WO2013084627A1

WO2013084627A1 - Differential pressure detection device for engine

Info

Publication number: WO2013084627A1
Application number: PCT/JP2012/078213
Authority: WO
Inventors: 伸一笹岡
Original assignee: Ｕｄトラックス株式会社
Priority date: 2011-12-05
Filing date: 2012-10-31
Publication date: 2013-06-13
Also published as: JP2013117470A

Abstract

The invention of the present application relates to a differential pressure detection device for detecting differential pressure in an exhaust pipe line of an engine. A differential pressure type flow meter (47) measures an exhaust gas flow rate by detecting the differential pressure across a throttle mechanism (471) provided in an EGR pipe (34A) by a differential pressure sensor (472). A communication pipe (474) for causing a pair of pressure guiding pipes (473a, 473b) for guiding the pressure of exhaust gas to the differential pressure sensor (472) to communicate with each other is provided, and an electromagnetic opening/closing valve (473b) for opening and closing the communication pipe (474) is provided. In a state in which the engine is being rotated and the supply of fuel to the engine is being stopped, the electromagnetic opening/closing valve (473b) is controlled to be opened. Consequently, clogging of the pressure guiding pipes (473a, 473b) is suppressed by causing the exhaust gas to flow via the pressure guiding pipe (473a), the communication pipe (474), and the pressure guiding pipe (473b) to thereby perform scavenging for blowing off soot and the like hitherto deposited in the pressure guiding pipes (473a, 473b).

Description

Engine differential pressure detector

The present invention relates to an engine differential pressure detection device that detects a differential pressure in a pipe line through which engine exhaust flows.

2. Description of the Related Art Conventionally, as an exhaust gas recirculation device (EGR device) that recirculates part of engine exhaust gas to an intake system, a flow rate sensor that measures the flow rate of exhaust gas is provided in an EGR pipe, and the opening of an EGR control valve is based on the output of the flow rate sensor. There is a device that controls the above (for example, see Patent Document 1).

JP 2010-144700 A

By the way, when a differential pressure type flow meter that uses the differential pressure before and after the throttle mechanism is used as a flow sensor for measuring the flow rate of the exhaust, a pressure guide pipe that leads the exhaust pressure to the differential pressure sensor, a soot contained in the engine exhaust, etc. As a result, the pressure guiding tube may become clogged and the flow rate measurement accuracy may be reduced.
When the measurement accuracy of the exhaust flow rate is reduced, the exhaust flow rate actually recirculated with respect to the target exhaust flow rate according to the engine operating state is caused, for example, when the flow rate of the recirculated exhaust gas exceeds the target. There is a problem that the amount of air is insufficient and the generation of soot is increased.

Therefore, in view of the above-mentioned problems of the prior art, an object of the present invention is to provide an engine differential pressure detection device that can suppress clogging of a pressure guiding pipe that introduces exhaust pressure to a differential pressure sensor.

For this reason, the differential pressure detection device for an engine according to the present invention is provided with a communication pipe that communicates a pair of pressure guiding pipes that guide the exhaust pressure to the differential pressure sensor, and an open / close valve that opens and closes the communication pipe is operated in the engine. Open control was performed according to conditions, and the inside of the pair of pressure guiding tubes was scavenged.

According to the present invention, if the on-off valve is controlled to be closed, the differential pressure can be detected by the differential pressure sensor. On the other hand, if the on-off valve is controlled to open, the differential pressure passes through one of the pressure guiding pipe, the communication pipe, and the other pressure guiding pipe. When the exhaust gas flows, the inside of the pressure guiding tube is scavenged, and soot and the like that have been accumulated in the pressure guiding tube are blown off so that clogging of the pressure guiding tube can be suppressed.

Schematic which shows the diesel engine in embodiment of this invention. Partial enlarged view showing in detail the structure of the differential pressure type flow meter shown in FIG. Flow chart showing the flow of scavenging control of the pressure guiding tube of the differential pressure type flow meter

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows a diesel engine 10 for a vehicle to which a differential pressure detecting device according to the present invention is applied. The diesel engine 10 sucks air through the intake pipe 14 and the intake manifold 12.
The intake pipe 14 includes, in order from the upstream side, an air cleaner 16 that filters dust in the air, a compressor 18A of a turbocharger 18 that performs intake air supercharging, and an intercooler that cools the intake air that has passed the compressor 18A and has become hot. 20 is provided.

