DE3118501A1 - SAFETY DEVICE FOR A DIESEL INJECTION COMBUSTION ENGINE WITH EXHAUST TURBOCHARGER - Google Patents

Description

Safety device for a diesel injection internal combustion engine with exhaust gas turbocharger

The invention relates to a safety device for a diesel injection internal combustion engine with exhaust gas turbocharger, with a fault detector that, when a Error a ventilation valve for a boost pressure-dependent Vollastansehlag for the control element of the injection pump controls.

In a known safety device of this type the fault detector speaks of an excessive temperature of the exhaust gases (US Pat. No. 4,157,701). The exhaust gas temperature is for the particularly critical error in a charged diesel internal combustion engine, an excessively high boost pressure imprecise and sluggish indicator. Such a fault occurs, for example, in an exhaust gas turbocharger in which a bypass control on the supercharger or turbine side limits the maximum charge pressure to when the one used for this purpose Bypass valve fails. Excessive boost pressure can result in engine damage.

The invention is based on the object eii. Safety device to create the type mentioned at the beginning, which is able to react quickly and safely to an increase in the pressure appeals to.

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The invention solves this problem in that the fault detector is a pressure sensor to which the charging pressure is applied which responds to an excessive boost pressure value.

Such a pressure sensor reacts immediately and quickly to excessively high boost pressure and controls it Immediately the vent valve falls, so that the full load stop is withdrawn and thus the maximum Injection quantity is reduced * This astonishingly simple measure can cause engine damage in the majority the errors that occur can be avoided.

,and through

The withdrawal of the stop triggered by a sensor caused for the control element of the injection pump

From DE-AS 21 55 420 is known per se torque reduction of the internal combustion engine. As in the invention, a ventilation valve is controlled for the full load stop. A safety device for an internal combustion engine is also known (DE-Gm Jk 37 6T4), which takes back the full load stop for the control element of the injection pump in the event of an impermissibly high boost pressure. A servomotor is used for this. It is also known (DE-OS 27 09 667) to ventilate an actuator that can be acted upon by the charge air pressure in order to adapt the control characteristic in accordance with the changing charge air pressure when the charge air pressure is too high. None of the cited publications shows the measure according to the invention of ventilating the boost pressure-dependent full load stop at an impermissibly high boost pressure.

None of the publications deal with you further problem, which is solved by the invention. In the ideal case, a conventional pressure sensor has no switching hysteresis. This means that when its response value is exceeded, it causes the full-load stop to be ventilated

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and this ends again immediately * if it falls below its target value. Since the response value is often not reached relatively quickly due to the ventilation of the full load stop, the ventilation is ended just as quickly. If there is an error such as the failure of the bypass control valve mentioned at the beginning, the boost pressure immediately rises again above the response value when the ventilation is terminated, whereupon the ventilation of the full load stop immediately starts again * The result is a so-called sawing and associated with it a frequent overshoot of a boost pressure value that is critical for the internal combustion engine. By means of a further development of the invention, this problem can be eliminated in a surprisingly simple manner. For this purpose, the pressure sensor has a response in such a way that it only switches the ventilation valve ineffective again far below a normal value of the boost pressure. If _{necessary, the} boost pressure can only rise again when the ventilation valve is closed again. To do this, however, the boost pressure must have dropped considerably. As a result, the rise and fall periods of the boost pressure are considerably lengthened, as a result of which the critical response value of the pressure sensor is exceeded much less frequently.

The pressure sensor and the auxiliary valve can be in different Cooperate way .. The pressure sensor can be a generate electrical signal and a 41ektromagnetisries Control ventilation valve ^., This * solution is characterized by constructive simplicity from »

Furthermore, the ßruoicseiisor and the ventilation valve can be designed in one piece as a three-way valve. The two intake ports are loaded with "the loading pressure or with atmo> spherical pressure * The ^ outfeed Ansehl% is related to the full-load in combination. A double valve member for the two feed ^ports! Keeps the connection

* and possibly at the same time an acoustic and / or optical warning display ■ _; ..

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to boost pressure under the action of a spring against the

Boost pressure open up to the response value of the boost pressure and closes the connection to the atmosphere. At and above that Response value of the boost pressure, the double valve member closes the connection to the boost pressure and opens the connection to the atmosphere. This solution is particularly inexpensive and fail-safe. '

To increase safety, a relief valve can be arranged in a gas duct of the internal combustion engine the boost pressure is limited to a maximum value above the response value of the pressure sensor. It has shown, that especially in the case of highly charged diesel internal combustion engines by reducing the full load stop a sufficient boost pressure and thus torque reduction cannot be achieved in every case. By using a relief valve, the maximum boost pressure can now be exceeded with certainty It is known (US Pat. No. 3,913,542) to use a relief valve to reduce the boost pressure of a turbocharged To keep internal combustion engine at a constant value. The relief valve does not serve as a Safety device that is only effective in the event of a fault, but is always, d. H. even under normal operating conditions effective. A special safety device in the event of an error is not provided.

