Patent Application
20170138254
The disclosure generally relates to an internal combustion engine, and a method of controlling the internal combustion engine.
Internal combustion engines include a crankshaft that rotates about a crank axis. When possible, the engine is balanced to eliminate or minimize vibration caused by the crankshaft and reciprocating components rotating about the crank axis. Engine vibration caused by the crankshaft and the large end of the connecting rods and rod bearings can be balanced by counterweights on the crankshaft. However, the slider-crank mechanism on single or multi-cylinder engines causes primary and secondary forces and couples which are not inherently balanced because of the reciprocating mass and arrangement of the cylinders relative to each other. As used herein, the term “couple” or “couples” is defined as a pair of parallel forces acting in opposite directions and tending to produce rotation. Some engine configurations, particularly in-line four cylinder engines for example, cannot be balanced.
In order to smooth the operation and reduce engine vibration, some internal combustion engines are equipped with a balancing shaft or shafts, typically two counter-rotating balancing shafts which rotate at twice engine speed, to balance the engine as the crankshaft rotates about the crank axis. In-line three cylinder engines and 90 degree V6 engines have a primary couple which can be balanced by a single shaft rotating at engine speed in a direction opposite to the engine's rotation. In-line six cylinder engines are inherently balanced. Ninety degree V8 engines with conventional cross-plane crankshafts have a primary rotating couple which can be balanced with crankshaft counterweights. Some in-line five cylinder engines have been balanced with twin counter-rotating shafts rotating at twice engine speed.
The balancing shafts are coupled to and rotatably driven by the crankshaft, such as through a gear, belt, or chain drive. The coordinated rotation of the balancing shaft or shafts with the crankshaft balances and smoothens the operation of the engine. The engine inertial imbalance becomes more significant at higher engine rotational speeds, whereas the engine inertia imbalance is less significant and it may not be objectionable to the vehicle occupants at lower engine rotational speeds. Some smaller displacement engines do not need balance shafts because the reciprocating forces are small enough to not be a problem.
An internal combustion engine is provided. The internal combustion engine includes a block, and a crankshaft supported by the block. The crankshaft is rotatable about a crank axis relative to the block. A first balance shaft is supported by the block or a balance shaft housing, and is rotatable about a first balance axis relative to the block or the balance shaft housing. The first balance shaft rotates about the first balance axis to balance the engine during rotation of the crankshaft about the crank axis. A torque transmitting mechanism is selectively moveable between an engaged position and a disengaged position. When the torque transmitting mechanism is disposed in the engaged position, the torque transmitting mechanism connects the crankshaft and the first balance shaft in torque communication for rotating the first balance shaft with the crankshaft. When the torque transmitting mechanism is disposed in the disengaged position, the torque transmitting mechanism disconnects torque communication between the crankshaft and the first balance shaft for not rotating the first balance shaft with the crankshaft as the crankshaft rotates about the crank axis.
A method of controlling an internal combustion engine is also provided. The internal combustion engine includes a crankshaft and at least one balance shaft for balancing the engine during rotation of the crankshaft about a crank axis. The method includes sensing a rotational speed of the crankshaft with a rotational speed sensor. A torque transmitting mechanism is signaled with an engine control module, to connect torque communication between the crankshaft and the balance shaft when the rotational speed of the crankshaft is equal to or greater than a rotational speed threshold. The torque transmitting mechanism is signaled with the engine control module to disconnect torque communication between the crankshaft and the balance shaft when the rotational speed of the crankshaft is less than the rotational speed threshold.
Accordingly, the balancing shaft may be engaged to balance the engine by positioning the torque transmitting mechanism in the engaged position, and the balancing shaft may be disengaged to not affect the crankshaft when the torque transmitting mechanism is disposed in the disengaged position. When the torque transmitting mechanism is disposed in the disengaged position, the internal combustion engine does not incur any energy losses associated with rotating the balancing shaft. As such, disengaging the balancing shaft increases the operating efficiency of the engine. The torque transmitting mechanism may be moved into the disengaged position to disengage the balancing shaft during low engine rotational speeds, when vibration in the engine is not noticeable, thereby reducing energy losses in the engine. The torque transmitting mechanism may be moved into the engaged position to engage the balance shaft and balance the engine during high engine rotational speeds, when vibration in the engine increases and would otherwise be noticeable.
