GB2155665A - Device for regulating the temperature of air drawn-in by internal combustion engines - Google Patents

Abstract

A device for regulating the temperature of air drawn-in by internal combustion engines includes a pivotable control flap (23) in an inlet pipe (20) of an air filter (4) for simultaneously controlling the aperture formed both in a heated air conduit (21) and in an unheated air conduit (22). A temperature sensor (50) is disposed downstream of the control flap (23) and transmits temperature signals to a measurement signal converter circuit (53). The measurement signal converter circuit (53) transmits control signals to a setting drive (30) which includes a direct-current motor (33) and pivots the control flap through the intermediary of linkage means (24). The control signals for controlling the direct-current motor are pulse trains having a constant pulse duration, a constant pulse height, but a frequency which is variable in dependence upon the temperature signals. <IMAGE>

Description

SPECIFICATION Device for regulating the temperature of air drawn-in by internal combustion engines The present invention relates to a device for regulating the temperature of air drawn-in by internal combustion engines, including a control valve member which is pivotable in the inlet pipe of an air filter for simultaneously controlling the aperture formed both in a heated air conduit and in an unheated air conduit, a setting motor acting upon said flap through the intermediary of a drive linkage or- lever system, and a temperature sensor which is disposed downstream of the control flap and transmits temperature signals to a signal measurement converted which controls the setting motor.

A device of this type is known (German Offenlegungsschrift No. 2 935 009). In this device, the setting motor is a hydraulic intensifier having a diaphragm acting upon the drive linkage, a heating resistor being accommodated within the air-filled pressure box.

Depending upon the desired values, therefore, the transducer permits a pre-determined current to flow through the heating resistor, thereby causing the pressure-box to expand to a pre-determined extent and, in consequence, causing the control flap to assume a predetermined position.

A device of this. type is also known (German Offenlegungsschrift No. 2 833 833), in which the setting motor is a pneumatic setting motor driven by an oscillating-armature-type air pump. The oscillating armature air pump is actuated by the transducer.

Both of these known arrangements have proved satisfactory.

The basic problem encountered when regulating the air drawn-in by internal combustion engines resides in the fact that the control flap needs to move rapidly if there is a considerable difference between the actual value and the desired value, yet needs to move more and more slowly as the equalisation point on the regulating scale is increasingly approached. The control signals, therefore, are dependent not only upon the difference between the actual value and the desired value, but also upon the time taken for this difference to be adjusted.

The present invention seeks to provide a device for regulating the air drawn-in by internal combustion engines, the regulating behav iourbf such a device being further improved and increased accuracy being achieved, particularly in the vicinity of the equalisation point on the regulating scale. In addition, it should be possible, by simple means, to be able to take into consideration as many parameters as possible for the regulating operation.

To achieve this object according to the invention, the setting motor is an electric motor and the measurement signal converter transmits pulsed control signals, the frequency of said signals being adjustable in dependence upon the temperature signals. By adjusting the frequency of the pulsed signals, it is possible to alter the speed of the electric motor without reducing the torque transmitted by the electric motor. Even at low rotational speeds, therefore, i.e. in the region of the equalisation point on the regulating scale, it is possible to achieve a high torque so that the friction, which necessarily exists, is positively overcome and, as a result, the control member or flap accurately assumes the desired position, even in the region of the equalisation point.

The invention also proposes that the electric motor may be a direct-current motor. Directcurrent motors can also be actuated by pulse trains of adjustable frequency to achieve different speeds.

The invention also proposes that the electric motor be a stepping motor.

A suitable speed reduction gear disposed between the motor and the control valve can ensure that the stepping motor, which operates discontinuously in exactly the same way as the direct-current motor, will nevertheless provide a quasi continuous adjustment of the control valve member.

In principle, it is possible to allow the electric motor to operate counter to the action of a spring so that, in the absence of any control pulses, the restoring spring returns the control valve member to an end position.

However, as the invention further proposes, it is particularly advantageous if the polarity of the control signals is adjustable. The arrangement is then such that, in the absence of any control signals, the control remains stationary, whereas pulses of one polarity cause the control valve member flap to advance in one direction and the pulses of opposite polarity cause the control valve member to move in the opposite direction.

It is particularly advantageous when the control signals have a constant pulse duration, a constant pulse height and an adjustable pulse interval.

This arrangement permits the pulse duration to be selected so that it is long enough to set the electric motor in motion with maximum torque. The pulse height corresponds to the operational voltage of the electric motor.

