JPS63176616A - Secondary air supplier for engine - Google Patents

Abstract

PURPOSE:To aim at improvement in fuel consumption, by installing two air pumps for supply of secondary air to an exhaust passage, and selecting these pumps according to a driving state. CONSTITUTION:A supercharging pump 15, serving both as a supercharger and a secondary air supplying air pump, is installed in a supercharging passage 9, and it is connected to an engine output shaft via a solenoid clutch 29. A small flowing air pump 28, driven by a motor via this solenoid clutch 29, is installed in a secondary air passage 27. Separately at the time of stationary driving of an engine and at the transition, it is selected to a state of supplying secondary air from the small flowing air pump 28 and another state of supplying it from the supercharging pump 15 or both air pumps. With this constitution, load being imposed on these air pumps are reduced, and fuel consumption is improvable.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a secondary air supply device for an engine that controls the supply of secondary air to an exhaust passage.

(Prior Art) Various secondary air supply devices for engines that supply secondary air to an exhaust passage to promote exhaust purification are known. For example, in an engine that has a naturally aspirated passage and a supercharging passage equipped with a supercharger, a secondary air passage branched from the supercharging passage downstream of the supercharger is connected to the exhaust passage, and the supercharging passage is connected to the exhaust passage. It is known that the air pump also functions as an air pump for supplying secondary air (Japanese Unexamined Patent Publication No. 58-51
(See Publication No. 221). Alternatively, there are also those equipped with an electric or other air pump exclusively for supplying secondary air.

By the way, when the above-mentioned supercharger is also used as an air pump for supplying secondary air, the supercharger is always driven in the operating range where secondary air should be supplied when not supercharging, especially when the required amount of secondary air is Even in a small operating range, a supercharger with an unnecessarily large pump capacity is driven considering the amount of secondary air required at that time, and a relatively large load is applied to the engine, resulting in poor fuel efficiency. It is disadvantageous. In addition, even when using an air pump exclusively for secondary air, in order to supply secondary air to the entire secondary air supply area with one air pump, it is necessary to
Since it is necessary to use an air pump large enough to meet the maximum required amount of secondary air, fuel efficiency cannot be sufficiently improved.

(Object of the Invention) In view of the above circumstances, the present invention uses a small air pump in an operating range where the required amount of secondary air is small, and uses another air pump or The basic objective is to reduce the load on the air pumps as much as possible and improve fuel efficiency while meeting the secondary air requirements according to the operating conditions by controlling the switching so that two air pumps are used.

In addition, when switching the secondary air supply by using two air pumps in this way, if the switching point is set constant to meet the requirements during steady operation, the above-mentioned Since the conditions such as the temperature and air-fuel ratio of the exhaust system at the switching point are different from those during steady operation, there is a problem that an appropriate amount of secondary air supply cannot necessarily be obtained, but the present invention also focuses on this point. Another object of the present invention is to enable appropriate secondary air supply in accordance with steady operation and transient operation.

(Structure of the Invention) The present invention provides an engine secondary air supply device that controls the supply of secondary air to an exhaust passage according to the operating state of the engine, in which two air pumps are used for supplying secondary air. and at least one of the air pumps is a small-flow air pump that meets the demand for secondary air in an operating range where the demand for secondary air is low, and secondary air is supplied from the small-flow air pump according to the operating state. a secondary air supply control means for switching the secondary air supply between a state in which secondary air is supplied from the other air pump or both air pumps, and a switching point for the secondary air supply by the secondary air supply control means to A switching point changing means is provided to change the switching point between steady operation and transient operation.

With this configuration, two air pumps can be used depending on the amount of secondary air required, which changes depending on the operating condition, and
The secondary air supply is also adjusted in response to differences in conditions such as the temperature of the exhaust system between steady-state operation and transient operation.

