Patent Description:
The present disclosure relates generally to exhaust gas recirculation ("EGR") systems.

In internal combustion engines, a process known as EGR is used to reduce the amount of nitrogen oxide (NOx) emissions. In general, EGR involves routing a portion of the exhaust gas back into the intake air flow. Conventionally, external piping is used to transfer the exhaust gas from the exhaust side of the engine to the intake side, and an EGR valve operatively coupled to the piping is used to regulate and time the EGR flow.

An engine with an EGR cross over tube integrated in the cylnder head is known from <CIT>.

An example not part of the claimed invention includes an apparatus comprising a cylinder head that defines an EGR crossover tube integrally formed in the cylinder head. The EGR crossover tube includes a first end fluidly coupled to an exhaust port of an engine. A second end is fluidly coupled to an intake port of the engine. A Venturi tube configuration is positioned between the first and second ends. A first sensor port extends through the cylinder head to the EGR crossover tube. The first sensor port is positioned at a restriction of the Venturi tube configuration. A second sensor port extends through the cylinder head to the EGR crossover tube. The second sensor port is positioned proximate the first end. A differential pressure sensor includes a first pressure sensor positioned in the first sensor port and a second pressure sensor positioned in the second sensor port. Pressure measurements from the differential pressure sensor are used to determine a flow rate of exhaust gas through the EGR crossover tube.

Another example embodiment includes an engine comprising a cylinder head that defines an EGR crossover tube integrally formed in the cylinder head. The EGR crossover tube includes a Venturi tube configuration. A differential pressure sensor is operatively coupled to the Venturi tube configuration. A controller is operatively coupled to the differential pressure sensor. The controller includes an exhaust gas recirculation flow rate circuit structured to receive differential pressure measurements from the differential pressure sensor, interpret the differential pressure measurements, and determine a flow rate of exhaust gas through the exhaust gas recirculation crossover tube determined directly from the interpreted pressure measurements from the differential pressure sensor.

These and other features, together with the organization and manner of operation thereof, will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, wherein like components have like numerals throughout the several drawings described below.

Other features, aspects, and advantages of the disclosure will become apparent from the description, the drawings, and the claims.

It will be recognized that some or all of the figures are schematic representations for purposes of illustration. The figures are provided for the purpose of illustrating one or more implementations with the explicit understanding that they will not be used to limit the scope or the meaning of the claims.

In engine systems including EGR, a flow rate of the EGR gas is measured for controlling EGR valve position and for on-board diagnostics ("OBD"). Some engine systems measure EGR flow rate indirectly by measuring the fresh air intake flow rate (e.g., using an intake mass air flow sensor), and estimating the EGR flow rate algorithmically using that measurement. For example, some systems estimate the EGR flow rate by comparing (e.g., by an engine control module ("ECM")) the fresh air intake flow rate measurement with the engine's theoretical air requirement, which may be calculated based on various factors (e.g., engine RPM).

Various embodiments relate to an EGR crossover tube integrally formed in a cylinder head of an engine. The EGR crossover tube extends between a first end fluidly coupled to an exhaust port of the engine and a second end fluidly coupled to an intake port of the engine. The EGR crossover tube defines a Venturi tube configuration at a position between the first and second ends. The cylinder head defines first and second sensor ports that extend into the EGR crossover tube. The first sensor port is positioned at the Venturi tube configuration, and the second sensor port is positioned proximate the first end. A differential pressure sensor includes a first pressure sensor positioned in the first sensor port and a second pressure sensor positioned in the second sensor port. Pressure measurements from the differential pressure sensor are used to determine a flow rate of EGR gas through the EGR cross-over tube.

Embodiments described herein provide various advantages over conventional EGR crossover tubes. For example, by integrally forming the EGR crossover tube in the cylinder head (e.g., via casting in-place), the instant EGR crossover tube eliminates the need for external piping to route the exhaust gas from the exhaust side of the engine to the intake side. Accordingly, the instant EGR crossover tube reduces part count and cost. Additionally, the instant EGR crossover tube reduces the space occupied by the engine by eliminating the need for external crossover piping.

