JPS61178539A - Flow rate detecting device for engine - Google Patents

Abstract

PURPOSE:To detect accurate flow rate at all times by providing a pressure difference sensor for detecting flow rate in an intake system or an exhaust system, and a correcting means for correcting the value of detected flow rate by means of balanced point error of said pressure difference sensor. CONSTITUTION:An orifice 21 is provided on the uppermost course side of a secondary air supply passage 17. And, a pressure difference sensor 25 which detects the quantity of a secondary air which is fed from an intake side surge tank 10 to an exhaust system, is provided. The detected value of this pressure difference sensor 25 is inputted into a control unit 30. A correcting means is provided on the control unit 30, to correct the value of detected flow rate by means of a balanced point error of the pressure difference sensor 25, in an unflowing condition of a fluid except in a specified driving condition. Thereby, accurate detection of flow rate can be carried out at all times.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a flow rate detection device for an engine equipped with a differential pressure sensor.

(Prior art) Conventionally, the technical idea of supplying pressurized air to the engine in addition to naturally aspirated air to increase intake air filling efficiency and improve engine output is known as a supercharged engine. .

In such a supercharged engine, when adopting an electronically controlled fuel injection device that sets the optimal fuel injection amount according to the intake air amount, the amount of pressurized air supplied by the supercharger (Supercharging air amount) is an important measurement element for setting the above-mentioned fuel injection amount. In order to detect this supercharging air amount, generally speaking, the main intake passage and the supercharging passage are separated, and an air amount detection device such as an air flow meter is installed in the intake passage upstream of the branch point. The simplest method is to install one and detect the flow rate.

However, this type of supercharging is not always carried out over the entire engine load range, and moreover, when the engine is at low load, it is necessary to supply the exhaust system with the secondary air necessary for the exhaust gas purification device. Therefore, in an engine equipped with the above-described supercharger, another part of the supercharged air discharged from the supercharger is supplied to the exhaust system as secondary air via the isthmus.

Therefore, depending on the operating state of the engine, the entire amount of air detected by the air amount detection device may not be supplied as is to the combustion chamber of the engine. Therefore, if the fuel injection amount is simply set according to the total air amount detected by the air amount detection device, there is a problem that the air-fuel ratio becomes excessively rich.

Therefore, when setting the above-mentioned fuel injection amount, in addition to detecting the above-mentioned intake air amount, the above-mentioned secondary air supply amount is also detected, and the calculation is performed by subtracting this detected value from the above-mentioned total intake air amount. There is a need. Therefore, the flow path for supplying secondary air to the exhaust system is generally provided with a flow rate detection device for detecting the flow rate of the secondary air.

Conventionally, as this flow rate detection device, a movable vane type flow rate sensor like a normal air flow meter has been employed (see, for example, Japanese Patent Publication No. 59-5781). However, in the case of this movable vane type flow rate detection device, the flow rate must be larger than the -window, and the inertia of the vane itself is large, resulting in poor responsiveness and the discharge pulsation of the supercharger. However, there are problems such as the fact that considerable malfunctions are likely to occur due to fluid pressure fluctuations such as pumping.

Therefore, the flow rate detection device is usually configured with a balanced bridge type differential pressure sensor, which generates an unbalanced output based on the differential pressure value between the upstream and downstream sides of the secondary air supply channel through the orifice. A conceivable method is to detect the secondary air flow rate based on the output value. Therefore, in this differential pressure sensor, it is necessary that the bridge is always accurately balanced when no input is applied.If the actual differential pressure value is zero and unbalanced when no input is applied, This will result in a detection error.

However, even in the differential pressure sensor described above, in reality, it often becomes unbalanced due to the effects of heat, vibration, and other factors, and has the drawback that it is likely to cause a certain degree of detection error. Therefore, in order to perform accurate detection, it is necessary to constantly correct the balance point (0 point) by some method.

(Object of the Invention) The present invention has been made based on the above-mentioned circumstances, and is based on the above-mentioned circumstances. It is an object of the present invention to provide a flow rate detection device for an engine that can always accurately detect a flow rate in an operating state where fluid such as air flows.

(Means for Achieving the Object) In order to achieve the above object, the present invention is provided in the intake system or exhaust system of an engine to control the flow of fluid flowing through the intake system or exhaust system during a specific operating state. In an engine equipped with a differential pressure sensor for detecting flow rate, the engine is provided with a correction means for correcting a detected flow rate value due to an equilibrium point error of the differential pressure sensor in a non-circulating state of the fluid outside of the specific operating condition. .

