Pwm frequency control method and device of solenoid valve, vvt device and automobile

Abstract

The application relates to the field of automobile engines, and discloses a PWM frequency control method and device of an electromagnetic valve, a VVT device and an automobile. The method comprises the following steps: when the camshaft axial motion frequency is lower than a first frequency threshold value, the PWM frequency of the electromagnetic valve in the VVT device is controlled to be kept at a first specified frequency, and the difference between the first specified frequency and the camshaft axial motion frequency is greater than a preset frequency difference value; when the camshaft axial motion frequency is greater than or equal to the first frequency threshold value, the PWM frequency is controlled to be a second specified frequency, the difference between the second specified frequency and the camshaft axial motion frequency is greater than the preset frequency difference value, and at least one second specified frequency is greater than or smaller than the first specified frequency. The application can ensure the stability of the VVT device without increasing the production cost of the automobile.

Description

Technical Field

[0001] This invention relates to the field of automotive engines, and more particularly to a PWM frequency control method, device, VVT device, and automobile for a solenoid valve. Background Technology

[0002] VVT (Variable Valve Timing) is an important component of automobile engines. By adjusting the phase of the engine camshaft, the VVT ​​system changes the opening and closing times of the valves according to the engine speed, greatly improving charging efficiency and increasing engine power.

[0003] Current mainstream VVT devices are all vane-type VVT ​​devices, which can achieve continuous phase adjustment. Depending on the location of the oil control valve, they can be divided into side-mounted control valve VVT ​​devices and center-mounted control valve VVT ​​devices. The former has lower cost and a higher market share; the latter offers better performance but is more expensive, and its market share is gradually increasing.

[0004] In VVT devices, the PWM (Pulse Width Modulation) frequency of the solenoid valve is a fixed frequency, exhibiting the following characteristics: 1. When a lower PWM frequency is selected for the solenoid valve, the growth curve of the PWM frequency intersects with the axial motion frequency of the engine camshaft. When the PWM frequency equals the axial motion frequency of the engine camshaft, the solenoid valve resonates with the engine, causing the solenoid valve's pin to be unable to be fully controlled by the PWM signal issued by the ECU (Electronic Control Unit), resulting in VVT phase fluctuations; 2. When a higher PWM frequency is selected for the solenoid valve, the growth curve of the PWM frequency does not intersect with the axial motion frequency of the engine camshaft, thus preventing resonance. However, solenoid valves with higher PWM frequencies are prone to hysteresis, requiring heat treatment or additional coating treatment, which increases costs.

[0005] Therefore, it is necessary to find a new PWM frequency control method for solenoid valves to ensure the stability of VVT devices without increasing the cost of automobiles. Summary of the Invention

[0006] Therefore, it is necessary to provide a PWM frequency control method, device, VVT device, and automobile for solenoid valves to address the above-mentioned technical problems, so as to ensure the stability of the VVT ​​device without increasing the automobile production cost.

[0007] A PWM frequency control method for a solenoid valve, comprising: When the axial motion frequency of the camshaft is lower than the first frequency threshold, the PWM frequency of the solenoid valve in the VVT ​​device is maintained at the first specified frequency, and the difference between the first specified frequency and the axial motion frequency of the camshaft is greater than the preset frequency difference. When the axial motion frequency of the camshaft is greater than or equal to the first frequency threshold, the PWM frequency is controlled to be a second specified frequency. The difference between the second specified frequency and the axial motion frequency of the camshaft is greater than the preset frequency difference, and at least one of the second specified frequencies is greater than or less than the first specified frequency.

[0008] A PWM frequency control device for a solenoid valve, comprising: The first control module is used to control the PWM frequency of the solenoid valve in the VVT ​​device to be maintained at a first specified frequency when the axial motion frequency of the camshaft is lower than a first frequency threshold. The difference between the first specified frequency and the axial motion frequency of the camshaft is greater than a preset frequency difference. The second control module is used to control the PWM frequency to a second specified frequency when the axial motion frequency of the camshaft is greater than or equal to the first frequency threshold. The difference between the second specified frequency and the axial motion frequency of the camshaft is greater than the preset frequency difference, and at least one of the second specified frequencies is greater than or less than the first specified frequency.

[0009] A VVT device, the VVT ​​device including a solenoid valve, the solenoid valve being controlled by any of the above-described solenoid valve PWM frequency control methods.

[0010] An automobile includes an engine equipped with the aforementioned VVT device.

[0011] The aforementioned PWM frequency control method, device, VVT device, and automobile for the solenoid valve employ a variable frequency control strategy to ensure that the difference between the PWM frequency of the solenoid valve and the axial motion frequency of the camshaft is greater than a preset frequency difference. This solves the VVT ​​fluctuation problem caused by resonance between the solenoid valve and the camshaft at specific speeds. This invention can ensure the stability of the VVT ​​device without increasing automobile production costs. Attached Figure Description

[0012] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1This is a flowchart illustrating a PWM frequency control method for a solenoid valve according to an embodiment of the present invention; Figure 2 This is a curve showing the relationship between the PWM frequency of the solenoid valve, the axial motion frequency of the camshaft, and the engine speed in one embodiment of the present invention (excluding the high-frequency band). Figure 3 This is a curve showing the relationship between the PWM frequency of the solenoid valve, the axial motion frequency of the camshaft, and the engine speed (including the high-frequency band) in one embodiment of the present invention. Figure 4 This is a schematic diagram of the phase architecture of a closed-loop control VVT device in one embodiment of the present invention; Figure 5 This is a curve showing the relationship between the PWM frequency of the solenoid valve, the axial motion frequency of the camshaft, and the engine speed (inline three-cylinder engine or V6 engine) in one embodiment of the present invention. Figure 6 This is a curve showing the relationship between the PWM frequency of the solenoid valve, the axial motion frequency of the camshaft, and the engine speed (inline five-cylinder engine) in one embodiment of the present invention. Figure 7 This is a curve showing the relationship between the PWM frequency of the solenoid valve, the axial motion frequency of the camshaft, and the engine speed (inline six-cylinder engine) in one embodiment of the present invention. Figure 8 This is a curve showing the relationship between the PWM frequency of the solenoid valve, the axial motion frequency of the camshaft, and the engine speed (inline four-cylinder engine or V8 engine) in one embodiment of the present invention. Figure 9 This is a schematic diagram of the PWM frequency control device for a solenoid valve in one embodiment of the present invention. Detailed Implementation

[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] In one embodiment, such as Figure 1 As shown, a PWM frequency control method for a solenoid valve is provided, including the following steps S10-S20.

