LU82264A1 - BRAKE-ENGINE SYSTEM AND CORRESPONDING BRAKING METHOD - Google Patents

Description

Ji *

Engine brake system and corresponding braking method.

The invention relates to an engine brake system and a corresponding braking method. It relates more particularly to a braking system which is characterized by the combination of the engine brake of the compression reduction type with a supercharging turbine which is constituted by an exhaust gas turbine comprising a divided volute and a air compressor, this combination allowing, as will be seen below, better braking and better engine performance.

Normally, in turbocharged engines, the turbocharger is not necessary during braking because the engine does not receive fuel. As a result, both the volume and the temperature of the exhaust gases are reduced. This has two disadvantageous effects: (1) the engine operating temperature becomes lower than the desired value since the cooling system removes more heat than is produced and (2) a decrease in the volume of the the exhaust gases produced (due to the absence of combustion) and the decrease in the volume of the gases (as a result of the drop in the temperature of the gases) cause a reduction in the speed of the turbofan. These disadvantageous effects appear when the engine brake is necessary, for example during a long descent. By the time you get to the bottom of the descent, the engine temperature has dropped considerably and the charge turbine has slowed down. Under these conditions, it is difficult to accelerate the engine rapidly, as may be necessary for a steep climb which usually follows a descent.

These disadvantageous effects are generally overcome by providing a braking system which combines the supercharging turbine, constituted by an exhaust gas turbine, with a rating brake with reduction of the pressure, the turbine of supercharging cooperating with the braking system, and the braking operation promoting the operation of the turbocharger turbine.

With the braking system according to the invention, the turbocharger is controlled so as to maximize the air flow in the engine during the braking operation, by diverting all the exhaust gases into a part of the turbine so as to increase the compression work performed by the engine.

More particularly, the invention provides a system; engine brake block allowing better engine performance, for an internal combustion engine comprising intake and exhaust pipes, characterized in that it comprises in combination a engine brake with reduction of compression , operating during the opening of at least one combustion engine exhaust valve in the vicinity of the end of the compression stroke of the engine cylinder with which said exhaust valve is associated, and a supercharging turbine 20 constituted by an exhaust gas turbine comprising a divided volute and an air compressor which supplies compressed air to said engine intake manifold, said supercharging turbine comprising a bypass valve coupled on one side to the exhaust manifold and on the other side to the subdivided volute, in order to direct, with a predetermined braking action, the flow of exhaust gases from the exhaust manifold to a single tie of said subdivided volute instead of the two, as is the case when braking less than said predetermined braking action.

By diverting the exhaust gases in a part of the turbine, the pressure of the gases in the exhaust manifold increases. This effect not only increases the retarding power developed by the engine, but also increases the temperature of the air in the engine. The increase in the air temperature in turn causes an increase in the energy of the exhaust gases, ¥ 3, which increases the efficiency and, consequently, the speed of rotation of the turbine. Thus, the combination of a compression reduction brake with a supercharging turbine having a four-four subdivided scroll produces a synergistic result which increases the available deceleration power provided by the compression reduction brake. Another advantage of this combination for normal operation arises from the braking operation. During the braking operation, part of the kinetic energy of the vehicle is transformed into heat which is dissipated by the engine cooling system, which keeps the engine at normal operating temperature or in the vicinity of this one.

In previously known systems, brakes 15 of the compression reduction type (US Patent No. 3,220,392) are normally used only for braking. In other previously known systems, turbochargers comprising a subdivided volute and bypass mechanisms (US Pat. Nos. 4,008,572, 3,559,397, 3,137,477, 3 .313,518 or 3,975,911) normally operate so as to increase the air flow in order to increase the engine power during the fuel supply. So far, no one has realized that synergistic effects could be obtained by using a compression reduction brake to improve the operation of a supercharged engine and to use a supercharged engine with one; subdivided scroll and a bypass mechanism to improve the operation of the compression reduction brake.

