Variable coordination volume type eight-stroke engine

The present invention provides a variable coordination volume type eight-stroke engine for increasing the fuel efficiency in the heavy load operation by regulating the maximum air-pressure in the charge-coordinate-channel and adjusting the initiation timing of the injection-process as the engine load changes; wherein the maximum air-pressure of the charge-coordinate-channel will be regulated with a buffer piston in the range of 25% to 75% of the concurrent maximum combustion pressure of the mastery cylinder.In addition the overall temperature of the master cylinder and the slave cylinder will be reduced in the heavy load condition by injecting a flow of high-density-air at lower temperature in the heavy load operation, thereby achieving better durability and higher fuel efficiency.

FIELD OF THE INVENTION

The present invention relates to a variable coordination volume type eight-stroke engine; and more particularly to the improvements on the coordination system of the eight-stroke engine.

The present invention is a continuing application of the eight-stroke internal combustion engine (filed on Jul. 15, 2003with application number 10/619,147).

The present invention can be used in the field of transportation vehicle, power generation.

BACKGROUND OF THE INVENTION

The present invention is a continuing application of the eight-stroke internal combustion engine, which was filed as U.S. Pat. No. 6,918,358 (application Ser. No. 10/619,147), and the engine of this type can also be abbreviated as the eight-stroke engine.

The fuel efficiency of the eight-stroke engine is relatively higher than the conventional four-stroke engine (over 35% for gasoline type eight-stroke engine and 45% for diesel type eight-stroke engine) under the condition that the engine load remains within the designated load condition.

However, unlike conventional engines, the eight-stroke engine requires to adjust the initiation timing of the injection-process (the process to inject a flow of high-density-air into the master cylinder) as the load changes, otherwise, the power-to-weight ratio will significantly decrease due to the compression energy loss and the heat loss during the slave-compression-process in the heavy load condition.

Therefore the main objective of the present invention is to provide an improved eight-stroke engine capable of adjusting the initiation timing and regulating the maximum compression pressure according to the engine load condition.

SUMMARY OF THE INVENTION

It is the main objective of the present invention to provide a variable coordination volume type eight-stroke engine capable of adjusting the initiation timing of the injection-process to increase the fuel efficiency in the heavy load condition.

It is the second objective of the present invention to provide a variable coordination volume type eight-stroke engine capable of regulating the maximum compression pressure of the charge-coordinate-channel within 25% to 75% of the maximum concurrent combustion pressure of the master cylinder.

Operation Table.1L shows the 8-process-sequence performed by the eight-stroke engine with 80 degree phase-difference in the light load condition.

Operation Table.1M shows the 8-process-sequence performed by the eight-stroke engine with 80 degree phase-difference in the medium load condition.

Operation Table.1H shows the 8-process-sequence performed by the eight-stroke engine with 80 degree phase-difference in the heavy load condition.

Operation Table.2M shows the 8-process-sequence performed by the eight-stroke engine with the phase-difference of 120 degree in the medium load condition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The variable coordination volume type eight-stroke engine is an improved eight-stroke engine that can perform with a relatively higher power-to-weight ratio and boarder operational range and better fuel efficiency in comparison to the original eight-stroke engine.

The eight-stroke-operation of the eight-stroke engine includes the master-intake-stroke, the slave-intake-stroke, the master-compression-stroke, the slave-compression-stroke, the master-expansion-stroke, the slave-expansion-stroke, the master-exhaust-stroke, the slave-exhaust-stroke.

The master-intake-stroke, the slave-intake-stroke, the master-expansion-stroke, the slave-expansion-stroke are down-strokes.

The master-compression-stroke, the slave-compression-stroke, the master-exhaust-stroke, the slave-exhaust-stroke are up-strokes.

As the present invention will describe the detailed air-flows in the master cylinder and slave cylinder, an 8-process-sequence is introduced to elaborate the operation of the eight-stroke engine based on the air-flows.

The 8-process-sequence consists of 8 processes, which are performed in the following order, the master-intake-process, the slave-intake-process, the master-compression-process, the slave-compression-process, the hot-combustion-process, the injection-process, the cold-expansion-process, the slave-exhaust-process.