[0016] S10. When the axial motion frequency of the camshaft is lower than the first frequency threshold, the PWM frequency of the solenoid valve in the VVT ​​device is controlled to remain at the first specified frequency, and the difference between the first specified frequency and the axial motion frequency of the camshaft is greater than the preset frequency difference.

[0017] Understandably, such as Figure 2 As shown, Figure 2 This is a curve showing the relationship between the PWM frequency of the solenoid valve, the axial motion frequency of the camshaft, and the engine speed in an example. The axial motion frequency of the camshaft increases with increasing engine speed. The first frequency threshold can refer to the frequency at point A'. When the axial motion frequency of the camshaft is lower than the first frequency threshold (i.e., the low-frequency range from point 0 to point A), the PWM frequency of the solenoid valve in the VVT ​​device can be maintained at a first specified frequency, which is the frequency at point A. In one example, the first specified frequency can be one of 100Hz to 140Hz.

[0018] When the camshaft axial motion frequency is below the first frequency threshold, the camshaft axial motion frequency increases with engine speed, but its maximum value is less than the frequency at point A'. Therefore, when the difference between the first specified frequency and the frequency at point A' (the former minus the latter) is greater than the preset frequency difference, it can be ensured that the difference between the first specified frequency and the camshaft axial motion frequency is greater than the preset frequency difference. The preset frequency difference can be set according to actual needs, such as 5Hz to 15Hz. In one example, the preset frequency difference is set to 10Hz.

[0019] Because the camshaft axial motion frequency varies with engine speed, in some cases, the preset frequency difference can also be converted into the engine's resonant speed range. That is, the PWM frequency needs to be outside the resonant speed range of the current engine speed. In one example, the resonant speed range could be ±300 r / min.

[0020] S20. When the axial motion frequency of the camshaft is greater than or equal to the first frequency threshold, the PWM frequency is controlled to be a second specified frequency, the difference between the second specified frequency and the axial motion frequency of the camshaft is greater than the preset frequency difference, and at least one of the second specified frequencies is greater than or less than the first specified frequency.

[0021] Understandably, as the axial motion frequency of the camshaft increases, the difference between the first specified frequency and the axial motion frequency of the camshaft continuously decreases. Figure 2In the example, when the engine speed reaches approximately 5500 rpm, the camshaft axial motion frequency begins to exceed the first specified frequency. If the solenoid valve's PWM frequency remains at the first specified frequency, the solenoid valve and camshaft will resonate, making precise control of the solenoid valve impossible. Therefore, when the camshaft axial motion frequency is greater than or equal to the first frequency threshold, the PWM frequency is controlled to a second specified frequency. In one example, the second specified frequency can increase with the engine speed, ensuring that the difference between the second specified frequency and the camshaft axial motion frequency (the former minus the latter) is greater than a preset frequency difference. In this case, at least one second specified frequency is greater than the first specified frequency.

[0022] In other cases, the second specified frequency can also be a smaller value, ensuring that the difference between the second specified frequency and the camshaft axial motion frequency (the latter minus the former) is greater than the preset frequency difference. In this case, at least one second specified frequency is less than the first specified frequency. The second specified frequency can be a fixed value (such as a frequency value between 170Hz and 200Hz, or a frequency value between 80Hz and 100Hz), or a value that varies with engine speed.

[0023] The PWM frequency control method for the solenoid valve provided in this embodiment adopts a frequency conversion control strategy to ensure that the difference between the PWM frequency of the solenoid valve and the axial motion frequency of the camshaft is greater than a preset frequency difference, thus solving the VVT ​​fluctuation problem caused by resonance between the solenoid valve and the camshaft at a specific speed. Specifically, the PWM frequency of the solenoid valve is in two frequency bands: a low-frequency band (corresponding to step S10) and an interpolation band (corresponding to step S20).

[0024] Optionally, the PWM frequency control method for the solenoid valve also includes: S30. When the axial motion frequency of the camshaft is greater than or equal to the second frequency threshold, the PWM frequency is controlled to be maintained at a third specified frequency. The difference between the third specified frequency and the axial motion frequency of the camshaft is greater than the preset frequency difference, and the second frequency threshold is greater than the first frequency threshold.

[0025] Understandably, such as Figure 3As shown, the second frequency threshold can refer to the frequency at point B'. The growth slope of the second specified frequency (segment AB) can be greater than the growth slope of the camshaft axial motion frequency (segment A'B'). When the second specified frequency reaches the third specified frequency (the frequency at point B), the difference between the third specified frequency and the maximum camshaft axial motion frequency (i.e., the camshaft axial motion frequency corresponding to the highest engine speed) is already greater than the preset frequency difference. Therefore, the PWM frequency of the solenoid valve can be maintained at the third specified frequency and does not need to be increased further. The third specified frequency can be a fixed value (e.g., a frequency value between 170Hz and 200Hz).

[0026] In this embodiment, the PWM frequency of the solenoid valve is increased by a high-frequency band (the band corresponding to step S30), which can ensure that the engine does not resonate in the medium and high speed range.

[0027] Optionally, when the axial movement frequency of the camshaft is greater than or equal to the first frequency threshold and less than the second frequency threshold, the second specified frequency increases with the increase of engine speed.

[0028] Understandably, when the camshaft axial motion frequency is greater than or equal to the first frequency threshold and less than the second frequency threshold, the second specified frequency can increase with increasing engine speed. The second specified frequency can increase linearly or non-linearly. It is important to note that here, the difference between the second specified frequency and the camshaft axial motion frequency must be greater than a preset frequency difference.

[0029] Optionally, before step S10, i.e., when the axial motion frequency of the camshaft is lower than the first frequency threshold, the PWM frequency of the VVT ​​device is kept at the first specified frequency, the method further includes: S11. Obtain the speed-frequency curves for the dangerous order of the engine; S12. Set the first frequency threshold and the first specified frequency according to the speed-frequency curve and the maximum PWM frequency of the solenoid valve, wherein the first specified frequency is greater than half of the maximum PWM frequency of the solenoid valve.

[0030] Understandably, engines typically have different orders of speed-frequency curves, such as first-order, 1.5-order, and second-order speed-frequency curves. The order of danger generally differs for different engine specifications. For example, for an inline three-cylinder engine (or V6 engine), the 1.5-order vibration is the most dangerous; for an inline four-cylinder engine (or V8 engine), the 1.5-order and 2-order vibrations are the most dangerous; for an inline five-cylinder engine, the 1.5-order, 2-order, and 2.5-order vibrations are the most dangerous; and for an inline six-cylinder engine, the 1.5-order, 2-order, 2.5-order, and 3-order vibrations are the most dangerous.

