A multi-stage pressure regulating relay valve

Abstract

A multi-stage pressure-regulating relay valve comprises a main body, a first pressure-regulating device and a second pressure-regulating device. The main body comprises a reaction air chamber and a fourth control air chamber. A first air passage is connected between the reaction air chamber and the first pressure-regulating device, a second air passage is connected between the fourth control air chamber and the first pressure-regulating device; a pressure-regulating air passage is connected between the first pressure-regulating device and the second pressure-regulating device. The valve has the advantages of improving braking efficiency and ensuring braking effect.

Description

Technical Field

[0001] The invention relates to the technical field of automobile braking, and more specifically to a multi-stage pressure regulating relay valve. Background Art

[0002] The existing automobile and trailer braking systems generally use air supply braking, that is, the control air controls the relay valve, and the gas in the air reservoir passes through the relay valve to the brake chamber to implement braking. The existing relay valve pressure regulation method can only adjust the brake pressure of light vehicles and heavy vehicles together, so there is a problem that either the light vehicle is locked or the heavy vehicle cannot be braked, which not only causes serious damage to the car and trailer, but also easily causes accidents. Summary of the invention

[0003] In order to solve the above problems and overcome the shortcomings of the prior art, the present invention provides a multi-stage pressure-regulating relay valve that can separately adjust the braking pressure required for a light vehicle and the braking pressure required for a heavy vehicle, and arbitrarily adjust the braking air pressure to start increasing when the control air pressure reaches a predetermined pressure, so that a light vehicle will not be locked and a heavy vehicle can be braked.

[0004] To achieve the above-mentioned object, the present invention provides a multi-stage pressure regulating relay valve, comprising a body, a first pressure regulating device and a second pressure regulating device, the body comprising a reaction gas chamber and a fourth control gas chamber, a first gas passage is connected between the reaction gas chamber and the first pressure regulating device, and a second gas passage is connected between the fourth control gas chamber and the first pressure regulating device;

[0005] A pressure regulating air passage is connected between the first pressure regulating device and the second pressure regulating device.

[0006] Further, the first pressure regulating device includes a first pressure regulating nut, a first pressure spring, a first diaphragm, a first valve stem, a one-way valve and a one-way valve spring;

[0007] The first pressure regulating nut is engaged with the body, a first pressure spring is arranged inside the first pressure regulating nut, the lower end of the first pressure spring is pressed on the upper end of the first valve stem, a first diaphragm is arranged between the first pressure spring and the first valve stem, the outer edge of the first diaphragm is fixedly connected to the body, the lower end of the first valve stem is pressed on the upper end of the one-way valve, and a one-way valve spring is arranged below the one-way valve;

[0008] One end outlet of the pressure regulating gas channel is close to the first valve stem.

[0009] Further, the second pressure regulating device includes a second pressure regulating nut, a second pressure spring, a second diaphragm, a second valve stem and a leather pad;

[0010] The second pressure regulating nut is engaged with the body, a second pressure spring is arranged inside the second pressure regulating nut, the lower end of the second pressure spring is pressed on the upper end of the second valve stem, a second diaphragm is arranged between the second pressure spring and the second valve stem, the outer edge of the second diaphragm is fixedly connected with the body, and the lower end of the second valve stem is pressed on the upper end of the leather pad;

[0011] An exhaust port is arranged inside the second valve stem, and the exhaust port is communicated with the pressure regulating air channel.

[0012] Furthermore, an air vent connected to the atmosphere is provided at the upper end of the second pressure regulating nut.

[0013] Further, the body includes an upper cover, a middle body, a lower body, a lower cover, a main valve stem, a valve, a main spring, a lower diaphragm, an upper diaphragm and a piston;

[0014] The upper cover, middle body, lower body and lower cover which are connected in sequence from top to bottom are all provided with through holes which are interconnected to form a cavity. The main valve stem, valve and piston are arranged in sequence from top to bottom in the cavity. The upper half of the main valve stem is provided with an upper diaphragm, and the outer edge of the upper diaphragm is squeezed and fixed at the connection between the upper cover and the middle body; the lower half of the main valve stem is provided with a lower diaphragm, and the outer edge of the lower diaphragm is squeezed and fixed at the connection between the middle body and the lower body; the lower end of the main valve stem is against the upper end of the valve, and the lower end of the valve is movably sleeved inside the piston.