On the other hand, the diesel engine 10 emits exhaust through the exhaust manifold 22 and the exhaust pipe 24.
The exhaust pipe 24 includes, in order from the upstream side, an exhaust turbine 18B of the turbocharger 18, an injection device 25 having an injection nozzle for injecting fuel into the exhaust pipe 24, a continuously regenerating DPF device 26, and urea as a reducing agent precursor. A reducing agent injection device 28 having an injection nozzle for injecting an aqueous solution into the exhaust pipe 24, an SCR catalyst 30 for reducing NOx using ammonia as a reducing agent generated from an aqueous urea solution, and oxidizing the ammonia that has passed through the SCR catalyst 30 An ammonia oxidation catalyst 32 is provided.

The continuous regeneration type DPF device 26 includes a DOC (Diesel Oxidation Catalyst) 26A that oxidizes nitric oxide NO to nitrogen dioxide NO ₂ , and a DPF (Diesel Particulate Filter) that collects and removes PM (Particulate Matter) in the exhaust gas. 26B.
As the exhaust purification filter, a CSF (Catalyzed Soot Filter) in which a catalyst composed of an active component and an additive component is supported on the filter surface can be used instead of the DPF 26B.

The diesel engine 10 also includes an EGR (Exhaust Gas Recirculation) device 34 that lowers the combustion temperature by recirculating a part of the exhaust to the intake side and reduces the NOx concentration in the exhaust.
The EGR device 34 has an EGR pipe 34A that recirculates part of the exhaust gas flowing through the exhaust pipe 24 to the intake pipe 14, an EGR cooler 34B that cools the exhaust gas that flows through the EGR pipe 34A, and a flow rate of exhaust gas that is recirculated to the intake pipe 14. And an EGR control valve 34C to be controlled.

The EGR pipe 34A is a pipe line that connects the exhaust pipe 24 upstream of the exhaust turbine 18B and the intake pipe 14 downstream of the intercooler 20, and when the EGR control valve 34C is opened, the exhaust side pressure is reduced. By being higher than the intake side pressure, a part of the exhaust gas is recirculated to the intake side via the EGR pipe 34A.

The engine control unit 42 with a built-in computer is connected to the intake pipe 14 via the rotation speed sensor 44 that detects the rotation speed NE of the diesel engine 10, the load sensor 46 that detects the load Q of the diesel engine 10, and the EGR pipe 34A. Output signals of various sensors such as a differential pressure type flow meter 47 that measures the flow rate of the exhaust gas that is recirculated and a vehicle speed sensor 48 that detects the traveling speed VS of the vehicle are input.
Further, the engine control unit 42 inputs a signal of an engine switch 49 for switching operation / stop of the diesel engine 10.

Here, the load sensor 46 detects a state quantity closely related to the torque of the diesel engine 10 such as an intake air flow rate, an intake pressure, a supercharging pressure, and an accelerator opening degree as a state quantity indicating the load Q of the diesel engine 10. .
The differential pressure type flow meter 47 is a flow meter that measures the flow rate of the exhaust gas recirculated to the intake system by detecting the differential pressure before and after the throttle mechanism, and as an example, between the EGR cooler 34B and the EGR control valve 34C. The EGR flow rate is measured in the EGR pipe 34A.

As shown in FIG. 2, the differential pressure type flow meter 47 includes a throttle mechanism 471, a differential pressure sensor 472, a pair of

pressure guiding pipes

473 a and 473 b, a communication pipe 474, and an electromagnetic opening / closing valve 475.
The throttle mechanism 471 is a mechanism that throttles the EGR pipe 34A, which is a conduit through which exhaust flows, and reduces the downstream pressure compared to the upstream pressure, and a known mechanism such as an orifice or a venturi is used. In the example shown in FIG. 2, a venturi is used as the diaphragm mechanism.

The differential pressure sensor 472 includes, for example, two pressure chambers separated by a diaphragm, detects a pressure applied to the diaphragm by a pressure difference between the two pressure chambers using a piezoresistor, a strain gauge, and the like. It is a sensor that outputs an electric signal indicating an applied pressure, that is, a differential pressure.
The flow rate detected based on the differential pressure is a volume flow rate, and the mass flow rate can be obtained from the detection result of the volume flow rate and the density (exhaust temperature) data.