[0031] Based on the principle that resonance occurs when the solenoid valve's PWM frequency and the camshaft's axial motion frequency are consistent, a first frequency threshold and a first specified frequency can be selected. Ideally, the first specified frequency should fall between the upper limit and the median of the solenoid valve's PWM frequency, as close as possible to the upper-middle range of the PWM frequency. This broadens the applicable speed range for the low-frequency band. Furthermore, it is necessary to ensure a sufficient gap (i.e., greater than the preset frequency difference) between the first specified frequency and the first frequency threshold to prevent abnormal phase fluctuations in the solenoid valve.

[0032] Optionally, after step S12, that is, after setting the first frequency threshold and the first specified frequency according to the speed-frequency curve and the maximum PWM frequency of the solenoid valve, the method further includes: S13. Verify the availability of the first frequency threshold, the first specified frequency, the second specified frequency, and the preset frequency difference through actual testing. S14. If the availability fails verification, a modification instruction is received, and at least one of the first frequency threshold, the first specified frequency, the second specified frequency, and the preset frequency difference is modified according to the modification instruction until the availability passes verification.

[0033] Understandably, real-world testing refers to testing on a real vehicle. Specifically, a control configuration file (such as a PWM frequency MAP) for the solenoid valve can be generated based on a first frequency threshold, a first specified frequency, a second specified frequency, and a preset frequency difference. Then, testing can be conducted on a real vehicle to verify whether the PWM frequency control of the solenoid valve is abnormal. If the PWM frequency control of the solenoid valve is normal, the usability of the first frequency threshold, the first specified frequency, the second specified frequency, and the preset frequency difference has been verified. If the PWM frequency control of the solenoid valve is abnormal, the usability of the first frequency threshold, the first specified frequency, the second specified frequency, and the preset frequency difference has not been verified.

[0034] If availability fails verification, at least one of the following must be modified: the first frequency threshold, the first specified frequency, the second specified frequency, and the preset frequency difference. The modification command can be input by staff via an input device. After modification, a new control configuration file can be generated, and testing can be repeated until availability verification is successful.

[0035] Optionally, step S20, namely, controlling the PWM frequency to a second specified frequency when the axial motion frequency of the camshaft is greater than or equal to the first frequency threshold, includes: S201. Acquire phase data of the VVT ​​device through a phase sensor, acquire crankshaft position data through a crankshaft position sensor, calculate the actual opening degree of the VVT ​​device based on the phase data and the position data; acquire engine speed, and determine the axial motion frequency of the camshaft based on the engine speed. S202. When the axial movement frequency of the camshaft is greater than or equal to the first frequency threshold, the PMW control command of the solenoid valve is set according to the second specified frequency and the actual opening degree. S203. Control the solenoid valve according to the PMW control command.

[0036] Understandably, phase data of the VVT ​​device can be collected by a phase sensor mounted on the device, and position data of the crankshaft (an important engine component) can be collected by a crankshaft position sensor. The vehicle's ECU (Electronic Control Unit) can calculate the actual opening degree of the VVT ​​device based on the aforementioned phase and position data. The vehicle's ECU can also obtain the engine speed and, based on this engine speed, query the engine speed-camshaft axial motion frequency relationship curve to obtain the current camshaft axial motion frequency.

[0037] When the axial motion frequency of the camshaft is greater than or equal to the first frequency threshold, the PMW frequency of the solenoid valve needs to be adjusted, changing the first specified frequency to a second specified frequency. At this time, the PMW control command of the solenoid valve can be set according to the second specified frequency and the actual opening degree. Then, the PMW control command is sent to the solenoid valve, which acts according to the PMW control command, thereby adjusting the phase of the VVT ​​device. The PMW control command of the solenoid valve can be generated using a PID (Proportional-Integral-Derivative) algorithm. In one example, such as... Figure 4 As shown, the VVT ​​device employs closed-loop phase control. The solenoid valve receives a PWM control signal from the ECU, and adjusts the solenoid valve accordingly, thereby adjusting the rotor angle to achieve the purpose of changing or stabilizing the camshaft phase. The P, I, and D values ​​are obtained through experimentation and experience, and are compiled into a lookup table stored in the ECU.

[0038] In one example, the solenoid valve (mounted on the camshaft) consists of an electromagnet and a valve core. A return spring is located at the rear of the valve core, and a push pin is inside the electromagnet. When the electromagnet is energized, the push pin extends under pressure, pushing a push rod in the valve core to move, thus switching the oil circuit. When the electromagnet is de-energized, the return spring pushes the push rod, which in turn pushes the push pin back to its original position. By controlling the timing of the electromagnet's energization and de-energization, the position of the push rod can be controlled, enabling functions such as VVT device hold, pre-adjustment, and post-adjustment. The electromagnet's current switching uses pulse width modulation (PWM). Here, the PWM frequency refers to the number of times the high and low levels can switch per second. The VVT ​​device can be a centrally located solenoid valve type. Compared to a side-mounted solenoid valve type, a centrally located solenoid valve type, although more expensive, has the advantages of a shorter oil circuit, less oil pressure loss, and superior performance.

[0039] When the solenoid valve operates within the engine speed range, the axial movement of the solenoid valve's pin resonates with the axial movement of the camshaft at specific speeds. At this time, the axial movement of the camshaft and the axial movement of the solenoid valve pin are at the same frequency, causing resonance. This results in the solenoid valve pin not being fully controlled by the PWM signal from the vehicle's ECU, causing increased VVT phase fluctuations at specific speeds, even exceeding specifications. This embodiment prevents resonance by changing the PWM frequency, ensuring the accuracy of VVT phase control.

[0040] Optionally, if the VVT ​​device is installed on an inline three-cylinder engine or a V6 engine, the first specified frequency and the second specified frequency are both fixed values, the second specified frequency is less than the first specified frequency, and the difference between the first specified frequency and the second specified frequency is greater than twice the preset frequency difference.

[0041] Understandably, such as Figure 5 As shown, Figure 5 This is a curve showing the relationship between the PWM frequency of the solenoid valve, the camshaft axial motion frequency, and engine speed in a VVT device installed in an inline three-cylinder or V6 engine. The danger order for the inline three-cylinder or V6 engine is 1.5. The camshaft axial motion frequency increases with engine speed. When the camshaft axial motion frequency is below a first frequency threshold (i.e., the low-frequency segment 1 from point C to point A), the PWM frequency of the solenoid valve in the VVT ​​device can be maintained at a first specified frequency, which is the frequency at point A. When the camshaft axial motion frequency is greater than or equal to the first frequency threshold (i.e., the low-frequency segment 1 from point A' to point B), the PWM frequency is controlled at a second specified frequency, which is the frequency at point A'.

