DE2048955A1 - Intermittent fuel injection system - Google Patents

Description

29-9.1970 Lr / Bo

Attachment to
Patent application

ROBERT BOSCH GMBH, Stuttgart Intermittent fuel injection system

The invention relates to an electrically controlled, intermittent fuel injection system for Internal combustion engines with at least one electromagnetic actuatable injection valve - preferably with several injection valves, one of which is one of the cylinders is assigned - and with one for the magnetization winding of the valve in series with a power transistor as well as a transistor switching device connected upstream of it. the synchronous to the crankshaft revolutions of the combustion

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BATH ORIGINAL

209816/0496

Robert Bosch GMBH . R. 26 Lr / Bo

Stuttgart

combustion engine with simultaneous opening of the injection valve is turned on and is kept on for the respective injection quantity determining duration which is variable in dependence on the intake air amount of the internal combustion engine, arranged for measuring the intake air a is flowing through a heating current, temperature-dependent ψ resistance in the intake passage of the internal combustion engine .

In known injection systems of this type, the temperature-dependent one arranged in the intake duct of the internal combustion engine is Resistance externally heated in that a heating winding is provided in its immediate vicinity, which through Radiation or conduction is supposed to transfer a constant amount of heat to the resistor, whereby the one heated in this way The greater the amount of intake air, and the greater its electrical conductivity, the more it is cooled down changes considerably. About these changes, each dependent on the amount of intake air, for controlling the opening duration to be able to use the injection valve or valves is the temperature-dependent resistance in the known system arranged in a measuring bridge circuit and generates in the diagonal branch a voltage that is greater the higher the amount of intake air is. In the known system for controlling the tilting period, the diagonal voltage should be one with two Multivibrators equipped with mutually blocking transistors are used, the Kip |) of which lasts the opening time of the valves.

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Robert Bosch GMBH ' . R. 26 Lr / Bo Stuttgart

If the heat effective at the temperature-dependent resistor is generated by a separate heating resistor, go in the accuracy of the air volume measurement all changes in the operating voltage provided for the heating resistor a. Much greater accuracy can be achieved when the temperature-dependent resistor is heated by a heating current flowing through it and this heating current is set by an electronic controller to such a level that the operating temperature of the temperature-dependent Resistance remains practically constant. In this case, the level of the heating current is a safe and precise information about the mean value of the intake air volume over time. The product of the mean value Q of the amount of intake air drawn in in the unit of time and a period of circulation T, which is used for traversing a specified crankshaft final angle of rotation is required, results in one to the pro Work cycle missing air volume proportional size. The respective opening duration t must be linearly dependent on this. of the injector or injectors are determined. Under Use of the above-mentioned control device to keep the operating temperature of the temperature-dependent resistor constant can this dependency according to the invention by a

Voltage U = J * T simulated v: he the one at which J the one Amount of heating current for a given time I mean value Q means un which the heating current remains constant Temperature must be increased compared to the initial heating current value J required for Q = O. Particularly useful it is when in a further embodiment of the invention rr.it the heating current supplied by the electronic controller, the

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Robert Bosch GmbH R. 26 Lr / Bo

Stuttgart

is hereinafter referred to as regulator current or an integrating capacitor during the revolution time T is charged with a current proportional to this auxiliary current, further, the voltage of • integrating capacitor reached at the end of the round trip time with a constant discharge current is reduced during a obtained as ψ intermediate variable discharge time, and further during this Discharge time a second integrating capacitor is charged with the regulator current or with an auxiliary current proportional to this. The storage voltage generated at this second integrating capacitor can then be reduced in a simple linear manner with a constant discharge current, the duration of this discharge being used directly or indirectly as the opening duration for the valves.

Another possibility of achieving a variable analogous to the product of the square of the control current and the period of circulation results in a further development of the invention in that a capacitor with a number of pulses each time during one Step duration t is charged with a charging current J and that the capacitor storage voltage Ur reached at the end of the cycle time T. f * t * J "T to obtain the pulse duration t. is reduced with a constant discharge current and that of the factors f, t _r , J and T which determine the capacitor storage voltage U, two factors are made proportional to the regulator current. J. In a preferred embodiment of the invention it is provided that at least one of the two in-

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Robert Bosch GmbHR. 26 Lr / Bo

Stuttgart

integrating capacitors in the feedback branch of an operational amplifier is arranged, which at one of its inputs (its minus input) with a proportional to the control current Voltage is connected and at its other input (plus input) is connected to a fixed voltage.

