SE529870C2 - Exhaust Brake Control - Google Patents

Abstract

The invention relates to obstruction of the exhaust gasses from an internal combustion engine of a vehicle, such that during the engine's exhaust stroke a brake torque is accomplished, which counteracts a drive torque produced during the engine's combustion phase. An adjustable valve in an exhaust conduit from the engine is controlled in response to a control signal. A set value designating a desired brake torque is received (410), an exhaust gas pressure in the exhaust conduit is registered (420), an input pressure in an air intake to the engine is also registered (430) as well as an engine parameter reflecting a speed of the engine (440). Then, a reference parameter is generated (450) in response to the input pressure engine parameter, the engine speed and either of the set value or the exhaust gas pressure. Finally, the control signal is produced (460) based on the reference parameter and either of the exhaust gas pressure or the set value.

Description

20 åæ 30 35 529 870 uncertainties and tolerances in the components included in the exhaust brake control chain (eg including the engine, control unit, exhaust system and throttle valve) mean that an actual braking torque generated by the exhaust brake cannot be predicted with sufficient accuracy directly on the basis of the adjustment of the valve. Consequently, the actual braking torque may deviate more or less from the desired value. If the braking torque is too low, the vehicle may fail to comply with applicable legal and / or certification requirements. "If, on the other hand, the braking torque is too high, there is a risk of the exhaust brake system and its components being damaged. working in the exhaust system is damaged.

SUMMARY OF THE INVENTION The object of the present invention is therefore to provide a solution which alleviates the above problems, and thus offers a predictable, reliable and efficient exhaust brake function.

According to one aspect of the invention, the object is achieved by the initially described exhaust brake system, the system including a second pressure sensor adapted to register an inlet pressure in an air inlet to the engine. In addition, the braking torque regulator includes a machining means, which is adapted to receive the registered inlet pressure and to receive an engine parameter reflecting a speed of the engine. The processing means is further “adapted to model a gas exchange work performed by the engine and based on this model generate a reference parameter in response to the registered inlet pressure and the engine parameter. The braking torque regulator also includes a control means which is adapted to receive at least the reference parameter, and on the basis thereof generate the control signal. That is, the control signal is generated, directly or indirectly, based on the registered exhaust pressure, the reference parameter and a given value, which indicates a desired braking torque.

An important advantage achieved with this system is that the control signal is generated on the basis of a model that describes a gas exchange work performed by the engine. Preferably, a feedback loop is used to determine how well a current adjustment of the exhaust brake valve matches the desired braking torque. This allows the valve to be adjusted very precisely regardless of whether one or more components in the control chain deviate reasonably much from its nominal characteristics. According to an embodiment of this aspect of the invention, the processing means is adapted to receive the specified value, and on a further basis thereof, generate the reference parameter in the form of a first modeled parameter reflecting an estimate of the exhaust pressure in the exhaust line. Thus, the gas exchange model for the engine can be implemented by the processing means basing its generated estimate of the exhaust pressure on the inlet pressure registered in the air inlet to the engine, the engine speed and the specified value.

Preferably, the control means is further adapted to receive this estimate of the exhaust pressure and to receive the exhaust pressure registered in the engine exhaust line. In response, the control means is adapted to generate the control signal to the adjustable valve. Accordingly, the control means can generate the control signal in order to minimize an error between the registered and the estimated exhaust pressure. According to another embodiment of this aspect of the invention, the control means is specifically adapted to implement a proportional-integrating-derivative-algorithm. This ensures a desirable balance between response time, accuracy and stability.

According to yet another embodiment of this aspect of the invention, the processing means is instead adapted to receive the registered exhaust pressure. On a further basis thereof, the processing means is adapted to generate the estimated reference parameter in the form of a second modeled parameter reflecting an estimate of the desired braking torque. Thus, a gas exchange model for the engine, which is implemented by the processing means, can base its estimation of the desired braking torque on the registered inlet pressure in the air intake to the engine, the exhaust pressure registered in the exhaust line and the engine speed.

Consequently, the control means can generate the control signal in order to minimize an error between the estimated braking torque and the actually desired braking torque (determined by the specified value).

According to another embodiment of this aspect of the invention, the control means is specifically adapted to implement a proportional-integrating-derivative algorithm, which offers a desirable balance between response time, accuracy and stability.