[0042] When the engine speed increases, before reaching the engine speed at point A, the PWM frequency operates at frequency segment 1, maintaining the first specified frequency. When the engine speed reaches the engine speed at point A, the PWM frequency switches to frequency segment 2, maintaining the second specified frequency.

[0043] When the engine speed decreases but before reaching the engine speed at point A', the PWM frequency operates at frequency segment 2, maintaining the second specified frequency. When the engine speed reaches the engine speed at point A', the PWM frequency switches to frequency segment 1, maintaining the first specified frequency.

[0044] Optionally, if the VVT ​​device is installed in an inline five-cylinder engine, the first specified frequency is a fixed value, and the second specified frequency is distributed across several frequency bands; the camshaft axial motion frequency includes a 1.5th order motion frequency, a 2nd order motion frequency, and a 2.5th order motion frequency; step S20 includes: S21. When the engine speed is greater than the first speed limit point but less than the second speed limit point, the second specified frequency is in the first frequency range. The second specified frequency increases with the increase of engine speed. At the same engine speed, the second specified frequency is greater than the second-order motion frequency and less than the 2.5-order motion frequency. The difference between the 2.5-order motion frequency and the second specified frequency is greater than the preset frequency difference. The difference between the second specified frequency and the second-order motion frequency is greater than the preset frequency difference. S22. When the engine speed is greater than the second-order overspeed point and less than the third-order overspeed point, the second specified frequency is in the second frequency range. The second specified frequency increases with the increase of engine speed. At the same engine speed, the second specified frequency is greater than the 1.5th order motion frequency and less than the 2nd order motion frequency. The difference between the 2nd order motion frequency and the second specified frequency is greater than the preset frequency difference. The difference between the second specified frequency and the 1.5th order motion frequency is greater than the preset frequency difference. S23. When the engine speed is greater than the third-order overspeed point, the second specified frequency is in the third frequency range, the second specified frequency is a constant value, the second specified frequency is less than the 1.5th order motion frequency, and the difference between the 1.5th order motion frequency and the second specified frequency is greater than the preset frequency difference value.

[0045] Understandably, such as Figure 6 As shown, Figure 6 This is a curve showing the relationship between the PWM frequency of the solenoid valve, the camshaft axial motion frequency, and engine speed in a VVT system installed in an inline five-cylinder engine, as an example. The dangerous orders for an inline five-cylinder engine include orders 1.5, 2, and 2.5. The camshaft axial motion frequency increases with engine speed in each order.

[0046] When the camshaft axial motion frequency is lower than the first frequency threshold (engine speed is lower than the first overspeed point, i.e., low frequency band 1), the PWM frequency of the solenoid valve in the VVT ​​device can be maintained at a first specified frequency, which is around 150Hz. When the camshaft axial motion frequency is greater than or equal to the first frequency threshold (frequency bands other than low frequency band 1), the control PWM frequency is a second specified frequency, which is distributed across several frequency bands, namely the first frequency band (interpolation band 1), the second frequency band (interpolation band 2), and the third frequency band (low frequency band 2).

[0047] When the engine speed is greater than the first speed jump point (speed jump 1, which can be 3000 r / min) and less than the second speed jump point (speed jump 2, which can be 4000 r / min), the second specified frequency is within the first frequency range. Figure 6 In segment AB (interpolation segment 1), the second specified frequency increases with engine speed. The PWM frequency line segment of the first frequency segment lies precisely between the 2nd-order motion frequency curve and the 2.5th-order motion frequency curve. At the same engine speed, the second specified frequency is greater than the 2nd-order motion frequency but less than the 2.5th-order motion frequency. The difference between the 2.5th-order motion frequency and the second specified frequency is greater than the preset frequency difference, and the difference between the second specified frequency and the 2nd-order motion frequency is also greater than the preset frequency difference. In other words, in interpolation segment 1, the PWM frequency of the solenoid valve maintains a sufficiently large distance from the 2nd-order and 2.5th-order motion frequencies to prevent resonance in the solenoid valve.

[0048] When the engine speed is greater than the second-order speed jump point (speed jump 2) but less than the third-order speed jump point (speed jump 3, which can be 5000 r / min), the second specified frequency is in the second frequency range. Figure 6 In segment CD (interpolation segment 2), the second specified frequency increases with engine speed. The PWM frequency line segment of the second frequency segment lies precisely between the 2nd-order motion frequency curve and the 1.5th-order motion frequency curve. At the same engine speed, the second specified frequency is greater than the 1.5th-order motion frequency but less than the 2nd-order motion frequency. The difference between the 2nd-order motion frequency and the second specified frequency is greater than the preset frequency difference, and the difference between the second specified frequency and the 1.5th-order motion frequency is also greater than the preset frequency difference. In other words, in interpolation segment 2, the PWM frequency of the solenoid valve maintains a sufficiently large distance from the 2nd-order and 1.5th-order motion frequencies to prevent resonance in the solenoid valve.

[0049] When the engine speed exceeds the third-order overspeed point (overspeed 3), the second specified frequency falls within the third frequency band (low-frequency band 2), and the second specified frequency is a constant. The PWM frequency line segment of the second frequency band is exactly below the 1.5-order motion frequency curve. The second specified frequency is less than the 1.5-order motion frequency, and the difference between the 1.5-order motion frequency and the second specified frequency is greater than the preset frequency difference. In other words, in low-frequency band 2, the PWM frequency of the solenoid valve maintains a sufficiently large distance from the 1.5-order motion frequency to prevent resonance in the solenoid valve.

[0050] Optionally, if the VVT ​​device is installed in an inline six-cylinder engine, the first specified frequency is a fixed value, and the second specified frequency is distributed across several frequency bands; the camshaft axial motion frequency includes a 1.5th order motion frequency, a 2nd order motion frequency, a 2.5th order motion frequency, and a 3rd order motion frequency; step S20 includes: S24. When the engine speed is greater than the first speed limit point but less than the second speed limit point, the second specified frequency is in the first frequency range. The second specified frequency increases with the increase of engine speed. At the same engine speed, the second specified frequency is greater than the 2.5th order motion frequency and less than the 3rd order motion frequency. The difference between the 3rd order motion frequency and the second specified frequency is greater than the preset frequency difference. The difference between the second specified frequency and the 2.5th order motion frequency is greater than the preset frequency difference. S25. When the engine speed is greater than the second-order overspeed point and less than the third-order overspeed point, the second specified frequency is in the second frequency range. The second specified frequency increases with the increase of engine speed. At the same engine speed, the second specified frequency is greater than the second-order motion frequency and less than the 2.5-order motion frequency. The difference between the 2.5-order motion frequency and the second specified frequency is greater than the preset frequency difference. The difference between the second specified frequency and the second-order motion frequency is greater than the preset frequency difference. S26. When the engine speed is greater than the third-order overspeed point and less than the fourth-order overspeed point, the second specified frequency is in the third frequency range. The second specified frequency increases with the increase of engine speed. At the same engine speed, the second specified frequency is greater than the 1.5th order motion frequency and less than the 2nd order motion frequency. The difference between the 2nd order motion frequency and the second specified frequency is greater than the preset frequency difference. The difference between the second specified frequency and the 1.5th order motion frequency is greater than the preset frequency difference. S27. When the engine speed is greater than the fourth-order overspeed point, the second specified frequency is in the fourth frequency range, the second specified frequency is a constant value, the second specified frequency is less than the 1.5th order motion frequency, and the difference between the 1.5th order motion frequency and the second specified frequency is greater than the preset frequency difference value.