[0015] Furthermore, the main valve stem, the upper cover and the upper diaphragm form a first control air chamber.

[0016] The main valve stem, upper diaphragm and middle body form a reaction air chamber.

[0017] The main valve stem and the middle body form the second control air chamber.

[0018] The main valve stem, middle body and lower diaphragm form the third control air chamber.

[0019] The main valve stem, lower body and lower diaphragm form the fourth control air chamber.

[0020] The valve, the piston and the lower body enclose a fifth control air chamber;

[0021] The upper cover is provided with a control air inlet connected to the first control air chamber, the lower body is provided with an air tank inlet connected to the fifth control air chamber, the lower body is provided with a brake air outlet connected to the fourth control air chamber, and the lower part of the piston is provided with a sixth control air chamber.

[0022] Further, it also includes a middle spring and a lower spring;

[0023] The upper end of the middle spring abuts against the upper end of the valve, and the lower end of the middle spring abuts against the lower end of the piston;

[0024] The upper end of the lower spring abuts against the lower end of the piston, and the lower end of the lower spring abuts against the lower cover.

[0025] Furthermore, an air outlet is provided at the lower portion of the lower cover.

[0026] Furthermore, a third air passage connecting the third control air chamber and the control air inlet is arranged inside the middle body.

[0027] Furthermore, a fourth air passage communicating with the first control air chamber and the second control air chamber is arranged inside the main valve stem.

[0028] The beneficial effects of the present invention are:

[0029] The multi-stage pressure regulating relay valve provided by the present invention has the advantages of improving braking efficiency and ensuring braking effect, and can separately adjust the braking pressure required for light vehicles and the braking pressure required for heavy vehicles. That is, it can arbitrarily adjust the pressure at which the control air pressure starts to increase. It can prevent light vehicles from locking and heavy vehicles from braking, thus solving the problem that light vehicles lock while heavy vehicles cannot be braked in current cars and trailers. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Attached Figure 1 It is a schematic diagram of the structure of the present invention;

[0031] Attached Figure 2 is an enlarged schematic diagram of the structure of the first adjusting device and the second adjusting device of the present invention;

[0032] In the accompanying drawings: 1, upper cover, 2, middle body, 3, lower body, 4, lower cover, 5, main valve stem, 6, air outlet, 7, valve, 8, main spring, 9, lower diaphragm, 10, upper diaphragm, 11, piston;

[0033] 21. first control air chamber, 22. reaction air chamber, 23. second control air chamber, 24. third control air chamber, 25. fourth control air chamber, 26. fifth control air chamber, 27. sixth control air chamber;

[0034] 30. second pressure regulating nut, 31. air vent, 32. second pressure spring, 33. second diaphragm, 34. air vent, 35. second valve stem, 36. leather pad, 37. pressure regulating airway;

[0035] 40. first pressure regulating nut, 41. first pressure spring, 42. first diaphragm, 43. first valve stem, 44. one-way valve, 45. one-way valve spring;

[0036] 51. Control air inlet, 52. Air tank inlet, 53. Brake air outlet;

[0037] 60. First airway, 61. Second airway, 62. Third airway, 63. Fourth airway. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the present invention more clear, the following will be combined with the appended claims of the present invention. Figure 1 ~Attached Figure 2 , the present invention is described in more detail.