To initiate the above-mentioned loading and unloading processes, one can expediently use a known V / eise with the crankshaft coupled control switch and a controlled by this, bistable multivibrator can be provided during every crankshaft revolution - preferably at equal intervals - at least twice from one of its two bista- = bilen positions is reversed by the control switch in the opposite operating position and two to each other has opposite potential outputs. In this case, in a further embodiment of the invention one of the outputs of the multivibrator, the base of a switching transistor can be connected to its emitter-collector path is connected in series to two V / i resistors, at whose connection point the voltage proportional to the controller current is fed in (e.g. via a first Zener diode) and a voltage divider consisting of two V / i resistors is connected at the tap of the minus input of the operational amplifier.

A simplified circuit arrangement results if, in a further embodiment of the invention, parallel to that in the feedback circuit of the operational amplifier

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Robert Bosch GmbH R. 26 Lr / Bo

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capacitor a second Zener diode is arranged. This Zener diode is conductive when the charge is reversed of the first integrating capacitor is the capacitor voltage reaches the value of the breakdown voltage of the zener diode. In a further embodiment of the invention, a switching transistor can be arranged in series with the Zener diode, which for Avoidance of an otherwise flowing diode residual current is blocked during the charging period of the integrating capacitor.

Appropriately, instead of a threshold switch to the Integrating capacitor connected to a differentiating circuit, which contains an operational amplifier as an essential component, the minus input of which is connected via a coupling con- ' capacitor is connected to the output of the integration stage and is also connected to a feedback signal connected to the output of the operational amplifier, the comprises two diodes, the first of which is connected from the junction of two to the output of the operational amplifier Working resistances to the fiine input of the operational amplifier leads.

Further details and useful configurations emerge from the following description of some of the drawings illustrated embodiments.

Show it:

1 shows an anemometer-based air flow measurement Petrol injection system in an overview and in a partially schematic representation,

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Robert Bosch GMBH . E. 26 Lr / Bo

Stuttgart

2 shows a characteristic curve to explain the relationship between the heating current and the amount of intake air,

Fig. 3 is a time chart for explaining the basic mode of operation of the gasoline injection system according to Fig. and the integration levels used in it,

Fig. 4 shows an expanded block diagram for a electrical device with which, with two integration steps, from the one supplied by a controller Heating current an opening duration t proportional to the amount of air drawn in. for the injectors the injection system according to Fig. 1 obtained ν; can be grounded,

5 shows a circuit diagram of one of the two integration stages and

6 shows a circuit diagram for one of the two differentiating stages the device according to FIG. 4.

The gasoline injection system shown is intended for the operation of a four-cylinder four-stroke internal combustion engine 10 and includes as essential components four electromagnetically actuated injection valves 11, which from a distributor 12 The fuel to be injected via a pipe 13 each is supplied, an electric motor driven fuel feed pump 15, a pressure regulator 16 that controls the fuel pressure regulates to a constant value, sov.de an electronic control device described in more detail below, the through an irdt of the camshaft 1? the internal combustion engine coupled Signal transmitter IS two times for every I camshaft rotation

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Robert Bosch GmbH R. 26 Lr / Bo

Stuttgart

times triggered and then each a rectangular, electrical opening pulse S for the injectors 11 delivers. The duration indicated in the drawing t. the opening impulse determines the duration of the injection valve opening and consequently the amount of fuel which during the respective opening period from the interior which exits the injection valve 11, which is under a practically constant fuel pressure of 2 atmospheres. The magnet windings 19 of the injection valves are each connected in series to a decoupling resistor 20 and to a common one Amplification and power stage connected, which contains at least one power transistor indicated at 22, which with its emitter-collector path arranged in series with the decoupling resistors 20 and the magnet windings 19 connected to ground on one side is.

In the case of mixture-compressing internal combustion engines of the type shown operating with spark ignition, the amount of air entering a cylinder during a single intake stroke defines the amount of fuel that can be completely burned during the subsequent work cycle. For good utilization of the internal combustion engine, it is also necessary that there is no substantial excess of air after the work cycle. In order to achieve the desired stoichiometric ratio between intake air and fuel, a temperature-dependent resistor 30 through which a heating current J ^ flows is provided in the intake pipe 25 of the internal combustion engine in the direction of flow behind its filter 26 and behind its throttle valve 28, which can be adjusted with an accelerator pedal.

