JPH0315025B2 - - Google Patents

Description

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

[Prior Art] As one of the exhaust gas recirculation control devices for a diesel engine, a movable member is used that uses a control valve to displace negative pressure from a negative pressure source such as a vacuum pump in accordance with the amount of depression of an accelerator pedal. The negative pressure is adjusted according to the amount of displacement, and this negative pressure drives a diaphragm-type exhaust gas recirculation control valve to recirculate exhaust gas at an EGR rate that decreases as the amount of accelerator pedal depression increases. An exhaust gas recirculation control device constructed as described above is proposed in Japanese Patent Application Laid-Open No. 56-47651.

This is because in diesel engines, when exhaust gas recirculation is performed during high-load operation, the engine's maximum output decreases and the black smoke in the exhaust gas increases. It controls circulation.

[Problem to be Solved by the Invention] In a diesel engine in which the amount of exhaust gas recirculation is controlled by a diaphragm type exhaust gas recirculation control valve, it is necessary to stop the exhaust gas recirculation during high load operation of the engine. Theoretically, control that modifies the fluid pressure such as negative pressure supplied to the diaphragm of the exhaust gas recirculation control valve in the valve closing direction as the amount of depression of the accelerator pedal increases, is theoretically possible when the engine load reaches a predetermined high load. It is sufficient that the exhaust gas recirculation control valve closes exactly when the exhaust gas recirculation control valve closes, but diaphragm-operated control valves open and close unstablely near the critical point of opening and closing due to slight fluctuations in fluid pressure that occur in the diaphragm chamber. The operation is repeated, and especially in exhaust gas recirculation control, there is exhaust pulsation in the exhaust pipe, so this effect is also added, and the engine operates just around the critical point of turning on and off exhaust gas recirculation. If this happens, there is a risk that engine operation will become unstable due to unstable on/off switching of exhaust gas recirculation.

The present invention addresses the above-mentioned problem in controlling to stop exhaust gas recirculation in a diesel engine equipped with a diaphragm type exhaust gas recirculation control valve, and provides a diesel engine that solves this problem. The object of the present invention is to provide an exhaust gas recirculation control device for an engine.

[Means for Solving the Problems] According to the present invention, the above-mentioned problems are solved by the exhaust gas recirculation passage leading a part of the engine exhaust gas to the engine intake system and the fluid pressure introduced into the diaphragm chamber. Exhaust gas recirculation that opens when the fluid pressure changes across a predetermined value and controls the flow rate of exhaust gas flowing through the exhaust gas recirculation passage by an opening amount that increases as the change in fluid pressure increases. The exhaust gas recirculation control valve includes a control valve, a fluid pressure source, and a movable member that is displaced according to the amount of depression of the accelerator pedal, and the fluid pressure from the fluid pressure source is applied to the exhaust gas recirculation control valve in response to an increase in the amount of depression of the accelerator pedal. a fluid pressure control valve that supplies fluid to the diaphragm chamber by correcting the degree of opening of The valve is responsive to a fluid pressure controlled for the exhaust gas recirculation control valve by the fluid pressure control valve such that the fluid pressure is less than the first predetermined value on the valve opening side of the exhaust gas recirculation control valve. Achieved by an exhaust gas recirculation control device for a diesel engine, characterized in that the exhaust gas recirculation control device for a diesel engine is configured to open the fluid passage to the atmosphere when the first predetermined value is closer to the first predetermined value than the second predetermined value. be done.