[0039] The multi-stage pressure-regulating relay valve provided by the present invention comprises a main body, a first pressure-regulating device and a second pressure-regulating device, the main body comprises a reaction air chamber and a fourth control air chamber, a first air passage is connected between the reaction air chamber and the first pressure-regulating device, a second air passage is connected between the fourth control air chamber and the first pressure-regulating device; a pressure-regulating air passage is connected between the first pressure-regulating device and the second pressure-regulating device; the first pressure-regulating device comprises a first pressure-regulating nut, a first pressure spring, a first diaphragm, a first valve stem, a one-way valve and a one-way valve spring; the first pressure-regulating nut is meshed with the main body, a first pressure spring is arranged inside the first pressure-regulating nut, the lower end of the first pressure spring is pressed against the upper end of the first valve stem, a first diaphragm is arranged between the first pressure spring and the first valve stem, and an outer edge of the first diaphragm is fixedly connected to the main body The lower end of the first valve stem is pressed on the upper end of the one-way valve, and a one-way valve spring is arranged below the one-way valve; an outlet of one end of the pressure regulating air channel is close to the first valve stem; the second pressure regulating device comprises a second pressure regulating nut, a second pressure spring, a second diaphragm, a second valve stem and a leather pad; the second pressure regulating nut is meshed with the body, a second pressure spring is arranged inside the second pressure regulating nut, the lower end of the second pressure spring is pressed on the upper end of the second valve stem, a second diaphragm is arranged between the second pressure spring and the second valve stem, the outer edge of the second diaphragm is fixedly connected to the body, and the lower end of the second valve stem is pressed on the upper end of the leather pad; an exhaust port is arranged inside the second valve stem, and the exhaust port is connected to the pressure regulating air channel; an exhaust port connected to the atmosphere is arranged on the upper end of the second pressure regulating nut; the body comprises an upper cover, a middle body, a lower body, a lower cover, a main valve stem, Valve, main spring, lower diaphragm, upper diaphragm and piston; the upper cover, middle body, lower body and lower cover connected in sequence from top to bottom are all provided with through holes interconnected to form a cavity, and the main valve stem, valve and piston are arranged in sequence from top to bottom in the cavity, the upper half of the main valve stem is provided with an upper diaphragm, and the outer edge of the upper diaphragm is squeezed and fixed at the connection between the upper cover and the middle body; the lower half of the main valve stem is provided with a lower diaphragm, and the outer edge of the lower diaphragm is squeezed and fixed at the connection between the middle body and the lower body; the lower end of the main valve stem is against the upper end of the valve, and the lower end of the valve is movably sleeved inside the piston; the main valve stem, upper cover and upper diaphragm form a first control air chamber, the main valve stem, upper diaphragm and middle body form a reaction air chamber, the main valve stem and middle body form a second control air chamber, the main valve stem, The middle body and the lower diaphragm form a third control air chamber, the main valve stem, the lower body and the lower diaphragm form a fourth control air chamber, and the valve, the piston and the lower body form a fifth control air chamber; the upper cover is provided with a control air inlet connected to the first control air chamber, the lower body is provided with an air tank inlet connected to the fifth control air chamber, the lower body is provided with a brake air outlet connected to the fourth control air chamber, and the lower part of the piston is provided with a sixth control air chamber; it also includes a middle spring and a lower spring; the upper end of the middle spring abuts against the upper end of the valve, and the lower end of the middle spring abuts against the lower end of the piston; the upper end of the lower spring abuts against the lower end of the piston, and the lower end of the lower spring abuts against the lower cover; the lower part of the lower cover is provided with an air outlet; the interior of the middle body is provided with a third air channel connected to the third control air chamber and the control air inlet;A fourth air passage connecting the first control air chamber and the second control air chamber is arranged inside the main valve stem. ;

[0040] One embodiment of the present invention is as follows:

