SE530717C2 - Exhaust Brake Control - Google Patents

Description

25 30 539 71? a shut-off valve for the EGR valve which is activated when the exhaust brake is activated.

JP 2001-280173 shows an exhaust braking device for an internal combustion engine. Here, a bypass passage over the exhaust brake device is opened in the event of an electrical short circuit of the exhaust brake device. Thus, unintentional exhaust braking can be avoided.

However, there is still no solution whereby information regarding the actual position of the exhaust brake valve is fed back to the unit responsible for the exhaust brake function. Thus, the de facto valve can be closed even if a control signal has been generated which is suitable for controlling the valve to an open position, or at least to a different position than what the control signal reflects. This in turn can result in property damage (for example to the engine and / or to its affected valves and turbo units) as well as to safety risks due to an unexpected braking of the vehicle.

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 reliable monitoring of the function of the exhaust brake valve.

According to one aspect of the invention, the object is achieved by the initially described exhaust brake system, wherein the control unit is adapted to examine whether the setpoint indicates a braking torque below a first threshold level and the engine is controlled to a driving torque below a second threshold level. If both of these conditions are met, the control unit is adapted to: generate the second control signal so that the second adjustable valve is adjusted to a closed position, generate the third control signal so that the turbo unit opens to a maximum of the exhaust gases, and test if the exhaust pressure level exceeds a third threshold level. If this is found to be the case, the control unit is adapted to generate an alarm triggering signal 10 15 20 25 30 530 717 with respect to the first adjustable valve.

This system is advantageous because it offers an automatic testing of the exhaust brake, which can be performed on repeated occasions during normal operation of the vehicle.

According to an embodiment of this aspect of the invention, the first and second threshold levels represent a state in which the engine does not drive the vehicle. As a result, no disturbing pressures will build up in the exhaust line during the test procedure.

According to another embodiment of this aspect of the invention, the control unit is adapted to receive a status signal indicating a functional state of an actuator adapted to influence the adjustment of the first adjustable valve. For example, the actuator may include a piston member and a valve member. The piston means is controlled here in response to a pressurized fluid (for example compressed air or hydraulic oil), and the valve means is controlled in response to the first control signal. The valve means is adapted to pass the pressurized fluid to the piston means. The control unit is further adapted to test whether or not the status signal meets an alarm criterion, and if so, generates the second control signal so that the second adjustable valve is adjusted to a predetermined position, preferably a fully open position. Thus, in addition to detecting a faulty exhaust brake, the proposed system can also reduce the effects of certain malfunctions.

According to yet another embodiment of this aspect of the invention, the first control signal is an electrical type signal, and the status signal is based on at least one electrical parameter associated with the actuator. For example, the first control signal may have a pulse width modulation (PWM) format, and the first adjustable valve may be adapted to open a passage for the exhaust gases from the engine based on a pulse width of the first control signal. Consequently, a short circuit of the first adjustable valve to the supply voltage could be interpreted as an order to completely close the exhaust brake valve. However, this highly undesirable effect is avoided by the above-suggested testing of the status signal.

According to another aspect of the invention, the object is achieved by the motor vehicle initially described, the vehicle comprising the exhaust brake system proposed above which is 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, in which it is examined whether the setpoint indicates a braking torque below a first threshold level and the motor is controlled to a driving torque below a second threshold level. If both of these conditions are met, the method further includes: generating the second control signal so that the second adjustable valve is adjusted to a closed position, generating the third control signal so that the turbo unit opens to a maximum for the exhaust gases, testing if the exhaust pressure level exceeds a third threshold level, and if this is the case, generating an alarm triggering signal with respect to the first adjustable valve. The advantages of this method, as well as of the preferred embodiments thereof, appear from the discussion above with reference to the proposed vehicle arrangement.

According to a further aspect of the invention, the object is achieved by a computer program product loadable to the memory of a computer. The program product includes software adapted to control the method proposed above when the program product is run on a computer.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be explained in more detail by means of embodiments, which are described by way of example, and with reference to the accompanying drawings.

Figure 1 shows a block diagram of an exhaust brake system 10 15 20 25 30 530 71? according to an embodiment of the invention, Figures 2a-b show diagrams illustrating a format of a control signal and its relation to an opening of the exhaust brake valve according to an embodiment of the invention, Figure 3 shows a motor vehicle including the proposed exhaust brake system, and, Figure 4 shows a flow chart illustrating the general method according to the invention.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION We refer initially to Figure 1, which shows a block diagram of an exhaust brake system for a motor vehicle according to an embodiment of the invention.

