EP0085120A1 - Device for supplying air to internal-combustion engines under thrust conditions - Google Patents

Abstract

The invention relates to a device for supplying preferably hot air to the intake pipe (10, 20) of an internal combustion engine (60) downstream of the throttle valve (40) via a valve (22) and an air line (21), the cross-section of which approximately corresponds to the cross-section of the intake pipe at its narrowest point. A control device (50) opens the valve (22) when the overrun-mode sensor (53) signals the closing of the throttle valve (40) and the speed transmitter (51) signals speeds above the idling speed. In parallel with the valve (22), a fuel valve (23) which connects the fuel pressure line (93) and fuel return line (94) of a fuel injection system is opened and the fuel supply is disconnected. The overrun-mode sensor (53) is connected with a flow probe (120) to the intake pipe (10). The device is shown in various combinations with a turbo compressor (61) and control systems of various types (75, 77) for forming the mixture. <IMAGE>

Description

The invention relates to a device for supplying air into an intake pipe of an internal combustion engine downstream behind a throttle valve and possibly a carburetor via an air line with a valve which is controlled by a control device as a function of output signals from a speed sensor at an engine shaft speed above the idle speed and a coasting detector .

Various devices of the type mentioned are known, for. B. from DE-OS 29 52 550, in which the task is to determine the ratio of the air-fuel mixture depending on different load cases and operating conditions, for. B. optimize engine temperature. For this purpose, an air line that is narrow relative to the cross section of the intake pipe is opened via a valve that is pneumatically controlled by the negative pressure downstream of the throttle valve, and the mixture is emaciated when the negative pressure is increased.

The known devices have the disadvantage that the negative pressure required for control is reduced by the auxiliary air, so that the reduction in negative pressure is only possible to a limited extent. This creates a mixture that is too rich and oil mist is sucked in from the crankshaft housing, causing a high pollutant content in the exhaust gases.

The object of the present invention is to disclose a device which enables a further reduction in fuel consumption, in particular in overrun mode.

The solution of the invention is that the valve is an - electromagnetically controlled valve and the cross section of the valve and the air line corresponds approximately to the narrowest cross section of the intake pipe and preferably the air line is connected to a heat exchanger and / or a turbo compressor which is connected to a hot water line or an exhaust pipe is connected, or the air pipe is connected directly to the exhaust pipe.

By using an air line and a valve with a large cross-section, it is possible to reduce the negative pressure by hand. A free-wheeling effect is achieved in overrun mode since the suction losses are avoided. Furthermore, the intake of fuel from the idle nozzle is avoided, if there is one. There are therefore no combustion gases.

So that the strong supply of air without fuel does not cool the walls of the combustion chambers, which would result in condensation losses of the fuel when the gas is subsequently applied, the supplied air is preferably preheated in a heat exchanger or turbo compressor or taken directly from the exhaust pipe. When using the turbo compressor, the freewheeling effect is further enhanced, since the engine then runs air-tight in the short circuit and there is no braking excess pressure on the compressor in the exhaust pipe. An advantage of the invention is that both the fuel requirement and the oil consumption are reduced and also the generation of harmful gases is reduced.

In known metering devices for fuel, the thrust condition is determined by a throttle valve contact or a geepedal contact. Such a contact query is subject to tolerances compared to a flow measurement preferably used in the intake pipe.

This flow measurement is e.g. B. either by a vacuum detector, which is arranged upstream of the throttle valve, or by a differential pressure meter, which is connected to the intake manifold by means of a pitot tube near the throttle valve, where the strongest flow prevails when the throttle valve is almost closed. The connection of the vacuum detector or the pitot tube, through which the air speed is determined, are designed so that they are not influenced by the air supplied via the valve, as is the case with the known vacuum control line connection downstream of the throttle valve and also when a branch of the air line is attached the intake pipe is the case.

Other known air speed detectors, e.g. B. with heat rotation or with mechanical-electrical converters instead of contact detectors as differential pressure or vacuum detectors, can also be used in conjunction with an electronic threshold circuit that responds to the flow or the vacuum with the throttle valve almost closed.