The present invention will be better understood with the aid of the following description of a preferred but nonlimiting embodiment shown in the appended drawings in which: FIG. 1 is a diagram, partially in section, of an engine comprising a compression reduction brake, an exhaust gas bypass device and a supercharging turbine consisting of a '' * 4 double inlet turbine or a subdivided volute, - Figure 2 is a diagram, partially in section, of the compression reduction retarder, 5 - Figure 2A is a diagram of the electrical control system for the improved retarder according to the invention, - Figure 3 is a cross-sectional view of a supercharging turbine by a double inlet or sub-scrolled turbine which can be used according to the present invention, - Figure 4 is a plan view of a butterfly type bypass valve which can be used as follows: vant the present invention, - Figure 5 is a sectional view along line 5-5 of Figure 4, - Figure 6 is a graph showing the relationship between pressure and volume in an engine cylinder, during a complete cycle, according to a previously known type of operation using a compression reduction brake, - Figure 7 is a graph showing the relationship between pressure and volume in an engine cylinder, during a couplet cycle, according to the present invention, and, - Figure 8 is a graph showing the deceleration power developed by an engine using a compression reduction brake alone and the greater deceleration power obtained according to the invention.

Referring more particularly to FIG. 1, an engine is designated by the reference 10. The engine 10 may be of the carburetor type or of the Diesel type and may include any number of cylinders. However, the present invention has been described with reference to a typical six-cylinder diesel engine having an intake manifold 12 and a subdivided exhaust manifold comprising a front exhaust manifold 14 and a * 5 manifold rear exhaust 16. Exhaust pipes 18 and 20 respectively lead front and rear exhaust pipes to a bypass valve 22 of the exhaust gases, The bypass valve 5 22 of the exhaust gases is shown in the figures 4 and 5 and will be described in more detail below. A . double pipe 24 for the exhaust gases establishes a communication between the outlet of the bypass valve 22 and the inlet of a turbine 26 with double inlet or with sub-divided lute-10, which, in association with a compressor 28, constitutes an integral supercharging turbine 30. The supercharging turbine 30 is shown in FIG. 3 and will be described in more detail below. After passing through the turbine 26, the exhaust gases pass through the exhaust system 32 of the engine.

Air is sent to the engine 10 via a conventional air filter 34, the inlet channel 36 of a compressor, a compressor 28, and the line 38 which establishes communication between the outlet 20 of the air compressor 28 and the intake manifold 12. As shown diagrammatically in FIG. 1, and in more detail in FIG. 3, the compressor 28 is driven by the turbine 26 and typically comprises a integral supercharging turbine 30.

Referring now to Figure 2, the motor 10 includes a housing 40 which contains the conventional compression reduction braking system shown schematically in Figure 2. Oil 42 from a reservoir 44 which can be , for example, the motor casing 30 is pumped through a line 46, by a low pressure pump 48, to arrive at the inlet 50 of a solenoid valve 52 mounted in the housing 40.

Low pressure oil 42 is sent through a container. line 56, from the solenoid valve 52, to a control cylinder 54, which is also located in the housing 40. A control valve 58 is housed so as to move back and forth in the control cylinder and is loaded to the closed position by a 6 compression spring 60. The control valve 58 has an inlet line 62, closed by a ball check valve 64 which is loaded to the closed position by a spring compression 66, and an outlet line 68. When the control valve is in the open position (as shown in FIG. 2), the outlet line 68 coincides with the outlet line 7o of the control cylinder which communicates with it - even with the entry of a slave cylinder 72 also located in the housing 40. It will be understood that the low pressure oil 42 passing through the solenoid valve 52 enters the control cylinder 54 and lifts the control valve 58 to open position e. Then, the ball check valve 64 opens against the force of the spring 66 and the oil flows into the slave cylinder 72.

From the outlet 74 of the slave cylinder 72, the oil 42 passes through a line 76 to arrive in the main cylinder 78 located in the housing 40.

A slave piston 80 is mounted so as to reciprocate in the slave cylinder 72.

