GB2608166A - Cam switching mechanism - Google Patents

Cam switching mechanism Download PDF

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Publication number
GB2608166A
GB2608166A GB2109109.5A GB202109109A GB2608166A GB 2608166 A GB2608166 A GB 2608166A GB 202109109 A GB202109109 A GB 202109109A GB 2608166 A GB2608166 A GB 2608166A
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GB
United Kingdom
Prior art keywords
switching mechanism
cam switching
cylinder
valve
slave cylinder
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
GB2109109.5A
Other versions
GB202109109D0 (en
Inventor
Stackhouse Ryden
Bedborough David
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mechadyne International Ltd
Original Assignee
Mechadyne International Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mechadyne International Ltd filed Critical Mechadyne International Ltd
Priority to GB2109109.5A priority Critical patent/GB2608166A/en
Publication of GB202109109D0 publication Critical patent/GB202109109D0/en
Publication of GB2608166A publication Critical patent/GB2608166A/en
Pending legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L9/00—Valve-gear or valve arrangements actuated non-mechanically
    • F01L9/10—Valve-gear or valve arrangements actuated non-mechanically by fluid means, e.g. hydraulic
    • F01L9/11—Valve-gear or valve arrangements actuated non-mechanically by fluid means, e.g. hydraulic in which the action of a cam is being transmitted to a valve by a liquid column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L13/00—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations
    • F01L13/0015—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for optimising engine performances by modifying valve lift according to various working parameters, e.g. rotational speed, load, torque
    • F01L13/0036—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for optimising engine performances by modifying valve lift according to various working parameters, e.g. rotational speed, load, torque the valves being driven by two or more cams with different shape, size or timing or a single cam profiled in axial and radial direction
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B69/00—Internal-combustion engines convertible into other combustion-engine type, not provided for in F02B11/00; Internal-combustion engines of different types characterised by constructions facilitating use of same main engine-parts in different types
    • F02B69/06—Internal-combustion engines convertible into other combustion-engine type, not provided for in F02B11/00; Internal-combustion engines of different types characterised by constructions facilitating use of same main engine-parts in different types for different cycles, e.g. convertible from two-stroke to four stroke
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
    • F01L1/36—Valve-gear or valve arrangements, e.g. lift-valve gear peculiar to machines or engines of specific type other than four-stroke cycle
    • F01L1/38—Valve-gear or valve arrangements, e.g. lift-valve gear peculiar to machines or engines of specific type other than four-stroke cycle for engines with other than four-stroke cycle, e.g. with two-stroke cycle
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2400/00—Control systems adapted for specific engine types; Special features of engine control systems not otherwise provided for; Power supply, connectors or cabling for engine control systems
    • F02D2400/02—Four-stroke combustion engines with electronic control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2400/00—Control systems adapted for specific engine types; Special features of engine control systems not otherwise provided for; Power supply, connectors or cabling for engine control systems
    • F02D2400/04—Two-stroke combustion engines with electronic control

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Valve Device For Special Equipments (AREA)

Abstract

A cam switching mechanism for an engine is disclosed for selectively enabling a valve 10 to be operated by any one of a plurality of cams 12, 14. The mechanism is a hydraulic mechanism that comprises a plurality of master cylinders 30, 32 each associated with a given cam lobe, and a single slave cylinder 40 associated with the valve. The master cylinders are connected to the slave cylinder by valving, such as a spool valve 20, that permits only one selected master cylinder to communicate with the slave cylinder at any one time. When each master cylinder is not connected to the slave cylinder it can be connected to an accumulator 50 or use a deactivation mechanism. The system can be used to maximize engine economy, minimize emissions or to switch between four-stroke and two-stroke modes.