Friction is proportional to diameter cubed times length of journal bearings, and also to rotational speed squared. Accordingly, there is a greater friction benefit for decoupling the balance shafts from an engine with secondary balance shafts (which rotate at twice engine speed) than a primary shaft because of the number of bearings and the rotational speed of the balance shafts.
The above features and advantages and other features and advantages of the present teachings are readily apparent from the following detailed description of the best modes for carrying out the teachings when taken in connection with the accompanying drawings.
Those having ordinary skill in the art will recognize that terms such as “above,” “below,” “upward,” “downward,” “top,” “bottom,” etc., are used descriptively for the figures, and do not represent limitations on the scope of the disclosure, as defined by the appended claims. Furthermore, the teachings may be described herein in terms of functional and/or logical block components and/or various processing steps. It should be realized that such block components may be comprised of any number of hardware, software, and/or firmware components configured to perform the specified functions.
Referring to the Figures, wherein like numerals indicate like parts throughout the several views, an internal combustion engine is generally shown at 20. The internal combustion engine 20 may include, but is not limited to a gasoline engine or a diesel engine, and may be configured in any suitable style and/or configuration. While the teachings of the disclosure are particularly relevant to engine configurations which are not inherently balanced, such as but not limited to an in-line four cylinder engine configuration, it should be appreciated that the teachings of the disclosure may be applied to any style and/or configuration of the internal combustion engine 20.
The internal combustion engine 20 includes an engine block 24. The block 24 rotatably supports the crankshaft 22. A plurality of pistons (not shown) are attached to the crankshaft 22 via connecting rods and piston pins (not shown), and move in a reciprocating motion within cylinder bores (not shown) defined by the block 24. Combustion of fuel in the cylinder bores drives the pistons, which cause the crankshaft 22 to rotate relative to the block 24, about a crank axis 26, as is known in the art.
Referring to
A torque transmitting mechanism 34 connects and disconnects torque communication between the first balance shaft 28A, the second balance shaft 28B, and the crankshaft 22. The torque transmitting mechanism 34 is selectively moveable between an engaged position and a disengaged position. When disposed in the engaged position, the torque transmitting mechanism 34 connects torque communication between the crankshaft 22 and both the first balance shaft 28A and the second balance shaft 28B. The torque transmitting mechanism 34 connects torque communication between the crankshaft 22, the first balance shaft 28A, and the second balance shaft 28B to rotate the first balance shaft 28A and the second balance shaft 28B with the crankshaft 22. When the torque transmitting mechanism 34 is disposed in the disengaged position, the torque transmitting mechanism 34 disconnects torque communication between the crankshaft 22 and both the first balance shaft 28A and the second balance shaft 28B. The torque transmitting mechanism 34 disconnects torque communication between the crankshaft 22, the first balance shaft 28A, and the second balance shaft 28B so that the crankshaft 22 does not rotate the first balance shaft 28A or the second balance shaft 28B, as the crankshaft 22 rotates about the crank axis 26.
The specific configuration of the torque transmitting mechanism 34, and the manner in which the torque transmitting mechanism 34 operates to connect and disconnect torque communication between the crankshaft 22, the first balance shaft 28A, and the second balance shaft 28B, is dependent upon the specific manner in which torque is transmitted from the crankshaft 22 to the first balance shaft 28A and the second balance shaft 28B. In the exemplary embodiment of the internal combustion engine 20 shown in
In the exemplary embodiment of the internal combustion engine 20 shown in
The torque transmitting mechanism 34 is configured and/or sized to provide an adequate rate of increasing torque communication, in order to accelerate the balance shafts 28 from a rotational speed of zero to a rotational speed corresponding to the threshold crankshaft rotational speed, while connecting full torque communication between the balance shafts 28 to the crankshaft 22 in a reasonable amount of time. The torque transmitting mechanism 34 may be configured and/or sized to connect torque communication between the balance shafts 28 and the crankshaft 22 to provide an engagement rate that provides a seamless engagement action that is not generally noticeably to an occupant. The torque transmitting mechanism 34 may be sized based on the moment of inertia of the balance shafts 28, and the amount of torque transmitted between the crankshaft 22 and the balance shafts 28.
