. The GPF4 is housed in the GPF case 4A, and the internal space of the GPF case 4A forms part of the exhaust passage 9A.

[0017] Vehicle 10 is equipped with a flow velocity sensor 7, which detects the flow velocity of exhaust gas between the three-way catalytic converter 3 and the GPF 4 in the exhaust passage 9A of the exhaust pipe 9. The flow velocity sensor 7 transmits a detection signal to the ECU 1.

[0018] Vehicle 10 is equipped with a differential pressure sensor 8, which measures the pressure difference between the upstream and downstream of the GPF4 in the exhaust passage 9A of the exhaust pipe 9. The differential pressure sensor 8 transmits a detection signal to the ECU1.

[0019] The vehicle 10 includes a secondary air supply device 11. The secondary air supply device 11 is composed of an air pump 5 and an injection nozzle 6. The air pump 5 compresses air and accumulates the compressed air. The injection nozzle 6 is connected to the air pump 5 and injects air in the direction along the exhaust gas flow upstream of the GPF 4 in the exhaust passage 9A. The injection nozzle 6 has a valve (not shown), and air is injected when the valve is opened according to the instruction of the ECU 1. The injection nozzle 6 is provided at the upstream part (the immediately preceding part) of the GPF 4 in the GPF case 4A.

[0020] The ECU 1 is composed of a computer unit including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory for storing backup data and the like, an input port, and an output port.

[0021] In the ROM of this computer unit, a program for making the computer unit function as the ECU 1 is stored together with various constants, various maps, and the like. That is, when the CPU executes the program stored in the ROM using the RAM as a working area, these computer units function as the ECU 1 in this embodiment.

[0022] Various sensors including the aforementioned flow velocity sensor 7 and differential pressure sensor 8 are connected to the input port of the ECU 1.

[0023] Various controlled objects including the air pump 5 and the injection nozzle 6 are connected to the output port of the ECU 1. The ECU 1 controls various controlled objects including the internal combustion engine 2 based on the information obtained from various sensors.

[0024] The ECU1 performs a regeneration operation of the GPF4 when predetermined conditions are met. This regeneration operation involves raising the temperature of the exhaust gas by retarding the ignition timing, etc., and using this heat to raise the temperature of the GPF4, thereby burning off the particulate matter accumulated on the GPF4. The ECU1 also controls the injection of air from the injection nozzle 6.

[0025] Here, the particulate matter collection efficiency in GPF4 is affected by the pressure drop of the exhaust gas in GPF4. In other words, as the pressure drop of the exhaust gas increases, the exhaust gas becomes less able to flow, making it easier to collect particulate matter. The pressure drop of the exhaust gas changes depending on the amount of particulate matter deposited in GPF4 and the flow velocity of the exhaust gas. Specifically, when the pressure drop is below a predetermined upper limit, the greater the amount of particulate matter deposited and the faster the flow velocity of the exhaust gas, the greater the pressure drop and the better the particulate matter collection efficiency. Therefore, by controlling the flow velocity of the exhaust gas so that the pressure drop is within an appropriate range below the upper limit, it is possible to maintain a high particulate matter collection efficiency in GPF4.

[0026] Therefore, the ECU1 estimates the exhaust gas pressure drop based on the amount of particulate matter deposited in the GPF4 and the exhaust gas flow velocity. When the pressure drop is below a predetermined threshold, it injects air into the exhaust passage 9A using the injection nozzle 6 to increase the exhaust gas flow velocity and thus increase the exhaust gas pressure drop, thereby improving the collection efficiency of particulate matter in the GPF4. The predetermined threshold is the pressure drop value at which the collection efficiency of the GPF4 drops below a predetermined collection efficiency. This value varies depending on the specifications of the GPF4, etc., and is determined in advance through experiments or other means and stored in the ECU1.

[0027] More specifically, the ECU1 estimates the amount of particulate matter deposited in the GPF4 based on the output value of the differential pressure sensor 8, estimates or measures the flow velocity of the exhaust gas upstream of the GPF4 in the exhaust passage 9A, and estimates the pressure drop of the exhaust gas in the GPF4 based on the estimated amount of particulate matter deposited and the estimated or measured flow velocity of the exhaust gas. Then, if the estimated pressure drop value is less than a predetermined threshold, the ECU1 performs air injection from the injection nozzle 6.

[0028] Furthermore, the ECU1 adjusts the air injection pressure from the injection nozzle 6 according to the estimated exhaust gas pressure drop value. The ECU1 adjusts the air injection pressure so that the pressure drop value remains approximately constant within an appropriate range that is above a threshold and below an upper limit.