Description

Cam Switching Mechanism
Field of the invention
The present invention relates to a cam switching mechanism for an engine valve, to permit the valve to be operated at different times by cams having different profiles.
Background of the invention
The optimal times at which an engine valve is operated, i.e., opened and closed, depend on the mode of operation of the engine. For example, the valve timing required to maximize performance differs from the timing required to maximize economy or minimize emissions. Also, if an engine can operate both in four-stroke and two-stroke modes, the opening and closing times of the valves will be entirely different. In particular, intake and exhaust valves of a cylinder are required to open and close once in every crankshaft rotation when the engine is operating in two-stroke mode, but only once every two crankshaft rotations when the engine is operating in four-stroke mode.
It is already known for a valve to be associated with two different cam profiles, which may be different cam lobes on the same camshaft or cam lobes of two different camshafts, and to provide a mechanism for switching between the cam profiles. The present invention relates to a cam switching mechanism for such a valve train.
Summary of the invention
According to the present invention, there is provided a cam switching mechanism for selectively enabling a valve to be operated by any one of a plurality of cams, the mechanism being a hydraulic mechanism comprising a plurality of master cylinders each associated with a respective one of the cams, and a single slave cylinder associated with the valve, the master cylinders being connected to the slave cylinder by valving that permits only one selected master cylinder to communicate with the slave cylinder at any one time In some embodiments, each master cylinder not connected to the slave cylinder may be connected to a respective, or a common, dummy slave cylinder or variable volume accumulator. In such embodiment, each master cylinder may continue to be operated by its associated cam at all times. -2 -
In alternative embodiments, hydraulic lines of master cylinders not connected at any one time to the slave cylinder may be closed by the valving and a deactivation mechanism may be provided to prevent the master cylinder from following the associated cam profile when its hydraulic line is closed.
It is important to ensure that no engine damage be caused by incorrectly timing a switch between different cams acting on the same valve For any single engine valve, there is a safe period during each cycle when switching can be effected without risk of engine damage but the safe periods do not necessarily coincide for different types of valve (intake/exhaust) of the same cylinders, nor for the valves of different cylinders of a multi-cylinder engine.
For this reason, in some embodiments, a separate cam switching mechanism is provided is for valves of different types of the same cylinder and for valves of different engine cylinders. In other words, two intake or two exhaust valves of the same cylinder may share a cam switching mechanism but valves of different types of the same cylinder should not share a switching mechanism nor should valves, even of the same type, of different engine cylinders.
Advantageously, an engine may be provided with a control system to initiate cam switching of the engine valves at different crank angles from each other to ensure a smooth and safe transition between engine operating modes.
The valving of each cam switching mechanism may suitably comprise a spool valve, having multiple input ports for connection to the respective master cylinders, an output port leading to the slave cylinder, and sealing lands on the spool associated with each input port.
In some embodiments, the spool valve may also have at least one output port for connection to a dummy slave cylinder or a variable volume accumulator.
The spool of the spool valve may be displaced by a solenoid or hydraulically. In the latter case, the spool may be spring biased at one end and acted on at its opposite end by the pressure in a chamber connected selectively to an oil supply or to a drain. -3 -
Brief description of the drawings
The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagram of the opening times of the intake and exhaust valves of an engine cylinder when operating in two-stroke and four-stroke modes, Figure 2 is a diagram of a cam switching mechanism of the invention when set for engine operation in four-stroke mode, Figure 3 is a diagram of the cam switching mechanism of Figure 2 when set for engine operation in two-stroke mode, and Figure 4 is a schematic representation of a further embodiment of a cam switching mechanism of the invention.
Detailed description of the drawings
The invention is applicable to any engine in which valves need to be operated by different cams depending on the operation mode of the engine. For example, a cam switching mechanism may be used to switch between cams that provide different lifts or different event durations with a view to improving performance and/or reducing emissions. In the description below, the cam switching mechanism is used to enable an engine to operate selectively in a two-stroke mode and in a four-stroke mode.
Multi-mode engines that transition between a four-stroke cycle operating mode and a two-stroke cycle operating mode are not new, see for example US 7,481,185. Figure 1 shows in solid lines the valve events of a four-stroke cycle and in dotted lines the valve events of a two-stroke cycle. From this diagram, it will be seen that two-stroke operation requires twice as many valve events compared to four-stroke operation, the timing of which does not allow the two-stroke lifts to be 'masked' by the four-stroke lifts. This makes existing lost-motion switching rocker systems unfeasible solutions. Furthermore, the very small angular 'window' for the switching event makes many existing profile-switching mechanisms impracticable, as it is desirable for the switching event to occur within one engine revolution.
