An electro-hydraulic control variable valve timing adjusting method and device

Abstract

The application discloses an electro-hydraulic control variable valve timing and lift adjustment method and device, and belongs to the field of power machinery control. The application constructs a working mode suitable for the electro-hydraulic control variable valve timing and lift adjustment device, including a full lift mode, an early intake valve closing mode, a late intake valve opening mode and a multiple intake valve mode; the profile of a cam, the diameter of a driving receiving piston, the diameter of a high-pressure oil way and a solenoid valve are optimized; based on the working characteristics of a high-speed solenoid valve for controlling the on-off of an oil way, a solenoid valve current waveform and a power driving circuit are designed to realize the thermal protection and quick opening and closing of the solenoid valve; according to the requirements of different modes, corresponding control strategies are designed, a controller module judges the current cylinder number according to a camshaft signal and sends a control signal to a driving circuit according to a crankshaft signal to control the accurate opening and closing of the solenoid valve, so that the multi-mode adjustment of valve timing and lift is realized. The application has the advantages of high controllability and strong practicability and is suitable for the requirements of continuously adjusting the valve timing and lift of a high-power vehicle.

Description

Technical Field

[0001] This invention relates to an electro-hydraulic control method and device for variable gas distribution regulation, belonging to the field of power machinery control. Background Technology

[0002] Internal combustion engines are developing towards electrification, energy conservation, and intelligence. Variable valve timing (VVT) technology can adopt different valve timing strategies according to different operating conditions, and it is widely used in modern internal combustion engines due to its high cost-effectiveness and significant improvement in combustion efficiency. Simply changing valve lift or valve timing is no longer sufficient to meet the needs of various new technologies. Valve timing systems need to be improved to be more controllable and flexible. This higher requirement for valve timing systems prompts us to further research more advanced variable valve timing systems.

[0003] Existing variable valve timing mechanisms can be broadly categorized into cam-driven and camless mechanisms. Cam-driven variable valve timing systems primarily use mechanical structures to switch between several valve timing states and are less affected by engine operating conditions. However, this type of system cannot achieve continuous changes in timing angle or valve lift, and therefore cannot optimize for all operating conditions. Camless variable valve timing systems offer greater control flexibility and can adjust valve timing under all engine operating conditions. However, they require a special transmission medium to control valve movement, thus increasing development complexity.

[0004] The camshaft-hydraulic variable valve timing system retains the intake and exhaust camshafts while adding a hydraulic system between the camshaft and the valves. This eliminates the need for an additional power source and provides the high controllability of a hydraulic system. The use of a single camshaft also makes the engine structure more compact and lighter. Due to these advantages, the camshaft-hydraulic variable valve timing system has long been favored by research institutions and automakers. Summary of the Invention

[0005] To address the problem that traditional cam-driven variable valve timing systems cannot achieve continuous changes in timing angle or lift, and that the development of camless variable valve timing systems is difficult, the main objective of this invention is to provide an electro-hydraulic controlled variable valve timing adjustment method and device. By acquiring camshaft and crankshaft signals, sending control signals, and driving solenoid valves, continuous adjustment of valve timing and lift can be achieved.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] This invention discloses an electro-hydraulic controlled variable valve timing method and apparatus, applicable to the working modes of an electro-hydraulic controlled variable valve timing device, including full-lift mode, early intake closing mode, late intake opening mode, and multiple intake mode. The cam profile, the diameter of the drive receiving piston, the diameter of the high-pressure oil passage, and the solenoid valve parameters are optimized. Based on the working characteristics of the high-speed solenoid valve controlling the on / off state of the oil circuit, the solenoid valve current waveform and power drive circuit are designed to achieve thermal protection and rapid opening and closing of the solenoid valve. Corresponding control strategies are designed according to the requirements of different modes. The controller module determines the current cylinder number based on the camshaft signal and sends control signals to the drive circuit based on the crankshaft signal to control the accurate opening and closing of the solenoid valve, thereby realizing multi-mode valve timing adjustment.

[0008] This invention discloses an electro-hydraulic control method for variable gas distribution, comprising the following steps:

[0009] Step 1: Construct operating modes suitable for electro-hydraulic control variable valve timing devices, including full-lift mode, early intake closing mode, late intake opening mode, and multiple intake mode; optimize the parameters of the cam profile, the diameter of the drive receiving piston, the diameter of the high-pressure oil passage, and the solenoid valve.

[0010] Full-lift mode achieves maximum output power. The solenoid valve needs to remain closed throughout the entire camshaft lift phase, with the valve fully following the camshaft's movement to maximize engine power. In this mode, the solenoid valve closes before the camshaft lift curve begins and opens after it ends; theoretically, the valve lift is the same as the camshaft lift. Early intake valve closing mode closes the valve early at low speeds, increasing engine torque and allowing as much air-fuel mixture as possible to enter the cylinder. In full-lift mode, the solenoid valve closes before the camshaft lift phase begins and opens before the camshaft descent phase ends, at which point the valve returns to its original position under the action of elastic elements and hydraulic pressure. Late intake valve opening mode is used for partial load and idling conditions. By opening the intake valve late and closing it early, it reduces the engine's intake air volume while increasing the intake velocity of the air-fuel mixture entering the cylinder, thereby promoting in-cylinder combustion and optimizing engine emissions. In late intake valve opening mode, the solenoid valve closes after entering the camshaft lift phase and opens before the camshaft descent phase ends, resulting in a smaller valve face value. The multi-intake mode is used in urban driving conditions where vehicles frequently start and stop. In this mode, the valves are opened and closed multiple times. At the beginning of the camshaft rise, the solenoid valve closes and opens rapidly, completing one valve operation. Then, the solenoid valve closes and opens again, and then remains open, waiting for the next cycle. By increasing the intake swirl through the intake valve operation, the combustion in the cylinder is promoted, improving fuel economy in urban driving conditions.

