JP2013117470A - Differential pressure detection device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the jamming of a lead pipe for introducing the pressure of exhaust air to a differential pressure sensor by blowing away soot or the like accumulated in the lead pipe.SOLUTION: A differential pressure type flowmeter 47 which measure an EGR flow rate by detecting a differential pressure before and after a diaphragm mechanism 471 provided in an EGR pipe 34A includes: a communication pipe 474 for making a pair of lead pipes 473a and 473b for introducing the pressure of exhaust air to a differential pressure sensor 472 communicate with each other; and an electromagnetic opening/closing valve 473b for opening and closing the communication pipe 474. Then, in a state that the supply of fuel to an engine is stopped during the rotation of the engine, the opening control of the electromagnetic opening/closing valve 473b is executed so that exhaust air can be made to flow via the lead pipe 473a, the communication pipe 474 and the lead pipe 473b. Thus, it is possible to execute scavenging air of blowing away soot or the like accumulated in the lead pipes 473a and 473b until that time.

Description

  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.

  Conventionally, as an exhaust gas recirculation device that recirculates part of engine exhaust gas to an intake system, a flow rate sensor for measuring the flow rate of recirculated exhaust gas (EGR gas flow rate) is provided in an EGR pipe, and an EGR valve is opened based on the output of the flow rate sensor. There is a device that controls the degree (see, for example, Patent Document 1).

JP 2010-144700 A

By the way, when using a differential pressure type flow meter that utilizes the differential pressure before and after the throttle mechanism as a flow sensor for measuring the EGR gas flow rate, a soot contained in the engine exhaust, etc. As a result of adhering and depositing, the pressure guiding tube is clogged, and the measurement accuracy of the EGR gas flow rate may be lowered.
When the measurement accuracy of the EGR gas flow rate decreases, the actual EGR gas flow rate becomes excessive or insufficient with respect to the target EGR gas flow rate according to the engine operating state. For example, the EGR flow rate becomes excessive, resulting in insufficient air. This causes problems such as increasing the generation of wrinkles.

  SUMMARY OF THE INVENTION In view of the above-described 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 causes the one pressure guiding tube, the communication tube, and the other pressure guiding tube to be detected. As 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 away 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 exhaust pipe injection device 25 having an injection nozzle for injecting fuel gas oil into the exhaust pipe 24, a continuously regenerating DPF device 26, a reducing agent precursor. As a reducing agent injection device 28 having an injection nozzle for injecting a urea aqueous solution into the exhaust pipe 24, an SCR catalyst 30 for reducing NOx using ammonia (reducing agent) generated from the urea aqueous solution, and the SCR catalyst 30. An ammonia oxidation catalyst 32 for oxidizing ammonia is provided.

The continuous regeneration type DPF device 26 includes a DOC (Diesel Oxidation Catalyst) 26A that oxidizes NO (nitrogen monoxide) to NO2 (nitrogen dioxide) and a DPF (Diesel) that collects and removes PM (Particulate Matter) in the exhaust gas. Particulate Filter) 26B.
As the exhaust purification filter, a CSF (Catalyzed Soot Filter) having a catalyst (active component and additive component) 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 includes an EGR pipe 34A as an exhaust gas recirculation pipe that recirculates a 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 flowing through the EGR pipe 34A, and a return to the intake pipe 14. And an EGR control valve 34C for controlling the flow rate of exhaust gas (in other words, the EGR rate).

  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.

An engine control unit (ECU) 42 having a built-in computer intakes air via a rotational speed sensor 44 that detects the rotational speed NE of the diesel engine 10, a load sensor 46 that detects the load Q of the diesel engine 10, and an EGR pipe 34A. Output signals of various sensors such as a differential pressure type flow meter (differential pressure detecting device) 47 for measuring the flow rate of exhaust gas recirculated to the pipe 14 (EGR flow rate), and a vehicle speed sensor 48 for detecting the traveling speed (vehicle speed) VS of the vehicle. input.
Further, the engine control unit 42 inputs a signal of an engine switch (engine key switch) 49 that switches 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 EGR flow rate (the flow rate of the exhaust gas recirculated to the intake system) by detecting the differential pressure before and after the throttle mechanism. As an example, the EGR cooler 34B and the EGR control valve 34C are used. The EGR flow rate is measured in the EGR pipe 34A between the two.

