Matched power amplifier with multiple loaded chokes for inductively heated fuel injection systems

Abstract

Featuring a tuned power amplifier: - a tuning capacitor with a first terminal and a second terminal; - a large number of loaded throttles, whereby - - the tuning capacitor is connected in series with the loaded chokes, so that a multitude of series circuits, each containing the tuning capacitor and one of the loaded chokes, are created according to the multitude of loaded chokes, - - the multitude of loaded chokes is configured to represent an inductance of an oscillator, - -the multitude of series circuits includes a first series connection point and a second series connection point that differs from the first series connection point, - - the plurality of loaded chokes comprises a first loaded choke and a second loaded choke, each of the loaded chokes comprising a first terminal for coupling to a common voltage source and a second terminal, - - the first terminal of the tuning capacitor is connected to the second terminal of the first loaded choke at the first series connection point and the second terminal of the tuning capacitor is connected to the second terminal of the second loaded choke at the second series connection point, - - the loaded chokes each have an induction heating coil of an inductively heated fuel injector, so that the respective induction heating coil of the inductive fuel injector acts as both a load and a load inductance, and a resonant network is formed between the several induction heating coils and the common tuning capacitor; - a plurality of semiconductor power switches connected to the plurality of series connections between the tuning capacitor and the corresponding plurality of loaded chokes, wherein the plurality of semiconductor switches comprises a first power semiconductor switch and a second power semiconductor power switch, and each of the power semiconductor power switches comprises a first line terminal, a second line terminal and a control terminal, wherein the first line terminal of the first power semiconductor power switch is connected to the first series connection point and the first line terminal of the second power semiconductor power switch is connected to the second series connection point.

Description

BACKGROUND

[0001] Embodiments of the invention generally relate to the power electronics for induction heating devices and more precisely to induction heating device drivers for variable spray fuel injection devices or fuel injection devices with variable spray jet.

[0002] There is a continuing need to improve the emission quality of internal combustion engines. At the same time, there is pressure to minimize engine start-up times and the time from start-up to departure, while maintaining maximum fuel efficiency. This type of pressure applies to engines powered by alternative fuels, such as ethanol, as well as those powered by gasoline.

[0003] When starting a conventional spark-ignition internal combustion engine from cold, it is characterized by high hydrocarbon emissions and poor ignition and combustibility of the fuel. Unless the engine is already at a high temperature after being switched off and allowed to cool down, the starting time may be excessive, or the engine may fail to start at all. At higher engine speeds and loads, the operating temperature increases, and fuel atomization and mixing improve.

[0004] During a true cold start, the enrichment required to initiate the engine results in a non-stoichiometric fuel supply, leading to high tailpipe hydrocarbon emissions. The worst emissions occur during the first few minutes of engine operation, after which the catalytic converter and engine approach operating temperature. Regarding ethanol-powered vehicles, as the ethanol percentage of the fuel increases to 100%, the cold-start capability is progressively reduced. This leads some manufacturers to implement a dual-fuel system, where the engine is started using conventional gasoline and then runs on ethanol. Such systems are costly and redundant.

[0005] Another solution to cold-start emissions and low-temperature starting difficulties is to preheat the fuel to a temperature at which it rapidly vaporizes or instantly evaporates ("flash boils") when released to the exhaust manifold or compressed air. Preheating the fuel, in terms of fuel condition, mimics a hot engine.

[0006] Several preheating methods have been proposed, most of which involve preheating in a fuel injection system. Fuel injection systems are widely used to meter fuel into the intake manifold or cylinders of motor vehicle engines. Fuel injection systems typically include a housing containing a volume of pressurized fuel, a fuel inlet section, a nozzle section with a needle valve, and an electromechanical actuator, such as an electromagnetic solenoid, a piezoelectric actuator, or some other mechanism, for actuating the needle valve. When the needle valve is actuated, the pressurized fuel is sprayed out through an opening in the valve seat and into the engine.

[0007] One technique used in preheating fuel is the inductive heating of metal elements of the fuel injection system with a time-varying magnetic field. Exemplary fuel injection systems with induction heating are disclosed in U.S. Patent No. 7,677,468 and U.S. Patent Application Publications 20070235569, 20070235086, 20070221874, 20070221761, and 20070221747, the contents of which are hereby incorporated in full by reference. The energy is converted into heat in a component that is suitable in terms of geometry and material to be heated by the hysteresis and eddy current losses induced by the time-varying magnetic field.

[0008] The heated fuel injection system is useful not only in solving the problems described above that are associated with gasoline systems, but also in preheating ethanol-type fuels to achieve successful starting without a redundant gasoline fuel system.

[0009] Since the induction heating technology uses a time-varying magnetic field, the system includes electronics to supply an induction coil in the fuel injection device with an appropriate high-frequency alternating current.