209816/0496

BATH ORIGINAL

Robert Bosch GMBH . E. 26 Lr / Bo

Stuttgart

The resistor 30 is wound from a thin wire, which consists of platinum and a resistance temperature coefficient # of 3 »9 * 10 / degree has. He warms up under the influence of the heating current J flowing through it, and is the stronger by the intake air flow flowing in the intake pipe 25, which is indicated by an arrow 32 cooled, the greater the flow velocity of the Intake air flow is and consequently the greater the in the Unit of time sucked in air quantity Q is. In order to be as stable as possible and from external conditions, for example from the respective .genladtng independent of the battery, not shown in the drawing, which cooperates with the internal combustion engine 10 To get ratios, the temperature dependent resistor 30 is one of four bridge members in one Resistance bridge arranged, the remaining three resistors 33ί 34- and 35 largely temperature-independent and outside of the intake air duct are arranged. The input of a control amplifier R is connected to the diagonal of this bridge, which supplies the heating current J, and for this purpose provides an operating voltage on the other bridge diagonal that is around the bigger it gets, the bigger the cooling of the temperature-dependent Resistance 30 caused bridge imbalance. In the event that the internal combustion engine is at a standstill and consequently the amount of intake air has the value zero, the controller R is set so that it is indicated by J in FIG Initial value of the heating current and thus a certain operating temperature dec wire results. With increasing intake air volume Q, the heating current J must be increased in the V / eise recognizable from FIG. 2 according to the approximation formula J, = / A + B '/ Gj, where A and B are system constants. Do the from the two reflections

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Robert Bosch GmbH R. 26 Lr / Bo

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stand 33 and 34- left bridge branch that of Regulator R divides the supply voltage delivered in a constant Y.eise, the result is the tendency of the Controller R so that it increases the heating current J, until the operating temperature of the resistor 30 when the Initial value Q = O set target temperature reached as close as possible, this approximation all the more perfect is, the higher the one provided by the controller Gain is.

The above-described dependency of the heating current on the amount of intake air results in a difficult relationship between the opening duration t to be provided by the electronic control unit of the injection system and the amount of intake air allocated to each cylinder of the internal combustion engine. The amount of air lost per cylinder is proportional to the product of the time average value Q and the cycle time T that is required to run through a specified crankshaft rotation angle. The opening duration t · is simulated according to the invention by a voltage U = J * T proportional to it, where J ₃ denotes the amount of heating current J ^ shown in FIG so that the temperature at the measuring resistor 30 is the same as for the initial value J of the heating current when the internal combustion engine is at a standstill and consequently with an air quantity QO.

For this purpose, according to the block diagram indicated in FIG. 1

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BATH ORIGINAL

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Robert Bosch GmbH R. 26 Lr / Bo

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the controller current J are fed to an integrator 40 during the cycle time T, which is kept switched on by a "bistable multivibrator 41 over an angle of rotation of the camshaft 17 of 90 ° during the cycle time T, which in the manner shown in FIG. 3 at the end During the circulation time a voltage U ^, which has arisen through integration, is set, which is then reduced with a constant discharge current 3 and then the voltage Ug proportional to the control current J is _{integrated into a storage voltage U 0} during the time t, which is then converted directly into the opening pulses S used to control the valves 11 in a subsequent pulse shaper stage can be.

In the exemplary embodiment given in somewhat more detail in FIG. 4 in its block diagram, the two can Integrating stages 40 and 43 have the structure shown in FIG to have. At the input E_ of such an integration stage

This is followed by a Zener diode D ^, which allows the probe voltage U, which is generated at the resistor 35 of the Keßbrücke and is proportional to the heating current J, to be transferred into a working range in which the initial heating current value J required for the air volume value Q = O corresponding initial concept U _{Q is} suppressed. As a further essential component, the integrators contain an operational amplifier K ^, which is connected to its minus input via a resistor 5 "

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Robert Bosch GmbH R. 26 Lr / Bo

Stuttgart

with the Zener diode D _x , and with two in the collector _{circuit of a first switching transistor T x} , arranged resistors 53 and 54- is connected. The first switching transistor T _x . is connected via a limiting resistor 52 to the output E _x , a bistable multivibrator 41 which has the two outputs E _x and Ep and is referred to below as a flip-flop. The second output Ep of this flip-flop always leads to an _{opposite potential to the output E x} and consequently holds the second switching transistor Tp of the pnp type blocked, even if the first switching transistor T _x belonging to the npn type. is kept locked during a rotation period T belonging to a camshaft rotation range from 0 to 90 ° NW.

During such a blocking period, a current can flow through the resistor 51, which through the at the plus input of the Amplifier lying voltage divider 55 * 56 and from the am Amplifier input E_ depends on the probe voltage U present.

s s

This current flows through the from the output _{terminal A x} , bzv :. A, to the minus input of the amplifier M _x . leading integrating _{capacitor C x} J. As long as the amount of air Q = 0, no current may flow through the capacitor C ^. In this case, the current flowing in through resistor 5I must be removed again. This is done via the lying with the resistor · 51 in series resistance 57 · When the engine is running and, consequently, the heating current J, goes to the drawn in Fig. 2 value J on the initial heating value J exceeds the sensor voltage U ₀ the to

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^BA D OR | Q | _NAL

Robert Bosch GMBH . R. 26 Lr / Bo.