The temperature sensor to be used may be any sensor which issues electrical signals either independently or in conjunction with some other means. Thus, for example, it is possible to combine an expansion element with an expansion measuring strip having a resistance which changes with mechanical expansion. However, it is particularly advantageous when the temperature sensor is an electrical resistor having a temperature-dependent resistance. A hot conductor or even a cold conductor may be used for example, for this purpose. With this type of temperature gauge, it is particularly easy to process the temperature signals which are produced.

The invention also proposes that the frequency of the control signals be adjustable in dependence upon a settable desired value.

The desired value may be set, for example, by a pressure switch detecting reduced pressure in the inlet suction manifold or pipe and prescribing in the partial load range a desired temperature which differs from that in the full load range. It is also possible to effect the changeover between at least two desired values when the accelerator pedal is in a predetermined position. It is also possible for the desired value to be continuously prescribed.

This may be achieved, for example, when the accelerator pedal or the reduced pressure in the inlet pipe actuates a potentiometer.

The particular solution, proposed by the invention, of actuating an electric motor by pulse trains of adjustable frequency considerably facilitates the taking into consideration of all-of these possible parameters.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic view of an intake air filter which is connected to the inlet of an induction manifold of an internal combustion engine and is provided with a regulating arrangement or device according to the invention, said device being shown in simplified schematic form; Figure 2 is an enlarged, axial, sectional view of the setting drive used in the arrangement of Fig. 1; Figure 3 is a sectional view taken along the line 3-3 of Fig. 2; Figure 4 is a block circuit diagram of the measurement signal converter circuit in the arrangement of Fig. 1; and Figure 5 is a schematic view of a pulse train for actuating the electric motor.

An induction port of manifold 1 of an internal combustion engine (not shown) in cludes-a carburettor 2 provided with a main throttle valve 3 which is operable as desired.

The carburettor 2 supports an air filter 4 having a generally cup-shaped filter housing 5 and a detachable housing cover 6. An annular filter insert 10 is clamped in an axially sealed manner in the air filter 4 and is radially traversable from the outside to the inside. The insert 10 comprises a filter paper star 11 and end sealing members 1 2 and 1 3-made of a resilient plastics material-which components 11, 1 2 and 1 3 are joined together in annular form. The filter insert 10 encloses a filtered air chamber 14 and is surrounded by an unfiltered air chamber 1 5.

The drawn-in air is supplied to the unfiltered air chamber 1 5 through inlet duct or pioe 20 into which a heated air conduit 21 and an unheated air conduit 22 extend. The inlet pipe 20 includes a control flap 23 which simultaneously controls the aperture formed both in the heated air conduit 21 and in the unheated air conduit 22 and thereby establishes a pre-determined mixing ratio between the drawn-in heated air and the drawn-in unheated air.

An adjusting or setting drive 30 is provided for controlling the control valve of flap 23 and has a drive housing 31 which is securedly connected to the inlet pipe 20 and is sealed by housing cover 32. (see Fig. 2). A directcurrent motor 33, having a vertically downwardly extending axle, drives a threaded spindle 36 through the intermediary of a pinion 34, disposed on the underside of said motor and through the intermediary of a toothed wheel 35 which meshes with said pinion. The threaded spindle 36 also extends vertically and parallel to the motor axle and engages in a threaded bore 37 formed in a drive sleeve 39. As is apparent from Fig. 3, the external configurations of the drive sleeve 39 are noncircular because of two longitudinal guide projections or rails 40 and 41 which are disposed in axis-parallel manner relative to the threaded spindle 36.The drive sleeve 39 extends, with slight clearance, through an aperture which is formed in the drive housing 31 and is adapted to the external configurations of said sleeve 39, so that the drive sleeve 39 can slide in this aperture. The drive sleeve 39 is thus prevented from rotating, so that the drive sleeve 39 is displaced longitudinally during rotation of the threaded spindle 36. The drive sleeve 39 acts upon the pivotal lever 24 of the control flap 23 through the intermediary of a drive linkage 42. Thus, when the motor 33 is operating, the control flap 23 is caused to pivot.

A temperature transducer or sensor 50 is disposed between the air filter housing 5 and the carburettor 2, i.e. downstream of the control flap 23, for measuring the temperature of the mixed air leaving the air filter 4. In this region the mixture of heated and unheated air is already homogeneous in such a way that the temperature sensor 50 accurately determines the mixed air temperature. Sensor 50 is an electrical resistor having a temperature-dependent resistance and is connected to a signal converter circuit 53 via electrical lines 51 and 52. Temperature signals are transmitted, therefore, from the sensor 50 to the circuit 53 via the lines 51 and 52. In turn, the circuit 53 is connected to the directcurrent motor 33 of the setting drive 30 via electrical lines 54 and 55. The measurement signal converter circuit 53 transmits control signals via these lines, and said signals cause the direct-current motor 33 to start operating and, in consequence, cause the control flap 23 to pivot. The type and form of the signals will be described more fully hereinafter. In addition, the circuit 53 is connected to the starter battery (not shown) of the internal combustion engine via electrical lines 56 and 57.