[0011] Based on the cam profile, the cam profile is determined; the diameters of the driving piston and the receiving piston are determined from the perspective of system load and layout; the oil passage parameters are determined based on the influence of the oil passage on the oil pressure fluctuation inside the system; and the relevant parameters of the normally open solenoid valve are determined based on the requirements of the electro-hydraulic control variable valve timing system for the solenoid valve.

[0012] Step 2: Based on the working characteristics of the high-speed solenoid valve that controls the on / off state of the oil circuit, design the solenoid valve current waveform and power drive circuit to achieve thermal protection and rapid opening and closing of the solenoid valve.

[0013] Sufficient electromagnetic force is generated by increasing the current to achieve high-speed switching of the solenoid valve. After the solenoid valve is engaged, the current value in the coil is reduced to alleviate the overheating problem caused by excessive coil current. This current waveform is controlled by adjusting the voltage pulse, which consists of three parts: a main pulse, a zero pulse, and a PWM wave. When the valve opening angle is reached, the drive current rises rapidly under the action of the main pulse voltage, reaching its maximum value I. a The solenoid valve then closes; the zero-pulse function is to reduce the coil current. During the zero-pulse phase, the current in the solenoid valve coil drops rapidly, until it reaches the holding current I. b The zero-pulse phase then ends; the hold pulse is a PWM wave with a fixed duty cycle that maintains the solenoid valve in a closed state and keeps the current in the solenoid valve coil at I. b When the valve closing angle is reached, the pulse ends and the solenoid valve opens.

[0014] The valve opening and closing angles refer to the corresponding crankshaft rotation angles. The crankshaft signal disk used is a 58-tooth signal disk with two empty teeth. The interval between each pair of teeth is 6°CA. The first tooth after the empty tooth is designated as tooth number 1. The crankshaft rotation angle value is calculated based on the crankshaft tooth number.

[0015] The method for setting the angle is as follows:

[0016] In full lift mode, the valve opening angle is 9°CA (14th tooth of the crankshaft) and the valve closing angle is 315°CA (5th tooth after the empty tooth of the crankshaft).

[0017] In other modes, the valve opening angle α = (number of teeth n - 14) * 6 + 9, and the valve closing angle α = (number of teeth n - 14) * 6 + 9;

[0018] The aforementioned pulses are generated by the controller's PWM module and require a solenoid valve drive circuit to enhance the driving capability of the control signal. The core of the solenoid valve drive circuit is a high-speed switching MOSFET. The signal output from the control chip is transmitted to the source and gate terminals of the MOSFET after passing through the MOSFET driver chip, controlling the switching between the drain and source terminals, thus becoming a drive signal with an amplitude of 12V.

[0019] Step 3: Design corresponding control strategies according to the needs of different modes, and analyze the valve seating pattern and pressure fluctuation pattern; the controller module determines the current cylinder number based on the camshaft signal, and sends control signals to the drive circuit based on the crankshaft signal to control the accurate opening and closing of the solenoid valve, thereby realizing continuous adjustment of valve distribution in multiple modes.

[0020] The various modules within the control chip are initialized, with preliminary parameter settings for the required ECT, PWM, and delay modules. Then, system interrupts are enabled, and the chip begins operation. The camshaft and crankshaft signals, conditioned by the signal conditioning circuit, are input to the control chip's ECT module. The current cylinder number is first determined based on the camshaft signal. When the crankshaft gear signal corresponding to the valve opening angle arrives, the control chip's control module sends a pre-set control signal, energizing and closing the solenoid valve, causing the valve to open under hydraulic pressure. When the crankshaft gear signal corresponding to the valve closing angle arrives, the control module terminates the control signal, the solenoid valve is de-energized and opens, the valve begins to close, and the system waits for the next working cylinder. This completes the operation of one mode.

[0021] Valve seating pattern: When the solenoid valve opens at the same time, as the engine speed increases, the valve seating angle also increases. Therefore, when the engine speed increases, the engine needs to open the solenoid valve earlier to allow the valve to begin to fall, in order to counteract the late valve closing caused by an excessively large valve seating angle. When the engine oil temperature is low, the valve seating angle increases significantly. This is because the decrease in engine oil temperature leads to an increase in engine oil viscosity, making valve seating more difficult and even risking that the valve may not close properly. Therefore, at low temperatures, the late valve opening and early closing mode should be selected as much as possible to avoid the problem of an excessively large valve seating angle by reducing the valve lift. Other operating modes should be adopted after the engine oil temperature rises to the normal operating temperature.