The master cylinder includes a master piston, air-intake means, fuel-supplying-means, ignition means, a reverse-channel for providing a one-way passage from the master cylinder to the slave cylinder; wherein said reverse-channel will only be opened after the slave-compression-stroke has started.

The slave cylinder includes a slave piston, air-intake means, exhaust-means, a charge-coordinate-channel for providing an one-way passage from the slave cylinder to the master cylinder; wherein said charge-coordinate-channel will only be opened after the air-pressure of the charge-coordinate-channel has increased to higher than the pressure of the master cylinder.

Said charge-coordinate-coordinate-channel includes a movable member or a buffer piston to control the effective volume in the charge-coordinate-channel, so that the maximum compression pressure in the charge-coordinate-channel will not exceed 75% of the concurrent maximum combustion pressure of the master cylinder.

The concurrent maximum combustion pressure of the master cylinder refers to the maximum combustion pressure in that specific load condition; for example, during the light load operation with a maximum combustion pressure of 320 psi (pound per square inch) in the master cylinder at about 365 degree of crankshaft, the concurrent maximum combustion pressure is 320 psi, so the maximum compression pressure of the charge-coordinate-channel will be limited to lower than 240 psi; for another example, during the heavy load operation with a maximum combustion pressure of 700 psi in the master cylinder at about 365 degree of crankshaft reference angle, the concurrent maximum combustion pressure is 700 psi, so the maximum compression pressure of the charge-coordinate-channel will be limited lower than 525 psi.

A slave-pressure-sensor will be preferable to be installed in the slave cylinder or the charge-coordinate-channel to detect the maximum compression pressure during the slave-compression-process; for the type of the buffer piston controlled by a servo motor with the ECU (engine control unit), the slave-compression-sensor will be a basic requirement.

The master piston and the slave piston will be constructed with a phase-difference between 60 degree and 150 degree to perform the eight-stroke-operation.

Unlike the original eight-stroke engine that uses a coordinate-port and a coordinate-valve to manage the air-flows between the master cylinder and the slave cylinder, the present invention uses at least two dedicated channels (reverse-channel and charge-coordinate-channel) for each purpose, this can increase the fuel efficiency and provide better control of the initiation timing of the injection-process.

The concept of the 8-process-sequence is explained as follows:

The master-intake-process is to provide air into the master cylinder during the master-intake-stroke.

The slave-intake-process is to provide air into the slave cylinder during the slave-intake-stroke.

The master-compression-process is to compress the air in the master cylinder during the master-compression-stroke, and the fuel will be supplied into the master cylinder before the end of the master-compression-process.

The slave-compression-process is to compress the air into the charge-coordinate-channel as the high-density-air; at the end of the slave-compression-process, the air-pressure in the charge-coordinate-channel will increase to over the pressure in the master cylinder.

The hot-combustion-process is to ignite and combust the air-fuel mixture as a hot-combustion-medium in the master cylinder during the earlier portion of the master-expansion-stroke.

The fuel supplying means of the master cylinder can be a carburetor, a direction-injection-nozzle, a fuel pump (mainly for diesel), or a propane converter (for natural gas).

The injection-process is to inject the high-density-air of the charge-coordinate-channel into the master cylinder to mix with the hot-combustion-medium, wherein a cold-expansion-medium is formed in the master cylinder by the end of the injection-process.

The duration of the injection-process can vary between 5 degree and 60 degree of crankshaft rotation, the initiation timing of the injection-process can range from 30 degree after the TDC of the master-expansion-stroke and 30 degree before the TDC of the slave-compression-stroke; in other words the initiation of injection-process can occur between first 30 degree of the master-expansion-stroke to the last 30 degree of the slave-compression-process.

The earliest initiation timing of the injection-process should at least 15 degree after the hot-combustion-process is started; for example with an eight-stroke engine ignites the master cylinder at 380 degree of crankshaft reference angle (late ignition timing is common in large engine application), the earliest initiation timing of the injection-process will be shifted to 395 degree of crankshaft reference angle.

