JPS6350545B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas recirculation control device for a diesel engine installed in a vehicle such as an automobile.

As one of the exhaust gas recirculation control devices for diesel engines, a fluid pressure control valve creates fluid pressure in accordance with the amount of displacement of a movable member that is displaced in accordance with the amount of depression of the accelerator pedal. An exhaust gas recirculation control device has been proposed that is configured to drive an exhaust gas recirculation control valve to perform exhaust gas recirculation at an EGR rate depending on the engine load.

According to the exhaust gas recirculation control device as described above,
If the amount of depression of the accelerator pedal is constant, exhaust gas recirculation is performed at the same EGR rate regardless of engine speed.

In a diesel engine, during high-speed, high-load operation, the exhaust gas flow rate is large and the exhaust gas temperature is high. Naturally, the temperature of the recirculated exhaust gas also increases at this time. If gas recirculation is carried out, especially if it is carried out for a long time, the exhaust gas recirculation control components can suffer thermal damage and
There is a possibility that their durability will be significantly reduced.

In addition to the above-mentioned problems, in order to ensure engine performance during high-speed, high-load operation, the engine rotation speed and engine load are detected, and based on these, the time of high-speed, high-load operation is determined, and the exhaust gas is adjusted during high-speed, high-load operation. It is contemplated to stop gas recirculation.

However, if exhaust gas recirculation is stopped during high-speed, high-load operation using the control procedure described above, this is not necessarily done in response to the thermal conditions of the exhaust gas recirculation control components, and therefore the exhaust gas recirculation is stopped. Exhaust gas recirculation is also stopped when the circulation control components are not subject to thermal damage and, conversely, when the exhaust gas recirculation control components may be subject to thermal damage. It happens that something is not done.

An object of the present invention is to provide an exhaust gas recirculation control device that accurately stops exhaust gas recirculation only in high temperature conditions from the viewpoint of thermal protection of exhaust gas recirculation control components.

According to the present invention, this purpose is to provide an exhaust gas recirculation passageway that guides a portion of exhaust gas to the intake system, and an exhaust gas recirculation passageway that changes the opening amount depending on the fluid pressure introduced into the diaphragm chamber. an exhaust gas recirculation control valve that controls the flow rate of exhaust gas flowing through the diaphragm chamber; and an exhaust gas recirculation control valve that controls the flow rate of exhaust gas flowing through the diaphragm chamber. a fluid pressure control valve supplied to the engine; a rotation speed detection means for detecting the rotation speed of the diesel engine; a temperature detection means for detecting the temperature of the exhaust gas recirculation; the rotation speed detection means and the temperature detection means; The exhaust gas recirculation control valve operates based on a signal generated by the exhaust gas recirculation control valve and brings the exhaust gas recirculation control valve to the fully closed position when the speed of the diesel engine is above a predetermined value and the temperature of the exhaust gas recirculation passage is above a predetermined value. This is achieved by an exhaust gas recirculation control device for a diesel engine, characterized in that it has a circulation cutoff device.

The invention will now be described in detail by way of example embodiments with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing a diesel engine incorporating an exhaust gas recirculation control device according to the present invention. In the figure, reference numeral 1 indicates a diesel engine, which has a cylinder bore 2 in which a piston 3 is slidably received. The piston 3 defines a combustion chamber 4 above it. The diesel engine 1 has a swirl chamber 5, into which liquid fuel for the diesel engine is injected and supplied from a fuel injection nozzle (not shown).

The diesel engine 1 sucks air into a combustion chamber 4 through an intake tube 6, an intake manifold 7, and an intake port 8, and from the combustion chamber 4 to an exhaust port 9.
The exhaust gas is discharged to the exhaust manifold 10 through the exhaust gas. The intake port 8 and the exhaust port 9 are each opened and closed by poppet valves, and in the figure, only the exhaust poppet valve 11 is shown.

12 indicates an exhaust gas recirculation control valve. The exhaust gas recirculation control valve 12 has its inlet port 13
The outlet port 15 is connected by a conduit 14 to an exhaust gas collection port 10' formed in the exhaust manifold 10, and the outlet port 15 is connected by a conduit 16 to an exhaust gas injection port 6' formed in the intake tube 6. Exhaust gas recirculation control valve 12 includes a valve element 18 that cooperates with valve seat 17 to open and close input port 13 and to control its effective opening area. The valve element 18 is connected by a valve rod 19 to a diaphragm device 20 and is adapted to be driven by the diaphragm device 20. The diaphragm device 20 includes a diaphragm 21 .
is driven to the right in the figure against the action of the compression coil spring 23 in response to an increase in the negative pressure introduced into the diaphragm chamber 22, and moves the valve element 18 to the right to open the inlet port. 13 and increase its effective opening cross-sectional area.