Stuttgart

Initial value J _Q belonging voltage value U and generates a current through the resistor 51? which is greater than the current flowing through the resistor 57. With the excess current, the charge on the capacitor C ^ is changed, so that the voltage at the output A _x drops. At the end of the cycle time T, the two switching transistors T * and Tp are ^{controlled by the} flip-flop 41 in their current-conducting state. Then the two resistors 53 and 5 ^ located in the collector circuit of the first switching transistor T ^ act as a voltage divider, which is dimensioned so that the Zener diode D. blocks and the current flowing through the resistor 51, now constant and independent of the probe voltage U_, is smaller is than the current flowing through the resistor 57. The missing current is supplied by the capacitor C ^, which has the consequence that the voltage at the output A ^ of the integrator increases linearly. _{A second Zener diode D 2} is also switched on in the parallel circuit containing the emitter-collector path of the second switching transistor Tp. This Zener diode can take over the current supplied since then by the capacitor when, after the time indicated by t in FIG. 3, that voltage s value is reached at which the Zener diode D2 becomes conductive. The charge of the capacitor C ^ is then not changed any further, and the output voltage at the output A. of the integrator then remains constant.

Because the second Zener diode Dp has a relatively large residual current the integration process would be significantly disturbed during the orbital period T as long as the temporal change

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speed of the voltage on the capacitor CL as a result an only small intake air volume also has only small values. This residual current is caused by the during the cycle time T blocked second switching transistor T ~ prevented.

The voltage rise occurring at the output A ^ of the first integrator 40 during the time t is detected by the subsequent first differentiating stage 42 and converted into a square pulse of the same duration t. This pulse begins at the beginning of the voltage rise and ends as soon as the rise has stopped, that is, as soon as the Zener diode Dp of the integrating element 40 becomes conductive. In detail, the differentiating element 42 contains a second operational amplifier Mp, the minus input of which can be connected to the output A _x via a differentiating capacitor 60 and a resistor 61 in series with it. In its output circuit, the operational amplifier Mp contains two series-connected working resistors 62 and 63 and two negative feedback _{circuits, each with a diode D 5} , respectively. D,. The diode D in the first negative feedback branch leads directly from the output Ap of the operational amplifier to its negative input and the diode D in the second negative feedback branch leads directly from the connection point of the two working resistors 62 and 63 to the negative input. The positive input of the operational amplifier is at the junction of two resistors 65 and 66 acting as voltage dividers. The use of a differentiating element according to FIG

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Robert Bosch GmbH R. 26 Lr / Bo

Stuttgart

the great advantage over a threshold switch of known design with it, for example, by strong increase in the operating temperature occurring change due to the breakdown voltage of the Zener diode Dp, which the final value the capacitor voltage occurring at the capacitor C ^ is determined, remains without influence on the duration t. In addition, the error that could arise as a result of is the threshold of such a threshold switch something set below the final voltage of the capacitor CL must become.

v.'ie derives from the block diagram of FIG. 4, closes at the output Ap of the first differentiating stage 42 a second integration stage 43, which is also constructed according to FIG. 5; and during the time t obtained at the output of the first differentiating stage in the form of the probe voltage U integrated measured values and then to their

s
Output A ^ supplies a voltage which, with a second differentiating stage 44 constructed in accordance with FIG. 6, in pulses of the duration t. is converted, many can be used directly to control the power transistor 22.

Assuming that the probe voltage U is proportional to the controller current J, the result for the storage occurring at the output J, U - T of the first integrating stage 40 is rather the voltage V. a relationship XL · = k * J * T. The storage voltage Up occurring at the output of the second integration stage 43 has the value ^U 2 = ^K 2 * * c ' ^J r = ^k 4' ^J r * % ' ^J r = ^K * V * ^T _P ' ^da t = K ₃ * J _r * T _p is.

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Robert Bosch GMBH . R. 26 Lr / Bo

Stuttgart

The opening time t. the valve is therefore in the general

Desired way J "T can be displayed proportionally and consequently with sufficient accuracy to the amount of intake air

P proportional.