[0051] Understandably, such as Figure 7As shown, Figure 7 This is a curve showing the relationship between the PWM frequency of the solenoid valve, the camshaft axial motion frequency, and engine speed in a VVT system installed in an inline six-cylinder engine, as an example. The dangerous orders for an inline six-cylinder engine include orders 1.5, 2, 2.5, and 3. The camshaft axial motion frequency increases with engine speed in each order.

[0052] When the camshaft axial motion frequency is lower than the first frequency threshold (engine speed is lower than the first overspeed point, i.e., low frequency band 1), the PWM frequency of the solenoid valve in the VVT ​​device can be maintained at a first specified frequency, which is around 150Hz. When the camshaft axial motion frequency is greater than or equal to the first frequency threshold (frequency bands other than low frequency band 1), the PWM frequency is controlled at a second specified frequency, which is distributed across several frequency bands, namely the first frequency band (interpolation band 1), the second frequency band (interpolation band 2), the third frequency band (interpolation band 3), and the fourth frequency band (low frequency band 2).

[0053] When the engine speed is greater than the first speed jump point (speed jump 1, which can be 2700 r / min) and less than the second speed jump point (speed jump 2, which can be 3000 r / min), the second specified frequency is within the first frequency range. Figure 7 In segment AB (interpolation segment 1), the second specified frequency increases with engine speed. The PWM frequency line segment of the first frequency segment lies precisely between the 3rd-order motion frequency curve and the 2.5th-order motion frequency curve. At the same engine speed, the second specified frequency is greater than the 2.5th-order motion frequency but less than the 3rd-order motion frequency. The difference between the 3rd-order motion frequency and the second specified frequency is greater than the preset frequency difference, and the difference between the second specified frequency and the 2.5th-order motion frequency is also greater than the preset frequency difference. In other words, in interpolation segment 1, the PWM frequency of the solenoid valve maintains a sufficiently large distance from the 3rd-order and 2.5th-order motion frequencies to prevent resonance in the solenoid valve.

[0054] When the engine speed is greater than the second-order speed jump point (speed jump 2) but less than the third-order speed jump point (speed jump 3, which can be 4000 r / min), the second specified frequency is in the second frequency range. Figure 7In segment CD (interpolation segment 2), the second specified frequency increases with engine speed. The PWM frequency line segment of the second frequency segment lies precisely between the 2.5th-order motion frequency curve and the 2nd-order motion frequency curve. At the same engine speed, the second specified frequency is greater than the 2nd-order motion frequency but less than the 2.5th-order motion frequency. The difference between the 2.5th-order motion frequency and the second specified frequency is greater than the preset frequency difference, and the difference between the second specified frequency and the 2nd-order motion frequency is also greater than the preset frequency difference. In other words, in interpolation segment 2, the PWM frequency of the solenoid valve maintains a sufficiently large distance from the 2.5th-order and 2nd-order motion frequencies to prevent resonance in the solenoid valve.

[0055] When the engine speed is greater than the third-order speed jump point (speed jump 3) but less than the third-order speed jump point (speed jump 4, which can be around 5300 r / min), the second specified frequency is in the third frequency range. Figure 7 In the EF segment (interpolation segment 3), the second specified frequency increases with engine speed. The PWM frequency line segment of the second frequency segment lies precisely between the 2nd-order motion frequency curve and the 1.5th-order motion frequency curve. At the same engine speed, the second specified frequency is greater than the 1.5th-order motion frequency but less than the 2nd-order motion frequency. The difference between the 2nd-order motion frequency and the second specified frequency is greater than the preset frequency difference, and the difference between the second specified frequency and the 1.5th-order motion frequency is also greater than the preset frequency difference. In other words, in interpolation segment 3, the PWM frequency of the solenoid valve maintains a sufficiently large distance from the 2nd-order and 1.5th-order motion frequencies to prevent resonance in the solenoid valve.

[0056] When the engine speed exceeds the fourth-order overspeed point (overspeed 4), the second specified frequency is in the fourth frequency band (low-frequency band 2), and the second specified frequency is a constant. The PWM frequency line segment of the second frequency band is exactly below the 1.5-order motion frequency curve. The second specified frequency is less than the 1.5-order motion frequency, and the difference between the 1.5-order motion frequency and the second specified frequency is greater than the preset frequency difference. In other words, in low-frequency band 2, the PWM frequency of the solenoid valve maintains a sufficiently large distance from the 1.5-order motion frequency to prevent resonance in the solenoid valve.

[0057] Optionally, if the VVT ​​device is installed in an inline four-cylinder engine or a V8 engine, the first specified frequency is a fixed value, and the second specified frequency is distributed across several frequency bands; the camshaft axial motion frequency includes a 1.5th order motion frequency and a 2nd order motion frequency; step S20 includes: S28. When the engine speed is greater than the first speed limit point but less than the second speed limit point, the second specified frequency is in the first frequency range. The second specified frequency increases with the increase of engine speed. At the same engine speed, the second specified frequency is greater than the 1.5th order motion frequency and less than the 2nd order motion frequency. The difference between the 2nd order motion frequency and the second specified frequency is greater than the preset frequency difference. The difference between the second specified frequency and the 1.5th order motion frequency is greater than the preset frequency difference. S29. When the engine speed is greater than the second-order overspeed point, the second specified frequency is in the second frequency range, the second specified frequency is a constant value, the second specified frequency is less than the 1.5th order motion frequency, and the difference between the 1.5th order motion frequency and the second specified frequency is greater than the preset frequency difference value.

[0058] Understandably, such as Figure 8 As shown, Figure 8 This is a curve showing the relationship between the PWM frequency of the solenoid valve, the camshaft axial motion frequency, and engine speed in a VVT device installed in an inline four-cylinder or V8 engine. The dangerous orders for the inline four-cylinder or V8 engine include order 1.5 and order 2. The camshaft axial motion frequency increases with engine speed in each order.

