JP6070492B2 - Exhaust gas recirculation device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas recirculation device that recirculates a part of exhaust gas discharged from an internal combustion engine to an intake side as EGR gas.

As a prior art, for example, there is an exhaust gas recirculation device disclosed in Patent Document 1.
This exhaust gas recirculation device includes an EGR valve that opens and closes an EGR passage, valve driving means that drives the EGR valve using a motor as a power source, a spring that urges the EGR valve in the valve closing direction, and electric power supplied to the motor Motor control means for controlling the motor. The valve driving means is a gear train (gear train) that amplifies the driving torque of the motor and transmits it to the EGR valve.
By the way, at the time of failure in which power supply to the motor is interrupted due to some trouble, the EGR valve needs to return to the fully closed position by the torque of the spring.
A factor that resists the torque of the spring is the cogging torque of the motor, and this cogging torque increases as the temperature decreases. Therefore, in order to ensure the self-returning property of the EGR valve even at a low temperature, it is necessary to increase the torque of the spring so as to overcome the cogging torque of the motor.

JP 2007-285123 A

However, when the torque of the spring increases, the motor load when opening and closing the EGR valve increases, so that the settable torque of the spring is limited. For this reason, when the engine is started in a low temperature environment, there is a problem that the operation of the EGR valve cannot be started until the atmospheric temperature of the motor becomes high and the cogging torque falls below the spring torque.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an exhaust gas recirculation device for an internal combustion engine that can start the opening / closing operation of an EGR valve at an early stage. .

The present invention relates to an EGR passage that recirculates a portion of exhaust (referred to as EGR gas) from an exhaust passage of an internal combustion engine to an intake passage, an EGR valve that adjusts the flow rate of EGR gas that flows through the EGR passage, and a permanent magnetic field. A motor that uses a magnet, a gear train that amplifies the drive torque of the motor and transmits it to the EGR valve, a spring that urges the EGR valve in the valve closing direction, and the EGR valve to drive it to a predetermined opening In an exhaust gas recirculation device for an internal combustion engine comprising an EGR control means for controlling power supplied to the motor, when controlling the opening / closing operation of the EGR valve in accordance with the operating state of the internal combustion engine is referred to as valve opening control. EGR control means holds the EGR valve for supplying a predetermined power to the motor immediately after starting the internal combustion engine to the fully closed position, the temperature of the intake air flowing through the intake passage Estimating the ambient temperature of the motor from the detected value of the intake air temperature sensor to be detected, it starts a valve opening control at the time the temperature exceeds a threshold value. Alternatively, a temperature sensor is arranged inside the motor chamber that houses the motor, and the valve opening control is started when the temperature detected by the temperature sensor exceeds a threshold value. The threshold value is set as a numerical value that makes the cogging torque of the motor smaller than the torque of the spring.

  According to the first aspect of the present invention, since the motor generates heat by supplying predetermined electric power to the motor immediately after the internal combustion engine is started, the ambient temperature of the motor is increased even in a low temperature environment, and the cogging torque of the motor is decreased. . Therefore, since the cogging torque of the motor falls below the spring torque at an early stage, the EGR valve opening / closing operation (valve opening degree control) can be started at an early stage. Since the EGR valve is held in the fully closed position while the predetermined electric power is supplied to the motor, the EGR gas recirculates to the intake passage until normal valve opening degree control is started. There is no.

It is sectional drawing of the EGR apparatus which concerns on a reference example . It is a top view of an EGR device showing arrangement of a gear train concerning a reference example . It is a block diagram which feedback-controls the opening degree of an EGR valve by ECU. It is a system diagram of an exhaust gas recirculation device. It is a time chart which concerns on the action | operation description of a reference example . 6 is a cross-sectional view of an EGR device according to Embodiment 2. FIG.

  The mode for carrying out the present invention will be described in detail with reference to the following examples.