The slave piston 80 is loaded upwards (as shown in FIG. 2) against an adjustable stop 82, by a compression spring 84 which is mounted in the slave piston 80 and bears against a support 86 housed in the cylinder. servo 72. The lower end of the servo piston 80 acts on an exhaust valve cap 88 mounted on the stem of an exhaust valve 90 which, in turn, is mounted in the engine 10. A spring 92 loads normally the exhaust valve 90 to the 3o closed position, as shown in Figure 2. Normally, the adjustable stop 82 is adjusted so as to leave. ser a desired clearance between the servo piston 80 and the cha skin 88 of the exhaust valve when the latter is • closed, that the servo piston is pressed against the adjustable stop 82 and that the engine is cold. The desired clearance is provided to take into account the expansion of the elements constituting the exhaust valve when the engine is hot, without opening the exhaust valve 90, and 7 to control the instant of opening of the exhaust valve .

A main piston 94 is mounted so as to reciprocate inside the main cylinder 78, and is loaded upwards (as shown in FIG. 2) by a small leaf spring 96. The lower end of the main piston 94 makes contact with a mechanism 98 for adjusting a rocker arm 100 controlled by a push rod 102 driven by the camshaft 10 (not shown) of the engine.

It will be understood that when the solenoid valve 52 is opened, oil 42 lifts the control valve 58 and fills the slave cylinder 72 and the main cylinder 78. The ball check valve 64 prevents oil from escaping from the slave cylinder 72 and main cylinder 78. However, once the system is filled with oil, the upward movement of the push rod 102 drives the main piston 94 upward and the hydraulic pressure in turn drives the slave piston 20 80 downwards to open the exhaust valve 90.

The actuation times of the valves are chosen so that the exhaust valve 90 opens in the vicinity of the end of the compression stroke of the cylinder with which the exhaust valve 90 is associated. Thus, the work done by the piston in compressing air during the compression stroke is dissipated to the engine exhaust system and is not recovered during the rebound stroke of the engine. In some engines it may be convenient to control the main piston from the injector push rod associated with the cylinder with which the slave piston communicates, while in other engines it may be desirable to use a push rod associated with an intake or exhaust valve for another cylinder. In either case, the result is the same since the exhaust valve is open in the vicinity of the end of the compression stroke.

When it is desired to deactivate the compression brake, the solenoid valve 52 is closed / as a result of which the oil 42 in the cylinder 54 of the control valve passes through line 56, the valve to solenoid 52 and return line 104 to reach reservoir 44. When the control valve 58 descends, as shown in FIG. 2, part of the oil being in the slave cylinder 72 and the main cylinder 78 is sent beyond the control valve 58 and is returned to the tank 44 by lines 10 (not shown).

The electrical control system for the present invention is shown schematically in Figure 2A to which reference will now be made. A terminal of the battery 106 of the vehicle is connected to earth 108. The other terminal of the battery is connected in series with a fuse 110, a switch 112 for the dashboard, a switch 114 for the clutch. and a switch 116 for the fuel pump, and preferably returns to earth 108 by a diode 118. A selector switch 120 with several positions is also connected in series with the switches 112, 114 and 116. For obtain different degrees of braking power through the retarder and the exhaust gas bypass system, it may be desirable to use the selector switch 120 which, as shown in Figure 2A, includes three positions. In position 1 (as shown in FIG. 2A), the selector switch 120 supplies the front solenoids 122 which, for example, control the solenoid valves 30 52 associated with half of the engine cylinders (three in the case of the six cylinders shown in Figure 1). In position 2, the selector switch 120 supplies the front solenoids 122 and the rear solenoids 124 so as to control the solenoid valves 52 associated with all of the engine cylinders, which increases engine braking. In position 3, the selector switch 120 supplies not only all of the solenoid valves 52, but also the bypass valve 22, via a solenoid 126, so as to obtain maximum engine braking power, as will be described in more detail below. It will be understood that other compositions can be provided for the selector switch 120 so that the engine brake acts at one or more engine cylinders, as desired. Naturally, the selector switch 120 can also be eliminated if it is desired to have the maximum engine brake at all times, i.e. 10 at all of the engine cylinders plus the braking due to the bypass valve. 22. Switches 112, 114 and 116 are also provided to supplement the control system and ensure safe operation of the system.

Switch 112 is a manual command to shut down the entire system. The switch 114 is an automatic switch connected so as to stop the system each time the clutch is released, so as to prevent the engine from stalling. The switch 116 is a second automatic switch connected to the fuel system to prevent the supply of fuel to the engine when the engine brake is operating.