As shown in FIG. 2, the differential pressure type flow meter 47 (differential pressure detection device) 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 on-off 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 or a strain gauge, and adds the pressure chamber to the diaphragm. It is a sensor that outputs an electric signal indicating a 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. The pressure pipe 473b flows in this order, whereby the pressure guiding pipe 473a upstream of the connection portion of the communication pipe 474 and the pressure guide pipe 473b downstream 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 increase the length of the scavenged pipe 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 (exhaust particulates) on the pressure guiding pipes 473a and 473b, and the detection error of the differential pressure (EGR flow rate) due to clogging of the pressure guiding pipes 473a and 473b is detected. Suppresses the occurrence.
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 warm-up completion 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 (in other words, the EGR cut state), 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 (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. EGR flow rate) can be measured.

Therefore, in such a state after the warm-up, feedback control of the EGR flow rate that adjusts the opening degree of the EGR control valve 34C so that the actual EGR flow rate detected based on the output of the differential pressure type flow meter 47 approaches the target EGR flow rate. To implement.
In step S103, when the electromagnetic on-off valve 475 is closed (the closed state of the communication pipe 474), it is determined whether or not the fuel supply state to the diesel engine 10 is temporarily stopped. It is determined whether or not it is an engine operating region in which cutting is performed.

As an example, the fuel cut is performed in an engine operation region (accelerator return region) in which the accelerator is fully closed (accelerator off) and the engine rotation speed exceeds the set speed.
If it is not in the fuel cut state (engine operating region where the fuel cut is performed), the process proceeds to step S107, bypassing the scavenging control processing steps in steps S104 to S106.

On the other hand, if it is in the fuel cut state (engine operating region where fuel cut is performed), the process proceeds to step S104, and the electromagnetic on-off valve 475 is opened.
In the fuel cut state in which combustion stops, exhaust gas recirculation for NOx reduction is unnecessary and feedback control of the EGR flow rate can be stopped, so that the differential pressure detection can be stopped, and the fuel can be stopped. In the cut state, although the combustion is stopped, the diesel engine 10 is rotated by inertial force, and air that does not contain soot (exhaust particulates) or the like is discharged from the diesel engine 10.

Therefore, in the fuel cut state, the electromagnetic on-off valve 475 is opened to make the differential pressure detection (EGR flow rate detection) impossible.
Even during fuel cut, if the EGR flow rate feedback control based on the detected value of the EGR flow rate by the differential pressure type flow meter 47 is performed, the feedback control is forced when the electromagnetic on-off valve 475 is opened. And the opening degree of the EGR control valve 34C is shifted to the open control state in which the opening degree is controlled to the basic opening degree corresponding to the operating conditions.

