JPS6321003B2 - - Google Patents

Abstract

An internal combustion engine comprising a spring-loaded engine valve (13) actuatable by means of a cam (2), a tappet (4) and a push rod (10), the cam (2) having a pre-lift ramp (5) for effecting exhaust braking of the engine. A single piston (6) is slidable in the tappet (4) between a bottom stop (8) and a top stop (7) therein and biased by a spring (9) against the top stop (7) and/or the push rod (10). The tappet (4) has an inlet (14) for hydraulic, control fluid to bias the piston (6) towards the top stop (7). There is also a valve (17) preventing escape of hydraulic fluid from the tappet (4) during exhaust braking. During normal operation of the engine when the pre-lift ramp (5) lifts the tappet (4) the valve (17) is held open and hydraulic control fluid flows from the tappet (4) so that the piston (6) contacts the bottom stop (8) and the engine valve (13) remains closed, whereas during exhaust braking of the engine when the pre-lift ramp (5) lifts the tappet (4) the valve (17) is closed and hydraulic control fluid cannot flow from the tappet (4) so that the pistons (6) remains against the stop (7) and the engine valve (13) opened to effect exhaust braking. <IMAGE>

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention includes a hydraulic tappet in a valve drive device, in which a piston is guided so as to be longitudinally movable between a lower stopper and an upper stopper. The piston is constantly loaded by the force of a spring, and during engine braking, the piston is held against the upper stop by supplying a hydraulic control medium, so that the tappet The present invention relates to an internal combustion engine with an engine brake configured to control by opening a gas exchange valve in a manner that increases the effective length of the engine.

An internal combustion engine of this kind is already known from German Patent No. 1057385. In this known internal combustion engine, a piston located in the tappet of the valve drive is pressed against a lower stop by the force of a spring during normal engine operation, so that the tappet is It is designed to ensure the normal length required to open and close the applicable gas exchange valve. During engine braking, oil under high pressure forces the piston, which moves against the force of the spring to the upper stop, lengthening the tappet and thus keeping the gas exchange valve at a constant size. This results in a reduction in the compression work in that cylinder of the engine.

A second piston serving as a valve play compensator is movably supported in the piston used for engine braking, the second piston being biased by a spring or by means of oil. By doing so, it comes into contact with the tapepet rod or upper stopper. Since the oil used in the play compensation device can be extracted from the engine's lubricating oil circuit, very high pressures must be ensured to energize the pistons used for engine braking. This is because the force of the spring acting on the piston and the force of the valve spring must be overcome in the manner described above.

As a result, it is common practice to run two oil lines, each with a check valve, to the tappet and install two sets of pumps producing different pressures; In addition to the complicated structure, it is necessary to prepare a complete set of expensive control systems. It goes without saying that a pump can be used to supply oil to the conventionally known tappet.
The number of control devices required to generate different pressures increases.

Due to the use of complex tappets and control devices, it is no surprise that there is a high risk of failure. This applies in particular to hydraulic valve play compensation devices. Because when using this hydraulic valve play compensation device,
This is because oil leakage loss increases as the engine speed increases, making it impossible to accurately limit the opening and closing of the valve. In addition, during engine braking operation, the line pressure may not be sufficient to counteract the forces generated for a long time.
Another idea is to virtually keep the valve open at all times.

It is therefore an object of the invention to provide an internal combustion engine with an engine brake of the initially mentioned type, which eliminates the above-mentioned disadvantages of those previously known, i.e. as simple as possible in construction and control. At the same time, it is an object of the present invention to provide an internal combustion engine that functions reliably, has a short response time, and is improved so that failures of the entire valve drive section are minimized.

According to the invention, the valve tappet of the exhaust valve is provided with a piston for braking, and when the engine is running normally, the piston is moved by the force of a spring to the upper stopper and/or The tappet rod is held resiliently against the tappet rod, the cam for operating the tappet is provided with a front ridge for moving the tappet, especially during the compression stroke, and a hydraulic control medium is used. The spring and the valve spring are mutually adjusted, if necessary under the complementary action of the control medium, so that when the fully energized state is released, the tappet moves and the piston rests against the lower stop. This was achieved by doing so.