[0029] Furthermore, ECU1 prohibits air injection by the injection nozzle 6 while GPF4 regeneration control is being performed. In this embodiment, since ECU1 is in charge of the execution of regeneration control, ECU1 itself directly determines whether or not regeneration control is being performed. On the other hand, since the temperature of the exhaust gas or the temperature of GPF4 rises above a predetermined temperature while regeneration control is being performed, if another controller is in charge of the execution of regeneration control, ECU1 can indirectly determine whether or not regeneration control is being performed based on whether or not the temperature of the exhaust gas or the temperature of GPF4 has risen above a predetermined temperature.

[0030] An example of the air injection control operation by the ECU1 of the vehicle 10 configured as described above will be explained with reference to the flowcharts shown in Figures 2 and 3.

[0031] In Figure 2, ECU1 estimates the amount of particulate matter (indicated as PM in the figure) deposited in GPF4 (Step S1).

[0032] Next, ECU1 determines whether the amount of deposit is less than the regeneration control threshold (step S2). If it is determined in step S2 that the amount is not less than the regeneration control threshold (No in step S2), ECU1 returns to step S1.

[0033] If ECU1 determines in step S2 that the regeneration control threshold is below the threshold (Yes in step S2), it determines whether or not GPF4 regeneration control is in progress (step S3). If ECU1 determines in step S3 that GPF4 regeneration control is in progress (Yes in step S3), ECU1 prohibits air injection by the injection nozzle 6 (step S8) and terminates the current operation.

[0034] If ECU1 determines in step S3 that it is not controlling the regeneration of GPF4 (No in step S3), it permits air injection by the injection nozzle 6 (step S4).

[0035] Next, ECU1 determines whether the GPF pressure loss value is below a threshold (step S5). The GPF pressure loss value is the pressure loss value of the exhaust gas in GPF4. If step S5 determines that the GPF pressure loss value is not below a threshold (No in step S5), ECU1 prohibits air injection by the injection nozzle 6 (step S8) and terminates the current operation.

[0036] If ECU1 determines in step S5 that the GPF pressure drop value is below the threshold (Yes in step S5), it sets the air injection pressure (step S6). Details of step S6 will be described later.

[0037] Next, ECU1 performs air injection (step S7) and concludes this operation.

[0038] The details of the air injection pressure setting operation in step S6 will be explained below with reference to Figure 3.

[0039] In Figure 3, the ECU1 calculates the amount of particulate matter (indicated as PM in the figure) deposited in the GPF4 based on the detection results of the differential pressure sensor 8 (step S11).

[0040] Next, ECU1 calculates an estimated GPF pressure loss based on the exhaust gas flow velocity upstream of GPF4 in the exhaust passage 9A (step S12). In step S12, ECU1 calculates an estimated GPF pressure loss based on the amount of particulate matter deposited and the exhaust gas flow velocity calculated in step S11.

[0041] Next, the ECU1 calculates the air injection pressure of the injection nozzle 6 (step S13). Here, the ECU1 sets the air injection pressure according to the pressure loss value estimated in step S12.

[0042] Next, ECU1 determines whether or not air injection by the injection nozzle 6 is permitted (step S14). If it determines that air injection is not permitted (No in step S14), ECU1 returns to step S11.

[0043] If ECU1 determines in step S14 that air injection is permitted (Yes in step S14), it outputs the value of the air injection pressure (step S15) and terminates this operation.

[0044] Referring to the timing chart in Figure 4, the changes in the vehicle state during air injection control will be explained. In Figure 4, the vertical axis represents pressure loss, pressure loss judgment flag, presence or absence of air injection prohibition, injection nozzle state, air injection pressure, and exhaust gas flow velocity, while the horizontal axis represents time.

[0045] In the initial state at time t0, since the regeneration control of GPF4 is not being performed, the air injection prohibition is set to 0 (permitted). Also, since the pressure loss is below the threshold and the pressure loss judgment flag is 1 (below threshold), air is being injected from the injection nozzle 6. As a result, the exhaust gas flow velocity increases, and the pressure loss increases.

[0046] Subsequently, at time t1, the pressure loss increased beyond the threshold, causing the pressure loss judgment flag to switch to 0 (above the threshold), and the injection of air from the injection nozzle 6 is stopped.

[0047] Subsequently, at time t2, the pressure loss decreases to below the threshold, and the pressure loss judgment flag switches to 1 (below threshold). At the same time, at time t2, the regeneration control of GPF4 is started, so the air injection prohibition switches to 1 (prohibited). Therefore, the cessation of air injection from injection nozzle 6 continues.