[0010] Conventionally, induction heating is achieved by hard switching of the power, or switching when both the voltage and current in the switching device are non-zero. Typically, the switching occurs at a frequency close to the resonant frequency of a resonator or tank circuit. The resonator contains an inductor and a capacitor, which are selected and optimized to resonate at a frequency suitable for maximizing energy coupling into the heated component.

[0011] The natural resonant frequency of a tank circuit is fr=1 / (2πLC), where L is the circuit inductance and C is the circuit capacitance. The peak voltage at resonance is limited by the energy losses of the inductor and capacitor or the reduced quality factor, Q, of the circuit. Hard switching can be achieved with so-called half-bridge or full-bridge circuits, each containing one or two pairs of semiconductor switches, respectively. Hard switching of power leads to the negative consequences of switching noise and high-amplitude current pulses at a resonant frequency of the power supply or its harmonics. Hard switching also dissipates power during the linear turn-on and turn-off periods if the switching device is neither fully conducting nor fully insulating. The higher the frequency of a hard-switched circuit, the higher the switching losses.

[0012] A conventional heating circuit that drives or controls a heated fuel injection device, with switching occurring at the lowest possible power interruption, was disclosed in U.S. Patent 7,628,340 entitled "Constant Current Zero-Voltage Switching Induction Heater Driver for Variable Spray Injection." Ideally, energy should be replenished to the fuel circuit when either the voltage or current in the switching device is zero. It is known that electromagnetic noise is lower during zero-voltage or zero-current switching, and lowest during zero-voltage switching, as utilized in U.S. Patent No. 7,628,340. It is also known that the switching device dissipates the least power during zero switching. This ideal switching point occurs twice per cycle when the sine wave passes through zero and the polarity inverts or reverses; i.e.,, when the sine wave passes through zero in a first direction from positive to negative and when the sine wave passes through zero in a second direction from negative to positive.

[0013] An additional method for driving or controlling a heated fuel injection device, whereby switching occurs with the lowest possible interrupted power, is disclosed in US patent publication 20120267359, invented by Perry Czimmek, entitled Synchronous Full-Bridge Power Oscillator. The disclosed topology uses two pairs of complementary power-switching transistors in a modified full-bridge or H-bridge configuration. The difference from a full-bridge driver is that the bridge is driven by a constant-current source inductor, and the load section of the conventional full-bridge is replaced by the resonant tank circuit. Another difference from a conventional full-bridge is the oscillator-synchronous inherent zero-switching topology, which drives the gates of the complementary pairs of transistors in alternating sequence of the diagonal pairs.

[0014] US 3 781 503 A discloses an economical cooking appliance with a smooth work surface for inductive heating of cookware, preferably consisting of a flat air core induction heating coil driven by a simplified one-thyristor, one-transistor or two-transistor resonant converter at an ultrasonic frequency.

[0015] US 5,159,915 A discloses a fuel injector nozzle for injecting heated fuel into an internal combustion engine, comprising an electromagnetic coil for generating a fluctuating magnetic flux density, a fuel heating element in which the fluctuating magnetic flux density is generated by the electromagnetic coil, such that the fuel heating element is heated by the fluctuating magnetic flux density and heat energy generated by the fluctuating magnetic flux density of the fuel heating element is transferred to the fuel.

[0016] Improved techniques for controlling a heated fuel injection system, whereby switching is performed with the least possible interrupted power, would advance the state of the art. BRIEF SUMMARY

[0017] The invention is defined by the independent claims. Advantageous embodiments of the invention are specified in the dependent claims.

[0018] Embodiments of the invention relate to a tuned power amplifier comprising: a tuning capacitor connected in series with several loaded inductors representing the inductance of an oscillator, and several semiconductor power switches connected to the series circuits between the tuning capacitor and the loaded inductors. The loaded inductors may be induction heating coils of inductively heated fuel injection devices. The induction heating coils may be connected to a common voltage source. An on-state and an off-state of the semiconductor power switches may be synchronized with a self-resonant frequency of the tuned power amplifier or with a frequency below it. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a simplified electrical circuit diagram of a conventional load arrangement of a Class E or Class F amplifier. Fig. Figure 2 is a simplified electrical circuit diagram of a tuned power amplifier according to embodiments of the invention. Fig. Figure 3 is a diagram of a SPICE simulation of a tuned power amplifier according to embodiments of the invention. Fig. Figure 4 is an exemplary graphical representation of a simulation result for a set of conditions of the tuned power amplifier of the Fig. 3. Fig. Figure 5 is a simplified electrical circuit diagram of a tuned power amplifier with multiple loaded chokes according to embodiments of the invention. Fig. Figure 6 is a diagram of a SPICE simulation of a tuned power amplifier with multiple loaded chokes according to embodiments of the invention. Fig. Figure 7 is an exemplary graphical representation of a simulation result for a set of conditions of the tuned power amplifier of the Fig. 6. DETAILED DESCRIPTION

[0019] Embodiments of the invention are directed towards controlling a heated fuel injection device, wherein switching with the lowest possible interrupted power is carried out via a reduced number of electronic components, resulting in cost savings associated with the reduction in the number of components, while still achieving switching with the lowest possible interrupted power.

