EP0018257B1 - Warming-up device for starting an internal-combustion engine of the diesel type or the like - Google Patents

Description

The invention relates to a preheating device for starting an internal combustion engine, of the Diesel type or the like, comprising a glow plug, mounted in each cylinder, suitable for being supplied by a source of electrical energy for ensuring the preheating of a combustion chamber, comprising a rapid preheating circuit ensuring the connection of each glow plug under a relatively high electrical voltage, this rapid preheating circuit being activated from the start of preheating by closing the contact starter, and a slow preheating circuit, capable of ensuring the connection of each glow plug under a lower electrical voltage after a rapid preheating period determined by first delay means.

The document GB ― A ― 2 002 449 shows a preheating device of this kind in which the rapid preheating circuit is obtained by short-circuiting an electrical resistance. When the rapid preheating circuit opens, the electric current is supplied to the glow plugs through the electrical resistor belonging to the slow preheating circuit. The duration of rapid preheating is determined by a timing circuit which is not indicated to be sensitive to the temperature of the engine or spark plugs. In other words, the duration of rapid preheating will be the same regardless of the engine or spark plug temperature conditions. In addition, this device includes an indicator light which lights up during the preheating period; when the preheating is sufficient, the light goes out and gives the operator the start signal; at this time, the operator must act on the ignition key to move it from a preheating and driving position to a transient, unstable, starting position, to start the engine.

It is immediately understood that the starting operation of a diesel type engine or the like with such a device has drawbacks compared to the starting operation of internal combustion engines. Indeed, after turning the ignition key, the driver must wait for the appearance of a signal, formed by the extinction of an indicator light, to actuate, then, the starter for the launch of the engine. In addition, since the duration of rapid preheating is not modified according to the temperature of the engine or the spark plugs, the effectiveness of rapid preheating must be limited so as to maintain a margin of safety and not to destroy the spark plugs when the engine or the candles are already hot when starting.

The document US Pat. No. 4,088,109 relates to a preheating device for starting a diesel engine in which a single preheating circuit is provided. The device also includes two indicator lights. When the first of these warning lights is on (and the second is off), the driver must wait before acting on the ignition key to start the engine using the starter; when the first warning light goes out and the second warning light comes on, the driver can act on the ignition key to pass it into a fleeting position corresponding to the starter supply.

With such a device, there are the drawbacks mentioned above of the indicator light.

The document FR ― A― 2 394 223 relates to an electrically operating device for rapidly heating assemblies in motor vehicles. This device can be used to heat the ignition devices in a self-igniting internal combustion engine. This rapid heating device is arranged to rapidly raise the temperature of a heating element and to maintain this temperature at a determined level. Two time intervals are provided during the heating process: a first interval during the heating process, and a second immediately following time interval during which the heating current is supplied in the form of pulses, essentially in order to maintain the temperature reached. Various means are provided for determining the end of the first time interval; one can, for example, detect the temperature of the heating element and stop the first interval when the heating element has reached a determined temperature.

Although provision is made for the use of such a heater to heat the ignition devices in self-igniting internal combustion engines, no details are given on the starting sequence and the driver operations.

The object of the invention is, above all to make the preheating device of the kind defined above such that it no longer has or to a lesser degree the drawbacks outlined above and that, in particular, it makes it possible to start a Diesel or similar type motor vehicle practically as easy as starting a vehicle fitted with a petrol engine.

According to the invention, a preheating device of this kind is characterized in that the aforementioned first time delay means are combined with means sensitive to the temperature of the engine arranged in such a way that the rapid preheating time depends on the temperature of the engine, and that control means, actuated by closing the starter contact, are provided to automatically close the starter supply circuit when the fast preheating circuit is cut off and to close the slow preheating circuit.

Means sensitive to the engine speed are provided to control the engine shutdown and slow preheating when the internal combustion engine is running at sufficient speed.

Preferably, the device comprises means sensitive to a previous start order combined with control means so as to prohibit or stop the actuation of the rapid preheating circuit during a determined time interval following a start attempt or the engine shutdown.

It is thus possible to very quickly raise the temperature of the glow plugs and the combustion chambers while preserving the glow plugs from overheating, particularly in the case where, after a first attempt to start, a second attempt would take place almost immediately after the first attempt.

To minimize the preheating time, the rapid preheating circuit ensures the connection of glow plugs under a temporary electrical overvoltage such that the temperature rise of the plugs is rapid.

The first delay means are, advantageously, electronic, and comprise, for example, a CTN resistor (with a negative temperature coefficient) sensitive to the temperature of the motor; this resistance plunges, in particular, in the engine cooling water.

The means sensitive to an attempt to start advantageously comprise second time delay means.

According to a first solution, these second timing means are triggered when, after closing then opening of the starter contact, there is opening of the general contact, said second timing means then delivering a signal prohibiting the actuation of the rapid preheating circuit, having a predetermined duration, while allowing slow preheating and launching of the starter.

Means are provided to prevent the triggering of the second time delay means if there has been closing and then opening of the general contact, without the starter contact having been closed then opened.

Advantageously, the output of the first timing means is connected; on the one hand, at an input of an AND gate, the output of which controls, possibly via an amplifier and a relay, the activation of rapid preheating and, on the other hand, 'input of an inverting gate whose output is connected to the input of an OR gate; the output of this OR gate is connected to an input of a second AND gate, the output of which controls, in particular via an amplifier and a relay, the activation of the slow preheating and of the starter; the output of the second timing means is connected. to another entrance to the OR gate, and, via a reversing gate, to another input to. the first AND gate; a second input of the second AND gate is attacked by a signal produced when the starter contact closes. Preferably, the first and second AND doors have a third input connected to an engine speed detector, arranged so as to provide a preheating prohibition signal when the engine is running at a sufficient speed.

Still within the framework of this first solution, means can be provided allowing the automatic sequence of the rapid preheating and slow preheating with launching of the starter, without it being necessary to keep the starter contact closed, the sudits means automatically triggering the sequence from a simple fugitive closing of the starter contact.

These means are suitable for storing the fugitive closing of the starter contact, in order to maintain, on the input of the second AND gate, normally attacked by the closing signal of the starter contact, an order to start preheating. slow and starting.

These storage means are advantageously formed by a flip-flop D whose clock input is connected so as to be attacked by the fugitive signal for closing the starter contact, while the input D (data) of this flip-flop is connected to the output of a third aND gate having two inputs respectively attacked by the signal at the output of the engine speed sensor and a signal appearing at the closure of the _general contact; the output of flip-flop D is connected to an input of the second AND gate.

According to a second solution, the means sensitive to a previous start order comprise means sensitive to the temperature of the glow plug combined with second timing means, the assembly being arranged in such a way that rapid preheating is stopped if the temperature of the candle reaches or exceeds a value 8a during a time interval; which follows the closing of the starter contact, less than the duration of tilting of the second timing means, the leng preheating and the launching of the starter then being controlled.

The means sensitive to the temperature of the candle are advantageously constituted by an intensity detector which makes it possible to deduce, from the intensity which passes through the candle powered by a known electric voltage source, the temperature of this spark plug.

The output of the intensity detector is connected, via a flip-flop RS, to an input of a "NAND" gate, another input of which is connected to the output of the second delay means; the output of this "NON Er" gate is connected to the input of a flip-flop, an output of which is connected to an input for resetting the first delay means to zero.