[0048] Subsequently, at time t3, the regeneration control of GPF4 is completed, and the air injection prohibition is switched to 0 (allowed). Also, since the pressure loss is below the threshold and the pressure loss judgment flag is 1 (below threshold), air is injected from injection nozzle 6.

[0049] Subsequently, at time t4, the pressure loss increased beyond the threshold, causing the pressure loss judgment flag to switch to 0 (above the threshold), and the injection of air from the injection nozzle 6 was stopped.

[0050] Subsequently, at time t5, the pressure loss decreased below the threshold, causing the pressure loss determination flag to switch to 1 (below threshold), and air injection from the injection nozzle 6 was initiated.

[0051] Subsequently, at time t6, the pressure loss increased beyond the threshold, causing the pressure loss judgment flag to switch to 0 (above the threshold), and the injection of air from the injection nozzle 6 was stopped.

[0052] As described above, in this embodiment, the ECU1 estimates the amount of particulate matter deposited in the GPF4 based on the output value of the differential pressure sensor 8, estimates or measures the flow velocity of the exhaust gas upstream of the GPF4 in the exhaust passage 9A, and estimates the pressure drop of the exhaust gas in the GPF4 based on the estimated amount of particulate matter deposited and the estimated or measured flow velocity of the exhaust gas. If the estimated pressure drop value is less than a predetermined threshold, the ECU1 performs air injection from the injection nozzle 6.

[0053] As a result, when the pressure drop value is below a predetermined threshold, air injection by the injection nozzle 6 is performed upstream of the GPF4 in the exhaust passage 9A, increasing the exhaust gas flow velocity and thus increasing the exhaust gas pressure drop in the GPF4, thereby improving the collection efficiency of particulate matter in the GPF4. Consequently, the exhaust gas flow velocity in the GPF4 can be controlled, and the collection efficiency of particulate matter in the GPF4 can be improved.

[0054] In this embodiment, the ECU1 adjusts the pressure of the air injection from the injection nozzle 6 according to the estimated value of the exhaust gas pressure loss.

[0055] As a result, the amount of air injected from the injection nozzle 6 is appropriately adjusted according to the pressure loss of the exhaust gas, thereby more effectively controlling the pressure loss of the exhaust gas and improving the collection efficiency of particulate matter into the GPF 4.

[0056] Furthermore, in this embodiment, the ECU1 prohibits air injection by the injection nozzle 6 while the regeneration control of the GPF4 is being performed.

[0057] Therefore, if air injection from the injection nozzle 6 is performed during the regeneration control of GPF4, which would cause the temperature of GPF4 to become high, it may lower the temperature of GPF4 and hinder the regeneration control. In such cases, prohibiting air injection from the injection nozzle 6 allows for optimal regeneration of GPF4.

[0058] While embodiments of the present invention have been disclosed, it will be apparent to those skilled in the art that modifications can be made without departing from the scope of the invention. All such modifications and equivalents are intended to be included in the following claims. [Explanation of Symbols]

[0059] 1 ECU (control unit) 2 Internal Combustion Engine 3 three-way catalyst 4 GPF 6. Spray nozzle 8. Differential pressure sensor 9A Exhaust passage 10 vehicles 11. Secondary air supply device

Claims

1. An internal combustion engine that uses gasoline as fuel, An exhaust passage through which exhaust gas discharged from the internal combustion engine passes, A three-way catalytic converter is provided in the exhaust passage for purifying exhaust gas, An exhaust treatment device mounted on a vehicle, comprising a GPF provided in the exhaust passage for collecting particulate matter in the exhaust gas, A secondary air supply device having an injection nozzle that injects air in a direction along the flow of exhaust gas upstream of the GPF in the exhaust passage, A differential pressure sensor for measuring the pressure difference between the upstream and downstream of the GPF in the exhaust passage, The system includes a control unit that controls the injection of air from the injection nozzle, The control unit, Based on the output value of the differential pressure sensor, the amount of particulate matter deposited in the GPF is estimated. The flow velocity of the exhaust gas upstream of the GPF in the exhaust passage is estimated or measured. Based on the estimated amount of particulate matter deposited and the estimated or measured exhaust gas flow velocity, the exhaust gas pressure loss in the GPF is estimated. An exhaust treatment apparatus characterized by performing air injection from the injection nozzle when the estimated pressure loss value is less than a predetermined threshold.

2. The exhaust gas treatment apparatus according to claim 1, characterized in that the control unit adjusts the pressure of the air injection from the injection nozzle according to the estimated value of the exhaust gas pressure loss.

3. The exhaust gas treatment apparatus according to claim 1 or 2, characterized in that the control unit prohibits air injection by the injection nozzle while the regeneration control of the GPF is being performed.

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