[0020] Embodiments of the invention are directed to modifying a class E / F amplifier with a high-frequency choke by replacing the load as part of the high-frequency choke in order to achieve inductive heating of the loaded loss component.

[0021] Embodiments of the invention eliminate the conventional position of the load and load inductor and replace the high-frequency choke with a choke that incorporates the load inductor and the load as the heating coil of an inductively heated fuel injection device. In this way, a dedicated high-frequency choke, which is typically required by conventional methods, is no longer necessary.

[0022] Class E, E / F, and F amplifiers are described for practical purposes as tuned switching-mode inverters that convert direct current to alternating current. Efficiency is relatively high with Class E, E / F, and F amplifiers, and their conductance is typically close to 50%. The conductance, or conducting state, is selected to switch on and off in synchronization with the self-resonance of one or more tuned circuits with an inductive and a capacitive component. The tuned circuit is conventionally connected in parallel or in series with the load component. Fig. Figure 1 represents a load in series with the tuned circuit in a conventional manner. A separate high-frequency inductor is included to replenish the energy lost in the tuned circuit and the load. A high-frequency inductor is not conventionally part of this tuned circuit, nor is it a loss component for the purpose of induction heating. Embodiments of the invention combine the high-frequency inductor with the loss component for the purpose of induction heating. In this way, the inductor, its inherent effect on its own self-inductance, and the tuning capacitor are what remains for tuning.

[0023] Embodiments of the invention eliminate the conventional position of the load and the load inductor and replace the high-frequency choke with a choke that now incorporates the load inductor and the load as the heating coil of an inductively heated injection device, as shown in Fig. 2 shown. This substitution is shown in the equivalent circuit of the SPICE model of the Fig. Figure 3 illustrates that, according to embodiments of the invention, the load and the load inductor are represented at their respective new locations by resistor R6 and inductor L4:L7, respectively. A dedicated high-frequency choke, which is usually required by conventional methods, is not needed. Likewise, additional power switches are not required, so that a tuned power amplifier according to embodiments of the invention can operate with a single n-MOSFET. In this way, a resonant network can be formed between the choke or the load inductor and the tuning capacitor.

[0024] Ideally, energy should be replenished to the tank circuit when either the voltage or the current in the switching device is zero. It is known that electromagnetic noise is lower during zero-voltage or zero-current switching, and lowest during zero-voltage switching. It is also known that the switching device dissipates the least power during zero-voltage switching. Energy replenishment is enabled by semiconductor switches, and the zero-voltage switching is synchronized with the resonance of the tuned circuit. This is confirmed by the simulation results presented in Fig. Figure 4 shows the switching points synchronized with the drain voltage, which is also the capacitor voltage.

[0025] The tuning capacitor and the choke form the tuned circuit. The resonant frequency of the tuned circuit is fr=1 / (2πLC), where L is the inductance of the choke and C is the capacitance of the tuning capacitor. The peak voltage in the tuned circuit is close to the ratio V. out = π*V in , where V in The supply voltage is determined by the current level in the tuned circuit based on the energy balance of... 12LI2=12CV2 certainly.

[0026] The load caused by the resistive or ohmic loss and hysteresis loss of the heated component in the injection device heating coil of the choke is reflected back as a loss in the tuned circuit. This loss is replenished by current flowing into the choke from the supply voltage according to embodiments of the invention. The choke also provides a temporary isolation of the tuned circuit from the voltage source, so that the tank voltage can be immediately higher than the source voltage during oscillation.

[0027] Temperature control can be achieved by querying the tuned frequency of a parameter such as the time-varying gate charge of one or more of the oscillator power switches. This method, which uses the gate charge to determine the tank frequency, was previously disclosed in U.S. Patent Publication 20100288755, invented by Perry Czimmek, entitled "Frequency to Voltage Converter Using Gate Voltage Sampling of Power Oscillator," the entire contents of which are hereby incorporated by reference.

[0028] Fig. Figure 3 is a diagram of a SPICE simulation of a tuned power amplifier according to embodiments of the invention.

