JPS6235879Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an EGR control device for a diesel engine, and particularly to an EGR control device that corrects the amount of EGR in accordance with temperature changes.

[Conventional technology]

Conventionally, in EGR control for diesel engines, unlike gasoline engines, there is no pressure source that changes with load, so a negative pressure control valve as shown in Utility Model Application No. 57-49548 has been used. This negative pressure control valve adjusts the negative pressure supplied from the vacuum pump according to the load, and changes the negative pressure output to the EGR control valve. For this reason, the valve holding member installed on the diaphragm that partitions the inside of the valve casing into a diaphragm chamber to which negative pressure is supplied from the vacuum pump and an atmospheric chamber that is open to the atmosphere is provided with a valve holding member installed in the diaphragm chamber and the atmospheric chamber, respectively. Of the springs provided, the spring force received from the spring provided on the atmospheric chamber side changes in conjunction with the accelerator pedal. In this way, the negative pressure in the diaphragm chamber when the valve holding member starts to move toward the diaphragm chamber changes due to the pressure difference between the atmospheric chamber and the diaphragm chamber, and the negative pressure output to the EGR control valve changes depending on the engine load. controlled.

[Problem that the invention attempts to solve]

By the way, the characteristics of EGR control according to engine load are determined by comprehensively evaluating performance, emissions, black smoke, white smoke, drivability, etc. at room temperature. However, when the outside air or the inside of the engine room becomes hot, the air density decreases. Therefore, the actual amount of intake air decreases and the excess air ratio decreases, so that even with the same amount of fuel, the amount of inert gas in the exhaust gas increases. Therefore, when the same amount of EGR as at room temperature is injected into the combustion chamber, the excess air ratio becomes smaller and smaller, which not only increases the generation of black smoke but also promotes the ignition delay caused by EGR. As a result, emissions increase (particularly HC and CO) due to deterioration in combustion, white smoke generation, fuel consumption, vibration and
Various problems such as noise, deterioration of drivability, and necessity of injection timing correction may occur.

Therefore, the technical problem of the present invention is to ensure an optimal amount of EGR in response to changes in engine load and temperature by reducing EGR as the outside air or the inside of the engine room becomes hotter.

[Means for solving problems]

According to the EGR control device for a diesel engine of the present invention, the measures taken to solve the above technical problems are such that the pressure difference when communicating between the diaphragm chamber and the atmospheric chamber can be reduced by increasing the temperature of outside air or the engine room. The purpose is to change the equilibrium negative pressure generated in the diaphragm chamber by providing the negative pressure control valve with a temperature compensator that is set to a small temperature.

[Effect]

According to this means, even if the engine load remains the same, the equilibrium negative pressure in the diaphragm chamber decreases as the temperature increases, similar to when the engine load increases.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of the present invention.

An EGR control valve 1 is provided in the middle of an EGR passage 2 from an exhaust manifold (not shown) to an intake manifold. In this EGR control valve 1, a valve body 3 that increases or decreases a passage opening area that determines the amount of EGR is locked to a diaphragm 5 via a rod 4.
A compression spring 6 is provided in the negative pressure chamber 7 defined by the diaphragm 5 to constantly bias the diaphragm 5 downward. A controlled negative pressure generated by a negative pressure control valve 8 is applied to this negative pressure chamber 7 via a communication pipe 10 . Therefore, the greater the controlled negative pressure, the greater the stroke of the diaphragm 5 to pull the valve body 3 upward in the figure, increasing the EGR amount.

The negative pressure control valve 8 outputs negative pressure according to the opening degree of a speed control lever 25 of a fuel injection pump (not shown), and has a valve casing 11. The valve casing 11 is connected to a diaphragm chamber 9 by a diaphragm 12. and an atmospheric chamber 13. Further, the valve casing 11 is provided with a negative pressure intake port 9a communicating with the diaphragm chamber 9, a negative pressure outlet port 9b, an atmosphere release port 13a communicating with the atmospheric chamber 13, and a filter 14. A valve holding member 15 is provided on the diaphragm 12 . This valve holding member 15
is guided by a filter 14, and holds a valve element 17 therein via a valve element pressing spring 16.