(Function) According to the above means, the differential pressure sensor used in a specific operating state where a fluid such as secondary air actually flows is corrected for its equilibrium point error in a state where the fluid is not circulating outside the specific operating state. Accurate flow rate detection is performed under specific operating conditions. Therefore, the differential pressure sensor can always perform an accurate flow rate detection operation under specific operating conditions. Moreover, the correction of the equilibrium error mentioned above is
Since this is carried out outside a specific operating state where no fluid such as secondary air flows, it is possible to carry out freely and accurately without being affected by external disturbances.

(Embodiment) FIGS. 1 to 5 show a first embodiment of the present invention, and a sixth embodiment of the present invention.
The figure shows a flowchart for a second embodiment of the invention.

FIG. 1 is a schematic diagram showing the overall system configuration of an engine flow rate detection device according to both embodiments of the present invention, and first, reference numeral 1 indicates an engine equipped with a supercharger. This engine 1 has two intake boats, ie, a main intake valve 22.
The main intake boat 2 includes a main intake boat 2 having a sub-intake valve 33, a sub-intake boat 3 including a sub-intake valve 33, and an exhaust boat 4 further including an exhaust valve 44. Among these intake boats 2.3 and exhaust boats 4, the main intake boat 2 has a main intake passage 5,
Further, sub-intake passages 6 are connected to the sub-intake boats 3, respectively.

The main intake passage 5 and the auxiliary intake passage 6 are made to merge with each other on the intake upstream side, and the air cleaner 11 and the air flow meter 1
2. Further, a main throttle valve 8 and an injector 13 for fuel injection are attached to the intake downstream side of the main intake passage 5. The opening of the main throttle valve 8 is detected by a throttle opening sensor 14 and input to a control unit 30, which will be described later.

On the other hand, the sub-intake passage 6 has a surge tank IO in its middle part.
At the same time, an intercooler 15 is installed at a position immediately upstream of the surge tank summer 0, and a mechanical supercharger 16 driven by the rotational force of the engine is installed at a position immediately upstream of the intercooler I5. It is being

Further, an auxiliary throttle valve 9 is attached to the auxiliary intake passage 6 at a position downstream of the surge tank 10 . This auxiliary throttle valve 9 is connected to the auxiliary intake passage 6 when supercharging is not required.
By closing the surge tank 10 on the downstream side of the surge tank 10, the air pressure in the surge tank 10 is increased by the supercharger 16, which acts to improve supercharging and responsiveness at the start of supercharging. The operating characteristics of the main throttle valve 8 provided in the main intake passage 5 are defined so that the valve opens when the main throttle valve 8 is opened beyond the opening degree for starting supercharging, in other words, when a supercharging request is issued. There is. In this case, when the auxiliary throttle valve 9 is opened, the intake supercharging by the supercharger 16 is not performed continuously during the entire intake stroke of the engine 1, but the opening timing of the auxiliary intake valve 33 is normally the same. is set so that the auxiliary intake valve 33 opens when the main intake valve 22 closes close to the fully closed position during its intake stroke, and at the end of the natural intake action from the main intake passage 5, the auxiliary intake valve 33 is It is designed to introduce supercharged intake air.

On the other hand, the exhaust passage 7 and the surge tank 10 are communicated with each other via a secondary air supply passage 17.

A pressure-responsive passage opening/closing valve 18 for controlling opening/closing of the secondary air supply passage 17 is provided at an intermediate portion of the secondary air flow passage of the secondary air supply passage 17 . The pressure chamber 18a of this passage opening/closing valve 18 is communicated downstream of the main throttle valve 8 of the main intake passage 5 via a negative pressure introduction passage 19. When the solenoid valve 20 provided in the pressure chamber 18a is opened and atmospheric air is introduced into the pressure chamber 18a, the secondary air supply passage I7 is closed, and the solenoid valve 20 is closed and air is introduced into the pressure chamber 18a. When pressure is introduced, it acts to open the secondary air supply passage 17. This solenoid valve 20 is connected to a control unit 30 which will be described later.
ON/OFF control is performed by a valve control signal from.

Further, an orifice 21 is provided at the most upstream side of the secondary air supply passage 17, and from the pressure difference between the upstream side and the downstream side of this orifice 21, the air is passed through the secondary air supply passage 17 and placed in the intake side surge tank 10. A balanced bridge type differential pressure sensor 25 is provided to detect the amount of secondary air (secondary air supply amount) supplied to the exhaust system from the above, and the detected value (differential pressure output) of this differential pressure sensor 25 is , is input to the control unit 30 as a control factor for calculating the fuel injection amount.