The torque transmitting mechanism 34 may be attached to and supported by one of the crankshaft 22, the first balance shaft 28A, and/or the second balance shaft 28B. Preferably, and in the exemplary embodiment shown in
Referring to
Referring to
As is known in the art, rotation of the balance shafts 28 must be timed with the rotation of the crankshaft 22 to properly balance the engine 20. Accordingly, the torque transmitting mechanism 34 is configured to include only a single locating position that connects the first balance shaft 28A and the second balance shaft 28B in only a single position relative to the crankshaft 22. The single locating position is designed to ensure that when the torque transmitting mechanism 34 is disposed in the engaged position, the first balance shaft 28A and the second balance shaft 28B are properly oriented relative to the crankshaft 22, so that the first balance shaft 28A and the second balance shaft 28B are properly timed with the crankshaft 22.
For example, referring to
Referring to
While the exemplary embodiment of the internal combustion engine 20 described herein and shown in the Figures defines the actuator 46 as the solenoid valve 50 controlling fluid communication between the fluid pressure source 52 and the torque transmitting mechanism 34, it should be appreciated that the actuator 46 may be configured differently, and may include some other device capable of actuating the torque transmitting mechanism 34, such as but not limited to an electrically actuated device, hydraulically actuated device, or a pneumatically actuated device.
As noted above, the engine control module 48 is coupled to the torque transmitting mechanism 34, and is operable to control actuation of the torque transmitting mechanism 34 between the engaged position and the disengaged position. Preferably, the engine control module 48 is operable to position the torque transmitting mechanism 34 in the engaged position when a rotational speed of the crankshaft 22 is equal to or greater than a rotational speed threshold. The engine control module 48 is operable to position the torque transmitting mechanism 34 in the disengaged position when the rotational speed of the crankshaft 22 is less than the rotational speed threshold.
The engine control module 48 may include a computer and/or processor, and include all software, hardware, memory, algorithms, connections, sensors, etc., necessary to manage and control the operation of the internal combustion engine 20. As such, a method, described below, may be embodied as a program operable on the engine control module 48. It should be appreciated that the engine control module 48 may include any device capable of analyzing data from various sensors, comparing data, making the necessary decisions required to control the operation of the torque transmitting mechanism 34, and executing the required tasks necessary to control the operation of the torque transmitting mechanism 34.
The engine control module 48 may be embodied as one or multiple digital computers or host machines each having one or more processors, read only memory (ROM), random access memory (RAM), electrically-programmable read only memory (EPROM), optical drives, magnetic drives, etc., a high-speed clock, analog-to-digital (A/D) circuitry, digital-to-analog (D/A) circuitry, and any required input/output (I/O) circuitry, I/O devices, and communication interfaces, as well as signal conditioning and buffer electronics.
The computer-readable memory may include any non-transitory/tangible medium which participates in providing data or computer-readable instructions. Memory may be non-volatile or volatile. Non-volatile media may include, for example, optical or magnetic disks and other persistent memory. Example volatile media may include dynamic random access memory (DRAM), which may constitute a main memory. Other examples of embodiments for memory include a floppy, flexible disk, or hard disk, magnetic tape or other magnetic medium, a CD-ROM, DVD, and/or any other optical medium, as well as other possible memory devices such as flash memory.
The engine control module 48 includes tangible, non-transitory memory on which are recorded computer-executable instructions, including an engine balancing control algorithm. The processor of the engine control module 48 is configured for executing the engine balancing control algorithm. The engine balancing control algorithm implements a method of engaging and disengaging the torque transmitting mechanism 34, to engage and/or disengage the balance shafts 28 of the internal combustion engine 20.