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Claims (9)

- ip - Robert Bosch GmbH ήφ R. 26 Lr / Bo Stuttgart 2048955 Expectations . Ί ^ electrically controlled intermittently operating fuel injection system for internal combustion engines with at least one electromagnetically actuable injection valve - preferably with a plurality of injection valves, of which $ e is associated with a one of the cylinders - and t a lying to the magnetization coil of the valve in series with the power transistor sov / ie with a transistor switching device connected upstream of this, which is switched on synchronously with the crankshaft revolutions of the internal combustion engine with simultaneous opening of the injection valve and is kept switched on for an opening duration which determines the respective injection quantity and which can be changed as a function of the intake air quantity of the internal combustion engine, with one of one for measuring the intake air quantity Heating current flowing through, temperature-dependent resistor is arranged in the intake duct of the internal combustion engine, dg that a hot current (Jy ₁ ) delivering, the temperature-dependent V / resistance At least approximately at a constant temperature holding desire (R) is provided and that the opening duration t. - 18 - BATH ORIGINAL 209816/0496 Robert Bosch GmbH E. 26 l! R / ko Stuttgart time T and the time average Q of the sucked Air volume in the relationship t. = Q * T stands through a voltage U = J "T proportional to the opening duration is simulated, at which J means the amount of heating current at a respective time average value Q by which the heating current must be increased at constant temperature compared to the initial heating current value J _{Q required for Q = O.} 2. Plant according to claim 1, dg that with the controller current J _r or an auxiliary current proportional to this, an integrating capacitor is charged during the cycle time T, that the voltage reached at the end of the cycle time (U ^) with a constant discharge current during a discharge time t is reduced and that during this discharge time a second integrating capacitor (Cp) is charged with the controller current or an auxiliary current proportional to this and then linearly discharged, v / whether ei the duration of this discharge as the opening time t, - is used for the valves will. 3. Plant according to claim 1, dg that in each case during a cycle time T a capacitor (C _x ) with a number f pulses in steps, each time during a period of time t is charged with a charging current (J) and that the am a a - 13 - 209816/0496 bathroom original Robert Bosch GmbH R. 26 Lr / Bo Stuttgart Capacitor storage voltage reached at the end of the cycle time T U, = f * t * J * T to obtain the pulse duration t. with constant discharge current is dismantled and that of the capacitor storage voltage U ^ determining factors f, t, J two each proportional to the controller current J IA-.UVt X P.
power are. 4-, plant according to claim 2, d.g. that at least one of the Capacitors (CL) is arranged in the feedback branch of an operational amplifier (M ^), the pn one of its inputs (Cinema input) with one proportional to the controller current (J) Voltage (E_) is connected and at its other input is connected to a fixed voltage. f 5. System according to claim ^ 4-, with a control switch coupled to the crankshaft and with a bistable multivibrator, which during each crankshaft rotation - ■ preferably in gif-ich en intervals - at least twice from one of its two bistable positions through the control switch in the opposite Operating situation reversed v: ird and r, v: oi to each other gev / cils eiitge ^ & ngenetstee Fotent:.: -! au. ^ v.'f'i ^ rjnüo lair.graste Lr- *:,. ^r '. =%, c, e ^: l rrit eir.cr: ö -ir 209816 / 0A96 "~ BAD ORIGINAL Robert Bosch GmbH R.-26 Lr / Bo Stuttgart Outputs of the multivibrator the base of a switching transistor (T ,,) is connected, which is connected with its emitter-collector path to two resistors (R ^, R ₂ ) in series, at their connection point (P.) ) proportional voltage (E) is fed in via a first Zener diode (D, -) and a voltage divider consisting of two resistors (5 "1» 57) is connected, to whose tap the minus input of the operational amplifier is connected. 6. Plant according to claim 5> d.g. that parallel to the im Feedback circuit of the operational amplifier lying integrating capacitor (C ^.) A second Zener diode (Do) is arranged. 7. Plant according to claim 6, dg that the second Zener diode (Dp) is in series with the emitter-collector path of a second switching transistor (T ₂ ) which is connected with its base to the second output of the monostable multivibrator. 8. Plant according to claim 7, dg that at the output of the operational amplifier via a capacitor a TAi- - 21 - 2098 16/0496 BATH ORIGINAL Robert Bosch GmbH R. 26 Lr / Bo Stuttgart fenzierstufe is connected during the discharge time t of the integrating capacitor an auxiliary pulse J supplies the same duration that is used to control a postc the following second integration stage is used. 9. Plant according to claim 8, d.g. that the differentiation stage one with its negative input via a coupling capacitor and preferably one in series with it Resistance to the output (A ^) of the first integrator (40) connected, second operational amplifier includes, which contains two series-connected working resistors in its output circuit and two each one Diode has negative feedback circuits, the first of which is from the output of the operational amplifier and the second leads from the connection point of the load resistors to the negative input of the operational amplifier. 209816AO496