The first delay means are started by closing, even fleeting, the starter contact so that rapid preheating begins with this closing.

However, if the intensity detector gives information showing that the candle was already hot, the first delay means are reset and rapid preheating is stopped.

These first time delay means are adjusted so as to have a maximum switching time such that if a glow plug having a temperature equal to θ _o , is subjected, during this maximum switching time, to the relatively high electrical voltage (rapid preheating ), it is certain that at the end of this maximum tilting time, the temperature reached by the glow plug is not detrimental to this plug.

The assembly is arranged in such a way that, in the case of a cold spark plug, the first time delay means and the rapid preheating are triggered when the starter contact is closed and that, when the glow plug reaches the temperature 8 ₀ , the first time delay means are retriggered so that the glow plug is subjected to rapid preheating during a maximum time interval Δt1 + Δtm determined by the time delay from time to.

Because it is possible to match the temperature faire _o , an intensity io absorbed by the spark plug (at a known determined voltage), the intensity detector is arranged to control, when crossing a corresponding value i _o at the temperature θ _o , by the intensity absorbed, a change of state of the output of the associated flip-flop, this change of state commanding the rediscovering of the first time delay means.

Advantageously, a bypass circuit of the first delay means is provided, comprising, in particular, an AND gate.

Means are also provided for controlling the stopping of rapid preheating and the transition to slow preheating with starting, if the engine is sufficiently hot.

These means include third time-delay means, capable of delivering a tilting slot of fixed duration, and means for reading the charge of a capacitor through a CTN resistor sensitive to the temperature of the motor; if the voltage across the capacitor reaches a determined value in a time less than the tilting window of the third time delay means (which translates to a low value of the CTN resistance and therefore a relatively high temperature of the motor), the rapid preheating is stopped and the start of the slow preheating and the starter is controlled.

The means for reading the charge of the capacitor comprise a comparator capable of comparing the voltage across the terminals of the capacitor with a reference voltage, the output of this comparator being connected to an input of a "NAND" gate, the other input of which is connected to the output of the third time delay means.

The duration of the tilting slot of these third time delay means can be of the order of 0.5 seconds.

The invention consists, apart from the arrangements set out above, of certain other arrangements which will be more explicitly discussed below in connection with particular embodiments described with reference to the attached drawings, but which are in no way limiting. .

• Figure 1 of these drawings is a diagram of a preheating device according to the invention, according to the first solution mentioned above.
• Figure 2 is a block diagram of the electronic assembly of a device according to FIG. 1, in the case of an assisted start, that is to say with maintenance, by the driver, of the closing of the starter contact.
• Figure 3 is a block diagram of the electronic assembly in the case of a fully automatic start, that is to say with fugitive closing of the starter contact and release of the ignition key.
• Figure 4 is a diagram summarizing the operation of the starting device according to the first solution.
• Figure 5 is an overall diagram of a preheating device according to the invention, according to the second solution mentioned above.
• FIG. 6 is a block diagram of the electronic assembly of the device of FIG. 5.
• FIG. 7 gives representative schematic curves of the heating of a candle, the temperature 0 of which is plotted on the ordinate, as a function of the time t plotted on the abscissa, for rapid preheating and for slow preheating.
• FIG. 8 is a diagram summarizing the operation of the device of FIGS. 5 and 6.
• FIG. 9 is a diagram representing the logic states at different points of the electronic circuit of the diagram in FIG. 6.
• FIG. 10 is a diagram of an additional electronic circuit making it possible to maintain post-heating after start-up.
• FIG. 11 is a diagram of an electronic circuit enabling the glow plugs to be supplied under reduced power, for slow preheating or post-heating.
• FIG. 12 is a variant of the diagram in FIG. 11.
• FIG. 13 is a diagram of a circuit capable of limiting the supply time of the starter to a determined value.
• FIG. 14, finally, is a diagram of a circuit capable of authorizing the launching of the starter only if safety measures are respected.

Referring to Figure 1 of the drawings, one can see a preheating device P for starting an internal combustion engine, of the Diesel type, not shown.

This preheating device comprises, mounted in each cylinder, a glow plug b shown diagrammatically in the form of an electrical resistance. In the diagram of FIG. 1, four candles b have been represented; each spark plug ensures the preheating of a combustion chamber associated with the cylinder. The candles b are suitable for being powered by a source of electrical energy whose pole + is connected to the conductor / and the pole ― is connected to ground. This energy source is generally constituted by the battery of a vehicle equipped with the internal combustion engine.

The device P comprises an electronic control unit E in which are provided first timing means 1 (fig. 2 and 3).

As shown in Figure 1, the device P comprises a rapid preheating circuit Cr ensuring the connection of each glow plug b under a relatively high electrical voltage. The closing of this circuit Cr is controlled by a working contact of an electromagnetic relay R3 whose control coil is connected between earth and an output of the control assembly E; alternatively, the rotten coil be connected between the + pole and the assembly E.

The preheating circuit Cr ensures the direct connection of the glow plugs b in parallel between the terminals of the electric power source and earth. The voltage thus applied to the spark plugs b is greater than the nominal operating voltage of the spark plugs, b; this voltage is such that if the candles b were kept for a relatively long time, they would be brought to a temperature too high for them to be able to resist. Generally, this voltage is of the order of 12 volts, while the spark plugs b have a nominal voltage of the order of 7 volts.

Referring to FIG. 7, we can see the curve Sr of heating of the spark plug as a function of time (the temperature 0 of the spark plug is plotted on the ordinate, while the heating time t is plotted on the abscissa) in the case where the rapid preheating circuit Cr is in service. The slope of this curve is an increasing function of the voltage applied across the plugs.

The device P also includes a slow preheating circuit CI which can be closed by the working contact of an electromagnetic control relay R2, the control winding of which is connected between ground and an output of the assembly E; according to a variant, this winding could be connected between the pole + and E. This circuit Ci comprises a falling resistor 2 (fig. 1). The closing of the circuit CI ensures the supply in parallel, of the candles b, through this resistor 2; the voltage applied to the candles is therefore lower.

The curve S1, in FIG. 7, which has a markedly lower slope than Sr, corresponds to the heating of the spark plug when only the circuit CI is in action.

To minimize the preheating time, the curve Sr (fig. 7) is given as steep a slope as possible.

The first time delay means 1 are arranged to cut off the rapid preheating circuit Cr after a time t1 (fig. 7) determined in such a way that the spark plugs are not likely to be damaged, that is to say in such a way that the temperature of the spark plugs is limited to a value 0r lower than the destruction temperature 9d of the spark plug.

The device P also includes control means 3 (fig. 2) provided to ensure, when the rapid heating circuit Cr is opened, the leng CI heating circuit is closed (closing of the working contact of the relay R2 in FIG. 1) and the closing of the starter M supply circuit.

This closing of the starter circuit M is ensured by means of a work contact of a power relay Rd (fig. 1), the control winding of which is supplied via a work contact of a relay R1. The winding of R1 is connected between earth and an output of the control assembly E; alternatively, this winding could be connected between the + pole and E.