Embodiments also provide a robust and cost-effective system by which EGR flow can be measured directly rather than indirectly. As mentioned above, many conventional systems measure EGR flow indirectly by measuring fresh air intake flow and estimating EGR flow algorithmically. Some conventional systems directly measure EGR flow; however, such systems require specially-machined orifices in the external piping. In contrast, the instant EGR crossover tube including the Venturi tube configuration enables a differential pressure sensor to be mounted directly to the cylinder head and into the EGR crossover tube via bores drilled therein. Although some conventional systems may include intake port runners with varying cross-section, such systems use the varying cross-section to provide a smooth transition between different diameter sections to minimize flow restriction. In contrast, the Venturi tube configuration described with respect to embodiments of the present disclosure incorporates a flow restriction to provide for pressure differential measurement. By integrating direct EGR flow measurement into the EGR crossover tube instead of requiring a separate component to create the pressure differential for EGR flow measurement, the instant EGR crossover tube including the Venturi tube configuration provides improved performance and reduced part count, which ultimately reduces component and manufacturing costs.

<FIG> is a schematic diagram of an engine <NUM>, according to an embodiment. As will be appreciated, the schematic diagram of <FIG> illustrates the components of the engine <NUM>, but does not necessarily indicate the specific arrangement or relative sizes of the components on the engine <NUM>. The engine <NUM> includes an engine block <NUM>, a cylinder head <NUM>, an intake manifold <NUM>, an exhaust manifold <NUM>, and an EGR crossover tube <NUM> integrally formed in the cylinder head <NUM>. The engine <NUM> may be an internal combustion engine, such as a compression ignition or spark ignition engine, and may be fueled by various types of fuels, such as diesel, gasoline, compressed natural gas, ethanol, etc. In some embodiments, the engine block <NUM> and the cylinder head <NUM> are discrete and removably coupleable components. However, in other embodiments, the engine block <NUM> and the cylinder head <NUM> are integral such that the engine <NUM> is a "monoblock" type structure. In some embodiments, the EGR crossover tube <NUM> in a monoblock configuration further reduces space occupied by the engine <NUM> by extending through portions of the engine <NUM> conventionally taken up by head bolts and bosses in a non-monoblock configuration.

The engine block <NUM> defines a plurality of cylinders <NUM>. Each of the plurality of cylinders are fluidly coupled to the intake manifold <NUM> via one or more intake ports <NUM>, and fluidly coupled to the exhaust manifold <NUM> via one or more exhaust ports <NUM>.

The EGR crossover tube <NUM> fluidly couples one or more of the exhaust ports <NUM> to one or more of the intake ports <NUM>. In some embodiments, the EGR crossover tube <NUM> is fluidly coupled to the exhaust manifold <NUM> and to an EGR mixer <NUM> so as to transmit EGR gas from the exhaust manifold <NUM> to the EGR mixer <NUM>, and subsequently to the intake manifold <NUM>. As used herein, the term "EGR gas" refers to a portion of exhaust gas that is routed back to the intake manifold <NUM> rather than being expelled into the external environment or to downstream components of the exhaust system. The EGR mixer <NUM> is structured to mix fresh intake air with EGR gas and convey the mixture to the intake manifold <NUM>. In some embodiments, the EGR crossover tube <NUM> is positioned downstream of an EGR valve <NUM> and an EGR cooler (not shown). In some embodiments, the EGR valve <NUM> is positioned downstream of the EGR crossover tube <NUM>. The EGR valve <NUM> and the EGR cooler are external to the cylinder head <NUM>. The EGR valve <NUM> receives exhaust gas from the exhaust manifold <NUM> and directs the exhaust gas flow into the EGR cooler. Then, for example, cooled EGR gas is passed through a first elbow (not shown) cast into a valve body of the EGR valve <NUM> and into a second elbow (not shown) cast into the exhaust manifold <NUM>, and subsequently flows into the EGR crossover tube <NUM>.