The cold-expansion-process is to expand the cold-expansion-medium in both the master cylinder and the slave cylinder during the later portion of the master-expansion-stroke, wherein the cold-expansion-medium will expand and transfer from the master cylinder into the slave cylinder through the reverse-channel.

The slave-exhaust-process is to expel the cold-expansion-medium out with the exhaust means of the slave cylinder during the slave-exhaust-stroke and the earlier portion of the slave-expansion-stroke; for high speed applications, an auxiliary exhaust valve may be installed in the master cylinder to directly expel the cold-expansion-medium out of the master cylinder during the master-exhaust-stroke, whereas, for the medium speed application with no auxiliary exhaust valve, the cold-expansion-medium of the master cylinder will be transferred to the slave cylinder through the reverse-channel by the end of the master-exhaust-stroke.

A turbocharger system is preferable to be equipped with the eight-stroke engine, wherein a compressor of the turbocharger is charging a flow of pressurized air into the slave cylinder during the slave-intake-process, the cold-expansion-medium expelled from the eight-stroke engine is charged into a turbine of the turbocharger, so that the energy recovered from the cold-expansion-medium is used to increase the intake pressure of the slave cylinder, thereby increasing the fuel efficiency to over 40%.

To further raise the fuel efficiency and prevent the pollution in the light load operation, a catalytic converter is preferable to be installed in the reverse-channel, therefore, the cold-expansion-medium will pass through the catalytic converter during the cold-expansion-process.

Now the concept and the advantages of the variable coordination volume type eight-stroke engine will be explained as follows: the variable coordination volume type eight-stroke engine will increase the volume available in the charge-coordinate-channel as the engine load increases, this can be achieved with two different control methods, and they are explained in the first embodiment and the second embodiment, wherein the first embodiment requires more precise machining and better heat-resistance material, but the first embodiment has better control over all operational load condition, the second embodiment has a low manufacturing cost but less adaptability to the load condition; wherein for the clarity purpose, both the first embodiment and the second embodiment will employ a phase-difference of 80 degree between the master piston and the slave piston.

Now referring toFIG. 1Afor the first embodiment, the first embodiments includes a master cylinder110, a slave cylinder120, a master piston111, a slave piston121, master crankshaft101, slave crankshaft102, a master-intake-valve112, a slave-intake-valve122, a charge-coordinate-channel160, a reverse-channel180, a charge-coordinate-valve161, a reverse-input-valve181, a reverse-output-valve182, a slave-exhaust-valve126, a buffer piston162(also referred as a volume-control member for the ease of comprehension, various other shapes can be constructed with the same concept), a compressor of the turbocharger191, a turbine of the turbocharger192, a spark plug150(as the ignition means for the master cylinder), a slave-pressure-sensor170, a volume-control actuator163, an ECU (engine control unit which is shown in the drawing) for determining the required volume in the charge-coordinate-channel; wherein the charge-coordinate-valve161can only be actuated after the air-pressure of the charge-coordinate-channel160is increased to higher than the pressure in the master cylinder110; wherein and the reverse-input-valve181and the reverse-output-valve182can only be actuated after the slave-expansion-stroke has started; wherein the compression pressure in the charge-coordinate-channel160will be regulated within 75% to 25% of the concurrent maximum combustion pressure of the master cylinder110.

The master cylinder110will take in air during the master-intake-process with the master-intake-valve112as inFIG. 1A; the slave cylinder120will take in air during the slave-intake-process with slave-intake-valve122as shown inFIG. 1B; the master cylinder110will compress the air therein during the master-compression-process as inFIG. 1C; the slave cylinder120will compress the air into the charge-coordinate-channel160during the slave-compression-process as inFIG. 1D; the master cylinder110will ignite an air-fuel mixture in the master cylinder110during the hot-combustion-process as inFIG. 1E; a flow of high-density-air is injected into the master cylinder110from the charge-coordinate-channel160during the injection-process as inFIG. 1F; a cold-expansion-medium will expand in both the master cylinder110and the slave cylinder120through the reverse-channel180during the cold-expansion-process as inFIG. 1G; the cold-expansion-medium will be expelled out of the slave cylinder120during the slave-exhaust-process as inFIG. 1H.