As visible in FIG. 1, an input of the control assembly E is connected to the conductor /, connected to the + terminal of the battery, by a switch 4 suitable for being closed when the vehicle ignition key is placed in the closed position of the general contact. Another input of the assembly E is connected to the driver by means of a switch 5 suitable for being closed when the vehicle ignition key is placed in the "start" position. Two inputs of the set E are connected to the terminals of a resistor CTN (negative temperature coefficient) 6 sensitive to the temperature of the motor. This resistor 6 can, in particular, be immersed in the circuit engine cooling water. The two inputs of the assembly E connected to this resistor 6 are connected to two inputs of the first timing means 1 as visible in FIG. 2.

Two other inputs of the assembly E (connected as visible in FIG. 2 to a engine speed detector 7) are connected to the terminals of a tachometric sensor 8 sensitive to the speed of rotation of the engine.

Another input of the control unit E is permanently connected by a conductor 9 (fig. 1) to the conductor I.

The device P comprises means 8 (fig. 2), sensitive to an attempt to start, combined with control means 10 (fig. 2) so as to prohibit or stop the actuation of the rapid preheating circuit Cr during a time interval Δt following a first start-up attempt.

The sensitive means B comprise second timing means 11.

According to a first solution (FIGS. 1, 2 and 3) these second delay means 11 are triggered when, after closing then opening of the starter contact 5, there is opening of the general contact 4.

Means G (Figs. 2 and 3) are provided to prevent the triggering of the second delay means 11 if there has been closing then opening of the single general contact 4, without the starter contact 5 having been closed then opened.

These second timing means 11 are suitable for delivering, when they have been triggered, a signal prohibiting the actuation of the rapid preheating circuit, while allowing slow preheating and the launching of the starter.

We will now describe, in more detail, with reference to FIG. 2, the control assembly E.

The trigger input of the first delay means 1 is connected to the output of an anti-rebound circuit or shaping circuit 12. The input of this circuit 12 is connected so as to receive a ligic signal "1" when closing the starter contact 5.

The trigger input of the second timing means 11 is connected to the output of an inverter 13. The input of this inverter 13 is connected to the output of a flip-flop D, designated by the reference g1, belonging to the means G .

The data input g11 of this flip-flop is connected to the output of an anti-rebound circuit 14 or of shaping; the input of this circuit 14 is attacked by a trigger signal when the general contact 4 is cut.

The clock input g12 of the flip-flop g1 is connected to a complemented input g13 of reset; the transition from state "1" to state "0" of this input g13 therefore resets the output of flip-flop g1 to zero.

The clock input g12 is also connected to the output Q of a flip-flop (R / S) g2, also belonging to the means G. The input S of the flip-flop g2 is connected to the output of the circuit anti-rebound 12. The input R of the flip-flop g2 is connected to the output of a reversing gate g3 whose input is connected to the output of the anti-rebound circuit 14.

The control means 10 comprise an AND gate 15 of which an input 1 5e is connected to the output of the first timing means 1, a second input 15f of this AND gate is connected to the output of an inverter 16 whose input is connected to the output of the second timing means 11.

A third door input 15g is connected to the output of the speed detector 7.

The output of the speed detector 7 is in logic state "1" when the engine is stopped or is running at a speed lower than a determined limit (or threshold).

The first and second time delay means 1 and 11, when triggered, show, at their output, for a determined time, the logic state "1".

The output of the AND gate 15 controls, by means of an amplifier 17, the energization of the relay R3 for controlling the rapid heating circuit Cr and the closing of the working contact ensuring the supply of the candles b by this rapid heating circuit.

The control means 3 comprise an inverter circuit 18 whose input is connected to the output of the first timing means 1 and whose output is connected to an input 19e of an OR gate 19. Another input 19f of this prote OR is connected to the output of the second timing means 11.

The output of the OR gate 19 is connected to an input 20e of an AND gate 20; a second input 20f of this door is connected to the output of the anti-rebound circuit 12. A third input 20g of the door 20 is connected to the output of the speed detector 7.

The output of the gate 20 controls, via an amplifier 21, the relay R2 for actuation of the slow preheating circuit C /, as well as the relay R1 for actuation of the starter.

The operation of a preheating device P equipped with a control assembly E in accordance with FIG. 2 is as follows.

It is an operation with assisted starting, that is to say with maintenance of the "ignition" key in the "starting" position and therefore maintenance of the contact 5, of FIG. 1, closed.

First start order―

It is considered that this is a first start order when the period of stopping the internal combustion engine has been sufficient or when, in the event of a cut-off during preheating, the ignition has been switched off long enough a long time, so that the temperature of glow plugs drops to a relatively low temperature, close to room temperature.

In practice, the duration of the signal of the second time delay means 11 is chosen to be equal to or greater than the interval t2 (fig. 7) necessary for a glow plug b, starting from its maximum permissible temperature Om (fig. 7) cools down to a temperature close to ambient temperature, by cooling in a motor which does not run, the two circuits Cr and CI being open.

During this first attempt (or first order) to start, in the sense specified above, the second delay means 11 are at rest and their output is in the state "0",

Closing with maintenance of the starting contact 5 produces a signal "1" at the output of the circuit 12; the first delay means 1 are triggered by the rising edge of this signal; these first delay means 1 deliver a signal "1" at their output, the duration of which depends on the value of the thermistor 6 and therefore on the temperature of the motor. The duration of the signal is lower the higher the engine temperature.

The signal "1" arrives at the 15th entrance of door 15.

The signal "0", present at the output of the second timing means 11, is transformed, by the inverter 16, into signal "1" present on the second input 15f of the door 15.

In addition, because the internal combustion engine is stopped, the speed detector 7 gives at its output a signal "1", also present on the third input 15g of door 15.

This AND gate gives, at its output, a signal "1" commanding the closing of the working contact of the relay R3 and the actuation of the rapid preheating circuit Cr.

The two inputs of the OR gate 19 are attacked by a signal "0" so that the output of the gate 19 and therefore the output of the AND gate 20 are also in the state "0", preventing the actuation of the slow heating circuit CI and the launching of the starter.

At the end of the time delay, the output of the first time delay means 1 returns to the state "0" so that the output of the door 15 also goes to the state "0" and controls the cutting of the heating circuit fast Cr. Referring to FIG. 7, it can be seen that the temperature of the spark plug has substantially reached the value Gold on the curve Sr.

The output of the first timing means 1 having passed to "0", the inverter 18 gives at its output a signal "1" which attacks the 19th input of the OR gate 19. The output of this gate goes to state "1" as well as the input 20e of the door 20. The second input 20f of this door is also in the state "1" because the contact 5 is kept closed; the third 20g input is also in state "1" since the engine has not started. The output of door 20 is in state "1" and commands the closing of relay R2 and relay R1, which causes the slow preheating circuit CI to be actuated and the starter M to be started.

When the internal combustion engine has started, the output of the speed sensor 7 goes to state "0" so that the output of AND gate 20 also goes to state "0" which commands the stop slow preheating and starter M.

Second start order -

• a) après avoir roulé avec le véhicule, le conducteur coupe le contact et repart peu après;
• b) le conducteur a interrompu une tentative de démarrage et en effectue une seconde;
• c) une première tentative de démarrage s'est soldée par un échec et une seconde tentative a lieu.

By second start order (or simply 2nd start), a start attempt is designated which is carried out shortly after the general contact has been switched off; there may be several reasons for this, such as:

• a) after driving with the vehicle, the driver switches off the ignition and leaves shortly after;
• b) the driver has interrupted a start attempt and is making a second;
• c) a first start-up attempt was unsuccessful and a second attempt is made.