The pair of

pressure guiding pipes

473a and 473b are pipes that guide the exhaust pressure before and after the throttle mechanism 471 to each pressure chamber of the differential pressure sensor 472, and communicate the inside of the EGR pipe 34A and the pressure chamber of the differential pressure sensor 472, respectively. Let
The pressure guiding pipe 473a guides the exhaust pressure on the upstream side of the throttle mechanism 471 to the one pressure chamber of the differential pressure sensor 472, and the pressure guiding pipe 473b is on the side where the pressure on the downstream side of the throttle mechanism 471 decreases. The exhaust pressure is guided to the other pressure chamber of the differential pressure sensor 472.

The communication pipe 474 is a pipe line that allows the pair of

pressure guiding pipes

473 a and 473 b to communicate with each other, and an electromagnetic opening / closing valve 475 that opens and closes the communication pipe 474 is provided in the middle of the communication pipe 474. The communication pipe 474 and the electromagnetic opening / closing valve 475 are provided for scavenging the

pressure guiding pipes

473a and 473b, as will be described later.
That is, if the electromagnetic on-off valve 475 is closed, the

pressure guiding pipes

473a and 473b perform the function of independently guiding the exhaust pressure before and after the throttle mechanism 471 to the differential pressure sensor 472, thereby detecting the differential pressure. Can be done.

On the other hand, when the electromagnetic on-off valve 475 is opened, the

pressure guiding pipes

473a and 473b communicate with each other through the communication pipe 474, and the reflux exhaust is caused by the pressure difference between the front and rear of the throttle mechanism 471 and the pressure guiding pipe 473a, the communication pipe 474, The pressure pipe 473b flows in this order, whereby the pressure guiding pipe 473a on the upstream side of the connection portion of the communication pipe 474 and the pressure guide tube 473b on the downstream side of the connection portion of the communication pipe 474 are scavenged. Become.

The electromagnetic on-off valve 475 can be a normally closed electromagnetic valve that maintains a closed state when not energized and opens when energized.
Further, in order to lengthen the length of the pipeline that is scavenged among the

pressure guiding tubes

473a and 473b, the communication tube 474 communicates with the

pressure guiding tubes

473a and 473b at a position as close as possible to the differential pressure sensor 472.

The engine control unit 42 executes a control program stored in a non-volatile memory such as a built-in ROM (Read Only Memory), thereby injecting and reducing fuel to the diesel engine 10 based on signals from various sensors and switches. The operation of the diesel engine 10 is controlled by outputting operation signals such as the urea aqueous solution injection by the agent injection device 28, the exhaust gas recirculation amount by the EGR device 34, and the opening of the variable nozzle in the turbocharger 18.

The engine control unit 42 calculates the target EGR flow rate based on the engine rotational speed, engine load, etc. as an example of the engine operating conditions as control of the exhaust gas recirculation amount by the EGR device 34, and outputs the target EGR flow rate to the output of the differential pressure type flow meter 47. Feedback control is performed in which the opening degree of the EGR control valve 34C is adjusted so that the actual EGR flow rate detected based on the EGR flow rate approaches the target EGR flow rate.

Further, the engine control unit 42 performs scavenging control for suppressing accumulation of soot on the

pressure guiding tubes

473a and 473b, and suppresses occurrence of a differential pressure detection error due to clogging of the

pressure guiding tubes

473a and 473b.
The flowchart of FIG. 3 shows the flow of scavenging control by the engine control unit 42. Below, scavenging control is demonstrated in detail, referring the flowchart of this FIG.

First, in step S101, it is determined whether or not the diesel engine 10 has been warmed up. For example, if the temperature of the cooling water of the diesel engine 10 or the temperature of the lubricating oil exceeds the determination temperature, it is determined that the warm-up has been completed.
In the cold state from the start of the diesel engine 10 to the completion of warm-up, that is, the condition in which exhaust gas recirculation is not performed, the determination in step S101 is repeated, and the process proceeds to step S102 after the completion of warm-up.
When the diesel engine 10 is in a cold state, the electromagnetic on-off valve 475 is kept closed, and the communication pipe 474 that communicates the

pressure guiding pipes

473a and 473b is kept closed.

When the warm-up is completed and the process proceeds to step S102, the electromagnetic on-off valve 475 is kept closed while the warm-up is continued, and the communication pipe 474 that connects the

pressure guiding pipes

473a and 473b is kept closed.
When the electromagnetic on-off valve 475 is closed, that is, when the communication pipe 474 is closed, the exhaust pressure before and after the throttle mechanism 471 is introduced into the two pressure chambers of the differential pressure sensor 472, respectively. Can be measured.