(Embodiment) FIG. 1 shows the structure of an apparatus according to an embodiment of the present invention. The engine 1 shown in this figure is a rotary piston engine, and includes a casing 2 having a predetermined shape and a rotor 3 that rotates planetarily within the casing 2. An operating chamber 4 is formed within the casing 2. Casing 2 of this engine 1
, there is a main intake port 5 that opens into the working chamber 4 during the intake stroke, and a supercharging port 6 that closes later than the main intake port 5.
and an exhaust port 7 opening into the working chamber 4 of the exhaust stroke are formed, and these ports 5, 6, 7 communicate with the main intake passage 8, the supercharging passage 9, and the exhaust passage 10, respectively.

The upstream end side of the main intake passage 8 is connected to an air cleaner 11, and the main intake passage 8 is provided with an air flow meter 12 for detecting an intake air flow rate, a throttle valve 13, and a fuel injection valve 14 in this order from the upstream side. ing. On the other hand, the upstream end side of the supercharging passage 9 is connected to the main intake passage 8 downstream of the air flow meter 12, and this supercharging passage 9 has a supercharging pump 15 that serves both as a supercharger and an air pump for supplying secondary air. is provided, and this supercharging pump 15 is connected to an electromagnetic clutch 1.
It is connected to the output shaft (not shown) of the engine 1 via the shaft 6 and is driven by the engine 1. The supercharging passage 9 includes a supercharging control valve 17 that is controlled by a signal from a control unit 31 (described later) and is opened in an operating range above a predetermined load, and a rotary valve 18 that regulates the timing of supplying supercharging air to the engine 1. is provided.

A secondary air passage 21 branches from the supercharging passage 9 upstream of the supercharging control valve 17 and downstream of the supercharging pump 15, and this passage 21 has a secondary air control valve (hereinafter referred to as [supercharging pump side ACVJ)]. 22 and an air 70-meter 23 for detecting the flow rate of secondary air. The downstream end of the secondary air passage 21 is connected to the exhaust passage 10, and the exhaust boat 7 is configured to supply boat air upstream of an exhaust purification device 24 such as a catalytic converter provided in the exhaust passage 10, for example.
Connected to the neighborhood. Furthermore, a relief passage 25 is formed in the supercharging passage 9 and connects the downstream and upstream sides of the supercharging pump 15, and this passage 25 is provided with a relief control valve 26.

In addition, a secondary air passage 21 branched from the supercharging passage 9 described above.
Separately, a secondary air passage 27 whose upstream end side is connected to the air cleaner 11 is formed, and in this secondary air passage 27,
A small electric air pump (air pump for small flow rate) driven by a motor (not shown) via an electromagnetic clutch 29
28 are provided. A secondary air control valve (hereinafter referred to as the electric air pump side ACVJ) 30 is provided downstream of the electric air pump 28 in the secondary air passage 27, and downstream of the secondary air control valve 30 is used to supply boat air to the upstream side of the exhaust purification device 24, Each passage 27a is for supplying split air to the intermediate portion of the purifier 24 and for relief upstream of the air cleaner 11.

27b and 27c are formed.

31 is a control unit using a microcomputer, etc., and this control unit 31 includes an air flow meter 1.
2, 23, a detection signal from the rotation speed sensor 32 that detects the engine rotation speed, a detection signal from the throttle opening sensor 33 that detects the opening of the throttle valve 13, etc. is supercharging pump 1
A signal for controlling the clutch 16 of the electric air pump 28, the supercharging pump side ACV 22, and the supercharging control valve 17, respectively, and a signal for controlling the clutch 29 of the electric air pump 28 and the electric air pump side ACV 30, respectively, are output.
4, a signal to control the relief control valve 26, etc. are also output.

The control unit 31 is supplied with secondary air in a specific operating range, and also has a state in which secondary air is supplied from the electric air pump 28 and a state in which secondary air is supplied from the supercharging pump 15 depending on the operating state. a switching hole changing means 35 that changes the switching point of the secondary air supply by the secondary air supply control means 34 between a steady state and a transient state of the engine; It is included.