Finally, the expression "second start order" (or 2nd start) implies that an attempt to start is made when the glow plugs are already hot; during this second start attempt, it is therefore necessary to prevent rapid preheating. The ignition key and control circuit system is arranged, in a conventional manner, such that after a failed start attempt, it is necessary, before being able to make a new attempt, to open the general contact 4, then to close it again.

During a second start-up attempt, contact 4 was therefore cut off beforehand.

The means G intervene to ensure that this interruption of the contact 4 does not trigger the second time delay means 11 unless it has taken place after closing and then opening of the starter contact 5.

Recall that a flip-flop (D) -g1 passes, on its output, the state which is on its "data" input, when the clock input is in the state "1".

The flip-flop g1 is used to let pass a signal for triggering the second delay means 11, when the contact 4 is opened, only if there has been an attempt to start, that is to say if the contact 5 has been formed_ then opened.

In fact, if the contact 4 is closed then opened, without there having been closing then opening of the starter contact 5, the output Q of the flip-flop g2 remains at "0". The clock input g12 of the flip-flop g1 is at "0" as well as the complemented input g13 of reset to zero, so that the output of the flip-flop gl 1 remains at "0".

If, after closing contact 4, there is an attempt to start by closing contact 5, the input S of the flip-flop (R / S) g2 is attacked by a signal which changes the output to "1" tie Q, and therefore the clock input g12 of the flip-flop (D) g1. The state "1" which is on the entry g11 is then transmitted, by the rocker. (D) -g1 at its exit.

When the contact 4 is cut off, the reversing gate g3 transmits to the input R of the flip-flop g2 a signal which changes the output Q from the state "1" to the state "0".

The inputs g12 (clock) and g13 of the flip-flop g1 are brought to the state "0", and the output of the flip-flop g1 is reset to "0".

The reversing gate 13 transforms the falling edge from the transition from "1" to "0" from the output of g1 into a rising edge from "0" to "1" on the input of the second timing means 1.1 which are thus triggered.

If the time interval between the end of the first attempt and the start of the second start attempt is less than the switching time of the second delay means 11, during the second start attempt, upon closing of the start contact , the first timing means 1 are started, while the second timing means 11 are still triggered.

It follows that the input 15f of the door 15 is in the state "0" ("1" at the output of 11 therefore "0" at the output of 16); although the input 15th is raised to "1", the output of door 15 remains at "0" and rapid preheating does not take place.

On the other hand, the input 19f of the OR gate 19 is in the state "1", the output of the gate 19 is also in the state "1". The three inputs of door 20 will be in state "1".

The output of door 20 is therefore in state 1 and controls the slow preheating and the actuation of the starter.

Referring to Figure 7, we see that the temperature of the spark plug, even if it was close to 0r during the debate of this second attempt to start, will not wait for a detrimental value since the heating takes place following the preheating slow, with a sufficiently slight slope.

The control assembly E, the diagram of which is given in FIG. 3, allows an automatic starting sequence so that it is not necessary to keep the starting contact 5 closed; it suffices to make a fleeting closure of this contact 5 and release the ignition key, to trigger the automatic start sequence.

Most of the elements of the diagram in Figure 3 are identical to those already described with reference to Figure 2, and are designated by the same reference numerals.

However, the control assembly of FIG. 3 includes means 22 suitable for storing the fleeting closing of the starter contact 5 in order to maintain, on the input 20f of the AND gate, a corresponding state "1" (when the other two inputs 20e and 20g are in state "1") at a start-up command for slow preheating and starting.

The storage means 22 include a "flip-flop D" 23 whose clock input 23c is connected to the output of the anti-rebound circuit 12. The "data" input 23d of this flip-flop is connected to the output d an AND gate 24. This input 23d is also connected to the input 23r for resetting to "0" of the rocker.

It is recalled that the reset to "0" of the flip-flop "D" -23 is obtained either by leveling the input 23r at "0", or by sending a pulse on the clock input 23c when the data input 23d is at level "0".

The connection of the flip-flop 23 is such that its output is reset to "0" each time the contact 4 is cut (fig. 1).

The AND gate 24 has two inputs connected respectively to the output of the flip-flop g1 and to the output of the speed detector 7.

As the starting sequence is fully automatic, in the event of a false operation, the driver's reaction time to switch off the ignition will be longer because he has released the ignition key.

To avoid accidents, the starting device is completed by a safety device shown in phantom in Figure 1 comprising two safety contactors S 1, S2, connected in series between earth and an input of the control device E. These Safety switches are suitable for closing respectively when the gearbox is in neutral and when the hood is locked. If at least one of these contactors is open, there is a ban on starting the starter. This prohibition can be achieved, for example, by providing an additional input (not shown) on the AND gate 20 of FIG. 3 and by connecting to this input a conductor to which a signal "1" is applied when the two contactors S1, S2 are closed and a "0" signal when at least one of these contactors is open.

The operation of the starting device equipped with the control assembly, the diagram of which is given in FIG. 3 is identical to that described with reference to FIG. 2, with the only difference that in the case of the diagram of FIG. 3, it It suffices to make a temporary closure of the starting contact 5 and then release the key. The start-up sequence is then automatic.

The general contact 4 closes for an angular position of the ignition key located before the starter contact 5 closes. The contact 4 closes causes the output of the anti-rebound circuit 14 to go to "1". The subsequent fugitive closing of the starting contact 5 switches the output of the anti-rebound circuit 12 to the state "1" for a certain period of time. The output Q of flip-flop g2, as explained above, changes to state "1"; the clock input g12 of the flip-flop D-g1 being attacked by a signal "1", the state "1" of the input g11 passes on the output of the flip-flop D-g1 and therefore on an input of the "AND" output 24 and on the input of the reversing door 13.

The other input of the "AND" door 24 connected to the speed detector 7 is also in the "1" state, the engine being assumed to be stopped. The output of AND gate 24 is therefore in state "1".

The state "1" present on the output of the circuit 12 is also sent to the clock input 23c of the flip-flop 23, which transits the state "1" which is on the input 23d (connected to the output of the AND gate 24) at the output of the lever 23 and therefore on the input 20f of the gate 20.

In addition, the passage to state "1" of the output of circuit 12 triggers the first delay means 1.

If it is a first start in the sense. defined above, the output of the second timing means 11 is at "0" so that the output of the reversing door 16 is in the state "1"; the two inputs of the AND gate 15 are in state "1" so that rapid preheating is controlled. The two inputs of the OR gate 19 are in the "0" state so that the slow preheating relay R2 and the starting relay Rd are not energized.

When the output of the first delay means 1 returns to the state "0", the rapid preheating is stopped and the launching of the starter and the control of the slow preheating are ensured.

In the event that the driver is led to make a second start attempt (second start order in the sense defined above), the operations would be as follows.

First, in a classic way; to make such a second attempt, the driver must return the ignition key to the position where the general contact 4 is cut.

The means G intervene as described above.

When the output of circuit 14 goes to state "0", the same is true for the output of flip-flop g1, the output of AND gate 24 and input 23d, as well as input 23r. Bringing this input 23r to the low level causes the output of the flip-flop 23 to be reset to "0".

