Method for fine tuning the air pressure of a breast pump piston pump

Abstract

The application discloses a method for fine adjustment of the air pressure of a piston pump of a breast pump, which comprises connecting a cylinder of the piston pump with a pressure sensor and an exhaust electromagnetic valve; during the reciprocating exhaust and suction movement of a piston of the piston pump, the pressure sensor is used to detect the air pressure change in the cylinder in real time; and according to a set working mode, the exhaust electromagnetic valve is controlled to be switched to adjust the air pressure. The method can detect the air pressure change in the cylinder in real time through the pressure sensor according to the use requirement, accurately adjust the air pressure, and meet the comfortable requirements of different people on the breast suction negative pressure.

Description

Technical Field

[0001] This patent relates to the field of piston pumps, specifically to a method for fine-tuning the air pressure of a breast pump piston pump. Background Technology

[0002] Currently, breast pumps on the market are divided into those that use diaphragm pumps or piston pumps to pump milk by drawing air. For example, in a breast pump that uses a piston pump, the cylinder is connected to a three-way connector on the breast pump via an air tube. The first port of this three-way connector is a large flared opening that rests against the breast, the second port connects to the milk storage bottle below, and the third port connects to the air tube via a three-way diaphragm. The piston pump provides negative pressure, controlling the contraction of the three-way diaphragm, thereby creating negative pressure inside the breast pump to achieve milk expression.

[0003] The patent, entitled "Pressure Relief Device System and Method for Relieving Pressure in the Chamber of a Reciprocating Motion Device Assembly" (application number CN201880017362.8), employs a deformable seal that partially disengages from the head during the piston's return stroke to achieve pressure relief.

[0004] The existing piston pump design involves the piston reaching the bottom of the cylinder and contacting a mechanical exhaust valve with a limit switch to open and release air. When the piston moves back to perform negative pressure suction, it disengages from the limit switch, and the mechanical exhaust valve automatically closes. The limit switch and the mechanical exhaust valve are integrated. This control method can only simply control the complete discharge of gas from the cylinder during the piston's stroke cycle or close the valve for suction. It cannot flexibly control the piston at any position in the cylinder to adjust the air pressure and meet the different suction needs of various users. For example, for breast pumping, a higher negative pressure and a slower suction / release frequency are required, necessitating that the piston be controlled to reach the bottom of the cylinder for the suction / release action. Similarly, mothers with large breasts may prefer a lower suction for comfort, while mothers with poor milk production may require a stronger suction to express milk effectively. If you want to provide a gentle massage to the breasts, you need a small negative pressure and a faster frequency of air intake and exhaust. In this case, you need to monitor the air pressure value and precisely control the movement of the valve and piston. However, existing piston pumps only allow the valve to close or release air when the piston reaches the bottom of the cylinder and touches the limit switch. This results in a fixed negative pressure value, which cannot achieve the function of fine-tuning the air pressure. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a method for finely adjusting the air pressure of a breast pump piston pump. According to usage needs, the pressure sensor can detect changes in air pressure inside the cylinder in real time and precisely adjust the air pressure to meet the comfort requirements of different groups for the amount of negative pressure during breast pumping.

[0006] This invention provides a method for fine-tuning the air pressure of a breast pump piston pump, comprising connecting the cylinder of the piston pump to a pressure sensor and an exhaust solenoid valve. When the piston of the piston pump performs reciprocating air exhaust and suction movements, the pressure sensor detects the air pressure change in the cylinder in real time, and controls the exhaust solenoid valve to switch on and off to adjust the air pressure according to the set working mode.

[0007] Furthermore, it also includes setting the piston pump's speed settings to correspond to different working modes, including a milk pumping mode and a lactation mode; in the milk pumping mode, the piston pump generates a large negative pressure suction and a low suction frequency; in the lactation mode, the piston pump generates a small negative pressure suction and a high suction frequency.

[0008] In the breast pumping mode, the negative pressure generated by the piston pump is 20-50 kPa, and the piston suction frequency is 30-80 times / minute; in the lactation mode, the negative pressure generated by the piston pump is 10-35 kPa, and the piston suction frequency is 120-150 times / minute.

[0009] Furthermore, different operating modes correspond to different air pressure values. The pressure sensor detects in real time whether the air pressure in the cylinder has reached the set air pressure value, and controls the piston pump motor to move and / or the exhaust solenoid valve to switch to adjust the air pressure.