According to another aspect of the invention, the object is achieved by the motor vehicle described initially, the vehicle including an internal combustion engine and the exhaust brake system proposed above. This system is in turn configured to apply an adjustable braking torque with respect to at least one drive shaft of the engine. According to another aspect of the invention, the object is achieved by the method initially described, wherein an inlet pressure is registered in an air inlet to the engine; an engine parameter 'is recorded which reflects an engine speed. A reference parameter is generated based on a model for a gas exchange work performed by the engine and in response to the registered inlet pressure and the registered engine parameter. Finally, the control signal is generated on an additional basis by the reference parameter.

The advantages of this method, as well as the preferred embodiments thereof, are apparent from the discussion above with reference to the proposed exhaust brake system.

According to a further aspect of the invention, the object of a computer program product is achieved directly chargeable to the internal memory of a computer comprising software for controlling the above-proposed 'method when' said program is run on a computer.

According to another aspect of the invention, the object is achieved by a computer-readable medium with a program stored thereon, the program being adapted to cause a computer to control the method proposed above.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail by means of embodiments, which are described by way of example, and with reference to the accompanying drawings. shows a block diagram of an exhaust brake system according to a first embodiment of an exhaust brake system according to the invention, * Figure 1 shows a block diagram of an exhaust brake system according to a second embodiment of an exhaust brake system according to the invention, Figure 2 schematically shows a motor vehicle equipped with the proposed exhaust brake system , and Figure 3 Figure 4 shows a flow chart illustrating the general method according to the invention. DESCRIPTION OF EMBODIMENTS OF THE INVENTION We first refer to Figure 1, which shows a block diagram of an exhaust brake system according to a first embodiment of an exhaust brake system 100 according to the invention. The proposed system 100 operates against an internal combustion engine 110 of a vehicle, the engine 110 receiving incoming air Am via an air intake 140 and emitting exhaust gases Em via an exhaust line 150. The system 100 includes an adjustable valve 135, a first pressure - sensor 155, a second pressure sensor 145 and a braking torque regulator 160, here in the form of an electronic control unit (ECU = electronic control unit). This controller 160 in turn includes a controller 130 and a processing means 120. Each of the means 120 and 130 may be implemented in hardware as well as in firmware or software. That is, one or both of the organs 120 and 130, respectively, can be represented by a physical unit, or a firmware / software module. The adjustable valve 135 is arranged in the exhaust line 150.

The valve is adapted to prevent the exhaust gases EN, in the line 150 in response to a control signal C. The valve 135 is preferably connected to an arm and piston arrangement (not shown), which is controlled, for example, electronically or pneumatically. A braking effect is produced if the control signal C, which may be a pulse width modulated (PWM = pulse width modulated) electrical or optical signal, controls at least one obstructing element of the valve 135 to assume a position in which the exhaust gases experience a resistance that is higher than otherwise. Thus, a braking torque occurs during the exhaust phase of the engine 110. The braking torque either counteracts a driving torque generated during the combustion phase of the engine 110, or it produces a torque that reduces the vehicle's kinetic energy (or torque), for example when the vehicle rolls down a slope. As a result, a braking effect arises with respect. on the drive shaft of the engine 110 (that is, the shaft intended to transmit propulsive energy to the drive wheels of the vehicle). Especially for heavy vehicles, such as trucks and buses, this is a desirable complement to the conventional braking system.

The first pressure sensor 155 is adapted to register an exhaust pressure Pm in the exhaust line 150 between the engine 110 and the valve 135. Of course, the gas pressure Pm for a given amount of exhaust emissions from the engine 110 becomes higher if the adjustable valve 135 is adjusted in a more obstructive mode.

The control means 135 is adapted to receive the exhaust pressure Pm registered by the first pressure sensor 155, and to generate the control signal C at least in part based on this pressure Pm. The control signal C is also generated, directly or indirectly, based on a specified value.

Tæq which indicates a desired braking torque. The specified value Tæq can in turn either be assigned manually by an operator driver (for example via a pedal or lever), or this parameter can be generated automatically by a control means in the vehicle, which is for example adapted to limit the amount delivered. white smoke, or to provide a rapid heating of the engine 110.