In this control unit 31, a supercharging area, a secondary air supply area from each pump, etc. are set in advance as shown in FIG. In other words, the operating region where the throttle opening (engine load) is larger than a predetermined value is defined as the supercharging region, while the secondary air is supplied during non-supercharging to the lower load side (the range shown by diagonal lines) than the predetermined line DC1. ) is the boat air supply area, and among these, the electric air pump 28
The area on the lower rotation side than the predetermined rotation speed RO, which is the range that can cover the secondary air requirement during steady operation, is defined as the boat air supply area pa by the electric air pump, and the predetermined rotation speed R
The region on the higher rotation side than O is defined as the port air supply region pb by the supercharging pump.

In this embodiment, the secondary air supply by each pump is switched at the predetermined rotation speed RO, and the switching point is shifted by providing a delay in switching during deceleration. Note that DC2 indicates a fuel cut line during deceleration, and fuel supply is stopped on the lower load side than this line DC2.

FIG. 3 is a flowchart showing a specific example of control by the control unit 31. In this flowchart, first, in step S1, the intake flow rate Q1, engine rotation speed RPM, and throttle opening TVO detected by the air flow meter 12 are read, and in step S2, fuel injection is performed according to the intake flow rate per engine revolution, etc. valve 14
Calculate the pulse width τ of the injection pulse for Next, in step S3, the operating state determined from the engine speed and throttle opening at that time is determined by line D in FIG.
Check whether it is on the lower load side (boat air supply area) than C1.

When the determination result in step $3 is NQ, it is determined whether the operating state is in the supercharging region (step 84), and if it is in the supercharging region, the clutch 16 of the supercharging pump 15 is
is turned on (step S''5), and if it is not in the supercharging region, the clutch 16 is set to 0FF (step Ss), and
In either case, the supercharging pump side ACV 22 is closed (step S7), and then the process moves to step $8, where fuel is injected from the fuel injection valve 14 with the above pulse width.

When the determination result in step S3 is YES (when the operating state is in the boat air region), step S3 is further performed.
At step 9, it is checked whether the engine speed PPM is less than or equal to a predetermined speed Ro. When the determination result in step S9 is No, the clutch 16 of the supercharging pump 15 is turned on and the supercharging pump side ACV 22 is opened (step S1o
, S+1), thereby causing the supercharging pump 15 to supply secondary air, and the clutch 29 of the electric air pump 28 is turned off (step 512). Furthermore, in this case, the secondary air flow rate Q2 detected by the air flow meter 23 is read, and the injection pulse width τ is corrected based on the value obtained by subtracting the secondary air flow rate Q2 from the intake flow rate Q1 (steps S13 and S14). .

Then, the process moves to step S15, and it is checked whether the load is on the lower side than the fuel cut line DC2 in FIG.
If o, fuel cut is performed (step 516).

When it is determined in step S9 that the engine speed PPM is equal to or lower than the predetermined speed Ro, it is determined whether the engine speed was previously larger than the predetermined speed Ro (step 5).
Step 818) Based on step 17), immediately after the engine speed drops below a predetermined speed, the deceleration is checked based on changes in the engine speed and a corresponding delay time A is set in the timer TM.
Thereafter, the timer TM is decremented until it reaches O (step S19.520). The above delay time A is
When the deceleration is sufficiently small, it is set to approximately O, and as the deceleration increases, it is set to a larger value.

Then, when the timer M becomes ○, that is, when the delay time A has elapsed, the electric air pump 28
Step S21.522) of turning ON the clutch 29 and opening the V30 to the electric air pump side, and
Turn off the clarifier 16 of the supercharging pump 15 and close the ACV 22 on the supercharging pump side (steps 823, 8
24>. In this way, secondary air is supplied by the electric air pump 28. Then, the determination in step S15 and the corresponding step S8 or step S1 are made.
Perform the process in step 6.

According to the above-mentioned device, in a region below a predetermined rotation speed Ro where the required amount of secondary air is relatively small in the secondary air supply region, the small electric air pump is By supplying secondary air to the exhaust passage 10 by 28, the load for driving the pump is reduced compared to when the supercharging pump 15 is driven. On the other hand, in the operating range above the predetermined rotation speed Ro where the required amount of secondary air is large and the electric air pump 28 lacks secondary air, the supercharging pump 15 supplies secondary air and the required amount of secondary air is be paid for.