The EGR valve <NUM> is controllably actuatable between an open position, a closed position, and various intermediate positions therebetween. For example, in the open position, EGR gas flows from the exhaust manifold <NUM> and through the EGR crossover tube <NUM>, through which flow of the EGR gas is not restricted by the EGR valve <NUM>. The EGR gas flows from the EGR crossover tube <NUM> to the EGR mixer <NUM>, in which the EGR gas is mixed with fresh intake air and transmitted to the intake manifold <NUM>. When in the closed position, the EGR valve <NUM> blocks airflow through the EGR crossover tube <NUM>. Accordingly, in the closed position, all of the intake air provided to the intake manifold <NUM> is fresh intake air. When in intermediate positions between the open and closed position, the EGR valve <NUM> permits a controllable amount of airflow through the EGR crossover tube <NUM> based on the position of the EGR valve <NUM>.

According to various embodiments, the EGR crossover tube <NUM> is integrally formed in the cylinder head <NUM>. For example, in some embodiments, the EGR crossover tube <NUM> is cast-in-place when the cylinder head <NUM> is cast. Accordingly, the EGR crossover tube <NUM> does not require piping and other components required by conventional external EGR crossovers.

In the embodiment illustrated in <FIG>, the cylinder head <NUM> is a crossflow cylinder head in which the intake and exhaust ports <NUM>, <NUM> are on opposite sides of the engine <NUM>. Accordingly, the EGR crossover tube <NUM> is structured to transmit EGR gas from one or more of the exhaust ports <NUM> to one or more of the intake ports <NUM>. Although <FIG> illustrates the EGR crossover tube <NUM> on one side of the engine <NUM>, it should be understood that the EGR crossover tube <NUM> is integral to the engine <NUM>, and more specifically to the cylinder head <NUM>, and may be positioned in any of various locations within the cylinder head <NUM>. Additionally, although <FIG> illustrates a single EGR crossover tube <NUM>, some embodiments include one EGR crossover tube <NUM> for each of two or more of the cylinders <NUM>.

As discussed below in connection with <FIG>, the EGR crossover tube <NUM> is tapered in a Venturi tube configuration. The tapered structure of the EGR crossover tube <NUM> enables direct EGR flow measurements via a differential pressure sensor <NUM> operatively coupled to the EGR crossover tube <NUM>. The differential pressure sensor <NUM> includes a first pressure sensor <NUM> positioned in a first sensor port <NUM> and a second pressure sensor <NUM> positioned in a second sensor port <NUM>. The first and second sensor ports <NUM>, <NUM> extend through the cylinder head <NUM> to the EGR crossover tube <NUM>. The first sensor port <NUM> is positioned at the narrowest location of the Venturi tube configuration. The second sensor port <NUM> is positioned proximate an inlet of the EGR crossover tube <NUM>. As will be appreciated, the differential pressure sensor <NUM> is structured to measure pressure of the EGR flow via pressure measurements by the first and second pressure sensors <NUM>, <NUM> (or directly from a pressure differential therebetween). A pressure differential between the two locations is calculated and used to determine a mass flow rate of the EGR gas through the EGR crossover tube <NUM>.

A controller <NUM> is operatively coupled to the engine <NUM> and to the differential pressure sensor <NUM>. In some embodiments, the controller <NUM> is also operatively coupled to the EGR valve <NUM>. The controller <NUM> may be further operatively coupled to an intake air flow sensor (not shown), such as a mass airflow sensor. In some embodiments, the controller <NUM> is still further operatively coupled to other sensors (not shown), such as a NOx sensor and/or a particulate matter sensor positioned in an exhaust aftertreatment system operatively coupled to the exhaust manifold <NUM> of the engine <NUM>. The controller <NUM> includes a processor <NUM> and one or more memory devices <NUM>. The processor <NUM> may be implemented as any type of processor including one or more application specific integrated circuits (ASICs), one or more field programmable gate arrays (FPGAs), one or more digital signal processors (DSPs), a group of processing components, other suitable electronic processing components, or a combination thereof. The one or more memory devices <NUM> may store data and/or computer code for facilitating the various processes described herein. Thus, the one or more memory devices <NUM> may be communicably connected to the processor <NUM> and provide computer code or instructions for executing the processes described in regard to the controller <NUM> herein. Moreover, the one or more memory devices <NUM> may be, or may include, tangible, non-transient volatile memory or non-volatile memory (e.g., NVRAM, RAM, ROM, Flash Memory, etc.). Accordingly, the one or more memory devices <NUM> may include database components, object code components, script components, or any other type of information structure for supporting the various activities and information structures described herein.

