JPS5979060A - Altitude compensating device for egr system - Google Patents

Abstract

PURPOSE:To effect the altitude compensation of the EGR device with a low cost by utilizing a fact that the absolute pressure of the vacuum source of a vacuum pump is made smaller as compared to the variation of atmospheric pressure. CONSTITUTION:A pressure actuator 2 is integrated with an EGR valve 3 while a pressure chamber 20 is constituted by a case 23 and a diaphragm chamber 21. The pressure port 26 of the case 23 is communicated with the suction port 11 of the vacuum pump 1. The EGR valve 3 shuts up an EGR path 8 by the energizing force of springs 22, 23 when the pressures of the pressure chamber 20 and a vacuum chamber 30 are same as the atmospheric pressure and, further, shuts the path 8 when the vacuum of the vacuum chamber 30 is smaller than a value corresponding to the energizing force of the spring 32 even if the pressure of the pressure chamber 20 becomes the same as the suction pressure of the vacuum pump. In case the suction pressure of the vacuum pump is utilized, little leakage from sealing positions may be allowed, therefore, the diaphragm type pressure actuator may be obtained by an inexpensive material such as rubber or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas recirculation device (hereinafter referred to as an EGR device) for purifying engine exhaust gas, and particularly to altitude compensation thereof.

It is well known that the EGR of diesel engines must be reduced at high altitudes. Therefore, EGR
In order to achieve altitude compensation, conventionally, an atmospheric pressure sensor using a vacuum pressure sensor, a control circuit, an actuator, etc. based on the sensor have been used.

Therefore, there is a problem that the cost of the system is high in the conventional device, and it is desired to realize a low-cost system.

The present invention was devised in view of the above problem, and takes advantage of the fact that the absolute pressure of the vacuum source of a vacuum pump is extremely small compared to changes in atmospheric pressure, compares this pressure with atmospheric pressure, and compares this pressure with atmospheric pressure. The aim is to simplify the components of the EGR device by controlling the amount of

A first embodiment of the present invention will be described below with reference to FIG.

Main components are negative pressure pump 1, pneumatic actuator 2, EG
They are an R valve 3, a negative pressure control valve 4, a control circuit 5, a rotation sensor 6, and an injection pump lever opening sensor 7.

The negative pressure pump 1 is usually constituted by a well-known vane pump, and is driven by an engine (not shown).

The pneumatic actuator 2 is configured to be integrated with the EGR valve 3. A diaphragm 21 is stretched over the opening of a bell-shaped case 23, and the case 23 and the diaphragm 21 constitute a pressure chamber 20.

Both sides of the diaphragm 21 are attached to the diaphragm holder 24.
25 is clamped and fixed. Also, the holder 24 and the case 2
A spring 22 is compressed and installed between the bottom of the holder and the bottom of the holder. A pressure boat 26 is provided at one location of the case 23, and the pressure boat and the suction port 11 of the negative pressure pump 1 are in communication.

The EGR valve 3 is provided in the middle of an EGR communication passage that connects an intake pipe (not shown) and an exhaust pipe of the diesel engine. This EGR valve 3 includes a cylindrical case 33,
It is composed of a spring 32, a diaphragm 31, and a valve body 36. The other end of the diaphragm 21 of the cylindrical case 33 is stretched, and both sides of the diaphragm 31 are sandwiched and fixed by holders 34 and 35. A spring 32 is compressed and installed between the holder 34 and the holder 2. The EG and R valve bodies 36 are fixed and integrated with the holder 35 at its center. A negative pressure boat 37 is provided in a negative pressure chamber 30 composed of a cylindrical case 33 and a diaphragm 21.31, and communicates with the negative pressure control valve 4. The EGR valve 3 shuts off the EGR communication passage by the urging force of springs 22 and 23 when the pressure in the pressure chamber 20 and the negative pressure chamber 30 is the same as atmospheric pressure, and furthermore, the pressure in the pressure chamber 20 is at the same pressure as the suction pressure of the negative pressure pump. Even if the negative pressure chamber 30
When the negative pressure is smaller than the value corresponding to the biasing force of the spring 32, the passage 8 is closed. And negative positive chamber 3
When the zero pressure becomes even more negative, the spring 32 contracts and the valve body 36 is pulled up, opening the EGR communication passage.

