JP2007239655A - Compression pressure release type engine brake - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To extend an adjustment range of braking force by enabling to increase and decrease intake air quantity in an adjustment range wider than a former engine brake. <P>SOLUTION: An compression pressure release type engine brake providing braking force by releasing compression pressure by forcibly opening an exhaust valve at a position near compression top dead center of an engine, is provided with a variable valve gear 27 adjusting open and close timing and lift of an intake valve 4í of each cylinder 1, and is constructed to enable to adjust braking force by suitably increasing and decreasing intake air quantity at a time of braking by the variable valve gear 27. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a compression pressure release type engine brake.

  Conventionally, in large vehicles such as trucks and buses, since the vehicle weight is originally large and a load is applied, the inertial force acts greatly at the time of deceleration, which increases the burden on the service brake device.

  Therefore, when braking is frequently performed on downhills, etc., engine brakes are generally used together. However, when the load is large or the slope is steep, it is sufficient. The engine brake effect may not be obtained.

  For this reason, the braking force obtained in the compression stroke is reduced by forcibly opening the exhaust valve near the compression top dead center of the engine and releasing the compression pressure to reduce the generation of the force that pushes down the piston in the next expansion stroke. It has been practiced to equip with a compression pressure release type engine brake that effectively works.

  FIG. 3 shows an example of a conventional compression pressure release type engine brake. In FIG. 3, 1 is a cylinder, 2 is a combustion chamber, 3 is a piston, 4 is an exhaust valve, and 5 is an exhaust passage. Then, the exhaust cam 7 mounted on the camshaft 6 pushes the base end up through the roller 8a and the tip of the rocker arm 8 tilts to push down both the exhaust valves 4 through the valve bridge 9, thereby opening the combustion chamber 2. The exhaust gas 10 is scavenged from the exhaust passage 5 to the exhaust passage 5.

  Here, in the illustrated example, an adjustment screw 15 for adjusting the distance to the top of the valve bridge 9 is provided at the tip of the rocker arm 8, and the valve bridge is provided at the lower end of the adjustment screw 15. A tip 15a is swingably mounted so as to be able to always come into contact with the top of 9 in a horizontal state.

  When both exhaust valves 4 are pushed down by the tip of the rocker arm 8 via the valve bridge 9 and opened, the master piston provided at the upper hydraulic unit 11 has the base end of the rocker arm 8 12 is pushed up, pressure is generated in the oil passage 13 formed in the hydraulic unit 11, and the slave piston 14 located above another cylinder 1 is driven and lowered. The upper part of the rocker arm 8 is pushed down so that both exhaust valves 4 can be opened via the valve bridge 9.

  That is, the operation of the master piston 12 of another cylinder 1 that is in the exhaust stroke causes the slave piston 14 of the cylinder 1 that is in the vicinity of the compression top dead center to be driven, and the slave pistons of the cylinders 1 that have the same stroke timing are driven. 14 and the master piston 12 are connected by an oil passage 13, and a solenoid valve 16 which is a hydraulic oil supply means for switching between holding and releasing the oil pressure of the oil passage 13 and a control are connected to the oil passage 13. The hydraulic oil 18 (engine oil) is supplied through the valve 17.

  Here, the solenoid valve 16 supplies and shuts off the hydraulic oil 18 by a control signal 16a from a control device 19 constituting an engine control computer (ECU: Electronic Control Unit), and the control valve 17 opens the solenoid valve 16. It functions as a check valve so that the oil pressure of the oil passage 13 is maintained in the state, and functions to release the oil pressure of the oil passage 13 to the relief port 20 when the solenoid valve 16 is closed.

  In FIG. 3, 21 is intake air, 22 is an intake flow path, 23 is a rocker shaft that pivotally supports a rocker arm 8 that performs intake and exhaust, and forms a tilt axis of the rocker arm 8, and 24 is a compressor. A variable geometry turbocharger comprising 24a and a turbine 24b is shown.