[Operation of the invention] As described above, the valve opens when the fluid pressure supplied to the diaphragm chamber changes across the first predetermined value, and the opening amount increases as the fluid pressure changes. The fluid pressure supplied to the diaphragm chamber of the exhaust gas recirculation control valve that controls the flow rate of exhaust gas flowing through the exhaust gas recirculation passage has a movable member that is displaced according to the amount of depression of the accelerator pedal. In addition to being controlled by a fluid pressure control valve that operates to supply the diaphragm chamber with an output fluid pressure modified to reduce the opening of the exhaust gas recirculation control valve in response to an increase in the amount of fluid It is also controlled by a switching valve provided in the middle of the fluid passage leading from the pressure source to the diaphragm chamber, and this switching valve is controlled by the fluid pressure control valve to the fluid pressure controlled for the exhaust gas recirculation control valve. and opening the diaphragm chamber to the atmosphere when the fluid pressure is closer to the first predetermined value than the second predetermined value, which is on the valve opening side of the exhaust gas recirculation control valve than the first predetermined value. By being configured, when the amount of depression of the accelerator pedal increases, the diaphragm chamber of the exhaust gas recirculation control valve is configured such that when the amount of depression of the accelerator pedal increases, the amount of depression increases when the exhaust gas recirculation control valve is controlled only by the fluid pressure control valve. Since the exhaust gas recirculation control valve is released to the atmosphere by the switching valve just before the exhaust gas recirculation control valve reaches the closing value, the diaphragm type exhaust gas recirculation control valve has a diaphragm type exhaust gas recirculation control valve in which the fluid pressure acting on the diaphragm chamber just opens and closes the valve. In other words, the fluid pressure acting on the diaphragm chamber of the exhaust gas recirculation control valve as the amount of depression of the accelerator pedal increases increases. During the process of changing the opening to zero, in a fluid pressure region where the diaphragm exhaust gas recirculation control valve still operates stably, the valve suddenly and reliably closes. brought to you. In this way, the risk of unstable operation of the engine due to instability of the exhaust gas recirculation is reliably avoided.

[Example] The present invention will be described in detail below 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 designates a diesel engine which slidably receives a piston 3 in a cylinder bore 2, which piston defines a combustion chamber 4 above it. The diesel engine 1 has a swirl chamber 5 communicating with a combustion chamber 4, and liquid fuel for the diesel engine is injected into the swirl chamber from a fuel injection nozzle (not shown). There is.

The diesel engine 1 passes through an intake tube 6, an intake manifold 7, and an intake port 8 into a combustion chamber 4.
Air is sucked into the combustion chamber 4, and exhaust gas is discharged from the combustion chamber 4 through the exhaust port 9 to the exhaust manifold 10. 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 is connected at its inlet port 13 to an exhaust gas collection port 10' formed in the exhaust manifold 10 by a conduit 14 and at its outlet port 15 to the intake tube 6 by a conduit 16. It is connected to the exhaust gas injection port 6'. Exhaust gas recirculation control valve 12 is valve element 1
8, the valve element is adapted to cooperate with the valve seat 17 to open and close the inlet port 13 and to control its effective opening area. This valve element 18 is connected to a diaphragm device 20 by a valve rod 19;
It is designed to be driven by this diaphragm device. The diaphragm device 20 includes a diaphragm 21, which is driven to the right in the figure against the action of a compression coil spring 23 in response to an increase in the negative pressure introduced into its diaphragm chamber 22, causing the valve to close. The element 18 is moved to the right to open the inlet port 13 and to increase its effective opening cross-sectional area.

32 is a vacuum pump driven by the diesel engine 1, and in this embodiment, the fluid pressure for operating the exhaust gas recirculation control device is negative pressure using the vacuum pump as a fluid pressure source. In this embodiment, the negative pressure generated by the vacuum pump 32 is supplied to a vacuum servo unit of the brake system (not shown in the figure) via a conduit 33, and is also supplied to a conduit 34, a throttle device 35, a conduit 36a,
Fluid pressure control valve 37 via switching valve 59 and conduit 36b
It is now being supplied to

The fluid 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 engages with the valve holding member 45 at one end, and engages with the flange 54 of the movable spring receiving member 53 supported by the valve casing 37 at the other end. The movable spring receiving member 53 is provided so as to be movable in the axial direction of the compression coil spring 47, and as the movable spring receiving member 53 moves to the left in the figure, the spring force exerted by the compression coil spring 47 on the valve holding member increases. Therefore, as the movable spring receiving member 53 moves to the left in the figure, the chamber 4
The equilibrium negative pressure value of 0 becomes smaller.