During this cut-off of the general contact (after opening and cut-off of the starter contact 5), the output of the reversing door 13 has changed to state "1" which has triggered the second delay means 11, the output of which switches to l 'state "1" for a predetermined time. The output of the inverting door 16 changes to the "0" state so that the output of the AND gate 15 remains in the "0" state during the entire tilting time of the seconds. delay means 11.

During the closing, for this second attempt, of the general contact 4, then of the fugitive closing of the starter contact 5, the output of the flip-flop 23 changes to state "1" and remains in this state "1" for as long that the general contact is not cut.

The output of the second timing means 11 being in the state "1", the input 20e of the door 20 is also in the state "1"; the 2Og input is in state "1" because the motor is stopped.

The output of the AND gate 20 is in state "1" and the launching of the starter with slow preheating is immediately commanded during this second attempt.

The diagram in FIG. 4 summarizes, summarily, the operation of the preheating device in FIGS. 1 to 3. It seems unnecessary to insist on this diagram any longer, which corresponds entirely to the explanations. previously provided. It should be noted that this diagram of FIG. 4, like that of FIG. 8 moreover, are to be considered as part of the description.

A second solution, which will now be described with reference to FIGS. 5 and following, provides means H sensitive to the intensity which passes through the glow plugs and therefore, as explained. further on, at the temperature of these candles; these means H are combined with the second timing means 11 a so as to form the means B sensitive to a first start order.

The: elements and circuits of the second solution of FIGS. 5 and following which are identical or which play roles similar to elements and circuits already described with reference to the first solution are designated by the same numbers or letters of reference, possibly followed by the letter a.

The diagram in FIG. 5 of the preheating device Pa in accordance with this second solution differs from the device P represented in FIG. 1 essentially by its control assembly Ea and by the presence of a shunt s mounted · on the conductor d electrical supply of the spark plugs, the two terminals of the shunt s being connected to two inputs of the control assembly Ea.

This shunt belongs to the means H sensitive to the temperature of the candles.

This shunt makes it possible to measure the intensity of the current which feeds the candles b. Because these candles b are supplied with a well-determined voltage, corresponding to that of the vehicle battery, it is known that at a given intensity corresponds a determined resistance of each candle. The correspondence between the resistance of a candle and its temperature being known with good precision, it can be considered that the information on the intensity of feeding of the candles is equivalent to information on the temperature of these candles.

The detailed description. of the control unit Ea is given with reference to FIG. 6.

The input of the anti-rebound circuit 12 is connected to the output of an AND gate 25. An input of this gate 25 is connected to the starter contact 5 so as to be brought to the state "1" when this contact 5 is closed; another input of door 25 is connected to the safety contacts S1, S2 so that this input is brought to state "1" when these contacts are closed, that is to say when the gearbox lever is in neutral position and when the cover is closed (possibly); if necessary, other safety devices could be provided and connected to an entrance to door ET 25.

The output of the anti-rebound circuit 12 is connected to the input S of a flip-flop 26 of the RS type (set― reset; trigger-reset), by means of a reversing gate n.

The output Q of this flip-flop 26 is connected, on the one hand, to the input of a monostable flip-flop 27, on the other hand, to an input of an AND gate 28 and, on the other hand, finally, to an entry from another door ET 20a.

The complemented output Q of the flip-flop 26 is connected to the input of the second timing means 11 a.

It should be noted that the flip-flop RS 26, as well as all the flip-flops RS which will be discussed below, are arranged so that their output Q changes state when the input S is attacked by a falling edge, c ' that is to say when passing from state "1" to state "0" of input S.

The monostable flip-flop is arranged so as to deliver at its output a slot (transition from its output from state "0" to state "1") of a very short duration, for example of the order of a few milliseconds , when the Q output of flip-flop 26 changes from state "0" to state "1".

The assembly is arranged so that when the general contact 4 is cut, the pulses sent by the circuit 29 on all the inputs R of the flip-flops RS, reset the outputs Q to "0".

The second delay means 11a are triggered during the passage of the output Q from flip-flop 26 from state "1" to state "0". The output of the second timing means 11a is connected to an input of a NAND gate 30.

A second input of this gate 30 is connected to the output a of an RS flip-flop 31. The input S of this flip-flop 31 is connected to the output of an intensity detector circuit K, connected to the terminals of the shunt s. This intensity detector K is arranged so as to give its output, and therefore on the input S of the flip-flop 31, a state "1" when the intensity of the electric current passing through the shunt s is greater than a value i ₀ . When the intensity becomes equal to or less than this limit, the output of detector K changes to state "0".

The output Q is, moreover, connected to an input of a NOT OR gate 32. Another input of this gate 32 is connected to the output of the monostable flip-flop 27. The output of this gate 32 is connected to the input for triggering the first delay means 1 a.

These first delay means 1a are suitable for being triggered by a falling edge, that is to say passage from state "1" to state "0" on their input; their triggering causes the presence of a state "1" on their output for a determined time. We find the presence of the thermistor 6 connected to these first timing means 1a as explained with reference to Figures 2 and 3.

Complementary output Q of the flip-flop 31 is connected to a second input of the door 28.

The output of gate 30 is connected to the input S of a flip-flop RS 33, the output Q of which is connected to a reset input to "0" of the first delay means 1 a; the passage of the output Q of the flip-flop 33 from the state "1" to the state "0" resets to "0" the output of the first means, of timing 1 a.

The first delay means 1 a comprise a capacitor Q1 connected in such a way that when the first delay means 1 a are triggered, this capacitor Q1 is crossed by a charge current passing through the thermistor 6; the charge of this capacitor and therefore the rise of the electric voltage across the terminals of this capacitor will be all the faster the lower the value of the thermistor 6. Because this thermistor has a negative temperature coefficient, the rise in electrical voltage will be all the faster the warmer the engine.

The maximum tilting time Δtm of the first timing means 1a is such that if a glow plug, having a temperature equal to θ _o (θ _o corresponds to the intensity i _o passing through the shunt s), is subjected, during this duration maximum tilting Δtm, at high electrical voltage (rapid preheating), it is certain that at the end of this tilting time, the temperature 0, reached by the glow plug is not detrimental to this plug, in other words , we are sure that θ _f is less than or equal to θ _m (fig. 7).

Reading means L of the charge of the capacitor Q1 are provided. These means L comprise a comparator 34, one input (non-inverting) of which is connected to one terminal of the capacitor Q1 and the other input (inverting) of which is connected to the cursor 35 of a potentiometer 36 so as to define a reference electrical voltage. adjustable by the position of the cursor. Comparator 34 is able to compare the voltage across the terminals of capacitor Q1 with this reference voltage.

When the voltage across the capacitor Q1 is lower than the reference voltage, the output of comparator 34 is in the state "0"; when the voltage across the capacitor Q1 becomes equal to or greater than the reference voltage, the output of comparator 34 changes to state "1". This output of comparator 34 is connected to an input of a NAND gate 37. Another input of this gate 37 is connected to the output of third delay means 38. The trigger input of these third delay means 38 is connected to the output of the monostable scale 27. The triggering of these third. timer means 38, that is to say the passage from state "0" to state "1" of their output is controlled by the passage from state "0" to state "1" of the output of the monostable scale 27.

The tripping time of the third delay means 38 is advantageously of the order of 0.5 seconds.

The output of the first timing means 1a is connected to an input of an OR gate 39, another input of which is connected to the output of the gate 28.