In this embodiment of the invention, the processing means 120 is adapted to receive an inlet pressure Pm registered by the second pressure sensor 145, which is arranged in the air inlet 140.

In addition, the processing means 120 is adapted to receive an engine parameter rpm reflecting a speed of the engine 110 (i.e., the number of revolutions per minute performed by the crankshaft of the engine 110). The processing means 120 is adapted to generate a reference parameter Pm_mod in response to these parameters rpm, Pin and Tæq. According to the invention, the processing means 120 is adapted to model a gas exchange work performed by the engine 110. Here the processing means 120 generates the reference parameter in the form of a first modeled parameter Pm_mod which reflects an estimate of the exhaust pressure in the exhaust line 150 between the engine 110 and the valve 135. The first modeled parameter Pmmcd is generated based on the engine speed rpm, the exhaust pressure Pm and the specified value T, eq.

The control means 130 is adapted to receive the reference parameter (i.e. here the first modeled parameter Pm_m ° d) and generate the control signal C on the basis thereof together with the above-mentioned gas pressure Pm. Preferably, the controller 130 is specifically adapted to implement a proportional-integrating-derivative algorithm, which in turn is adapted to generate the control signal C in order to minimize an error between the registered exhaust pressure Pm and the first modeled parameter Pm_m ° d (which represents the estimator's estimate of this pressure).

Thus, a stable and precise adjustment of the valve 135 can be effected, so that an actual braking torque is applied to the drive shaft of the vehicle, which quickly approaches the desired braking torque determined by the specified value Tæq.

Figure 2 shows a block diagram of an exhaust brake system according to a second embodiment of an exhaust brake system according to the invention. All reference numerals appearing in Figure 2, which are identical to those used in Figure 1, indicate the same entities, parameters and variables as described above with reference to this figure. Similarly to the embodiment shown in Figure 1, in this embodiment of the invention the control means 130 is thus adapted to receive a reference parameter Tmod and generate the control signal C based thereon. In this case, however, the controller 130 also receives the specified value Tæq directly. Preferably, the controller 130 is specifically adapted to implement a proportional-integrating-derivative algorithm, which in turn is adapted to generate the control signal C in order to minimize an error between the specified value Treq and the second modeled parameter Tmod. In addition, in this embodiment of the invention, the processing means 120 is adapted to receive both the registered inlet pressure Pin and the registered exhaust pressure Pm in addition to the engine parameter rpm which reflects the engine 110 speed. Based on these parameters Pm, Pm and rpm, the processing means 120 is adapted to generate the reference parameter Tmod, which here reflects an estimate of the desired braking torque determined by the specified value Treq.

Accordingly, the processing means 120 is adapted to apply a model of the gas exchange work performed by the engine 110, which is substantially the opposite of the model applied by the control means shown in Figure 1. Such a model reversal is relatively straightforward if the modeled relationship between braking torque and exhaust pressure is linear.

Figure ~ 3 schematically shows a motor vehicle 200 in the form of a truck, which is equipped with the proposed exhaust brake system 100. The vehicle 200 includes an internal combustion engine 110 with an air inlet 140 and an exhaust line 150 for receiving air Am and emitting exhaust gas Em, respectively. The exhaust brake system 100 is configured to apply an adjustable braking torque g to at least one drive shaft of the engine 110 by adjusting a valve in the exhaust line 150 so that the exhaust gases Em from the engine 110 experience increased resistance.

Preferably, the system 100 includes, or is associated with, a computer readable medium 170 (e.g., a memory module) which stores a program adapted to cause at least one controller in the vehicle 200 to perform the steps described above.

For the purpose of summarizing, the general method according to the invention will now be described below with reference to the flow chart in Figure 4.

A first step 410 receives a specified value which determines a desired braking torque to apply to the drive shaft of the vehicle; a second stage 420 records an exhaust pressure in an exhaust line from an internal combustion engine in the vehicle; a third stage 430 registers an inlet pressure in an air inlet to the engine; and a fourth step 440 records a speed of the engine. Steps 410, 420, 430 and 440 can be completed in any order relative to each other, as well as in parallel.