To address these problems, the present invention uses hydraulic lines between the cams required for the different operating modes and the engine valves and employs hydraulic valving to switch between cams operating on a common engine valve. -4 -
Figure 2 shows an engine poppet valve 10 that may be selectively operated either by a cam 12 when the engine is operating in four-stroke mode or by a cam 14 when the engine is operating in two-stroke mode. Both of the cams 12 and 14 rotate at half the crankshaft speed, but the four-stroke cam 12 has only one lift peak while the two-stroke cam 14 has two lift peaks. Conventionally, cams act on their associated valve by way of a mechanical coupling, such as a bucket, a push rod or a rocker, but in Figure 2 the coupling between the cams 12, 14 and the engine valve 1 0 is a hydraulic circuit that comprises two master cylinders 30 and 32, each associated with a respective one of the cams 12 and 14, connected by a spool valve 20 to a common slave cylinder 40 which may either act on a single valve or two valves of the same cylinder, if they are of the same type, i.e. both intake or both exhaust valves.
The hydraulic circuit also comprises a dummy slave cylinder or accumulator 50. Though only one accumulator is shown connected to two different outlet ports of the spool valve 20, it would be alternatively possible to connect each of the latter two output ports to a respective accumulator.
The spool valve 20 has a body 22 with two inlet ports each connected by a hydraulic line 34, 36 to a respective one of the master cylinders 30, 32 and two outlet ports each connected by a hydraulic line 38, 52 to a respective one of the slave cylinder 40 and the accumulator 50. The spool valve 20 is a two-position change-over valve which in one position connects the master cylinder 30 to the slave cylinder 40 and the master cylinder 32 to the accumulator 50 and in the second position reverses the connection between the inlet and outlet ports, connecting the master cylinder 32 to the slave cylinder 40 and the master cylinder 30 to the accumulator 50 In this way, in one position of the spool 24, the engine valve 10 is operated by the cam 12 and the engine operates in four-stroke mode, while the two-stroke cam 14 continues to operate the second master cylinder 32 without it having any effect on the engine valve 10, the pumped fluid merely being stored in the accumulator 50. In the second position of the spool 24, the engine valve 10 is operated by the cam 14 while fluid displaced by the master cylinder 30 is stored temporarily in the accumulator 50.
The spool 24 is illustrated as being displaced axially by hydraulic pressure. A solenoid operated valve 60 connects a working chamber 64 at one end of the spool 24 either to fluid under pressure derived from a pump or to a drain, the opposite end of the spool 24 being acted upon by a spring 62. In the position shown in Figure 2 oil under pressure has moved -5 -the spool 24 against the action of the spring to connect the master cylinder 30 to the slave cylinder 40. In Figure 3, the solenoid valve 60 has connected the working chamber 64 at the end of the spool 24 to a drain, allowing the spring 62 to move the spool 24 to its other end position in which the second master cylinder 32 is connected to the slave cylinder 40 The embodiment shown in Figure 4 has many components common to Figures 2 and 3 and in order to avoid repeating their description, they have been allocated reference numerals with the same two least significant digits but in the 100 series A first possible modification that is shown in Figure 4 is that the spool can be operated directly by means of a solenoid 166 instead of using a hydraulic circuit to move the spool.
A second modification shown in Figure 4 is that it is possible to dispense with a dummy slave cylinder or accumulator if a deactivator 180, 182 is associated with each of the master cylinders 130, 132 to prevent the cam 112, 114 that is not acting on the engine valve 110 at any given time from acting on its associated master cylinder.
Numerous cylinder deactivation mechanisms are known in the art. As an example, Figures 2 and 3 show each master cylinder operated by a rocker pivotable about a fixed point at one end and carrying a cam follower at a point between the fixed pivot point and the opposite rocker end that acts on the master cylinder. In such a configuration, a master cylinder can be deactivated by releasing a locking device and allowing the fixed pivot point to retract against a spring that is weaker than the spring acting on the engine valve.
While the spool has been described as being axially displaceable, it is alternatively possible for the spool to be rotatable, whereupon switching between cams can be performed by an electric motor, such as a stepper motor, acting on the valve spool For any given engine valve, if cam switching is not to cause engine damage, it must take place within a narrow time window, i.e. during specific camshaft angles. These time windows are not the same for intake and exhaust valves, nor are they the same for cylinders of a multi cylinder engine. Each valve type of each cylinder therefore requires its own cam switching mechanism and, as mode switching should take place within a single operating cycle, in a multi-cylinder engine, a control system receiving an input signal from a camshaft or crankshaft angular position sensor may be provided to activate the spools of the different cam switching mechanisms in sequence, each within its own permitted range of camshaft angles. -6 -

