GB2130301A

GB2130301A - Apparatus for preheating intake air for an internal combustion engine

Info

Publication number: GB2130301A
Application number: GB08330218A
Authority: GB
Inventors: Jorg Abthoff; Hans-Dieter Schuster; Karlwalter Schmidt; Manfred Boenki
Original assignee: Daimler Benz AG
Current assignee: Daimler Benz AG
Priority date: 1982-11-20
Filing date: 1983-11-11
Publication date: 1984-05-31
Also published as: DE3243001A1; JPS59103952A; FR2536463A1; IT8323753A0; GB8330218D0; IT1172442B

Abstract

The apparatus comprises a lubricant circuit (22), Fig. 2 (not shown), or a coolant circuit 21, Fig. 1, an intake air system 1, 4 and an exhaust-gas system 6. A heat-exchanger 7 is assigned to the stream of exhaust gas, through which heat- exchanger the intake air of the internal combustion engine can flow. In order to avoid effects which degrade the operating behaviour of the internal combustion engine, the intake air heated in the exchanger 7 is admitted to a heat-exchanger 8 which is connected to either the engine lubricant circuit (22) or to the engine coolant circuit 21, whereby the heated air assists in warming up the lubricant or coolant more rapidly. <IMAGE>

Description

SPECIFICATION Apparatus for preheating the intake air for an internal combustion engine The invention relates to an apparatus for preheating the intake air of an internal combustion engine.

German Offenlegungsschrift 2,650,946 discloses an installation for preheating the combustion air of an internal combustion engine, in which a portion of the exhaust pipe is surrounded by a jacket and the combustion air is drawn into and through the interspace thus formed between the exhaust and the jacket, and is heated. The disadvantage of an arrangement of this kind, however, is that the intake air of the internal combustion engine can reach a temperature at which the fuel evaporates in the carburettor, or in the injection nozzles, and this can lead to combustion which is accompanied by knocking.

The present invention seeks to avoid such degradation of the operating behaviour of the internal combustion engine while employing the heat contained in the exhaust gas of the internal combustion engine for the purpose of shortening the period the engine requires in order to warm up.

According to one aspect of the present invention there is provided apparatus for preheating the intake air of an internal combustion engine, having a lubricant circuit, an intake-air system and an exhaust-gas system, the apparatus including a butterfly type control valve located, in use, in the air intake system and first and second heat-exchangers located in an air intake bypass line which bypasses the butterfly-type control valve, the intake air of the internal combustion engine flowing, in use, successively through these heat-exchagers, the first heat-exchanger through which the intake air of the internal combustion engine flows first, being adapted to receive the exhaust-gas of the internal combustion engine for heat exchange between the intake air and the exhaust gas, the intake air heated in the first heat-exchanger then passing through the second heat-exchanger to which the lubricant circuit is connected, in operation, for heat exchange between the intake air and the lubricant in the lubricant circuit.

According to a second aspect the invention provides apparatus for preheating the intake air of an internal combustion engine having a coolant circuit, an intake-air system and an exhaust-gas system, the apparatus including a butterfly-type control valve located, in use, in the air intake system and first and second heat-exchangers located in an air intake bypass line which bypasses the butterfly-type control valve, the intake air of the internal combustion engine flowing, in use, successively through these heat-exchangers, the first heat-exchanger through which the intake air of the internal combustion engine flows first, being adapted to receive the exhaust-gas of the internal combustion engine for heat exchange between the intake air and the exhaust gas, the intake air heated in the first heat exchanger then passing through the second heat exchanger, to which the coolant circuit is connected in operation, for heat exchange between the intake air and the coolant in the coolant circuit.

The apparatus according to the invention, for preheating the intake air of an internal combustion engine has the advantage that its liquid coolant or, as the case may be, its lubricating oil is heated more quickly, thus enabling heat, for heating purposes, to be made available, without any delay, to the passenger-compartment heating system of a motor vheicle. Overheating of the intake air cannot occur, since it is cooled in the second heat-exchanger, thus eliminating the danger of premature evaporation of the fuel.

Two embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows an installation for preheating the intake air of an internal combustion engine, in which installation the heated intake air participates in heat-exchange with the engine coolant circuit, and Figure 2 shows an arrangement for preheating the intake air of an internal combustion engine, in which the heated intake air participates in heat-exchange with the engine lubricating-oil circuit.

An intake system, marked 1 in Fig. 1, comprises an intake pipe 2, a bypass line 3, and an induction manifold 4, this system being attached, together with an exhaust-gas system 6, to an internal combustion engine 5.

The bypass line 3 possesses a first heatexchanger 7, and a second heat-exchanger 8.

The exhaust gases from the internal combustion engine 5 flow through one side of the heat-exchanger 7, while its intake air flows through the other side of this heat-exchanger 7. The heated intake air then flows through one side of the second heat-exchanger 8, and the liquid coolant of the internal combustion engine 5 flows through the other side of this heat-exchanger 8 for heat exchange with the heated intake air. A butterfly-type control valve 9 is located in the intake pipe 2, and is connected to a diaphragm-type servo actuator 10 by means of an articulated lever 1 3. A working space 1 4 of the diaphragm-type servo actuator 10 is connected to the induction manifold via a three-way valve 12, which is governed by the temperature of the internal combustion engine, and via a line 11.A tension spring 1 5 is installed between a supporting bracket 16 and the articulated lever 1 3. The liquid coolant contained in the cool ant circuit 21 of the internal combustion engine 5 is led, through a line 17, to a connection-point on the heat-exchanger 8, and is returned, from a tapping-point on the heatexchanger 8, to the engine coolant circuit, in the region marked 49, by means of a line 1 8.