FIG. 3, to which reference will now be made, shows a conventional supercharging turbine 30 which can be used according to the invention. The supercharging turbine 25 comprises a double inlet turbine 26 and a compressor 28 mounted coaxially on a tu-rillonée shaft 128, so as to be able to rotate, in bearings 130, in a fixed housing 132, The turbine 26, represented here in the form of a radial circulation turbine, 30 comprises a subdivided volute 134 comprising two series of nozzles 136, 138 directed towards the fins of a wheel 140 fixed on the shaft 128. The gases passing through the subdivided volute 134 are accelerated when they pass through the nozzles 136, 138 and communicate their kinetic energy to the wheel 140. It will be noted that the speed of the wheel 140 is a function of the volume of gas circulating in the volute 134 which determines the speed of flow in nozzles 136, 138. It is known that at relatively low gas flow rates, the efficiency of the turbine decreases and that greater efficiency can be obtained if, at low gas flow rates, all of the gas is directed to part of the scroll 134.

The wheel 140 of the turbine 26 is coupled to the rotor 142 of the compressor 28, shown here in the form of a centrifugal compressor. The rotation of the rotor 142 draws air through the inlet port 144 and sends the air at a higher pressure, via the volute 10 146 of the compressor, to the line 38 of the manifold. admission. It will be noted that although a radial circulation supercharging turbine has been shown and described according to the invention, it is possible to use different types of supercharging turbines provided that the turbine 15 is of a type in which all of the gases exhaust used as drive fluid can be supplied to part of the turbine wheel when desired.

FIGS. 4 and 5 represent a typical embodiment of a bypass valve 22 intended to divert the flow of exhaust gases from the lines 18 and 20 to a part of the line 24, and therefore to a single part of the volute 134 of the turbine 26. As shown, the bypass valve 22 has two relatively thick plates 148, 150 25 which constitute a housing intended to be placed between the lines 18, 20 and the split line 24. The plates 148 , 150 are provided with holes 152 intended to receive bolts for fixing these plates on flanges located on the conduits 18, 20 and 24. An opening 30 154 is provided in each plate 148, 150. A butterfly valve 156 is mounted inside the opening 154, on axes 158, 160 journalled so as to be able to rotate relative to the plates 148, 150 from a closed position substantially parallel to the plates towards an open position substantially normal to plaques.

A second butterfly valve 162 is mounted in the opening 154, on an axis 164 journalled so as to be able to rotate relative to the plates 148, 150 from w * 11 from a closed position substantially normal to the plates towards an open position in which the plane of the butterfly valve 162 forms an acute angle with the plane of the plates 148, 150. It will be understood that when the butterfly valve 156 is in the open position, and that the butterfly valve 162 is in the closed position, the flow of gas from the pipes 18, 20 enters the two parts of the subdivided pipe 24 and, consequently, in the two parts of the volute 10 subdivided 134 of the turbine 26. However, when the valve to throttle valve 156 is in the closed position and the butterfly valve 162 is in the open position, the flow of gas from the lines 18 and 20 is diverted to a part of the subdivided line 24 15 and, therefore, to a part of the volu te subdivided 134 of the turbine 26. It suffices to control the position of the butterfly valves 156 and 162 between a fully open position and a completely closed position. Therefore, they can easily be actuated by the solenoid 126 (Figure 2A) via suitable coupling systems (not shown), as will be understood by those familiar with this technique. Since these actuating mechanisms are not part of the invention, there is no need to describe them in detail. Although a specific embodiment of a bypass valve has been shown and described, it will be understood that according to the invention, different types of valves or bypass mechanisms can be used, provided that these devices are capable of bypassing all the exhaust gases from the engine to a single pipe leading to a single part of the turbine, which makes it possible to increase the efficiency and the speed of the turbine when the flow rate of the exhaust gases is low.