32 indicates a vacuum pump driven by the diesel engine 1. In this embodiment, the negative pressure generated by the vacuum pump 32 is as follows:
It is supplied through a conduit 33 to a vacuum servo unit of the brake system (not shown), and is also supplied to a negative pressure control valve 37 through a conduit 34, a throttle device 35, and a conduit 36.

The negative pressure control valve 37 has a valve casing 38, which is partitioned into two chambers 40, 41 by a diaphragm 39. The valve casing 38 includes a negative pressure intake port 42 and a negative pressure outlet port 43 that communicate with the chamber 40 .
An atmosphere release port 44 that communicates with 1 is provided. Diaphragm 39 carries a valve retaining member 45 which in turn carries a valve element 46 . The valve element 46 is a compression coil spring 47
and 48 on the valve holding member 45, the compression coil spring 49 on the valve element 46, and the force on the diaphragm 39 due to the pressure difference between the chambers 40 and 41. When the negative pressure in the chamber 40 is smaller than a predetermined value, the valve seat 50 is engaged and the chambers 40 and 4 are driven, as shown in the figure.
1, and also allows negative pressure to be introduced into the chamber 40 from the negative pressure intake port 42 away from the valve seat 51. On the other hand, when the negative pressure in the chamber 40 becomes larger than a predetermined value, By displacing the valve holding member 45 to the left in the figure, it engages with the valve seat 51 to prevent negative pressure from being introduced into the chamber 40 from the negative pressure intake port 42, and also moves away from the valve seat 50. room 40
and 41 are connected to each other through a port 52 provided in the valve holding member 45 to reduce the negative pressure in the chamber 40. By operating the valve element 46 as described above, the negative pressure in the chamber 40 is maintained at a predetermined equilibrium negative pressure value. Compression coil spring 4
7 is a plunger 5 that engages with the valve holding member 45 at one end and is supported by the valve casing 37 at the other end.
It is engaged with the flange 54 of No. 3. plunger 5
3 is provided to be movable in the axial direction of a compression coil spring 47, and as this moves leftward in the figure, the spring force exerted by the compression coil spring 47 on the valve holding member increases. Therefore, as the plunger 53 moves to the left in the figure, the equilibrium negative pressure value of the chamber 40 becomes smaller.

FIG. 2 shows the relationship between the equilibrium negative pressure value of the chamber 40, in other words, the output negative pressure of the negative pressure control valve 38, and the displacement amount of the plunger 53. As is clear from this graph, as the amount of displacement of the plunger 53 to the left in the figure increases, the output negative pressure decreases in proportion to the amount of displacement.

The plunger 53 engages at one end with an accelerator link 56 that is pivotally supported by a pivot 55, and is driven as the accelerator link rotates. The accelerator link 56 is drivingly connected to an accelerator pedal (not shown), and rotates clockwise in the figure in response to depression of the accelerator pedal, thereby driving the plunger 53 to the left in the figure. It's getting old. The accelerator link 56 is pivotally connected at its other end to a rod 57 by which it is drivingly connected to a control lever of a fuel injection pump (not shown in the figure), which controls the control lever in response to depression of the accelerator. It is becoming more and more like driving. The negative pressure outlet port 43 of the negative pressure control valve 37 is connected to a conduit 58, a negative pressure switching valve 59,
It is connected to the diaphragm chamber 22 via a conduit 60.

The negative pressure switching valve 59 cuts off communication between the conduit 58 and the conduit 60 and connects the conduit 60 to the atmospheric air intake port 61 when the solenoid is not energized, whereas the solenoid is energized. When the
1 and connect it to a conduit 58. Power supply control to this solenoid is performed by a control device 62.

The control device 62 receives a signal generated by a rotation speed sensor 63 that detects the rotation speed of the diesel engine 1 and a signal generated by a temperature sensor 64 provided in the conduit 14 and detects the temperature of the exhaust gas recirculation passage. Ru. The control device 62 includes a comparator that compares the signal generated by the rotation speed sensor 63 with a reference signal.
When the output signal is larger than the reference signal, for example, when the engine speed is 2800 rpm or higher, an off signal is output, and when it is lower than that, an on signal is output. The control device 62 also includes a temperature sensor 6.
The temperature sensor 6 includes a comparator for comparing the signal generated by the temperature sensor 6 with a reference signal.
When the output signal of 4 is smaller than the reference signal, for example
It outputs an on signal when the temperature is below 300°C, and an off signal at other times. The control device 62 controls the diesel engine 1 only when both of the comparators output off signals.
The solenoid of the negative pressure switching valve 59 is de-energized only when it is operated at high speed and the temperature of the exhaust gas recirculation passage is above a predetermined value, and is energized at other times.

The exhaust gas recirculation control device constructed as described above operates as follows.