[0022] Pressure fluctuation pattern: The later the solenoid valve closes and the closer the signal is to the cam's apex, the greater the pressure fluctuation amplitude inside the cylinder. This is because a later closing angle corresponds to a higher piston speed, resulting in greater compression of the surrounding fluid and thus a larger compression wave amplitude, leading to a larger pressure fluctuation amplitude. Significant pressure fluctuations occur in the first half of the valve lift, while the fluctuations are minimal in the latter half. Therefore, to avoid losses caused by pressure fluctuations, control signals should not be sent too late during operation, and control signals should not be terminated during the cam's rise phase. As engine speed increases, the piston's speed also increases. Higher speeds allow the piston to rise to a greater speed in a shorter time and then descend more quickly. This process makes the piston's effect on the surrounding fluid more pronounced, significantly enhancing the amplitudes of both compression and expansion waves, resulting in a larger pressure fluctuation amplitude. Since the propagation speed of pressure fluctuations is not affected by engine speed, higher speeds result in shorter cycle times, fewer pressure fluctuations, and less stable pressure values. Therefore, avoiding late valve opening at high speeds reduces pressure fluctuations within the system and protects internal components.

[0023] This invention discloses an electro-hydraulic controlled variable gas distribution regulating device for implementing the aforementioned electro-hydraulic controlled variable gas distribution regulating method. The electro-hydraulic controlled variable gas distribution regulating device includes a magnetoelectric speed sensor, a signal conditioning circuit, a central computing unit, and a power drive circuit.

[0024] The magnetoelectric speed sensor is installed next to the cam signal disk and the crankshaft signal disk respectively to collect the tooth signals of the cam disk and the crankshaft disk; the signal conditioning circuit converts the sinusoidal signal of the magnetoelectric speed sensor into a square wave signal with the same phase and frequency and sends it to the central computing unit; the central computing unit sends the control pulse to the drive circuit; the power drive circuit improves the driving capability of the control signal, thereby driving the high-speed solenoid valve.

[0025] The signal conditioning circuit filters the sinusoidal signal obtained from the magnetoelectric sensor and sets positive and negative threshold values. When the signal exceeds the threshold value range, the signal completes the conversion from high level to low level. Therefore, the conditioning circuit outputs a square wave signal with the same phase and frequency as the sinusoidal signal.

[0026] The central computing unit is a circuit based on the MC9S12XDP512. The camshaft and crankshaft signals output by the signal conditioning circuit are input to the ECT module of the MC9S12 chip. Based on the camshaft signal, the current cylinder number is determined, and the system starts waiting for the crankshaft tooth corresponding to the starting angle to arrive. When the starting crankshaft tooth arrives, the control module of the MC9S12 starts sending a pre-set control signal. When the crankshaft reaches the set ending tooth, the sending of the control signal stops, and the system starts waiting for the working cylinder again.

[0027] The core of the power drive circuit is a high-speed switching MOSFET. The signal output from the control chip is transmitted to the source and gate terminals of the MOSFET after passing through the power drive chip, controlling the switching of the drain and source terminals. This results in a 12V drive signal, which drives the solenoid valve. During the high-speed opening and closing process of the solenoid valve, a large induced voltage is generated. If the drain and source terminals of the MOSFET are subjected to this reverse voltage for an extended period, irreversible damage will occur. Therefore, to ensure stable operation of the drive circuit over a long period, a reverse voltage protection circuit needs to be added between the MOSFET's drain and source terminals. This protection circuit not only shunts the induced voltage but also redirects the energy contained in the induced voltage back to the 12V battery to charge it.

[0028] Beneficial effects

[0029] 1. This invention discloses an electro-hydraulic control variable valve timing method and device, proposing several working modes suitable for the system, including full-lift mode, early intake closing mode, late intake opening mode, and multiple intake mode. The parameters of core components such as the profile of the cam, the diameter of the drive receiving piston, the diameter of the high-pressure oil passage, and the solenoid valve are optimized. This electro-hydraulic control variable valve timing system is easy to develop and has the high controllability of a hydraulic system.

[0030] 2. The present invention discloses an electro-hydraulic control variable valve timing method and device, which designs a solenoid valve current waveform and power drive circuit to realize the thermal protection and rapid opening and closing of the solenoid valve; according to the needs of different modes, corresponding control programs are designed. The controller module determines the current cylinder number based on the camshaft signal and sends a control signal to the drive circuit based on the crankshaft signal to control the rapid opening and closing of the solenoid valve, thereby realizing the continuous adjustability of the valve timing angle and lift.

[0031] 3. The electro-hydraulic control variable valve timing adjustment device disclosed in this invention includes a magnetoelectric speed sensor, a signal conditioning circuit, a central computing unit, and a power drive circuit. Combined with the adjustment method disclosed in this invention, it can complete the acquisition of system signals, the identification of signals, and the transmission of control signals, thereby realizing multi-mode valve timing adjustment. It has high controllability, strong practicality, and meets the needs of high-power vehicles for continuous adjustment of valve timing and lift. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of an embodiment of the present invention;

[0033] Figure 2 This is a control structure diagram of an electro-hydraulic control variable gas distribution regulating device disclosed in this invention;

[0034] Among them: 1-Signal conditioning circuit, 2-MC9S12 controller, 3-Signal conditioning circuit, 4-Drive circuit, 5-Solenoid valve, 6-Cam signal disc, 7-Oil tank, 8-Acquisition system, 9-Valve lift signal, 10-Crankshaft speed signal, 11-Laser displacement sensor, 12-Valve, 13-Camshaft, 14-Chain, 15-Crankshaft signal disc, 16-Magnetic speed sensor, 17-Asynchronous AC motor.

