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EP-4264023-B1 - ROCKER ARM VALVE MECHANISM

EP4264023B1EP 4264023 B1EP4264023 B1EP 4264023B1EP-4264023-B1

Inventors

  • KARLIN, MICHAEL
  • LINDBERG, Ulric
  • SJÖGREN, Johan
  • MOHLIN, JOHAN

Dates

Publication Date
20260506
Application Date
20211210

Claims (8)

  1. A valve mechanism system in a hydraulic rocker arm (1) for a combustion engine, comprising a check valve spring (2) and a check valve ball (3), wherein said spring (2) is arranged to be in contact with the check valve ball (3) and wherein said spring (2) and ball (3) are arranged in a seat (4) in a recess (5) in the rocker arm (1), the recess (5) having a first opening (6) to a rocker arm channel (7) connected to a hydraulic element and a second opening (8) to a rocker arm oil supply via a second channel (9), the system further comprising a control piston (10) having a first end with a pin (11) axially aligned with the control piston (10) arranged in contact with said check valve ball (3) on the opposite side of the check valve ball (3) from the check valve spring (2), the check valve ball (3) being movable between a first position allowing oil to flow to and from the oil supply and a second position stopping oil from flowing between the two channels (7, 9), wherein a control piston spring (12) is arranged on a second end of the control piston (10) such that it biases the control piston (10) towards the check valve ball (3), wherein the control piston (10) in an axial direction is movably arranged in a cylinder shaped cartridge (13) and that the cartridge has a first end arranged towards the outside of the rocker arm (1) and a second end in the axial direction opposite inner end, wherein the cartridge is arranged in said recess (5) in the rocker arm (1) wherein the second end of the cartridge (13) has an opening (14) that is larger than the diameter of the pin (11) of the control piston (10) and smaller than the control piston diameter wherein the cartridge (13) comprises two parts, a first part (16) comprising the first end with an inside cylinder shape to house the control piston (10) and a second seat part (17) comprising the second end characterised in having at least two openings (18) arranged to allow oil to flow to and from a rocker arm oil supply via the second opening (8) in the recess when the check valve ball (3) is in said first position.
  2. The valve mechanism system according to claim 1, wherein the hydraulic element is a piston.
  3. The valve mechanism system according to any of the preceding claims, wherein the outside of the second end of the cartridge has a seat (15) for the check valve ball (3).
  4. The valve mechanism system according to any of the preceding claims, wherein the cartridge (13) comprises an outer circumferential ledge (19) and wherein a seat (20) for said ledge (19) is provided in the rocker arm (1).
  5. The valve mechanism system according to any one of the preceding claims, wherein the second seat part (17) of the cartridge comprises an outer circumferential ledge (19) and wherein a seat (20) for said ledge (19) is provided in the rocker arm (1).
  6. The valve mechanism system according to any of the preceding claims, wherein the cartridge (13) has outer threads (21) for engaging with inner threads (22) of the recess (5) in the rocker arm (1).
  7. The valve mechanism system according to any one of the preceding claims, wherein the first part (16) of the cartridge (13) has outer threads (21) for engaging with inner threads (22) of the recess (5) in the rocker arm (1).
  8. The valve mechanism system according to any of the claims 6 and 7, wherein the first end of the cartridge (13) has a tool engagement structure (23).

Description

TECHNICAL FIELD The present invention relates to a valve mechanism system in a hydraulic rocker arm for a combustion engine, comprising a check valve spring and a check valve ball. Said spring is arranged to be in contact with the check valve ball and wherein said spring and ball are arranged in a seat in a recess in the rocker arm. The recess has a first opening to a rocker arm channel connected to a hydraulic element (piston) and a second opening to a rocker arm oil supply via a second channel. The system further comprises a control piston having a first end with a pin axially aligned with the control piston arranged in contact with said check valve ball on the opposite side of the check valve ball from the check valve spring. The check valve ball is movable between a first position allowing oil to flow to and from the oil supply and a second position stopping oil from flowing between the two channels. A control piston spring is arranged on a second end of the control piston such that it biases the control piston towards the check valve ball. BACKGROUND The role of the decompression release exhaust brake, hereafter called engine brake, is to convert a power-producing engine into a power-absorbing retarding mechanism and the valve train is a significant part of this mechanism. The engine braking mechanism for a four-stroke diesel engine is as follows. On the normal intake stroke, the intake valve opens, and air is forced into the cylinder by boost pressure from the turbocharger. Then, in the compression stroke, air is compressed by the engine piston. The energy required to compress this air is produced by the driving wheels of the vehicle. Near top dead center, the engine brake opens the exhaust valves, venting high-pressure air and dissipating the stored energy through the exhaust system. On the downward stroke, essentially no energy is returned to the piston and to the driving wheels. There is a loss of energy and this loss is how the retarding work is accomplished. The timing of the valve opening event is important because the piston at top dead center has done the maximum amount of work. If the valve is opened early, not much power will be absorbed. Similarly, if the valve is opened after top dead center, some power has been returned to the crank by the compressed air. As the valve opening event moves away from top dead center, the engine brake becomes less effective. In practice, it is necessary to use a cam or rocker motion that occurs close to top dead center for timing the valve opening event. One common characteristic of all engine brakes is that retarding power increases as engine revolutions per minute increase. In general, the same things that affect retarding performance are engine displacement, compression ratio, turbo boost, and the timing of the valve opening event. In its simplest description, the engine brake converts a diesel engine into an air compressor. Higher compression ratios producing higher cylinder pressures would result in higher retarding performance. For the engine brake to function correctly, the valve lash must be eliminated. The lubrication system of the engine is used for this purpose. It activates a power piston in the exhaust rocker arm by means of a solenoid valve in the cylinder head and this piston eliminates the valve lash. The lower part of the piston is in contact with the exhaust valves either directly or through intermediate components e.g. ball socket and valve bridge. During normal operation, the oil supply pressure in the rocker shaft is low and the power piston stays in its original position. The control piston is resting against the check valve ball and prevents it from closing. No hydraulic lock is created. When the engine brake is activated, the oil supply pressure in the rocker shaft is raised by the solenoid valve in the cylinder head and the control piston moves away from check valve ball enabling it to close against the valve seat. The power piston moves outward and eliminates the valve lash. When the brake lift cam event starts, the check valve closes and creates a hydraulic lock between cam lobe and exhaust valves. The camshaft is now in direct contact with the exhaust valves, and the extra cams provides the engine brake lift events. To deactivate the engine brake, the solenoid valve lowers the rocker shaft oil supply pressure whereby the control piston pin opens the check valve. The hydraulic lock is eliminated, power piston retracts which increases valve lash and there are no brake lift events available. Optionally, a pressure-limiting valve is built into the power piston, which opens to drain oil if the oil pressure becomes abnormally high. Previously, it was the driver's job to ascertain the correct transmission gear to use, depending on, for example, the steepness of the grade and the truck's load. However, the job of the driver has to a large extent been taken over by the powertrain and vehicle control system. Various improvements have been ma