  Thus, in such a compression pressure release type engine brake, when the solenoid valve 16 is opened by the control signal 16a, the control valve 17 functions as a check valve and the oil passage 13 is closed. When each of them approaches the pressure top dead center at different timing, the master piston 12 is pushed up via the rocker arm 8 by pushing up the exhaust cam 7 for opening the exhaust valve 4 of another cylinder 1 in the exhaust stroke. As a result, pressure is generated in the oil passage 13 and the slave piston 14 of the cylinder 1 near the compression top dead center is driven to open one of the exhaust valves 4, so that the combustion chamber 2 to the exhaust passage 5 is opened. Thus, the compressed air is released and the generation of a force for pushing down the piston 3 in the next expansion stroke is reduced, and the braking force obtained in the compression stroke is effectively utilized.

  If the solenoid valve 16 is closed by the control signal 16a, the oil pressure of the oil passage 13 is released by the control valve 17, and no pressure is generated in the oil passage 13, so that the slave piston 14 is not driven and the exhaust valve 4 is opened only in the exhaust stroke by a normal valve opening operation, and is not opened near the compression top dead center.

  However, in the method in which the master piston 12 is operated by the rocker arm 8 as described above, the cylinders 1 having the timings are connected to each other by the oil passage 13, so that the oil passage 13 is complicated and the oil passage 13 is complicated. In addition, since the valve opening / closing timing of each cylinder 1 is uniquely determined, it is difficult to open the exhaust valve 4 of each cylinder 1 at an optimal timing near the compression top dead center. .

  Therefore, in recent years, in order to enable the exhaust valve 4 to be opened at an optimal timing near the compression top dead center without requiring a complicated oil passage 13, as shown in FIG. Brake-dedicated cam 7 ″ is added to camshaft 6 equipped with intake cam 7 ′ for opening operation through arm 8 ′ and exhaust cam 7 for opening exhaust valve 4 through rocker arm 8. It has been proposed that the master piston 12 is operated near the compression top dead center through the brake rocker arm 8 "by the brake cam 7".

  Here, the specific structure of the brake rocker arm 8 ″ is as shown in FIG. 5. In the brake rocker arm 8 ″ shown here, the base end side is tiltably removed with respect to the rocker shaft 23. The lever structure is fitted, and is brought into contact with the brake dedicated cam 7 "through the rollable roller 8a" provided at the lower end of the tip, and pushed up by the brake dedicated cam 7 ", whereby the rocker shaft The master piston 12 is pushed up at the upper end on the tip side by tilting around the center 23.

  In this manner, if a system in which the brake dedicated cam 7 ″ is added to the camshaft 6 and the master piston 12 is operated via the brake rocker arm 8 ″ is adopted, the oil passage 13 is completed for each cylinder 1. Therefore, each oil passage 13 can be simplified, and the exhaust valve 4 of each cylinder 1 can be opened at an optimal timing near the compression top dead center.

  In such a conventional compression pressure release type engine brake, a relatively high braking force can be effectively obtained. However, even if just a good braking force is obtained in a transport vehicle having a large load, the load is small. In a transport vehicle, etc., the braking force is more effective than necessary, which may lead to a deterioration in fuel consumption. Therefore, the variable geometry turbocharger 24 increases or decreases the intake air amount to increase the braking force of the engine brake with the compression pressure released. You can adjust it.

  That is, since the braking force obtained by releasing the compression pressure near the compression top dead center of the engine depends on the amount of compressed working gas, the amount of intake air that forms this working gas is changed to the variable geometry turbocharger. If it increases or decreases by 24, the braking force of the compression pressure release type engine brake is adjusted.

  Here, in the variable geometry turbocharger 24, the opening degree of the nozzle vane 25 is adjusted by tilting the nozzle vane 25 of the turbine 24b by the actuator 26. For example, a control signal 26a is sent from the control device 19 to the variable geometry turbocharger 24. When the actuator 26 is operated to output and the opening degree of the nozzle vane 25 is greatly opened with respect to a certain amount of exhaust gas, the rotational speed of the exhaust gas 10 in the turbine 24b of the variable geometry turbocharger 24 is lowered, and thereby the turbine 24b Decreases the intake air amount on the compressor 24a side.

  On the other hand, when the opening degree of the nozzle vane 25 is reduced with respect to a certain amount of exhaust gas, the rotational speed of the exhaust gas 10 in the turbine 24b of the variable geometry turbocharger 24 is increased, whereby the rotational speed of the turbine 24b is increased. And the intake air amount on the compressor 24a side increases.