[0059] When the camshaft axial motion frequency is lower than the first frequency threshold (engine speed is lower than the first overspeed point, i.e., low frequency band 1), the PWM frequency of the solenoid valve in the VVT ​​device can be maintained at a first specified frequency, which is around 150Hz. When the camshaft axial motion frequency is greater than or equal to the first frequency threshold (frequency bands other than low frequency band 1), the control PWM frequency is a second specified frequency, which is distributed across several frequency bands, namely the first frequency band (interpolation band 1) and the second frequency band (low frequency band 2).

[0060] When the engine speed is greater than the first speed-over-speed point (speed-over-speed 1, which can be 3500 r / min) and less than the second speed-over-speed point (speed-over-speed 2, which can be 4800 r / min), the second specified frequency is within the first frequency range. Figure 8 In the AB segment (i.e., the interpolation segment), the second specified frequency increases with engine speed. The PWM frequency segment of the first frequency segment lies precisely between the 2nd-order motion frequency curve and the 1.5th-order motion frequency curve. At the same engine speed, the second specified frequency is greater than the 1.5th-order motion frequency but less than the 2nd-order motion frequency. The difference between the 2nd-order motion frequency and the second specified frequency is greater than the preset frequency difference, and the difference between the second specified frequency and the 1.5th-order motion frequency is also greater than the preset frequency difference. In other words, in the interpolation segment, the PWM frequency of the solenoid valve maintains a sufficiently large distance from the 2nd-order and 1.5th-order motion frequencies to prevent resonance in the solenoid valve.

[0061] When the engine speed exceeds the second-order overspeed point (overspeed 2), the second specified frequency is in the second frequency range (low-frequency range 2), and the second specified frequency is a constant. The PWM frequency line segment of the second frequency range is exactly below the 1.5-order motion frequency curve. The second specified frequency is less than the 1.5-order motion frequency, and the difference between the 1.5-order motion frequency and the second specified frequency is greater than the preset frequency difference. In other words, in low-frequency range 2, the PWM frequency of the solenoid valve maintains a sufficiently large distance from the 1.5-order motion frequency to prevent resonance in the solenoid valve.

[0062] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0063] In one embodiment, a PWM frequency control device for a solenoid valve is provided, which corresponds one-to-one with the PWM frequency control method for the solenoid valve in the above embodiments. For example... Figure 9 As shown, the PWM frequency control device for this solenoid valve includes a first control module 10 and a second control module 20. Detailed descriptions of each functional module are as follows: The first control module 10 is used to control the PWM frequency of the solenoid valve in the VVT ​​device to be maintained at a first specified frequency when the axial motion frequency of the camshaft is lower than a first frequency threshold. The difference between the first specified frequency and the axial motion frequency of the camshaft is greater than a preset frequency difference. The second control module 20 is used to control the PWM frequency to a second specified frequency when the axial motion frequency of the camshaft is greater than or equal to the first frequency threshold. The difference between the second specified frequency and the axial motion frequency of the camshaft is greater than the preset frequency difference, and at least one of the second specified frequencies is greater than or less than the first specified frequency.

[0064] Optionally, the PWM frequency control device for the solenoid valve also includes: The third control module is used to control the PWM frequency to remain at a third specified frequency when the axial motion frequency of the camshaft is greater than or equal to the second frequency threshold. The difference between the third specified frequency and the axial motion frequency of the camshaft is greater than the preset frequency difference, and the second frequency threshold is greater than the first frequency threshold.

[0065] Optionally, when the axial movement frequency of the camshaft is greater than or equal to the first frequency threshold and less than the second frequency threshold, the second specified frequency increases with the increase of engine speed.

[0066] Optionally, the PWM frequency control device for the solenoid valve also includes: The module for obtaining the danger level curve is used to obtain the speed-frequency curve of the danger level of the engine. The parameter setting module is used to set the first frequency threshold and the first specified frequency according to the speed-frequency curve and the maximum PWM frequency of the solenoid valve, wherein the first specified frequency is greater than half of the maximum PWM frequency of the solenoid valve.

[0067] Optionally, the PWM frequency control device for the solenoid valve also includes: The availability verification module is used to verify the availability of the first frequency threshold, the first specified frequency, the second specified frequency, and the preset frequency difference through actual testing. The parameter correction module is used to receive a modification instruction if the availability fails verification, and modify at least one of the first frequency threshold, the first specified frequency, the second specified frequency, and the preset frequency difference according to the modification instruction until the availability passes verification.

[0068] Optionally, the second control module 20 includes: The data acquisition unit is used to acquire phase data of the VVT ​​device through a phase sensor, acquire crankshaft position data through a crankshaft position sensor, calculate the actual opening degree of the VVT ​​device based on the phase data and the position data, acquire engine speed, and determine the axial motion frequency of the camshaft based on the engine speed. A control instruction generation unit is used to set the PMW control instruction of the solenoid valve according to the second specified frequency and the actual opening degree when the axial motion frequency of the camshaft is greater than or equal to the first frequency threshold. The PMW control module is used to control the solenoid valve according to the PMW control command.

[0069] Optionally, if the VVT ​​device is installed on an inline three-cylinder engine or a V6 engine, the first specified frequency and the second specified frequency are both fixed values, the second specified frequency is less than the first specified frequency, and the difference between the first specified frequency and the second specified frequency is greater than twice the preset frequency difference.

[0070] Optionally, if the VVT ​​device is installed in an inline five-cylinder engine, the first specified frequency is a fixed value, and the second specified frequency is distributed across several frequency bands; the camshaft axial motion frequency includes a 1.5th order motion frequency, a 2nd order motion frequency, and a 2.5th order motion frequency; the second control module 20 includes: The first control unit is configured to, when the engine speed is greater than the first speed limit point but less than the second speed limit point, the second specified frequency is in the first frequency range, the second specified frequency increases with the increase of engine speed, and at the same engine speed, the second specified frequency is greater than the second-order motion frequency and less than the 2.5-order motion frequency, the difference between the 2.5-order motion frequency and the second specified frequency is greater than the preset frequency difference, and the difference between the second specified frequency and the second-order motion frequency is greater than the preset frequency difference. The second control unit is configured to operate when the engine speed is greater than the second-order overspeed point but less than the third-order overspeed point, the second specified frequency is in the second frequency range, the second specified frequency increases with the increase of engine speed, and at the same engine speed, the second specified frequency is greater than the 1.5th order motion frequency and less than the 2nd order motion frequency, the difference between the 2nd order motion frequency and the second specified frequency is greater than the preset frequency difference, and the difference between the second specified frequency and the 1.5th order motion frequency is greater than the preset frequency difference. The third control unit is configured to operate when the engine speed is greater than the third-order overspeed point, the second specified frequency is in the third frequency range, the second specified frequency is a constant value, the second specified frequency is less than the 1.5th order motion frequency, and the difference between the 1.5th order motion frequency and the second specified frequency is greater than the preset frequency difference.