[0010] Furthermore, a maximum negative pressure protection value is also set. When the pressure sensor detects in real time that the air pressure in the cylinder reaches the maximum negative pressure protection value, it controls the exhaust solenoid valve to open immediately to release air, preventing excessive negative pressure suction from causing harm to the human body.

[0011] Furthermore, the cylinder of the breast pump piston pump is connected to the three-way diaphragm of the breast pump shield through an air guide tube. The piston pump provides negative pressure to control the contraction of the three-way diaphragm, thereby creating negative pressure inside the breast pump shield to achieve milk suction.

[0012] As one implementation, an initial position recognition switch located at the bottom of the cylinder is used to identify whether the piston has moved back to the bottom of the cylinder, and to control the exhaust solenoid valve switch to adjust the air pressure.

[0013] As another improved implementation, it also includes a mechanical exhaust valve located at the bottom of the cylinder, which is connected to the initial position recognition switch. When it is determined that the piston has moved back to the bottom of the cylinder, the mechanical exhaust valve is opened to release air; when it is determined that the piston has left the bottom of the cylinder, the mechanical exhaust valve is immediately closed.

[0014] Another embodiment of the present invention provides a method for fine-tuning the air pressure of a breast pump piston pump, comprising connecting the cylinder of the piston pump to a pressure sensor and a mechanical exhaust valve, wherein a photoelectric switch connected to the mechanical exhaust valve is disposed at the bottom of the cylinder, and when the motor of the breast pump drives the piston of the piston pump to perform reciprocating air exhaust and suction movements, the pressure sensor detects the air pressure change in the cylinder in real time, and according to the set working mode, the pressure sensor transmits a signal to the motor and the photoelectric switch to control the opening and closing of the mechanical exhaust valve to adjust the air pressure.

[0015] The method also includes setting the piston pump's speed settings to correspond to different operating modes, including a milk pumping mode and a lactation mode. In the milk pumping mode, the piston pump generates a strong negative pressure suction and a low suction frequency; in the lactation mode, the piston pump generates a weak negative pressure suction and a high suction frequency. Setting different operating modes corresponds to different air pressure values. The pressure sensor detects in real time whether the air pressure inside the cylinder reaches the set air pressure value, and controls the motor movement and / or the mechanical exhaust valve to adjust the air pressure.

[0016] The present invention offers the following advantages:

[0017] 1. Compared to existing piston pumps, which cannot detect changes in air pressure and can only control the complete discharge of gas in the cylinder or close the valve to extract air during the piston stroke cycle, resulting in a fixed negative pressure value, this invention, through a pressure sensor combined with an exhaust solenoid valve, or a combination of a pressure sensor, mechanical exhaust valve, and photoelectric switch, can greatly improve the precise control of air extraction and release throughout the piston's movement. The adjustable pressure value reaches 0.1 kPa, breaking through the limitations of traditional exhaust valves. This patented solution, by adding a pressure sensor to continuously monitor changes in air pressure within the cylinder, thereby controlling the valve to open and close, allows for flexible fine-tuning of the air pressure within the negative pressure pump according to usage requirements, meeting the different needs of various users for negative pressure suction.

[0018] 2. Through research and testing with hundreds of mothers, the inventors scientifically set multiple speed settings for the piston pump, corresponding to different working modes, including a breast pumping mode and a lactation mode. Specifically, the negative pressure range and suction / discharge frequency for each working mode were scientifically determined. In the breast pumping mode, the piston pump generates a negative pressure of 20-50 kPa, and the piston suction / discharge frequency is 30-80 times / minute. In the lactation mode, the piston pump generates a negative pressure of 10-35 kPa, and the piston suction / discharge frequency is 120-150 times / minute.

[0019] Different operating modes can be set to correspond to different air pressure values ​​and motor speeds. The pressure sensor detects in real time whether the air pressure in the cylinder has reached the set value, and controls the piston pump motor movement and / or the exhaust valve switching action to adjust the air pressure. This greatly improves the ability to control the piston pump's air intake and exhaust program logic and set waveforms for different gears, making the control of the piston's full stroke movement more precise, and allowing air pressure control at any position of the piston.