[ Reference example ]
As shown in FIG. 4, the exhaust gas recirculation device is a system that recirculates a part of the exhaust gas discharged from the combustion chamber 1a of the engine 1 to the intake side as EGR gas. An exhaust gas recirculation passage 4 communicating with the passage 3 is provided with an EGR device 5.
An air cleaner 6 that filters air is disposed at the upstream end of the intake passage 3. An air flow meter 7 for measuring the intake air amount is attached to the outlet of the air cleaner 6, and a throttle valve 8 for adjusting the intake air amount is disposed downstream of the air flow meter 7.
A surge tank 9 is provided downstream of the throttle valve 8, and the downstream end of the exhaust gas recirculation passage 4 is connected to the surge tank 9. Further, an EGR cooler 10 for cooling the EGR gas is attached to the exhaust gas recirculation passage 4 on the upstream side (exhaust passage 2 side) from the EGR device 5.

As shown in FIG. 1, the EGR device 5 includes a housing 12 that forms an EGR passage 11, an EGR valve 13 that adjusts the flow rate of EGR gas, and valve drive means (described later) that drives the EGR valve 13; A spring 14 that urges the EGR valve 13 in the valve closing direction, a rotation angle sensor (described later) that detects the opening degree of the EGR valve 13, and the like are provided. The valve closing direction refers to a direction in which the opening area of the EGR passage 11 decreases.
The housing 12 has an upstream end of the EGR passage 11 connected to the exhaust gas recirculation passage 4 on the exhaust side, and a downstream end of the EGR passage 11 connected to the exhaust gas recirculation passage 4 on the intake side.
The EGR valve 13 includes a valve shaft 16 that is rotatably supported by the housing 12 via a bearing 15, and a disc-like valve body 17 that is attached to one end of the valve shaft 16. 17 rotates integrally with the valve shaft 16 to vary the opening area of the EGR passage 11.

The valve driving means includes a motor 18 that generates torque upon receiving electric power, and a gear train (gear train) that amplifies the driving torque of the motor 18 and transmits the amplified torque to the valve shaft 16.
The motor 18 is, for example, a DC motor using a permanent magnet as a field, and is accommodated in a motor chamber 19 formed in the housing 12.
As shown in FIGS. 1 and 2, the gear train includes a motor gear 20 attached to the output shaft 18 a of the motor 18, a valve gear 21 attached to the other end of the valve shaft 16, and rotation of the motor gear 20 to the valve gear 21. It consists of an intermediate gear that transmits.
The intermediate gear includes a large-diameter gear 22 that meshes with the motor gear 20 and a small-diameter gear 23 that meshes with the valve gear 21, and both gears 22, 23 are integrally formed on the same axis and rotate around a common intermediate shaft 24. It is supported freely.

The gear train is disposed in the gear chamber 25 that opens to the end surface of the housing 12, and is covered with a sensor cover 26. 2 illustrates the gear train disposed in the gear chamber 25 in a state where the sensor cover 26 is not present (a state where the sensor cover 26 is removed).
The sensor cover 26 is, for example, a resin molded product, and is assembled to the end surface of the housing 12 where the gear chamber 25 is opened via a seal part 27 (see FIG. 1), and is fixed to the housing 12 by tightening a screw or the like.

The spring 14 biases the EGR valve 13 to the fully closed position when the engine is stopped, that is, when the power supply to the motor 18 is stopped. Further, when the power supply to the motor 18 is interrupted due to some trouble during the operation of the engine 1, the EGR valve 13 can be returned to the fully closed position by the torque of the spring 14. The fully closed position of the EGR valve 13 refers to the opening degree of the EGR valve 13 at which the opening area of the EGR passage 11 is minimized.
The rotation angle sensor is configured, for example, by arranging a Hall IC 29 inside a permanent magnet 28 attached to the inner periphery of the valve gear 21. The Hall IC 29 outputs an electric signal (voltage) proportional to the magnetic flux density penetrating the Hall element to the ECU 30 (see FIG. 3) by rotating the permanent magnet 28 together with the valve gear 21.

As shown in FIG. 3, the ECU 30 calculates a target opening degree of the EGR valve 13 according to the operating state of the engine 1 grasped from the accelerator opening degree, the engine speed, etc., and detects the EGR valve by the rotation angle sensor. The power supplied to the motor 18 is feedback-controlled so that the actual opening of 13 coincides with the target opening.
Hereinafter, the control for matching the actual opening of the EGR valve 13 with the target opening according to the operating state of the engine 1 is referred to as valve opening control.