As shown, the controller <NUM> includes various circuits for completing the activities described herein. In one embodiment, the circuits of the controller <NUM> may utilize the processor <NUM> and/or memory <NUM> to accomplish, perform, or otherwise implement various actions described herein with respect to each particular circuit. The processor <NUM> and/or memory <NUM> may be shared components across each circuit, or at least one of the circuits may include their own dedicated processing circuit having a processor and a memory device. In this latter embodiment, the circuit may be structured as an integrated circuit or an otherwise integrated processing component. In yet another embodiment, the activities and functionalities of circuits may be embodied in the memory <NUM>, or combined in multiple circuits, or as a single circuit. In this regard and while various circuits with particular functionality are shown in <FIG>, it should be understood that the controller <NUM> may include any number of circuits for completing the functions and activities described herein. For example, the activities of multiple circuits may be combined as a single circuit, as an additional circuit(s) with additional functionality, etc. Further, it should be understood that the controller <NUM> may further control other activity beyond the scope of the present disclosure.

Certain operations of the controller <NUM> described herein include operations to interpret and/or to determine one or more parameters. Interpreting or determining, as utilized herein, includes receiving values by any method known in the art, including at least receiving values from a datalink or network communication, receiving an electronic signal (e.g. a voltage, frequency, current, or PWM signal) indicative of the value, receiving a computer generated parameter indicative of the value, reading the value from a memory location on a non-transient computer readable storage medium, receiving the value as a run-time parameter by any means known in the art, and/or by receiving a value by which the interpreted parameter can be calculated, and/or by referencing a default value that is interpreted to be the parameter value.

As shown, the controller <NUM> includes an EGR flow rate circuit <NUM> and an EGR flow control circuit <NUM>. The EGR flow rate circuit <NUM> is structured to interpret pressure measurements from the first and second pressure sensors <NUM>, <NUM> of the differential pressure sensor <NUM>, and to determine the EGR flow rate based on the interpreted pressure values. In some embodiments, the EGR flow rate circuit <NUM> is also structured to determine a proportion (e.g., ratio) of fresh intake air to EGR gas provided to the intake manifold <NUM>. For example, in some embodiments, the EGR flow rate circuit <NUM> receives a flow rate measurement value from a mass airflow sensor (not shown) structured to measure a flow rate of the fresh intake air upstream of the EGR mixer <NUM>. The EGR flow rate circuit <NUM> is structured to interpret flow rate measurement values received from the mass airflow sensor so as to determine a flow rate of the fresh intake air upstream of the EGR mixer <NUM>. In some embodiments, the EGR flow rate circuit <NUM> is structured to estimate the fresh intake air flow rate algorithmically using the interpreted EGR flow rate, based on the engine's <NUM> theoretical intake air requirement. The EGR flow rate circuit <NUM> calculates the proportion of fresh air to EGR gas using the interpreted fresh intake air flow rate and the EGR flow rate.

The EGR flow control circuit <NUM> is structured to transmit a control signal to the EGR valve <NUM> in response to the determined EGR flow rate. For example, the EGR flow control circuit <NUM> may be structured to transmit a control signal to the EGR valve <NUM> so as to maintain a target ratio of fresh air to EGR gas. In some embodiments, the EGR flow control circuit <NUM> is structured to receive and interpret NOx measurement values of the exhaust gas and to transmit a control signal to the EGR valve <NUM> so as to maintain a NOx level of the exhaust gas below a threshold level. In some embodiments, the EGR flow control signal is structured to receive and interpret particulate matter measurement values of the exhaust gas and to transmit a control signal to the EGR valve <NUM> so as to maintain a particulate matter level of the exhaust gas below a threshold level.