The output of gate 39. is connected to an input of an AND gate 40. Another input of this gate 40 is connected to the complemented output Q of a flip-flop RS 41. The input S of this flip-flop 41 is connected to the output of door 37.

The output of gate 40 is connected to an input of AND gate 15a. The output of door 40 is also connected to the input of an inverter circuit 40b; the output of circuit 40b is connected to an input of an AND gate 42.

Another input of this gate 42 is connected to the complemented output Q of a flip-flop RS 43. The input S of this flip-flop 43 is connected to the output of the speed detector 7. It will be recalled that the output of the detector 7 is at state "1" when the engine is stopped or when the speed is below a determined threshold.

The reset R input to "0" of flip-flop 43 like all the other reset R inputs to "0" of flip-flops 26, 31, 33 and 41 are connected to the output of circuit 29.

The output of AND gate 42 is connected to an input of AND gate 20a; the other input of this door 20a is connected both to the output Q of the flip-flop 26 and to an input of the door 15a different from that to which the output of the gate 40 is connected.

The outputs of the gates 15a and 20a are connected, as in the case of FIGS. 2 and 3, to the relays R3 and R2, R1, respectively by means of amplifiers 17, 21.

The operation of the starting device Da in FIGS. 5 and 6 is as follows.

In the case of a first start-1 ° / The engine is cold

The fleeting closing of the starter contact 5 sends a pulse "1" to an input of door 2.5; if the safety devices are respected (gearbox in neutral, cover closed), the other input of this door 25 is also in state "1" and the output of this door also changes to state "1".

The anti-rebound circuit 12 provides a slot at its output; the rising edge of this slot is transformed, by the inverter n, into a falling edge, which by attacking the input S of the flip-flop 26, changes the output Q to state "1" and the complemented output Q to l 'state "0".

It should be noted that if the driver keeps the starter contact 5 closed, the signal at the output of the reversing door n remains formed by a falling edge produced when the contact 5 closes; this falling edge is always available for the control of the flip-flop 26.

The passage of the output Q of this flip-flop 26 to the state "1" triggers the monostable bscule 27 which delivers, at its exit, a positive slot (passage from the state "0" to the state "1"); the output of the NOT OR gate 32 delivers a negative slot (passage from state "1" to state "0" with return to state "1") on the input of the first delay means 1 a. The falling edge of this negative slot triggers the first delay means 1 a. The output of these first timing means goes to state "1" and this state is transmitted by the OR gate 39 and by the AND gates 40 and 15a (for the reasons explained below) to the amplifier 17 which controls the relay R2 so that the fast preheating Cr circuit closes (fig. 5).

The glow plugs are then supplied with electric current and an intensity crosses the shunt s. The engine being assumed to be cold, the glow plugs are cold and their resistance is relatively low; the intensity passing through the shunt s is greater than i0 and the output of the detector 32 is in the state "1". The Q output of flip-flop 31 remains in the "0" state. The other input of the door 30 is in the state "1" during the switching time of the second timing means 11 a which have been triggered, during the fugitive closing of the contact 5, by the passage of the complemented output Q , of flip-flop 26, from state "1" to state "0".

As long as the output Q of flip-flop 31 is in state "0", the output of gate 30 remains in state "1" and the output Q of flip-flop 33 remains in state "0".

The tilting of the monostable 27 also triggered the third time delay means 38 which deliver at their output a signal in state "1" of a determined duration.

As the motor is assumed to be cold, the resistance of the CTN thermistor 6 is relatively high so that the voltage across the terminals of the capacitor Q1 increases relatively slowly. This voltage does not reach the reference value before the end of the slot delivered by the third delay means 38. It follows that the output of the comparator 34 remains in the state "0" while the output of the third delay means 38 is in state "1".

The output of the NAND gate 37, one input of which is in the "0" state and the other in the "1" state, is in the "1" state. The input S of the flip-flop 41 is in the state "1"; the Q output is in the "0" state while the complemented output is in the "1" state.

The second entrance of part 40 connected to this exit Q is therefore in state 1, which explains why the state "1" present at the output of the first time delay means 1 a is transmitted to the input of gate 15a.

The second entry of this door 15a is in the state "1 which is that of the exit Q of the rocker 26. This explains why the state" 1 " is also transmitted to the amplifier 17 which controls the. fast heating Cr circuit closed.

The inverter circuit 40b applies the state "0" to one of the two inputs of door 42 so that the output of this door 42 and the corresponding input of door 20a are in the state "0"; it is the same for the output of the door 20a, which prohibits the activation of the slow preheating and the starter.

The maximum duration of switching over of the first delay means 1a is relatively short, and determined, as explained previously with reference to FIG. 7.

It is therefore possible that the output of the first delay means 1a return to the state "0" before the candle has reached the temperature 00, corresponding to the intensity io passing through the shunt s.

The bypass circuit established by the AND gate 28 enables rapid preheating to be maintained.

Indeed, the input of gate 28 connected to the complemented output Q of the flip-flop 31 is in the state "1" while the other input of this gate 28 connected to the output Q of flip-flop 28 is also in state "1". The output of the gate 28 connected to an input of the OR gate 39 is therefore in the state "1" and maintains the rapid preheating order.

When the glow plugs reach the temperature θ _o , their resistance (which increases with increasing temperature) is such that the intensity passing through the candles is equal to i _o , this intensity tending to decrease.

The crossing of this value i _o , in the direction of decreasing values, causes the tilting of the intensity detector K whose output goes to the state "0".

The falling edge, applied to the input S of the flip-flop 31, changes the output Q of this flip-flop to state "1" and the complemented output Q in state "0".

The output of the monostable 27 had returned to the state "0" well before the change of state of the output Q of the flip-flop 31. The two inputs of the NOR gate 32 were therefore in the state "0" and the output was in state "1".

The change of state of the output Q of the flip-flop 31 causes the passage from the state "1" to the state "0" of the output of the gate 32, which causes a re-triggering of the first time delay means 1a .

Therefore, from this rediscovery, the first delay means 1a will ensure the maintenance of rapid preheating for a time Δto≤Δtm.

We thus see, referring to Figure 7, that we apply to the glow plug, from the moment it crosses the temperature θ O, a rapid preheating which we are sure will not heat the candle above the temperature θf.

When the output of the first delay means 1 a after this re-trip returns to the state "0", the rapid preheating ceases. Indeed, the output of gate 28, since the complemented input Q of flip-flop 31 has changed to state "0", is also found in state "0". When returning to "0" from the output of the first. time delay means 1 a, the two inputs of OR gate 39 are at "0" which causes the state "0" at the output of gate 15a and the end of rapid preheating.

On the other hand, the inverter circuit 40b puts the associated inputs of door 42 in state "1", the output of which also changes to state "1"; it is the same for the output of the door 20a, which ensures the activation of the slow preheating and the starter.

The switching time Δto of timer 1a depends on the temperature of the motor sensed by the CTN 6 thermistor.

2 '/ The engine is warm (first start).

This is the case where the glow plugs are at a temperature well below θo, while the engine is warm.

Most of the explanations given above remain valid.

However, because the engine is hot, the value of the resistance of the CTN 6 thermistor is low. If the motor temperature exceeds a predetermined limit depending, in particular, on the value of the thermistor 6, the capacitor Q1 and the setting of the comparator 34, the voltage across the terminals of the capacitor Q1 will exceed the reference voltage, displayed by the cursor 35 , before the output of the third time delay means 38 has returned to "0".