35 FIG. 6 is a graph representing the pressure as a function of the volume for a Mack 676 diesel engine equipped with a compression reduction brake manufactured by Jacobs Manufacturing Co. The part of the diagram between the 12 points 1 and 2 represents the engine compression stroke, starting at bottom dead center. Before the piston reaches upper dead center, the exhaust valve 90 is opened by the engine brake and the cylinder pressure 5 begins to decrease. The compression stroke ends at point 2a and the piston movement is reversed, which would correspond to the engine stroke if the engine received fuel. Point 3 represents the end of the driving race at the bottom dead center. The part of the diagram between points 3 and 4 represents the exhaust stroke while the part of the diagram between points 4 and 1 represents the intake stroke. During the compression and exhaust strokes, work is provided by the engine, which compresses the air in the cylinder, while during the drive and intake strokes the engine delivers the energy stored in the cooling system. and the engine exhaust system. Consequently, the internal surface of the diagram is proportional to the retarding power developed by the engine when using the previously known Jacobs brake.

FIG. 8 (curve A) is a graph representing the variation of the deceleration power as a function of the engine speed, for a Mack 676 diesel engine equipped with a Jacobs brake of the type shown schematically in FIG. 2.

According to the present invention, there is provided a bypass valve of the type shown in Figures 4 and 5 in the exhaust manifold of a Mack 676 engine equipped with a supercharging turbine and a Jacobs brake. The remarkable improvement in braking as well as in engine operation is shown in Figures 7 and 8 which show braking performance.

. Figure 7 is a graph showing pressure versus volume, which is similar to Figure 6, but which shows the effect of adding the bypass valve. It will be noted that a considerably higher maximum pressure is obtained for the compression stroke, while the curve of the driving stroke varies relatively little, so that the area between the curves, which is proportional to the power of slowdown, increased. Likewise, the maximum pressure 5 (as well as the average effective pressure) during the exhaust stroke has increased, so that the area between the curves of the exhaust and intake strokes and the deceleration power they represent have also increased.

The curve B in FIG. 8 represents the deceleration power supplied by the device according to the invention. It will be noted that at all engine speeds in the useful operating range of this engine, the deceleration power provided by the engine operating according to the invention is greater than that which is available when the engine operates only with the standard Jacobs brake. In addition, at the higher engine speeds typically encountered during use of the engine brake, the improvement in braking performance is very marked.

The improvement in braking performance is due to the synergistic reaction of the Jacobs engine brake and the supercharging turbine comprising the split volute and the bypass valve. When a braking engine is required, for example during a long descent, the engine operates near the top of its operating speed range, but it does not receive fuel. As a result, both the volume and the temperature of the exhaust gases decrease.

This reveals the two disadvantageous effects mentioned above. These disadvantageous effects are eliminated by diverting all the exhaust gases available in a part of the turbine, so that the speed at the turbine nozzles increases, which increases the speed of the compressor. When the speed of the compressor increases, a greater mass of air can be introduced at the inlet of the engine, which increases the compression work carried out by the engine, as represented by the curve 1 '-2' in FIG. 7, with respect to curve 1 - 2 in FIG. 6. In addition, the bypass valve has the effect of forming a constriction in the exhaust manifold, which causes greater resistance during the race. exhaust. This last effect appears by comparing the curve 3 '- 4' of figure 7 to the curve 3 - 4 of figure 6. The more important work carried out by the engine during the races of compression and exhaust results in a temperature. -10 ture greater exhaust gas, which increases the volume of exhaust gas. As seen above, an increase in the volume of the exhaust gases increases the speed of the turbine, which increases the mass of air introduced into the engine 15 via the compressor. It thus appears that the new combination of the compression reduction engine brake and the supercharging turbine with its bypass valve has a synergistic effect according to which the compression reduction brake operates more efficiently and operates also as an exhaust brake.

In addition, not only is the braking performance improved, but the operation of the engine itself is improved. As mentioned previously, it is frequent that a climb immediately follows a long descent during which the engine brake had to be used. However, at the bottom of the descent, the engine temperature dropped considerably and the turbocharger slowed down. Under these conditions, as mentioned above, it is difficult to quickly accelerate the engine. Thanks to the combination according to the present invention, not only will the temperature of the engine be higher (due to the greater work done on the greater air flow during engine braking), but also the speed of the turbine of boost will be maintained by the combined effect of the bypass valve and the increased flow. Thus, the boost turbine will operate at a more desirable speed for rapid acceleration of the engine. Another advantage is that at the beginning when the engine receives fuel, the higher temperature and the higher air flow promote complete combustion and avoid the emission of exhaust fumes with loss of power. resulting. Maintaining engine temperature and air flow also tends to prevent carbon formation during engine brake mode operation.