<FIG> is a partial cross-sectional view of the cylinder head <NUM> of the engine <NUM> of <FIG>, illustrating a portion of the EGR crossover tube <NUM> defining a Venturi tube configuration <NUM>. The Venturi tube configuration <NUM> extends between a first end <NUM> and a second end <NUM>. The first end <NUM>, via the corresponding adjacent section of the EGR crossover tube <NUM>, is fluidly coupled to the exhaust port <NUM>. The second end <NUM>, via the corresponding adjacent section of the EGR crossover tube <NUM>, is fluidly coupled to the intake port <NUM>. Accordingly, the EGR crossover tube <NUM>, including the Venturi tube configuration <NUM>, is structured to transmit EGR gas from the exhaust port <NUM> to the intake port <NUM>. It should be understood that in some embodiments, the first end <NUM> is fluidly coupled to the exhaust port <NUM> via one or more additional components, such as the exhaust manifold <NUM>. Similarly, in some embodiments the second end <NUM> is fluidly coupled to the intake port <NUM> via one or more additional components, such as the intake manifold <NUM> and the EGR mixer <NUM>.

The Venturi tube configuration <NUM> of the EGR crossover tube <NUM> is positioned between the first and second ends <NUM>, <NUM>. The Venturi tube configuration <NUM> is a constricted section of the EGR crossover tube <NUM> that is structured to induce a Venturi effect in fluid (e.g., EGR gas) flowing through the EGR crossover tube <NUM>. The Venturi effect relates to a reduction in fluid pressure that results when fluid flows through a constricted section of a pipe. The Venturi effect uses the principles of conservation of mass and conservation of energy to determine a flow rate of a fluid based on a differential pressure measurement of the fluid. In one embodiment, the EGR crossover tube <NUM> has a generally circular cross-section having a first diameter at the first end <NUM>, a second diameter at the second end <NUM>, and a third diameter at a restriction <NUM> of the Venturi tube configuration <NUM>. The third diameter is smaller than each of the first and second diameters. In fact, the third diameter is the smallest diameter of the EGR crossover tube <NUM>. In some embodiments, the Venturi tube configuration <NUM> is tapered between the first end <NUM> and the restriction <NUM>, and between the restriction <NUM> and the second end <NUM>. In some embodiments, the Venturi tube configuration <NUM> is tapered at a constant rate; however, in other embodiments, the diameter of the Venturi tube configuration <NUM> varies nonlinearly between each of the first and second ends <NUM>, <NUM> and the Venturi tube configuration <NUM>.

The cylinder head <NUM> defines first and second sensor ports <NUM>, <NUM> extending through the cylinder head <NUM> and into the Venturi tube configuration <NUM>. The first sensor port <NUM> is positioned at the restriction <NUM> of the Venturi tube configuration <NUM> and the second sensor port <NUM> is positioned proximate the first end <NUM> of the Venturi tube configuration <NUM>. In other words, the first sensor port <NUM> is positioned at a location in the Venturi tube configuration <NUM> with a smallest diameter, and the second sensor port <NUM> is positioned between an inlet (e.g., the first end <NUM>) and a narrowest portion of the venturi tube configuration <NUM> (e.g., the restriction <NUM>). The positions of the first and second sensor ports <NUM>, <NUM> may also be described in relation to the EGR crossover tube <NUM> of <FIG>. For example, according to an embodiment, the first sensor port <NUM> is positioned at a restriction of the EGR crossover tube <NUM>, and the second sensor port <NUM> is positioned between an inlet of the EGR crossover tube <NUM> and the restriction. <FIG> is oriented as a partial cross-sectional bottom plan view, with the cross-section taken through the Venturi tube configuration <NUM>. Accordingly, as illustrated in <FIG>, the first and second sensor ports <NUM>, <NUM> extend through the cylinder head <NUM> to a top surface of the cylinder head <NUM>. In some embodiments, the first and second sensor ports <NUM>, <NUM> are drilled in the cylinder head <NUM> after the cylinder head <NUM> is cast. However, in other embodiments, the first and second sensor ports <NUM>, <NUM> are integrally cast-in-place with the cylinder head <NUM>.