[0035] Figure 3 This is a schematic diagram of the control current and control voltage waveforms according to an embodiment of the present invention;

[0036] (a) is a schematic diagram of the control current waveform; (b) is a schematic diagram of the control voltage waveform.

[0037] Figure 4 This is a schematic diagram of the driving circuit in this embodiment;

[0038] Figure 5 This is a schematic diagram of the control program in this embodiment;

[0039] Figure 6 This is a signal acquisition diagram for multiple air intake modes;

[0040] Figure (a) shows the acquired signal diagram when control signals are sent from teeth 14 to 24 and from teeth 29 to 55; Figure (b) shows the acquired signal diagram when control signals are sent from teeth 14 to 26 and from teeth 31 to 53; Figure (c) shows the acquired signal diagram when control signals are sent from teeth 14 to 28 and from teeth 33 to 51; Figure (d) is a comparison diagram of valve lift under three multiple intake modes.

[0041] Figure 7 These are test curves of valve lift and cylinder pressure in multiple intake modes;

[0042] Figure 8 It is a test curve of multiple intake modes and multiple speeds;

[0043] Figure 9 It describes the valve movement pattern at different oil temperatures. Detailed Implementation

[0044] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. The technical problems solved by the present invention and its beneficial effects are also described. It should be noted that the described embodiments are only intended to facilitate understanding of the present invention and do not constitute any limitation thereof.

[0045] For a certain type of engine with a variable valve timing mechanism, the actual vehicle engine using this mechanism requires continuous adjustment of valve timing and lift. In start-up mode, a small late valve closing angle is needed for easy starting; in high-power mode, a large late valve closing angle is required to achieve high power and low explosion pressure; under frequent start-stop conditions, the valves need to be opened and closed multiple times to increase intake swirl, promote in-cylinder combustion, and improve fuel economy. This paper combines the valve timing drive section, fuel supply section, valve timing mechanism section, signal acquisition section, and control system section to achieve continuous adjustment of valve timing and lift, demonstrating the effectiveness of the proposed electro-hydraulic control variable valve timing adjustment method and device.

[0046] The schematic diagram and control structure diagram of the variable valve timing device in this embodiment are as follows: Figure 1 , Figure 2 As shown, combined with Figure 1 , Figure 2 The working principle of this system for continuously adjusting valve timing and lift is as follows: An asynchronous AC motor 17, under the control of a frequency converter, drives the crankshaft signal disk 15 to rotate at a certain speed, simulating the operation of the engine crankshaft. Simultaneously, the crankshaft signal disk 15 drives the camshaft 13 to rotate via a chain 14, thereby compressing the drive piston. The liquid in the high-pressure chamber drives the receiving piston, causing the valve to move. The liquid in the hydraulic chamber is drawn from the oil tank 7 by an oil pump and injected into the hydraulic chamber through an oil passage. The opening and closing of the hydraulic chamber is controlled by the solenoid valve 5 above the test system. Magnetoelectric speed sensors 16 are installed on the camshaft signal disk 6 and the crankshaft signal disk 15, respectively. The signals from the magnetoelectric speed sensors 16 are processed and transmitted to the MC9S12 controller 2. After internal calculation, the controller outputs a control signal, which is then amplified by the drive circuit 4 to drive the opening and closing of the solenoid valve 5. A laser displacement sensor 11 is placed below the valve 12 to convert the valve lift signal 9 into a voltage signal and transmit it to the acquisition system 8. At the same time, the camshaft signal and the crankshaft signal are also transmitted to the acquisition system 8 to facilitate observation of the relationship between valve opening and closing and crankshaft cam phase.

[0047] This embodiment discloses an electro-hydraulic control method for variable gas distribution, the specific implementation steps of which are as follows:

[0048] Step 1: Construct working modes suitable for electro-hydraulic control variable valve timing device, including full-lift mode, early intake closing mode, late intake opening mode, and multiple intake mode; Based on electro-hydraulic control variable valve timing device, optimize the parameters of core components such as cam profile, diameter of drive receiving piston, diameter of high-pressure oil passage, and solenoid valve.