During the light load operation of the first embodiment, the volume-control actuator163adjusts the buffer piston162(volume-control member) to the lowest position as shown inFIG. 1.Light, the charge-coordinate-channel160will have the relatively smallest volume, therefore, as the slave piston121moves up during the slave-compression-stroke, the pressure of the high-density-air in the charge-coordinate-channel160is increased over the combustion pressure of the master cylinder at 390 degree of crankshaft reference angle, thereby initiating the injection-process by opening the charge-coordinate-valve161at 390 degree of crankshaft reference angle as shown in Operation Table.1L.

During the medium load operation of the first embodiment, the volume-control actuator163lifts the buffer piston (volume-control member) to a relatively higher position as shown inFIG. 1.Medium, the charge-coordinate-channel160will have more effective volume than that of the light load operation, therefore, as the slave piston121moves up during the slave-compression-stroke, the pressure of the high-density-air is increased relatively slower due to the bigger effective volume in the charge-coordinate-channel160, and the pressure of the high-density-air is then increased to over the combustion pressure of the master cylinder at 410 degree of crankshaft reference angle, thereby initiating the injection-process by opening the charge-coordinate-valve at 410 degree of crankshaft reference angle as shown in Operation Table.1M.

During the heavy load operation of the first embodiment, the volume-control actuator163lifts the buffer piston162(volume-control member) to the highest position as shownFIG. 1.Heavy, the charge-coordinate-channel160will have the maximum possible effective volume, therefore, as the slave piston121moves up during the slave-compression-stroke, the pressure of the high-density-air is eventually increased to over the combustion pressure of the master cylinder110at 420 degree of crankshaft reference angle, thereby initiating the injection-process at 420 degree of crankshaft reference angle as shown in Operation Table.1H.

Now comparing with the conventional eight-stroke engine in the heavy load operation, assuming the air of the slave cylinder is compressing to about 1/40 of its original volume in the conventional eight-stroke engine, the high-density-air of the charge-coordinate-channel is heated up to over 900 degree Celsius prior to the initiation point of the injection-process, even through the high-density-air will be injected into the master cylinder to form a cold-expansion-medium, wherein the hot-combustion-medium has a temperature of about 1200 degree Celsius at the initiation point of the injection-process, the cold-expansion-medium will then be formed at about 1000 degree Celsius, the cooling effect will be significantly reduced due to the high temperature characteristic of the high-density-air, and an excessive energy loss will be caused by the slave-compression-process.

For the present invention, the effective volume of the charge-coordinate-channel160will be adjusted according to the combustion condition of master cylinder110and the compression condition of the slave cylinder120, now assuming that the effective volume of the charge-coordinate-channel can be adjusted to 1/40 of the slave cylinder volume in the light load operation and 1/10 of the slave cylinder volume in the heavy load operation, the high-density-air is compressed to about 400 degree Celsius prior to the initiation of the injection-process in the heavy load operation, wherein the hot-combustion-medium is at about 1200 degree Celsius at the initiation point of the injection-process, so a cold-expansion-medium will be formed at a relatively lower temperature (about 600 degree to 800 degree Celsius) than that of the conventional eight-stroke engine, in addition the excessive energy loss is prevented, thereby achieving a fuel efficiency of 35% for gasoline type eight-stroke engine and 45% for diesel type eight-stroke engine.

In all of the abovementioned load conditions of the first embodiment, the ECU will compute the required effective volume of the charge-coordinate-channel for regulating the maximum compression pressure of the slave cylinder (the pressure of the high-density-air at the initiation of the injection process) within 75% to 25% of the maximum concurrent combustion pressure of the master cylinder. For the configuration with a turbocharger system or a supercharger system to boost the intake pressure of the slave cylinder, a slave-pressure-sensor is required to assist the ECU to compute the correct target position of the buffer piston.