The negative pressure control valve 37 is connected to the accelerator link 56
In other words, a negative pressure is applied to the negative pressure outlet port 43 that reduces the difference from atmospheric pressure in accordance with the rotation angle of the diesel engine 1, in other words, in approximately proportion to an increase in the load of the diesel engine 1.
At this time, if the exhaust gas recirculation passage temperature detected by the temperature sensor 64 is below a predetermined value, the control device 62 energizes the solenoid of the negative pressure switching valve 59 regardless of the engine speed detected by the rotation speed sensor 63. Let's do it. Therefore, at this time, the negative pressure switching valve 59 is connected to the conduit 5.
8 and 60 are connected. Therefore, the negative pressure applied to the negative pressure outlet port 43 is introduced into the diaphragm chamber 22 of the exhaust gas recirculation control valve 20 via the conduit 58, the negative pressure switching valve 59, and the conduit 60. This drives the valve element 18 in the valve opening direction, opening the inlet port 13 and effecting exhaust gas recirculation. The valve element 18 increases its opening amount in response to an increase in the negative pressure applied to the diaphragm chamber 22, in other words, in response to a decrease in engine load, and the effective opening area of the inlet port 13 increases. . Therefore, the EGR rate increases as the engine load decreases.

As the engine load increases, the exhaust gas temperature increases accordingly, the temperature detected by the temperature sensor 64 rises beyond the predetermined value, and the engine rotation speed detected by the engine rotation speed sensor 63 increases to the predetermined value. When this occurs, that is, when the exhaust gas recirculation control components are at risk of being thermally damaged, the control device 62 stops energizing the solenoid of the negative pressure switching valve 59. At this time, the negative pressure switching valve 59 cuts off communication between the conduits 58 and 60 and connects the conduit 60 to the atmospheric air intake port 61. At this time, therefore, atmospheric pressure is introduced into the diaphragm chamber 22 and the valve element 18 closes, completely closing the inlet port 13. Exhaust gas recirculation is thereby stopped.

As mentioned above, since the diesel engine is disabled from exhaust gas recirculation, thermal damage to the exhaust gas recirculation control components is avoided.

The present invention is not limited to the embodiments described above, and it goes without saying that the control valve may be driven by positive pressure. Further, the plunger of the control valve may be driven by a movable member other than the accelerator link, such as a control lever of a fuel injection pump, a control rack, etc., which is displaced in accordance with the amount of displacement of the accelerator pedal.

Although specific embodiments of the present invention have been described in detail above, the present invention is not limited thereto, and various embodiments are possible within the scope of the present invention. This will be clear to those skilled in the art.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram showing one embodiment of a diesel engine incorporating an exhaust gas recirculation control device according to the present invention, and Fig. 2 is a relationship between the displacement amount of the plunger of the negative pressure control valve and the output negative pressure. This is a graph showing. 1~diesel engine, 2~cylinder bore,
3-piston, 4-combustion chamber, 5-vortex chamber, 6-intake tube, 7-intake manifold, 8-intake port, 9-exhaust port, 10-exhaust manifold, 11-exhaust poppet valve, 12-exhaust gas recirculation control valve, 13-inlet port, 14-conduit, 1
5 - outlet port, 16 - conduit, 17 - valve seat, 18
- Valve element, 19 - Valve rod, 20 - Diaphragm device, 21 - Diaphragm, 22 - Diaphragm chamber, 23 - Compression coil spring, 32 - Vacuum pump, 33, 34 - Conduit, 35 - Throttle device, 36
~ Conduit, 37 ~ Negative pressure control valve, 38 ~ Valve casing, 39 ~ Diaphragm, 40, 41 ~ Chamber, 4
2~Negative pressure intake port, 43~Negative pressure outlet port, 44~Atmospheric release port, 45~Valve holding member,
46 - Valve element, 47, 48, 49 - Compression coil spring, 50, 51 - Valve seat, 52 - Port, 53 - Plunger, 54 - Flange, 55 - Pivot, 56 -
Accelerator link, 57 - rod, 58 - conduit, 59 - negative pressure switching valve, 60 - conduit, 61 - atmospheric intake port, 62 - control device, 63 - rotation speed sensor, 64 - temperature sensor.

Claims (1)

[Claims] 1. An exhaust gas recirculation passage that guides a portion of the exhaust gas to the intake system, and an exhaust that controls the flow rate of the exhaust gas flowing through the exhaust gas recirculation passage by changing the opening amount according to the fluid pressure introduced into the diaphragm chamber. a gas recirculation control valve; a fluid pressure control valve that corrects fluid pressure from a fluid pressure source in accordance with the amount of displacement of a movable member that is displaced in accordance with the amount of depression of an accelerator pedal and supplies the fluid pressure to the diaphragm chamber; A rotation speed detection means for detecting the rotation speed of the diesel engine, a temperature detection means for detecting the temperature of the exhaust gas recirculation passage, and the rotation speed detection means and the temperature detection means operate based on signals generated. and an exhaust gas recirculation cutoff device that brings the exhaust gas recirculation control valve to a fully closed position when the engine speed is above a predetermined value and the exhaust gas recirculation passage temperature is above a predetermined value. Features a diesel engine exhaust gas recirculation control device.