[0041] The multi-stage pressure regulating relay valve provided by the present invention comprises a body, a first pressure regulating device and a second pressure regulating device, the body comprises a reaction air chamber 22 and a fourth control air chamber 25, a first air passage 60 is connected between the reaction air chamber 22 and the first pressure regulating device, and a second air passage 61 is connected between the fourth control air chamber 25 and the first pressure regulating device; a pressure regulating air passage 37 is connected between the first pressure regulating device and the second pressure regulating device; the first pressure regulating device comprises a first pressure regulating nut 40, a first pressure spring 41, a first diaphragm 42, a first valve stem 43, a check valve 44 and a check valve spring 45; the first pressure regulating nut 40 is meshed with the body, a first pressure spring 41 is arranged inside the first pressure regulating nut 40, and the lower end of the first pressure spring 41 presses on the first At the upper end of the valve stem 43, a first diaphragm 42 is arranged between the first pressure spring 41 and the first valve stem 43, the outer edge of the first diaphragm 42 is fixedly connected to the body, the lower end of the first valve stem 43 is pressed on the upper end of the one-way valve 44, and a one-way valve spring 45 is arranged below the one-way valve 44; one end outlet of the pressure regulating airway 37 is close to the first valve stem 43; the second pressure regulating device includes a second pressure regulating nut 30, a second pressure spring 32, a second diaphragm 33, a second valve stem 35 and a leather pad 36; the second pressure regulating nut 30 is meshed with the body, a second pressure spring 32 is arranged inside the second pressure regulating nut 30, the lower end of the second pressure spring 32 is pressed on the upper end of the second valve stem 35, a second diaphragm 33 is arranged between the second pressure spring 32 and the second valve stem 35, and the second The outer edge of the diaphragm 33 is fixedly connected to the body, and the lower end of the second valve stem 35 is pressed on the upper end of the leather pad 36; an exhaust port 34 is arranged inside the second valve stem 35, and the exhaust port 34 is connected to the pressure regulating airway 37; the upper end of the second pressure regulating nut 30 is provided with an air vent 31 connected to the atmosphere; the body includes an upper cover 1, a middle body 2, a lower body 3, a lower cover 4, a main valve stem 5, a valve 7, a main spring 8, a lower diaphragm 9, an upper diaphragm 10 and a piston 11; the upper cover 1, the middle body 2, the lower body 3 and the lower cover 4 connected from top to bottom are all provided with through holes that are connected to each other and form a cavity, and the main valve stem 5, the valve 7 and the piston 11 are arranged in sequence inside the cavity from top to bottom, and the upper diaphragm 10 is arranged on the upper half of the main valve stem 5, and the outer edge of the upper diaphragm 10 squeezes The main valve stem 5 is fixed at the connection between the upper cover 1 and the middle body 2; the lower half of the main valve stem 5 is provided with a lower diaphragm 9, and the outer edge of the lower diaphragm 9 is squeezed and fixed at the connection between the middle body 2 and the lower body 3; the lower end of the main valve stem 5 is against the upper end of the valve 7, and the lower end of the valve 7 is movably sleeved inside the piston 11; the main valve stem 5, the upper cover 1 and the upper diaphragm 10 form a first control air chamber 21, the main valve stem 5, the upper diaphragm 10 and the middle body 2 form a reaction air chamber 22, the main valve stem 5 and the middle body 2 form a second control air chamber 23, the main valve stem 5, the middle body 2 and the lower diaphragm 9 form a third control air chamber 24, the main valve stem 5, the lower body 3 and the lower diaphragm 9 form a fourth control air chamber 25, and the valve 7, the piston 11 and the lower body 3 form a fifth control air chamber 26;The upper cover 1 is provided with a control air inlet 51 communicating with the first control air chamber 21, the lower body 3 is provided with an air tank inlet 52 communicating with the fifth control air chamber 26, the lower body 3 is provided with a brake air outlet 53 communicating with the fourth control air chamber 25, and the lower part of the piston 11 is provided with a sixth control air chamber 27; it also includes a middle spring and a lower spring; the upper end of the middle spring abuts against the upper end of the valve 7, and the lower end of the middle spring abuts against the lower end of the piston 11; the upper end of the lower spring abuts against the lower end of the piston 11, and the lower end of the lower spring abuts against the lower cover 4; the lower part of the lower cover 4 is provided with an outlet hole 6; the interior of the middle body 2 is provided with a third air passage 62 communicating with the third control air chamber 24 and the control air inlet 51; the interior of the main valve stem 5 is provided with a fourth air passage 63 communicating with the first control air chamber 21 and the second control air chamber 23. ;

[0042] One embodiment of the present invention is as follows:

[0043] The upper cover 1, the middle body 2, the lower body 3, and the lower cover 4 are connected by bolts respectively. The edge of the upper diaphragm 10 is pressed by the upper cover 1 and the middle body 2, and a nut is fixed to the upper end of the main valve stem 5 in the middle, dividing the upper cover 1 and the middle body 2 into a first control air chamber 21 and a reaction air chamber 22. The fourth air passage 63 in the middle of the main valve stem 5 is connected to the second control air chamber 23. The edge of the lower diaphragm 9 is pressed by the middle body 2 and the lower body 3, and connected to the main valve stem 5 by a nut, dividing the middle body 2 and the lower body 3 into a third control air chamber 24 and a fourth control air chamber 25. The main spring 8 is below the lower diaphragm 9, and the piston 11 is inside the lower body 3. The piston 11 has a middle spring and a support plate inside, and a retaining ring is fixed inside the piston 11. The first pressure regulating device and the second pressure regulating device are on the middle body 2.