Therefore, in such a state after warm-up, feedback control is performed in which the opening degree of the EGR control valve 34C is adjusted so that the actual exhaust flow rate detected based on the output of the differential pressure type flow meter 47 approaches the target flow rate.
In step S103, during operation of the diesel engine 10, whether or not it is in a fuel cut state in which fuel supply to the diesel engine 10 is temporarily stopped, in other words, an engine operation region in which fuel cut is performed. Determine whether or not.

As an example, the fuel cut is performed in an engine operation region where the accelerator is fully closed and the engine rotation speed exceeds the set speed.
Here, if the fuel cut state is not established, the process steps of the scavenging control in steps S104 to S106 are bypassed and the process proceeds to step S107.

On the other hand, when it is in the fuel cut state, the process proceeds to step S104 to open the electromagnetic on-off valve 475.
In the fuel cut state in which the combustion stops, exhaust gas recirculation for NOx reduction is unnecessary and the opening degree control of the EGR control valve 34C can be stopped, so that the differential pressure detection can be stopped. Further, in the fuel cut state, although the combustion is stopped, the diesel engine 10 is rotated by inertial force, and air containing no soot is discharged from the diesel engine 10.

Therefore, in the fuel cut state, the electromagnetic on-off valve 475 is opened to make it impossible to detect the differential pressure.
Even during fuel cut, when the opening control of the EGR control valve 34C is performed based on the detected value of the exhaust flow rate by the differential pressure type flow meter 47, the electromagnetic on-off valve 475 is opened for scavenging. In this case, the opening degree of the EGR control valve 34C is shifted to an open control state in which the opening degree is controlled to the basic opening degree according to the operating conditions.

On the other hand, when the EGR control valve 34C is controlled to be closed in the fuel cut state, the EGR control valve 34C is opened to the set opening when the electromagnetic opening / closing valve 475 is opened for scavenging. Exhaust gas flows through 34A, and the opening degree control of the EGR control valve 34C based on the differential pressure detection is stopped.
When the electromagnetic on-off valve 475 is opened in a state where the fuel is cut and the exhaust gas flows through the EGR pipe 34A, air that does not include soot or the like is introduced into the pressure guiding pipe 473a, the communication pipe 474, and the pressure guiding pipe 473b. In this way, scavenging is performed to blow off the soot and the like that have been deposited in the

pressure guiding tubes

473a and 473b until then, and the progress of soot deposition can be suppressed.

That is, the electromagnetic on-off valve 475 is opened during the fuel cut, and the exhaust gas flowing in the EGR pipe 34A is caused to flow through the pressure guiding pipe 473a, the communication pipe 474, and the pressure guiding pipe 473b, thereby affecting the EGR control for reducing NOx. Without giving the pressure, the

pressure guiding tubes

473a and 473b can be scavenged to blow away deposits such as soot.
As a result, it is possible to suppress the detection accuracy of the differential pressure in the differential pressure type flow meter 47 from deteriorating due to accumulation of soot on the

pressure guiding pipes

473a and 473b, and to maintain high detection accuracy over a long period of time. High drivability can be stably maintained by controlling the target according to the driving state with high accuracy.

Moreover, since the scavenging is performed by using the differential pressure in the EGR pipe 34A by opening the electromagnetic on-off valve 475, an excessively high load is not applied to the diaphragm or the like of the differential pressure sensor 472. Damage to the pressure sensor 472 can be suppressed.
In order to perform scavenging of the

pressure guiding pipes

473a and 473b efficiently, when scavenging is performed, the opening degree of the EGR control valve 34C is made larger than that during non-scavenging, and the exhaust gas flowing through the EGR pipe 34A is The amount can be increased.

Further, it is not necessary to carry out scavenging of the

pressure guiding pipes

473a and 473b every time a fuel cut is performed. For example, the operation time of the diesel engine 10 since the previous scavenging execution, the accumulated EGR amount, the travel distance of the vehicle, etc. It can be determined whether or not scavenging is performed according to the above.
Further, the opening / closing control of the electromagnetic on-off valve 475 is delayed with respect to the start of the fuel cut, and after the combustion exhaust of the diesel engine 10 is released and the combustion exhaust does not flow in the EGR pipe 34A, the electromagnetic on-off valve 475 is operated. Can be opened.