Furthermore, the surge tank IO is provided with a relief air passage 26.
The air flow meter 12 is connected to the downstream side of the air flow meter 12 via the air flow meter 12 . A first relief valve 27 and a second relief valve 28 are attached to the relief air passage 26. The first relief valve 27 is the surge tank 10
This is a valve for setting the maximum pressure (maximum supercharging pressure) of the surge tank IO, and when the internal pressure of the surge tank IO reaches the maximum supercharging pressure set by the spring force of the spring 27b, the valve opens and prevents the internal pressure from increasing. It works like this. Incidentally, intake negative pressure is introduced into the pressure chamber 27a of the first relief valve 27 via the negative pressure introduction passage 19.

Therefore, as the intake negative pressure increases (that is, as the opening degree of the main throttle valve 8 decreases), the opening pressure of the first relief valve 27 decreases, and the surge tank lO
The internal pressure of the engine is set lower than the maximum boost pressure set by the spring 27b (maximum boost pressure control based on the required boost amount of the engine).

On the other hand, the second relief valve 28 is constructed of a pressure-responsive valve similar to the first relief valve 27, and opens when negative intake pressure is introduced into the pressure chamber 28a, thereby reducing the pressure inside the surge tank 10. It is configured to release a portion of the pressurized air to the relief air passage 26 side. The second relief valve 28 is operated by the solenoid valve 20 similarly to the passage opening/closing valve 18, and when the solenoid valve 20 is closed and intake negative pressure is introduced into the pressure chamber 28a (i.e., the exhaust passage When secondary air is introduced into the surge tank IO), the valve opens and acts to lower the internal pressure of the surge tank IO. This is because the operating region in which secondary air is supplied to the exhaust passage 7 side (corresponding to the specific operating state in the claims) is a low-load operating region, and therefore no supercharging is performed. Moreover, the amount of pressurized air used as secondary air is smaller than the amount of pressurized air required during supercharging operation (in other words, the internal pressure of the surge tank 10 is even higher than during supercharging operation). Therefore, when introducing secondary air, the second relief valve 28 is opened outside the first relief valve 27 to fill the surge tank 1.
This is to efficiently suppress the rise in internal pressure of 0.

On the other hand, the control unit 30 is composed of a microcomputer with a predetermined capacity, and includes a CPU, an input/output interface (Ilo) section, and a necessary memory section (R
AM/ROM). In addition to the above-mentioned inputs, the control unit 30 receives an engine speed detection value N1 from the engine speed sensor 29 and a key-on signal (engine start signal) S from the starter switch 31. ing.

Next, the control operation of the engine flow rate detection device will be described in detail with reference to FIG. 2.

First, when the control operation is started, the control unit 30 first outputs the engine speed N1, the intake air amount Qas, the throttle opening TVO, and the differential pressure output Pn from the differential pressure sensor 25.
, engine start signal S (step S1
). Then, the engine starter switch 31
7!1 (Determine whether the engine has started or not based on the starting signal S indicating whether it is ON or not (step S2). As a result, if the engine has started (YES) In addition, whether or not the intake air supply state to the engine has been switched to a specific operating state, that is, the secondary air supply region (at low load), is determined based on the throttle opening TVO and engine speed, as shown in Figure 3. N (step S3).If it is in the secondary air supply region (YES), proceed to the next step S6 and set the value of the differential pressure P to the subtracted value of Pn-PO. (described later).

On the other hand, in step S, if the engine is not started (No) or if the engine is not in the secondary air supply region in step S (No), the process first moves to step S4 and the differential pressure is It is determined whether the differential pressure output value PnIJ (Pn-) of the sensor 25 is, that is, whether it is equal to the data one cycle ago.As a result,
In the case of (NO), the process directly moves to step S8 as the specific operating state, and in the other case (YES), the process moves to step S5 as not in the specific operating state. In step S5, the actual differential pressure P and the corresponding differential pressure sensor 2 shown in FIG.
5 itself, read the correct output value a of the differential pressure sensor when the actual differential pressure P is 0, and calculate the above output value a from the actual output value Pn+ of the differential pressure sensor outside the current specific operating state. (P n, -a) to obtain the correction value PO
Determine.

In the differential pressure detection operation in the specific operating state in step Ss, the correction value Po determined in step S is subtracted from the actual output Pn of the differential pressure sensor 25 (Pn-Pa). Accordingly, the actual correct differential pressure value P is calculated. Then, in step S, the secondary air ff1Qb specified by the high differential pressure value P and the engine speed N at that time is read out from the data map shown in FIG. Calculate the air amount Q actually supplied to the engine by subtracting (Qa - Qb,) from the intake air amount Qa. Step S
, ), and finally calculates an accurate fuel injection amount based on this air amount Qa (step S,).