The system includes a first adjustable valve 135, a second adjustable valve 107, a sensor means 155, a turbo unit 160 and a control unit 120, which is adapted to receive an exhaust pressure signal Pm from the sensor means 155 and a setpoint Tæq indicating a desired braking torque. to be applied by the exhaust brake. In addition, the control unit 120 is adapted to generate a first, a second and a third control signal C1, C2 and C3, respectively, and an alarm triggering signal A with respect to the first adjustable valve 135.

The first adjustable valve 135 is arranged in an exhaust line 150 from an internal combustion engine 110 of the vehicle and is adapted to prevent the exhaust gases Eout of the engine 110 in response to the first control signal C1, and as a result, cause a braking torque below the engine 110 exhaust phase. The second adjustable valve 107 is arranged in a recirculation passage 115 to the motor 110. The second adjustable valve 107 is controlled in response to the second control signal C2.

The sensor means 155 is arranged to register the exhaust pressure level 10 15 20 25 30 35 530.71? Pm in the exhaust line 150 between the engine 110 and the first adjustable valve 135, and pass the exhaust pressure signal Pm to the control unit 120. The turbo unit 160 is arranged in the exhaust line 150, and is controllable in response to the third control signal C3.

The control unit 120 is adapted to repeatedly examine whether the setpoint Tæq indicates a braking torque below a first threshold level. In addition, the control unit 120 is adapted to repeatedly examine whether the motor 110 is controlled to a drive torque below a second threshold level. Preferably, the first and second threshold levels are set to such values that they represent a state in which the engine 110 does not drive the vehicle (and at the same time only brakes the vehicle insignificantly). If the control unit 120 finds that both of these conditions are met simultaneously (i.e. the setpoint Tfeq indicates a braking torque below the first threshold level and the driving torque to which the motor is controlled is less than the second threshold level), the control unit 120 is adapted to generate the second control signal C2 so that the second adjustable valve 107 is adjusted to a closed position. Consequently, no exhaust gases E will be recirculated from the engine 110 exhaust outlet to the air intake. Figure 1 shows the second adjustable valve 107 arranged relatively close to the air intake. However, the valve 107 can just as easily be placed in any other position in the recirculation passage 115, for example at the connection between the recirculation passage 115 and the exhaust pipe 150.

At a simultaneous fulfillment of the two above conditions (i.e. the setpoint Tæq indicating the braking torque falls below a first threshold level and the driving torque falls below a second threshold level), the control unit 120 is also adapted to generate the third control signal C3 so that the turbo unit 160 opens up maximum for EM exhaust gases. Thus, the exhaust gases Em will have a minimal effect on the air Am fed into the air intake of the engine 110. More importantly, however, the turbocharger 160 will minimize obstruction of the exhaust gases Em. Therefore, the effect of the first adjustable valve 135 of the exhaust brake can be tested in a straightforward manner. For this purpose, the control unit 120 is adapted to test if the exhaust pressure level Pm exceeds a third threshold level. If this condition is found to be met, the control unit 120 is adapted to generate the alarm triggering signal A (i.e. to indicate a malfunction of the first adjustable valve 135). Preferably, the alarm trigger signal A reflects a state where the exhaust brake valve is stuck. The setpoint Tæq indicates a desired braking torque below the first threshold level, say a zero value, while the exhaust pressure level Pm shows an abnormally high value in excess of the third threshold level.

With reference to Figure 1, it is worth mentioning that the invention allows the turbo unit 160 to be arranged in any position relative to the first adjustable valve 135. For example, the turbo unit 160 may be located between the engine 110 and the first adjustable valve 135. In addition, it should be noted that the first adjustable valve 135 is a separate component separated from the turbo unit 160. Consequently, for example, the valve 135 cannot be constituted by the nozzle area of the adjusting flanges of a variable geometry turbo (VGT).

According to an embodiment of the invention, the control unit 120 is further adapted to receive a status signal etc. indicating a functional status of an actuator adapted to actuate the first adjustable valve 135. The actuator in turn preferably includes a piston means 130 and a valve means 145. The valve means 145 is controlled in response to the first control signal C1. This signal C1 can thus cause the valve means 145 to open and pass on a pressurized fluid Fp (for example in the form of compressed air or hydraulic oil) to the piston means 130. The pressurized fluid Fp is advantageously provided by a pump means 140 in the vehicle. The piston member 130 is controlled in response to a pressurized fluid Fp. This means that the piston member 130 will cause the first adjustable valve 135 to vary its position depending on the status of the valve member 145.

Specifically, the control unit 120 is adapted to test whether or not the status signal etc. from the valve means 145 satisfies an alarm 10 15 20 25 30 35 530 '71? criterion. If so, the control unit 120 is further adapted to generate the second control signal C2 so that the second adjustable valve 107 is adjusted to a predetermined position, preferably fully open.