When the opening control of the electromagnetic on-off valve 475 is performed in step S104, the process proceeds to step S105, and it is determined whether or not the fuel cut state continues.
If the fuel cut state continues, the process returns to step S104, and the opening control of the electromagnetic on-off valve 475 is continued.

In addition, when the scavenging time has elapsed since the start of scavenging, and the scavenging time has elapsed from the start of scavenging, without waiting for the fuel cut state to stop, that is, the resumption of fuel supply. The scavenging can be stopped by controlling the electromagnetic on-off valve 475 to close.
On the other hand, when the fuel cut is stopped and the fuel supply is restarted, the process proceeds from step S105 to step S106, and by closing control of the electromagnetic on-off valve 475, scavenging is stopped and the differential pressure can be detected. return. And if it is the implementation conditions of the feedback control of EGR flow volume, the feedback control which controls the opening degree of the EGR control valve 34C based on the differential pressure detected by the differential pressure type flow meter 47 is restarted.

In the next step S107, it is determined whether or not the engine switch 49 is turned off.
When the engine switch 49 is on and the operation of the diesel engine 10 is continued and the fuel cut state is not established, the process returns to step S102 and the electromagnetic on-off valve 475 is maintained in the closed state.

On the other hand, when the engine switch 49 is switched from on to off and the operation of the diesel engine 10 is stopped, the process proceeds to step S108, the electromagnetic on-off valve 475 is controlled to open, and scavenging of the

pressure guiding pipes

473a and 473b is performed. .
Although the fuel supply to the diesel engine 10 is stopped when the engine switch 49 is switched from on to off, the diesel engine 10 has a period during which the engine 10 continues to rotate due to inertia, and finally stops rotating after the inertial rotation period. To do.
Therefore, in step S108, the fuel supply is stopped, and the period during which the diesel engine 10 is rotating by inertia, in other words, the period from when the fuel supply is stopped until the rotation of the diesel engine 10 stops. The electromagnetic on-off valve 475 is controlled to open.

Here, when the EGR control valve 34C is set to be closed when the engine switch 49 is turned off, the EGR control valve 34C is opened to the set opening degree in parallel with the opening control of the electromagnetic on-off valve 475, The exhaust gas is allowed to flow through the EGR pipe 34A.
When the diesel engine 10 is rotating with inertia just before it is stopped, it is a condition that EGR control is unnecessary. Therefore, if scavenging of the

pressure guiding tubes

473a and 473b is performed at this time, the drivability of the diesel engine 10 is adversely affected. The

exhaust pipes

473a and 473b can be scavenged with exhaust gas that does not give soot and does not contain soot and the like, and accumulation of soot and the like on the

guide pipes

473a and 473b can be suppressed.

In step S109, it is determined whether or not the rotation of the diesel engine 10 is stopped. While the diesel engine 10 is rotating by inertia, the process returns to step S108, and the electromagnetic on-off valve 475 is opened, that is, the scavenging state. To maintain.
On the other hand, if it is determined in step S109 that the rotation of the diesel engine 10 has stopped, the exhaust gas does not flow through the EGR pipe 34A even when the EGR control valve 34C is in the open state. The differential pressure disappears and scavenging cannot be performed. Then, it progresses to step S110, the electromagnetic on-off valve 475 is switched to a closed state, and scavenging control is complete | finished.

The electromagnetic on-off valve 475 can be switched to an open state after the engine switch 49 is turned off, and the scavenging time stored in advance from the time when the engine switch 49 is turned off without determining whether the engine rotation has stopped. When elapses, the electromagnetic on-off valve 475 can be returned to the closed state.

Although the contents of the present invention have been specifically described with reference to the preferred embodiments, it is obvious that those skilled in the art can take various modifications based on the basic technical idea and teachings of the present invention. It is.
For example, in the present embodiment, the diesel engine 10 is assumed, but the differential pressure detection device according to the present invention can also be applied to a gasoline engine including an EGR device.

Further, the scavenging control when the engine is stopped is not limited to the time when the engine switch 49 is turned off. For example, the scavenging can be performed during the inertia rotation even when the engine is stopped under the idle stop control.
In addition, in the device that detects the clogging of the DPF 26B by measuring the pressure difference before and after the DPF 26B, a communication pipe that connects the pair of pressure guiding pipes of the differential pressure sensor is provided, and at the time of fuel cut or before the engine stops In the inertial rotation state, the pressure guide tube can be scavenged by controlling the opening and closing of the on-off valve that opens and closes the communication tube.