If the fuel is supplied via an injection device, the injection is expediently switched off in overrun mode for maximum fuel dispersion. The same signal from the control circuit, which determines the overrun mode and opens the valve, can open a fuel valve which connects the fuel pressure line to the fuel return line and thereby reduces the necessary injection pressure.

If the injection valves are controlled electromechanically, the control circuit of the injection can be overridden in a known manner by the signal that indicates the overrun mode, so that the injection valves are blocked as long as the air is supplied via the valve.

Since the greatest thrust loss occurs at high engine speeds and it is desirable to maintain a minimum engine speed (idling engine speed) for subsequent acceleration, the air supply via the valve is expediently closed when the engine speed reaches slightly above the idling speed and the fuel supply is restored.

There are various circuits for determining the speed are known, which are connected to the shaft of the engine directly or via gear and z. B. evaluate the signals from the ignition contact, which closes periodically depending on the shaft speed. In order to be able to switch off as precisely as possible and close above the idling speed, the average measuring time, e.g. B. the Vsrzögerungszeitstante the speed measuring device, shorter than the time in which the speed by z. B. drops 10% above the idle speed, selected; on the other hand, it is fastened to a multiple of the pulse spacing at the laser speed in order to enable the most accurate measurement possible.

A digital cut-off frequency filter or a digital pulse distance comparator for very precise and delay-free determination as to when the specified speed is undershot is expediently used for increased requirements or when the circuit is integrated with other digital switching elements.

Of course, other speed signals that are obtained by centrifugal contacts or from proportional electronic signals via a comparator can also be used to control the valve.

Various embodiments of the device according to the invention are shown in Figures 1 to 6.

• Fig. 1 shows a Vsrgaseranordnung with the air supply device and vacuum detector in section; out of scale,
• Fig. 2 shows a contact detector of the throttle valve position;
• FIG. 3 shows a cross-sectional arrangement of a vending machine with an air supply device and a reservoir for air speed measurement; out of scale,
• 4 shows an injection arrangement and turbo compressor system in connection with the air supply device and a fuel valve;
• Fig. 5 shows an injection arrangement with air supply device connected to the exhaust pipe and Abacheltsteusrung the injection valves;
• 6 shows a circuit arrangement for controlling the air supply device and the fuel cutoff.

The illustrated embodiments are selected combinations of the components of the invention, which can also be assembled in other combinations according to the invention. Components can also be provided by components with equivalent functions, e.g. B. the electronics, electromechanics or pneumatics can be exchanged.

1 shows a device according to the invention, in which the fuel is fed through a fuel line 13 via a carburetor 14 to the intake pipe 10 of the combustion air, which is cleaned via the upstream filter 33. The mass flow of the fuel-air mixture is determined via the throttle valve 40, which is pivotable about the axis 42. In idle, the throttle valve 40 is in position 41, in which the intake pipe is almost completely closed. The idle fuel and air supply is carried out in a known manner and is not shown here. Downstream of the throttle valve, the internal combustion engine (not shown) connects to the intake pipe section 20. A valve 22 is connected to the intake pipe section 20 with an air line, which valve is connected on the input side via air line 21 to a heat exchanger 31, which is connected to the engine via hot water lines 91, 92, to which air is supplied from a filter 32 via air line 11.

Upstream of the throttle valve 40 is to the intake pipe 10 with a vacuum line 122, for. 8. pneumatic vacuum sensor 52 connected to a low vacuum, for. B. 70 mbar, responds to the ambient air and thereby reports when the throttle valve 40 is open or almost closed, since a negative pressure is created by the air flow and the suction pressure reaches the detector when the throttle valve is open.

The message signal is fed to a control device 50, in which it is linked in a control circuit 50 with a signal from a speed sensor 51, which is connected to the engine, in such a way that a speed above the idle speed results in a control circuit 50 signal to open the valve 22 is released when the vacuum detector simultaneously reports the closed state of the throttle valve.

In a thrust condition, which is characterized by the closing of the throttle valve 40 at high speeds, filtered and preheated air is thus introduced into the intake pipe and the intake vacuum is thus reduced without the walls of the combustion chamber cooling down. The cross section of the air line 11, 21, the valve 22 of the heat exchanger 31 and the air filter 32 are dimensioned such that their flow resistance together is approximately the same as that of the carburetor 14, the intake pipe 10 and the air filter 33 together, that is, a lot of air to the engine is supplied, which creates a free-running effect.