In any case, these steps are followed by a step 450, in which a y reference parameter is generated. The reference parameter either reflects an estimate of the exhaust pressure in the exhaust line, or an estimate of the desired braking torque. The reference parameter is generated in response to (i) the inlet pressure, the engine parameter and the specified value, provided that the reference parameter reflects an estimate of the exhaust pressure; and (ii) if the reference parameter reflects an estimate of the desired braking torque, the reference parameter is generated in response to the inlet pressure, the exhaust pressure and the engine parameter.

Thereafter, a stage 460 generates a control signal for the adjustable valve, in order to prevent the exhaust gases from the engine and thus provide a braking torque during the exhaust phase of the engine to counteract a driving torque generated during the combustion phase of the engine.

The control signal is generated on the basis of the reference parameter and either of the exhaust pressure and the specified value. Specifically (i) the exhaust pressure is used if the reference parameter is based on the inlet pressure, the engine parameter and the specified value; and (ii) the specified value if the reference parameter is based on the inlet pressure, the exhaust pressure and the engine parameter.

Then the procedure loops back to steps 410, 420, 430 and 440 again. Although the above procedure has been described as a sequential process, the actual execution procedure is advantageously repeated, or continuously, so that, for example, while step 460 processes data recorded at a particular time t, steps 410, 420, 430 and 440 process data recorded at a slightly later time t + At.

All the method steps, as well as any sequence of steps, described with reference to Figure 4 above, can be controlled by means of a programmed computer apparatus. In addition, although the embodiments of the invention described above with reference to the figures include a computer and processes performed in a computer, the invention extends to computer programs, in particular computer programs on or in a carrier adapted to practically implement the invention. The program may be in the form of source code, object code, a code which constitutes an intermediate between source and object code, such as in partially compiled form, or in any other form suitable for use in implementing the process according to the invention.

The carrier can be any entity or device capable of carrying the program. For example, the carrier may comprise a storage medium such as a flash memory, a ROM (Read Only in Memory), for example a CD (Compact Disc) or a semiconductor ROM, an EPROM (Erasable Programmable ROM), an EEPROM (Electrically EPROM) or a magnetic recording medium , for example a floppy disk or hard disk. In addition, the carrier may be a transmitting carrier such as an electrical or optical signal, which may be conducted through an electrical or optical cable or via radio or otherwise. When the program is formed by a signal which can be conducted directly by a cable or other device or means, the carrier can be constituted by such a cable, device or means. Alternatively, the carrier may be an integrated circuit in which the program is embedded, where the integrated circuit is adapted to perform, or to be used in, the execution of the actual processes.

The invention is not limited to the embodiments described in the figures, but can be varied freely within the scope of the claims.

Claims (17)