[0071] Optionally, if the VVT ​​device is installed in an inline six-cylinder engine, the first specified frequency is a fixed value, and the second specified frequency is distributed across several frequency bands; the camshaft axial motion frequency includes a 1.5th order motion frequency, a 2nd order motion frequency, a 2.5th order motion frequency, and a 3rd order motion frequency; the second control module 20 includes: The fourth control unit is used when the engine speed is greater than the first speed limit point but less than the second speed limit point, the second specified frequency is in the first frequency range, the second specified frequency increases with the increase of engine speed, and at the same engine speed, the second specified frequency is greater than the 2.5th order motion frequency and less than the 3rd order motion frequency, the difference between the 3rd order motion frequency and the second specified frequency is greater than the preset frequency difference, and the difference between the second specified frequency and the 2.5th order motion frequency is greater than the preset frequency difference; The fifth control unit is used when the engine speed is greater than the second-order overspeed point but less than the third-order overspeed point, the second specified frequency is in the second frequency range, the second specified frequency increases with the increase of engine speed, and at the same engine speed, the second specified frequency is greater than the second-order motion frequency and less than the 2.5-order motion frequency, the difference between the 2.5-order motion frequency and the second specified frequency is greater than the preset frequency difference, and the difference between the second specified frequency and the second-order motion frequency is greater than the preset frequency difference; The sixth control unit is used when the engine speed is greater than the third-order overspeed point and less than the fourth-order overspeed point, the second specified frequency is in the third frequency range, the second specified frequency increases with the increase of engine speed, and at the same engine speed, the second specified frequency is greater than the 1.5th order motion frequency and less than the 2nd order motion frequency, the difference between the 2nd order motion frequency and the second specified frequency is greater than the preset frequency difference, and the difference between the second specified frequency and the 1.5th order motion frequency is greater than the preset frequency difference; The seventh control unit is used when the engine speed is greater than the fourth-order overspeed point, the second specified frequency is in the fourth frequency range, the second specified frequency is a constant value, the second specified frequency is less than the 1.5th order motion frequency, and the difference between the 1.5th order motion frequency and the second specified frequency is greater than the preset frequency difference value.

[0072] Optionally, if the VVT ​​device is installed in an inline four-cylinder engine or a V8 engine, the first specified frequency is a fixed value, and the second specified frequency is distributed across several frequency bands; the camshaft axial motion frequency includes a 1.5th order motion frequency and a 2nd order motion frequency; the second control module 20 includes: The eighth control unit is used when the engine speed is greater than the first speed limit point but less than the second speed limit point, the second specified frequency is in the first frequency range, the second specified frequency increases with the increase of engine speed, and at the same engine speed, the second specified frequency is greater than the 1.5th order motion frequency and less than the 2nd order motion frequency, the difference between the 2nd order motion frequency and the second specified frequency is greater than the preset frequency difference, and the difference between the second specified frequency and the 1.5th order motion frequency is greater than the preset frequency difference; The ninth control unit is used when the engine speed is greater than the second-order overspeed point, the second specified frequency is in the second frequency range, the second specified frequency is a constant value, the second specified frequency is less than the 1.5th order motion frequency, and the difference between the 1.5th order motion frequency and the second specified frequency is greater than the preset frequency difference value.

[0073] Specific limitations regarding the PWM frequency control device for solenoid valves can be found in the above description of the PWM frequency control method for solenoid valves, and will not be repeated here. Each module in the aforementioned PWM frequency control device for solenoid valves can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in hardware or independently of the processor in a computer device, or stored in software in the memory of a computer device, so that the processor can call and execute the corresponding operations of each module.

[0074] In one embodiment, a VVT device is provided, the VVT ​​device including a solenoid valve, the solenoid valve being controlled by any of the above-described solenoid valve PWM frequency control methods.

[0075] In one embodiment, a vehicle is provided, including an engine equipped with the aforementioned VVT device.

[0076] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A PWM frequency control method for a solenoid valve, characterized in that, include: When the axial motion frequency of the camshaft is lower than the first frequency threshold, the PWM frequency of the solenoid valve in the VVT ​​device is maintained at the first specified frequency, and the difference between the first specified frequency and the axial motion frequency of the camshaft is greater than the preset frequency difference. When the axial motion frequency of the camshaft is greater than or equal to the first frequency threshold, the PWM frequency is controlled to be a second specified frequency. The difference between the second specified frequency and the axial motion frequency of the camshaft is greater than the preset frequency difference, and at least one of the second specified frequencies is greater than or less than the first specified frequency.

2. The PWM frequency control method for the solenoid valve as described in claim 1, characterized in that, Also includes: When the axial motion frequency of the camshaft is greater than or equal to the second frequency threshold, the PWM frequency is controlled to be maintained at a third specified frequency. The difference between the third specified frequency and the axial motion frequency of the camshaft is greater than the preset frequency difference, and the second frequency threshold is greater than the first frequency threshold.

3. The PWM frequency control method for the solenoid valve as described in claim 2, characterized in that, When the axial motion frequency of the camshaft is greater than or equal to the first frequency threshold and less than the second frequency threshold, the second specified frequency increases with the increase of engine speed.

4. The PWM frequency control method for the solenoid valve as described in claim 1, characterized in that, The method of controlling the PWM frequency of the VVT ​​device to remain before the first specified frequency when the axial motion frequency of the camshaft is lower than the first frequency threshold also includes: Obtain the speed-frequency curves for the dangerous order of the engine; The first frequency threshold and the first specified frequency are set according to the speed-frequency curve and the maximum PWM frequency of the solenoid valve, wherein the first specified frequency is greater than half of the maximum PWM frequency of the solenoid valve.

5. The PWM frequency control method for the solenoid valve as described in claim 4, characterized in that, After setting the first frequency threshold and the first specified frequency based on the speed-frequency curve and the maximum PWM frequency of the solenoid valve, the method further includes: The usability of the first frequency threshold, the first specified frequency, the second specified frequency, and the preset frequency difference is verified through experimental testing. If the availability fails verification, a modification instruction is received, and at least one of the first frequency threshold, the first specified frequency, the second specified frequency, and the preset frequency difference is modified according to the modification instruction until the availability passes verification.