[0020] 3. To prevent pain caused by sudden excessive negative pressure during breast pumping, this invention also includes a maximum negative pressure protection value. When the pressure sensor detects that the air pressure inside the cylinder reaches the maximum negative pressure protection value, it immediately opens the exhaust solenoid valve to release air, preventing excessive negative pressure from harming the user. Current breast pumps do not offer this automatic protection function.

[0021] 4. As an example, in order to achieve high-frequency and rapid alternating opening and closing of the gas, an initial position recognition switch set at the bottom of the cylinder is used to identify whether the piston has moved back to the bottom of the cylinder, and to control the exhaust solenoid valve switch to adjust the gas pressure.

[0022] 5. As another improved embodiment, a mechanical exhaust valve located at the bottom of the cylinder is also included, connected to the initial position identification switch. When it is determined that the piston has moved back to the bottom of the cylinder, the mechanical exhaust valve is opened to release air; when it is determined that the piston has left the bottom of the cylinder, the mechanical exhaust valve is immediately closed. This combination of the mechanical exhaust valve and the exhaust solenoid valve to control the cylinder's opening and closing air release allows for more efficient piston pump operation. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating the method for fine-tuning the air pressure of the piston pump in a breast pump according to Embodiment 1 of the present invention.

[0024] Figure 2 This is a flowchart illustrating the method for fine-tuning the air pressure of the piston pump in a breast pump according to Embodiment 3 of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the patent will be described in further detail below with reference to the accompanying drawings.

[0026] like Figure 1As shown, Embodiment 1 of the present invention provides a method for fine-tuning the air pressure of a breast pump piston pump. The cylinder of the breast pump piston pump is connected to the three-way diaphragm of the breast pump shield via an air guide tube. The piston pump provides negative pressure, controlling the contraction of the three-way diaphragm, causing the breast pump shield to adhere tightly to the breast, thereby creating negative pressure inside the breast pump shield to achieve milk expression. The breast pump is equipped with a circuit board, which is electrically connected to a chip, a motor, a pressure sensor, and an exhaust solenoid valve. The bottom of the piston pump cylinder is connected to the pressure sensor and the exhaust solenoid valve. The control process includes: setting the piston pump's speed settings to correspond to different working modes, and controlling the motor to drive the piston movement and the exhaust solenoid valve to operate through a pre-set program.

[0027] During the process of the piston pump moving towards the bottom of the cylinder to exhaust air, the pressure sensor detects the change in air pressure inside the cylinder in real time. According to the set working mode, the exhaust solenoid valve is controlled to adjust the air pressure. When the piston reaches the bottom of the cylinder, the exhaust solenoid valve is opened to connect with the outside air to release air, so that the air pressure inside the cylinder, the air guide pipe and the outside air pressure are consistent, that is, the negative air pressure is returned to zero.

[0028] During the piston pump's suction motion, the exhaust solenoid valve is first closed to connect with the outside. The pressure sensor detects the air pressure changes in the cylinder in real time. According to the set working mode, the exhaust solenoid valve is controlled to adjust the air pressure. For different negative pressure values, the piston moves to any position in the cylinder to precisely control the opening and closing of the exhaust solenoid valve. The magnitude and waveform changes of the negative pressure at the piston pump end directly determine the magnitude and waveform changes of the negative pressure at the three-way diaphragm end. This allows for fine-tuning of the negative pressure suction to meet the requirements of different groups for negative pressure breastfeeding or massage.

[0029] The following example illustrates the process of fine-tuning the air pressure control of a breast pump piston pump. The function button on the breast pump casing is used to set the piston pump speed, corresponding to different working modes. Different working modes correspond to different negative pressure values ​​and motor speeds. The pressure sensor continuously monitors whether the negative pressure inside the cylinder reaches the set air pressure value, controlling the exhaust solenoid valve to adjust the air pressure.

[0030] The operating modes include a breast pumping mode and a lactation mode. In the breast pumping mode, the piston pump generates strong negative pressure suction with a low pumping frequency. Multiple experiments by the inventors have proven that a negative pressure of 20-50 kPa and a piston pumping frequency of 30-80 times / minute provide the most comfortable experience for the user. The negative pressure can also be set to 30 kPa, 35 kPa, or 40 kPa. For example, the most comfortable experience is achieved when the negative pressure is controlled at 25-45 kPa and the piston pumping frequency at 35-75 times / minute.