Fig. 4 illustrates the composition of the circuit 53. The signal converter circuit 53 is illustrated within the dotted box, and the temperature sensor 50 is connected to said circuit 53 via the line 51, said sensor being a resistor having a temperature dependent resistance. Depending on the temperature prevailing at the measuring location, this resistor therefore supplies a current of varying intensity. This temperature dependent signal is amplified in the amplifier 60, the output signal of which is supplied to a comparator 61.

The comparator 61 compares the amplified temperature signal with one of two desired values. A desired value transmitter 62, 63 is provided for each desired value, a switch 64 enables selection as to which of the two desired values is to be processed by the comparator 61. The comparator 61 produces an output signal which is dependent upon the difference between the desired value and the actual value and upon the instantaneous rate of change in the difference between the desired value and the actual value.

The switch 64 may be controlled, i.e.

changed-over, externally of the circuit 53.

This is indicated by the dash-dot line 65. The switch 64 may be- actuable, for example, by reduced pressure prevailing in the inlet pipe.

In the example which is illustrated, the circuit 53 has a second input 66 which is connected to a temperature sensor 67 via a line 68. Once again the temperature sensor is a resistor having a temperature-dependent resistance and is exposed to the temperature of the cooling water of the l.C. engine (not shown). Thus temperature sensor 67 also supplies a temperature representative or dependent value which is amplified by an amplifier 69 and fed to a comparator 70. A desired value transmitter 71 is connected to the comparator 70, and a desired value for the cooling water temperature is set at said transmitter. The comparator 70 compares the two signals at its inputs and then transmits a signal when the actual value of the cooling water temperature is below the desired value.

This signal is fed to the second input of an additional electronic circuit 72 via a line 73, the output signal of the comparator 61 being at the first input of said additional circuit 72.

If there is a signal on the line 73, the electronic circuit 72 ignores the output signal of the comparator 61 and transmits such an output signal that the motor 33 pivots the control flap 23 in such a way that only heated air is drawn-in.

If there is no signal on the line 73-which is equivalent to saying that the cooling water temperature has reached its desired value-the electronic circuit 72 allows the output signal of the comparator 61 to pass.

A pulse generator 74 is disposed at the output of the circuit 72 and transmits, at its output, a pulse train having a constant pulse duration, a constant pulse height and an adjustable pulse interval, the length of the pulse interval being dependent upon the signal which arrives at its input on the line 75.

Fig. 5 exemplifies a pulse train. The pulse train 76 includes individual square-wave pulses having a constant pulse duration 77 and a constant pulse height Uv. The pulse interval 78, i.e. the time gap between two pulses, is adjustable. The pulse interval 78 initially increases from left to right in Fig. 5, and this would signify that the electric motor 33 is turning more slowly. After the pulse interval 78', however, a pulse of opposite polarity is produced which causes the electric motor 33 to turn in the reverse direction and causes the control flap 23 to pivot in the opposite direction.

The pulse train illustrated in Fig. 5 is only shown by way of example to indicate that the pulse duration and height are constant, but that the pulse interval 78 may be adjusted.

Claims (8)

1. A device for regulating the temperature of air drawn-in by internal combustion engines, including a control valve member or flap which is pivotable in the inlet duct of an air filter for simultaneously controlling the aperture formed both in a heated air conduit and in an unheated air conduit, a setting motor acting upon said valve member through the intermediary of a drive linkage, and a temperature transducer or sensor which is disposed downstream of the control flap and transmits temperature signals to a measurement signal converter circuit which controls the setting motor, characterised in that the setting motor is an electric motor and the measurement signal converter circuit transmits pulsed control signals, the frequency of said signals being adjustable in dependence upon the temperature signals.

2. A device as claimed in claim 1, in which the electric motor is a direct-current motor.

3. A device as claimed in claim 1, in which the electric motor is a stepping motor.

4. A device as claimed in any one of claims 1 to 3, in which the polarity of the control signals is adjustable.

5. A device as claimed in any one of claims 1 to 4, in which the control signals have a constant pulse duration, a constant pulse height (Uv) and an adjustable pulse interval.

6. A device as claimed in any one of claims 1 to 5, in which the temperature transducer or sensor is an electrical resistor having a temperature-dependent resistance.

7. A device as claimed in any one of claims 1 to 6, in which the frequency of the control signals is adjustable in dependence upon a pre-settable desired value.

8. A device for regulating the temperature of induced air for an internal combustion engine substantially as herein described with reference to and as illustrated in the accompanying drawings.