6. The PWM frequency control method for the solenoid valve as described in claim 1, characterized in that, When the axial motion frequency of the camshaft is greater than or equal to the first frequency threshold, controlling the PWM frequency to a second specified frequency includes: Phase data of the VVT ​​device is acquired by a phase sensor, and position data of the crankshaft is acquired by a crankshaft position sensor. The actual opening degree of the VVT ​​device is calculated based on the phase data and the position data. The engine speed is acquired, and the axial motion frequency of the camshaft is determined based on the engine speed. When the axial movement frequency of the camshaft is greater than or equal to the first frequency threshold, the PMW control command of the solenoid valve is set according to the second specified frequency and the actual opening degree. The solenoid valve is controlled according to the PMW control command.

7. The PWM frequency control method for the solenoid valve as described in claim 1, characterized in that, If the VVT ​​device is installed on an inline three-cylinder engine or a V6 engine, then the first specified frequency and the second specified frequency are both fixed values, the second specified frequency is less than the first specified frequency, and the difference between the first specified frequency and the second specified frequency is greater than twice the preset frequency difference.

8. The PWM frequency control method for the solenoid valve as described in claim 1, characterized in that, If the VVT ​​device is installed on an inline five-cylinder engine, the first specified frequency is a fixed value, and the second specified frequency is distributed in several frequency ranges; the camshaft axial motion frequency includes the 1.5th order motion frequency, the 2nd order motion frequency, and the 2.5th order motion frequency; When the engine speed is greater than the first speed limit point but less than the second speed limit point, the second specified frequency is in the first frequency range. The second specified frequency increases with the increase of engine speed. At the same engine speed, the second specified frequency is greater than the second-order motion frequency and less than the 2.5-order motion frequency. The difference between the 2.5-order motion frequency and the second specified frequency is greater than the preset frequency difference. The difference between the second specified frequency and the second-order motion frequency is greater than the preset frequency difference. When the engine speed is greater than the second-order overspeed point but less than the third-order overspeed point, the second specified frequency is in the second frequency range. The second specified frequency increases with the increase of engine speed. At the same engine speed, the second specified frequency is greater than the 1.5th order motion frequency and less than the 2nd order motion frequency. The difference between the 2nd order motion frequency and the second specified frequency is greater than the preset frequency difference. The difference between the second specified frequency and the 1.5th order motion frequency is greater than the preset frequency difference. When the engine speed is greater than the third-order overspeed point, the second specified frequency is in the third frequency range. The second specified frequency is a constant value. The second specified frequency is less than the 1.5th order motion frequency. The difference between the 1.5th order motion frequency and the second specified frequency is greater than the preset frequency difference.

9. The PWM frequency control method for the solenoid valve as described in claim 1, characterized in that, If the VVT ​​device is installed on an inline six-cylinder engine, the first specified frequency is a fixed value, and the second specified frequency is distributed in several frequency ranges; the camshaft axial motion frequency includes the 1.5th order motion frequency, the 2nd order motion frequency, the 2.5th order motion frequency and the 3rd order motion frequency; When the engine speed is greater than the first speed limit point but less than the second speed limit point, the second specified frequency is in the first frequency range. The second specified frequency increases with the increase of engine speed. At the same engine speed, the second specified frequency is greater than the 2.5th order motion frequency and less than the 3rd order motion frequency. The difference between the 3rd order motion frequency and the second specified frequency is greater than the preset frequency difference. The difference between the second specified frequency and the 2.5th order motion frequency is greater than the preset frequency difference. When the engine speed is greater than the second-order overspeed point but less than the third-order overspeed point, the second specified frequency is in the second frequency range. The second specified frequency increases with the increase of engine speed. At the same engine speed, the second specified frequency is greater than the second-order motion frequency and less than the 2.5-order motion frequency. The difference between the 2.5-order motion frequency and the second specified frequency is greater than the preset frequency difference. The difference between the second specified frequency and the second-order motion frequency is greater than the preset frequency difference. When the engine speed is greater than the third speed limit point but less than the fourth speed limit point, the second specified frequency is in the third frequency range. The second specified frequency increases with the increase of engine speed. At the same engine speed, the second specified frequency is greater than the 1.5th order motion frequency and less than the 2nd order motion frequency. The difference between the 2nd order motion frequency and the second specified frequency is greater than the preset frequency difference. The difference between the second specified frequency and the 1.5th order motion frequency is greater than the preset frequency difference. When the engine speed is greater than the fourth-order overspeed point, the second specified frequency is in the fourth frequency range. The second specified frequency is a constant value. The second specified frequency is less than the 1.5th order motion frequency. The difference between the 1.5th order motion frequency and the second specified frequency is greater than the preset frequency difference.

10. The PWM frequency control method for the solenoid valve as described in claim 1, characterized in that, If the VVT ​​device is installed on an inline four-cylinder engine or a V8 engine, the first specified frequency is a fixed value, and the second specified frequency is distributed in several frequency ranges; the camshaft axial motion frequency includes a 1.5th order motion frequency and a 2nd order motion frequency; When the engine speed is greater than the first speed threshold but less than the second speed threshold, the second specified frequency is in the first frequency range. The second specified frequency increases with the increase of engine speed. At the same engine speed, the second specified frequency is greater than the 1.5th order motion frequency and less than the 2nd order motion frequency. The difference between the 2nd order motion frequency and the second specified frequency is greater than the preset frequency difference. The difference between the second specified frequency and the 1.5th order motion frequency is greater than the preset frequency difference. When the engine speed is greater than the second-order overspeed point, the second specified frequency is in the second frequency range. The second specified frequency is a constant value. The second specified frequency is less than the 1.5th order motion frequency. The difference between the 1.5th order motion frequency and the second specified frequency is greater than the preset frequency difference.

11. A PWM frequency control device for a solenoid valve, characterized in that, include: The first control module is used to control the PWM frequency of the solenoid valve in the VVT ​​device to be maintained at a first specified frequency when the axial motion frequency of the camshaft is lower than a first frequency threshold. The difference between the first specified frequency and the axial motion frequency of the camshaft is greater than a preset frequency difference. The second control module is used to control the PWM frequency to a second specified frequency when the axial motion frequency of the camshaft is greater than or equal to the first frequency threshold. The difference between the second specified frequency and the axial motion frequency of the camshaft is greater than the preset frequency difference, and at least one of the second specified frequencies is greater than or less than the first specified frequency.

12. A VVT device, characterized in that, The VVT ​​device includes a solenoid valve, which is controlled by the PWM frequency control method of the solenoid valve as described in any one of claims 1 to 10.

13. A car, characterized in that, Includes an engine, said engine being equipped with the VVT ​​device as described in claim 12.

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