[0029] Fig. Figure 4 is an exemplary graphical representation of a simulation result for a set of conditions of the tuned power amplifier of the Fig. 3. Fig. Figure 4 shows the drain voltage of Q1, which is a line of the MOSFET switch. The gate voltage is V2, which is the voltage that turns MOSFET Q1 on and off. The current is the current flowing through L4, which is the load inductor, or the high-frequency choke component. Fig. Figure 4 shows the time-varying current, which is the injection device current. It has a DC bias. This current rises to 32 amps and falls to -16 amps. This time-varying current generates the time-varying field in the load inductor, which generates heat, and the simulation shows that the circuit of the Fig. 3 works as intended.

[0030] In a way that the in Fig. Similar to the method shown in 2, embodiments of the invention eliminate the conventional position of the loads and load inductors and replace the high-frequency choke with multiple chokes, which now have the load inductors and loads as the heating coils of the multiple inductively heated fuel injection devices, as shown in Fig. Figure 5 shows this substitution. This substitution is shown in the equivalent circuit of the SPICE model. Fig. Figure 6 shows that, according to embodiments of the invention, the loads and load inductors are represented at their new locations by resistor R6 and inductor L4:L7, or by resistor R5 and inductor L1:L6, respectively. A dedicated high-frequency choke, which is usually required by conventional methods, is not needed. In this way, a resonant network can be formed between the multiple loaded chokes or load inductors and the shared tuning capacitor.

[0031] Fig. Figure 7 is an exemplary graphical representation of a simulation result for a set of conditions of the tuned power amplifier of the Fig. 6. How Fig. 4, which is discussed above, shows Fig. 7, that the circuit of Fig. 6 works as intended.

[0032] The embodiment of the Fig. Figure 2 can be considered to represent a single channel, such that there is an inductively heated fuel injection device at the throttle position. In the embodiment of the Fig. 5. A single, shared tuning capacitor is used to drive multiple injection devices. Each throttle represents an injection device. Therefore, to actuate four inductively heated fuel injection devices, instead of multiplying the embodiment fourfold, Fig. 2 for four separate channels the embodiment of the Fig.5 can be doubled, which advantageously reduces by half the number of tuning capacitors used to control the same number of inductively heated fuel injection devices.

[0033] The preceding detailed description is in every respect intended to be illustrative and exemplary, but not limiting, and the scope of the invention disclosed herein is to be determined not by the description of the invention, but rather by the claims, which are to be interpreted according to the full breadth permitted by patent law. For example, although the method mentions a specific class of amplifier, it is clear to anyone with technical skills that variations using other amplifier classes, or even no reference to any amplifier class at all, may be employed. It should be clear that the embodiments shown and described herein are merely illustrative of the principles of the present invention and that various modifications may be implemented by someone with technical skills without departing from the scope and essence of the invention.

Claims

[1] Featuring a tuned power amplifier: - a tuning capacitor with a first terminal and a second terminal; - a large number of loaded throttles, whereby - - the tuning capacitor is connected in series with the loaded chokes, so that a multitude of series circuits, each containing the tuning capacitor and one of the loaded chokes, are created according to the multitude of loaded chokes, - - the multitude of loaded chokes is configured to represent an inductance of an oscillator, - -the multitude of series circuits includes a first series connection point and a second series connection point that differs from the first series connection point, - - the plurality of loaded chokes comprises a first loaded choke and a second loaded choke, each of the loaded chokes comprising a first terminal for coupling to a common voltage source and a second terminal, - - the first terminal of the tuning capacitor is connected to the second terminal of the first loaded choke at the first series connection point and the second terminal of the tuning capacitor is connected to the second terminal of the second loaded choke at the second series connection point, - - the loaded chokes each have an induction heating coil of an inductively heated fuel injector, so that the respective induction heating coil of the inductive fuel injector acts as both a load and a load inductance, and a resonant network is formed between the several induction heating coils and the common tuning capacitor; - a plurality of semiconductor power switches connected to the plurality of series connections between the tuning capacitor and the corresponding plurality of loaded chokes, wherein the plurality of semiconductor switches comprises a first power semiconductor switch and a second power semiconductor power switch, and each of the power semiconductor power switches comprises a first line terminal, a second line terminal and a control terminal, wherein the first line terminal of the first power semiconductor power switch is connected to the first series connection point and the first line terminal of the second power semiconductor power switch is connected to the second series connection point. [2] Tuned power amplifier according to claim 2, wherein an on-state of the plurality of semiconductor power switches and an off-state of the plurality of semiconductor power switches are synchronized with a self-resonant frequency of the tuned power amplifier. [3] Tuned power amplifier according to one of the preceding claims, wherein an on-state of the plurality of semiconductor power switches and an off-state of the plurality of semiconductor power switches are synchronized at a frequency below a self-resonant frequency of the tuned power amplifier.

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