The valve element 17 has valve holding member pressing springs 18 and 19.
The spring force applied to the valve holding member 15 by the valve element pressing spring 16, the spring force applied to the valve element by the valve element pressing spring 16, and the force applied to the diaphragm 12 due to the pressure difference between the diaphragm chamber 9 and the atmospheric chamber 13. When the pressure difference between the diaphragm chamber 9 and the atmospheric chamber 13 is smaller than a predetermined value, the valve seat 1 of the valve holding member 15 is
5a, the diaphragm chamber 9 and the atmospheric chamber 13
At the same time, the negative pressure from the vacuum pump 21 is introduced into the diaphragm chamber 9 through the negative pressure intake port 9a away from the valve seat 20a of the negative pressure introduction pipe 20.

On the other hand, when the pressure difference between the diaphragm chamber 9 and the atmospheric chamber 13 becomes larger than a predetermined value, the valve holding member 15 is pulled upward in the figure by the diaphragm 12, so that the valve element 17 engages with the valve seat 20a. This prevents negative pressure from being introduced into the diaphragm chamber 9 from the negative pressure intake port 9a, and connects the diaphragm chamber 9 and the atmospheric chamber 13 to the valve holding member 15 at a distance from the valve seat 15a. The ports 15b are connected to each other to reduce the negative pressure in the diaphragm chamber 9.

Further, the valve holding member pressing spring 19 engages with the valve holding member 15 at one end, and engages with a thermowax plate 24, which is one of the heat sensitive members, at the other end. This thermowax plate 24 is provided in a flange groove 23a of a flange 23 that engages with the upper surface of the plunger 22. plunger 2
2 engages with a speed control lever 25 driven by an accelerator ring connected to an accelerator pedal, and is configured to be driven as the speed control lever 25 rotates. That is, the speed control lever 25 rotates in response to the depression of the accelerator pedal, rotates the plunger 22, and pushes the flange 23 upward when the accelerator pedal is depressed greatly, that is, when the load is large. As the flange 23 moves upward, it pushes the valve holding member pressing spring 19 upward through the thermowax plate 24 so as to compress it. Therefore, the valve holding member pressing spring 19 increases the spring force applied to the valve holding member 15 toward the diaphragm chamber 9 side, and the negative pressure inside the diaphragm chamber 9 pulls up the valve holding member 15 via the diaphragm 12. It will help you. Therefore, the larger the load, the more the valve holding member 1
The pressure difference when the diaphragm chamber 9 and the atmospheric chamber 13 communicate through the port 15b provided in the diaphragm chamber 9 becomes small, and the equilibrium negative pressure in the diaphragm chamber 9 becomes small.

On the other hand, the thermowax plate 24 is a sealed body in which the upper and lower plates 24a and 24b are connected by a telescopic bellows 24c.
d is enclosed. In this thermowax plate 24, the lower plate 24b is fixedly supported at the bottom of the flange groove 23a with an adhesive or the like, so it deforms as the thermowax 24d expands and contracts due to temperature changes, and the upper plate 24a moves up and down. I will do it. Therefore, apart from the movement of the flange 23 mentioned above, the thermowax plate 2
4, the movement of the upper plate 24a pushes up the valve holding member pressing spring 19 so as to compress it as the temperature rises, thereby increasing the spring force applied to the valve holding member 15. Therefore, the valve holding member pressing spring 19
Similarly, when the engine load increases, the negative pressure in the diaphragm chamber 9 will help pull the valve retaining member 15 up via the diaphragm 12. Therefore, as the temperature rises, the pressure difference when diaphragm chamber 9 and atmospheric chamber 13 communicate with each other becomes smaller, and the equilibrium negative pressure in diaphragm chamber 9 becomes smaller.

From the negative pressure control valve 8 configured as described above,
The characteristics of the negative pressure applied to the negative pressure chamber 7 of the EGR control valve 1 are shown in FIG. In the figure, a solid line 30 shows the characteristics at room temperature, and a broken line 31 shows the characteristics at high temperature. As shown in the figure, it can be seen that in addition to the conventional output negative pressure control based on the load, the output negative pressure can be controlled to be reduced as the outside air or the temperature inside the engine room becomes higher. In other words, the higher the temperature, the more the EGR control valve 1
Since the opening degree of the valve body 3 becomes smaller, the amount of EGR can be reduced. Furthermore, Thermowax 24d
The expansion and contraction of is continuous and smooth, so
For example, if the solid line 30 is the characteristic when the ambient temperature is 25℃, and the broken line 31 is the characteristic when the ambient temperature is 60℃, then 25℃~60℃
Until then, the output negative pressure characteristics change continuously, making it possible to prevent sudden changes in the EGR amount.