The movable spring receiving member 53 has one end engaged with an accelerator link 56 that is supported by a pivot 55, and is driven as the accelerator link 56 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, driving the movable spring receiving member 53 to the left in the figure. I'm starting to do that. As a result, the fluid pressure control valve 37 generates a negative pressure that decreases as the load on the diesel engine increases. The accelerator link 56 is pivotally connected at its other end to a rod 57;
This rod is drivingly connected to the control lever of the fuel injection pump, which is not shown in the diagram.
The control lever is activated in response to pressing the accelerator.

The negative pressure outlet port 43 of the fluid pressure control valve 37 is connected to the diaphragm chamber 22 via a conduit 58.

The switching valve 59 is an electromagnetic switching valve, and when the solenoid is not energized, the conduit 36a
and the conduit 36b, thereby closing the conduit 36a, and connecting the conduit 36b to the atmosphere intake port 60, while disconnecting the conduit 36b from the atmosphere intake port 60 when the solenoid is energized; This and the conduit 36a are connected in communication. 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, a signal generated by a negative pressure switch 64, and a signal generated by a temperature sensor 65 that detects the temperature of engine cooling water. is input. Negative pressure switch 64 takes in the negative pressure flowing through conduit 58 via conduit 66, and outputs an on signal to control device 62 when the negative pressure is greater than a predetermined value, and an off signal when the negative pressure is less than a predetermined value. It's becoming like that. The predetermined value for this negative pressure is a negative pressure value of a certain magnitude before the exhaust gas recirculation control valve 12 approaches the critical point of opening and closing and the negative pressure decreases to the extent that its operation becomes unstable. Ru.

The control device 62 further includes a comparator that compares the signal generated by the rotation speed sensor 63 with a reference signal, and when the output signal of the rotation speed sensor 63 is larger than the reference signal, for example, the engine rotation When the number is above 2800 rpm, an off signal is output, and when it is below, an on signal is output. The control device 62 also includes a comparator that compares the signal generated by the water temperature sensor 65 with a reference signal.
This comparator outputs an OFF signal when the output signal of the water temperature sensor 65 is smaller than the reference signal, for example, 70° C. or less, and outputs an ON signal at other times. The control device 62 cuts off the power to the solenoid of the switching valve 59 when at least one of the comparators outputs an off signal or when the negative pressure switch 64 outputs an off signal, and at other times turns off the energization to the solenoid of the switching valve 59. The solenoid is now energized. It is already well known in the technical field of exhaust gas recirculation to stop exhaust gas recirculation when the engine is running at high speed and to disable exhaust gas recirculation when the engine is cold. According to an embodiment of the present invention, the comparator 62 is used to
By simply adding 3 and the water temperature sensor 65, exhaust gas recirculation can be simultaneously achieved when the engine is running at high speed and when the engine is cold.

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

If the solenoid of the switching valve 59 is energized and the conduits 36a and 36b are connected, the negative pressure generated by the vacuum pump 32 will be applied to the negative pressure control valve 3.
It is supplied to the negative pressure intake port 42 of No. 7. In this case, the negative pressure control valve 37 is
A negative pressure is generated in the negative pressure outlet port 43 that decreases in accordance with the rotation angle of the diesel engine 1, in other words, in approximately proportion to the load of the diesel engine 1. Negative pressure outlet port 4
3 is introduced into the diaphragm chamber 22 of the exhaust gas recirculation control valve 20 via a conduit 58. This drives the valve element 18 in the valve-opening direction, opening the inlet port 13 and effecting exhaust gas recirculation. Valve element 18 is connected to diaphragm chamber 22
In other words, the valve opening amount is increased in response to an increase in the negative pressure applied to the engine, or in other words, in response to a decrease in engine load.
The effective opening area of the inlet port 13 is increased. Therefore, the EGR rate increases as the engine load decreases.