[0044] The middle is communicated through the pressure regulating air passage 37. The principle of the first pressure regulating device and the second pressure regulating device is basically the same. The second pressure regulating nut 30 and the first pressure regulating nut 40 are adjusted to press on the second pressure spring 32 and the first pressure spring 41. The second pressure spring 32 and the first pressure spring 41 are pressed on the second valve stem 35 and the first valve stem 43 respectively. The second valve stem 35 and the first valve stem 43 are fixed together with the second diaphragm 33 and the first diaphragm 42 respectively. The second valve stem 35 and the first valve stem 43 are pressed on the leather pad 36 and the one-way valve 44. There is a one-way valve spring 45 under the one-way valve 44.

[0045] The working principle is that when the driver steps on the brake pedal, the control air of the main vehicle enters the first control air chamber 21 through the control air inlet 51, and then enters the second control air chamber 23 and the third control air chamber 24 through the third air channel 62 and the fourth air channel 63 respectively, pressing down the lower diaphragm 9, the upper diaphragm 10 and the piston 11 in the middle of the main valve stem 5, and after overcoming the reaction force of the reaction air chamber 22, the main valve stem 5 is driven to move downward, and the main valve stem 5 pushes the valve 7 to move downward, and the gas in the fifth control air chamber 26 enters the sixth control air chamber 27, and the brake air implements braking through the brake air outlet 53.

[0046] When the driver lifts the brake pedal, the control air flows back, and the gas in the first control air chamber 21 and the third control air chamber 24 is discharged from the control air pipeline, and the air pressure is zero. The main valve stem 5 is pushed upward under the action of the main spring 8 and the air pressure in the fourth control air chamber 25, and the valve 7 also moves upward under the action of the spring. When the valve 7 and the piston 11 are closed, the connection between the fifth control air chamber 26 and the fourth control air chamber 25 is closed, and the main valve stem 5 continues to move upward under the action of the spring, and the bottom of the main valve stem 5 is disengaged from the valve 7. The gas in the fourth control air chamber 25 is discharged to the atmosphere through the sixth control air chamber 27 in the middle of the valve 7, completing one braking operation.

[0047] The present invention mainly changes the air pressure in the reaction air chamber 22, that is, by changing the pressure of the gas in the reaction air chamber 22, the downward speed of the main valve stem 5 is changed, thereby changing the air pressure in the fourth control air chamber 25, so as to achieve the purpose of changing the braking force.

[0048] That is, by adjusting the pressure values ​​of the first pressure spring 41 and the second pressure spring 32 of the first pressure regulating device and the second pressure regulating device, the pressure at which the pressure of the fourth control air chamber 25 starts to increase can be changed, that is, the original pressure of the control air and the brake air being the same is changed to the brake air pressure being greater than the control air pressure.

[0049] The second air passage 61 is communicated with the fourth control air chamber 25, the first air passage 60 in the first pressure regulating device is communicated with the decompression reaction air chamber 22, and the pressure regulating air passage 37 is connected with the first pressure regulating device and the second pressure regulating device.

[0050] The working principle of pressure regulation is as follows: the first pressure regulating device adjusts the one-way valve 44 through the pressure of the spring, and opens and closes the connection and disconnection of the fourth control air chamber 25 and the reaction air chamber 22 through the opening and closing of the one-way valve 44. When the air pressure of the fourth control air chamber 25 is greater than the sum of the pressures of the first pressure spring 41 and the reaction air chamber 22, the one-way valve 44 will push the first valve stem 43 upward to close the connection between the fourth control air chamber 25 and the reaction air chamber 22. When the air pressure continues to increase, the main valve stem 5 and the upper diaphragm 10 move downward to compress the gas in the reaction air chamber 22, so that the air pressure increases. If the pressure of the second pressure spring 32 in the second pressure regulating device is overcome, the second valve stem 35 leaves the leather pad 36, and the gas will be discharged to the atmosphere through the vent 31. The pressure of the gas in the reaction air chamber 22 is kept unchanged, which has the effect of boosting.

[0051] We can adjust the pressure at which the brake gas starts to increase pressure by adjusting the strength of the pressure springs of the first pressure regulating device and the second pressure regulating device.

[0052] The problem of asynchronous braking between the main vehicle and the trailer caused by different control air pressure of each main vehicle can be solved.

[0053] In addition, the present invention can also be used in a main vehicle, and can also be used in conjunction with ABS for better effect.