[0049] Full-lift mode achieves maximum output power. The solenoid valve needs to remain closed throughout the entire camshaft lift phase, with the valve fully following the camshaft's movement to maximize engine power. In this mode, the solenoid valve closes before the camshaft lift curve begins and opens after it ends; theoretically, the valve lift is the same as the camshaft lift. Early intake valve closing mode closes the valves earlier at low speeds, increasing engine torque and allowing as much air-fuel mixture as possible to enter the cylinder. In full-lift mode, the solenoid valve closes before the camshaft lift phase begins and opens before the camshaft descent phase ends, with the valve returning to its original position under the action of elastic elements and hydraulic pressure. Late intake valve opening mode is used for partial load and idling conditions, by delaying the opening of the intake valves. Early intake valve closing reduces the engine's intake air volume while increasing the intake velocity of the air-fuel mixture entering the cylinder, thereby promoting in-cylinder combustion and optimizing engine emissions. In late intake valve opening mode, the solenoid valve closes after entering the camshaft rise phase and opens before the camshaft fall phase ends, resulting in a smaller valve face value. The multi-intake mode is used for urban driving conditions requiring frequent vehicle starts and stops. In this multi-intake mode, the valve is opened and closed multiple times. At the beginning of the camshaft rise phase, the solenoid valve closes and opens rapidly, completing one valve operation. Then, the solenoid valve closes and opens again, and then remains open, waiting for the next cycle. By increasing the intake swirl through the intake valve action, in-cylinder combustion is promoted, improving fuel economy in urban driving conditions.

[0050] Based on the cam profile design theory, the determined cam profile is obtained, and its formula is as follows:

[0051]

[0052] The diameters of the driving piston and receiving piston are determined to be 25mm from the perspective of system load and layout; the oil passage parameters are determined based on the influence of the oil passage on the oil pressure fluctuation inside the system, and the oil passage diameter range is 6.0mm≤d≤11.2mm; the relevant parameters of the normally open solenoid valve are determined based on the requirements of the electro-hydraulic control variable valve timing system for the solenoid valve.

[0053] Step 2: Based on the working characteristics of the high-speed solenoid valve that controls the on / off state of the oil circuit, design the solenoid valve current waveform and power drive circuit to achieve thermal protection and rapid opening and closing of the solenoid valve.

[0054] High-speed switching of a solenoid valve requires a sufficiently large electromagnetic force. This electromagnetic force is directly proportional to the current in the solenoid coil and the square of the number of turns. Therefore, increasing the electromagnetic force requires either increasing the current in the coil or increasing the number of turns. However, an excessively large number of turns increases the inductance, slowing down the current response. Thus, increasing the electromagnetic force can only be achieved by increasing the current. Once the solenoid valve is engaged, a large current is not required to maintain this state. To mitigate the heat generated by excessive coil current, the current in the coil needs to be reduced after the valve is engaged. The ideal current waveform during this process is generally as follows: Figure 3 As shown in Figure (a).

[0055] To achieve this ideal current waveform, a voltage pulse is required. This pulse consists of three parts: a main pulse, a zero pulse, and a PWM wave, as shown in the diagram below. Figure 3 As shown in Figure (b), when the valve opening angle is reached, the drive current rises rapidly under the action of the main pulse voltage, reaching its maximum value I. a The solenoid valve then closes. The zero-pulse function reduces the coil current; during the zero-pulse phase, the current in the solenoid valve coil drops rapidly, until it reaches the holding current I. b The zero-pulse phase then ends. The hold pulse is a PWM wave with a fixed duty cycle that maintains the solenoid valve in the closed state and keeps the current in the solenoid valve coil at I. b When the valve closing angle is reached, the pulse ends and the solenoid valve opens.

[0056] The valve opening and closing angles refer to the corresponding crankshaft rotation angles. The crankshaft signal disk used is a 58-tooth signal disk with two empty teeth. The interval between each pair of teeth is 6°CA. The first tooth after the empty tooth is designated as tooth number 1. The crankshaft rotation angle value can be calculated based on the crankshaft tooth number.

[0057] The method for setting the angle is as follows:

[0058] In full lift mode, the valve opening angle is 9°CA (14th tooth of the crankshaft) and the valve closing angle is 315°CA (5th tooth after the empty tooth of the crankshaft).

[0059] In other modes, the valve opening angle α = (number of teeth n - 14) * 6 + 9, and the valve closing angle α = (number of teeth n - 14) * 6 + 9;

[0060] The aforementioned voltage pulses can be generated by the PWM module of the MC9S12, but the control signal power emitted by the control chip is too low to drive the high-speed solenoid valve, and the induced voltage generated by the solenoid valve during operation can damage the control chip and other components. Therefore, a solenoid valve drive circuit is needed to improve the driving capability of the control signal and absorb the reverse induced voltage generated during solenoid valve operation. The power drive circuit used in this experiment is as follows: Figure 4 As shown.

[0061] The core of the power drive circuit is a high-speed switching MOSFET. The signal output from the control chip is transmitted through the power drive chip to the source and gate terminals of the MOSFET, controlling the switching of the drain and source terminals, thereby generating a drive voltage with an amplitude of 12V. During the high-speed opening and closing process of the solenoid valve, a large induced voltage is generated. If the drain and source terminals of the MOSFET are subjected to this reverse voltage for an extended period, irreversible damage will occur. Therefore, to ensure stable operation of the drive circuit over a long period, a reverse voltage absorption circuit needs to be added between the MOSFET's drain and source terminals. This protection circuit not only shunts the induced voltage but also redirects the energy contained in the induced voltage back to the 12V battery to charge it.

[0062] Step 3: Design corresponding control programs according to the needs of different modes. The controller module determines the current cylinder number based on the camshaft signal and sends control signals to the drive circuit based on the crankshaft signal to control the accurate opening and closing of the solenoid valve, thereby realizing multi-mode valve distribution adjustment.