10 15 20 25 30 35 529 870 11 Patent claims An exhaust brake system for a motor vehicle, comprising: an adjustable valve (135) adapted to prevent the exhaust gases from an internal combustion engine (110) of the vehicle in response to a control signal (C) to provide a braking torque during the exhaust phase of the engine (110); a first pressure sensor (155) adapted to detect an exhaust pressure (Pm) in an exhaust line (150) from the engine (110), and a braking torque regulator (160) adapted to generate the control signal (C) based on the registered exhaust pressure (Pm) and a specified value (Tæq) indicating a desired braking torque, characterized in that the system comprises a second pressure sensor (145) adapted to register an inlet pressure (Pm) in an air inlet (140) to the motor (110), and the braking torque regulator (160) comprises: a processing means (120) adapted to: receive the registered inlet pressure (Pm), receive an engine parameter (rpm) reflecting a speed of the engine (110), model a gas exchange work performed by the engine (110), and generate a reference parameter ter (P ,,, _ ,,, ° d; Tmod) based on this model and in response to the registered inlet pressure (Pm) and the motor parameter (rpm), and a control means (130) adapted to receive the reference parameter (Pm_m ° d; Tmod) and on that basis generate the control signal (C) . The system according to claim 1, characterized in that the processing means (120) is adapted to receive the specified value (TM), and on further basis thereof generate the reference parameter in the form of a first modeled parameter (Pmmod) reflecting an estimate of the exhaust pressure in the exhaust line (150). The system according to claim 2, characterized in that the control means (130) is adapted to: receive the registered exhaust pressure (Pm), receive the first modeled parameter (Pm_m ° d), and in response generate the control signal (C). 10 15 20 25 30 529 870 12 The system according to any one of claims 2 or 3, characterized in that the control means (130) is adapted to implement a proportional-integrating-derivative algorithm adapted to generate the control signal (C) in order to minimize an error between the registered the exhaust pressure (Pm) and the first modeled parameter (Pm mode) - The system of claim 1, characterized in that the processing means (120) is adapted to: receive the recorded exhaust pressure (Pm), and on a further basis thereof generate the estimated reference parameter in the form of a second modeled parameter (Tmod) reflecting an estimate the desired braking torque. The system according to claim 5, characterized in that the control means (130) is adapted to: receive the second modeled parameter (Tmod), receive the specified value (Tæq), and in response therewith generate the control signal (C). The system according to any one of claims 5 or 6, characterized in that the control means (130) is adapted to implement a proportional-integrating-derivative algorithm adapted to generate the control signal (C) in order to minimize an error between the specified value ( Tæq) and the second modeled parameter (Tmd). A motor vehicle comprising an internal combustion engine (110), characterized in that the vehicle (200) comprises an exhaust brake system (100) according to any one of claims 1 to 7, wherein the system (100) is configured to apply an adjustable braking torque with respect to on at least one drive shaft of the engine (110). A method of controlling an adjustable valve (135) in an exhaust brake system of a motor vehicle with an internal combustion engine (110) in such a way that the exhaust gases from the engine (110) are prevented in order to provide a braking torque below the engine (110). exhaust phase, the method comprising: recording an exhaust pressure (Pm) in an exhaust line (150) from the engine (110), and generating a control signal (C) for the adjustable valve (135) based on the registered exhaust pressure (Pm) and a specified value (Tæq) indicating a desired braking torque, where the control signal (C) is adapted to control the adjustable valve (135), characterized by: registration of an inlet pressure (Pin) in an air inlet (140) to the engine (110), recording an engine parameter (rpm) reflecting a speed of the engine (110), and generating a reference parameter (Pmanode: Tmod) based on a model for a gas exchange work performed by the engine (110). ) and in response to the registered inlet pressure (Pm) o ch the registered motor parameter (rpm), and generating the control signal (C) on an additional basis of the reference parameter (P ,,, _ ,,,,, d; Tmod). The method according to claim 9, characterized by: receiving the specified value (Tæq), and generating the reference parameter in the form of a first modeled parameter (P ,,, _ ,,,,, d) reflecting an estimate of exhaust gas - the pressure in the exhaust line (150), where the first modeled parameter (P ,,, _ ,,,,,, d) is generated on the basis of the registered inlet pressure (Pm) and the specified value (Tæq). The method according to claim 10, characterized by: receiving the registered exhaust pressure (Pm), receiving the first modeled parameter (Pmmod), and generating the control signal (C) in response thereto. The method according to any one of claims 10 or 11, characterized in that the control signal (C) is generated based on a proportional-integrating-derivative algorithm adapted in order to minimize an error between the registered exhaust pressure (Pm) and the first mode. divided parameter (Pm _ ,,, ° d). 10 15 20 529 870 14 The method according to claim 9, characterized by: receiving the recorded exhaust pressure (Pm), and generating the estimated reference parameter in the form of a second modeled parameter (Tmod) reflecting an estimate of the desired braking torque, where the second model The registered parameter (Tmod) is generated based on the registered inlet pressure (Pm), the registered engine parameter (rpm) and the registered exhaust pressure (Pm). The method according to claim 13, characterized by: receiving the second modeled parameter (Tmd), receiving the specified value (Tæq), and generating the control signal (C) in response thereto. The method according to any one of claims 13 or 14, characterized in that the control signal (C) is generated based on a proportional-integrating-derivative algorithm adapted to generate the control signal (C) in order to minimize an error between the specified value (Tæq ) and the second modeled parameter (Tmod). A computer program product directly chargeable to the internal memory of a computer, characterized in that the computer program product comprises software for controlling the steps according to any one of claims 9 to 15 when said program is run on the computer. A computer-readable medium (170) having a program stored thereon, characterized in that the program is adapted to cause a computer to control the steps according to any one of claims 9 to 15.