[0031] For example, in the high-pressure breast pumping mode, a large negative pressure of 50 kPa is required. The gear is set to the first gear. When the piston moves to the bottom of the cylinder, the exhaust solenoid valve is opened to release all the air and then immediately closed. The piston then moves back to pump air. The pressure sensor detects the pressure change in the cylinder in real time. When the negative pressure of 50 kPa is reached, the piston stops pumping air, completing the entire stroke.

[0032] For example, in the low-pressure breast pumping mode, a negative pressure of 42 kPa is required. The gear is set to the second gear. When the piston moves to the bottom of the cylinder, the exhaust solenoid valve is opened to release air and then immediately closed. The piston then moves back to pump air. The pressure sensor detects the pressure change in the cylinder in real time. When the set value of 42 kPa is reached, the piston stops pumping air. Then, the piston is immediately controlled to move back to the bottom of the cylinder. The piston does not complete its full stroke, so a smaller negative pressure value can be obtained, making the breast pumping feel gentler.

[0033] In the lactation mode, the piston pump generates low negative pressure suction and high motor speed with a high suction frequency, simulating manual massage. For example, the suction frequency is 120-150 times / minute, generating a negative pressure of 10-35 kPa. For instance, in the lactation model working mode, a negative pressure of 30 kPa is required. With the gear set to the third level, the piston moves to the bottom of the cylinder, and the exhaust solenoid valve opens to release air and then immediately closes. The piston then moves back to draw air in. The pressure sensor monitors the pressure change in the cylinder in real time. Once the set value of 30 kPa is reached, the piston stops drawing air in and immediately moves back to the bottom of the cylinder. This results in a shorter piston travel distance and a higher reciprocating frequency compared to the pumping mode, achieving a lower negative pressure value. This high-frequency, low-negative-pressure massage of the breasts provides a more comfortable experience.

[0034] Compared to existing breast pumps, which generate a continuous and regular sinusoidal negative pressure value during the piston's stroke cycle, this invention can also regulate air pressure by controlling the piston pump motor and / or the exhaust solenoid valve during different piston stroke cycles. This produces a negative pressure waveform with irregular peaks, such as sawtooth or stepped waveforms. This simulates the intermittent sucking process of an infant with varying strengths, making the mother feel more natural and resulting in smoother milk flow.

[0035] In addition, as a unique protective measure of this invention, to prevent pain caused to the user due to sudden excessive negative pressure suction during breast pumping, this invention also sets a maximum negative pressure protection value, such as a negative air pressure of 51 kPa. When the pressure sensor detects in real time that the air pressure in the cylinder reaches the maximum negative pressure protection value, it controls the exhaust solenoid valve to immediately open and allow air to pass through, preventing excessive negative pressure suction from harming the human body. Existing breast pumps do not have a maximum negative pressure protection value; they simply control the piston to move up and down at a fixed negative pressure value to pump and release air, which is unscientific and unsafe, and lacks attention to the user experience.

[0036] Embodiment 2 of the present invention provides a method for fine-tuning the air pressure of a breast pump piston pump, which is an improvement on the method of Embodiment 1. The breast pump also uses an initial position recognition switch located at the bottom of the cylinder to identify whether the piston has moved back to the bottom of the cylinder. A mechanical exhaust valve is also provided at the bottom of the cylinder, connected to the initial position recognition switch. When it is determined that the piston has moved back to the bottom of the cylinder, the mechanical exhaust valve is opened to release air; when it is determined that the piston has moved away from the bottom of the cylinder, the mechanical exhaust valve is closed.

[0037] The cylinder's opening and closing of air is controlled by a combination of a mechanical exhaust valve and an exhaust solenoid valve. The mechanical exhaust valve is larger and has a larger airflow. The exhaust solenoid valve is smaller and has a smaller airflow. For different negative pressure values, the solenoid valve can be precisely controlled to open and close at any position within the cylinder, primarily serving to fine-tune the air pressure. This allows for more efficient opening and closing of the piston pump, enabling high-frequency, rapid alternation of opening and closing. It also allows the three-way diaphragm to fully reset in high-frequency operating mode, ensuring sufficient negative pressure is generated during each pumping cycle. This meets the requirements of different users for negative pressure breast pumping or massage, resulting in a better user experience.