In operation, a differential pressure sensor includes a first pressure sensor positioned in the first sensor port <NUM> and a second pressure sensor positioned in the second sensor port <NUM>. Pressure measurements from the first and second pressure sensors are interpreted and compared to determine a differential pressure. The differential pressure is used to determine a flow rate of EGR gas through the EGR crossover tube <NUM>.

It should be understood that no claim element herein is to be construed under the provisions of <NUM> U. § <NUM>(f), unless the element is expressly recited using the phrase "means for. " The schematic flow chart diagrams and method schematic diagrams described above are generally set forth as logical flow chart diagrams. As such, the depicted order and labeled steps are indicative of representative embodiments. Other steps, orderings and methods may be conceived that are equivalent in function, logic, or effect to one or more steps, or portions thereof, of the methods illustrated in the schematic diagrams. Further, reference throughout this specification to "one embodiment," "an embodiment," "an example embodiment," or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment," "in an embodiment," "in an example embodiment," and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

Additionally, the format and symbols employed are provided to explain the logical steps of the schematic diagrams and are understood not to limit the scope of the methods illustrated by the diagrams. Although various arrow types and line types may be employed in the schematic diagrams, they are understood not to limit the scope of the corresponding methods. Indeed, some arrows or other connectors may be used to indicate only the logical flow of a method. For instance, an arrow may indicate a waiting or monitoring period of unspecified duration between enumerated steps of a depicted method. Additionally, the order in which a particular method occurs may or may not strictly adhere to the order of the corresponding steps shown. It will also be noted that each block of the block diagrams and/or flowchart diagrams, and combinations of blocks in the block diagrams and/or flowchart diagrams, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and program code.

Many of the functional units described in this specification have been labeled as circuits, in order to more particularly emphasize their implementation independence. For example, a circuit may be implemented as a hardware circuit comprising custom very-large-scale integration (VLSI) circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A circuit may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices or the like.

As mentioned above, circuits may also be implemented in machine-readable medium for execution by various types of processors, such as the processor <NUM> of <FIG>. An identified circuit of executable code may, for instance, comprise one or more physical or logical blocks of computer instructions, which may, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified circuit need not be physically located together, but may comprise disparate instructions stored in different locations which, when joined logically together, comprise the circuit and achieve the stated purpose for the circuit. Indeed, a circuit of computer readable program code may be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within circuits, and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different storage devices, and may exist, at least partially, merely as electronic signals on a system or network.

The computer readable medium (also referred to herein as machine-readable media or machine-readable content) may be a tangible computer readable storage medium storing the computer readable program code. The computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, holographic, micromechanical, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. As alluded to above, examples of the computer readable storage medium may include but are not limited to a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a portable compact disc read-only memory (CD-ROM), a digital versatile disc (DVD), an optical storage device, a magnetic storage device, a holographic storage medium, a micromechanical storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, and/or store computer readable program code for use by and/or in connection with an instruction execution system, apparatus, or device.

Computer readable program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages.

Claim 1:
An engine, comprising:
a cylinder head (<NUM>) defining an exhaust gas recirculation crossover tube (<NUM>) integrally formed in the cylinder head, the exhaust gas recirculation crossover tube comprising a Venturi tube configuration;
a differential pressure sensor (<NUM>) operatively coupled to the Venturi tube configuration; and
a controller (<NUM>) operatively coupled to the differential pressure sensor, the controller comprising an exhaust gas recirculation flow rate circuit (<NUM>) structured to receive differential pressure measurement values from the differential pressure sensor, interpret the differential pressure measurement values, and determine a flow rate of exhaust gas through the exhaust gas recirculation crossover tube directly from the interpreted pressure measurement values received from the differential pressure sensor.