[0063] The program written to the MC9S12 control chip sends control pulses to the drive circuit at a set phase angle based on the camshaft and crankshaft speed signals. The flowchart of this program is shown below. Figure 5 As shown. First, the various modules within the MC9S12 control chip are initialized, including preliminary parameter settings for the required ECT, PWM, and delay modules. Then, system interrupts are enabled, and the chip begins operation. The conditioned camshaft and crankshaft signals are input to the MC9S12 chip's ECT module. The module first determines the current cylinder number based on the camshaft signal. When the starting crankshaft tooth signal corresponding to the valve opening angle arrives, the MC9S12 control module begins sending pre-set control signals. When the ending crankshaft tooth signal corresponding to the valve closing angle arrives, the control signal transmission stops, and the module restarts waiting for the working cylinder.

[0064] Step 4: Conduct multi-mode experimental research using the corresponding control program. In the multiple intake valve mode, the control system sends a control signal at the beginning of the camshaft's working phase, closing the solenoid valve and opening the valve. The first control signal ends before the camshaft reaches its maximum lift, opening the solenoid valve and closing the valve. After the crankshaft rotates a few teeth, a second control signal is sent, closing the solenoid valve and opening the valve a second time. After the camshaft reaches its maximum lift, the control signal ends, opening the solenoid valve and closing the valve again.

[0065] Figure 6 Figure (a) shows the acquired signal diagrams when control signals are sent from teeth 14 to 24 and from teeth 29 to 55; Figure (b) shows the acquired signal diagrams when control signals are sent from teeth 14 to 26 and from teeth 31 to 53; Figure (c) shows the acquired signal diagrams when control signals are sent from teeth 14 to 28 and from teeth 33 to 51; Figure (d) is a comparison diagram of valve lift under three opening and closing angles. As can be seen from the figures, the effect of two valve openings and closings is significant. Furthermore, as the number of teeth increases during the first opening and decreases during the second opening, the maximum lift during the first opening gradually increases, while the maximum lift during the second opening gradually decreases.

[0066] Figure 7 This is a test curve of valve lift and cylinder pressure in multiple intake modes. As can be seen from the graph, after the first control signal ends, the valve does not immediately begin to close, but continues to rise by 6°CA before closing, causing the initial valve lift to be delayed by 6°CA on the camshaft. This is because during valve opening, the fluid in the cylinder also moves. This fluid has a certain inertia, and after the solenoid valve opens, it does not immediately flow into the intermediate pressure chamber, but continues to drive the valve open for a short distance before flowing out of the high-pressure chamber and into the intermediate pressure chamber. After the second control signal is sent, the valve does not open immediately, but only begins to open after 8°CA. This is because although the cylinder pressure rises at 8°CA, it is not enough to overcome the resistance of the system's elastic element. Only after 8°CA does the cylinder pressure exceed the resistance of the system's elastic element, at which point the valve can open. The large fluctuations in the cylinder pressure curve all occur in the first half of the valve lift, while the fluctuations in the second half are very small. The cylinder pressure fluctuation is larger when the valve opens for the second time. This is because the later the solenoid valve is energized and closes, the greater the speed of the driving piston, and the greater the degree of compression of the surrounding liquid by the piston. Therefore, the compression wave amplitude is larger, and thus the pressure fluctuation amplitude is larger.

[0067] Figure 8This is a multi-intake mode, multi-speed test curve. The engine speeds were adjusted to 1000 rpm, 1500 rpm, and 2000 rpm, with the solenoid valves closing at teeth 14-24 and 29-55. The graph shows that the valves generally open and close at the given angles, but the valve lift varies significantly; the higher the engine speed, the greater the valve lift. For the first solenoid valve closure, the valve lift reached 2.7 mm, 3.2 mm, and 3.7 mm respectively. For the second solenoid valve closure, the valve lift reached 1.9 mm, 2.7 mm, and 4.2 mm respectively. Engine speed also affects the final valve closing angle; the higher the speed, the larger the final closing angle. The higher the engine speed, the greater the velocity of the fluid in the high-pressure chamber. Therefore, when the solenoid valves open simultaneously during the rising phase of the camshaft, the higher the engine speed, the more difficult it is for the valve to fall back, resulting in a larger angle along the camshaft and thus a greater valve lift. The higher the engine speed, the greater the angle required for the valve to sit. Therefore, at speeds of 1500 rpm and 2000 rpm, the valve is opened a second time before it is fully closed.

[0068] Figure 9 This diagram illustrates the valve movement at different oil temperatures. The solenoid valve closes when energized at 25°C and opens when de-energized at 210°C. The graph shows that at normal operating oil temperatures between 70°C and 110°C, the valve seat angle is essentially consistent. However, due to variations in oil viscosity, the resistance encountered during valve opening differs, causing a slight decrease in valve lift as oil temperature increases. At a lower oil temperature of 20°C, the higher oil viscosity results in a larger valve closing angle, closing approximately 90° later. This indicates that the system requires a certain amount of heating to start operating at low temperatures; otherwise, improper valve closure may occur.

[0069] The present invention discloses an electro-hydraulic control variable valve timing adjustment method that can realize multi-mode adjustment of valve timing by acquiring camshaft and crankshaft signals, sending control signals and driving solenoid valves. This variable valve timing system is easy to develop and has the high controllability of a hydraulic system. It is highly practical and can meet the needs of continuous adjustment of valve timing and lift.