The main components of the negative pressure control valve 4 are a spool valve 42, a solenoid coil 43, a diaphragm 44, an iron core 45, a core 46,
This is the spring 47. The sleeve 41 fitted with the spool valve 42 has an atmospheric boat 411 and a negative pressure boat 410.
are provided and are connected to the atmosphere and the negative pressure pump 1, respectively. In addition, the spool valve 42 has a communication passage 421 in the center.
The diaphragm chamber 440 is configured to communicate with either the atmospheric boat 411 or the negative pressure boat 410 described above. The diaphragm chamber 440 is constructed by placing a diaphragm 44 on one end surface of a cylinder constituting the sleeve 41, and the diaphragm 44 and the sleeve 4
1 and a spring 47 is compressed and installed. Further, a core 46 and the aforementioned spool valve 42 are fixed to the diaphragm 44 on the front and back surfaces, respectively, and the iron core 45 at the center of the solenoid coil 43 faces the core 46. The control boat 413 is provided on the wall of the diaphragm chamber 440. Further, an atmosphere communication hole 441 is provided in the case to apply atmospheric pressure to a surface of the diaphragm 44 that is not desired in the diaphragm chamber 440. A lead wire terminal 431 of the solenoid coil 43 is connected to the control circuit 5. Therefore, when the control circuit 5 determines the signal current to be applied to the power supply coil 43, the control board 413
This determines the negative pressure to be output. In other words, increase the signal current by 1
'', the output negative pressure increases.

The control circuit 5 is connected to a variable resistor 7 that rotatably moves in conjunction with a lever of a fuel injection pump (not shown) of a diesel engine, and an engine rotation speed detector 6. The rotation speed detector 6 has a known structure in which a coil 63 is wound around a magnet body 62 to detect changes in magnetic flux density.

As is well known, altitude compensation for EGR requires reducing the amount of EaR under high altitude conditions compared to level ground. This example is characterized by the atmospheric pressure detection means, and the atmospheric pressure detection function will be explained below.

Automotive diesel engines have brakes and other
A vane pump type negative pressure pump 1 is incorporated to drive negative pressure actuators such as the GR valve and the intake throttle valve. Generally, the relationship between the discharge pressure and suction pressure of the pump 1 is given by the compression ratio ε of the pump.

In other words, assuming that there is no leakage during the compression stroke of the pump,
It is well known that it can be expressed as I), = P Oεn. P is the pressure before compression, Pl is the pressure after compression, and n is the polytropic index. Therefore, once the specifications of the pump are determined, εn becomes a constant value, resulting in a relationship of P+0CPO. εn is usually a value of about 0.025 to 0.020, so (ΔPI/ΔP o) −0,02
~0.025.

This shows that even if there is a change in atmospheric pressure, P+ (suction pressure) will only change by about 1150~1/4o. can detect changes in That is, if atmospheric pressure and the suction negative pressure of this pump 1 are applied to both sides of the diaphragm 21, the force applied to the diaphragm 21 changes as the atmospheric pressure changes. This is balanced with the spring 22 to change the position.

The operation of this embodiment will be explained below with reference to the drawings.

As shown in FIG. 2, the absolute pressure P of the suction pressure of the negative pressure pump 1 remains at about 10 wHg while the atmospheric pressure changes from 760 mm 11 g to 630 tuna 11 g.

Therefore, the differential pressure between the atmospheric pressure PO and the absolute pressure P changes almost linearly and at the same level as the amount of change in atmospheric pressure, as shown in FIG. This ΔP acts on both sides of the diaphragm 21 of the pneumatic actuator 2, and the diaphragm 21
1 moves to the 5th point due to the compression force of the spring 22.

Here, the displacement amount of the valve body 36 is assumed to be positive upward and is 1. 1
takes only positive values. Further, the amount of displacement of the diaphragm 21 is assumed to be X. The same way.'' The two directions are positive. spring 2
The initial set load and spring constant of 2 and spring 32 are F
, l01F20%KI, K2, and the diaphragm 21.
Let the effective areas of 31 be AI and A2. FI[1=F20
The pressure in the atmospheric pressure chamber where P is satisfied, the pressure in the negative pressure chamber is Ps, and the atmospheric pressure P
If O, then P<Ps<PO. Considering the balance of forces, for the spring 22, (Ps-P)AI4- (Po Ps)Δ2=F+o
+ Nini 1 □ ■, K2 ('J X>4-F2o= (Po-Ps)
A2□ ■ holds true. For convenience, let AI=A2 and PO−P=ΔP
% PO-Ps=Px, and if you eliminate Mata, '1=Px/
2 + ΔP/K + + (K 2−
K l )/■(1・K2□■ is obtained. The meaning of this equation 0 is that ΔP becomes smaller as the atmospheric pressure decreases, indicating that the predetermined value becomes smaller. The third term on the right side of the equation is a negative value. Furthermore, if the opening pressure of the valve body 36 is 1-0 using the 0 formula, ■n x = (2 to K-)
・F Io/K + −ΔP ・K
If 2/K + □ (2) is obtained and the atmospheric pressure decreases, ΔP will become smaller, and (2) the remaining cloth side will become larger.