[0054] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A multi-stage pressure regulating relay valve, characterized in that: It comprises a body, a first pressure regulating device and a second pressure regulating device, the body comprises a reaction air chamber and a fourth control air chamber, a first air passage is connected between the reaction air chamber and the first pressure regulating device, and a second air passage is connected between the fourth control air chamber and the first pressure regulating device; A pressure regulating airway is connected between the first pressure regulating device and the second pressure regulating device; The second pressure regulating device comprises a second pressure regulating nut, a second pressure spring, a second diaphragm, a second valve stem and a leather pad; The second pressure regulating nut is meshed with the body, a second pressure spring is arranged inside the second pressure regulating nut, the lower end of the second pressure spring is pressed on the upper end of the second valve stem, a second diaphragm is arranged between the second pressure spring and the second valve stem, the outer edge of the second diaphragm is fixedly connected with the body, and the lower end of the second valve stem is pressed on the upper end of the leather pad; An exhaust port is provided inside the second valve stem, and the exhaust port is communicated with the pressure regulating air channel; The first pressure regulating device comprises a first pressure regulating nut, a first pressure spring, a first diaphragm, a first valve stem, a one-way valve and a one-way valve spring; The first pressure regulating nut is meshed with the body, a first pressure spring is arranged inside the first pressure regulating nut, the lower end of the first pressure spring is pressed on the upper end of the first valve stem, a first diaphragm is arranged between the first pressure spring and the first valve stem, the outer edge of the first diaphragm is fixedly connected to the body, the lower end of the first valve stem is pressed on the upper end of the one-way valve, and a one-way valve spring is arranged below the one-way valve; One end outlet of the pressure regulating air channel is close to the first valve stem.

2. The multi-stage pressure regulating relay valve according to claim 1, characterized in that: The upper end of the second pressure regulating nut is provided with an air vent connected to the atmosphere.

3. The multi-stage pressure regulating relay valve according to claim 1, characterized in that: The body comprises an upper cover, a middle body, a lower body, a lower cover, a main valve stem, a valve, a main spring, a lower diaphragm, an upper diaphragm and a piston; The upper cover, middle body, lower body and lower cover, which are connected in sequence from top to bottom, are all provided with through holes that are interconnected to form a cavity. The main valve stem, valve and piston are arranged in sequence from top to bottom in the cavity. The upper half of the main valve stem is provided with an upper diaphragm, and the outer edge of the upper diaphragm is squeezed and fixed at the connection between the upper cover and the middle body; the lower half of the main valve stem is provided with a lower diaphragm, and the outer edge of the lower diaphragm is squeezed and fixed at the connection between the middle body and the lower body; the lower end of the main valve stem abuts against the upper end of the valve, and the lower end of the valve is movably sleeved inside the piston.

4. The multi-stage pressure regulating relay valve according to claim 3, characterized in that: The main valve stem, the upper cover and the upper diaphragm form a first control air chamber. The main valve stem, the upper diaphragm and the middle body form a reaction air chamber. The main valve stem and the middle body form a second control air chamber. The main valve stem, the middle body and the lower diaphragm form a third control air chamber. The main valve stem, the lower body and the lower diaphragm form a fourth control air chamber. The valve, piston and lower body form a fifth control air chamber; The upper cover is provided with a control air inlet connected to the first control air chamber, the lower body is provided with an air tank inlet connected to the fifth control air chamber, the lower body is provided with a brake air outlet connected to the fourth control air chamber, and the lower part of the piston is provided with a sixth control air chamber.

5. The multi-stage pressure regulating relay valve according to claim 3, characterized in that: Also includes middle and lower springs; The upper end of the middle spring abuts against the upper end of the valve, and the lower end of the middle spring abuts against the lower end of the piston; The upper end of the lower spring abuts against the lower end of the piston, and the lower end of the lower spring abuts against the lower cover.

6. The multi-stage pressure regulating relay valve according to claim 3, characterized in that: The lower part of the lower cover is provided with an air outlet.

7. The multi-stage pressure regulating relay valve according to claim 4, characterized in that: A third air passage communicating with the third control air chamber and the control air inlet is arranged inside the middle body.

8. The multi-stage pressure regulating relay valve according to claim 4, characterized in that: A fourth air passage communicating with the first control air chamber and the second control air chamber is arranged inside the main valve stem.

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