Since the intake pressure is greatly reduced, hardly any fuel is drawn in through an open idle nozzle. If the idling nozzle (not shown) is controllable, it could also be blocked by the control signal of the valve 22.

As soon as the predetermined switching speed is undershot, the valve 22 is closed and normal idling occurs, in which the negative pressure on the mounting tube section 20 is available and can be stored for control functions for servo systems.

Limitation of the suction vacuum when idling can be carried out using known means, or it could also be brought about by partial closure of the valve in the idling state. The invention is not affected by such additional improvement measures.

Instead of the vacuum detector 52, a detector 54 of the throttle valve position, as shown in FIG. 2, can also serve as the overrun operation detector. A contact 54, which can be actuated by a cam 43, is arranged near the throttle valve shaft 42 and is also closed when the throttle valve 40 is closed and thus signals the overrun operation and idling. The contact could of course also be actuated by the throttle valve 40 itself or the accelerator pedal or throttle linkage, or a similar device that adjusts the throttle valve directly or indirectly. Instead of a galvanic contact, a capacitive or inductive or similar converter can also be used. The actuation of all of these overrun mode detectors, which are actuated by the throttle valve position and not directly by the air flow in the intake pipe 10, is subject to certain tolerances.

An embodiment of the device, which is equipped with an air speed detector 53 as a coasting operation detector, is shown in FIG. 3. The flow measurement has the advantage that it is independent of absolute pressure conditions and also a pressure drop at the air filter or a reduced negative pressure from the engine does not affect the measurement affects. It also offers the additional possibility of connecting the air line 11 on the inlet side to the intake pipe 10 by means of connection 15, as a result of which a separate air filter is not required. The negative pressure created by the flow resistance on the air filter 33 has no effect on the measurement; the probe 120 of the air speed detector 53 is arranged downstream of the connection 15 of the air line 11 and upstream of the air line 21 in the intake pipe 10, and this is particularly favorable in the vicinity of the remaining gap of the throttle valve.

In the example shown, the probe 120 consists of a pitot tube 121, which is directed against the flow, and a vacuum line 122, which is concentric to it and has openings on the side, each of which leads into chambers 531, 532 of a differential pressure detector, which work against the force of a spring 533 movable diaphragm 534 are separated. The diaphragm 534 is deflected by a certain differential pressure to such an extent that a contact 535 connected to it opens.

Since only the differential pressure or the flow is evaluated for reporting, the probe 120 could also be arranged downstream of the throttle valve 40. It can also be used in conjunction with a turbocharger 61, FIG. 4, since the boost pressure has no effect on the measurement.

In the use of the device according to the invention shown in FIG. 4 in connection with a turbo compressor, there is also the possibility of dispensing with a heat exchanger in the air line 21, since the compressed air is already warmed up by the compression process. The turbo compressor 61 is connected in a known manner on the drive side into the exhaust line 62, 63 and on the output side into the intake pipe 10. The valve 22 is placed with the air line 21 parallel to the throttle valve 40. The probe 120 lies between the connections of the air line 21 in the intake pipe 10.

In the known turbocompressor systems, a flow meter 78 for metering fuel in the air supply in front of the compressor 61 is located. Since the flow meter 78 signals a large fuel requirement when the valve 22 is open, provision is made for the fuel supply to be completely prevented at the same time as the valve 22 is opened.

Such an interruption of the fuel supply is shown in detail for a known injection system. Fuel is supplied from the fuel tank 74 via a pump 70, a memory 71 and a filter 72 on a fuel pressure line 93 to a metering device 75, which u. a. is influenced by the signal of the flow meter 78 via a control 77 in such a way that, under a controlled pressure, fuel is supplied to the injection nozzles 76 via the fuel pressure line 95 and excess fuel is returned to the tank 74 via the fuel return line 94. A fuel valve 23 is connected between the fuel pressure line 93 and the fuel return line and is actuated in parallel to the valve 22. This will remove the injection pressure. When the fuel valve 23 is closed, however, the full pressure is immediately available again, and any desired acceleration of the engine with a high fuel requirement can start without delay, since the metering device 75 is openly controlled. The fuel valve 23 can also be connected to the line 95 instead of the fuel pressure line 93 in order to achieve the same effect.