That is, as the atmospheric pressure decreases, the valve opening pressure also increases. This situation is not shown in Figure 4. As the atmospheric pressure decreases, ΔP decreases as ΔP1, ΔP2, and ΔP3, and the valve lift 1 becomes a small value for the same Px. Even with the same signal from the control circuit, the lift of the EGR valve body 36 changes as the atmospheric pressure changes, making it possible to perform altitude compensation.

Next, a second embodiment of the present invention is shown in FIG.

In this embodiment, a surge tank 80 and a restriction jill 9 are interposed in the path 200 that connects the negative pressure sensor 2 and the negative pressure pump 1. When other actuators 4 and 4', such as a brake or an intake throttle valve, which are activated by negative or positive signals, are suddenly activated depending on operating conditions, the pressure of the negative pressure pump 1 changes temporarily. Therefore, it is necessary to distinguish this temporary change in pressure from a change in atmospheric pressure, so a surge tank 80 is provided as an accumulator, and a throttle jet 9 is provided as an accumulator.
This structure prevents the slight fluctuations in pressure from being transmitted to the negative pressure sensor. Note that since the responsiveness of detecting atmospheric pressure may be within several seconds, the aperture diameter of the aperture jet 9 may be 0.51 or less.

Next, a third embodiment of the present invention will be described based on FIG. 6. In the embodiment described above, the pneumatic actuator 2
Although the set pressure of the spring 32 of the GR valve 3 is adjusted, in this embodiment, the EGR valve 3 is installed in the EGR passage 8.
They are arranged in series.

Then, the second EGR valve body 2 is activated by the pneumatic actuator 2.
00 directly. In this configuration, when the atmospheric pressure decreases, the diaphragm 2 of the pneumatic actuator 2
1 is a relative pressure, and a small pressure is applied, and the valve body 200 moves downward in the figure, and the opening amount of the valve body becomes small.

Therefore, the amount of EGR adjusted by the normal system using the EGR valve 3 becomes smaller as the atmospheric pressure decreases even under the same operating conditions.

A simple and inexpensive altitude compensation sensor for automobiles is desired, but as explained above, if the suction pressure of a negative pressure pump is used, leakage from the seal part is allowed if it is a small amount. A diaphragm-type pneumatic actuator can be obtained using inexpensive materials such as rubber and simple processing. Therefore, the device of the present invention has an excellent effect in that altitude compensation of EGR can be achieved at low cost.

[Brief Description of the Drawings] Fig. 1 is a configuration diagram showing the first embodiment of the device of the present invention, Fig. 2 is a graph showing the relationship between atmospheric pressure and vacuum pump suction negative pressure, and Fig. 3 is a graph showing the relationship between atmospheric pressure and vacuum pump suction negative pressure. A graph showing the relationship between the diaphragm 21 and the differential pressure, Fig. 4 (a graph showing the relationship between the atmospheric pressure and the valve lift, Fig. 5) A configuration diagram showing the second embodiment of the device of the present invention, Fig. 6 No. It is a configuration diagram showing a third embodiment of the device of the present invention. ■... Vacuum pump, 2... Air pressure actuator; 3... EGR valve, 36... EGR valve body, 8...
...EGR passage. Representative Patent Attorney Takashi Okabe Diagram 1 O Diagram 2 Ne (rpm) @ Diagram 3 Po (mmHg) Continued from page 1 0 Inventor Nippondenso Co., Ltd., 1-1 Showa-cho, Hishinuma Shukariya City ■Applicant Toyota Motor Corporation 1 Toyota-cho, Toyota City

Claims (3)

[Claims] (1) An EGR passage that connects the exhaust pipe and intake pipe of an internal combustion engine, an EGR valve body that is disposed in this EGR1ffl passage and controls the opening area of the EGRm passage, and a a pneumatic actuator that variably controls the amount of CE
Is the valve body configured to be driven? : Altitude compensation device for EGR equipment. (2) The EGR device according to claim 81, wherein the EGR valve body controls the EGR passage opening area according to the pressure in the pressure chamber and the set pressure of a spring, and the pneumatic actuator varies the set pressure of the spring. altitude compensator. (3) Two EGR valve bodies are disposed in the EGR passage, and the pneumatic actuator controls one of the EGR valve bodies.
An altitude compensation device for an EGR device according to claim 1, which drives a valve body.