Further, for example, in a diesel engine that is operated with a high excess air ratio in a low load region to suppress soot generation, the diesel engine is burned with a high excess air ratio, in other words, included in the exhaust. In the combustion state in which soot is minimized, the opening control of the EGR control valve is stopped, the open / close valve for opening and closing the communication pipe is opened, and the pressure guiding pipe is scavenged.

In addition, the

pressure guiding tubes

473a, 473b and the communication tube 474 are in communication with the connection portion between the pressure guiding tube 473a and the communication tube 474, and the connection portion between the pressure guiding tube 473b and the communication tube 474, and the

pressure guiding tubes

473a, 473b. And a switching valve for switching between the pressure chamber of the differential pressure sensor 472 and the pressure chamber of the differential pressure sensor 472 can be provided to close the pressure chamber of the differential pressure sensor 472 in the scavenging state.

Further, by alternately repeating the opening control and the closing control of the electromagnetic on-off valve 475, the electromagnetic on-off valve 475 is periodically opened and closed, and the scavenging is repeatedly executed / interrupted, so that deposits such as soot are shaken and deposited. The effect of blowing off objects can be enhanced.
The on-off valve that opens and closes the communication pipe 474 is not limited to an electromagnetic type, and an on-off valve driven by a motor, an on-off valve driven by a cylinder, or the like can be used.
Further, when the output of the differential pressure sensor 472 does not change with the switching of the electromagnetic on / off valve 475 that opens and closes the communication pipe 474, the occurrence of a failure in the differential pressure sensor 472 and / or the electromagnetic on / off valve 475 can be diagnosed. it can.

DESCRIPTION OF SYMBOLS 10 Diesel engine 24 Exhaust pipe 25 Exhaust pipe injection device 26 Continuous regeneration type DPF device 26A DOC
26B DPF
28 Reducing agent injection device 30 SCR catalyst 32 Ammonia oxidation catalyst 34 EGR device 34A EGR pipe (exhaust gas recirculation pipe)
34B EGR cooler 34C EGR control valve 42 Control unit 47 Differential pressure flow meter (Differential pressure detector)
471 Throttle mechanism 472

Differential pressure sensor

473a, 473b Pressure guiding pipe 474 Communication pipe 475 Electromagnetic on-off valve 49 Engine switch

Claims

A differential pressure detecting device for detecting a differential pressure in a pipe line through which exhaust of an engine flows,
A differential pressure sensor,
A pair of pressure guiding pipes for guiding the pressure of the exhaust to the differential pressure sensor;
A communication pipe for communicating the pair of pressure guiding pipes with each other;
An on-off valve for opening and closing the communication pipe,
An engine differential pressure detection device that opens the on-off valve in accordance with an operating condition of the engine to scavenge the pair of pressure guiding pipes.
2. The engine according to claim 1, wherein when the engine is rotating and fuel supply to the engine is stopped, the on-off valve is controlled to open and the inside of the pair of pressure guiding pipes is scavenged. Differential pressure detection device.
3. The engine differential pressure detection device according to claim 2, wherein in the engine operating region in which fuel cut is performed, the on-off valve is controlled to open and the inside of the pair of pressure guiding pipes is scavenged.
3. The engine differential pressure detection device according to claim 2, wherein the on-off valve is controlled to open and the inside of the pair of pressure guiding pipes is scavenged from when the engine switch is turned off until the rotation of the engine stops.
The differential pressure detection device for an engine according to claim 1, wherein a differential pressure between an upstream side and a downstream side of a throttle mechanism provided in the pipeline is detected, and a flow rate of exhaust gas flowing through the pipeline is measured.
The engine differential pressure detection device according to claim 5, wherein the pipe line is an exhaust gas recirculation pipe for recirculating exhaust gas to an intake system, and the exhaust gas recirculation amount is measured based on the differential pressure.
The engine differential pressure detection device according to claim 1, wherein the opening control and the closing control of the on-off valve are alternately repeated to scavenge the pair of pressure guiding pipes.
The engine differential pressure detection device according to claim 1, wherein the differential pressure detection device diagnoses the presence or absence of a failure in the differential pressure detection device based on an output change of the differential pressure sensor accompanying opening and closing of the on-off valve.
The engine differential pressure detection device according to claim 1, wherein the pressure chamber of the differential pressure sensor is closed when scavenging the pair of pressure guiding pipes.