Although the combination according to the invention has the function of increasing the pressure in the exhaust manifold and is, in this respect, substantially similar to an exhaust brake, it does not have one of the main disadvantages of the brake at the exhaust, at sa-15 see the problem of valve flutter. Usually, the pressure in the exhaust manifold is limited by the requirement that it should not exceed the spring force of the exhaust valve. However, the use of the engine brake ensures that the pressure on the combustion side of the exhaust valve is significantly higher during the intake cycle than that which exists when using an exhaust brake alone. With this higher pressure, the compression reduction brake operates at higher pressure in the exhaust manifold without having the problem of valve flutter. Eliminating valve flutter results in maintaining greater pressure in the exhaust manifold, which increases the deceleration power.

Another advantage coming from the combination according to the invention relates to the reliability of the performances of the supercharging turbine. The effect of the higher pressure in the intake manifold is to reduce the pressure difference across the boost turbine between the compressor and the turbine. This means that the lateral thrust on the bearings of the charge turbine is reduced, so that the reliability of the charge turbine is increased.

16

Another advantage of the combination according to the present invention over an engine brake and an exhaust brake designed to provide the same deceleration power lies in the reduction of the pressure in the turbine casing, which which increases the life of the turbine and its reliability. The exhaust brake necessarily increases the pressure in the exhaust manifold, while the combination according to the present invention increases the pressure in the intake manifold, with only a relatively small increase in the pressure in the exhaust manifold. exhaust. The fact that the present invention provides the same retarding power with a smaller increase in the pressure in the exhaust manifold 15 means that the stresses of the turbine housing are lower and therefore the lifetime of the turbine is increased.

As goes without saying, and as already follows from the above, the invention is in no way limited to those of its embodiments and of application which have been more especially envisaged; on the contrary, it embraces all its variants.

Claims (5)

1. Engine brake system allowing better engine performance, for an internal combustion engine comprising intake and exhaust pipes, characterized in that it comprises in combination an engine brake with reduction of compression, operating when at least one exhaust valve of the combustion engine is opened in the vicinity of the end of the compression stroke of the cylinder of the engine with which said exhaust valve is associated, and a turbine supercharging (30) consisting of an exhaust gas turbine (26) comprising a subdivided volute and an air compressor (28) which supplies compressed air to said intake manifold (12) of the engine, said turbine 15-supply air comprising a bypass valve (22) coupled on one side to the exhaust manifold (14, 16) and on the other side to the divided volute, to direct, with a predetermined braking action , the exhaust gas stream from the exhaust manifold towards one part of said subdivided volute instead of the two, as is the case when braking less than said predetermined braking action. 2. System according to claim 1, characterized in that the exhaust gas turbine is a radial flow turbine. 3. System according to one of claims 1 or 2, characterized in that the bypass valve.de is a butterfly valve (156) actuated by a solenoid. 4. Braking method, with better engine perfor-30 mance, of an internal combustion engine vehicle, characterized in that it consists in equipping the vehicle with a supercharged engine comprising a supercharging turbine comprising a subdivided volute and a compression reduction type engine brake directing the exhaust gases from the exhaust pipe of the engine upon predetermined actuation of said reduction type engine brake of compression, towards a part of said volute subdivided i 18 to increase the speed of rotation of the supercharging turbine to a value greater than that which it would take if the exhaust gases were directed towards the two parts of the subdivided volute, which increases, as a function of the higher speed of rotation of the supercharging turbine, the mass flow of air in the supercharging turbine, thereby preventing exhaust gases t come out of the exhaust manifold, and continuously compresses the greater air flow, better braking and better engine performance resulting from the release of the greater mass of compressed air towards the exhaust manifold near the end of the engine compression stroke. 5. Method according to claim 4, characterized in that when one stops using the engine brake with reduction \ iction of compression, the flow of exhaust gases is directed towards the two parts of the volute subdivided.