While the internal combustion engine 5 is warming up, the three-way valve 1 2 is turned to a position such that the working space 14 is subjected to the sub-atmospheric pressure which prevails in the induction manifold 4.

The sub-atmospheric pressure, from the induction manifold 4, acting in the working space 1 4 of the diaphragm-type servo actuator 10, causes this actuator 10 to deflect the butterfly-type control valve 9 into the position closing the cross-sectional area of the intake pipe 2, by means of the articulated lever 1 3 (idling). The intake air of the internal combustion engine 5 then flows through the bypass line 3, and is heated in the heat-exchanger 7. This heated intake air participates, in the heatexchanger 8, in heat-exchange with the liquid coolant of the internal combustion engine 5, as a result of which the temperature of the liquid coolant is raised, while the intake-air temperature approximates to that of the liquid coolant.

If the throttle valve 20 moves into the partial-load range of the internal combustion engine 5, the pressure-depression in the induction manifold 4 decreases, as a result of which the diaphragm-type servo actuator 10 partially opens the butterfly-type control valve, by means of the articulated lever 1 3, in a manner such that this control valve only partially closes the cross-section of the intake pipe 2. Due to the flow-resistance created by the partially open butterfly-type control valve in the intake pipe 2, some of the intake air for the internal combustion engine 5 flows through the bypass line 3, and some through the intake pipe 2.

When the internal combustion engine reaches its normal operating temperature, the three-way valve 1 2 is turned to a closed position, such that the connection between the working space 14 and the induction manifold 4 is interrupted, and ambient air pressure is admitted to the working space 1 4. The tension spring 1 5 swings the butterfly-type control valve 9 into a fully open position in which the cross-section of the intake pipe 2 is not appreciably affected. The flow-resistance presented by the bypass line 3 is so high that the intake air flows exclusively through the intake pipe 2. The intake air is no longer heated.

Fig. 2 represents an embodiment of the invention which differs from the embodiment shown in Fig. 1 merely by virtue of the fact that the coolant circuit 21 of the internal combustion engine 5 does not flow through the heat-exchanger 8, but is replaced by the engine lubricant circuit 22.

In a further embodiment of the invention, the liquid coolant or the lubricant of the internal combustion engine can be heated by a stream of air which is independent of the intake air. In such an installation, the exhaustgases from the internal combustion engine are admitted to a heat-exchanger, through which ambient air flows, delivered by a fan. The heated ambient air is admitted to a heatexchanger, through which the liquid coolant or the lubricant of the internal combustion engine flows. This ambient air can also, for example, be supplied to the intake air of the internal combustion engine. A solution of this nature possesses the advantage that no modifications need be carried out on the intake pipe, and that the heated ambient air can be regulated independently of the intake air.

If a mechanical, undriven fuel-injection system is used, it is necessary to install the airflow-measuring device at that point in the intake system at which the total quantity of intake air can be measured.

Claims

1. Apparatus for preheating the intake air of an internal combustion engine, having a lubricant circuit, an intake-air system and an exhaust-gas system, the apparatus including a butterfly-type control valve located, in use, in the air intake system and first and second heat-exchangers located in an air intake bypass line which bypasses the butterfly-type control valve, the intake air of the internal combustion engine flowing, in use, successively through these heat-exchangers, the first heat-exchanger through which the intake air of the internal combustion engine flows first, being adapted to receive the exhaust-gas of the internal combustion engine for heat exchange between the intake air and the exhaust gas, the intake air heated in the first heat exchanger then passing through the second heat-exchanger to which the lubricant circuit is connected, in operation, for heat exchange between the intake air and the lubricant in the lubricant circuit.

2. Apparatus for preheating the intake air of an internal combustion engine having a coolant circuit, an intake-air system and an exhaust-gas system, the apparatus including a butterfly-type control valve located, in use, in the air intake system and first and second heat-exchangers located in an air intake bypass line which bypasses the butterfly-type control valve, the intake air of the internal combustion engine flowing, in use, successively through these heat-exchangers, the first heat-exchanger through which the intake air of the internal combustion engine flows first, being adapted to receive the exhaust-gas of the internal combustion engine for heat exchange between the intake air and the exhaust gas, the intake air heated in the first heat exchanger then passing through the sec ond heat exchanger, to which the coolant circuit is connected, in operation, for heat exchange between the intake air and the coolant in the coolant circuit.

3. Apparatus according to claim 1 or 2 wherein the butterfly-type control valve is adjustable by means of a diaphragm-type servo actuator which, in use, causes the butterflytype control valve to be positioned in dependence upon the pressure in the induction manifold of the intake-air system.

4. Apparatus according to claim 3, wherein the servo actuator is adapted to be turned on and off, in dependence upon a temperature of the internal combustion engine, by means of a thtee-way valve which is located in a control line connecting the servo actuator to the induction manifold.

5. Apparatus according to any one of claims 1 to 4 wherein, means for heating the coolant or the lubricant is provided, said means comprising heated ambient air.

6. Apparatus according to claim 5 wherein the ambient air is, in use, delivered by a fan to a heat exchanger for heat exchange with the exhaust gas.

7. Apparatus for preheating the intake air of an internal combustion engine substantially as described herein with reference to, and as illustrated in Fig. 1 or Fig. 2 of the accompanying drawings.