As prior art document information related to this type of compression pressure release type engine brake, there is the following Patent Document 1 and the like.
Japanese Patent Laid-Open No. 10-18866

  However, even though the variable geometry turbocharger 24 increases or decreases the amount of intake air, the rotation speed of the exhaust gas 10 in the turbine 24b is changed by adjusting the opening of the nozzle vane 25, whereby the rotational speed of the turbine 24b (turbine efficiency) ) To increase or decrease the intake air amount, there is a problem that the adjustment range of the braking force cannot be wide because the adjustment range of the intake air amount that can be increased or decreased is narrow.

  The present invention has been made in view of the above-described circumstances, and has an object to expand the adjustment range of the braking force of the compression pressure release type engine brake so that the intake air amount can be increased or decreased in a wider adjustment range than before. Yes.

  The present invention relates to a compression pressure release type engine brake that obtains a braking force by forcibly opening an exhaust valve in the vicinity of the compression top dead center of an engine to release the compression pressure. A variable valve mechanism that adjusts the opening / closing timing and lift of the valve is provided, and the variable valve mechanism is configured to adjust the braking force by appropriately increasing / decreasing the amount of intake air during braking. .

  Thus, when the intake valve is opened at the timing and lift when the volumetric efficiency of the cylinder is maximized, the intake air amount taken into the cylinder is maximized and the braking force is maximized. Also, if the volumetric efficiency is intentionally deteriorated by making the intake valve closing timing earlier or later than this time, the intake air amount is reduced by the amount that the volumetric efficiency has deteriorated, and the braking force is reduced. In addition, it is possible to reduce the braking force by further reducing the intake air amount by making the lift when the intake valve is opened smaller than usual.

  In the present invention, the variable valve mechanism and the variable geometry turbocharger can be used in combination so that the braking force can be adjusted. In this way, the intake air amount can be adjusted wider. The range can be increased or decreased, and the adjustment range of the braking force can be further expanded.

  According to the above-described compression pressure release type engine brake of the present invention, the intake air is intentionally deteriorated by decelerating the closing timing of the intake valve in the intake stroke from the timing with the highest volumetric efficiency, thereby intentionally deteriorating the volumetric efficiency. The amount of intake air can be reduced, and the intake air amount can be further narrowed by reducing the lift when the intake valve is opened to a lower level than usual. As a result, the braking force adjustment range can be greatly expanded.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows an example of an embodiment for carrying out a compression pressure release type engine brake according to the present invention, and parts denoted by the same reference numerals as in FIGS. 3 to 5 represent the same items.

  In this embodiment, a brake dedicated cam 7 ″ (see FIGS. 4 and 5) is mainly added to the camshaft 6 and a master piston 12 (FIG. 5) is provided via a brake rocker arm 8 ″ (see FIGS. 4 and 5). Exhaust cam 7 (see FIG. 3) for opening the exhaust valve 4 (see FIG. 3) of another cylinder 1 in the exhaust stroke is targeted. The compression pressure release type engine brake adopting a method in which the master piston 12 (see FIG. 3) is operated via the rocker arm 8 (see FIG. 3) by pushing up, and the compression pressure using any method can be used. Even in an open type engine brake, a variable valve mechanism 27 for adjusting the opening / closing timing and lift of the intake valve 4 ′ of each cylinder 1 is provided, and braking is performed by the variable valve mechanism 27. Is characterized by composing the intake air amount as appropriate may adjust the braking force by increasing or decreasing the.

  In other words, in the example shown in FIG. 1, a rocker arm 28 is mounted on the rocker shaft 23 and tilted by one end being pushed up by the intake cam 7 'via the roller 28a. The master piston 30 provided in the unit 29 is pushed up to generate hydraulic pressure in the valve opening oil passage 31 formed in the hydraulic unit 29 to lower the slave piston 32 directly above the valve bridge 9. Thus, both intake valves 4 ′ can be pushed down through the valve bridge 9 to be opened.