[0038] like Figure 2 As shown, Embodiment 3 of the present invention provides a method for fine-tuning the air pressure of a breast pump piston pump. The breast pump is equipped with a circuit board, which is electrically connected to a chip, a motor, a pressure sensor, a photoelectric switch, and a mechanical exhaust valve. The mechanical exhaust switch and the photoelectric switch are two independent mechanisms. The cylinder of the piston pump is connected to the pressure sensor and the mechanical exhaust valve. The photoelectric switch, connected to the mechanical exhaust valve, is located at the bottom of the cylinder. When the piston reaches the bottom of the cylinder, it triggers the photoelectric switch, which in turn controls the opening of the mechanical exhaust valve. When the piston leaves the bottom of the cylinder, it disconnects the photoelectric switch and closes the mechanical exhaust valve. The control process includes: setting the piston pump's speed settings to correspond to different working modes, and controlling the motor to drive the piston movement and the mechanical exhaust valve to operate through a programmed control. The control waveform program for controlling the breast pump's operation, as well as the air pressure threshold value for the corresponding speed settings, can be stored in the chip.

[0039] When the motor of the breast pump drives the piston of the piston pump to perform reciprocating air exhaust and suction movements, the pressure sensor detects the changes in air pressure in the cylinder in real time. According to the set working mode, the pressure sensor transmits signals to the motor and photoelectric switch, which in turn control the mechanical exhaust valve to adjust the air pressure.

[0040] The method also includes selecting the function button on the breast pump casing to set the piston pump's speed, corresponding to different working modes, including a milk pumping mode and a lactation mode; in the milk pumping mode, the piston pump generates a strong negative pressure suction and a low suction frequency; in the lactation mode, the piston pump generates a weak negative pressure suction and a high suction frequency.

[0041] Different operating modes correspond to different air pressure values. The pressure sensor detects in real time whether the air pressure in the cylinder has reached the set air pressure value, and controls the motor movement and / or the mechanical exhaust valve to adjust the air pressure.

[0042] In the described breast pumping mode, the user experiences comfort when the negative pressure is 20-50 kPa and the piston suction / relief frequency is 30-80 times / minute. The negative pressure can also be set to 30 kPa, 35 kPa, or 40 kPa. For example, the most comfortable experience is achieved when the negative pressure is 25-45 kPa and the piston suction / relief frequency is 35-75 times / minute. In the described lactation mode, the piston pump generates a negative pressure of 10-35 kPa, and the piston suction / relief frequency is 120-150 times / minute.

[0043] For example, in the low-pressure breast pumping mode, a negative pressure of 38 kPa is required. The gear is set to the second gear. When the piston reaches the bottom of the cylinder, the photoelectric switch is triggered, which controls the opening of the mechanical exhaust valve. After the air is completely released, the valve is immediately closed. The piston then moves back to pump air. The pressure sensor detects the change in negative pressure in the cylinder in real time. When the set value of 38 kPa is reached, the piston stops pumping air, the motor reverses, and immediately controls the piston to move to the bottom of the cylinder. The piston does not complete its full stroke, so a smaller negative pressure value can be obtained, making the breast pumping feel gentler.

[0044] Of course, in order to prevent the user from experiencing pain due to excessive negative pressure suction during the breast pumping process, the present invention also sets a maximum negative pressure protection value, such as a negative air pressure of 51 kPa. When the pressure sensor detects in real time that the air pressure in the cylinder reaches the maximum negative pressure protection value, it immediately controls the mechanical exhaust valve to open and ventilate, preventing excessive negative pressure suction from causing harm to the human body.

[0045] In the lactation mode, a negative pressure of 28 kPa is required, and the gear is set to the third gear. When the piston reaches the bottom of the cylinder, the photoelectric switch is triggered, which controls the opening of the mechanical exhaust valve. After the air is completely released, the valve immediately closes. The piston then moves back to draw air in. The pressure sensor detects the air pressure change in the cylinder in real time. When the set value of 28 kPa is reached, the piston stops moving back to draw air in, and the motor reverses, immediately controlling the piston to move to the bottom of the cylinder. In this way, the piston travels a shorter distance than in the breast pumping mode, the reciprocating motion frequency is higher, and the negative pressure value is lower. The high-frequency, low-negative-pressure massage of the breasts feels more comfortable.