When the negative pressure in the diaphragm chamber 22 detected by the negative pressure switch 64 becomes smaller than the predetermined value, which corresponds to the lower limit of the negative pressure for stably operating the exhaust gas recirculation control valve 12, the solenoid of the switching valve 59 is energized. will be stopped. At this time, the conduit 36a
The communication between the conduit 36b and the conduit 36b is cut off, the conduit 36a is closed, and the conduit 36b is connected to the atmospheric intake port 60. As a result, atmospheric pressure is supplied to the negative pressure intake port 42 of the fluid pressure control valve 37, and this atmospheric pressure is applied to the fluid pressure control valve 37 and the conduit 58.
The gas is then supplied to the diaphragm chamber 22 of the exhaust gas recirculation control valve 20. This introduction of atmospheric pressure into the diaphragm chamber 12 closes the valve element 18, completely closing the inlet port 13 and stopping exhaust gas recirculation.

Also, at this time, as described above, the conduit 36a is connected to the switching valve 5.
9, the negative pressure generated by the vacuum pump 32 at this time is not wasted in the exhaust gas recirculation control device, thereby reducing the pumping loss of the vacuum pump 32. .

It goes without saying that the present invention is not limited to the embodiments described above, and the control valve may be driven by positive pressure. In addition to the accelerator link, the control valve may have its movable spring receiving member driven by a movable member 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.

[Effects of the Invention] Thus, according to the present invention, the diaphragm of the exhaust gas recirculation control valve is controlled by the fluid pressure control valve 37 in the middle of the conduit leading from the vacuum pump 32, which is a fluid pressure source, to the diaphragm chamber 22. Room 22
The diaphragm chamber 22 is activated in response to the fluid pressure applied to the exhaust gas recirculation control valve, and when the fluid pressure decreases below a predetermined value that maintains stable opening operation of the exhaust gas recirculation control valve, this is sensed and the diaphragm chamber 22 is immediately released to the atmosphere. By providing the switching valve 59 that controls the operation of the exhaust gas recirculation control valve 12, it is possible to reliably prevent the exhaust gas recirculation control valve 12 from operating in the unstable ON/OFF critical region. Circulation control is obtained.

[Brief explanation of the drawing]

The figure is a schematic configuration diagram showing one embodiment of an exhaust gas recirculation control device for a diesel engine according to the present invention. 1... Diesel engine, 2... Cylinder bore, 3... Piston, 4... Combustion chamber, 5... Swirl 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, 15 ... 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, 36a, 36b... Conduit, 37... Fluid pressure Control valve, 38... Valve casing, 39... Diaphragm, 40, 41... Chamber, 42... 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...
Movable spring receiving member, 54... flange, 55...
Axis, 56... Accelerator link, 57...
Rod, 58... Conduit, 59... Switching valve, 60...
...Air intake port, 62...Control device, 63...
...Rotation speed sensor, 64...Negative pressure switch, 65...
...Water temperature sensor, 66... Conduit.

Claims (1)

[Claims] 1 An exhaust gas recirculation passageway for guiding a portion of the engine exhaust gas to the engine intake system; an exhaust gas recirculation control valve that controls the flow rate of exhaust gas flowing through the exhaust gas recirculation passage with an opening amount that increases in accordance with an increase in change; a fluid pressure source; and an exhaust gas recirculation control valve that is displaced according to the amount of depression of an accelerator pedal A fluid having a movable member and correcting the fluid pressure from the fluid pressure source in a direction to reduce the opening degree of the exhaust gas recirculation control valve in response to an increase in the amount of depression of an accelerator pedal, and supplying the fluid to the diaphragm chamber. a pressure control valve; and a switching valve provided in the middle of a fluid passage leading from the fluid pressure source to the diaphragm chamber, and the switching valve is configured to control the exhaust gas recirculation control valve by the fluid pressure control valve. in response to a controlled fluid pressure, when the fluid pressure is closer to the first predetermined value than a second predetermined value that is closer to the valve opening side of the exhaust gas recirculation control valve than the first predetermined value; An exhaust gas recirculation control device for a diesel engine, characterized in that the exhaust gas recirculation control device for a diesel engine is configured to open the fluid passageway to the atmosphere.