According to an embodiment of the invention, the valve means 145 is configured to be driven by a supply voltage + U, and the first control signal C1 is an electrical type signal. In this case, the status signal etc. is based on an electrical parameter related to the operation of the valve means 145. For example, the status signal etc. here may reflect whether or not the valve means 145 has been short-circuited to the supply voltage + U.

Figure 2a shows a diagram illustrating a format of the first control signal C1 according to an embodiment of the invention.

The signal Ct has a PWM format. In addition, the opening of the first adjustable valve 135 is inversely proportional to a pulse width of the signal C1, so that a relatively narrow pulse, say 0, 25T, results in a relatively large valve opening, and a relatively wide pulse, say 0.95T, results in a relatively small valve opening.

Figure 2b shows a diagram specifically illustrating this relationship, where the vertical axis reflects the aperture angle tp of the first adjustable valve 135 and the horizontal axis indicates the pulse width PWC, for the PWM signal Ct from zero to a maximum value T (given by the period time). at the PWM signal C1). Thus, a largest possible opening angle (p) corresponds to a fully open FO valve 135, and a zero opening angle tp corresponds to a fully closed FC valve 135.

We now return to Figure 2a and see that the first control signal C1 switches between ground level voltage and the supply voltage + U with a pulse cycle T. The widest possible pulse (i.e. with a pulse width PWC, = T) is thus equivalent to the first control signal C1 is constantly equal to + U. Consequently, a short circuit of the valve member 145 to the supply voltage + U has the same effect as a conscious control of the valve 135 to a completely closed position. An unintentional closing of the valve 135 (for example due to a short circuit of the valve member 145) can, however, lead to highly undesirable results, such as damage to the engine 110, the exhaust line 150 and / or the turbo unit 160. Of course, the vehicle can also be braked, which could cause handling problems (for example, behavior such as skidding or oversteer), especially if the vehicle is connected to a lightly loaded or unloaded trailer. Nevertheless, one embodiment of the invention alleviates this problem by opening the EGR valve (107) as described above.

Figure 3 shows a motor vehicle 200 including the proposed exhaust brake system, which is configured to apply an adjustable braking torque to at least one drive shaft of the engine 110.

Thus, the system has a control unit 120 adapted to test the operating status of the first adjustable valve 135 as described above.

For the purpose of summarizing, the general method for testing an exhaust brake in a motor vehicle according to the invention will now be described below with reference to the flow chart in Figure 4.

A first step 410 examines whether or not a setpoint has been received indicating an exhaust braking torque below a first threshold level. Step 410 also examines whether or not the motor is controlled to a drive torque below a second threshold level. If it turns out that both of these conditions are met at the same time, a step 420 follows. Otherwise, the procedure loops back and stops in step 410 (i.e. it turns out that the setpoint indicates an exhaust braking torque equal to or higher than the first threshold level and / or the drive torque is equal to or higher than the second threshold level).

Step 420 generates a signal so that the EGR valve (i.e., represented by the second adjustable valve 107 in Figure 1) is adjusted to a closed position. Then a stage 430 generates a control signal so that the turbo unit opens up to the maximum for the exhaust gases. Then, a step 440 tests if the exhaust pressure level exceeds a third threshold level. and if so, a step 450 follows.A- 10 15 20 25 30 530 71? 10 nars loops the procedure back to step 410. Step 450 generates an alarm triggering signal with respect to the first adjustable valve. Thereafter, the procedure can either end, or it can loop back to step 410 for continued monitoring of the exhaust brake system.

All the method steps, as well as any sub-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, especially 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 which is capable of carrying the program.

For example, the carrier may comprise a storage medium such as a flash memory, a ROM (Read Only 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 performing, 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 (16)