The method of controlling the internal combustion engine 20 to engage and/or disengage the torque transmitting mechanism 34 includes sensing a rotational speed of the crankshaft 22 with a rotational speed sensor 54. The rotational speed sensor 54 may include any sensor capable of sensing or otherwise determining the rotational speed of the crankshaft 22. For example, the rotational speed sensor 54 may include a crankshaft 22 position sensor that senses a rotational position of the crankshaft 22, and communicates the sensed position of the crankshaft 22 over time to the engine control module 48, which may then determine the rotational speed of the crankshaft 22.
The engine control module 48 may then compare the rotational speed of the crankshaft 22 to a rotational speed threshold. The rotational speed threshold is a pre-defined rotational speed. The rotational speed threshold may be defined to equal any rotational speed, and is dependent upon the specific type, size, and/or configuration of the internal combustion engine 20, as well as the specific application of the internal combustion engine 20. For example, the rotational speed threshold may be defined to equal a value that correlates to a rotational speed of the crankshaft 22, below which vibration from the unbalanced crankshaft 22 is either not noticeable or is negligible, and above which is noticeable. For example, in one exemplary embodiment, the rotational speed threshold may be defined to equal a rotational speed of 2,800 revolutions per minute.
If the engine control module 48 determines that the rotational speed of the crankshaft 22 is equal to or greater than the rotational speed threshold, then the engine control module 48 may signal the actuator 46 to position the torque transmitting mechanism 34 in the engaged position to connect torque communication between the crankshaft 22 and the balance shafts 28. In one exemplary embodiment, signaling the actuator 46 to position the torque transmitting mechanism 34 in the engaged position may include signaling the solenoid valve 50 to open or close fluid communication between the fluid pressure source 52 and the torque transmitting mechanism 34 to position the torque transmitting mechanism 34 in the engaged position and establish torque communication between the crankshaft 22 and the balance shafts 28.
If the engine control module 48 determines that the rotational speed of the crankshaft 22 is less than the rotational speed threshold, then the engine control module 48 may signal the actuator 46 to position the torque transmitting mechanism 34 in the disengaged position to disconnect torque communication between the crankshaft 22 and the balance shafts 28. In one exemplary embodiment, signaling the actuator 46 to position the torque transmitting mechanism 34 in the disengaged position may include signaling the solenoid valve 50 to open or close fluid communication between the fluid pressure source 52 and the torque transmitting mechanism 34 to position the torque transmitting mechanism 34 in the disengaged position and prevent torque communication between the crankshaft 22 and the balance shafts 28.
In order to avoid excessive engagement and disengagement of the balance shafts 28 when the engine 20 is operating around the connecting and disconnecting threshold crankshaft rotational speed, the control algorithm may include actuation hysteresis. This hysteresis may be achieved by setting different crankshaft rotational speed values for connecting and disconnecting the balance shafts 28, along with specific algorithm conditions. These control algorithm conditions may include, but are not limited to, minimum time limits for the crankshaft rotational speed to be above or below the crankshaft rotational peed values for engaging and disengaging the balance shafts 28.
By following the above described process, the engine control module 48 may control the torque transmitting mechanism 34 so that the balance shafts 28 are only being rotated when the crankshaft 22 is rotating at high rotational speeds, and engine vibration becomes noticeable. During most driving conditions, the crankshaft 22 operates at rotational speeds less than the rotational speed threshold, engine vibration is not noticeable, and therefore the internal combustion engine 20 does not require the use of the balance shafts 28 to balance the engine 20. By disengaging the balance shafts 28, the spin losses associated with rotating the balance shafts 28 at these lower rotational speeds may be eliminated. The balance shafts 28 may be engaged at higher rotational speeds to balance the engine 20, and reduce vibration in the internal combustion engine 20.
The detailed description and the drawings or figures are supportive and descriptive of the disclosure, but the scope of the disclosure is defined solely by the claims. While some of the best modes and other embodiments for carrying out the claimed teachings have been described in detail, various alternative designs and embodiments exist for practicing the disclosure defined in the appended claims.