When the operating state shifts from the secondary air supply region by the supercharging pump 15 to the secondary air supply region by the electric air pump 28, when the operating state shifts slowly to near steady operation, as shown in FIG. 4(a), At the time To when the predetermined rotation speed Ro is reached, the supercharging pump drive state is switched to the electric air pump drive state, thereby adjusting the amount of secondary air supplied to match the amount of secondary air required during steady operation. . Also,
During deceleration, when the engine speed suddenly decreases, use the method shown in Figure 4 (
As in b), the switching is delayed by a period of time corresponding to the deceleration, thereby suppressing the temperature rise of the exhaust gas purification device 24. In other words, from the supercharging pump 15 to the electric air pump 28
When switching to , the secondary air that had been supplied in a relatively large amount decreases, and the cooling effect of the secondary air decreases, which tends to increase the temperature of the exhaust purification device 24, especially at high rotation speeds. During sudden deceleration from a high load, the temperature of the exhaust purification device 24 is already high and the main intake passage 8
Since there is a large amount of fuel attached to the wall surface, if the switching point is the same as during steady operation, the temperature will rise significantly as shown by the two-dot chain line in FIG. 4(b). On the other hand, if the switching point is delayed as described above, a relatively large amount of secondary air is supplied from the supercharging pump 15 during this time, and a cooling effect is obtained, as shown in FIG.
As shown by the solid line in b), the temperature rise in the exhaust gas purification device 24 is suppressed.

In the above embodiment, the electric air pump 28 is used as the small flow rate air pump, and the supercharging pump 15 is also used as the other secondary air supply air pump, but the small flow rate air pump is not limited to the electric air pump. If so, a mechanical pump etc. driven by an engine may be used.
Other air pumps are not limited to the supercharger, and a pump exclusively for supplying secondary air may be provided. Also, in terms of how to use the two air pumps, in areas where the amount of secondary air required is small, only one air pump supplies secondary air, and in areas where the amount of secondary air required is large, secondary air is supplied from both air pumps. In this case, both air pumps can be relatively small pumps.

(Effects of the Invention) As described above, the present invention provides two air pumps, at least one of which is a small, small-flow near pump, for supplying secondary air to the exhaust passage. Switching control is performed between supplying secondary air from the air pump and supplying secondary air from the other air pump or both air pumps, making it possible to meet the required amount of secondary air depending on the operating status. While doing so, it is possible to reduce the load on the air pump in an operating range where the amount of secondary air required is small, and improve fuel efficiency. In addition, because the switching point of the secondary air supply is changed depending on whether the operation is steady or transient, it is possible to handle differences in conditions such as temperature and air-fuel ratio between steady operation and transient operation. The amount of secondary air supplied can be adjusted accordingly.

[Brief explanation of the drawing]

Fig. 1 is an overall schematic diagram showing one embodiment of the present invention, Fig. 2 is an explanatory diagram showing the area of secondary air supply from each pump and the supercharging area, etc., Fig. 3 is a flowchart of control, Figure 4 (a>(b) is an explanatory diagram showing switching of secondary air supply during steady operation and deceleration, and accompanying changes in secondary air supply amount and exhaust temperature. 1... Engine , 15... Supercharging pump that also serves as an air pump for secondary air supply, 28... Electric air pump (
small flow rate air pump), 21.27...Secondary air passage, 22.30...Secondary air control valve, 31
. . . control unit, 34 . . . secondary air supply control means, 35 . . . switching point changing means.

Claims (1)

[Claims] 1. In an engine secondary air supply device that controls the supply of secondary air to the exhaust passage according to the operating state of the engine, two air pumps are provided for supplying the secondary air, and at least one of the The air pump should be a small-flow air pump that meets the demand for secondary air in an operating range where the demand for secondary air is low, and depending on the operating condition, the secondary air can be supplied from the above-mentioned small-flow air pump, or the other air pump or a secondary air supply control means for switching the secondary air supply to a state in which secondary air is supplied from both air pumps;
A secondary air supply device for an engine, characterized in that it is provided with switching point changing means for changing the switching point of the secondary air supply by the secondary air supply control means between during steady operation and during transient operation of the engine.