  Here, an oil supply passage 34 is provided in the valve opening oil passage 31 in the hydraulic unit 29 via a solenoid valve 33 (hydraulic supply means) for switching between holding and releasing the oil pressure of the valve opening oil passage 31. The hydraulic oil 18 that is connected and fed by an oil pump (not shown) is introduced into the valve opening oil passage 31 to fill the valve opening oil passage 31. When the master piston 30 is operated, control from the control device 19 is performed. Based on the signal 33a, the opening / closing timing and lift of the intake valve 4 'can be adjusted by appropriately switching between holding and opening of the hydraulic pressure of the valve opening oil passage 31 and controlling the follow-up timing and operation amount of the slave piston 32. It is.

  That is, when the master piston 30 is operated, if the hydraulic pressure of the valve opening oil passage 31 is maintained by closing the solenoid valve 33, the slave piston 32 is operated immediately following the operation of the master piston 30, and If the hydraulic pressure in the valve opening oil passage 31 is released to the accumulator or the like by opening the solenoid valve 33, the slave piston 32 will not follow even if the master piston 30 is actuated. It becomes possible to do.

  Further, in the present embodiment, a variable geometry turbocharger 24 that can adjust the opening degree of the nozzle vane 25 of the turbine 24b by the control device 19 is also provided. If necessary, the variable geometry turbocharger 24 is used. Control for adjusting the amount of intake air can be used together.

  Thus, in this way, the intake air taken into the cylinder 1 when the intake valve 4 'is opened with the timing and lift at which the volumetric efficiency of the cylinder is maximized as indicated by A in FIG. The amount is maximized and the braking force is also maximized. Also, the timing for closing the intake valve 4 'may be advanced as shown in Fig. 2B or delayed as shown in Fig. 2C. When the volumetric efficiency is intentionally deteriorated, the amount of intake air is reduced by the amount that the volumetric efficiency is deteriorated, and the braking force is reduced.

  Moreover, as indicated by D in FIG. 2, the timing of closing the intake valve 4 ′ is further advanced than B in FIG. 2 so that the intake valve 4 ′ starts to be closed before reaching the maximum lift. It is also possible to further reduce the intake air amount by making the lift of the air intake smaller than usual.

  Note that E in FIG. 2 indicates the timing and lift of the forced opening operation of the exhaust valve 4 (see FIG. 3) executed to release the compression pressure near the compression top dead center.

  In the present embodiment, the variable valve mechanism 27 and the variable geometry turbocharger 24 can be used together to adjust the braking force, so that the intake air amount can be increased or decreased within a wider adjustment range. Thus, the adjustment range of the braking force can be further expanded.

  Therefore, according to the above embodiment, the volumetric efficiency is intentionally deteriorated to reduce the intake air amount by advancing or delaying the closing timing of the intake valve 4 'in the intake stroke from the most efficient timing. In addition, the intake air amount can be further reduced by making the lift when the intake valve 4 ′ is opened smaller than usual. Further, the intake air amount by the variable geometry turbocharger 24 can be reduced. Therefore, the intake air amount can be increased or decreased in a wider adjustment range than before, and the adjustment range of the braking force can be greatly expanded.

  The compression pressure release type engine brake of the present invention is not limited only to the above-described embodiments, and the variable valve mechanism is not necessarily limited to the illustrated examples, and other within the scope not departing from the gist of the present invention. Of course, various changes can be made.

It is the schematic which shows an example of the form which implements this invention. It is a graph explaining control of the intake valve by a variable valve mechanism. It is the schematic which shows an example of the conventional compression pressure release type engine brake. It is a top view which shows the example which extended the cam only for a brake to the cam shaft. It is a side view of the rocker arm for brakes of FIG.

Explanation of symbols

1 cylinder 4 exhaust valve 4 'intake valve 10 exhaust gas 21 intake air 24 variable geometry turbocharger 27 variable valve mechanism

Claims (2)

  A compression pressure release type engine brake that obtains braking force by forcibly opening the exhaust valve near the compression top dead center of the engine to release the compression pressure, and the intake valve opening and closing timing of each cylinder And a variable valve mechanism that adjusts the lift, and the variable pressure mechanism can be used to adjust the braking force by appropriately increasing or decreasing the amount of intake air during braking.   2. The compression pressure release type engine brake according to claim 1, wherein the variable pressure mechanism and the variable geometry turbocharger are used in combination so that the braking force can be adjusted.

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