SE457899B - Turbocharged automobile engine with antiknock control - Google Patents

Abstract

The engine has a knock detector (22) attached to the engine block coupled to a microprocessor controlling the charging press and the ignition timing angle. When engine knock of a given intensity is detected the charging press is reduced via a control valve (13) while at the same time the ignition timing angle is increased, so that the knock is eliminated. The reduction in the charging press is balanced by the increase in the ignition timing angle to maintain the engine exhaust temp. at a constant value below a given max. when the engine is switched from one fuel to another with a different octane rating. The anti-knock control allows the engine to operate at its optimum point just below the knock threshold.

Description

40,457,899 to allow an increase in the charging pressure to a maximum level above the predetermined level and within a certain time the regulating means affect the lowering of the charging pressure to the predetermined level.

The invention is based on the insight that transient overcharging levels significantly above the possible level in a stable operating condition only slowly lead to knocking occurring, which i.a. caused by delays before inlet air, liquids, goods and combustion chamber temperature reach higher values. By a short-term controlled increase of the supercharging level over a car operating condition, the performance of a temporary motor is thus achieved in order, for example, to increase the acceleration short of a overtaking maneuver. The invention is described in more detail with reference to Fig. 1 schematically shows a turbocharged internal combustion engine with a device according to the invention for controlling the charge pressure and Fig. 2 shows an exemplary embodiment, in which Fig. 2 a diagram of the device according to the invention in a modified simplified embodiment.

The engine 1 shown in Fig. 1 is a four-cylinder otto engine with a per se known turbocharger unit 2, comprising a turbine part 3 in communicating connection with the engine exhaust manifold 4 and a compressor part 5 in communicating connection with the engine intake manifold 6 via a charge air cooler 7 of air-I-air type and a throttle body 8, containing the engine throttle 9.

The gas flow through the turbine 3 is regulated in a known manner by means of a shunt valve 11 connected in a shunt line 10, the damper of which is operated by a pneumatic actuator 12 and in the closed position directs the entire gas flow through the turbine. The pressure in the actuator 12 and thus the setting of the shunt valve is determined by an electromagnetic valve 13 in a line 14, which via a calibrated choke 15 connects the suction and pressure side of the compressor to each other and from which a line 16 to the actuator branches.

The valve 13 is controlled by a microprocessor 17, into which signals representing the charge air pressure are input. These signals are obtained from a sensor 18, which may be a piezoresistive transducer.

The processor is also connected to a damper position sensing H0 3 457 seem potentiometer 20 and can with the aid of the signals from this calculate the switching speed of the damper, ie. the change in the gas input. The processor stores a value of the maximum permissible boost pressure at steady state and a higher value of the maximum permissible boost pressure at transient load, e.g. during acceleration when overtaking. The processor is programmed to at a certain predetermined minimum speed of load increase, represented by a certain damper opening speed, e.g. 1 rpm, allow the charge pressure to rise to the above-mentioned higher pressure, which can be up to H5% above the first-mentioned pressure, and that thereafter within a certain period of time, e.g. about 20 seconds, gradually lower the limit of the permissible boost pressure to the level at stable operating condition. In order to prevent thermal overload due to successively transient overcharges, the processor is suitably also programmed to prevent renewed transient overcharging during a certain minimum period, after lowering the pressure to the level at a stable operating condition, e.g. about M seconds. Furthermore, the processor can be programmed to trigger the transient function by increasing the opening angle of the damper by at least 150 to prevent the influence of minor movements of the damper caused by engine vibrations or movements of the vehicle.

Fig. 2 shows the system according to the invention in a modified embodiment, where details having their equivalent in the system in Fig. 1 have received the same reference numerals as in Fig. 1.