During this overrun, the output of comparator 34 changes to state "1" so that the two inputs of NAND gate 37 are in state "1"; the output of this gate 37 goes from state "1" to state "0". The falling edge changes the complemented output Q of the flip-flop 41 from state "1" to state "0". The output of door 40 goes to state "0" so that rapid preheating is stopped, while the activation of slow preheating and the starter is controlled.

Case of a hot glow plug.

This is the case of the second start order mentioned previously; this is, in particular, a start command given shortly after the engine has been switched off after running (engine still warm) or a start command which follows shortly after, a start command previous.

The first delay means 1a will be triggered when the contact 5 of the starter is closed as explained above.

However, if the temperature of the candles is close to 00 or higher than 00, the intensity which crosses the shunt s, will become or is lower than i _o . The output of the intensity detector K will pass from state "1" to state "0" which changes the output Q of flip-flop 31 to state "1".

The second timing means 11a are adjusted so that when the spark plug, at the start, has a temperature slightly lower (or a fortiori higher) at 00, the passage of the output Q of the flip-flop 31 to the state "1 "occurs before the output of the second timing means 11a has returned to the state" 0 ". The two inputs of the NAND gate 30 being in state "1", the output of this gate 30 changes from state "1" to state "0" which causes the output Q to change state of flip-flop 33, this output Q passing from state "0" to state "1".

This transition to state "1" of the output Q of the flip-flop 33 resets to "0" the output of the first delay means 1a. As, moreover, the complemented output Q of the flip-flop 31 is in the state "0", the output of the gate 28 is also in the state "0". The two inputs of OR gate 39 are in the "0" state and rapid preheating is stopped.

The activation of the slow preheating and the starter is controlled via the doors 42 and 20a.

It should be noted that, in all cases, when the internal combustion engine reaches a sufficient speed causing the output of the speed detector 7 to go from the state "1" to the state "0", the output Q of the flip-flop 43 changes from state "1" to state "0"; the output of door 42 also goes to state "0", which controls the stopping of slow preheating and of the starter supply.

The diagram in FIG. 8 summarizes the explanations of operation given above.

FIG. 9 is a diagram summarizing the states at different points of the circuit of FIG. 6.

The upper line in FIG. 9 represents the output of the anti-rebound circuit 12.

The second line represents the output of the inverter n.

The third line represents the Q output of flip-flop 26.

The fourth line represents the exit Q of this rocker 26.

The fifth line represents the output of the second timing means 11a.

The sixth line represents the output of the monostable seesaw 27.

The seventh line represents the states at the exit Q of rocker 31.

The eighth line represents the states at the. door exit NO OR 32.

The ninth line represents the state at the output of the first timer means la.

The tenth line represents the states at the output of AND gate 28.

The eleventh line represents the closing time of the rapid preheating circuit.

The re-triggering of the first delay means 1a, when the intensity passing through the shunt passes through the value i _o appears clearly on the tenth line of the diagram of FIG. 9.

Quick spark plugs b generally having a low thermal inertia, it is advantageous to maintain post-heating after starting the internal combustion engine to avoid stalling.

Figure 10 shows a circuit for performing such post-heating.

The output Q of the flip-flop 43 of FIG. 6 is connected to the input of a timer 44 which is triggered by the transition from state "0" to state "1" of output Q. The output of timer 44 controls, via an amplifier 45, the commissioning of a post-heating circuit; this post-heating circuit can be confused with the slow heating circuit CI. In this case, the amplifier 45 commands the closing of the working contact of the relay R2 (FIG. 5).

The time during which the candles b are kept supplied with post-heating can be of the order of 10 to 30 seconds.

FIG. 11 is a diagram showing an alternative embodiment of the slow preheating circuit Post-heating nail, according to which the reduction in the voltage applied to the spark plugs b, instead of being obtained by a voltage drop through a resistor 2 (fig 5) with loss of electrical energy, is obtained by chopping, over time, the candle supply.

The spark plugs b are connected in parallel in the emitter circuit of a power transistor 46 of the NPN type. The base of this transistor is connected to the output of an AND gate 47 whose input 47a permanently receives slots 48 (whose duty cycle can be adjusted), delivered by a multi-vibrator 49. The frequency of the signals 48 is relatively low, on the order of 1 Hz.

Another input 47b of door 47 is connected to a point on the control circuit on which a state "1" appears when the slow preheating or postheating order is given; for example, this input of door 47 can be connected to the output of amplifier 21 in FIG. 6, and, optionally, to that of amplifier 45 in FIG. 10.

When slow preheating or post-heating is activated, the output of gate 47 will periodically change to state "1" in synchronism with signals 48. Transistor 46 will be periodically conductive; the plugs b supplied by a chopped current will be subjected to an average voltage lower than that of the battery.

The transistor 46 could be replaced by a GTO thyristor (whose trigger makes it possible to stop the conduction).

Figure 12 is a variant of the diagram of Figure 11 in which the transistor 46 controls the spark plugs b via a relay 50 whose control winding is connected in the collector circuit of the tran sistor 46; a working contact of this relias 50 is mounted on the supply circuit in parallel with the spark plugs b, from the + pole of the battery. This work contact will open and close in synchronism with signals 48.

FIG. 13 is a diagram intended to introduce a limitation of the time during which the starter is supplied with electric current during an attempt to start.

The output of gate 20a in FIG. 6 is connected on the one hand, to an input of an AND gate 51, and on the other hand, to the input for triggering a timer 52. The output of this timer 52 is connected to another entrance to door 51.

. The output of gate 51 is connected to amplifier 21.

The output of timer 52 goes to state "1" and remains in this state for a determined time, when the output of gate 20a goes to state "1".

As soon as the output of the timer 52 returns to the state "0", the output of the gate 51 returns to the state "0" and the starter supply ceases.

In the absence of such a device, the starter M would run the risk of depleting the battery, in particular in the case of an engine whose pump would be primed.

The diagram in Figure 14 is that of a safety circuit intended to prevent the starter from being supplied if conditions such as gear shift lever in neutral position, hood closed, etc. are not met.

For this, the output of the door 20a shown in Figure 6, is connected to an input of a door AND which can be the door 51 of Figure 13. Another input of this door 51 is connected to the contact line security which leads to an entry of the door 25 of FIG. 6. The safety contact line gives the state "1" only when all the safeties are satisfied.

The connection of the safety contacts S1, S2 to an input of the door 25 (fig. 6) does not involve the safety devices which for the period preceding the launching of the start-up sequence.

The device of FIG. 14 or a similar device makes the safeties operative after the launching of the start-up sequence.

It should be noted, in general, that the various electronic circuits remain normally, permanently supplied with electric current by the link 9 (fig. 1 and 5) after switching off the contacts 5 and 4. The various time delays provided in the device are advantageously with integrated circuits of the CMOS type who consume little.

Means can be provided, in the event of a cut in the electrical supply to the electronic circuits, to restore all the circuits to the desired states. In the case where the vehicle includes a diagnostic socket connected to a tachometer sensor, this sensor advantageously forms the sensor 8.

• θo de l'ordre de 550°C
• 0d de l'ordre de 1200°C
• 0m de l'ordre de 1100°C
• θf de l'ordre de 1050°C
• Δtm de l'ordre de 5 s.