[0046] The present invention provides a method for fine-tuning the air pressure of a breast pump piston pump. According to usage needs, the pressure sensor can detect changes in air pressure in the cylinder in real time and precisely adjust the air pressure to meet the comfort requirements of different groups of people for the amount of negative pressure during breast pumping.

Claims

1. A method for fine-tuning the air pressure of a breast pump piston pump, characterized in that, include: The cylinder of the piston pump is connected to a pressure sensor and an exhaust solenoid valve. When the piston of the piston pump moves back and forth to exhaust and pump air, the pressure sensor detects the change in air pressure in the cylinder in real time. According to the set working mode, the exhaust solenoid valve is controlled to switch on and off to adjust the air pressure. The piston pump has different speed settings corresponding to different working modes, including a milk pumping mode and a lactation mode. In the milk pumping mode, the piston pump generates a strong negative pressure suction and a low suction frequency. In the lactation mode, the piston pump generates a weak negative pressure suction and a high suction frequency. Different working modes correspond to different air pressure values. The pressure sensor detects in real time whether the air pressure in the cylinder reaches the set air pressure value, and controls the piston pump motor to move and / or the exhaust solenoid valve to switch to adjust the air pressure. A maximum negative pressure protection value is set. When the pressure sensor detects that the air pressure in the cylinder reaches the maximum negative pressure protection value in real time, it controls the exhaust solenoid valve to open immediately to protect the human body. According to the set working mode, the exhaust solenoid valve is controlled to adjust the air pressure. For different negative pressure values, the piston moves to any position in the cylinder to precisely control the opening and closing of the exhaust solenoid valve. During different stroke cycles of the piston, the piston pump motor is controlled to move and / or the exhaust solenoid valve is switched to regulate the air pressure, generating a negative pressure waveform with irregular peaks.

2. The method for fine-tuning the air pressure of a breast pump piston pump according to claim 1, characterized in that, In the breast pumping mode, the negative pressure generated by the piston pump is 20-50 kPa, and the piston suction frequency is 30-80 times / minute; in the lactation mode, the negative pressure generated by the piston pump is 10-35 kPa, and the piston suction frequency is 120-150 times / minute.

3. The method for fine-tuning the air pressure of a breast pump piston pump according to claim 1, characterized in that, It also uses an initial position recognition switch located at the bottom of the cylinder to identify whether the piston has moved back to the bottom of the cylinder, and controls the exhaust solenoid valve switch to adjust the air pressure.

4. The method for fine-tuning the air pressure of a breast pump piston pump according to claim 3, characterized in that, It also includes a mechanical exhaust valve located at the bottom of the cylinder, which is connected to the initial position recognition switch. When it is determined that the piston has moved back to the bottom of the cylinder, the mechanical exhaust valve is opened to release air; when it is determined that the piston has left the bottom of the cylinder, the mechanical exhaust valve is closed.

5. A method for fine-tuning the air pressure of a breast pump piston pump, characterized in that, include The cylinder of the piston pump is connected to a pressure sensor and a mechanical exhaust valve. A photoelectric switch connected to the mechanical exhaust valve is set at the bottom of the cylinder. When the motor of the breast pump drives the piston of the piston pump to perform reciprocating exhaust and suction movements, the pressure sensor detects the change in air pressure in the cylinder in real time. According to the set working mode, the pressure sensor transmits a signal to the motor and the photoelectric switch, which cooperates to control the mechanical exhaust valve and the exhaust solenoid valve to adjust the air pressure. The piston pump has different speed settings corresponding to different working modes, including a milk pumping mode and a lactation mode. In the milk pumping mode, the piston pump generates a strong negative pressure suction and a low suction frequency. In the lactation mode, the piston pump generates a weak negative pressure suction and a high suction frequency. Different working modes correspond to different air pressure values. The pressure sensor detects in real time whether the air pressure in the cylinder has reached the set air pressure value, and controls the motor movement and / or the mechanical exhaust valve to adjust the air pressure. The cylinder is controlled to open and close by combining the mechanical exhaust valve and the exhaust solenoid valve. For different negative pressure values, the piston can be moved to any position in the cylinder to precisely control the opening and closing of the exhaust solenoid valve. During different stroke cycles of the piston, the piston pump motor is controlled to move and / or the exhaust solenoid valve is switched to regulate the air pressure, generating a negative pressure waveform with irregular peaks.

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