As described above, the structure of the tapepet is simple, easy to manufacture, and does not require any maintenance.
Since the piston is not biased by hydraulic control means and is held by the spring against the upper stop or tappet rod, no play occurs in the entire valve drive. German patent no.
Unlike in No. 1057385, during engine braking, the exhaust valve is opened by a front ridge or front cam during the compression stroke. Due to the constant pump effect, leakage losses can always be compensated for depending on the control mode. Separation or blowing out of the air from the control medium can be suitably carried out, as is already known, by orienting the piston guide upwards and vertically. As will be explained later, the damping effect caused by the arrangement of the spring on the vibrations of the valve drive device that occur even when the engine is running normally is as follows: In this region, the tappet is filled with control medium, which is then discharged back into the control circulation system.

In a further embodiment of the invention, it is proposed that the maximum lift of the piston is equal to the height of the cam's front elevation. It is advantageous to use oil as control medium, which oil can be taken from the engine lubricant circuit.

In another embodiment of the invention, the control medium supply line extending inside the tappet is provided with a shutoff valve consisting of a spring and a closing body for preventing backflow of the control medium, and the engine is It is proposed that during normal movement the closure can be moved into the open position by means of a pin projecting into the control medium supply line. In this case, the pin can be constructed as a piston rod of a pneumatic cylinder and held in the position of use by a spring which is engaged with the piston of the pneumatic cylinder. In this arrangement, the engine's lubrication pump can be used to supply the hydraulic control medium.

Instead of the above-mentioned shut-off valves, all the control medium supply lines of the engine extending into the tappets communicate with a common collecting pipe, which is connected to a pump, preferably a high-pressure pump, and which is connected to a pump, preferably a high-pressure pump. It is proposed according to the invention that an overflow valve, which keeps the pressure of the medium constant, and a cut-off valve, which regulates the flow of the control medium, are attached to the collecting pipe. Preferably, a solenoid valve is used as the shutoff valve.

A number of additional advantages can be obtained with the last described arrangement. For example, by using a pump it is possible to close the shut-off valve and bring the piston in the tappet into contact with the upper stop very quickly, while quickly compensating for any leakage losses that have occurred and allowing the piston to rest against the upper stop. A very limited valve lift can be maintained. By using a pump, the working pressure of the piston can be generated forcibly, so that the air contained in the oil does not play any role. Dirt generated from oil becomes fine mechanical particles that do not settle but mainly migrate through the leaked oil. Furthermore, according to the above arrangement, regardless of the number of cylinders, only one set of pump and one set of shutoff valve is required for the entire engine, so the entire device can be easily inspected. It is less likely to break down and is inexpensive.

Finally, considering the power required for the pump, it is very desirable that the power required for the pump is only a few kilowatts, and that power is required only for engine braking.

When the engine is running normally, the shutoff valve is open, so the pump simply rotates without pressure and consumes no power.

The present invention will now be described in detail with reference to the accompanying drawings, which illustrate the invention.

As shown in FIG. 1, a tappet 4 having a cavity 3 inside and operated by a cam 2
is pivotally supported in the main body 1 so as to be movable in the longitudinal direction. The cam 2 is additionally provided with a front elevation or a front cam 5 . The piston 6 is mounted movably in the cavity 3 of the tappet 4 between an upper stop 7 and a lower stop 8, and in the normal case, under the force of a spring 9, the upper stop 7 or the tappet rod 10 It is pressed against the lower edge of the Note that the tapepet rod 10 is
Via the conceptually illustrated tilting lever 11 it is intended to act on an exhaust valve 13 of an engine cylinder (not shown) which is held in the closed position by the force of a valve spring 12.

The cavity 3 of the tapepet 4 has one or more holes 1
4 and the control medium supply conduit 16 through the ring groove 15.
A shutoff valve consisting of a spherical closure body 17 and a spring 18 is arranged in the control medium supply line 16. Designed as a piston rod of the pneumatic cylinder 20, when the engine is running normally, the spring 22 engaged with the piston 21 of the pneumatic cylinder 20 acts on the closing body 17 and opens it. A pin 19 that holds it in position projects into the control medium supply line 16. piston 2
1 can be operated against the force of a spring 22 by means of compressed air supplied via line 23. The conduit 24 is provided to prevent the control medium from entering the pneumatic cylinder 20 and to discharge any leakage.

When the engine is running normally, the closing body 17
is held in the open position by pin 19, allowing the control medium to circulate freely. Since the force exerted on the piston 6 by the control medium and the spring 9 is significantly smaller than the force of the valve spring 12, the front bulge 5
When the piston 6 passes the lower stopper 8
Since the exhaust valve 13 is pressed against the exhaust valve 13, the exhaust valve 13 remains closed.