The charge-coordinate-valve161can be actuated with various actuation mechanisms as long as the charge-coordinate-valve161is actuated after the air-pressure of the charge-coordinate-channel160has increased to over the pressure of the master cylinder110; wherein said actuation mechanisms can be a servo motor, a hydraulic actuator, a variable timing camshaft system, or a spring actuator.

The first embodiment can also employ more than one charge-coordinate-channel and charge-coordinate-valve, wherein each charge-coordinate-channel can have an individual volume-control member to regulate the maximum compression pressure within 25% to 75% of the concurrent maximum combustion pressure.

Now referring toFIG. 2AtoFIG. 2Dfor the second embodiment, the second embodiments includes a master cylinder210, a slave cylinder220, a master piston211, a slave piston221, a master crankshaft201, a slave crankshaft202, a master-intake-valve212, a slave-intake-valve222, a slave-exhaust-valve226, a master-intake-port213, a slave-intake-port223, a slave-exhaust-port227, a charge-coordinate-channel260, a reverse-channel280, a charge-coordinate-valve261, a reverse-input-valve281, a reverse-output-valve282, a spring-buffer-piston262(also referred as an volume-oscillating-member for the ease of comprehension, various other shapes can be constructed with the same concept), a compressor291of the turbocharger, a turbine292of the turbocharger, a slave-pressure-sensor270, a spark plug250(as the ignition means for the master cylinder); wherein the charge-coordinate-valve261can only be actuated after the air-pressure of the charge-coordinate-channel260is increased to higher than the pressure in the master cylinder210; wherein and the reverse-input-valve281and the reverse-output-valve282can only be actuated after the slave-expansion-stroke has started; wherein the compression pressure in the charge-coordinate-channel260will be regulated within 75% to 25% of the concurrent maximum combustion pressure of the master cylinder210.

The 8-process-sequence performed with the second embodiment are the basically the same as that of the first embodiment, wherein the Operational Table.1M can also be used a reference to the following explanation.

For the second embodiment as shown inFIG. 2AtoFIG. 2D, the basic concept is the same, except the effective volume of the charge-coordinate-channel260is controlled with a spring-buffer-piston262, wherein said spring-buffer-piston262will oscillate its position along with the compression pressure in the charge-coordinate-channel260; the cylinder conditions is explained as follows:

Referring toFIG. 2A, the eight-stroke engine is at the end of the slave-intake-process at about 260 degree of crankshaft reference angle, as the slave cylinder220has not started the compressing the air, the pressure in the charge-coordinate-channel260is still low (assuming the pressure now is at 20 psi), the spring-buffer-piston262is then at its lowest position.

Referring toFIG. 2B, the eight-stroke engine is in the middle of the slave-compression-process at about 340 degree of crankshaft reference angle, as the pressure in the charge-coordinate-channel260will increase as the slave piston221reciprocates up toward the TDC position (assuming the pressure now is at 40 psi), the spring-buffer-piston262is pushed up with the compressed air.

Referring toFIG. 2C, the eight-stroke engine is at the end of the slave-compression-process at about 410 degree of crankshaft reference angle, the spring-buffer-piston262is pushed up according to the air-pressure in the charge-coordinate-channel260(assuming the pressure now is at 300 psi), and the charge-coordinate-valve261is about to be opened to initiate the injection-process; during the next 30 degree of crankshaft rotation, the high-density-air of the charge-coordinate-channel260is injected into the master cylinder210to mix with the hot-combustion-medium.

Referring toFIG. 2D, the eight-stroke engine has just finished the injection-process at about 440 degree of crankshaft reference angle, the spring-buffer-piston262will oscillate down as the high-density-air has been injected into the master cylinder210(assuming the pressure now has dropped to 50 psi since the charge-coordinate-valve261is shut and the slave piston221starts to reciprocate downward, the reverse-input-valve281and the reverse-output-valve282are about to open to initiate the cold-expansion-process).