The ECU 30 functions as EGR control means of the present invention.
That is, as shown in FIG. 5, the ECU 30 (EGR control means) supplies predetermined power to the motor 18 immediately after the engine 1 is started (time t0) to hold the EGR valve 13 in the fully closed position. The valve opening degree control is started after a predetermined time has elapsed (time t1) after the predetermined power is supplied to. Hereinafter, the control for supplying predetermined electric power to the motor 18 and holding the EGR valve 13 in the fully closed position is referred to as valve fully closed control. In addition, the “specified time” from when the predetermined power is supplied to the motor 18 until the valve opening degree control is started, for example, the ambient temperature of the motor 18 exceeds the specified value in the assumed minimum low temperature environment. It can be set according to the time until.

[ Operation and effect of reference example ]
In the reference example , immediately after the engine 1 is started, the ECU 30 performs valve full-close control. That is, immediately after the engine 1 is started, predetermined power is supplied to the motor 18 to hold the EGR valve 13 in the fully closed position, so that the motor 18 generates heat before starting normal valve opening control. As a result, as shown in FIG. 5, the ambient temperature of the motor 18 gradually increases even in a low temperature environment, and the cogging torque of the motor 18 decreases accordingly. As a result, since the cogging torque of the motor 18 quickly falls below the torque of the spring 14, the opening / closing operation (valve opening degree control) of the EGR valve 13 can be started early. That is, even when the engine 1 is started in a low temperature environment, the time until the cogging torque of the motor 18 falls below the torque of the spring 14 can be shortened by performing the valve full-close control immediately after the engine 1 is started. Therefore, compared with the conventional EGR control in which the valve fully closed control is not performed immediately after the engine 1 is started, the valve opening degree control can be started earlier.

Since the EGR valve 13 is held in the fully closed position while the predetermined electric power is supplied to the motor 18, the EGR gas is supplied to the intake passage 3 until the normal valve opening degree control is started. There is no reflux.
The fully closed position of the EGR valve 13 held by the torque of the spring 14 (referred to as mechanical fully closed position) and the fully closed position of the EGR valve 13 held by the valve fully closed control of the ECU 30 (on control) It is not always necessary to agree with the “fully closed position”. That is, the mechanical fully closed position and the control fully closed position can be intentionally shifted.

The following describes engagement Ru real施例the present invention.
Note that components and configurations common to the reference example are denoted by the same reference numerals as those of the reference example, and detailed description thereof is omitted.
[ Example 1 ]
In the first embodiment , as shown in FIG. 4, the ECU 30 (EGR control means) estimates the ambient temperature of the motor 18 from the detected value of the intake air temperature sensor 31 attached to the air flow meter 6, and the temperature is preset. In this example, valve opening control is started when the threshold value is exceeded.

In the above reference example , the “specified time” from when the ECU 30 performs the valve full-close control until the valve opening control is started is uniformly set. On the other hand, in the first embodiment , the time from when the ECU 30 performs the valve fully closed control until the detected value of the intake air temperature sensor 31 exceeds the threshold value can be read as “specified time”. Therefore, the “specified time” is not uniform and varies depending on the detection value of the intake air temperature sensor 31. In this case, since it can be determined that the ambient temperature of the motor 18 has exceeded the specified value when the detection value of the intake air temperature sensor 31 exceeds the threshold value, the valve opening degree control can be started earlier.

[ Example 2 ]
In the second embodiment , as shown in FIG. 6, a temperature sensor 32 is disposed in a motor chamber 19 formed in the housing 12 of the EGR device 5, and the valve is opened when the detected temperature of the temperature sensor 32 exceeds a threshold value. This is an example of starting degree control.
Also in the second embodiment , as in the first embodiment , the “specified time” from when the ECU 30 performs the valve full-closed control to when the valve opening control is started is not uniform and depends on the temperature detected by the temperature sensor 32. fluctuate.
Further, since the temperature sensor 32 is disposed in the motor chamber 19, the ambient temperature of the motor 18 can be directly detected by the temperature sensor 32. For this reason, it is not necessary to consider the difference between the intake air temperature and the ambient temperature of the motor 18, and the valve opening degree control can be started early when the temperature detected by the temperature sensor 32 exceeds the threshold value.