[0070] The above detailed description further illustrates the purpose, technical examples, and beneficial effects of the invention. It should be understood that the above description is merely a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electro-hydraulic control method for variable gas distribution, characterized in that: Includes the following steps: Step 1: Construct operating modes suitable for electro-hydraulic control variable valve timing devices, including full-lift mode, early intake closing mode, late intake opening mode, and multiple intake mode; optimize the parameters of the cam profile, the diameter of the drive receiving piston, the diameter of the high-pressure oil passage, and the solenoid valve. Step 2: Based on the working characteristics of the high-speed solenoid valve that controls the on / off state of the oil circuit, design the solenoid valve current waveform and power drive circuit to achieve thermal protection and rapid opening and closing of the solenoid valve. Step 3: Design corresponding control strategies according to the needs of different modes, and analyze the valve seating pattern and pressure fluctuation pattern; the controller module determines the current cylinder number based on the camshaft signal, and sends control signals to the drive circuit based on the crankshaft signal to control the accurate opening and closing of the solenoid valve, thereby realizing continuous adjustment of valve distribution in multiple modes.

2. The electro-hydraulic control variable gas distribution method as described in claim 1, characterized in that: The implementation method for step one is as follows: Full-lift mode achieves maximum output power. The solenoid valve needs to remain closed throughout the entire camshaft lift phase, with the valve fully following the camshaft's movement to maximize engine power. In this mode, the solenoid valve closes before the camshaft lift curve begins and opens after it ends; theoretically, the valve lift is the same as the camshaft lift. Early intake valve closing mode closes the valves earlier at low speeds, increasing engine torque and allowing as much air-fuel mixture as possible to enter the cylinder. In full-lift mode, the solenoid valve closes before the camshaft lift phase begins and opens before the camshaft descent phase ends, with the valve returning to its original position under the action of elastic elements and hydraulic pressure. Late intake valve opening mode is used for partial load and idling conditions, by delaying the opening of the intake valves. Early intake valve closing reduces the engine's intake air volume while increasing the intake velocity of the air-fuel mixture entering the cylinder, thereby promoting in-cylinder combustion and optimizing engine emissions. In late intake valve opening mode, the solenoid valve closes after entering the camshaft rise phase and opens before the camshaft fall phase ends, resulting in a smaller valve face value. The multi-intake mode is used for urban driving conditions requiring frequent vehicle starts and stops. In this multi-intake mode, the valve is opened and closed multiple times. At the beginning of the camshaft rise phase, the solenoid valve closes and opens rapidly, completing one valve operation. Then, the solenoid valve closes and opens again, and then remains open, waiting for the next cycle. By increasing the intake swirl through the intake valve action, in-cylinder combustion is promoted, improving fuel economy in urban driving conditions. Based on the cam profile, the determined cam profile is obtained; The diameters of the driving piston and receiving piston are determined from the perspective of system load and layout; the oil passage parameters are determined based on the influence of the oil passage on the oil pressure fluctuation inside the system; and the relevant parameters of the normally open solenoid valve are determined based on the requirements of the electro-hydraulic control variable valve timing system for the solenoid valve.

3. The electro-hydraulic control variable gas distribution method as described in claim 1, characterized in that: The implementation method for step two is as follows: By increasing the current to generate a sufficiently large electromagnetic force, the high-speed switching of the solenoid valve can be achieved. After the solenoid valve is engaged, in order to reduce the heat generated by excessive coil current, the current value in the coil is reduced. The aforementioned current waveform regulation is achieved by controlling the voltage pulse. The voltage pulse consists of three parts: the main pulse, the zero pulse, and the PWM wave. When the valve opening angle arrives, the drive current rises rapidly under the action of the main pulse voltage, reaching its maximum value I. a The solenoid valve then closes; The purpose of the zero-pulse is to reduce the coil current. During the zero-pulse phase, the current in the solenoid valve coil drops rapidly, until it reaches the holding current I. b The zero-pulse phase then ends; the hold pulse is a PWM wave with a fixed duty cycle that maintains the solenoid valve in a closed state and keeps the current in the solenoid valve coil at I. b When the valve closing angle is reached, the pulse ends and the solenoid valve opens; The valve opening and closing angles refer to the corresponding crankshaft rotation angles. The crankshaft signal disk used is a 58-tooth signal disk with two empty teeth. The interval between each pair of teeth is 6°CA. The first tooth after the empty tooth is taken as tooth number 1. The crankshaft rotation angle value is calculated based on the crankshaft tooth number. The method for setting the angle is as follows: In full-lift mode, the valve opening angle is 9°CA and the valve closing angle is 315°CA. In other modes, the valve opening angle α = (number of teeth n - 14) * 6 + 9, and the valve closing angle α = (number of teeth n - 14) * 6 + 9; The aforementioned pulses are generated by the controller's PWM module and require a solenoid valve drive circuit to enhance the driving capability of the control signal. The core of the solenoid valve drive circuit is a high-speed switching MOSFET. The signal output by the control chip is transmitted to the source and gate terminals of the MOSFET after passing through the MOSFET driver chip, controlling the switching of the drain and source terminals, thus becoming a drive signal with an amplitude of 12V.