5 shows another embodiment of the device according to the invention with a further embodiment of a fuel injection system. The valve 20 with the air line 21 is arranged directly between the exhaust pipe 62 and the intake pipe 20. A separate heat exchanger is not required since the warm exhaust air is fed directly back into the intake pipe 20. A combustion process does not take place because the fuel supply is cut off. This arrangement can also be used advantageously in connection with a turbo compressor, as shown in FIG. 4. The compressor losses are further reduced in this way, since the back pressure drops and the motor is braked less.

Injectors 761 are used in the fuel injection system shown in FIG. 5. These are connected directly to a fuel pressure line 93 and are controlled in a known manner by signals from a control circuit 771, the control circuit being influenced with the signal which opens the valve 22 in such a way that all the injection valves 761, including any idling valves which may be present, are closed stay.

Since no air flow occurs in the intake manifold 10 in the recirculation circuit shown, with a suitable combination of the circuit arrangements 50 and 771, only one probe 120 or one flow meter 78 can be provided for the metering function in normal operation and the switching functions in overrun mode.

From the separate representation of the functional elements, their independence from the already known functions can easily be seen. This results in the simple retrofitting of already existing internal combustion engines of various types, even if they are equipped with complex control and regulating devices, since these are not influenced. In the case of new designs or systems in which a so-called overrun cutoff of the fuel supply in overrun mode is already provided, u. U. As shown, an integration of the control system can be provided, or existing signals can be used to control the valve 20.

6 shows a relatively simple and reliable circuit arrangement for the control of the valve 22, which is therefore also particularly suitable for retrofitting. The ignition pulse generator z. B. the ignition contact. It controls a monostable timer, which gives pulses of the same length to an integrator 81, at the output of which a voltage signal is generated which corresponds to the pulse frequency or the speed of the motor shaft.

In order to switch as precisely and with as little delay as possible in the speed range in which the engine is to switch from coasting to idling, the time constant of the integrator 81 is selected so that it is a multiple of the pulse intervals at a given idling speed and, on the other hand, it is shorter than that Duration of the speed drop of 10% above the idle speed.

If there is a switchover at a speed that is 15% above the idle speed, the idle speed during switchover will not fall below the prescribed idle speed even if the message is delayed by the time constant. In addition, the integrator output signal can be limited somewhat above the switchover value by suitable selection of the working range of the integrator. The circuit from the modules 80 and 81 thus represents a frequency voltage inverter.

The value of the output voltage of the circuit mentioned for the speed, which is 15% above the idling speed, that is to say the switchover value U, is compared in a voltage comparison circuit 82 with the output voltage. The resulting switchover signal, which reports the idle state, is logically combined in an AND circuit 83 with the signal of the coasting mode detector 52, 53 or 54, so that an output signal is generated only in coasting mode at high speeds, which amplifies the control windings 221, 231 by the amplifier 84 of the valve 22 and possibly the fuel valve 23 and opens them.

The frequency-to-voltage converter 80, 81 shown can also be replaced by other known circuits, and the frequency monitoring circuit 86 can also be replaced by known digital circuits Cutoff frequency filter or a digital pulse distance comparator can be replaced, the z. 8. emits an active output signal above a predetermined frequency.

The switching can be carried out in the manner shown as a gate or can be formed by arranging the push-button detector in series with the output of the speed sensor. If the cut-off frequency monitoring circuit 86 is also designed as a contact, e.g. B. in the form of a centrifugal contact, the entire circuit can be formed by the series connection of such a contact with the overrun mode contact 52,53,54; and amplifier 84 can then also be omitted. Such an arrangement thus represents another possible solution for the circuit.

It is not necessary to control the device depending on the temperature of the engine, especially under starting conditions, since under these conditions the generally available automatic or manual auxiliary air supplies, which are connected in parallel with the throttle valve or limit or prevent the throttle valve from closing Intake pipe there is sufficient air flow or a pressure drop that an, in this case undesirable, overrun operation message does not occur. This is a further advantage, since this independence means that existing motor vehicles can also be retrofitted without any problems. If, due to the inertia of existing control devices, in particular when retrofitting a device according to the invention, operational disturbances would occur when the valve 22 is actuated quickly, it is expediently replaced by a parallel connection of a plurality of valves which are operated in succession, e.g. depending on stepped speeds, are operated, or the opening of the valve cross-section is controlled depending on the speed, for which purpose a continuously adjustable valve is used.