When the engine is in braking condition, the piston 21
is biased by the compressed air, so that the pin 19 moves to the right in FIG. . When the front elevation 5 hits the tappet 4, the piston cannot move, so that the tappet rod 10 is lifted, so that the exhaust valve 13 remains open by a certain partial lift. The leakage losses occurring in the piston 6 and the tappet guide are compensated by the control medium supply line 16 while the tappet 6 is moving on the base circle of the cam 2. When the tappet 4 moves downwards to such an extent that the piston 6 can no longer be pushed downwards due to the tappet rod 10, only the force of the spring 9 acts;
The piston 6 presses against the upper stop and the closing body 17 leaves the valve seat, so that the control medium is sucked in again.

In FIG. 2, the same parts are given the same reference numerals as in FIG. 1, and the construction of the tappet is also the same.
Regarding the control, the control medium supply lines 16 for all tappets 4 of the engine are connected to a common collecting line 25 which is connected via line 26 to a high-pressure pump 27.
is connected to. An overflow valve 28 and an electromagnetic cutoff valve 29 are attached to the conduit 25.

When the engine is running normally, shutoff valve 2
9 is in the position shown, and the control medium is continuously discharged, so that no pressure is created in the pipe line 26 and the collecting pipe 25. When the front protuberance 5 is below the tappet 4, the piston 6 moves downward and the exhaust valve 13 does not open. When the shutoff valve 26 is switched to the second position, engine braking begins and the collector pipe 25
A pressure is created in the cavity 3 of the tappet 4, but this pressure is set by the overflow valve 28, and even when the front bulge 5 lifts the tappet 4, the piston 6 is kept against the upper stop 7. It is set to be large enough to be held in contact with it.

In general, the valve lift during controlled operation is as large as the height of the front elevation 5. And it is worth noting that this means that the pistons of the engine must be pocketed as much as possible to avoid bumps on the exhaust side.
In addition, when appropriately selecting the preload (pressure applied to the tip of the cam) and the length of close contact between the valve spring, consideration must be given to further increasing the valve lift.

[Brief explanation of the drawing]

1 is a longitudinal sectional view of a tappet equipped with a control valve according to the invention, and FIG. 2 is a purely sectional view of the same tappet as in FIG. A schematic diagram conceptually shown. 1... Body, 2... Cam, 3... Blank space, 4...
Tappet, 5... Front raised part, 6... Piston,
7... Upper stopper, 8... Lower stopper,
9... Spring, 10... Tappet rod, 11...
... Inclined lever, 12 ... Valve spring, 13 ... Exhaust valve, 14 ... Hole, 15 ... Annular groove, 16 ... Control medium supply pipe, 17 ... Closing body, 18 ... Spring, 19 ... Pin, 20...Pneumatic cylinder, 21...Piston, 22...Spring, 2
3...Compressed air pipe line, 24...Pipe line for discharging leaked control medium, 25...Common collection pipe line, 2
6...Pipe line, 27...High pressure pump, 28...Overflow valve, 29...Solenoid cutoff valve.

Claims (1)

[Scope of Claims] 1. An internal combustion engine in which braking is performed by opening an exhaust valve during a compression stroke, and the exhaust valve loaded with a spring force is operated via an inclined lever and a tapered rod.
connected to a hydraulic tappet abutting the cam, in which a spring-loaded piston is disposed for longitudinal movement between a lower stop and an upper stop; The hydraulic tappet 4 is operated in an internal combustion engine having a hydraulic source equipped with a pump and a control medium supply pipe equipped with a shutoff valve that can be opened and closed. The cam 2 has a front ridge 5, the height of which is equal to the maximum stroke of the piston 6 in the tappet 4, and the spring 9 of the piston 6 placed in the tappet 4 ensures that the piston is on the tappet rod. An internal combustion engine characterized by being arranged in contact with a piston on a surface opposite to a surface in contact with the piston. 2. In the internal combustion engine according to claim 1, the cutoff valve is a check valve 17, and a pneumatic cylinder 20 is provided in the control medium supply pipe 16.
An internal combustion engine in which a pin 19, a piston rod, is arranged, which pin opens the check valve during normal operation and closes it during braking. 3. In the internal combustion engine according to claim 1, all the control medium supply lines 16 are connected to a common collection line 25, and the collection line 25 is connected to the pump 24 via an additional line 26. connected to the conduit 26
An internal combustion engine is provided with an overflow valve 28 and the cutoff valve 29, and the cutoff valve is opened and closed electromagnetically.