On the other hand, when the EGR cut (stop of exhaust gas recirculation; control for closing the EGR control valve 34C) is performed in the fuel cut state, the EGR control valve 34C is set to the set opening when the electromagnetic on-off valve 475 is opened. By forcibly opening the exhaust gas, the exhaust gas flows in the EGR pipe 34A, while feedback control based on differential pressure detection (EGR flow rate detection) is not performed.
If the electromagnetic on-off valve 475 is opened in a state where the fuel is cut and the exhaust flows through the EGR pipe 34A, the exhaust (air) that does not include soot or the like is supplied to the pressure guiding pipe 473a, the communication pipe 474, Scavenging is performed in which the soot or the like that has flown through the path formed by the pressure guiding pipe 473b and has been deposited on the pressure guiding pipes 473a and 473b so far is performed, and the progress of accumulation of soot and the like 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 (flow rate) in the differential pressure type flow meter 47 from deteriorating due to accumulation of soot or the like on the pressure guiding tubes 473a and 473b, and high detection accuracy can be maintained over a long period of time. High drivability can be stably maintained by controlling the target EGR flow rate according to the 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, scavenging of the pressure guiding pipes 473a and 473b is not essential for every fuel cut. For example, scavenging is performed according to the operation time of the diesel engine 10, the accumulated EGR amount, the travel distance of the vehicle, etc. from the previous scavenging execution. It is possible to determine whether or not to perform the scavenging, and to perform scavenging when the fuel is cut.
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 (the engine operation region where the fuel cut is performed) continues.
If the fuel cut state (the engine operation region where the fuel cut is performed) continues, the process returns to step S104, and the open control of the electromagnetic on-off valve 475 (the scavenging state of the pressure guiding tubes 473a and 473b) is continued.

Note that when the scavenging time has elapsed since the start of scavenging and the scavenging time has elapsed since the start of scavenging, without waiting for the fuel cut state to stop (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 (when the engine is out of the engine operating range where the fuel cut is performed), the process proceeds from step S105 to step S106, and the electromagnetic on-off valve 475 is controlled to be closed. Then, the scavenging is stopped and the differential pressure (EGR flow rate) can be detected. And if it is the implementation conditions of the feedback control of EGR flow volume, the feedback control which controls the opening degree of EGR control valve 34C based on the EGR flow volume (differential pressure) detected with the differential pressure type flowmeter 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 closed by turning off the engine switch 49, the EGR control valve 34C is forcibly opened to the set opening degree in parallel with the opening control of the electromagnetic opening / closing valve 475. In this way, the exhaust gas flows in the EGR pipe 34A.
As described above, if the scavenging of the pressure guiding pipes 473a and 473b is performed while the diesel engine 10 is rotating with inertia just before stopping, the EGR flow rate (differential pressure) cannot be detected. Since EGR is an unnecessary condition, the operability is not adversely affected, and the pressure guiding pipes 473a and 473b can be scavenged with exhaust gas that does not contain soot, and so on. Deposition can be suppressed.

In step S109, it is determined whether or not the rotation of the diesel engine 10 has stopped. While the diesel engine 10 is rotating with inertia, the process returns to step S108 to maintain the open state (scavenging state) of the electromagnetic on-off valve 475. Let
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. Since the differential pressure disappears and scavenging cannot be performed, the process proceeds to step S110, the electromagnetic on-off valve 475 is switched to the closed state, and scavenging control is terminated.

  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 a combustion state in which soot is minimized, the feedback of the EGR flow rate is stopped, and the open / close valve that opens and closes the communication pipe is controlled to be scavenged.

  In addition, a state in which the pressure guiding tubes 473a, 473b and the communication tube 474 are communicated with a connection portion between the pressure guiding tube 473a and the communication tube 474, and a 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.

In addition, by periodically opening and closing the electromagnetic on-off valve 475 and repeating scavenging execution / interruption, it is possible to enhance the effect of shaking deposits such as soot and blowing away deposits.
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 (6)

A differential pressure detection device for detecting a differential pressure in a pipe line through which engine exhaust 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.   The engine differential pressure detection device according to claim 2, wherein in the operating region of the engine in which fuel cut is performed, the opening and closing valve is controlled to scavenge the pair of pressure guiding pipes.   4. The differential pressure detection device for an engine according to claim 2, wherein between the time when the engine switch is turned off and before the rotation of the engine is stopped, the on-off valve is controlled to scavenge the pair of pressure guiding pipes. 5. .   The engine according to any one of claims 1 to 4, wherein a differential pressure between an upstream side and a downstream side of a throttle mechanism provided in the pipe line is detected, and a flow rate of exhaust gas flowing through the pipe line is measured. Differential pressure detection device.   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 measures an exhaust gas recirculation amount based on a differential pressure.

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