The microprocessor is here replaced by a pressure switch 30 in a line 31, which communicates with the engine inlet pipe 6. Between the inlet pipe 6 and the pressure switch 30 a delay device 32 is connected which can be a calibrated throttle with non-return valve function, involving a throttled connection in the direction of the pressure switch 30 but unstressed connection in opposite direction. In the connection between the inlet pipe 6 and the actuator 12 of the shunt valve 11, a delay device formed by the calibrated choke 15 lies in the line lü. In addition, there is a throttle line 53 in front of the valve 13.

When the load increases (acceleration), the transient function is achieved by a delay under the influence of the throttle 32 4571 899 i ~ - from the time when the pressure in the inlet pipe reaches the pressure gauge's switching pressure and to the moment when this pressure is built up in the pressure switch. the pipe above the permissible maximum value at stable operating condition.

As soon as the pressure switch is affected by the cover pressure, the valve 13 closes, whereby the shunt valve begins to open to lower the boost pressure to the level of maximum permissible pressure in a stable operating condition. How large the extra overload will be and how long it will last is determined by the size of the throttles 15 and 33. The time of the valve closing is determined by the calibration of the throttle 32. As an alternative to the throttle 32, a time relay affected by the engine throttle can be used, which, for example, activates the accelerator pedal and is stepped on the bottom. when When tests were performed with a conventional turbocharged engine supplemented with the system according to the invention, the shunt valve actuator 12 was set to open the valve at 0.67 bar overcharging.

The switch pressure of the pressure switch 30 was set to 0.55 bar overload. The throttles 32, 15 and 33 were set, so that the maximum overcharging at acceleration was 0.8 bar and the period for closing the valve 13 was about 10 seconds.

During this time interval, the pressure in the inlet rises.

Claims (7)

10 15 20 25 30 35 457 899 Patent claims 1. l. Device for controlling the charge air pressure in a turbocharged preheating notch, comprising control means. which are arranged to limit the charge air pressure to a predetermined level. k ä n n e t e c k n a d by the fact that said regulating bodies (ll. 12) are coordinated down bodies (13. 17; 13, 30, 32). which in the event of a load increase down a certain speed influences the control means to allow the charging pressure to be raised to a naxinal level above the predetermined level and within a certain time influences the control means to lower the charging pressure to the predetermined level. Device according to claim 1, in which the control means comprise a shunt valve arranged in a shunt line past the turbine of the turbocharger. It is known that the means (13. 17; 13. 30, 32) arranged with the control means are arranged to control an actuator (12) for the shunt valve (II). that the shunt valve, when the load increases down to a certain speed, opens at a charge pressure, which is higher than the maximum permissible pressure at constant load. '' " Device according to claim 2, characterized in that the means coordinated with the control means comprise a liquor processor (17). son controls an electromagnetic valve (13). which in turn controls the shunt valve actuator (12). that a value of the maximum permissible charge air pressure at constant load and a higher value of the maximum permissible charge air pressure at load increase are stored in the processor and that the processor is connected to means for increasing the load. for example engine throttle (9) and is arranged to, when registering a certain setting speed: edge increase of the charge air pressure to the said higher pressure and then time-controlled lower the pressure to the next maximum permissible pressure at constant load. 10 15 20 25 457 899 Device according to claim 3, characterized in that the microprocessor (17) is programmed to allow, after lowering the pressure to the maximum pressure at a constant load, a renewed increase to the higher pressure only after a predetermined period of time. 5. Device according to claim 2, characterized in that the means salvaged by the control means comprise a pressure switch (30) loaded by the charging pressure on the inlet side of the notary. which at a predetermined pressure causes the shunt valve (II) to open, a delay means (32) being arranged between the inlet side of the engine and the pressure switch to provide a time interval dependent on the speed of the pressure increase in the inlet inlet between the time when the boost pressure rises to said predetermined pressure and the time of the press officer's strike. Device according to claim 5, characterized in that further delay means (15, 33) are arranged to provide a time interval between the time of onset of the pressure switch (30) and the time of opening of the shunt valve (II). Device according to claims 4 and 5. characterized in that the delay means (15. 32. 33) are pneumatic throttles.