The relief valve can be arranged in various ways. So it is possible to switch this valve between the Internal combustion engine and the turbine to be arranged in parallel to the bypass valve that is usually provided. In contrast an increase in the accuracy with regard to the point of use can be achieved in a simple manner in that the Blow-off valve in the intake duct between the charger of the exhaust gas turbocharger and the internal combustion engine is and at maximum value of the boost pressure Opens. As an alternative or in addition to such a blow-off valve, in the intake duct Before or after the charger, a throttle valve can also be arranged, which is at the maximum value of the boost pressure is switched on.

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A further improvement in the interaction between the pressure sensor and this relief valve in terms of effectiveness can be achieved in that the tolerance range of the boost pressure values for opening the relief valve to the Response value of the pressure sensor or its tolerance range connects continuously. This avoids the relief valve toler -! ^ conditionally before the pressure sensor responds opens and the amount of air supplied to the internal combustion engine is reduced while the amount of fuel remains unchanged. The consequence of this would be a considerable impairment of both the internal combustion engine and the environment, since coking phenomena the internal combustion engine and soot formation would inevitably be the result. Üuroh this training the invention ensures that the reduction in the amount of fuel precedes the reduction in the amount of air or = in the worst case coincides with it. This means that there is always a sufficient amount of air for a soot-free Combustion of the amount of fuel supplied.

Independent protection is claimed for the features of claims 2, 5, 6 and 8.

The invention is illustrated by means of one in the drawing Embodiment further explained. This shows a safety device for a diesel injection internal combustion engine with exhaust gas turbocharger to avoid a dangerously high jn for the internal combustion engine Boost pressure value.

A schematically illustrated diesel injection internal combustion engine 1 with several cylinders 2 is ¹ ″, an exhaust gas turbocharger 3 with a charger 5 and one driven by it

Assigned to turbine 4. The turbine 4 are via an exhaust duct 6, the exhaust gases of the internal combustion engine 1 are supplied. From the Exhaust duct 6 branches off a bypass line 7 in which a

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Control valve 8 is arranged. This controls the amount of exhaust gas carried past the turbine 4 as a function of the Boost pressure «;

The boost pressure is rigidly coupled with the turbine 4 Loader 5 generated. The air supplied to the charger 5 via an intake duct 9 is compressed by the charger 5 and arrives via a charge air line 10 in a charge air collector 11, from which it is fed to the cylinders 2 will.

The valve chamber 13 is connected via a connecting line 12 of the control valve 8 is connected to the charger 5 and therefore subjected to the charge air pressure. This becomes the control valve 8 adjusted according to the charge air pressure against the action of a spring 14 so that the turbine 4 supplied The amount of exhaust gas is approximately constant. The boost pressure therefore also has a constant value of z. B. 0.8 bar.

The injection of the amount of fuel required in each case takes place with the aid of an injection pump 15 whose control element not shown in its movement by a pneumatically controlled with the help of a pressure cell 16, also in detail not shown full load stop is limited in a known manner. The pressurized can 16 is, provided the boost pressure has the specified normal value, with the charge air collector 11 via a line 17 connected and therefore acted upon with the charge air pressure.

If the charge air pressure, for example in the case of a faulty Failure to open the control valve 8 increases, two safety measures are to avoid engine damage intended.

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The first consists in an electromagnetic ventilation valve 18, which is arranged in the line 17 and its valve member 19 shown schematically is controlled by a pressure sensor 20. The pressure sensor 20 is also charged with the charge air pressure and speaks at an excessive charge air pressure of z. B. 0.9 bar. He then controls the ventilation valve 18, the valve member 19 of which is dashed from the position shown in the figure position shown is moved electromagnetically. In this the connection of the line 17 to the charge air collector 11 interrupted and the part of the line leading to the pressure cell 16 is ventilated. The valve member 19 is a connection for this purpose 2 1 of the ventilation valve 18 exposed to the atmosphere »

By venting the pressure cell 16, the full load stop of the injection pump 15 is reduced adjusted to the maximum amount of fuel. The consequence of this can be actual, depending on the position of the control element Reduction in the amount of fuel injected be »This has a reduction in the amount of exhaust gas and therefore a reduction in the turbine speed result. This can often lead to a reduction in the charge air pressure to the normal value can be achieved.

Especially in the case of highly charged internal combustion engines, this reduction in the maximum amount of fuel can be insufficient be. In order to avoid a possible further increase in the charge air pressure in this case, the second safety measure is a relief valve 22 is arranged in the charge air line 10 at a charge air pressure of ζ. Β. 1 bar opens and the charge air pressure to this value limited. This ensures in any case that the charge air pressure under no circumstances has a value Vt η 1 bar overlooks. This value is chosen so that even then

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if the charge air pressure were to assume this value continuously, engine damage is very likely can be avoided.