Claims (11)

1. Device for supplying air into an intake pipe (10, 20) of an internal combustion engine (60) downstream behind a throttle valve (40) and possibly a carburetor (13, 14) via an air line (11, 21, 23) with a valve (22), which is controlled by a control device (50) as a function of output signals from a speed sensor (51) at an engine shaft speed above the idling speed and its overrun mode detector (52, 53, 54), characterized in that the valve (22) is an electromagnetically controlled one Valve and the cross section of the valve (22) and the air line (11,21) corresponds approximately to the narrowest cross section (14) of the intake pipe (10,20) and preferably the air line (21) to a heat exchanger (31) and / or Turbo compressor (61) is connected, which is connected to a hot water line (91, 92) or an exhaust line (62, 63) or the air line (21) is connected directly to the exhaust line (62). 2. Device according to claim 1, characterized in that the overrun operation detector (54) is a contact detector which is actuated in the closed position (41) of the throttle valve (40). 3. Apparatus according to claim 1, characterized in that the overrun operation detector (52) is a vacuum detector, which is connected upstream of the throttle valve (40) via a vacuum line (122) to the intake pipe (10) and the air of the air line (11) is preferably via a filter (32) separately from the suction line (10), and that the vacuum detector (52) at a negative pressure with a slight opening of the throttle valve (40) of z. B. 70 m bar below the external air pressure, preferably turns off. 4. The device according to claim 1, characterized in that the overrun operation detector (53) is an air velocity detector which upstream of the introduction of the air line (21) into the suction line (20) and optionally downstream of a connection (15) of the air line (11) the suction line (10) is connected to a probe (120) and the probe (120) is preferably connected through a pitot tube (121) and a vacuum line (122) to chambers (531, 532) of a differential pressure detector (53), and this at a differential pressure that arises when the throttle valve (40) opens slightly, switches, preferably switches off. 5. Device according to one of claims 1 to 4, characterized in that the control device (50) is a control circuit, the output signal parallel to the valve (22) opens a fuel valve (23) which has a fuel pressure line (93.95) and - Return line (94) of a fuel injection system (70-78) connects and reduces the injection pressure below a nozzle outlet pressure. 6. Device according to one of claims 1 to 5, characterized in that the output signal of the control circuit (50) of a control circuit (771) is fed to a fuel injection system which blocks all injectors (761) when there is an output signal. 7. Circuit arrangement for operating a device according to claim 1 to 6, characterized in that the output signal of the speed sensor (51) is guided to a cut-off frequency monitoring circuit (86), which preferably consists of a frequency-voltage converter (80, 81) and a voltage comparison circuit (82) whose one input with the output of the frequency voltage converter and the other input of which is connected to an adjustable comparison voltage (U), as a result of which it emits an active output signal above a frequency which is approximately 15% above the idling speed, which is switched in an switching circuit (83) to the signal of the coasting mode detector (52, 53 ) is linked, the output signal of which is fed via an amplifier (84) to control windings (221, 231) of the valve (22) and, if appropriate, the fuel valve (23). 3. Switching device according to claim 7, characterized in that the frequency-voltage converter (80, 81) consists of a monostable pulse generator (80) and an integrator (81), the time constant of which is a multiple of the pulse intervals at a predetermined idling speed and is shorter than the time , in which the engine speed drops by 10% to the idle speed. 9. Circuit arrangement according to claim 7, characterized in that the cut-off frequency monitoring circuit (86) is a digital cut-off frequency filter or a digital pulse distance comparator which outputs an active output signal at input frequencies above a predetermined frequency or pulse intervals below a predetermined pulse interval. 10. The device according to claim 1, characterized in that the valve (22) is opened further with increasing speed. 11. The device according to claim 10, characterized in that the valve (22) consists of several sub-valves, which are preferably arranged in parallel, which are opened in succession with increasing speed.

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