4. The electro-hydraulic control variable gas distribution method as described in claim 1, characterized in that: The implementation method for step three is as follows: The various modules within the control chip are initialized, including preliminary parameter settings for the required ECT, PWM, and delay modules. Then, system interrupts are enabled, and the chip begins operation. The camshaft and crankshaft signals, conditioned by the signal conditioning circuit, are input to the control chip's ECT module. The current cylinder number is determined based on the camshaft signal. When the crankshaft gear signal corresponding to the valve opening angle arrives, the control chip's control module sends a pre-set control signal, energizing and closing the solenoid valve, causing the valve to open under hydraulic pressure. When the crankshaft gear signal corresponding to the valve closing angle arrives, the control module terminates the control signal, de-energizing and opening the solenoid valve, causing the valve to close and waiting for a new working cylinder. This completes the operation of one mode. Valve seating pattern: When the solenoid valves are opened at the same time, as the engine speed increases, the valve seating angle also increases. Therefore, when the engine speed increases, the engine needs to open the solenoid valve earlier to allow the valve to begin to fall in order to counteract the late valve closing caused by an excessively large valve seating angle. When the engine oil temperature is low, the valve seating angle increases significantly. This is because the decrease in engine oil temperature leads to an increase in engine oil viscosity, making valve seating more difficult and even risking that the valve may not close properly. Therefore, at low temperatures, the late valve opening and early closing mode should be selected as much as possible to avoid the problem of an excessively large valve seating angle by reducing the valve lift. Other operating modes should be adopted after the engine oil temperature rises to the normal operating temperature. Pressure fluctuation pattern: The later the solenoid valve closes and the closer the signal is to the cam's apex, the greater the pressure fluctuation amplitude inside the cylinder. This is because a later closing angle corresponds to a higher piston speed, resulting in greater compression of the surrounding fluid and thus a larger compression wave amplitude, leading to a larger pressure fluctuation amplitude. Significant pressure fluctuations occur in the first half of the valve lift, while the fluctuations are minimal in the latter half. Therefore, to avoid losses caused by pressure fluctuations, control signals should be sent as late as possible during operation, and the control signal should not be terminated during the cam's rise phase. As the engine speed increases, the piston's speed also increases. Higher speeds allow the piston to rise to a greater speed in a shorter time and then descend more quickly. This process makes the piston's effect on the surrounding fluid more pronounced, significantly enhancing the amplitudes of both compression and expansion waves, resulting in a larger pressure fluctuation amplitude. Since the propagation speed of pressure fluctuations is not affected by engine speed, higher speeds result in shorter cycle times, fewer pressure fluctuations, and less stable pressure values. Therefore, avoiding late valve opening at high speeds reduces pressure fluctuations within the system and protects internal components.

5. An electro-hydraulic controlled variable gas distribution regulating device, used to implement the electro-hydraulic controlled variable gas distribution regulating method as described in claim 1, 2, 3 or 4, characterized in that: It includes a magnetoelectric speed sensor, a signal conditioning circuit, a central computing unit, and a power drive circuit. The magnetoelectric speed sensor is installed next to the cam signal disk and the crankshaft signal disk, respectively, to collect the tooth signals of the cam disk and the crankshaft disk. The signal conditioning circuit converts the sinusoidal signal from the magnetoelectric speed sensor into a square wave signal with the same phase and frequency and sends it to the central computing unit. The central computing unit sends control pulses to the drive circuit according to the built-in algorithm. The power drive circuit improves the driving capability of the control signal, thereby driving the high-speed solenoid valve.

6. The electro-hydraulic controlled variable gas distribution regulating device as described in claim 5, characterized in that: The signal conditioning circuit filters the sinusoidal signal obtained from the magnetoelectric sensor and sets positive and negative threshold values. When the signal exceeds the threshold value range, the signal completes the conversion from high level to low level. Therefore, the conditioning circuit outputs a square wave signal with the same phase and frequency as the sinusoidal signal.

7. The electro-hydraulic control variable gas distribution regulating device as described in claim 5, characterized in that: The central computing unit is a circuit based on the MC9S12XDP512. The camshaft and crankshaft signals output by the signal conditioning circuit are input to the ECT module of the MC9S12 chip. The current cylinder number is determined based on the camshaft signal. When the crankshaft tooth corresponding to the valve opening angle arrives, the control module of the MC9S12 starts to send a pre-set control signal. When the crankshaft tooth corresponding to the valve closing angle arrives, the sending of the control signal ends and the system restarts to wait for the working cylinder.

8. The electro-hydraulic control variable gas distribution regulating device as described in claim 5, characterized in that: The core of the power drive circuit is a high-speed switching MOSFET. The signal output by the control chip is transmitted to the source and gate terminals of the MOSFET after passing through the MOSFET driver chip, controlling the switching of the drain and source terminals, thus becoming a drive signal with an amplitude of 12V to drive the solenoid valve. In order to enable the drive circuit to work stably for a long time, a reverse voltage protection circuit is added between the MOSFET's drain and source terminals. The protection circuit not only shunts the induced voltage, but also draws the energy contained in the induced voltage back to the 12V battery to charge the battery.

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