10 15 20 25 30 530 71? 11 Patent claims An exhaust brake system for a motor vehicle comprising: a first adjustable valve (135) adapted to prevent the exhaust gases from (Em) an internal combustion engine (110) of the vehicle in response to a first control signal (C1) and thereby provide a braking torque below the engine ( 110) exhaust phase, a second adjustable valve (107) controlled in response to a second control signal (C2) and arranged in a recirculation passage (115) connecting an exhaust line (150) from the engine (110) to an air intake (105) to the engine (105). 110), a sensor means (155) arranged to register an exhaust pressure level (Pm) in the exhaust line (150) between the engine (110) and the first adjustable valve (135), a turbo unit (160) arranged in the exhaust line (150) and controllable in response to a third control signal (C3), and a control unit (120) adapted to generate the first control signal (C1) in response to a setpoint (Tæq) indicating a desired braking torque, characterized in that the control unit (120) is adapted sat to: examine whether the setpoint (Tæq) indicates a braking torque below a first threshold level and the motor (110) is controlled to a driving torque below a second threshold level, and if both of these conditions are met, the second control signal (C2) is generated so that the second adjustable valve (107) is adjusted to a closed position, generate the third control signal (C3) so that the turbo unit (160) opens to the maximum for the exhaust gases (Eoul), test if the exhaust pressure level (Pm) exceeds a third threshold level, and if so generate an alarm triggering signal (A) with respect to on the first adjustable valve (135). The system of claim 1, wherein the first and second threshold levels represent a state in which the engine (110) does not drive the vehicle. 10 15 20 25 30 5343 717 12 The system according to any one of claims 1 or 2, wherein the control unit (120) is adapted to: receive a status signal (etc.) indicating a function shut-off of an actuator (145, 130) adapted to influence the adjustment of the first adjustable valve (135), test whether or not the status signal (etc.) meets an alarm criterion, and if so, generate the second control signal (C2) so that the second adjustable valve (107) is adjusted to a predetermined position. The system of claim 3, wherein the predetermined position represents an adjustment of the second adjustable valve (107) to a fully open position. The system of any of claims 3 or 4, wherein the actuator comprises: a piston means (130) controlled in response to a pressurized fluid (Fp), and a valve means (145) controlled in response to the first control signal ( C1) and adapted to pass the pressurized fluid (FP) to the piston means (130). The system according to any one of claims 3 to 5, wherein the first control signal (C1) is an electrical type signal, and the status signal (etc.) is based on at least one electrical parameter associated with the actuator (145, 130). The system of claim 6, wherein the first control signal (C1) has a pulse width modulation format and the first adjustable valve (135) is adapted to open a passage for the exhaust gases (Em) from the engine (110) based on a pulse width (PWC) of the the first control signal (C1). A motor vehicle (200) comprising an internal combustion engine (110), characterized in that the vehicle (200) comprises an exhaust brake system according to any one of claims 1 to 7, wherein the system is configured to apply an adjustable braking torque with respect to at least one drive shaft of the engine (110). 10 15 20 25 30 530 71? 13 A method of controlling an exhaust brake in a motor vehicle, wherein a first adjustable valve (135) is adapted to prevent the exhaust gases from (Em) an internal combustion engine (110) of the vehicle in response to a first control signal (C1) and thereby provide a braking torque during the exhaust phase of the engine (110), a second adjustable valve (107) is controlled in response to a second control signal (C2) and arranged in a recirculation passage (115) connecting an exhaust line (150) from the engine (110) to an air intake. (105) to the engine (110), a sensor means (155) is arranged to register an exhaust pressure level (Pm) in the exhaust line (150) between the engine (110) and the first adjustable valve (135), and a turbo unit (160) is provided in the exhaust line (150) and is controllable in response to a third control signal (C3), the method comprising generating the first control signal (C1) in response to a setpoint (Tæq) indicating a desired braking torque, characterized by: examination of the setpoint ( Tæq) indicates a brake rlwmeflï understi a first threshold level and the motor (110) is controlled to a drive torque below a second threshold level, and if both of these conditions are met, the second control signal (C2) is met so that the second adjustable valve (107) is adjusted to a closed position, generating the third control signal (C3) so that the turbo unit (160) is opened to a maximum of the exhaust gases (EM), testing if the exhaust pressure level (Pm) exceeds a third threshold level, and if so generating an alarm triggering signal (A) with respect to the first adjustable the valve (135). The method of claim 9, wherein the first and second threshold levels represent a state in which the engine (110) does not drive the vehicle. The method of any of claims 9 or 10, comprising: receiving a status signal (etc.) indicating an operating state of an actuator (145, 130) adapted to affect the adjustment of the first adjustable valve (135), 539 717 14 testing whether or not the status signal (etc.) meets an alarm criterion, and if so, generating the second control signal (C2) so that the second adjustable valve (107) is adjusted to a predetermined position. The method of claim 11, wherein the predetermined position represents an adjustment of the second adjustable valve (107) to a fully open position. The method according to any one of claims 11 or 12, wherein the first control signal (C1) is an electrical type signal, and the status signal (etc.) is based on at least one electrical parameter associated with the actuator (145, 130). The method of claim 13, wherein the first control signal (C1) has a pulse width modulation format and the first adjustable valve (135) is adapted to open a passage for the exhaust gases (Eout) from the engine (110) based on a pulse width (PWC) of the the first control signal (C1). A computer program product rechargeable to a memory (125) of a computer included in a motor vehicle (200), which is equipped with an exhaust brake system and an exhaust recirculation system, the computer program product comprising software adapted to control the steps of any of claims 9 to 14 when the program product is run on the computer. The computer software product of claim 15, wherein the software product is stored on a carrier.