[Modification]
In the reference example , the DC motor 18 that uses a permanent magnet for the field as a power source for driving the EGR valve 13 is described. However, the DC motor 18 is not limited to the DC motor 18, and for example, the field magnet (rotor) has a permanent magnet. It is also possible to use an AC motor or a stepping motor having That is, any permanent magnet motor that generates a cogging torque that is a magnetic attractive force when the rotor is rotated in a non-excited state (a state in which no current flows through the armature winding) may be used.
The intake air temperature sensor 31 described in the first embodiment is not necessarily attached to the air flow meter 6, and can be installed in the intake passage 3 separately from the air flow meter 6.

1 engine (internal combustion engine)
2 Exhaust passage 3 Intake passage 11 EGR passage 13 EGR valve 14 Spring 18 Motor 19 Motor chamber 20 Motor gear (gear train)
21 Valve gear (gear train)
22 Large diameter gear (gear train)
23 Small-diameter gear (gear train)
30 ECU (EGR control means)
31 Intake air temperature sensor 32 Temperature sensor

Claims (2)

An EGR passage (11) for recirculating a part of exhaust (referred to as EGR gas) from the exhaust passage (2) of the internal combustion engine (1) to the intake passage (3);
An EGR valve (13) for adjusting the flow rate of EGR gas flowing through the EGR passage (11);
A motor (18) using a permanent magnet for the field;
A gear train (20, 21, 22, 23) for amplifying the drive torque of the motor (18) and transmitting it to the EGR valve (13);
A spring (14) for urging the EGR valve (13) in the valve closing direction;
In an exhaust gas recirculation device for an internal combustion engine, comprising an EGR control means (30) for controlling power supplied to the motor (18) in order to drive the EGR valve (13) to a predetermined opening degree.
Controlling the opening / closing operation of the EGR valve (13) according to the operating state of the internal combustion engine (1) is referred to as valve opening control.
The EGR control means (30) supplies a predetermined electric power to the motor (18) immediately after the internal combustion engine (1) is started to hold the EGR valve (13) in a fully closed position, and the intake passage. (3) the ambient temperature of the motor (18) is estimated from the detected value of the intake air temperature sensor for detecting the temperature of intake air flowing through (31), to start the valve opening control at the time the temperature exceeds a threshold value ,
The exhaust gas recirculation device for an internal combustion engine, wherein the threshold value is set to a value at which the cogging torque of the motor (18) is smaller than the torque of the spring (14) . An EGR passage (11) for recirculating a part of exhaust (referred to as EGR gas) from the exhaust passage (2) of the internal combustion engine (1) to the intake passage (3);
An EGR valve (13) for adjusting the flow rate of EGR gas flowing through the EGR passage (11);
A motor (18) using a permanent magnet for the field;
A gear train (20, 21, 22, 23) for amplifying the drive torque of the motor (18) and transmitting it to the EGR valve (13);
A spring (14) for urging the EGR valve (13) in the valve closing direction;
In an exhaust gas recirculation device for an internal combustion engine, comprising an EGR control means (30) for controlling power supplied to the motor (18) in order to drive the EGR valve (13) to a predetermined opening degree.
A temperature sensor (32) is disposed inside the motor chamber (19) that houses the motor (18),
Controlling the opening / closing operation of the EGR valve (13) according to the operating state of the internal combustion engine (1) is referred to as valve opening control.
The EGR control means (30) supplies predetermined electric power to the motor (18) immediately after starting the internal combustion engine (1) to hold the EGR valve (13) in a fully closed position, and the temperature sensor ( The valve opening control is started when the temperature detected in step 32) exceeds the threshold value,
The exhaust gas recirculation device for an internal combustion engine, wherein the threshold value is set to a value at which the cogging torque of the motor (18) is smaller than the torque of the spring (14) .

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