In this way, even if the differential pressure sensor 25 itself is unbalanced for some reason, the current unbalanced state can be determined based on its original correct balanced state output. By detecting the amount of error and subtracting this amount of error from the actual output, it is possible to always correct the output value to the correct value. Moreover, the determination of the correction value is performed outside of a specific operating state that does not require the supply of secondary air. Therefore, the correction can be performed accurately and freely without being affected by any disturbance. As a result, this embodiment is particularly effective when a supercharged engine such as this embodiment employs an electronically controlled fuel injection device that automatically sets the amount of fuel to be injected depending on the amount of intake air.

Further, the control operations of steps 84 to S9 described above can be further modified as shown in steps 84 to S1° shown in FIG. 6 as a second embodiment.

In this second embodiment, in the operation of step S4, the current output value Pn of the differential pressure sensor is specified to be equal to the already stored value Pn+ of the input Pn one cycle before. If it is not in operation status (YE
First, the output value Pn is directly set as the reference value PO for correction (step S5). Then, based on the reference value PO, the secondary air flow rate QO corresponding to the differential pressure value is read out from the data map shown in FIG. 5 (step S). This secondary air flow rate QO is in a state where secondary air is not originally flowing outside the specific operating state, and indicates the amount of error due to a slight error of the differential pressure sensor.

Then, the process moves to step S7, and in step S7, the output value Pn of the differential pressure sensor 25 in the specific operating state at that time is directly set as the output value P for control. and,
The secondary air amount Qb corresponding to the value P is read from the data map (step S). Next, the process moves to flow rate correction step S, in which the normal secondary air amount Qb in step S and the error flow rate QO in step S6 are subtracted from the intake air amount Qa.

That is, here, the error flow rate due to the comparison point error of the differential pressure sensor is corrected, and the fuel injection amount is calculated based on this corrected correct flow value (step S).

). Even in this case, the same objective as the control operation shown in FIG. 2 described above can be achieved.

In addition, in the above embodiment, secondary air supplied to the exhaust system was illustrated as the fluid to be detected for the flow rate, but it is understood that the fluid targeted by the present invention is not limited to such secondary air. It should be.

(Effects of the Invention) As described above, the present invention provides a differential pressure that is provided in the intake system or exhaust system of an engine to detect the flow rate of fluid flowing through the intake system or exhaust system during a specific operating state. The present invention is characterized in that it includes a sensor, and further includes a correction means for correcting a detected flow rate value due to a slight error of the differential pressure sensor in a state where the fluid is not flowing outside the specific operating state.

Therefore, according to the present invention, the differential pressure sensor used in a specific operating state where a fluid such as secondary air actually flows is corrected for its slight error in a state where the fluid is not circulating outside the specific operating state, and the differential pressure sensor is corrected in the specific operating state. In the usage state, accurate flow rate detection is performed. Therefore, the differential pressure sensor can always accurately detect the flow rate under specific operating conditions. Moreover, since the above-mentioned correction of the slight error is carried out outside the specific operating state in which no fluid such as secondary air flows, it is carried out freely and accurately without being affected by external disturbances.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the overall system configuration of an engine flow rate detection device according to an embodiment of the present invention, and FIG. 2 shows a control operation of the flow rate detection device according to the first embodiment of the present invention. Flowchart, Figure 3 is a graph showing the secondary air supply area, Figure 4 is a characteristic diagram showing the relationship between the actual differential pressure and differential pressure sensor output in the control operation of Figure 2, and Figure 5 is a graph showing the supply area of secondary air. , a data map showing the value of the secondary air amount specified by the engine speed and the differential pressure output in the control operation shown in FIG. 2, and FIG. 12 is a flowchart showing the control operation of the second embodiment. l...Engine 2...Main intake boat 3...Sub-intake boat 4...Exhaust boat 5...Main intake passage 6...Sub-intake Passage 7...Exhaust passage 12...Air flow meter 16...Supercharger 17...Secondary air supply passage 21...Orifice 25... Differential pressure sensor 30--Fist control unit Fig. 1/Gu. ...Main intake passage≦1-...Sub-intake passage 7...Exhaust passage/2...Air flow meter/B...Supercharger/7...Secondary Air supply passage 2/... Orifice 25... Differential pressure sensor 30... Funtrol unit Figure 3 Figure 4

Claims (1)

[Claims] A differential pressure sensor is provided in the intake system or exhaust system of the engine to detect the flow rate of fluid flowing through the intake system or exhaust system during a specific operating state, and further includes a non-circulation of the fluid outside the specific operating state. A flow rate detection device for an engine, characterized in that it is provided with a correction means for correcting a detected flow rate value due to an equilibrium point error of the differential pressure sensor in the above-mentioned state.