The uninterrupted persistence of such a high charge air pressure can be avoided in most cases by taking another measure. For this purpose, the pressure sensor 20 is included provided a response hysteresis, such that it the ventilation valve 18 only well below the normal value of the Charge air pressure switches ineffective. This switching point can be, for example, at 0.5 bar - only when the charge air pressure has fallen below this value, the valve member 19 resumes the position shown firmly and closes the atmosphere connection 21.

In order to prevent the relief valve 22 from opening due to tolerances before the pressure sensor 20 responds, is the Tolerance range of the pressure sensor 20 and the relief valve 22 selected so that both connect to one another. The tolerance range of the pressure sensor 20 is, for example, 0.9 +/- 0.1 bar, while the relief valve 22 is unfavorable Case opens at 1 bar. This avoids that the amount of air with an unchanged amount of fuel is reduced with the aid of the relief valve 22. Soot formation and coking phenomena are excluded.

Instead of the pressure sensor 20 shown and the electromagnetic ventilation valve 18 controlled by it, The pressure sensor and ventilation valve can be designed in one piece as a three-way valve 23. This is in the lower part of the Drawing shown and has two supply connections 24 and 25 for the connection with the charge air collector or the atmosphere. A double valve member 26 closes up to a charge air pressure of z. B. 0.9 bar under the effect

a spring 27 the connection 25 and keeps the connection 24 open »This means that the pressure cell connected to the discharge connection 28 is subjected to the boost pressure up to zxx < this value of the charge air pressure and controls the full load stop of the injection pump 15 in a known manner.

if the load exceeds * ¹ nf \. If you press this response value, the double valve member 26 is _{shifted to the right in s of} the drawing, whereby the terminal 24 is closed and the connection 25 is opened. The connection between the pressure cell and the charge air collector Ti is interrupted at the expense of a connection to the atmosphere. The pressure cell 16 is thereby ventilated and ensures a reduction in the maximum injection quantity in the manner described. If the charge air pressure wieder'absinkt ^1, enters the double valve member 26 again iniudie 'drawn position, whereby the connection of the pressure box ^1ß: interrupted to the atmosphere and is restored to the charge air collector. 11

In order to increase the charge air pressure due to an error, also the The driver can clearly see the distance through the pressure sensor 20 At the same time as the ventilation valve 18, there is also an optical one «Nd / or acoustic warning display permanent or like that Valve 18 is switched on O · - This is shown as Marnlarape 30 shown.

In addition or as an alternative to the blow-off valve 22, a throttle valve 31 can also be arranged in the intake duct 9 or in the charge air line 10, which is activated at the maximum value of the boost pressure - for example, controlled by a further pressure sensor (not shown) and thus also an increase in the Boost pressure over the maxj.ma; len value prevented.

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Claims (1)

Patent claims: 1. / Safety device for a diesel injection internal combustion engine with exhaust gas turbocharger, with a fault detector that, if a fault occurs, a ventilation valve for a boost pressure-dependent full load stop for the control element of the injection pump controls, characterized in that the error detector is a pressure sensor (20) to which the boost pressure is applied which responds to an excessive boost pressure value. Safety device according to Claim 1, characterized in that the pressure sensor (20) has a response hysteresis possesses such that it only becomes ineffective in the ventilation valve (18) far below / a normal value of the boost pressure switches. Safety device according to claim 1 or 2, dar arch characterized in that the pressure sensor (20) controls an electromagnetic ventilation valve (18). H. Safety device according to claim 3, characterized in that the pressure sensor (20) also ei. -? audible and / or visual warning display (30) controls. BATH ORIGINAL 5. Safety device according to claim 1 or 2, characterized in that the pressure sensor and the ventilation valve are integrally formed as a three-way valve (23), the two feed connections (24, 25) with the Boost pressure or atmospheric pressure are applied and its discharge connection (28) with the full load stop (Pressure cell 16) is in connection and in which a double valve member (26) for the two supply connections (24, 25) by means of a spring (27) against the boost pressure, the connection (24) to the boost pressure up to the response value of the boost pressure keeps open and closes the connection (25) to the atmosphere. 6. Safety device according to one of claims 1 to 5, characterized in that the in a gas duct Internal combustion engine, a relief valve (22) is arranged, which the boost pressure to one above the response value of the pressure sensor (20) is limited. . 7. Safety device according to claim 6, characterized in that that the relief valve (22) in the intake duct (charge air line 10) between the charger (4) of the exhaust gas turbocharger (3) and the internal combustion engine (1) and opens at the maximum value of the boost pressure. 8. Safety device according to claim 6 or 7, characterized in that the tolerance range of the boost pressure values for opening the relief valve (22) to the response value of the pressure sensor (20 continuously connects. 9. Safety device according to one of claims 1 to 8, characterized in that a throttle valve (31) is arranged in the intake duct (10) before or after the charger (5) which is switched on at the maximum value of the boost pressure. BATH ORIGINAL