Claims (1)

  1. CLAIMS1. A cam switching mechanism for selectively enabling a valve to be operated by any one of a plurality of cams, the mechanism being a hydraulic mechanism comprising a plurality of master cylinders each associated with a respective one of the cams, and a single slave cylinder associated with the valve, the master cylinders being connected to the slave cylinder by valving that permits only one selected master cylinder to communicate with the slave cylinder at any one time.c 2. A cam switching mechanism as claimed in claim 1, wherein each master cylinder not connected to the slave cylinder is connected to a respective, or a common, dummy slave cylinder or variable volume accumulator.3. A cam switching mechanism as claimed in claim 1, wherein the valving is operative to close off hydraulic lines of master cylinders not connected at any one time to the slave cylinder and wherein a deactivation mechanism is provided to prevent each master cylinder from following the profile of the associated cam when the hydraulic line of the master cylinder is closed off.4. A cam switching mechanism as claimed in any one of the preceding claims, wherein a separate cam switching mechanism is provided for valves of different types of the same cylinder and for valves of different engine cylinders.5. A cam switching mechanism as claimed in claim 4, further comprising a control system connected to a camshaft or crankshaft angular position sensor and operative to initiate cam switching of the engine valves at different crank angles from each other.6. A cam switching mechanism as claimed in any one of the preceding claims, wherein the valving of each cam switching mechanism comprises a spool valve, having multiple input ports for connection to the respective master cylinders, an output port leading to the slave cylinder, and sealing lands on the spool associated with each input port.7. A cam switching mechanism as claimed in claim 6 when appended to claim 2, wherein the spool valve has at least one output port for connection to a dummy slave cylinder or a variable volume accumulator. -7 -8 A cam switching mechanism as claimed in claim 6 or 7, wherein the spool of the spool valve is displaceable axially by means of a solenoid, or hydraulically.9 A cam switching mechanism as claimed in claim 6 or 7, wherein the spool of the spool valve is rotatable by means of a motor.
GB2109109.5A 2021-06-24 2021-06-24 Cam switching mechanism Pending GB2608166A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB2109109.5A GB2608166A (en) 2021-06-24 2021-06-24 Cam switching mechanism

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB2109109.5A GB2608166A (en) 2021-06-24 2021-06-24 Cam switching mechanism

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GB202109109D0 GB202109109D0 (en) 2021-08-11
GB2608166A true GB2608166A (en) 2022-12-28

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS58180791A (en) * 1982-04-19 1983-10-22 Nippon Denso Co Ltd Variable capacity rotary compressor
US6267098B1 (en) * 1997-11-24 2001-07-31 Diesel Engine Retarders, Inc. Valve operating system having full authority lost motion
GB2402708A (en) * 2003-06-11 2004-12-15 Thomas Tsoi Hei Ma Selectable two-stroke/four-stroke lost-motion valve actuation system for i.c. engines
GB2568044A (en) * 2017-11-01 2019-05-08 Eaton Srl Valve train assembly

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS58180791A (en) * 1982-04-19 1983-10-22 Nippon Denso Co Ltd Variable capacity rotary compressor
US6267098B1 (en) * 1997-11-24 2001-07-31 Diesel Engine Retarders, Inc. Valve operating system having full authority lost motion
GB2402708A (en) * 2003-06-11 2004-12-15 Thomas Tsoi Hei Ma Selectable two-stroke/four-stroke lost-motion valve actuation system for i.c. engines
GB2568044A (en) * 2017-11-01 2019-05-08 Eaton Srl Valve train assembly

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Publication number Publication date
GB202109109D0 (en) 2021-08-11

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