As the load increases for the eight-stroke engine in the second embodiment, the spring-buffer-piston262will be pushed up to a relatively higher position to provide a relatively bigger effective volume in the charge-coordinate-channel260, thereby regulating the maximum compression pressure of the slave cylinder220within 25% to 75% of the concurrent maximum combustion pressure of the master cylinder210.

A spring-tension-adjustor can be installed in the engine head for adjusting the spring tension of the spring-buffer-piston for a wider operational load range with the second embodiment; since the eight-stroke engine generally requires an intake-charger system (such as turbocharger or supercharger) to boos the intake pressure of the slave cylinder, a slave pressure sensor270can also be installed in the slave cylinder220or the charge-coordinate-channel260to provide the information required to adjust said spring-tension-adjustor of the spring-buffer-piston262in the second embodiment.

The charge-coordinate-valve261can be actuated with various actuation mechanisms as long as the charge-coordinate-valve261is actuated after the air-pressure of the charge-coordinate-channel260has increased to over the pressure of the master cylinder210; wherein said actuation mechanisms can be a servo motor, a hydraulic actuator, a variable timing camshaft system, or a spring actuator.

The eight-stroke engine of the present invention can be configured with various cylinder arrangements, the master piston and the slave-piston can be connected with single crankshaft or two separate crankshafts coupled to synchronize the rotation speed with gears.

An example of the possible cylinder arrangements is to dispose master cylinder and the slave cylinder so that the master piston511and the slave piston521reciprocate towards each other as in the A-type cylinder arrangement shown inFIG. 5, wherein the cold-expansion-medium can expand with less pumping loss; the components are labeled as the master piston511, the slave piston521, the engine head550(consists of all required valves and channels and ports), the master crankshaft501, the slave crankshaft502.

Another example of the cylinder arrangements is shown inFIG. 4, wherein the master cylinder and the slave cylinder are connected to the first crankshaft and the second crankshaft in alternating order, wherein, the first master cylinder430is co-acting with the first slave cylinder432, the second master cylinder440is co-acting with the second slave cylinder442, the third master cylinder450is co-acting with the third slave cylinder452, the fourth master cylinder460is co-acting with the fourth slave cylinder462; the first master cylinder430and the third master cylinder450is connected to the first crankshaft401, the second master cylinder440and the fourth master cylinder460is connected to the second crankshaft402, whereas the first slave cylinder432and the third slave cylinder452is connected to the second crankshaft402, the second slave cylinder442and the fourth slave cylinder462is connected to the first crankshaft401.

A catalytic converter can be included in the reverse-channel for both the first embodiment and the second embodiment; an example is shown inFIG. 1I(the eight-stroke engine is in beginning of the cold-expansion-process), wherein the cold-expansion-medium of the master cylinder110will pass through the catalytic converter183before entering the slave cylinder120.

The charge-coordinate-valve is preferable to be constructed with air-guiding-grooves as shown inFIG. 3to improve the cooling effect of the injection-process.

An example of the radial type eight-stroke engine is demonstrated inFIG. 6, wherein 5 sets of master cylinders601and slave cylinders602are arranged in radial configuration to share the crankshaft600; the components are labeled as the crankshaft600, the master cylinder601, the slave cylinder602, the master-intake-port612, the slave-intake-port623, the slave-exhaust-port628.

The fuel type of the eight-stroke engine of the present invention can be gasoline, diesel, natural gas, methanol with corresponding fuel supplying means and ignition means.

The initiation point (ignition) of the hot-combustion-process can be set between the last 35 degree of the master-compression-stroke and the first 40 degree of the master-expansion-stroke; in other words, the ignition timing of the master cylinder can be set between 35 degree before the TDC of the master-compression-stroke and the 40 degree after the TDC of the master-expansion-stroke; wherein the injection-process should only be initiated after the hot-combustion-process has commenced over 15 degree of crankshaft rotation.

The phase-difference between the master piston and the slave piston can be adjusted from 60 degree to 150 degree to perform the eight-stroke-operation; Operation Table.2M provides an example of the eight-stroke-operation for the configuration of 120 degree phase-difference.