3 to 6 show second to fifth embodiments of the present invention, and the same components as in the first embodiment are denoted by the same reference numerals.

FIG. 3 shows a second embodiment of the present invention, in which the plunger 2
2 is provided with a plunger groove 22a, the bottom of which is sealed with thermowax 24da by means of a piston 24e. The thermowax 24d expands due to the rise in temperature and pushes up the piston 24e, thereby achieving the same effect as in the first embodiment.

FIG. 4 shows a third embodiment of the present invention, in which the negative pressure control valve 8
An inner chamber 25a is provided within the speed control lever 25, which is a part of the speed control lever 25, and a thermowax plate 24 is provided within the inner chamber 25a.

FIG. 5 shows a fourth embodiment of the present invention, in which a bimetal flange 40 made of bimetal is used. The bimetal flange 40 is a flat plate at room temperature, for example 25° C., but is made of bimetal that becomes concave upward as the ambient temperature increases, as shown in the figure.
Therefore, the valve holding member pressing spring 19 is compressed and pushed upward as the temperature rises, and the same effects as in the first to third embodiments described above can be obtained.

FIG. 6 shows a fifth embodiment of the present invention, in which a bimetal plate 41 is inserted into the negative pressure intake port 9a through the insertion hole 41a in the diaphragm chamber 9, and locks the valve holding member pressing spring 18. are doing.
This bimetal plate 41 is heated at room temperature, for example, at 25°C.
At ℃, it forms a downward convex shape as shown in the figure.
As the temperature rises, it becomes flat and is pressed against the wall of the valve casing 11 by the valve holding member pressing spring 18. Therefore, the spring force with which the valve holding member pressing spring 18 urges the valve holding member 15 downward becomes weaker as the temperature becomes higher. In other words, this is the same as increasing the spring force that pushes up the valve holding member 15. Therefore, as shown in the first to fourth embodiments, the higher the temperature, the more the valve body holding member 15 is pushed up. You can get the same effect as .

[Effect of the invention] In this way, according to the means taken by the invention, as the engine load increases, as the temperature rises, the negative pressure supplied from the negative pressure control valve to the EGR control valve is reduced. By reducing EGR
Since the amount of EGR is reduced by adjusting the valve opening of the control valve, the optimal amount of EGR can be obtained regardless of engine load or temperature changes.

Furthermore, since the negative pressure control valve is provided with a heat-sensitive member, a new temperature sensor or the like is not required, and the apparatus can be simplified.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an EGR control device for a diesel engine according to a first embodiment of the present invention;
Figure 2 shows the EGR of the diesel engine of this invention.
FIG. 3 is a diagram showing the characteristics of the negative pressure control valve provided in the control device, and FIG. 4 is a partial sectional view of a negative pressure control valve provided in an EGR control device for a diesel engine according to a third embodiment of the present invention, and FIG. 5 is an EGR control device for a diesel engine according to a fourth embodiment of the present invention. FIG. 6 is a partial sectional view of a negative pressure control valve provided in an EGR control device for a diesel engine according to a fifth embodiment of the present invention. 1...EGR control valve, 8...Negative pressure control valve, 9...
...Diaphragm chamber, 11...Valve casing,
12...Diaphragm, 13...Atmospheric chamber, 21...
... Vacuum pump, 24 ... Thermowax plate, 40 ... Bimetal flange, 41 ...
bimetal plate.

Claims (1)

[Scope of utility model registration request] The inside of the valve casing is partitioned into a diaphragm chamber that receives negative pressure from the vacuum pump and an atmospheric chamber that is open to the atmosphere, and when the diaphragm chamber and the atmospheric chamber are communicated, a balanced negative EGR of a diesel engine is equipped with a negative pressure control valve whose pressure is set to decrease as the load increases, and adjusts the valve opening of the EGR control valve by supplying the balanced negative pressure in the diaphragm chamber.
In the control device, the negative pressure control valve is provided with a temperature compensator that sets a pressure difference when the diaphragm chamber and the atmospheric chamber communicate with each other to be smaller as the outside air or the temperature in the engine room increases. A diesel engine characterized by changing the equilibrium negative pressure.
EGR control device.