To clarify the ideas, one can indicate the following numerical values which are not limiting:

• θo of the order of 550 ° C
• 0d of the order of 1200 ° C
• 0m of the order of 1100 ° C
• θf around 1050 ° C
• Δtm of the order of 5 s.

The device of the invention therefore makes it possible to considerably reduce the preheating time without danger of deterioration of the spark plugs.

It is clear that it is not essential, in certain cases, to provide a special slow preheating circuit; closing the starter supply circuit may be sufficient to cause the voltage across the glow plugs to drop in a sensible manner, leading to slow preheating.

Claims (20)

1. Warming-up device for starting an internal combustion engine of the Diesel type or the like comprising a heater plug (b) in each cylinder, the heater plug being adapted to be energized electrically to preheat a combustion chamber, the device comprising a fast preheat circuit (Cr) adapted to connect each heater plug (b) to a relatively high voltage, the fast preheat circuit (Cr) being put into operation at the start of preheating by closure of the starter contact (5), the device also comprising a slow preheat circuit (CI) adapted to connect each heater plug to a lower voltage after a fast preheat period determined by first delay means (1, 1 a), characterised in that the first delay means (1, 1 a)are combined with engine-temperature-sensitive means (6; 6, Q₁, L) devised so that the fast preheat time depends upon engine temperature; and control means (3, 3a) actuated by closure of the starter contact (5) are adapted to close the starter (M) energization circuit automatically upon interruption of the fast preheat circuit (Cr) and to close the slow preheat circuit (CI).

2. A device according to claim 1, characterised in that it has means (B) which are sensitive to a previous start order and which are so combined with control means (3, 3a) as to inhibit or stop actuation of the fast preheat circuit for a predetermined period of time after a start attempt.

3. A device according to claim 1 or 2, characterised in that it has means (7) which are sensitive to engine conditions and which are adapted to initiate stoppage of the starter (M) and of slow preheat (CI) when the engine runs fast enough.

4. A device according to claim 2, characterised in that the means (B) sensitive to a previous start order comprise second delay means (11, 11 a).

5. A device according to claim 4, characterised in that the second delay means (11) are triggered when, after a closure followed by an opening of a starter contact (5), a main contact (4) opens.

6. A device according to claim 5, characterised in that it has means (G) to prevent triggering of the second delay means (11) if there has been a closure and subsequent opening of the main contact (4) without any closure followed by an opening of the starter contact (5), the means (G) comprising a trigger stage D (g1) and a trigger stage R/S (g2) in combination.

7. A device according to any of claims 4 to 6, characterised in that when triggered the second delay means (11) output a signal inhibiting actuation of the fast preheat circuit for a predetermined time but allowing slow preheat and energization of the starter.

8. A device according to claim 7, characterised in that the output of the first delay means (1) is connected: to one input of an AND-gate (15) whose output controls, possibly by way of an amplifier (17) and relay (R3), actuation of the fast preheat; and to the input of an inverting gate (18) whose output is connected to the input of an OR-gate (19), the output thereof being connected to an input of a second AND-gate (20) whose output controls, by way of an amplifier (21) and relay (R2, R1), actuation of the slow preheat and of the starter, the output of the second delay means (11) being connected to another input of the OR-gate (19) and, by way of an inverting gate (16), to another input of the first AND-gate (15), a second input (20f) of the second AND-gate (20) being driven by a signal produced upon closure of the starter contact (5).

9. A device according to claim 8, characterised in that the first AND-gate (15) and the second AND-gate (20) have a third input connected to an engine conditions detector (7) adapted to output a preheat-inhibiting signal when the engine runs fast enough.

10. A device according to claim 8 and/or 9, characterised in that, to automate the sequence of fast preheat and slow preheat with energization of the starter, it comprises means (22) adapted to store the transient closure of the starter contact in order to maintain, at that input of the second AND-gate (20) which is normally energized by the starter contact closure signal, an instruction to actuate the slow preheat and energization of the starter.

11. A device according to claim 10, characterised in that the storage means (22) comprise a trigger stage D (23) whose timing input (23c) is adapted' to be energized by the transient starter contact (5) closure signal, while its input D (data) (23d) is connected to the output of a third AND-gate (24) having two inputs, one receiving the output signal of the engine condition detector (7) and the other receiving a signal appearing upon closure of the main contact (4), the output of trigger stage D being connected to an input of the second AND-gate (20).

12. A device according to claim 4, characterised in that the means (B) which respond to a previous start order comprise means (H) sensitive to the temperature of the heater plug in combination with second delay means (11 a), the whole being so devised that rapid preheat stops if the plug temperature reaches or exceeds a value θ_o in a time interval subsequent to closure of the starter contact (5) and less than the trigger time of the second delay means (11a), in which event slow preheat and 'energization of the starter are initiated.

13. A'device according to claim 12, characterised in that the plug-temperature-sensitive means (H) take the form of a current detector (s, K) serving to deduce the plug temperature from the current drawn by the plug when energized at a known voltage.

14. A device according to claim 13, characterised in that the output of the current detector (K) is connected by way of trigger stage RS (31) to one input of a NAND gate (30) having another input connected to the output of the second delay means (11 a), the output of the NAND gate (30) being connected to the input of a trigger stage (33) having an output connected to a zero resetting input of the first delay means (1a).

15. A device according to any of claims 12 to 14, characterised in that the first delay means (la) are adjusted for a maximum triggering time (Atm) such that if a heater plug at a temperature of θ_o experiences for this maximum triggering time a relatively high (rapid preheat) voltage, the temperature. (θf) which will be reached by the heater plug at the end of the maximum triggering time will definitely not damage the heater plug.

16. A device according to any of claims 12 to 15, characterised in that the whole is so devised that, in the event of a plug being cold, the first delay means (1a) and the fast preheat are triggered upon closure of the starter contact (5), and when the heater plug reaches the temperature 0₀ at an instant of time to, the first delay means (1a) are retriggered so that the heater plug experiences fast preheat for a maximum time Δt1 +Atm, depending upon the delay, with effect from the instant of time to.

17. A device according to the whole of claim 13 and claim 16, characterised in that the current detector (K) is adapted to actuate, upon a value i_o (corresponding to the temperature 8₀) being reached, on the basis of the current drawn, a change of state of the output of the associated trigger stage (31), such change of state initiating retriggering of the first delay means ( a).

18. A device according to claim 16 or 17, characterised in that it comprises a bypass circuit for the first delay means (1a), the bypass circuit comprising and AND-gate (28) and enabling fast heating to be maintained.

19. A device according to any of claims 12 to 18, characterised in that the means for controlling the stoppage of fast preheat and the changeover to slow preheat with starting if the engine is warm enough comprise: third delay means (38) adapted to output a triggering pulse of predetermined duration; and means (L) for reading the charge of a capacitor (Q1) through an engine-temperature-sensitive resistance CTN (6), fast preheat being stopped and slow preheat being started together with energization of the starter if the voltage across the capacitor (Q1) reaches a predetermined value in a time less than the triggering pulse of the third delay means (38), the pulse duration possibly being of the order of 0.5 second.

20. A device according to claim 19, characterised in that the means (L) for reading the charge of the capacitor (Q1) comprise a comparator (34) adapted to compare the voltage across the capacitor (Q1) with a reference voltage, the comparator output being connected to one input of a NAND gate (37) whose other input is connected to the output of the third delay means (38).

Images